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Sample records for reinforced concrete structures

  1. STRUCTURAL PERFORMANCE OF DEGRADED REINFORCED CONCRETE MEMBERS.

    SciTech Connect

    Braverman, J.I.; Miller, C.A.; Ellingwood, B.R.; Naus, D.J.; Hofmayer, C.H.; Bezler, P.; Chang, T.Y.

    2001-03-22

    This paper describes the results of a study to evaluate, in probabilistic terms, the effects of age-related degradation on the structural performance of reinforced concrete members at nuclear power plants. The paper focuses on degradation of reinforced concrete flexural members and shear walls due to the loss of steel reinforcing area and loss of concrete area (cracking/spalling). Loss of steel area is typically caused by corrosion while cracking and spalling can be caused by corrosion of reinforcing steel, freeze-thaw, or aggressive chemical attack. Structural performance in the presence of uncertainties is depicted by a fragility (or conditional probability of failure). The effects of degradation on the fragility of reinforced concrete members are calculated to assess the potential significance of various levels of degradation. The fragility modeling procedures applied to degraded concrete members can be used to assess the effects of degradation on plant risk and can lead to the development of probability-based degradation acceptance limits.

  2. Research progress of microbial corrosion of reinforced concrete structure

    NASA Astrophysics Data System (ADS)

    Li, Shengli; Li, Dawang; Jiang, Nan; Wang, Dongwei

    2011-04-01

    Microbial corrosion of reinforce concrete structure is a new branch of learning. This branch deals with civil engineering , environment engineering, biology, chemistry, materials science and so on and is a interdisciplinary area. Research progress of the causes, research methods and contents of microbial corrosion of reinforced concrete structure is described. The research in the field is just beginning and concerted effort is needed to go further into the mechanism of reinforce concrete structure and assess the security and natural life of reinforce concrete structure under the special condition and put forward the protective methods.

  3. Monitoring corrosion in reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Kung, Peter; Comanici, Maria I.

    2014-06-01

    Many defects can cause deterioration and cracks in concrete; these are results of poor concrete mix, poor workmanship, inadequate design, shrinkage, chemical and environmental attack, physical or mechanical damage, and corrosion of reinforcing steel (RS). We want to develop a suite of sensors and systems that can detect that corrosion is taking place in RS and inform owners how serious the problem is. By understanding the stages of the corrosion process, we can develop special a sensor that detects each transition. First, moisture ingress can be monitored by a fiber optics humidity sensor, then ingress of Chloride, which acts as a catalyst and accelerates the corrosion process by converting iron into ferrous compounds. We need a fiber optics sensor which can quantify Chloride ingress over time. Converting ferric to ferrous causes large volume expansion and cracks. Such pressure build-up can be detected by a fiber optic pressure sensor. Finally, cracks emit acoustic waves, which can be detected by a high frequency sensor made with phase-shifted gratings. This paper will discuss the progress in our development of these special sensors and also our plan for a field test by the end of 2014. We recommend that we deploy these sensors by visually inspecting the affected area and by identifying locations of corrosion; then, work with the designers to identify spots that would compromise the integrity of the structure; finally, drill a small hole in the concrete and insert these sensors. Interrogation can be done at fixed intervals with a portable unit.

  4. Acoustic emission monitoring of reinforced and prestressed concrete structures

    NASA Astrophysics Data System (ADS)

    Fowler, Timothy J.; Yepez, Luis O.; Barnes, Charles A.

    1998-03-01

    Acoustic emission is an important global nondestructive test method widely used to evaluate the structural integrity of metals and fiber reinforced plastic structures. However, in concrete, application of the technology is still at the experimental stage. Microcracking and crack growth are the principal sources of emission in concrete. Bond failure, anchor slippage, and crack rubbing are also sources of emission. Tension zone cracking in reinforced concrete is a significant source of emission and has made application of the technique to concrete structures difficult. The paper describes acoustic emission monitoring of full-scale prestressed concrete girders and a reinforced concrete frame during loading. The tests on the prestressed concrete girders showed three sources of emission: shear-induced cracking in the web, flexural cracking at the region of maximum moment, and strand slippage at the anchorage zone. The reinforced concrete frame was monitored with and without concrete shear panels. The research was directed to early detection of the cracks, signature analysis, source location, moment tensor analysis, and development of criteria for acoustic emission inspection of concrete structures. Cracking of concrete in the tension areas of the reinforced concrete sections was an early source of emission. More severe emission was detected as damage levels in the structure increased.

  5. 19. Virginia Route 605 grade separation structure. This reinforced concrete ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    19. Virginia Route 605 grade separation structure. This reinforced concrete rigid frame structure. This reinforced concrete rigid frame structure was built in 1950. It is an example of the most common ornament used on the parkway where the headwall, wingwalls, and railing is faced rusticated stone, but not the interior abutment walls and the bottom of the arch are plain concrete. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  6. Monitoring corrosion of steel bars in reinforced concrete structures.

    PubMed

    Verma, Sanjeev Kumar; Bhadauria, Sudhir Singh; Akhtar, Saleem

    2014-01-01

    Corrosion of steel bars embedded in reinforced concrete (RC) structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP) method. This paper also presents few techniques to protect concrete from corrosion. PMID:24558346

  7. Fiberglass reinforced concrete - a possibility to build earthquake resistant structures

    SciTech Connect

    Bischoff, Th.; Wulfhorst, B.; Franzke, F.; Offermann, P.

    1996-12-31

    The results from first investigations to use multi-axial warp knitted layer fabris (non crimp fabrics) as reinforcement for concrete and mortar applications will be discussed. Reinforced concrete specimen have been prepared and tested with dimensions of 300 mm x 60 mm x 11,5 mm. The optimum type of textile structure will be evaluated by comparison of the flexural strength of the test specimen. Using this knowledge first demonstration components have been manufactured. These were girders, like window lintels, geometrically measuring 700 mm x 140 mm x 140 mm as a hollow profile, which have been tested in 4-point bending tests. Derived from the results of the experiments it will be presented how multi-axial layer fabrics can be used to build earthquake resistant structures with textile reinforced concrete.

  8. Report on aging of nuclear power plant reinforced concrete structures

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1996-03-01

    The Structural Aging Program provides the US Nuclear Regulatory Commission with potential structural safety issues and acceptance criteria for use in continued service assessments of nuclear power plant safety-related concrete structures. The program was organized under four task areas: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technology, and Quantitative Methodology for Continued Service Determinations. Under these tasks, over 90 papers and reports were prepared addressing pertinent aspects associated with aging management of nuclear power plant reinforced concrete structures. Contained in this report is a summary of program results in the form of information related to longevity of nuclear power plant reinforced concrete structures, a Structural Materials Information Center presenting data and information on the time variation of concrete materials under the influence of environmental stressors and aging factors, in-service inspection and condition assessments techniques, repair materials and methods, evaluation of nuclear power plant reinforced concrete structures, and a reliability-based methodology for current and future condition assessments. Recommendations for future activities are also provided. 308 refs., 61 figs., 50 tabs.

  9. Perspective view. Fivestory reinforced concrete factory building reveals the structural ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view. Five-story reinforced concrete factory building reveals the structural frame on the exterior of the facade. Twelve bay facade facing onto Clay Avenue (north facade) has first floor openings bricked up. Mix of typical factory windows and glass block windows fill the majority of the openings on the rest of building - Russell Industrial Center, 1600 Clay Avenue, Detroit, MI

  10. Modeling Blast Loading on Buried Reinforced Concrete Structures with Zapotec

    DOE PAGESBeta

    Bessette, Greg C.

    2008-01-01

    A coupled Euler-Lagrange solution approach is used to model the response of a buried reinforced concrete structure subjected to a close-in detonation of a high explosive charge. The coupling algorithm is discussed along with a set of benchmark calculations involving detonations in clay and sand.

  11. 10. Interior view looking SE showing reinforced concrete structural system ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Interior view looking SE showing reinforced concrete structural system at ground floor of Paint Shop. - Central of Georgia Railway, Savannah Repair Shops & Terminal Facilities, Paint & Coach Barn, Bounded by West Broad, Jones, West Boundary & Hull Streets, Savannah, Chatham County, GA

  12. Structural Behavior of Concrete Beams Reinforced with Basalt Fiber Reinforced Polymer (BFRP) Bars

    NASA Astrophysics Data System (ADS)

    Ovitigala, Thilan

    The main challenge for civil engineers is to provide sustainable, environmentally friendly and financially feasible structures to the society. Finding new materials such as fiber reinforced polymer (FRP) material that can fulfill the above requirements is a must. FRP material was expensive and it was limited to niche markets such as space shuttles and air industry in the 1960s. Over the time, it became cheaper and spread to other industries such as sporting goods in the 1980-1990, and then towards the infrastructure industry. Design and construction guidelines are available for carbon fiber reinforced polymer (CFRP), aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFRP) and they are currently used in structural applications. Since FRP is linear elastic brittle material, design guidelines for the steel reinforcement are not valid for FRP materials. Corrosion of steel reinforcement affects the durability of the concrete structures. FRP reinforcement is identified as an alternative to steel reinforcement in corrosive environments. Although basalt fiber reinforced polymer (BFRP) has many advantages over other FRP materials, but limited studies have been done. These studies didn't include larger BFRP bar diameters that are mostly used in practice. Therefore, larger beam sizes with larger BFRP reinforcement bar diameters are needed to investigate the flexural and shear behavior of BFRP reinforced concrete beams. Also, shear behavior of BFRP reinforced concrete beams was not yet studied. Experimental testing of mechanical properties and bond strength of BFRP bars and flexural and shear behavior of BFRP reinforced concrete beams are needed to include BFRP reinforcement bars in the design codes. This study mainly focuses on the use of BFRP bars as internal reinforcement. The test results of the mechanical properties of BFRP reinforcement bars, the bond strength of BFRP reinforcement bars, and the flexural and shear behavior of concrete beams

  13. Three year tests on cathodic prevention of reinforced concrete structures

    SciTech Connect

    Bertolini, L.; Bolzoni, F.; Pedeferri, P.; Pastore, T.

    1997-12-01

    The effectiveness of cathodic protection applied to new reinforced or prestressed concrete structures exposed to chloride environments for preventing pitting corrosion has been studied. The operating conditions have been evaluated with long term tests on reinforced concrete slabs polarized with current densities ranging from 0.5 to 20 mA/m{sup 2} and subjected to chloride ponding. Laboratory tests were carried out to estimate the pitting potential versus the chloride content and to evaluate the effect of low cathodic currents on the chloride migration in the concrete cover. The results show that cathodic prevention may be effective in preventing pitting corrosion initiation by increasing the critical chloride content and that this technique can be safely applied also to new prestressed structures. The effect of current densities up to 2 mA/m{sup 2} on chloride migration was negligible during the first three years of test.

  14. Mixed Consolidation Solution for a Reinforced Concrete Structure

    NASA Astrophysics Data System (ADS)

    Lute, M.

    2016-06-01

    During the last years, reinforced concrete structures become subject for rehabilitation due to two factors: their long life span and large change in norms that leaded to a large increase of seismic loads in Eastern Europe. These lead to a necessity for rehabilitation of existing building stock in order to use them during their entire life span at the maximum potential. The present paper proposes a solution for rehabilitation for three reinforced concrete building of a hospital, that consumed a half of their life span and do not correspond anymore to present norms. The chosen solution is a combination between CFRP rehabilitation and increase of structural elements cross section in order to achieve the stiffness balance in the structure nodes that is required by present norms. As a further matter, correction in stiffness of local elements diminished the lateral drifts of the structure and improved the global seismic response of the building.

  15. Code System for Analysis of 3-D Reinforced Concrete Structures.

    Energy Science and Technology Software Center (ESTSC)

    1999-11-22

    Version 00 NONSAP-C is a finite element program for determining the static and dynamic response of three-dimensional reinforced concrete structures. Long-term, or creep, behavior of concrete structures can also be analyzed. Nonlinear constitutive relations for concrete under short-term loads are incorporated in two time-independent models, a variable-modulus approach with orthotropic behavior induced in the concrete due to the development of different tangent moduli in different directions and an elastic-plastic model in which the concrete ismore » assumed to be a continuous, isotropic, and linearly elastic-plastic strain-hardening-fracture material. A viscoelastic constitutive model for long-term thermal creep of concrete is included. Three-dimensional finite elements available in NONSAP-C include a truss element, a multinode tendon element for prestressed and post tensioned concrete structures, an elastic-plastic membrane element to represent the behavior of cavity liners, and a general isoparametric element with a variable number of nodes for analysis of solids and thick shells.« less

  16. Development of ductile hybrid fiber reinforced polymer (D-H-FRP) reinforcement for concrete structures

    NASA Astrophysics Data System (ADS)

    Somboonsong, Win

    The corrosion of steel rebars has been the major cause of the reinforced concrete deterioration in transportation structures and port facilities. Currently, the Federal Highway Administration (FHWA) spends annually $31 billion for maintaining and repairing highways and highway bridges. The study reported herein represents the work done in developing a new type of reinforcement called Ductile Hybrid Fiber Reinforced Polymer or D-H-FRP using non-corrosive fiber materials. Unlike the previous FRP reinforcements that fail in a brittle manner, the D-H-FRP bars exhibit the stress-strain curves that are suitable for concrete reinforcement. The D-H-FRP stress-strain curves are linearly elastic with a definite yield point followed by plastic deformation and strain hardening resembling that of mild steel. In addition, the D-H-FRP reinforcement has integrated ribs required for concrete bond. The desirable mechanical properties of D-H-FRP reinforcement are obtained from the integrated design based on the material hybrid and geometric hybrid concepts. Using these concepts, the properties can be tailored to meet the specific design requirements. An analytical model was developed to predict the D-H-FRP stress-strain curves with different combination of fiber materials and geometric configuration. This model was used to optimize the design of D-H-FRP bars. An in-line braiding-pultrusion manufacturing process was developed at Drexel University to produce high quality D-H-FRP reinforcement in diameters that can be used in concrete structures. A series of experiments were carried out to test D-H-FRP reinforcement as well as their individual components in monotonic and cyclic tensile tests. Using the results from the tensile tests and fracture analysis, the stress-strain behavior of the D-H-FRP reinforcement was fully characterized and explained. Two series of concrete beams reinforced with D-H-FRP bars were studied. The D-H-FRP beam test results were then compared with companion

  17. Interfacial chemistry of zinc anodes for reinforced concrete structures

    SciTech Connect

    Covino, B.S. Jr.; Bullard, S.J.; Cramer, S.D.; Holcomb, G.R.; McGill, G.E.; Cryer, C.B.; Stoneman, A.; Carter, R.R.

    1997-12-01

    Thermally-sprayed zinc anodes are used in both galvanic and impressed current cathodic protection systems for reinforced concrete structures. The Albany Research Center, in collaboration with the Oregon Department of Transportation, has been studying the effect of electrochemical aging on the bond strength of zinc anodes for bridge cathodic protection systems. Changes in anode bond strength and other anode properties can be explained by the chemistry of the zinc-concrete interface. The chemistry of the zinc-concrete interface in laboratory electrochemical aging studies is compared with that of several bridges with thermal-sprayed zinc anodes and which have been in service for 5 to 10 years using both galvanic and impressed current cathodic protection systems. The bridges are the Cape Creek Bridge on the Oregon coast and the East Camino Undercrossing near Placerville, CA. Also reported are interfacial chemistry results for galvanized steel rebar from the 48 year old Longbird Bridge in Bermuda.

  18. A yield line evaluation methodology for reinforced concrete structures

    SciTech Connect

    Mertz, G.E.

    1997-03-01

    Yield line theory is an analytical technique that can be used to determine the ultimate bending capacity of flat reinforced concrete plates. Alternately, yield line theory, combined with rotation limits, can be used to determine the energy absorption capacity of plates subjected to impulsive and impact loadings. Typical components analyzed by yield line theory are basements, floor and roof slabs subjected to vertical loads, and walls subjected to out of plane loadings. Yield line theory equates plastic strain energy to external work for postulated collapse mechanisms. Multiple collapse mechanisms are evaluated and the mechanism with the minimum strain energy corresponds to the collapse load. Numerous investigators have verified yield line theory by experiment. Analysis by yield line theory is currently accepted by the ACI-318 Building Code Requirements for Reinforced Concrete and ACI-349 Code Requirements for Nuclear Safety Related Concrete Structures. One limitation of yield line theory is that it is computational difficult to evaluate some collapse mechanism. This problem is aggravated by the complex geometry nd reinforcing layouts commonly found in practice. The Yield Line Evaluator (YLE) is a computer program which was developed to solve computationally tedious yield line mechanisms. The program has the capability to either evaluate a single user-defined mechanism or to iterate over a range of mechanisms to determine the minimum ultimate capacity. The program is verified by comparison to a series of yield line mechanisms with known solutions.

  19. A damage detection technique for reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Wu, Ai-Lun; Yang, Jann N.; Loh, Chin-Hsiung

    2012-04-01

    Civil engineering structures, such as reinforced concrete frames, exhibit nonlinear hysteretic behavior when subject to dynamic loads, such as earthquakes. The ability to detect damages in structures after a major earthquake will ensure their reliability and safety. Innovative analysis techniques for damage detection of structures have been extensively studied recently. However, practical and effective damage identification techniques remain to be developed for nonlinear structures, in particular hysteretic reinforced concrete (RC) structures. In this paper, a smooth hysteretic model with stiffness and strength degradations and with the pinching effect is used to represent the dynamic characteristics of reinforced concrete (RC) frames. A system identification method capable of detecting damages in nonlinear structures, referred to as the adaptive quadratic sum-square error with unknown inputs (AQSSE-UI), is used to detect damages in hysteretic RC frames. The performance of the AQSSE-UI technique is demonstrated by the experimental data. A 1/3 scale 2-story RC frame has been tested experimentally on the shake table at NCREE, Taiwan. This 2-story RC frame was subject to different levels of ground excitations back to back. The RC frame is firstly considered as a linear model with rotational springs and the tracking of the degradation of the stiffness parameters is carried out using the AQSSE-UI technique. Then the same RC frame is considered as a nonlinear structure with plastic hinges following a smooth hysteretic model. Experimental results show that the AQSSE-UI technique is quite effective for tracking of : (i) the stiffness degradation of linear structures, and (ii) the non-linear hysteretic parameters with stiffness and strength degradations.

  20. Reinforced concrete offshore platform

    SciTech Connect

    Martyshenko, J.P.; Martyshenko, S.J.; Kotelnikov, J.S.; Kutukhtin, E.G.; Petrosian, M.S.; Ilyasova, N.I.; Volkov, J.S.; Vardanian, A.M.

    1987-10-20

    A reinforced concrete offshore platform is described comprising a honeycomb foundation (A), a supporting structure (B) and an above-surface section (C) carrying appropriate equipment. The honeycomb foundation (A) and the supporting structure (B) are made of prefabricated reinforced concrete elements which are polyhedral hollow prisms arranged with gaps between the external sides thereof and joined by a system of prestressed vertical diaphragm walls and horizontal diaphragm walls formed by pre-tensioning reinforcing bars placed in the gaps between the faces of the prisms and casting in-situ the gaps later on.

  1. Seismic retrofitting of reinforced concrete frame structures using GFRP-tube-confined-concrete composite braces

    NASA Astrophysics Data System (ADS)

    Moghaddasi B., Nasim S.; Zhang, Yunfeng; Hu, Xiaobin

    2012-03-01

    This paper presents a new type of structural bracing intended for seismic retrofitting use in framed structures. This special composite brace, termed glass-fiber-reinforced-polymer (GFRP)-tube-confined-concrete composite brace, is comprised of concrete confined by a GFRP tube and an inner steel core for energy dissipation. Together with a contribution from the GFRP-tube confined concrete, the composite brace shows a substantially increased stiffness to control story drift, which is often a preferred feature in seismic retrofitting. An analysis model is established and implemented in a general finite element analysis program — OpenSees, for simulating the load-displacement behavior of the composite brace. Using this model, a parametric study of the hysteretic behavior (energy dissipation, stiffness, ductility and strength) of the composite brace was conducted under static cyclic loading and it was found that the area ratio of steel core to concrete has the greatest influence among all the parameters considered. To demonstrate the application of the composite brace in seismic retrofitting, a three-story nonductile reinforced concrete (RC) frame structure was retrofitted with the composite braces. Pushover analysis and nonlinear time-history analyses of the retrofitted RC frame structure was performed by employing a suite of 20 strong ground motion earthquake records. The analysis results show that the composite braces can effectively reduce the peak seismic responses of the RC frame structure without significantly increasing the base shear demand.

  2. Flexural retrofitting of reinforced concrete structures using Green Natural Fiber Reinforced Polymer plates

    NASA Astrophysics Data System (ADS)

    Cervantes, Ignacio

    An experimental study will be carried out to determine the suitability of Green Natural Fiber Reinforced Polymer plates (GNFRP) manufactured with hemp fibers, with the purpose of using them as structural materials for the flexural strengthening of reinforced concrete (RC) beams. Four identical RC beams, 96 inches long, are tested for the investigation, three control beams and one test beam. The first three beams are used as references; one unreinforced, one with one layer of Carbon Fiber Reinforced Polymer (CFRP), one with two layers of CFRP, and one with n layers of the proposed, environmental-friendly, GNFRP plates. The goal is to determine the number of GNFRP layers needed to match the strength reached with one layer of CFRP and once matched, assess if the system is less expensive than CFRP strengthening, if this is the case, this strengthening system could be an alternative to the currently used, expensive CFRP systems.

  3. New Fiber Reinforced Waterless Concrete for Extraterrestrial Structural Applications

    NASA Technical Reports Server (NTRS)

    Toutanji, H.; Tucker, D.; Ethridge, E.

    2005-01-01

    Commercial use of sulfur concrete on Earth is well established, particularly in corrosive, e.g., acid and salt, environments. Having found troilite (FeS) on the Moon raises the question of using extracted sulfur as a lunar construction mate: iii an attractive alternative to conventional concrete as it does not require water For the purpose of this paper it is assumed that lunar ore is mined, refined, and the raw sulfur processed with appropriate lunar regolith to form, for example, brick and beam elements. Glass fibers produced from regolith were used as a reinforcement to improve the mechanical properties of the sulfur concrete. Glass fibers and glass rebar were produced by melting the lunar regolith simulant. Lunar regolith stimulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline 46100 high temperature MoSi2 furnace at melting temperatures of 1450 to 1600G. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The viability of sulfur concrete as a construction material for extraterrestrial application is presented. The mechanical properties of the glass fiber reinforced sulfur concrete were investigated.

  4. EXPERIMENTAL STUDY ON THE APPLICATION OF HIGH STRENGTH FIBER REINFORCED MORTAR TO PRESTRESSED CONCRETE STRUCTURES

    NASA Astrophysics Data System (ADS)

    Sakurada, Michihiro; Mori, Takuya; Ohyama, Hiroaki; Seki, Hiroshi

    In order to study the application of high strength fiber reinforced mortar which has design compressive strength 120N/mm2 to prestressed concrete structures, the authors carried out material tests, bending tests and shear tests of prestressed concrete beam specimens. From the material tests, we obtained material properties for the design of prestressed concrete structures such as compressive strength, tensile strength, Young's modulus, coefficient of creep, dry shrinkage and so on. The results of the bending tests and the shear tests of prestressed concrete beam specimen shows that experimental flexural strength and shear strength of prestressed concrete beam using high strength fiber reinforced mortar exceeds strength calculated by traditional design method. It is confirmed that high strength fiber reinforced mortar can be applied to prestressed concrete structures.

  5. Evaluation of passivation method and corrosion inhibitors for steel-reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Brown, Richard; Lee, K. Wayne; Cao, Yong

    1999-02-01

    Corrosion of reinforcing steel due to the ingression of chloride ions from deicing salt and/or seawater has been a major cause of the deterioration of reinforced concrete structures. Typically reinforcing steel is protected from corrosion by the formation of passive film because of highly alkaline concrete environment. The film can be damaged with the introduction of chloride ions to concrete, then corrosion occurs. There are mainly three approaches to tackle this problem, i.e., protective coating, cathodic protection and corrosion inhibitors.

  6. Yield Line Evaluation Methodology for Reinforced Concrete Structures

    Energy Science and Technology Software Center (ESTSC)

    1998-12-30

    Yield line theory is an analytical technique that can be used to determine the ultimate bending capacity of flat reinforced concrete plates subject to distributed and concentrated loadings. Alternately, yield line theory, combined with rotation limits can be used to determine the energy absorption capacity of plates subject to impulsive and impact loadings. Typical components analyzed by yield line theory are basemats, floor and roof slabs subject to vertical loads along with walls subject tomore » out of plane loadings. One limitation of yield line theory is that it is computationally difficult to evaluate some mechanisms. This problem is aggravated by the complex geometry and reinforcing layouts commonly found in practice. The program has the capability to either evaluate a single user defined mechanism or to iterate over a range of mechanisms to determine the minimum ultimate capacity. The program is verified by comparison to a series of yield line mechanisms with known solutions.« less

  7. Yield Line Evaluation Methodology for Reinforced Concrete Structures

    SciTech Connect

    1998-12-30

    Yield line theory is an analytical technique that can be used to determine the ultimate bending capacity of flat reinforced concrete plates subject to distributed and concentrated loadings. Alternately, yield line theory, combined with rotation limits can be used to determine the energy absorption capacity of plates subject to impulsive and impact loadings. Typical components analyzed by yield line theory are basemats, floor and roof slabs subject to vertical loads along with walls subject to out of plane loadings. One limitation of yield line theory is that it is computationally difficult to evaluate some mechanisms. This problem is aggravated by the complex geometry and reinforcing layouts commonly found in practice. The program has the capability to either evaluate a single user defined mechanism or to iterate over a range of mechanisms to determine the minimum ultimate capacity. The program is verified by comparison to a series of yield line mechanisms with known solutions.

  8. Numerical Investigations on a Blast Loaded Laced Reinforced Concrete Structure using an Equivalent Constitutive Property

    NASA Astrophysics Data System (ADS)

    Anandavalli, N.; Lakshmanan, N.; Prakash, Amar; Rajasankar, J.; Iyer, Nagesh R.

    2015-12-01

    A Laced Reinforced Concrete (LRC) structural element consists of continuously inclined shear reinforcement in the form of lacing that tie the longitudinal reinforcements on both faces of the structural element. LRC is used particularly in blast resistant construction. Conventional finite element modeling of reinforced concrete (RC) structures requires concrete and steel to be considered as separate entities and interaction between them to be defined through smeared, discrete or embedded approach. In this paper, a new approach for modeling RC structures is adopted to analyse a blast loaded LRC structure. Present approach considers RC/LRC as a homogenous material, whose constitutive property is derived based on the moment-curvature relationship of the structural component. An equivalent single-degree-of-freedom system obtained based on a proven technique is analysed to verify the results of the finite element analysis. Present approach significantly reduces the modeling effort and in turn, the computational demand for a given accuracy in the results.

  9. Microwave NDE for Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Arunachalam, Kavitha; Melapudi, Vikram R.; Rothwell, Edward J.; Udpa, Lalita; Udpa, Satish S.

    2006-03-01

    Nondestructive assessment of the integrity of civil structures is of paramount importance for ensuring safety. In concrete imaging, radiography, ground penetrating radar and infrared thermography are some of the widely used techniques for health monitoring. Other emerging technologies that are gaining impetus for detecting and locating flaws in steel reinforcement bar include radioactive computed tomography, microwave holography, microwave and acoustic tomography. Of all the emerging techniques, microwave NDT is a promising imaging modality largely due to their ability to penetrate thick concrete structures, contrast between steel rebar and concrete and their non-radioactive nature. This paper investigates the feasibility of a far field microwave NDE technique for reinforced concrete structures.

  10. Modelling Dowel Action of Discrete Reinforcing Bars in Cracked Concrete Structures

    SciTech Connect

    Kwan, A. K. H.; Ng, P. L.; Lam, J. Y. K.

    2010-05-21

    Dowel action is one of the component actions for shear force transfer in cracked reinforced concrete. In finite element analysis of concrete structures, the use of discrete representation of reinforcing bars is considered advantageous over the smeared representation due to the relative ease of modelling the bond-slip behaviour. However, there is very limited research on how to simulate the dowel action of discrete reinforcing bars. Herein, a numerical model for dowel action of discrete reinforcing bars crossing cracks in concrete is developed. The model features the derivation of dowel stiffness matrix based on beam-on-elastic-foundation theory and the direct assemblage of dowel stiffness into the concrete element stiffness matrices. The dowel action model is incorporated in a nonlinear finite element programme with secant stiffness formulation. Deep beams tested in the literature are analysed and it is found that the incorporation of dowel action model improves the accuracy of analysis.

  11. A proposed standard for evaluating structural integrity of reinforced concrete beams by acoustic emission

    SciTech Connect

    Yuyama, Shigenori; Okamoto, Takahisa; Shigeishi, Mitsuhiro; Ohtsu, Masayasu; Kishi, Teruo

    1999-07-01

    A series of studies has been performed to evaluate the structural integrity of reinforced concrete (RC) beams by acoustic emission (AE). Cyclic loadings were applied to RC beams with a single reinforcing bar, large repaired beams, beams deteriorated due to corrosion of reinforcement, and two beams with different damage levels in an aging dock. The test results demonstrated that the Kaiser effect starts to break down when shear cracking starts to play a primary role. It has been also shown that high AE activity is observed during unloadings after serious damage (slips between the concrete and the reinforcement or those between the original concrete and the repaired part) has occurred. A standard for evaluating structural integrity of RC beams by AE is proposed, based on these results.

  12. Development of structural health monitoring and early warning system for reinforced concrete system

    SciTech Connect

    Iranata, Data E-mail: data@ce.its.ac.id; Wahyuni, Endah; Murtiadi, Suryawan; Widodo, Amien; Riksakomara, Edwin; Sani, Nisfu Asrul

    2015-04-24

    Many buildings have been damaged due to earthquakes that occurred recently in Indonesia. The main cause of the damage is the large deformation of the building structural component cannot accommodate properly. Therefore, it is necessary to develop the Structural Health Monitoring System (SHMS) to measure precisely the deformation of the building structural component in the real time conditions. This paper presents the development of SHMS for reinforced concrete structural system. This monitoring system is based on deformation component such as strain of reinforcement bar, concrete strain, and displacement of reinforced concrete component. Since the deformation component has exceeded the limit value, the warning message can be sent to the building occupies. This warning message has also can be performed as early warning system of the reinforced concrete structural system. The warning message can also be sent via Short Message Service (SMS) through the Global System for Mobile Communications (GSM) network. Hence, the SHMS should be integrated with internet modem to connect with GSM network. Additionally, the SHMS program is verified with experimental study of simply supported reinforced concrete beam. Verification results show that the SHMS has good agreement with experimental results.

  13. Development of structural health monitoring and early warning system for reinforced concrete system

    NASA Astrophysics Data System (ADS)

    Iranata, Data; Wahyuni, Endah; Murtiadi, Suryawan; Widodo, Amien; Riksakomara, Edwin; Sani, Nisfu Asrul

    2015-04-01

    Many buildings have been damaged due to earthquakes that occurred recently in Indonesia. The main cause of the damage is the large deformation of the building structural component cannot accommodate properly. Therefore, it is necessary to develop the Structural Health Monitoring System (SHMS) to measure precisely the deformation of the building structural component in the real time conditions. This paper presents the development of SHMS for reinforced concrete structural system. This monitoring system is based on deformation component such as strain of reinforcement bar, concrete strain, and displacement of reinforced concrete component. Since the deformation component has exceeded the limit value, the warning message can be sent to the building occupies. This warning message has also can be performed as early warning system of the reinforced concrete structural system. The warning message can also be sent via Short Message Service (SMS) through the Global System for Mobile Communications (GSM) network. Hence, the SHMS should be integrated with internet modem to connect with GSM network. Additionally, the SHMS program is verified with experimental study of simply supported reinforced concrete beam. Verification results show that the SHMS has good agreement with experimental results.

  14. Improvement in performance of reinforced concrete structures using shape memory alloys

    NASA Astrophysics Data System (ADS)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2015-04-01

    Shape memory alloys (SMA) are a unique class of materials which have ability to undergo large deformation and also regain its undeformed shape by removal of stress or by heating. This unique property could be effectively utilized to enhance the safety of a structure. This paper presents the pushover analysis performance of a Reinforced Concrete moment resistance frame with the traditional steel reinforcement replaced partially with Nickel-Titanium (Nitinol) SMA. The results are compared with the RC structure reinforced with conventional steel. Partial replacement of traditional steel reinforcement by SMA shows better performance.

  15. Active tendon control of reinforced concrete frame structures subjected to near-fault effects

    NASA Astrophysics Data System (ADS)

    Nigdeli, Sinan Melih; Boduroǧlu, M. Hasan

    2013-10-01

    A reinforced concrete (RC) frame structure was controlled with active tendons under the excitation of near-fault ground motions. Proportional Integral Derivative (PID) type controllers were used and the controller was tuned by using a numerical algorithm. In order to prevent brittle fracture of the structure, the aim of the control is to reduce maximum base shear force. The RC structure was investigated for different characteristic strengths of concrete and the approach is applicable for the structure with 14 MPa concrete strength or higher.

  16. Damage Source Identification of Reinforced Concrete Structure Using Acoustic Emission Technique

    PubMed Central

    Panjsetooni, Alireza; Bunnori, Norazura Muhamad; Vakili, Amir Hossein

    2013-01-01

    Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures. PMID:23997681

  17. Life cycle CO{sub 2} evaluation on reinforced concrete structures with high-strength concrete

    SciTech Connect

    Tae, Sungho; Baek, Cheonghoon Shin, Sungwoo

    2011-04-15

    The purpose of this study is to evaluate the environment performance of high-strength concrete used in super tall buildings as material of environmental load reduction. To this end, this study proposed a plan for the evaluation of energy consumption and CO{sub 2} emission throughout the life cycle of the building, and calculated the energy consumption and CO{sub 2} emission throughout the life cycle of tall apartment building that was actually constructed using this plan. Then, we evaluated the energy consumption and CO{sub 2} emission reduction performance for the life cycle of the building by the decrease of concrete and reinforced rebar quantities and the increase of building lifespan obtained through conversion of existing building's concrete compressive strength to 40 MPa high-strength concrete. As a result, the life cycle energy consumption in case 3, a high-strength concrete building, decreased 15.53% and 2.95% respectively compared with cases 1 and 2. The evaluation of the general strength concrete buildings and the life cycle CO{sub 2} emission also decreased 16.70% and 3.37% respectively, compared with cases 1 and 2.

  18. Gaussian mixture modeling of acoustic emissions for structural health monitoring of reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Farhidzadeh, Alireza; Dehghan-Niri, Ehsan; Salamone, Salvatore

    2013-04-01

    Reinforced Concrete (RC) has been widely used in construction of infrastructures for many decades. The cracking behavior in concrete is crucial due to the harmful effects on structural performance such as serviceability and durability requirements. In general, in loading such structures until failure, tensile cracks develop at the initial stages of loading, while shear cracks dominate later. Therefore, monitoring the cracking modes is of paramount importance as it can lead to the prediction of the structural performance. In the past two decades, significant efforts have been made toward the development of automated structural health monitoring (SHM) systems. Among them, a technique that shows promises for monitoring RC structures is the acoustic emission (AE). This paper introduces a novel probabilistic approach based on Gaussian Mixture Modeling (GMM) to classify AE signals related to each crack mode. The system provides an early warning by recognizing nucleation of numerous critical shear cracks. The algorithm is validated through an experimental study on a full-scale reinforced concrete shear wall subjected to a reversed cyclic loading. A modified conventional classification scheme and a new criterion for crack classification are also proposed.

  19. Fatigue-loaded fiber optic strain gauges performance in reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    de Vries, Marten J.; Nasta, Manish H.; Claus, Richard O.; Masri, Sami F.

    1994-02-01

    This paper reports the performance of short gage length optical fiber sensors embedded in a reinforced concrete specimen for the quantitative measurement of periodic strain. We report the use of practical, short gage length relative and absolute strain sensors for the measurement of strain in a reinforced concrete specimen. Both types of fiber sensors were attached to steel reinforcement rods prior to filling with concrete, and were collocated with conventional foil strain gages to allow direct comparison of output signals. The relative fiber sensors were of the extrinsic Fabry-Perot interferometric type operating at a wavelength of 1300 nm and the absolute strain sensors used wavelength information to measure absolute strain. The results of this work show that such optical fiber elements may be considered for long term quantitative evaluation of civil structure components.

  20. An expert system for the evaluation of reinforced concrete structure durability

    SciTech Connect

    Berra, M.; Bertolini, L.; Briglia, M.C.; Lazzari, L.; Pastore, T.

    1999-11-01

    A user-friendly expert system has been developed to evaluate primarily the durability of reinforced concrete structures, either in the design phase or during service life related to reinforcement corrosion. Besides the durability module, the ES has been provided with three other expert modules in order to support the user during the following activities: inspections, corrosion diagnosis and repair strategy (of concrete and reinforcement). Corrosion induced by carbonation and chlorides penetration and caused by concrete degradation such as sulfate attack, freeze/thaw cycles, alkali silica reaction are considered. The knowledge used for the expert system is based both on open literature and international standards as well as on specific experiences and proprietary databases. The paper describes main features of the system, including the modeling of the knowledge, input data, the algorithms, the rules and the outputs for each module.

  1. Structural and seismic analyses of waste facility reinforced concrete storage vaults

    SciTech Connect

    Wang, C.Y.

    1995-07-01

    Facility 317 of Argonne National Laboratory consists of several reinforced concrete waste storage vaults designed and constructed in the late 1940`s through the early 1960`s. In this paper, structural analyses of these concrete vaults subjected to various natural hazards are described, emphasizing the northwest shallow vault. The natural phenomenon hazards considered include both earthquakes and tornados. Because these vaults are deeply embedded in the soil, the SASSI (System Analysis of Soil-Structure Interaction) code was utilized for the seismic calculations. The ultimate strength method was used to analyze the reinforced concrete structures. In all studies, moment and shear strengths at critical locations of the storage vaults were evaluated. Results of the structural analyses show that almost all the waste storage vaults meet the code requirements according to ACI 349--85. These vaults also satisfy the performance goal such that confinement of hazardous materials is maintained and functioning of the facility is not interrupted.

  2. Ultrasonic assessment of service life of concrete structures subject to reinforcing steel corrosion

    NASA Astrophysics Data System (ADS)

    Udegbunam, Ogechukwu Christian

    Over half of the bridges in the United States were built before 1970. Such bridges and the network of roads that they carry include the Inter State system, which was built as part of the great public works program, following the end of the Second World War. During that era, the emphasis was on strength design and economical construction of new structures, and not much premium was placed on durability and maintainability concerns. Since the end of this construction boom in the early 1970s, the concern for the durability of transportation infrastructure has steadily gained prominence among those agencies that must secure, program and administer funds for maintaining highway networks. The objective of this research was to develop a nondestructive method of assessing the durability of concrete bridge decks susceptible to damage from corrosion of embedded reinforcing steel. This was accomplished by formulating a holistic approach that accounts for the major factors that influence corrosion based deterioration of reinforced concrete. In this approach, the assessment of the durability of concrete bridge decks is based on a model that estimates the time it takes for the cover concrete to fail a result of stresses caused by expansion of reinforcing steel bars, due to corrosion activities. This time to failure is comprised of two distinct periods that must be evaluated before the problem can be solved. The research consisted of an experimental program and an analytical study. In the experimental program concrete specimens were cast and tested to determine their diffusivity and mechanical properties. The diffusivity was used to evaluate the period it takes for corrosion of the reinforcing bars to commence. In the analytical study, the resistance of the concrete structure against the internal forces caused by corrosion was evaluated with the finite element techniques. This resistance was used to evaluate the period defining the failure of the cover concrete. These two periods

  3. Concrete material characterization reinforced concrete tank structure Multi-Function Waste Tank Facility

    NASA Astrophysics Data System (ADS)

    Winkel, B. V.

    1995-03-01

    The purpose of this report is to document the Multi-Function Waste Tank Facility (MWTF) Project position on the concrete mechanical properties needed to perform design/analysis calculations for the MWTF secondary concrete structure. This report provides a position on MWTF concrete properties for the Title 1 and Title 2 calculations. The scope of the report is limited to mechanical properties and does not include the thermophysical properties of concrete needed to perform heat transfer calculations. In the 1970's, a comprehensive series of tests were performed at Construction Technology Laboratories (CTL) on two different Hanford concrete mix designs. Statistical correlations of the CTL data were later generated by Pacific Northwest Laboratories (PNL). These test results and property correlations have been utilized in various design/analysis efforts of Hanford waste tanks. However, due to changes in the concrete design mix and the lower range of MWTF operating temperatures, plus uncertainties in the CTL data and PNL correlations, it was prudent to evaluate the CTL data base and PNL correlations, relative to the MWTF application, and develop a defendable position. The CTL test program for Hanford concrete involved two different mix designs: a 3 kip/sq in mix and a 4.5 kip/sq in mix. The proposed 28-day design strength for the MWTF tanks is 5 kip/sq in. In addition to this design strength difference, there are also differences between the CTL and MWTF mix design details. Also of interest, are the appropriate application of the MWTF concrete properties in performing calculations demonstrating ACI Code compliance. Mix design details and ACI Code issues are addressed in Sections 3.0 and 5.0, respectively. The CTL test program and PNL data correlations focused on a temperature range of 250 to 450 F. The temperature range of interest for the MWTF tank concrete application is 70 to 200 F.

  4. Concrete material characterization reinforced concrete tank structure Multi-Function Waste Tank Facility

    SciTech Connect

    Winkel, B.V.

    1995-03-03

    The purpose of this report is to document the Multi-Function Waste Tank Facility (MWTF) Project position on the concrete mechanical properties needed to perform design/analysis calculations for the MWTF secondary concrete structure. This report provides a position on MWTF concrete properties for the Title 1 and Title 2 calculations. The scope of the report is limited to mechanical properties and does not include the thermophysical properties of concrete needed to perform heat transfer calculations. In the 1970`s, a comprehensive series of tests were performed at Construction Technology Laboratories (CTL) on two different Hanford concrete mix designs. Statistical correlations of the CTL data were later generated by Pacific Northwest Laboratories (PNL). These test results and property correlations have been utilized in various design/analysis efforts of Hanford waste tanks. However, due to changes in the concrete design mix and the lower range of MWTF operating temperatures, plus uncertainties in the CTL data and PNL correlations, it was prudent to evaluate the CTL data base and PNL correlations, relative to the MWTF application, and develop a defendable position. The CTL test program for Hanford concrete involved two different mix designs: a 3 kip/in{sup 2} mix and a 4.5 kip/in{sup 2} mix. The proposed 28-day design strength for the MWTF tanks is 5 kip/in{sup 2}. In addition to this design strength difference, there are also differences between the CTL and MWTF mix design details. Also of interest, are the appropriate application of the MWTF concrete properties in performing calculations demonstrating ACI Code compliance. Mix design details and ACI Code issues are addressed in Sections 3.0 and 5.0, respectively. The CTL test program and PNL data correlations focused on a temperature range of 250 to 450 F. The temperature range of interest for the MWTF tank concrete application is 70 to 200 F.

  5. Probabilistic failure modelling of reinforced concrete structures subjected to chloride penetration

    NASA Astrophysics Data System (ADS)

    Nogueira, Caio Gorla; Leonel, Edson Denner; Coda, Humberto Breves

    2012-12-01

    Structural durability is an important criterion that must be evaluated for every type of structure. Concerning reinforced concrete members, chloride diffusion process is widely used to evaluate durability, especially when these structures are constructed in aggressive atmospheres. The chloride ingress triggers the corrosion of reinforcements; therefore, by modelling this phenomenon, the corrosion process can be better evaluated as well as the structural durability. The corrosion begins when a threshold level of chloride concentration is reached at the steel bars of reinforcements. Despite the robustness of several models proposed in literature, deterministic approaches fail to predict accurately the corrosion time initiation due the inherent randomness observed in this process. In this regard, structural durability can be more realistically represented using probabilistic approaches. This paper addresses the analyses of probabilistic corrosion time initiation in reinforced concrete structures exposed to chloride penetration. The chloride penetration is modelled using the Fick's diffusion law. This law simulates the chloride diffusion process considering time-dependent effects. The probability of failure is calculated using Monte Carlo simulation and the first order reliability method, with a direct coupling approach. Some examples are considered in order to study these phenomena. Moreover, a simplified method is proposed to determine optimal values for concrete cover.

  6. Analysis and design of on-grade reinforced concrete track support structures

    NASA Technical Reports Server (NTRS)

    Mclean, F. G.; Williams, R. D.; Greening, L. R.

    1972-01-01

    For the improvement of rail service, the Department of Transportation, Federal Rail Administration, is sponsoring a test track on the Atchison, Topeka, and Santa Fe Railway. The test track will contain nine separate rail support structures, including one conventional section for control and three reinforced concrete structures on grade, one slab and two beam sections. The analysis and design of these latter structures was accomplished by means of the finite element method, NASTRAN, and is presented.

  7. Primer on Durability of Nuclear Power Plant Reinforced Concrete Structures - A Review of Pertinent Factors

    SciTech Connect

    Naus, Dan J

    2007-02-01

    The objective of this study was to provide a primer on the environmental effects that can affect the durability of nuclear power plant concrete structures. As concrete ages, changes in its properties will occur as a result of continuing microstructural changes (i.e., slow hydration, crystallization of amorphous constituents, and reactions between cement paste and aggregates), as well as environmental influences. These changes do not have to be detrimental to the point that concrete will not be able to meet its performance requirements. Concrete, however, can suffer undesirable changes with time because of improper specifications, a violation of specifications, or adverse performance of its cement paste matrix or aggregate constituents under either physical or chemical attack. Contained in this report is a discussion on concrete durability and the relationship between durability and performance, a review of the historical perspective related to concrete and longevity, a description of the basic materials that comprise reinforced concrete, and information on the environmental factors that can affect the performance of nuclear power plant concrete structures. Commentary is provided on the importance of an aging management program.

  8. Seismic fragility of reinforced concrete structures and components for application to nuclear facilities

    SciTech Connect

    Gergely, P.

    1984-09-01

    The failure and fragility analyses of reinforced concrete structures and elements in nuclear reactor facilities within the Seismic Safety Margins Research Program (SSMRP) at the Lawrence Livermore National Laboratory are evaluated. Uncertainties in material modeling, behavior of low shear walls, and seismic risk assessment for nonlinear response receive special attention. Problems with ductility-based spectral deamplification and prediction of the stiffness of reinforced concrete walls at low stress levels are examined. It is recommended to use relatively low damping values in connection with ductility-based response reductions. The study of static nonlinear force-deflection curves is advocated for better nonlinear dynamic response predictions. Several details of the seismic risk analysis of the Zion plant are also evaluated. 73 references.

  9. Reinforced concrete structures loaded by snow avalanches : numerical and experimental approaches.

    NASA Astrophysics Data System (ADS)

    Ousset, I.; Bertrand, D.; Brun, M.; Limam, A.; Naaim, M.

    2012-04-01

    Today, due to the extension of occupied areas in mountainous regions, new strategies for risk mitigation have to be developed. In the framework of risk analysis, these latter have to take into account not only the natural hazard description but also the physical vulnerability of the exposed structures. From a civil engineering point of view, the dynamic behavior of column or portico was widely investigated especially in the case of reinforced concrete and steel. However, it is not the case of reinforced concrete walls for which only the in-plan dynamic behavior (shear behavior) has been studied in detail in the field of earthquake engineering. Therefore, the aim of this project is to study the behavior of reinforced concrete civil engineering structures submitted to out-of-plan dynamic loadings coming from snow avalanche interaction. Numerical simulations in 2D or 3D by the finite element method (FEM) are presented. The approach allows solving mechanical problems in dynamic condition involving none linearities (especially none linear materials). Thus, the structure mechanical response can be explored in controlled conditions. First, a reinforced concrete wall with a L-like shape is considered. The structure is supposed to represent a French defense structure dedicated to protect people against snow avalanches. Experimental pushover tests have been performed on a physical model. The experimental tests consisted to apply a uniform distribution of pressure until the total collapse of the wall. A 2D numerical model has been developed to simulate the mechanical response of the structure under quasi-static loading. Numerical simulations have been compared to experimental datas and results gave a better understanding of the failure mode of the wall. Moreover, the influence of several parameters (geometry and the mechanical properties) is also presented. Secondly, punching shear experimental tests have also been carried out. Reinforced concrete slabs simply supported have

  10. 1. U.S. Route 250 grade separation structure. This reinforced concrete, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. U.S. Route 250 grade separation structure. This reinforced concrete, rigid frame structure was built in 1941. Its relatively flat arch provided maximum useful clearance in a short span and the physics of the design eliminated the need for extensive abutments to contain the thrust of traditional arches, making it ideally suited as a grade separation structure. BLRI designers made extensive use of theses bridges for crossing small streams and creeks, and grade separation structures, ornamenting them with a rustic stone facade. View is of the south-southeast elevation. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  11. Corrosion process and structural performance of a 17 year old reinforced concrete beam stored in chloride environment

    SciTech Connect

    Vidal, T. Castel, A. Francois, R.

    2007-11-15

    The long-term corrosion process of reinforced concrete beams is studied in this paper. The reinforced concrete elements were stored in a chloride environment for 17years under service loading in order to be representative of real structural conditions. At different stages, cracking maps were drawn, total chloride contents were measured and mechanical tests were performed. Results show that the bending cracks and their width do not influence significantly the service life of the structure. The chloride threshold at the reinforcement depth, used by standards as a single parameter to predict the end of the initiation period, is a necessary but not a sufficient parameter to define service life. The steel-concrete interface condition is also a determinant parameter. The bleeding of concrete is an important cause of interface de-bonding which leads to an early corrosion propagation of the reinforcements. The structural performance under service load (i.e.: stiffness in flexure) is mostly affected by the corrosion of the tension reinforcement (steel cross-section and the steel-concrete bond reduction). Limit-state service life design based on structural performance reduction in terms of serviceability shows that the propagation period of the corrosion process is an important part of the reinforced concrete service life.

  12. Nonlinear FE simulations of structural behavior parameters of reinforced concrete beam with epoxy-bonded FRP

    NASA Astrophysics Data System (ADS)

    Sasmal, Saptarshi; Kalidoss, S.

    2015-05-01

    In the present study, investigations on fiber-reinforced plastic (FRP) plated-reinforced concrete (RC) beam are carried out. Numerical investigations are performed by using a nonlinear finite element analysis by incorporating cracking and crushing of concrete. The numerical models developed in the present study are validated with the results obtained from the experiment under monotonic load using the servo-hydraulic actuator in displacement control mode. Further, the validated numerical models are used to evaluate the influence of different parameters. It is found from the investigations that increase in the elastic modulus of adhesive layer and CFRP laminate increases the interfacial stresses whereas increase in laminate modulus decreases the displacement and reinforcement strain of the beam. It is also observed that increase in the adhesive layer can largely reduce the interfacial stresses, whereas increase in laminate thickness increases it. However, increase in laminate thickness decreases the displacement and reinforcement strain of the beam significantly. It is mention worthy that increase in laminate length reduces the interfacial stresses, whereas CFRP width change does not affect the interfacial stresses. The study will be useful for the design and practicing engineers for arriving at the FRP-based strengthening schemes for RC structures judiciously.

  13. Development of structural health assessment system for steel and reinforced concrete structures using acceleration data

    NASA Astrophysics Data System (ADS)

    Suzuki, Yu; Mita, Akira

    2014-03-01

    Because of the repeated earthquake and the problem such as the aging of buildings, a number of studies of Structural Health Monitoring (SHM) is have been done. Now, the writer is developing structural health assessment system for steel and reinforced concrete structures aiming for completion in 2014. In this system, following three programs for automatically estimating the physical quantity that is important for assessing the integrity of the structure are planned. First program is what automatically estimate the modal parameters (natural frequency and damping ratio) of the structure by the time history by using the subspace method. Second program is what automatically estimate the inter-layer parameters (stiffness and damping coefficient) by the time history by using the adaptive Kalman filter. Third program is what automatically estimate the story drift angle by time history by using the adaptive Kalman filter. The proposed method is expected to be estimated in consideration of the higher order modes than the conventional method by reverse modal analysis.

  14. Transverse Reinforcement in Reinforced Concrete Columns

    NASA Astrophysics Data System (ADS)

    Gramblička, Štefan; Veróny, Peter

    2013-11-01

    In the article we are dealing with the influence of transverse reinforcement to the resistance of a cross-section of the reinforced concrete columns and also with the effective detailing of the column reinforcement. We are verifying the correctness of design guides for detailing of transverse reinforcement. We are also taking into account the diameter of stirrups and its influence over transverse deformation of column.

  15. Preparation and characterization of glass fibers - polymers (epoxy) bars (GFRP) reinforced concrete for structural applications

    NASA Astrophysics Data System (ADS)

    Alkjk, Saeed; Jabra, Rafee; Alkhater, Salem

    2016-06-01

    The paper presents some of the results from a large experimental program undertaken at the Department of Civil Engineering of Damascus University. The project aims to study the ability to reinforce and strengthen the concrete by bars from Epoxy polymer reinforced with glass fibers (GFRP) and compared with reinforce concrete by steel bars in terms of mechanical properties. Five diameters of GFRP bars, and steel bars (4mm, 6mm, 8mm, 10mm, 12mm) tested on tensile strength tests. The test shown that GFRP bars need tensile strength more than steel bars. The concrete beams measuring (15cm wide × 15cm deep × and 70cm long) reinforced by GFRP with 0.5 vol.% ratio, then the concrete beams reinforced by steel with 0.89 vol.% ratio. The concrete beams tested on deflection test. The test shown that beams which reinforced by GFRP has higher deflection resistance, than beams which reinforced by steel. Which give more advantage to reinforced concrete by GFRP.

  16. Slender reinforced concrete columns strengthened with fibre reinforced polymers

    NASA Astrophysics Data System (ADS)

    Gajdošová, K.; Bilčík, J.

    2011-06-01

    The requirement for a long life with relatively low maintenance costs relates to the use of building structures. Even though the structure is correctly designed, constructed and maintained, the need for extensions of its lifetime can appear. The preservation of the original structure with a higher level of resistance or reliability is enabled by strengthening. Conventional materials are replaced by progressive composites - mainly carbon fibre reinforced polymers (CFRP). They are used for strengthening reinforced concrete columns in two ways: added reinforcement in the form of CFRP strips in grooves or CFRP sheet confinement and eventually their combination. This paper presents the effect of the mentioned strengthening methods on slender reinforced concrete columns.

  17. Reinforced concrete structural corrosion monitoring using Hi-Bi photonic crystal fibres in a fiber loop structure

    NASA Astrophysics Data System (ADS)

    Bravo, M.; McCague, C.; Fabian, M.; Jaroszewicz, L.; Mergo, P.; Lopez-Amo, M.; Grattan, K. T. V.; Sun, T.

    2014-05-01

    A novel sensing approach has been developed for in-situ corrosion monitoring of steel in reinforced concrete structures, using a fibre loop interferometer sensor system based on a Hi-Bi photonic crystal fibre (PCF). To do so an accurate fibre alignment procedure has been implemented in order to improve the performance of the sensor system embedded into the concrete structure when it is subjected to an accelerated corrosion test. The positive results obtained have confirmed the effectiveness of such a sensor system for applications in structural health monitoring.

  18. Experimental investigation and numerical modeling of carbonation process in reinforced concrete structures Part II. Practical applications

    SciTech Connect

    Saetta, Anna V.; Vitaliani, Renato V

    2005-05-01

    The mathematical-numerical method developed by the authors to predict the corrosion initiation time of reinforced concrete structures due to carbonation process, recalled in Part I of this work, is here applied to some real cases. The final aim is to develop and test a practical method for determining the durability characteristics of existing buildings liable to carbonation, as well as estimating the corrosion initiation time of a building at the design stage. Two industrial sheds with different ages and located in different areas have been analyzed performing both experimental tests and numerical analyses. Finally, a case of carbonation-induced failure in a prestressed r.c. beam is presented.

  19. Update on sacrificial anode cathodic protection on steel reinforced concrete structures in seawater

    SciTech Connect

    Kessler, R.J.; Powers, R.G.; Lasa, I.R.

    1995-12-01

    Various configurations of sacrificial zinc anodes have been successfully used to provide cathodic protection in the tidal zone of steel reinforced concrete structures. Studies conducted by the Florida Department of Transportation have shown that zinc anodes configured in simple fashion can provide long term cathodic protection. These simple systems represent an attractive alternative to conventional cathodic protection where rectifiers are used. This paper discusses a cathodic protection system comprised of zinc sheet anodes used in conjunction with a submerged bulk zinc anode. An overview of long term performance is presented along with estimated service life and costs.

  20. Structural Health Monitoring of a Reinforced Concrete Building during the Severe Typhoon Vicente in 2012

    PubMed Central

    2013-01-01

    The goal of this study is to investigate the structural performance of reinforced concrete building under the influence of severe typhoon. For this purpose, full-scale monitoring of a 22-story reinforced concrete building was conducted during the entire passage process of a severe typhoon “Vicente.” Vicente was the eighth tropical storm developed in the Western North Pacific Ocean and the South China Sea in 2012. Moreover, it was the strongest and most devastating typhoon that struck Macao since 1999. The overall duration of the typhoon affected period that lasted more than 70 hours and the typhoon eye region covered Macao for around one hour. The wind and structural response measurements were acquired throughout the entire typhoon affected period. The wind characteristics were analyzed using the measured wind data including the wind speed and wind direction time histories. Besides, the structural response measurements of the monitored building were utilized for modal identification using the Bayesian spectral density approach. Detailed analysis of the field data and the typhoon generated effects on the structural performance are discussed. PMID:24282385

  1. Comparison of UPE and GPR systems for the survey of reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Derobert, Xavier; Villain, Géraldine; Joubert, Anaelle

    2014-05-01

    The objective of this study is to compare two non-destructive techniques using sonic and radar pulses for the survey of reinforced concre structures. The first studied testing method is a Ultrasonic (US) Pulse-Echo (model M2502, from Acoustic Control Systems manufacturer) composed of an array of 12 S-wave transmitters and 12 receivers in one bloc. Their central frequency is equal to 55 kHz. As the averaged USvelocities in concrete tend to 1800-3000 m/s, the corresponding wavelengths tend to 3-5 cm. The Ground-penetrating radar (GPR) system has been performed with high frequency antennas above 1 GHz (1.5 and 2.6 GHz antennas), which lead to the same range of EM wavelengths than the US ones. Measurements have been performed on some thick reinforced concrete elements of structures, and then are compared in term of resolution, depth penetration and ease to use. One of the studied elements is a concrete beam (dimensions : 16 m long, 0.5 m width and 1 m high) designed in an European Projet (FP7_ISTIMES) and damaged by controled impacts of blocks of several tons dropped from few meters [1]. Therefore, the objective of this studyis to compare the two techniques, and for the last studied element to detect the major cracks and the spallings of the cover concrete which are visible from the opposite side. References: Malhotra V.M., Carino, N.J., CRC Handbook on Nondestructive Testing of Concrete, CRC Press LLC, , 1991, 343p. Taffe A., Wiggenhauser H., Validation for Thickness Measurement in Civil Engineering with Ultrasonic Echo, International Symposium NDT-CE, Saint-Louis, USA, 2006, pp506-512. Géraldine Villain, Anaëlle Luczak, Olivier Durand, Xavier Dérobert, Deepening of the measurement technique by Ultrasonic Pulse Echo UPE, Report, IFSTTAR, January 2011, 22p. Catapano I., Di Napoli R., Soldovieri F., Bavusi M., Loperte A., Dumoulin J. (2012), « Structural monitoring via microwave tomography-enhanced GPR : the Montagnole test site », J. Geophys. Eng., Vol. 9, pp. 100-107.

  2. Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

    PubMed Central

    Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

    2011-01-01

    In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring. PMID:22346672

  3. Brillouin corrosion expansion sensors for steel reinforced concrete structures using a fiber optic coil winding method.

    PubMed

    Zhao, Xuefeng; Gong, Peng; Qiao, Guofu; Lu, Jie; Lv, Xingjun; Ou, Jinping

    2011-01-01

    In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring. PMID:22346672

  4. Pounding Effects on the Earthquake Response of Adjacent Reinforced Concrete Structures Strengthened by Cable Elements

    NASA Astrophysics Data System (ADS)

    Liolios, Angelos; Liolios, Asterios; Hatzigeorgiou, George; Radev, Stefan

    2014-06-01

    A numerical approach for estimating the effects of pounding (seismic interaction) on the response of adjacent Civil Engineering structures is presented. Emphasis is given to reinforced concrete (RC) frames of existing buildings which are seismically strengthened by cable-elements. A double discretization, in space by the Finite Element Method and in time by a direct incremental approach is used. The unilateral behaviours of both, the cable-elements and the interfaces contact-constraints, are taken strictly into account and result to inequality constitutive conditions. So, in each time-step, a non-convex linear complementarity problem is solved. It is found that pounding and cable strengthening have significant effects on the earthquake response and, hence, on the seismic upgrading of existing adjacent RC structures.

  5. Towards Practical Carbonation Prediction and Modelling for Service Life Design of Reinforced Concrete Structures

    NASA Astrophysics Data System (ADS)

    Ekolu, O. S.

    2015-11-01

    Amongst the scientific community, the interest in durability of concrete structures has been high for quite a long time of over 40 years. Of the various causes of degradation of concrete structures, corrosion is the most widespread durability problem and carbonation is one of the two causes of steel reinforcement corrosion. While much scientific understanding has been gained from the numerous carbonation studies undertaken over the past years, it is still presently not possible to accurately predict carbonation and apply it in design of structures. This underscores the complex nature of the mechanisms as influenced by several interactive factors. Based on critical literature and some experience of the author, it is found that there still exist major challenges in establishing a mathematical constitutive relation for realistic carbonation prediction. While most current models employ permeability /diffusion as the main model property, analysis shows that the most practical material property would be compressive strength, which has a low coefficient of variation of 20% compared to 30 to 50% for permeability. This important characteristic of compressive strength, combined with its merit of simplicity and data availability at all stages of a structure's life, promote its potential use in modelling over permeability. By using compressive strength in carbonation prediction, the need for accelerated testing and permeability measurement can be avoided. This paper attempts to examine the issues associated with carbonation prediction, which could underlie the current lack of a sound established prediction method. Suggestions are then made for possible employment of different or alternative approaches.

  6. Concrete Materials and Structures

    SciTech Connect

    Wilby, C.B.

    1991-12-31

    Concrete Materials and Structures provides one of the most comprehensive treatments on the topic of concrete engineering. The author covers a gamut of concrete subjects ranging from concrete mix design, basic reinforced concrete theory, prestressed concrete, shell roofs, and two-way slabs-including a through presentation of Hillerborg`s strip method. Prior to Wilby`s book, the scope of these topics would require at least four separate books to cover. With this new book he has succeeded, quite remarkably, in condensing a fairly complete knowledge of concrete engineering into one single easy-to-carry volume.

  7. Structural damage detection based on the reconstructed phase space for reinforced concrete slab: Experimental study

    NASA Astrophysics Data System (ADS)

    Nie, Zhenhua; Hao, Hong; Ma, Hongwei

    2013-02-01

    In this paper, a parameter based on geometry changes of the reconstructed multidimensional phase space of the measured vibration signals for structural damage identification is proposed. The choice of the proper delay time steps and embedding dimensions for phase space reconstruction of linear systems is discussed. Using the determined delay time and embedding dimensions, an index Changes of Phase Space Topology (CPST) with multiple embedding dimensions is calculated and then used to identify the structural damage. To demonstrate the reliability of the proposed method, vibration test data corresponding to different damage states of a continuous reinforced concrete slab is used to calculate the CPST value for damage identification. The results indicate that except the measurement points at structural supports, the CPST values at all the measurement points on the structure increase with structural damage level irrespective of the damage location, indicating that using a single or a minimum number of measurement points and their CPST value can effectively identify damage existence in the structure. The traditional modal-based indices are also calculated using the same vibration data for comparison. It is found that the proposed method with CPST is the most sensitive to structural damage than any modal-based index. The results demonstrate that the proposed method with CPST value is very effective in identifying damage existence in the structure. Although it cannot quantify the damage, it can be a good candidate for continuous structural health monitoring because it needs only a few sensors to detect damage existence in the entire structure.

  8. A vision-based technique for damage assessment of reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Farhidzadeh, Alireza; Ebrahimkhanlou, Arvin; Salamone, Salvatore

    2014-03-01

    The most common damage assessment technique for concrete structures is visual inspection (VI). Condition assessed by VI is subjective in nature, meaning it depends on the experience, knowledge, expertise, measurement accuracy, mental attention, and judgment of the inspector carrying out the assessment. In many post-event assessments, cracks data including width and pattern provide the most indicative information about the health or damage state of the structure. Residual cracks are sometimes the only available data for VI. However, due to adjacent elastic members, earthquake displacement spectrum, or re-centering systems, these measurements may lead to erroneous decisions. To overcome this problem, this paper proposes a novel damage index based upon Fractal Dimension (FD) analysis of residual cracks as a complementary method for VI. FD can quantify crack patterns and enhance the routine inspection procedure by establishing a crack pattern recognition system. This algorithm was validated through an experimental study on a large scale reinforced concrete shear wall (RCSW). The results demonstrate the novel technique as a quite accurate estimator for damage grades and stiffness loss of the wall.

  9. Radio frequency tomography for the investigation of cracks in reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Negishi, Tadahiro; Gennarelli, Gianluca; Soldovieri, Francesco; Erricolo, Danilo

    2016-04-01

    We are interested in investigating the presence of cracks inside reinforced concrete structures using Radio Frequency Tomography (RFT). RFT applies electromagnetic waves to probe the environment and is based on the use of multiple transmitting and receiving antennas. RFT is a multistatic system where the volume under investigation is illuminated and observed from different directions, which results into an increase in resolution. In an application of RFT there are two main phases: the forward problem and the inverse reconstruction. The forward problem consists in the determination of the electromagnetic field scattered by the volume under investigation, which is illuminated by the transmitters. The scattered field depends on the spatial distribution of the dielectric permittivity in the volume under investigation. This distribution determines the contrast function. The inverse problem consists of the reconstruction of the contrast function from the scattered electromagnetic field. One of the challenges in RFT is the determination of the best approach to solve the inverse problem. In order to focus solely on the behavior of the inverse approach, we consider simplified geometries for the volume under investigation, such as a cylindrical concrete pillar with a metallic steel bar that is coaxial to the cylinder. In this way, it is possible to analytically evaluate the scattered electromagnetic field in an exact way. We then investigate the behavior of the reconstruction approach from the point of view of (1) geometry of the illumination and observation antennas; (2) frequency used to illuminate the volume under interest; (3) fusion of the results obtained at various frequencies.

  10. A galvanic zinc-hydrogel system for cathodic protection of reinforced concrete structures

    SciTech Connect

    Wehling, J.E.

    1999-07-01

    Installations of galvanic cathodic protection anodes have been completed on bridge structures in Illinois, Virginia, Florida, Wisconsin, and Oregon, on parking garages in Illinois and Wisconsin, on high voltage transmission tower footings in California, and on condominium balconies in Florida. Some of these installations involve prestressed concrete. The installation of these systems will be described in detail and monitoring data will be presented for at least six months of active service. The system consists of a 10 mil zinc foil bonded to an ionically conductive hydrogel adhesive, which is applied directly to the surface of the steel-reinforced concrete. A copper wire connects the zinc anode to multiple steel rebars and/or strands. The performance is monitored by measuring the current flow in the wire, by measuring the amount of zinc consumed or, more generally, by taking depolarization readings at regular intervals. All of these measurements are an indication of the performance of the galvanic system and the corrosion of the steel rebars that is being prevented.

  11. Enamel coated steel reinforcement for improved durability and life-cycle performance of concrete structures: microstructure, corrosion, and deterioration

    NASA Astrophysics Data System (ADS)

    Tang, Fujian

    This study is aimed (a) to statistically characterize the corrosion-induced deterioration process of reinforced concrete structures (concrete cracking, steel mass loss, and rebar-concrete bond degradation), and (b) to develop and apply three types of enamel-coated steel bars for improved corrosion resistance of the structures. Commercially available pure enamel, mixed enamel with 50% calcium silicate, and double enamel with an inner layer of pure enamel and an outer layer of mixed enamel were considered as various steel coatings. Electrochemical tests were respectively conducted on steel plates, smooth bars embedded in concrete, and deformed bars with/without concrete cover in 3.5 wt.% NaCl or saturated Ca(OH)2 solution. The effects of enamel microstructure, coating thickness variation, potential damage, mortar protection, and corrosion environment on corrosion resistance of the steel members were investigated. Extensive test results indicated that corrosion-induced concrete cracking can be divided into four stages that gradually become less correlated with corrosion process over time. The coefficient of variation of crack width increases with the increasing level of corrosion. Corrosion changed the cross section area instead of mechanical properties of steel bars. The bond-slip behavior between the corroded bars and concrete depends on the corrosion level and distribution of corrosion pits. Although it can improve the chemical bond with concrete and steel, the mixed enamel coating is the least corrosion resistant. The double enamel coating provides the most consistent corrosion performance and is thus recommended to coat reinforcing steel bars for concrete structures applied in corrosive environments. Corrosion pits in enamel-coated bars are limited around damage locations.

  12. Capillary transport of water through textile-reinforced concrete applied in repairing and/or strengthening cracked RC structures

    SciTech Connect

    Lieboldt, M.; Mechtcherine, V.

    2013-10-15

    The use of textile-reinforced concrete (TRC) has great potential for innovative solutions in repairing, protecting, and strengthening concrete and RC structures. The article at hand reports on an investigation on composite concrete specimens made of cracked ordinary concrete as substrate and textile-reinforced concrete (TRC) as a cover layer for its strengthening and repair. The TRC cover layer was assessed with regard to its effectiveness as a protective layer against the ingress of water through capillary action. Since in real applications such TRC layers may be cracked or presumed to be so, thereby activating the load-carrying function of the textile reinforcement, the TRC layer was cracked for purposes of this study. The water transport in the cracked ordinary concrete specimens without the TRC layer was used as a reference. Gravimetric measurements and neutron radiography served as the testing techniques. In ordinary concrete quick and deep ingress of water through relatively wide macro-cracks of approximately 100 μm width, followed by transport through the capillary pore system, caused saturation of large areas in a rather short time. TRC applied to the RC surface reduced the ingress of water to a large extent. Its small crack widths of 15 to 20 μm changed suction behaviour fundamentally. In the cracked substrate of ordinary concrete, capillary suction was prevented, and transport through the pore system of the matrix became the prevailing transport mechanism of capillary action. Not only was the mechanism altered, but the transport of water deep into inner regions was markedly retarded as well.

  13. Influence of Steel Reinforcement on In-Situ Stress Evaluation in Concrete Structures by the Core-Drilling Method

    SciTech Connect

    McGinnis, M. J.; Pessiki, S.

    2006-03-06

    The core-drilling method is an emerging technique for evaluating in-situ stress in a concrete structure. A small hole is drilled into the structure, and the deformations in the vicinity of the hole are measured and related via elasticity theory to the stress. The method is similar to the ASTM hole-drilling strain-gauge method excepting that displacements rather than strains are the measured quantities. The technique may be considered nondestructive since the ability of the structure to perform its function is unaffected, and the hole is easily repaired. Displacement measurements in the current work are performed using 3D digital image correlation and industrial photogrammetry. The current paper addresses perturbations in the method caused by steel reinforcement within the concrete. The reinforcement is significantly stiffer than the surrounding concrete, altering the expected displacement field. A numerical investigation performed indicates an under-prediction of stress by as much as 18 percent in a heavily reinforced structure, although the effect is significantly smaller for more common amounts of reinforcement.

  14. The performance analysis of distributed Brillouin corrosion sensors for steel reinforced concrete structures.

    PubMed

    Wei, Heming; Zhao, Xuefeng; Kong, Xianglong; Zhang, Pinglei; Cui, Yanjun; Sun, Changsen

    2013-01-01

    The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 με, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage. PMID:24379048

  15. The Performance Analysis of Distributed Brillouin Corrosion Sensors for Steel Reinforced Concrete Structures

    PubMed Central

    Wei, Heming; Zhao, Xuefeng; Kong, Xianglong; Zhang, Pinglei; Cui, Yanjun; Sun, Changsen

    2014-01-01

    The Brillouin optical time-domain analysis (BOTDA)-based optical fiber method has been proposed to measure strain variations caused by corrosion expansion. Spatial resolutions of 1 m can be achieved with this kind of Brillouin sensor for detecting the distributed strain. However, when the sensing fiber is wound around the steel rebar in a number of circles in a range of several meters, this spatial resolution still has limitations for corrosion monitoring. Here, we employed a low-coherent fiber-optic strain sensor (LCFS) to survey the performance of Brillouin sensors based on the fact that the deformation measured by the LCFS equals the integral of the strains obtained from Brillouin sensors. An electrochemical accelerated corrosion experiment was carried out and the corrosion expansion was monitored by both BOTDA and the LCFS. Results demonstrated that the BOTDA can only measure the expansion strain of about 1,000 με, which was generated by the 18 mm steel rebar corrosion, but, the LCFS had high sensitivity from the beginning of corrosion to the destruction of the structure, and no obvious difference in expansion speed was observed during the acceleration stage of the corrosion developed in the reinforced concrete (RC) specimens. These results proved that the BOTDA method could only be employed to monitor the corrosion inside the structure in the early stage. PMID:24379048

  16. Application of fiber-reinforced plastic rods as prestressing tendons in concrete structures. Final report

    SciTech Connect

    Mattock, A.H.; Babaei, K.

    1989-08-01

    The study is concerned with the possibility of utilizing fiber-reinforced plastic rods as prestressing tendons, in place of traditional steel tendons, in elements of prestressed-concrete bridges exposed to corrosive environments. A survey was made of available information on the behavior characteristics of fiber-reinforced plastic tension elements and, in particular, those of glass-fiber-reinforced (GFR) tension elements. Also, an analytical study was made of the flexural behavior of concrete elements prestressed by GFR tendons. Based on the analytical study and on the survey of available information, an assessment is made of the impact on the design of prestressed-concrete members if GFR tendons are used. Some preliminary design recommendations are made, together with proposals for research needed before GFR prestressing tendons should be used in practice. Four GFR tendons with Con-Tech Systems anchorages were tested, the primary variable being the embedded length of the GFR rods in the anchorages. All the tendons failed by the rods pulling out of the anchorages. For embedded lengths of 15.2 in or greater, the failure loads were 90% of the advertised tendon strength of 220 ksi, or about 100% of the guaranteed tensile strength of 197 ksi (60 kN/rod).

  17. A zinc/hydrogel system for cathodic protection of reinforced concrete structures

    SciTech Connect

    Bennett, J.; Firlotte, C.

    1996-11-01

    A zinc/hydrogel system has been developed for the cathodic protection of steel in reinforced concrete. This system consists of a thin foil of zinc which is attached to the concrete surface by an ionically conductive hydrogel adhesive. A direct electrical connection between the zinc and the reinforcing steel allows the zinc to function galvanically, polarizing the steel and protecting it from corrosion. Zinc, aluminum, and several aluminum alloys were tested as anodes in contact with hydrogel adhesives, and zinc was found to offer the best combination of working potential, resistance to passivation, cost and availability. Several hydrogels used for medical applications were found to be inadequate for this use, but a hydrogel adhesive was developed specifically to bond sacrificial anodes to concrete. This hydrogel achieved a total charge in accelerated testing equal to 12 years of life at current densities normally used for cathodic protection. Zinc/hydrogel was installed on about 1000 ft{sup 2} (100 m{sup 2}) of a fishing pier in Ft. Pierce, Florida on members including prestressed pilings, conventionally reinforced pile caps, and prestressed beams. Installation of this system was relatively easy, and initial performance is encouraging. After 5 months of service, adhesion is good and current densities remain high.

  18. Experimental evaluation of natural period of masonry and reinforced concrete structures during operative conditions

    NASA Astrophysics Data System (ADS)

    Carlo Ponzo, Felice; Ditommaso, Rocco; Auletta, Gianluca; Nigro, Antonella; Iacovino, Chiara; Salvatore Nigro, Domenico

    2016-04-01

    This work focuses on the experimental evaluation of the fundamental period of buildings of various types (masonry and reinforced concrete) using measurements of ambient vibrations on real buildings located in Basilicata (Italy) and numerical analyses. The results are compared with the simplified formula provided by the Seismic Italian Code (NTC2008), that is function of structural typology and height for both near collapse and limited damage limit states and experimental results provided by the recent scientific literature. With the intention of proposing simplified relationships to evaluate the fundamental period of buildings, several numerical and experimental campaigns, on different structures all around the world, have been carried out in the last years in order to calibrate different kind of formulas. Most of formulas retrieved from both numerical and experimental analyses provides vibration periods smaller than those suggested by the NTC2008. However, it is well known that the fundamental period of a structure play a key role in the correct evaluation of the spectral acceleration for seismic static analyses. Generally, simplified approaches impose the use of safety factors greater than those related to in depth nonlinear analyses with the aim to cover possible unexpected uncertainties. Using the simplified formula proposed by the Italian seismic code the fundamental period is quite higher than fundamental periods experimentally evaluated on real structures, with the consequence that the spectral acceleration adopted in the seismic static analysis may be significantly different than real spectral acceleration. This approach could produces a decreasing in safety factors obtained using linear seismic static analyses. Based on numerical and experimental evidences, the authors suggest a possible update of the seismic codes formula for the simplified estimation of the fundamental period of vibration of existing masonry and RC buildings. Acknowledgements This study

  19. Corrosion Assessment of Steel Bars Used in Reinforced Concrete Structures by Means of Eddy Current Testing.

    PubMed

    de Alcantara, Naasson P; da Silva, Felipe M; Guimarães, Mateus T; Pereira, Matheus D

    2015-01-01

    This paper presents a theoretical and experimental study on the use of Eddy Current Testing (ECT) to evaluate corrosion processes in steel bars used in reinforced concrete structures. The paper presents the mathematical basis of the ECT sensor built by the authors; followed by a finite element analysis. The results obtained in the simulations are compared with those obtained in experimental tests performed by the authors. Effective resistances and inductances; voltage drops and phase angles of wound coil are calculated using both; simulated and experimental data; and demonstrate a strong correlation. The production of samples of corroded steel bars; by using an impressed current technique is also presented. The authors performed experimental tests in the laboratory using handmade sensors; and the corroded samples. In the tests four gauges; with five levels of loss-of-mass references for each one were used. The results are analyzed in the light of the loss-of-mass and show a strong linear behavior for the analyzed parameters. The conclusions emphasize the feasibility of the proposed technique and highlight opportunities for future works. PMID:26712754

  20. Corrosion Assessment of Steel Bars Used in Reinforced Concrete Structures by Means of Eddy Current Testing

    PubMed Central

    de Alcantara, Naasson P.; da Silva, Felipe M.; Guimarães, Mateus T.; Pereira, Matheus D.

    2015-01-01

    This paper presents a theoretical and experimental study on the use of Eddy Current Testing (ECT) to evaluate corrosion processes in steel bars used in reinforced concrete structures. The paper presents the mathematical basis of the ECT sensor built by the authors; followed by a finite element analysis. The results obtained in the simulations are compared with those obtained in experimental tests performed by the authors. Effective resistances and inductances; voltage drops and phase angles of wound coil are calculated using both; simulated and experimental data; and demonstrate a strong correlation. The production of samples of corroded steel bars; by using an impressed current technique is also presented. The authors performed experimental tests in the laboratory using handmade sensors; and the corroded samples. In the tests four gauges; with five levels of loss-of-mass references for each one were used. The results are analyzed in the light of the loss-of-mass and show a strong linear behavior for the analyzed parameters. The conclusions emphasize the feasibility of the proposed technique and highlight opportunities for future works. PMID:26712754

  1. Impact of structural aging on seismic risk assessment of reinforced concrete structures in nuclear power plants

    SciTech Connect

    Ellingwood, B.; Song, J.

    1996-03-01

    The Structural Aging Program is addressing the potential for degradation of concrete structural components and systems in nuclear power plants over time due to aging and aggressive environmental stressors. Structures are passive under normal operating conditions but play a key role in mitigating design-basis events, particularly those arising from external challenges such as earthquakes, extreme winds, fires and floods. Structures are plant-specific and unique, often are difficult to inspect, and are virtually impossible to replace. The importance of structural failures in accident mitigation is amplified because such failures may lead to common-cause failures of other components. Structural condition assessment and service life prediction must focus on a few critical components and systems within the plant. Components and systems that are dominant contributors to risk and that require particular attention can be identified through the mathematical formalism of a probabilistic risk assessment, or PRA. To illustrate, the role of structural degradation due to aging on plant risk is examined through the framework of a Level 1 seismic PRA of a nuclear power plant. Plausible mechanisms of structural degradation are found to increase the core damage probability by approximately a factor of two.

  2. Self-centering seismic retrofit scheme for reinforced concrete frame structures: SDOF system study

    NASA Astrophysics Data System (ADS)

    Zhang, Yunfeng; Hu, Xiaobin

    2010-06-01

    This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose, an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters — the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio, peak acceleration ratio, energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.

  3. Evaluation of corrosion effect in reinforced concrete by chloride exposure

    NASA Astrophysics Data System (ADS)

    Loreto, G.; Di Benedetti, M.; Iovino, R.; Nanni, A.; Gonzalez, M. A.

    2011-04-01

    Durability is generally described as the ability of a material to maintain its physical and mechanical properties over time. In reinforced concrete (RC) structures, concrete is the ideal material to protect the steel reinforcement given its high alkalinity. In environments subjected to highly aggressive conditions, mostly due to the presence of chlorides, concrete may lose its protective characteristics and allow for accelerated ageing. Concrete degradation and steel reinforcement corrosion are phenomena closely connected. The aim of this research work is the characterization of the relationship between steel reinforcement corrosion and concrete degradation under accelerated ageing in a 3% sodium chloride solution. The method of linear polarization is used for identification of the corrosion rate of the steel bar. Additionally, the values of concrete residual strength are obtained, and correlated to both the corrosion rate and width of concrete cracks. Finally, the prediction of the concrete cover useful life is estimated.

  4. Simulating distributed reinforcement effects in concrete analysis

    SciTech Connect

    Marchertas, A.H.

    1985-01-01

    The effect of the bond slip is brought into the TEMP-STRESS finite element code by relaxing the equal strain condition between concrete and reinforcement. This is done for the elements adjacent to the element which is cracked. A parabolic differential strain variation is assumed along the reinforcement from the crack, which is taken to be at the centroid of the cracked element, to the point where perfect bonding exists. This strain relationship is used to increase the strain of the reinforcement in the as yet uncracked elements located adjacent to a crack. By the same token the corresponding concrete strain is decreased. This estimate is made assuming preservation of strain energy in the element. The effectiveness of the model is shown by examples. Comparison of analytical results is made with structural test data. The influence of the bonding model on cracking is portrayed pictorially. 5 refs., 6 figs.

  5. Infilled masonry walls contribution in mitigating progressive collapse of multistory reinforced concrete structures according to UFC guidelines

    NASA Astrophysics Data System (ADS)

    Helmy, Huda; Hadhoud, Hamed; Mourad, Sherif

    2015-09-01

    A structure is subjected to progressive collapse when an element fails, resulting in failure of adjoining structural elements which, in their turn, cause further structural failure leading eventually to partial or total collapse. The failure of a primary vertical support might occur due to extreme loadings such as bomb explosion in a terrorist attack, gas explosion and huge impact of a car in the parking area. Different guidelines such as the General Services Administration (GSA 2003) and the Unified Facilities Criteria (UFC 2009) addressed the structural progressive collapse due to the sudden loss of a main vertical support. In the current study, a progressive collapse assessment according to the UFC guidelines is carried out for a typical ten-story reinforced concrete framed structure designed according to codes [(ACI 318-08) and (ASCE 7-10)] for minimum design loads for buildings and other structures. Fully nonlinear dynamic analysis for the structure was carried out using Applied Element Method (AEM). The investigated cases included the removal of a corner column, an edge column, an edge shear wall, internal columns and internal shear wall. The numerical analysis showed that simplification of the problem into 3D bare frames would lead to uneconomical design. It was found for the studied case that, the infilled masonry walls have a valuable contribution in mitigating progressive collapse of the reinforced concrete framed structures. Neglecting these walls would lead to uneconomical design.

  6. Design and installation of a cathodic protection system for a large reinforced concrete intake structure in the Arabian Gulf

    SciTech Connect

    Ali, M.; Al-Ghannam, H.

    1997-09-01

    The paper describes the condition survey methodology, design and installation of a cathodic protection (C.P.) system for a large reinforced concrete reservoir and sea water intake structure. The structure is critical for the supply of cooling water for a 2.4 million metric ton steel plant. The C.P. System consisting of mixed metal oxide coating on titanium mesh type anodes and automatic voltage/current controlled rectifiers was successfully installed and has been operating within design guidelines for the past 15 months.

  7. Research on corrosion detection for steel reinforced concrete structures using the fiber optical white light interferometer sensing technique

    NASA Astrophysics Data System (ADS)

    Zhao, Xuefeng; Cui, Yanjun; Wei, Heming; Kong, Xianglong; Zhang, Pinglei; Sun, Changsen

    2013-06-01

    In this paper, a novel kind of steel rebar corrosion monitoring technique for steel reinforced concrete structures is proposed, designed, and tested. The technique is based on the fiber optical white light interferometer (WLI) sensing technique. Firstly, a feasibility test was carried out using an equal-strength beam for comparison of strain sensing ability between the WLI and a fiber Bragg grating (FBG). The comparison results showed that the sensitivity of the WLI is sufficient for corrosion expansion strain monitoring. Then, two WLI corrosion sensors (WLI-CSs) were designed, fabricated, and embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion. Their performance was studied in an accelerated electrochemical corrosion test. Experimental results show that expansion strain along the fiber optical coil winding area can be detected and measured accurately by the proposed sensor. The advantages of the proposed monitoring technique allow for quantitative corrosion expansion monitoring to be executed in real time for reinforced concrete structures and with low cost.

  8. Neutron imaging of water penetration into cracked steel reinforced concrete

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Wittmann, F. H.; Zhao, T.; Lehmann, E. H.

    2010-04-01

    Service life and durability of reinforced concrete structures have become a crucial issue because of the economical and ecological implications. Service life of reinforced concrete structures is often limited by penetration of water and chemical compounds dissolved in water into the porous cement-based material. By now it is well-known that cracks in reinforced concrete are preferential paths for ingress of aggressive substances. Neutron radiography was successfully applied to study the process of water penetration into cracked steel reinforced concrete. In addition, the effectiveness of integral water repellent concrete to prevent ingress of water and salt solutions was investigated. Results are described in detail in this contribution. It will be shown that neutron radiography is a powerful method to visualize the process of water penetration into cracked and uncracked cement-based materials. On the basis of the obtained experimental data, it is possible to quantify the time-dependent water distributions in concrete with high accuracy and spatial resolution. It is of particular interest that penetration of water and salt solutions into damaged interfaces between concrete and steel can be visualized by means of neutron radiography. Deteriorating processes in cracked reinforced concrete structures can be studied in a completely new way. This advanced technology will help and find adequate ways to improve durability and service life of reinforced concrete structures. This will mean at the same time an essential contribution to improved sustainability.

  9. Prestressed concrete using KEVLAR reinforced tendons

    SciTech Connect

    Dolan, C.W.

    1989-01-01

    KEVLAR is a high strength, high modulus synthetic fiber manufactured by the E.I. DuPont de Nemours Company. The fiber is resistant to chloride and alkali attack. The resistance is enhanced when the fibers are assembled into a resin matrix and fabricated as rods. These properties suggest that KEVLAR reinforced rods may be a substitute for high strength steel prestress tendons in certain applications such as bridge decks and parking structures. This dissertation presents the background, theoretical development, and experimental investigations of KEVLAR reinforced rod strength, anchorage, fabrication and performance in prestressed concrete structures. The study concludes that KEVLAR has significant potential for these prestressed concrete applications. However, the reliability of the long term anchorage of the KEVLAR reinforced rods must be improved before production applications are undertaken. KEVLAR has a low shear strength compared to its tensile capacity. The anchorage of KEVLAR reinforced rods is sensitive to the shear forces generated in the anchorage assembly. Finite element analyses, using interface elements to simulate the addition of a mold release agent in a conic anchor, predict the behavior of resin socketed anchors. Test results confirm that mold release agents reduce the anchor shear stresses and suggest that moderate strength resins may be used in the anchor. KEVLAR is nearly linearly elastic to failure, yet ductility of a structure is an important design concern. Prestressed concrete beam tests using both bonded and unbonded tendons demonstrated that ductile structural behavior is obtained. Methods of predicting the strength and deflection behavior of the prestressed beams are presented and the theoretical predictions are compared to the experimental results. The overall correlation between predicted and theoretical results is satisfactory.

  10. Carbonation and its effects in reinforced concrete

    SciTech Connect

    Broomfield, J.P.

    2000-01-01

    Carbonation is the result of interaction of carbon dioxide (CO{sub 2}) gas in the atmosphere with the alkaline hydroxides in the concrete. CO{sub 2} diffuses through the concrete and rate of movement of the carbonation front roughly follows Fick's law of diffusion. Carbonation depth can be measured by exposing fresh concrete and spraying it with phenolphthalein indicator solution. An example of the test on a reinforced concrete mullion is given.

  11. The Effect of Shear Wall Distribution on the Dynamics of Reinforced Concrete Structures

    SciTech Connect

    Helou, S. H.; Touqan, A. R.

    2008-07-08

    The inclusion of a soft storey in multistory concrete buildings is a feature gaining popularity in urban areas where land is of exorbitant cost. In earthquake prone zones, this feature has been observed in post earthquake investigations. Although engineers are prepared to accept the notion that a soft storey poses a weak link in Seismic Design, yet the idea demands better understanding. The following study illustrates the importance of the judicious distribution of shear walls. The selected building is analyzed through nine numerical models which address the behavior of framed structures. The parameters discussed include, inter alias, the fundamental period of vibration, lateral displacements, axial and shear forces. It is noticed that an abrupt change in stiffness between the soft storey and the level above is responsible for increasing the strength demand on first storey columns. Extending the elevator shafts throughout the soft storey is strongly recommended.

  12. Optimal seismic design of reinforced concrete structures under time-history earthquake loads using an intelligent hybrid algorithm

    NASA Astrophysics Data System (ADS)

    Gharehbaghi, Sadjad; Khatibinia, Mohsen

    2015-03-01

    A reliable seismic-resistant design of structures is achieved in accordance with the seismic design codes by designing structures under seven or more pairs of earthquake records. Based on the recommendations of seismic design codes, the average time-history responses (ATHR) of structure is required. This paper focuses on the optimal seismic design of reinforced concrete (RC) structures against ten earthquake records using a hybrid of particle swarm optimization algorithm and an intelligent regression model (IRM). In order to reduce the computational time of optimization procedure due to the computational efforts of time-history analyses, IRM is proposed to accurately predict ATHR of structures. The proposed IRM consists of the combination of the subtractive algorithm (SA), K-means clustering approach and wavelet weighted least squares support vector machine (WWLS-SVM). To predict ATHR of structures, first, the input-output samples of structures are classified by SA and K-means clustering approach. Then, WWLS-SVM is trained with few samples and high accuracy for each cluster. 9- and 18-storey RC frames are designed optimally to illustrate the effectiveness and practicality of the proposed IRM. The numerical results demonstrate the efficiency and computational advantages of IRM for optimal design of structures subjected to time-history earthquake loads.

  13. Analytical modeling of concrete box beams reinforced by GFRP rebars

    SciTech Connect

    Zhao, Y.; Pang, S.S.

    1998-12-31

    An FRP rebar reinforced concrete box beam has been studied in this paper. Static analysis has been performed on the beams subjected to tension, bending, and torsion, based on a conceptual box beam structure. Linear vibration analysis has been conducted to predict the natural frequencies of the structures. Three dimensional finite element analysis has also been carried out to predict the stress, strain, deflection, and natural frequencies of the box beam structures. The results show that an FRP rebar deforms more compatibly with surrounding concrete than a steel rebar does. The results suggest that the concrete beams with FRP reinforcement are much more likely to be subject to compression failure (breakage of concrete on compression side) when compared to the box beams reinforced with steel rebars under the same loading conditions.

  14. Behaviour of concrete beams reinforced withFRP prestressed concrete prisms

    NASA Astrophysics Data System (ADS)

    Svecova, Dagmar

    The use of fibre reinforced plastics (FRP) to reinforce concrete is gaining acceptance. However, due to the relatively low modulus of FRP, in comparison to steel, such structures may, if sufficient amount of reinforcement is not used, suffer from large deformations and wide cracks. FRP is generally more suited for prestressing. Since it is not feasible to prestress all concrete structures to eliminate the large deflections of FRP reinforced concrete flexural members, researchers are focusing on other strategies. A simple method for avoiding excessive deflections is to provide sufficiently high amount of FRP reinforcement to limit its stress (strain) to acceptable levels under service loads. This approach will not be able to take advantage of the high strength of FRP and will be generally uneconomical. The current investigation focuses on the feasibility of an alternative strategy. This thesis deals with the flexural and shear behaviour of concrete beams reinforced with FRP prestressed concrete prisms. FRP prestressed concrete prisms (PCP) are new reinforcing bars, made by pretensioning FRP and embedding it in high strength grout/concrete. The purpose of the research is to investigate the feasibility of using such pretensioned rebars, and their effect on the flexural and shear behaviour of reinforced concrete beams over the entire loading range. Due to the prestress in the prisms, deflection of concrete beams reinforced with this product is substantially reduced, and is comparable to similarly steel reinforced beams. The thesis comprises both theoretical and experimental investigations. In the experimental part, nine beams reinforced with FRP prestressed concrete prisms, and two companion beams, one steel and one FRP reinforced were tested. All the beams were designed to carry the same ultimate moment. Excellent flexural and shear behaviour of beams reinforced with higher prestressed prisms is reported. When comparing deflections of three beams designed to have the

  15. Non-linear finite element-based material constitutive law for zero slump steel fiber reinforced concrete pipe structures

    NASA Astrophysics Data System (ADS)

    Mikhaylova, Alena

    This study presents a comprehensive investigation of performance and behavior of steel-fiber reinforced concrete pipes (SFRCP). The main goal of this study is to develop the material constitutive model for steel fiber reinforced concrete used in dry-cast application. To accomplish this goal a range of pipe sizes varying from 15 in. (400 mm) to 48 in. (1200 mm) in diameter and fiber content of 0.17%, 0.25%, 0.33%, 0.5%, 0.67% and 83% by volume were produced. The pipes were tested in three-edge bearing condition to obtain the load-deformation response and overall performance of the pipe. The pipes were also subjected to hydrostatic joint and joint shear tests to evaluate the performance of the fiber-pipe joints for water tightness and under differential displacements, respectively. In addition, testing on hardened concrete was performed to obtain the basic mechanical material properties. High variation in the test results for material testing was identified as a part of experimental investigation. A three-dimensional non-linear finite element model of the pipe under the three edge bearing condition was developed to identify the constitutive material relations of fiber-concrete composite. A constitutive model of concrete implementing the concrete plasticity and continuum fracture mechanics was considered for defining the complex non-linear behavior of fiber-concrete. Three main concrete damage algorithms were examined: concrete brittle cracking, concrete damaged plasticity with adaptive meshing technique and concrete damaged plasticity with visco-plastic regularization. The latter was identified as the most robust and efficient to model the post-cracking behavior of fiber reinforced concrete and was used in the subsequent studies. The tension stiffening material constitutive law for composite concrete was determined by converging the FEM solution of load-deformation response with the results of experimental testing. This was achieved by iteratively modifying the non

  16. Node-Wise Topological Shape Optimum Design for Structural Reinforced Modeling of Michell-Type Concrete Deep Beams

    NASA Astrophysics Data System (ADS)

    Lee, Dongkyu; Park, Sungsoo; Shin, Soomi

    This study presents an associated structural design to continuous material topology optimization and a particular case of shape optimization using node-wise densities as design parameters. The generation of optimal shapes and topologies represented in this study is based on a three-dimensional density function bilinearly interpolated by element shape functions and nodal densities. The material interface between void and solid regions is described by a specific 0.5 cut-off level of continuous and smooth iso-lines of the nodal density function on a fixed mesh. This approach allows us to perform a simultaneous node-wise topology and shape optimization, which can be easily implemented by existing gradient-based optimization codes. Contrary to those of conventional material topology optimization methods, these optimal solutions are similar to ideal optimal solutions from analytical optimization techniques. Numerical examples for structural reinforced modeling of Michell-type concrete deep beams are used to demonstrate the efficiency and superiority of the resolutions of the present method.

  17. The effects of sulfate ion on concrete and reinforced concrete

    SciTech Connect

    Yilmaz, A.B.; Yazici, B.; Erbil, M.

    1997-08-01

    The effects of the sulfate ions and the pH on the strength of concrete and reinforcement steel have been investigated. Concrete and reinforced concrete samples prepared by using mixing water having different sulfate ion concentrations (standard, 400 ppm and 3,500 ppm) were cured in a water bath containing the same ion concentrations of mixing water or distilled water at two different pH values (8 and 5). The samples were exposed to the environments for 90 days. The compressive strength of concrete, pH values of bath, galvanic current changes and potentials (vs. Ag/AgCl) of reinforcing steel were measured. It was observed that the compressive strength of the concrete decreases as the SO{sub 4}{sup {minus}2} ion concentration increases. The galvanic currents were high for the first 28 days and then these currents decreased steadily. It was found that the potentials have been rising up to the passive potential of the reinforcing steel where the SO{sub 4}{sup {minus}2} concentration is low.

  18. Finite element modeling of the dynamic response of a composite reinforced concrete bridge for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Zanjani Zadeh, V.; Patnaik, A.

    2014-06-01

    This paper describes three-dimensional (3D) finite element (FE) modeling of a composite steel stinger supported reinforced concrete (RC) deck highway bridge subjected to moving truck loads. FE models were validated using test data that were generated elsewhere for structural health monitoring. The FE models were established using a commercial FE analysis package called ABAQUS/standard. The case study bridge was discretized to a combination of shell and solid elements which represent the deck and piers, respectively. Numerous constrain interactions were defined to make the model suitable to obtain accurate results. Moving loads induced by two standard AASHTO trucks were developed through a specific load-time history, applied on 35 nodes on the superstructure. To study the dynamic behavior of the bridge under a moving load, a modal analysis followed by an implicit dynamic analysis was carried out. Acceptable agreement was found between the field measurements and FE simulation. Most concerned dynamic response was strains at different locations in bridge girders and columns, because it is the only critical parameter that can be measured with confidence during SHM at site. The range of strains determined in analysis was reasonably close to the measured strains at the site of the study bridge. Several parameters including damping, truck weight and speed, and material properties were studied. Truck speed had the highest effect on strain response of both girders and columns.

  19. Modeling, Analysis, and Preservation Techniques for Historic Reinforced Concrete Structures in Seismic Prone Regions Case Study: Augusta Airship Hangar, Sicily

    SciTech Connect

    Cronin, Kelly; Whyte, Catherine; Reiner, Tom

    2008-07-08

    also can be used as an example for the rehabilitation of other historic structures. The techniques and processes discussed in this paper can be applied to other historic reinforced concrete structures and can be expanded upon in future investigations.

  20. Modeling, Analysis, and Preservation Techniques for Historic Reinforced Concrete Structures in Seismic Prone Regions Case Study: Augusta Airship Hangar, Sicily

    NASA Astrophysics Data System (ADS)

    Cronin, Kelly; Reiner, Tom; Whyte, Catherine

    2008-07-01

    also can be used as an example for the rehabilitation of other historic structures. The techniques and processes discussed in this paper can be applied to other historic reinforced concrete structures and can be expanded upon in future investigations.

  1. Solar-Array Substrate From Glass-Reinforced Concrete

    NASA Technical Reports Server (NTRS)

    Eirls, J. L.

    1985-01-01

    Design elminiates glass superstrate and associated metal framing. Panel has two trapezoidal stiffening ribs for structural support. Strategic placement of ribs with embedded support tubes (standard PVC tubing) minimizes bending moments and resulting stresses produced by installation and windloads. Glass-reinforced concrete panel has smooth flat surface suitable for solar substrate and includes structural bracing for rigidity and design adaptable to mass production.

  2. Aerated concrete with mineral dispersed reinforcing additives

    NASA Astrophysics Data System (ADS)

    Berdov, G. I.; Ilina, L. V.; Mukhina, I. N.; Rakov, M. A.

    2015-01-01

    To guarantee the production of aerated concrete with the lowest average density while ensuring the required strength it is necessary to use a silica component with a surface area of 250-300 m2 / kg. The article presents experimental data on grinding the silica component together with clinker to the optimum dispersion. This allows increasing the strength of non-autoclaved aerated concrete up to 33%. Furthermore, the addition to aerated concrete the mixture of dispersed reinforcing agents (wollastonite, diopside) and electrolytes with multiply charged cations and anions (1% Fe2 (SO4)3; Al2 (SO4)3) provides the growth of aerated concrete strength at 30 - 75%. As a cohesive the clinker, crushed together with silica and mineral supplements should be used. This increases the strength of aerated concrete at 65% in comparing with Portland cement.

  3. Assessment of concrete damage and strength degradation caused by reinforcement corrosion

    NASA Astrophysics Data System (ADS)

    Nepal, Jaya; Chen, Hua-Peng

    2015-07-01

    Structural performance deterioration of reinforced concrete structures has been extensively investigated, but very limited studies have been carried out to investigate the effect of reinforcement corrosion on time-dependent reliability with consideration of the influence of mechanical characteristics of the bond interface due to corrosion. This paper deals with how corrosion in reinforcement creates different types of defects in concrete structure and how they are responsible for the structural capacity deterioration of corrosion affected reinforced concrete structures during their service life. Cracking in cover concrete due to reinforcement corrosion is investigated by using rebar-concrete model and realistic concrete properties. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution due to reinforcement corrosion, which is examined by the experimental data available. The time-dependent reliability analysis is undertaken to calculate the life time structural reliability of corrosion damaged concrete structures by stochastic deterioration modelling of reinforced concrete. The results from the numerical example show that the proposed approach is capable of evaluating the damage caused by reinforcement corrosion and also predicting the structural reliability of concrete structures during their lifecycle.

  4. CREATION OF MUSIC WITH FIBER REINFORCED CONCRETE

    NASA Astrophysics Data System (ADS)

    Kato, Hayato; Takeuchi, Masaki; Ogura, Naoyuki; Kitahara, Yukiko; Okamoto, Takahisa

    This research focuses on the Fiber Reinforcement Concrete(FRC) and its performance on musical tones. Thepossibility of future musical instruments made of this concrete is discussed. Recently, the technical properties of FRC had been improved and the different production styles, such as unit weight of binding material and volume of fiber in the structure, hardly affects the results of the acoustics. However, the board thickness in the FRC instruments is directly related with the variety of musical tone. The FRC musical effects were compared with those produced with wood on wind instruments. The sounds were compared with those produced with woodwind instruments. The sound pressure level was affected by the material and it becomes remarkably notorious in the high frequency levels. These differences had great influence on the spectrum analysis of the tone in the wind instruments and the sensory test. The results from the sensory test show dominant performances of brightness, beauty and power in the FRC instruments compared with those made of wood.

  5. Introduction to Concrete Reinforcing. Instructor Edition. Introduction to Construction Series.

    ERIC Educational Resources Information Center

    Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    This instructor's guide contains the materials required to teach a competency-based introductory course in concrete reinforcing to students who have chosen to explore careers in construction. It contains three units: concrete reinforcing materials, concrete reinforcing tools, and applied skills. Each instructional unit includes some or all of the…

  6. A new, high current output, galvanic (sacrificial) anode, electrochemical rehabilitation system for reinforced and prestressed concrete structures

    SciTech Connect

    Clear, K.C.

    1999-07-01

    This paper summarizes 1995 through 1998 laboratory, outdoor exposure facility, and field data on the subject concrete rehab system. The system shows promise as a means of providing cathodic protection to the reinforcing, as a chloride removal process, as a re-alkalization process, and/or as a lithium injection procedure to minimize alkali-aggregate reactions in the concrete. Unique characteristics of the system include: (1) Surrounding each galvanic anode with a highly corrosive liquid which maintains it (the anode) at peak output voltage throughout its life; and (2) Placing an ionic transfer layer between the anode and the concrete surface that is high volume, low resistivity and deliquescent (i.e. pulls water vapor out of the air at relative humidities of 35% or higher). The ionic transfer layer typically consists of sponge, felt or sand loaded with calcium chloride (and/or other chemicals such as sodium hydroxide, potassium acetate, and lithium-salts). In some cases it also contains a wetting agent and is encapsulated (fully or partially) in vapor permeable, but water impermeable materials. The ionic transfer layer will not freeze at temperatures as low as {minus}20 C ({minus}5 F), and provides sufficient space for all anode corrosion products, thus preventing undesirable stresses on the concrete, the anode assembly and any cosmetic covering.

  7. Detection and Inspection of Steel Bars in Reinforced Concrete Structures Using Active Infrared Thermography with Microwave Excitation and Eddy Current Sensors

    PubMed Central

    Szymanik, Barbara; Frankowski, Paweł Karol; Chady, Tomasz; John Chelliah, Cyril Robinson Azariah

    2016-01-01

    The purpose of this paper is to present a multi-sensor approach to the detection and inspection of steel bars in reinforced concrete structures. In connection with our past experience related to non-destructive testing of different materials, we propose using two potentially effective methods: active infrared thermography with microwave excitation and the eddy current technique. In this article active infrared thermography with microwave excitation is analyzed both by numerical modeling and experiments. This method, based on thermal imaging, due to its characteriatics should be considered as a preliminary method for the assessment of relatively shallowly located steel bar reinforcements. The eddy current technique, on the other hand, allows for more detailed evaluation and detection of deeply located rebars. In this paper a series of measurement results, together with the initial identification of certain features of steel reinforcement bars will be presented. PMID:26891305

  8. Detection and Inspection of Steel Bars in Reinforced Concrete Structures Using Active Infrared Thermography with Microwave Excitation and Eddy Current Sensors.

    PubMed

    Szymanik, Barbara; Frankowski, Paweł Karol; Chady, Tomasz; John Chelliah, Cyril Robinson Azariah

    2016-01-01

    The purpose of this paper is to present a multi-sensor approach to the detection and inspection of steel bars in reinforced concrete structures. In connection with our past experience related to non-destructive testing of different materials, we propose using two potentially effective methods: active infrared thermography with microwave excitation and the eddy current technique. In this article active infrared thermography with microwave excitation is analyzed both by numerical modeling and experiments. This method, based on thermal imaging, due to its characteriatics should be considered as a preliminary method for the assessment of relatively shallowly located steel bar reinforcements. The eddy current technique, on the other hand, allows for more detailed evaluation and detection of deeply located rebars. In this paper a series of measurement results, together with the initial identification of certain features of steel reinforcement bars will be presented. PMID:26891305

  9. Wing walls for enhancing the seismic performance of reinforced concrete frame structures

    NASA Astrophysics Data System (ADS)

    Yang, Weisong; Guo, Xun; Xu, Weixiao; Yuan, Xin

    2016-06-01

    A building retrofitted with wing walls in the bottom story, which was damaged during the 2008 M8.0 Wenchuan earthquake in China, is introduced and a corresponding 1/4 scale wing wall-frame model was subjected to shake table motions to study the seismic behavior of this retrofitted structural system. The results show that wing walls can effectively protect columns from damage by moving areas that bear reciprocating tension and compression to the sections of the wing walls, thus achieving an extra measure of seismic fortification. A `strong column-weak beam' mechanism was realized, the flexural rigidity of the vertical member was strengthened, and a more uniform distribution of deformation among all the stories was measured. In addition, the joint between the wing walls and the beams suffered severe damage during the tests, due to an area of local stress concentration. A longer area of intensive stirrup is suggested in the end of the beams.

  10. Fracture of concrete caused by the reinforcement corrosion products

    NASA Astrophysics Data System (ADS)

    Nguyen, Q. T.; Millard, A.; Caré, S.; L'Hostis, V.; Berthaud, Y.

    2006-11-01

    One of the most current degradations in reinforced concrete structures is related to the corrosion of the reinforcements. The corrosion products during active corrosion induce a mechanical pressure on the surrounding concrete that leads to cover cracking along the rebar. The objective of this work is to study the cracking of concrete due to the corrosion of the reinforcements. The phenomenon of corrosion/cracking is studied in experiments through tests of accelerated corrosion on plate and cylindrical specimens. A CCD camera is used to take images every hour and the pictures are analyzed by using the intercorrelation image technique (Correli^LMT) to derive the displacement and strain field. Thus the date of appearance of the first through crack is detected and the cinematic crack initiations are observed during the test. A finite element model that allows prediction of the mechanical consequences of the corrosion of steel in reinforced concrete structures is proposed. From the comparison between the test results and numerical simulations, it may be concluded that the model is validated in term of strains up to the moment when the crack becomes visible, and in terms of crack pattern.

  11. TEMP-STRESS---A thermomechanical finite element program for the analysis of plane and axisymmetric reinforced/prestressed concrete structures: User`s manual

    SciTech Connect

    Kennedy, J. M.; Pfeiffer, P. A.; Marchertas, A. H.

    1989-01-01

    TEMP-STRESS has been developed to improve the understanding of the behavior of concrete subjected to mechanical loadings and high temperatures simulating the effects of coolant spills, molten debris, etc. The capability to model concrete structures subjected to static and dynamic overpressures, such as LWR and LMR containments with complex axisymmetric geometries, can be solved. The computer code is a finite element program which has a weakly coupled thermomechanical formulation. It can handle transient and steady state problems through the use of explicit time integration and dynamic relaxation. There is a plane or axisymmetric continuum element and flexural beam and shell elements for concrete discretization. The continuum element is a four node quadrilateral using numerical integration and elastic hourglass control. Variable material properties as a function of temperature are available. Thermal and/or mechanical loading can be handled. The concrete material model has the following characteristics: (a) elastic-plastic response, (b) variable loading surface capability, (c) cracking normal to maximum principal strain at specified failure surface, (d) post-failure element treatment, and (e) variable temperature dependence. Concrete can be reinforced and/or prestressed. 15 refs., 33 figs., 24 tabs.

  12. CP systems for steel reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Cramer, Stephen D.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Ziomek-Moroz, Margaret; Soltesz, Steven M.

    2004-01-01

    Thermal-sprayed zinc anodes are used for cathodic protection (CP) systems in Oregon?s reinforced concrete coastal bridges to prevent chloride-induced corrosion damage. Thermal-sprayed zinc performs well as an ICCP anode but the service life of the zinc anode is directly related to the average current density used to operate the systems. Oregon Department of Transportation (DOT) is investigating ways of monitoring the rebar corrosion in reinforced concrete bridges to identify conditions when protection of the rebar is needed. This approach reflects the fact that external protection may not be needed for all environmental conditions, leading Oregon DOT to examine the use of intermittent, galvanic, and constant voltage cathodic protection systems. Results from these types of systems are reported.

  13. An integrated degradation and structural model for predicting the service life of buried reinforced concrete structures for low- and intermediate-level radioactive waste disposal

    SciTech Connect

    Brandstetter, E.R.; Lolcama, J.L.; Reed, S.R.

    1994-03-01

    The primary focus of this study was to determine the possible rates of roof and wall failure and the times to structural collapse of the roof and walls of three vault designs at the Department of Energy`s Savannah River Site near Aiken, South Carolina. Failure was defined as a loss of ability to divert soil water around the vault. Collapse was defined as the total loss of structure integrity of the vault. Failure and eventual collapse of the three vault types results from concrete deterioration under stress, in the presence of corrosive soil water. Degradation rates for reinforced concrete were utilized, and the resultant changes in properties (such as strength, thickness, cracking and hydraulic conductivity) were evaluated. Baseline times to failure and collapse of the walls and roof components were modeled, and sensitivity analyses were conducted to provide boundaries on these estimated times. Thus, the goal of the project was to provide a bounding analysis of the time to roof and wall failure and potential collapse, rather than an actual prediction of the time to failure, and collapse.

  14. Investigation of Mechanical Properties of Steel Fibre- Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Ryabchikov, A.; Tamme, V.; Laurson, M.

    2015-11-01

    Steel fibre-reinforced concrete (SFRC) is widely used in the structural elements of buildings: industrial floors, slabs, walls, foundation, etc. When a load is applied to a fibre- reinforced composite consisting of a low-modulus matrix reinforced with high-strength, high- modulus fibres, the plastic flow of the matrix under stress transfers the load to the fibre; this results in high-strength, high-modulus material which determines the stiffness and stress of the composite. In this study the equivalent flexural strength, equivalent flexural ratio Re,3 and the compressing strength of SFRC are investigated. Notched test specimens with five different dosages of steel fibres (20, 25, 30, 35, 40 kg/m3) were prepared using industrial concrete. Determination of flexural tension strength was carried out according to the EU norm EVS-EN 14651:2005+A1:2007. The equivalent flexural strength and subsequent equivalent flexural ratio Re,3 of SFRC with a dosage of 20, 25, 30, 35 kg/m3 similar to their average values and with a dosage of 40 kg/m3 were 31% higher than their average values. The compressive strength of the steel fibre-reinforced concrete was slightly higher compared to plain concrete, except specimens with the dosage of 40 kg/m3 where the increase was 30%.

  15. CORROSION PROCESS IN REINFORCED CONCRETE IDENTIFIED BY ACOUSTIC EMISSION

    NASA Astrophysics Data System (ADS)

    Kawasaki, Yuma; Kitaura, Misuzu; Tomoda, Yuichi; Ohtsu, Masayasu

    Deterioration of Reinforced Concrete (RC) due to salt attack is known as one of serious problems. Thus, development of non-destructive evaluation (NDE) techniques is important to assess the corrosion process. Reinforcement in concrete normally does not corrode because of a passive film on the surface of reinforcement. When chloride concentration at reinfo rcement exceeds the threshold level, the passive film is destroyed. Thus maintenance is desirable at an early stage. In this study, to identify the onset of corrosion and the nucleation of corrosion-induced cracking in concrete due to expansion of corrosion products, continuous acoustic emission (AE) monitoring is applied. Accelerated corrosion and cyclic wet and dry tests are performed in a laboratory. The SiGMA (Simplified Green's functions for Moment tensor Analysis) proce dure is applied to AE waveforms to clarify source kinematics of micro-cracks locations, types and orientations. Results show that the onset of corrosion and the nu cleation of corrosion-induced cracking in concrete are successfully identified. Additionally, cross-sections inside the reinforcement are observed by a scanning electron microscope (SEM). From these results, a great promise for AE techniques to monitor salt damage at an early stage in RC structures is demonstrated.

  16. Cohesive fracture model for functionally graded fiber reinforced concrete

    SciTech Connect

    Park, Kyoungsoo; Paulino, Glaucio H.; Roesler, Jeffery

    2010-06-15

    A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.

  17. Behaviour of fibre reinforced polymer confined reinforced concrete columns under fire condition

    NASA Astrophysics Data System (ADS)

    Chowdhury, Ershad Ullah

    In recent years, fibre reinforced polymer (FRP) materials have demonstrated enormous potential as materials for repairing and retrofitting concrete bridges that have deteriorated from factors such as electro-chemical corrosion and increased load requirements. However, concerns associated with fire remain an obstacle to applications of FRP materials in buildings and parking garages due to FRP's sensitivity to high temperatures as compared with other structural materials and to limited knowledge on their thermal and mechanical behaviour in fire. This thesis presents results from an ongoing study on the fire performance of FRP materials, fire insulation materials and systems, and FRP wrapped reinforced concrete columns. The overall goal of the study is to understand the fire behaviour of FRP materials and FRP strengthened concrete columns and ultimately, provide rational fire safety design recommendations and guidelines for FRP strengthened concrete columns. A combined experimental and numerical investigation was conducted to achieve the goals of this research study. The experimental work consisted of both small-scale FRP material testing at elevated temperatures and full-scale fire tests on FRP strengthened columns. A numerical model was developed to simulate the behaviour of unwrapped reinforced concrete and FRP strengthened reinforced concrete square or rectangular columns in fire. After validating the numerical model against test data available in literature, it was determined that the numerical model can be used to analyze the behaviour of concrete axial compressive members in fire. Results from this study also demonstrated that although FRP materials experience considerable loss of their mechanical and bond properties at temperatures somewhat below the glass transition temperature of the resin matrix, externally-bonded FRP can be used in strengthening concrete structural members in buildings, if appropriate supplemental fire protection system is provided over

  18. Advance study of fiber-reinforced self-compacting concrete

    SciTech Connect

    Mironova, M. Ivanova, M. Naidenov, V.; Georgiev, I.; Stary, J.

    2015-10-28

    Incorporation in concrete composition of steel macro- and micro – fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

  19. Advance study of fiber-reinforced self-compacting concrete

    NASA Astrophysics Data System (ADS)

    Mironova, M.; Ivanova, M.; Naidenov, V.; Georgiev, I.; Stary, J.

    2015-10-01

    Incorporation in concrete composition of steel macro- and micro - fiber reinforcement with structural function increases the degree of ductility of typically brittle cement-containing composites, which in some cases can replace completely or partially conventional steel reinforcement in the form of rods and meshes. Thus, that can reduce manufacturing, detailing and placement of conventional reinforcement, which enhances productivity and economic efficiency of the building process. In this paper, six fiber-reinforced with different amounts of steel fiber cement-containing self-compacting compositions are investigated. The results of some of their main strength-deformation characteristics are presented. Advance approach for the study of structural and material properties of these type composites is proposed by using the methods of industrial computed tomography. The obtained original tomography results about the microstructure and characteristics of individual structural components make it possible to analyze the effective macro-characteristics of the studied composites. The resulting analytical data are relevant for the purposes of multi-dimensional modeling of these systems. Multifactor structure-mechanical analysis of the obtained with different methods original scientific results is proposed. It is presented a conclusion of the capabilities and effectiveness of complex analysis in the studies to characterize the properties of self-compacting fiber-reinforced concrete.

  20. Corrosion of reinforced concrete in the Persian Gulf region

    SciTech Connect

    Novokshchenov, V.

    1995-01-01

    The Kuwait liquefied gas/sulfur (LGS) plant is located on a small island in the southern part of the Persian Gulf. The plant was built in phases between 1973 and 1977. Designed to manufacture liquefied natural and petroleum gas and to extract sulfur, the LGS plant consists of two similar process unit trains served by a common boiler and utility plant. The major reinforced-concrete structures at the plant include the cooling water outfall, the cooling water intake, the operations building, structures supporting elevated pipe and equipment, boiler stack foundations, bridge over the flume, the loading jetty, sulfur plant structures, substations, and storage tank foundations. The first signs of distress in the plant structures were reported in 1980: cracking, spalling, and delamination of concrete cover and corrosion of reinforcing steel. In some cases, deterioration had progressed to the extent that safety and life expectancy of the structures were at risk. Subsequently, several investigations were conducted on various structures from 1980 to 1987 to identify the causes of the deterioration. The principal cause of the deterioration was corrosion of reinforcing steel caused by the presence of chlorides; marine salts were the main source. Construction-related contributing factors included insufficient concrete cover, use of sulfate-resistant (ASTM Type V) portland cement, and an elevated water-to-cement ratio.

  1. Design and behavior of reinforced concrete beams strengthened with fiber-reinforced plastics (FRP)

    NASA Astrophysics Data System (ADS)

    El-Mihilmy, Mahmoud Tharwat

    A comprehensive investigation of the design and behavior of reinforced concrete beams strengthened with externally bonded FRP laminates has been conducted. The study has confirmed the applicability of the strain compatibility method for calculating the increased ultimate moment capacity of the repaired beams. An upper limit to the amount of FRP that can be added to a specific structure was recommended to ensure ductile behavior. Design charts to facilitate calculations of the ultimate moment capacity for reinforced concrete beams strengthened with FRP laminates were developed. The results of a subsequent parametric investigation indicate that strengthening reinforced concrete beams with FRP laminates can enhance their ultimate capacity by as much as three times the original strength, especially for beams with a low steel ratio. It was also determined that, increasing the concrete compressive strength and the FRP modulus of elasticity increases the beam ultimate flexural capacity significantly; however, the repaired beams are less ductile than the pre-repaired concrete beams. During the course of the study, it had been noticed that the current ACI recommended method for calculating deflections for ordinary reinforced concrete beams does not render an accurate estimate for reinforced concrete beams strengthened with FRP laminates. A simplified equation for predicting the deflection of reinforced concrete beams repaired with FRP was developed and verified with comparisons to experimental results. The effectiveness of strengthening an existing bridge with externally bonded FRP laminates was investigated through comprehensive static and dynamic finite element analyses. The results of these analyses correlate well with field load test results. The repaired girders exhibited an average reduction in reinforcing steel stresses of 11 percent and an average reduction in midspan girder deflections of 9 percent. The results of the study also indicated that existing methods for

  2. Failure of underground concrete structures subjected to blast loadings

    NASA Technical Reports Server (NTRS)

    Ross, C. A.; Nash, P. T.; Griner, G. R.

    1979-01-01

    The response and failure of two edges of free reinforced concrete slabs subjected to intermediate blast loadings are examined. The failure of the reinforced concrete structures is defined as a condition where actual separation or fracture of the reinforcing elements has occurred. Approximate theoretical methods using stationary and moving plastic hinge mechanisms with linearly varying and time dependent loadings are developed. Equations developed to predict deflection and failure of reinforced concrete beams are presented and compared with the experimental results.

  3. 7. Detail view of reinforced concrete archrings comprising dam's upstream ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Detail view of reinforced concrete arch-rings comprising dam's upstream face. Impressions of the wooden formwork used in construction are visible in the concrete. - Little Rock Creek Dam, Little Rock Creek, Littlerock, Los Angeles County, CA

  4. Crack detection and leakage monitoring on reinforced concrete pipe

    NASA Astrophysics Data System (ADS)

    Feng, Qian; Kong, Qingzhao; Huo, Linsheng; Song, Gangbing

    2015-11-01

    Reinforced concrete underground pipelines are some of the most widely used types of structures in water transportation systems. Cracks and leakage are the leading causes of pipeline structural failures which directly results in economic losses and environmental hazards. In this paper, the authors propose a piezoceramic based active sensing approach to detect the cracks and the further leakage of concrete pipelines. Due to the piezoelectric properties, piezoceramic material can be utilized as both the actuator and the sensor in the active sensing approach. The piezoceramic patch, which is sandwiched between protective materials called ‘smart aggregates,’ can be safely embedded into concrete structures. Circumferential and axial cracks were investigated. A wavelet packet-based energy analysis was developed to distinguish the type of crack and determine the further leakage based on different stress wave energy attenuation propagated through the cracks.

  5. Glass fiber reinforced concrete for terrestrial photovoltaic arrays

    NASA Technical Reports Server (NTRS)

    Maxwell, H.

    1979-01-01

    The use of glass-fiber-reinforced concrete (GRC) as a low-cost structural substrate for terrestrial solar cell arrays is discussed. The properties and fabrication of glass-reinforced concrete structures are considered, and a preliminary design for a laminated solar cell assembly built on a GRC substrate is presented. A total cost for such a photovoltaic module, composed of a Korad acrylic plastic film front cover, an aluminum foil back cover, an ethylene/vinyl acetate pottant/adhesive and a cotton fabric electrical isolator in addition to the GRC substrate, of $9.42/sq m is projected, which is less than the $11.00/sq m cost goal set by the Department of Energy. Preliminary evaluations are concluded to have shown the design capabilities and cost effectiveness of GRC; however, its potential for automated mass production has yet to be evaluated.

  6. 150. Credit ER. Building reinforced concrete portion of Coleman Canal ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    150. Credit ER. Building reinforced concrete portion of Coleman Canal inverted siphon #2. Longitudinal steel reinforcing rods are visible at bottom. (ER, v. 64 1911 p. 702). - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

  7. Anodes for cathodic protection of reinforced concrete

    SciTech Connect

    S.J. Bullard; B.S. Covino, Jr.; S.D. Cramer; G.R. Holcomb; J.H. Russell

    2000-03-01

    Consumable anodes were evaluated in the laboratory for use in cathodic protection systems for steel reinforced concrete bridges in coastal environments and in areas where de-icing salts are employed. The anode materials include Zn-hydrogel and thermal-sprayed Zn, Zn-15Al, and Al-12Zn-0.2In. These anodes were evaluated for service in both galvanic (GCP) and impressed current (ICCP) cathodic protection systems. ICCP anodes were electrochemically aged at a factor of 15 times greater than used by the Oregon Department of Transportation in typical coastal ICCP systems (2.2 mA/m{sup 2} based on anode area). Increasing moisture at the anode-concrete interface reduced the operating voltage of all the anodes. The pH at the anode-concrete interface fell to 7 to 8.5 with electrochemical age. Bond strength between the anodes and concrete decreased with electrochemical aging. Interfacial chemistry was the critical link between long-term anode performance and electrochemical age. Zn-hydrogel and the rmal-sprayed Zn and Al-12Zn-0.2In GCP anodes appear to supply adequate protection current to rebar in the Cape Perpetua Viaduct.

  8. Curvature ductility of reinforced and prestressed concrete columns

    SciTech Connect

    Suprenant, B.A.

    1984-01-01

    Engineers are concerned with the survival of reinforced and prestressed concrete columns during earthquakes. The prediction of column survival can be deduced from moment-curvature curves of the column section. An analytical approach is incorporated into a computer model. The computer program is based on assumed stress-strain relations for confined and unconfined concrete, nonprestressed and prestressing steel. The results of studies on reinforced and prestressed concrete columns indicate that reinforced concrete columns may be designed to resist earthquakes, while prestressed concrete columns may not. The initial reduction in moment capacity, after concrete cover spalling, of a prestressed concrete column could be as much as 50%. Analyses indicate that the bond between concrete and prestressing strand after concrete cover spalling is not critical.

  9. Evaluation of Concrete Consolidation: DSS-35 Antenna Reinforced Concrete Pedestal, Canberra Deep Space Communications Complex, Australia

    NASA Astrophysics Data System (ADS)

    Saldua, B. P.; Dodge, E. C.; Kolf, P. R.; Olson, C. A.

    2016-02-01

    Antenna structures for the Deep Space Network track spacecraft that are millions of miles away. Therefore, these structures have tight specifications for translation, rotation, and differential settlement. This article presents several nondestructive test methods that were used to evaluate, locate, and repair imperfections in the reinforced concrete pedestal that supports the DSS-35 antenna structure. These methods include: (1) impulse response (IR), (2) ultrasonic shear-wave tomography (MIRA), and (3) ground-penetrating radar (GPR).

  10. Bond of fiber reinforced plastic (FRP) rods to concrete

    SciTech Connect

    Al-Zahrani, M.M.; Nanni, A.; Al-Dulaijan, S.U.; Bakis, C.E.

    1996-11-01

    The bond behavior between FRP rods and concrete is one of the most important aspects to predicting the short- and long-term performance of FRP reinforced concrete structures including development and transfer length. In this research, the direct pull-out test was used to study the FRP/concrete bond behavior. This method allows measurement of the loaded- and free-end slip of the FRP rod and placement of a strain probe inside the rod to measure internal strain distribution in both axial and radial directions along the bonded length without affecting the FRP/concrete interface. Knowledge of strain distribution is necessary to study the load transfer mechanism between FRP rod and concrete. The scope of this paper include experimental results obtained with the direct pull-out test using 12.7 mm glass and carbon FRP rods with smooth and axisymmetrical deformed surfaces. The typical results are given as nominal bond and shear stress vs. free- and loaded-end slip. Experimental results obtained from strain probes used during pull-out tests are also presented as nominal bond and shear stress vs. strain. For smooth rods, friction is the main controlling factor. For deformed rods, bond tends to be controlled by strength and mechanical action of the axisymmetrical deformations rather than adhesion and friction. The strength of concrete appears to have no effect on the bond strength and failure mechanism of these particular machined FRP rods when concrete splitting is avoided.

  11. Analytical investigation of a three-dimensional FRP-retrofitted reinforced concrete structure's behaviour under earthquake load effect in ANSYS program

    NASA Astrophysics Data System (ADS)

    Altun, F.; Birdal, F.

    2012-12-01

    In this study, a 1:3 scaled, three-storey, FRP (Fiber Reinforced Polymer) retrofitted reinforced concrete model structure whose behaviour and crack development were identified experimentally in the laboratory was investigated analytically. Determination of structural behaviour under earthquake load is only possible in a laboratory environment with a specific scale, as carrying out structural experiments is difficult due to the evaluation of increased parameter numbers and because it requires an expensive laboratory setup. In an analytical study, structure was modelled using ANSYS Finite Element Package Program (2007), and its behaviour and crack development were revealed. When experimental difficulties are taken into consideration, analytical investigation of structure behaviour is more economic and much faster. At the end of the study, experimental results of structural behaviour and crack development were compared with analytical data. It was concluded that in a model structure retrofitted with FRP, the behaviour and cracking model can be determined without testing by determining the reasons for the points where analytical results are not converged with experimental data. Better understanding of structural behaviour is analytically enabled with the study.

  12. Flexural strengthening of Reinforced Concrete (RC) Beams Retrofitted with Corrugated Glass Fiber Reinforced Polymer (GFRP) Laminates

    NASA Astrophysics Data System (ADS)

    Aravind, N.; Samanta, Amiya K.; Roy, Dilip Kr. Singha; Thanikal, Joseph V.

    2015-01-01

    Strengthening the structural members of old buildings using advanced materials is a contemporary research in the field of repairs and rehabilitation. Many researchers used plain Glass Fiber Reinforced Polymer (GFRP) sheets for strengthening Reinforced Concrete (RC) beams. In this research work, rectangular corrugated GFRP laminates were used for strengthening RC beams to achieve higher flexural strength and load carrying capacity. Type and dimensions of corrugated profile were selected based on preliminary study using ANSYS software. A total of twenty one beams were tested to study the load carrying capacity of control specimens and beams strengthened with plain sheets and corrugated laminates using epoxy resin. This paper presents the experimental and theoretical study on flexural strengthening of Reinforced Concrete (RC) beams using corrugated GFRP laminates and the results are compared. Mathematical models were developed based on the experimental data and then the models were validated.

  13. Nonlinear Finite Element Analysis of FRP Strengthened Reinforced Concrete Beams

    NASA Astrophysics Data System (ADS)

    Sasmal, S.; Kalidoss, S.; Srinivas, V.

    2012-12-01

    This paper focuses on nonlinear analysis of parent and fiber reinforced polymer (FRP) strengthened reinforced concrete (RC) beam using general purpose finite element software, ANSYS. Further, it is aimed to investigate the suitability of different elements available in ANSYS library to represent FRP, epoxy and interface. 3-D structural RC solid element has been used to model concrete and truss element is employed for modeling the reinforcements. FRP has been modelled using 3-D membrane element and layered element with number of layers, epoxy is modelled using eight node brick element, and eight node layered solid shell is used to mathematically represent the concrete-FRP interface behavior. Initially, the validation of the numerical model for the efficacy of different elements (SOLID65 for concrete and LINK8 for reinforcement) and material models is carried out on the experimental beam reported in literature. The validated model, elements and material properties is used to evaluate the load-displacement and load-strain response behavior and crack patterns of the FRP strengthened RC beams. The numerical results indicated that significant improvement in the displacement in the strengthened RC beams with the advancement of cracks. The study shows that FRP with shell elements is recommended when single layer of FRP is used. When multi layered FRP is used, solid layered element can be a reasonably good choice whereas the epoxy matrix with linear solid element does not need further complicated model. Interfacial element makes the analysis minimally improved at the cost of complicated modeling issues and considerable computation time. Hence, for nonlinear analysis of usual strengthened structures, unless it is specifically required for, interface element may not be required and a full contact can be assumed at interface.

  14. Inspection of reinforced concrete samples by Compton backscattering technique

    NASA Astrophysics Data System (ADS)

    Boldo, E. M.; Appoloni, C. R.

    2014-02-01

    Reinforced concrete structures require frequent monitoring to ensure the concrete quality during its service life and for evaluation of in situ existing conditions. Compton backscattering of gamma rays is a nondestructive technique used for material characterization and detection of defects and inclusions in materials and can be employed on reinforced concrete. The methodology allows one-sided inspection of large structures, is relatively inexpensive and can be portable. The concept is based on detection of backscattered radiation produced from a collimated beam aimed at the sample. By measuring the spectrum of these scattered gamma rays it is possible to determine local density perturbations. In this work we used the Compton backscattering technique to locate and measure steel, defects and crushed stone inside concrete. The samples were irradiated with gamma rays from a Ø2 mm diameter collimated 241Am (100 mCi) source and the inelastically scattered photons were recorded at an angle of 135° by a high resolution CdTe semiconductor detector. Scanning was achieved by lateral movement of the sample blocks across the source and detector field of view in steps of 1 mm. A previous optimization of the experimental setup was performed with Monte Carlo simulation. The results showed that it was possible to locate inclusions and defects with Ø8 mm positioned at a depth of 20 mm below the surface of the sample. It was observed that aggregates such as crushed stone could mask defects at specific points due to high attenuation of the incident and scattered beam.

  15. 77 FR 18973 - Reinforced Concrete in Construction, and Preventing Backover Injuries and Fatalities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-29

    ... Reinforced Concrete in Construction, and Preventing Backover Injuries and Fatalities AGENCY: Occupational... aware of employee safety risks in two areas, reinforcing operations in concrete work (construction only... following methods (submissions relating to Reinforced Concrete in Construction to Docket No....

  16. Evaluating cover depth of steel fiber reinforced concrete using impact-echo testing

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Feng

    2014-04-01

    The purpose of this research is to estimate of the cover depth of steel fiber reinforced concrete using the impact-echo testing. In order to evaluate the security of the construction, usually need to estimate the cover depth of the reinforced concrete. At present, the examination technique of the cover depth of the reinforced concrete without the steel fiber is mainly applied in the magnetic and electrical methods, its rapid detection and good results. But the research of the reactive powder concrete be gradually progress, with the steel fiber concrete structure will be increased, if should still operate the examination with the magnetic and electrical methods, theoretically the steel fiber will have the interference to its electromagnetism field. Therefore, this research designs four kinds of reinforced concrete plate that include different steel fiber contents, to evaluate test results of estimate of the cover depth of the reinforcing bar. The results showed that: estimate of the cover depth of steel fiber reinforced concrete reinforcing bar using the impact-echo testing, the variety of the steel fiber content does not have much influence, the test measurement error within ± 10%, and the most important source of uncertainty is the velocity of concrete.

  17. Acoustic emission monitoring of concrete columns and beams strengthened with fiber reinforced polymer sheets

    NASA Astrophysics Data System (ADS)

    Ma, Gao; Li, Hui; Zhou, Wensong; Xian, Guijun

    2012-04-01

    Acoustic emission (AE) technique is an effective method in the nondestructive testing (NDT) field of civil engineering. During the last two decades, Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening concrete structures. The damage state of FRP strengthened concrete structures has become an important issue during the service period of the structure and it is a meaningful work to use AE technique as a nondestructive method to assess its damage state. The present study reports AE monitoring results of axial compression tests carried on basalt fiber reinforced polymer (BFRP) confined concrete columns and three-point-bending tests carried on BFRP reinforced concrete beams. AE parameters analysis was firstly utilized to give preliminary results of the concrete fracture process of these specimens. It was found that cumulative AE events can reflect the fracture development trend of both BFRP confined concrete columns and BFRP strengthened concrete beams and AE events had an abrupt increase at the point of BFRP breakage. Then the fracture process of BFRP confined concrete columns and BFRP strengthened concrete beams was studied through RA value-average frequency analysis. The RA value-average frequency tendencies of BFRP confined concrete were found different from that of BFRP strengthened concrete beams. The variation tendency of concrete crack patterns during the loading process was revealed.

  18. Estimation of Structure-Borne Noise Reduction Effect of Steel Railway Bridge Equipped with Floating Ladder Track and Floating Reinforced-Concrete Deck

    NASA Astrophysics Data System (ADS)

    Watanabe, Tsutomu; Sogabe, Masamichi; Asanuma, Kiyoshi; Wakui, Hajime

    A number of steel railway bridges have been constructed in Japan. Thin steel members used for the bridges easily tend to vibrate and generate structure-borne noise. Accordingly, the number of constructions of steel railway bridges tends to decrease in the urban areas from a viewpoint of environmental preservation. Then, as a countermeasure against structure-borne noise generated from steel railway bridges, we have developed a new type of the steel railway bridge equipped with a floating-ladder track and a floating reinforced-concrete (RC) deck. As a result of train-running experiment, it became apparent that the new steel railway bridge installed by double floating system has reduced a vibration velocity level by 10.5 dB(A) at main girder web as compared with a steel railway bridge installed by directly fastened track. This reduction effect was achieved by the ladder track and RC deck supported by resilient materials.

  19. The Behaviour of Reinforced Concrete Subjected to Reversed Cyclic Shear

    NASA Astrophysics Data System (ADS)

    Ruggiero, David Michael Volpe

    Reversed cyclic loading, as may occur during seismic events, can cause sudden and brittle shear failures in reinforced concrete structural members. This thesis presents both experimental and analytical investigations into the behaviour of members subjected to reversed cyclic shear loading, and culminates in the development of a new, rational model to describe this behaviour. In the experimental phase of the research, ten reinforced concrete shell elements were tested under reversed cyclic in-plane shear loads. Data collected by means of several acquisition systems allowed extensive analysis of the experiments, and provided insight into the behaviour of the crack interfaces. In comparison with existing models, such as the Modified Compression Field Theory, it was found that the shear strengths of these reversed cyclically loaded specimens were as much as 25% lower than monotonic predictions. The results of the experimental program informed the development of a new analytical model, the General Crack Component Model (GCCM). The central concept of the GCCM is that the reversed cyclic behaviour of a shear panel depends on the behaviour of multiple crack systems, each with its own constitutive properties. A rigorous framework based on the principles of compatibility and equilibrium was formulated in order to allow for the appropriate combination of the stiffnesses of the three components of the model: concrete, steel, and cracks. The GCCM was validated for reversed cyclic and monotonic loading by comparison with the experimental results as well as data from other researchers. It was shown that the model provides good estimates of the behaviour of reinforced concrete subjected to reversed cyclic loads, and that it can be used as part of a larger structural analysis, ultimately helping engineers to design safer structures and more accurately assess the safety of existing construction.

  20. Evaluating the integrity of the reinforced concrete structure repaired by epoxy injection using simulated transfer function of impact-echo response

    SciTech Connect

    Cheng, Chia-Chi; Yu, Chih-peng; Wu, Jiunn-Hong; Hsu, Keng-Tsan; Ke, Ying-Tsu

    2014-02-18

    Cracks and honeycombs are often found inside reinforced concrete (RC) structure caused by excessive external force, or improper casting of concrete. The repairing method usually involves epoxy injection. The impact-echo method, which is a sensitive for detecting of the interior voids, may not be applicable to assess the integrity of the repaired member as both air and epoxy are less in acoustic impedances. In this study, the repaired RC structure was evaluated by the simulated transfer function of the IE displacement waveform where the R-wave displacement waveform is used as a base of a simulated force-time function. The effect of different thickness of the epoxy layer to the amplitude corresponding to the interface is studied by testing on specimen containing repaired naturally delaminated cracks with crack widths about 1 mm, 3 mm and 5 mm. The impact-echo responses were compared with the drilling cores at the test positions. The results showed the cracks were not fully filled with epoxy when the peak amplitude corresponding to the interface dropped less than 20%. The peak corresponding to the thicker epoxy layer tends to be larger in amplitude. A field study was also performed on a column damaged by earthquake before and after repairing.

  1. An experiment on the use of disposable plastics as a reinforcement in concrete beams

    NASA Technical Reports Server (NTRS)

    Chowdhury, Mostafiz R.

    1992-01-01

    Illustrated here is the concept of reinforced concrete structures by the use of computer simulation and an inexpensive hands-on design experiment. The students in our construction management program use disposable plastic as a reinforcement to demonstrate their understanding of reinforced concrete and prestressed concrete beams. The plastics used for such an experiment vary from plastic bottles to steel reinforced auto tires. This experiment will show the extent to which plastic reinforcement increases the strength of a concrete beam. The procedure of using such throw-away plastics in an experiment to explain the interaction between the reinforcement material and concrete, and a comparison of the test results for using different types of waste plastics are discussed. A computer analysis to simulate the structural response is used to compare the test results and to understand the analytical background of reinforced concrete design. This interaction of using computers to analyze structures and to relate the output results with real experimentation is found to be a very useful method for teaching a math-based analytical subject to our non-engineering students.

  2. Comparative testing of nondestructive examination techniques for concrete structures

    NASA Astrophysics Data System (ADS)

    Clayton, Dwight A.; Smith, Cyrus M.

    2014-03-01

    A multitude of concrete-based structures are typically part of a light water reactor (LWR) plant to provide foundation, support, shielding, and containment functions. Concrete has been used in the construction of nuclear power plants (NPPs) because of three primary properties, its inexpensiveness, its structural strength, and its ability to shield radiation. Examples of concrete structures important to the safety of LWR plants include containment building, spent fuel pool, and cooling towers. Comparative testing of the various NDE concrete measurement techniques requires concrete samples with known material properties, voids, internal microstructure flaws, and reinforcement locations. These samples can be artificially created under laboratory conditions where the various properties can be controlled. Other than NPPs, there are not many applications where critical concrete structures are as thick and reinforced. Therefore, there are not many industries other than the nuclear power plant or power plant industry that are interested in performing NDE on thick and reinforced concrete structures. This leads to the lack of readily available samples of thick and heavily reinforced concrete for performing NDE evaluations, research, and training. The industry that typically performs the most NDE on concrete structures is the bridge and roadway industry. While bridge and roadway structures are thinner and less reinforced, they have a good base of NDE research to support their field NDE programs to detect, identify, and repair concrete failures. This paper will summarize the initial comparative testing of two concrete samples with an emphasis on how these techniques could perform on NPP concrete structures.

  3. Ethical considerations for a better collaboration between architects and structural engineers: design of buildings with reinforced concrete frame systems in earthquake zones.

    PubMed

    Hurol, Yonca

    2014-06-01

    Architects design building structures, although structural design is the profession of structural engineers. Thus, it is better for architects and structural engineers to collaborate starting from the initial phases of the architectural design. However, this is not very common because of the contradictory design processes and value systems held within the two professions. This article provides a platform upon which architects and structural engineers can resolve the value conflicts between them by analysing phases of the structural design of reinforced concrete frame systems in architecture, the criteria of the structural design for each phase and determining the conflicting values for each criterion. The results shown in the article demonstrate that the architectural design of structures is a complex process, which is based on contradictory values and value systems. Finally, the article suggests to architects and structural engineers to use Value Sensitive Design and to choose an appropriate team leader in order to resolve the unethical conflict between them and to avoid any unreasonable decision making. PMID:23700122

  4. Application of Cu-Al-Mn superelastic alloy bars as reinforcement elements in concrete beams

    NASA Astrophysics Data System (ADS)

    Shrestha, Kshitij C.; Araki, Yoshikazu; Nagae, Takuya; Yano, Hayato; Koetaka, Yuji; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Ishida, Kiyohito

    2012-04-01

    Experimental works are done to assess the seismic behavior of concrete beams reinforced with superelastic alloy (SEA) bars. Applicability of newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, have been proposed as partial replacements for conventional steel bars in order to reduce residual deformations in structures during and after intense earthquakes. Four-point reverse-cyclic bending tests were done on 1/3 scale concrete beams comprising three different types of specimens - conventional steel reinforced concrete (ST-RC), SEA reinforced concrete (SEA-RC), and SEA reinforced concrete with pre-tensioning (SEA-PC). The results showed that SEA reinforced concrete beams demonstrated significant enhancement in crack recovery capacity in comparison to steel reinforced beam. Average recovery of cracks for each of the specimens was 21% for ST-RC, 84% for SEA-RC, and 86% for SEA-PC. In addition, SEA-RC and SEA-PC beams demonstrated strong capability of recentering with comparable normalized strength and ductility relative to conventional ST-RC beam specimen. ST-RC beam, on the other hand, showed large residual cracks due to progressive reduction in its re-centering capability with each cycle. Both the SEA-RC and SEA-PC specimens demonstrated superiority of Cu-Al-Mn SEA bars to conventional steel reinforcing bars as reinforcement elements.

  5. Damage assessment in reinforced concrete using nonlinear vibration techniques

    NASA Astrophysics Data System (ADS)

    Van Den Abeele, K.; De Visscher, J.

    2000-07-01

    Reinforced concrete (RC) structures are subject to microcrack initiation and propagation at load levels far below the actual failure load. In this paper, nonlinear vibration techniques are applied to investigate stages of progressive damage in RC beams induced by static loading tests. At different levels of damage, a modal analysis is carried out, assuming the structure to behave linearly. At the same time, measurement of resonant frequencies and damping ratios as function of vibration amplitude are performed using a frequency domain technique as well as a time domain technique. We compare the results of the linear and nonlinear techniques, and value them against the visual damage evaluation.

  6. Tipping point analysis of cracking in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Perry, M.; Livina, V.; Niewczas, P.

    2016-01-01

    In this work, we demonstrate that tipping point analysis of strain data can provide reactive and predictive indicators of cracking and structural transitions in a reinforced concrete system. The method is able to detect trend-driven transitions in a short time series of approximately 2000 datapoints, providing a clear indication of when a concrete beam under gradual bending progresses from a linear to a nonlinear strain response. The method is also able to provide an early warning signal of the appearance of bifurcations, such as cracks, with a forewarning of 200-500 datapoints. The method, which was originally developed for applications in geophysics, shows promising results in the area of structural health monitoring, in particular, for real-time observations of civil constructions.

  7. Experimental investigation of bond in concrete members reinforced with shape memory alloy bars

    NASA Astrophysics Data System (ADS)

    Daghash, S. M.; Sherif, M. M.; Ozbulut, O. E.

    2015-04-01

    Conventional seismic design of reinforced concrete structures relies on yielding of steel reinforcement to dissipate energy while undergoing residual deformations. Therefore, reinforced concrete structures subjected to strong earthquakes experience large permanent displacements and are prone to severe damage or collapse. Shape memory alloys (SMAs) have gained increasing acceptance in recent years for use in structural engineering due to its attractive properties such as high corrosion resistance, excellent re-centering ability, good energy dissipation capacity, and durability. SMAs can undergo large deformations in the range of 6-8% strain and return their original undeformed position upon unloading. Due to their appealing characteristics, SMAs have been considered as an alternative to traditional steel reinforcement in concrete structures to control permanent deformations. However, the behavior of SMAs in combination with concrete has yet to be explored. In particular, the bond strength is important to ensure the composite action between concrete and SMA reinforcements. This study investigates the bond behavior between SMA bars and concrete through pull-out tests. To explore the size effect on bond strength, the tests are performed using various diameters of SMA bars. For the same diameter, the tests are also conducted with different embedment length to assess the effect of embedment length on bond properties of SMA bars. To monitor the slippage of the SMA reinforcement, an optical Digital Image Correlation method is used and the bond-slip curves are obtained.

  8. Fracture Behavior and Properties of Functionally Graded Fiber-Reinforced Concrete

    SciTech Connect

    Roesler, Jeffery; Bordelon, Amanda; Gaedicke, Cristian; Park, Kyoungsoo; Paulino, Glaucio

    2008-02-15

    In concrete pavements, a single concrete mixture design is selected to resist mechanical loading without attempting to adversely affect the concrete pavement shrinkage, ride quality, or noise attenuation. An alternative approach is to design distinct layers within the concrete pavement surface which have specific functions thus achieving higher performance at a lower cost. The objective of this research was to address the structural benefits of functionally graded concrete materials (FGCM) for rigid pavements by testing and modeling the fracture behavior of different combinations of layered plain and synthetic fiber-reinforced concrete materials. Fracture parameters and the post-peak softening behavior were obtained for each FGCM beam configuration by the three point bending beam test. The peak loads and initial fracture energy between the plain, fiber-reinforced, and FGCM signified similar crack initiation. The total fracture energy indicated improvements in fracture behavior of FGCM relative to full-depth plain concrete. The fracture behavior of FGCM depended on the position of the fiber-reinforced layer relative to the starter notch. The fracture parameters of both fiber-reinforced and plain concrete were embedded into a finite element-based cohesive zone model. The model successfully captured the experimental behavior of the FGCMs and predicted the fracture behavior of proposed FGCM configurations and structures. This integrated approach (testing and modeling) demonstrates the viability of FGCM for designing layered concrete pavements system.

  9. Surface treated polypropylene (PP) fibres for reinforced concrete

    SciTech Connect

    López-Buendía, Angel M.; Romero-Sánchez, María Dolores; Climent, Verónica

    2013-12-15

    Surface treatments on a polypropylene (PP) fibre have contributed to the improvement of fibre/concrete adhesion in fibre-reinforced concrete. The treatments to the PP fibre were characterized by contact angle measurements, ATR-IR and XPS to analyse chemical alterations. The surface topography and fibre/concrete interaction were analysed by several microscopic techniques, namely optical petrographic, and scanning electron microscopy. Treatment modified the surface chemistry and topography of the fibre by introducing sodium moieties and created additional fibre surface roughness. Modifications in the fibre surface led to an increase in the adhesion properties between the treated fibres and concrete and an improvement in the mechanical properties of the fibre-reinforced concrete composite as compared to the concrete containing untreated PP fibres. Compatibility with the concrete and increased roughness and mineral surface was also improved by nucleated portlandite and ettringite mineral association anchored on the alkaline PP fibre surface, which is induced during treatment.

  10. Perspective view of threestory reinforced concrete factory. The factory is ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view of three-story reinforced concrete factory. The factory is painted pink with factory windows infilling the structural frame exposed on the exterior facade. On the east facade of the three-story factory is a two-story, seven bay addition that is painted the same tone as the larger factory. The last two bays of the two-story addition are newer. A brick base surrounds both the factory and the addition and runs the entire length of the building on Clay Ave. and Morrow St. (Duplicate Color view of HAER MI-334-1) - Ivan Doverspike Company, 1925 Clay Avenue, Detroit, MI

  11. Perspective view of threestory reinforced concrete factory. The factory is ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view of three-story reinforced concrete factory. The factory is painted pink with factory windows infilling the structural frame exposed on the exterior facade. On the east facade of the three-story factory is a two-story, seven bay addition that is painted the same tone as the larger factory. The last two bays of the two-story addition are newer. A brick base surrounds both the factory and the addition and runs the entire length of the building on Clay Ave. and Morrow St - Ivan Doverspike Company, 1925 Clay Avenue, Detroit, MI

  12. Investigation of rectangular concrete columns reinforced or prestressed with fiber reinforced polymer (FRP) bars or tendons

    NASA Astrophysics Data System (ADS)

    Choo, Ching Chiaw

    Fiber reinforced polymer (FRP) composites have been increasingly used in concrete construction. This research focused on the behavior of concrete columns reinforced with FRP bars, or prestressed with FRP tendons. The methodology was based the ultimate strength approach where stress and strain compatibility conditions and material constitutive laws were applied. Axial strength-moment (P-M) interaction relations of reinforced or prestressed concrete columns with FRP, a linearly-elastic material, were examined. The analytical results identified the possibility of premature compression and/or brittle-tension failure occurring in FRP reinforced and prestressed concrete columns where sudden and explosive type failures were expected. These failures were related to the rupture of FRP rebars or tendons in compression and/or in tension prior to concrete reaching its ultimate strain and strength. The study also concluded that brittle-tension failure was more likely to occur due to the low ultimate tensile strain of FRP bars or tendons as compared to steel. In addition, the failures were more prevalent when long term effects such as creep and shrinkage of concrete, and creep rupture of FRP were considered. Barring FRP failure, concrete columns reinforced with FRP, in some instances, gained significant moment resistance. As expected the strength interaction of slender steel or FRP reinforced concrete columns were dependent more on column length rather than material differences between steel and FRP. Current ACI minimum reinforcement ratio for steel (rhomin) reinforced concrete columns may not be adequate for use in FRP reinforced concrete columns. Design aids were developed in this study to determine the minimum reinforcement ratio (rhof,min) required for rectangular reinforced concrete columns by averting brittle-tension failure to a failure controlled by concrete crushing which in nature was a less catastrophic and more gradual type failure. The proposed method using rhof

  13. Evaluation of post-fire strength of concrete flexural members reinforced with glass fiber reinforced polymer (GFRP) bars

    NASA Astrophysics Data System (ADS)

    Ellis, Devon S.

    Owing to their corrosion resistance and superior strength to weight ratio, there has been, over the past two decades, increased interest in the use of fiber-reinforced polymer (FRP) reinforcing bars in reinforced concrete structural members. The mechanical behavior of FRP reinforcement differs from that of steel reinforcement. For example, FRP reinforcement exhibit a linear stress-strain behavior until the bar ruptures and the strength, stiffness and bond properties of FRP reinforcement are affected more adversely by elevated temperatures. All structures are subject to the risk of damage by fire and fires continue to be a significant cause of damage to structures. Many structures do not collapse after being exposed to fire. The safety of the structure for any future use is dependent on the ability to accurately estimate the post-fire load capacity of the structure. Assuming that the changes, due to fire exposure, in the mechanical behavior of the GFRP reinforcing bar and concrete, and the bond between the reinforcing bar and the concrete are understood, an analytical procedure for estimating the post-fire strength of GFRP reinforced concrete flexural elements can be developed. This thesis investigates the changes in: a) tensile properties and bond of GFRP bars; and b) the flexural behavior of GFRP reinforced concrete beams flexural after being exposed to elevated temperatures up to 400°C and cooled to ambient temperature. To this end, twelve tensile tests, twelve pullout bond tests and ten four-point beam tests were performed. The data from the tests were used to formulate analytical procedures for evaluating the post-fire strength of GFRP reinforced concrete beams. The procedure produced conservative results when compared with the experimental data. In general, the residual tensile strength and modulus of elasticity of GFRP bars decrease as the exposure temperature increases. The loss in properties is however, smaller than that observed by other researchers when

  14. Natural Corrosion Inhibitors for Steel Reinforcement in Concrete — a Review

    NASA Astrophysics Data System (ADS)

    Raja, Pandian Bothi; Ghoreishiamiri, Seyedmojtaba; Ismail, Mohammad

    2015-04-01

    Reinforced concrete is one of the widely used construction materials for bridges, buildings, platforms and tunnels. Though reinforced concrete is capable of withstanding a large range of severe environments including marine, industrial and alpine conditions, there are still a large number of failures in concrete structures for many reasons. Either carbonation or chloride attack is the main culprit which is due to depassivation of reinforced steel and subsequently leads to rapid steel corrosion. Among many corrosion prevention measures, application of corrosion inhibitors play a vital role in metal protection. Numerous range of corrosion inhibitors were reported for concrete protection that were also used commercially in industries. This review summarizes the application of natural products as corrosion inhibitors for concrete protection and also scrutinizes various factors influencing its applicability.

  15. Phyllanthus muellerianus and C6H15NO3 synergistic effects on 0.5 M H2SO4-immersed steel-reinforced concrete: Implication for clean corrosion-protection of wind energy structures in industrial environment

    NASA Astrophysics Data System (ADS)

    Okeniyi, Joshua Olusegun; Omotosho, Olugbenga Adeshola; Popoola, Abimbola Patricia Idowu; Loto, Cleophas Akintoye

    2016-07-01

    This paper investigates Phyllanthus muellerianus leaf-extract and C6H15NO3 (triethanolamine: TEA) synergistic effects on reinforcing-steel corrosion-inhibition and the compressive-strength of steel-reinforced concrete immersed in 0.5 M H2SO4. This is to assess suitability of the synergistic admixture usage for wind-energy steel-reinforced concrete structures designed for industrial environments. Steel-reinforced concrete specimens were admixed with individual and synergistic designs of Phyllanthus muellerianus leaf-extract and C6H15NO3 admixtures and immersed in the 0.5 M H2SO4. Electrochemical monitoring of corrosion potential, as per ASTM C876-91 R99, and corrosion current were obtained and statistically analysed, as per ASTM G16-95 R04, for modelling noise resistance. Post-immersion compressive-strength testing then followed, as per ASTM C39/C39M-03, for detailing the admixture effect on load-bearing strength of the steel-reinforced concrete specimens. Results showed that while individual Phyllanthus muellerianus leaf-extract concentrations exhibited better inhibition-efficiency performance than C6H15NO3, synergistic additions of C6H15NO3 to Phyllanthus muellerianus leaf-extract improved steel-rebar corrosion-inhibition. Thus, 6 g Phyllanthus muellerianus + 2 g C6H15NO3 synergistically improved inhibition-efficiency to η = 84.17%, from η = 55.28% by the optimal chemical or from η = 74.72% by the optimal plant-extract admixtures. The study also established that improved compressive strength of steel-reinforced concrete with acceptable inhibition of the steel-rebar corrosion could be attained through optimal combination of the Phyllanthus muellerianus leaf-extract and C6H15NO3 admixtures.

  16. 9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  17. 2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  18. 3. SOUTH FLAME DEFLECTOR FROM THE REINFORCED CONCRETE ROOF, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. SOUTH FLAME DEFLECTOR FROM THE REINFORCED CONCRETE ROOF, VIEW TOWARDS EAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  19. 3. View of reinforced concrete and through truss eleveated rightofway, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. View of reinforced concrete and through truss eleveated right-of-way, Shaker Rapid Transit, at E. 80th St in Cleveland. Constructed ca. 1920. - Shaker Heights Rapid Transit Line, Cleveland, Cuyahoga County, OH

  20. Detail view of the reinforced concrete viaduct over the Union ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail view of the reinforced concrete viaduct over the Union Pacific Railroad corridor, view looking east - Grande Ronde River Bridge, Sprnning Grande Ronde River on Old Oregon Trail Highway (Oregon Route 6), La Grande, Union County, OR

  1. 4. EAST ELEVATION. TOWER, OF REINFORCED CONCRETE CONSTRUCTION, WAS BUILT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. EAST ELEVATION. TOWER, OF REINFORCED CONCRETE CONSTRUCTION, WAS BUILT IN 1944 TO SPEED UP THE FUELING OF LOCOMOTIVE TENDERS DURING WARTIME. - Collinwood Railroad Yard Coal Tipple, Between East 146th Street & East 152nd Street, Cleveland, Cuyahoga County, OH

  2. IET. Exhaust stack foundation under construction. Reinforced concrete footings for ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    IET. Exhaust stack foundation under construction. Reinforced concrete footings for duct at right of stack. Foundation is in octagonal shape. Date: October 29, 1954. INEEL negative no. 12711 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  3. 10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEASTERN EDGE, ACCESS RAMPS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEASTERN EDGE, ACCESS RAMPS AT LEFT AND RIGHT, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  4. 11. REINFORCED CONCRETE SLAB ROOF FROM THE SOUTHERN EDGE, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. REINFORCED CONCRETE SLAB ROOF FROM THE SOUTHERN EDGE, VIEW TOWARDS NORTH. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  5. 12. REINFORCED CONCRETE SLAB ROOF FROM NORTHEASTERN EDGE, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. REINFORCED CONCRETE SLAB ROOF FROM NORTHEASTERN EDGE, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  6. 7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR AT RIGHT, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  7. 13. REINFORCED CONCRETE SLAB ROOF FROM SOUTHWESTERN EDGE, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. REINFORCED CONCRETE SLAB ROOF FROM SOUTHWESTERN EDGE, VIEW TOWARDS NORTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  8. 13. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  9. 9. REINFORCED CONCRETE SLAB ROOF FROM NORTHEAST EDGE, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. REINFORCED CONCRETE SLAB ROOF FROM NORTHEAST EDGE, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  10. 11. REINFORCED CONCRETE SLAB ROOF, FLAME DEFLECTOR AT RIGHT, CONTROL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. REINFORCED CONCRETE SLAB ROOF, FLAME DEFLECTOR AT RIGHT, CONTROL BUILDING B AT FAR CENTER RIGHT. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  11. 10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  12. 12. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW TOWARDS SOUTH. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  13. 8. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, ACCESS RAMP ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, ACCESS RAMP IN FOREGROUND, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  14. 11. REINFORCED CONCRETE SLAB ROOF, GUARD RAIL AT CENTER, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. REINFORCED CONCRETE SLAB ROOF, GUARD RAIL AT CENTER, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  15. Application of bamboo for flexural and shear reinforcement in concrete beams

    NASA Astrophysics Data System (ADS)

    Schneider, Nathan Alan

    As the developing world is industrializing and people migrate to cities, the need for infrastructure is growing quickly and concrete has become one of the most widely used construction materials. One poor construction practice observed widely across the developing world is the minimal use of reinforcement for concrete structures due to the high cost of steel. As a low-cost, high-performance material with good mechanical properties, bamboo has been investigated as an alternative to steel for reinforcing concrete. The goal of this research is to add to the knowledge base of bamboo reinforced concrete (BRC) by investigating a unique stirrup design and testing the lap-splicing of flexural bamboo reinforcement in concrete beams. Component tests on the mechanical properties of Moso bamboo (Phyllostachys edulis) were performed, including tensile tests and pull-out tests. The results of the component tests were used to design and construct 13 BRC beams which were tested under monotonic gravity loading in 3 and 4-point bending tests. Three types of beams were designed and tested, including shear controlled, flexure controlled, and lap-spliced flexure controlled beams. The test results indicated that bamboo stirrups increased unreinforced concrete beam shear capacities by up to 259%. The flexural bamboo increased beam capacities by up to 242% with an optimal reinforcement ratio of up to 3.9%, assuming sufficient shear capacity. Limitations of the bamboo reinforcement included water absorption as well as poor bonding capability to the concrete. The test results show that bamboo is a viable alternative to steel as tensile reinforcement for concrete as it increases the ultimate capacity of the concrete, allows for high deflections and cracks, and provides warning of impending structural failure.

  16. Computational models for the nonlinear analysis of reinforced concrete plates

    NASA Technical Reports Server (NTRS)

    Hinton, E.; Rahman, H. H. A.; Huq, M. M.

    1980-01-01

    A finite element computational model for the nonlinear analysis of reinforced concrete solid, stiffened and cellular plates is briefly outlined. Typically, Mindlin elements are used to model the plates whereas eccentric Timoshenko elements are adopted to represent the beams. The layering technique, common in the analysis of reinforced concrete flexural systems, is incorporated in the model. The proposed model provides an inexpensive and reasonably accurate approach which can be extended for use with voided plates.

  17. Monitoring the Corrosion Process of Reinforced Concrete Using BOTDA and FBG Sensors

    PubMed Central

    Mao, Jianghong; Chen, Jiayun; Cui, Lei; Jin, Weiliang; Xu, Chen; He, Yong

    2015-01-01

    Expansion and cracking induced by the corrosion of reinforcement concrete is the major factor in the failure of concrete durability. Therefore, monitoring of concrete cracking is critical for evaluating the safety of concrete structures. In this paper, we introduce a novel monitoring method combining Brillouin optical time domain analysis (BOTDA) and fiber Bragg grating (FBG), based on mechanical principles of concrete expansion cracking. BOTDA monitors concrete expansion and crack width, while FBG identifies the time and position of cracking. A water-pressure loading simulation test was carried out to determine the relationship between fiber strain, concrete expansion and crack width. An electrical accelerated corrosion test was also conducted to evaluate the ability of this novel sensor to monitor concrete cracking under practical conditions. PMID:25884790

  18. Monitoring the corrosion process of reinforced concrete using BOTDA and FBG sensors.

    PubMed

    Mao, Jianghong; Chen, Jiayun; Cui, Lei; Jin, Weiliang; Xu, Chen; He, Yong

    2015-01-01

    Expansion and cracking induced by the corrosion of reinforcement concrete is the major factor in the failure of concrete durability. Therefore, monitoring of concrete cracking is critical for evaluating the safety of concrete structures. In this paper, we introduce a novel monitoring method combining Brillouin optical time domain analysis (BOTDA) and fiber Bragg grating (FBG), based on mechanical principles of concrete expansion cracking. BOTDA monitors concrete expansion and crack width, while FBG identifies the time and position of cracking. A water-pressure loading simulation test was carried out to determine the relationship between fiber strain, concrete expansion and crack width. An electrical accelerated corrosion test was also conducted to evaluate the ability of this novel sensor to monitor concrete cracking under practical conditions. PMID:25884790

  19. Feasibility of Cu-Al-Mn superelastic alloy bars as reinforcement elements in concrete beams

    NASA Astrophysics Data System (ADS)

    Shrestha, Kshitij C.; Araki, Yoshikazu; Nagae, Takuya; Koetaka, Yuji; Suzuki, Yusuke; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Ishida, Kiyohito

    2013-02-01

    Experimental and numerical works are reported to assess the cyclic response of concrete beams reinforced with superelastic alloy (SEA) bars. The feasibility of newly developed Cu-Al-Mn SEA bars, characterized by large recovery strain, low material cost and high machinability, is examined as partial replacements for conventional steel bars, in order to reduce residual cracks in structures during and after intense earthquakes. Four-point reverse cyclic bending tests were done on one-third scale concrete beams comprising three different types of specimens—conventional steel reinforced concrete, SEA reinforced concrete and SEA reinforced concrete (RC) with pre-tensioning. The results showed that SEA reinforced concrete beams demonstrated strong recentering capability and significant enhancement in crack recovery capacity, in comparison to steel reinforced beams. Furthermore, corresponding finite element models were generated to simulate the experimental observations. Both the experimental observations and finite element computations illustrated the superiority of SEA bars to conventional steel bars in providing RC beam specimens with recentering and crack recovery capabilities.

  20. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths (τ (app)) and slip coefficient (β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle (ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  1. Bond characteristics of steel fiber and deformed reinforcing steel bar embedded in steel fiber reinforced self-compacting concrete (SFRSCC)

    NASA Astrophysics Data System (ADS)

    Aslani, Farhad; Nejadi, Shami

    2012-09-01

    Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of the self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, fracture toughness and cracking. Although the available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates the bond characteristics between steel fiber and SCC firstly. Based on the available experimental results, the current analytical steel fiber pullout model (Dubey 1999) is modified by considering the different SCC properties and different fiber types (smooth, hooked) and inclination. In order to take into account the effect of fiber inclination in the pullout model, apparent shear strengths ( τ ( app)) and slip coefficient ( β) are incorporated to express the variation of pullout peak load and the augmentation of peak slip as the inclined angle increases. These variables are expressed as functions of the inclined angle ( ϕ). Furthurmore, steel-concrete composite floors, reinforced concrete floors supported by columns or walls and floors on an elastic foundations belong to the category of structural elements in which the conventional steel reinforcement can be partially replaced by the use of steel fibers. When discussing deformation capacity of structural elements or civil engineering structures manufactured using SFRSCC, one must be able to describe thoroughly both the behavior of the concrete matrix reinforced with steel fibers and the interaction between this composite matrix and discrete steel reinforcement of the conventional type. However, even though the knowledge on bond behavior is essential for evaluating the overall behavior of structural components containing reinforcement and steel fibers

  2. Strength and deformability of concrete beams reinforced by non-metallic fiber and composite rebar

    NASA Astrophysics Data System (ADS)

    Kudyakov, K. L.; Plevkov, V. S.; Nevskii, A. V.

    2015-01-01

    Production of durable and high-strength concrete structures with unique properties has always been crucial. Therefore special attention has been paid to non-metallic composite and fiber reinforcement. This article describes the experimental research of strength and deformability of concrete beams with dispersed and core fiber-based reinforcement. As composite reinforcement fiberglass reinforced plastic rods with diameters 6 mm and 10 mm are used. Carbon and basalt fibers are used as dispersed reinforcement. The developed experimental program includes designing and production of flexural structures with different parameters of dispersed fiber and composite rebar reinforcement. The preliminary testing of mechanical properties of these materials has shown their effectiveness. Structures underwent bending testing on a special bench by applying flexural static load up to complete destruction. During the tests vertical displacements were recorded, as well as value of actual load, slippage of rebars in concrete, crack formation. As a result of research were obtained structural failure and crack formation graphs, value of fracture load and maximum displacements of the beams at midspan. Analysis of experimental data showed the effectiveness of using dispersed reinforcement of concrete and the need for prestressing of fiberglass composite rebar.

  3. Application of artificial neural networks to predict the deflections of reinforced concrete beams

    NASA Astrophysics Data System (ADS)

    Kaczmarek, Mateusz; Szymańska, Agnieszka

    2016-06-01

    Nonlinear structural mechanics should be taken into account in the practical design of reinforced concrete structures. Cracking is one of the major sources of nonlinearity. Description of deflection of reinforced concrete elements is a computational problem, mainly because of the difficulties in modelling the nonlinear stress-strain relationship of concrete and steel. In design practise, in accordance with technical rules (e.g., Eurocode 2), a simplified approach for reinforced concrete is used, but the results of simplified calculations differ from the results of experimental studies. Artificial neural network is a versatile modelling tool capable of making predictions of values that are difficult to obtain in numerical analysis. This paper describes the creation and operation of a neural network for making predictions of deflections of reinforced concrete beams at different load levels. In order to obtain a database of results, that is necessary for training and testing the neural network, a research on measurement of deflections in reinforced concrete beams was conducted by the authors in the Certified Research Laboratory of the Building Engineering Institute at Wrocław University of Science and Technology. The use of artificial neural networks is an innovation and an alternative to traditional methods of solving the problem of calculating the deflections of reinforced concrete elements. The results show the effectiveness of using artificial neural network for predicting the deflection of reinforced concrete beams, compared with the results of calculations conducted in accordance with Eurocode 2. The neural network model presented in this paper can acquire new data and be used for further analysis, with availability of more research results.

  4. Determination of chlorine, sulfur and carbon in reinforced concrete structures by double-pulse laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Labutin, Timur A.; Popov, Andrey M.; Zaytsev, Sergey M.; Zorov, Nikita B.; Belkov, Mikhail V.; Kiris, Vasilii V.; Raikov, Sergey N.

    2014-09-01

    Accurate and reliable quantitative determination of non-metal corrosion agents in concrete is still an actual task of analytical use of LIBS. Two double-pulse LIBS systems were tested as a tool for the determination of chlorine, sulfur and carbon in concretes. Both systems had collinear configuration; a laboratory setup was equipped with an ICCD and two lasers (355/532 nm + 540 nm), but a CCD was a detector for a mobile system with one laser (1064 nm). Analytical lines of Cl I at 837.59 nm, S I at 921 nm and C I at 247.86 nm were used to plot calibration curves. Optimal interpulse delays for the laboratory setup were 4 μs for chlorine and 2.8 μs for carbon, while an interpulse delay of 2 μs was optimal for chlorine and sulfur determination with the mobile system. We suggested the normalization of the Cl I line at 837.59 nm to the Mg II line at 279.08 nm (visible at 837.23 nm in the third order) to compensate for pulse-to-pulse fluctuations of chlorine lines. It provided the decrease of the detection limit of chlorine from 400 ppm to 50 ppm. Therefore, we reported that LIBS can be used to determine main corrosive active substances under ambient conditions in concrete below critical threshold values. Moreover, the application of the mobile system for in-situ qualitative assessment of corrosion way of a steel cage of a swimming pool dome was also demonstrated. It was found that chloride corrosion due to the disinfection of water was the main way for corrosion of the open part steel and the steel rebar inside the concrete.

  5. Modeling of concrete cracking due to corrosion process of reinforcement bars

    SciTech Connect

    Bossio, Antonio; Monetta, Tullio; Bellucci, Francesco; Lignola, Gian Piero; Prota, Andrea

    2015-05-15

    The reinforcement corrosion in Reinforced Concrete (RC) is a major reason of degradation for structures and infrastructures throughout the world leading to their premature deterioration before design life was attained. The effects of corrosion of reinforcement are: (i) the reduction of the cross section of the bars, and (ii) the development of corrosion products leading to the appearance of cracks in the concrete cover and subsequent cover spalling. Due to their intrinsic complex nature, these issues require an interdisciplinary approach involving both material science and structural design knowledge also in terms on International and National codes that implemented the concept of durability and service life of structures. In this paper preliminary FEM analyses were performed in order to simulate pitting corrosion or general corrosion aimed to demonstrate the possibility to extend the results obtained for a cylindrical specimen, reinforced by a single bar, to more complex RC members in terms of geometry and reinforcement. Furthermore, a mechanical analytical model to evaluate the stresses in the concrete surrounding the reinforcement bars is proposed. In addition, a sophisticated model is presented to evaluate the non-linear development of stresses inside concrete and crack propagation when reinforcement bars start to corrode. The relationships between the cracking development (mechanical) and the reduction of the steel section (electrochemical) are provided. Finally, numerical findings reported in this paper were compared to experimental results available in the literature and satisfactory agreement was found.

  6. Short Time Impulse Response Function (STIRF) for automatic evaluation of the variation of the dynamic parameters of reinforced concrete framed structures during strong earthquakes.

    NASA Astrophysics Data System (ADS)

    Carlo Ponzo, Felice; Ditommaso, Rocco

    2015-04-01

    the results provided in this study, the methodology seems to be able to evaluate fast variations (over time) of dynamic parameters of a generic reinforced concrete framed structure. Further analyses are necessary to better calibrate the length of the moving time-window (in order to minimize the spurious frequency within each Interferometric Response Function evaluated on both weak and strong motion phases) and to verify the possibility to use the STIRF to analyse the nonlinear behaviour of general systems. Acknowledgements This study was partially funded by the Italian Civil Protection Department within the project DPC-RELUIS 2014 - RS4 ''Seismic observatory of structures and health monitoring''. References R. Ditommaso, F.C. Ponzo (2015). Automatic evaluation of the fundamental frequency variations and related damping factor of reinforced concrete framed structures using the Short Time Impulse Response Function (STIRF). Engineering Structures, 82 (2015), 104-112. http://dx.doi.org/10.1016/j.engstruct.2014.10.023.

  7. Analysis of concrete targets with different kinds of reinforcements subjected to blast loading

    NASA Astrophysics Data System (ADS)

    Oña, M.; Morales-Alonso, G.; Gálvez, F.; Sánchez-Gálvez, V.; Cendón, D.

    2016-05-01

    In this paper we describe an experimental campaign carried out to study and analyse the behaviour of concrete slabs when subjected to blast loading. Four different types of concrete have been tested: normal strength concrete with steel rebar, normal strength concrete with steel rebar retrofitted with Kevlar coating, steel fibre reinforced concrete (SFRC) and polypropylene fibre reinforced concrete (PFRC). The major asset of the experimental setup used is that it allows to subject up to four specimens to the same blast load what, besides being cost effective, makes possible to have a measure of the experimental scatter. The results of SFRC and PFRC concretes have been analysed by using a previously developed material model for the numerical simulation of concrete elements subjected to blast. The experimental campaign and preliminary results of this numerical analysis show how the high strain rates, in spite of improving the mechanical properties of these kinds of fibre reinforced concretes, lead to an embrittlement of the material, which may be dangerous from the point of view of the structural behaviour.

  8. Application of Composite Mechanics to Composites Enhanced Concrete Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Gotsis, Pascal K.

    2006-01-01

    A new and effective method is described to design composites to repair damage or enhance the overload strength of concrete infrastructures. The method is based on composite mechanics which is available in computer codes. It is used to simulate structural sections made from reinforced concrete which are typical in infrastructure as well as select reinforced concrete structures. The structural sections are represented by a number of layers through the thickness where different layers are used in concrete, and for the composite. The reinforced concrete structures are represented with finite elements where the element stiffness parameters are from the structural sections which are represented by composite mechanics. The load carrying capability of the structure is determined by progressive structural fracture. Results show up to 40 percent improvements for damage and for overload enhancement with relatively small laminate thickness for the structural sections and up to three times for the composite enhanced select structures (arches and domes).

  9. Non-traditional shape GFRP rebars for concrete reinforcement

    NASA Astrophysics Data System (ADS)

    Claure, Guillermo G.

    The use of glass-fiber-reinforced-polymer (GFRP) composites as internal reinforcement (rebars) for concrete structures has proven to be an alternative to traditional steel reinforcement due to significant advantages such as magnetic transparency and, most importantly, corrosion resistance equating to durability and structural life extension. In recent years, the number of projects specifying GFRP reinforcement has increased dramatically leading the construction industry towards more sustainable practices. Typically, GFRP rebars are similar to their steel counterparts having external deformations or surface enhancements designed to develop bond to concrete, as well as having solid circular cross-sections; but lately, the worldwide composites industry has taken advantage of the pultrusion process developing GFRP rebars with non-traditional cross-sectional shapes destined to optimize their mechanical, physical, and environmental attributes. Recently, circular GFRP rebars with a hollow-core have also become available. They offer advantages such as a larger surface area for improved bond, and the use of the effective cross-sectional area that is engaged to carry load since fibers at the center of a solid cross-section are generally not fully engaged. For a complete understanding of GFRP rebar physical properties, a study on material characterization regarding a quantitative cross-sectional area analysis of different GFRP rebars was undertaken with a sample population of 190 GFRP specimens with rebar denomination ranging from #2 to #6 and with different cross-sectional shapes and surface deformations manufactured by five pultruders from around the world. The water displacement method was applied as a feasible and reliable way to conduct the investigation. In addition to developing a repeatable protocol for measuring cross-sectional area, the objectives of establishing critical statistical information related to the test methodology and recommending improvements to

  10. Effect of hot-dry environment on fiber-reinforced self-compacting concrete

    NASA Astrophysics Data System (ADS)

    Tioua, Tahar; Kriker, Abdelouahed; Salhi, Aimad; Barluenga, Gonzalo

    2016-07-01

    Drying shrinkage can be a major reason for the deterioration of concrete structures. Variation in ambient temperature and relative humidity cause changes in the properties of hardened concrete which can affect their mechanical and drying shrinkage characteristics. The present study investigated mechanical strength and particularly drying shrinkage properties of self-compacting concretes (SCC) reinforced with date palm fiber exposed to hot and dry environment. In this study a total of nine different fibers reinforced self compacting concrete (FRSCC) mixtures and one mixture without fiber were prepared. The volume fraction and the length of fibers reinforcement were 0.1-0.2-0.3% and 10-20-30 mm. It was observed that drying shrinkage lessened with adding low volumetric fraction and short length of fibers in curing condition (T = 20 °C and RH = 50 ± 5 %), but increased in hot and dry environment.

  11. Nondestructive inspection of corrosion and delamination at the concrete-steel reinforcement interface

    NASA Astrophysics Data System (ADS)

    Miller, Tri Huu

    The proposed study explores the feasibility of detecting and quantifying corrosion and delamination (physical separation) at the interface between reinforcing steel bars and concrete using ultrasonic guided waves. The problem of corrosion of the reinforcing steel in structures has increased significantly in recent years. The emergence of this type of concrete deterioration, which was first observed in marine structures and chemical manufacturing plants, coincided with the increased applications of deicing salts (sodium and calcium chlorides) to roads and bridges during winter months in those states where ice and snow are of major concern. Concrete is strengthened by the inclusion of the reinforcement steel such as deformed or corrugated steel bars. Bonding between the two materials plays a vital role in maximizing performance capacity of the structural members. Durability of the structure is of concern when it is exposed to aggressive environments. Corrosion of reinforcing steel has led to premature deterioration of many concrete members before their design life is attained. It is therefore, important to be able to detect and measure the level of corrosion in reinforcing steel or delamination at the interface. The development and implementation of damage detection strategies, and the continuous health assessment of concrete structures then become a matter of utmost importance. The ultimate goal of this research is to develop a nondestructive testing technique to quantify the amount of corrosion in the reinforcing steel. The guided mechanical wave approach has been explored towards the development of such methodology. The use of an embedded ultrasonic network for monitoring corrosion in real structures is feasible due to its simplicity. The ultrasonic waves, specifically cylindrical guided waves can p ropagate a long distance along the reinforcing steel bars and are found to be sensitive to the interface conditions between steel bars and concrete. Ultrasonic

  12. Seismic analysis of a reinforced concrete containment vessel model

    SciTech Connect

    RANDY,JAMES J.; CHERRY,JEFFERY L.; RASHID,YUSEF R.; CHOKSHI,NILESH

    2000-02-03

    Pre-and post-test analytical predictions of the dynamic behavior of a 1:10 scale model Reinforced Concrete Containment Vessel are presented. This model, designed and constructed by the Nuclear Power Engineering Corp., was subjected to seismic simulation tests using the high-performance shaking table at the Tadotsu Engineering Laboratory in Japan. A group of tests representing design-level and beyond-design-level ground motions were first conducted to verify design safety margins. These were followed by a series of tests in which progressively larger base motions were applied until structural failure was induced. The analysis was performed by ANATECH Corp. and Sandia National Laboratories for the US Nuclear Regulatory Commission, employing state-of-the-art finite-element software specifically developed for concrete structures. Three-dimensional time-history analyses were performed, first as pre-test blind predictions to evaluate the general capabilities of the analytical methods, and second as post-test validation of the methods and interpretation of the test result. The input data consisted of acceleration time histories for the horizontal, vertical and rotational (rocking) components, as measured by accelerometers mounted on the structure's basemat. The response data consisted of acceleration and displacement records for various points on the structure, as well as time-history records of strain gages mounted on the reinforcement. This paper reports on work in progress and presents pre-test predictions and post-test comparisons to measured data for tests simulating maximum design basis and extreme design basis earthquakes. The pre-test analyses predict the failure earthquake of the test structure to have an energy level in the range of four to five times the energy level of the safe shutdown earthquake. The post-test calculations completed so far show good agreement with measured data.

  13. Designing concrete EDS maglev guideways: Power losses in metallic reinforcement

    SciTech Connect

    Beto, D.; Plotkin, D.

    1997-05-01

    Conventional reinforced concrete designs will have to be altered when designing a guideway for a maglev using an electrodynamically suspended (EDS) propulsion system. This type of propulsion system generates large magnetic fields that will develop magnetically induced, circulating eddy currents in any conventional steel reinforcement in close proximity to the magnets. These eddy currents, if large enough, may produce significant power losses that could adversely effect operation of the system. This paper presents a method and explanation for civil engineers to use for estimating the power losses due to the presence of metallic reinforcement. This procedure may be used to help guide future designs in the selection and placement of reinforcing material.

  14. Geopolymer concrete for structural use: Recent findings and limitations

    NASA Astrophysics Data System (ADS)

    Nuruddin, M. F.; Malkawi, A. B.; Fauzi, A.; Mohammed, B. S.; Almattarneh, H. M.

    2016-06-01

    Geopolymer binders offer a possible solution for several problems that facing the current cement industry. These binders exhibit similar or better engineering properties compared to cement and can utilize several types of waste materials. This paper presents the recent research progress regarding the structural behaviour of reinforced geopolymer concrete members including beams, columns and slabs. The reported results showed that the structural behaviour of the reinforced geopolymer concrete members is similar to the known behaviour of the ordinary reinforced concrete members. In addition, the currently available standards have been conservatively used for analysis and designing of reinforced geopolymer concrete structures. On the other hand, the main hurdles facing the spread of geopolymer concrete was the absence of standards and the concerns about the long-term properties. Other issues included the safety, cost and liability.

  15. Finite Element Modeling of Reinforced Concrete Corners Under Opening Bending Moment

    NASA Astrophysics Data System (ADS)

    Bansal, N.; Kwatra, N.; Kanwar, V. S.

    2013-03-01

    In the past few years, there has been growing use of finite element method for analysis of RCC structures to eliminate the expensive testing. However, validations of numerical models are instrumental towards making models reliable, which is, fundamental towards truly predictive prototyping. Keeping this in view, paper presents the results of numerical study of Reinforced Concrete Corners under opening moments using general-purpose finite element analysis software (ANSYS) and the comparison of results to the experimental results available in the literature [Singh and Kaushik, J Inst Eng (India), 84:201-209, 2003]. The Load deflection behaviour obtained is compared with the results corresponding to four different reinforcement detailing investigated experimentally [Singh and Kaushik, J Inst Eng (India), 84:201-209, 2003]. Details of the FE modeling of Reinforced Concrete Corners with four different reinforcement detailing have been presented. The best reinforcement detailing of Reinforced Concrete Corners on the basis of load deflection behaviour has been judged and advocated further on the basis of finite element analysis. The second phase of the study, investigates the effect of diameter of main steel, grade of concrete and spacing of shear reinforcement on load deformation behavior of the corners under opening bending moments.

  16. The effect of chloride ion concentration gradients on the initiation of localized corrosion of steel in reinforced concrete

    SciTech Connect

    Kane, M.J.; Brown, R.

    1994-12-31

    It has been established that for steel reinforced concrete roads treated with deicing salts or exposed to a marine environment, chloride ions are introduced at the surface of the concrete structure. Two models were discussed in which chloride ion concentration gradients would form in a steel reinforced concrete structure. Electrochemical testing to investigate the models was conducted on plain carbon steel specimens in a simulated concrete environment of saturated calcium hydroxide solution with varying concentrations of sodium chloride. The varying chloride ion concentrations promoted open circuit potential shifts. These potential shifts may lead to galvanic corrosion effects depending on the chloride ion concentration gradients in the structure.

  17. Ultimate pressure capacity of reinforced and prestressed concrete containments

    SciTech Connect

    Sharma, S.; Wang, Y.K.; Reich, M.

    1985-05-01

    This report presents the results of an in-depth evaluation of current modeling techniques and analysis procedures for determining ultimate pressure capacity of reinforced and prestressed concrete containments. The material used for describing the nonlinear material behavior of concrete and steel are reviewed in detail. Special attention is focused on post-cracking behavior of concrete which controls one of the containment failure modes, i.e., the shear failure. Various finite element idealizations utilized for containment analysis are reviewed. The effects of major assumptions pertaining to containment geometry, basemat restraint, finite element mesh, rebar locations and orientations, are evaluated. Finally, failure analyses of two selected reinforced and prestressed concrete containments are performed and results are compared with those presented in the literature. 27 refs., 25 figs.

  18. Blast impact behaviour of concrete with different fibre reinforcement

    NASA Astrophysics Data System (ADS)

    Drdlová, Martina; Čechmánek, René; Řídký, Radek

    2015-09-01

    The paper summarizes the results of the development of special concrete intended for the explosion resistance applications, with the emphasis on minimal secondary fragments formation at the explosion. The fine-grained concrete matrix has been reinforced by various types of short dispersed fibers (metallic, mineral and polymer) of different sizes and by their combination and the effect of the fibre reinforcement on the physico-mechanical properties and blast resistance was observed. The concrete prism specimens have been subjected to the determination of mechanical parameters (compressive and flexural strength at quasi-static load). The blast tests were conducted on the slab specimens prepared from selected mixtures. The material characteristics and explosion test data have been used for numerical investigation, which defined the optimal wall composition and dimensions of the concrete element which should resist the explosion defined by type, size, weight and placement of the blast. In the next step the test elements resistance was verified by real explosion test.

  19. Polymer concrete reinforced with recycled-tire fibers: Mechanical properties

    NASA Astrophysics Data System (ADS)

    Martínez-Cruz, E.; Martínez-Barrera, G.; Martínez-López, M.

    2013-06-01

    Polymer Concrete was reinforced with recycled-tire fibers in order to improve the compressive and flexural strength. Polymer concrete specimens were prepared with 70% of silicious sand, 30% of polyester resin and various fiber concentrations (0.3, 0.6, 0.9 and 1.2 vol%). The results show increment of 50% in average of the compressive and flexural strength as well as on the deformation when adding 1.2 vol% of recycled-fibers.

  20. Analyses of a Reinforced Concrete Containment with Liner Corrosion Damage

    SciTech Connect

    Cherry, J.L.; Smith, J.A.

    1998-11-19

    Incidents of liner corrosion in nuclear power containment structures have been recorded. These incidents and concerns of other possible liner corrosion in containment have prompted an interest in determining g the capacity of a degraded containment. Finite element analyses of a typical pressurized water reactor (PWR) reinforced concrete containment with liner corrosion were conducted using the A13AQUS finite element code with the ANACAP-U nonlinear concrete constitutive model. The effect of liner corrosion on containment capacity was investigated. A loss of coolant accident was simulated by applying pressure and temperature changes to the structure without corrosion to determine baseline failure limits, followed by multiple analyses of the containment with corrosion at different locations and varying degrees of liner degradation. The corrosion locations were chosen at the base of the containment wall, near the equipment hatch, and at the midheight of the containment wall. Using a strain-based failure criterion the different scenarios were evaluated to prioritize their effect on containment capacity

  1. Continuous acoustic emission monitoring of reinforced concrete under accelerated corrosion

    NASA Astrophysics Data System (ADS)

    Di Benedetti, M.; Loreto, G.; Nanni, A.; Matta, F.; Gonzalez-Nunez, M. A.

    2011-04-01

    The development of techniques capable of evaluating deterioration of reinforced concrete (RC) structures is instrumental to the advancement of techniques for the structural health monitoring (SHM) and service life estimate for constructed facilities. One of the main causes leading to degradation of RC is the corrosion of the steel reinforcement. This process can be modeled phenomenologically, while laboratory tests aimed at studying durability responses are typically accelerated in order to provide useful results within a realistic period of time. To assess the condition of damage in RC, a number of nondestructive methods have been recently studied. Acoustic emission (AE) is emerging as a nondestructive tool to detect the onset and progression of deterioration mechanisms. In this paper, the development of accelerated corrosion and continuous AE monitoring test set-up for RC specimens are presented. Relevant information are provided with regard to the characteristics of the corrosion circuit, continuous measurement and acquisition of corrosion potential, selection of AE sensors and AE parameter setting. The effectiveness of the setup in detecting and characterizing the initiation and progression of the corrosion phenomenon is discussed on the basis of preliminary results from small-scale, pre-cracked RC specimens, which are representative of areas near the clear cover in typical RC bridge members.

  2. On the effectiveness of smart technologies in the seismic protection of existing buildings Part II: Reinforced concrete structures

    SciTech Connect

    Mandara, A.; Ramundo, F.; Spina, G.

    2008-07-08

    The second part of a study concerning innovative intervention techniques for seismic protection of existing buildings is presented in this paper. The case of an existing framed r.c. structure, not designed for horizontal forces and extremely vulnerable to seismic action, is analyzed both in terms of maximum response reduction and energy dissipation. The proposed intervention approach, based on steel braces linked to the existing structure by passive or smart devices comes out appropriate and effective in the case of this type of buildings. The adopted control strategy produces a significant reducing effect on the elastic strain energy transmitted by the external perturbation to the structure, which is itself a fundamental safeguard aspect. The results prove the significantly improved capability of the system to dissipate input energy without structural damage, regardless of the specific seismic input.

  3. On the effectiveness of smart technologies in the seismic protection of existing buildings Part II: Reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Mandara, A.; Ramundo, F.; Spina, G.

    2008-07-01

    The second part of a study concerning innovative intervention techniques for seismic protection of existing buildings is presented in this paper. The case of an existing framed r.c. structure, not designed for horizontal forces and extremely vulnerable to seismic action, is analyzed both in terms of maximum response reduction and energy dissipation. The proposed intervention approach, based on steel braces linked to the existing structure by passive or smart devices comes out appropriate and effective in the case of this type of buildings. The adopted control strategy produces a significant reducing effect on the elastic strain energy transmitted by the external perturbation to the structure, which is itself a fundamental safeguard aspect. The results prove the significantly improved capability of the system to dissipate input energy without structural damage, regardless of the specific seismic input.

  4. Nondestructive evaluation of thick concrete structures

    NASA Astrophysics Data System (ADS)

    Clayton, Dwight A.

    2015-03-01

    Concrete has been used in the construction of nuclear power plants (NPPs) due to three primary properties: its low cost, structural strength, and ability to shield radiation. Examples of concrete structures important to the safety of Light Water Reactor (LWR) plants include the containment building, spent fuel pool, and cooling towers. Use in these structures has made concrete's long-term performance crucial for the safe operation of commercial NPPs. Extending LWR operating period to 60 years and beyond will likely increase susceptibility and severity of known forms of degradation. New mechanisms of materials degradation are also possible. This creates the need to be able to nondestructively evaluate the current subsurface concrete condition of aging concrete material in NPP structures. The size and complexity of NPP containment structures and heterogeneity of Portland cement concrete make characterization of the degradation extent a difficult task. Specially designed and fabricated test specimens can provide realistic flaws that are similar to actual flaws in terms of how they interact with a particular nondestructive evaluation (NDE) technique. Artificial test blocks allow the isolation of certain testing problems as well as the variation of certain parameters. Representative large heavily reinforced concrete specimens would allow for comparative testing to evaluate the state-of-the-art NDE in this area and to identify additional developments necessary to address the challenges potentially found in NPPs.

  5. Performance of Straight Steel Fibres Reinforced Alkali Activated Concrete

    NASA Astrophysics Data System (ADS)

    Faris, Meor Ahmad; Bakri Abdullah, Mohd Mustafa Al; Nizar Ismail, Khairul; Muniandy, Ratnasamy; Putra Jaya, Ramadhansyah

    2016-06-01

    This paper focus on the performance of alkali activated concrete produced by using fly ash activated by sodium silicate and sodium hydroxide solutions. These alkali activated concrete were reinforced with straight steel fibres with different weight percentage starting from 0 % up to 5 %. Chemical composition of raw material in the production alkali activated concrete which is fly ash was first identified by using X-ray fluorescence. Results reveal there have an effect of straight steel fibres inclusion to the alkali activated concrete. Highest compressive strength of alkali activated concrete which is 67.72 MPa was obtained when 3 % of straight fibres were added. As well as flexural strength, highest flexural strength which is 6.78 MPa was obtained at 3 % of straight steel fibres inclusions.

  6. Delamination detection in reinforced concrete using thermal inertia

    SciTech Connect

    Del Grande, N K; Durbin, P F

    1998-11-30

    We investigated the feasibility of thermal inertia mapping for bridge deck inspections. Using pulsed thermal imaging, we heat-stimulated surrogate delaminations in reinforced concrete and asphalt-concrete slabs. Using a dual-band infrared camera system, we measured thermal inertia responses of Styrofoam implants under 5 cm of asphalt, 5 cm of concrete, and 10 cm of asphalt and concrete. We compared thermal maps from solar-heated concrete and asphalt-concrete slabs with thermal inertia maps from flash-heated concrete and asphalt-concrete slabs. Thermal inertia mapping is a tool for visualizing and quantifying subsurface defects. Physically, thermal inertia is a measure of the resistance of the bridge deck to temperature change. Experimentally, it is determined from the inverse slope of the surface temperature versus the inverse square root of time. Mathematically, thermal inertia is the square root of the product of thermal conductivity, density, and heat capacity. Thermal inertia mapping distinguishes delaminated decks which have below-average thermal inertias from normal or shaded decks. Key Words: Pulsed Thermal Imaging, Thermal Inertia, Detection Of Concrete Bridgedeck Delaminations

  7. Damage evaluation of reinforced concrete frame based on a combined fiber beam model

    NASA Astrophysics Data System (ADS)

    Shang, Bing; Liu, ZhanLi; Zhuang, Zhuo

    2014-04-01

    In order to analyze and simulate the impact collapse or seismic response of the reinforced concrete (RC) structures, a combined fiber beam model is proposed by dividing the cross section of RC beam into concrete fiber and steel fiber. The stress-strain relationship of concrete fiber is based on a model proposed by concrete codes for concrete structures. The stress-strain behavior of steel fiber is based on a model suggested by others. These constitutive models are implemented into a general finite element program ABAQUS through the user defined subroutines to provide effective computational tools for the inelastic analysis of RC frame structures. The fiber model proposed in this paper is validated by comparing with experiment data of the RC column under cyclical lateral loading. The damage evolution of a three-dimension frame subjected to impact loading is also investigated.

  8. Electrical resistance tomography of concrete structures

    SciTech Connect

    Daily, W.; Ramirez, A.; Binley, A.; Henry-Poulter, S.

    1993-10-01

    The purpose of this work is to determine the feasibility of using Electrical resistance tomography (ERT) to nondestructively examine the interior of concrete structures such as bridge pillars and roadways. We report the results of experiments wherein ERT is used to image the two concrete specimens in the laboratory. Each specimen is 5 inches square and 12 inches long and contained steel reinforcing rods along its length. Twenty electrodes were placed on each sample and an-image of electrical resistivity distribution was generated from current and voltage measurements. We found that the images show the general location of the reinforcing steel and, what`s more important, delineate the absence of the steel. The method may therefore be useful for determining if such steel has been destroyed by corrosion, however to make it useful, the technique must have better resolution so that individual reinforcing steel units are resolved.

  9. Humectant use in the cathodic protection of reinforced concrete

    SciTech Connect

    Holcomb, Gordon R.; Covino, Bernard S., Jr.; Russell, James H.; Bullard, Sophie J.; Cramer, Stephen D.; Collins, W.K.; Bennett, J.E.; Laylor, H.M.

    2000-11-01

    Use of humectants to improve the thermal-sprayed zinc anode performance during the cathodic protection (CP) of reinforced concrete was examined. A humectant is a hygroscopic material. It is applied onto the surface of the zinc anode to keep the concrete-anode interface moist and a good conductor. The thermodynamics of humectants are discussed. Laboratory results are presented on the effects of using lithium bromide (LiBr) and lithium nitrate (LiNO{sub 3}) as humectants in galvanic cathodic protection (GCP) and impressed current cathodic protection (ICCP) systems, in high and low relative humidities, and on new and previously electrochemically aged CP systems. LiNO{sub 3} and LiBr promoted more effective CP performance. Both improved the performance of aged slabs, suggesting that application of humectants onto existing CP systems would be of benefit. Microscopy showed that humectant-treated slabs develop the same cement-reaction zone, zinc anode structures as untreated slabs. Microscopy of LiBr-treated slabs revealed that the highest concentration of bromide was in the reaction zone. In GCP tests, LiBr was more effective than LiNO{sub 3}. In accelerated ICCP tests, LiNO{sub 3} was more effective than LiBr. It was surmised that bromide could be oxidized in the high-voltage accelerated ICCP tests. At the lower impressed currents of most installed ICCP systems, LiBr may perform as well as or better than LiNO{sub 3}.

  10. Humectant use in the cathodic protection of reinforced concrete

    SciTech Connect

    Holcomb, G.R.; Covino, B.S. Jr.; Russell, J.H.; Bullard, S.J.; Cramer, S.D.; Collins, W.K.; Bennett, J.E.; H.M. Laylor

    2000-03-01

    The use of humectants to improve the thermal-sprayed zinc anode performance during the cathodic protection (CP) of reinforced concrete is examined. A humectant is a hygroscopic material. It is applied onto the surface of the zinc anode to keep the concrete-anode interface moist and a good conductor. The thermodynamics of humectants are discussed. Laboratory results are presented on the effects of using LiBr and LiNO{sub 3} as humectants in galvanic (GCP) and impressed current (ICCP) systems, in high and low relative humidities, and on new and previously electrochemically aged CP systems. LiNO{sub 3} and LiBr promoted more effective CP performance. Both improved the performance of aged slabs, suggesting that application of humectants onto existing CP systems would be of benefit. Microscopy showed that humectant-treated slabs develop the same cement-reaction zone-zinc anode structures as untreated slabs. Microscopy of LiBr-treated slabs revealed that the highest concentration of bromide was in the reaction zone. In GCP tests, LiBr was more effective than LiNO{sub 3}. In accelerated ICCP tests, LiNO{sub 3} was more effective than LiBr. It was surmised that bromide could be oxidized in the high-voltage accelerated ICCP tests. At the lower impressed currents of most installed ICCP systems, LiBr may perform as well as or better than LiNO{sub 3}.

  11. Quantitative evaluation and visualization of cracking process in reinforced concrete by a moment tensor analysis of acoustic emission

    SciTech Connect

    Yuyama, Shigenori; Okamoto, Takahisa; Shigeishi, Mitsuhiro; Ohtsu, Masayasu

    1995-06-01

    Fracture tests are conducted on two types of reinforced concrete specimens under cyclic loadings. Cracking process is quantitatively evaluated and visualized by applying a moment tensor analysis to the AE waveforms detected during the fracture. First, bending tests are performed on reinforced concrete beams. It is found that both tensile and shear cracks are generated around the reinforcement in the low loading stages. However, shear cracks become dominant as the cracking process progresses. In the final stages, shear cracks are generated near the interface between the reinforcement and concrete even during unloadings. A bond strength test, made second, shows that tensile cracks are produced around the reinforcement in the early stages. They spread apart from the reinforcement to wider areas in the later stages. An intense AE cluster due to shear cracks is observed along the interface between the reinforcement and concrete. The previous result from an engineering structure is also presented for comparison. All these results demonstrate a great promise of the analysis for quantitative evaluation and visualization of the cracking process in reinforced concrete. The relationship between the opening width of surface cracks and the Kaiser effect is intensively studied. It is shown that a breakdown of the Kaiser effect and high AE activities during unloading can be effective indices to estimate the level of deterioration in concrete structures.

  12. RETENTION BASIN. ERECTING REINFORCING STEEL FOR CONCRETE DECK. STACK RISES ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RETENTION BASIN. ERECTING REINFORCING STEEL FOR CONCRETE DECK. STACK RISES AT TOP LEFT. CAMERA FACES WEST. INL NEGATIVE NO. 2581. Unknown Photographer, 6/18/1951 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  13. 15. Reinforced Concrete Arch over Truckee River at Reno, Nevada. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. Reinforced Concrete Arch over Truckee River at Reno, Nevada. January 28, 1920. C. R. Hill, Consulting Engineer, Reno, Nevada. Various sectional and detail views of railings. lamp posts, and brackets. Paper (same as NV-10-13 and NV-10-14). Drawing No. B-73 (VB-10-26). - Riverside Bridge, Spanning Truckee River at Booth Street, Reno, Washoe County, NV

  14. 14. Reinforced Concrete Arch over Truckee River at Reno, Nevada. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Reinforced Concrete Arch over Truckee River at Reno, Nevada. January 24, 1920. C. R. Hill, Consulting Engineer, Reno, Nevada. Various plan, section, and detail views. Paper (same as NV-10-13). Drawing No. B-72 (VB-10-25) - Riverside Bridge, Spanning Truckee River at Booth Street, Reno, Washoe County, NV

  15. 3. DRAINING & DRYING BUILDING, REINFORCED CONCRETE MUSHROOM COLUMNS WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. DRAINING & DRYING BUILDING, REINFORCED CONCRETE MUSHROOM COLUMNS WITH DROP PANELS SUPPORTING DRAINING BINS (IRON VALVES OF DRAINING BINS ARE EMBEDDED IN THE CEILING), VIEW LOOKING WEST - Mill "C" Complex, Sand Draining & Drying Building, South of Dee Bennet Road, near Illinois River, Ottawa, La Salle County, IL

  16. 8. WEST FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, FORMER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. WEST FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, FORMER DRAINAGE AREA IN THE DISTANCE, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  17. 6. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, CONNECTING TUNNEL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, CONNECTING TUNNEL VISIBLE AT CENTER RIGHT AND FAR RIGHT, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  18. 10. REINFORCED CONCRETE SLAB ROOF FROM THE WESTERN EDGE, ACCESS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. REINFORCED CONCRETE SLAB ROOF FROM THE WESTERN EDGE, ACCESS RAMPS AT LEFT AND RIGHT, VIEW TOWARDS EAST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  19. Analysis of polarization decay of reinforced concrete in saltwater

    SciTech Connect

    Kumar, A.; Boy, J.H.

    1996-11-01

    Electrochemical impedance spectroscopy (EIS), polarization resistance, and polarization decay measurements techniques were used to analyze uncoated steel reinforcing rods encased in concrete and exposed to saltwater. A nested equivalent circuit containing a Warburg impedance was utilized to analyze the results. When rust is present on the steel, the Warburg impedance dominated the impedance response.

  20. 9. Photocopy of Reinforced Concrete Details drawing (from the BPA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Photocopy of Reinforced Concrete Details drawing (from the BPA Engineering Vault, Drawing C13-J2-342-D1, Sheet 6, 13 March 1939) - Bonneville Power Administration South Bank Substation, I-84, South of Bonneville Dam Powerhouse, Bonneville, Multnomah County, OR

  1. 15. DETAIL EXTERIOR VIEW LOOKING NORTH SHOWING REINFORCED CONCRETE PILLBOX ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. DETAIL EXTERIOR VIEW LOOKING NORTH SHOWING REINFORCED CONCRETE PILLBOX ON BRADFORD ISLAND END OF DAM/SPILLWAY; THE PILLBOX WAS BUILT DURING WORLD WAR II TO HELP PROTECT THE DAM/SPILLWAY FROM SABOTAGE. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR

  2. 3. Occident Terminal Elevator. Reinforced concrete. First total "electric" elevator ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. Occident Terminal Elevator. Reinforced concrete. First total "electric" elevator at Duluth. (Powered by electrical substation instead of steam generator). - Occident Terminal Elevator & Storage Annex, South side of second slip, north from outer end of Rice's Point, east of Garfield Avenue, Duluth, St. Louis County, MN

  3. Axisymmetric analysis of a 1:6-scale reinforced concrete containment building using a distributed cracking model for the concrete

    SciTech Connect

    Weatherby, J.R.

    1987-09-01

    Results of axisymmetric structural analyses of a 1:6 scale model of a reinforced concrete nuclear containment building are presented. Both a finite element shell analysis and a simplified membrane analysis were made to predict the structural response and ultimate pressure capacity of the model. Analytical results indicate that the model will fail at an internal pressure of 187 psig when the stress level in the hoop reinforcement at the midsection of the cylinder exceeds the ultimate strength of the bar splices. 5 refs., 34 figs., 6 tabs.

  4. Refined modeling of reinforced concrete columns of seismic analysis

    NASA Astrophysics Data System (ADS)

    Kaba, S. A.; Mahin, S. A.

    1984-04-01

    The fiber representation of a section is extended to make possible the analysis of reinforced concrete or steel members independently or as part of two dimensional frames. Slice locations are specified along the length of the element. Each slice is further discretized into steel and/or concrete fibers. By monitoring the various fibers and slices, it is possible to obtain the local response at critical sections including moment curvature and shear histories. Bond slip and shear effects are not considered so the multislice fiber element is suitably for modeling beams and columns in a steel or reinforced concrete especially when the effects of axial loads on strength and stiffness are significant. The element can account for axial load bending moment interaction and the pinching of hysteresis loops due to compressive loads acting on the element. The functioning of the element is tested separately and as part of a general dynamic two dimensional frame analysis program.

  5. Flexural rigidity of biaxially loaded reinforced concrete rectangular column sections

    NASA Astrophysics Data System (ADS)

    Resheidat, M.; Ghanma, M.; Sutton, C.; Chen, Wai-Fah

    1995-05-01

    An exact analysis is carried out utilizing the parabola-rectangle stress-strain curve for concrete and a typical idealized stress-strain curve for steel to develop the moment-curvature relationship for biaxially loaded reinforced concrete rectangular column sections. Based on that, the flexural rigidity EI of the section is determined at the yield curvature. A computer program is written by FORTRAN 77 to handle the required computations. The influence of material properties, the effect of steel ratios, and the impact of axial loads on the EI estimation were investigated. This study leads to the development of a new equation to estimate the flexural rigidity EI of reinforced concrete biaxially loaded rectangular columns in which these factors were considered. It is shown that the new equation stems from the actual behavior of the column. Therefore, it is recommended for general use in the design of slender columns.

  6. NONSAP-C. Nonlinear Stress Concrete Structures

    SciTech Connect

    Anderson, C.A.; Smith, P.D.; Carruthers, L.M.; Taylor, C.

    1992-01-13

    NONSAP-C is a finite element program for determining the static and dynamic response of three-dimensional reinforced concrete structures. Long-term, or creep, behavior of concrete structures can also be analyzed. Nonlinear constitutive relations for concrete under short-term loads are incorporated in two time-independent models, a variable-modulus approach with orthotropic behavior induced in the concrete due to the development of different tangent moduli in different directions and an elastic-plastic model in which the concrete is assumed to be a continuous, isotropic, and linearly elastic-plastic strain-hardening-fracture material. A viscoelastic constitutive model for long-term thermal creep of concrete is included. Three-dimensional finite elements available in NONSAP-C include a truss element, a multinode tendon element for prestressed and post tensioned concrete structures, an elastic-plastic membrane element to represent the behavior of cavity liners, and a general isoparametric element with a variable number of nodes for analysis of solids and thick shells.

  7. Mitigation of chloride and sulfate based corrosion in reinforced concrete via electrokinetic nanoparticle treatment

    NASA Astrophysics Data System (ADS)

    Kupwade-Patil, Kunal

    Concrete is a porous material which is susceptible to the migration of highly deleterious species such as chlorides and sulfates. Various external sources, including sea salt spray, direct seawater wetting, deicing salts and chlorides can contaminate reinforced concrete. Chlorides diffuse into the capillary pores of concrete and come into contact with the reinforcement. When chloride concentration at the reinforcement exceeds a threshold level it breaks down the passive oxide layer, leading to chloride induced corrosion. The application of electrokinetics using positively charged nanoparticles for corrosion protection in reinforced concrete structures is an emerging technology. This technique involves the principle of electrophoretic migration of nanoparticles to hinder chloride diffusion in the concrete. The return of chlorides is inhibited by the electrodeposited assembly of the nanoparticles at the reinforcement interface. This work examined the nanoparticle treatment impact on chloride and sulfate induced corrosion in concrete. Electrokinetic Nanoparticle (EN) treatments were conducted on reinforced cylindrical concrete, rectangular ASTM G109 specimens that simulate a bridge deck and full scale beam specimens. EN treatment to mitigate external sulfate attack in concrete was performed on cylindrical concrete specimens. Corrosion results indicated lower corrosion potentials and rates as compared to the untreated specimens. Scanning electron microscopy (SEM) showed a dense microstructure within the EN treated specimens. Chemical analysis (Raman spectroscopy, X ray-diffraction, and Fourier transform infrared spectroscopy FTIR) showed the presence of strength enhancing phases such as calcium aluminate hydrate (C-A-H) and increased amounts of calcium silicate hydrate (C-S-H) within the EN treated specimens. Strength and porosity results showed an increase in strength and a reduction in porosity among the EN treated specimens. EN treatment acted as a protective

  8. Delamination detection in reinforced concrete using thermal inertia

    NASA Astrophysics Data System (ADS)

    DelGrande, Nancy; Durbin, Philip F.

    1999-02-01

    We investigated the feasibility of thermal inertia mapping for bridge deck inspections. Using pulsed thermal imaging, we heat-stimulated surrogate delaminations in reinforced concrete and asphalt-concrete slabs. Using a dual-band infrared camera system, we measured thermal inertia responses of Styrofoam implants under 5 cm of asphalt, 5 cm of concrete, and 10 cm of asphalt and concrete. We compared thermal maps from solar-heated concrete and asphalt-concrete slabs with thermal inertia maps from flash-heated concrete and asphalt-concrete slabs. Thermal inertia mapping is a tool for visualizing and quantifying subsurface defects. Physically, thermal inertia is a measure of the resistance of the bridge deck to temperature change. Experimentally, it is determined from the inverse slope of the surface temperature versus the inverse square root of time. Mathematically, thermal inertia is the square root of the product of thermal conductivity, density, and heat capacity. Thermal inertia mapping distinguishes delaminated decks which have below-average thermal inertias from normal or shaded decks.

  9. Design aid for shear strengthening of reinforced concrete T-joints using carbon fiber reinforced plastic composites

    NASA Astrophysics Data System (ADS)

    Gergely, Ioan

    The research presented in the present work focuses on the shear strengthening of beam column joints using carbon fiber composites, a material considered in seismic retrofit in recent years more than any other new material. These composites, or fiber reinforced polymers, offer huge advantages over structural steel reinforced concrete or timber. A few of these advantages are the superior resistance to corrosion, high stiffness to weight and strength to weight ratios, and the ability to control the material's behavior by selecting the orientation of the fibers. The design and field application research on reinforced concrete cap beam-column joints includes analytical investigations using pushover analysis; design of carbon fiber layout, experimental tests and field applications. Several beam column joints have been tested recently with design variables as the type of composite system, fiber orientation and the width of carbon fiber sheets. The surface preparation has been found to be critical for the bond between concrete and composite material, which is the most important factor in joint shear strengthening. The final goal of this thesis is to develop design aids for retrofitting reinforced concrete beam column joints. Two bridge bents were tested on the Interstate-15 corridor. One bent was tested in the as-is condition. Carbon fiber reinforced plastic composite sheets were used to externally reinforce the second bridge bent. By applying the composite, the displacement ductility has been doubled, and the bent overall lateral load capacity has been increased as well. The finite element model (using DRAIN-2DX) was calibrated to model the actual stiffness of the supports. The results were similar to the experimental findings.

  10. Field performance of sprayed zinc anodes in controlling corrosion of steel reinforced concrete

    SciTech Connect

    Tinnea, J.

    1998-12-31

    The deterioration of concrete structures often results from the corrosion of their steel reinforcement. Cathodic protection (CP) is a proven means to stop rebar corrosion. One anode material gaining acceptance in the infrastructure corrosion fight is zinc thermal spray coating. This paper discusses an investigation of such CP systems.

  11. Flexural Behaviour Of Reinforced Concrete Beams Containing Expanded Glass As Lightweight Aggregates

    NASA Astrophysics Data System (ADS)

    Khatib, Jamal; Jefimiuk, Adrian; Khatib, Sammy

    2015-12-01

    The flexural properties of reinforced concrete beams containing expanded glass as a partial fine aggregate (sand) replacement are investigated. Four concrete mixes were employed to conduct this study. The fine aggregate was replaced with 0%, 25%, 50% and 100% (by volume) expanded glass. The results suggest that the incorporation of 50% expanded glass increased the workability of the concrete. The compressive strength was decreasing linearly with the increasing amount of expanded glass. The ductility of the concrete beam significantly improved with the incorporation of the expanded glass. However, the load-carrying capacity of the beam and load at which the first crack occurs was reduced. It was concluded that the inclusion of expanded glass in structural concrete applications is feasible.

  12. High-temperature testing of high performance fiber reinforced concrete

    NASA Astrophysics Data System (ADS)

    Fořt, Jan; Vejmelková, Eva; Pavlíková, Milena; Trník, Anton; Čítek, David; Kolísko, Jiří; Černý, Robert; Pavlík, Zbyšek

    2016-06-01

    The effect of high-temperature exposure on properties of High Performance Fiber Reinforced Concrete (HPFRC) is researched in the paper. At first, reference measurements are done on HPFRC samples without high-temperature loading. Then, the HPFRC samples are exposed to the temperatures of 200, 400, 600, 800, and 1000 °C. For the temperature loaded samples, measurement of residual mechanical and basic physical properties is done. Linear thermal expansion coefficient as function of temperature is accessed on the basis of measured thermal strain data. Additionally, simultaneous difference scanning calorimetry (DSC) and thermogravimetry (TG) analysis is performed in order to observe and explain material changes at elevated temperature. It is found that the applied high temperature loading significantly increases material porosity due to the physical, chemical and combined damage of material inner structure, and negatively affects also the mechanical strength. Linear thermal expansion coefficient exhibits significant dependence on temperature and changes of material structure. The obtained data will find use as input material parameters for modelling the damage of HPFRC structures exposed to the fire and high temperature action.

  13. Behavior of Concrete Panels Reinforced with Synthetic Fibers, Mild Steel, and GFRP Composites Subjected to Blasts

    SciTech Connect

    C. P. Pantelides; T. T. Garfield; W. D. Richins; T. K. Larson; J. E. Blakeley

    2012-03-01

    The paper presents experimental data generated for calibrating finite element models to predict the performance of reinforced concrete panels with a wide range of construction details under blast loading. The specimens were 1.2 m square panels constructed using Normal Weight Concrete (NWC) or Fiber Reinforced Concrete (FRC). FRC consisted of macro-synthetic fibers dispersed in NWC. Five types of panels were tested: NWC panels with steel bars; FRC panels without additional reinforcement; FRC panels with steel bars; NWC panels with glass fiber reinforced polymer (GFRP) bars; and NWC panels reinforced with steel bars and external GFRP laminates on both faces. Each panel type was constructed with three thicknesses: 152 mm, 254 mm, and 356 mm. FRC panels with steel bars had the best performance for new construction. NWC panels reinforced with steel bars and external GFRP laminates on both faces had the best performance for strengthening or rehabilitation of existing structures. The performance of NWC panels with GFRP bars was strongly influenced by the bar spacing. The behavior of the panels is classified in terms of damage using immediate occupancy, life safety, and near collapse performance levels. Preliminary dynamic simulations are compared to the experimental results.

  14. Monitoring of Concrete Structures Using Ofdr Technique

    NASA Astrophysics Data System (ADS)

    Henault, J. M.; Salin, J.; Moreau, G.; Delepine-Lesoille, S.; Bertand, J.; Taillade, F.; Quiertant, M.; Benzarti, K.

    2011-06-01

    Structural health monitoring is a key factor in life cycle management of infrastructures. Truly distributed fiber optic sensors are able to provide relevant information on large structures, such as bridges, dikes, nuclear power plants or nuclear waste disposal facilities. The sensing chain includes an optoelectronic unit and a sensing cable made of one or more optical fibers. A new instrument based on Optical Frequency Domain Reflectometry (OFDR), enables to perform temperature and strain measurements with a centimeter scale spatial resolution over hundred of meters and with a level of precision equal to 1 μstrain and 0.1 °C. Several sensing cables are designed with different materials targeting to last for decades in a concrete aggressive environment and to ensure an optimal transfer of temperature and strain from the concrete matrix to the optical fiber. Tests were carried out by embedding various sensing cables into plain concrete specimens and representative-scale reinforced concrete structural elements. Measurements were performed with an OFDR instrument; meanwhile, mechanical solicitations were imposed to the concrete element. Preliminary experiments are very promising since measurements performed with distributed sensing system are comparable to values obtained with conventional sensors used in civil engineering and with the Strength of Materials Modelling. Moreover, the distributed sensing system makes it possible to detect and localize cracks appearing in concrete during the mechanical loading.

  15. Detection of active corrosion in reinforced and prestressed concrete: overview of NIST TIP project

    NASA Astrophysics Data System (ADS)

    Gonzalez-Nunez, M. A.; Nanni, A.; Matta, F.; Ziehl, P.

    2011-04-01

    The US transportation infrastructure has been receiving intensive public and private attention in recent years. The Federal Highway Administration estimates that 42 percent of the nearly 600,000 bridges in the Unites States are in need of structural or functional rehabilitation1. Corrosion of reinforcement steel is the main durability issue for reinforced and prestressed concrete structures, especially in coastal areas and in regions where de-icing salts are regularly used. Acoustic Emission (AE) has proved to be a promising method for detecting corrosion in steel reinforced and prestressed concrete members. This type of non-destructive test method primarily measures the magnitude of energy released within a material when physically strained. The expansive ferrous byproducts resulting from corrosion induce pressure at the steel-concrete interface, producing longitudinal and radial microcracks that can be detected by AE sensors. In the experimental study presented herein, concrete block specimens with embedded steel reinforcing bars and strands were tested under accelerated corrosion to relate the AE activity with the onset and propagation stages of corrosion. AE data along with half cell potential measurements and galvanic current were recorded to examine the deterioration process. Finally, the steel strands and bars were removed from the specimens, cleaned and weighed. The results were compared vis-à-vis Faraday's law to correlate AE measurements with degree of corrosion in each block.

  16. Study on reinforced concrete beams strengthened using shape memory alloy wires in combination with carbon-fiber-reinforced polymer plates

    NASA Astrophysics Data System (ADS)

    Li, Hui; Liu, Zhi-qiang; Ou, Jin-ping

    2007-12-01

    It has been proven that carbon-fiber-reinforced polymer (CFRP) sheets or plates are capable of improving the strength of reinforced concrete (RC) structures. However, residual deformation of RC structures in service reduces the effect of CFRP strengthening. SMA can be applied to potentially decrease residual deformation and even close concrete cracks because of its recovery forces imposed on the concrete when heated. Therefore, a method of a RC structure strengthened by CFRP plates in combination with SMA wires is proposed in this paper. The strengthening effect of this method is investigated through experiments and numerical study based on the nonlinear finite element software ABAQUS in simple RC beams. Parametric analysis and assessment of damage by defining a damage index are carried out. The results indicate that recovery forces of SMA wires can decrease deflections and even close cracks in the concrete. The recovery rate of deflection of the beam increases with increasing the ratio of SMA wires. The specimen strengthened with CFRP plates has a relatively large stiffness and smaller damage index value when the residual deformation of the beam is first reduced by activation of the SMA wires. The effectiveness of this strengthening method for RC beams is verified by experimental and numerical results.

  17. Digital fast neutron radiography of steel reinforcing bar in concrete

    NASA Astrophysics Data System (ADS)

    Mitton, K.; Jones, A.; Joyce, M. J.

    2014-12-01

    Neutron imaging has previously been used in order to test for cracks, degradation and water content in concrete. However, these techniques often fall short of alternative non-destructive testing methods, such as γ-ray and X-ray imaging, particularly in terms of resolution. Further, thermal neutron techniques can be compromised by the significant expense associated with thermal neutron sources of sufficient intensity to yield satisfactory results that can often precipitate the need for a reactor. Such embodiments are clearly not portable in the context of the needs of field applications. This paper summarises the results of a study to investigate the potential for transmission radiography based on fast neutrons. The objective of this study was to determine whether the presence of heterogeneities in concrete, such as reinforcement structures, could be identified on the basis of variation in transmitted fast-neutron flux. Monte-Carlo simulations have been performed and the results from these are compared to those arising from practical tests using a 252Cf source. The experimental data have been acquired using a digital pulse-shape discrimination system that enables fast neutron transmission to be studied across an array of liquid scintillators placed in close proximity to samples under test, and read out in real time. Whilst this study does not yield sufficient spatial resolution, a comparison of overall flux ratios does provide a basis for the discrimination between samples with contrasting rebar content. This approach offers the potential for non-destructive testing that gives less dose, better transportability and better accessibility than competing approaches. It is also suitable for thick samples where γ-ray and X-ray methods can be limited.

  18. Perspective view. The threestory reinforced concrete building faced with brick ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view. The three-story reinforced concrete building faced with brick has direct frontage onto neighboring railroad line. The facade says: "The Fairmont Creamery Company" in white stone. The facade is divided into bays by large brick piers capped with a square accent piece. A large stone band runs just above the windows and between the second and third floors - The Fairmont Creamery Company, 608 East Milwaukee Avenue, Detroit, MI

  19. 83. ARAIII. A blast wall of reinforced concrete separated the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    83. ARA-III. A blast wall of reinforced concrete separated the GCRE control room from the reactor. Blast wall goes up at left of view. Camera stands at the southwest corner of the control building (ARA-607) and faces east. October 14, 1958. Ineel photo no. 58-5085. Photographer: Jack L. Anderson. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

  20. View from intersection. Ninestory reinforced concrete building infilled with brick. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View from intersection. Nine-story reinforced concrete building infilled with brick. The street facades on beaubien and east grand are faced with stone accents and elaborate brick work. Brick pilasters run the entire height of the building. Steel tiebacks are apparent running up the height of the building on the east side. The large tower appears at the northeast and southeast corners - Detroit Storage Company, 2937 East Grand Boulevard, Detroit, MI

  1. Fibre Reinforced Polymers (FRP) as Reinforcement for Concrete According to German Approvals

    NASA Astrophysics Data System (ADS)

    Alex, R.

    2015-11-01

    This article demonstrates the possibility of the application of joint principles to develop test programs for national approval or European Technical Assessments of FRP reinforcement for concrete. The limits of different systems are shown, which until now have been approved in Germany.

  2. Degradation and mechanism of the mechanics and durability of reinforced concrete slab in a marine environment

    NASA Astrophysics Data System (ADS)

    Wu, Sheng-xing; Liu, Guan-guo; Bian, Han-bing; Lv, Wei-bo; Jiang, Jian-hua

    2016-04-01

    An experimental research was conducted to determine the corrosion and bearing capacity of a reinforced concrete (RC) slab at different ages in a marine environment. Results show that the development of corrosion-induced cracks on a slab in a marine environment can be divided into three stages according to crack morphology at the bottom of the slab. In the first stage, cracks appear. In the second stage, cracks develop from the edges to the middle of the slab. In the third stage, longitudinal and transverse corrosion-induced cracks coexist. The corrosion ratio of reinforcements nonlinearly increases with the age, and the relationship between the corrosion ratio of the reinforcements and the corrosion-induced crack width of the concrete is established. The flexural capacity of the corroded RC slab nonlinearly decreases with the age, and the model for the bearing capacity factor of the corroded RC slab is established. The mid-span deflection of the corroded RC slab that corresponds to the yield of the reinforcements linearly increases with the increase in corrosion ratio. Finally, the mechanisms of corrosion morphology and the degradation of the mechanical properties of an RC slab in a marine environment are discussed on the basis of the basic theories of steel corrosion in concrete and concrete structure design.

  3. Numerical simulation of monitoring corrosion in reinforced concrete based on ultrasonic guided waves.

    PubMed

    Zheng, Zhupeng; Lei, Ying; Xue, Xin

    2014-01-01

    Numerical simulation based on finite element method is conducted to predict the location of pitting corrosion in reinforced concrete. Simulation results show that it is feasible to predict corrosion monitoring based on ultrasonic guided wave in reinforced concrete, and wavelet analysis can be used for the extremely weak signal of guided waves due to energy leaking into concrete. The characteristic of time-frequency localization of wavelet transform is adopted in the corrosion monitoring of reinforced concrete. Guided waves can be successfully used to identify corrosion defects in reinforced concrete with the analysis of suitable wavelet-based function and its scale. PMID:25013865

  4. Numerical Simulation of Monitoring Corrosion in Reinforced Concrete Based on Ultrasonic Guided Waves

    PubMed Central

    Zheng, Zhupeng; Lei, Ying; Xue, Xin

    2014-01-01

    Numerical simulation based on finite element method is conducted to predict the location of pitting corrosion in reinforced concrete. Simulation results show that it is feasible to predict corrosion monitoring based on ultrasonic guided wave in reinforced concrete, and wavelet analysis can be used for the extremely weak signal of guided waves due to energy leaking into concrete. The characteristic of time-frequency localization of wavelet transform is adopted in the corrosion monitoring of reinforced concrete. Guided waves can be successfully used to identify corrosion defects in reinforced concrete with the analysis of suitable wavelet-based function and its scale. PMID:25013865

  5. Radiation exposure inside reinforced concrete buildings at Nagasaki

    SciTech Connect

    Rhoades, W.A.; Childs, R.L.; Ingersoll, D.T.

    1989-05-01

    The biological effects on the residents of Hiroshima and Nagasaki due to initial-irradiation exposure during the nuclear attacks of World War II was recognized immediately as an important source of information. After the war, an extensive effort gathered data concerning the locations of individuals at the time of the attack and their subsequent medical histories. The data from personnel located in reinforced concrete buildings are particularly significant, since large groups of occupants received radiation injury without complications due to blast and thermal effects. In order to correlate the radiation dose with physiological effects, the dose to each individual must be calculated. Enough information about the construction of the buildings was available after the war to allow a radiation transport model to be constructed, but the accurate calculation of penetration into such large, thick-walled three dimensional structures was beyond the scope of computing technology until recently. Now, the availability of Cray vector computers and the development of a specially-constructed discrete ordinates transport code, TORT, have combined to allow the successful completion of such a study. This document describes the radiation transport calculations and tabulates the resulting doses by source component and individual case location. An extensive uncertainty analysis is also included. These data are to be used in another study as input to a formal statistical analysis, resulting in a new value for the LD50 dose, i.e., the dose at which the mortality risk is 50%. 55 refs., 67 figs., 70 tabs.

  6. Impact Resistance Performance of Kenaf Fibre Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Liyana Mohd Kamal, Nur; Syamsir, Agusril; Sheng, Chiam Yung; Beddu, Salmia; Nasharuddin Mustapha, Kamal; Thiruchelvam, Sivadass; Usman, Fathoni; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the performance of kenaf fibre mesh reinforced concrete (KFMRC) with varied kenaf fibre mesh reinforcement content for the concrete slab of 300mm × 300mm size reinforced with different mesh diameter at constant spacing with varied slab thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.40 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of mesh reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against kenaf fiber diameters by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the slab thickness. The threshold (highest) values for service crack and ultimate crack is 47.9 N/mm2 and 130.58 N/mm2 respectively observed and computed for 50 mm slab with 7 mm diameter mesh.

  7. Parametric Study of Shear Strength of Concrete Beams Reinforced with FRP Bars

    NASA Astrophysics Data System (ADS)

    Thomas, Job; Ramadass, S.

    2016-06-01

    Fibre Reinforced Polymer (FRP) bars are being widely used as internal reinforcement in structural elements in the last decade. The corrosion resistance of FRP bars qualifies its use in severe and marine exposure conditions in structures. A total of eight concrete beams longitudinally reinforced with FRP bars were cast and tested over shear span to depth ratio of 0.5 and 1.75. The shear strength test data of 188 beams published in various literatures were also used. The model originally proposed by Indian Standard Code of practice for the prediction of shear strength of concrete beams reinforced with steel bars IS:456 (Plain and reinforced concrete, code of practice, fourth revision. Bureau of Indian Standards, New Delhi, 2000) is considered and a modification to account for the influence of the FRP bars is proposed based on regression analysis. Out of the 196 test data, 110 test data is used for the regression analysis and 86 test data is used for the validation of the model. In addition, the shear strength of 86 test data accounted for the validation is assessed using eleven models proposed by various researchers. The proposed model accounts for compressive strength of concrete (f ck ), modulus of elasticity of FRP rebar (E f ), longitudinal reinforcement ratio (ρ f ), shear span to depth ratio (a/d) and size effect of beams. The predicted shear strength of beams using the proposed model and 11 models proposed by other researchers is compared with the corresponding experimental results. The mean of predicted shear strength to the experimental shear strength for the 86 beams accounted for the validation of the proposed model is found to be 0.93. The result of the statistical analysis indicates that the prediction based on the proposed model corroborates with the corresponding experimental data.

  8. Flexural behavior of reinforced concrete beams strengthened with advanced composite materials

    SciTech Connect

    Shahawy, M.A.; Beitelman, T.

    1996-12-31

    This paper presents the results of a feasibility study to investigate the flexural behavior of structurally damaged reinforced and prestressed concrete members retrofitted with bonded carbon fiber materials. The effect of CFRP laminates, bonded to the soffit of precracked reinforced concrete rectangular and tee beams, is investigated in terms of flexural strength, deflections, cracking behavior and failure modes. The results indicate that strengthening of significantly cracked structural members by bonding Carbon laminates is structurally efficient and that the retrofitted members are restored to stiffness and strength values nearly equal to or greater than those of the original. The results indicate that the retrofitted members maintained adequate structural integrity and composite action at all stages of testing up to failure.

  9. Nuclear Power Plant Concrete Structures

    SciTech Connect

    Basu, Prabir; Labbe, Pierre; Naus, Dan

    2013-01-01

    A nuclear power plant (NPP) involves complex engineering structures that are significant items of the structures, systems and components (SSC) important to the safe and reliable operation of the NPP. Concrete is the commonly used civil engineering construction material in the nuclear industry because of a number of advantageous properties. The NPP concrete structures underwent a great degree of evolution, since the commissioning of first NPP in early 1960. The increasing concern with time related to safety of the public and environment, and degradation of concrete structures due to ageing related phenomena are the driving forces for such evolution. The concrete technology underwent rapid development with the advent of chemical admixtures of plasticizer/super plasticizer category as well as viscosity modifiers and mineral admixtures like fly ash and silica fume. Application of high performance concrete (HPC) developed with chemical and mineral admixtures has been witnessed in the construction of NPP structures. Along with the beneficial effect, the use of admixtures in concrete has posed a number of challenges as well in design and construction. This along with the prospect of continuing operation beyond design life, especially after 60 years, the impact of extreme natural events ( as in the case of Fukushima NPP accident) and human induced events (e.g. commercial aircraft crash like the event of September 11th 2001) has led to further development in the area of NPP concrete structures. The present paper aims at providing an account of evolution of NPP concrete structures in last two decades by summarizing the development in the areas of concrete technology, design methodology and construction techniques, maintenance and ageing management of concrete structures.

  10. Nonlinear finite element analysis of nuclear reinforced prestressed concrete containments up to ultimate load capacity

    SciTech Connect

    Gupta, A.; Singh, R.K.; Kushwaha, H.S.; Mahajan, S.C.; Kakodkar, A.

    1996-06-01

    For safety evaluation of nuclear structures a finite element code ULCA (Ultimate Load Capacity Assessment) has been developed. Eight/nine noded isoparametric quadrilateral plate/shell element with reinforcement as a through thickness discrete but integral smeared layer of the element is presented to analyze reinforced and prestressed concrete structures. Various constitutive models such as crushing, cracking in tension, tension stiffening and rebar yielding are studied and effect of these parameters on the reserve strength of structures is brought out through a number of benchmark tests. A global model is used to analyze the prestressed concrete containment wall of a typical 220 MWe Pressurized Heavy Water Reactor (PHWR) up to its ultimate capacity. This demonstrates the adequacy of Indian PHWR containment design to withstand severe accident loads.

  11. Numerical Study on Mixed-mode Fracture in Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Yu, Rena C.; Saucedo, Luis; Ruiz, Gonzalo

    2010-05-01

    The object of this work is to model the propagation of fracture in mixed-mode in lightly reinforced concrete beams. When a notched beam does not have enough shear reinforcement, fracture can initiate and propagate unstably and lead to failure through diagonal tension. In order to study this phenomenon numerically, a model capable of dealing with both static and dynamic crack propagation as well as the natural transition of those two regimes is necessary. We adopt a cohesive model for concrete fracture and an interface model for the deterioration between concrete and steel re-bar, both combined with an insertion algorithm. The static process is solved by dynamic relaxation (DR) method together with a modified technique [1] to enhance convergence rate. The same DR method is used to detect a dynamic process and switch to a dynamic calculation. The numerically obtained load-displacement curves, load-CMOD curves and crack patterns fit reasonably well with their experimental counterparts, having in mind that we fed the calculations only with parameters measured experimentally.

  12. Intermittent cathodic protection for steel reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Ziomek-Moroz, Margaret; Cramer, Stephen D.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Russell, James H.; Soltesz, S.M.

    2002-01-01

    Thermal-sprayed zinc anodes are used for impressed current cathodic protection (ICCP) systems on Oregon's reinforced concrete coastal bridges to prevent chloride-induced corrosion damage. Thermal-sprayed zinc performs well as an ICCP anode but the service life of the zinc anode is directly related to the average current density used to operate the systems. After a ICCP system is turned off, the rebar in the concrete remains passive and protected for a period of time. Intermittent operation of CP systems is possible when continuous corrosion rate monitoring is used to identify conditions when the CP system needs to be turned on to reestablish protection conditions for the rebar. This approach applies CP protection only when needed and reflects the fact that external protection may not be needed for a range of environmental conditions. In doing so, intermittent CP would lower the average current necessary to protect rebar, increase the anode service life, and reduce the lifetime costs for protecting reinforced concrete bridges.

  13. Corrosion of Steels in Steel Reinforced Concrete in Cassava Juice

    NASA Astrophysics Data System (ADS)

    Oluwadare, G. O.; Agbaje, O.

    The corrosion of two types of construction steels, ST60Mn and RST37-2♦, in a low cyanide concentration environment (cassava juice) and embedded in concrete had been studied. The ST60 Mn was found to be more corrosion resistant in both ordinary water and the cassava juice environment. The cyanide in cassava juice does not attack the steel but it provides an environment of lower pH around the steel in the concrete which leads to breakdown of the passivating film provided by hydroxyl ions from cement. Other factors such as the curing time of the concrete also affect the corrosion rates of the steel in the concrete. The corrosion rate of the steel directly exposed to cassava juice i.e., steel not embedded in concrete is about twice that in concrete. Long exposure of concrete structure to cassava processing effluent might result in deterioration of such structures. Careful attention should therefore be paid to disposal of cassava processing effluents, especially in a country like Nigeria where such processing is now on the increase.

  14. Time reverse modeling of acoustic emissions in a reinforced concrete beam.

    PubMed

    Kocur, Georg Karl; Saenger, Erik H; Grosse, Christian U; Vogel, Thomas

    2016-02-01

    The time reverse modeling (TRM) is applied for signal-based acoustic emission (AE) analysis of reinforced concrete (RC) specimens. TRM uses signals obtained from physical experiments as input. The signals are re-emitted numerically into a structure in a time-reversed manner, where the wavefronts interfere and appear as dominant concentrations of energy at the origin of the AE. The experimental and numerical results presented for selected AE signals confirm that TRM is capable of localizing AE activity in RC caused by concrete cracking. The accuracy of the TRM results is corroborated by three-dimensional crack distributions obtained from X-ray computed tomography images. PMID:26518525

  15. Durability Studies on Confined Concrete using Fiber Reinforced Polymer

    NASA Astrophysics Data System (ADS)

    Ponmalar, V.; Gettu, R.

    2014-06-01

    In this study, 24 concrete cylinders with a notch at the centre were prepared. Among them six cylinders were wrapped using single and double layers of fiber reinforced polymer; six cylinders were coated with epoxy resin; the remaining cylinders were used as a control. The cylinders were exposed to wet and dry cycling and acid (3 % H2SO4) solution for the period of 120 days. Two different concrete strengths M30 and M50 were considered for the study. It is found that the strength, ductility and failure mode of wrapped cylinders depend on number of layers and the nature of exposure conditions. It was noticed that the damage due to wet and dry cycling and acid attack was severe in control specimen than the epoxy coated and wrapped cylinders.

  16. Electrical resistance tomography for imaging concrete structures

    SciTech Connect

    Buettner, M.; Ramirez, A.; Daily, W.

    1995-11-08

    Electrical Resistance Tomography (ERT) has been used to non-destructively examine the interior of reinforced concrete pillars in the laboratory during a water infiltration experiment. ERT is a technique for determining the electrical resistivity distribution within a volume from measurement of injected currents and the resulting electrical potential distribution on the surface. The transfer resistance (ratio of potential to injected current) data are inverted using an algorithm based on a finite element forward solution which is iteratively adjusted in a least squares sense until the measured and calculated transfer resistances agree to within some predetermined value. Laboratory specimens of concrete pillars, 61.0 cm (24 in) in length and 20.3 cm (8 in) on a side, were prepared with various combinations of steel reinforcing bars and voids (1.27 cm diameter) which ran along the length of the pillars. An array of electrodes was placed around the pillar to allow for injecting current and measuring the resulting potentials. After the baseline resistivity distribution was determined, water was added to a void near one comer of the pillar. ERT was used to determine the resistivity distribution of the pillar at regular time intervals as water was added. The ERT images show very clearly that the water was gradually imbibed into the concrete pillar during the course of the experiment. The resistivity decreased by nearly an order of magnitude near the point of water addition in the first hour, and by nearly two orders of magnitude by the end of the experiment. Other applications for this technology include monitoring of curing in concrete structures, detecting cracks in concrete structures, detecting rebar location and corrosion state, monitoring slope stability and the stability of footings, detecting and monitoring leaks from storage tanks, monitoring thermal processes during environmental remediation, and for detecting and monitoring contaminants in soil and groundwater.

  17. CONCRETE POURS HAVE PRODUCED A REINFORCED SUPPORT BASE FOR MTR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    CONCRETE POURS HAVE PRODUCED A REINFORCED SUPPORT BASE FOR MTR REACTOR. PIPE TUNNEL IS UNDER CONSTRUCTION AT CENTER OF VIEW. PIPES WILL CARRY RADIOACTIVE WATER FROM REACTOR TO WATER PROCESS BUILDING. CAMERA LOOKS SOUTH INTO TUNNEL ALONG WEST SIDE OF REACTOR BASE. TWO CAISSONS ARE AT LEFT SIDE OF VIEW. NOTE "WINDOW" IN SOUTH FACE OF REACTOR BASE AND ALSO GROUP OF PENETRATIONS TO ITS LEFT. INL NEGATIVE NO. 733. Unknown Photographer, 10/6/1950 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  18. Postcrack creep of polymeric fiber-reinforced concrete in flexure

    SciTech Connect

    Kurtz, S.; Balaguru, P.

    2000-02-01

    Results of an experimental investigation of the creep-time behavior of polypropylene and nylon fiber-reinforced concrete (FRC) are presented. Gravity loads were applied in flexure to precracked low volume fraction (0.1%) polypropylene and nylon FRC beams. Beams were tested at a range of stress levels to produce three outcomes: load sustained indefinitely (low stress), creep failure (intermediate stress), and rapid failure (high stress). Emphasis was placed on determining the maximum flexural stress that is sustainable indefinitely. The results indicate that polypropylene FRC has higher initial strength but nylon FRC can sustain a higher stress level. For both groups the sustainable stress is much lower than the postcrack strength.

  19. Impact of ASCE-95 wind provisions on reinforced concrete chimneys

    SciTech Connect

    Joshi, J.R.; Porthouse, R.A.

    1999-11-01

    This paper presents a summary of the study on the impact of the ASCE 7-95 provisions primarily on the along wind load calculations for reinforced concrete chimneys. The results of this study provided, in part, a basis for the adoption of the revised load and strength factors for wind load design in ACI 307-98. The study was undertaken to: compare unfactored along wind chimney loads resulting from fastest miles per hour (FMPH) and three second gust (TSG) procedures; quantify design changes resulting from FMPH to TSG in terms of the reinforcing steel; review the historical basis for the current load factors (LF) and strength factors (SF); and to recommend a set of LF and SF for the design of chimneys without significantly changing the present design confidence level.

  20. Strength and deformability of compressed concrete elements with various types of non-metallic fiber and rods reinforcement under static loading

    NASA Astrophysics Data System (ADS)

    Nevskii, A. V.; Baldin, I. V.; Kudyakov, K. L.

    2015-01-01

    Adoption of modern building materials based on non-metallic fibers and their application in concrete structures represent one of the important issues in construction industry. This paper presents results of investigation of several types of raw materials selected: basalt fiber, carbon fiber and composite fiber rods based on glass and carbon. Preliminary testing has shown the possibility of raw materials to be effectively used in compressed concrete elements. Experimental program to define strength and deformability of compressed concrete elements with non-metallic fiber reinforcement and rod composite reinforcement included design, manufacture and testing of several types of concrete samples with different types of fiber and longitudinal rod reinforcement. The samples were tested under compressive static load. The results demonstrated that fiber reinforcement of concrete allows increasing carrying capacity of compressed concrete elements and reducing their deformability. Using composite longitudinal reinforcement instead of steel longitudinal reinforcement in compressed concrete elements insignificantly influences bearing capacity. Combined use of composite rod reinforcement and fiber reinforcement in compressed concrete elements enables to achieve maximum strength and minimum deformability.

  1. Monitoring of transverse displacement of reinforced concrete beams under flexural loading with embedded arrays of optical fibers

    NASA Astrophysics Data System (ADS)

    Gonzalez-Tinoco, Juan E.; Gomez-Rosas, Enrique R.; Guzmán-Olguín, Héctor; Khotiaintsev, Sergei; Zuñiga-Bravo, Miguel A.

    2015-04-01

    We present results of an ongoing study of structural health monitoring of concrete elements by means of arrays of telecommunications-grade optical fibers embedded in such elements. In this work, we show a possibility of using this technique for monitoring the transverse displacement of the reinforced concrete beams under flexural loading. We embedded a number of multimode silica-core/polymer-clad/polymer-coated optical fibers in a mold with preinstalled reinforcing steel bars and fresh concrete mix. Then the concrete was compacted and cured. Some optical fibers were broken during the fabrication process. The fiber survival rate varied with concrete grade, compacting technique and optical fiber type. The fibers that survived the fabrication process were employed for the monitoring. They were connected to the optical transmitter and receiver that formed a part of a larger measurement system. The system continuously measured the optical transmission of all optical fibers while the reinforced concrete beams were subjected to incremental transverse loading. We observed a quasi-linear decrease in optical transmission in all optical fibers of the array vs. the applied load and respective flexural displacement. Although the underlying phenomena that lead to such a variation in optical transmission are not clear yet, the observed behavior might be of interest for assessing the transverse displacement of the reinforced concrete beams under flexural loading.

  2. Integrity assessment of grouted posttensioning cables and reinforced concrete of a nuclear containment building

    NASA Astrophysics Data System (ADS)

    Philipose, K.; Shenton, B.

    2011-04-01

    The Containment Buildings of CANDU Nuclear Generating Stations were designed to house nuclear reactors and process equipment and also to provide confinement of releases from a potential nuclear accident such as a Loss Of Coolant Accident (LOCA). To meet this design requirement, a post-tensioning system was designed to induce compressive stresses in the structure to counteract the internal design pressure. The CANDU reactor building at Gentilly-1 (G-1), Quebec, Canada (250 MWe) was built in the early 1970s and is currently in a decommissioned state. The structure at present is under surveillance and monitoring. In the year 2000, a field investigation was conducted as part of a condition assessment and corrosion was detected in some of the grouted post-tension cable strands. However, no further work was done at that time to determine the cause, nature, impact and extent of the corrosion. An investigation of the Gentilly-1 containment building is currently underway to assess the condition of grouted post-tensioning cables and reinforced concrete. At two selected locations, concrete and steel reinforcements were removed from the containment building wall to expose horizontal cables. Individual cable strands and reinforcement bars were instrumented and measurements were taken in-situ before removing them for forensic examination and destructive testing to determine the impact of ageing and corrosion. Concrete samples were also removed and tested in a laboratory. The purpose of the field investigation and laboratory testing, using this structure as a test bed, was also to collect material ageing data and to develop potential Nondestructive Examination (NDE) methods to monitor Containment Building Integrity. The paper describes the field work conducted and the test results obtained for concrete, reinforcement and post-tensioning cables.

  3. Prediction of reinforcement corrosion using corrosion induced cracks width in corroded reinforced concrete beams

    SciTech Connect

    Khan, Inamullah; François, Raoul; Castel, Arnaud

    2014-02-15

    This paper studies the evolution of reinforcement corrosion in comparison to corrosion crack width in a highly corroded reinforced concrete beam. Cracking and corrosion maps of the beam were drawn and steel reinforcement was recovered from the beam to observe the corrosion pattern and to measure the loss of mass of steel reinforcement. Maximum steel cross-section loss of the main reinforcement and average steel cross-section loss between stirrups were plotted against the crack width. The experimental results were compared with existing models proposed by Rodriguez et al., Vidal et al. and Zhang et al. Time prediction models for a given opening threshold are also compared to experimental results. Steel cross-section loss for stirrups was also measured and was plotted against the crack width. It was observed that steel cross-section loss in the stirrups had no relationship with the crack width of longitudinal corrosion cracks. -- Highlights: •Relationship between crack and corrosion of reinforcement was investigated. •Corrosion results of natural process and then corresponds to in-situ conditions. •Comparison with time predicting model is provided. •Prediction of load-bearing capacity from crack pattern was studied.

  4. Classroom Application of Structured Reinforcement.

    ERIC Educational Resources Information Center

    Bemis, Katherine A.; Schroeder, Glenn B.

    Results of pilot and field tests suggest that teachers should be encouraged to use the classroom management technique of structured reinforcement. In the 1967-68 pilot test 18 teachers (eight experimental and 10 control) systematically varied several parameters of reinforcement in classroom situations to determine their effects on the attainment…

  5. Preliminary investigation on the suitablity of using fiber reinforced concrete in the construction of a hazardous waste disposal vessel

    SciTech Connect

    Ramey, M.R.; Daie-e, G.

    1988-07-01

    There are certain hazardous wastes that must be contained in an extremely secure vessel for transportation and disposal. The vessel, among other things, must be able to withstand relatively large impacts without rupturing. Such containment vessels therefore must be able to absorb substantial amounts of energy during an impact and still perform their function. One of the impacts that the vessel must withstand is a 30-foot fall onto an unyielding surface. For some disposal scenarios it is proposed to encase the waste in a steel enclosure which is to be surrounded by a thick layer of concrete which, in turn, is encased by a relatively thin steel shell. Tests on concrete in compression and flexure, including static, dynamic and impact tests, have shown that low modulus concretes tend to behave in a less brittle manner than higher modulus concretes. Tests also show that fiber reinforced concretes have significantly greater ductility, crack propagation resistance and toughness than conventional concretes. Since it is known that concrete is a reasonably brittle material, it is necessary to do impact tests on sample containment structures consisting of thin-walled metal containers having closed ends which are filled with concrete, grout, or fiber reinforced concrete. This report presents the results of simple tests aimed at observing the behavior of sample containment structures subjected to impacts due to a fall from 30 feet. 8 figs., 4 tabs.

  6. Numerical Study Of The Effects Of Preloading, Axial Loading And Concrete Shrinkage On Reinforced Concrete Elements Strengthened By Concrete Layers And Jackets

    SciTech Connect

    Lampropoulos, A. P.; Dritsos, S. E.

    2008-07-08

    In this study, the technique of seismic strengthening existing reinforced concrete columns and beams using additional concrete layers and jackets is examined. The finite element method and the finite element program ATENA is used in this investigation. When a reinforced jacket or layer is being constructed around a column it is already preloaded due to existing service loads. This effect has been examined for different values of the axial load normalized to the strengthened column. The techniques of strengthening with a concrete jacket or a reinforced concrete layer on the compressive side of the column are examined. Another phenomenon that is examined in this study is the shrinkage of the new concrete of an additional layer used to strengthen an existing member. For this investigation, a simply supported beam with an additional reinforced concrete layer on the tensile side is examined. The results demonstrate that the effect of preloading is important when a reinforced concrete layer is being used with shear connectors between the old and the new reinforcement. It was also found that the shrinkage of the new concrete reduces the strength of the strengthened beam and induces an initial sliding between the old and the new concrete.

  7. Acoustic emission of fire damaged fiber reinforced concrete

    NASA Astrophysics Data System (ADS)

    Mpalaskas, A. C.; Matikas, T. E.; Aggelis, D. G.

    2016-04-01

    The mechanical behavior of a fiber-reinforced concrete after extensive thermal damage is studied in this paper. Undulated steel fibers have been used for reinforcement. After being exposed to direct fire action at the temperature of 850°C, specimens were subjected to bending and compression in order to determine the loss of strength and stiffness in comparison to intact specimens and between the two types. The fire damage was assessed using nondestructive evaluation techniques, specifically ultrasonic pulse velocity (UPV) and acoustic emission (AE). Apart from the strong, well known, correlation of UPV to strength (both bending and compressive), AE parameters based mainly on the frequency and duration of the emitted signals after cracking events showed a similar or, in certain cases, better correlation with the mechanical parameters and temperature. This demonstrates the sensitivity of AE to the fracture incidents which eventually lead to failure of the material and it is encouraging for potential in-situ use of the technique, where it could provide indices with additional characterization capability concerning the mechanical performance of concrete after it subjected to fire.

  8. Computer-Aided Construction at Designing Reinforced Concrete Columns as Per Ec

    NASA Astrophysics Data System (ADS)

    Zielińska, M.; Grębowski, K.

    2015-02-01

    The article presents the authors' computer program for designing and dimensioning columns in reinforced concrete structures taking into account phenomena affecting their behaviour and information referring to design as per EC. The computer program was developed with the use of C++ programming language. The program guides the user through particular dimensioning stages: from introducing basic data such as dimensions, concrete class, reinforcing steel class and forces affecting the column, through calculating the creep coefficient taking into account the impact of imperfection depending on the support scheme and also the number of mating members at load shit, buckling length, to generating the interaction curve graph. The final result of calculations provides two dependence points calculated as per methods of nominal stiffness and nominal curvature. The location of those points relative to the limit curve determines whether the column load capacity is assured or has been exceeded. The content of the study describes in detail the operation of the computer program and the methodology and phenomena which are indispensable at designing axially and eccentrically the compressed members of reinforced concrete structures as per the European standards.

  9. Alternate anode materials for cathodic protection of steel reinforced concrete

    SciTech Connect

    Russell, James H.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Cryer, Curtis B.

    2001-01-01

    Consumable and non-consumable anodes were evaluated in the laboratory for use in cathodic protection (CP) systems for steel reinforced concrete bridges in coastal environments and in areas where deicing salts are employed. The anode materials included Zn-hydrogel and thermal-sprayed Zn, Zn-15Al, Al-12Zn-0.2In, and cobalt-sprayed Ti. These anodes were evaluated for service in both galvanic (GCP) and impressed current (ICCP) cathodic protection systems. Impressed current CP anodes were electrochemically aged at a current density 15 times as great as that used by the Oregon Department of Transportation in typical coastal ICCP systems (2.2 mA/m2 based on anode area). Increasing moisture at the anode-concrete interface reduced the operating voltage of all the anodes. Bond strength between the anodes and concrete decreased with electrochemical aging. The Zn-15Al and Al-12Zn-0.2In anodes provided adequate protection in GCP but their life was too short in the accelerated ICCP tests. Zinc had an adequate life in ICCP tests but was inadequate as a galvanic anode. Zinc-hydrogel performed well in both tests when the hydrogel was kept moist. Titanium was an excellent anode for ICCP, but is not suitable for GCP.

  10. Free vibration of composite re-bars in reinforced structures

    NASA Astrophysics Data System (ADS)

    Kadioglu, Fethi

    2005-11-01

    The effect of composite rebar's shape in reinforced concrete beam-type structures on the natural frequencies and modes shapes is investigated through finite element analysis in this paper. Steel rebars are being replaced with composite rebars due to their better ability to resist corrosion in reinforced concrete structures for many infrastructure applications. A variety of composite rebar shapes can be obtained through the pultrusion process. It will be interesting to investigate their shape on free vibration characteristics. The results of natural frequencies and mode shapes are presented and compared for the different composite rebar shapes. The effects of various boundary conditions for different rebar shapes are also investigated.

  11. Nonlinear failure analysis of a reinforced concrete containment under internal pressure

    SciTech Connect

    Sharma, S.; Wang, Y.K.; Reich, M.

    1984-01-01

    A detailed nonlinear finite element model is used to investigate the failure response of the Indian Point containment building under severe accident pressures. Refined material models are used to describe the complex stress-strain behavior of the liner and rebar steels, the plain concrete and the reinforced concrete. Structural geometry of the containment is idealized by eight layers of axisymmetric finite elements through the wall thickness in order to closely model the actual placement of the rebars. Soil stiffness under the containment base mat is modeled by a series of nonlinear spring elements. Numerical results presented in the paper describe cracking and plastic deformation (in compression) of the concrete, yielding of the liner and rebar steels and eventual loss of the load carrying capacity of the containment. The results are compared with available data from the previous studies for this containment. 8 references, 9 figures.

  12. 77 FR 64127 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-18

    ... both the domestic interested party group response to its notice of institution (77 FR 39254, July 2... COMMISSION Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and... determine whether revocation of the antidumping duty orders on steel concrete reinforcing bar from...

  13. 78 FR 55755 - Steel Concrete Reinforcing Bar From Mexico and Turkey; Institution of Antidumping and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-11

    ... amended. The amendments took effect on November 7, 2011. See 76 FR 61937 (Oct. 6, 2011) and the newly... COMMISSION Steel Concrete Reinforcing Bar From Mexico and Turkey; Institution of Antidumping and... from Mexico and Turkey of steel concrete reinforcing bar, primarily provided for in subheadings...

  14. Diagnosing delayed ettringite formation in concrete structures

    SciTech Connect

    Thomas, Michael Folliard, Kevin Drimalas, Thano Ramlochan, Terry

    2008-06-15

    There has been a number of cases involving deteriorated concrete structures in North America where there has been considerable controversy surrounding the respective contributions of alkali-silica reaction (ASR) and delayed ettringite formation (DEF) to the observed damage. The problem arises because the macroscopic symptoms of distress are not unequivocal and microscopical examinations of field samples often reveal evidence of both processes making it difficult to separate the individual contributions. This paper presents the results of an investigation of a number of concrete columns carrying a raised expressway in North America; prior studies had implicated both DEF and ASR as possible causes of deterioration. Although the columns were not deliberately heat-cured, it is estimated that the peak internal temperature would have exceeded 70 deg. C and perhaps even 80 deg. C, in some cases. The forensic investigation included scanning electron microscopy with energy-dispersive X-ray analysis and expansion testing of cores extracted from the structure. Small-diameter cores stored in limewater expanded significantly (0.3 to 1.3%) and on the basis of supplementary tests on laboratory-produced concrete specimens it was concluded that expansion under such conditions is caused by DEF as the conditions of the test will not sustain ASR. In at least one column, DEF was diagnosed as the sole contributory cause of damage with no evidence of any contribution from ASR or any other deterioration process. In other cases, both ASR and DEF were observed to have contributed to the apparent damage. Of the columns examined, only concrete containing fly ash appeared to be undamaged. The results of this study confirm that, under certain conditions, the process of DEF (acting in isolation of other processes) can result in significant deterioration of cast-in-place reinforced concrete structures.

  15. The behavior of reinforced concrete knee joints under earthquake loads

    NASA Astrophysics Data System (ADS)

    Angelakos, Bill

    The poor performance of knee joint connections during recent earthquakes motivated a number of experimental investigations of knee joint behavior under reversed cyclic loading. In this work the knee joint design problem is studied through a collective evaluation of the available experimental results and analytical modeling. The objective is to identify the critical response variables controlling the mechanics of knee joints under earthquake loads and to quantify the influence they have on the strength and deformation capacity of the joint. A knee joint model is derived from simple mechanical constructs of equilibrium and compatibility. The parametric dependence of knee joint behavior is investigated for critical design parameters such as concrete strength, amounts and yield strengths of horizontal and vertical transverse reinforcement, and bond demand. Three different limiting equations are developed from the model limiting the joint shear resistance according with the three alternative modes of joint shear failure. These are: (i) yielding of horizontal and vertical transverse reinforcement, (ii) and (iii) yielding in either of the two principal reinforcing directions accompanied by crushing of the concrete in compression (here the softening influence of orthogonal tensile deformations is considered). For those test specimens from the experimental database that experienced a joint shear failure, the simple knee joint model predicts their joint shear capacity well. Consistent with observations from interior connections it is shown that anchorage of the main reinforcement in the knee joint region prevails as the determining factor of the response of the joint panel. In addition, the same basic physical model that describes the source of resistance in interior connections also applies to knee joints; truss action, and diagonal strut action. By favorably anchoring the beam and column bars it is possible to develop the joint shear strength which is associated with one

  16. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review.

    SciTech Connect

    Naus, Dan J

    2006-03-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  17. Drying shrinkage of fibre-reinforced lightweight aggregate concrete containing fly ash

    SciTech Connect

    Kayali, O.; Haque, M.N.; Zhu, B.

    1999-11-01

    Lightweight aggregate concretes containing fly ash with a compressive strength between 61 to 67 NPa were produced. The lightweight aggregate used was sintered fly ash. The concretes were reinforced with either polypropylene or steel fibres. The fibres did not affect the compressive strength, but did increase the tensile strength of these concretes. The modulus of elasticity of all the lightweight concretes tested was about 21 GPa, compared to 35 GPa for the normal-weight concrete. Fibre reinforcement did not affect the value of the elastic modulus. This type of lightweight concrete, containing fly ash as 23% of the total cementitious content, resulted in long-term shrinkage that is nearly twice as large as normal-weight concrete of somewhat similar strength. Polypropylene fibre reinforcement did not reduce drying shrinkage, while steel fibres did. Early shrinkage behavior of this type of lightweight concrete was similar to normal-weight concrete. However, the rate of shrinkage of the lightweight concrete remained constant until nearly 100 days of drying. This is different from normal-weight concrete that showed appreciably after 56 days. Shrinkage of normal-weight concrete stabilized after 400 days, which shrinkage of lightweight concrete did not appear to stabilize after a similar period of continuous drying.

  18. Study of a reinforced concrete beam strengthened using a combination of SMA wire and CFRP plate

    NASA Astrophysics Data System (ADS)

    Liu, Zhi-qiang; Li, Hui

    2006-03-01

    Traditional methods used for strengthening of reinforced concrete (RC) structures, such as bonding of steel plates, suffer from inherent disadvantages. In recent years, strengthening of RC structures using carbon fiber reinforced polymer (CFRP) plates has attracted considerable attentions around the world. Most existing research on CFRP plate bonding for flexural strengthening of RC beams has been carried out for the strength enhancement. However, little research is focused on effect of residual deformations on the strengthening. The residual deformations have an important effect on the strengthening by CFRP plates. There exists a very significant challenge how the residual deformations are reduced. Shape memory alloy (SMA) has showed outstanding functional properties as an actuator. It is a possibility that SMA can be used to reduce the residual deformation and make cracks of concrete close by imposing the recovery forces on the concrete in the tensile zone. It is only an emergency damage repair since the SMA wires need to be heated continuously. So, an innovative method of a RC beam strengthened by CFRP plates in combination with SMA wires was first investigated experimentally in this paper. In addition, the nonlinear finite element software of ABAQUS was employed to further simulate the behavior of RC beams strengthened through the new strengthening method. It can be found that this is an excellent and effective strengthening method.

  19. A Wireless Passive Sensing System for Displacement/Strain Measurement in Reinforced Concrete Members

    PubMed Central

    Ozbey, Burak; Erturk, Vakur B.; Demir, Hilmi Volkan; Altintas, Ayhan; Kurc, Ozgur

    2016-01-01

    In this study, we show a wireless passive sensing system embedded in a reinforced concrete member successfully being employed for the measurement of relative displacement and strain in a simply supported beam experiment. The system utilizes electromagnetic coupling between the transceiver antenna located outside the beam, and the sensing probes placed on the reinforcing bar (rebar) surface inside the beam. The probes were designed in the form of a nested split-ring resonator, a metamaterial-based structure chosen for its compact size and high sensitivity/resolution, which is at µm/microstrains level. Experiments were performed in both the elastic and plastic deformation cases of steel rebars, and the sensing system was demonstrated to acquire telemetric data in both cases. The wireless measurement results from multiple probes are compared with the data obtained from the strain gages, and an excellent agreement is observed. A discrete time measurement where the system records data at different force levels is also shown. Practical issues regarding the placement of the sensors and accurate recording of data are discussed. The proposed sensing technology is demonstrated to be a good candidate for wireless structural health monitoring (SHM) of reinforced concrete members by its high sensitivity and wide dynamic range. PMID:27070615

  20. A Wireless Passive Sensing System for Displacement/Strain Measurement in Reinforced Concrete Members.

    PubMed

    Ozbey, Burak; Erturk, Vakur B; Demir, Hilmi Volkan; Altintas, Ayhan; Kurc, Ozgur

    2016-01-01

    In this study, we show a wireless passive sensing system embedded in a reinforced concrete member successfully being employed for the measurement of relative displacement and strain in a simply supported beam experiment. The system utilizes electromagnetic coupling between the transceiver antenna located outside the beam, and the sensing probes placed on the reinforcing bar (rebar) surface inside the beam. The probes were designed in the form of a nested split-ring resonator, a metamaterial-based structure chosen for its compact size and high sensitivity/resolution, which is at µm/microstrains level. Experiments were performed in both the elastic and plastic deformation cases of steel rebars, and the sensing system was demonstrated to acquire telemetric data in both cases. The wireless measurement results from multiple probes are compared with the data obtained from the strain gages, and an excellent agreement is observed. A discrete time measurement where the system records data at different force levels is also shown. Practical issues regarding the placement of the sensors and accurate recording of data are discussed. The proposed sensing technology is demonstrated to be a good candidate for wireless structural health monitoring (SHM) of reinforced concrete members by its high sensitivity and wide dynamic range. PMID:27070615

  1. Damage Evaluation in Shear-Critical Reinforced Concrete Beam using Piezoelectric Transducers as Smart Aggregates

    NASA Astrophysics Data System (ADS)

    Chalioris, Constantin E.; Papadopoulos, Nikos A.; Angeli, Georgia M.; Karayannis, Chris G.; Liolios, Asterios A.; Providakis, Costas P.

    2015-10-01

    Damage detection at early cracking stages in shear-critical reinforced concrete beams, before further deterioration and their inevitable brittle shear failure is crucial for structural safety and integrity. The effectiveness of a structural health monitoring technique using the admittance measurements of piezoelectric transducers mounted on a reinforced concrete beam without shear reinforcement is experimentally investigated. Embedded "smart aggregate" transducers and externally bonded piezoelectric patches have been placed in arrays at both shear spans of the beam. Beam were tested till total shear failure and monitored at three different states; healthy, flexural cracking and diagonal cracking. Test results showed that transducers close to the critical diagonal crack provided sound and graduated discrepancies between the admittance responses at the healthy state and thedamage levels.Damage assessment using statistical indices calculated from the measurements of all transducers was also attempted. Rational changes of the index values were obtained with respect to the increase of the damage. Admittance responses and index values of the transducers located on the shear span where the critical diagonal crack formed provided cogent evidence of damage. On the contrary, negligible indication of damage was yielded by the responses of the transducers located on the other shear span, where no diagonal cracking occurred.

  2. Quantitative analysis of magnetic anomaly of reinforcements in bored in-situ concrete pilesℜ

    NASA Astrophysics Data System (ADS)

    Sun, Bin; Dong, Ping; Wang, Chong; Pu, Xiaoxuan; Wu, Yongjing

    2009-09-01

    We quantitatively study magnetic anomalies of reinforcement rods in bored in-situ concrete piles for the first time and summarized their magnetic anomaly character. Key factors such as measuring borehole orientation, borehole-reinforcement distance, and multiple-section reinforcement rods are discussed which contributes valid and quantitative reference for using the magnetic method to detect reinforcement rods. Through tests with model piles, we confirm the accuracy of theoretical computations and then utilize the law discovered in theoretical computations to explain the characteristics of the actual testing curves. The results show that the Za curves of the reinforcement rod reflect important factors regarding the reinforcement rods, such as rod length, change of reinforcement ratio, length of overlap, and etc. This research perfects the magnetic method for detecting reinforcement rods in bored in-situ concrete piles and the method has great importance for preventing building contractor fraud.

  3. Bond variability of glass-fiber-reinforcing-plastic reinforcement in concrete

    SciTech Connect

    Hanus, J.P.

    1998-12-01

    This report summarizes an experimental program that investigated the bond variability of glass-fiber-reinforced-polymer (GFRP) reinforcement in concrete. The variables in the study were manufacturer (Marshall Industries Composites, Incorporated M1 and Corrosion Proof Products/Hughes Brothers M2), bar size (Number 5 and 6), cover (2 and 3 bar diameters), and embedment length (10 through 47 inch). Tensile tests were also performed on the GFRP rebar for comparison to bond tests that exhibited bar failure. Eighty-four inverted half-beam bond specimens were tested while monitoring load, loaded-end slip, free-end slip, cracking, and acoustic emissions on the embedded bar and concrete. Three to six replicate tests were conducted for each set of variables. The results of each test within a series were examined to investigate the relative variability with respect to the failure types. The M1 rebar was observed to rely primarily on mechanical interlock to develop bond strength. This conclusion was based on investigations of the rebar surface condition, bar deformation geometry, slip curves, AE results, crack patterns and forensic investigations. Additionally, the ultimate loads for the bond tests with the Ml rebar were affected by changes in embedment lengths but did not vary for tests with 2 and 3d(b) cover. Overall, the M1 rebar had coefficients of variation (COV) of 14.3 and 8.9% for bond tests that exhibited bar failure and tensile test bar failures, respectively. The bond tests that failed in concrete splitting had COVs from 5.2 to 5.9%.

  4. Strength and Durability of Fly Ash-Based Fiber-Reinforced Geopolymer Concrete in a Simulated Marine Environment

    NASA Astrophysics Data System (ADS)

    Martinez Rivera, Francisco Javier

    This research is aimed at investigating the corrosion durability of polyolefin fiberreinforced fly ash-based geopolymer structural concrete (hereafter referred to as GPC, in contradistinction to unreinforced geopolymer concrete referred to as simply geopolymer concrete), where cement is completely replaced by fly ash, that is activated by alkalis, sodium hydroxide and sodium silicate. The durability in a marine environment is tested through an electrochemical method for accelerated corrosion. The GPC achieved compressive strengths in excess of 6,000 psi. Fiber reinforced beams contained polyolefin fibers in the amounts of 0.1%, 0.3%, and 0.5% by volume. After being subjected to corrosion damage, the GPC beams were analyzed through a method of crack scoring, steel mass loss, and residual flexural strength testing. Fiber reinforced GPC beams showed greater resistance to corrosion damage with higher residual flexural strength. This makes GPC an attractive material for use in submerged marine structures.

  5. ASSESSMENT OF 90SR AND 137CS PENETRATION INTO REINFORCED CONCRETE (EXTENT OF 'DEEPENING') UNDER NATURAL ATMOSPHERIC CONDITIONS

    SciTech Connect

    Farfan, E.; Jannik, T.

    2011-10-01

    When assessing the feasibility of remediation following the detonation of a radiological dispersion device or improvised nuclear device in a large city, several issues should be considered including the levels and characteristics of the radioactive contamination, the availability of resources required for decontamination, and the planned future use of the city's structures and buildings. Currently, little is known about radionuclide penetration into construction materials in an urban environment. Knowledge in this area would be useful when considering costs of a thorough decontamination of buildings, artificial structures, and roads in an affected urban environment. Pripyat, a city substantially contaminated by the Chernobyl Nuclear Power Plant accident in April 1986, may provide some answers. The main objective of this study was to assess the depth of {sup 90}Sr and {sup 137}Cs penetration into reinforced concrete structures in a highly contaminated urban environment under natural weather conditions. Thirteen reinforced concrete core samples were obtained from external surfaces of a contaminated building in Pripyat. The concrete cores were drilled to obtain sample layers of 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, and 40-50 mm. Both {sup 90}Sr and {sup 137}Cs were detected in the entire 0-50 mm profile of the reinforced cores sampled. In most of the cores, over 90% of the total {sup 137}Cs inventory and 70% of the total {sup 90}Sr inventory was found in the first 0-5 mm layer of the reinforced concrete. {sup 90}Sr had penetrated markedly deeper into the reinforced concrete structures than {sup 137}Cs.

  6. Assessment of (90)sr and (137)cs penetration into reinforced concrete (extent of "deepening") under natural atmospheric conditions.

    PubMed

    Farfán, Eduardo B; Gaschak, Sergey P; Maksymenko, Andrey M; Donnelly, Elizabeth H; Bondarkov, Mikhail D; Jannik, G Tim; Marra, James C

    2011-09-01

    When assessing the feasibility of remediation following the detonation of a radiological dispersion device or improvised nuclear device in a large city, several issues should be considered, including the levels and characteristics of the radioactive contamination, the availability of resources required for decontamination and the planned future use of the city's structures and buildings. Currently, little is known about radionuclide penetration into construction materials in an urban environment. Knowledge in this area would be useful when considering costs of a thorough decontamination of buildings, artificial structures and roads in an affected urban environment. Pripyat, a city substantially contaminated by the Chernobyl Nuclear Power Plant accident in April 1986, may provide some answers. The main objective of this study was to assess the depth of (90)Sr and (137)Cs penetration into reinforced concrete structures in a highly contaminated urban environment under natural weather conditions. Thirteen reinforced concrete core samples were obtained from external surfaces of a contaminated building in Pripyat. The concrete cores were drilled to obtain sample layers of 0-5, 5-10, 10-15, 15-20, 20-30, 30-40 and 40-50 mm. Both (90)Sr and (137)Cs were detected in the entire 0-50 mm profile of the reinforced cores sampled. In most of the cores, over 90% of the total (137)Cs inventory and 70% of the total (90)Sr inventory was found in the first 0-5 mm layer of the reinforced concrete. Strontium-90 ((90)Sr) had penetrated markedly deeper into the reinforced concrete structures than (137)Cs. PMID:21799347

  7. Self-sensing CF-GFRP rods as mechanical reinforcement and sensors of concrete beams

    NASA Astrophysics Data System (ADS)

    Nanni, F.; Auricchio, F.; Sarchi, F.; Forte, G.; Gusmano, G.

    2006-02-01

    In this paper testing carried out on concrete beams reinforced with self-sensing composite rods is presented. Such concrete beams, whose peculiarity is to be reinforced by self-sensing materials able to generate an alarm signal when fixed loads are reached, were designed, manufactured and tested. The reinforcing rods were manufactured by pultrusion and consisted of self-sensing hybrid composites containing both glass and carbon fibres in an epoxy resin. The experimentation was carried out by performing simultaneously mechanical tests on the reinforced beams and electrical measurements on the composite rods. The results showed that the developed system reached the target proposed, giving an alarm signal.

  8. Cracking assessment in concrete structures by distributed optical fiber

    NASA Astrophysics Data System (ADS)

    Rodríguez, Gerardo; Casas, Joan R.; Villaba, Sergi

    2015-03-01

    In this paper, a method to obtain crack initiation, location and width in concrete structures subjected to bending and instrumented with an optical backscattered reflectometer (OBR) system is proposed. Continuous strain data with high spatial resolution and accuracy are the main advantages of the OBR system. These characteristics make this structural health monitoring technique a useful tool in early damage detection in important structural problems. In the specific case of reinforced concrete structures, which exhibit cracks even in-service loading, the possibility to obtain strain data with high spatial resolution is a main issue. In this way, this information is of paramount importance concerning the durability and long performance and management of concrete structures. The proposed method is based on the results of a test up to failure carried out on a reinforced concrete slab. Using test data and different crack modeling criteria in concrete structures, simple nonlinear finite element models were elaborated to validate its use in the localization and appraisal of the crack width in the testing slab.

  9. The effect of recycled concrete aggregate properties on the bond strength between RCA concrete and steel reinforcement

    SciTech Connect

    Butler, L. West, J.S.; Tighe, S.L.

    2011-10-15

    The purpose of this study was to investigate the influence that replacing natural coarse aggregate with recycled concrete aggregate (RCA) has on concrete bond strength with reinforcing steel. Two sources of RCA were used along with one natural aggregate source. Numerous aggregate properties were measured for all aggregate sources. Two types of concrete mixture proportions were developed replacing 100% of the natural aggregate with RCA. The first type maintained the same water-cement ratios while the second type was designed to achieve the same compressive strengths. Beam-end specimens were tested to determine the relative bond strength of RCA and natural aggregate concrete. On average, natural aggregate concrete specimens had bond strengths that were 9 to 19% higher than the equivalent RCA specimens. Bond strength and the aggregate crushing value seemed to correlate well for all concrete types.

  10. Impedance spectroscopy of concrete cover on bridge decks with reinforcing steel

    NASA Astrophysics Data System (ADS)

    Bartholomew, Paul; Blankenagel, Bryan; Guthrie, Spencer; Mazzeo, Brian

    2011-10-01

    Chloride-induced corrosion of reinforcing steel is a major problem for aging bridge structures near marine environments or in cold regions where deicing salts are applied as part of winter maintenance. Corrosion is the result of the interaction of diffused chloride ions with the embedded steel. One property of affected decks that facilitates detection of chloride ions is their ability to conduct electricity. Impedance spectroscopy can be used to measure concrete conductivity and thereby identify areas of increased chloride concentration characterized by elevated risks of corrosion. A new probe and measurement apparatus has been engineered to measure large areas of concrete on bridge decks. Comparison between measurements obtained in the laboratory and in the field will be presented.

  11. Assessment of Reinforced Concrete Surface Breaking Crack Using Rayleigh Wave Measurement

    PubMed Central

    Lee, Foo Wei; Chai, Hwa Kian; Lim, Kok Sing

    2016-01-01

    An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters of interest and crack characteristics (depth and degree of inclination) were obtained, which were then validated by experimental measurement of concrete specimens instigated with vertical and inclined artificial cracks of different depths. Wave parameters including velocity and amplitude attenuation for each case were studied. The correlations allowed us to estimate the depth and inclination of cracks measured experimentally with acceptable discrepancies, particularly for cracks which are relatively shallow and when the crack depth is smaller than the wavelength. PMID:26959028

  12. Ultimate pressure capacity analysis of a post-tensioned reinforced concrete nuclear reactor containment building

    SciTech Connect

    Dooley, W.T.; Macek, R.W.; Sadik, S.

    1983-01-01

    This paper presents a three dimensional nonlinear structural analysis of a post-tensioned reinforced concrete nuclear reactor containment building. The objective of the analysis was to develop and demonstrate modeling techniques appropriate for determining the global ultimate internal pressure capacity of this type of containment. The structural model developed for the ADINA computer code employed nonlinear material models with truss, shell and three dimensional continuum elements to represent the major structural members (tendons, rebars, ties, concrete and liner). In addition a special uniaxial elastic plastic shell material model was developed to facilitate representation of the dome tendon lacing pattern. Effective use of symmetry permitted all three dimensional effects to be represented in a 30/sup 0/ (0.52 rad) segment of the structure. The analysis suggested that gross failure of the structure at a quasistatic internal pressure of 99 psi (0.68 MPa) may have been precipitated by the nonaxisymmetric three dimensional nature of the stress field in the concrete near the tendon anchorages.

  13. Ultimate capacity evaluation of reinforced concrete slabs using yield line analysis

    SciTech Connect

    Mertz, G.E.

    1995-12-31

    Yield line theory offers a simplified nonlinear analytical method that can determine the ultimate bending capacity of flat reinforced concrete planes subject to distributed and concentrated loads. Alternately, yield line theory, combined with hinge rotation limits can determine the energy absorption capacity of plates subject to impulsive and impact loads. This method is especially useful in evaluating existing structures that cannot be qualified using conservative simplifying analytical assumptions. Typical components analyzed by yield line theory are basements, floor and roof slabs subject to vertical loads along with walls subject to out of plant wall loads. One limitation of yield line theory is that it is difficult to evaluate some mechanisms; this is aggravated by the complex geometry and reinforcing layouts commonly found in practice. A yield line evaluation methodology is proposed to solve computationally tedious yield line mechanisms. This methodology is implemented in a small PC based computer program that allows the engineer to quickly evaluate multiple yield line mechanisms.

  14. Experimental data of the static behavior of reinforced concrete beams at room and low temperature

    PubMed Central

    Mirzazadeh, M. Mehdi; Noël, Martin; Green, Mark F.

    2016-01-01

    This article provides data on the static behavior of reinforced concrete at room and low temperature including, strength, ductility, and crack widths of the reinforced concrete. The experimental data on the application of digital image correlation (DIC) or particle image velocimetry (PIV) in measuring crack widths and the accuracy and precision of DIC/PIV method with temperature variations when is used for measuring strains is provided as well. PMID:27158650

  15. Experimental data of the static behavior of reinforced concrete beams at room and low temperature.

    PubMed

    Mirzazadeh, M Mehdi; Noël, Martin; Green, Mark F

    2016-06-01

    This article provides data on the static behavior of reinforced concrete at room and low temperature including, strength, ductility, and crack widths of the reinforced concrete. The experimental data on the application of digital image correlation (DIC) or particle image velocimetry (PIV) in measuring crack widths and the accuracy and precision of DIC/PIV method with temperature variations when is used for measuring strains is provided as well. PMID:27158650

  16. Feasibility research report of villa constructed of glass fiber reinforced concrete

    NASA Astrophysics Data System (ADS)

    Li, Shengli; Lu, Yu; Wang, Dongwei

    2011-04-01

    With the development of economy and improvement degree of modernization, the villa project design program tend to focus on the green, high-tech, humanities, and more emphasis on the integrity of space, noble and elegant feeling. Therefore, based on the study of literatures, this paper discussed the present situation and issue and features of Glass Fiber Reinforced Concrete and the feature of assembly house, and confirmed that the villa of assemble house is feasible by built of Glass Fiber Reinforced Concrete.

  17. Alternative consumable anodes for cathodic protection of reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Russell, James H.; Cryer, C.B.; Laylor, H.M.

    1999-01-01

    Alternative consumable anodes were evaluated in the laboratory for use in cathodic protection systems for steel reinforced concrete bridges in coastal environments and in areas where deicing salts are employed. The anode materials included zinc hydrogel foil and thermal-sprayed Zn, Zn-15Al, and Al-12Zn-0.2In alloys. They were evaluated for service in both impressed current (ICCP) and galvanic (GCP) cathodic protection systems. ICCP anodes were electrochemically aged at current densities of five to fifteen times that used by the Oregon Department of Transportation (Oregon DOT) in typical coastal CP systems (2.2 mA/m2 based on anode area). GCP anodes were electrochemically aged at a rate defined by the steel-anode couple. Both types of anodes were exposed to 80°F, a relative humidity of 85 pct, and were periodically wetted with deionized water. The Zn anode gave the best performance in ICCP systems. The four anodes all produced sufficient current density suitable for use in GCP systems. The anodes materials, ranked in increasing order of GCP current output, were: thermal-sprayed Al-12Zn-0.2In, Zn hydrogel, thermal-sprayed Zn-15Al, and thermal-sprayed Zn.

  18. Durability of a reinforced concrete designed for the construction of an intermediate-level radioactive waste disposal facility

    NASA Astrophysics Data System (ADS)

    Duffó, G. S.; Arva, E. A.; Schulz, F. M.; Vazquez, D. R.

    2012-01-01

    The National Atomic Energy Commission of the Argentine Republic is developing a nuclear waste disposal management programme that contemplates the design and construction of a facility for the final disposal of intermediate-level radioactive wastes. The repository is based on the use of multiple, independent and redundant barriers. The major components are made in reinforced concrete so, the durability of these structures is an important aspect for the facility integrity. This work presents an investigation performed on a reinforced concrete specifically designed for this purpose, to predict the service life of the intermediate level radioactive waste disposal facility from data obtained with several techniques. Results obtained with corrosion sensors embedded in a concrete prototype are also included. The information obtained will be used for the final design of the facility in order to guarantee a service life more or equal than the foreseen durability for this type of facilities.

  19. Studies on the corrosion resistance of reinforced steel in concrete with ground granulated blast-furnace slag--An overview.

    PubMed

    Song, Ha-Won; Saraswathy, Velu

    2006-11-16

    The partial replacement of clinker, the main constituent of ordinary Portland cement by pozzolanic or latent hydraulic industrial by-products such as ground granulated blast furnace slag (GGBFS), effectively lowers the cost of cement by saving energy in the production process. It also reduces CO2 emissions from the cement plant and offers a low priced solution to the environmental problem of depositing industrial wastes. The utilization of GGBFS as partial replacement of Portland cement takes advantage of economic, technical and environmental benefits of this material. Recently offshore, coastal and marine concrete structures were constructed using GGBFS concrete because high volume of GGBFS can contribute to the reduction of chloride ingress. In this paper, the influence of using GGBFS in reinforced concrete structures from the durability aspects such as chloride ingress and corrosion resistance, long term durability, microstructure and porosity of GGBFS concrete has been reviewed and discussed. PMID:16930831

  20. Modeling the dynamic stiffness of cracked reinforced concrete beams under low-amplitude vibration loads

    NASA Astrophysics Data System (ADS)

    Xu, Tengfei; Castel, Arnaud

    2016-04-01

    In this paper, a model, initially developed to calculate the stiffness of cracked reinforced concrete beams under static loading, is used to assess the dynamic stiffness. The model allows calculating the average inertia of cracked beams by taking into account the effect of bending cracks (primary cracks) and steel-concrete bond damage (i.e. interfacial microcracks). Free and forced vibration experiments are used to assess the performance of the model. The respective influence of bending cracks and steel-concrete bond damage on both static and dynamic responses is analyzed. The comparison between experimental and simulated deflections confirms that the effects of both bending cracks and steel-concrete bond loss should be taken into account to assess reinforced concrete stiffness under service static loading. On the contrary, comparison of experimental and calculated dynamic responses reveals that localized steel-concrete bond damages do not influence significantly the dynamic stiffness and the fundamental frequency.

  1. History of the Development of Liquid-Applied Coatings for Protection of Reinforced Concrete

    NASA Technical Reports Server (NTRS)

    Curran, Joseph J.; Hansen, marlin H.

    2005-01-01

    Corrosion of reinforcing steel in concrete is an insidious problem for structures at Kennedy Space Center (KSC). KSC is located on the coast of Florida in a highly corrosive atmosphere. Launch pads, highway bridge infrastructure, and buildings are strongly affected. To mitigate these problems, NASA initiated a development program for a Galvanic Liquid-Applied Coating System (GLACS). A breakthrough in this area would have great commercial value in transportation, marine and construction industry infrastructures. The patented NASA GLACS system has undergone considerable testing to meet the needs of commercialization. A moisture-cure coating gives excellent adhesion with ease of application compared to existing galvanic products on the market. The latest development, GalvaCori; can be sprayed or hand applied to almost any structure shape. A self-adhesive conductive tape system has been devised to simplify current collection within the coating areas. In testing programs, millivolt potential and milliamp output per square foot of anode have been closely studied at actual test sites. These two parameters are probably the most challenging items of a resin-based, room-temperature-applied, galvanic coating. Extensive re-formulation has resulted in a system that provides the needed polarization for catholic protection of reinforcing steel in concrete in a variety of structure environments. The rate of corrosion of rebar in concrete is greatly affected by the environment of the structure. In addition to this, for any given concrete structure; moisture level, carbonization, and chloride contamination influences the rate of rebar corrosion. Similarly, the cathodic protection level of galvanic systems is also dependent on the moisture level of the concrete. GalvaCorr is formulated to maintain galvanic activity as the moisture level of the structure declines. GalvaCorr is available as a three-part kit. The mixing step requires about ten minutes. The viscosity can be easily

  2. Experimental and analytical behavior of strengthened reinforced concrete columns with steel angles and strips

    NASA Astrophysics Data System (ADS)

    Khalifa, Essam S.; Al-Tersawy, Sherif H.

    2014-06-01

    The need of strengthening reinforced concrete columns, due to loss of strength and/or stiffness, is an essential requirement due to variation of the loads and environmental conditions applied on these columns. Steel jackets around the reinforced concrete (RC) columns are usually made by means of steel plates covering all over the column surface area. For the value of engineering purposes, another technique was developed using steel angles at the corners of the RC columns connected with discrete steel strips. In this paper, an experimental program is designed to evaluate the improvement in load-carrying capacity, stiffness and ductility of strengthened RC columns, concomitant with steel angles and strips. Despite of prevailing a substantially increased loading capacity and strength a pronounced enhancement in ductility and stiffness has been reported. A need for experimental test results with low value of concrete strength to mimic the local old-age structures condition that required strengthening in local countries. Seven columns specimens are tested to evaluate the strength improvement provided by steel strengthening of columns. The method of strengthened steel angles with strips is compared with another strengthening technique. This technique includes connected and unconnected steel-casing specimens. The observed experimental results describe load-shortening curves, horizontal strains in stirrups and steel strips, as well as description of failure mode. The extra-confinement pressure, due to existence of steel cage, of the strengthened RC column can be also observed from experimental results. The code provisions that predict the load-carrying capacity of the strengthened RC composite column has a discrepancy in the results. For this reason, an analytical model is developed in this paper to compare the code limit with experimental observed results. The proposed model accounts for the composite action for concrete confinement and enhancement of the local buckling

  3. Tensile properties of glass/natural jute fibre-reinforced polymer bars for concrete reinforcement

    NASA Astrophysics Data System (ADS)

    Han, J. W.; Lee, S. K.; Kim, K. W.; Park, C. G.

    2015-12-01

    The tensile performance of glass/natural jute fibre-reinforced polymer (FRP) bar, intended for concrete reinforcement was evaluated as a function of volume fraction of natural jute fibre. Natural jute fibre, mixed at a ratio of 7:3 with vinyl ester, was surface-treated with a silane coupling agent and used to replaced glass fibre in the composite in volume fractions of 0%, 30%, 50%, 70%, and 100%. The tensile load-displacement curve showed nearly linear elastic behaviour up to 50% natural jute fibre, but was partially nonlinear at a proportion of 70%. However, the glass/natural jute FRP bars prepared using 100% natural jute fibre showed linear elastic behaviour. Tensile strength decreased as the natural jute fibre volume fraction increased because the tensile strength of natural jute fibre is much lower than that of glass fibre (about 1:8.65). The degree of reduction was not proportional to the natural jute fibre volume fraction due to the low density of natural jute fibre (1/2 that of glass fibre). Thus, as the mix proportion of natural jute fibre increased, the amount (wt%) and number of fibres used also increased.

  4. Joint shear strength of FRP reinforced concrete beam-column joints

    NASA Astrophysics Data System (ADS)

    Saravanan, Jagadeesan; Kumaran, Ganapathy

    2011-03-01

    An assessment of the joint shear strength of exterior concrete beam-column joints reinforced internally with Glass Fibre Reinforced Polymer (GFRP) reinforcements under monotonically increasing load on beams keeping constant load on columns is carried out in this study. Totally eighteen numbers of specimens are cast and tested for different parametric conditions like beam longitudinal reinforcement ratio, concrete strength, column reinforcement ratio, joint aspect ratio and influence of the joint stirrups at the joint. Also finite element analysis is performed to simulate the behaviour of the beam-column joints under various parametric conditions. Based on this study, a modified design equation is proposed for assessing the joint shear strength of the GFRP reinforced beam-column specimens based on the experimental results and the review of the prevailing design equations.

  5. Optimization of the Infrastructure of Reinforced Concrete Reservoirs by a Particle Swarm Algorithm

    NASA Astrophysics Data System (ADS)

    Kia, Saeed; Sebt, Mohammad Hassan; Shahhosseini, Vahid

    2015-03-01

    Optimization techniques may be effective in finding the best modeling and shapes for reinforced concrete reservoirs (RCR) to improve their durability and mechanical behavior, particularly for avoiding or reducing the bending moments in these structures. RCRs are one of the major structures applied for reserving fluids to be used in drinking water networks. Usually, these structures have fixed shapes which are designed and calculated based on input discharges, the conditions of the structure's topology, and geotechnical locations with various combinations of static and dynamic loads. In this research, the elements of reservoir walls are first typed according to the performance analyzed; then the range of the membrane based on the thickness and the minimum and maximum cross sections of the bar used are determined in each element. This is done by considering the variable constraints, which are estimated by the maximum stress capacity. In the next phase, based on the reservoir analysis and using the algorithm of the PARIS connector, the related information is combined with the code for the PSO algorithm, i.e., an algorithm for a swarming search, to determine the optimum thickness of the cross sections for the reservoir membrane's elements and the optimum cross section of the bar used. Based on very complex mathematical linear models for the correct embedding and angles related to achain of peripheral strengthening membranes, which optimize the vibration of the structure, a mutual relation is selected between the modeling software and the code for a particle swarm optimization algorithm. Finally, the comparative weight of the concrete reservoir optimized by the peripheral strengthening membrane is analyzed using common methods. This analysis shows a 19% decrease in the bar's weight, a 20% decrease in the concrete's weight, and a minimum 13% saving in construction costs according to the items of a checklist for a concrete reservoir at 10,000 m3.

  6. Nondestructive evaluation of concrete structures by nonstationary thermal wave imaging

    NASA Astrophysics Data System (ADS)

    Mulaveesala, Ravibabu; Panda, Soma Sekhara Balaji; Mude, Rupla Naik; Amarnath, Muniyappa

    2012-06-01

    Reinforced concrete structures (RCS) have potential application in civil engineering and with the advent of nuclear engineering RCS to be capable enough to withstanding a variety of adverse environmental conditions. However, failures/loss of durability of designed structures due to premature reinforcement corrosion of rebar is a major constrain. Growing concern of safety of structure due to pre-mature deterioration has led to a great demand for development of non-destructive and non-contact testing techniques for monitoring and assessing health of RCS. This paper presents an experimental investigation of rebar corrosion by non-stationary thermal wave imaging. Experimental results have been proven, proposed approach is an effective technique for identification of corrosion in rebar in the concrete samples.

  7. Fundamental period of Italian reinforced concrete buildings: comparison between numerical, experimental and Italian code simplified values

    NASA Astrophysics Data System (ADS)

    Ditommaso, Rocco; Carlo Ponzo, Felice; Auletta, Gianluca; Iacovino, Chiara; Nigro, Antonella

    2015-04-01

    Aim of this study is a comparison among the fundamental period of reinforced concrete buildings evaluated using the simplified approach proposed by the Italian Seismic code (NTC 2008), numerical models and real values retrieved from an experimental campaign performed on several buildings located in Basilicata region (Italy). With the intention of proposing simplified relationships to evaluate the fundamental period of reinforced concrete buildings, scientists and engineers performed several numerical and experimental campaigns, on different structures all around the world, to calibrate different kind of formulas. Most of formulas retrieved from both numerical and experimental analyses provides vibration periods smaller than those suggested by the Italian seismic code. However, it is well known that the fundamental period of a structure play a key role in the correct evaluation of the spectral acceleration for seismic static analyses. Generally, simplified approaches impose the use of safety factors greater than those related to in depth nonlinear analyses with the aim to cover possible unexpected uncertainties. Using the simplified formula proposed by the Italian seismic code the fundamental period is quite higher than fundamental periods experimentally evaluated on real structures, with the consequence that the spectral acceleration adopted in the seismic static analysis may be significantly different than real spectral acceleration. This approach could produces a decreasing in safety factors obtained using linear and nonlinear seismic static analyses. Finally, the authors suggest a possible update of the Italian seismic code formula for the simplified estimation of the fundamental period of vibration of existing RC buildings, taking into account both elastic and inelastic structural behaviour and the interaction between structural and non-structural elements. Acknowledgements This study was partially funded by the Italian Civil Protection Department within the

  8. Long-term deflections of reinforced concrete elements: accuracy analysis of predictions by different methods

    NASA Astrophysics Data System (ADS)

    Gribniak, Viktor; Bacinskas, Darius; Kacianauskas, Rimantas; Kaklauskas, Gintaris; Torres, Lluis

    2013-08-01

    Long-term deflection response of reinforced concrete flexural members is influenced by the interaction of complex physical phenomena, such as concrete creep, shrinkage and cracking, which makes their prediction difficult. A number of approaches are proposed by design codes with different degrees of simplification and accuracy. This paper statistically investigates accuracy of long-term deflection predictions made by some of the most widely used design codes ( Eurocode 2, ACI 318, ACI 435, and the new Russian code SP 52-101) and a numerical technique proposed by the authors. The accuracy is analyzed using test data of 322 reinforced concrete members from 27 test programs reported in the literature. The predictions of each technique are discussed, and a comparative analysis is made showing the influence of different parameters, such as sustained loading duration, compressive strength of concrete, loading intensity and reinforcement ratio, on the prediction accuracy.

  9. Corrosion detection of steel reinforced concrete using combined carbon fiber and fiber Bragg grating active thermal probe

    NASA Astrophysics Data System (ADS)

    Li, Weijie; Ho, Siu Chun Michael; Song, Gangbing

    2016-04-01

    Steel reinforcement corrosion is one of the dominant causes for structural deterioration for reinforced concrete structures. This paper presents a novel corrosion detection technique using an active thermal probe. The technique takes advantage of the fact that corrosion products have poor thermal conductivity, which will impede heat propagation generated from the active thermal probe. At the same time, the active thermal probe records the temperature response. The presence of corrosion products can thus be detected by analyzing the temperature response after the injection of heat at the reinforcement-concrete interface. The feasibility of the proposed technique was firstly analyzed through analytical modeling and finite element simulation. The active thermal probe consisted of carbon fiber strands to generate heat and a fiber optic Bragg grating (FBG) temperature sensor. Carbon fiber strands are used due to their corrosion resistance. Wet-dry cycle accelerated corrosion experiments were performed to study the effect of corrosion products on the temperature response of the reinforced concrete sample. Results suggest a high correlation between corrosion severity and magnitude of the temperature response. The technique has the merits of high accuracy, high efficiency in measurement and excellent embeddability.

  10. Behavior Of A Confined Tension Lap Splice In High-Strength Reinforced Concrete Beams

    NASA Astrophysics Data System (ADS)

    Abdel-Kareem, Ahmed H.; Abousafa, Hala; El-Hadidi, Omaia S.

    2015-09-01

    The results of an experimental program conducted on seventeen simply supported concrete beams to study the effect of transverse reinforcement on the behavior of the lap splice of a steel reinforcement in tension zones in high-strength concrete beams are presented. The parameters included in the experimental program were the concrete compressive strength, the lap splice length, the amount of transverse reinforcement provided within the splice region, and the shape of the transverse reinforcement around the spliced bars. The experimental results showed that the displacement ductility increased and the mode of failure changed from a splitting bond failure to a flexural failure when the amount of the transverse reinforcement in the splice region increased, and the compressive strength increased up to 100 MPa. The presence of the transverse reinforcement around the spliced bars had a pronounced effect on increasing the ultimate load, the ultimate deflection, and the displacement ductility. The prediction of maximum steel stresses for spliced bars using the ACI 318-05 building code was compared with the experimental results. The comparison showed that the effect of the transverse reinforcement around spliced bars has to be considered into the design equations for lap splice length in high-strength concrete beams.

  11. Non-destructive inspection protocol for reinforced concrete barriers and bridge railings

    NASA Astrophysics Data System (ADS)

    Chintakunta, Satish R.; Boone, Shane D.

    2014-02-01

    Reinforced concrete highway barriers and bridge railings serve to prevent errant vehicles from departing the travel way at grade separations. Despite the important role that they play in maintaining safety and their ubiquitous nature, barrier inspection rarely moves beyond visual inspection. In August 2008, a tractor-trailer fatally departed William Preston Lane, Jr. Memorial Bridge after it dislodged a section of the bridge barrier. Investigations following the accident identified significant corrosion of the anchor bolts attaching the bridge railing to the bridge deck. As a result of the information gathered during its investigation of the accident, the National Transportation Safety Board (NTSB) made recommendations to the Federal Highway Administration concerning Non-Destructive Evaluation (NDE) of concrete bridge railings. The Center for nondestructive evaluation (NDE) at Turner Fairbank Highway Research Center in McLean, VA is currently evaluating feasibility of using four technologies - ground penetrating radar (GPR), ultrasonic pulse-echo, digital radiography and infrared thermal imaging methods to develop bridge inspection methods that augment visual inspections, offer reliable measurement techniques, and are practical, both in terms of time and cost, for field inspection work. Controlled samples containing predefined corrosion levels in reinforcing steel were embedded at barrier connection points for laboratory testing. All four NDE techniques were used in the initial phase I testing. An inspection protocol for detecting and measuring the corrosion of reinforced steel embedded in the anchorage system will be developed as part of phase II research. The identified technologies shall be further developed for field testing utilizing a structure with a barrier in good condition and a structure with a barrier in poor condition.

  12. Non-destructive inspection protocol for reinforced concrete barriers and bridge railings

    SciTech Connect

    Chintakunta, Satish R.; Boone, Shane D.

    2014-02-18

    Reinforced concrete highway barriers and bridge railings serve to prevent errant vehicles from departing the travel way at grade separations. Despite the important role that they play in maintaining safety and their ubiquitous nature, barrier inspection rarely moves beyond visual inspection. In August 2008, a tractor-trailer fatally departed William Preston Lane, Jr. Memorial Bridge after it dislodged a section of the bridge barrier. Investigations following the accident identified significant corrosion of the anchor bolts attaching the bridge railing to the bridge deck. As a result of the information gathered during its investigation of the accident, the National Transportation Safety Board (NTSB) made recommendations to the Federal Highway Administration concerning Non-Destructive Evaluation (NDE) of concrete bridge railings. The Center for nondestructive evaluation (NDE) at Turner Fairbank Highway Research Center in McLean, VA is currently evaluating feasibility of using four technologies - ground penetrating radar (GPR), ultrasonic pulse-echo, digital radiography and infrared thermal imaging methods to develop bridge inspection methods that augment visual inspections, offer reliable measurement techniques, and are practical, both in terms of time and cost, for field inspection work. Controlled samples containing predefined corrosion levels in reinforcing steel were embedded at barrier connection points for laboratory testing. All four NDE techniques were used in the initial phase I testing. An inspection protocol for detecting and measuring the corrosion of reinforced steel embedded in the anchorage system will be developed as part of phase II research. The identified technologies shall be further developed for field testing utilizing a structure with a barrier in good condition and a structure with a barrier in poor condition.

  13. Corrosion of Carbon Steel and Corrosion-Resistant Rebars in Concrete Structures Under Chloride Ion Attack

    NASA Astrophysics Data System (ADS)

    Mohamed, Nedal; Boulfiza, Mohamed; Evitts, Richard

    2013-03-01

    Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., highway bridges, marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed to avoid these high-cost repairs. Thus, it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements. This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three-electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4™ potentiostat manufactured by Gamry Instruments (Warminster, PA). DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution.

  14. A micromorphic model for steel fiber reinforced concrete.

    PubMed

    Oliver, J; Mora, D F; Huespe, A E; Weyler, R

    2012-10-15

    A new formulation to model the mechanical behavior of high performance fiber reinforced cement composites with arbitrarily oriented short fibers is presented. The formulation can be considered as a two scale approach, in which the macroscopic model, at the structural level, takes into account the mesostructural phenomenon associated with the fiber-matrix interface bond/slip process. This phenomenon is contemplated by including, in the macroscopic description, a micromorphic field representing the relative fiber-cement displacement. Then, the theoretical framework, from which the governing equations of the problem are derived, can be assimilated to a specific case of the material multifield theory. The balance equation derived for this model, connecting the micro stresses with the micromorphic forces, has a physical meaning related with the fiber-matrix bond slip mechanism. Differently to previous procedures in the literature, addressed to model fiber reinforced composites, where this equation has been added as an additional independent ingredient of the methodology, in the present approach it arises as a natural result derived from the multifield theory. Every component of the composite is defined with a specific free energy and constitutive relation. The mixture theory is adopted to define the overall free energy of the composite, which is assumed to be homogeneously constituted, in the sense that every infinitesimal volume is occupied by all the components in a proportion given by the corresponding volume fraction. The numerical model is assessed by means of a selected set of experiments that prove the viability of the present approach. PMID:24049211

  15. A new discrete-element approach for the assessment of the seismic resistance of composite reinforced concrete-masonry buildings

    SciTech Connect

    Calio, I.; Cannizzaro, F.; Marletta, M.; Panto, B.; D'Amore, E.

    2008-07-08

    In the present study a new discrete-element approach for the evaluation of the seismic resistance of composite reinforced concrete-masonry structures is presented. In the proposed model, unreinforced masonry panels are modelled by means of two-dimensional discrete-elements, conceived by the authors for modelling masonry structures, whereas the reinforced concrete elements are modelled by lumped plasticity elements interacting with the masonry panels through nonlinear interface elements. The proposed procedure was adopted for the assessment of the seismic response of a case study confined-masonry building which was conceived to be a typical representative of a wide class of residential buildings designed to the requirements of the 1909 issue of the Italian seismic code and widely adopted in the aftermath of the 1908 earthquake for the reconstruction of the cities of Messina and Reggio Calabria.

  16. Nonlinear Earthquake Analysis of Reinforced Concrete Frames with Fiber and Bernoulli-Euler Beam-Column Element

    PubMed Central

    Karaton, Muhammet

    2014-01-01

    A beam-column element based on the Euler-Bernoulli beam theory is researched for nonlinear dynamic analysis of reinforced concrete (RC) structural element. Stiffness matrix of this element is obtained by using rigidity method. A solution technique that included nonlinear dynamic substructure procedure is developed for dynamic analyses of RC frames. A predicted-corrected form of the Bossak-α method is applied for dynamic integration scheme. A comparison of experimental data of a RC column element with numerical results, obtained from proposed solution technique, is studied for verification the numerical solutions. Furthermore, nonlinear cyclic analysis results of a portal reinforced concrete frame are achieved for comparing the proposed solution technique with Fibre element, based on flexibility method. However, seismic damage analyses of an 8-story RC frame structure with soft-story are investigated for cases of lumped/distributed mass and load. Damage region, propagation, and intensities according to both approaches are researched. PMID:24578667

  17. Marine concrete

    SciTech Connect

    Marshall, A.L.

    1990-01-01

    This book examines how the chemical and physical properties of the oceans affect the durability, fatigue, and corrosion of structures. Structure types addressed include oil platforms, arctic structures, and sea walls. Reviews qualities of plain, reinforced, prestressed, and floating concrete. Discusses the inspection, maintenance, and repair of concrete structures.

  18. Novel hybrid columns made of ultra-high performance concrete and fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Zohrevand, Pedram

    The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore, new stress-strain models for FRP-confined UHPC were developed through an analytical study. In the other part of this research, a novel steel-free UHPC-filled FRP tube (UHPCFFT) column system was developed and its cyclic behavior was studied. The proposed steel-free UHPCFFT column showed much higher strength and stiffness, with a reasonable ductility, as compared to its conventional reinforced concrete (RC) counterpart. Using the results of the first phase of column tests, a second series of UHPCFFT columns were made and studied under pseudo-static loading to study the effect of column

  19. Numerical analysis on seismic behavior of reinforced concrete beam to concrete filled steel tubular column connections with ring-beam

    NASA Astrophysics Data System (ADS)

    Zhao, Yi.; Xu, Li. Hua.

    2016-06-01

    This paper presents numerical study of the seismic behavior of reinforced concrete beam to concrete filled steel tube column connections with ring-beam. The material stress-strain relations, element type and boundary condition are selected, which are consistent with actual situation. Then the seismic behavior of this type of joint are researched by ABAQUS, and finite element analyses are conducted under cyclic loading. Its parameters are discussed including thickness of steel tubular column wall, sectional dimension of the ring-beam and strength of the core concrete. The results show that the ultimate capacity of the connections is improved with sectional dimension of the ring-beam increased. In the meanwhile, the influence on skeleton curve of the joints is slight of which included thickness of steel tubular column wall and strength of the core concrete.

  20. Layer model for long-term deflection analysis of cracked reinforced concrete bending members

    NASA Astrophysics Data System (ADS)

    Bacinskas, Darius; Kaklauskas, Gintaris; Gribniak, Viktor; Sung, Wen-Pei; Shih, Ming-Hsiang

    2012-05-01

    A numerical technique has been proposed for the long-term deformation analysis of reinforced concrete members subjected to a bending moment. The technique based on the layer approach in a simple and rational way deals with such complex issues as concrete cracking and tension-stiffening as well as creep and shrinkage. The approach uses the material stress-strain relationships for compressive concrete, cracked tensile concrete and steel. Such effects as linear and nonlinear creep, cracking, tension-stiffening as well as the reduction in concrete tension strength due to sustained loading have been taken into account. The shrinkage effect has been modeled by means of adequate actions of axial force and bending moment. A statistical deflection calculation analysis has been carried out for 322 experimental reinforced concrete beams reported in the literature. The comparative analysis of the experimental and the modeling results has shown that the proposed technique has well captured the time-deflection behavior of reinforced concrete flexural members. The results of the predictions by ACI 318 and Eurocode 2 design codes have been also discussed.

  1. Numerical Evaluation Of Shape Memory Alloy Recentering Braces In Reinforced Concrete Buildings Subjected To Seismic Loading

    NASA Astrophysics Data System (ADS)

    Charles, Winsbert Curt

    Seismic protective techniques utilizing specialized energy dissipation devices within the lateral resisting frames have been successfully used to limit inelastic deformation in reinforced concrete buildings by increasing damping and/or altering the stiffness of these structures. However, there is a need to investigate and develop systems with self-centering capabilities; systems that are able to assist in returning a structure to its original position after an earthquake. In this project, the efficacy of a shape memory alloy (SMA) based device, as a structural recentering device is evaluated through numerical analysis using the OpenSees framework. OpenSees is a software framework for simulating the seismic response of structural and geotechnical systems. OpenSees has been developed as the computational platform for research in performance-based earthquake engineering at the Pacific Earthquake Engineering Research Center (PEER). A non-ductile reinforced concrete building, which is modelled using OpenSees and verified with available experimental data is used for the analysis in this study. The model is fitted with Tension/Compression (TC) SMA devices. The performance of the SMA recentering device is evaluated for a set of near-field and far-field ground motions. Critical performance measures of the analysis include residual displacements, interstory drift and acceleration (horizontal and vertical) for different types of ground motions. The results show that the TC device's performance is unaffected by the type of ground motion. The analysis also shows that the inclusion of the device in the lateral force resisting system of the building resulted in a 50% decrease in peak horizontal displacement, and inter-story drift elimination of residual deformations, acceleration was increased up to 110%.

  2. Performance of Zinc Anodes for Cathodic Protection of Reinforced Concrete Bridges

    SciTech Connect

    Covino, Bernard S. Jr.; Cramer, Stephen D.; Bullard, Sophie J.; Holcomb, Gordon R.; Russell, James H.; Collins, W. Keith; Laylor, Martin H.; Cryer, Curtis B.

    2002-03-01

    Operation of thermal spray zinc (Zn) anodes for cathodic protection (CP) of reinforced concrete structures was investigated in laboratory and field studies conducted by the Albany Research Center (ARC) in collaboration with the Oregon Department of Transportation. The purposes of the research presented in this report were: evaluate the need for preheating concrete to improve the adhesion of the anode; estimate the service life of thermal spray Zn CP anodes; determine the optimum thickness for Zn CP anodes; characterize the anode-concrete interfacial chemistry; and correlate field and laboratory results. Laboratory studies involved accelerated electrochemical aging of thermal sprayed Zn anodes on concrete slabs, some of which were periodically wetted while others were unwetted. Concrete used in the slabs contained either 1.2 or 3 kg NaCl /m3 (2 or 5 lbs NaCl /yd3) as part of the concrete mix design. The Zn anodes were applied to the slabs using the twin wire arc-spray technique. Half of the slabs were preheated to 120-160 C (250-320 F) to improve the initial Zn anode bond strength and the other half were not. Accelerated aging was done at a current density of 0.032 A/m2 (3 mA/ft2), 15 times that used on Oregon DOT Coastal bridges, i.e, . 0.0022 A/m2 (0.2 mA/ft2) Cores from the Cape Creek Bridge (OR), the Richmond San Rafael Bridge (CA), and the East Camino Underpass (CA) were used to study the anode-concrete interfacial chemistry, to relate the chemistry to electrochemical age at the time of sampling, and to compare the chemistry of the field anodes to the chemistry of anodes from the laboratory studies. Cores from a CALTRANS study of a silane sealant used prior to the application of the Zn anodes and cores with galvanized rebar from the Longbird Bridge (Bermuda) were also studied. Aged laboratory and field anodes were characterized by measuring some or all of the following parameters: thickness, bond strength, anode-concrete interfacial chemistry, bulk chemistry

  3. Influence of cyclic freeze-thaw on the parameters of the electric response to the pulse mechanical excitation of concrete reinforced by glass fibre reinforced polymer bars

    NASA Astrophysics Data System (ADS)

    Fursa, T. V.; Petrov, M. V.; Korzenok, I. N.

    2016-02-01

    Studies of the influence of cyclic freeze-thaw on the parameters of electric response from samples of concrete reinforced by glass fibre reinforced polymer (GFRP) bars were conducted. It is found that an increase in the number of freeze-thaw cycles increases the attenuation coefficient of energy of electric responses and moves the centre of gravity of spectrum to the low-frequency area. The results can be used to develop a method of nondestructive testing of reinforced concrete.

  4. Analytical Prediction of the Seismic Response of a Reinforced Concrete Containment Vessel

    SciTech Connect

    James, R.J.; Rashid, Y.R.; Cherry, J.L.; Chokshi, N.; Tsurumaki, S.

    1999-03-19

    Under the sponsorship of the Ministry of International Trade and Industry (MITI) of Japan, the Nuclear Power Engineering Corporation (NUPEC) is investigating the seismic behavior of a Reinforced Concrete Containment Vessel (RCCV) through scale-model testing using the high-performance shaking table at the Tadotsu Engineering Laboratory. A series of tests representing design-level seismic ground motions was initially conducted to gather valuable experimental measurements for use in design verification. Additional tests will be conducted with increasing amplifications of the seismic input until a structural failure of the test model occurs. In a cooperative program with NUPEC, the US Nuclear Regulatory Commission (USNRC), through Sandia National Laboratories (SNL), is conducting analytical research on the seismic behavior of RCCV structures. As part of this program, pretest analytical predictions of the model tests are being performed. The dynamic time-history analysis utilizes a highly detailed concrete constitutive model applied to a three-dimensional finite element representation of the test structure. This paper describes the details of the analysis model and provides analysis results.

  5. Reinforcement of asphalt concrete pavement by segments of exhausted fiber used for sorption of oil spill

    NASA Astrophysics Data System (ADS)

    Lukashevich, V. N.; Efanov, I. N.

    2015-01-01

    The paper is aimed at construction of the experimental road pavement made of dispersed reinforced asphalt concrete. Electronic paramagnetic resonance, infrared spectroscopy and fluorescent bitumen studies were used to prove that disperse reinforcement of asphalt concrete mixtures with fibers of exhausted sorbents reduce the selective filtration of low polymeric fractions of petroleum bitumen and improve its properties in the adsorption layer. Sesquioxides are neutralized as catalysts aging asphalt binder. This leads to improvement in the elasticity of bitumen films at low temperatures and provide better crack resistance of coatings to reduce the intensity of the aging of asphalt binder, and, therefore, to increase the durability of road pavements. The experimental road pavement made of dispersed reinforced asphalt concrete operated during 4 years and demonstrated better transport- performance properties in comparison with the analogue pavements.

  6. Bond slip model in cylindrical reinforced concrete elements confined with stirrups

    NASA Astrophysics Data System (ADS)

    Coccia, Simona; Di Maggio, Erica; Rinaldi, Zila

    2015-12-01

    An analytical model able to evaluate the bond-slip law of confined reinforced concrete elements is developed and presented in this paper. The model is based on the studies developed by Tepfers and by den Uijl and Bigaj on the thick-walled cylinder model and extended to the case of the presence of transverse reinforcement. The bond strength and the considered failure modes (splitting or pull-out failure) are expressed as a function of the geometrical (concrete cover and transverse reinforcement) and mechanical (concrete strength) parameters of the element. The application of the proposed methodology allows to forecast the failure mode, and equations for the bond-slip law are finally proposed for a range of steel strain lower than the yielding one.

  7. Destruction of concrete beams with metal and composite reinforcement under impulse action

    NASA Astrophysics Data System (ADS)

    Radchenko, A. V.; Radchenko, P. A.; Batuev, S. P.; Plevkov, V. S.; Utkin, D. G.

    2015-11-01

    This work presents results of integrated experimental and numerical study of destruction of reinforced concrete beam made of concrete and fiber concrete under shortterm dynamic loading. Experimental studies were carried out using pile driver. Short-term dynamic loading acting on a beam was applied by falling weight, 450 kg, from the height 700 mm. The value of dynamic load in experiments was defined by means of force gauge, linear displacement transducers were used to define linear displacements. Numerical simulation was held three-dimensionally within phenomenological approach of continuum mechanics, the reinforcing elements were clearly defined. Finite element method was modified to solve dynamic tasks. Impact of load on a beam in calculations was replaced by impulse. The dependence of impulse on time was defined from the experiment. The influence of reinforcement on deformation and beam destruction was studied. Correlation of experimental and numerical data was performed.

  8. Debris velocity of concrete structures subjected to explosive loading

    NASA Astrophysics Data System (ADS)

    Xu, Kai; Lu, Yong

    2006-08-01

    When designing above-ground ammunition storage facilities, one has to take into account the debris hazard resulting from accidental explosions. The purpose of this paper is to develop a predictive method for debris dispersion around an ammunition storage site in case of an accidental detonation in a reinforced concrete storage structure. The concrete slabs/walls break up into debris when it is overloaded by the internal blast. The debris velocity is one of the important parameters to describe the debris dispersion. The parameters that affect the debris velocity are complex. This study adopts the energy approach to simplify the formulation. The failure process in a relatively thin concrete slab/wall is treated using the concept of expansion. Based on energy conservation, a general formula is derived for the debris launch velocity in a cubicle structure subjected to internal blast loading. The dynamic strength of concrete and reinforcement are considered in the fracture process. The analytical results are found to be consistent with the relevant experimental results.

  9. Corrosion in Reinforced Concrete Panels: Wireless Monitoring and Wavelet-Based Analysis

    PubMed Central

    Qiao, Guofu; Sun, Guodong; Hong, Yi; Liu, Tiejun; Guan, Xinchun

    2014-01-01

    To realize the efficient data capture and accurate analysis of pitting corrosion of the reinforced concrete (RC) structures, we first design and implement a wireless sensor and network (WSN) to monitor the pitting corrosion of RC panels, and then, we propose a wavelet-based algorithm to analyze the corrosion state with the corrosion data collected by the wireless platform. We design a novel pitting corrosion-detecting mote and a communication protocol such that the monitoring platform can sample the electrochemical emission signals of corrosion process with a configured period, and send these signals to a central computer for the analysis. The proposed algorithm, based on the wavelet domain analysis, returns the energy distribution of the electrochemical emission data, from which close observation and understanding can be further achieved. We also conducted test-bed experiments based on RC panels. The results verify the feasibility and efficiency of the proposed WSN system and algorithms. PMID:24556673

  10. 27. DIVERSION STRUCTURE WITH CONCRETE SIDEWALLS AND CONCRETE CHANNEL BEYOND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. DIVERSION STRUCTURE WITH CONCRETE SIDEWALLS AND CONCRETE CHANNEL BEYOND, A SHORT DISTANCE WEST OF D STREET ABOUT ONE-QUARTER MILE SOUTH OF 9TH AVENUE (SECTION 26). - Highline Canal, Sand Creek Lateral, Beginning at intersection of Peoria Street & Highline Canal in Arapahoe County (City of Aurora), Sand Creek lateral Extends 15 miles Northerly through Araphoe County, City & County of Denver, & Adams County to its end point, approximately 1/4 mile Southest of intersectioin of D Street & Ninth Avenue in Adams County (Rocky Mountain Arsenal, Commerce City Vicinity), Commerce City, Adams County, CO

  11. Concrete structural analysis tools and properties for Hanford site waste tank evaluation

    SciTech Connect

    Moore, C.J.; Peterson, W.S.; Winkel, B.V.; Weiner, E.O.

    1995-09-01

    As Hanford Site Contractors address maintenance and future structural demands on nuclear waste tanks built as early as 1943, it is necessary to address their current safety margins and ensure safe margins are maintained. Although the current civil engineering practice has building codes for reinforced concrete design guidelines, the tanks were not constructed to today`s building codes and future demands potentially result in loads and modifications to the tanks that are outside the original design basis and current practice. The Hanford Site engineering staff has embraced nonlinear finite-element modeling of concrete in an effort to obtain a more accurate understanding of the actual tank margins. This document brings together and integrates past Hanford Site nonlinear reinforced concrete analysis methods, past Hanford Site concrete testing, public domain research testing, and current concrete research directions. This document, including future revisions, provides the structural engineering overview (or survey) for a consistent, accurate approach to nonlinear finite-element modeling of reinforced concrete for Hanford Site waste storage tanks. This report addresses concrete strength and modulus degradation with temperature, creep, shrinkage, long-term sustained loads, and temperature degradation of rebar and concrete bonds. Recommendations are given for parameter studies and evaluation techniques for review of nonlinear finite-element analysis of concrete.

  12. Performance Evaluation for Enhancement of Some of the Engineering Properties of Bamboo as Reinforcement in Concrete

    NASA Astrophysics Data System (ADS)

    Kute, S. Y.; Wakchaure, M. R.

    2013-11-01

    Bamboo is one of the alternative materials with strong potential for reinforcing the cement matrices. Unlike steel, during casting and curing of concrete, reinforced bamboo absorbs water and expands, which results in radial cracking of surrounding concrete. When curing is stopped, bamboo starts shrinking slowly loosing the contact with concrete. The dimensional changes of bamboo resulting from moisture and temperature variations, causes de-bonding which affects the bond strength severely. This paper presents the results of experimental investigations made to evaluate potential of bamboo to be used as concrete reinforcement. Specimens with and without node were extracted from well seasoned Dendrocalamus strictus variety of bamboo. They were tested for water absorption, dimensional changes, tensile and bond strength in M20 concrete with twenty different treatments. The paper also presents the comparison of bond strength of mild steel, TMT steel and untreated bamboo with that of bamboo having different low cost treatments for reducing the water absorption thereby enhancing bond strength of bamboo in concrete.

  13. Analytical study on failure process of reinforced concrete wall-type skewed pier

    NASA Astrophysics Data System (ADS)

    Kyoda, Hidehiro; Mikami, Takashi; Nishi, Hiroaki

    Wall-type reinforced concrete piers have been broadly constructed out of urban area under space limitation. However the deformation capacity against earthquake should be evaluated appropriately as a function of the skewed angle. This paper aims to grasp the behavior of wall-type skewed piers under cyclic loading using the three dimensional fiber model analysis. As a result, it was found that the fiber mode l analysis could simulate the experimental results before failure of the longitudinal reinforcement.

  14. 75 FR 7562 - Certain Steel Concrete Reinforcing Bars From Turkey: Notice of Court Decision Not in Harmony With...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-22

    ..., Rescission of Antidumping Duty Administrative Review in Part, and Determination To Revoke in Part, 70 FR... International Trade Administration Certain Steel Concrete Reinforcing Bars From Turkey: Notice of Court Decision... certain steel concrete reinforcing bars (rebar) from Turkey covering the period of review (POR) of April...

  15. Strut Deformation in CFRP-Strengthened Reinforced Concrete Deep Beams

    PubMed Central

    Panjehpour, Mohammad; Chai, Hwa Kian; Voo, Yen Lei

    2014-01-01

    Strut-and-tie model (STM) method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions). It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP) as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level. PMID:25197698

  16. Strut deformation in CFRP-strengthened reinforced concrete deep beams.

    PubMed

    Panjehpour, Mohammad; Chai, Hwa Kian; Voo, Yen Lei

    2014-01-01

    Strut-and-tie model (STM) method evolved as one of the most useful designs for shear critical structures and discontinuity regions (D-regions). It provides widespread applications in the design of deep beams as recommended by many codes. The estimation of bottle-shaped strut dimensions, as a main constituent of STM, is essential in design calculations. The application of carbon fibre reinforced polymer (CFRP) as lightweight material with high tensile strength for strengthening D-regions is currently on the increase. However, the CFRP-strengthening of deep beam complicates the dimensions estimation of bottle-shaped strut. Therefore, this research aimed to investigate the effect of CFRP-strengthening on the deformation of RC strut in the design of deep beams. Two groups of specimens comprising six unstrengthened and six CFRP-strengthened RC deep beams with the shear span to the effective depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were constructed in this research. These beams were tested under four-point bending configuration. The deformation of struts was experimentally evaluated using the values of strain along and perpendicular to the strut centreline. The evaluation was made by the comparisons between unstrengthened and CFRP-strengthened struts regarding the widening and shortening. The key variables were a/d ratio and applied load level. PMID:25197698

  17. Nonlinear finite-element analysis of a reinforced-concrete Mark III containment under pressure and gravity loads. [BWR

    SciTech Connect

    Sharma, S.; Reich, M.; Shteyngart, S.; Chang, T.Y.

    1983-01-01

    An analysis of a Mark III reactor containment vessel subjected to a uniformly increasing internal pressure and gravity loads is carried out in order to ascertain the load carrying capacity of the structure under hydrogen burn. The analysis is conducted by using a nonlinear finite element model that includes nonlinearities in the strain-displacement relations as well as in the material constitutive equations. In this analysis, the nonlinear behavior of the liner and reinforcement steels is described by a von Mises elastic-plastic model with isotropic hardening. A recently developed elastic-plastic-fracture model that includes both the cracking and crushing limit states is used for the plain concrete. Consistent smearing and de-smearing procedures are then used to represent the composite material properties of the reinforced concrete by an anisotropic and locally homogeneous continuum. Results pertaining to the critical regions of the containment where cracking of the concrete, yielding of the reinforcement bars, and substantial straining of the liner take place are discussed.

  18. Separate effects testing and analyses to investigate liner tearing of the 1:6-scale reinforced concrete containment building

    SciTech Connect

    Spletzer, B.L.; Lambert, L.D.; Bergman, V.L.

    1995-06-01

    The overpressurization of a 1:6-scale reinforced concrete containment building demonstrated that liner tearing is a plausible failure mode in such structures under severe accident conditions. A combined experimental and analytical program was developed to determine the important parameters which affect liner tearing and to develop reasonably simple analytical methods for predicting when tearing will occur. Three sets of test specimens were designed to allow individual control over and investigation of the mechanisms believed to be important in causing failure of the liner plate. The series of tests investigated the effect on liner tearing produced by the anchorage system, the loading conditions, and the transition in thickness from the liner to the insert plate. Before testing, the specimens were analyzed using two- and three-dimensional finite element models. Based on the analysis, the failure mode and corresponding load conditions were predicted for each specimen. Test data and post-test examination of test specimens show mixed agreement with the analytical predictions with regard to failure mode and specimen response for most tests. Many similarities were also observed between the response of the liner in the 1:6-scale reinforced concrete containment model and the response of the test specimens. This work illustrates the fact that the failure mechanism of a reinforced concrete containment building can be greatly influenced by details of liner and anchorage system design. Further, it significantly increases the understanding of containment building response under severe conditions.

  19. Practical method for analysis and design of slender reinforced concrete columns subjected to biaxial bending and axial loads

    NASA Astrophysics Data System (ADS)

    Bouzid, T.; Demagh, K.

    2011-03-01

    Reinforced and concrete-encased composite columns of arbitrarily shaped cross sections subjected to biaxial bending and axial loads are commonly used in many structures. For this purpose, an iterative numerical procedure for the strength analysis and design of short and slender reinforced concrete columns with a square cross section under biaxial bending and an axial load by using an EC2 stress-strain model is presented in this paper. The computational procedure takes into account the nonlinear behavior of the materials (i.e., concrete and reinforcing bars) and includes the second - order effects due to the additional eccentricity of the applied axial load by the Moment Magnification Method. The ability of the proposed method and its formulation has been tested by comparing its results with the experimental ones reported by some authors. This comparison has shown that a good degree of agreement and accuracy between the experimental and theoretical results have been obtained. An average ratio (proposed to test) of 1.06 with a deviation of 9% is achieved.

  20. An accelerated carbonation procedure for studies of corrosion in reinforced concrete

    SciTech Connect

    Al-Kadhimi, T.K.H.; Banfill, P.F.G.; Millard, S.G.; Bungey, J.H.

    1995-10-01

    Carbonation of the concrete leading to reduced alkalinity around the steel is one of the main reasons for the corrosion of reinforced concrete. Studies of carbonation induced corrosion and of rehabilitation methods, such as electrochemical realkalization, require the convenient preparation of realistically large specimens of carbonated concrete in a sufficiently short time. This paper describes a rapid method of preparing carbonated concrete by exposing concrete, which has been dried to an internal relative humidity of 60%, to a pure atmosphere of carbon dioxide gas at 15 bar pressure (1,500 kPa). The pressure chamber used can accommodate specimens up to 150mm diameter or 100 x 100 mm section and such specimens can be fully carbonated in 2 weeks, much more quickly than by other methods. Carbonation increases the electrical resistivity and strength of the concrete and reduces the water absorption. Optical and electron microscopical investigations on the carbonated concrete confirm that the microstructure is no different from that produced in concrete by carbonation under natural exposure. The accelerated carbonation method can be used for development work on materials and repair methods and has been used by the authors in preparing carbonated concrete specimens for re-alkalization tests.

  1. Application of concrete in marine structures

    SciTech Connect

    Rashid, A.; Nygaard, C.

    1997-07-01

    The use of concrete in marine environment has gained tremendous popularity in the past decade and is continued to be a very popular material for marine industry in the world today. It has a very diversified use from large offshore platforms and floating structures in the North Sea, Canada and South America to offshore loading terminals and junction platforms in shallow waters in the marshes of southern Louisiana in the Gulf of Mexico. Also, precast concrete sections are extensively used all over the world in the construction of marine structures. Because of their large variety of shapes and sizes, they can be tailored to fit multiple applications in marine environment. The added quality control in the fabrication yard and the ease of installation by lifting makes them a very attractive option. The use of precast concrete sections is gaining a lot of popularity in South America. A lot of fabrication yards are manufacturing these sections locally. There are hundreds of offshore concrete platforms utilizing these sections in Lake Maracaibo, Venezuela. The paper discusses the use of concrete for offshore structures including floaters. It describes some general concepts and advantages to be gained by the use of concrete (precast and cast-in-place) in marine environment. It also discusses some general design considerations required for the use of different types of precast concrete sections that can be utilized for oil and gas platforms and loading terminals. Lastly the paper describes some typical examples of concrete platforms built out of concrete piles, precast concrete girders and beam sections and concrete decking.

  2. Simulation of crack propagation in fiber-reinforced concrete by fracture mechanics

    SciTech Connect

    Zhang Jun; Li, Victor C

    2004-02-01

    Mode I crack propagation in fiber-reinforced concrete (FRC) is simulated by a fracture mechanics approach. A superposition method is applied to calculate the crack tip stress intensity factor. The model relies on the fracture toughness of hardened cement paste (K{sub IC}) and the crack bridging law, so-called stress-crack width ({sigma}-{delta}) relationship of the material, as the fundamental material parameters for model input. As two examples, experimental data from steel FRC beams under three-point bending load are analyzed with the present fracture mechanics model. A good agreement has been found between model predictions and experimental results in terms of flexural stress-crack mouth opening displacement (CMOD) diagrams. These analyses and comparisons confirm that the structural performance of concrete and FRC elements, such as beams in bending, can be predicted by the simple fracture mechanics model as long as the related material properties, K{sub IC} and ({sigma}-{delta}) relationship, are known.

  3. Non-destructive Inspection of Chloride Ion in Concrete Structures Using Attenuated Total Reflection of Millimeter Waves

    NASA Astrophysics Data System (ADS)

    Tripathi, Saroj R.; Inoue, Hiroo; Hasegawa, Tsuyoshi; Kawase, Kodo

    2013-02-01

    The chloride induced corrosion of reinforcing steel bar is one of the major causes of deterioration of concrete structures. Therefore, it is essential to periodically monitor the level of chloride ion (Cl-) concentration in concrete structures. In this work, we developed millimeter wave attenuated total reflection measurement setup in order to determine the Cl- concentration in concrete structures. We prepared concrete samples with different compositions and varying Cl- concentrations and we measured their attenuated total reflectance at 65 GHz. We observed that the reflectance decreases almost linearly with the increase in Cl- concentration indicating that this technique could be used to inspect the Cl- concentration in concrete structures nondestructively.

  4. Mechanical properties of fiber reinforced lightweight concrete composites

    SciTech Connect

    Perez-Pena, M. ); Mobasher, B. )

    1994-01-01

    Hybrid composites with variable strength/toughness properties can be manufactured using combinations of brittle or ductile mesh in addition to brittle and ductile matrix reinforcements. The bending and tensile properties of thin sheet fiber cement composites made from these mixtures were investigated. Composites consisted of a woven mesh of either polyvinyl chloride (PVC) coated E-glass or polypropylene (PP) fibers for the surface reinforcement. In addition, chopped polypropylene, acrylic, nylon, and alkali-resistant (AR) glass fibers were used for the core reinforcement. It is shown that by controlling fiber contents, types, and combinations, design objectives such as strength, stiffness and toughness, can be achieved. Superior post-cracking behavior was measured for composites reinforced both with glass mesh and PP mesh. Load carrying capacity of PP mesh composites can be increased with the use of 1% or higher chopped PP fibers. Glass mesh composites with short AR glass fibers as matrix reinforcement indicate an increased matrix cracking strength and modulus of rupture. Combinations of PP mesh/short AR glass did not show a substantial improvement in the matrix ultimate strength. An increased nylon fiber surface area resulted in improved post peak response.

  5. Autoclave foam concrete: Structure and properties

    NASA Astrophysics Data System (ADS)

    Mestnikov, Alexei; Semenov, Semen; Strokova, Valeria; Nelubova, Viktoria

    2016-01-01

    This paper describes the technology and properties of autoclaved foam concrete taking into account practical experience and laboratory studies. The results of study of raw materials and analysis of structure and properties of foam-concrete before and after autoclave treatment are basic in this work. Experimental studies of structure and properties of foam concrete are carried out according to up-to-date methods and equipment on the base of the shared knowledge centers. Results of experimental studies give a deep understanding of properties of raw materials, possible changes and new formations in inner layers of porous material providing the improvement of constructional and operational properties of autoclaved foam concrete. Principal directions of technology enhancement as well as developing of production of autoclave foam concretes under cold-weather conditions in Russia climate are justified.

  6. 76 FR 48802 - Certain Steel Concrete Reinforcing Bars From Turkey; Notice of Amended Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... Determination To Revoke in Part, 73 FR 66218 (Nov. 7, 2008). The period of review (POR) is April 1, 2006... Countervailing Duty Proceedings: Assessment of Antidumping Duties, 68 FR 23954 (May 6, 2003). This clarification... International Trade Administration Certain Steel Concrete Reinforcing Bars From Turkey; Notice of Amended...

  7. 78 FR 73838 - Steel Concrete Reinforcing Bar From Turkey: Postponement of Preliminary Determination in the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-09

    ... Investigations, 78 FR 60831 (October 2, 2013) (Initiation Notice). \\2\\ See Memorandum for the Record from Paul... International Trade Administration Steel Concrete Reinforcing Bar From Turkey: Postponement of Preliminary... Department of Commerce (the Department) initiated a countervailing duty investigation on steel...

  8. 78 FR 68090 - Steel Concrete Reinforcing Bar from Mexico and Turkey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-13

    ..., Washington, DC, and by publishing the notice in the Federal Register of September 11, 2013 (78 FR 55755). The... authority of Title VII of the Tariff Act of 1930 have been tolled by 16 days. 78 FR 64011, October 25, 2013... COMMISSION Steel Concrete Reinforcing Bar from Mexico and Turkey Determinations On the basis of the record...

  9. 77 FR 71631 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-03

    ... electronic filing have been amended. The amendments took effect on November 7, 2011. See 76 FR 61937 (Oct. 6... COMMISSION Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and Ukraine; Scheduling of Full Five-Year Reviews Concerning the Antidumping Duty Orders on Steel...

  10. 77 FR 39254 - Steel Concrete Reinforcing Bar From Belarus, China, Indonesia, Latvia, Moldova, Poland, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... concrete reinforcing bar from Belarus, China, Indonesia, Latvia, Moldova, Poland, and Ukraine (66 FR 46777... part 207), as most recently amended at 74 FR 2847 (January 16, 2009). \\1\\ No response to this request..., Indonesia, Latvia, Moldova, Poland, and Ukraine (72 FR 44830). The Commission is now conducting...

  11. Driving Energy of Reinforcing Steel Bar for Discriminating Background Medium of Concrete

    NASA Astrophysics Data System (ADS)

    Toh, Ryo; Motooka, Seiichi

    2008-05-01

    A method for discriminating the background media of concrete using the quality factor of elastic waves multireflected in the concrete was proposed. A reinforcing steel bar buried inside the concrete is employed as a sound source driven by the induction of impact electromagnetic field radiated from a spiral coil placed on the surface of the concrete. In this paper, the appropriate energy for driving the reinforcing steel bar, to obtain stable quality factors with clear differences between different background media, is studied experimentally. With various driving energies, multireflected elastic waves corresponding to three types of background medium, air, sand, and water, are measured. The quality factors are calculated by the linear predictive coefficient analysis method. The results show that the quality factors tend to increase when the driving energy is at its lower region, and they remain comparatively stable when the driving energy is higher than a certain value. For reinforcing steel bars with different diameters, the curves of quality factors versus driving energies agree well by introducing a newly defined volume-normalized driving energy. For the reinforcing steel bar of 13 mm diameter, the appropriate driving energy for background media discrimination is approximately 0.5 J.

  12. Acoustic emission characterization of the onset of corrosion in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Di Benedetti, M.; De Cais, E.; Karim, Z.; Loreto, G.; Presuel, F.; Nanni, A.

    2012-04-01

    The development of techniques capable of evaluating deterioration of reinforced concrete (RC) is instrumental to the advancement of the structural health monitoring (SHM) and service life estimate for constructed facilities. One of the main causes leading to degradation of RC is the corrosion of the steel reinforcement. This process can be modeled phenomenologically, while laboratory tests aimed at studying durability responses are typically accelerated in order to provide useful results within a realistic period of time. Among nondestructive methods, acoustic emission (AE) is emerging as a tool to detect the onset and progression of deterioration mechanisms. In this paper, the development of accelerated corrosion and continuous AE monitoring test set-up for RC specimens are presented. Relevant information are provided with regard to the characteristics of the corrosion circuit, continuous measurement and acquisition of corrosion potential, selection of AE sensors and AE parameter setting. Results from small-scale pre-notched RC specimens aim to isolate the frequency spectrum where the corrosion first takes place. Waveform analysis critical in the definition of a prognosis model will extend the AE dataset for the onset of corrosion.

  13. Damage assessed by wavelet scale bands and b-value in dynamical tests of a reinforced concrete slab monitored with acoustic emission

    NASA Astrophysics Data System (ADS)

    Zitto, Miguel E.; Piotrkowski, Rosa; Gallego, Antolino; Sagasta, Francisco; Benavent-Climent, Amadeo

    2015-08-01

    The complex Morlet Continuous Wavelet Transform (CWT) was applied to acoustic emission (AE) signals from dynamic tests conducted on a reinforced concrete slab with a shaking table. The steel reinforcement bars did not yield during the tests, but a severe loss of bond between reinforcement bars and surrounding concrete was detected. Comparison of the evolution of the scale position of maximum values of CWT coefficients and the histories of response acceleration obtained in different seismic simulations allowed us to identify the (45-64 kHz) frequency band corresponding to the fracture of concrete. The Cumulative Acoustic Emission Energy (CAE) obtained by reconstructing the AE signals in this scale (frequency) band was compared with the Cumulative Dissipated Energy (CDE) of the tested structure. The CDE is accepted as a good parameter for characterizing the mechanical damage in structures. A reasonably good agreement was found between the normalized histories of CAE and CDE. This made it possible to categorize the cracking of concrete as the main source of damage in the reinforced concrete slab. Conversely, the differences between the CAE and CDE curves observed for high levels of peak acceleration applied to the shaking table can be attributed to the deformation of the steel that formed the columns. The AE coming from the plastic deformation of the steel is not detected by CAE due to the threshold amplitude (45 dB) used in the AE monitoring, but the strain energy dissipated by the steel through plastic deformations is included in the CDE. Further, a study of the evolution of the b-value in the successive seismic simulations revealed that the b-value can capture the inception of severe cracking in the concrete, which the tests described in this study attributed mainly to the loss of bond between reinforcing steel and surrounding concrete.

  14. Studies on Geometries for Inducing Homogeneous Magnetic Fields in the Application of Real Time Imaging of Steel Reinforcing Bars Embedded Within Pre-Stressed and Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Quek, S.; Benitez, D.; Gaydecki, P.; Torres, V.

    2006-03-01

    This paper addresses fundamental issues associated with the development of a real time inductive scanning system for non-destructive testing of pre-stressed and reinforced concrete. Simulated results has indicated that given a coil dimension of 300mm×300mm×2.5mm, 10mm rebars can be imaged down to a depth of 100 mm. Studies also indicate that the vertical component of the induced magnetic field is most favourable as it can be readily reconstructed to yield geometry and dimensional information pertaining to the rebar structure.

  15. Methodology for Assessing the Probability of Corrosion in Concrete Structures on the Basis of Half-Cell Potential and Concrete Resistivity Measurements

    PubMed Central

    2013-01-01

    In recent years, the corrosion of steel reinforcement has become a major problem in the construction industry. Therefore, much attention has been given to developing methods of predicting the service life of reinforced concrete structures. The progress of corrosion cannot be visually assessed until a crack or a delamination appears. The corrosion process can be tracked using several electrochemical techniques. Most commonly the half-cell potential measurement technique is used for this purpose. However, it is generally accepted that it should be supplemented with other techniques. Hence, a methodology for assessing the probability of corrosion in concrete slabs by means of a combination of two methods, that is, the half-cell potential method and the concrete resistivity method, is proposed. An assessment of the probability of corrosion in reinforced concrete structures carried out using the proposed methodology is presented. 200 mm thick 750 mm  ×  750 mm reinforced concrete slab specimens were investigated. Potential Ecorr and concrete resistivity ρ in each point of the applied grid were measured. The experimental results indicate that the proposed methodology can be successfully used to assess the probability of corrosion in concrete structures. PMID:23766706

  16. A New Evaluation Method of Stored Heat Effect of Reinforced Concrete Wall of Cold Storage

    NASA Astrophysics Data System (ADS)

    Nomura, Tomohiro; Murakami, Yuji; Uchikawa, Motoyuki

    Today it has become imperative to save energy by operating a refrigerator in a cold storage executed by external insulate reinforced concrete wall intermittently. The theme of the paper is to get the evaluation method to be capable of calculating, numerically, interval time for stopping the refrigerator, in applying reinforced concrete wall as source of stored heat. The experiments with the concrete models were performed in order to examine the time variation of internal temperature after refrigerator stopped. In addition, the simulation method with three dimensional unsteady FEM for personal-computer type was introduced for easily analyzing the internal temperature variation. Using this method, it is possible to obtain the time variation of internal temperature and to calculate the interval time for stopping the refrigerator.

  17. Effect of Mesh Distribution on Impact Resistance Performance of Kenaf Fibre Reinforced Concrete

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Thiruchelvam, Sivadass; Syamsir, Agusril; Sheng, Chiam Yung; Beddu, Salmia; Nasharuddin Mustapha, Kamal; Usman, Fathoni; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the mesh distribution on the impact performance of kenaf fibre mesh reinforced concrete (KFMRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and mesh diameter subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.40 m height has been used in this research work. The objective of this research is to study the effect of the mesh distribution on the impact resistance kenaf fibre mesh concrete for various slab thickness and mesh diameter. 2-layers one Top and one Bottom mesh distribution kenaf mesh is the most efficient in the ability to control crack formation and propagation against impact energy followed by 1-layer Middle mesh distribution and lastly the 1-layer Top mesh distribution is the least effective.

  18. A reliability assessment of physical vulnerability of reinforced concrete walls loaded by snow avalanches

    NASA Astrophysics Data System (ADS)

    Favier, P.; Bertrand, D.; Eckert, N.; Naaim, M.

    2014-03-01

    Snow avalanches are a threat to many kinds of elements (human beings, communication axes, structures, etc.) in mountain regions. For risk evaluation, the vulnerability assessment of civil engineering structures such as buildings and dwellings exposed to avalanches still needs to be improved. This paper presents an approach to determine the fragility curves associated with reinforced concrete (RC) structures loaded by typical avalanche pressures and provides quantitative results for different geometrical configurations. First, several mechanical limit states of the RC wall are defined using classical engineering approaches (Eurocode 2), and the pressure of structure collapse is calculated from the usual yield line theory. Next, the fragility curve is evaluated as a function of avalanche loading using a Monte Carlo approach, and sensitivity studies (Sobol indices) are conducted to estimate the respective weight of the RC wall model inputs. Finally, fragility curves and relevant indicators such a their mean and fragility range are proposed for the different structure boundary conditions analyzed. The influence of the input distributions on the fragility curves is investigated. This shows the wider fragility range and/or the slight shift in the median that has to be considered when a possible slight change in mean/standard deviation/inter-variable correlation and/or the non-Gaussian nature of the input distributions is accounted for.

  19. A reliability assessment of physical vulnerability of reinforced concrete walls loaded by snow avalanches

    NASA Astrophysics Data System (ADS)

    Favier, P.; Bertrand, D.; Eckert, N.; Naaim, M.

    2013-06-01

    Snow avalanches are a threat to many kinds of elements (human beings, communication axes, structures, etc.) in mountain regions. For risk evaluation, the vulnerability assessment of civil engineering structures such as buildings and dwellings exposed to avalanches still needs to be improved. This paper presents an approach to determine the fragility curves associated with Reinforced Concrete (RC) structures loaded by typical avalanche pressures and provides quantitative results for different geometrical configurations. First, several mechanical limit states of the RC wall are defined using classical engineering approaches (Eurocodes - EC2), and the pressure of structure collapse is calculated from the usual yield line theory. Next, the failure probability is evaluated as a function of avalanche loading using a Monte Carlo approach, and sensitivity studies (Sobol indexes) are conducted to estimate the respective weight of the RC wall model inputs. Finally, fragility curves and relevant indicators such a their mean and fragility range are proposed for the different structure boundary conditions tested. The influence of the input distributions on the fragility curves is investigated. This shows the wider fragility range and/or the slight shift in the median that has to be considered when the possible correlation/non-Gaussian nature of the input distributions is accounted for.

  20. Treatment Prevents Corrosion in Steel and Concrete Structures

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In the mid-1990s, to protect rebar from corrosion, NASA developed an electromigration technique that sends corrosion-inhibiting ions into rebar to prevent rust, corrosion, and separation from the surrounding concrete. Kennedy Space Center worked with Surtreat Holding LLC, of Pittsburgh, Pennsylvania, a company that had developed a chemical option to fight structural corrosion, combining Surtreat's TPS-II anti-corrosive solution and electromigration. Kennedy's materials scientists reviewed the applicability of the chemical treatment to the electromigration process and determined that it was an effective and environmentally friendly match. Ten years later, NASA is still using this approach to fight concrete corrosion, and it has also developed a new technology that will further advance these efforts-a liquid galvanic coating applied to the outer surface of reinforced concrete to protect the embedded rebar from corrosion. Surtreat licensed this new coating technology and put it to use at the U.S. Army Naha Port, in Okinawa, Japan. The new coating prevents corrosion of steel in concrete in several applications, including highway and bridge infrastructures, piers and docks, concrete balconies and ceilings, parking garages, cooling towers, and pipelines. A natural compliment to the new coating, Surtreat's Total Performance System provides diagnostic testing and site analysis to identify the scope of problems for each project, manufactures and prescribes site-specific solutions, controls material application, and verifies performance through follow-up testing and analysis.

  1. Reinforced Concrete Condition Assessment in Architectural Heritage. The Lion Chambers (Glasgow, UK) and the Theatre E. Duni (Matera, Italy)

    NASA Astrophysics Data System (ADS)

    Guida, A.; Dimitrijevic, B.; Pagliuca, A.

    2012-04-01

    The research objective is to provide new qualitative information on the strength of reinforced concrete structures of two prominent examples of modern architecture by using innovative, non-invasive testing techniques. The first one is Lion Chambers in Glasgow (Scotland, United Kingdom) designed by the architects Salmon, Son and Gillespie and completed in 1907. It was the second example of the use of François Hennebique's reinforced concrete system in a building in Glasgow and one of the earliest in Britain. The second example is Duni Theatre in Matera (Southern Italy), designed by the architect Ettore Stella and completed in 1949. The tests on the internal reinforced concrete columns were undertaken by using "SonReb" (SONic + REBound) method that enables assessing the concrete resistance by combining the speed of ultrasound waves and the index of surface bounce through a scleorometric test. In fact, the sclerometer index only gives information regarding the surface layer of the building's structure. In fact, due to the effects of the natural ageing, catalysed by the presence of humidity, surface layers of concrete are affected over time by carbonatation, which increases surface rigidity, providing as a result a greatly "altered" rebound index (much greater than one would have under normal conditions). On the other hand, the ultrasound speed, on the contrary to resistance, is inversely proportional to the age of the concrete (this seems to be due to the cracks that occur and reduce the speed). The hardening process continues over time with a consequent increase in resistance, which diminishes with the passage of time. The paper provides the results of the tests run on the structure of the Lion Chambers and the Duni Theatre. The tests carried out are the basis of a diagnostic project that is possible to implement and monitor to guarantee a deeper knowledge, with the goal of attaining a level of thorough understanding aimed at the preservation of "Modern Architecture

  2. Assessment of dynamic mechanical behaviour of reinforced concrete beams using a blast simulator

    NASA Astrophysics Data System (ADS)

    Peroni, Marco; Solomos, George; Caverzan, Alessio; Larcher, Martin; Valsamos, Georgios

    2015-09-01

    Critical infrastructures may become the target of terrorist bombing attacks or may have to withstand explosive loads due to accidents. The impulsive load connected to explosions is delivered to the structure in a few milliseconds forcing it to respond or fail in a peculiar mode. With reference to the above scientific framework this work presents an innovative apparatus designed and developed at the European Laboratory for Structural Assessment to reproduce a blast pressure history without using explosives. This apparatus is practically a hybrid nitrogen-spring-driven actuator that accelerates masses of up to 100 kg to a maximum velocity of about 25 m/s that impact against the tested structure. The pressure-load history applied to the structure is modulated and reshaped using appropriate layers of elastic soft materials (such as polymeric foams) placed between the specimen and the impacting masses. Specific instrumentation has extensively been utilised to investigate the blast simulator performance and to precisely measure the pressure loads applied to the specimen. A series of tests on real scale reinforced concrete beams/columns (250 × 250 × 2200 mm) has been performed to efficiently assess the performance and potentiality of the new blast simulator. Results are under evaluation. In addition to the experimental work, a series of numerical simulations by means of the explicit FEM code EUROPLEXUS have been carried out to support and improve the equipment design.

  3. Posttest analysis of a 1:6-scale reinforced concrete reactor containment building

    SciTech Connect

    Weatherby, J.R. )

    1990-02-01

    In an experiment conducted at Sandia National Laboratories, 1:6-scale model of a reinforced concrete light water reactor containment building was pressurized with nitrogen gas to more than three times its design pressure. The pressurization produced one large tear and several smaller tears in the steel liner plate that functioned as the primary pneumatic seal for the structure. The data collected from the overpressurization test have been used to evaluate and further refine methods of structural analysis that can be used to predict the performance of containment buildings under conditions produced by a severe accident. This report describes posttest finite element analyses of the 1:6-scale model tests and compares pretest predictions of the structural response to the experimental results. Strain and displacements calculated in axisymmetric finite element analyses of the 1:6-scale model are compared to strains and displacement measured in the experiment. Detailed analyses of the liner plate are also described in the report. The region of the liner surrounding the large tear was analyzed using two different two-dimensional finite elements model. The results from these analyzed indicate that the primary mechanisms that initiated the tear can be captured in a two- dimensional finite element model. Furthermore, the analyses show that studs used to anchor the liner to the concrete wall, played an important role in initiating the liner tear. Three-dimensional finite element analyses of liner plates loaded by studs are also presented. Results from the three-dimensional analyses are compared to results from two-dimensional analyses of the same problems. 12 refs., 56 figs., 1 tab.

  4. Effects of manufacturing techniques on the flexural behavior of steel fiber-reinforced concrete

    SciTech Connect

    Toutanji, H.; Bayasi, Z.

    1998-01-01

    This paper presents experimental research investigating the effects of manufacturing techniques on the mechanical properties of steel fiber-reinforced concrete. Both the effects of curing environments and that of testing direction relative to casting direction on the mechanical properties of fiber-reinforced concrete are reported. Specimens were cured in three different environmental conditions: steam, moisture, and air. Results show that steam curing, as compared to moisture curing, does not enhance the flexural strength of steel fibrous concrete but does reduce flexural toughness. As expected, air curing shows detrimental effects on all aspects of the test results, as compared to steam and moisture curing. The flexural behavior of steel fiber-reinforced concrete is strongly affected by testing direction. When testing direction is perpendicular to casting direction, specimens exhibit reductions in both flexural strength and toughness compared to the case when testing and casting directions are parallel. The effect of testing direction relative to casting direction on flexural strength and toughness increases with increasing the flowability (workability) of the fibrous mixture, which encourages fiber settlement during placement.

  5. Development of a geographical information system for risk mapping of reinforced concrete buildings subjected to atmospheric corrosion in Cyprus using optical remote sensing data

    NASA Astrophysics Data System (ADS)

    Neocleous, Kyriacos; Agapiou, Athos; Christofe, Andreas; Themistocleous, Kyriacos; Achillides, Zenon; Panayiotou, Marilia; Hadjimitsis, Diofantos G.

    2014-08-01

    Concrete reinforced with steel rebars remains one of the most widely used construction materials. Despite its excellent mechanical performance and expected service life of at least 50 years, reinforced concrete is subjected to corrosion of the steel rebars which normally leads to concrete spalling, deterioration of the reinforced concrete's (RC) mechanical properties and eventual reduction of the structural load capacity. In Cyprus, especially in coastal regions where almost 60% of the population resides, many structural problems have been identified in RC structures, which are mainly caused by the severe corrosion of steel rebars. Most RC buildings, located in coastal areas, show signs of corrosion within the first 15-20 years of their service life and this affects their structural integrity and reliability, especially against seismic loading. This paper presents the research undertaken as part of the STEELCOR project which aims to extensively evaluate the steel corrosion of RC buildings in coastal areas of Cyprus and conduct a risk assessment relating to steel corrosion. Non-destructive testing of corroded RC structures measurements were used to estimate the simplified index of structural damage. These indices were imported into a Geographical Information System to develop a digital structural integrity map of Cyprus which would show the areas with high risk of steel corrosion of RC buildings. In addition, archive optical remote sensing dataset was used to map the urban expansion footprint during the last 30 years in Cyprus with the aim of undertaking corrosion risk scenarios by utilizing the estimated indices.

  6. Symptoms and signs of degenerative back disease in concrete reinforcement workers.

    PubMed

    Wickström, G

    1978-01-01

    Concrete reinforcement work causes great static loads on the back from the prolonged adoption of bent-double work postures during the tying of steel rods and from substantial dynamic loads during the lifting and pulling of rods from the stack. Subjective manifestations and objective signs of "degenerative back disease" are common in active reinforcement workers. An age- and sex-adjusted comparison of the findings was, however, possible only with one other occupational group, computer technicians, who also often work in awkward positions. A history of sciatica and pain during forward bending in a clinical examination were significantly more common in reinforcement workers than in computer technicians. This finding suggests an effect of reinforcement work on the back, but definite conclusions require further study. PMID:149368

  7. 1994 Triggered Lightning Test Program: Measured responses of a reinforced concrete building under direct lightning attachments

    SciTech Connect

    Schnetzer, G.H.; Chael, J.; Davis, R.; Fisher, R.J.; Magnotti, P.J.

    1995-08-01

    A rocket-triggered lightning test was carried out during the summer of 1994 on a specially designed steel reinforced concrete test building located at Ft. McClellan, Alabama. Currents, voltages, and magnetic fields were measured at 24 instrumented locations during 42 return strokes triggered to designated points on the structure and its lightning protection systems. As was found during an earlier similar lightning test of an earth covered munitions storage building, the buried power service conduits carried a much larger fraction of incident stroke current away from the building than did the intended grounding elements of the lightning protection system. Electrical breakdown and subsequent arcing occurred repeatedly to create dominant current paths to earth that were not accounted for in pretest linear modeling. Potential hazard level transient voltages, surprisingly more resistive than inductive in nature, were recorded throughout the structure. Also surprisingly, strikes to a single grounded protection mast system resulted in internal environments that were generally comparable to those occurring during strikes to roof-mounted air terminals. A description of the test structure, experimental procedures, and a full set of the resultant data are presented in this two-volume report.

  8. Probabilistic lifetime assessment of marine reinforced concrete with steel corrosion and cover cracking

    NASA Astrophysics Data System (ADS)

    Lu, Chun-Hua; Jin, Wei-Liang; Liu, Rong-Gui

    2011-06-01

    In order to study the durability behavior of marine reinforced concrete structure suffering from chloride attack, the structural service life is assumed to be divided into three critical stages, which can be characterized by steel corrosion and cover cracking. For each stage, a calculated model used to predict the lifetime is developed. Based on the definition of durability limit state, a probabilistic lifetime model and its time-dependent reliability analytical method are proposed considering the random natures of influencing factors. Then, the probabilistic lifetime prediction models are applied to a bridge pier located in the Hangzhou Bay with Monte Carlo simulation. It is found that the time to corrosion initiation t 0 follows a lognormal distribution, while that the time from corrosion initiation to cover cracking t 1 and the time for crack to develop from hairline crack to a limit crack width t 2 can be described by Weibull distributions. With the permitted failure probability of 5.0%, it is also observed that the structural durability lifetime mainly depends on the durability life t 0 and that the percentage of participation of the life t 0 to the total service life grows from 61.5% to 83.6% when the cover thickness increases from 40 mm to 80 mm. Therefore, for any part of the marine RC bridge, the lifetime predictions and maintenance efforts should also be directed toward controlling the stage of corrosion initiation induced by chloride ion.

  9. Reliability and flexural behavior of triangular and T-reinforced concrete beams

    NASA Astrophysics Data System (ADS)

    Al-Ansari, Mohammed S.

    2015-12-01

    The paper studied the behavior of reinforced concrete triangular and T-beams. Three reinforced concrete beams were tested experimentally and analyzed analytically using the finite element method. Their reliability was also assessed using the reliability index approach. The results showed that the finite element vertical displacements compared well with those obtained experimentally. They also showed that the vertical displacements obtained using the finite element method were larger than those obtained experimentally. This is a strong indication that the finite element results were conservative and reliable. The results showed that the triangular beams exhibited higher ductility at failure than did the T-beam. The plastic deformations at failure of the triangular beams were higher than that of the T-beam. This is a strong indication of the higher ductility of the triangular beams compared to the T-beam. Triangular beams exhibited smaller cracks than did T-beams for equal areas of steel and concrete. The design moment strengths M c computed using the American Concrete Institute (ACI) design formulation were safe and close to those computed using experimental results. The experimental results validated the reliability analysis results, which stated that the triangular beams are more reliable than T-beams for equal areas of steel and concrete.

  10. Dynamic response of concrete beams externally reinforced with carbon fiber reinforced plastic (CFRP) subjected to impulsive loads

    SciTech Connect

    Jerome, D.M.; Ross, C.A.

    1996-12-31

    A series of 54 laboratory scale concrete beams 3 x 3 x 30 in. in size were impulsively loaded to failure in a drop weight impact machine. The beams had no internal reinforcement, but instead were externally reinforced on the bottom or tension side of the beams with 1, 2, and 3 ply AS4C/1919 graphite epoxy panels. In addition, several of the beams were also reinforced on the sides with 3 ply CFRP. The beams were simply supported in a drop weight machine and subjected to impact loads with amplitudes up to 10 kips, and durations less than 1 ms, at beam midspan. Measurements made during the loading event included beam total load, midspan displacement, as well as midspan strain at 3 locations in the beam`s cross-section. A high speed framing camera was also used to record the beam`s displacement-time behavior as well as to gain insight into the failure mechanisms. Beam midspan accelerations were determined by double differentiation of the displacement versus time data, and in turn, the beam`s inertial loads were calculated using the beam`s equivalent mass. Beam dynamic bending loads versus time were determined from the difference between the total load versus time and the inertial load versus time data. Bending loads versus displacements were also determined along with fracture energies. Failure to correct the loads for inertia will result in incorrect conclusions being drawn from the data, especially for bending resistance of brittle concrete test specimens. A comparison with quasistatic bending (fracture) energy data showed that the dynamic failure energy absorbed by the beams was always less than the static fracture energy, due to the brittle nature of concrete when impulsively loaded.

  11. Unified procedure for the nonlinear finite-element analysis of concrete structures based on a new model for tension stiffening

    SciTech Connect

    Ojdrovic, N.P.

    1988-01-01

    A unified procedure for the analysis of reinforced, partially prestressed, and prestressed concrete frames was formulated. Reinforced concrete is treated as a special case of prestressed concrete with zero prestressing force. A large variety of structures can be analyzed, from simple reinforced concrete beams, to reinforced or prestressed concrete frames, to structures whose various parts are made of different materials. Pretensioning and posttensioning with bonded and unbonded tendons are considered. The finite-element method based on the displacement formulation is used to solve the system of nonlinear equilibrium equations. Geometric and material nonlinearities are considered. Large displacements are accounted for using an updated Lagrangian formulation. The nonlinear behavior of concrete in compression is modeled using the Hognestad's parabola. Reinforcing steel is modeled as an elastic-perfectly plastic materials. To account for tension stiffening, a new model for the stress-strain relationship for concrete in tension is proposed. Results obtained in the numerical analyses show good agreement with experiments, although the proposed stress-strain model is based on only one concrete parameter, compressive strength.

  12. The stopping of cracks inside a reinforced concrete pipe as a result of using cathodic protection

    SciTech Connect

    Peris, M.G.; Guillen, M.A.

    1997-12-01

    Many pipes including reinforced and prestressed concrete, steel and cast iron, have an interior lined with a covering of mortar serving to isolate the steel from the aggressive environment surrounding it. Should this covering crack, and the fissure extend to the metal, a small anodic zone quickly forms which can lead to a process of pitting corrosion. This paper shows how a certain secondary reaction resulting from cathodic protection, such as that caused by the reduction of oxygen leading to alkalinization, can be fundamental in the filling of fissures appearing in concrete. At first, several small trial tests were performed. Later, the results are applied on an industrial scale, with satisfactory results.

  13. Computational aspects of crack growth in sandwich plates from reinforced concrete and foam

    NASA Astrophysics Data System (ADS)

    Papakaliatakis, G.; Panoskaltsis, V. P.; Liontas, A.

    2012-12-01

    In this work we study the initiation and propagation of cracks in sandwich plates made from reinforced concrete in the boundaries and from a foam polymeric material in the core. A nonlinear finite element approach is followed. Concrete is modeled as an elastoplastic material with its tensile behavior and damage taken into account. Foam is modeled as a crushable, isotropic compressible material. We analyze slabs with a pre-existing macro crack at the position of the maximum bending moment and we study the macrocrack propagation, as well as the condition under which we have crack arrest.

  14. The determination of the constitutive parameters of a medium with application to a reinforced concrete pad

    NASA Astrophysics Data System (ADS)

    Poggio, A. J.; Burke, G. L.; Pennock, S. T.

    1995-06-01

    This report describes the experimental and analytical efforts performed to determine the constitutive parameters of a reinforced concrete pad on which an aircraft (the NASA Boeing 757) was parked while its internal electromagnetic environment was measured. This concrete pad is part of the Large Electromagnetic System-Level Illuminator (LESLI) test facility at the Phillips Laboratory, Kirtland Air Force Base, New Mexico. The relative dielectric constant, conductivity, index of refraction, and reflection coefficient have been determined over the frequency range of 0 to 300 MHz and are presented.

  15. The determination of the constitutive parameters of a medium with application to a reinforced concrete pad

    NASA Technical Reports Server (NTRS)

    Poggio, A. J.; Burke, G. L.; Pennock, S. T.

    1995-01-01

    This report describes the experimental and analytical efforts performed to determine the constitutive parameters of a reinforced concrete pad on which an aircraft (the NASA Boeing 757) was parked while its internal electromagnetic environment was measured. This concrete pad is part of the Large Electromagnetic System-Level Illuminator (LESLI) test facility at the Phillips Laboratory, Kirtland Air Force Base, New Mexico. The relative dielectric constant, conductivity, index of refraction, and reflection coefficient have been determined over the frequency range of 0 to 300 MHz and are presented.

  16. Use Impact-Echo Method to Evaluate Bond of Reinforced Concrete Subjected to Early-Age Vibration

    NASA Astrophysics Data System (ADS)

    Hsu, Keng-Tsang; Cheng, Chia-Chi; Lin, Yiching

    The purpose of this paper is to develop a non-destructive test method for evaluating the bond of reinforcing bars in concrete structure which was damaged by earthquake while still cast in the form. In the experimental design, the specimens containing a steel reinforcing bar with one end extruded outside were constructed. Different degrees of damage on the rebar-concrete interfaces were successfully created by the resonant vibration of exposed steel bar induced by the cyclic motion of the specimen. The local bond-loss of the steel bars was evaluated by both non-destructive impact-echo tests and the destructive pullout tests. To create different kinds of failure mode in the pullout test, some of the specimens contain stirrups surrounding reinforcing bar. Poor-bond was quantitatively evaluated before the pullout test by the amplitude of the peak corresponding to the multiple reflections from the steel bar in the normalized spectra derived from the impact-echo tests. As a result, two empirical formulas displaying the proportional relations between the percentage of loss of local bond-stress and loss of steel-amplitude for specimens failed by split failure and pull-out failure modes were established.

  17. Behaviour of fibre-reinforced high-performance concrete in exterior beam-column joint

    NASA Astrophysics Data System (ADS)

    Muthupriya, P.; Boobalan, S. C.; Vishnuram, B. G.

    2014-09-01

    This paper presents the effect of reinforced high performance concrete (HPC) in exterior beam-column joint with and without fibre under monotonic loading. In this experimental investigation, cross-diagonal bars have been provided at the joint for reducing the congestion of reinforcement in joints, and also M75 grade of concrete with optimum mix proportion of 10 % silica fume and 0.3 % glass fibre was used. Four exterior beam-column joint sub-assemblages were tested. The specimens were divided into two types based on the reinforcement detailing. Type A comprises two joint sub-assemblages with joint detailing as per construction code of practice in India (IS 456-2000), and Type B comprises two joint sub-assemblages with joint detailing as per ductile detailing code of practice in India (IS 13920-1993). In each group there was one specimen of control mix and the remaining one specimen of fibre-reinforced mix. All the test specimens were designed to satisfy the strong column-weak beam concept. The performances of specimens were compared with the control mix and the fibre-reinforced mix. The results show that exterior beam-column joint specimens with silica fume and glass fibre in the HPC mix showed better performance.

  18. Self-diagnosis of structures strengthened with hybrid carbon-fiber-reinforced polymer sheets

    NASA Astrophysics Data System (ADS)

    Wu, Z. S.; Yang, C. Q.; Harada, T.; Ye, L. P.

    2005-06-01

    The correlation of mechanical and electrical properties of concrete beams strengthened with hybrid carbon-fiber-reinforced polymer (HCFRP) sheets is studied in this paper. Two types of concrete beams, with and without reinforcing bars, are strengthened with externally bonded HCFRP sheets, which have a self-structural health monitoring function due to the electrical conduction and piezoresistivity of carbon fibers. Parameters investigated include the volume fractions and types of carbon fibers. According to the investigation, it is found that the hybridization of uniaxial HCFRP sheets with several different types of carbon fibers is a viable method for enhancing the mechanical properties and obtaining a built-in damage detection function for concrete structures. The changes in electrical resistance during low strain ranges before the rupture of carbon fibers are generally smaller than 1%. Nevertheless, after the gradual ruptures of carbon fibers, the electrical resistance increases remarkably with the strain in a step-wise manner. For the specimens without reinforcing bars, the electrical behaviors are not stable, especially during the low strain ranges. However, the electrical behaviors of the specimens with reinforcing bars are relatively stable, and the whole range of self-sensing function of the HCFRP-strengthened RC structures has realized the conceptual design of the HCFRP sensing models and is confirmed by the experimental investigations. The relationships between the strain/load and the change in electrical resistance show the potential self-monitoring capacity of HCFRP reinforcements used for strengthening concrete structures.

  19. Computational modeling of high performance steel fiber reinforced concrete using a micromorphic approach

    NASA Astrophysics Data System (ADS)

    Huespe, A. E.; Oliver, J.; Mora, D. F.

    2013-12-01

    A finite element methodology for simulating the failure of high performance fiber reinforced concrete composites (HPFRC), with arbitrarily oriented short fibers, is presented. The composite material model is based on a micromorphic approach. Using the framework provided by this theory, the body configuration space is described through two kinematical descriptors. At the structural level, the displacement field represents the standard kinematical descriptor. Additionally, a morphological kinematical descriptor, the micromorphic field, is introduced. It describes the fiber-matrix relative displacement, or slipping mechanism of the bond, observed at the mesoscale level. In the first part of this paper, we summarize the model formulation of the micromorphic approach presented in a previous work by the authors. In the second part, and as the main contribution of the paper, we address specific issues related to the numerical aspects involved in the computational implementation of the model. The developed numerical procedure is based on a mixed finite element technique. The number of dofs per node changes according with the number of fiber bundles simulated in the composite. Then, a specific solution scheme is proposed to solve the variable number of unknowns in the discrete model. The HPFRC composite model takes into account the important effects produced by concrete fracture. A procedure for simulating quasi-brittle fracture is introduced into the model and is described in the paper. The present numerical methodology is assessed by simulating a selected set of experimental tests which proves its viability and accuracy to capture a number of mechanical phenomenon interacting at the macro- and mesoscale and leading to failure of HPFRC composites.

  20. Effect of Steel Fibres Distribution on Impact Resistance Performance of Steel Fibre Reinforced Concrete (SFRC)

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Liyana Mohd Kamal, Nur; Syamsir, Agusril; Shao Yang, Chen; Beddu, Salmia; Nasharuddin Mustapha, Kamal; Thiruchelvam, Sivadass; Usman, Fathoni; Itam, Zarina; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the mesh distribution on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced with varied thickness and fraction volume subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the effect of the mesh distribution on the impact resistance SFRC for various slab thickness and fraction volume. Random fibre distribution is the more effective than the top and bottom fibre distribution in terms of absorption of impact energy, crack resistance, the ability to control crack formation and propagation against impact energy.

  1. Effect of Thickness and Fibre Volume Fraction on Impact Resistance of Steel Fibre Reinforced Concrete (SFRC)

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Usman, Fathoni; Syamsir, Agusril; Shao Yang, Chen; Nasharuddin Mustapha, Kamal; Beddu, Salmia; Thiruchelvam, Sivadass; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Itam, Zarina; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the thickness and fibre volume fraction (VF) on the impact performance of steel fibre reinforced concrete (SFRC) for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.57 m height has been used in this research work. The objective of this research is to study the relationship of impact resistance SFRC against slab thickness and volume fraction. There is a good linear correlation between impact resistances of SFRC against slab thickness. However the impact resistance of SFRC against percentage of volume fraction exhibit a non-linear relationship.

  2. LONG-TERM EFFECTS OF WASTE SOLUTIONS ON CONCRETE AND REINFORCING STEEL

    SciTech Connect

    DANIEL JI; START DC; KAAR PH

    1983-05-28

    This report has been prepared for the In Situ Waste Disposal Program Tank Assessment Task (WG-11) as part of an investigation to evaluate the long-term performance of waste storage tanks at the Hanford Site. This report, prepared by the Portland Cement Association, presents the results of four years of concrete degradation studies which exposed concrete and reinforcing steel, under load and at 180 F, to simulated double-shell slurry, simulated salt cake solution, and a control solution. Exposure length varied from 3 months to 36 months. In all cases, examination of the concrete and reinforcing steel at the end of the exposure indicated there was no attack, i.e., no evidence of rusting, cracking, disruption of mill scale or loss of strength. Radioactive waste resulting from the chemical processing of reactor fuel for recovery of special nuclear materials (primarily plutonium), has been accumulating at the Hanford Site since 1944. The defense waste is currently being stored in underground waste tanks and in capsules stored in water basins. Current U.S. Department of Energy (DOE) strategy is to emphasize development and implementation of technology for removal, solidification, and final disposition of defense waste at the Savannah River Site first, then at the Hanford Site. Final disposal of waste in tanks at Hanford is expected to consist of in-place stabilization of most tanks. Selected tank wastes may be retrieved. Disposal operations will be carried out during the next several decades. Consequently, defense waste will remain in the existing underground tanks at Hanford for at least several decades. To ensure the safe storage of the waste, the waste storage tanks are being evaluated for continued service as part of the DOE Waste Tank Evaluation Program (AR-005-10-02-G). Technical studies and laboratory tests have been conducted to determine the effect of the stored waste's chemicals and temperature on the reinforced concrete. Waste solutions, which can be

  3. Field Testing of High Current Electrokinetic Nanoparticle Treatment for Corrosion Mitigation in Reinforced Concrete

    NASA Technical Reports Server (NTRS)

    Cardenas, Henry; Alexander, Joshua; Kupwade-Patil, Kunal; Calle, Luz marina

    2010-01-01

    Electrokinetic Nanoparticle (EN) treatment was used as a rapid repair measure to mitigate chloride induced corrosion of reinforced concrete in the field. EN treatment uses an electric field to transport positively charged nanoparticles to the reinforcement through the concrete capillary pores. Cylindrical reinforced concrete specimens were batched with 4.5 wt % salt content (based on cement mass). Three distinct electrokinetic treatments were conducted using high current density (up to 5 A/m2) to form a chloride penetration barrier that was established in 5 days, as opposed to the traditional 6-8 weeks, generally required for electrochemical chloride extraction (ECE). These treatments included basic EN treatment, EN with additional calcium treatment, and basic ECE treatment. Field exposures were conducted at the NASA Beachside Corrosion Test Site, Kennedy Space Center, Florida, USA. The specimens were subjected to sea water immersion at the test site as a posttreatment exposure. Following a 30-day post-treatment exposure period, the specimens were subjected to indirect tensile testing to evaluate treatment impact. The EN treated specimens exhibited 60% and 30% increases in tensile strength as compared to the untreated controls and ECE treated specimens respectively. The surfaces of the reinforcement bars of the control specimens were 67% covered by corrosion products. In contrast, the EN treated specimens exhibited corrosion coverage of only 4%. Scanning electron microscopy (SEM) revealed a dense concrete microstructure adjacent to the bars of the treated specimens as compared to the control and ECE specimens. Energy dispersive spectroscopic (EDS) analysis of the polished EN treated specimens showed a reduction in chloride content by a factor of 20 adjacent to the bars. This study demonstrated that EN treatment was successful in forming a chloride penetration barrier rapidly. This work also showed that the chloride barrier was effective when samples were exposed to

  4. Digital-image-correlation-based experimental stress analysis of reinforced concrete beams, strengthened using carbon composites

    NASA Astrophysics Data System (ADS)

    Helm, Jeffrey; Kurtz, Stephen

    2004-12-01

    The strengthening of reinforced concrete beams through the use of epoxy-bonded carbon composites has been widely researched in the United States since 1991. Despite the widespread attention of researchers, however, there are no reliable methods of predicting the failure of the repaired and strengthened beams by peeling of the fiber reinforced polymer (FRP) material from the parent concrete. To better understand peeling failure, several investigators have presented analytical work to predict the distribution of stresses along the interface between the FRP and the concrete. Several closed-form solutions can be found in the literature to predict the levels of shear stress present between the bonded composite plate and the parent concrete beam. However, there has been very little experimental verification of these analytical predictions because few experiments on large-scale beams have had sufficient instrumentation to facilitate the comparison. Some experiments have been presented1 in which electrical resistance strain gages were placed along the length of the carbon plate in order to deduce the interfacial shear stress using first differences. This method, though very crude, demonstrated that there are substantial differences between the distributions of interfacial shear stresses in actual repaired beams versus the analytical predictions. This paper presents a new test program in which large-scale carbon-fiber-strengthened reinforced concrete beams are load-tested to failure, while employing digital image correlation (DIC) to record the strains in the carbon fiber plate. Relying on the linear elasticity of carbon fiber, the interfacial shear can be determined and compared with the analytical predictions of the literature. The focus of this paper is the presentation of the experimental shear stress distributions and comparisons of these distributions with previous results available in the literature.

  5. Digital-image-correlation-based experimental stress analysis of reinforced concrete beams strengthened using carbon composites

    NASA Astrophysics Data System (ADS)

    Helm, Jeffrey; Kurtz, Stephen

    2005-01-01

    The strengthening of reinforced concrete beams through the use of epoxy-bonded carbon composites has been widely researched in the United States since 1991. Despite the widespread attention of researchers, however, there are no reliable methods of predicting the failure of the repaired and strengthened beams by peeling of the fiber reinforced polymer (FRP) material from the parent concrete. To better understand peeling failure, several investigators have presented analytical work to predict the distribution of stresses along the interface between the FRP and the concrete. Several closed-form solutions can be found in the literature to predict the levels of shear stress present between the bonded composite plate and the parent concrete beam. However, there has been very little experimental verification of these analytical predictions because few experiments on large-scale beams have had sufficient instrumentation to facilitate the comparison. Some experiments have been presented1 in which electrical resistance strain gages were placed along the length of the carbon plate in order to deduce the interfacial shear stress using first differences. This method, though very crude, demonstrated that there are substantial differences between the distributions of interfacial shear stresses in actual repaired beams versus the analytical predictions. This paper presents a new test program in which large-scale carbon-fiber-strengthened reinforced concrete beams are load-tested to failure, while employing digital image correlation (DIC) to record the strains in the carbon fiber plate. Relying on the linear elasticity of carbon fiber, the interfacial shear can be determined and compared with the analytical predictions of the literature. The focus of this paper is the presentation of the experimental shear stress distributions and comparisons of these distributions with previous results available in the literature.

  6. Numerical Modelling of Reinforced Concrete Slabs under Blast Loads of Close-in Detonations Using the Lagrangian Approach

    NASA Astrophysics Data System (ADS)

    Shuaib, M.; Daoud, O.

    2015-07-01

    This paper includes an investigation for the deformations, including deflections and damage modes, which occur in reinforced concrete (RC) slabs when subjected to blast loads of explosions. The slab considered for the investigation is a one-way square RC slab with the dimensions of 1000 x 1000 x 40 mm, fixed supported at two opposite sides. It was subjected to close-in detonations of three different charge weights for a constant standoff distance. For the study, the slab was analysed using the numerical method by means of nonlinear finite element analysis. The slab was modelled as 3-D structural continuum using LS-DYNA software. For concrete modelling, two constitutive models were selected, namely the KCC and Winfrith concrete models. Blast loads were applied to the slab through the Lagrangian approach, and the blast command available in the software, namely LOAD_BLAST_ENHANCED, was selected for the application. The deflections and damage modes results obtained were compared to those from a previously published experiment. From the study, both the KCC and Winfrith concrete models effectively and satisfactorily estimated the actual slab maximum deflection. For damage modes, the KCC model appeared to be capable to capture satisfactorily the general damage mode including flexural cracks. However, the model could not capture the local shear mode at the middle of slab (spallation) because the Lagrangian approach does not simulate the interaction between the ambient air and the solid slab.

  7. Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

    NASA Astrophysics Data System (ADS)

    Yan, Changwang; Jia, Jinqing

    2010-09-01

    To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete (SRUHSC) columns and steel reinforced concrete (SRC) beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirrup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete (SRC) frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

  8. Concrete structure construction on the Moon

    NASA Astrophysics Data System (ADS)

    Matsumoto, Shinji; Namba, Haruyuki; Kai, Yoshiro; Yoshida, Tetsuji

    1992-09-01

    This paper describes a precast prestressed concrete structure system on the Moon and erection methods for this system. The horizontal section of the structural module is hexagonal so that various layouts of the modules are possible by connecting the adjacent modules to each other. For erection of the modules, specially designed mobile cranes are used.

  9. Concrete structure construction on the Moon

    NASA Technical Reports Server (NTRS)

    Matsumoto, Shinji; Namba, Haruyuki; Kai, Yoshiro; Yoshida, Tetsuji

    1992-01-01

    This paper describes a precast prestressed concrete structure system on the Moon and erection methods for this system. The horizontal section of the structural module is hexagonal so that various layouts of the modules are possible by connecting the adjacent modules to each other. For erection of the modules, specially designed mobile cranes are used.

  10. Utilization of power plant bottom ash as aggregates in fiber-reinforced cellular concrete.

    PubMed

    Lee, H K; Kim, H K; Hwang, E A

    2010-02-01

    Recently, millions tons of bottom ash wastes from thermoelectric power plants have been disposed of in landfills and coastal areas, regardless of its recycling possibility in construction fields. Fiber-reinforced cellular concrete (FRCC) of low density and of high strength may be attainable through the addition of bottom ash due to its relatively high strength. This paper focuses on evaluating the feasibility of utilizing bottom ash of thermoelectric power plant wastes as aggregates in FRCC. The flow characteristics of cement mortar with bottom ash aggregates and the effect of aggregate type and size on concrete density and compressive strength were investigated. In addition, the effects of adding steel and polypropylene fibers for improving the strength of concrete were also investigated. The results from this study suggest that bottom ash can be applied as a construction material which may not only improve the compressive strength of FRCC significantly but also reduce problems related to bottom ash waste. PMID:19910181

  11. A study of inelastic behavior of reinforced concrete shells using supercomputers

    SciTech Connect

    Min Chang Shik.

    1992-01-01

    This study intends to relate the point-wise limit state design method to the ultimate behavior of reinforced-concrete shells as a unified approach. A vector algorithm developed on a Cray Y-MP supercomputer is suitable to implement an inelastic finite element program. A bending inelastic finite element model, which incorporates the rotating cracking model by layering the subdivided elements, is developed. Effects of large-deformation, tension-stiffening, and dowel action are ignored, and the bond between the concrete and steel and among the subdivided layers is assumed to be perfect. The biaxial behavior of uncracked concrete and the uniaxial behavior of a cracked element are assumed to be linear elastic in compression and in tension. Based on this analysis, the current design method provides adequate strength against an ultimate failure.

  12. Field Testing of High Current Electrokinetic Nanoparticle Treatment for Corrosion Mitigation in Reinforced Concrete

    NASA Technical Reports Server (NTRS)

    Calle, Luz Marina; Alexander, Joshua B.; Cardenas, Henry E.; Kupwade-Patil, Kunal

    2008-01-01

    This work examines field performance of nanoscale pozzolan treatments delivered el ctrokinetically to suppress chloride induced corrosion of concrete reinforcement. The particles are 20 nm silica spheres coated with 2 nm alumina particles that carry a net positive charge. Earlier work demonstrated that the alumina particles were stripped from the silica carriers and formed a dense phase with an interparticle spacing that is small enough to inhibit the transport of solvated chlorides. A D.C. field was used to inject the particles into the pores of concrete specimens, directly toward the mild steel bars that were embedded within each 3 inch diameter by 6 inch length concrete specimen. The voltage was held constant at 25 v per inch of concrete cover for a period of 7 days. These voltages permitted current densities as high as 3 A/sq m. During the final 3 days, a 1 molar solution of calcium nitrate tetrahydrate was used to provide a source of calcium to facilitate stronger and more densified phase formation within the pores. In a departure from prior work the particle treatments were started concurrent with chloride extraction in order to determine if particle delivery would inhibit chloride transport. Following treatment the specimens were immersed in seawater for 4 weeks. After this posttreatment exposure, the specimens were tested for tensile strength and the steel reinforcement was examined for evidence of corrosion. Scanning electron microscopy was conducted to assess impact on microstructure.

  13. Figure of Merit for Chlorine Measurement in Reinforced Concrete Using {sup 252}Cf-Based Nondestructive Testing Method

    SciTech Connect

    Habeeb H. Saleh; Richard A. Livington

    2000-11-12

    The objective of this study is to design, fabricate, and evaluate a portable system for nondestructive determination of chloride concentration in reinforced portland cement concrete (PCC) structures. The need for such an instrument arises from the massive deterioration of the reinforced PCC, which has been used to construct a major part of the highway infrastructure. This deterioration of PCC is due to corrosion of the reinforcing steel, which is greatly promoted by the chloride ions. The sources of chloride include deicing salts, set accelerator, and seawater, either in the form of concrete-mixing water or as airborne droplets from ocean spray. The system consists of a high-purity germanium detector for gamma-ray detection and a portable {sup 252}Cf neutron source. Tradeoffs in the design of the neutron source include data quality, operational efficiency, and radiation safety. The number of photons detected in the germanium detector is directly proportional to the neutron source strength and the chloride nuclei concentration in the sample under testing. Therefore, assuming a uniform distribution of chloride, the figure of merit of the number of photons detected in the detector can be expressed as F = C/SN, where C = number of (6111) keV gamma rays detected per second, N = concentration of chloride nuclei, and S = neutron source strength (n/s). Under the assumption that the neutron source strength is fixed, the figure of merit in this case can have at least two uses. One is to optimize the thermalization efficiency of the neutron moderator. The second is to evaluate how effective the detector configuration is in detecting the gamma rays generated in the concrete. Using the figure-of-merit approach, it is possible to find an optimum size of moderator. This is important for a portable system. Other variables such as source/detector separation or detector gamma-ray shielding can also be evaluated.

  14. Vibration based baseline updating method to localize crack formation and propagation in reinforced concrete members

    NASA Astrophysics Data System (ADS)

    Wahalathantri, Buddhi L.; Thambiratnam, David P.; Chan, Tommy H. T.; Fawzia, Sabrina

    2015-05-01

    Structural Health Monitoring (SHM) schemes are useful for proper management of the performance of structures and for preventing their catastrophic failures. Vibration based SHM schemes has gained popularity during the past two decades resulting in significant research. It is hence evitable that future SHM schemes will include robust and automated vibration based damage assessment techniques (VBDAT) to detect, localize and quantify damage. In this context, the Damage Index (DI) method which is classified as non-model or output based VBDAT, has the ability to automate the damage assessment process without using a computer or numerical model along with actual measurements. Although damage assessment using DI methods have been able to achieve reasonable success for structures made of homogeneous materials such as steel, the same success level has not been reported with respect to Reinforced Concrete (RC) structures. The complexity of flexural cracks is claimed to be the main reason to hinder the applicability of existing DI methods in RC structures. Past research also indicates that use of a constant baseline throughout the damage assessment process undermines the potential of the Modal Strain Energy based Damage Index (MSEDI). To address this situation, this paper presents a novel method that has been developed as part of a comprehensive research project carried out at Queensland University of Technology, Brisbane, Australia. This novel process, referred to as the baseline updating method, continuously updates the baseline and systematically tracks both crack formation and propagation with the ability to automate the damage assessment process using output only data. The proposed method is illustrated through examples and the results demonstrate the capability of the method to achieve the desired outcomes.

  15. Acoustic Emission Monitoring of Multicell Reinforced Concrete Box Girders Subjected to Torsion

    PubMed Central

    Bagherifaez, Marya; Behnia, Arash; Majeed, Abeer Aqeel; Hwa Kian, Chai

    2014-01-01

    Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothed b-value analysis. PMID:25180203

  16. Refinement of Strut-and-Tie Model for Reinforced Concrete Deep Beams.

    PubMed

    Panjehpour, Mohammad; Chai, Hwa Kian; Voo, Yen Lei

    2015-01-01

    Deep beams are commonly used in tall buildings, offshore structures, and foundations. According to many codes and standards, strut-and-tie model (STM) is recommended as a rational approach for deep beam analyses. This research focuses on the STM recommended by ACI 318-11 and AASHTO LRFD and uses experimental results to modify the strut effectiveness factor in STM for reinforced concrete (RC) deep beams. This study aims to refine STM through the strut effectiveness factor and increase result accuracy. Six RC deep beams with different shear span to effective-depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were experimentally tested under a four-point bending set-up. The ultimate shear strength of deep beams obtained from non-linear finite element modeling and STM recommended by ACI 318-11 as well as AASHTO LRFD (2012) were compared with the experimental results. An empirical equation was proposed to modify the principal tensile strain value in the bottle-shaped strut of deep beams. The equation of the strut effectiveness factor from AASHTTO LRFD was then modified through the aforementioned empirical equation. An investigation on the failure mode and crack propagation in RC deep beams subjected to load was also conducted. PMID:26110268

  17. Refinement of Strut-and-Tie Model for Reinforced Concrete Deep Beams

    PubMed Central

    Panjehpour, Mohammad; Chai, Hwa Kian; Voo, Yen Lei

    2015-01-01

    Deep beams are commonly used in tall buildings, offshore structures, and foundations. According to many codes and standards, strut-and-tie model (STM) is recommended as a rational approach for deep beam analyses. This research focuses on the STM recommended by ACI 318-11 and AASHTO LRFD and uses experimental results to modify the strut effectiveness factor in STM for reinforced concrete (RC) deep beams. This study aims to refine STM through the strut effectiveness factor and increase result accuracy. Six RC deep beams with different shear span to effective-depth ratios (a/d) of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were experimentally tested under a four-point bending set-up. The ultimate shear strength of deep beams obtained from non-linear finite element modeling and STM recommended by ACI 318-11 as well as AASHTO LRFD (2012) were compared with the experimental results. An empirical equation was proposed to modify the principal tensile strain value in the bottle-shaped strut of deep beams. The equation of the strut effectiveness factor from AASHTTO LRFD was then modified through the aforementioned empirical equation. An investigation on the failure mode and crack propagation in RC deep beams subjected to load was also conducted. PMID:26110268

  18. Posttest analysis of the 1:6-scale reinforced concrete containment

    SciTech Connect

    Pfeiffer, P.A.; Kennedy, J.M.; Marchertas, A.H.

    1989-01-01

    A prediction of the response of the Sandia National Laboratories 1:6- scale reinforced concrete containment model test was made by Argonne National Laboratory. ANL along with nine other organizations performed a detailed nonlinear response analysis of the 1:6-scale model containment subjected to overpressurization in the fall of 1986. The two-dimensional code TEMP-STRESS and the three-dimensional NEPTUNE code were utilized (1) to predict the global response of the structure, (2) to identify global failure sites and the corresponding failure pressures and (3) to identify some local failure sites and pressure levels. A series of axisymmetric models was studied with the two-dimensional computer program TEMP-STRESS. The comparison of these pretest computations with test data from the containment model has provided a test for the capability of the respective finite element codes to predict global failure modes, and hence serves as a validation of these codes. Only the two-dimensional analyses will be discussed in this paper. 3 refs., 10 figs.

  19. Impact Resistance Behaviour of Light Weight Rice Husk Concrete with Bamboo Reinforcement

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Beddu, Salmia; Syamsir, Agusril; Sigar Ating, Joshua; Liyana Mohd Kamal, Nur; Nasharuddin Mustapha, Kamal; Thiruchelvam, Sivadass; Usman, Fathoni; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the performance of lightweight rice husk concrete (LWRHC) with varied bamboo reinforcement content for the concrete slab of 300mm × 300mm size reinforced with varied slab thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at 0.65 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of bamboo reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against bamboo diameters and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the bamboo reinforcement diameter and slab thickness. 5% RH content exhibit better first and ultimate crack resistance up to 1.80 times and up to 1.72 times respectively against 10% RH content.

  20. Cistern for liquid or gas, constructed of reinforced concrete

    SciTech Connect

    Pulkkinen, J.

    1988-01-05

    A cistern structure for use as a subterranean cistern is described comprising: a shell forming an inner surface of the cistern structure and formed of a material impermeable to substance to be stored therewithin; mutually-spaced, annular juncture elements, encircling the shell; at least one anchoring element provided in each juncture element for anchoring the cistern structure into surrounding rock or soil; structural elements arranged one above the other and joined with the annular juncture elements to form a compound structure; and an intermediate layer of material situated between the mutually-spaced juncture elements.

  1. Calculation of reinforced-concrete frame strength under a simultaneous static cross section load and a column lateral impact

    NASA Astrophysics Data System (ADS)

    Belov, Nikolay; Yugov, Nikolay; Kopanitsa, Dmitry; Kopanitsa, Georgy; Yugov, Alexey; Kaparulin, Sergey; Plyaskin, Andrey; Kalichkina, Anna; Ustinov, Artyom

    2016-01-01

    When designing buildings with reinforced concrete that are planned to resist dynamic loads it is necessary to calculate this structural behavior under operational static and emergency impact and blast loads. Calculations of the structures under shock-wave loads can be performed by solving dynamic equations that do not consider static loads. Due to this fact the calculation of reinforced concrete frame under a simultaneous static and dynamic load in full 3d settings becomes a very non trivial and resource consuming problem. This problem can be split into two tasks. The first one is a shock-wave problem that can be solved using software package RANET-3, which allows solving the problem using finite elements method adapted for dynamic task. This method calculates strain-stress state of the material and its dynamic destruction, which is considered as growth and consolidation of micro defects under loading. On the second step the results of the first step are taken as input parameters for quasi static calculation of simultaneous static and dynamic load using finite elements method in AMP Civil Engineering-11.

  2. Fragility Curve Construction for Low-Rise Reinforced Concrete Buildings Affected by Debris Flow

    NASA Astrophysics Data System (ADS)

    Akbas, S.; Sterlacchini, S.

    2009-04-01

    In landslide risk research, the majority of past studies has focused on hazard analysis, landslide zonation, and modeling, but there is limited amount of work on the concept of vulnerability, with no consensus on a generalized methodology. However, assessment of vulnerabilities along with the associated uncertainties are of utmost importance from a quantitative risk analysis point of view. This study aims at estimating the vulnerability by developing fragility curves, specifically for low-rise reinforced concrete buildings affected by debris flows. The effect of debris flow on structures is modeled as an impulsive load. The behavior of a structure under an impulsive load is in many ways is similar to that of an earthquake excitation. Based on this similarity, and using a well developed approach from the field of earthquake engineering, corresponding fragility curves are constructed for three structural damage limit states: serviceability, damage control, and collapse prevention. This is achieved by (1) representing the buildings as equivalent single degree-of-freedom systems, and conducting nonlinear time history analyses of these systems, (2) obtaining response statistics in terms of maximum displacement, (3) obtaining the conditional probability of attainment or exceedance of each limit state at a specific debris flow intensity level, and (4) plotting the computed conditional probability with respect to the selected debris flow hazard parameter. The resulting fragility curves give the damage state probability as a function of debris flow velocity. The uncertainty in the structural parameters, such as the natural period, are considered by using a building database from the city of Duzce, Turkey, which was affected by two major earthquakes in 1999. The comparison of the results obtained from this study with those obtained using a different database employing the same methodology, will highlight if the country-specific characteristics of the fragility curves are

  3. Bond-slip detection of concrete-encased composite structure using electro-mechanical impedance technique

    NASA Astrophysics Data System (ADS)

    Liang, Yabin; Li, Dongsheng; Parvasi, Seyed Mohammad; Kong, Qingzhao; Lim, Ing; Song, Gangbing

    2016-09-01

    Concrete-encased composite structure is a type of structure that takes the advantages of both steel and concrete materials, showing improved strength, ductility, and fire resistance compared to traditional reinforced concrete structures. The interface between concrete and steel profiles governs the interaction between these two materials under loading, however, debonding damage between these two materials may lead to severe degradation of the load transferring capacity which will affect the structural performance significantly. In this paper, the electro-mechanical impedance (EMI) technique using piezoceramic transducers was experimentally investigated to detect the bond-slip occurrence of the concrete-encased composite structure. The root-mean-square deviation is used to quantify the variations of the impedance signatures due to the presence of the bond-slip damage. In order to verify the validity of the proposed method, finite element model analysis was performed to simulate the behavior of concrete-steel debonding based on a 3D finite element concrete-steel bond model. The computed impedance signatures from the numerical results are compared with the results obtained from the experimental study, and both the numerical and experimental studies verify the proposed EMI method to detect bond slip of a concrete-encased composite structure.

  4. Transient thermography for structural investigation of concrete and composites in the near surface region

    NASA Astrophysics Data System (ADS)

    Maierhofer, Ch.; Brink, A.; Röllig, M.; Wiggenhauser, H.

    2002-06-01

    The cooling down process of building structures after heating up with an external radiation source was analysed to detect voids inside and below the surface of a concrete test specimen containing voids with different sizes at various depth or covered with carbon fibre reinforcing laminates. These experimental investigations were compared to the results of simulations performed with a finite difference program.

  5. Effect of Waste Plastic Shreds on Bond Resistance between Concrete and Steel Reinforcement

    NASA Astrophysics Data System (ADS)

    Osifala, K. B.; Salau, M. A.; Adeniyi, A. A.

    2015-11-01

    This paper investigates the effect of waste plastic shreds on steel-concrete bond. Forty RILEM test specimens with 16mm and 20mm diameter high-yield reinforcing bars were cast and tested. Fifteen specimens with 16mm and 20mm each were cast with the addition of waste plastic shreds at varying percentages of 1%, 1.5% and 2%; another ten RILEM specimens with 16mm and 20mm diameter bars at 0% of waste plastic shreds were cast as reference. Nine 150mm cubes, with three taken from each batch of various percentages of waste plastic shreds, were used to monitor the concrete strength. From the test results and analysis, the compressive strength of concrete was found to reduce with increased percentages of waste plastic shreds, while the waste plastic shreds material was found not to improve the bond resistance between concrete and steel. However, though lower than normal concrete, there was an increase in the bond resistance with increase in the percent of plastic shreds. The bond resistance of 16mm was also found to be higher than that of 20mm in all the specimens tested.

  6. Rebar corrosion monitoring in concrete structure under salt water enviroment using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Pan, Yuheng; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Wang, Shuang; He, Pan; Yan, Jinlin

    2015-08-01

    Monitoring corrosion of steel reinforcing bars is critical for the durability and safety of reinforced concrete structures. Corrosion sensors based on fiber optic have proved to exhibit meaningful benefits compared with the conventional electric ones. In recent years, Fiber Bragg Grating (FBG) has been used as a new kind of sensing element in an attempt to directly monitor the corrosion in concrete structure due to its remarkable advantages. In this paper, we present a novel kind of FBG based rebar corrosion monitoring sensor. The rebar corrosion is detected by volume expansion of the corroded rebar by transferring it to the axial strain of FBG when concrete structure is soaked in salt water. An accelerated salt water corrosion test was performed. The experiment results showed the corrosion can be monitored effectively and the corrosion rate is obtained by volume loss rate of rebar.

  7. Evaluation of alternative concrete cutting techniques for massive concrete structures

    SciTech Connect

    Craig, K.; Boing, L.

    1994-12-31

    Various methods for removing massive concrete structures during decontamination and decommissioning (D&D), such as the map tube facility and waste storage vaults located in the 317 Area of Argonne National Laboratory, have been evaluated by NES, Inc./integrated Environmental Services. Five of the most feasible cutting technologies are described in terms of their ability to perform the required tasks; their performance characteristics; radiological, safety, and environmental impacts; and cost and schedule considerations. These cutting techniques are consequential in the D&D process for reducing the amount of radioactive waste requiring disposal and decreasing worker exposure to contamination. Table I lists the cutting technologies that were analyzed and the key parameters of each. This synopsis permits a rapid comparison of the techniques. For each cutting technique, the cutting speed is based on compilation of vendor information. Costs are given for the individual cutting system.

  8. Strain evaluation of strengthened concrete structures using FBG sensors

    NASA Astrophysics Data System (ADS)

    Lau, Kin-tak; Zhou, Li-min; Ye, Lin

    1999-12-01

    Fibre-optic Bragg Grating (FBG) sensor presents a great deal of potential in monitoring the internal status of the concrete structures after repairing or strengthening by an external adhered reinforcement. It can be used in a variety of configurations ranging from pointwise to multi-point strain measurement in order to investigate the strain distribution of the structures. In this paper, an experimental investigation on the rectangular notched-concrete beam, which was strengthened by glass fibre composites with the embedment of multiplexing FBG sensors is presented. Three point bending test was performed to investigate the strain profile of the specimen. Frequency modulated continuous wave (FMCW) technique was used to measure the strain variation of the fibre-grating regions. The results give a good agreement with the electrical resistance strain gauge in early loading condition. The difference of the strain-measuring results between the strain-gauge and FBG sensor was increased when further increasing the applied load. It was suspected that the micro/marco cracks occurred on the concrete surface and that the externally bonded strain-measuring device cannot be detected.

  9. Strain evaluation of strengthened concrete structures using FBG sensors

    SciTech Connect

    Lau Kintak; Zhou Limin; Ye Lin

    1999-12-02

    Fibre-optic Bragg Grating (FBG) sensor presents a great deal of potential in monitoring the internal status of the concrete structures after repairing or strengthening by an external adhered reinforcement. It can be used in a variety of configurations ranging from pointwise to multi-point strain measurement in order to investigate the strain distribution of the structures. In this paper, an experimental investigation on the rectangular notched-concrete beam, which was strengthened by glass fibre composites with the embedment of multiplexing FBG sensors is presented. Three point bending test was performed to investigate the strain profile of the specimen. Frequency modulated continuous wave (FMCW) technique was used to measure the strain variation of the fibre-grating regions. The results give a good agreement with the electrical resistance strain gauge in early loading condition. The difference of the strain-measuring results between the strain-gauge and FBG sensor was increased when further increasing the applied load. It was suspected that the micro/marco cracks occurred on the concrete surface and that the externally bonded strain-measuring device cannot be detected.

  10. Evaluation of irradiation effects on concrete structure

    SciTech Connect

    Kontani, O.; Ishizawa, A.; Maruyama, I.; Takizawa, M.; Sato, O.

    2012-07-01

    In assessing the soundness of irradiated concrete of nuclear power plants operated for more than 30 years, reference levels are employed: 1x10{sup 20} n/cm{sup 2} for fast neutrons and 2x10{sup 10} rad (2x10{sup 5} kGy) for gamma rays. Concrete structures are regarded as sound when the estimated irradiance levels after 60 years of operation are less than the reference levels. The reference levels were obtained from a paper by Hilsdorf. It was found, however, that the test conditions in which data were obtained by the researchers referred in that paper are very different from the irradiation and heat conditions usually found in a Light Water Reactor (LWR), and therefore aren't appropriate for assessing the soundness of irradiated concrete of an LWR. This paper investigates the interactions between radiation and concrete and presents the results of gamma ray irradiation tests on cement paste samples in order to provide a better understanding of the irradiation effects on concrete. (authors)

  11. NDE application of ultrasonic tomography to a full-scale concrete structure.

    PubMed

    Choi, Hajin; Popovics, John S

    2015-06-01

    Newly developed ultrasonic imaging technology for large concrete elements, based on tomographic reconstruction, is presented. The developed 3-D internal images (velocity tomograms) are used to detect internal defects (polystyrene foam and pre-cracked concrete prisms) that represent structural damage within a large steel reinforced concrete element. A hybrid air-coupled/contact transducer system is deployed. Electrostatic air-coupled transducers are used to generate ultrasonic energy and contact accelerometers are attached on the opposing side of the concrete element to detect the ultrasonic pulses. The developed hybrid testing setup enables collection of a large amount of high-quality, through-thickness ultrasonic data without surface preparation to the concrete. The algebraic reconstruction technique is used to reconstruct p-wave velocity tomograms from the obtained time signal data. A comparison with a one-sided ultrasonic imaging method is presented for the same specimen. Through-thickness tomography shows some benefit over one-sided imaging for highly reinforced concrete elements. The results demonstrate that the proposed through-thickness ultrasonic technique shows great potential for evaluation of full-scale concrete structures in the field. PMID:26067042

  12. Use of slurry infiltrated fiber concrete (SIFCON) in hinge regions of earthquake resistant structures

    NASA Astrophysics Data System (ADS)

    Wood, Bryan Thane

    This dissertation reports on an experimental and analytical study of the use of precast slurry infiltrated fiber concrete (SIFCON) flexural hinges to improve the seismic resistance of reinforced concrete moment frames. The main thrust of the research was to investigate how different variables effect the nonlinear, cyclic, flexural behavior of reinforced SIFCON hinges, and to determine how to optimize hinge performance. In addition, a conceptual analysis was performed to evaluate the improvement in seismic resistance from using SIFCON hinges in concrete structures. Seven 10″ wide, 16″ deep, and 26″ long reinforced SIFCON hinges were designed and fabricated, then tested under quasi-static loading. All specimens were fabricated using between 9 and 11%, by volume, Dramix 30/50 fibers, made by the Bekaert Corporation. Grade 60, Grade 75, and ASTM A722 (Dywidag) bars were used, in combination with three different SIFCON compression strengths. Additionally, various end connection details were used in testing three different reinforcing arrangements. It was shown that precast SIFCON hinges can exhibit better performance than reinforced concrete hinges. The maximum curvature ductility achieved was 26.4 over a 4″ inch long interior region of a specimen. The curvature ductility of this hinge specimen, when taken over the full 26 inch hinge length, was 10.5. SIFCON hinges absorb approximately 30% more energy than fiber-reinforced concrete hinges. SIFCON hinge ductility is limited by the ultimate tensile strain of the reinforcing steel. Grade 60 reinforcing resulted in the best hinge behavior seen in testing. Transverse ties may be required to prevent buckling of compression reinforcing. SIFCON flexural stiffness is approximately half that of comparable strength reinforced concrete beams. It was found that SIFCON material behavior is highly variable. Fiber orientation and size effects are the main variables that affect SIFCON behavior. Fabrication technique and skill of

  13. Investigation of factors influencing chloride extraction efficiency during electrochemical chloride extraction from reinforcing concrete

    NASA Astrophysics Data System (ADS)

    Sharp, Stephen R.

    2005-11-01

    Electrochemical chloride extraction (ECE) is an accelerated bridge restoration method similar to cathodic protection, but operates at higher current densities and utilizes a temporary installation. Both techniques prolong the life of a bridge by reducing the corrosion rate of the reinforcing bar when properly applied. ECE achieves this by moving chlorides away from the reinforcement and out of the concrete while simultaneously increasing the alkalinity of the electrolyte near the reinforcing steel. Despite the proven success, significant use of ECE has not resulted in part due to an incomplete understanding in the following areas: (1) An estimation of the additional service life that can be expected following treatment when the treated member is again subjected to chlorides; (2) The cause of the decrease in current flow and, therefore, chloride removal rate during treatment; (3) Influence of water-to-cement (w/c) ratio and cover depth on the time required for treatment. This dissertation covers the research that is connected to the last two areas listed above. To begin examining these issues, plain carbon steel reinforcing bars (rebar) were embedded in portland cement concrete slabs of varying water-to-cement (w/c) ratios and cover depths, and then exposed to chlorides. A fraction of these slabs had sodium chloride added as an admixture, with all of the slabs subjected to cyclical ponding with a saturated solution of sodium chloride. ECE was then used to remove the chlorides from these slabs while making electrical measurements in the different layers between the rebar (cathode) and the titanium mat (anode) to follow the progress of the ECE process. During this study, it was revealed that the resistance of the outer concrete surface layer increases during ECE, inevitably restricting current flow, while the resistance of the underlying concrete decreases or remains constant. During ECE treatment, a white residue formed on the surface of the concrete. Analyses of the

  14. The Non-Destructive Test of Steel Corrosion in Reinforced Concrete Bridges Using a Micro-Magnetic Sensor.

    PubMed

    Zhang, Hong; Liao, Leng; Zhao, Ruiqiang; Zhou, Jianting; Yang, Mao; Xia, Runchuan

    2016-01-01

    This paper presents a non-destructive test method for steel corrosion in reinforced concrete bridges by using a 3-dimensional digital micro-magnetic sensor to detect and analyze the self-magnetic field leakage from corroded reinforced concrete. The setup of the magnetic scanning device and the measurement mode of the micro-magnetic sensor are introduced. The numerical analysis model is also built based on the linear magnetic charge theory. Compared to the self-magnetic field leakage data obtained from magnetic sensor-based measurement and numerical calculation, it is shown that the curves of tangential magnetic field at different lift-off height all intersect near the edge of the steel corrosion zone. The result indicates that the intersection of magnetic field curves can be used to detect and evaluate the range of the inner steel corrosion in engineering structures. The findings of this work propose a new and effective non-destructive test method for steel corrosion, and therefore enlarge the application of the micro-magnetic sensor. PMID:27608029

  15. Experimental Study on the Strength Characteristics and Water Permeability of Hybrid Steel Fibre Reinforced Concrete.

    PubMed

    Singh, M P; Singh, S P; Singh, A P

    2014-01-01

    Results of an investigation conducted to study the effect of fibre hybridization on the strength characteristics such as compressive strength, split tensile strength, and water permeability of steel fibre reinforced concrete (SFRC) are presented. Steel fibres of different lengths, that is, 12.5 mm, 25 mm, and 50 mm, having constant diameter of 0.6 mm, were systematically combined in different mix proportions to obtain mono, binary, and ternary combinations at each of 0.5%, 1.0%, and 1.5% fibre volume fraction. A concrete mix containing no fibres was also cast for reference purpose. A total number of 1440 cube specimens of size 100∗100∗100 mm were tested, 480 each for compressive strength, split tensile strength, and water permeability at 7, 28, 90, and 120 days of curing. It has been observed from the results of this investigation that a fibre combination of 33% 12.5 mm + 33% 25 mm + 33% 50 mm long fibres can be adjudged as the most appropriate combination to be employed in hybrid steel fibre reinforced concrete (HySFRC) for optimum performance in terms of compressive strength, split tensile strength and water permeability requirements taken together. PMID:27379298

  16. Experimental Study on the Strength Characteristics and Water Permeability of Hybrid Steel Fibre Reinforced Concrete

    PubMed Central

    Singh, M. P.; Singh, S. P.; Singh, A. P.

    2014-01-01

    Results of an investigation conducted to study the effect of fibre hybridization on the strength characteristics such as compressive strength, split tensile strength, and water permeability of steel fibre reinforced concrete (SFRC) are presented. Steel fibres of different lengths, that is, 12.5 mm, 25 mm, and 50 mm, having constant diameter of 0.6 mm, were systematically combined in different mix proportions to obtain mono, binary, and ternary combinations at each of 0.5%, 1.0%, and 1.5% fibre volume fraction. A concrete mix containing no fibres was also cast for reference purpose. A total number of 1440 cube specimens of size 100∗100∗100 mm were tested, 480 each for compressive strength, split tensile strength, and water permeability at 7, 28, 90, and 120 days of curing. It has been observed from the results of this investigation that a fibre combination of 33% 12.5 mm + 33% 25 mm + 33% 50 mm long fibres can be adjudged as the most appropriate combination to be employed in hybrid steel fibre reinforced concrete (HySFRC) for optimum performance in terms of compressive strength, split tensile strength and water permeability requirements taken together. PMID:27379298

  17. A micromechanical approach to elastic and viscoelastic properties of fiber reinforced concrete

    SciTech Connect

    Pasa Dutra, V.F.; Maghous, S. Campos Filho, A.; Pacheco, A.R.

    2010-03-15

    Some aspects of the constitutive behavior of fiber reinforced concrete (FRC) are investigated within a micromechanical framework. Special emphasis is put on the prediction of creep of such materials. The linear elastic behavior is first examined by implementation of a Mori-Tanaka homogenization scheme. The micromechanical predictions for the overall stiffness prove to be very close to finite element solutions obtained from the numerical analysis of a representative elementary volume of FRC modeled as a randomly heterogeneous medium. The validation of the micromechanical concepts based on comparison with a set of experiments, shows remarkable predictive capabilities of the micromechanical representation. The second part of the paper is devoted to non-ageing viscoelasticity of FRC. Adopting a Zener model for the behavior of the concrete matrix and making use of the correspondence principle, the homogenized relaxation moduli are derived analytically. The validity of the model is established by mean of comparison with available experiment measurements of creep strain of steel fiber reinforced concrete under compressive load. Finally, the model predictions are compared to those derived from analytical models formulated within a one-dimensional setting.

  18. Application of smart BFRP bars with distributed fiber optic sensors into concrete structures

    NASA Astrophysics Data System (ADS)

    Tang, Yongsheng; Wu, Zhishen; Yang, Caiqian; Wu, Gang; Zhao, Lihua; Song, Shiwei

    2010-04-01

    In this paper, the self-sensing and mechanical properties of concrete structures strengthened with a novel type of smart basalt fiber reinforced polymer (BFRP) bars were experimentally studied, wherein the sensing element is Brillouin scattering-based distributed optical fiber sensing technique. First, one of the smart bars was applied to strengthen a 2m concrete beam under a 4-points static loading manner in the laboratory. During the experiment, the bar can measure the inner strain changes and monitor the randomly distributed cracks well. With the distributed strain information along the bar, the distributed deformation of the beam can be calculated, and the structural health can be monitored and evaluated as well. Then, two smart bars with a length of about 70m were embedded into a concrete airfield pavement reinforced by long BFRP bars. In the field test, all the optical fiber sensors in the smart bars survived the whole concrete casting process and worked well. From the measured data, the concrete cracks along the pavement length can be easily monitored. The experimental results also confirmed that the bars can strengthen the structures especially after the yielding of steel bars. All the results confirm that this new type of smart BFRP bars show not only good sensing performance but also mechanical performance in the concrete structures.

  19. Effects of near-fault ground motions on the nonlinear behaviour of reinforced concrete framed buildings

    NASA Astrophysics Data System (ADS)

    Mazza, Mirko

    2015-07-01

    The design provisions of current seismic codes are generally not very accurate for assessing effects of near-fault ground motions on reinforced concrete (r.c.) spatial frames, because only far-fault ground motions are considered in the seismic codes. Strong near-fault earthquakes are characterized by long-duration (horizontal) pulses and high values of the ratio α PGA of the peak value of the vertical acceleration, PGAV, to the analogous value of the horizontal acceleration, PGAH, which can become critical for girders and columns. In this work, six- and twelve-storey r.c. spatial frames are designed according to the provisions of the Italian seismic code, considering the horizontal seismic loads acting (besides the gravity loads) alone or in combination with the vertical ones. The nonlinear seismic analysis of the test structures is performed using a step-by-step procedure based on a two-parameter implicit integration scheme and an initial stress-like iterative procedure. A lumped plasticity model based on the Haar-Kàrmàn principle is adopted to model the inelastic behaviour of the frame members. For the numerical investigation, five near-fault ground motions with high values of the acceleration ratio α PGA are considered. Moreover, following recent seismological studies, which allow the extraction of the largest (horizontal) pulse from a near-fault ground motion, five pulse-type (horizontal) ground motions are selected by comparing the original ground motion with the residual motion after the pulse has been extracted. The results of the nonlinear dynamic analysis carried out on the test structures highlighted that horizontal and vertical components of near-fault ground motions may require additional consideration in the seismic codes.

  20. Thermal-sprayed zinc anodes for cathodic protection of steel-reinforced concrete bridges

    SciTech Connect

    Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; McGill, Galen E.

    1996-01-01

    Thermal-sprayed zinc anodes are being used in Oregon in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges. The U.S. Department of Energy, Albany Research Center, is collaborating with the Oregon Department of Transportation (ODOT) to evaluate the long-term performance and service life of these anodes. Laboratory studies were conducted on concrete slabs coated with 0.5 mm (20 mil) thick, thermal-sprayed zinc anodes. The slabs were electrochemically aged at an accelerated rate using an anode current density of 0.032 A/m2 (3mA/ft2). Half the slabs were preheated before thermal-spraying with zinc; the other half were unheated. Electrochemical aging resulted in the formation at the zinc-concrete interface of a thin, low pH zone (relative to cement paste) consisting primarily of ZnO and Zn(OH)2, and in a second zone of calcium and zinc aluminates and silicates formed by secondary mineralization. Both zones contained elevated concentrations of sulfate and chloride ions. The original bond strength of the zinc coating decreased due to the loss of mechanical bond to the concrete with the initial passage of electrical charge (aging). Additional charge led to an increase in bond strength to a maximum as the result of secondary mineralization of zinc dissolution products with the cement paste. Further charge led to a decrease in bond strength and ultimately coating disbondment as the interfacial reaction zones continued to thicken. This occurred at an effective service life of 27 years at the 0.0022 A/m2 (0.2 mA/ft2) current density typically used by ODOT in ICCP systems for coastal bridges. Zinc coating failure under tensile stress was primarily cohesive within the thickening reaction zones at the zinc-concrete interface. There was no difference between the bond strength of zinc coatings on preheated and unheated concrete surfaces after long service times.

  1. Computer simulation of fracture processes of concrete using mesolevel models of lattice structures

    SciTech Connect

    Leite, J.P.B.; Slowik, V.; Mihashi, H

    2004-06-01

    Mesolevel simulations were used to describe fracture processes in concrete. A new stochastic-heuristic algorithm was developed for generating the composite structure of concrete in 3-D space, producing specimens with comparably high aggregate content and realistic distribution. Aggregate particles were described as ellipsoids, allowing control in shape and size distributions. The continuum was discretised into lattices of linear elements, in structural analyses. For 2-D analyses, slices from the 3-D specimen were idealised as planar trusses/frames, while for the 3-D analyses the specimens were idealised as space structures. Fibre-reinforced concrete (FRC) was also modelled by introducing additional linear elements interconnecting distant nodes of the lattice. Compression, direct tension and wedge-splitting tests were simulated. Parametrical study was carried out to investigate the effect of different material properties and proportions in concrete admixtures. Simulation results are in agreement with experimental observations. Applicability and enhancements for such models are discussed and future research directions are proposed.

  2. Quantitative estimation of carbonation and chloride penetration in reinforced concrete by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Eto, Shuzo; Matsuo, Toyofumi; Matsumura, Takuro; Fujii, Takashi; Tanaka, Masayoshi Y.

    2014-11-01

    The penetration profile of chlorine in a reinforced concrete (RC) specimen was determined by laser-induced breakdown spectroscopy (LIBS). The concrete core was prepared from RC beams with cracking damage induced by bending load and salt water spraying. LIBS was performed using a specimen that was obtained by splitting the concrete core, and the line scan of laser pulses gave the two-dimensional emission intensity profiles of 100 × 80 mm2 within one hour. The two-dimensional profile of the emission intensity suggests that the presence of the crack had less effect on the emission intensity when the measurement interval was larger than the crack width. The chlorine emission spectrum was measured without using the buffer gas, which is usually used for chlorine measurement, by collinear double-pulse LIBS. The apparent diffusion coefficient, which is one of the most important parameters for chloride penetration in concrete, was estimated using the depth profile of chlorine emission intensity and Fick's law. The carbonation depth was estimated on the basis of the relationship between carbon and calcium emission intensities. When the carbon emission intensity was statistically higher than the calcium emission intensity at the measurement point, we determined that the point was carbonated. The estimation results were consistent with the spraying test results using phenolphthalein solution. These results suggest that the quantitative estimation by LIBS of carbonation depth and chloride penetration can be performed simultaneously.

  3. Degradation processes of reinforced concretes by combined sulfate–phosphate attack

    SciTech Connect

    Secco, Michele; Lampronti, Giulio Isacco; Schlegel, Moritz-Caspar; Maritan, Lara; Zorzi, Federico

    2015-02-15

    A novel form of alteration due to the interaction between hydrated cement phases and sulfate and phosphate-based pollutants is described, through the characterization of concrete samples from an industrial reinforced concrete building. Decalcification of the cement matrices was observed, with secondary sulfate and phosphate-based mineral formation, according to a marked mineralogical and textural zoning. Five alteration layers may be detected: the two outermost layers are characterized by the presence of gypsum–brushite solid solution phases associated with anhydrous calcium sulfates and phosphates, respectively, while a progressive increase in apatite and ammonium magnesium phosphates is observable in the three innermost layers, associated with specific apatite precursors (brushite, octacalcium phosphate and amorphous calcium phosphate, respectively). The heterogeneous microstructural development of secondary phases is related to the chemical, pH and thermal gradients in the attacked cementitious systems, caused by different sources of pollutants and the exposure to the sun's radiation.

  4. On the scattering behaviour of elastic waves in textile reinforced concrete

    NASA Astrophysics Data System (ADS)

    Weber, W.; Zastrau, B. W.

    2010-06-01

    An exact analytical solution for the scattering of antiplane elastic waves by a layered elastic eccentric inclusion is derived beginning from the solution of the wave equation in elliptic coordinates. The solution and its degenerate cases are compared with other models, e.g. the scattering due to concentric circular scatterers. The effects of the geometrical properties of the interphase are studied. Hereby the focus lies on geometric parameters which fit the needs of Textile Reinforced Concrete (TRC). The calculations are performed for material properties as they occur with TRC. The numerical results show an enormous influence of eccentricities within TRC to its wave scattering behaviour.

  5. Experimental Studies on Behaviour of Reinforced Geopolymer Concrete Beams Subjected to Monotonic Static Loading

    NASA Astrophysics Data System (ADS)

    Madheswaran, C. K.; Ambily, P. S.; Dattatreya, J. K.; Ramesh, G.

    2015-06-01

    This work describes the experimental investigation on behaviour of reinforced GPC beams subjected to monotonic static loading. The overall dimensions of the GPC beams are 250 mm × 300 mm × 2200 mm. The effective span of beam is 1600 mm. The beams have been designed to be critical in shear as per IS:456 provisions. The specimens were produced from a mix incorporating fly ash and ground granulated blast furnace slag, which was designed for a compressive strength of 40 MPa at 28 days. The reinforced concrete specimens are subjected to curing at ambient temperature under wet burlap. The parameters being investigated include shear span to depth ratio (a/d = 1.5 and 2.0). Experiments are conducted on 12 GPC beams and four OPCC control beams. All the beams are tested using 2000 kN servo-controlled hydraulic actuator. This paper presents the results of experimental studies.

  6. The determination of the constitutive parameters of a medium with application to a reinforced concrete pad

    SciTech Connect

    Poggio, A.J.; Burke, G.J.; Pennock, S.T.

    1995-01-15

    This report describes the experimental and analytical program performed to determine the constitutive parameters of the reinforced concrete pad in the test facility used during the Low Power On-the-Ground portion of the NASA Boeing 757 HIRF Tests. These tests were conducted during the period September 20 to October 21, 1994 in the LESLI facility at the Phillips Laboratory, Kirtland AFB, NM. The on-the-ground tests were designed to meet several objectives including support of a flight test series and the generation of data for the validation of codes and models that could be used to predict the electromagnetic environment in transport aircraft. To satisfy these objectives, tests were to be executed in a known environment and the data compared to modeling results. A critical feature of this testing was the ``known environment`` which implies knowledge of the parameters which are critical to an effective modeling activity and which could include, among many other things, definitions of the airplane and its physical and electrical configuration, the ground upon which it sits when stationary, the fields impinging on the aircraft, and the radiating or bounding structure in the simulator. The authors would want to specify the electromagnetic characteristics of the entire space that would likely enter into a mathematical modeling effort so that the model can be made as ``close`` to physical reality as desired prior to exercising computational algorithms which might introduce their own uncertainties. Since the authors are evaluating codes used for determination of the electromagnetic environment in aircraft and since the on-the-ground test involved an airplane parked on a pad in the simulator facility, they would require a definition of the constitutive parameters of the pad.

  7. Experimental studies on behavior of fully grouted reinforced-concrete masonry shear walls

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Wang, Fenglai

    2015-12-01

    An experimental study is conducted on fully grouted reinforced masonry shear walls (RMSWs) made from concrete blocks with a new configuration. Ten RMSWs are tested under reversed cyclic lateral load to investigate the influence of different reinforcements and applied axial stress values on their seismic behavior. The results show that flexural strength increases with the applied axial stress, and shear strength dominated by diagonal cracking increases with both the amount of horizontal reinforcement and applied axial stress. Yield displacement, ductility, and energy dissipation capability can be improved substantially by increasing the amount of horizontal reinforcement. The critical parameters for the walls are derived from the experiment: displacement ductility values corresponding to 15% strength degradation of the walls reach up to 2.6 and 4.5 in the shear and flexure failure modes, respectively; stiffness values of flexure- and shear-dominated walls rapidly degrade to 17%-19% and 48%-57% of initial stiffness at 0.50 D max (displacement at peak load). The experiment suggests that RMSWs could be assigned a higher damping ratio (˜14%) for collapse prevention design and a lower damping value (˜7%) for a fully operational limit state or serviceability limit state.

  8. Nondestructive Evaluation of Thick Concrete Structures

    SciTech Connect

    Clayton, Dwight A

    2015-01-01

    Materials issues are a key concern for the existing nuclear reactor fleet in the United States as material degradation can lead to increased maintenance, increased downtime, and increased risk. Extending reactor life to 60 years and beyond will likely increase susceptibility and severity of both known and new forms of degradation. A multitude of concrete-based structures are typically part of a light water reactor plant to provide foundation, support, shielding, and containment functions. The size and complexity of nuclear power plant containment structures and the heterogeneity of Portland cement concrete make characterization of the degradation extent a difficult task. This paper examines the benefits of using time-frequency analysis with Synthetic Aperture Focusing Technique (SAFT). By using wavelet packet decomposition, the original ultrasound signals are decomposed into various frequency bands that facilitates highly selective analysis of the signal’s frequency content and can be visualized using the familiar SAFT image reconstruction algorithm.

  9. Health monitoring and rehabilitation of a concrete structure using intelligent materials

    NASA Astrophysics Data System (ADS)

    Song, G.; Mo, Y. L.; Otero, K.; Gu, H.

    2006-04-01

    This paper presents the concept of an intelligent reinforced concrete structure (IRCS) and its application in structural health monitoring and rehabilitation. The IRCS has multiple functions which include self-rehabilitation, self-vibration damping, and self-structural health monitoring. These functions are enabled by two types of intelligent (smart) materials: shape memory alloys (SMAs) and piezoceramics. In this research, Nitinol type SMA and PZT (lead zirconate titanate) type piezoceramics are used. The proposed concrete structure is reinforced by martensite Nitinol cables using the method of post-tensioning. The martensite SMA significantly increases the concrete's damping property and its ability to handle large impact. In the presence of cracks due to explosions or earthquakes, by electrically heating the SMA cables, the SMA cables contract and close up the cracks. In this research, PZT patches are embedded in the concrete structure to detect possible cracks inside the concrete structure. The wavelet packet analysis method is then applied as a signal-processing tool to analyze the sensor signals. A damage index is defined to describe the damage severity for health monitoring purposes. In addition, by monitoring the electric resistance change of the SMA cables, the crack width can be estimated. To demonstrate this concept, a concrete beam specimen with reinforced SMA cables and with embedded PZT patches is fabricated. Experiments demonstrate that the IRC has the ability of self-sensing and self-rehabilitation. Three-point bending tests were conducted. During the loading process, a crack opens up to 0.47 inches. Upon removal of the load and heating the SMA cables, the crack closes up. The damage index formed by wavelet packet analysis of the PZT sensor data predicts and confirms the onset and severity of the crack during the loading. Also during the loading, the electrical resistance value of the SMA cable changes by up to 27% and this phenomenon is used to

  10. Smart CFRP systems for the controlled retrofitting of reinforced concrete members

    NASA Astrophysics Data System (ADS)

    Schaller, M.-B.; Käseberg, S.; Kuhne, M.

    2010-09-01

    During the last ten years an increasing amount of Carbon Fiber Reinforced Polymer (CFRP) applications to rehabilitate damaged concrete elements was observed. Thereby some important disadvantages of the brittle materials must be considered, for example the low ductility of the bond between CFRP and concrete and brittle failure of FRP. With embedded sensor systems it is possible to measure crack propagation and strains. In this paper a sensor based CFRP system will be presented, that can be used for strengthening and measuring. The used optical fibers with Fiber Bragg Gratings (FBG) have a large number of advantages in opposite to electrical measuring methods. Examples are small dimensions, low weight as well as high static and dynamic resolution of measured values. The main problem during the investigations was the fixing of the glass fiber and the small FBG at the designated position. In this paper the possibility of setting the glass fiber with embroidery at the reinforcing fiber material will be presented. On the basis of four point bending tests on beams (dimensions of 700 x 150 x 150 mm) and tests on wrapped columns the potential of the Smart CFRP system is introduced.

  11. Distributed Long-Gauge Optical Fiber Sensors Based Self-Sensing FRP Bar for Concrete Structure.

    PubMed

    Tang, Yongsheng; Wu, Zhishen

    2016-01-01

    Brillouin scattering-based distributed optical fiber (OF) sensing technique presents advantages for concrete structure monitoring. However, the existence of spatial resolution greatly decreases strain measurement accuracy especially around cracks. Meanwhile, the brittle feature of OF also hinders its further application. In this paper, the distributed OF sensor was firstly proposed as long-gauge sensor to improve strain measurement accuracy. Then, a new type of self-sensing fiber reinforced polymer (FRP) bar was developed by embedding the packaged long-gauge OF sensors into FRP bar, followed by experimental studies on strain sensing, temperature sensing and basic mechanical properties. The results confirmed the superior strain sensing properties, namely satisfied accuracy, repeatability and linearity, as well as excellent mechanical performance. At the same time, the temperature sensing property was not influenced by the long-gauge package, making temperature compensation easy. Furthermore, the bonding performance between self-sensing FRP bar and concrete was investigated to study its influence on the sensing. Lastly, the sensing performance was further verified with static experiments of concrete beam reinforced with the proposed self-sensing FRP bar. Therefore, the self-sensing FRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as reinforcing materials for concrete structures. PMID:26927110

  12. Distributed Long-Gauge Optical Fiber Sensors Based Self-Sensing FRP Bar for Concrete Structure

    PubMed Central

    Tang, Yongsheng; Wu, Zhishen

    2016-01-01

    Brillouin scattering-based distributed optical fiber (OF) sensing technique presents advantages for concrete structure monitoring. However, the existence of spatial resolution greatly decreases strain measurement accuracy especially around cracks. Meanwhile, the brittle feature of OF also hinders its further application. In this paper, the distributed OF sensor was firstly proposed as long-gauge sensor to improve strain measurement accuracy. Then, a new type of self-sensing fiber reinforced polymer (FRP) bar was developed by embedding the packaged long-gauge OF sensors into FRP bar, followed by experimental studies on strain sensing, temperature sensing and basic mechanical properties. The results confirmed the superior strain sensing properties, namely satisfied accuracy, repeatability and linearity, as well as excellent mechanical performance. At the same time, the temperature sensing property was not influenced by the long-gauge package, making temperature compensation easy. Furthermore, the bonding performance between self-sensing FRP bar and concrete was investigated to study its influence on the sensing. Lastly, the sensing performance was further verified with static experiments of concrete beam reinforced with the proposed self-sensing FRP bar. Therefore, the self-sensing FRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as reinforcing materials for concrete structures. PMID:26927110

  13. Distributed fiber optic sensors for monitoring reinforced concrete piles using Brillouin scattering

    NASA Astrophysics Data System (ADS)

    de Battista, N.; Kechavarzi, C.; Soga, K.

    2016-05-01

    In this paper we report on advances made in the installation and use of distributed fiber optic sensors to monitor reinforced concrete piles subjected to static load tests. Eight concrete test piles, at three construction sites in London, have recently been instrumented with embedded DFOS. The Brillouin optical time domain reflectometry (BOTDR) technique was used to measure the changes in internal strain and temperature of the piles, during concrete curing and during load testing. These data were used to assess the quality of the pile and derive the load capacity parameters to be used in the foundation design of tall buildings which are to be erected on these sites. The measurements obtained from the DFOS system agreed well with the measurements taken simultaneously using conventional point sensors embedded in the piles. Whereas the conventional sensors only provided measurements at a small number of locations within the piles, the DFOS system made it possible to record the complete strain / temperature profiles along the length of the piles.

  14. Using emissivity-corrected thermal maps to locate deep structural defects in concrete bridge decks

    NASA Astrophysics Data System (ADS)

    DelGrande, Nancy; Durbin, Philip F.

    1995-05-01

    Dual-band infrared (DBIR) thermal imaging is a promising, noncontact, nondestructive evaluation tool to evaluate the amount of deteriorated concrete on asphalt-covered bridge decks. We conducted proof-of-principle demonstrations to characterize defects in concrete structures which could be detected with DBIR thermal imaging. We constructed two identical concrete slabs with synthetic delaminations, e.g., 1.8-in. thick styrofoam squares, implanted just above the 2-in. deep steel reinforcement bars. We covered one of the slabs with a 2-in. layer of asphalt. We mounted the DBIR cameras on a tower platform, to simulate the optics needed to conduct bridge-deck inspections from a moving vehicle. We detected 4-in. implants embedded in concrete and 9-in. implants embedded in asphalt-cevered concrete. The midday (above ambient) and predawn (below ambient) delamination-site temperatures correlated with the implant sizes. Using DBIR image ratios, we enhanced thermal-constrast and removed emissivity-noise, e.g., from concrete compositional variations and clutter. Using the LLNL/VIEW code, we removed the asphalt thermal-gradient mask to depict the 4-in. deep, 9- in. square, concrete implant site. We plan to image bridge deck defects from a moving vehicle for accurate estimations of the amount of deteriorated concrete impairing the deck integrity. Potential longterm benefits are affordable and reliable rehabilitation for asphalt-covered decks.

  15. Using emissivity-corrected thermal maps to locate deep structural defects in concrete bridge decks

    SciTech Connect

    Del Grande, N.K.; Durbin, P.F.

    1995-04-05

    Dual-band infrared (DBIR) thermal imaging is a promising, non-contact, nondestructive evaluation tool to evaluate the amount of deteriorated concrete on asphalt-covered bridge decks. We conducted proof-of-principle demonstrations to characterize defects in concrete structures which could be detected with DBIR thermal imaging. We constructed two identical concrete slabs with synthetic delaminations, e.g., 1/8-in. thick styrofoam squares, implanted just above the 2-in.-deep steel reinforcement bars. We covered one of the slabs with a 2-in. layer of asphalt. We mounted the DBIR cameras on a tower platform, to simulate the optics needed to conduct bridge-deck inspections from a moving vehicle. We detected 4-in. implants embedded in concrete and 9-in. implants embedded in asphalt-covered concrete. The midday (above-ambient) and predawn (below-ambient) delamination-site temperatures correlated with the implant sizes. Using DBIR image ratios, we enhanced thermal-contrast and removed emissivity-noise, e.g., from concrete compositional variations and clutter. Using the LLNL/VIEW code, we removed the asphalt thermal-gradient mask, to depict the 4-in. deep, 9-in. square, concrete implant size. We plan to image bridge deck defects, from a moving vehicle, for accurate estimations of the amount of deteriorated concrete impairing the deck integrity. Potential longterm benefits are affordable and reliable rehabilitation for asphalt-covered decks.

  16. Bond slip detection of concrete-encased composite structure using shear wave based active sensing approach

    NASA Astrophysics Data System (ADS)

    Zeng, Lei; Parvasi, Seyed Mohammad; Kong, Qingzhao; Huo, Linsheng; Lim, Ing; Li, Mo; Song, Gangbing

    2015-12-01

    Concrete-encased composite structure exhibits improved strength, ductility and fire resistance compared to traditional reinforced concrete, by incorporating the advantages of both steel and concrete materials. A major drawback of this type of structure is the bond slip introduced between steel and concrete, which directly reduces the load capacity of the structure. In this paper, an active sensing approach using shear waves to provide monitoring and early warning of the development of bond slip in the concrete-encased composite structure is proposed. A specimen of concrete-encased composite structure was investigated. In this active sensing approach, shear mode smart aggregates (SAs) embedded in the concrete act as actuators and generate desired shear stress waves. Distributed piezoceramic transducers installed in the cavities of steel plates act as sensors and detect the wave response from shear mode SAs. Bond slip acts as a form of stress relief and attenuates the wave propagation energy. Experimental results from the time domain analysis clearly indicate that the amplitudes of received signal by lead zirconate titanate sensors decreased when bond slip occurred. In addition, a wavelet packet-based analysis was developed to compute the received signal energy values, which can be used to determine the initiation and development of bond slip in concrete-encased composite structure. In order to establish the validity of the proposed method, a 3D finite element analysis of the concrete-steel bond model is further performed with the aid of the commercial finite element package, Abaqus, and the numerical results are compared with the results obtained in experimental study.

  17. DYNAPCON: a computer code for dynamic analysis of prestressed concrete structures. [LMFBR

    SciTech Connect

    Marchertas, A.H.

    1982-09-01

    A finite element computer code for the transient analysis of prestressed concrete reactor vessels (PCRVs) for LMFBR containment is described. The method assumes rotational symmetry of the structure. Time integration is by an explicit method. The quasistatic prestressing operation of the PCRV model is performed by a dynamic relaxation technique. The material model accounts for the crushing and tensile cracking in arbitrary direction in concrete and the elastic-plastic behavior of reinforcing steel. The variation of the concrete tensile cracking and compressive crushing limits with strain rate is taken into account. Relative slip is permitted between the concrete and tendons. Several example solutions are presented and compared with experimental results. These sample problems range from simply supported beams to small scale models of PCRV's. It is shown that the analytical methods correlate quite well with experimental results, although in the vicinity of the failure load the response of the models tend to be quite sensitive to input parameters.

  18. Two layer structure for reinforcing pothole repair

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Yuan, Kuo-Yao; Zou, Linhua; Yang, Jenn-Ming; Ju, Jiann-Wen; Kao, Wei; Carlson, Larry

    2013-04-01

    We have applied dicyclopentadiene (DCPD) resin for reinforcing pothole patch materials due to its unique properties - low cost, low viscosity at beginning and ultra-toughness after curing, chemical compatibility with tar, tunable curing profile through catalyst design. In this paper, we have designed a two layer structure - well compacted base layer and DCPD reinforced 1-1.5" top layer - for pothole repair. By choosing two graded asphalt mixes, a porous top layer and fully compacted base layer was prepared after compaction and ready for DCPD resin infiltration. The DCPD curing and infiltration profile within this porous top layer was measured with thermocouples. The rutting resistance was tested with home-made wheel rutter. The cage effect due to the p-DCPD wrapping was characterized with wheel penetration test. The results showed that this two layer structure pothole repair has greatly improved properties and can be used for pothole repair to increase the service life.

  19. Impact resistance performance of green construction material using light weight oil palm shells reinforced bamboo concrete slab

    NASA Astrophysics Data System (ADS)

    Muda, Z. C.; Usman, F.; Beddu, S.; Alam, M. A.; Thiruchelvam, S.; Sidek, L. M.; Basri, H.; Saadi, S.

    2013-06-01

    This paper investigate the performance of lightweight oil palm shells (OPS) concrete with varied bamboo reinforcement content for the concrete slab of 300mm x 300mm size reinforced with different thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.2 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of bamboo reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against bamboo diameters and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the bamboo reinforcement diameter for a constant spacing for various slab thickness using 0.45 OPS and 0.6 OPS bamboo reinforced concrete. The increment in bamboo diameter has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Increment in slab thickness of the slab has more effect on the crack resistance as compare to the increment in the diameter of the bamboo reinforcement.

  20. 2D and 3D Ground Penetrating Radar monitoring of a reinforced concrete asphalt plate affected by mechanical deformation.

    NASA Astrophysics Data System (ADS)

    Bavusi, M.; Dumoulin, J.; Loperte, A.; Rizzo, E.; Soldovieri, F.

    2012-04-01

    The main facility of Hydrogeosite Laboratory of the Italian National Research Council (Marsico Nuovo, CNR) is a 3m x 7m x 10m reinforced concrete pool filled by siliceous sand designed for hydrologic experiments. One of its peculiarities is the possibility to vary the water table depth by using a proper hydraulic system [1]. In the framework of the FP7 ISTIMES project (Integrated System for Transport Infrastructure surveillance and Monitoring by Electromagnetic Sensing), a 3m x 3m layered structure has been purposely built and placed in the pool of the Hydrogeosite Laboratory with the aim to carry out a long term monitoring, by using jointly several electromagnetic sensing technologies, during two different phases simulating the rising of the water table and a mechanical solicitation. Several layers composed the structure from the top to the bottom, such as: 5 cm of asphalt; 5-10 cm of reinforced concrete; 20-25 cm of conglomerate, 55 cm of sand. Moreover, in the sand layer, three (metallic and plastic) pipes of different size were buried to simulate utilities. Ground Penetrating Radar (GPR) surveys were performed by using a the GSSI SIR 3000 system equipped with 400 MHz and 1500 MHz central frequency antennas. Surveys carried out by means of 400 MHz antenna allowed to detect and localize the three pipes (one in plastic and two in metal) and to investigate the effects of the sand water content on their radar signature. Surveys carried out by using 1500 MHz antenna were focused to characterize the shallower layers of the structure. The Hydrogeosite experiment consisted in following stages: • Arising of a water table by infiltration from the bottom; • Water gravity infiltration condescendingly; • Infiltration by peristaltic pump in the very shallow layers of the structure; • Water table drawdown; • Mechanical structure deformation; • Asphalt plate restoration after mechanical solicitation. After each stage a series of GPR surveys was performed. Moreover

  1. Aging Management of Nuclear Power Plant Concrete Structures - Overview and Suggested Research Topics

    SciTech Connect

    Naus, Dan J

    2008-10-01

    Nuclear power plant concrete structures are described and their operating experience noted. Primary considerations related to management of their aging are noted and an indication of their status provided: degradation mechanisms, damage models, and material performance; assessment and remediation (i.e., component selection, in-service inspection, nondestructive examinations, and remedial actions); and estimation of performance at present or some future point in time (i.e., application of structural reliability theory to the design and optimization of in-service inspection/maintenance strategies, and determination of the effects of degradation on plant risk). Several activities are identified that provide background information and data on areas of concern with respect to nondestructive examination of nuclear power plant concrete structures: inspection of thick-walled, heavily-reinforced sections, basemats, and inaccessible areas of the containment metallic pressure boundary. Topics are noted where additional research would be of benefit to aging management of nuclear power plant concrete structures.

  2. Strength of concrete structures under dynamic loading

    NASA Astrophysics Data System (ADS)

    Kumpyak, O. G.; Galyautdinov, Z. R.; Kokorin, D. N.

    2016-01-01

    The use of elastic supports is one the efficient methods of decreasing the dynamic loading. The paper describes the influence of elastic supports on the stress-strain state of steel concrete structures exposed to one-time dynamic loading resulting in failure. Oblique bending beams on elastic supports and their elastic, elastoplastic, and elastoplastic consolidation behavior are considered in this paper. For numerical calculations the developed computer program is used based on the finite element method. Research findings prove high efficiency of elastic supports under dynamic loading conditions. The most effective behavior of elastic supports is demonstrated at the elastoplastic stage. A good agreement is observed between the theoretical and experimental results.

  3. Deterioration of concrete structures in coastal environment due to carbonation.

    PubMed

    Balaji, K V G D; Gopalaraju, S S S V; Trilochan, Jena

    2010-07-01

    Failure of existing concrete structures takes place due to lack of durability, and not due to less structural strength. One of the important aspects of durability is carbonation depth. The rate of carbonation in concrete is influenced by both its physical properties and exposure conditions. Rebar corrodes when carbonation reaches to a depth of concrete cover provided. In the present work, various concrete structures with different life periods and exposed to different weather conditions have been considered to study the carbonation effect. It is observed that the effect of carbonation is more in the structures located near to the sea coast and on windward face of the structure. PMID:21391402

  4. Retrofit of hollow concrete masonry infilled steel frames using glass fiber reinforced plastic laminates

    NASA Astrophysics Data System (ADS)

    Hakam, Zeyad Hamed-Ramzy

    2000-11-01

    This study focuses on the retrofit of hollow concrete masonry infilled steel frames subjected to in-plane lateral loads using glass fiber reinforced plastic (GFRP) laminates that are epoxy-bonded to the exterior faces of the infill walls. An extensive experimental investigation using one-third scale modeling was conducted and consisted of two phases. In the first phase, 64 assemblages, half of which were retrofitted, were tested under various combined in-plane loading conditions similar to those which different regions of a typical infill wall are subjected to. In the second phase, one bare and four masonry-infilled steel frames representative of a typical single-story, single-bay panel were tested under diagonal loading to study the overall behavior and the infill-frame interaction. The relative infill-to-frame stiffness was varied as a test parameter by using two different steel frame sections. The laminates altered the failure modes of the masonry assemblages and reduced the variability and anisotropic nature of the masonry. For the prisms which failed due to shear and/or mortar joint slip, significant strength increases were observed. For those exhibiting compression failure modes, a marginal increase in strength resulted. Retrofitting the infilled frames resulted in an average increase in initial stiffness of two-fold compared to the unretrofitted infilled frames, and seemed independent of the relative infill-to-frame stiffness. However, the increase in the load-carrying capacity of the retrofitted frames compared to the unretrofitted counterparts was higher for those with the larger relative infill-to-frame stiffness parameter. Unlike the unretrofitted infill walls, the retrofitted panels demonstrated almost identical failure modes that were characterized as "strictly comer crushing" in the vicinity of the loaded comers whereas no signs of distress were evident throughout the remainder of the infill. The laminates also maintained the structural integrity of

  5. Wireless surface acoustic wave sensors for displacement and crack monitoring in concrete structures

    NASA Astrophysics Data System (ADS)

    Perry, M.; McKeeman, I.; Saafi, M.; Niewczas, P.

    2016-03-01

    In this work, we demonstrate that wireless surface acoustic wave devices can be used to monitor millimetre displacements in crack opening during the cyclic and static loading of reinforced concrete structures. Sensors were packaged to extend their gauge length and to protect them against brittle fracture, before being surface-mounted onto the tensioned surface of a concrete beam. The accuracy of measurements was verified using computational methods and optical-fibre strain sensors. After packaging, the displacement and temperature resolutions of the surface acoustic wave sensors were 10 μ {{m}} and 2 °C respectively. With some further work, these devices could be retrofitted to existing concrete structures to facilitate wireless structural health monitoring.

  6. Embedded intrinsic Fabry-Perot optical fiber sensors in cement concrete structures

    NASA Astrophysics Data System (ADS)

    Kim, Ki S.; Yoo, Jae-Wook; Kim, Seung Kwan; Kim, Byoung Yoon

    1996-05-01

    Intrinsic Fabry-Perot optical fiber sensors were embedded to the tensile side of the 20 cm by 20 cm by 150 cm cement concrete structures. The sensors were attached to the reinforcing steels and then, the cement concretes were applied. It took 30 days for curing the specimens. After that, the specimens were tested with 4-point bending method by a universal testing machine. Strains were measured and recorded by the strain gauges embedded near optical fiber sensors. Output data of fiber sensor showed good linearity to the strain data from the strain gauges up to 2000 microstrain. The optical fiber sensors showed good response after yielding of the structure while embedded metal film strain gauges did not show any response. We also investigated the behavior of the optical fiber sensor when the specimens were broken down. In conclusion, the optical fiber sensors can be used as elements of health monitoring systems for cement concrete infra-structures.

  7. 75 FR 22552 - Certain Steel Concrete Reinforcing Bars from Turkey; Notice of Amended Final Results Pursuant to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-29

    ... Administrative Review, 74 FR 65515 (Dec. 10, 2009) and Certain Steel Concrete Reinforcing Bars from Turkey: Notice of Court Decision Not in Harmony with Final Results of Administrative Review, 75 FR 7562 (Feb. 22... in Part, 70 FR 67665 (Nov. 8, 2005) (Final Results). In the Final Results the Department followed...

  8. 75 FR 47260 - Certain Steel Concrete Reinforcing Bars from Turkey: Notice of Amended Final Results Pursuant to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-05

    ... Antidumping Duty Administrative Review and New Shipper Review and Determination To Revoke in Part, 72 FR 62630... from Turkey: Notice of Court Decision Not in Harmony with Final Results of Administrative Review, 74 FR... International Trade Administration (A-489-807) Certain Steel Concrete Reinforcing Bars from Turkey: Notice...

  9. Determination of dominant fibre orientations in fibre-reinforced high-strength concrete elements based on computed tomography scans

    NASA Astrophysics Data System (ADS)

    Vicente, Miguel A.; González, Dorys C.; Mínguez, Jesús

    2014-04-01

    Computed tomography (CT) is a nondestructive technique, based on absorbing X-rays, that permits the visualisation of the internal structure of materials in micron-range resolution. In this paper, the CT scan is used to determine the position and orientation of the fibres in steel fibre-reinforced high-strength concrete elements. The aim of this paper was to present a numerical procedure, automated through a MATLAB routine specially developed by the authors, which enables, fast and reliable, to obtain the orientation of each and every one of the fibres and their centre of gravity. The procedure shown is directly extrapolated to any type of fibre-reinforced material, only if there is a wide difference between density of fibres and density of matrix. The mathematical basis of this procedure is very simple and robust. The result is a fast algorithm and a routine easy to use. In addition, the validation tests show that the error is almost zero. This algorithm can help the industry to implement the technology of CT in the protocols of product quality control.

  10. Numerical simulation of tests for the evaluation of the performance of the reinforced concrete slabs strengthening by FRCM

    NASA Astrophysics Data System (ADS)

    Anania, Laura; Badalá, Antonio; D'Agata, Giuseppe

    2016-01-01

    In this work the attention is focused to the numerical simulation of the experimental bending tests carried out on a total of six reinforced concrete r.c. plates the latter aimed to provide a basic understanding of the its performance when strengthened by Fiber Reinforced Cementitius Matrix (FRCM) Composites. Three of those were used as control specimens. The numerical simulation was carried out by LUSAS software. A good correlation between the FE results and data obtained from the test, both in the load-deformation behavior and the failure load was highlighted. This permits to prove that applied strengthening system gives back an enhancement 2.5 times greater in respect of the unreinforced case. A greater energy dissipation ability and a residual load-bearing capacity makes the proposed system very useful in the retrofitting as well as in the case of strengthening of bridge structures. Based on the validation of the FE results in bending, the numerical analysis was also extended to characterize the behavior of this strengthening system in tensile.

  11. Specification of the process of chloride extraction from reinforced concrete based on the inverse task of the diffusion equation

    NASA Astrophysics Data System (ADS)

    Alsabry, A.; Zybura, A.

    2016-05-01

    When the structure of reinforcement is in danger of chloride corrosion it is possible to prevent this disadvantageous phenomenon through exposing the cover to the influence of an electric field. The forces of an electric field considerably reduce chloride ions in pore liquid in concrete, which helps to rebuild a passive layer on the surface of the reinforcement and stops corrosion. The process of removing chlorides can be described with multi-component diffusion equations. However, an essential parameter of these equations, the diffusion coefficient, can be determined on the basis of an inverse task. Since the solution was achieved for one-dimension flow, the method applied can be confirmed by experimental results and the material parameters of the process can be determined theoretically. Some examples of numerical calculations of the effective electro-diffusion coefficient of chloride ions confirmed the usefulness of the theoretical solution for generalizing experimental results. Moreover, the calculation process of the numerical example provides some practical clues for future experimental research, which could be carried out in close connection with the theoretical solution.

  12. Void detection beneath reinforced concrete sections: The practical application of ground-penetrating radar and ultrasonic techniques

    NASA Astrophysics Data System (ADS)

    Cassidy, Nigel J.; Eddies, Rod; Dods, Sam

    2011-08-01

    Ground-penetrating radar (GPR) and ultrasonic 'pulse echo' techniques are well-established methods for the imaging, investigation and analysis of steel reinforced concrete structures and are important civil engineering survey tools. GPR is, arguably, the more widely-used technique as it is suitable for a greater range of problem scenarios (i.e., from rebar mapping to moisture content determination). Ultrasonic techniques are traditionally associated with the engineering-based, non-destructive testing of concrete structures and their integrity analyses (e.g., flaw detection, shear/longitudinal velocity determination, etc). However, when used in an appropriate manner, both techniques can be considered complementary and provide a unique way of imaging the sub-surface that is suited to a range of geotechnical problems. In this paper, we present a comparative study between mid-to-high frequency GPR (450 MHz and 900 MHz) and array-based, shear wave, pulse-echo ultrasonic surveys using proprietary instruments and conventional GPR data processing and visualisation techniques. Our focus is the practical detection of sub-metre scale voids located under steel reinforced concrete sections in realistic survey conditions (e.g., a capped, relict mine shaft or vent). Representative two-dimensional (2D) sections are presented for both methods illustrating the similarities/differences in signal response and the temporal-spatial target resolutions achieved with each technique. The use of three-dimensional data volumes and time slices (or 'C-scans') for advanced interpretation is also demonstrated, which although common in GPR applications is under-utilised as a technique in general ultrasonic surveys. The results show that ultrasonic methods can perform as well as GPR for this specific investigation scenario and that they have the potential of overcoming some of the inherent limitations of GPR investigations (i.e., the need for careful antenna frequency selection and survey design in

  13. EXPERIMENTAL STUDY ON SHEAR CA PACITY OF REINFORCED CONCRETE BEAMS OF SOLID CIRCULAR CROSS SECTION

    NASA Astrophysics Data System (ADS)

    Watanabe, Ken; Oishi, Shunya; Yonehana, Moe; Niwa, Junichiro

    The shear-resisting mechanism of solid circular RC lin ear members is different from that of rectangular RC members. The objective of this re search is to propose the equation fo r evaluating the shear capacity of reinforced concrete (RC) beams of solid circular cross section. The bending tests of solid circular RC beams were conducted under simply-supported condition. A series of experimental results indicated that conventional evaluation methods were difficult to predict the shear capacity of solid circular RC beams. Distributed longitudinal bars, angle of diagonal crack, shape of stirrups were taken into account. Finally, the paper proposed the equations that can predict the shear capacity of solid circular RC beams accurately.

  14. Use of Glass Reinforced Concrete (GRC) as a substrate for photovoltaic modules

    NASA Technical Reports Server (NTRS)

    Eirls, J. L.

    1980-01-01

    A substrate for flat plate photovoltaic solar panel arrays using a glass fiber reinforced concrete (GRC) material was developed. The installed cost of this GRC panel is 30% less than the cost goal of the Near Term Low-Cost Flat Plate Photovoltaic Solar Array Program. The 4 ft by 8 ft panel is fabricated from readily available inexpensive materials, weighs a nominal 190 lbs., has exceptionally good strength and durability properties (rigid and resists weathering), is amenable to mass production and is easily installed on simple mountings. Solar cells are encapsulated in ethylene/vinyl acetate with Tedlar backing and Korad cover film. The laminates are attached to the GRC substrate with acrylic transfer tape and edge sealed with silicone RTV adhesive.

  15. Performance based seismic qualification of reinforced concrete nuclear materials processing facilities

    SciTech Connect

    Mertz, G.E.; Loceff, F.; Houston, T.; Rauls, G.; Mulliken, J.

    1997-09-01

    A seismic qualification of a reinforced concrete nuclear materials processing facility using performance based acceptance criteria is presented. Performance goals are defined in terms of a minimum annual seismic failure frequency. Pushover analyses are used to determine the building`s ultimate capacity and relate the capacity to roof drift and joint rotation. Nonlinear dynamic analyses are used to quantify the building`s drift using a suite of ground motion intensities representing varying soil conditions and levels of seismic hazard. A correlation between joint rotation and building drift to damage state is developed from experimental data. The damage state and seismic hazard are convolved to determine annual seismic failure frequency. The results of this rigorous approach is compared to those using equivalent force methods and pushover techniques recommended by ATC-19 and FEMA-273.

  16. Experimental and numerical investigations of higher mode effects on seismic inelastic response of reinforced concrete shear walls

    NASA Astrophysics Data System (ADS)

    Ghorbanirenani, Iman

    ) methods using the shake table feedback signals as input. Good agreement was generally obtained between numerical and experimental results. Both computer programs were able to predict the natural frequency of the walls in the undamaged and damaged conditions. Both modeling techniques could predict that the maximum bending moment at the base of the walls reached the actual wall moment capacity. The inelastic response and the dual plastic hinge behaviour of the walls could be adequately reproduced using the fibre element and finite element analysis programs. The fibre element method is a good alternative in terms of computing time. It produces reasonable results in comparison with the finite element method, although particular attention needs to be given to the selection of the damping ratios. The different parametric analyses performed in this thesis showed that, for both models, adding a small amount of global viscous damping in combination with a refined reinforced concrete hysteretic model could predict better the seismic behaviour of the tested structures. For the VecTor2 program, a viscous damping of 1% led to reasonable results for the studied RC walls. For the OpenSees program, 2% damping resulted in a good match between test and predictions for the 100% EQ test on the initially undamaged wall. When increasing the earthquake intensities, the damping had to be reduced between 1.5% and 1% to achieve good results for a damaged wall with elongated vibration periods. According to the experimental results and numerical analyses on reinforced concrete shear walls subjected to ground motions from Eastern North America earthquakes, there is a high possibility of having a second plastic hinge forming in the upper part of walls in addition to the one assumed in design at the base. This second hinge could dissipate the earthquake energy more effectively and decrease the force demand on the wall. A dual plastic hinge design approach in which the structures become plastic in the

  17. Structural properties of autoclaved aerated concrete masonry

    SciTech Connect

    Matthys, J.H.; Nelson, R.L.

    1999-07-01

    Autoclaved aerated concrete masonry units are manufactured from portland cement, quartz sand, water, lime, gypsum and a gas forming agent. The units are steam cured under pressure in an autoclave transforming the material into a hard calcium silicate. The autoclaved aerated concrete masonry units are large-size solid rectangular prisms which are laid using thin-bed mortar layers into masonry assemblages. The system and product are not new--patented in 1924 by Swedish architect Johan Eriksson. Over a period of 60 years this product has been used in all areas of residential and industrial construction and in virtually all climates. However, the principal locations of application have been generally outside the US Little information in the US is available on the structural properties of this product. Due to the interest in use of this product in the construction industry and the construction of production plants in the US, the Construction Research Center at the University of Texas at Arlington and Robert L. Nelson & Associates conducted a series of tests to determine some of the basic structural properties of this product. This paper presents the findings of those investigations.

  18. Man-made vitreous fiber produced from incinerator ash using the thermal plasma technique and application as reinforcement in concrete.

    PubMed

    Yang, Sheng-Fu; Wang, To-Mai; Lee, Wen-Cheng; Sun, Kin-Seng; Tzeng, Chin-Ching

    2010-10-15

    This study proposes using thermal plasma technology to treat municipal solid waste incinerator ashes. A feasible fiberization method was developed and applied to produce man-made vitreous fiber (MMVF) from plasma vitrified slag. MMVF were obtained through directly blending the oxide melt stream with high velocity compressed air. The basic technological characteristics of MMVF, including morphology, diameter, shot content, length and chemical resistance, are described in this work. Laboratory experiments were conducted on the fiber-reinforced concrete. The effects of fibrous content on compressive strength and flexural strength are presented. The experimental results showed the proper additive of MMVF in concrete can enhance its mechanical properties. MMVF products produced from incinerator ashes treated with the thermal plasma technique have great potential for reinforcement in concrete. PMID:20580155

  19. High rate response of ultra-high-performance fiber-reinforced concretes under direct tension

    SciTech Connect

    Tran, Ngoc Thanh; Tran, Tuan Kiet; Kim, Dong Joo

    2015-03-15

    The tensile response of ultra-high-performance fiber-reinforced concretes (UHPFRCs) at high strain rates (5–24 s{sup −} {sup 1}) was investigated. Three types of steel fibers, including twisted, long and short smooth steel fibers, were added by 1.5% volume content in an ultra high performance concrete (UHPC) with a compressive strength of 180 MPa. Two different cross sections, 25 × 25 and 25 × 50 mm{sup 2}, of tensile specimens were used to investigate the effect of the cross section area on the measured tensile response of UHPFRCs. Although all the three fibers generated strain hardening behavior even at high strain rates, long smooth fibers produced the highest tensile resistance at high rates whereas twisted fiber did at static rate. The breakages of twisted fibers were observed from the specimens tested at high strain rates unlike smooth steel fibers. The tensile behavior of UHPFRCs at high strain rates was clearly influenced by the specimen size, especially in post-cracking strength.

  20. A visual approach to efficient analysis and quantification of ductile iron and reinforced sprayed concrete.

    PubMed

    Fritz, Laura; Hadwiger, Markus; Geier, Georg; Pittino, Gerhard; Gröller, M Eduard

    2009-01-01

    This paper describes advanced volume visualization and quantification for applications in non-destructive testing (NDT), which results in novel and highly effective interactive workflows for NDT practitioners. We employ a visual approach to explore and quantify the features of interest, based on transfer functions in the parameter spaces of specific application scenarios. Examples are the orientations of fibres or the roundness of particles. The applicability and effectiveness of our approach is illustrated using two specific scenarios of high practical relevance. First, we discuss the analysis of Steel Fibre Reinforced Sprayed Concrete (SFRSpC). We investigate the orientations of the enclosed steel fibres and their distribution, depending on the concrete's application direction. This is a crucial step in assessing the material's behavior under mechanical stress, which is still in its infancy and therefore a hot topic in the building industry. The second application scenario is the designation of the microstructure of ductile cast irons with respect to the contained graphite. This corresponds to the requirements of the ISO standard 945-1, which deals with 2D metallographic samples. We illustrate how the necessary analysis steps can be carried out much more efficiently using our system for 3D volumes. Overall, we show that a visual approach with custom transfer functions in specific application domains offers significant benefits and has the potential of greatly improving and optimizing the workflows of domain scientists and engineers. PMID:19834207

  1. Measurement and simulation of millimeter wave scattering cross-sections from steel-reinforced concrete

    NASA Astrophysics Data System (ADS)

    Hassan, A. M.; Martys, N. S.; Garboczi, E. J.; McMichael, R. D.; Stiles, M. D.; Plusquellic, D. F.; Stutzman, P. E.; Wang, S.; Provenzano, V.; Surek, J. T.; Novotny, D. R.; Coder, J. B.; Janezic, M. D.; Kim, S.

    2014-02-01

    Some iron oxide corrosion products exhibit antiferromagnetic magnetic resonances (AFMR) at frequencies on the order of 100 GHz at ambient temperatures. AFMR can be detected in laboratory conditions, which serves as the basis for a new non-destructive spectroscopic method for detecting early corrosion. When attempting to measure the steel corrosion in reinforced concrete in the field, rebar geometry must be taken into account. Experiments and numerical simulations have been developed at frequencies near 100 GHz to sort out these effects. The experimental setup involves a vector network analyzer with converter heads to up-convert the output frequency, which is then connected to a horn antenna followed by a 7.5 cm diameter polymer lens to focus the waves on the sample. Two sets of samples were studied: uniform cylindrical rods and rebar corrosion samples broken out of concrete with different kinds of coatings. Electromagnetic scattering from uniform rods were calculated numerically using classical modal expansion. A finite-element electromagnetic solver was used to model more complex rebar geometry and non-uniform corrosion layers. Experimental and numerical data were compared to help quantify and understand the anticipated effect of local geometrical features on AFMR measurements.

  2. Development of steel-fiber-reinforced concrete cribs to replace wood cribs in underground coal mines

    SciTech Connect

    Tanious, N.S.; Becket, R.D.; Bollinger, E.R.

    1984-02-01

    The need to provide better mine roof support and control in longwall tailgate entries prompted the Bureau of Mines to search for a replacement product for wood cribs. Their search isolated steel-fiber-reinforced concrete (SFC) as the most effective replacement. Through successful laboratory and underground mine tests, handmade SFC cribs proved to be a viable and more effective roof support system. However, to ensure wider usage, U.S. Steel Mining Co. initiated a joint development and evaluation program with Burrell Construction Company in order to mass produce SFC blocks of reasonable dimension, weight, and cost. Small specimens and full-size cribs were evaluated during this program to determine their compressive strength and post failure characteristics. After considerable testing and adjusting of various concrete mixtures, a final formulation for the SFC crib blocks was selected. That formulation permitted the construction of SFC cribs possessing a nominal crib strength of 3200 psi (22.1 x 10/sup 6/ Pa) and a nominal modulus of elasticity of 1.0 x 10/sup 6/ psi (6894.76 x 10/sup 6/ Pa). These SFC cribs can support from 3.5 to 14.5 times as much load as a wood crib, depending on the size of the wood crib being replaced. Both laboratory and limited mine tests, conducted by U.S. Steel Mining Co. have shown the SFC crib to be an economical and effective means of roof control.

  3. Progressive collapse of a two-story reinforced concrete frame with embedded smart aggregates

    NASA Astrophysics Data System (ADS)

    Laskar, Arghadeep; Gu, Haichang; Mo, Y. L.; Song, Gangbing

    2009-07-01

    This paper reports the experimental and analytical results of a two-story reinforced concrete frame instrumented with innovative piezoceramic-based smart aggregates (SAs) and subjected to a monotonic lateral load up to failure. A finite element model of the frame is developed and analyzed using a computer program called Open system for earthquake engineering simulation (OpenSees). The finite element analysis (FEA) is used to predict the load-deformation curve as well as the development of plastic hinges in the frame. The load-deformation curve predicted from FEA matched well with the experimental results. The sequence of development of plastic hinges in the frame is also studied from the FEA results. The locations of the plastic hinges, as obtained from the analysis, were similar to those observed during the experiment. An SA-based approach is also proposed to evaluate the health status of the concrete frame and identify the development of plastic hinges during the loading procedure. The results of the FEA are used to validate the SA-based approach for detecting the locations and occurrence of the plastic hinges leading to the progressive collapse of the frame. The locations and sequential development of the plastic hinges obtained from the SA-based approach corresponds well with the FEA results. The proposed SA-based approach, thus validated using FEA and experimental results, has a great potential to be applied in the health monitoring of large-scale civil infrastructures.

  4. Physical and mechanical properties of carbon fiber reinforced smart porous concrete for planting

    NASA Astrophysics Data System (ADS)

    Park, Seung-Bum; Kim, Jung-Hwan; Seo, Dae-Seuk

    2005-05-01

    The reinforcement strength of porous concrete and its applicability as a recycled aggregate was measured. Changes in physical and mechanical properties, subsequent to the mixing of carbon fiber and silica fume, were examined, and the effect of recycled aggregate depending on their mixing rate was evaluated. The applicability of planting to concrete material was also assessed. The results showed that there were not any remarkable change in the porosity and strength characteristics although its proportion of recycled aggregate increased. Also, the mixture of 10% of silica was found to be most effective for strength enforcement. In case of carbon fiber, the highest flexural strength was obtained with its mixing rate being 3%. It was also noticed that PAN-derived carbon fiber was superior to Pitch-derived ones in view of strength. The evaluation of its use for vegetation proved that the growth of plants was directly affected by the existence of covering soil, in case of having the similar size of aggregate and void.

  5. Mechanical characterization and structural analysis of recycled fiber-reinforced-polymer resin-transfer-molded beams

    NASA Astrophysics Data System (ADS)

    Tan, Eugene Wie Loon

    1999-09-01

    The present investigation was focussed on the mechanical characterization and structural analysis of resin-transfer-molded beams containing recycled fiber-reinforced polymers. The beams were structurally reinforced with continuous unidirectional glass fibers. The reinforcing filler materials consisted entirely of recycled fiber-reinforced polymer wastes (trim and overspray). The principal resin was a 100-percent dicyclo-pentadiene unsaturated polyester specially formulated with very low viscosity for resin transfer molding. Variations of the resin transfer molding technique were employed to produce specimens for material characterization. The basic materials that constituted the structural beams, continuous-glass-fiber-reinforced, recycled-trim-filled and recycled-overspray-filled unsaturated polyesters, were fully characterized in axial and transverse compression and tension, and inplane and interlaminar shear, to ascertain their strengths, ultimate strains, elastic moduli and Poisson's ratios. Experimentally determined mechanical properties of the recycled-trim-filled and recycled-overspray-filled materials from the present investigation were superior to those of unsaturated polyester polymer concretes and Portland cement concretes. Mechanical testing and finite element analyses of flexure (1 x 1 x 20 in) and beam (2 x 4 x 40 in) specimens were conducted. These structurally-reinforced specimens were tested and analyzed in four-point, third-point flexure to determine their ultimate loads, maximum fiber stresses and mid-span deflections. The experimentally determined load capacities of these specimens were compared to those of equivalent steel-reinforced Portland cement concrete beams computed using reinforced concrete theory. Mechanics of materials beam theory was utilized to predict the ultimate loads and mid-span deflections of the flexure and beam specimens. However, these predictions proved to be severely inadequate. Finite element (fracture propagation

  6. Load-induced debonding of FRP composites applied to reinforced concrete

    NASA Astrophysics Data System (ADS)

    Blok, Joel; Brown, Jeff

    2009-05-01

    Fiber-reinforced polymer (FRP) composites are widely used to increase the flexural and shear capacity of reinforced concrete (RC) elements. One potential disadvantage is that strengthened surfaces are no longer visible and cracks or delaminations that result from excessive loading or fatigue may go undetected. This research investigated thermal imaging techniques for monitoring and evaluating load-induced delamination of FRP composites applied to small scale RC beams. Two beams (3.5 in x 4.5 in x 58 in) were loaded monotonically to failure. Infrared thermography (IRT) inspections were performed at various load levels through failure using a composite phase imaging technique. Two similar beams were tested in fatigue and periodic IRT inspections were performed at 50,000-cycle intervals. Individual phase values for each pixel were designated as "well-bonded", "suspect" or "unbonded" to indicate the quality of FRP bond. Suspect areas included regions of excess thickened-epoxy tack-coat and smaller installation defects in the unloaded specimens. The long-term objective of this research is to develop a practical framework for conducting quantitative IRT inspections of FRP composites applied to RC and incorporating these results into acceptance criteria for new installations and predictions for the remaining service life of in-service FRP systems. This method may also offer insight into the necessity for repairs to in-service systems.

  7. Structural health monitoring of concrete columns subjected to seismic excitations using piezoceramic-based sensors

    NASA Astrophysics Data System (ADS)

    Liao, Wen-I.; Wang, J. X.; Song, G.; Gu, H.; Olmi, C.; Mo, Y. L.; Chang, K. C.; Loh, C. H.

    2011-12-01

    Structural health monitoring of concrete structures under seismic loads has always attracted a lot of attention in the earthquake engineering community. In this paper, two tests of structural health monitoring of concrete columns using piezoceramic-based sensors are presented. The first test was a shake table test of a reinforced concrete (RC) column. A piezoceramic-based device, called a 'smart aggregate', was pre-embedded and adopted for the structural health monitoring of the concrete column under earthquake excitations. The second test of this study was the in situ health monitoring of RC piers of Niu-Dou Bridge in Taiwan, under seismic loading. RC piers instrumented with the post-embedded piezoceramic-based sensors were tested using reversed cyclic loading. During the shake table test and the in situ reversed cyclic loading test, one sensor was used as an actuator to generate propagating waves, and the other sensors were used to detect the waves. By analyzing the wave response, the existence of cracks can be detected and the severity can be estimated. The experimental results demonstrate the sensitivity and the effectiveness of the piezoceramic-based approach in the structural health monitoring of large-scale concrete structures under earthquake loading.

  8. A&M. TAN607. Construction detail showing structural steel framework with reinforcing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    A&M. TAN-607. Construction detail showing structural steel framework with reinforcing steel in place prior to pouring concrete for biparting doors between hot shop and special equipment service (SES) room. Facing north. Hot shop to left, SES room to right. slot for north half of door shows at upper left of view. Date: May 21, 1954. INEEL negative no. 10548 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  9. Earthquake Resilient Tall Reinforced Concrete Buildings at Near-Fault Sites Using Base Isolation and Rocking Core Walls

    NASA Astrophysics Data System (ADS)

    Calugaru, Vladimir

    This dissertation pursues three main objectives: (1) to investigate the seismic response of tall reinforced concrete core wall buildings, designed following current building codes, subjected to pulse type near-fault ground motion, with special focus on the relation between the characteristics of the ground motion and the higher-modes of response; (2) to determine the characteristics of a base isolation system that results in nominally elastic response of the superstructure of a tall reinforced concrete core wall building at the maximum considered earthquake level of shaking; and (3) to demonstrate that the seismic performance, cost, and constructability of a base-isolated tall reinforced concrete core wall building can be significantly improved by incorporating a rocking core-wall in the design. First, this dissertation investigates the seismic response of tall cantilever wall buildings subjected to pulse type ground motion, with special focus on the relation between the characteristics of ground motion and the higher-modes of response. Buildings 10, 20, and 40 stories high were designed such that inelastic deformation was concentrated at a single flexural plastic hinge at their base. Using nonlinear response history analysis, the buildings were subjected to near-fault seismic ground motions as well as simple close-form pulses, which represented distinct pulses within the ground motions. Euler-Bernoulli beam models with lumped mass and lumped plasticity were used to model the buildings. Next, this dissertation investigates numerically the seismic response of six seismically base-isolated (BI) 20-story reinforced concrete buildings and compares their response to that of a fixed-base (FB) building with a similar structural system above ground. Located in Berkeley, California, 2 km from the Hayward fault, the buildings are designed with a core wall that provides most of the lateral force resistance above ground. For the BI buildings, the following are investigated

  10. 3D mapping of reinforcement and tendon ducts on pre-stressed concrete bridges by means of Ground Penetrating Radar (GPR)

    NASA Astrophysics Data System (ADS)

    Cheilakou, E.; Theodorakeas, P.; Koui, M.; Zeris, C.

    2014-03-01

    The present study evaluates the potential of GPR for the inspection of pre-stressed concrete bridges and its usefulness to provide non visible information of the interior structural geometry and condition, required for strengthening and rehabilitation purposes. For that purpose, different concrete blocks of varying dimensions with embedded steel reinforcement bars, tendon ducts and fabricated voids, were prepared and tested by means of GPR in a controlled laboratory environment. 2D data acquisition was carried out in reflection mode along single profile lines of the samples in order to locate the internal structural elements. 3D surveys were also performed in a grid format both along horizontal and vertical lines, and the individual profiles collected were interpolated and further processed using a 3D reconstruction software, in order to provide a detailed insight into the concrete structure. The obtained 2D profiles provided the accurate depth and position of the embedded rebars and tendon ducts, verifying the original drawings. 3D data cubes were created enabling the presentation of depth slices and providing additional information such as shape and localization of the internal elements. The results obtained from this work showed the effectiveness and reliability of the GPR technique for pre-stressed concrete bridge investigations.

  11. Evaluating the strength of concrete structure on terrace houses

    NASA Astrophysics Data System (ADS)

    Hasbullah, Mohd. Amran; Yusof, Rohana; Rahman, Mohd Nazaruddin Yusoff @ Abdul

    2016-08-01

    The concrete structure is the main component to support the structure of the building, but when concrete has been used for an extended period hence, it needs to be evaluated to determine the current strength, durability and how long it can last. The poor quality of concrete structures will cause discomfort to the user and, the safety will be affected due to lack of concrete strength. If these issues are not monitored or not precisely known performance, and no further action done then, the concrete structure will fail and eventually it will collapse. Five units of terrace houses that are built less than 10 years old with extension or renovations and have cracks at Taman Samar Indah, Samarahan, Sarawak have been selected for this study. The instrument used in this research is Ultrasonic Pulse Velocity (UPV), with the objective to determine the current strength and investigate the velocity of a pulse at the concrete cracks. The data showed that the average velocity of the pulse is less than 3.0 km/s and has shown that the quality of the concrete in the houses too weak scale / doubt in the strength of concrete. It also indicates that these houses need to have an immediate repair in order to remain secure other concrete structures.

  12. Concrete containment structural element tests. Volume 1. Half-thickness element tests - description and results. Final report

    SciTech Connect

    Julien, J.T.; Schultz, D.M.; Weinmann, T.L.

    1984-11-01

    Understanding the structural behavior of nuclear reactor containment buildings under extreme internal pressures can lead to more realistic estimates of risk from severe core accidents. This study provides test data on the behavior, under biaxial tensile loads, of large-scale segments of a containment building with reinforced and prestressed concrete designs.

  13. 206. Big Witch Road grade separation structure. This concrete box ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    206. Big Witch Road grade separation structure. This concrete box culvert, built in 1950, is unusual in that the culvert's concrete bottom extends beyond the structure to the ends of its perpendicular wing walls. Facing northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  14. Structural nominal concrete strength derived by statistical mechanics

    NASA Astrophysics Data System (ADS)

    Limam, Oualid; Aidi, Mohamed; Zenzri, Hatem

    2014-02-01

    The purpose of this paper is to model the effects of the structural size and temperature on the nominal strength of concrete structures. Based on thermodynamics of irreversible processes, concrete damage theory and statistical mechanics, a constitutive behaviour of concrete was first derived. Then, generalized Boltzmann entropy was calculated by using the number of failure surfaces defined in the concrete microstructure. The number of states is defined as the number of possible failure surfaces. It was shown that states are correlated. This gives a nonadditive entropy for small structures. A theoretical nominal strength taking into account the structural size and temperature effects was deduced. Thereafter, a one parameter rigid failure mechanism was considered to model experimental tests performed on concrete structures. The theoretical approach was applied to experimental tests performed on notched beams. A lower size effect is highlighted for lower temperatures. Theoretical results were compared with experimental test results performed on notched beams under bending. Comparison showed a good agreement.

  15. Thermographic inspection of bond defects in Fiber Reinforced Polymer applied to masonry structures

    NASA Astrophysics Data System (ADS)

    Masini, N.; Aiello, M. A.; Capozzoli, L.; Vasanelli, E.

    2012-04-01

    Nowadays, externally bonded Fiber Reinforced Polymers (FRP) are extensively used for strengthening and repairing masonry and reinforced concrete existing structures; they have had a rapid spread in the area of rehabilitation for their many advantages over other conventional repair systems, such as lightweight, excellent corrosion and fatigue resistance, high strength, etc. FRP systems applied to masonry or concrete structures are typically installed using a wet-layup technique.The method is susceptible to cause flaws or defects in the bond between the FRP system and the substrate, which may reduce the effectiveness of the reinforcing systems and the correct transfer of load from the structure to the composite. Thus it is of primary importance to detect the presence of defects and to quantify their extension in order to eventually provide correct repair measurements. The IR thermography has been cited by the several guidelines as a good mean to qualitatively evaluate the presence of installation defects and to monitor the reinforcing system with time.The method is non-destructive and does not require contact with the composite or other means except air to detect the reinforcement. Some works in the literature have been published on this topic. Most of the researches aim at using the IR thermography technique to characterize quantitatively the defects in terms of depth, extension and type in order to have an experimental database on defect typology to evaluate the long term performances of the reinforcing system. Nevertheless, most of the works in the literature concerns with FRP applied to concrete structures without considering the case of masonry structures. In the present research artificial bond defects between FRP and the masonry substrate have been reproduced in laboratory and the IR multi temporal thermography technique has been used to detect them. Thermographic analysis has been carried out on two wall samples having limited dimensions (100 x 70 cm) both

  16. Numerical and Experimental Studies on Impact Loaded Concrete Structures

    SciTech Connect

    Saarenheimo, Arja; Hakola, Ilkka; Karna, Tuomo; Hyvarinen, Juhani

    2006-07-01

    An experimental set-up has been constructed for medium scale impact tests. The main objective of this effort is to provide data for the calibration and verification of numerical models of a loading scenario where an aircraft impacts against a nuclear power plant. One goal is to develop and take in use numerical methods for predicting response of reinforced concrete structures to impacts of deformable projectiles that may contain combustible liquid ('fuel'). Loading, structural behaviour, like collapsing mechanism and the damage grade, will be predicted by simple analytical methods and using non-linear FE-method. In the so-called Riera method the behavior of the missile material is assumed to be rigid plastic or rigid visco-plastic. Using elastic plastic and elastic visco-plastic material models calculations are carried out by ABAQUS/Explicit finite element code, assuming axisymmetric deformation mode for the missile. With both methods, typically, the impact force time history, the velocity of the missile rear end and the missile shortening during the impact were recorded for comparisons. (authors)

  17. Effects of cement alkalinity, exposure conditions and steel-concrete interface on the time-to-corrosion and chloride threshold for reinforcing steel in concrete

    NASA Astrophysics Data System (ADS)

    Nam, Jingak

    Effects of (1) cement alkalinity (low, normal and high), (2) exposure conditions (RH and temperature), (3) rebar surface condition (as-received versus cleaned) and (4) density and distribution of air voids at the steel-concrete interface on the chloride threshold and time-to-corrosion for reinforcing steel in concrete have been studied. Also, experiments were performed to evaluate effects of RH and temperature on the diffusion of chloride in concrete and develop a method for ex-situ pH measurement of concrete pore water. Once specimens were fabricated and exposed to a corrosive chloride solution, various experimental techniques were employed to determine time-to-corrosion, chloride threshold, diffusion coefficient and void density along the rebar trace as well as pore water pH. Based upon the resultant data, several findings related to the above parameters have been obtained as summarized below. First, time for the corrosion initiation was longest for G109 concrete specimens with high alkalinity cement (HA). Also, chloride threshold increased with increasing time-to-corrosion and cement alkalinity. Consequently, the HA specimens exhibited the highest chloride threshold compared to low and normal alkalinity ones. Second, high temperature and temperature variations reduced time-to-corrosion of reinforcing steel in concrete since chloride diffusion was accelerated at higher temperature and possibly by temperature variations. The lowest chloride threshold values were found for outdoor exposed specimens suggesting that variation of RH or temperature (or both) facilitated rapid chloride diffusion. Third, an elevated time-to-corrosion and chloride threshold values were found for the wire brushed steel specimens compared to as-received ones. The higher ratio of [OH-]/[Fe n+] on the wire brushed steel surface compared to that of as-received case can be the possible cause because the higher ratio of this parameter enables the formation of a more protective passive film on

  18. Interior view of coffee processing structure No. 1, showing concrete ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Interior view of coffee processing structure No. 1, showing concrete reservoirs on floor, view towards the west - Finca Silem, Coffee Processing Structure No. 1, Highway 139, Kilometer 9.3, Maraguez, Ponce Municipio, PR

  19. 1. VARIABLEANGLE LAUNCHER (VAL) CONCRETE 'A' FRAME STRUCTURE SHOWING CAMERA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VARIABLE-ANGLE LAUNCHER (VAL) CONCRETE 'A' FRAME STRUCTURE SHOWING CAMERA TOWER STRUCTURE LOOKING SOUTH AND ARCHED OPENING FOR ROADWAY. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  20. Behavior and design of reinforced concrete column-type lapped splices subjected to high-intensity cyclic loading

    NASA Astrophysics Data System (ADS)

    Sivakumar, B.; White, R. N.; Gergely, P.

    1982-10-01

    The behavior and design of lapped splices in reinforced concrete column type specimens under high intensity flexural cyclic loads was studied. Special attention is focused on the transverse steel requirements of specimens with more than two splices in a layer; the use of offsets in spliced bars; the effect of concrete strength on splice strength and behavior; and the strength of epoxy-repaired splices. Procedures are provided for the design of reinforced lapped splices to sustain at least twenty reversing load cycles beyond yield and a maximum rebar strain at the splice of at least 2.5 times the yield strain. The key aspect of the design is the provision of closely spaced uniformly distributed stirrup ties in the splice region. Equations are developed for the spacing of stirrups and the minimum splice length requirement.

  1. VIEW OF GUN EMPLACEMENT AND THE TABLELIKE CAST CONCRETE STRUCTURE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF GUN EMPLACEMENT AND THE TABLE-LIKE CAST CONCRETE STRUCTURE SHOWING THE SPALLED AREA ON ITS EAST SIDE (LEFT) WHERE THE SECOND PROJECTING ARM WAS BROKEN OFF. NOTE THE SLOPED CONCRETE PAD IN THE BACKGROUND. VIEW FACING SOUTHWEST - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, East Gun Emplacement, Ford Island, Pearl City, Honolulu County, HI

  2. Analytical investigations of seismic responses for reinforced concrete bridge columns subjected to strong near-fault ground motion

    NASA Astrophysics Data System (ADS)

    Su, Chin-Kuo; Sung, Yu-Chi; Chang, Shuenn-Yih; Huang, Chao-Hsun

    2007-09-01

    Strong near-fault ground motion, usually caused by the fault-rupture and characterized by a pulse-like velocity-wave form, often causes dramatic instantaneous seismic energy (Jadhav and Jangid 2006). Some reinforced concrete (RC) bridge columns, even those built according to ductile design principles, were damaged in the 1999 Chi-Chi earthquake. Thus, it is very important to evaluate the seismic response of a RC bridge column to improve its seismic design and prevent future damage. Nonlinear time history analysis using step-by-step integration is capable of tracing the dynamic response of a structure during the entire vibration period and is able to accommodate the pulsing wave form. However, the accuracy of the numerical results is very sensitive to the modeling of the nonlinear load-deformation relationship of the structural member. FEMA 273 and ATC-40 provide the modeling parameters for structural nonlinear analyses of RC beams and RC columns. They use three parameters to define the plastic rotation angles and a residual strength ratio to describe the nonlinear load-deformation relationship of an RC member. Structural nonlinear analyses are performed based on these parameters. This method provides a convenient way to obtain the nonlinear seismic responses of RC structures. However, the accuracy of the numerical solutions might be further improved. For this purpose, results from a previous study on modeling of the static pushover analyses for RC bridge columns (Sung et al. 2005) is adopted for the nonlinear time history analysis presented herein to evaluate the structural responses excited by a near-fault ground motion. To ensure the reliability of this approach, the numerical results were compared to experimental results. The results confirm that the proposed approach is valid.

  3. Hysteretic behavior of special shaped columns composed of steel and reinforced concrete (SRC)

    NASA Astrophysics Data System (ADS)

    Chen, Zongping; Xu, Jinjun; Xue, Jianyang

    2015-06-01

    This paper describes a series of experimental investigations on seventeen specimens of steel reinforced concrete special shaped (SRCSS) columns under low cyclic reversed loading using parallel crosshead equipment. Nine T-shaped SRC columns, four L-shaped SRC columns and four +-shaped SRC columns were tested to examine the effects of shape steel configuration, loading angle, axial compressive ratio and shear-span ratio on the behavior (strength, stiffness, energy dissipation, ductility, etc.) of SRCSS column specimens. The failure modes and hysteretic performance of all the specimens were obtained in the tests. Test results demonstrate that the shear-span ratio is the main parameter affecting the failure modes of SRCSS columns. The specimens with small shear-span ratio are prone to shear failure, and the primary failure planes in SRCSS columns are parallel to the loading direction. As a result, there is a symmetry between positive and negative loading directions in the hysteretic curves of the SRCSS columns. The majority of displacement ductility coefficients for all the specimens are over 3.0, so that the SRCSS columns demonstrate a better deformation capacity. In addition, the equivalent viscous damping coefficients of all the specimens are greater than 0.2, indicating that the seismic behavior of SRCSS columns is adequate. Finally, the superposition theory was used to calculate the limits of axial compressive ratio for the specimens, and it is found that the test axial compressive ratio is close to or smaller than the calculated axial compressive ratio limit.

  4. Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

    PubMed Central

    Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

    2015-01-01

    A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl−]/[OH−] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels. PMID:26673425

  5. Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

    NASA Astrophysics Data System (ADS)

    Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

    2015-12-01

    A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl-]/[OH-] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

  6. Analysis of concrete containment structures under severe accident loading conditions

    SciTech Connect

    Porter, V.L.

    1993-12-31

    One of the areas of current interest in the nuclear power industry is the response of containment buildings to internal pressures that may exceed design pressure levels. Evaluating the response of structures under these conditions requires computing beyond design load to the ultimate load of the containment. For concrete containments, this requirement means computing through severe concrete cracking and into the regime of wide-spread plastic rebar and/or tendon response. In this regime of material response, an implicit code can have trouble converging. This paper describes some of the author`s experiences with Version 5.2 of ABAQUS Standard and the ABAQUS concrete model in computing the axisymmetric response of a prestressed concrete containment to ultimate global structural failure under high internal pressures. The effects of varying the tension stiffening parameter in the concrete material model and variations of the parameters for the CONTROLS option are discussed.

  7. Study on the effect of the infill walls on the seismic performance of a reinforced concrete frame

    NASA Astrophysics Data System (ADS)

    Zhang, Cuiqiang; Zhou, Ying; Zhou, Deyuan; Lu, Xilin

    2011-12-01

    Motivated by the seismic damage observed to reinforced concrete (RC) frame structures during the Wenchuan earthquake, the effect of infill walls on the seismic performance of a RC frame is studied in this paper. Infill walls, especially those made of masonry, offer some amount of stiffness and strength. Therefore, the effect of infill walls should be considered during the design of RC frames. In this study, an analysis of the recorded ground motion in the Wenchuan earthquake is performed. Then, a numerical model is developed to simulate the infill walls. Finally, nonlinear dynamic analysis is carried out on a RC frame with and without infill walls, respectively, by using CANNY software. Through a comparative analysis, the following conclusions can be drawn. The failure mode of the frame with infill walls is in accordance with the seismic damage failure pattern, which is strong beam and weak column mode. This indicates that the infill walls change the failure pattern of the frame, and it is necessary to consider them in the seismic design of the RC frame. The numerical model presented in this paper can effectively simulate the effect of infill walls on the RC frame.

  8. Application of petrographic examination techniques to the assessment of fire-damaged concrete and masonry structures

    SciTech Connect

    Ingham, Jeremy P.

    2009-07-15

    The number of building fires has doubled over the last 50 years. There has never been a greater need for structures to be assessed for fire damage to ensure safety and enable appropriate repairs to be planned. Fortunately, even after a severe fire, concrete and masonry structures are generally capable of being repaired rather than demolished. By allowing direct examination of microcracking and mineralogical changes, petrographic examination has become widely used to determine the depth of fire damage for reinforced concrete elements. Petrographic examination can also be applied to fire-damaged masonry structures built of materials such as stone, brick and mortar. Petrography can ensure accurate detection of damaged geomaterials, which provides cost savings during building repair and increased safety reassurance. This paper comprises a review of the role of petrography in fire damage assessments, drawing on a range of actual fire damage investigations.

  9. Performance of corrosion inhibiting admixtures for structural concrete -- assessment methods and predictive modeling

    SciTech Connect

    Yunovich, M.; Thompson, N.G.

    1998-12-31

    During the past fifteen years corrosion inhibiting admixtures (CIAs) have become increasingly popular for protection of reinforced components of highway bridges and other structures from damage induced by chlorides. However, there remains considerable debate about the benefits of CIAs in concrete. A variety of testing methods to assess the performance of CIA have been reported in the literature, ranging from tests in simulated pore solutions to long-term exposures of concrete slabs. The paper reviews the published techniques and recommends the methods which would make up a comprehensive CIA effectiveness testing program. The results of this set of tests would provide the data which can be used to rank the presently commercially available CIA and future candidate formulations utilizing a proposed predictive model. The model is based on relatively short-term laboratory testing and considers several phases of a service life of a structure (corrosion initiation, corrosion propagation without damage, and damage to the structure).

  10. Behavior of reinforcement SCC beams under elevated temperatures

    NASA Astrophysics Data System (ADS)

    Fathi, Hamoon; Farhang, Kianoosh

    2015-09-01

    This experimental study focuses on the behavior of heated reinforced concrete beams. Four types of concrete mixtures were used for the tested self-compacting concrete beams. A total of 72 reinforced concrete beams and 72 standard cylindrical specimens were tested. The compressive strength under uniaxial loading at 23 °C ranged from 30 to 45 MPa. The specimens were exposed to different temperatures. The test parameters of interest were the compressive strength and the temperature of the specimens. The effect of changes in the parameters was examined so as to control the behavior of the tested concrete and that of the reinforced concrete beam. The results indicated that flexibility and compressive strength of the reinforced concrete beams decreased at higher temperatures. Furthermore, heating beyond 400 °C produced greater variations in the structural behavior of the materials in both the cylindrical samples and the reinforced concrete beams.

  11. Detection of chloride in reinforced concrete using a dualpulsed laser-induced breakdown spectrometer system: comparative study of the atomic transition lines of Cl I at 594.85 and 837.59 nm.

    PubMed

    Gondal, Mohammed Ashraf; Dastageer, Mohamed Abdulkader; Maslehuddin, Mohammed; Alnehmi, Abdul Jabar; Al-Amoudi, Omar Saeed Baghabra

    2011-07-10

    The presence of chloride in reinforced concrete can cause severe damage to the strength and durability of buildings and bridges. The detection of chloride in concrete structures at early stages of the corrosion buildup process is, therefore, very important. However, detection of chlorine in trace amounts in concrete is not a simple matter. A dual-pulsed laser-induced breakdown spectrometer (LIBS) has been developed at our laboratory for the detection of chloride contents in reinforced concrete by using two atomic transition lines of neutral chlorine (Cl I) at 594.8 and 837.5 nm. A calibration curve was also established by using standard samples containing chloride in known concentration in the concrete. Our dual-pulsed LIBS system demonstrated a substantial improvement in the signal level at both wavelengths (594.8 and 837.5 nm). However, the new atomic transition line at 594.8 nm shows a significant improvement compared to the line at 837.5 nm in spite of the fact that the relative intensity of the former is 0.1% of the latter. This weak signal level of the 837.5 nm transition line of chlorine can be attributed to some kind of self-absorption process taking place in the case of the concrete sample. PMID:21743558

  12. Smart acoustic emission system for wireless monitoring of concrete structures

    NASA Astrophysics Data System (ADS)

    Yoon, Dong-Jin; Kim, Young-Gil; Kim, Chi-Yeop; Seo, Dae-Cheol

    2008-03-01

    Acoustic emission (AE) has emerged as a powerful nondestructive tool to detect preexisting defects or to characterize failure mechanisms. Recently, this technique or this kind of principle, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures. Concrete is one of the most widely used materials for constructing civil structures. In the nondestructive evaluation point of view, a lot of AE signals are generated in concrete structures under loading whether the crack development is active or not. Also, it was required to find a symptom of damage propagation before catastrophic failure through a continuous monitoring. Therefore we have done a practical study in this work to fabricate compact wireless AE sensor and to develop diagnosis system. First, this study aims to identify the differences of AE event patterns caused by both real damage sources and the other normal sources. Secondly, it was focused to develop acoustic emission diagnosis system for assessing the deterioration of concrete structures such as a bridge, dame, building slab, tunnel etc. Thirdly, the wireless acoustic emission system was developed for the application of monitoring concrete structures. From the previous laboratory study such as AE event patterns analysis under various loading conditions, we confirmed that AE analysis provided a promising approach for estimating the condition of damage and distress in concrete structures. In this work, the algorithm for determining the damage status of concrete structures was developed and typical criteria for decision making was also suggested. For the future application of wireless monitoring, a low energy consumable, compact, and robust wireless acoustic emission sensor module was developed and applied to the concrete beam for performance test. Finally, based on the self-developed diagnosis algorithm and compact wireless AE sensor, new AE system for practical

  13. Optical fiber sensor for measurement of concrete structure stress

    NASA Astrophysics Data System (ADS)

    Zangaro, Renato A.; Silveira, Landulfo, Jr.; Barreto da Silva, R.

    1994-09-01

    In this work we describe an optical sensor to determine the stress applied at a concrete structure. The optical sensor is a monomode fiber optic, that is embedded in the concrete. The principle of these sensors is based on photoelastic effect, that produces a birefringence in the optical fiber and induces a rotation on the polarization angle of the guided polarized light. The photoelastic effect is produced due to a controlled applied charge in the center of the concrete structure. The shift of polarization is analyzed by a polaroid analyzer.

  14. Credit BG. Southeast and northeast facades of concrete block structure ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Credit BG. Southeast and northeast facades of concrete block structure built in the late 1960s. It is now used to store miscellaneous equipment - Edwards Air Force Base, North Base, Liquid Oxygen Storage Facility, Second Street, Boron, Kern County, CA

  15. 12. CONCRETE DROP STRUCTURE ON NORTH SIDE CANAL WITH TWO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. CONCRETE DROP STRUCTURE ON NORTH SIDE CANAL WITH TWO TURNOUTS IN BACKGROUND, T4S R7E S24. VIEW LOOKING EAST - San Carlos Irrigation Project, North Side Canal, North of Gila River, Coolidge, Pinal County, AZ

  16. Storage Area (1942 section), looking east, showing concrete structural elements ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Storage Area (1942 section), looking east, showing concrete structural elements and wall opening to vaults - Fort McNair, Film Store House, Fort Lesley J. McNair, P Street between Third & Fourth Streets, Southwest, Washington, District of Columbia, DC

  17. Application of optical fiber distributed sensing to health monitoring of concrete structures

    NASA Astrophysics Data System (ADS)

    Villalba, Sergi; Casas, Joan R.

    2013-08-01

    The use of Optical Backscatter Reflectometer (OBR) sensors is a promising measurement technology for Structural Health Monitoring (SHM) as it offers the possibility of continuous monitoring of strain and temperature along the fiber. Several applications to materials used in the aeronautical construction have demonstrated the feasibility of such technique. These materials (composites, steel, aluminum) apart from having a smooth surface where the bonding of the sensor is easily carried out, they also have a continuous strain field when subject to external loading and therefore the bonding of the OBR on the material surface is not in danger for high levels of loading as the OBR can easily follow the strain in the material. The application of such type of sensor to concrete structures may present some difficulties due to (1) the roughness of the concrete surface and the heterogeneity due to the presence of aggregates of several sizes, (2) the fact that reinforced concrete cracks at very low level of load, appearance of a discontinuity in the surface and the strain field that may provoke a break or debonding of the optical fiber. However the feasibility of using OBR in the SHM of civil engineering constructions made of concrete is also of great interest, mainly because in this type of structures it is impossible to know where the crack may appear and therefore severe cracking (dangerous for the structure operation) can appear without warning of the monitoring if sensors are not placed in the particular location where the crack appears. In order to explore the potentiality of detecting cracks as they appear without failure or debonding, as well as the compatibility of the OBR bonding to the concrete surfaces, this paper shows the test carried out in the loading up to failure of a concrete slab.

  18. Coating concrete secondary containment structures exposed to agrichemicals

    SciTech Connect

    Broder, M.F.; Nguyen, D.T.

    1995-06-01

    Concrete has traditionally been the material of choice for building secondary containment structures because it is relatively inexpensive and has structural properties which make it ideal for supporting the loads of vehicles and large tanks. However, concrete`s chemical properties make it susceptible to corrosion by some common fertilizers. Though fairly impervious to water movement, concrete is easily penetrated by vapors and solvents. It is also prone to cracking. For these reasons, the Environmental Protection Agency (EPA) believes that concrete alone may not provide an effective barrier to pesticide movement and has proposed that concrete in pesticide secondary containment structures be sealed or coated to reduce its permeability. Some state secondary containment regulations require that concrete exposed to fertilizers and pesticides be sealed or protected with a coating. Lacking guidelines, some retailers have used penetrating sealants to satisfy the law, even though these products provide little protection from chemical attack nor do they prevent pesticide egress. Other retailers who have applied thick film coatings which were properly selected have had disastrous results because the application was poorly done. Consequently, much skepticism exists regarding the performance and benefit of protective coatings.

  19. Sensitivity study on durability variables of marine concrete structures

    NASA Astrophysics Data System (ADS)

    Zhou, Xin'gang; Li, Kefei

    2013-06-01

    In order to study the influence of parameters on durability of marine concrete structures, the parameter's sensitivity analysis was studied in this paper. With the Fick's 2nd law of diffusion and the deterministic sensitivity analysis method (DSA), the sensitivity factors of apparent surface chloride content, apparent chloride diffusion coefficient and its time dependent attenuation factor were analyzed. The results of the analysis show that the impact of design variables on concrete durability was different. The values of sensitivity factor of chloride diffusion coefficient and its time dependent attenuation factor were higher than others. Relative less error in chloride diffusion coefficient and its time dependent attenuation coefficient induces a bigger error in concrete durability design and life prediction. According to probability sensitivity analysis (PSA), the influence of mean value and variance of concrete durability design variables on the durability failure probability was studied. The results of the study provide quantitative measures of the importance of concrete durability design and life prediction variables. It was concluded that the chloride diffusion coefficient and its time dependent attenuation factor have more influence on the reliability of marine concrete structural durability. In durability design and life prediction of marine concrete structures, it was very important to reduce the measure and statistic error of durability design variables.

  20. Quantitative ultrasonic evaluation of concrete structures using one-sided access

    NASA Astrophysics Data System (ADS)

    Khazanovich, Lev; Hoegh, Kyle

    2016-02-01

    Nondestructive diagnostics of concrete structures is an important and challenging problem. A recent introduction of array ultrasonic dry point contact transducer systems offers opportunities for quantitative assessment of the subsurface condition of concrete structures, including detection of defects and inclusions. The methods described in this paper are developed for signal interpretation of shear wave impulse response time histories from multiple fixed distance transducer pairs in a self-contained ultrasonic linear array. This included generalizing Kirchoff migration-based synthetic aperture focusing technique (SAFT) reconstruction methods to handle the spatially diverse transducer pair locations, creating expanded virtual arrays with associated reconstruction methods, and creating automated reconstruction interpretation methods for reinforcement detection and stochastic flaw detection. Interpretation of the reconstruction techniques developed in this study were validated using the results of laboratory and field forensic studies. Applicability of the developed methods for solving practical engineering problems was demonstrated.