Science.gov

Sample records for concrete slab track

  1. Optimization of reinforced concrete slabs

    NASA Technical Reports Server (NTRS)

    Ferritto, J. M.

    1979-01-01

    Reinforced concrete cells composed of concrete slabs and used to limit the effects of accidental explosions during hazardous explosives operations are analyzed. An automated design procedure which considers the dynamic nonlinear behavior of the reinforced concrete of arbitrary geometrical and structural configuration subjected to dynamic pressure loading is discussed. The optimum design of the slab is examined using an interior penalty function. The optimization procedure is presented and the results are discussed and compared with finite element analysis.

  2. Behavior of Partially Restrained Reinforced Concrete Slabs.

    DTIC Science & Technology

    1986-09-01

    Experimental Deflections and Coupling Forces. ........ 72 3.4 Method of Approximating Support Rotations . . . 76 3.5 Free-Body Diagram Used in Computing...common types of structural elements. Slabs are found in practically every type of structural system, ’ whether steel or concrete, single -story or...Because of the nature of reinforced concrete slabs, accurate evaluations of stresses, strains, and deflections are difficult to make by elasticity

  3. 31. VIEW OF CONCRETE SLAB AT WEST ENTRANCE OF WALKWAY. ...

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

    31. VIEW OF CONCRETE SLAB AT WEST ENTRANCE OF WALKWAY. '1944 JOE LANDETA' SCRATCHED INTO FRESH CONCRETE. March 1987 - Verde River Sheep Bridge, Spanning Verde River (Tonto National Forest), Cave Creek, Maricopa County, AZ

  4. Interior view of groundfloor porch showing exposed concrete floor slab ...

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

    Interior view of ground-floor porch showing exposed concrete floor slab system, facing west. - Albrook Air Force Station, Field Officer's Quarters, West side of Dargue Avenue Circle, Balboa, Former Panama Canal Zone, CZ

  5. 23. Surrender interview site, showing Pemberton Avenue concrete slab road ...

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

    23. Surrender interview site, showing Pemberton Avenue concrete slab road type with gutter (asphalt construction typical on Union and Confederate Avenues), view to the sw. - Vicksburg National Military Park Roads & Bridges, Vicksburg, Warren County, MS

  6. 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

  7. 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

  8. DETAIL OF NORTH GUARDRAIL AND EXPANSION JOINT IN CONCRETE SLAB, ...

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

    DETAIL OF NORTH GUARDRAIL AND EXPANSION JOINT IN CONCRETE SLAB, SHOWING DAMAGED SECTION OF GUARDRAIL AND ALUMINUM REPLACEMENT. VIEW TO NORTHWEST. - Hassayampa Bridge, Spanning Hassayampa River at old U.S. Highway 80, Arlington, Maricopa County, AZ

  9. Evaluation and Repair of Concrete Slabs

    DTIC Science & Technology

    1992-01-01

    is duce a readily flowable concrete that is capable of listed in Table 1. completely filling the formed area. For large surface areas, it may be...Poor compaction, irregular surfaces, expansive soils , and the presence of mud or soft organic material can all result in a yielding subgrade. Again... fill all the spaces around the coarse aggregate. It is easily recognized by voids in the surface where the concrete appears as coarse aggregate

  10. 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

  11. 18. FOURTH FLOOR BLDG. 28, RAISED CONCRETE SLAB FLOOR WITH ...

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

    18. FOURTH FLOOR BLDG. 28, RAISED CONCRETE SLAB FLOOR WITH BLOCKS AND PULLEYS OVERHEAD LOOKING NORTHEAST. - Fafnir Bearing Plant, Bounded on North side by Myrtle Street, on South side by Orange Street, on East side by Booth Street & on West side by Grove Street, New Britain, Hartford County, CT

  12. 49. VIEW OF WOOD FRAME STUCCO STRUCTURES ON CONCRETE SLABS, ...

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

    49. VIEW OF WOOD FRAME STUCCO STRUCTURES ON CONCRETE SLABS, REPUTED HOUSES FOR PROSTITUTES, LOOKING NORTH. NOTICE SIMILAR RUIN IN BACKGROUND RIGHT. THREE OR FOUR SIMILAR RUINS ALONG RIVER ROAD NORTH OF MINE WORKINGS. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  13. DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE ...

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

    DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE SOUTH END OF THE ABOVE-GROUND PORTION. NOTE STEP DOWN TO THE STEEL PLATE IN BACKGROUND. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  14. DETAIL OF STEEL PLATE SET INTO THE CONCRETE SLAB OF ...

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

    DETAIL OF STEEL PLATE SET INTO THE CONCRETE SLAB OF THE NORTH END OF THE ABOVE-GROUND PORTION. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  15. Effects of Reinforcement Configuration on Reserve Capacity of Concrete Slabs

    DTIC Science & Technology

    1985-08-01

    Reinforced concreted Tensile membrane,, Buried shelters/ Shelters/ ..i, Civil defense, Slab capacity, 120. A34TlRACT rCcnhma in~ r aidit noe..era aad...CHAPTER 1 I XTPODLCT, CI At the- iiti it io., of this Study civil d~efense plwlgcalled for the .;evacuation of nonessenrt*I51 pezrsonnel to safe (lower...lqbal and Derecho (Reference 10). The reinforcement ratio, p , was 0.0062 in "Christianscn’s te,;tts and varied from 0.0023 to 0.0093 in Roberts’ tests

  16. An investigation on the behaviour and stiffness of reinforced concrete slabs subjected to torsion

    NASA Astrophysics Data System (ADS)

    Nguyen, M. C. T.; Pham, P. T.

    2017-01-01

    This paper presents an investigation on RC slab under torsion, by both experiment and finite element analysis. The torsion tests were done on three similar square RC slabs with dimensions of 1900×1900×150 mm. The behaviour of slabs at pre-cracking and post-cracking of concrete phases were investigated, via Load-displacement, twisting moment-curvature relationships, and torsional stiffness of slabs. The experimental results are compared with the FEA and the results in literatures. The torsional stiffness of slab at the phase of concrete cracked and steel yield is about 1/25 of the stiffness at the pre-cracking phase.

  17. 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.

  18. Investigation of compressive membrane action in ultra high performance concrete slab strips

    NASA Astrophysics Data System (ADS)

    Foust, Bradley Wade

    Reinforced concrete slabs are found in very common structural systems in both civilian and military applications. The boundary conditions that support the slab play an important role in the response to a particular load. Specifically, the amount of lateral and rotational restraint dictates how a slab responds to a particular load. Compressive membrane (i.e., in-plane) forces are present in slabs when the boundaries are sufficiently stiff, therefore restricting the slab from both lateral translations and rotations. Advancements have been made to account for the additional capacity due to compressive membrane forces in conventional strength concrete. In today's world, concrete performance is improving because of increasing compressive strengths and additional ductility present in concrete members. As a result of this current improvement, there is an urgent need to investigate compressive membrane theory in ultra-high-performance concrete (UHPC) slabs to better understand their behavior. Existing compressive membrane theory should be revisited to determine if current theory is applicable, or if it is not, what modifications should be made. This study will provide insight into the validity of existing theory that is currently used to predict the ultimate capacity in conventional-strength concrete slabs and attempt to modify the existing equations to account for high-strength concrete materials. A matrix of 14 normal-strength concrete (NSC) and 13 UHPC slabs was tested both statically and dynamically to better understand the behavior of each material set and the effects that boundary conditions have on slab response. The results from these experiments were then compared to response calculations made from existing theory as well as finite element analyses. Valuable data sets on rigidly restrained UHPC slab response were obtained through an experimental research program. The experiments helped to validate the associated numerical analysis that was performed. It was

  19. United States Air Force Research on Airfield Pavement Repairs Using Precast Portland Cement Concrete (PCC) Slabs (BRIEFING SLIDES)

    DTIC Science & Technology

    2008-08-28

    AFRL-RX-TY-TP-2008-4582 POSTPRINT UNITED STATES AIR FORCE RESEARCH ON AIRFIELD PAVEMENT REPAIRS USING PRECAST PORTLAND CEMENT CONCRETE ...pavement Portland cement concrete (PCC) slab repairs using precast PCC slab panels. AFRL is leading the technology development by critically reviewing the...technology transfer activities including, but not limited to, training, reports and preparation of ETLs. 2 The use of precast concrete slabs for repair of

  20. 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.

  1. 76 FR 34890 - Track Safety Standards; Concrete Crossties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-15

    ... Federal Railroad Administration 49 CFR Part 213 RIN 2130-AC01 Track Safety Standards; Concrete Crossties... mandates specific requirements for effective concrete crossties, for rail fastening systems connected to concrete crossties, and for automated inspections of track constructed with concrete crossties. The...

  2. 76 FR 55819 - Track Safety Standards; Concrete Crossties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-09

    ... Federal Railroad Administration 49 CFR Part 213 RIN 2130-AC35 Track Safety Standards; Concrete Crossties... concrete crossties, for rail fastening systems connected to concrete crossties, and for automated inspections of track constructed with concrete crossties. This document amends and clarifies the final...

  3. 76 FR 18073 - Track Safety Standards; Concrete Crossties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-01

    ... Federal Railroad Administration 49 CFR Part 213 RIN 2130-AC01 Track Safety Standards; Concrete Crossties... over track constructed with concrete crossties. In particular, FRA is mandating specific requirements for effective concrete crossties, for rail fastening systems connected to concrete crossties, and...

  4. Effects of Shear Stirrup Details on Ultimate Capacity and Tensile Membrane Behavior of Reinforced Concrete Slabs

    DTIC Science & Technology

    1985-08-01

    anticipation of the construction of 20,000 to 40,000 of the shelters, economical design requirements are very important. Because of high labor intensity... Derecho (Reference 35) stated that no data are available for one-way slabs tested under uniformly distributed load. During the same year that Iqbal and... Derecho reported their work (1969), *- Keenan (Reference 36) tested four laced reinforced concrete one-way slabs to failure under a uniformly

  5. Behavior of reinforced concrete slabs subjected to combined punching shear and biaxial tension

    SciTech Connect

    Jau, W.C.; White, R.N.; Gergely, P.

    1982-09-01

    This investigation was a continuing study of peripheral (punching) shear strength of precracked, biaxially tensioned, orthogonally reinforced concrete slabs. This research was motivated by the need to determie the strength of a reinforced concrete containment vessel wall when subjected to combined internal pressure and punching shear loads normal to the wall. The study served to determine the effect of three major variables (shear span, size of loaded area, and reinforcing steel ratio) on punching shear strength of slabs that were precracked in biaxial tension and then held at one of the two tension levels (0 or 0.8f/sub y/) during shear load application.

  6. NORTH SIDE FACING TRACK, SHOWING ELECTRICAL BOX AND CONCRETE VAULT ...

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

    NORTH SIDE FACING TRACK, SHOWING ELECTRICAL BOX AND CONCRETE VAULT - Edwards Air Force Base, South Base Sled Track, Electrical Distribution Station, South side of Sled Track, Lancaster, Los Angeles County, CA

  7. 75 FR 52490 - Track Safety Standards; Concrete Crossties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... Federal Railroad Administration 49 CFR Part 213 RIN 2130-AC01 Track Safety Standards; Concrete Crossties... promote the safety of railroad operations over track constructed with concrete crossties. In particular, FRA is proposing specific requirements for effective concrete crossties, for rail fastening...

  8. The dynamic response of slab track constructions and their benefit with respect to conventional ballasted track

    NASA Astrophysics Data System (ADS)

    Bezin, Y.; Farrington, D.; Penny, C.; Temple, B.; Iwnicki, S.

    2010-12-01

    A recently developed Flexible Track System Model integrated with a multibody dynamics software tool was used to simulate the dynamic interaction between a vehicle and two innovative slab track designs, comparing their performance with respect to conventional ballasted track. The design concepts are presented and the modelling assumptions are given. Simulations are then carried out to quantify, for example, the impact of ballasted track degraded state using the case of a hanging sleeper. In comparison, the benefit of the two innovative track designs is highlighted as they prevent this type of localised defect from occurring. The alternative track designs were also shown to be capable of carrying a vehicle safely and with less impact on the system over a localised weakened formation support, by simulating a washout event.

  9. Radon penetration of concrete slab cracks, joints, pipe penetrations, and sealants.

    PubMed

    Nielson, K K; Rogers, V C; Holt, R B; Pugh, T D; Grondzik, W A; de Meijer, R J

    1997-10-01

    Radon movement through 12 test slabs with different cracks, pipe penetrations, cold joints, masonry blocks, sealants, and tensile stresses characterized the importance of these anomalous structural domains. Diffusive and advective radon transport were measured with steady-state air pressure differences controlled throughout the deltaP = 0 to 60 Pa range. Diffusion coefficients (deltaP = 0) initially averaged 6.5 x 10(-8) m2 s(-1) among nine slabs with only 8% standard deviation, but increased due to drying by 0.16% per day over a 2-y period to an average of 2.0 x 10(-7) m2 s(-1). An asphalt coating reduced diffusion sixfold but an acrylic surface sealant had no effect. Diffusion was 42 times higher in solid masonry blocks than in concrete and was not affected by small cracks. Advective transport (deltaP < or = 60 Pa) was negligible for the slabs (10(-16) m2 permeability), pipe penetrations, and caulked gaps, but was significant for cracks, disturbed pipe penetrations, cold joints, masonry blocks, and concrete under tensile stress. Crack areas calculated to be as small as 10(-7) m2 significantly increased radon advection. Algebraic expressions predict air velocity and effective crack width from enhanced radon transport and air pressures. Masonry blocks, open cracks, and slab cold joints enhance radon penetration but stressed slabs, undisturbed pipe penetrations, and sealed cracks may not.

  10. 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.

  11. [Differential dose albedo for high-energy X-rays on concrete slab].

    PubMed

    Kato, Hideki

    2006-08-20

    We computed the differential dose albedo (alpha(D)) for high-energy X-rays on a concrete slab when the incident angle, reflection angle, and azimuth angle were changed, by means of Monte Carlo simulation. We found that alpha(D) changed with incident, reflection, and azimuth angles to the concrete slab. On the whole, the larger the incident angle, the larger alpha(D) tended to become. If the incident angle and reflection angle were the same, the larger the azimuth angle, the smaller alpha(D) tended to become. When the incident, reflection, and azimuth angles were the same, the smaller the X-ray energy was, the larger alpha(D) became, in the order of 10 MV, 6 MV, and 4 MV X-rays.

  12. AREA FACTOR DETERMINATIONS FOR AN INDUSTRIAL WORKER EXPOSED TO A CONCRETE SLAB END-STATE

    SciTech Connect

    Jannik, T; Patricia Lee, P; Eduardo Farfan, E; Jesse Roach, J

    2007-02-08

    The U.S. Department of Energy's (DOE) Savannah River Site (SRS) is decommissioning many of its excess facilities through removal of the facility structures leaving only the concrete-slab foundations in place. Site-specific, risk-based derived concentration guideline levels (DCGLs) for radionuclides have been determined for a future industrial worker potentially exposed to residual contamination on these concrete slabs as described in Jannik [1]. These risk-based DCGLs were estimated for an exposure area of 100 m{sup 2}. During deactivation and decommissioning (D&D) operations at SRS, the need for area factors for larger and smaller contaminated areas arose. This paper compares the area factors determined for an industrial worker exposed to a concrete slab end-state for several radionuclides of concern at SRS with (1) the illustrative area factors provided in MARSSIM [2], (2) the area correction factors provided in the U.S. Environmental Protection Agency's (EPA) Soil Screening Guidance [3], and (3) the hot spot criterion for field application provided in the RESRAD User's Manual [4].

  13. Radon mitigation by depressurization of concrete walls and slabs.

    PubMed

    Leung, J K; Tso, M Y; Hung, L C

    1999-10-01

    A special laboratory, the Radioisotope Unit Radon Analysis Laboratory, has been built for the study of radon mitigation in high-rise buildings. Reduction of radon exhalation rate from concrete walls as a result of depressurizing the interior of the wall was studied by embedding tunnels in a wall and pumping away the radon in the wall. The reduction in exhalation rate was quantified against the applied depressurization, the separation of the tunnels, the depth of the tunnel, and the thickness of the wall. Results show that radon exhalation rate from a wall embedded with tunnels can be reduced significantly by applying depressurization. For example, the radon exhalation rate from a wall of 20 cm thickness containing tunnels separated by 0.7 m can be reduced by 60% at a depressurization of 67 kPa (20 in Hg). This paper summarizes the effect of depressurization and suggests practical ways of applying the technique in radon mitigation in high-rise commercial buildings.

  14. Façade Greening: High-rise apartment building in Milan using pre-stressed concrete slab

    NASA Astrophysics Data System (ADS)

    Sun, Wenning; Li, Mingxin; Han, Yinong; Wang, Moqi; Ansourian, Peter

    2016-08-01

    In this project, one single level of the Façade Greening was designed and modelled using finite element method in Strand7. A static analysis was performed in order to understand the deflection and the stress due to the extra loads imposed by the soil and plants. The results produced by the linear static solver are compared with the strength of the materials and the European limitations. The maximum tension stress which exceeds the tensile strength in concrete is found in the root of the cantilever balcony. An alternative design of the cantilevered balcony with pre-stressed concrete slab is modelled separately for the balcony. Decrease is found in the tension stress and the significant improvement of deflection of the balcony with pre-stressed concrete slab. The dynamic loads such as wind and earthquake did not suggest significant effect on the pre-stressed concrete slab.

  15. Enhancement of concrete properties for pavement slabs using waste metal drillings and silica fume.

    PubMed

    Hassani, Abolfazl; Arjmandi, Mohsen

    2010-01-01

    This paper presents a comparative study on the effects of steel fibres and waste metal drillings on the mechanical/physical behaviour of conventional and silica fume concrete. The amount of silica fume used was 10% of cement by mass and the amount of steel fibres and metal drillings used in both concrete mixtures was 0.5% by concrete volume for steel fibres and 0.0, 0.25, 0.50 and 0.75% for metal drillings, respectively. In total, 10 different mixtures were made and tested for compressive strength, modulus of elasticity, flexural strength and toughness. Our data reveal the significant impact of the effect of silica fume, steel fibres and industrial waste metal drillings on the mechanical and physical characteristics of concrete mixtures. The results also show that mixtures with steel fibres and waste metal drillings have comparable behaviour. Hence, there is a potential for use of waste metal drillings as an alternative to steel fibres for specific cases such as concrete pavement slabs.

  16. Effects of shear stirrup details on ultimate capacity and tensile-membrane behavior of reinforced concrete slabs. Final report

    SciTech Connect

    Woodson, S.C.

    1985-08-01

    At the time this study was initiated, civil defense planning in the United States called for the evacuation of nonessential personnel to safe host areas when a nuclear attack is probable, requiring the construction of blasts shelters to protect the keyworkers remaining in the risk areas. The placement of shear stirrups in the one-way reinforced concrete roof slabs of the shelters will contribute significantly to project costs. Ten one-way reinforced concrete slabs were statically and uniformly loaded with water pressure, primarily to investigate the effect of stirrups and stirrup details on the load-response behavior of the slabs. The slabs had clear spans of 24.0 inches, span to effective depth ratios of 12.4, tensile reinforcement of 0.75%, and concrete strengths of approximately 5,000 psi. The test series significantly increased the data base for uniformly loaded one-way slabs. Support rotations between 13.1 and 20.6 degrees were observed. A more ductile behavior was observed in slabs with construction details, implying better concrete confinement due to more confining steel (i.e., closely spaced stirrups, double-leg stirrups, and closely spaced principal reinforcing bars). The parameters investigated did not appear to have a significant effect on ultimate load capacity.

  17. 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.

  18. A numerical model for calculating vibration due to a harmonic moving load on a floating-slab track with discontinuous slabs in an underground railway tunnel

    NASA Astrophysics Data System (ADS)

    Hussein, M. F. M.; Hunt, H. E. M.

    2009-03-01

    This paper presents a new method for modelling floating-slab tracks with discontinuous slabs in underground railway tunnels. The track is subjected to a harmonic load moving with a constant velocity. The model consists of two sub-models. The first is an infinite track with periodic double-beam unit formulated as a periodic infinite structure. The second is modelled with a new version of the Pipe-in-Pipe (PiP) model that accounts for a tunnel wall embedded in a half-space. The two sub-models are coupled by writing the force transmitted from the track to the tunnel as a continuous function using Fourier series representation and satisfying the compatibility condition. The displacements at the free surface are calculated for a track with discontinuous slab and compared with those of a track with continuous slab. The results show that the far-field vibration can be significantly increased due to resonance frequencies of slabs for tracks with discontinuous slabs.

  19. DESIGN OF A CONCRETE SLAB FOR STORAGE OF SNF AND HLW CASKS

    SciTech Connect

    J. Bisset

    2005-02-14

    This calculation documents the design of the Spent Nuclear Fuel (SNF) and High-Level Waste (HLW) Cask storage slab for the Aging Area. The design is based on the weights of casks that may be stored on the slab, the weights of vehicles that may be used to move the casks, and the layout shown on the sketch for a 1000 Metric Ton of Heavy Metal (MTHM) storage pad on Attachment 2, Sht.1 of the calculation 170-C0C-C000-00100-000-00A (BSC 2004a). The analytical model used herein is based on the storage area for 8 vertical casks. To simplify the model, the storage area of the horizontal concrete modules and their related shield walls is not included. The heavy weights of the vertical storage casks and the tensile forces due to pullout at the anchorages will produce design moments and shear forces that will envelope those that would occur in the storage area of the horizontal modules. The design loadings will also include snow and live loads. In addition, the design will also reflect pertinent geotechnical data. This calculation will document the preliminary thickness and general reinforcing steel requirements for the slab. This calculation also documents the initial design of the cask anchorage. Other slab details are not developed in this calculation. They will be developed during the final design process. The calculation also does not include the evaluation of the effects of cask drop loads. These will be evaluated in this or another calculation when the exact cask geometry is known.

  20. A theoretical investigation on influences of slab tracks on vertical dynamic responses of railway viaducts

    NASA Astrophysics Data System (ADS)

    Shi, Li; Cai, Yuanqiang; Wang, Peng; Sun, Honglei

    2016-07-01

    A railway viaduct model consisting of infinite spans of elastically-supported girders carrying a slab track of infinite length is established to investigate the influence of the slabs on the vertical dynamic response of the viaduct, when a moving harmonic point load or a moving sprung wheel is applied. The infinite rail, the discontinuous slabs and girders of identical span lengths are idealized as Euler-Bernoulli beams. The rail fasteners, the cushion layer beneath the slab and the elastic bearings at the girder supports are represented by discretely distributed springs of hysteretic damping. Due to the repetitive nature of the girders, the model can be divided into periodic three-beam units by the span length of the girder, and then solved analytically in the frequency domain using the property of periodic structure. Besides the first natural frequency of the girder with elastic bearings, it is found that the resonance frequency of the slab on the cushion layer has a significant influence on the dynamic response of the track and the girder. Parametric excitations due to the moving wheel periodically passing the discontinuous slabs contribute significantly to the wheel/rail interactions.

  1. Design Criteria for Deflection Capacity of Conventionally reinforced Concrete Slabs. Phase III. Summary of Design Criteria and Design and Construction Details - Design Examples.

    DTIC Science & Technology

    1980-10-01

    Precast Bearing Wall Buildings to Withstand Abnormal Loads ," Journal of the Prestressed Concrete Institute, Vol. 21, No. 2, March/April 1976. - -76...details necessary to develop tensile membrane capacity of reinforced concrete slabs under uniform load . Major emphasis is placed on the deflection...on Johansen’s work (4). The theory has proved effective in predic- ting the initial hinging load in reinforced concrete slabs with

  2. Slab fragmentation, edge flow and the origin of the Yellowstone hotspot track

    NASA Astrophysics Data System (ADS)

    James, David E.; Fouch, Matthew J.; Carlson, Richard W.; Roth, Jeffrey B.

    2011-11-01

    The Snake River Plain/Yellowstone (SRP/Y) volcanic province is widely considered a classic example of a plume generated continental hotspot. Here we present new S-wave and P-wave tomographic images that suggest an alternative subduction-related process by which volcanism along the SRP/Y hotspot track results from slab fragmentation, trench retreat, and mantle upwelling at the tip and around the truncated edges of the descending plate. Our seismic images of the upper mantle in the depth range 300-600 km show that the subducted oceanic plate extends locally eastward well into the mantle beneath stable North America. The break-up and along-strike fragmentation of the descending plate is related in both time and space to the onset of flood volcanism and the formation of the SRP/Y hotspot. A sub-horizontal branch of the subducting oceanic plate, orphaned from the descending plate by the northward migration of the Mendocino triple junction, resides in the mantle transition zone (400-600 km) directly beneath the SRP/Y track. Its truncated northern edge is parallel to the northwestern margin of the hotspot track and marks the southern edge of a slab gap. A number of recent numerical and physical tank model studies suggest that a rapidly retreating and severely fragmented downgoing plate drives mantle flow around both the tip and the edges of the descending slab. Our seismic results show that the morphology of the subducting slab is appropriate for generating large-scale poloidal flow (producing flood volcanism) in the upper mantle during the re-initiation phase of slab descent ca 20 Ma and for generating smaller-scale toroidal and poloidal upwellings (producing hotspot volcanism) around both the leading tip and northern edge of the slab as it descends into the deeper upper mantle. Plate reconstructions are consistent with the timing and position of both flood and hotspot volcanism.

  3. 7. Concrete Railing along Buffalo River side of tracks emerging ...

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

    7. Concrete Railing along Buffalo River side of tracks emerging from second level of DL&W train shed. Signal Tower/Boiler Room is just out of sight at right of photo. Skyway shows at extreme left. - Delaware, Lackawanna & Western Railroad, Lackawanna Terminal, Main Street & Buffalo River, Buffalo, Erie County, NY

  4. 49 CFR 213.234 - Automated inspection of track constructed with concrete crossties.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... concrete crossties. 213.234 Section 213.234 Transportation Other Regulations Relating to Transportation... § 213.234 Automated inspection of track constructed with concrete crossties. Link to an amendment... track inspection required under § 213.233, for Class 3 main track constructed with concrete...

  5. Seismic joint analysis for non-destructive testing of asphalt and concrete slabs

    USGS Publications Warehouse

    Ryden, N.; Park, C.B.

    2005-01-01

    A seismic approach is used to estimate the thickness and elastic stiffness constants of asphalt or concrete slabs. The overall concept of the approach utilizes the robustness of the multichannel seismic method. A multichannel-equivalent data set is compiled from multiple time series recorded from multiple hammer impacts at progressively different offsets from a fixed receiver. This multichannel simulation with one receiver (MSOR) replaces the true multichannel recording in a cost-effective and convenient manner. A recorded data set is first processed to evaluate the shear wave velocity through a wave field transformation, normally used in the multichannel analysis of surface waves (MASW) method, followed by a Lambwave inversion. Then, the same data set is used to evaluate compression wave velocity from a combined processing of the first-arrival picking and a linear regression. Finally, the amplitude spectra of the time series are used to evaluate the thickness by following the concepts utilized in the Impact Echo (IE) method. Due to the powerful signal extraction capabilities ensured by the multichannel processing schemes used, the entire procedure for all three evaluations can be fully automated and results can be obtained directly in the field. A field data set is used to demonstrate the proposed approach.

  6. Using Wireless Sensor Networks and Trains as Data Mules to Monitor Slab Track Infrastructures

    PubMed Central

    Cañete, Eduardo; Chen, Jaime; Díaz, Manuel; Llopis, Luis; Reyna, Ana; Rubio, Bartolomé

    2015-01-01

    Recently, slab track systems have arisen as a safer and more sustainable option for high speed railway infrastructures, compared to traditional ballasted tracks. Integrating Wireless Sensor Networks within these infrastructures can provide structural health related data that can be used to evaluate their degradation and to not only detect failures but also to predict them. The design of such systems has to deal with a scenario of large areas with inaccessible zones, where neither Internet coverage nor electricity supply is guaranteed. In this paper we propose a monitoring system for slab track systems that measures vibrations and displacements in the track. Collected data is transmitted to passing trains, which are used as data mules to upload the information to a remote control center. On arrival at the station, the data is stored in a database, which is queried by an application in order to detect and predict failures. In this paper, different communication architectures are designed and tested to select the most suitable system meeting such requirements as efficiency, low cost and data accuracy. In addition, to ensure communication between the sensing devices and the train, the communication system must take into account parameters such as train speed, antenna coverage, band and frequency. PMID:26131668

  7. Craters in concrete slabs due to detonation - drawbacks of material models with a Mohr-Coulomb yield surface

    NASA Astrophysics Data System (ADS)

    Conrad, Markus

    2015-09-01

    Numerical simulations have been performed with a commercial distributed explicit FE-solver and the results have been compared with experiments. High explosive was placed in front of different concrete slabs with the dimension 100 × 100 × 16 cm. Some of the results of the simulations, in particular the profile of the craters, are not in agreement with the test results. Therefore the key characteristics of the constitutive equation based on Mohr-Coulomb yield surfaces and a damage evolution linked to the plastic strain has been reviewed.

  8. Low-frequency vibration control of floating slab tracks using dynamic vibration absorbers

    NASA Astrophysics Data System (ADS)

    Zhu, Shengyang; Yang, Jizhong; Yan, Hua; Zhang, Longqing; Cai, Chengbiao

    2015-09-01

    This study aims to effectively and robustly suppress the low-frequency vibrations of floating slab tracks (FSTs) using dynamic vibration absorbers (DVAs). First, the optimal locations where the DVAs are attached are determined by modal analysis with a finite element model of the FST. Further, by identifying the equivalent mass of the concerned modes, the optimal stiffness and damping coefficient of each DVA are obtained to minimise the resonant vibration amplitudes based on fixed-point theory. Finally, a three-dimensional coupled dynamic model of a metro vehicle and the FST with the DVAs is developed based on the nonlinear Hertzian contact theory and the modified Kalker linear creep theory. The track irregularities are included and generated by means of a time-frequency transformation technique. The effect of the DVAs on the vibration absorption of the FST subjected to the vehicle dynamic loads is evaluated with the help of the insertion loss in one-third octave frequency bands. The sensitivities of the mass ratio of DVAs and the damping ratio of steel-springs under the floating slab are discussed as well, which provided engineers with the DVA's adjustable room for vibration mitigation. The numerical results show that the proposed DVAs could effectively suppress low-frequency vibrations of the FST when tuned correctly and attached properly. The insertion loss due to the attachment of DVAs increases as the mass ratio increases, whereas it decreases with the increase in the damping ratio of steel-springs.

  9. Design Criteria for Deflection Capacity of Conventionally Reinforced Concrete Slabs. Phase II. Design and Construction Requirements.

    DTIC Science & Technology

    1980-10-01

    A T DERECHO , M IGRAL N68305-79-C00 UNCLASSIFIED CEL-CR-.A07 NL .... DTIC tC’ 80-EV27 T-4 CIVIL ENGINEERING LABORATORY Naval Construction Battalion...Design and Construction Requirements by T. Takayanagi, A.T. Derecho , and M. Iqbal* 1. INTRODUCTION 1.1 Objective and Scope The primary objective of this...functions are constructed for 6ult/L from slab test data and for cu from slab data and coupon tesY data other than slab data. This second approach allows a

  10. Temperature and pore pressure distribution in a concrete slab during the microwave decontamination process

    SciTech Connect

    Li, W.; Ebadian, M.A.; White, T.L.; Grubb, R.G.; Foster, D. Jr.

    1994-10-01

    As an application of microwave engineering, the new technology of concrete decontamination and decommissioning using microwave energy has been recently developed. The temperature and pore pressure within the concrete are studied theoretically in this paper. The heat and mass transfer within the porous concrete, coupled with temperature dependent dielectric property are investigated. The effects of microwave frequency (f), microwave power intensity (Q{sub 0,ave}), concrete porosity ({phi}) on the temperature and pore pressure distributions and their variations are fully discussed. The effects of the variation of complex dielectric permittivity ({epsilon}) and presentation of different steel reinforcements are also illustrated.

  11. 49 CFR 213.234 - Automated inspection of track constructed with concrete crossties.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... concrete crossties. 213.234 Section 213.234 Transportation Other Regulations Relating to Transportation... § 213.234 Automated inspection of track constructed with concrete crossties. (a) General. Except for... constructed with concrete crossties over which regularly scheduled passenger service trains operate, and...

  12. 49 CFR 213.234 - Automated inspection of track constructed with concrete crossties.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... concrete crossties. 213.234 Section 213.234 Transportation Other Regulations Relating to Transportation... § 213.234 Automated inspection of track constructed with concrete crossties. (a) General. Except for... constructed with concrete crossties over which regularly scheduled passenger service trains operate, and...

  13. 49 CFR 213.234 - Automated inspection of track constructed with concrete crossties.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... concrete crossties. 213.234 Section 213.234 Transportation Other Regulations Relating to Transportation... § 213.234 Automated inspection of track constructed with concrete crossties. (a) General. Except for... constructed with concrete crossties over which regularly scheduled passenger service trains operate, and...

  14. Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 2, ventilated concrete slab

    SciTech Connect

    Chen, Yuxiang; Galal, Khaled; Athienitis, A.K.

    2010-11-15

    This paper is the second of two papers that describe the modeling and design of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) adopted in a prefabricated, two-storey detached, low energy solar house and their performance assessment based on monitored data. The VCS concept is based on an integrated thermal-structural design with active storage of solar thermal energy while serving as a structural component - the basement floor slab ({proportional_to}33 m{sup 2}). This paper describes the numerical modeling, design, and thermal performance assessment of the VCS. The thermal performance of the VCS during the commissioning of the unoccupied house is presented. Analysis of the monitored data shows that the VCS can store 9-12 kWh of heat from the total thermal energy collected by the BIPV/T system, on a typical clear sunny day with an outdoor temperature of about 0 C. It can also accumulate thermal energy during a series of clear sunny days without overheating the slab surface or the living space. This research shows that coupling the VCS with the BIPV/T system is a viable method to enhance the utilization of collected solar thermal energy. A method is presented for creating a simplified three-dimensional, control volume finite difference, explicit thermal model of the VCS. The model is created and validated using monitored data. The modeling method is suitable for detailed parametric study of the thermal behavior of the VCS without excessive computational effort. (author)

  15. Numerical simulation on slabs dislocation of Zipingpu concrete faced rockfill dam during the Wenchuan earthquake based on a generalized plasticity model.

    PubMed

    Xu, Bin; Zhou, Yang; Zou, Degao

    2014-01-01

    After the Wenchuan earthquake in 2008, the Zipingpu concrete faced rockfill dam (CFRD) was found slabs dislocation between different stages slabs and the maximum value reached 17 cm. This is a new damage pattern and did not occur in previous seismic damage investigation. Slabs dislocation will affect the seepage control system of the CFRD gravely and even the safety of the dam. Therefore, investigations of the slabs dislocation's mechanism and development might be meaningful to the engineering design of the CFRD. In this study, based on the previous studies by the authors, the slabs dislocation phenomenon of the Zipingpu CFRD was investigated. The procedure and constitutive model of materials used for finite element analysis are consistent. The water elevation, the angel, and the strength of the construction joints were among major variables of investigation. The results indicated that the finite element procedure based on a modified generalized plasticity model and a perfect elastoplastic interface model can be used to evaluate the dislocation damage of face slabs of concrete faced rockfill dam during earthquake. The effects of the water elevation, the angel, and the strength of the construction joints are issues of major design concern under seismic loading.

  16. Numerical Simulation on Slabs Dislocation of Zipingpu Concrete Faced Rockfill Dam during the Wenchuan Earthquake Based on a Generalized Plasticity Model

    PubMed Central

    Xu, Bin; Zou, Degao

    2014-01-01

    After the Wenchuan earthquake in 2008, the Zipingpu concrete faced rockfill dam (CFRD) was found slabs dislocation between different stages slabs and the maximum value reached 17 cm. This is a new damage pattern and did not occur in previous seismic damage investigation. Slabs dislocation will affect the seepage control system of the CFRD gravely and even the safety of the dam. Therefore, investigations of the slabs dislocation's mechanism and development might be meaningful to the engineering design of the CFRD. In this study, based on the previous studies by the authors, the slabs dislocation phenomenon of the Zipingpu CFRD was investigated. The procedure and constitutive model of materials used for finite element analysis are consistent. The water elevation, the angel, and the strength of the construction joints were among major variables of investigation. The results indicated that the finite element procedure based on a modified generalized plasticity model and a perfect elastoplastic interface model can be used to evaluate the dislocation damage of face slabs of concrete faced rockfill dam during earthquake. The effects of the water elevation, the angel, and the strength of the construction joints are issues of major design concern under seismic loading. PMID:25013857

  17. Shear strength of non-shear reinforced concrete elements. Part 3: Prestressed hollow-core slabs

    SciTech Connect

    Hoang, L.C.

    1997-12-31

    This paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions. In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding model developed by Jin-Ping Zhang. The model takes into account the resistance against the formation of cracks due to prestressing as well as the variation of the prestressing force in the transfer zone. Due to the fact that the anchorage of the reinforcement takes place by bond, a rotation failure, which is indeed by a crack formed at the support with subsequent slip of the reinforcement, is also considered. This failure mode is likely to occur in cases with a high prestressing force combined with a short shear span. The theoretical calculations are compared with test results form the literature. A good agreement has been found.

  18. 7. 'Tunnel No 14, Concrete Lining,' Southern Pacific Standard SingleTrack ...

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

    7. 'Tunnel No 14, Concrete Lining,' Southern Pacific Standard Single-Track Tunnel, ca. 1909. Under current numbering, this is now Tunnel 29 (HAER No. CA-205). - Central Pacific Transcontinental Railroad, Sacramento to Nevada state line, Sacramento, Sacramento County, CA

  19. Design Criteria for Deflection Capacity of conventionally Reinforced Concrete Slabs. Phase I. State-of-the-Art Report.

    DTIC Science & Technology

    1980-10-01

    Affecting Slab Behavior 115 9.5.1 Short Span of Slab 115 9.5.2 Lateral Movement of Slab Edges 115 9.5.3 Span-Depth Ratio 115 9.5.4 Combined Short Span-Steel...account the influence of slab geometry, section properties, boundary conditions, mate- rial properties, and load distribution on incipient collapse...outwards as slab deflection increases. If the outer edges are restrained against movement , compressive forces are induced in the slab, as shown in

  20. An Eye-Tracking Study of Learning from Science Text with Concrete and Abstract Illustrations

    ERIC Educational Resources Information Center

    Mason, Lucia; Pluchino, Patrik; Tornatora, Maria Caterina; Ariasi, Nicola

    2013-01-01

    This study investigated the online process of reading and the offline learning from an illustrated science text. The authors examined the effects of using a concrete or abstract picture to illustrate a text and adopted eye-tracking methodology to trace text and picture processing. They randomly assigned 59 eleventh-grade students to 3 reading…

  1. 6. 'Tunnel No. 6, Concrete Lining,' Southern Pacific Standard SingleTrack ...

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

    6. 'Tunnel No. 6, Concrete Lining,' Southern Pacific Standard Single-Track Tunnel, ca. 1909. Compare to photos in documentation set for Tunnel 27 (HAER No. CA-203). - Central Pacific Transcontinental Railroad, Sacramento to Nevada state line, Sacramento, Sacramento County, CA

  2. Risk-Based Radionuclide Derived Concentration Guideline Levels For An Industrial Worker Exposed To Concrete-Slab End States At The Savannah River Site

    SciTech Connect

    GERALD, JANNIK

    2005-04-25

    Dose and risk assessments are an integral part of decommissioning activities. Most human health risk assessments are performed for a reasonable maximum exposure to an individual with assumed intake and exposure parameters that depend on the end state of the decommissioning activities and the likely future use of the site. Regardless of how the potentially exposed individual is defined, the subsequent calculated human health risk is not a measurable quantity. To demonstrate compliance with risk-based acceptance or cleanliness criteria, facility-specific risk assessments usually are performed after final-verification sampling and analysis. Alternatively, conservative, a priori, guideline concentrations for residual contaminants can be calculated and rapidly compared to the subsequently measured contaminant concentrations to demonstrate compliance. In response to the request for accelerated cleanup at U.S. Department of Energy facilities, the Savannah River Site (SRS) is decommissioning its excess facilities through removal of the facility structures leaving only the concrete-slab foundations in place. Site-specific, risk-based derived concentration guideline levels (DCGLs) for radionuclides have been determined for a future industrial worker potentially exposed to residual contamination on these concrete slabs. When appropriate, these conservative DCGLs will be used at SRS in lieu of facility-specific risk assessments to further accelerate the decommissioning process. This paper discusses and describes the methods and scenario-specific parameters used to estimate the risk-based DCGLs for the SRS decommissioning end state.

  3. Cracking in Concrete near Joints in Steelconcrete Composite Slab / Zarysowanie Płyty Żelbetowej W Strefie Przywęzłowej Stropu Zespolonego

    NASA Astrophysics Data System (ADS)

    Niedośpiał, Marcin; Knauff, Michał; Barcewicz, Wioleta

    2015-03-01

    In this paper results of the experimental tests of four full-scale composite steel-concrete elements are reported. In the steel-concrete composite elements, a steel beam was connected with a slab cast on profiled sheeting, by shear studs. The end-plates were (the thickness of 8 mm, 10 mm and 12 mm) thinner than in ordinary design. Joints between the column and the beams have been designed as semi-rigid, i.e. the deformations of endplates affect the distribution of forces in the adjacent parts of the slab. The paper presents the theory of cracking in reinforced concrete and steel-concrete composite members (according to the codes), view of crack pattern on the surface of the slabs and a comparison of the tests results and the code calculations. It was observed, that some factors influencing on crack widths are not taken in Eurocode 4 (which is based on Eurocode 2 with taking into account the phenomenon called "tension stiffening"). W artykule przedstawiono wyniki badań czterech elementów zespolonych. Kształtownik stalowy połączony był z betonowym stropem wykonanym na blasze fałdowej. W modelu zastosowano cienkie blachy czołowe (o grubości 8 mm, 10 mm i 12 mm), cieńsze niż zwykle przyjmowane w praktyce projektowej. Połączenie to zaprojektowano jako podatne tzn. takie, w którym odkształcenia blach czołowych mają istotny wpływ na rozkład sił w połączeniu. Przedstawiono normową teorię dotyczącą zarysowania elementów żelbetowych i zespolonych, obraz zarysowania stropu oraz porównano otrzymane wyniki z obliczeniami wykonanymi wg aktualnych norm. Zauważono, iż nie wszystkie czynniki obliczania szerokości rys w konstrukcjach zespolonych są zdefiniowane w normie projektowania konstrukcji zespolonych (która w tej kwestii odwołuje się do normy projektowania konstrukcji żelbetowych z uwzględnieniem zjawiska "tension stiffening").

  4. 51. DETAIL VIEW OF VIVIANNA ERA CONCRETE HOUSE WITH CONCRETE ...

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

    51. DETAIL VIEW OF VIVIANNA ERA CONCRETE HOUSE WITH CONCRETE PATIO SLAB LOOKING SOUTHWEST. NOTICE MINE WORKINGS BACKGROUND LEFT. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  5. Investigation of the Use of Viscoelastic Damping Devices to Rehabilitate a Lightly Reinforced Concrete Slab- Column Structure

    DTIC Science & Technology

    1998-09-01

    priceless direction and assistance with instrumentation, test conduct, and data reduction. William Gordon and Ernest Westfield provided valuable...American Concrete Institute, Volume 89, Number 1, January-February 1992, pp 37-45. 42. Sause, R, Hemingway , G, and Kasai, K, "Simplified Seismic

  6. Biaxial Behavior of Ultra-High Performance Concrete and Untreated UHPC Waffle Slab Bridge Deck Design and Testing

    NASA Astrophysics Data System (ADS)

    D'Alessandro, Kacie Caple

    Ultra-high performance concrete (UHPC) was evaluated as a potential material for future bridge deck designs. Material characterization tests took place to identify potential challenges in mixing, placing, and curing UHPC. Biaxial testing was performed to evaluate behavior of UHPC in combined tension and compression stress states. A UHPC bridge deck was designed to perform similarly to a conventional concrete bridge deck, and a single unit bridge deck section was tested to evaluate the design methods used for untreated UHPC. Material tests identified challenges with placing UHPC. A specified compressive strength was determined for structural design using untreated UHPC, which was identified as a cost-effective alternative to steam treated UHPC. UHPC was tested in biaxial tension-compression stress states. A biaxial test method was developed for UHPC to directly apply tension and compression. The influence of both curing method and fiber orientation were evaluated. The failure envelope developed for untreated UHPC with random fiber orientation was suggested as a conservative estimate for future analysis of UHPC. Digital image correlation was also evaluated as a means to estimate surface strains of UHPC, and recommendations are provided to improve consistency in future tests using DIC methods. A preliminary bridge deck design was completed for untreated UHPC and using established material models. Prestressing steel was used as primary reinforcement in the transverse direction. Preliminary testing was used to evaluate three different placement scenarios, and results showed that fiber settling was a potential placement problem resulting in reduced tensile strength. The UHPC bridge deck was redesigned to incorporate preliminary test results, and two single unit bridge deck sections were tested to evaluate the incorporated design methods for both upside down and right-side up placement techniques. Test results showed that the applied design methods would be conservative

  7. Precast Slab Literature Review Report: Repair of Rigid Airfield Pavements Using Precast Concrete Panels - A State-of-the-Art Review

    DTIC Science & Technology

    2010-06-01

    Miller Super-Slab® Method .......................................................................................18 4.7.2. Flowable Fill (Michigan Method...From Underneath[9] ........................................................................18 12. Flowable Fill Used by Michigan Method[16...Michigan Single panel Dowels cast into the precast panel Flowable fill No 14 URETEK Single or connected panel Fibreglass ties inserted after the

  8. Precast Concrete Pavements

    DTIC Science & Technology

    1981-11-01

    Gorsuch 1962, Kruse 1966, Jacoby 1967, and Hargett 1970). The final slab design used in construction is shown in Figure 2. These slabs were 6 ft wide, 24...Experiment Station, CE, Vicksburg, Miss. Gorsuch , R. F. 1962. "Preliminary Investigation of Precast Prestressed Concrete Pavements," MS Thesis, South Dakota

  9. Cracking behavior of structural slab bridge decks

    NASA Astrophysics Data System (ADS)

    Baah, Prince

    Bridge deck cracking is a common problem throughout the United States, and it affects the durability and service life of concrete bridges. Several departments of transportation (DOTs) in the United States prefer using continuous three-span solid structural slab bridges without stringers over typical four-lane highways. Recent inspections of such bridges in Ohio revealed cracks as wide as 0.125 in. These measured crack widths are more than ten times the maximum limit recommended in ACI 224R-01 for bridge decks exposed to de-icing salts. Measurements using digital image correlation revealed that the cracks widened under truck loading, and in some cases, the cracks did not fully close after unloading. This dissertation includes details of an experimental investigation of the cracking behavior of structural concrete. Prism tests revealed that the concrete with epoxy-coated bars (ECB) develops the first crack at smaller loads, and develops larger crack widths compared to the corresponding specimens with uncoated (black) bars. Slab tests revealed that the slabs with longitudinal ECB developed first crack at smaller loads, exhibited wider cracks and a larger number of cracks, and failed at smaller ultimate loads compared to the corresponding test slabs with black bars. To develop a preventive measure, slabs with basalt and polypropylene fiber reinforced concrete were also included in the test program. These test slabs exhibited higher cracking loads, smaller crack widths, and higher ultimate loads at failure compared to the corresponding slab specimens without fibers. Merely satisfying the reinforcement spacing requirements given in AASHTO or ACI 318-11 is not adequate to limit cracking below the ACI 224R-01 recommended maximum limit, even though all the relevant design requirements are otherwise met. Addition of fiber to concrete without changing any steel reinforcing details is expected to reduce the severity and extent of cracking in reinforced concrete bridge decks.

  10. Slab reformer

    DOEpatents

    Spurrier, F.R.; DeZubay, E.A.; Murray, A.P.; Vidt, E.J.

    1984-02-07

    Slab-shaped high efficiency catalytic reformer configurations are disclosed particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot combustion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant. 14 figs.

  11. Slab reformer

    DOEpatents

    Spurrier, Francis R.; DeZubay, Egon A.; Murray, Alexander P.; Vidt, Edward J.

    1985-03-12

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot combustion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  12. Slab reformer

    DOEpatents

    Spurrier, Francis R.; DeZubay, Egon A.; Murray, Alexander P.; Vidt, Edward J.

    1984-02-07

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot comubstion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  13. Chlorine signal attenuation in concrete.

    PubMed

    Naqvi, A A; Maslehuddin, M; ur-Rehman, Khateeb; Al-Amoudi, O S B

    2015-11-01

    The intensity of prompt gamma-ray was measured at various depths from chlorine-contaminated silica fume (SF) concrete slab concrete specimens using portable neutron generator-based prompt gamma-ray setup. The intensity of 6.11MeV chloride gamma-rays was measured from the chloride contaminated slab at distance of 15.25, 20.25, 25.25, 30.25 and 35.25cm from neutron target in a SF cement concrete slab specimens. Due to attenuation of thermal neutron flux and emitted gamma-ray intensity in SF cement concrete at various depths, the measured intensity of chlorine gamma-rays decreases non-linearly with increasing depth in concrete. A good agreement was noted between the experimental results and the results of Monte Carlo simulation. This study has provided useful experimental data for evaluating the chloride contamination in the SF concrete utilizing gamma-ray attenuation method.

  14. Tracking neural coding of perceptual and semantic features of concrete nouns

    PubMed Central

    Sudre, Gustavo; Pomerleau, Dean; Palatucci, Mark; Wehbe, Leila; Fyshe, Alona; Salmelin, Riitta; Mitchell, Tom

    2015-01-01

    We present a methodological approach employing magnetoencephalography (MEG) and machine learning techniques to investigate the flow of perceptual and semantic information decodable from neural activity in the half second during which the brain comprehends the meaning of a concrete noun. Important information about the cortical location of neural activity related to the representation of nouns in the human brain has been revealed by past studies using fMRI. However, the temporal sequence of processing from sensory input to concept comprehension remains unclear, in part because of the poor time resolution provided by fMRI. In this study, subjects answered 20 questions (e.g. is it alive?) about the properties of 60 different nouns prompted by simultaneous presentation of a pictured item and its written name. Our results show that the neural activity observed with MEG encodes a variety of perceptual and semantic features of stimuli at different times relative to stimulus onset, and in different cortical locations. By decoding these features, our MEG-based classifier was able to reliably distinguish between two different concrete nouns that it had never seen before. The results demonstrate that there are clear differences between the time course of the magnitude of MEG activity and that of decodable semantic information. Perceptual features were decoded from MEG activity earlier in time than semantic features, and features related to animacy, size, and manipulability were decoded consistently across subjects. We also observed that regions commonly associated with semantic processing in the fMRI literature may not show high decoding results in MEG. We believe that this type of approach and the accompanying machine learning methods can form the basis for further modeling of the flow of neural information during language processing and a variety of other cognitive processes. PMID:22565201

  15. Methodology for assessing the probability of corrosion in concrete structures on the basis of half-cell potential and concrete resistivity measurements.

    PubMed

    Sadowski, Lukasz

    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 E corr 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.

  16. 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

  17. Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 1, BIPV/T system and house energy concept

    SciTech Connect

    Chen, Yuxiang; Athienitis, A.K.; Galal, Khaled

    2010-11-15

    This paper is the first of two papers that describe the modeling, design, and performance assessment based on monitored data of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) in a prefabricated, two-storey detached, low energy solar house. This house, with a design goal of near net-zero annual energy consumption, was constructed in 2007 in Eastman, Quebec, Canada - a cold climate area. Several novel solar technologies are integrated into the house and with passive solar design to reach this goal. An air-based open-loop BIPV/T system produces electricity and collects heat simultaneously. Building-integrated thermal mass is utilized both in passive and active forms. Distributed thermal mass in the direct gain area and relatively large south facing triple-glazed windows (about 9% of floor area) are employed to collect and store passive solar gains. An active thermal energy storage system (TES) stores part of the collected thermal energy from the BIPV/T system, thus reducing the energy consumption of the house ground source heat pump heating system. This paper focuses on the BIPV/T system and the integrated energy concept of the house. Monitored data indicate that the BIPV/T system has a typical efficiency of about 20% for thermal energy collection, and the annual space heating energy consumption of the house is about 5% of the national average. A thermal model of the BIPV/T system suitable for preliminary design and control of the airflow is developed and verified with monitored data. (author)

  18. Instrumentation by accelerometers and distributed optical fiber sensors of a real ballastless track structure

    NASA Astrophysics Data System (ADS)

    Chapeleau, Xavier; Cottineau, Louis-Marie; Sedran, Thierry; Cailliau, Joël; Gueguen, Ivan; Dumoulin, Jean

    2015-04-01

    While relatively expensive to build, ballastless track structures are presently seen as an attractive alternative to conventional ballast. Firstly, they are built quickly since the slabs can be cast in place in an automated fashion by a slipform paver. Secondly, with its service life of at least 60 years, they requires little maintenance and hence they offers great availability. Other reasons for using ballastless tracks instead of ballasted tracks are the lack of suitable ballast material and the need of less noise and vibration for high-speed, in particularly. In the framework of a FUI project (n° 072906053), a new ballastless track structure based on concrete slabs was designed and its thermal-mechanical behavior in fatigue under selected mechanical and thermal conditions was tested on a real scale mockup in our laboratory [1,2]. By applying to the slabs both together mechanical stresses and thermal gradients, finite elements simulation and experimental results show that the weather conditions influence significantly the concrete slabs curvatures and by the way, the contact conditions with the underlaying layers. So it is absolutely necessary to take into account this effect in the design of the ballastless track structures in order to guarantee a long target life of at least of 50 years. After design and experimental tests in laboratory, a real ballastless track structure of 1km was built in France at the beginning of year 2013. This structure has 2 tracks on which several trains circulate every day since the beginning of year 2014. Before the construction, it was decided to monitor this structure to verify that the mechanical behavior is conform to the simulations. One part of the instrumentation is dedicated to monitor quasi-continuously the evolution of the curvature of a concrete slab. For this, 2 accelerometers were fixed on the slab under the track. One was placed on the edge and the other in the middle of the slab. The acquisition of the signals by a

  19. RADON GENERATION AND TRANSPORT IN AGED CONCRETE

    EPA Science Inventory

    The report gives results of a characterization of radon generation and transport in Florida concretes sampled from 12- to 45-year-old residential slabs. It also compares measurements from old concrete samples to previous measurements on newly poured Florida residential concretes....

  20. Dynamics of slab detachment

    NASA Astrophysics Data System (ADS)

    Duretz, T.; Schmalholz, S. M.; Gerya, T. V.

    2012-04-01

    Our study investigates the dynamics of slab detachment and evaluates the amount of time necessary for slabs to detach. We combine both the results of two-dimensional numerical modeling with the prediction of a one-dimensional analytical solution for viscous necking under gravity. This tidy suggest that the dominant deformation mechanisms leading to slab detachment is viscous necking, independently of the depth of slab detachment. Localised simple shear may also occur when the slab dip is moderate, especially in the colder parts of the slab. Brittle fracturing, or breaking, plays a minor role during the slab detachment process. 2D thermo-mechanical simulations indicate that the duration of slab detachment is short (< 4 Ma) and can occur in less than 0.5 Ma. No simple correlation between the slab detachment depth and duration was found. Our results suggest that deep slab detachments (> 250 km) can also occur within a short time (< 1 Ma). On the other hand, slab detachments taking place between 35 and 250 km depth may last less than 2 Ma. This aspect has implications for geodynamic interpretations using slab detachment as explanation for processes such as melting, exhumation or surface uplift.

  1. Bonded Concrete Overlays: Construction and Performance.

    DTIC Science & Technology

    1980-09-01

    report provides a review and summary of surface preparation of the existing slab, joint and crack treatment, bonding methods, concrete overlay mixtures...34Bonded, Thin-Lift Portland Cement Concrete Re- surfacing," Report on Project HRlgl, Clayton County and Iowa Highway Research Board, September 1977...34Resurfacing and Patching Concrete Pavement with Bonded Concrete ," Proceedings, Highway Research Board, Vol. 35, 1956. 8. Gillette, R. W.,"A 10-Year Report

  2. 16. 'Concrete Bridge Over Salt River, Port Kenyon, Humboldt County, ...

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

    16. 'Concrete Bridge Over Salt River, Port Kenyon, Humboldt County, California, A.J. Logan, County Surveyor, H.J. Brunnier, Consulting Engineer, March 7, 1919,' showing detail of floor beam at central pier, half section of cantilever slab at end of bridge, floor beam end panels, slab reinforcing, plan of slab reinforcing, diagram of slab bars, typical floor girder. - Salt River Bridge, Spanning Salt River at Dillon Road, Ferndale, Humboldt County, CA

  3. How Concrete Is Concrete?

    ERIC Educational Resources Information Center

    Gravemeijer, Koeno

    2011-01-01

    If we want to make something concrete in mathematics education, we are inclined introduce, what we call, "manipulatives", in the form of tactile objects or visual representations. If we want to make something concrete in a everyday-life conversation, we look for an example. In the former, we try to make a concrete model of our own,…

  4. Deepest hypocentral distributions associated with stagnant slabs and penetrated slabs

    NASA Astrophysics Data System (ADS)

    Fukao, Y.; Obayashi, M.

    2013-12-01

    We constructed a new P-wave tomographic model of the mantle, GAP_P4, using more than ten millions of travel time data, including waveform-based differential travel times from ocean bottoms, to all of which the finite frequency kernels were applied in the inversion. Based on this model, we made a systematic survey for subducted slab images around the Circum Pacific. This survey revealed a progressive lateral variation of slab configuration along arc(s), where a subducted slab is in general in one or two of the following four stages: I. slab stagnant above the 660, II. slab penetrating the 660, III. slab trapped in the uppermost lower mantle (660 to ˜1000 km in depth), and IV. slab descending well into the deep lower mantle. The majority of the slab images are either at stage I or III. We interpret I to IV as the successive stages of slab subduction through the transition region with the 660 at the middle. There is a remarkable correlation of the slab configuration with the deepest shock hypocentral distribution. Subhorizontal distributions of deepest shocks are associated with stagnant slabs in the transition zone (slabs at stage I). Their focal depths are limited to shallower than ˜620 km. Steeply dipping deepest shock distributions are associated with penetrating slabs across the 660-km discontinuity or trapped slabs below it (slabs at stages II and III). Their focal depths extend well beyond ˜620 km. There are no cases of association of either a stagnant slab (at stage I) with subvertical distribution of deepest shocks or a trapped slab (at stage II or III) with their subhorizontal distribution. Only steeply dipping slabs appear to penetrate the 660 to be trapped in the uppermost lower mantle. The along-arc variations of stagnant-slab configuration and deepest shock distribution beneath the Bonin arc indicate a process of how the slab begins to penetrate the 660-km discontinuity after the slab stagnation. Those beneath the Java arc and Kermadec arc commonly

  5. Requalification analysis of a circular composite slab for seismic load

    SciTech Connect

    Srinivasan, M.G.; Kot, C.A.

    1992-11-01

    The circular roof slab of an existing facility was analyzed to requalify the structure for supporting a significant seismic load that it was not originally designed for. The slab has a clear span of 66 ft and consists of a 48 in thick reinforced concrete member and a steel liner plate. Besides a number of smaller penetrations, the slab contains two significant cutouts: a 9 ft square opening and a 3 ft dia hole. The issues that complicated the analysis of this non-typical structure, i.e., composite action and nonlinear stiffness of reinforced concrete (R. C.) sections, are discussed. It was possible to circumvent the difficulties by making conservative and simplifying assumptions. If codes incorporate guidelines on practical methods for dynamic analysis of R. C. structures, some of the unneeded conservatism could be eliminated in future designs.

  6. Polypropylene Fibers in Portland Cement Concrete Pavements.

    DTIC Science & Technology

    1992-08-01

    Bibliography on Fiber- Reinforced Cement and Concrete," Miscellaneous Paper C-76-6, with supplements 1, 2, 3, and 4 ( 1977 , 1979, 1980, and 1982), US Army... Mindess , S., Bentur, A., Yan, C., and Vondran, G., "Impact Resistance of Concrete Containing Both Conventional Steel Reinforcement and Fibrillated...Roads, Streets, Walks, and Open Storage Areas," TM 5-822-6/AFM 88-7, Chap. 7, Washington, DC, 1977 . 18. __ , "Concrete Floor Slabs on Grade Subjected

  7. First application of second-generation steel-free deck slabs for bridge rehabilitation

    NASA Astrophysics Data System (ADS)

    Eden, Ruth; Klowak, Chad; Mufti, Aftab A.; Tadros, Gamil; Bakht, Baidar; Loewen, Eric

    2004-07-01

    The arching action in concrete deck slabs for girder bridges is utilized fully in steel-free deck slabs. These concrete slabs, requiring no tensile reinforcement, are confined longitudinally by making them composite with the girders, and transversely by external steel straps connecting the top flanges of external girders. Between 1995 and 1999, five steel-free deck slabs without any tensile reinforcement were cast on Canadian bridges. All these slabs developed fairly wide full-depth cracks roughly midway between the girders. While extensive fatigue testing done in the past three years has confirmed that the presence of even wide cracks does not pose any danger to the safety of the structures, wide cracks are generally not acceptable to bridge engineers. The developers of the steel-free deck slabs have now conceded that these slabs should be reinforced with a crack-control mesh of nominal glass fibre reinforced polymer (GFRP) bars. Steel-free deck slabs with crack-control meshes are being referred as the second generation slabs. With the help of testing on full-scale models, it has been found that deck slabs with GFRP bars have the best fatigue resistance and those with steel bars the worst.

  8. Shear Resistance between Concrete-Concrete Surfaces

    NASA Astrophysics Data System (ADS)

    Kovačovic, Marek

    2013-12-01

    The application of precast beams and cast-in-situ structural members cast at different times has been typical of bridges and buildings for many years. A load-bearing frame consists of a set of prestressed precast beams supported by columns and diaphragms joined with an additionally cast slab deck. This article is focused on the theoretical and experimental analyses of the shear resistance at an interface. The first part of the paper deals with the state-of-art knowledge of the composite behaviour of concrete-concrete structures and a comparison of the numerical methods introduced in the relevant standards. In the experimental part, a set of specimens with different interface treatments was tested until failure in order to predict the composite behaviour of coupled beams. The experimental part was compared to the numerical analysis performed by means of FEM basis nonlinear software.

  9. Modeling radon entry into Florida slab-on-grade houses.

    PubMed

    Revzan, K L; Fisk, W J; Sextro, R G

    1993-10-01

    Radon entry into a Florida house whose concrete slab is supported by a permeable concrete-block stem wall and a concrete footer is modeled. The slab rests on backfill material; the same material is used to fill the footer trench. A region of undisturbed soil is assumed to extend 10 m beyond and below the footer. The soil is assumed homogeneous and isotropic except for certain simulations in which soil layers of high permeability or radium content are introduced. Depressurization of the house induces a pressure field in the soil and backfill. The Laplace equation, resulting from Darcy's law and the continuity equation, is solved using a steady-state finite-difference model to determine this field. The mass-transport equation is then solved to obtain the diffusive and advective radon entry rates through the slab; the permeable stem wall; gaps at the intersections of the slab, stem wall, and footer; and gaps in the slab. These rates are determined for variable soil, backfill, and stem-wall permeability and radium content, slab-opening width and position, slab and stem-wall diffusivity, and water table depth. The variations in soil permeability and radium content include cases of horizontally stratified soil. We also consider the effect of a gap between the edge of the slab and the stem wall that restricts the passage of soil gas from the stem wall into the house. Calculations indicate that the total radon entry rate is relatively low unless the soil or backfill permeability or radium content is high. Variations in most of the factors, other than the soil permeability and radium content, have only a small effect on the total radon entry rate. However, for a fixed soil permeability, the total radon entry rate may be reduced by a factor of 2 or more by decreasing the backfill permeability, by making the stem wall impermeable and gap-free, (possibly by constructing a one-piece slab/stem-wall/footer), or by increasing the pressure in the interior of the stem wall (by

  10. Cordilleran slab windows

    SciTech Connect

    Thorkelson, D.J.; Taylor, R.P. )

    1989-09-01

    The geometry and geologic implications of subducted spreading ridges are topics that have bedeviled earth scientists ever since the recognition of plate tectonics. As a consequence of subduction of the Kula-Farallon and East Pacific rises, slab windows formed and migrated beneath the North American Cordillera. The probable shape and extent of these windows, which represent the asthenosphere-filled gaps between two separating, subducting oceanic plates, are depicted from the Late Cretaceous to the present. Possible effects of the existence and migration of slab windows on the Cordillera at various times include cessation of arc volcanism and replacement by rift or plate-edge volcanism; lithospheric uplift, attenuation, and extension; and increased intensity of compressional tectonism. Eocene extensional tectonism and alkaline magmatism in southern British Columbia and the northwestern United States were facilitated by slab-window development.

  11. The Role of Subducting Ridges in the Formation of Flat Slabs: Insights from the Peruvian Flat Slab

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, Sanja; Wagner, Lara; Kumar, Abhash; Beck, Susan; Long, Maureen; Zandt, George; Eakin, Caroline M.

    2015-04-01

    Flattening of the subducting plate is often used to explain various geological features removed far from the subducting margins, including basement-cored uplifts, the cessation of arc volcanism, ignimbrite flare-ups, and the formation of high plateaus and ore deposits [Humphreys et al., 2003; Gutscher et al., 2000; Rosenbaum et al., 2005, Kay and Mpodozis, 2001]. Today, flat slab subduction is observed in central Chile and Peru, representing the modern analogues to the immense paleo-flat slab that subducted beneath the North American continent during the Laramide orogeny (80-55 Ma) [English et al., 2003]. However, how flat slabs form and what controls their inboard and along-strike extent is still poorly understood. To better understand modern and paleo-flat slabs, we focus on the Peruvian flat slab, where the Nazca plate starts to bend at ~90 km depth and travels horizontally for several hundred kilometers beneath the South American plate. Earlier studies propose a correlation between the flat slab and the subducting Nazca Ridge that has been migrating to the south over the past 11 ~Ma [Hampel et al., 2004, Gutscher et al., 2003]. Combining 3D shear wave velocity structure and Rayleigh wave phase anisotropy between ~10° and 18° S, we find that the flat slab has the greatest inboard extent along the track of the subducting Nazca Ridge. North of the ridge track, where the flat slab was initially formed, the flat slab starts to sag, tear and re-initiate steep slab subduction, allowing inflow of warm asthenosphere. Based on our new constraints on the geometry of the subducted plate, we find that the subduction of buoyant oceanic features with overthickened oceanic crust plays a vital role in the formation of flat slabs. We further develop a model of temporal evolution of the Peruvian flab slab that forms as a result of the combined effects of the subducting ridge, trench retreat, and suction forces. Once the buoyant ridge subducts to ~90 km depth, it will fail to

  12. Slab Leaf Bowls

    ERIC Educational Resources Information Center

    Suitor, Cheryl

    2012-01-01

    In science class, fourth graders investigate the structure of plants and leaves from trees and how the process of photosynthesis turns sunlight into sugar proteins. In this article, the author fuses art and science for a creative and successful clay slab project in her elementary art classroom. (Contains 1 online resource.)

  13. Modeling radon entry into Florida slab-on-grade houses

    SciTech Connect

    Revzan, K.L.; Fisk, W.J.; Sextro, R.G. )

    1993-10-01

    Radon entry into a Florida house whose concrete slab is supported by a permeable concrete-block stem wall and a concrete footer is modeled. The slab rests on backfill material; the same material is used to fill the footer trench. A region of undisturbed soil is assumed to extend 10 m beyond and below the footer. The soil is assumed homogeneous and isotropic except for certain simulations in which soil layers of high permeability or radium content are introduced. Depressurization of the house induces a pressure field in the soil and backfill. The Laplace equation, resulting from Darcy's law and the continuity equation, is solved using a steady-state finite-difference model to determine this field. The mass-transport equation is then solved to obtain the diffusive and advective radon entry rates through the slab; the permeable stem wall; gaps at the intersections of the slab, stem wall, and footer; and gaps in the slab. These rates are determined for variable soil, backfill, and stem-wall permeability and radium content, slab-opening width and position, slab and stem-wall diffusivity, and water table depth. The variations in soil permeability and radium content include cases of horizontally stratified soil. We also consider the effect of a gap between the edge of the slab and the stem wall that restricts the passage of soil gas from the stem wall into the house. Calculations indicate that the total radon entry rate is relatively low unless the soil or backfill permeability or radium content is high. Variations in most of the factors, other than the soil permeability and radium content, have only a small effect on the total radon entry rate. However, for a fixed soil permeability, the total radon entry rate may be reduced by a factor of 2 or more by decreasing the backfill permeability, by making the stem wall impermeable and gap-free, (possibly by constructing a one-piece slab/stem-wall/footer), or by increasing the pressure in the interior of the stem wall.

  14. Pentek concrete scabbling system: Baseline report; Summary

    SciTech Connect

    1997-07-31

    The Pentek concrete scabbling system consists of the MOOSE{reg_sign} scabbler, the SQUIRREL{reg_sign}-I and SQUIRREL{reg_sign}-III scabblers, and VAC-PAC. The scabblers are designed to scarify concrete floors and slabs using cross section, tungsten carbide tipped bits. The bits are designed to remove concrete in 3/8 inch increments. The bits are either 9-tooth or demolition type. The scabblers are used with a vacuum system designed to collect and filter the concrete dust and contamination that is removed from the surface. The safety and health evaluation during the human factors assessment focused on two main areas: noise and dust.

  15. Studies on Punching Shear Resistance of Two Way Slab Specimens with Partial Replacement of Cement by GGBS with Different Edge Conditions

    NASA Astrophysics Data System (ADS)

    Nemani, Ravi Dakshina Murthy; Rao, M. V. S.; Grandhe, Veera Venkata Satya Naranyana

    2016-09-01

    The present work is an effort to quantify the punching shear load resistance effect on two way simply supported slab specimens with replacement of cement by Ground Granulated Blast Furnace Slag (GGBS) with different edge conditions at various replacement levels and evaluate its efficiency. GGBS replacement has emerged as a major alternative to conventional concrete and has rapidly drawn the concrete industry attention due to its cement savings, cost savings, environmental and socio-economic benefits. The two way slab specimens were subjected to punching shear load by in house fabricated apparatus. The slab specimens were cast using M30 grade concrete with HYSD bars. The cement was partially replaced with GGBS at different percentages i.e., 0 to 30 % at regular intervals of 10 %. The test results indicate that the two way slab specimens with partial replacement of cement by GGBS exhibit high resistance against punching shear when compared with conventional concretes slab specimens.

  16. Piled-Slab Searches

    DTIC Science & Technology

    2006-12-01

    tinuously as one moves away from the origin (Figure 1). Because such a search is both strategically optimal and locally random, we will refer to it as SOLR ...approximating the inverted cup with a solid composed of n piled slabs. The resulting detection proba- bility will, of course, be smaller than the SOLR ...total effort density in the annulus between Ri−1 and Ri (Figure 2). The total Figure 1. The inverted SOLR cup has the greatest search effort density at

  17. Carbon dioxide slab laser

    SciTech Connect

    Tulip, J.

    1988-01-12

    A gas slab laser is described comprising: first and second elongated electrodes each including a planar light reflecting surface disposed so as to form a light guide only in a plane perpendicular to the planar surface and to define a gas discharge gap therebetween; a laser gas disposed in the gap; and means for applying a radio frequency current between the first and second electrodes to establish a laser-exciting discharge in the laser gas.

  18. Effects of edge restraint on slab behavior. Final report

    SciTech Connect

    Guice, L.K.

    1986-02-01

    This study was performed in conjunction with a Federal Emergency Management Agency program to plan, design, and construct keyworker blast shelters which would be used in high-risk areas of the country during and after a nuclear attack. The shelters considered in this study were box-type structures in which damage is much more likely to occur in the roof slab than in the walls or floor. In this part of the program, the effect of edge restraint on slab behavior was investigated. The primary objective was to determine the effects of partial rotational restraint on slab strength, ductility, and mechanism of failure. Sixteen one-way, reinforced concrete plate elements were tested in a reaction structure under uniform static water pressure.

  19. WORKERS FABRICATE ROOF SLABS FOR MTR BUILDING AT THE CONSTRUCTION ...

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

    WORKERS FABRICATE ROOF SLABS FOR MTR BUILDING AT THE CONSTRUCTION SITE. FORMS WERE MADE OF STEEL. AFTER AN INCH OF CONCRETE HAD BEEN POURED IN THE FORM, A MAT OF REINFORCING STEEL WAS PLACED ON IT. THE REMAINDER OF THE FORM WAS FILLED, AND THE CONCRETE WAS VIBRATED, STRUCK, AND TROWELED. GROOVES AT CORNER WILL HAVE 1/4 INCH RODS WELDED INTO THE EYE OF THE STEEL MAT FOR GROUNDING. INL NEGATIVE NO. 578. Unknown Photographer, 9/1/1950 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  20. View of Flume Tunnel #5 showing an example of concrete ...

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

    View of Flume Tunnel #5 showing an example of concrete flume covered with concrete slabs as it enters a tunnel under the road (FS 502). Looking southwest - Childs-Irving Hydroelectric Project, Childs System, Flume Tunnel No. 5, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

  1. Electro-osmotic techniques for removal of chloride from concrete and for emplacement of concrete sealants

    NASA Astrophysics Data System (ADS)

    Jayaprakash, G. P.; Bukovatz, J. E.; Ramamurti, K.; Gilliland, W. J.

    1982-08-01

    Chloride ion from bridge deck concrete can be removed by application of a direct current potential between bridge reinforcing steel (-) and a copper screen (+) conductor on the bridge surface. Soaring prices of all types of energy would make removal of all chloride prohibitatively expensive. The importance of verification of all electrical connections prior to the treatment is emphasized by the demonstration of concrete cracking when the steel was made a positive instead of a negative electrode. Data on effectiveness of calcium nitrite corrosion inhibitor added to the concrete overlay placed on electrotreated concrete is not extensive due to accidental damage to the test slabs.

  2. A Comparative Study of Strength of Two-Way Rectangular Slabs with and without Openings

    NASA Astrophysics Data System (ADS)

    Ravindra, M.; Rakesh, V.; Rambabu, K.

    2016-09-01

    The present work uses yield-line theory to find the strength of uniformly loaded rectangular reinforced concrete slabs with and without rectangular openings. Five positions of openings are considered, i.e. the slab centre, the slab corner, the centre of a short side, the centre of a long side and the opening eccentric to the slab centre. All possible admissible yield line patterns are considered for all given configurations of the slab subjected to uniformly distributed load keeping in view the basic principles of yield line theory. The ratios of the corresponding lengths of the sides of the opening and the slab are different and sizes of opening up to 0.4× the length of the slab sides are considered. Symmetric edge conditions like continuous slab, simply supported, two long sides continuous and two short sides continuous are considered for various sizes of openings in order to plot the design charts for isotropic reinforcement coefficients only. Affine transformation is also performed for slab with openings.

  3. 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.

  4. SUB-SLAB PROBE INSTALLATION

    EPA Science Inventory

    Sub-slab sampling has become an integral part of vapor intrusion investigations. It is now recommended in guidance documents developed by EPA and most states. A method for sub-slab probe installation was devised in 2002, presented at conferences through 2005, and finally docume...

  5. Shear wave velocities in the Pampean flat-slab region from Rayleigh wave tomography: Implications for slab and upper mantle hydration

    NASA Astrophysics Data System (ADS)

    Porter, Ryan; Gilbert, Hersh; Zandt, George; Beck, Susan; Warren, Linda; Calkins, Josh; Alvarado, Patricia; Anderson, Megan

    2012-11-01

    The Pampean flat-slab region, located in central Argentina and Chile between 29° and 34°S, is considered a modern analog for Laramide flat-slab subduction within western North America. Regionally, flat-slab subduction is characterized by the Nazca slab descending to ˜100 km depth, flattening out for ˜300 km laterally before resuming a more "normal" angle of subduction. Flat-slab subduction correlates spatially with the track of the Juan Fernandez Ridge, and is associated with the inboard migration of deformation and the cessation of volcanism within the region. To better understand flat-slab subduction we combine ambient-noise tomography and earthquake-generated surface wave measurements to calculate a regional 3D shear velocity model for the region. Shear wave velocity variations largely relate to changes in lithology within the crust, with basins and bedrock exposures clearly defined as low- and high-velocity regions, respectively. We argue that subduction-related hydration plays a significant role in controlling shear wave velocities within the upper mantle. In the southern part of the study area, where normal-angle subduction is occurring, the slab is visible as a high-velocity body with a low-velocity mantle wedge above it, extending eastward from the active arc. Where flat-slab subduction is occurring, slab velocities increase to the east while velocities in the overlying lithosphere decrease, consistent with the slab dewatering and gradually hydrating the overlying mantle. The hydration of the slab may be contributing to the excess buoyancy of the subducting oceanic lithosphere, helping to drive flat-slab subduction.

  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. Topological susceptibility from slabs

    NASA Astrophysics Data System (ADS)

    Bietenholz, Wolfgang; de Forcrand, Philippe; Gerber, Urs

    2015-12-01

    In quantum field theories with topological sectors, a non-perturbative quantity of interest is the topological susceptibility χ t. In principle it seems straightforward to measure χ t by means of Monte Carlo simulations. However, for local update algorithms and fine lattice spacings, this tends to be difficult, since the Monte Carlo history rarely changes the topological sector. Here we test a method to measure χ t even if data from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as slabs. Assuming a Gaussian distribution of these charges, this method enables the evaluation of χ t, as we demonstrate with numerical results for non-linear σ-models.

  8. The Effect of Thickness and Mesh Spacing on the Impact Resistance of Ferrocement Slab

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Ashraful Alam, Md; Syamsir, Agusril; Sulleman, Sorefan; Beddu, Salmia; Nasharuddin Mustapha, Kamal; Thiruchelvam, Sivadass; Ismail, Firas B.; Usman, Fathoni; Liyana Mohd Kamal, Nur; Birima, Ahmed H.; Itam, Zarina; Zaroog, O. S.

    2016-03-01

    This paper investigates the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm x 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 height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against slab thickness and mesh reinforcement spacing. There is a good linear correlation between impact resistance of ferrocement against slab thickness and its mesh spacing. The first and ultimate crack impact resistance for 40 mm slab are 2.00 times and 1.84 times respectively against the 20 mm slab with the same mesh spacing. The first and ultimate crack impact resistance for 40 mm slab with 20 mm mesh spacing are 2.24 times and 3.70 times respectively against 50 mm mesh spacing with the same slab thickness. The mesh with higher content of reinforcement provides more contribution to the slab resistance as compare with the thickness.

  9. New evidence about the subduction of the Copiapó ridge beneath South America, and its connection with the Chilean-Pampean flat slab, tracked by satellite GOCE and EGM2008 models

    NASA Astrophysics Data System (ADS)

    Álvarez, Orlando; Gimenez, Mario; Folguera, Andres; Spagnotto, Silvana; Bustos, Emilce; Baez, Walter; Braitenberg, Carla

    2015-11-01

    Satellite-only gravity measurements and those integrated with terrestrial observations provide global gravity field models of unprecedented precision and spatial resolution, allowing the analysis of the lithospheric structure. We used the model EGM2008 (Earth Gravitational Model) to calculate the gravity anomaly and the vertical gravity gradient in the South Central Andes region, correcting these quantities by the topographic effect. Both quantities show a spatial relationship between the projected subduction of the Copiapó aseismic ridge (located at about 27°-30° S), its potential deformational effects in the overriding plate, and the Ojos del Salado-San Buenaventura volcanic lineament. This volcanic lineament constitutes a projection of the volcanic arc toward the retroarc zone, whose origin and development were not clearly understood. The analysis of the gravity anomalies, at the extrapolated zone of the Copiapó ridge beneath the continent, shows a change in the general NNE-trend of the Andean structures to an ENE-direction coincident with the area of the Ojos del Salado-San Buenaventura volcanic lineament. This anomalous pattern over the upper plate is interpreted to be linked with the subduction of the Copiapó ridge. We explore the relation between deformational effects and volcanism at the northern Chilean-Pampean flat slab and the collision of the Copiapó ridge, on the basis of the Moho geometry and elastic thicknesses calculated from the new satellite GOCE data. Neotectonic deformations interpreted in previous works associated with volcanic eruptions along the Ojos del Salado-San Buenaventura volcanic lineament is interpreted as caused by crustal doming, imprinted by the subduction of the Copiapó ridge, evidenced by crustal thickening at the sites of ridge inception along the trench. Finally, we propose that the Copiapó ridge could have controlled the northern edge of the Chilean-Pampean flat slab, due to higher buoyancy, similarly to the control

  10. Instrumentation by distributed optical fiber sensors of a new ballastless track structure

    NASA Astrophysics Data System (ADS)

    Chapeleau, Xavier; Cottineau, Louis-Marie; Sedran, Thierry; Gueguen, Ivan; Cailliau, Joël

    2013-04-01

    While relatively expensive to build, ballastless track structures are presently seen as an attractive alternative to conventional ballast. With its service life of at least 60 years, they require little maintenance and hence they offer great availability. Other reasons for using ballastless tracks instead of ballasted tracks are the lack of suitable ballast material and the need of less noise and vibration for high-speed, in particularly. A new ballastless track structure has been designed to be circulated up to 300km/h, with a target life of 100 years. It is an interoperable way on concrete slabs that are cast-in-place and slip formed. This structure has been built and tested at the scale one in our laboratory. Indeed, ten millions cyclic loads were applied at 2.5Hz to evaluate the fatigue behaviour under selected mechanical and thermal conditions. To monitor the thermo-mechanical behavior of this new structure and to verify the numerical simulations used for its design, a lot of sensors have been embedded. In particularly, we have tested an optical fiber as distributed sensors to measure strain distribution in the railway model. This sensor can also be used to detect, localize and monitor cracks in concrete slabs. The optical fiber sensing technique ("Rayleigh technique") used in this experimentation has a centimetric spatial resolution which allows to measure complex strain profiles unlike electrical strain gauges which only give local information. Firstly, optical cables used as sensors have been successfully embedded and attached to the reinforcing steel bars in the structure. We have noted that they are resistant enough to resist concrete pouring and working activities. Secondly, strains measured by conventional strain gauges has confirmed the quality of the strain profiles measurements obtained by optical fiber sensors. Moreover, we have found a good agreement between experimental profiles measurements and those obtained by numerical simulations. Early

  11. New Packaging for Amplifier Slabs

    SciTech Connect

    Riley, M.; Thorsness, C.; Suratwala, T.; Steele, R.; Rogowski, G.

    2015-03-18

    The following memo provides a discussion and detailed procedure for a new finished amplifier slab shipping and storage container. The new package is designed to maintain an environment of <5% RH to minimize weathering.

  12. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion.

    PubMed

    Bartholomew, Paul D; Guthrie, W Spencer; Mazzeo, Brian A

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  13. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion

    NASA Astrophysics Data System (ADS)

    Bartholomew, Paul D.; Guthrie, W. Spencer; Mazzeo, Brian A.

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  14. 29 CFR 1926.705 - Requirements for lift-slab construction operations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 8 2014-07-01 2014-07-01 false Requirements for lift-slab construction operations. 1926.705 Section 1926.705 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete...

  15. 29 CFR 1926.705 - Requirements for lift-slab construction operations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Requirements for lift-slab construction operations. 1926.705 Section 1926.705 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete...

  16. 29 CFR 1926.705 - Requirements for lift-slab construction operations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 8 2013-07-01 2013-07-01 false Requirements for lift-slab construction operations. 1926.705 Section 1926.705 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete...

  17. 29 CFR 1926.705 - Requirements for lift-slab construction operations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Requirements for lift-slab construction operations. 1926.705 Section 1926.705 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete...

  18. 29 CFR 1926.705 - Requirements for lift-slab construction operations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 8 2012-07-01 2012-07-01 false Requirements for lift-slab construction operations. 1926.705 Section 1926.705 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete...

  19. Quantification of vapor intrusion pathways into a slab-on-ground building under varying environmental conditions.

    PubMed

    Patterson, Bradley M; Davis, Greg B

    2009-02-01

    Potential hydrocarbon-vapor intrusion pathways into a building through a concrete slab-on-ground were investigated and quantified under a variety of environmental conditions to elucidate the potential mechanisms for indoor air contamination. Vapor discharge from the uncovered open ground soil adjacent to the building and subsequent advection into the building was unlikely due to the low soil-gas concentrations at the edge of the building as a result of aerobic biodegradation of hydrocarbon vapors. When the building's interior was under ambient pressure, a flux of vapors into the building due to molecular diffusion of vapors through the building's concrete slab (cyclohexane 11 and methylcyclohexane 31 mg m(-2) concrete slab day(-1)) and short-term (up to 8 h) cyclical pressure-driven advection of vapors through an artificial crack (cyclohexane 4.2 x 10(3) and methylcyclohexane 1.2 x 10(4) mg m(-2) cracks day(-1)) was observed. The average subslab vapor concentration under the center of the building was 25,000 microg L(-1). Based on the measured building's interiorvapor concentrations and the building's air exchange rate of 0.66 h(-1), diffusion of vapors through the concrete slab was the dominantvapor intrusion pathway and cyclical pressure exchanges resulted in a near zero advective flux. When the building's interior was under a reduced pressure (-12 Pa), advective transport through cracks or gaps in the concrete slab (cyclohexane 340 and methylcyclohexane 1100 mg m(-2) cracks day(-1)) was the dominant vapor intrusion pathway.

  20. The Effect of Mortar Grade and Thickness on the Impact Resistance of Ferrocement Slab

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Syamsir, Agusril; Nasharuddin Mustapha, Kamal; Sulleman, Sorefan; Beddu, Salmia; Thiruchelvam, Sivadass; Ismail, Firas B.; Usman, Fathoni; 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 mesh spacing on the impact of ferrocement 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 height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against the mortar grade and slab thickness. There is a good linear correlation between impact resistance of ferrocement against the mortar grade and the thickness of ferrocement slab. The first and ultimate crack impact resistance of mortar grade 43 (for 40 mm thick slab with mesh reinforcement) are 1.60 times and 1.53 times respectively against the mortar grade 17 slab (of same thickness with mesh reinforcement). The first and ultimate crack impact resistance for 40 mm thick slab (mortar grade 43 with mesh reinforcement) are 3.55 times and 4.49 times respectively against the 20 mm thick slab (of same mortar grade with mesh reinforcement).

  1. Waste tank roof slab resistance to sudden loads

    SciTech Connect

    Yau, W.W.F.

    1988-03-02

    The Department of Energy has requested that the Safety Analysis Report include an analysis of a tank top collapse event due to equipment overload. The overload is defined as a 3-ton truck plunging suddenly onto the tank roof. This memorandum reports the findings of a simplified analysis of the roof structure of a Type III waste tank. Based on a simplified and conservative analysis of the roof slab of a Type III waste tank, the reinforced concrete design is resistant to the impact loading of a 3-ton truck with a safety factor of at least five against large scale inelastic deformation.

  2. Phase 2 microwave concrete decontamination results

    SciTech Connect

    White, T.L.; Foster, D. Jr.; Wilson, C.T.; Schaich, C.R.

    1995-04-01

    The authors report on the results of the second phase of a four-phase program at Oak Ridge National Laboratory to develop a system to decontaminate concrete using microwave energy. The microwave energy is directed at the concrete surface through the use of an optimized wave guide antenna, or applicator, and this energy rapidly heats the free water present in the interstitial spaces of the concrete matrix. The resulting steam pressure causes the surface to burst in much the same way popcorn pops in a home microwave oven. Each steam explosion removes several square centimeters of concrete surface that are collected by a highly integrated wave guide and vacuum system. The authors call this process the microwave concrete decontamination, or MCD, process. In the first phase of the program the principle of microwaves concrete removal concrete surfaces was demonstrated. In these experiments, concrete slabs were placed on a translator and moved beneath a stationary microwave system. The second phase demonstrated the ability to mobilize the technology to remove the surfaces from concrete floors. Area and volume concrete removal rates of 10.4 cm{sup 2}/s and 4.9 cm{sup 3}/S, respectively, at 18 GHz were demonstrated. These rates are more than double those obtained in Phase 1 of the program. Deeper contamination can be removed by using a longer residence time under the applicator to create multiple explosions in the same area or by taking multiple passes over previously removed areas. Both techniques have been successfully demonstrated. Small test sections of painted and oil-soaked concrete have also been removed in a single pass. Concrete with embedded metal anchors on the surface has also been removed, although with some increased variability of removal depth. Microwave leakage should not pose any operational hazard to personnel, since the observed leakage was much less than the regulatory standard.

  3. Development of a Leave-in-Place Slab Edge Insulating Form System

    SciTech Connect

    Marc Hoeschele; Eric Lee

    2009-08-31

    Concrete slabs represent the primary foundation type in residential buildings in the fast-growing markets throughout the southern and southwestern United States. Nearly 75% of the 2005 U.S. population growth occurred in these southern tier states. Virtually all of these homes have uninsulated slab perimeters that transfer a small, but steady, flow of heat from conditioned space to outdoors during the heating season. It is estimated that new home foundations constructed each year add 0.016 quads annually to U.S. national energy consumption; we project that roughly one quarter of this amount can be attributed to heat loss through the slab edge and the remaining three quarters to deep ground transfers, depending upon climate. With rising concern over national energy use and the impact of greenhouse gas emissions, it is becoming increasingly imperative that all cost-effective efforts to improve building energy efficiency be implemented. Unlike other building envelope components that have experienced efficiency improvements over the years, slab edge heat loss has largely been overlooked. From our vantage point, a marketable slab edge insulation system would offer significant benefits to homeowners, builders, and the society as a whole. Conventional slab forming involves the process of digging foundation trenches and setting forms prior to the concrete pour. Conventional wood form boards (usually 2 x 10's) are supported by vertical stakes on the outer form board surface, and by supporting 'kickers' driven diagonally from the top of the form board into soil outside the trench. Typically, 2 x 10's can be used only twice before they become waste material, contributing to an additional 400 pounds of construction waste per house. Removal of the form boards and stakes also requires a follow-up trip to the jobsite by the concrete subcontractor and handling (storage/disposal) of the used boards. In the rare cases where the slab is insulated (typically custom homes with radiant

  4. Higher order modes in photonic crystal slabs.

    PubMed

    Gansch, Roman; Kalchmair, Stefan; Detz, Hermann; Andrews, Aaron M; Klang, Pavel; Schrenk, Werner; Strasser, Gottfried

    2011-08-15

    We present a detailed investigation of higher order modes in photonic crystal slabs. In such structures the resonances exhibit a blue-shift compared to an ideal two-dimensional photonic crystal, which depends on the order of the slab mode and the polarization. By fabricating a series of photonic crystal slab photo detecting devices, with varying ratios of slab thickness to photonic crystal lattice constant, we are able to distinguish between 0th and 1st order slab modes as well as the polarization from the shift of resonances in the photocurrent spectra. This method complements the photonic band structure mapping technique for characterization of photonic crystal slabs.

  5. Pentek concrete scabbling system: Baseline report

    SciTech Connect

    1997-07-31

    The Pentek scabbling technology was tested at Florida International University (FIU) and is being evaluated as a baseline technology. This report evaluates it for safety and health issues. It is a commercially available technology and has been used for various projects at locations throughout the country. The Pentek concrete scabbling system consisted of the MOOSE{reg_sign}, SQUIRREL{reg_sign}-I, and SQUIRREL{reg_sign}-III scabblers. The scabblers are designed to scarify concrete floors and slabs using cross-section, tungsten carbide tipped bits. The bits are designed to remove concrete in 318 inch increments. The bits are either 9-tooth or demolition type. The scabblers are used with a vacuum system designed to collect and filter the concrete dust and contamination that is removed from the surface. The safety and health evaluation during the human factors assessment focused on two main areas: noise and dust.

  6. The Dynamics of Double Slab Subduction

    NASA Astrophysics Data System (ADS)

    Holt, A. F.; Royden, L. H.; Becker, T. W.

    2017-01-01

    We use numerical models to investigate the dynamics of two interacting slabs with parallel trenches. Cases considered are: a single slab reference, outward dipping slabs (out-dip), inward dipping slabs (in-dip), and slabs dipping in the same direction (same-dip). Where trenches converge over time (same-dip and out-dip systems), large positive dynamic pressures in the asthenosphere are generated beneath the middle plate, and large trench-normal extensional forces are transmitted through the middle plate. This results in slabs that dip away from the middle plate at depth, independent of trench geometry. The single slab, the front slab in the same-dip case, and both out-dip slabs undergo trench retreat and exhibit stable subduction. However, slabs within the other double subduction systems tend to completely overturn at the base of the upper mantle, and exhibit either trench advance (rear slab in same-dip), or near-stationary trenches (in-dip). For all slabs, the net slab-normal dynamic pressure at 330 km depth is nearly equal to the slab normal force induced by slab buoyancy. For double subduction, the net outward force on the slabs due to dynamic pressure from the asthenosphere is effectively counterbalanced by the net extensional force transmitted through the middle plate. Thus, dynamic pressure at depth, inter-plate coupling, and lithospheric stresses are closely linked and their effects cannot be isolated. Our results provide insights into both the temporal evolution of double slab systems on Earth and, more generally, how the various components of subduction systems, from mantle flow/pressure to inter-plate coupling, are dynamically linked.

  7. 7. View showing reinforced concrete arch, east approach. The 591 ...

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

    7. View showing reinforced concrete arch, east approach. The 591 foot three-hinge steel arch that spans the Cuyahoga River is flanked by twelve such approach arches. Each concrete arch consists of four arch ribs, which support the beam and slab streetcar deck on spandrel columns. As the photograph illustrates, the spandrel columns continue above the lower deck to support the roadway. - Detroit Superior High Level Bridge, Cleveland, Cuyahoga County, OH

  8. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-04

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.

  9. Emplacement of the Kodiak batholith and slab-window migration

    USGS Publications Warehouse

    Farris, David W.; Haeussler, P.; Friedman, R.; Paterson, Scott R.; Saltus, R.W.; Ayuso, R.

    2006-01-01

    The Kodiak batholith is one of the largest, most elongate intrusive bodies in the forearc Sanak-Baranof plutonic belt located in southern Alaska. This belt is interpreted to have formed during the subduction of an oceanic spreading center and the associated migration of a slab window. Individual plutons of the Kodiak batholith track the location and evolution of the underlying slab window. Six U/Pb zircon ages from the axis of the batholith exhibit a northeastward-decreasing age progression of 59.2 ± 0.2 Ma at the southwest end to 58.4 ± 0.2 Ma at the northeast tip. The trench-parallel rate of age progression is within error of the average slab-window migration rate for the entire Sanak-Baranof belt (~19 cm/yr). Structural relationships, U/Pb ages, and a model of new gravity data indicate that magma from the Kodiak batholith ascended 5-10 km as a northeastward-younging series of 1-8-km-diameter viscoelastic diapirs. Individual plutons ascended by multiple emplacement mechanisms including downward flow, collapse of wall rock, stoping, and diking. Stokes flow xenolith calculations suggest ascent rates of 5-100 m/yr and an effective magmatic viscosity of 107-108 Pa s. Pre-existing structural or lithologic heterogeneities did not dominantly control the location of the main batholith. Instead, its location was determined by migration of the slab window at depth. 

  10. Influence of Elevated Temperatures on Pet-Concrete Properties

    NASA Astrophysics Data System (ADS)

    Albano, C.; Camacho, N.; Hernández, M.; Matheus, A.; Gutiérrez, A.

    2008-08-01

    Lightweight aggregate is an important material in reducing the unit weight of concrete complying with special concrete structures of large high-rise buildings. Besides, the use of recycled PET bottles as lightweight aggregate in concrete is an effective contribution for environment preservation. So, the objective of the present work was to study experimentally the flexural strength of the PET -concrete blends and the thermal degradation of the PET in the concrete, when the blends with 10 and 20% in volume of PET were exposed to different temperatures (200, 400, 600 °C). The flexural strength of concrete-PET exposed to a heat source is strongly dependent on the temperature, water/cement ratio, as well as the content and particle size of PET. However, the activation energy is affected by the temperature, location of the PET particles on the slabs and the water/cement ratio. Higher water content originates thermal and hydrolytic degradation on the PET, while on the concrete, a higher vapor pressure which causes an increase in crack formation. The values of the activation energy are higher on the center of the slabs than on the surface, since concrete is a poor heat conductor.

  11. Investigation of Electromagnetic Wave Absorber Based on Carbon Fiber Reinforced Aerated Concrete, Using Time-Domain Method

    NASA Astrophysics Data System (ADS)

    Laukaitis, A.; Sinica, M.; Balevičius, S.; Levitas, B.

    2008-03-01

    The electromagnetic wave absorbers prepared from autoclaved aerated concrete containing carbon fibers as additions in the shape of slabs with pyramids cut on one plane of these slabs were tested using dc microwave source and the time-domain method. It was demonstrated that autoclaved aerated concrete allows one to fabricate electromagnetic wave absorbers which have a reflection coefficient up to -30 dB in the frequency range from 2 GHz to 18 GHz.

  12. Modeling the electrokinetic decontamination of concrete

    SciTech Connect

    Harris, M.T.; DePaoli, D.W.; Ally, M.R.

    1997-01-01

    The decontamination of concrete is a major concern in many Department of (DOE) facilities. Numerous techniques (abrasive methods, manual methods, ultrasonics, concrete surface layer removal, chemical extraction methods, etc.) have been used to remove radioactive contamination from the surface of concrete. Recently, processes that are based on electrokinetic phenomena have been developed to decontaminate concrete. Electrokinetic decontamination has been shown to remove from 70 to over 90% of the surface radioactivity. To evaluate and improve the electrokinetic processes, a model has been developed to simulate the transport of ionic radionuclei constituents through the pores of concrete and into the anolyte and catholyte. The model takes into account the adsorption and desorption kinetics of the radionuclei from the pore walls, and ion transport by electro-osmosis, electromigration, and diffusion. A numerical technique, orthogonal collocation, is used to simultaneously solve the governing convective diffusion equations for a porous concrete slab and the current density equation. This paper presents the theoretical framework of the model and the results from the computation of the dynamics of ion transport during electrokinetic treatment of concrete. The simulation results are in good agreement with experimental data.

  13. 80. Laurel Fork Creek Bridge #2. Example of a concrete ...

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

    80. Laurel Fork Creek Bridge #2. Example of a concrete slab bridge with T beams. It was built in 1937 and the wing walls were faced with stone to blend with its surroundings. Looking northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  14. 129. Julian Price Memorial Park. Price Lake Dam. A concrete ...

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

    129. Julian Price Memorial Park. Price Lake Dam. A concrete slab bridge crosses the top of the dam impounding a forty-seven acre lake. Looking west. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  15. Preface: Deep Slab and Mantle Dynamics

    NASA Astrophysics Data System (ADS)

    Suetsugu, Daisuke; Bina, Craig R.; Inoue, Toru; Wiens, Douglas A.

    2010-11-01

    We are pleased to publish this special issue of the journal Physics of the Earth and Planetary Interiors entitled "Deep Slab and Mantle Dynamics". This issue is an outgrowth of the international symposium "Deep Slab and Mantle Dynamics", which was held on February 25-27, 2009, in Kyoto, Japan. This symposium was organized by the "Stagnant Slab Project" (SSP) research group to present the results of the 5-year project and to facilitate intensive discussion with well-known international researchers in related fields. The SSP and the symposium were supported by a Grant-in-Aid for Scientific Research (16075101) from the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government. In the symposium, key issues discussed by participants included: transportation of water into the deep mantle and its role in slab-related dynamics; observational and experimental constraints on deep slab properties and the slab environment; modeling of slab stagnation to constrain its mechanisms in comparison with observational and experimental data; observational, experimental and modeling constraints on the fate of stagnant slabs; eventual accumulation of stagnant slabs on the core-mantle boundary and its geodynamic implications. This special issue is a collection of papers presented in the symposium and other papers related to the subject of the symposium. The collected papers provide an overview of the wide range of multidisciplinary studies of mantle dynamics, particularly in the context of subduction, stagnation, and the fate of deep slabs.

  16. What really causes flat slab subduction?

    NASA Astrophysics Data System (ADS)

    Manea, V. C.; Perez-Gussinye, M.; Manea, M.

    2014-12-01

    How flat slab geometries are generated has been long debated. It has been suggested thattrenchward motion of thick cratons in some areas of South America and Cenozoic NorthAmerica progressively closed the asthenospheric wedge and induced flat subduction. Here wedevelop time-dependent numerical experiments to explore how trenchward motion of thickcratons may result in flat subduction. We find that as the craton approaches the trench andthe wedge closes, two opposite phenomena control slab geometry: the suction between oceanand continent increases, favoring slab flattening, while the mantle confined within the closingwedge dynamically pushes the slab backward and steepens it. When the slab retreats, as inthe Peru and Chile flat slabs, the wedge closure rate and dynamic push are small and suctionforces generate, in some cases, flat subduction. We model the past 30 m.y. of subduction in theChilean flat slab area and demonstrate that trenchward motion of thick lithosphere, 200-300km, currently ~700-800 km away from the Peru-Chile Trench, reproduces a slab geometrythat fits the stress pattern, seismicity distribution, and temporal and spatial evolution ofdeformation and volcanism in the region. We also suggest that varying trench kinematics mayexplain some differing slab geometries along South America. When the trench is stationaryor advances, the mantle flow within the closing wedge strongly pushes the slab backward andsteepens it, possibly explaining the absence of flat subduction in the Bolivian orocline.

  17. Noise reduction in urban LRT networks by combining track based solutions.

    PubMed

    Vogiatzis, Konstantinos; Vanhonacker, Patrick

    2016-10-15

    The overall objective of the Quiet-Track project is to provide step-changing track based noise mitigation and maintenance schemes for railway rolling noise in LRT (Light Rail Transit) networks. WP 4 in particular focuses on the combination of existing track based solutions to yield a global performance of at least 6dB(A). The validation was carried out using a track section in the network of Athens Metro Line 1 with an existing outside concrete slab track (RHEDA track) where high airborne rolling noise was observed. The procedure for the selection of mitigation measures is based on numerical simulations, combining WRNOISE and IMMI software tools for noise prediction with experimental determination of the required track and vehicle parameters (e.g., rail and wheel roughness). The availability of a detailed rolling noise calculation procedure allows for detailed designing of measures and of ranking individual measures. It achieves this by including the modelling of the wheel/rail source intensity and of the noise propagation with the ability to evaluate the effect of modifications at source level (e.g., grinding, rail dampers, wheel dampers, change in resiliency of wheels and/or rail fixation) and of modifications in the propagation path (absorption at the track base, noise barriers, screening). A relevant combination of existing solutions was selected in the function of the simulation results. Three distinct existing solutions were designed in detail aiming at a high rolling noise attenuation and not affecting the normal operation of the metro system: Action 1: implementation of sound absorbing precast elements (panel type) on the track bed, Action 2: implementation of an absorbing noise barrier with a height of 1.10-1.20m above rail level, and Action 3: installation of rail dampers. The selected solutions were implemented on site and the global performance was measured step by step for comparison with simulations.

  18. Response of structural concrete elements to severe impulsive loads

    NASA Astrophysics Data System (ADS)

    Krauthammer, T.; Shanaa, H. M.; Assadi, A.

    1994-10-01

    The behavior and response of structural concrete elements under severe short duration dynamic loads was investigated numerically. The analytical approach utilized the Timoshenko beam theory for the analysis of reinforced concrete beams and one-way slabs. Nonlinear material models were used to derive the flexural and shear resistances, and the differential equations of the Timoshenko beam theory were solved numerically by applying the finite difference technique. A simplified approach was developed for estimating the strain rate in structural concrete members, and the corresponding strain rate effects on the strength of the steel and concrete were incorporated into the analysis. Detailed failure criteria were established for predicting the collapse of structural concrete members. Five cases subjected to localized impact loads and eleven cases subjected to distributed explosive loads were analyzed, and the results were compared to experimental data obtained by other investigators.

  19. 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.

  20. Slab melting versus slab dehydration in subduction-zone magmatism

    PubMed Central

    Mibe, Kenji; Kawamoto, Tatsuhiko; Matsukage, Kyoko N.; Fei, Yingwei; Ono, Shigeaki

    2011-01-01

    The second critical endpoint in the basalt-H2O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770 °C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones. PMID:21536910

  1. Slab melting versus slab dehydration in subduction-zone magmatism.

    PubMed

    Mibe, Kenji; Kawamoto, Tatsuhiko; Matsukage, Kyoko N; Fei, Yingwei; Ono, Shigeaki

    2011-05-17

    The second critical endpoint in the basalt-H(2)O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770 °C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones.

  2. Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

    NASA Astrophysics Data System (ADS)

    Yao, Cui; Nakashima, Masayoshi

    2012-03-01

    Steel fiber reinforced cementitous composites (SFRCC) is a promising material with high strength in both compression and tension compared with normal concrete. The ductility is also greatly improved because of 6% volume portion of straight steel fibers. A steel beam-column connection with Steel fiber reinforced cementitous composites (SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld. The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs. The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams. The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test. Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.

  3. Damage assessment of a two-span RC slab using wavelet analysis

    NASA Astrophysics Data System (ADS)

    Zhu, X. Q.; Hao, H.

    2007-04-01

    A two-span RC slab that measures 6400mm×800mm×100mm with 3000mm spans and 200mm overhang on each end was tested to failure in the laboratory. UB sections were used as supports. The slab was designed according to the moment redistribution method with 11 N6 bars at 75mm centres for both positive and negative reinforcement. The slab was incrementally loaded at the middle of each span to different load levels to create crack damage using four-point loading. Twelve loading stages were performed with increasing maximum load level. Two load cells are used to record the static loads on left and right spans. The crack locations and lengths were monitored in addition to the displacement measurements. Four displacement transducers are located at two sides of the middle of each span to measure the deflection under the static load. Three sets of accelerometers with nine of them in each set are evenly distributed along the slab to measure the dynamic responses. The measured responses from the RC slab in different cracked damage states are analyzed using the wavelet transform (WT). The damping ratios and instantaneous frequency are extracted. The results show that the damping ratio and instantaneous frequency changes could be two good indicators of damage in the reinforced concrete structure.

  4. 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.

  5. Subducting slabs: Jellyfishes in the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Loiselet, Christelle; Braun, Jean; Husson, Laurent; Le Carlier de Veslud, Christian; Thieulot, Cedric; Yamato, Philippe; Grujic, Djordje

    2010-08-01

    The constantly improving resolution of geophysical data, seismic tomography and seismicity in particular, shows that the lithosphere does not subduct as a slab of uniform thickness but is rather thinned in the upper mantle and thickened around the transition zone between the upper and lower mantle. This observation has traditionally been interpreted as evidence for the buckling and piling of slabs at the boundary between the upper and lower mantle, where a strong contrast in viscosity may exist and cause resistance to the penetration of slabs into the lower mantle. The distribution and character of seismicity reveal, however, that slabs undergo vertical extension in the upper mantle and compression near the transition zone. In this paper, we demonstrate that during the subduction process, the shape of low viscosity slabs (1 to 100 times more viscous than the surrounding mantle) evolves toward an inverted plume shape that we coin jellyfish. Results of a 3D numerical model show that the leading tip of slabs deform toward a rounded head skirted by lateral tentacles that emerge from the sides of the jellyfish head. The head is linked to the body of the subducting slab by a thin tail. A complete parametric study reveals that subducting slabs may achieve a variety of shapes, in good agreement with the diversity of natural slab shapes evidenced by seismic tomography. Our work also suggests that the slab to mantle viscosity ratio in the Earth is most likely to be lower than 100. However, the sensitivity of slab shapes to upper and lower mantle viscosities and densities, which remain poorly constrained by independent evidence, precludes any systematic deciphering of the observations.

  6. Subducting Slabs: Jellyfishes in the Earth's Mantle

    NASA Astrophysics Data System (ADS)

    Loiselet, C.; Braun, J.; Husson, L.; Le Carlier de Veslud, C.; Thieulot, C.; Yamato, P.; Grujic, D.

    2010-12-01

    The constantly improving resolution of geophysical data, seismic tomography and seismicity in particular, shows that the lithosphere does not subduct as a slab of uniform thickness but is rather thinned in the upper mantle and thickened around the transition zone between the upper and lower mantle. This observation has traditionally been interpreted as evidence for the buckling and piling of slabs at the boundary between the upper and lower mantle, where a strong contrast in viscosity may exist and cause resistance to the penetration of slabs into the lower mantle. The distribution and character of seismicity reveal, however, that slabs undergo vertical extension in the upper mantle and compression near the transition zone. In this paper, we demonstrate that during the subduction process, the shape of low viscosity slabs (1 to 100 times more viscous than the surrounding mantle) evolves toward an inverted plume shape that we coin jellyfish. Results of a 3D numerical model show that the leading tip of slabs deform toward a rounded head skirted by lateral tentacles that emerge from the sides of the jellyfish head. The head is linked to the body of the subducting slab by a thin tail. A complete parametric study reveals that subducting slabs may achieve a variety of shapes, in good agreement with the diversity of natural slab shapes evidenced by seismic tomography. Our work also suggests that the slab to mantle viscosity ratio in the Earth is most likely to be lower than 100. However, the sensitivity of slab shapes to upper and lower mantle viscosities and densities, which remain poorly constrained by independent evidence, precludes any systematic deciphering of the observations.

  7. Sensitivity study of neutron transport through standard and rebar concrete

    SciTech Connect

    Bhuiyan, S.I.; Roussin, R.W.; Lucius, J.L.

    1982-01-01

    An investigation is under way at ORNL to (1) develop a data base pertinent to the transport of neutrons through thick concrete shields, (2) use the data base in an energy group boundary selection and collapsing scheme, and (3) develop a simple methodology to access the data base to provide rapid solutions to practical shielding problems. This paper describes work carried out to fulfill objective (1), the work consisting of calculations of the transport of fission neutrons through 1- and 2-m-thick slabs of standard concrete and rebar (steel-reinforced) concrete, together with calculations of the sensitivities of the results to total, absorption, and elastic cross sections. The transport calculations were performed with the one-dimensional discrete ordinates code ANISN in both forward and adjoint modes. The DLC-41C/VITAMIN-C cross-section library (171 neutron, 36 gamma groups) was employed, with a P/sub 3/ cross-section expansion and an S/sub 16/ angular quadrature. In all cases the fission source was assumed to be distributed within the first 1-cm thickness of the slab and the detector was assumed to occupy the last 1-cm thickness of the slab. For the rebar concrete the slab constituents were homogenized, with the horizontal and vertical No. 11 reinforcing steel rods comprising 7.6 vol. % of the slab. The quantity calculated was the absorbed dose rate, and care was taken in the mesh interval selection and source description to ensure agreement between the forward and adjoint results to within 0.02%.

  8. The slab geometry laser. I - Theory

    NASA Technical Reports Server (NTRS)

    Eggleston, J. M.; Kane, T. J.; Kuhn, K.; Byer, R. L.; Unternahrer, J.

    1984-01-01

    Slab geometry solid-state lasers offer significant performance improvements over conventional rod-geometry lasers. A detailed theoretical description of the thermal, stress, and beam-propagation characteristics of a slab laser is presented. The analysis includes consideration of the effects of the zig-zag optical path, which eliminates thermal and stress focusing and reduces residual birefringence.

  9. Slab stagnation and detachment under northeast China

    NASA Astrophysics Data System (ADS)

    Honda, Satoru

    2016-03-01

    Results of tomography models around the Japanese Islands show the existence of a gap between the horizontally lying (stagnant) slab extending under northeastern China and the fast seismic velocity anomaly in the lower mantle. A simple conversion from the fast velocity anomaly to the low-temperature anomaly shows a similar feature. This feature appears to be inconsistent with the results of numerical simulations on the interaction between the slab and phase transitions with temperature-dependent viscosity. Such numerical models predict a continuous slab throughout the mantle. I extend previous analyses of the tomography model and model calculations to infer the origins of the gap beneath northeastern China. Results of numerical simulations that take the geologic history of the subduction zone into account suggest two possible origins for the gap: (1) the opening of the Japan Sea led to a breaking off of the otherwise continuous subducting slab, or (2) the western edge of the stagnant slab is the previous subducted ridge, which was the plate boundary between the extinct Izanagi and the Pacific plates. Origin (2) suggesting the present horizontally lying slab has accumulated since the ridge subduction, is preferable for explaining the present length of the horizontally lying slab in the upper mantle. Numerical models of origin (1) predict a stagnant slab in the upper mantle that is too short, and a narrow or non-existent gap. Preferred models require rather stronger flow resistance of the 660-km phase change than expected from current estimates of the phase transition property. Future detailed estimates of the amount of the subducted Izanagi plate and the present stagnant slab would be useful to constrain models. A systematic along-arc variation of the slab morphology from the northeast Japan to Kurile arcs is also recognized, and its understanding may constrain the 3D mantle flow there.

  10. Cretaceous Arctic magmatism: Slab vs. plume? Or slab and plume?

    NASA Astrophysics Data System (ADS)

    Gottlieb, E. S.; Miller, E. L.; Andronikov, A. V.; Brumley, K.; Mayer, L. A.; Mukasa, S. B.

    2010-12-01

    Tectonic models for the Cretaceous paleogeographic evolution of the Arctic Ocean and its adjacent landmasses propose that rifting in the Amerasia Basin (AB) began in Jura-Cretaceous time, accompanied by the development of the High Arctic Large Igneous Province (HALIP). During the same timespan, deformation and slab-related magmatism, followed by intra-arc rifting, took place along the Pacific side of what was to become the Arctic Ocean. A compilation and comparison of the ages, characteristics and space-time variation of circum-Arctic magmatism allows for a better understanding of the role of Pacific margin versus Arctic-Atlantic plate tectonics and the role of plume-related magmatism in the origin of the Arctic Ocean. In Jura-Cretaceous time, an arc built upon older terranes overthrust the Arctic continental margins of North America and Eurasia, shedding debris into foreland basins in the Brooks Range, Alaska, across Chukotka, Russia, to the Lena Delta and New Siberian Islands region of the Russian Arctic. These syn-tectonic sediments have some common sources (e.g., ~250-300 Ma magmatic rocks) as determined by U-Pb detrital zircon geochronology. They are as young as Valanginian-Berriasian (~136 Ma, Gradstein et al., 2004) and place a lower limit on the age of formation of the AB. Subsequent intrusions of granitoid plutons, inferred to be ultimately slab-retreat related, form a belt along the far eastern Russian Arctic continental margin onto Seward Peninsula and have yielded a continuous succession of zircon U-Pb ages from ~137-95 Ma (n=28) and a younger suite ~91-82 Ma (n=16). All plutons dated were intruded in an extensional tectonic setting based on their relations to wall-rock deformation. Regional distribution of ages shows a southward migration of the locus of magmatism during Cretaceous time. Basaltic lavas as old as 130 Ma and as young as 80 Ma (40Ar/39Ar)) erupted across the Canadian Arctic Islands, Svalbard and Franz Josef Land and are associated with

  11. 4. AN IMAGE, LOOKING NORTH WEST, OF THE TRACK, BALLAST ...

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

    4. AN IMAGE, LOOKING NORTH WEST, OF THE TRACK, BALLAST AND CONCRETE BALUSTRADES, SHOWING HOW THE BRIDGE WAS DESIGNED TO TAKE TWO SETS OF TRACK. - Vandalia Railroad Bridge, Spanning U.S. Route 40, Indianapolis, Marion County, IN

  12. Refractory concretes

    DOEpatents

    Holcombe, Jr., Cressie E.

    1979-01-01

    Novel concrete compositions comprise particles of aggregate material embedded in a cement matrix, said cement matrix produced by contacting an oxide selected from the group of Y.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Sm.sub.2 O.sub.3, Eu.sub.2 O.sub.3 and Gd.sub.2 O.sub.3 with an aqueous solution of a salt selected from the group of NH.sub.4 NO.sub.3, NH.sub.4 Cl, YCl.sub.3 and Mg(NO.sub.3).sub.2 to form a fluid mixture; and allowing the fluid mixture to harden.

  13. Tracking dynamic team activity

    SciTech Connect

    Tambe, M.

    1996-12-31

    AI researchers are striving to build complex multi-agent worlds with intended applications ranging from the RoboCup robotic soccer tournaments, to interactive virtual theatre, to large-scale real-world battlefield simulations. Agent tracking - monitoring other agent`s actions and inferring their higher-level goals and intentions - is a central requirement in such worlds. While previous work has mostly focused on tracking individual agents, this paper goes beyond by focusing on agent teams. Team tracking poses the challenge of tracking a team`s joint goals and plans. Dynamic, real-time environments add to the challenge, as ambiguities have to be resolved in real-time. The central hypothesis underlying the present work is that an explicit team-oriented perspective enables effective team tracking. This hypothesis is instantiated using the model tracing technology employed in tracking individual agents. Thus, to track team activities, team models are put to service. Team models are a concrete application of the joint intentions framework and enable an agent to track team activities, regardless of the agent`s being a collaborative participant or a non-participant in the team. To facilitate real-time ambiguity resolution with team models: (i) aspects of tracking are cast as constraint satisfaction problems to exploit constraint propagation techniques; and (ii) a cost minimality criterion is applied to constrain tracking search. Empirical results from two separate tasks in real-world, dynamic environments one collaborative and one competitive - are provided.

  14. Detecting slab structure beneath the Mediterranean

    NASA Astrophysics Data System (ADS)

    Miller, Meghan S.; Sun, Daoyuan; Piana Agostinetti, Nicola

    2013-04-01

    The presence of subducted slabs in the Mediterranean has been well documented with seismic tomography, however, these images, which are produced by smoothed, damped inversions, underestimate the sharpness of the structures. The position and extent of the slabs and the presence possible tears or gaps in the subducted lithosphere are still debated, yet the shape and location these structures are important for kinematic reconstructions and evolution of the entire subduction zone system. Extensive distribution of broadband seismic instrumentation in the Mediterranean (Italian National Seismic Network in Italy and the NSF-PICASSO project in Spain and Morocco) has allowed us to use alternative methodologies to detect the position of the slabs and slab tears beneath the Central and Western Mediterranean. Using S receiver functions we are able to identify S-to-p conversions from the bottom of the subducted slab and a lack of these signals where there are gaps or tears in the slab. We also analyze broadband waveforms for changes in P wave coda from deep (> 300 km depth) local earthquakes. The waveform records for stations in southern Italy and around the Betic-Rif show large amplitude, high frequency (f > 5 Hz) late arrivals with long coda after relatively low-frequency onset. High frequency arrivals are the strongest from events whose raypaths travel within the slab to the stations where they are recorded allowing for mapping of where the subducted material is located within the upper mantle. These two methods, along with inferring the slab position from fast P-wave velocity perturbations in tomography and intermediate depth seismicity, provide additional geophysical evidence to aid in interpretation of the complex, segmented slab structure beneath the Mediterranean.

  15. RC Slabs Repaired and Strengthened by Alumina/Polymer Mortar and Prestressing Strands in the Tension Zone: Experimental Investigation Under Static and Fatigue Loadings

    NASA Astrophysics Data System (ADS)

    Han, K. B.; Hong, S. N.; Park, S. K.

    2012-11-01

    While the extent of repair and rehabilitation of existing old concrete structures is rapidly increasing, a vast number of repaired and rehabilitated structures do not function properly during their remaining service life. Especially in the case of using heterogeneous repair materials, it is very important to maintain the bonding performance between materials and to prevent the interface failure under static and fatigue loads. This paper focuses on the experimental investigation of reinforced concrete (RC) slabs, repaired and reinforced with an alumina/polymer (AP) mortar and a prestressing (PS) strand in the tension zone, under static and fatigue loadings. The variables in this experimental study were the space of strengthening, the number of strands, and AP mortar thickness. Attention is concentrated on the overall load-carrying capacity, deflection, strains of reinforcing bars, and the efficiency of repaired and reinforced RC slabs. Test results showed that the deflection of the repaired and reinforced RC slabs was approximately 40% lower than that of control RC slabs. The initial and horizontal cracking loads of a RC slab with an AP mortar of thickness 30 mm in the static test were approximately the same as those of a RC slab with a 20-mm-thick one. In the fatigue test, the deflection, the strain of reinforcing bars at the midspan, and the maximum shear stress of the repaired and strengthened RC slab were about 40 70% lower than those of the control RC slab. Therefore, it can be concluded that RC slabs with an AP mortar and PS strands have a good strengthening efficiency under both static and fatigue loadings, thanks to the high bonding capacity of the AP mortar.

  16. Response of earth-covered slabs in clay and sand backfills

    NASA Astrophysics Data System (ADS)

    Kiger, S. A.; Eagles, P. S.; Baylot, J. T.

    1984-10-01

    Five tests were conducted, three static and two dynamic, on identical 2-foot-wide, one-way reinforced concrete slabs. Each slab was 2 feet long and had a span-to-effective-depth ratio of 10. Static test were conducted using water over a waterproof membrane to apply a uniform surface pressure with the test slabs surface flush, 1 foot deep in clay soil backfill, and 1 foot deep in a sand backfill. The clay and sand backfill conditions were repeated in the two dynamic tests. The reaction structure supporting the slabs was rigid enough to prevent any slab support rotation at the clamped edges. The rigid reaction structure also eliminated any inplane thrust generated by lateral earth pressures. Therefore, compressive membrane thrust was not a variable between the tests. The surface-flush static test slab failed at about 174 psi, failure in the static clay backfill test occurred at about 835-psi overpressure. The approximately fivefold increase in static capacity in the sand backfill was due to soil arching in the high-shear-strength sand backfill. Peak dynamic pressure in the dynamic sand backfill test was approximately 3,300 psi and in the dynamic clay backfill about 860 psi. These test results indicate that soil arching, both static and dynamic, is much more important than current calculations indicate at this very shallow burial depth. The dynamic tests approximately simulated 0.027- and 0.010-KT nuclear weapons at about 3,300- and 860-psi peak overpressures, respectively. Assuming a 16-foot prototype span, these weapons scale up to approximately 14 and 5 KT, respectively.

  17. 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.

  18. Test of LOX compatibility for asphalt and concrete runway materials

    NASA Technical Reports Server (NTRS)

    Moyers, C. V.; Bryan, C. J.; Lockhart, B. J.

    1973-01-01

    A literature survey and a telephone canvass of producers and users of LOX is reported which yielded one report of an accident resulting from a LOX spill on asphalt, one discussion of hazardous conditions, and an unreferenced mention of an incident. Laboratory tests using standard LOX impact apparatus yielded reactions with both old and new alphalt, but none with concrete. In the final test, using a larger sample of asphalt, the reaction caused extensive damage to equipment. Initial field experiments using 2-meter square asphalt slabs covered with LOX, conducted during rainy weather, achieved no reaction with plummets, and limited reaction with a blasting cap as a reaction initiator. In a final plummet-initiated test on a dry slab, a violent reaction, which appeared to have propagated over the entire slab surface, destroyed the plummet fixture and threw fragments as far as 48 meters.

  19. Tensile Bond Strength of Latex-Modified Bonded Concrete Overlays

    NASA Astrophysics Data System (ADS)

    Dubois, Cameron; Ramseyer, Chris

    2010-10-01

    The tensile bond strength of bonded concrete overlays was tested using the in-situ pull-off method described in ASTM C 1583 with the goal of determining whether adding latex to the mix design increases bond strength. One slab of ductile concrete (f'c > 12,000 psi) was cast with one half tined, i.e. roughened, and one half steel-troweled, i.e. smooth. The slab surface was sectioned off and overlay mixtures containing different latex contents cast in each section. Partial cores were drilled perpendicular to the surface through the overlay into the substrate. A tensile loading device applied a direct tensile load to each specimen and the load was increased until failure occurred. The tensile bond strength was then calculated for comparison between the specimens.

  20. Mixing characterization in a slab tank

    SciTech Connect

    Stoots, C.M.; Gavlak, A.M.; Calabrese, R.V.; Kyser, E.A.; Tatterson, G.B.

    1989-01-01

    Due to safety requirements, slab tanks are often used to process radioactive materials. The configuration is that of a slit or a tank of rectangular cross section with very low aspect ratio. Due to its nonconventional geometry, very little is known about the slab tank mixing environment. To better understand it, experiments have been performed in a full scale standard configuration equipped with two stirrer shafts, each containing several axial impellers. To characterize the velocity field, mean and RMS turbulent velocities have been measured at several impeller speeds with a two-component Laser Doppler Anemometer (LDA). The LDA data have been supplemented with flow visualization, circulation time, and mixing time studies. Since the slab tank is often used as a precipitator, solids suspension studies have also been performed. The results of the various experiments will be presented and will be interpreted to elucidate slab tank dynamics. The implication to mixing efficiency will also be discussed.

  1. Damage assessment of two-way bending RC slabs subjected to blast loadings.

    PubMed

    Jia, Haokai; Yu, Ling; Wu, Guiying

    2014-01-01

    Terrorist attacks on vulnerable structures and their individual structural members may cause considerable damage and loss of life. However, the research work on response and damage analysis of single structural components, for example, a slab to blast loadings, is limited in the literature and this is necessary for assessing its vulnerability. This study investigates the blast response and damage assessment of a two-way bending reinforced concrete (RC) slab subjected to blast loadings. Numerical modeling and analysis are carried out using the commercial finite element code LS-DYNA 971. A damage assessment criterion for the two-way bending RC slab is defined based on the original and residual uniformly distributed load-carrying capacity. Parametric studies are carried out to investigate the effects of explosive weight and explosive position on the damage mode of the two-way RC slab. Some design parameters, such as the boundary conditions and the negative reinforcement steel bar length, are also discussed. The illustrated results show that the proposed criterion can apply to all failure modes. The damage assessment results are more accurate than the ones due to the conventional deformation criterion.

  2. Damage Assessment of Two-Way Bending RC Slabs Subjected to Blast Loadings

    PubMed Central

    Jia, Haokai; Wu, Guiying

    2014-01-01

    Terrorist attacks on vulnerable structures and their individual structural members may cause considerable damage and loss of life. However, the research work on response and damage analysis of single structural components, for example, a slab to blast loadings, is limited in the literature and this is necessary for assessing its vulnerability. This study investigates the blast response and damage assessment of a two-way bending reinforced concrete (RC) slab subjected to blast loadings. Numerical modeling and analysis are carried out using the commercial finite element code LS-DYNA 971. A damage assessment criterion for the two-way bending RC slab is defined based on the original and residual uniformly distributed load-carrying capacity. Parametric studies are carried out to investigate the effects of explosive weight and explosive position on the damage mode of the two-way RC slab. Some design parameters, such as the boundary conditions and the negative reinforcement steel bar length, are also discussed. The illustrated results show that the proposed criterion can apply to all failure modes. The damage assessment results are more accurate than the ones due to the conventional deformation criterion. PMID:25121134

  3. A simple analytical solution for slab detachment

    NASA Astrophysics Data System (ADS)

    Schmalholz, Stefan M.

    2011-04-01

    An analytical solution is presented for the nonlinear dynamics of high amplitude necking in a free layer of power-law fluid extended in layer-parallel direction due to buoyancy stress. The solution is one-dimensional (1-D) and contains three dimensionless parameters: the thinning factor (i.e. ratio of current to initial layer thickness), the power-law stress exponent, n, and the ratio of time to the characteristic deformation time of a viscous layer under buoyancy stress, t/ tc. tc is the ratio of the layer's effective viscosity to the applied buoyancy stress. The value of tc/ n specifies the time for detachment, i.e. the time it takes until the layer thickness has thinned to zero. The first-order accuracy of the 1-D solution is confirmed with 2-D finite element simulations of buoyancy-driven necking in a layer of power-law fluid embedded in a linear or power-law viscous medium. The analytical solution is accurate within a factor about 2 if the effective viscosity ratio between the layer and the medium is larger than about 100 and if the medium is a power-law fluid. The analytical solution is applied to slab detachment using dislocation creep laws for dry and wet olivine. Results show that one of the most important parameters controlling the dynamics of slab detachment is the strength of the slab which strongly depends on temperature and rheological parameters. The fundamental conclusions concerning slab detachment resulting from both the analytical solution and from earlier published thermo-mechanical numerical simulations agree well, indicating the usefulness of the highly simplified analytical solution for better understanding slab detachment. Slab detachment resulting from viscous necking is a combination of inhomogeneous thinning due to varying buoyancy stress within the slab and a necking instability due to the power-law viscous rheology ( n > 1). Application of the analytical solution to the Hindu Kush slab provides no "order-of-magnitude argument" against

  4. Photocatalytic, highly hydrophilic porcelain stoneware slabs

    NASA Astrophysics Data System (ADS)

    Raimondo, M.; Guarini, G.; Zanelli, C.; Marani, F.; Fossa, L.; Dondi, M.

    2011-10-01

    Photocatalytic, highly hydrophilic industrial porcelain stoneware large slabs were realized by deposition of nanostructured TiO2 coatings. Different surface finishing and experimental conditions were considered in order to assess the industrial feasibility. Photocatalytic and wetting behaviour of functionalized slabs mainly depends on surface phase composition in terms of anatase/rutile ratio, this involving - as a key issue - the deposition of TiO2 on industrially sintered products with an additional annealing step to strengthen coatings' performances and durability.

  5. 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}.

  6. Constraints of subducted slabs under the Indian Ocean on the northward motion of India from Gondwanaland towards Eurasia

    NASA Astrophysics Data System (ADS)

    Suppe, John; Lin, Chris D. J.; Wu, Jonny; Kanda, Ravi V. S.

    2013-04-01

    We find an extensive swath of slabs in the lower mantle under the Indian Ocean at depths of 1000-2200km, with shallower slabs to the north under India and Eurasia at ~200-1500km. These slabs closely correspond to the well-known track that India has travelled northward from Gondwanaland toward its collision with Eurasia, viewed in the Indo-Atlantic moving hotspot reference frame, and account for a significant proportion of the predicted loss of the Ceno- and Neo-Tethyan Oceans since ~140Ma. Our work is based on our methodology of [1] mapping subducted slabs in global tomography (MITP08, Li et al. 2008) as 3D mid-slab surfaces in the Gocad environment, [2] quantitatively unfolding these surfaces to the surface of the earth in a spherical Earth model, minimizing changes in area and distortion, and [3] incorporating them into Gplates global plate tectonic reconstructions (http://www.earthbyte.org). These unfolded subducted slabs provide substantial quantitative constraints for the original location and extent of India and Greater India and for the nature and history of Ceno- and Neo-Tethys. We observe a distinct discontinuity in amplitude of p- and s-wave velocity anomalies between the higher-amplitude Neo-Tethyan slabs to the north under India and the Middle East and the lower-amplitude Ceno-Tethyan slabs under the central Indian Ocean, which is in agreement with a predicted large ~100Ma discontinuity in age-at-subduction between Neo- and Ceno-Tethys in existing plate-tectonic models (e.g. Müller et al., 2008; Seton et al, 2012). We present a plate tectonic reconstruction that incorporates these mapped slab constraints, with the implication that a substantial fraction of the Tethyan Ocean (~3000km) subducted southward under India at an early stage in the northward motion of India from Gondwanaland.

  7. Was there a Laramide "flat slab"?

    NASA Astrophysics Data System (ADS)

    Jones, C. H.

    2014-12-01

    Slab-continent interactions drive most non-collisional orogenies; this has led us to usually anticipate that temporal changes or spatial variations in orogenic style are related to changes in the slab, most especially in the slab's dip. This is most dramatically evident for orogenies in the foreland, well away from the trench, such as the Laramide orogeny. However, the physical means of connecting slab geometry to crustal deformation remain obscure. Dickinson and Snyder (1978) and Bird (1984) laid out a conceptually elegant means of creating foreland deformation from shear between a slab and overriding continental lithosphere, but such strong shear removed all of the continental lithosphere in the western U.S. when included in a numerical simulation of flat slab subduction (Bird, 1988), a removal in conflict with observations of volcanic rocks and xenoliths in many locations. Relying on an increase in edge normal stresses results, for the Laramide, in requiring the little-deformed Colorado Plateau to either be unusually strong or to have risen rapidly enough and high enough to balance edge stresses with body forces. Early deformation in the Plateau rules out unusual strength, and the accumulation and preservation of Late Cretaceous near-sea level sedimentary rocks makes profound uplift unlikely (though not impossible). Relying on comparisons with the Sierras Pampeanas is also fraught with problems: the Sierras are not separated from the Andean fold-and-thrust belt by several hundred kilometers of little-deformed crust, nor were they buried under kilometers of marine muds as were large parts of the Laramide foreland. We have instead suggested that some unusual interactions of an obliquely subducting plate with a thick Archean continental root might provide a better explanation than a truly flat slab (Jones et al., 2011). From this, and given that several flat-slab segments today are not associated with foreland orogenesis and noting that direct evidence for truly

  8. Impact echo scanning of concrete and wood

    NASA Astrophysics Data System (ADS)

    Sack, Dennis A.; Olson, Larry D.; Aouad, Marwan F.

    1995-05-01

    This paper presents an overview of a new nondestructive testing (NDT) system that allows rapid nondestructive assessment of many types of structural materials. The new system is based on scanning impact echo (IE), using a rolling receiver, digitally controlled impact source, and a distance measurement wheel integrated into a system that is capable of performing over 3000 IE tests per hour. The system has been successfully used on both concrete and wood for condition assessment. Previously, impact echo testing has been limited to point-by-point testing at rates of typically 30 - 60 points per hour. The new system is usable on any flat, relatively smooth surface such as floor slabs, pavements, walls, columns, beams, etc. In addition to IE scanning, the new system has recently been expanded to allow the performance of spectral analysis of surface waves (SASW) scanning on concrete and wood. The SASW method allows the measurement of material stiffness (modulus) versus depth, and therefore can give a profile of the material condition versus depth. Included in this paper are brief discussions of the IE and SASW methods, the scanner system hardware, and the software which was developed to enable efficient processing, analysis, and display of the test data and results. Also included are sample data plots and a case history presentation of the use of the system in the field, including one in which 23,000 IE tests were performed on an elevated floor slab in approximately 16 hours of testing time.

  9. 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.

  10. Effects of change in slab geometry on the mantle flow and slab fabric in Southern Peru

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, Sanja; Wagner, Lara S.; Beck, Susan L.; Long, Maureen D.; Zandt, George; Tavera, Hernando

    2016-10-01

    The effects of complex slab geometries on the surrounding mantle flow field are still poorly understood. Here we combine shear wave velocity structure with Rayleigh wave phase anisotropy to examine these effects in southern Peru, where the slab changes its geometry from steep to flat. To the south, where the slab subducts steeply, we find trench-parallel anisotropy beneath the active volcanic arc that we attribute to the mantle wedge and/or upper portions of the subducting plate. Farther north, beneath the easternmost corner of the flat slab, we observe a pronounced low-velocity anomaly. This anomaly is caused either by the presence of volatiles and/or flux melting that could result from southward directed, volatile-rich subslab mantle flow or by increased temperature and/or decompression melting due to small-scale vertical flow. We also find evidence for mantle flow through the tear north of the subducting Nazca Ridge. Finally, we observe anisotropy patterns associated with the fast velocity anomalies that reveal along strike variations in the slab's internal deformation. The change in slab geometry from steep to flat contorts the subducting plate south of the Nazca Ridge causing an alteration of the slab petrofabric. In contrast, the torn slab to the north still preserves the primary (fossilized) petrofabric first established shortly after plate formation.

  11. 78 FR 76402 - Notice of Proposed Buy America Waiver for the Pad and Rubber Boot of a Concrete Block for a Low...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-17

    ... Concrete Block for a Low Vibration Track System AGENCY: Federal Transit Administration, DOT. ACTION: Notice... Buy America waiver for the pad and rubber boot of a concrete block for its Low Vibration Track (LVT...-availability waiver for the procurement of the pad and rubber boot of the concrete block used in its LVT...

  12. Capillary Break Beneath a Slab: Polyethylene Sheeting over Aggregate; Southwestern Pennsylvania (Fact Sheet)

    SciTech Connect

    Not Available

    2014-07-01

    This document provides content for three areas of the Building America Solution Center. First, "Insulating Closed Crawlspace Walls and Band Joist Area" describes how to install rigid foam insulation on the interior perimeter walls and band joist area in closed crawlspace foundations of homes. Second, "Removing Construction Debris from Flexible Ducts" describes how to clean flexible ducts after construction or major renovation of a home to remove debris resulting from building materials, particularly airborne dust and particulates. Third, images, CAD drawings, and a case study illustrate right and wrong ways to apply polyethylene sheeting over aggregate. Similarly, a CAD drawing is included that illustrates the use of a concrete slab over polyethylene.

  13. 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.

  14. Characterization of anisotropic acoustic metamaterial slabs

    NASA Astrophysics Data System (ADS)

    Park, Jun Hyeong; Lee, Hyung Jin; Kim, Yoon Young

    2016-01-01

    In an anisotropic acoustic metamaterial, the off-diagonal components of its effective mass density tensor should be considered in order to describe the anisotropic behavior produced by arbitrarily shaped inclusions. However, few studies have been carried out to characterize anisotropic acoustic metamaterials. In this paper, we propose a method that uses the non-diagonal effective mass density tensor to determine the behavior of anisotropic acoustic metamaterials. Our method accurately evaluates the effective properties of anisotropic acoustic metamaterials by separately dealing with slabs made of single and multiple unit cells along the thickness direction. To determine the effective properties, the reflection and transmission coefficients of an acoustic metamaterial slab are calculated, and then the wave vectors inside of the slab are determined using these coefficients. The effective material properties are finally determined by utilizing the spatial dispersion relation of the anisotropic acoustic metamaterial. Since the dispersion relation of an anisotropic acoustic metamaterial is explicitly used, its effective properties can be easily determined by only using a limited number of normal and oblique plane wave incidences into a metamaterial slab, unlike existing approaches requiring a large number of wave incidences. The validity of the proposed method is verified by conducting wave simulations for anisotropic acoustic metamaterial slabs with Z-shaped elastic inclusions of tilted principal material axes.

  15. Magnetohydrodynamic Waves in an Asymmetric Magnetic Slab

    NASA Astrophysics Data System (ADS)

    Allcock, Matthew; Erdélyi, Robert

    2017-02-01

    Analytical models of solar atmospheric magnetic structures have been crucial for our understanding of magnetohydrodynamic (MHD) wave behaviour and in the development of the field of solar magneto-seismology. Here, an analytical approach is used to derive the dispersion relation for MHD waves in a magnetic slab of homogeneous plasma enclosed on its two sides by non-magnetic, semi-infinite plasma with different densities and temperatures. This generalises the classic magnetic slab model, which is symmetric about the slab. The dispersion relation, unlike that governing a symmetric slab, cannot be decoupled into the well-known sausage and kink modes, i.e. the modes have mixed properties. The eigenmodes of an asymmetric magnetic slab are better labelled as quasi-sausage and quasi-kink modes. Given that the solar atmosphere is highly inhomogeneous, this has implications for MHD mode identification in a range of solar structures. A parametric analysis of how the mode properties (in particular the phase speed, eigenfrequencies, and amplitudes) vary in terms of the introduced asymmetry is conducted. In particular, avoided crossings occur between quasi-sausage and quasi-kink surface modes, allowing modes to adopt different properties for different parameters in the external region.

  16. Lunar concrete for construction

    NASA Technical Reports Server (NTRS)

    Cullingford, Hatice S.; Keller, M. Dean

    1988-01-01

    Feasibility of using concrete for lunar-base construction has been discussed recently without relevant data for the effects of vacuum on concrete. Experimental studies performed earlier at Los Alamos have shown that concrete is stable in vacuum with no deterioration of its quality as measured by the compressive strength. Various considerations of using concrete successfully on the moon are provided in this paper along with specific conclusions from the existing data base.

  17. Lunar concrete for construction

    NASA Technical Reports Server (NTRS)

    Cullingford, Hatice S.; Keller, M. Dean

    1992-01-01

    Feasibility of using concrete for lunar base construction was discussed recently without relevant data for the effects of vacuum on concrete. Our experimental studies performed earlier at Los Alamos have shown that concrete is stable in vacuum with no deterioration of its quality as measured by the compressive strength. Various considerations of using concrete successfully on the Moon are provided in this paper, along with specific conclusions from the existing database.

  18. Lunar concrete for construction

    SciTech Connect

    Cullingford, H.S.; Keller, M.D.

    1988-01-01

    Feasibility of using concrete for lunar-base construction has been discussed recently without relevant data for the effects of vacuum on concrete. Our experimental studies performed earlier at Los Alamos have shown that concrete is stable in vacuum with no deterioration of its quality as measured by the compressive strength. Various considerations of using concrete successfully on the moon are provided in this paper along with specific conclusions from the existing data base. 10 refs., 3 figs., 2 tabs.

  19. Slab tears and intermediate-depth seismicity

    USGS Publications Warehouse

    Meighan, Hallie E.; Ten Brink, Uri; Pulliam, Jay

    2013-01-01

    Active tectonic regions where plate boundaries transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. Well-documented slab tears that are associated with high rates of intermediate-depth seismicity are considered here: Gibraltar arc, the southern and northern ends of the Lesser Antilles arc, and the northern end of Tonga trench. Seismicity at each of these locations occurs, at times, in the form of swarms or clusters, and various authors have proposed that each marks an active locus of tear propagation. The swarms and clusters start at the top of the slab below the asthenospheric wedge and extend 30–60 km vertically downward within the slab. We propose that these swarms and clusters are generated by fluid-related embrittlement of mantle rocks. Focal mechanisms of these swarms generally fit the shear motion that is thought to be associated with the tearing process.

  20. Properties of Sulfur Concrete.

    DTIC Science & Technology

    1979-07-06

    This report summarizes the state of the art of sulfur concrete . Sulfur concrete is created by mixing molten sulfur with aggregate and allowing the...and many organic compounds. It works well as a rapid runway repair material. Sulfur concrete also has unfavorable properties. It has poor durability

  1. Organic compounds in concrete from demolition works.

    PubMed

    Van Praagh, M; Modin, H; Trygg, J

    2015-11-01

    This study aims to verify the effect of physically removing the outer surface of contaminated concrete on total contents and on potential mobility of pollutants by means of leaching tests. Reclaimed concrete from 3 industrial sites in Sweden were included: A tar impregnated military storage, a military tar track-depot, as well as concrete constructions used for disposing of pesticide production surplus and residues. Solid materials and leachates from batch and column leaching tests were analysed for metals, Cl, F, SO4, DOC and contents of suspected organic compounds (polycyclic aromatic hydrocarbons, PAH, and pesticides/substances for pesticide production such as phenoxy acids, chlorophenols and chlorocresols, respectively). In case of PAH contaminated concrete, results indicate that removing 1 or 5 mm of the surface lead to total concentrations below the Swedish guidelines for recycling of aggregates and soil in groundwork constructions. 3 out of 4 concrete samples contaminated with pesticides fulfilled Swedish guidelines for contaminated soil. Results from batch and column leaching tests indicated, however, that concentrations above environmental quality standards for certain PAH and phenoxy acids, respectively, might occur at site when the crushed concrete is recycled in groundwork constructions. As leaching tests engaged in the study deviated from leaching test standards with a limited number of samples, the potential impact of the leaching tests' equipment on measured PAH and pesticide leachate concentrations has to be evaluated in future work.

  2. Dual-band infrared imaging for concrete bridge deck inspection

    SciTech Connect

    Durbin, P.; Del Grande, N.

    1994-02-01

    Dual-band infrared (DBIR) imaging methods and unique image-correction algorithms used successfully for underground and obscured object imaging and detection (of buried mines, archaeological structures, geothermal aquifers and airframe defects) are adapted for inspection of concrete highways and bridge decks to provide early warnings of subsurface defects. To this end, we prepared small concrete test slabs with defects (embedded plastic layers). We used selective DBIR (3--5 {mu}m and 8--12 {mu}m) image ratios to depict the defect sites and remove the effects of surface clutter. We distinguish true temperature-difference signals (at surrogate delamination sites) from emissivity noise (at sites with oil stains, sand, gravel, metal parts and roughness differences) towards improved concrete bridge deck inspections.

  3. 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.

  4. Anomalous transmission of electromagnetic energy through a plasma slab

    NASA Astrophysics Data System (ADS)

    Gradov, O. M.; Stenflo, L.

    1982-05-01

    An electromagnetic wave, incident on a plasma slab, is considered. It is pointed out that the transmitted energy can be larger than the incident energy during restricted time intervals, if the slab density varies properly in time.

  5. Slab flattening, dynamic topography and normal faulting in the Cordillera Blanca region (northern Peru)

    NASA Astrophysics Data System (ADS)

    Margirier, A.; Robert, X.; Laurence, A.; Gautheron, C.; Bernet, M.; Simon-Labric, T.; Hall, S. R.

    2015-12-01

    Processes driving surface uplift in the Andes are still debated and the role of subduction processes as slab flattening on surface uplift and relief building in the Andes is not well understood. Some of the highest Andean summits, the Cordillera Blanca (6768 m) and the Cordillera Negra (5187 m), are located above a present flat subduction zone (3-15°S), in northern Peru. In this area, both the geometry and timing of the flattening of the slab are well constrained (Gutscher et al., 1999; Rosenbaum et al., 2005). This region is thus a perfect target to explore the effect of slab flattening on the Andean topography and uplift. We obtained new apatite (U-Th)/He and fission-track ages from three vertical profiles located in the Cordillera Blanca and the Cordillera Negra. Time-temperature paths obtained from inverse modeling of the thermochronological data indicates a Middle Miocene cooling for both Cordillera Negra profiles. We interpret it as regional exhumation in the Cordillera Occidental starting in Middle Miocene, synchronous with the onset of the subduction of the Nazca ridge (Rosenbaum et al., 2005). We propose that the Nazca ridge subduction at 15 Ma and onset of slab flattening in northern Peru drove regional positive dynamic topography and thus enhanced exhumation in the Cordillera Occidental. This study provides new evidence of the impact subduction processes and associated dynamic topography on paleogeography and surface uplift in the Andes.

  6. A two- and three-dimensional numerical modelling benchmark of slab detachment

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric; Glerum, Anne; Hillebrand, Bram; Schmalholz, Stefan; Spakman, Wim; Torsvik, Trond

    2014-05-01

    Subduction is likely to be the most studied phenomenon in Numerical Geodynamics. Over the past 20 years, hundreds of publications have focused on its various aspects (influence of the rheology and thermal state of the plates, slab-mantle coupling, roll-back, mantle wedge evolution, buoyancy changes due to phase change, ...) and results were obtained with a variety of codes. Slab detachment has recently received some attention (e.g. Duretz, 2012) but remains a field worth exploring due to its profound influence on dynamic topography, mantle flow and subsequent stress state of the plates, and is believed to have occured in the Zagros, Carpathians and beneath eastern Anatolia, to name only a few regions. Following the work of Schmalholz (2011), we propose a two- and three-dimensional numerical benchmark of slab detachment. The geometry is simple: a power-law T-shaped plate including an already subducted slab overlies the mantle whose viscosity is either linear or power-law. Boundary conditions are free-slip on the top and the bottom of the domain, and no-slip on the sides. When the system evolves in time, the slab stretches out vertically and shows buoyancy-driven necking, until it finally detaches. The benchmark is subdivided into several sub-experiments with gradually increase in complexity (free surface, coupling of the rheology with temperature, ...). An array of objective measurements is recorded throughout the simulation such as the width of the necked slab over time and the exact time of detachment. The experiments will be run in two-dimensions and repeated in three-dimensional, the latter case being designed so as to allow both poloidal and toroidal flow. We show results obtained with a multitude of Finite Element and Finite Difference codes, using either compositional fields, level sets or tracers to track the compositions. A good agreement is found for most of the measurements in the two-dimensional case, and preliminary three-dimensional measurements will

  7. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  8. Slab Ice Characterization on Martian Richardson Crater

    NASA Astrophysics Data System (ADS)

    Schmidt, F.; Andrieu, F.; Douté, S.

    2016-09-01

    We compare two models: granular and slab in order to study the ice properties in the Richardson crater using spectroscopy. Thanks to radiative transfer modeling, we determine compactness of CO2 ice, grain size, and abundances of water ice and dust.

  9. Oceanic slab melting and mantle metasomatism.

    PubMed

    Scaillet, B; Prouteau, G

    2001-01-01

    Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one.

  10. Multiple stationary solutions of an irradiated slab

    NASA Astrophysics Data System (ADS)

    Taylor, P. D.; Feltham, D. L.

    2005-04-01

    A mathematical model describing the heat budget of an irradiated medium is introduced. The one-dimensional form of the equations and boundary conditions are presented and analysed. Heat transport at one face of the slab occurs by absorption (and reflection) of an incoming beam of short-wave radiation with a fraction of this radiation penetrating into the body of the slab, a diffusive heat flux in the slab and a prescribed incoming heat flux term. The other face of the slab is immersed in its own melt and is considered to be a free surface. Here, temperature continuity is prescribed and evolution of the surface is determined by a Stefan condition. These boundary conditions are flexible enough to describe a range of situations such as a laser shining on an opaque medium, or the natural environment of polar sea ice or lake ice. A two-stream radiation model is used which replaces the simple Beer's law of radiation attenuation frequently used for semi-infinite domains. The stationary solutions of the governing equations are sought and it is found that there exists two possible stationary solutions for a given set of boundary conditions and a range of parameter choices. It is found that the existence of two stationary solutions is a direct result of the model of radiation absorption, due to its effect on the albedo of the medium. A linear stability analysis and numerical calculations indicate that where two stationary solutions exist, the solution corresponding to a larger thickness is always stable and the solution corresponding to a smaller thickness is unstable. Numerical simulations reveal that when there are two solutions, if the slab is thinner than the smaller stationary thickness it will melt completely, whereas if the slab is thicker than the smaller stationary thickness it will evolve toward the larger stationary thickness. These results indicate that other mechanisms (e.g. wave-induced agglomeration of crystals) are necessary to grow a slab from zero initial

  11. Necessity of the Ridge for the Flat Slab Subduction: Insights from the Peruvian Flat Slab

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, S.; Wagner, L. S.; Beck, S. L.; Long, M. D.; Zandt, G.; Tavera, H.

    2014-12-01

    Flattening of the subducting plate has been linked to the formation of various geological features, including basement-cored uplifts, the cessation of arc volcanism, ignimbrite flare-ups, and the formation of high plateaus and ore deposits [Humphreys et al., 2003; Gutscher et al., 2000; Rosenbaum et al., 2005]. However, the mechanism responsible for the slab flattening is still poorly understood. Here we focus on the Peruvian flat slab, where the Nazca plate starts to bend at ~80 km depth and travels horizontally for several hundred kilometers, at which point steep subduction resumes. Based on a 1500 km long volcanic gap and intermediate depth seismicity patterns, the Peruvian flat slab appears to have the greatest along-strike extent and, therefore, has been suggested as a modern analogue to the putative flat slab during the Laramide orogeny in the western United States (~80-55 Ma). Combining 3D shear wave velocity structure and Rayleigh wave phase anisotropy between ~10° and 18° S, we find that the subducting Nazca plate is not uniformly flat along the entire region, but fails to the north of the subducting Nazca Ridge. Our results show that, in combination with trench retreat, rapid overriding plate motion, and/or presence of a thick cratonic root, the subduction of buoyant overthickened oceanic crust, such as the Nazca Ridge, is necessary for the formation and sustainability of flat slabs. This finding has important implications for the formation of flat slabs both past and present.

  12. Three-dimensional dynamic analyses of track-embankment-ground system subjected to high speed train loads.

    PubMed

    Fu, Qiang; Zheng, Changjie

    2014-01-01

    A three-dimensional finite element model was developed to investigate dynamic response of track-embankment-ground system subjected to moving loads caused by high speed trains. The track-embankment-ground systems such as the sleepers, the ballast, the embankment, and the ground are represented by 8-noded solid elements. The infinite elements are used to represent the infinite boundary condition to absorb vibration waves induced by the passing of train load at the boundary. The loads were applied on the rails directly to simulate the real moving loads of trains. The effects of train speed on dynamic response of the system are considered. The effect of material parameters, especially the modulus changes of ballast and embankment, is taken into account to demonstrate the effectiveness of strengthening the ballast, embankment, and ground for mitigating system vibration in detail. The numerical results show that the model is reliable for predicting the amplitude of vibrations produced in the track-embankment-ground system by high-speed trains. Stiffening of fill under the embankment can reduce the vibration level, on the other hand, it can be realized by installing a concrete slab under the embankment. The influence of axle load on the vibration of the system is obviously lower than that of train speed.

  13. Three-Dimensional Dynamic Analyses of Track-Embankment-Ground System Subjected to High Speed Train Loads

    PubMed Central

    2014-01-01

    A three-dimensional finite element model was developed to investigate dynamic response of track-embankment-ground system subjected to moving loads caused by high speed trains. The track-embankment-ground systems such as the sleepers, the ballast, the embankment, and the ground are represented by 8-noded solid elements. The infinite elements are used to represent the infinite boundary condition to absorb vibration waves induced by the passing of train load at the boundary. The loads were applied on the rails directly to simulate the real moving loads of trains. The effects of train speed on dynamic response of the system are considered. The effect of material parameters, especially the modulus changes of ballast and embankment, is taken into account to demonstrate the effectiveness of strengthening the ballast, embankment, and ground for mitigating system vibration in detail. The numerical results show that the model is reliable for predicting the amplitude of vibrations produced in the track-embankment-ground system by high-speed trains. Stiffening of fill under the embankment can reduce the vibration level, on the other hand, it can be realized by installing a concrete slab under the embankment. The influence of axle load on the vibration of the system is obviously lower than that of train speed. PMID:24723838

  14. 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.

  15. Slab edge insulating form system and methods

    DOEpatents

    Lee, Brain E.; Barsun, Stephan K.; Bourne, Richard C.; Hoeschele, Marc A.; Springer, David A.

    2009-10-06

    A method of forming an insulated concrete foundation is provided comprising constructing a foundation frame, the frame comprising an insulating form having an opening, inserting a pocket former into the opening; placing concrete inside the foundation frame; and removing the pocket former after the placed concrete has set, wherein the concrete forms a pocket in the placed concrete that is accessible through the opening. The method may further comprise sealing the opening by placing a sealing plug or sealing material in the opening. A system for forming an insulated concrete foundation is provided comprising a plurality of interconnected insulating forms, the insulating forms having a rigid outer member protecting and encasing an insulating material, and at least one gripping lip extending outwardly from the outer member to provide a pest barrier. At least one insulating form has an opening into which a removable pocket former is inserted. The system may also provide a tension anchor positioned in the pocket former and a tendon connected to the tension anchor.

  16. Reinforced Concrete Modeling

    DTIC Science & Technology

    1982-07-01

    AFWL-TR-82-9 AFWL-TR-82-9 REINFORCED CONCRETE MODELING H. L. Schreyer J. W. Jeter, Jr. New Mexico Engineering Reseprch Institute University of New...Subtitle) S. TYPE OF REPORT & PERIOD COVERED REINFORCED CONCRETE MODELING Final Report 6. PERFORMING OtG. REPORT NUMBER NMERI TA8-9 7. AUTHORg) S...loading were identified and used to evaluate current concrete models . Since the endochronic and viscoplastic models provide satisfactory descriptions

  17. Friction evaluation of concrete paver blocks for airport pavement applications

    NASA Technical Reports Server (NTRS)

    Yager, Thomas J.

    1992-01-01

    The development and use of concrete paver blocks is reviewed and some general specifications for application of this type of pavement surface at airport facilities are given. Two different shapes of interlocking concrete paver blocks installed in the track surface at NASA Langley's Aircraft Landing Dynamics Facility (ALDF) are described. Preliminary cornering performance results from testing of 40 x 14 radial-belted and bias-ply aircraft tires are reviewed. These tire tests are part of a larger, ongoing joint NASA/FAA/Industry Surface Traction and Radial Tire (START) Program involving several different tire sizes. Both dry and wet surface conditions were evaluated on the two concrete paver block test surfaces and a conventional, nongrooved Portland cement concrete surface. Future test plans involving evaluation of other concrete paver block designs at the ALDF are indicated.

  18. Size effect law and fracture mechanics of the triggering of dry snow slab avalanches

    NASA Astrophysics Data System (ADS)

    Bažant, ZdeněK. P.; Zi, Goangseup; McClung, David

    2003-02-01

    A size effect law for fracture triggering in dry snow slabs of high enough length-to-thickness ratio is formulated, based on simplified one-dimensional analysis by equivalent linear elastic fracture mechanics. Viscoelastic effects during fracture are neglected. The derived law, which is analogous to Bažant's energetic size effect law developed for concrete and later for sea ice, fiber composites, rocks, and ceramics, is shown to agree with two-dimensional finite element analysis of mode II cohesive crack model with a finite residual shear stress. Fitting the proposed size effect law to fracture data for various slab thicknesses permits identifying the material fracture parameters. The value of preexisting shear stress in a thin weak zone of finite length is shown to have significant effect. There exists a certain critical snow depth, depending on the preexisting stress value, below which the size effect disappears. Practical applications require considering that the material properties (particularly the mode II fracture toughness or fracture energy) at the snow slab base are not constant but depend strongly on the slab thickness. This means that one must distinguish the material size effect from the structural size effect, and the combined size effect law must be obtained by introducing into the structural size effect law dependence of its parameters on snow thickness. The thickness dependence of these parameters can be obtained by matching the combined law to avalanche observations. Matching Perla's field data on 116 avalanches suggests that the mode II fracture toughness is approximately proportional to 1.8 power of snow thickness.

  19. Inherited weaknesses control deformation in the flat slab region of Central Argentina

    NASA Astrophysics Data System (ADS)

    Stevens, A.; Carrapa, B.; Larrovere, M.; Aciar, R. H.

    2015-12-01

    The Sierras Pampeanas region of west-central Argentina has long been considered a geologic type-area for flat-slab induced thick-skinned deformation. Frictional coupling between the horizontal subducting plate and South American lithosphere from ~12 Ma to the present provides an obvious causal mechanism for the basement block uplifts that characterize this region. New low temperature thermochronometry data show basement rocks from the central Sierras Pampeanas (~ longitude 66 ̊ W) including Sierras Cadena de Paiman, Velasco and Mazan retain a cooling history of Paleozoic - Mesozoic tectonics events. Results from this study indicate that less than 2 km of basement has been exhumed since at least the Mesozoic. These trends recorded by both apatite fission track (AFT) and apatite helium (AHe) thermochronometry suggest that recent Mio-Pliocene thick-skinned deformation associated with flat-slab subduction follow inherited zones of weakness from Paleozoic terrane sutures and shear zones and Mesozoic rifting. If a Cenozoic foreland basin exisited in this region, its thickness was minimal and was controlled by paleotopography. Pre-Cenozoic cooling ages in these ranges that now reach as high as 4 km imply significant exhumation of basement rocks before the advent of flat slab subduction in the mid-late Miocene. It also suggests that thick-skinned deformation associated with flat slab subduction may at least be facilitated by inherited crustal-scale weaknesses. At the most, pre-existing zones of weakness may be required in regions of thick-skinned deformation. Although flat-slab subduction plays an important role in the exhumation of the Sierras Pampeanas, it is likely not the sole mechanism responsible for thick-skinned deformation in this region. This insight sheds light on the interpretation of modern and ancient regions of thick-skinned deformation in Cordilleran systems.

  20. Roadmap 2030: The U.S. Concrete Industry Technology Roadmap

    SciTech Connect

    none,

    2002-12-01

    Roadmap 2030: The U.S. Concrete Industry Technology Roadmap tracks the eight goals published in the American Concrete Institute Strategic Development Council's Vision 2030: A Vision for the U.S. Concrete Industry. Roadmap 2030 highlights existing state-of-the-art technologies and emerging scientific advances that promise high potential for innovation, and predicts future technological needs. It defines enabling research opportunities and proposes areas where governmental-industrial-academic partnerships can accelerate the pace of development. Roadmap 2030 is a living document designed to continually address technical, institutional, and market changes.

  1. Slab photonic crystals with dimer colloid bases

    SciTech Connect

    Riley, Erin K.; Liddell Watson, Chekesha M.

    2014-06-14

    The photonic band gap properties for centered rectangular monolayers of asymmetric dimers are reported. Colloids in suspension have been organized into the phase under confinement. The theoretical model is inspired by the range of asymmetric dimers synthesized via seeded emulsion polymerization and explores, in particular, the band structures as a function of degree of lobe symmetry and degree of lobe fusion. These parameters are varied incrementally from spheres to lobe-tangent dimers over morphologies yielding physically realizable particles. The work addresses the relative scarcity of theoretical studies on photonic crystal slabs with vertical variation that is consistent with colloidal self-assembly. Odd, even and polarization independent gaps in the guided modes are determined for direct slab structures. A wide range of lobe symmetry and degree of lobe fusion combinations having Brillouin zones with moderate to high isotropy support gaps between odd mode band indices 3-4 and even mode band indices 1-2 and 2-3.

  2. Subduction zone earthquakes and stress in slabs

    NASA Technical Reports Server (NTRS)

    Vassiliou, M. S.; Hager, B. H.

    1988-01-01

    Simple viscous fluid models of subducting slabs are used to explain observations of the distribution of earthquakes as a function of depth and the orientation of stress axes of deep (greater than 300 km) and intermediate (70-300 km) earthquakes. Results suggest the following features in the distribution of earthquakes with depth: (1) an exponential decrease from shallow depths down to 250 to 300 km, (2) a minimum near 250 to 300 km, and (3) a deep peak below 300 km. Many shallow subducting slabs show only the first characteristic, while deeper extending regions tend to show all three features, with the deep peak varying in position and intensity. These data, combined with the results on the stress orientations of various-depth earthquakes, are consistent with the existence of a barrier of some sort at 670-km depth and a uniform viscosity mantle above this barrier.

  3. The effect of subducting slabs in global shear wave tomography

    NASA Astrophysics Data System (ADS)

    Lu, Chang; Grand, Stephen P.

    2016-05-01

    Subducting slabs create strong short wavelength seismic anomalies in the upper mantle where much of Earth's seismicity is located. As such, they have the potential to bias longer wavelength seismic tomography models. To evaluate the effect of subducting slabs in global tomography, we performed a series of inversions using a global synthetic shear wave traveltime data set for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method was applied to predict the traveltime anomalies produced by the 3-D slab model for paths corresponding to our current data used in actual tomography models. Inversion tests have been conducted first using the raw traveltime anomalies to check how well the slabs can be imaged in global tomography without the effect of earthquake mislocation. Our results indicate that most of the slabs can be identified in the inversion result but with smoothed and reduced amplitude. The recovery of the total mass anomaly in slab regions is about 88 per cent. We then performed another inversion test to investigate the effect of mislocation caused by subducting slabs. We found that source mislocation largely removes slab signal and significantly degrades the imaging of subducting slabs-potentially reducing the recovery of mass anomalies in slab regions to only 41 per cent. We tested two source relocation procedures-an iterative relocation inversion and joint relocation inversion. Both methods partially recover the true source locations and improve the inversion results, but the joint inversion method worked significantly better than the iterative method. In all of our inversion tests, the amplitudes of artefact structures in the lower mantle caused by the incorrect imaging of slabs (up to ˜0.5 per cent S velocity anomalies) are comparable to some large-scale lower-mantle heterogeneities seen in global tomography studies. Based on our inversion tests, we suggest including a-priori subducting slabs in the

  4. 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.

  5. Epoxy injection repairs to concrete in 225-B Building

    SciTech Connect

    Vollert, F.R.

    1996-09-19

    In 1982, the damaged anchor areas (67 total) in the Operating Gallery and cold manipulator shop ceiling reinforced concrete slabs were epoxy injection repaired by Construction Technology Laboratories (CTL), Portland Cement Association. The through depth vertical cracks (10 total) in the ceiling slabs in the galleries and manipulator shops were sealed and structurally repaired using epoxy injection procedures. The details of the epoxy reRair are reported. Sonic nondestructive (NDT) testing before and after the epoxy injection repairs were made by CTL to confirm that the repairs are structurally effective. CTL recommended to expedite the installation of lateral bracing for the manipulator monorail in order to avoid re-darnage to the repaired anchor areas.

  6. Fast Waves in Smooth Coronal Slab

    NASA Astrophysics Data System (ADS)

    Lopin, I.; Nagorny, I.

    2015-03-01

    This work investigates the effect of transverse density structuring in coronal slab-like waveguides on the properties of fast waves. We generalized previous results obtained for the exponential and Epstein profiles to the case of an arbitrary transverse density distribution. The criteria are given to determine the possible (trapped or leaky) wave regime, depending on the type of density profile function. In particular, there are plasma slabs with transverse density structuring that support pure trapped fast waves for all wavelengths. Their phase speed is nearly equal to the external Alfvén speed for the typical parameters of coronal loops. Our findings are obtained on the basis of Kneser’s oscillation theorem. To confirm the results, we analytically solved the wave equation evaluated at the cutoff point and the original wave equation for particular cases of transverse density distribution. We also used the WKB method and obtained approximate solutions of the wave equation at the cutoff point for an arbitrary transverse density profile. The analytic results were supplemented by numerical solutions of the obtained dispersion relations. The observed high-quality quasi-periodic pulsations of flaring loops are interpreted in terms of the trapped fundamental fast-sausage mode in a slab-like coronal waveguide.

  7. Convection in Slab and Spheroidal Geometries

    NASA Technical Reports Server (NTRS)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  8. Implementing slab solar water heating system

    NASA Astrophysics Data System (ADS)

    Raveendran, S. K.; Shen, C. Q.

    2015-08-01

    Water heating contributes a significant part of energy consumption in typical household. One of the most employed technologies today that helps in reducing the energy consumption of water heating would be conventional solar water heating system. However, this system is expensive and less affordable by most family. The main objective of this project is to design and implement an alternative type of solar water heating system that utilize only passive solar energy which is known as slab solar water heating system. Slab solar water heating system is a system that heat up cold water using the solar radiance from the sun. The unique part of this system is that it does not require any form of electricity in order to operate. Solar radiance is converted into heat energy through convection method and cold water will be heated up by using conduction method [1]. The design of this system is governed by the criteria of low implementation cost and energy saving. Selection of material in the construction of a slab solar water heating system is important as it will directly affect the efficiency and performance of the system. A prototype has been built to realize the idea and it had been proven that this system was able to provide sufficient hot water supply for typical household usage at any given time.

  9. Dynamic buckling of subducting slabs reconciles geological and geophysical observations

    NASA Astrophysics Data System (ADS)

    Lee, Changyeol; King, Scott D.

    2011-12-01

    Ever since the early days of the development of plate tectonic theory, subduction zones have been engrained in geological thinking as the place where steady, linear slabs descend into the mantle at a constant, uniform dip angle beneath volcanic arcs. However, growing evidence from geological and geophysical observations as well as analog and numerical modeling indicates that subducting slabs buckle in a time-dependent manner, in contrast to the steady-state, linear cartoons that dominate the literature. To evaluate the implication of time-dependent slab buckling of geological events, we conduct a series of 2-D numerical dynamic/kinematic subduction experiments by varying the viscosity increase across the 660 km discontinuity and the strength of the subducting slab. Our results show that slab buckling is a universal figure in all the experiments when rate of the trench migration ( Vtrench) is relatively slow ( Vtrench| < 2 cm/a) and viscosity increases across the 660 km discontinuity are greater than a factor of 30. Slab buckling is expressed as alternate shallowing and steepening dip of the subducting slab (from ~ 40 to ~ 100°) which is correlated with increasing and decreasing convergent rate of the incoming oceanic plate toward the trench. Further, the slab buckling in our experiments is consistent with the previously developed scaling laws for slab buckling; using reasonable parameters from subducted slabs the buckling amplitude and period are ~ 400 km and ~ 25 Myr, respectively. The slab buckling behavior in our experiments explains a variety of puzzling geological and geophysical observations. First, the period of slab buckling is consistent with short periodic variations (~ 25 Myr) in the motions of the oceanic plates that are anchored by subduction zones. Second, the scattered distributions of slab dips (from ~ 20 to ~ 90°) in the upper mantle are snapshots of time-dependent slab dip. Third, the current compressional and extensional stress environments in

  10. HIGH-COMPRESSIVE-STRENGTH CONCRETE.

    DTIC Science & Technology

    CONCRETE , COMPRESSIVE PROPERTIES), PERFORMANCE(ENGINEERING), AGING(MATERIALS), MANUFACTURING, STRUCTURES, THERMAL PROPERTIES, CREEP, DEFORMATION, REINFORCED CONCRETE , MATHEMATICAL ANALYSIS, STRESSES, MIXTURES, TENSILE PROPERTIES

  11. Viscous Dissipation and Criticality of Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Riedel, Mike; Karato, Shun; Yuen, Dave

    2016-04-01

    Rheology of subducting lithosphere appears to be complicated. In the shallow part, deformation is largely accomodated by brittle failure, whereas at greater depth, at higher confining pressures, ductile creep is expected to control slab strength. The amount of viscous dissipation ΔQ during subduction at greater depth, as constrained by experimental rock mechanics, can be estimated on the basis of a simple bending moment equation [1,2] 2ɛ˙0(z) ∫ +h/2 2 M (z) = h ṡ -h/2 4μ(y,z)y dy , (1) for a complex multi-phase rheology in the mantle transition zone, including the effects of a metastable phase transition as well as the pressure, temperature, grain-size and stress dependency of the relevant creep mechanisms; μ is here the effective viscosity and ɛ˙0(z) is a (reference) strain rate. Numerical analysis shows that the maximum bending moment, Mcrit, that can be sustained by a slab is of the order of 1019 Nm per m according to Mcrit˜=σp ∗h2/4, where σp is the Peierl's stress limit of slab materials and h is the slab thickness. Near Mcrit, the amount of viscous dissipation grows strongly as a consequence of a lattice instability of mantle minerals (dislocation glide in olivine), suggesting that thermo-mechanical instabilities become prone to occur at places where a critical shear-heating rate is exceeded, see figure. This implies that the lithosphere behaves in such cases like a perfectly plastic solid [3]. Recently available detailed data related to deep seismicity [4,5] seems to provide support to our conclusion. It shows, e.g., that thermal shear instabilities, and not transformational faulting, is likely the dominating mechanism for deep-focus earthquakes at the bottom of the transition zone, in accordance with this suggested "deep criticality" model. These new findings are therefore briefly outlined and possible implications are discussed. References [1] Riedel, M. R., Karato, S., Yuen, D. A. Criticality of Subducting Slabs. University of Minnesota

  12. Evolution and diversity of subduction zones controlled by slab width.

    PubMed

    Schellart, W P; Freeman, J; Stegman, D R; Moresi, L; May, D

    2007-03-15

    Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle, and geodynamic, seismic and geochemical studies offer insight into slab dynamics and subduction-induced flow. Most previous geodynamic studies treat subduction zones as either infinite in trench-parallel extent (that is, two-dimensional) or finite in width but fixed in space. Subduction zones and their associated slabs are, however, limited in lateral extent (250-7,400 km) and their three-dimensional geometry evolves over time. Here we show that slab width controls two first-order features of plate tectonics-the curvature of subduction zones and their tendency to retreat backwards with time. Using three-dimensional numerical simulations of free subduction, we show that trench migration rate is inversely related to slab width and depends on proximity to a lateral slab edge. These results are consistent with retreat velocities observed globally, with maximum velocities (6-16 cm yr(-1)) only observed close to slab edges (<1,200 km), whereas far from edges (>2,000 km) retreat velocities are always slow (<2.0 cm yr(-1)). Models with narrow slabs (< or =1,500 km) retreat fast and develop a curved geometry, concave towards the mantle wedge side. Models with slabs intermediate in width ( approximately 2,000-3,000 km) are sublinear and retreat more slowly. Models with wide slabs (> or =4,000 km) are nearly stationary in the centre and develop a convex geometry, whereas trench retreat increases towards concave-shaped edges. Additionally, we identify periods (5-10 Myr) of slow trench advance at the centre of wide slabs. Such wide-slab behaviour may explain mountain building in the central Andes, as being a consequence of its tectonic setting, far from slab edges.

  13. The trajectory of India towards Eurasia recorded by subducted slabs: evidence for southward subduction of the Tethys Ocean under India after 130 Ma

    NASA Astrophysics Data System (ADS)

    Suppe, John; Wu, Jonny; Lin, Chris D. J.; Kanda, Ravi V. S.

    2014-05-01

    At the ~130 Ma breakup of India from Australia-Antarctica, published paleomagnetic data estimate that India was located south of 30°S. As India began its northward journey that continues today, the 5000 km of Tethys Ocean that stood in the expanse between India and Eurasia gradually disappeared, leaving only traces of its existence in ophiolite sutures and accreted terranes at the Himalayas, the largest orogeny on Earth today. Here we present newly mapped, sub-horizontal slabs under the Indian Ocean at depths of 1600 to 2100 km and at latitudes between 35°S to 15°N. These slabs are further south than any published paleolatitudinal estimates of initial India-Asia collision and thus, the existence of these slabs cannot be explained by the popular idea of northward Tethys subduction under Eurasia. Instead, our slab constraints show for the first time that the majority of the Tethys Ocean was subducted southward after 130 Ma, overrun by a northward-moving India. When restored to the surface of a spherical model Earth, the slabs closely correspond to the well-known track of India from Eastern Gondwanaland to Eurasia that began at ~130 Ma, viewed in a mantle reference. We present a plate reconstruction that includes other restored slabs from the India-Eurasia collision zone, which are at shallower depths and ubiquitously located north of the equator. The reconstruction implies that the Tethys Ocean was subducted under Greater India, India and the post-breakup ocean at the eastern margin of the Indian plate - now identified as the enigmatic 'Burma slab'. Slab geometries were mapped from global P- and S-wave models and restored to the surface of a spherical Earth model. Gplates software was used to reconstruct the mapped slabs.

  14. Tectonic controls on earthquake size distribution and seismicity rate: slab buoyancy and slab bending

    NASA Astrophysics Data System (ADS)

    Nishikawa, T.; Ide, S.

    2014-12-01

    There are clear variations in maximum earthquake magnitude among Earth's subduction zones. These variations have been studied extensively and attributed to differences in tectonic properties in subduction zones, such as relative plate velocity and subducting plate age [Ruff and Kanamori, 1980]. In addition to maximum earthquake magnitude, the seismicity of medium to large earthquakes also differs among subduction zones, such as the b-value (i.e., the slope of the earthquake size distribution) and the frequency of seismic events. However, the casual relationship between the seismicity of medium to large earthquakes and subduction zone tectonics has been unclear. Here we divide Earth's subduction zones into over 100 study regions following Ide [2013] and estimate b-values and the background seismicity rate—the frequency of seismic events excluding aftershocks—for subduction zones worldwide using the maximum likelihood method [Utsu, 1965; Aki, 1965] and the epidemic type aftershock sequence (ETAS) model [Ogata, 1988]. We demonstrate that the b-value varies as a function of subducting plate age and trench depth, and that the background seismicity rate is related to the degree of slab bending at the trench. Large earthquakes tend to occur relatively frequently (lower b-values) in shallower subduction zones with younger slabs, and more earthquakes occur in subduction zones with deeper trench and steeper dip angle. These results suggest that slab buoyancy, which depends on subducting plate age, controls the earthquake size distribution, and that intra-slab faults due to slab bending, which increase with the steepness of the slab dip angle, have influence on the frequency of seismic events, because they produce heterogeneity in plate coupling and efficiently inject fluid to elevate pore fluid pressure on the plate interface. This study reveals tectonic factors that control earthquake size distribution and seismicity rate, and these relationships between seismicity and

  15. 24. REAR ELEVATION, HULETT ORE UNLOADERS. TRACKS CARRYING THE FRONT ...

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

    24. REAR ELEVATION, HULETT ORE UNLOADERS. TRACKS CARRYING THE FRONT END AND REAR LEGS OF THE HULETT UNLOADERS ARE LAID ON THE DOCK AND REAR WALLS, RESPECTIVELY; BOTH WALLS ARE MADE OF REINFORCED CONCRETE SUPPORTED ON CONCRETE PILES. - Pennsylvania Railway Ore Dock, Lake Erie at Whiskey Island, approximately 1.5 miles west of Public Square, Cleveland, Cuyahoga County, OH

  16. MODELNG RADON ENTRY INTO FLORIDA HOUSES WITH CONCRETE SLABS AND CONCRETE-BLOCK STEM WALLS, FLORIDA RADON RESEARCH PROGRAM

    EPA Science Inventory

    The report discusses results of modeling radon entry into a typical Florida house whose interior is slightly depressurized. he model predicts that the total radon entry rate is relatively low unless the soil or backfill permeability or radium content is high. ost of the factors c...

  17. Derivation of factors for estimating the scatter of diagnostic x-rays from walls and ceiling slabs.

    PubMed

    Martin, C J; Sutton, D G; Magee, J; McVey, S; Williams, J R; Peet, D

    2012-12-01

    Computed tomography (CT) scanning rooms and interventional x-ray facilities with heavy workloads may require the installation of shielding to protect against radiation scattered from walls or ceiling slabs. This is particularly important for the protection of those operating x-ray equipment from within control cubicles who may be exposed to radiation scattered from the ceiling over the top of the protective barrier and round the side if a cubicle door is not included. Data available on the magnitude of this tertiary scatter from concrete slabs are limited. Moreover, there is no way in which tertiary scatter levels can be estimated easily for specific facilities. There is a need for a suitable method for quantification of tertiary scatter because of the increases in workloads of complex x-ray facilities. In this study diagnostic x-ray air kerma levels scattered from concrete and brick walls have been measured to verify scatter factors. The results have been used in a simulation of tertiary scatter for x-ray facilities involving summation of scatter contributions from elements across concrete ceiling slabs. The majority of the ceiling scatter air kerma to which staff behind a barrier will be exposed arises from the area between the patient/x-ray tube and the staff. The level depends primarily on the heights of the ceiling and protective barrier. A method has been developed to allow tertiary scatter levels to be calculated using a simple equation based on a standard arrangement for rooms with different ceiling and barrier heights. Coefficients have been derived for a CT facility and an interventional suite to predict tertiary scatter levels from the workload, so that consideration can be given to the protection options available.

  18. Antifouling marine concrete

    SciTech Connect

    Vind, H P; Mathews, C W

    1980-07-01

    Various toxic agents were evaluated as the their capability to prevent or inhibit the attachment of marine fouling organisms to concrete. Creosote and bis-(tri-n-butyltin) oxide (TBTO) were impregnated into porous aggregate which was used in making concrete. Cuprous oxide, triphenyltin hydroxide (TPTH), and 2-2-bis-(p-methoxyphenyl)-1,1,1-trichloroethane (methoxychlor) were used as dry additives. Two proprietary formulations were applied as coatings on untreated concrete. Test specimens were exposed at Port Hueneme, CA, and Key Biscayne, FL. The efficacy of toxicants was determined by periodically weighing the adhering fouling organisms. Concrete prepared with an aggregate impregnated with a TBTO/creosote mixture has demonstrated the best antifouling performance of those specimens exposed for more than one year. The two proprietary coatings and the concrete containing methoxychlor, TPTH, and cuprous oxide as dry additives have exhibited good antifouling properties, but they have been exposed for a shorter time. The strength of concrete containing the toxicants was acceptable, and the toxicants did not increase the corrosion rate of reinforcing rods. Organotin compounds were essentially unchanged in concrete specimens exposed 6 1/2 years in seawater.

  19. Performance of Waterless Concrete

    NASA Technical Reports Server (NTRS)

    Toutanji, Houssam; Evans, Steve; Grugel, Richard N.

    2010-01-01

    The development of permanent lunar bases is constrained by performance of construction materials and availability of in-situ resources. Concrete seems a suitable construction material for the lunar environment, but water, one of its major components, is an extremely scarce resource on the Moon. This study explores an alternative to hydraulic concrete by replacing the binding mix of concrete (cement and water) with sulfur. Sulfur is a volatile element on the lunar surface that can be extracted from lunar soils by heating. Sulfur concrete mixes were prepared to investigate the effect of extreme environmental conditions on the properties of sulfur concrete. A hypervelocity impact test was conducted, having as its target a 5-cm cubic sample of sulfur concrete. This item consisted of JSC-1 lunar regolith simulant (65%) and sulfur (35%). The sample was placed in the MSFC Impact Test Facility s Micro Light Gas Gun target chamber, and was struck by a 1-mm diameter (1.4e-03 g) aluminum projectile at 5.85 km/s. In addition, HZTERN code, provided by NASA was used to study the effectiveness of sulfur concrete when subjected to space radiation.

  20. Antifouling marine concrete

    SciTech Connect

    Vind, H P; Mathews, C W

    1980-07-01

    Various toxic agents were evaluated as to their capability to prevent or inhibit the attachment of marine fouling organisms to concrete for OTEC plants. Creosote and bis-(tri-n-butyltin) oxide (TBTO) were impregnated into porous aggregate which was used in making concrete. Cuprous oxide, triphenyltin hydroxide (TPTH), and 2-2-bis-(p-methoxyphenyl)-1,1,1-trichloroethane (methoxychlor) were used as dry additives. Two proprietary formulations were applied as coatings on untreated concrete. Test specimens were exposed at Port Hueneme, CA, and Key Biscayne, FL. The efficacy of toxicants was determined by periodically weighing the adhering fouling organisms. Concrete prepared with an aggregate impregnated with a TBTO/creosote mixture has demonstrated the best antifouling performance of those specimens exposed for more than one year. The two proprietary coatings and the concrete containing methoxychlor, TPTH, and cuprous oxide as dry additives have exhibited good antifouling properties, but they have been exposed for a shorter time. The strength of concrete containing the toxicants was acceptable, and the toxicants did not increase the corrosion rate of reinforcing rods. Organotin compounds were essentially unchanged in concrete specimens exposed 6-1/2 years in seawater.

  1. Plume-subduction interaction in southern Central America: Mantle upwelling and slab melting

    NASA Astrophysics Data System (ADS)

    Gazel, Esteban; Hoernle, Kaj; Carr, Michael J.; Herzberg, Claude; Saginor, Ian; den Bogaard, Paul van; Hauff, Folkmar; Feigenson, Mark; Swisher, Carl

    2011-01-01

    The volcanic front in southern Central America is well known for its Galapagos OIB-like geochemical signature. A comprehensive set of geochemical, isotopic and geochronological data collected on volumetrically minor alkaline basalts and adakites were used to better constrain the mantle and subduction magma components and to test the different models that explain this OIB signature in an arc setting. We report a migration of back-arc alkaline volcanism towards the northwest, consistent with arc-parallel mantle flow models, and a migration towards the southeast in the adakites possibly tracking the eastward movement of the triple junction where the Panama Fracture Zone intersects the Middle America Trench. The adakites major and trace element compositions are consistent with magmas produced by melting a mantle-wedge source metasomatized by slab derived melts. The alkaline magmas are restricted to areas that have no seismic evidence of a subducting slab. The geochemical signature of the alkaline magmas is mostly controlled by upwelling asthenosphere with minor contributions from subduction components. Mantle potential temperatures calculated from the alkaline basalt primary magmas increased from close to ambient mantle (~ 1380-1410 °C) in the Pliocene to ~ 1450 °C in the younger units. The calculated initial melting pressures for these primary magmas are in the garnet stability field (3.0-2.7 GPa). The average final melting pressures range between 2.7 and 2.5 GPa, which is interpreted as the lithosphere-asthenosphere boundary at ~ 85-90 km. We provide a geotectonic model that integrates the diverse observations presented here. The slab detached after the collision of the Galapagos tracks with the arc (~ 10-8 Ma). The detachment allowed hotter asthenosphere to flow into the mantle wedge. This influx of hotter asthenosphere explains the increase in mantle potential temperatures, the northwest migration in the back-arc alkaline lavas that tracks the passage of the

  2. Penetration effect in gyrotropic slab: theory and applications.

    PubMed

    Vytovtov, Konstantin; Mospan, Lyudmila

    2012-06-01

    Scattering properties of a homogeneous anisotropic slab are investigated at fixed crystal anisotropy axis orientation. The penetration phenomenon for an incident wave propagating tangentially to the crystal surface is discussed. Slab-based nonreciprocal optical devices are proposed. Their operating principles are based on the slab scattering properties, but not on the Faraday effect. Numerical data for an optical isolator and frequency detector are presented.

  3. Lessons to be learned from rehabilitation of concrete structures in bleach plants in pulp and paper mills

    SciTech Connect

    Nixon, R.

    1995-12-01

    The deterioration of concrete structures due to chloride induced reinforcing steel corrosion such as in elevated concrete floor slabs, columns, and beams in bleach plants is a constant and growing problem within the pulp and paper industry. In general, the condition analysis methods used for assessing the extent of bleach plant concrete degradation include physical testing of drilled concrete core samples, chloride ion concentration testing, half-cell potential measurements, and physical sounding of concrete surfaces, i.e. chain drag for topside surfaces and hammer sounding of soffit surfaces. While this paper does not promote any vastly different evaluative methods, it does share learnings relative to interpreting the data provided by these typical test methods. It further offers some recommendations on how to improve the use of these typical evaluation techniques and offers some other test methods which should be considered as valuable additions for such evaluations. One of the most common methods which has been used in the past for large scale bleach plant concrete restoration has been the application of site dry mixed shotcrete for rebuilding the soffits of floor slabs and the faces of columns and beams. More often than not, bulk mixed dry shotcrete repairs have not been cost-effective because they prematurely failed due to excessive hydration related shrinkage cracking, lack of sufficient adhesion to the parent concrete substrate or other problems related to poor durability or construction practice.

  4. A Numerical Analysis of the Resistance and Stiffness of the Timber and Concrete Composite Beam

    NASA Astrophysics Data System (ADS)

    Szumigała, Ewa; Szumigała, Maciej; Polus, Łukasz

    2015-03-01

    The article presents the results of a numerical analysis of the load capacity and stiffness of the composite timber and concrete beam. Timber and concrete structures are relatively new, they have not been thoroughly tested and they are rarely used because of technological constraints. One of the obstacles to using them is difficulty with finding a method which would allow successful cooperation between concrete and timber, which has been proposed by the authors of the present article. The modern idea of sustainable construction design requires the use of new more environmentally-friendly solutions. Wood as an ecological material is easily accessible, less energy-consuming, and under certain conditions more corrosion-resistant than steel. The analysis presented in the article showed that cooperation between a wooden beam and a concrete slab on profiled steel sheeting is possible. The analysed composite beam has a greater load capacity and stiffness than the wooden beam.

  5. 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.

  6. Detection of sub-horizontal flaws in concrete using the synthetic aperture focusing technique

    NASA Astrophysics Data System (ADS)

    Hosseini, Zahra

    Concrete deteriorates over time due to environmental changes and/or poor construction processes which can eventually lead to partial or total failure of a structure. Deterioration in concrete manifests itself in different forms such as: freeze and thaw, chemical attack, surface and internal flaws. Concrete and shotcrete linings are widely used as support systems in underground excavations. Surprisingly, a fragmented, damaged shotcrete support system can actually create a less stable environment than the unsupported rock mass. Detection of internal flaws remains a difficult task as they are not always observable on the surface. Yet, the potential to expand and cause damage to the structure is omnipresent. The focus of this work is to locate and characterize two main and common features in concrete structures, (1) sub-horizontal cracks; (2) rock-concrete interfaces. Traditionally, this has been difficult to detect by currently available NDT methods. To obtain high resolution images of cracks in concrete, an extension of the ultrasonic nondestructive technique known as Synthetic Aperture Focusing Technique (SAFT) has been used. However, in order to achieve our research objective, we developed a modified SAFT code in this work. The results of this study demonstrate that the resolving power of our modified 3D SAFT algorithm can provide an accurate profile of both a rock-concrete interface and/or cracks with angles varying from 5 to 15 degrees within concrete slabs having thicknesses of up to twenty centimetres.

  7. Automated inspection of hot steel slabs

    DOEpatents

    Martin, R.J.

    1985-12-24

    The disclosure relates to a real time digital image enhancement system for performing the image enhancement segmentation processing required for a real time automated system for detecting and classifying surface imperfections in hot steel slabs. The system provides for simultaneous execution of edge detection processing and intensity threshold processing in parallel on the same image data produced by a sensor device such as a scanning camera. The results of each process are utilized to validate the results of the other process and a resulting image is generated that contains only corresponding segmentation that is produced by both processes. 5 figs.

  8. Automated inspection of hot steel slabs

    DOEpatents

    Martin, Ronald J.

    1985-01-01

    The disclosure relates to a real time digital image enhancement system for performing the image enhancement segmentation processing required for a real time automated system for detecting and classifying surface imperfections in hot steel slabs. The system provides for simultaneous execution of edge detection processing and intensity threshold processing in parallel on the same image data produced by a sensor device such as a scanning camera. The results of each process are utilized to validate the results of the other process and a resulting image is generated that contains only corresponding segmentation that is produced by both processes.

  9. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, Joseph W.; Carrano, Anthony V.; Davidson, James C.; Koo, Jackson C.

    1998-01-01

    A hybrid slab-microchannel gel electrophoresis system. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate.

  10. Photonic crystal slab quantum cascade detector

    SciTech Connect

    Reininger, Peter Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-09

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  11. Photonic crystal slab quantum well infrared photodetector

    NASA Astrophysics Data System (ADS)

    Kalchmair, S.; Detz, H.; Cole, G. D.; Andrews, A. M.; Klang, P.; Nobile, M.; Gansch, R.; Ostermaier, C.; Schrenk, W.; Strasser, G.

    2011-01-01

    In this letter we present a quantum well infrared photodetector (QWIP), which is fabricated as a photonic crystal slab (PCS). With the PCS it is possible to enhance the absorption efficiency by increasing photon lifetime in the detector active region. To understand the optical properties of the device we simulate the PCS photonic band structure, which differs significantly from a real two-dimensional photonic crystal. By fabricating a PCS-QWIP with 100x less quantum well doping, compared to a standard QWIP, we are able to see strong absorption enhancement and sharp resonance peaks up to temperatures of 170 K.

  12. Behavior of Restrained Two-Way Slabs.

    DTIC Science & Technology

    1979-02-22

    AC-AGOG "I NEWMARK (NATHAN M) CONSULTING ENGINEERING SERVICES U-ETC F/G 13/13 BEHAVIOR OF RESTRAINED TWO-WAY SLABS. (U) L FEB 79 1 D HALTIWANGER, W J...Building Urbana, Illinois 61801 22 February 1979 Interim Report for Period 1 September 1978-22 February 1979 CONTRACT No. DNA 0O1-78-C-0300 APPROVED FOR...FORM 1 . REPORT NUMBER 2. GOVT ACCESSION NO, 3 HECIPIENT’S CATALOG NUMBER DNA 4959Z ) -,A TYI-t OD 4. TITLE (and Subbiti. 5 rYPE OF REPORT & PERIOD

  13. MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE ...

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

    MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE RUN OUT INCLUDES THE TRAVELING TORCH WHICH CUTS SLABS TO DESIRED LENGTH, AN IDENTIFICATION SYSTEM TO INDICATE HEAT NUMBER AND TRACE IDENTITY OF EVERY SLAB, AND A DEBURRING DEVICE TO SMOOTH SLABS. AT LEFT OF ROLLS IS THE DUMMY BAR. DUMMY BAR IS INSERTED UP THROUGH CONTAINMENT SECTION INTO MOLD PRIOR TO START OF CAST. WHEN STEEL IS INTRODUCED INTO MOLD IT CONNECTS WITH BAR AS CAST BEGINS, AT RUN OUT DUMMY BAR DISCONNECTS AND IS STORED. - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  14. MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE ...

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

    MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE RUN OUT INCLUDES THE TRAVELING TORCH WHICH CUTS SLABS TO DESIRED LENGTH, AN IDENTIFICATION SYSTEM TO INDICATE HEAT NUMBER AND TRACE IDENTITY OF EVERY SLAB, AND A DEBURRING DEVICE TO SMOOTH SLABS. AT LEFT OF ROLLS IS THE DUMMY BAR. DUMMY BAR IS INSERTED UP THROUGH CONTAINMENT SECTION INTO MOLD PRIOR TO START OF CAST. WHEN STEEL IS INTRODUCED INTO MOLD IT CONNECTS WITH BAR AS CAST BEGINS, AT RUN OUT DUMMY BAR DISCONNECTS AND IS STORED - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  15. Electrokinetic Strength Enhancement of Concrete

    NASA Technical Reports Server (NTRS)

    Cardenas, Henry E. (Inventor)

    2016-01-01

    A method and apparatus for strengthening cementitious concrete by placing a nanoparticle carrier liquid in contact with a first surface of a concrete section and inducing a current across the concrete section at sufficient magnitude and for sufficient time that nanoparticles in the nanoparticle carrier liquid migrate through a significant depth of the concrete section.

  16. Electrokenitic Corrosion Treatment of Concrete

    NASA Technical Reports Server (NTRS)

    Cardenas, Henry E (Inventor)

    2015-01-01

    A method and apparatus for strengthening cementitious concrete by placing a nanoparticle carrier liquid in contact with a first surface of a concrete section and inducing a current across the concrete section at sufficient magnitude and for sufficient time that nanoparticles in the nanoparticle carrier liquid migrate through a significant depth of the concrete section.

  17. Sub-slab vs. Near-slab Soil Vapor Profiles at a Chlorinated Solvent Site (1)

    EPA Science Inventory

    A critical issue in assessing the vapor intrusion pathway is the distribution and migration of VOCs from the subsurface source to the near surface environment. Of particular importance is the influence of a slab. Therefore, EPA/ORD is funding a research program with the primary...

  18. Slab temperature controls on the Tonga double seismic zone and slab mantle dehydration

    PubMed Central

    Wei, S. Shawn; Wiens, Douglas A.; van Keken, Peter E.; Cai, Chen

    2017-01-01

    Double seismic zones are two-layered distributions of intermediate-depth earthquakes that provide insight into the thermomechanical state of subducting slabs. We present new precise hypocenters of intermediate-depth earthquakes in the Tonga subduction zone obtained using data from local island–based, ocean-bottom, and global seismographs. The results show a downdip compressional upper plane and a downdip tensional lower plane with a separation of about 30 km. The double seismic zone in Tonga extends to a depth of about 300 km, deeper than in any other subduction system. This is due to the lower slab temperatures resulting from faster subduction, as indicated by a global trend toward deeper double seismic zones in colder slabs. In addition, a line of high seismicity in the upper plane is observed at a depth of 160 to 280 km, which shallows southward as the convergence rate decreases. Thermal modeling shows that the earthquakes in this “seismic belt” occur at various pressures but at a nearly constant temperature, highlighting the important role of temperature in triggering intermediate-depth earthquakes. This seismic belt may correspond to regions where the subducting mantle first reaches a temperature of ~500°C, implying that metamorphic dehydration of mantle minerals in the slab provides water to enhance faulting. PMID:28097220

  19. Slab temperature controls on the Tonga double seismic zone and slab mantle dehydration.

    PubMed

    Wei, S Shawn; Wiens, Douglas A; van Keken, Peter E; Cai, Chen

    2017-01-01

    Double seismic zones are two-layered distributions of intermediate-depth earthquakes that provide insight into the thermomechanical state of subducting slabs. We present new precise hypocenters of intermediate-depth earthquakes in the Tonga subduction zone obtained using data from local island-based, ocean-bottom, and global seismographs. The results show a downdip compressional upper plane and a downdip tensional lower plane with a separation of about 30 km. The double seismic zone in Tonga extends to a depth of about 300 km, deeper than in any other subduction system. This is due to the lower slab temperatures resulting from faster subduction, as indicated by a global trend toward deeper double seismic zones in colder slabs. In addition, a line of high seismicity in the upper plane is observed at a depth of 160 to 280 km, which shallows southward as the convergence rate decreases. Thermal modeling shows that the earthquakes in this "seismic belt" occur at various pressures but at a nearly constant temperature, highlighting the important role of temperature in triggering intermediate-depth earthquakes. This seismic belt may correspond to regions where the subducting mantle first reaches a temperature of ~500°C, implying that metamorphic dehydration of mantle minerals in the slab provides water to enhance faulting.

  20. ORNL Soils Remediation and Slabs Removal - The Bridge from D and D to Redevelopment - 12342

    SciTech Connect

    Travaglini, Mike; Halsey, Pat; Conger, Malinda; Schneider, Ken

    2012-07-01

    The landscape of the Oak Ridge National Laboratory (ORNL) has dramatically changed over the past 2 years with demolition of aging facilities in the Central Campus. Removal of these infrastructure legacies was possible due to an influx of DOE-Environmental Management funding through the American Recovery and Reinvestment Act of 2009 (ARRA). Facility D and D traditionally removes everything down to the building slab, and the Soils and Sediments Program is responsible for slabs, below-grade footers and sub-grade structures, abandoned waste utilities, and soils contaminated above certain risk levels that must be removed before the site can be considered for redevelopment. DOE-EM has used a combination of base and ARRA funding to facilitate the clean-up process in ORNL's 2000 Area. Demolition of 13 buildings in the area was funded by the ARRA. Characterization of the remaining slabs, underground pipelines and soils was funded by DOE-EM base funding. Additional ARRA funding was provided for the removal of the slabs, pipelines and contaminated soils. Removal work is in progress and consists of removing and disposing of approximately 7,650 cubic meters (m{sup 3}) of concrete, 2,000 m{sup 3} of debris, and 400 m{sup 3} of contaminated soil. Immediately adjacent to the 2000 Area is the Oak Ridge Science and Technology Park and the modernized ORNL western campus. The Science and Technology Park is the only private sector business and technology park located within the footprint of a national laboratory. The completion of this work will not only greatly reduce the risk to the ORNL campus occupants but also allow this much sought after space to be available for redevelopment and site reuse efforts at ORNL. Demolition of aging facilities enabled by injection of ARRA funding has significantly altered the landscape at ORNL while reducing risk to laboratory personnel and operations and providing valuable central campus land parcels for redevelopment to expand and enhance the

  1. Corrosion-resistant sulfur concretes

    NASA Astrophysics Data System (ADS)

    McBee, W. C.; Sullivan, T. A.; Jong, B. W.

    1983-04-01

    Sulfur concretes have been developed by the Bureau of Mines as construction materials with physical and mechanical properties that suit them for use in acid and salt corrosive environments where conventional concretes fail. Mixture design methods were established for preparing sulfur concretes using different types of aggregates and recently developed mixed-modified sulfur cements. Bench-scale testing of the sulfur concretes has shown their potential value. Corrosion resistance, strength, and durability of sulfur concrete are superior to those of conventional materials. Field in situ evaluation tests of the sulfur concretes as replacement for conventional concrete materials are in progress in corrosive areas of 24 commercial chemical, fertilizer, and metallurgical plants.

  2. 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.

  3. 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.

  4. Permeability of Clay Concretes

    NASA Astrophysics Data System (ADS)

    Solomon, F.; Ekolu, S. O.

    2015-11-01

    This paper presents an investigation on the effect of clay addition on water permeability and air permeability of concretes. Clay concrete mixes consisted of 0 to 40% clay content incorporated as cement replacement. Flow methods using triaxial cells and air permeameters were used for measuring the injected water and air flows under pressure. It was found that the higher the clay content in the mixture, the greater the permeability. At higher water-cement ratios (w/c), the paste matrix is less dense and easily allows water to ingress into concrete. But at high clay contents of 30 to 40% clay, the variation in permeability was significantly diminished among different concrete mixtures. It was confirmed that air permeability results were higher than the corresponding water permeability values when all permeability coefficients were converted to intrinsic permeability values.

  5. Strengthening lightweight concrete

    NASA Technical Reports Server (NTRS)

    Auskern, A.

    1972-01-01

    Polymer absorption by lightweight concretes to improve bonding between cement and aggregate and to increase strength of cement is discussed. Compressive strength of treated cement is compared with strength of untreated product. Process for producing polymers is described.

  6. Lightweight polymer concrete composites

    SciTech Connect

    Fontana, J.J.; Steinberg, M.; Reams, W.

    1985-08-01

    Lightweight polymer concrete composites have been developed with excellent insulating properties. The composites consist of lightweight aggregates such as expanded perlites, multicellular glass nodules, or hollow alumina silicate microspheres bound together with unsaturated polyester or epoxy resins. These composites, known as Insulating Polymer Concrete (IPC), have thermal conductivites from 0.09 to 0.19 Btu/h-ft-/sup 0/F. Compressive strengths, dependent upon the aggregates used, range from 1000 to 6000 psi. These materials can be precast or cast-in-place on concrete substrates. Recently, it has been demonstrated that these materials can also be sprayed onto concrete and other substrates. An overlay application of IPC is currently under way as dike insulation at an LNG storage tank facility. The composites have numerous potentials in the construction industry such as insulating building blocks or prefabricated insulating wall panels.

  7. Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods

    NASA Astrophysics Data System (ADS)

    Wu, Jonny; Suppe, John; Lu, Renqi; Kanda, Ravi

    2016-06-01

    We reconstructed Philippine Sea and East Asian plate tectonics since 52 Ma from 28 slabs mapped in 3-D from global tomography, with a subducted area of ~25% of present-day global oceanic lithosphere. Slab constraints include subducted parts of existing Pacific, Indian, and Philippine Sea oceans, plus wholly subducted proto-South China Sea and newly discovered "East Asian Sea." Mapped slabs were unfolded and restored to the Earth surface using three methodologies and input to globally consistent plate reconstructions. Important constraints include the following: (1) the Ryukyu slab is ~1000 km N-S, too short to account for ~20° Philippine Sea northward motion from paleolatitudes; (2) the Marianas-Pacific subduction zone was at its present location (±200 km) since 48 ± 10 Ma based on a >1000 km deep slab wall; (3) the 8000 × 2500 km East Asian Sea existed between the Pacific and Indian Oceans at 52 Ma based on lower mantle flat slabs; (4) the Caroline back-arc basin moved with the Pacific, based on the overlapping, coeval Caroline hot spot track. These new constraints allow two classes of Philippine Sea plate models, which we compared to paleomagnetic and geologic data. Our preferred model involves Philippine Sea nucleation above the Manus plume (0°/150°E) near the Pacific-East Asian Sea plate boundary. Large Philippine Sea westward motion and post-40 Ma maximum 80° clockwise rotation accompanied late Eocene-Oligocene collision with the Caroline/Pacific plate. The Philippine Sea moved northward post-25 Ma over the northern East Asian Sea, forming a northern Philippine Sea arc that collided with the SW Japan-Ryukyu margin in the Miocene (~20-14 Ma).

  8. Numerical simulations and experimental measurements of steel and ice impacts on concrete for acoustic interrogation of delaminations in bridge decks

    SciTech Connect

    Mazzeo, Brian A.; Patil, Anjali N.; Klis, Jeffrey M.; Hurd, Randy C.; Truscott, Tadd T.; Guthrie, W. Spencer

    2014-02-18

    Delaminations in bridge decks typically result from corrosion of the top mat of reinforcing steel, which leads to a localized separation of the concrete cover from the underlying concrete. Because delaminations cannot be detected using visual inspection, rapid, large-area interrogation methods are desired to characterize bridge decks without disruption to traffic, without the subjectivity inherent in existing methods, and with increased inspector safety. To this end, disposable impactors such as water droplets or ice chips can be dropped using automatic dispensers onto concrete surfaces to excite mechanical vibrations while acoustic responses can be recorded using air-coupled microphones. In this work, numerical simulations are used to characterize the flexural response of a model concrete bridge deck subject to both steel and ice impactors, and the results are compared with similar experiments performed in the laboratory on a partially delaminated concrete bridge deck slab. The simulations offer greater understanding of the kinetics of impacts and the responses of materials.

  9. Transport processes in partially saturate concrete: Testing and liquid properties

    NASA Astrophysics Data System (ADS)

    Villani, Chiara

    properties and pore structure information as inputs. Concrete exposed to deicing salts resulted to have a reduced gas transport due to the higher degree of saturation (DOS). The higher DOS is believed to contribute to the premature deterioration observed in concrete pavements exposed to deicing salts. Moisture diffusion and moisture profiles in concrete are known to directly relate with the stresses generated during shrinkage and creep mechanisms. The alteration due to the presence of shrinkage reducing admixtures on drying was also investigated in this work. Liquid properties were used to predict the diffusion coefficient in presence of SRA. Moisture profiles obtained using Fick's second law for diffusion were compared to relative humidity profiles measured on concrete slabs. Results confirm that a qualitative prediction of drying in concrete elements is realistic when using this type of approach.

  10. Performance of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, H. A.; Grugel, R. N.

    2009-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in a lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and, by oxidation of the soil, iron and sulfur can be produced. Sulfur concrete specimens were cycled between liquid nitrogen (approx.]91 C) and room temperature (^21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (^21 C) and ^-101 C. Test results showed that due to temperature cycling, the compressive strength of cycled specimens was 20% of those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibres. The lunar regolith simulant was melted in a 25 cc Pt- Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to i hour. Glass fibres and small rods were pulled from the melt. The glass fibres were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Beams strengthened with glass fibres showed to exhibit an increase in the flexural strength by as much as 45%.

  11. CTH analyses of steel rod penetration into aluminum and concrete targets with comparisons to experimental data

    SciTech Connect

    Kmetyk, L.N.; Yarrington, P.

    1994-10-01

    Calculational results are presented here for a class of intermediate-velocity penetration problems. The problems of interest involve penetration of moderate-strength target materials by high-strength projectiles. Two series of metal penetration experiments and a series of concrete slab perforation tests were simulated in this study. The computer code used for the calculations was the CTH code, which employs a recently-developed ``boundary layer`` algorithm for treating penetration problems such as these.

  12. Ship Tracks

    Atmospheric Science Data Center

    2013-04-19

    article title:  Ship Tracks in a Stratiform Cloud Layer     ... stratocumulus. These striking linear patterns are known as "ship tracks", and are produced when fine particles (also called aerosols) from ... be used with the red filter placed over your left eye. Ship tracks are important examples of aerosol-cloud interactions. They are ...

  13. More economical but equally effective internally sealed concrete

    NASA Astrophysics Data System (ADS)

    White, R. M.; Taylor, M. A.; Haxo, H. E., Jr.

    1981-12-01

    Wax beads of several lower melting, lower cost wax blends can seal concrete as effectively as the paraffin-montan wax beads currently used in internally sealed concrete bridge decks, without affecting other important properties of the concrete. Savings of 5% to 25% in raw material costs can be expected to lower the cost of wax beads by approximately 5% to 20%. Since the minimum temperature required for melting the wax beads is about 25 F (14 C) lower than for the current beads, the cost of heating a bridge deck to achieve effective sealing should be reduced by approximately 15%. Beads of two formulations: 10% montan wax, 15% firbark wax, 75% paraffin 140/142 (FMP), and 5% stearic acid, 20% hydrogenated tallow, 75% paraffin 150/152 (STP), were produced in pilot plant quantities and were evaluated on two field tests. Damage to the beads during extended mixing of the concrete was suspected to be one of the causes of low strength and poor resistance to scaling of the test slabs in the first test. Some blocking of the lower melting beads at temperatures between 100 and 110 F (38 and 43 C) occurred during production in hot weather or storage for long times in warm locations. Coating the beads with 10% cement restored them to a free-flowing condition.

  14. A Simple Demonstration of Concrete Structural Health Monitoring Framework

    SciTech Connect

    Mahadevan, Sankaran; Agarwal, Vivek; Cai, Guowei; Nath, Paromita; Bao, Yanqing; Bru Brea, Jose Maria; Koester, David; Adams, Douglas; Kosson, David

    2015-03-01

    Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This ongoing research project is seeking to develop a probabilistic framework for health diagnosis and prognosis of aging concrete structures in a nuclear power plant subjected to physical, chemical, environment, and mechanical degradation. The proposed framework consists of four elements—damage modeling, monitoring, data analytics, and uncertainty quantification. This report describes a proof-of-concept example on a small concrete slab subjected to a freeze-thaw experiment that explores techniques in each of the four elements of the framework and their integration. An experimental set-up at Vanderbilt University’s Laboratory for Systems Integrity and Reliability is used to research effective combination of full-field techniques that include infrared thermography, digital image correlation, and ultrasonic measurement. The measured data are linked to the probabilistic framework: the thermography, digital image correlation data, and ultrasonic measurement data are used for Bayesian calibration of model parameters, for diagnosis of damage, and for prognosis of future damage. The proof-of-concept demonstration presented in this report highlights the significance of each element of the framework and their integration.

  15. 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%.

  16. Pentek concrete scabbling system: Baseline report; Greenbook (chapter)

    SciTech Connect

    1997-07-31

    The Pentek scabbling technology was tested at Florida International University (FIU) and is being evaluated as a baseline technology. This report evaluates it for safety and health issues. It is a commercially available technology and has been used for various projects at locations throughout the country. The Pentek concrete scabbling system consisted of the MOOSE, SQUIRREL-I, and SQUIRREL-III scabblers. The scabblers are designed to scarify concrete floors and slabs using cross-section, tungsten carbide tipped bits. The bits are designed to remove concrete in 318 inch increments. The bits are either 9-tooth or demolition type. The scabblers are used with a vacuum system designed to collect and filter the concrete dust and contamination that is removed from the surface. The safety and health evaluation conducted during the testing demonstration focused on two main areas of exposure: dust and noise. Dust exposure was minimal, but noise exposure was significant. Further testing for each of these exposures is recommended. Because of the outdoor environment where the testing demonstration took place, results may be inaccurate. It is feasible that the dust and noise levels will be higher in an enclosed operating environment. Other areas of concern were arm-hand vibration, whole-body vibration, ergonomics, heat stress, tripping hazards, electrical hazards, machine guarding, and lockout/tagout.

  17. Non-traditional shape GFRP rebars for concrete reinforcement

    NASA Astrophysics Data System (ADS)

    Claure, Guillermo G.

    existing provisions and standards allowing for a consistent universal norm for all GFRP rebars were reached. This dissertation also presents an evaluation of the structural behavior of reinforced concrete (RC) beams and slabs using the new type of GFRP rebar consisting of a non-traditional hollow-core shape compared to "traditional" solid round rebars with equivalent cross-sectional areas within the framework of two studies, respectively. To validate the design assumptions following ACI 440.1R design guidelines, two conditions were investigated: under-reinforced (failure controlled by rupture of GFRP rebar); and, over-reinforced (failure controlled by crushing of concrete). For comparison, a cyclic three-point bending load test matrix was developed: for beams, 3 under-reinforced and 3 over-reinforced with hollow-core and solid GFRP rebars, respectively, making a total of 12 RC specimens; for slabs, 3 under-reinforced and 3 over-reinforced with hollow-core and 2 types of solid GFRP rebars, respectively, making a total of 18 RC slabs. The studies on GFRP RC beams and slabs concluded that the hollow-core GFRP rebars were as effective as their solid counterpart and ACI 440.1R design guidelines were applicable to predict their performance. It was shown that final design may be controlled by the permissible deflections as governing parameter for elements under service conditions. Also, a final study with a test matrix containing six extra specimens was generated for post-fire residual strength evaluation of fire-exposed GFRP RC slabs along with temperature gradient in the slabs and dynamic mechanical analysis (DMA) investigation on GFRP samples extracted from the fire-exposed slabs. In this study, the ability of GFRP RC slabs to retain structural integrity during a standards fire exposure as well as determining the residual structural capacity were investigated. The residual strength evaluation of the fire-exposed slabs showed a range of results varying between +/- 10%, of the

  18. 42. PRESSING A SLAB OF CLAY ONTO A MOSAIC MOLD. ...

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

    42. PRESSING A SLAB OF CLAY ONTO A MOSAIC MOLD. THE MOLD, WHICH HAS A RAISED DESIGN, LEAVES AND OUTLINE IN THE SLAB, THE PIECES THUS DEFINED, ARE THEN CUT APART TO BE FIRED SEPARATELY AND REASSEMBLED. - Moravian Pottery & Tile Works, Southwest side of State Route 313 (Swamp Road), Northwest of East Court Street, Doylestown, Bucks County, PA

  19. How to produce flat slabs: insights from numeric modeling

    NASA Astrophysics Data System (ADS)

    Constantin Manea, Vlad; Perez-Gussinye, Marta; Manea, Marina

    2010-05-01

    Flat slab subduction occurs at ~10% of the active convergent margins and it is assumed that subduction of oceanic aseismic ridges or seamount chains is the main mechanism to produce very low angle subduction slabs. However, recent numeric and analog modeling showed that ridges alone of moderate dimensions subducted perpendicular to the trench are not sufficient to produce flat-slab geometries. Therefore an alternative mechanism able to produce flat-slabs is required. In this paper we present dynamic numeric modeling results of subduction in the vicinity of thick continental lithosphere, as a craton for example. We tailored our modeling setup for the Chilean margins at ~31° and our models are integrated back in time 30 Myr. Modeling results show that a craton thickness of 200 km or more when approaching the trench is capable of blocking the asthenospheric flow in the mantle wedge and increasing considerably the suction force. We were able to produce a flat slab that fits well the flat slab geometry in Chile (based on seismicity) and stress distribution. We conclude that thick cratons located in the vicinity of subduction zones, are capable to produce very low angle slabs, and probable a combination of buoyant ridge subduction with a neighbor thick craton represent a better mechanism to produce flat slabs.

  20. Slab-rollback induced upper mantle upwelling near lateral slab edges: A new mechanism for generating intra-plate magmatism in the central Mediterranean

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.

    2010-12-01

    Most volcanism on Earth is associated with plate boundaries and can thus be explained in a plate tectonic framework. Intra-plate volcanism, however, cannot directly be explained with plate tectonic theory. Intraplate volcanism is frequently explained with the plume model, in which a relatively fixed buoyant plume rises from the lower mantle to the surface and, as the overlying plate moves with respect to the plume source, produces a linear hotspot track along which the age of volcanoes progressively changes. This model has been applied to linear volcanic chains such as the Hawaii-Emperor Ridge in the Pacific and the Walvis Ridge in the Atlantic Ocean. Other intra-plate volcanism that does not occur in linear chains and does not show a preferred age progression in a specific geographical direction is more difficult to explain with the plume model, and might require an alternative explanation. There are several examples of intraplate volcanism on Earth located close to lateral slab edges, suggesting that they might be genetically related to these slab edges. One example of such volcanism is located in Sicily in the Mediterranean, which took place at ~7.0-1.1 Ma on the Iblean plateau and at 0.5 Ma to Present to form Mount Etna. The volcanics are located in close proximity but are laterally offset with respect to the Eolian magmatic arc and the Calabrian subduction zone, where Ionian oceanic lithosphere is subducting west-northwestward below Calabria. The volcanics in Sicily can therefore not be interpreted as arc volcanism. Previous work, primarily based on the geochemistry and petrology of the volcanics, suggests that the volcanism resulted from a plume. The volcanics in Sicily and surrounding seas, however, do not align along a linear chain and show no lateral age progression. Here it is proposed that Mount Etna and the Iblean volcanics are related to decompression melting of upper mantle material that is flowing around the southern Ionian slab edge to accommodate

  1. Forward modeling the perovskite-postperovskite transition in seismically anisotropic models beneath a slab

    NASA Astrophysics Data System (ADS)

    Cottaar, S.; Li, M.; Miyagi, L. M.; McNamara, A. K.; Romanowicz, B. A.; Wenk, H.

    2012-12-01

    Seismic observations of the lowermost mantle in subduction regions show strong seismic anisotropy as well as a seismic discontinuity. Both observations appear consistent with a perovskite to post-perovskite phase transition. The single crystal velocities of the post-perovksite phase are both faster and more anisotropic. How the seismic discontinuity appears in reflection studies will depend on the retainment of texturing across the phase transitions. In this study we test the texturing across the phase transition and its seismic detectability by forward modeling through a combination of geodynamics and mineral physics tools. Tracers in a 3D geodynamical model with a subducting slab (constrained at the surface) track the velocity gradient tensor along the slab. This information is fed into a viscoplastic polycrystal plasticity model along with major mineral components and different assumptions for their active slip systems and elastic properties. We include a perovskite to post-perovskite phase transition. We assume different models converting from perovskite to post-perovskite textured material, of which the simplest is a total randomization. Away from the discontinuity, the strong texturing towards the CMB will overprint the signature of any of these assumptions. Here we present radially anisotropic models expressed in terms of seismic SH and SV velocities, illustrating the seismic sensitivity to the texture conversion within the transition. Our geodynamical model has a large number of tracers that track different areas in the subducting slab and represent lateral variations in deformation. These variations result in a family of modeled seismic discontinuities, representing the spread in depth and sharpness of the discontinuity measured by seismic ScS precursor studies.

  2. Slab-geometry Nd:glass laser performance studies

    NASA Technical Reports Server (NTRS)

    Eggleston, J. M.; Kane, T. J.; Byer, R. L.; Unternahrer, J.

    1982-01-01

    It is noted that slab-geometry solid-state lasers potentially provide significant performance improvements relative to conventional rod-geometry lasers. Experimental measurements that use an Nd:glass test-bed slab laser are presented. A comparison is made between the results and computer-model predictions of the slab-geometry approach. The computer model calculates and displays the temperature and stress fields in the slab, and on the basis of these predicts birefringence and index-of-refraction distributions. The effect that these distributions have on optical propagation is determined in a polarization-sensitive ray-tracing section of the model. Calculations are also made of stress-induced surface curvature and the resulting focusing effects. The measurements are found to be in good agreement with the computer-model predictions. It is concluded that the slab configuration offers significant laser-performance advantages in comparison with the traditional rod-laser geometry.

  3. Electromagnetic Tunneling and Resonances in Pseudochiral Omega Slabs

    PubMed Central

    Razzaz, Faroq; Alkanhal, Majeed A. S.

    2017-01-01

    This paper presents theoretical investigation of the electromagnetic wave tunneling and anomalous transmission around the trapped modes in a pseudochiral omega slab. The dispersion relation, the conditions of the trapped modes, and the evanescent wave coupling and tunneling in two different reciprocal pseudochiral omega slab structures are derived. The Berreman’s matrix method is applied to obtain the transmission coefficients across the pseudochiral omega slab. When the structure is perturbed, a resonance phenomenon is detected around the trapped modes. This resonance results in transmission anomalies (total transmission and total reflection) and dramatic field amplifications around the trapped modes. The number of the discrete trapped modes and then the resonance frequencies are prescribed by the parameters of the pseudochiral omega slab such as the value of the omega parameter and its orientation and the slab thickness. PMID:28165058

  4. Compressive Membrane Capability Estimates in Laterally Edge Restrained Reinforced Concrete One-Way Slabs

    DTIC Science & Technology

    1999-05-01

    LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT NSN 7640-01-280-5500 Standard Form 298 (Rev. 2-69) Pre ;erlbed by ANSI Sti. Z39-18 298-102 MAqY...peak load capacity as in Park’s deformation theory, to equate work done by the loads to the dissipated energy. Each of these methods requires a pre ... pre -determined deflection, but instead required a pre -determined thrust value. The known thrust (i.e., prestress) was used in the axial force-moment

  5. Lithosphere-Mantle Interactions Associated with Flat-Slab Subduction

    NASA Astrophysics Data System (ADS)

    Gerault, M.; Becker, T. W.; Husson, L.; Humphreys, E.

    2014-12-01

    Episodes of flat-slab subduction along the western margin of the Americas may have lead to the formation of intra-continental basins and seas, as well as mountain belts and continental plateaux. Here, we explore some of the consequences of a flat slab morphology, linking dynamic topography and stress patterns in continents to slab and mantle dynamics. Using a 2-D cylindrical code, we develop general models and apply them to the North and South America plates. The results are primarily controlled by the coupling along the slab-continent interface (due to geometry and viscosity), the viscosity of the mantle wedge, and the buoyancy of the subducted lithosphere. All models predict broad subsidence, large deviatoric stresses, and horizontal compression above the tip of the flat slab and the deep slab hinge. In models where the slab lays horizontally for hundreds of kilometers, overriding plate compression focuses on both ends of the flat segment, where normal-dip subduction exerts a direct downward pull. In between, a broad low-stress region gets uplifted proportionally to the amount of coupling between the slab and the continent. Anomalously buoyant seafloor enhances this effect but is not required. The downward bending of the flat slab extremities causes its upper part to undergo extension and the lower part to compress. These results have potential for explaining the existence of relatively undeformed, uplifted regions surrounded by mountain belts, such as in the western U.S. and parts of the Andes. Adequately modeling topography and stress in the unusual setting of southwestern Mexico requires a low-viscosity subduction interface and mantle wedge. Our results are only partially controlled by the buoyancy of the subducting plate, suggesting that the viscosity and the morphology of the slab are important, and that the often-used low resolution and "Stokeslet" models may be missing substantial effects.

  6. Slab anisotropy from subduction zone guided waves in Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, K. H.; Tseng, Y. L.; Hu, J. C.

    2014-12-01

    Frozen-in anisotropic structure in the oceanic lithosphere and faulting/hydration in the upper layer of the slab are expected to play an important role in anisotropic signature of the subducted slab. Over the past several decades, despite the advances in characterizing anisotropy using shear wave splitting method and its developments, the character of slab anisotropy remains poorly understood. In this study we investigate the slab anisotropy using subduction zone guided waves characterized by long path length in the slab. In the southernmost Ryukyu subduction zone, seismic waves from events deeper than 100 km offshore northern Taiwan reveal wave guide behavior: (1) a low-frequency (< 1 Hz) first arrival recognized on vertical and radial components but not transverse component (2) large, sustained high-frequency (3-10 Hz) signal in P and S wave trains. The depth dependent high-frequency content (3-10Hz) confirms the association with a waveguide effect in the subducting slab rather than localized site amplification effects. Using the selected subduction zone guided wave events, we further analyzed the shear wave splitting for intermediate-depth earthquakes in different frequency bands, to provide the statistically meaningful shear wave splitting parameters. We determine shear wave splitting parameters from the 34 PSP guided events that are deeper than 100 km with ray path traveling along the subducted slab. From shear wave splitting analysis, the slab and crust effects reveal consistent polarization pattern of fast directions of EN-WS and delay time of 0.13 - 0.27 sec. This implies that slab anisotropy is stronger than the crust effect (<0.1 s) but weaker than the mantle wedge and sub-slab mantle effect (0.3-1.3 s) in Taiwan.

  7. Viscoelasticity of a homeotropic nematic slab

    NASA Astrophysics Data System (ADS)

    Oswald, Patrick

    2015-12-01

    The viscoelastic behavior of a homeotropic nematic slab is studied when it is subjected to a (dilation-compression) sinusoidal deformation of small amplitude (linear regime). I show that the nematic phase behaves as an isotropic liquid of viscosity ηc (ν3) at low (high) frequency, where ηc is the third Miesowicz viscosity and ν3 a smaller viscosity first introduced by Martin, Parodi, and Pershan. The crossover frequency f⊙ between these two asymptotic regimes scales as h2/D , where h is the sample thickness and D =K3/γ1 is the orientational diffusivity (with K3 the bend constant and γ1 the rotational viscosity). Between these two limits the sample behaves as a viscoelastic fluid whose elastic and loss moduli G' and G'' are calculated. These predictions are tested experimentally with a piezoelectric rheometer.

  8. Laser applications in machining slab materials

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping

    1990-10-01

    Since the invention of the laser back in 1960, laser technology has been extensively applied in many fields of science and technology. These has been a history of nearly two decades of using lasers as an energy source in machining materials, such as cutting, welding, ruling and boring, among other operations. With the development of flexible automation in production, the advantages of laser machining have has grown more and more obvious. The combination of laser technology and computer science further promotes the enhancement and upgrading of laser machining and related equipment. At present, many countries are building high quality laser equipment for machining slab materials, such as the Coherent and Spectra Physics corporations in the United States, the Trumpf Corporation in West Germany, the Amada Corporation in Japan, and the Bystronic Corporation in Switzerland, among other companies.

  9. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, J.W.; Carrano, A.V.; Davidson, J.C.; Koo, J.C.

    1998-05-05

    A hybrid slab-microchannel gel electrophoresis system is described. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate. 4 figs.

  10. Thermal Removal of Tritium from Concrete and Soil to Reduce Groundwater Impacts - 13197

    SciTech Connect

    Jackson, Dennis G.; Blount, Gerald C.; Wells, Leslie H.; Cardoso, Joao E.; Kmetz, Thomas F.; Reed, Misty L.

    2013-07-01

    Legacy heavy-water moderator operations at the Savannah River Site (SRS) have resulted in the contamination of equipment pads, building slabs, and surrounding soil with tritium. At the time of discovery the tritium had impacted the shallow (< 3-m) groundwater at the facility. While tritium was present in the groundwater, characterization efforts determined that a significant source remained in a concrete slab at the surface and within the associated vadose zone soils. To prevent continued long-term impacts to the shallow groundwater a CERCLA non-time critical removal action for these source materials was conducted to reduce the leaching of tritium from the vadose zone soils and concrete slabs. In order to minimize transportation and disposal costs, an on-site thermal treatment process was designed, tested, and implemented. The on-site treatment consisted of thermal detritiation of the concrete rubble and soil. During this process concrete rubble was heated to a temperature of 815 deg. C (1,500 deg. F) resulting in the dehydration and removal of water bound tritium. During heating, tritium contaminated soil was used to provide thermal insulation during which it's temperature exceeded 100 deg. C (212 deg. F), causing drying and removal of tritium. The thermal treatment process volatiles the water bound tritium and releases it to the atmosphere. The released tritium was considered insignificant based upon Clean Air Act Compliance Package (CAP88) analysis and did not exceed exposure thresholds. A treatability study evaluated the effectiveness of this thermal configuration and viability as a decontamination method for tritium in concrete and soil materials. Post treatment sampling confirmed the effectiveness at reducing tritium to acceptable waste site specific levels. With American Recovery and Reinvestment Act (ARRA) funding three additional treatment cells were assembled utilizing commercial heating equipment and common construction materials. This provided a total

  11. Thermal Removal Of Tritium From Concrete And Soil To Reduce Groundwater Impacts

    SciTech Connect

    Jackson, Dennis G.; Blount, Gerald C.; Wells, Leslie H.; Cardoso-Neto, Joao E.; Kmetz, Thomas F.; Reed, Misty L.

    2012-12-04

    Legacy heavy-water moderator operations at the Savannah River Site (SRS) have resulted in the contamination of equipment pads, building slabs, and surrounding soil with tritium. At the time of discovery the tritium had impacted the shallow (< 3-m) groundwater at the facility. While tritium was present in the groundwater, characterization efforts determined that a significant source remained in a concrete slab at the surface and within the associated vadose zone soils. To prevent continued long-term impacts to the shallow groundwater a CERCLA non-time critical removal action for these source materials was conducted to reduce the leaching of tritium from the vadose zone soils and concrete slabs. In order to minimize transportation and disposal costs, an on-site thermal treatment process was designed, tested, and implemented. The on-site treatment consisted of thermal detritiation of the concrete rubble and soil. During this process concrete rubble was heated to a temperature of 815 deg C (1,500 deg F) resulting in the dehydration and removal of water bound tritium. During heating, tritium contaminated soil was used to provide thermal insulation during which it's temperature exceeded 100 deg C (212 deg F), causing drying and removal of tritium. The thermal treatment process volatiles the water bound tritium and releases it to the atmosphere. The released tritium was considered insignificant based upon Clean Air Act Compliance Package (CAP88) analysis and did not exceed exposure thresholds. A treatability study evaluated the effectiveness of this thermal configuration and viability as a decontamination method for tritium in concrete and soil materials. Post treatment sampling confirmed the effectiveness at reducing tritium to acceptable waste site specific levels. With American Recovery and Reinvestment Act (ARRA) funding three additional treatment cells were assembled utilizing commercial heating equipment and common construction materials. This provided a total of

  12. 26. Evening view of concrete mixing plant, concrete placement tower, ...

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

    26. Evening view of concrete mixing plant, concrete placement tower, cableway tower, power line and derrick. Photographer unknown, 1927. Source: MWD. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  13. Sensitivity analysis of free vibration characteristics of an in situ railway concrete sleeper to variations of rail pad parameters

    NASA Astrophysics Data System (ADS)

    Kaewunruen, Sakdirat; Remennikov, Alex M.

    2006-11-01

    The vibration of in situ concrete sleepers in a railway track structure is a major factor causing cracking of prestressed concrete sleepers and excessive railway track maintenance cost. Not only does the ballast interact with the sleepers, but the rail pads also take part in affecting their free vibration characteristics. This paper presents a sensitivity analysis of free vibration behaviors of an in situ railway concrete sleeper (standard gauge sleeper), incorporating sleeper/ballast interaction, subjected to the variations of rail pad properties. Through finite element analysis, Timoshenko-beam and spring elements were used in the in situ railway concrete sleeper modeling. This model highlights the influence of rail pad parameters on the free vibration characteristics of in situ sleepers. In addition, information on the first five flexural vibration modes indicates the dynamic performance of railway track when using different types of rail pads, as it plays a vital role in the cracking deterioration of concrete sleepers.

  14. Electrokinetic decontamination of concrete

    SciTech Connect

    Lomasney, H.

    1995-10-01

    The U.S. Department of Energy has assigned a priority to the advancement of technology for decontaminating concrete surfaces which have become contaminated with radionuclides, heavy metals, and toxic organics. This agency is responsible for decontamination and decommissioning of thousands of buildings. Electrokinetic extraction is one of the several innovative technologies which emerged in response to this initiative. This technique utilizes an electropotential gradient and the subsequent electrical transport mechanism to cause the controlled movement of ionics species, whereby the contaminants exit the recesses deep within the concrete. This report discusses the technology and use at the Oak Ridge k-25 plant.

  15. Structural Materials: 95. Concrete

    SciTech Connect

    Naus, Dan J

    2012-01-01

    Nuclear power plant concrete structures and their materials of construction are described, and their operating experience noted. Aging and environmental factors that can affect the durability of the concrete structures are identified. Basic components of a program to manage aging of these structures are identified and described. Application of structural reliability theory to devise uniform risk-based criteria by which existing facilities can be evaluated to achieve a desired performance level when subjected to uncertain demands and to quantify the effects of degradation is outlined. Finally, several areas are identified where additional research is desired.

  16. Impact Resistance Behaviour of Banana Fiber Reinforced Slabs

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 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 BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content 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. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)

  17. A dipping, thick Farallon slab below central United States

    NASA Astrophysics Data System (ADS)

    Sun, D.; Gurnis, M.; Saleeby, J.; Helmberger, D. V.

    2015-12-01

    It has been hypothesized that much of the Laramide orogeny was caused by dynamic effects induced by an extensive flat slab during a period of plateau subduction. A particularly thick block containing the Shatsky Rise conjugate, now in the mid-mantle, left a distinctive deformation footprint from southern California to Denver, Colorado. Thus mid-mantle, relic slabs can provide fundamental information about past subduction and the history of plate tectonics if properly imaged. Here we find clear evidence for a northeastward dipping (35° dip), slab-like, but fat (up to 400-500 km thick) seismic anomaly within the top of the lower mantle below the central United States. Using a deep focus earthquake below Spain with direct seismic paths that propagate along the top and bottom of the anomaly, we find that the observed, stacked seismic waveforms recorded with the dense USArray show multi-pathing indicative of sharp top and bottom surfaces. Plate tectonic reconstructions in which the slab is migrated back in time suggest strong coupling of the slab to North America. In combination with the reconstructions, we interpret the structure as arising from eastward dipping Farallon subduction at the western margin of North America during the Cretaceous, in contrast with recent interpretations. The slab could have been fattened through a combination of pure shear thickening during flat-slab subduction and a folding instability during penetration into the lower mantle.

  18. Constraining Slab Breakoff Induced Magmatism through Numerical Modelling

    NASA Astrophysics Data System (ADS)

    Freeburn, R.; Van Hunen, J.; Maunder, B. L.; Magni, V.; Bouilhol, P.

    2015-12-01

    Post-collisional magmatism is markedly different in nature and composition than pre-collisional magmas. This is widely interpreted to mark a change in the thermal structure of the system due to the loss of the oceanic slab (slab breakoff), allowing a different source to melt. Early modelling studies suggest that when breakoff takes place at depths shallower than the overriding lithosphere, magmatism occurs through both the decompression of upwelling asthenopshere into the slab window and the thermal perturbation of the overriding lithosphere (Davies & von Blanckenburg, 1995; van de Zedde & Wortel, 2001). Interpretations of geochemical data which invoke slab breakoff as a means of generating magmatism mostly assume these shallow depths. However more recent modelling results suggest that slab breakoff is likely to occur deeper (e.g. Andrews & Billen, 2009; Duretz et al., 2011; van Hunen & Allen, 2011). Here we test the extent to which slab breakoff is a viable mechanism for generating melting in post-collisional settings. Using 2-D numerical models we conduct a parametric study, producing models displaying a range of dynamics with breakoff depths ranging from 150 - 300 km. Key models are further analysed to assess the extent of melting. We consider the mantle wedge above the slab to be hydrated, and compute the melt fraction by using a simple parameterised solidus. Our models show that breakoff at shallow depths can generate a short-lived (< 3 Myr) pulse of mantle melting, through the hydration of hotter, undepleted asthenosphere flowing in from behind the detached slab. However, our results do not display the widespread, prolonged style of magmatism, observed in many post-collisional areas, suggesting that this magmatism may be generated via alternative mechanisms. This further implies that using magmatic observations to constrain slab breakoff is not straightforward.

  19. The Propagation of Electromagnetic Waves in Thin Dielectric Slabs.

    DTIC Science & Technology

    1988-05-01

    Continue on reverse if recessary, and identify by block number) This report precents the solutions of Maxwell’s equations for the TE and TM modes of...field versus distance from slab center for two even and two odd TM modes .... 25 5. Electric field for TE even mode and magnetic field for TM even mode...34 vi1and/or ’it Special 6MEN Figures 6. Electric field versus distance from slab center for a slab of 0.35 [ tm thickness and dielectric coefficients of

  20. Amplification of acoustic evanescent waves using metamaterial slabs.

    PubMed

    Park, Choon Mahn; Park, Jong Jin; Lee, Seung Hwan; Seo, Yong Mun; Kim, Chul Koo; Lee, Sam H

    2011-11-04

    We amplified acoustic evanescent waves using metamaterial slabs with a negative effective density. For the amplifying effect of the slab to overcome the dissipation, it is necessary that the imaginary part of the effective density is much smaller than the real part, a condition not satisfied so far. We report the construction of membrane-based two-dimensional negative-density metamaterials which exhibited remarkably small dissipation. Using a slab of this metamaterial we realized a 17-fold net amplitude gain at a remote distance from the evanescent wave source. Potential applications include acoustic superlensing.

  1. On the parametric transparency of a magnetized plasma slab

    NASA Astrophysics Data System (ADS)

    Gradov, O. M.; Stenflo, L.

    1981-06-01

    A mechanism is proposed for the nonlinear transparency of a dense magnetized plasma slab to electromagnetic radiation. The mechanism is based on the parametric excitation of surface waves in a cold magnetized plasma slab. It is shown that a significant proportion of incident radiation will be able to penetrate the slab due to saturation caused by the nonlinear resonant absorption of the surface waves generated. The mechanism also predicts the presence of transmitted radiation at a frequency less than that of the incident radiation in a direction parallel to the incident pump-wave electric field, the external constant magnetic field and the plasma layer.

  2. May eclogite dehydration cause slab fracturation ?

    NASA Astrophysics Data System (ADS)

    Loury, Chloé; Lanari, Pierre; Rolland, Yann; Guillot, Stéphane; Ganino, Clément

    2015-04-01

    Petrological and geophysical evidences strongly indicate that fluids releases play a fundamental role in subduction zones as in subduction-related seismicity and arc magmatism. It is thus important to assess quantitatively their origin and to try to quantify the amount of such fluids. In HP metamorphism, it is well known that pressure-dependent dehydration reactions occur during the prograde path. Many geophysical models show that the variations in slab physical properties along depth could be linked to these fluid occurrences. However it remains tricky to test such models on natural sample, as it is difficult to assess or model the water content evolution in HP metamorphic rocks. This difficulty is bound to the fact that these rocks are generally heterogeneous, with zoned minerals and preservation of different paragenesis reflecting changing P-T conditions. To decipher the P-T-X(H2O) path of such heterogeneous rocks the concept of local effective bulk (LEB) composition is essential. Here we show how standardized X-ray maps can be used to constrain the scale of the equilibration volume of a garnet porphyroblast and to measure its composition. The composition of this equilibrium volume may be seen as the proportion of the rock likely to react at a given time to reach a thermodynamic equilibrium with the growing garnet. The studied sample is an eclogite coming from the carboniferous South-Tianshan suture (Central Asia) (Loury et al. in press). Compositional maps of a garnet and its surrounding matrix were obtained from standardized X-ray maps processed with the program XMapTools (Lanari et al, 2014). The initial equilibration volume was modeled using LEB compositions combined together with Gibbs free energy minimization. P-T sections were calculated for the next stages of garnet growth taking into account the fractionation of the composition at each stage of garnet growth. The modeled P-T-X(H2O) path indicates that the rock progressively dehydrates during the

  3. Online Tracking

    MedlinePlus

    ... used to track you on all kinds of internet-connected devices that have browsers, such as smart phones, tablets, laptop and desktop computers. How does tracking in mobile apps occur? When you access mobile applications, companies don’t have access to ...

  4. Beyond Tracking.

    ERIC Educational Resources Information Center

    Bates, Percy; And Others

    1992-01-01

    On the surface, educational tracking may seem like a useful tool for allowing students to work at their own pace, and to avoid discouraging competition, but abuses of the tracking idea have arisen through biased placement practices that have denied equal access to education for minority students. The articles in this issue explore a number of…

  5. Derailing Tracking.

    ERIC Educational Resources Information Center

    Black, Susan

    1993-01-01

    Reviews recent research on student achievement, self-concept, and curriculum and instruction showing the ineffectiveness of tracking and ability grouping. Certain court rulings show that tracking violates the equal protection clause of the Fourteenth Amendment. Innovative alternatives include cooperative learning, mastery learning, peer tutoring,…

  6. High temperature polymer concrete

    DOEpatents

    Fontana, J.J.; Reams, W.

    1984-05-29

    This invention is concerned with a polymer concrete composition, which is a two-component composition useful with many bases including metal. Component A, the aggregate composition, is broadly composed of silica, silica flour, portland cement, and acrylamide, whereas Component B, which is primarily vinyl and acrylyl reactive monomers, is a liquid system.

  7. Concrete Block Pavements

    DTIC Science & Technology

    1983-03-01

    1967, Cedergren 1974, Federal Highway .’,U .. V,47 -’":: 37 Administration 1980). Block pavements have essentially the same prob- lems with moisture...Vicksburg, Miss. Cedergren , H. R. 1974. Drainage of Highway and Airfield Pavements, John Wiley and Sons, New VOk. I Cement and Concrete Association

  8. Heidrun concrete TLP: Update

    SciTech Connect

    Munkejord, T.

    1995-10-01

    This paper gives a summary of the Heidrun substructure including tethers and foundations. The focus will although be on the concrete substructure. The Heidrun Field is located in 345 m water depth in the northern part of the Haltenbanken area, approximately 100N miles from the west coast of mid-Norway. The field is developed by means of a concrete Tension Leg Platform (TLP) by Conoco Norway Inc. The TLP will be moored by 16 steel tethers, arranged in groups of four per corner, which secure the substructure (hull) to the concrete foundations. A general view of the TLP is shown. The Heidrun TLP will be the northern most located platform in the North Sea when installed at Haltenbanken in 1995. Norwegian Contractors a.s (NC) is undertaking the Engineering, Procurement, Construction and Installation (EPCI) contract for the Heidrun TLP substructure. This comprises the complete delivery of the hull with two module support beams (MSB), including all mechanical outfitting. Furthermore, NC will perform all marine operations related to the substructure. For the concrete foundations NC has performed the detailed engineering work and has been responsible for the two to field and installation of the foundations.

  9. Micromechanics of Concrete.

    DTIC Science & Technology

    1988-01-25

    reflects the dispersion of the coarse aggregates on the mesoscale. Specifically, the experimental measure- ments indicate ( Mindess and Young 1981, Zaitsev...Mecanique des Materiaux Solides, Dunod, Paris. Mindess , S. and J. Young (1981), Concrete, Prentice-Hall Inc., Englewood Cliffs, NJ. Mura, T. (1982

  10. The effects of latex additions on centrifugally cast concrete for internal pipeline protection

    SciTech Connect

    Buchheit, R.G.; Hinkebein, T.E.; Hlava, P.F.; Melton, D.G.

    1993-07-01

    Centrifugally-cast concrete liners applied to the interiors of plain steel pipe sections were tested for corrosion performance in brine solutions. An American Petroleum Institute (API) standard concrete, with and without additions of a styrene-butadiene copolymer latex, was subjected to simulated service and laboratory tests. Simulated service tests used a mechanically pumped test manifold containing sections of concrete-lined pipe. Linear polarization probes embedded at steel-concrete interfaces tracked corrosion rates of these samples as a function of exposure time. Laboratory tests used electrochemical impedance spectroscopy to study corrosion occurring at the steel-concrete interfaces. Electron probe microanalysis (EPMA) determined ingress and distribution of damaging species, such as Cl, in concrete liners periodically returned from the field. Observations of concrete-liner fabrication indicate that latex loading levels were difficult to control in the centrifugal-casting process. Overall, test results indicate that latex additions do not impart significant improvements to the performance of centrifugally cast liners and may even be detrimental. Corrosion at steel-concrete interfaces appears to be localized and the area fraction of corroding interfaces can be greater in latex-modified concretes than in API baseline material. EPMA shows higher interfacial Cl concentration in the latex-modified concretes than in the API standard due to rapid brine transport through cracks to the steel surface.

  11. Magnetoelectric sensor excitations in hexaferrite slabs

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Izadkhah, Hessam; Somu, Sivasubramanian; Vittoria, Carmine

    2015-06-01

    We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite slabs in the frequency range of 100 Hz to 10 MHz. Novel circuit designs incorporating both spiral and solenoid coils and single and multi-capacitor banks were developed to probe the physics and properties of ME hexaferrites and explore ME effects for sensor detections. Fundamental measurements of the anisotropic tensor elements of the magneto-electric coupling parameter were performed using these novel techniques. In addition, for H-field sensing experiments we measured sensitivity of about 3000 Vm-1/G using solenoid coils and 8000 Vm-1/G using spiral coils. For E-field, sensing the sensitivity was 10-4 G/Vm-1 and using single capacitor detector. Sensitivity for multi-capacitor detectors was measured to be in the order of 10-3 G/Vm-1 and frequency dependent exhibiting a maximum value at ˜1 MHz. Tunability of 0.1%-90% was achieved for tunable inductor applications using both single and multi-capacitors excitation. We believe that significant (˜106) improvements in sensitivity and tunability are feasible with simple modifications of the fabrication process.

  12. Automated optimization of photonic crystal slab cavities

    NASA Astrophysics Data System (ADS)

    Minkov, Momchil; Savona, Vincenzo

    2014-05-01

    Thanks to their high quality factor, combined to the smallest modal volume, defect-cavities in photonic crystal slabs represent a promising, versatile tool for fundamental studies and applications in photonics. In paricular, the L3, H0, and H1 defects are the most popular and widespread cavity designs, due to their compactness, simplicity, and small mode volume. For these cavities, the current best optimal designs still result in Q-values of a few times 105 only, namely one order of magnitude below the bound set by fabrication imperfections and material absorption in silicon. Here, we use a genetic algorithm to find a global maximum of the quality factor of these designs, by varying the positions of few neighbouring holes. We consistently find Q-values above one million - one order of magnitude higher than previous designs. Furthermore, we study the effect of disorder on the optimal designs and conclude that a similar improvement is also expected experimentally in state-of-the-art systems.

  13. OVERVIEW LOOKING SOUTH OF CONTAINMENT SYSTEM (TOP), SLAB CASTING MACHINE ...

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

    OVERVIEW LOOKING SOUTH OF CONTAINMENT SYSTEM (TOP), SLAB CASTING MACHINE AND RUN OUT WITH TRAVELING TORCH. MACHINE IS CASTING IN TWIN MOLD. - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  14. Waveform effects of a metastable olivine tongue in subducting slabs

    NASA Technical Reports Server (NTRS)

    Vidale, John E.; Williams, Quentin; Houston, Heidi

    1991-01-01

    Velocity models of subducting slabs with a kinetically-depressed olivine to beta- and gamma-spinel transition are constructed, and the effect that such structures would have on teleseismic P waveforms are examined using a full-wave finite-difference method. These 2D calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO) to a depth of 670 km, as well as a plausible thermal anomaly; one model further included a 10-km-thick fast layer on the surface of the slab. The principal effect of MOTO is to produce grazing reflections at wide angles off the phase boundary, generating a secondary arrival 0 to 4 seconds after the initial arrival depending on the take-off angle. The amplitude and timing of this feature vary with the lateral location of the seismic source within the slab cross-section.

  15. 9. STONE SLAB CULVERT UNDER CARRIAGE ROAD AT HORSESHOE CURVE ...

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

    9. STONE SLAB CULVERT UNDER CARRIAGE ROAD AT HORSESHOE CURVE NEAR GIANT SLIDE TRAIL MARKER ON AROUND-THE-MOUNTAIN LOOP. - Rockefeller Carriage Roads, Mount Desert Island, Bar Harbor, Hancock County, ME

  16. 49. DETAIL VIEW OF SLOPE PREPARATION FOR VARIABLEANGLE LAUNCHER SLAB ...

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

    49. DETAIL VIEW OF SLOPE PREPARATION FOR VARIABLE-ANGLE LAUNCHER SLAB LOOKING NORTH, November 6, 1946. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  17. PERSPECTIVE OF UNDERSIDE SHOWING ARCHED GIRDER AND SLAB CONSTRUCTION. NOTE ...

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

    PERSPECTIVE OF UNDERSIDE SHOWING ARCHED GIRDER AND SLAB CONSTRUCTION. NOTE TWISTED BAR STOCK REINFORCING CAN BE SEEN. - Keggereis Ford Bridge, Spanning West Branch Conococheague Creek at State Route 4006, Willow Hill, Franklin County, PA

  18. 34. VAL, DETAIL OF STAIRS ON COUNTERWEIGHT SLAB WITH COUNTERWEIGHT ...

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

    34. VAL, DETAIL OF STAIRS ON COUNTERWEIGHT SLAB WITH COUNTERWEIGHT CAR RAILS ON RIGHT AND PERSONNEL CAR RAILS ON LEFT. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  19. Radiative Transfer Model for Translucent Slab Ice on Mars

    NASA Astrophysics Data System (ADS)

    Andrieu, F.; Schmidt, F.; Douté, S.; Schmitt, B.; Brissaud, O.

    2016-09-01

    We developed a radiative transfer model that simulates in VIS/NIR the bidirectional reflectance of a contaminated slab layer of ice overlaying a granular medium, under geometrical optics conditions to study martian ices.

  20. Slab crustal dehydration, melting and dynamics through time

    NASA Astrophysics Data System (ADS)

    van Hunen, Jeroen; Bouilhol, Pierre; Magni, Valentina; Maunder, Benjamin

    2015-04-01

    Melting subducted mafic crust is commonly assumed to be the main process leading to silicic melts with an adakitic signature, which may form Archaean granitoids and generate early continental crust. Alternatively, melting of the overriding lower mafic crust and near-Moho depth fractional crystallisation of mantle melts can form differentiated magmas with an adakitic signature. Previous work shows how only very young slabs melt through dehydration melting, or depict melting of dry eclogites via water addition from deeper slab dehydration. We quantify subduction dehydration and melting reactions in a warm subduction system using a thermo-mechanical subduction model with a thermodynamic database. We find that even young (hot) slabs dehydrate before reaching their solidus, which suppresses any slab dehydration melting and creates significant amounts of mantle wedge melting irrespective of slab age. Significant slab crust melting is only achieved in young slabs via water present melting if metamorphic fluids from the subducted mantle flux through the dry eclogites. These slab melts, however, are affected by massive mantle wedge melting and unlikely to participate in the overriding plate felsic magmatism, unlike the shallower, primitive mantle wedge melts. Understanding the overall flux of water carried by the descending slab mantle is therefore of prime importance. We thus inverstigated the deeper dehydration processes in subduction zones and implications for the water cycle throughout Earth's history. We estimate that presently ~26% of the global influx water is recycled into the mantle, and that deep water recycling was also significant (although less efficient, 2-13% at 2.8 Ga) in early Earth conditions, which has important implications for mantle dynamics and tectonic processes in the Early Earth. Alternatively, delamination and underplating of the mafic subducted crust would be a suitable mechanism to fit the geological record. We thus explore the conditions for

  1. Influence of content and particle size of waste pet bottles on concrete behavior at different w/c ratios.

    PubMed

    Albano, C; Camacho, N; Hernández, M; Matheus, A; Gutiérrez, A

    2009-10-01

    The goal of this work was to study the mechanical behavior of concrete with recycled Polyethylene Therephtalate (PET), varying the water/cement ratio (0.50 and 0.60), PET content (10 and 20 vol%) and the particle size. Also, the influence of the thermal degradation of PET in the concrete was studied, when the blends were exposed to different temperatures (200, 400, 600 degrees C). Results indicate that PET-filled concrete, when volume proportion and particle size of PET increased, showed a decrease in compressive strength, splitting tensile strength, modulus of elasticity and ultrasonic pulse velocity; however, the water absorption increased. On the other hand, the flexural strength of concrete-PET when exposed to a heat source was strongly dependent on the temperature, water/cement ratio, as well as on the PET content and particle size. Moreover, the activation energy was affected by the temperature, PET particles location on the slabs and water/cement ratio.

  2. Runoff of pyrethroid insecticides from concrete surfaces following simulated and natural rainfalls.

    PubMed

    Jiang, Weiying; Haver, Darren; Rust, Michael; Gan, Jay

    2012-03-01

    Intensive residential use of insecticides has resulted in their ubiquitous presence as contaminants in urban surface streams. For pest eradication, urban hard surfaces such as concrete are often directly treated with pesticides, and wind/water can also carry pesticides onto hard surfaces from surrounding areas. This study expanded on previous bench-scale studies by considering pesticide runoff caused by irrigation under dry weather conditions and rain during the wet season, and evaluated the effects of pesticide residence time on concrete, single versus recurring precipitations, precipitation intensity, and concrete surface conditions, on pesticide transferability to runoff water. Runoff from concrete 1 d after pesticide treatment contained high levels of bifenthrin (82 μg/L) and permethrin (5143 μg/L for cis and 5518 μg/L for trans), indicating the importance of preventing water contact on concrete after pesticide treatments. Although the runoff transferability quickly decreased as the pesticide residence time on concrete increased, detectable residues were still found in runoff water after 3 months (89 d) exposure to hot and dry summer conditions. ANOVA analysis showed that precipitation intensities and concrete surface conditions (i.e., acid wash, silicone seal, stamping, and addition of microsilica) did not significantly affect the pesticide transferability to runoff. For concrete slabs subjected to natural rainfalls during the winter wet season, pesticide levels in the runoff decreased as the time interval between pesticide application and the rain event increased. However, bifenthrin and permethrin were still detected at 0.15-0.17 and 0.75-1.15 μg/L in the rain runoff after 7 months (221 d) from the initial treatment. In addition, pesticide concentrations showed no decrease between the two rainfall events, suggesting that concrete surfaces contaminated by pesticides may act as a reservoir for pesticide residues, leading to sustained urban runoff

  3. Rover tracks

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Tracks made by the Sojourner rover are visible in this image, taken by one of the cameras aboard Sojourner on Sol 3. The tracks represent the rover maneuvering towards the rock dubbed 'Barnacle Bill.' The rover, having exited the lander via the rear ramp, first traveled towards the right portion of the image, and then moved forward towards the left where Barnacle Bill sits. The fact that the rover was making defined tracks indicates that the soil is made up of particles on a micron scale.

    Mars Pathfinder was developed and managed by the Jet Propulsion Laboratory (JPL) for the National Aeronautics and Space Administration.

  4. Scaling of Electron Thermal Conductivity during the Transition between Slab and Mixed Slab-Toroidal ETG Mode

    NASA Astrophysics Data System (ADS)

    Sokolov, Vladimir; Balbaky, Abed; Sen, Amiya K.

    2015-11-01

    Transition from the slab to the toroidal branch of the electron temperature gradient (ETG) mode has been successfully achieved in a basic experiment in Columbia Linear Machine CLM. We found a modest increase in saturated ETG potential fluctuations (~ 2 ×) and a substantial increase in the power density of individual mode peaks (~ 4 - 5 ×) with increased levels of curvature. We have obtained a set of experimental scalings for electron thermal conductivity χ⊥e as a function of the inverse radius of curvature Rc-1 for different fluctuation levels of the initial slab ETG mode. We found that thermal conductivity for pure slab modes is larger than it is for mixed slab-toroidal ETG modes with the same level of mode fluctuation. This effective reduction in diffusive transport can be partly explained by the flute nature of the toroidal ETG mode. This research was supported by the Department of Electrical Engineering of Columbia University.

  5. Characterizing Seismic Anisotropy across the Peruvian Flat-Slab Subduction Zone: Implications for the Dynamics of Flat-Slabs

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline; Long, Maureen; Beck, Susan; Wagner, Lara; Tavera, Hernando

    2014-05-01

    Although 10% of subduction zones worldwide today exhibit shallow or flat subduction, we are yet to fully understand how and why these slabs go flat. An excellent study location for such a problem is in Peru, where the largest region of flat-subduction currently exists, extending ~1500 km in length (from 3 °S to 15 °S) and ~300 km in width. Across this region we investigate the pattern of seismic anisotropy, an indicator for past and/or ongoing deformation in the upper mantle. To achieve this we conduct shear wave splitting analyzes at 40 broadband stations from the PULSE project (PerU Lithosphere and Slab Experiment). These stations were deployed for 2+ years across the southern half of the Peruvian flat-slab region. We present detailed shear wave splitting results for both teleseismic events (such as SKS, SKKS, PKS, sSKS) that sample the upper mantle column beneath the stations as well as direct S from local events that constrain anisotropy in the upper portion of the subduction zone. We analyze the variability of our results with respect to initial polarizations, ray paths, and frequency content as well as spatial variability between stations as the underlying slab morphology changes. Teleseismic results show predominately NW-SE fast polarizations (trench oblique to sub-parallel) over the flat-slab region east of Lima. These results are consistent with observations of more complex multi-layered anisotropy beneath a nearby permanent station (NNA) that suggests a trench-perpendicular fast direction in the lowest layer in the sub-slab mantle. Further south, towards the transition to steeper subduction, the splitting pattern becomes increasingly dominated by null measurements. Over to the east however, beyond Cuzco, where the mantle wedge might begin to play a role, we record fast polarizations quasi-parallel to the local slab contours. Local S results indicate the presence of weak (delay times typically less than 0.5 seconds) and heterogeneous supra-slab

  6. TESTING AND ANALYSIS OF CAP CONCRETE STRESS AND STRAIN DUE TO SHRINKAGE, CREEP, AND EXPANSION FINAL REPORT

    SciTech Connect

    Guerrero, H.; Restivo, M.

    2011-08-01

    In-situ decommissioning of Reactors P- and R- at the Savannah River Site will require filling the reactor vessels with a special concrete based on materials such as magnesium phosphate, calcium aluminate or silica fume. Then the reactor vessels will be overlain with an 8 ft. thick layer of Ordinary Portland Cement (OPC) steel reinforced concrete, called the 'Cap Concrete'. The integrity of this protective layer must be assured to last for a sufficiently long period of time to avoid ingress of water into the reactor vessel and possible movement of radioactive contamination into the environment. During drying of this Cap Concrete however, shrinkage strains are set up in the concrete as a result of diffusion and evaporation of water from the top surface. This shrinkage varies with depth in the poured slab due to a non-uniform moisture distribution. This differential shrinkage results in restraint of the upper layers with larger shrinkage by lower layers with lesser displacements. Tensile stresses can develop at the surface from the strain gradients in the bulk slab, which can lead to surface cracking. Further, a mechanism called creep occurs during the curing period or early age produces strains under the action of restraining forces. To investigate the potential for surface cracking, an experimental and analytical program was started under TTQAP SRNL-RP-2009-01184. Slab sections made of Cap Concrete mixture were instrumented with embedded strain gages and relative humidity sensors and tested under controlled environmental conditions of 23 C and relative humidities (RH) of 40% and 80% over a period of 50 days. Calculation methods were also developed for predictions of stress development in the full-scale concrete placement over the reactor vessels. These methods were evaluated by simulating conditions for the test specimens and the calculation results compared to the experimental data. A closely similar test with strain gages was performed by Kim and Lee for a

  7. Concrete lunar base investigation

    NASA Technical Reports Server (NTRS)

    Lin, T. D.; Senseney, Jonathan A.; Arp, Larry Dean; Lindbergh, Charles

    1989-01-01

    This paper presents results of structural analyses and a preliminary design of a precast, prestressed concrete lunar based subjected to one atmosphere internal pressure. The proposed infrastructure measures 120 ft in diameter and 72 ft in height, providing 33,000 sq ft of work area for scientific and industrial operations. Three loading conditions were considered in the design: (1) during construction; (2) under pressurization; and (3) during an air-leak scenario. A floating foundation, capable of rigid body rotation and translation as the lunar soil beneath it yields, was developed to support the infrastructure and to ensure the air-tightness of the system. Results reveal that it is feasible to use precast, prestressed concrete for construction of large lunar bases on the moon.

  8. Concrete lunar base investigation

    NASA Technical Reports Server (NTRS)

    Lin, T. D.; Senseny, Jonathan A.; Arp, Larry D.; Lindbergh, Charles

    1992-01-01

    This paper presents results of structural analyses and a preliminary design of a precast, prestressed concrete lunar base subjected to 1-atm internal pressure. The proposed infrastructure measures 120 ft in diameter and 72 ft in height, providing 33,000 sq ft of work area for scientific and industrial operations. Three loading conditions were considered in the design (1) during construction, (2) under pressurization, and (3) during an air-leak scenario. A floating foundation, capable of rigid body rotation and translation as the lunar soil beneath it yields, was developed to support the infrastructure and to ensure the airtightness of the system. Results reveal that it is feasible to use precast, prestressed concrete for construction of large lunar bases on the Moon.

  9. Penetration of concrete targets

    SciTech Connect

    Forrestal, M.J.; Cargile, J.D.; Tzou, R.D.Y.

    1993-08-01

    We developed penetration equations for ogive-nosed projectiles that penetrated concrete targets after normal impact. Our penetration equations predict axial force on the projectile nose, rigid-body motion, and final penetration depth. For target constitutive models, we conducted triaxial material experiments to confining pressures of 600 MPa and curve-fit these data with a linear pressure-volumetric strain relation and with a linear Mohr-Coulomb, shear strength-pressure relation. To verify our penetration equations, we conducted eleven penetration experiments with 0.90 kg, 26.9-mm-diameter, ogive-nosed projectiles into 1.37-m-diameter concrete targets with unconfined compressive strengths between 32-40 MPa. Predictions from our penetration equation are compared with final penetration depth measurements for striking velocities between 280--800 m/s.

  10. Standing sausage modes in curved coronal slabs

    NASA Astrophysics Data System (ADS)

    Pascoe, D. J.; Nakariakov, V. M.

    2016-09-01

    Context. Magnetohydrodynamic waveguides such as dense coronal loops can support standing modes. The ratios of the periods of oscillations for different longitudinal harmonics depend on the dispersive nature of the waveguide and so may be used as a seismological tool to determine coronal parameters. Aims: We extend models of standing sausage modes in low β coronal loops to include the effects of loop curvature. The behaviour of standing sausage modes in this geometry is used to explain the properties of observed oscillations that cannot be accounted for using straight loop models. Methods: We perform 2D numerical simulations of an oscillating coronal loop, modelled as a dense slab embedded in a potential magnetic field. The loop is field-aligned and so experiences expansion with height in addition to being curved. Standing sausage modes are excited by compressive perturbations of the loop and their properties are studied. Results: The spatial profiles of standing sausage modes are found to be modified by the expanding loop geometry typical for flaring loops and modelled by a potential magnetic field in our simulations. Longitudinal harmonics of order n > 1 have anti-nodes that are shifted towards the loop apex and the amplitude of anti-nodes near the loop apex is smaller than those near the loop footpoints. Conclusions: We find that the observation of standing sausage modes by the Nobeyama Radioheliograph in a flaring coronal loop on 12 January 2000 is consistent with interpretation in terms of the global mode (n = 1) and third harmonic (n = 3). This interpretation accounts for the period ratio and spatial structure of the observed oscillations.

  11. 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

  12. Reducing slab boundary artifacts in three‐dimensional multislab diffusion MRI using nonlinear inversion for slab profile encoding (NPEN)

    PubMed Central

    Koopmans, Peter J.; Frost, Robert; Miller, Karla L.

    2015-01-01

    Purpose To propose a method to reduce the slab boundary artifacts in three‐dimensional multislab diffusion MRI. Methods Bloch simulation is used to investigate the effects of multiple factors on slab boundary artifacts, including characterization of residual errors on diffusion quantification. A nonlinear inversion method is proposed to simultaneously estimate the slab profile and the underlying (corrected) image. Results Correction results of numerical phantom and in vivo data demonstrate that the method can effectively remove slab boundary artifacts for diffusion data. Notably, the nonlinear inversion is also successful at short TR, a regimen where previously proposed methods (slab profile encoding and weighted average) retain residual artifacts in both diffusion‐weighted images and diffusion metrics (mean diffusion coefficient and fractional anisotropy). Conclusion The nonlinear inversion for removing slab boundary artifacts provides improvements over existing methods, particularly at the short TRs required to maximize SNR efficiency. Magn Reson Med 76:1183–1195, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:26510172

  13. Concrete containment aging study

    SciTech Connect

    Pachner, J.; Tai, T.M.; Naus, D.

    1994-04-01

    In 1989, IAEA initiated a pilot study on the management of aging of nuclear power plant components. The Phase I and II studies of concrete containment are discussed. With the data base, plant owners will be able to review and enhance their existing programs. IAEA will analyze data provided by participating plants and the report is scheduled to be released by late 1994 (final report release mid-1995).

  14. Mechanics of Concrete II

    DTIC Science & Technology

    1990-10-18

    diffusivity of undamaged concrete is a problem in itself since the diffusivity of the thin transition zones (at the aggregate- cement matrix interface...C3A anhydride remains in the cement after the hydration. Assuming that the amount of gypsum added to portland cement3 clinker is 4% of Mcm (Biczok 1972...enables establishment of rational relationships between the chemical composition of the hardened cement paste, morphology of the pore system, and defect

  15. Tonsil concretions and tonsilloliths.

    PubMed

    Pruet, C W; Duplan, D A

    1987-05-01

    Although infrequently seen in many clinical practices, tonsillar concretions can be the source of both fetor oris and physical and social concern for the patient. Though stones rarely form in the tonsil or peritonsillar area, the findings of calcified objects or stones anywhere within the body has long been a subject of interest. The salient features of these entities and their relevance to clinical practice are discussed in this article.

  16. Nondestructive Concrete Characterization System

    DTIC Science & Technology

    2013-05-20

    Park, NC 27709-2211 15. SUBJECT TERMS Ultrasonic Pulse Velocity (UPV), Impact-Echo, Ultrasonic Pulse-Echo, Ultrasonic Attenuation, STTR Report Aldo... ultrasonic testing in conjunction with the resonance frequency. All results were within the specified tolerance of ±1 ft. The compressive strength of the...concrete blocks was measured by measuring the P-wave and S-wave time of travel with the pitch-catch method of ultrasonic testing. All results were

  17. Slab pull and the seismotectonics of subducting lithosphere

    USGS Publications Warehouse

    Spence, William

    1987-01-01

    This synthesis links many seismic and tectonic processes at subduction zones, including great subduction earthquakes, to the sinking of subducted plate. Earthquake data and tectonic modeling for subduction zones indicate that the slab pull force is much larger than the ridge push force. Interactions between the forces that drive and resist plate motions cause spatially and temporally localized stresses that lead to characteristic earthquake activity, providing details on how subduction occurs. Compression is localized across a locked interface thrust zone, because both the ridge push and the slab pull forces are resisted there. The slab pull force increases with increasing plate age; thus because the slab pull force tends to bend subducted plate downward and decrease the force acting normal to the interface thrust zone, the characteristic maximum earthquake at a given interface thrust zone is inversely related to the age of the subducted plate. The 1960 Chile earthquake (Mw 9.5), the largest earthquake to occur in historic times, began its rupture at an interface bounding oceanic plate <30 m.y. old. However, this rupture initiation was associated with the locally oldest subducting lithosphere (weakest coupling); the rupture propagated southward along an interface bounding progressively younger oceanic lithosphere, terminating near the subducting Chile Rise. Prior to a great subduction earthquake, the sinking subducted slab will cause increased tension at depths of 50–200 km, with greatest tension near the shallow zone resisting plate subduction. Plate sinking not only leads to compressional stresses at a locked interface thrust zone but may load compressional stresses at plate depths of 260–350 km, provided that the shallow sinking occurs faster than the relaxation time of the deeper mantle. This explains K. Mogi's observations of M ≥ 7 thrust earthquakes at depths of 260–350 km, immediately downdip and within 3 years prior to five great, shallow

  18. Modeling the surface photovoltage of silicon slabs with varying thickness

    NASA Astrophysics Data System (ADS)

    Vazhappilly, Tijo; Kilin, Dmitri S.; Micha, David A.

    2015-04-01

    The variation with thickness of the energy band gap and photovoltage at the surface of a thin semiconductor film are of great interest in connection with their surface electronic structure and optical properties. In this work, the change of a surface photovoltage (SPV) with the number of layers of a crystalline silicon slab is extracted from models based on their atomic structure. Electronic properties of photoexcited slabs are investigated using generalized gradient and hybrid density functionals, and plane wave basis sets. Si(1 1 1) surfaces have been terminated by hydrogen atoms to compensate for dangling bonds and have been described by large supercells with periodic boundary conditions. Calculations of the SPV of the Si slabs have been done in terms of the reduced density matrix of the photoactive electrons including dissipative effects due to their interaction with medium phonons and excitons. Surface photovoltages have been calculated for model Si slabs with 4-12, and 16 layers, to determine convergence trends versus slab thickness. Band gaps and the inverse of the SPVs have been found to scale nearly linearly with the inverse thickness of the slab, while the electronic density of states increases quadratically with thickness. Our calculations show the same trends as experimental values indicating band gap reduction and absorption enhancement for Si films of increasing thickness. Simple arguments on confined electronic structures have been used to explain the main effects of changes with slab thickness. A procedure involving shifted electron excitation energies is described to improve results from generalized gradient functionals so they can be in better agreement with the more accurate but also more computer intensive values from screened exchange hybrid functionals.

  19. Tomographic imaging of the effects of Peruvian flat slab subduction on the Nazca slab and surrounding mantle under central and southern Peru

    NASA Astrophysics Data System (ADS)

    Scire, A. C.; Zandt, G.; Beck, S. L.; Bishop, B.; Biryol, C. B.; Wagner, L. S.; Long, M. D.; Minaya, E.; Tavera, H.

    2014-12-01

    The modern central Peruvian Andes are dominated by a laterally extensive region of flat slab subduction. The Peruvian flat slab extends for ~1500 km along the strike of the Andes, correlating with the subduction of the Nazca Ridge in the south and the theorized Inca Plateau in the north. We have used data from the CAUGHT and PULSE experiments for finite frequency teleseismic P- and S-wave tomography to image the Nazca slab in the upper mantle below 95 km depth under central Peru between 10°S and 18°S as well as the surrounding mantle. Since the slab inboard of the subducting Nazca Ridge is mostly aseismic, our results provide important constraints on the geometry of the subducting Nazca slab in this region. Our images of the Nazca slab suggest that steepening of the slab inboard of the subducting Nazca Ridge locally occurs ~100 km further inland than was indicated in previous studies. The region where we have imaged the steepening of the Nazca slab inboard of the Nazca Ridge correlates with the location of the Fitzcarrald Arch, a long wavelength upper plate topographic feature which has been suggested to be a consequence of ridge subduction. When the slab steepens inboard of the flat slab region, it does so at a very steep (~70°) angle. The transition from the Peruvian flat slab to the more normally dipping slab south of 16°S below Bolivia is characterized by an abrupt bending of the slab anomaly in the mantle in response to the shift from flat to normal subduction. The slab anomaly appears to be intact south of the Nazca Ridge with no evidence for tearing of the slab in response to the abrupt change in slab dip. A potential tear in the slab is inferred from an observed offset in the slab anomaly north of the Nazca Ridge extending subparallel to the ridge axis between 130 and 300 km depth. A high amplitude (-5-6%) slow S-wave velocity anomaly is observed below the projection of the Nazca Ridge. This anomaly appears to be laterally confined to the mantle

  20. Fiber reinforced concrete solar collector

    SciTech Connect

    Slemmons, A. J.; Newgard, P. J.

    1985-05-07

    A solar collector is disclosed comprising a glass member having a solar selective coating thereon, and a molded, glass-reinforced concrete member bonded to the glass member and shaped to provide a series of passageways between the glass member and the fiber-reinforced concrete member capable of carrying heat exchanging fluid therethrough. The fiber-reinforced concrete member may be formed by spraying a thin layer of concrete and chopped fibers such as chopped glass fibers onto a mold to provide an inexpensive and lightweight, thin-walled member. The fiber-reinforced concrete member may have a lightweight cellular concrete backing thereon for insulation purposes. The collector is further characterized by the use of materials which have substantially matching thermal coefficients of expansion over the temperature range normally encountered in the use of solar collectors.

  1. 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

  2. Fire Resistance of Geopolymer Concretes

    DTIC Science & Technology

    2010-03-21

    1 Project report – Grant FA23860814096, "Fire resistance of geopolymer concretes" – J. Provis, University of Melbourne 1. Background and...experimental program This project provided funding for us to carry out fire testing of geopolymer concrete specimens and associated laboratory...testing. The focus of this report will be the outcomes of the series of pilot-scale (4’×4’×6”) tests on geopolymer concrete panels, which were conducted

  3. Cocos-Nazca slab window beneath Central America

    NASA Astrophysics Data System (ADS)

    Johnston, Stephen T.; Thorkelson, Derek J.

    1997-02-01

    Integration of petrologic and tectonic data favours a model of slab window formation beneath Central America in the Pliocene-Pleistocene. Central America has been the site of voluminous Cenozoic arc volcanism. The Cocos and Nazca plates, which are subducting beneath Central America, are diverging along the east-trending Cocos-Nazca spreading ridge. Since 25 Ma the Americas have advanced about 1800 km west over the ridge-transform system. Since at least 8 Ma, plate integrity and the ridge-transform configuration have been preserved during convergence, resulting in subduction of the spreading ridge and development of a slab window. The Panama fracture zone, an active transform fault, is the part of the ridge-transform system currently being subducted. The ridge-transform system formerly adjoining the northern end of the Panama fracture zone is likely to have been left-stepping. We use present-day plate motions to design a slab window to fit known variations in igneous composition, hypocentre distribution, and mantle anisotropy. The modeling demonstrates that subduction of ridge segments and resultant slab window development began between 6 and 10 Ma. Cessation of ridge subduction occurred between 1 and 3 Ma, when subduction of the Panama fracture zone is considered to have begun. The slab window is continuing to expand and migrate northeastward below the Central American volcanic arc. The absence of a Wadati-Benioff zone from southeastern Costa Rica through Panama corresponds to the position of the slab window. Within this region, dacitic and rhyolitic volcanic rocks have "adakitic" compositions, and are thought to result from anatexis of the young, buoyant crust which forms the trailing edges of the slabs bounding the window. Basalts in this area were derived from an enriched ocean-island type mantle source, whereas basalts from the rest of the arc, in Nicaragua, El Salvador and Guatemala, are mainly derived from slab-modified depleted mantle, characteristic of

  4. Systematic variation in the depths of slabs beneath arc volcanoes

    USGS Publications Warehouse

    England, P.; Engdahl, R.; Thatcher, W.

    2004-01-01

    The depths to the tops of the zones of intermediate-depth seismicity beneath arc volcanoes are determined using the hypocentral locations of Engdahl et al. These depths are constant, to within a few kilometres, within individual arc segments, but differ by tens of kilometres from one arc segment to another. The range in depths is from 65 km to 130 km, inconsistent with the common belief that the volcanoes directly overlie the places where the slabs reach a critical depth that is roughly constant for all arcs. The depth to the top of the intermediate-depth seismicity beneath volcanoes correlates neither with age of the descending ocean floor nor with the thermal parameter of the slab. This depth does, however, exhibit an inverse correlation with the descent speed of the subducting plate, which is the controlling factor both for the thermal structure of the wedge of mantle above the slab and for the temperature at the top of the slab. We interpret this result as indicating that the location of arc volcanoes is controlled by a process that depends critically upon the temperature at the top of the slab, or in the wedge of mantle, immediately below the volcanic arc.

  5. Fossil slabs attached to unsubducted fragments of the Farallon plate

    PubMed Central

    Wang, Yun; Forsyth, Donald W.; Rau, Christina J.; Carriero, Nina; Schmandt, Brandon; Gaherty, James B.; Savage, Brian

    2013-01-01

    As the Pacific–Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My. PMID:23509274

  6. Fossil slabs attached to unsubducted fragments of the Farallon plate.

    PubMed

    Wang, Yun; Forsyth, Donald W; Rau, Christina J; Carriero, Nina; Schmandt, Brandon; Gaherty, James B; Savage, Brian

    2013-04-02

    As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My.

  7. Sub-wavelength grating mode transformers in silicon slab waveguides.

    PubMed

    Bock, Przemek J; Cheben, Pavel; Schmid, Jens H; Delâge, André; Xu, Dan-Xia; Janz, Siegfried; Hall, Trevor J

    2009-10-12

    We report on several new types of sub-wavelength grating (SWG) gradient index structures for efficient mode coupling in high index contrast slab waveguides. Using a SWG, an adiabatic transition is achieved at the interface between silicon-on-insulator waveguides of different geometries. The SWG transition region minimizes both fundamental mode mismatch loss and coupling to higher order modes. By creating the gradient effective index region in the direction of propagation, we demonstrate that efficient vertical mode transformation can be achieved between slab waveguides of different core thickness. The structures which we propose can be fabricated by a single etch step. Using 3D finite-difference time-domain simulations we study the loss, polarization dependence and the higher order mode excitation for two types (triangular and triangular-transverse) of SWG transition regions between silicon-on-insulator slab waveguides of different core thicknesses. We demonstrate two solutions to reduce the polarization dependent loss of these structures. Finally, we propose an implementation of SWG structures to reduce loss and higher order mode excitation between a slab waveguide and a phase array of an array waveguide grating (AWG). Compared to a conventional AWG, the loss is reduced from -1.4 dB to < -0.2 dB at the slab-array interface.

  8. Cenozoic Plume-Slab Interaction Beneath the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Obrebski, M. J.; Allen, R. M.; Hung, S.; Pollitz, F. F.

    2009-12-01

    Here we present new images of the structure beneath the Pacific Northwest obtained by inverting both compressional and shear teleseismic body waves and using finite-frequency sensitivity kernels. The models use all available seismic data from the Earthscope Transportable Array, regional seismic networks and two Flexible Array experiments (Mendocino and FACES experiments) deployed on the west coast. By picking P, S and SKS arrivals manually and estimating station-to-station relative arrival times through cross correlation of the waveforms, we select only the highest quality data. East from the Juan de Fuca slab and north from the Mendocino Triple Junction, the mantle structure is dominated by high velocity blocks that are likely to be fragments of the Farallon slab. In the middle of the slab fragments, both our compressional (DNA09-P) and shear (DNA09-S) velocity models show a continuous low velocity anomaly that extends from the Yellowstone Caldera down into the lower mantle. We interpret this feature as a deep-seated mantle plume. The striking contrast between the slab-dominated mantle north from the MTJ and the continuous deep-seated Yellowstone mantle plume suggests the plume disrupted the Farallon slab during its ascent to the surface.

  9. Seismic tomography of the Pacific slab edge under Kamchatka

    NASA Astrophysics Data System (ADS)

    Jiang, Guoming; Zhao, Dapeng; Zhang, Guibin

    2009-02-01

    We determine a 3-D P-wave velocity structure of the mantle down to 700 km depth under the Kamchatka peninsula using 678 P-wave arrival times collected from digital seismograms of 75 teleseismic events recorded by 15 portable seismic stations and 1 permanent station in Kamchatka. The subducting Pacific slab is imaged clearly that is visible in the upper mantle and extends below the 660-km discontinuity under southern Kamchatka, while it shortens toward the north and terminates near the Aleutian-Kamchatka junction. Low-velocity anomalies are visible beneath northern Kamchatka and under the junction, which are interpreted as asthenospheric flow. A gap model without remnant slab fragment is proposed to interpret the main feature of high-V anomalies. Combining our tomographic results with other geological and geophysical evidences, we consider that the slab loss may be induced by the friction with surrounding asthenosphere as the Pacific plate rotated clockwise at about 30 Ma ago, and then it was enlarged by the slab-edge pinch-off by the asthenospheric flow and the presence of Meiji seamounts. As a result, the slab loss and the subducted Meiji seamounts have jointly caused the Pacific plate to subduct under Kamchatka with a lower dip angle near the junction, which made the Sheveluch and Klyuchevskoy volcanoes shift westward.

  10. Concrete Durability in Harsh Environmental Conditions Exposed to Freeze Thaw Cycles

    NASA Astrophysics Data System (ADS)

    Hamze, Youssef

    Under line Pathology of Materials; one of the environmental causes of damage effects on concrete is freeze thaw cycles, which deteriorate the concrete exposed to water in cold weather. An example of old concrete is a dam project that was built in Canada, in the early 1909-1913. This project was reconstructed in 1932, 1934 and 1972, and required renovation due to the ice abrasion with the freeze/thaw cycles. Before completing any renovation, it is required to analyze the structural stability and the concrete failures of this dam. An investigation was conducted to determine the quality of the concrete in the Piers and in the Bridge Deck Slab. It was also required to determine the basic materials' properties that constitute this project. This will improve the analysis of its stability [10]. Core samples were examined and used as test samples, for the Alkali-Silica reactivity test samples, as well as the compressive strength test, the Chloride Ion test, and the freeze thaw testing which was performed on two sets of 12 concrete core samples that were taken from different locations in the project. These locations are the representations of the age of the concrete. Thus, the age difference between the samples' two sets is four decades. Testing was performed on prisms cut from cores. ASTM C-666 procedure (A) was applied using an automatic test system [6]. It was suggested that a plan for renovation of this project should be performed after the analysis is undertaken to assess the conditions estimating the remaining life of the concrete in this project [15].

  11. A Monitoring Method Based on FBG for Concrete Corrosion Cracking.

    PubMed

    Mao, Jianghong; Xu, Fangyuan; Gao, Qian; Liu, Shenglin; Jin, Weiliang; Xu, Yidong

    2016-07-14

    Corrosion cracking of reinforced concrete caused by chloride salt is one of the main determinants of structure durability. Monitoring the entire process of concrete corrosion cracking is critical for assessing the remaining life of the structure and determining if maintenance is needed. Fiber Bragg Grating (FBG) sensing technology is extensively developed in photoelectric monitoring technology and has been used on many projects. FBG can detect the quasi-distribution of strain and temperature under corrosive environments, and thus it is suitable for monitoring reinforced concrete cracking. According to the mechanical principle that corrosion expansion is responsible for the reinforced concrete cracking, a package design of reinforced concrete cracking sensors based on FBG was proposed and investigated in this study. The corresponding relationship between the grating wavelength and strain was calibrated by an equal strength beam test. The effectiveness of the proposed method was verified by an electrically accelerated corrosion experiment. The fiber grating sensing technology was able to track the corrosion expansion and corrosion cracking in real time and provided data to inform decision-making for the maintenance and management of the engineering structure.

  12. A Monitoring Method Based on FBG for Concrete Corrosion Cracking

    PubMed Central

    Mao, Jianghong; Xu, Fangyuan; Gao, Qian; Liu, Shenglin; Jin, Weiliang; Xu, Yidong

    2016-01-01

    Corrosion cracking of reinforced concrete caused by chloride salt is one of the main determinants of structure durability. Monitoring the entire process of concrete corrosion cracking is critical for assessing the remaining life of the structure and determining if maintenance is needed. Fiber Bragg Grating (FBG) sensing technology is extensively developed in photoelectric monitoring technology and has been used on many projects. FBG can detect the quasi-distribution of strain and temperature under corrosive environments, and thus it is suitable for monitoring reinforced concrete cracking. According to the mechanical principle that corrosion expansion is responsible for the reinforced concrete cracking, a package design of reinforced concrete cracking sensors based on FBG was proposed and investigated in this study. The corresponding relationship between the grating wavelength and strain was calibrated by an equal strength beam test. The effectiveness of the proposed method was verified by an electrically accelerated corrosion experiment. The fiber grating sensing technology was able to track the corrosion expansion and corrosion cracking in real time and provided data to inform decision-making for the maintenance and management of the engineering structure. PMID:27428972

  13. Detecting flaws in Portland cement concrete using TEM horn antennae

    NASA Astrophysics Data System (ADS)

    Al-Qadi, Imad L.; Riad, Sedki M.; Su, Wansheng; Haddad, Rami H.

    1996-11-01

    To understand the dielectric properties of PCC and better correlate them with type and severity of PCC internal defects, a study was conducted to evaluate PCC complex permittivity and magnetic permeability over a wideband of frequencies using both time domain and frequency domain techniques. Three measuring devices were designed and fabricated: a parallel plate capacitor, a coaxial transmission line, and transverse electromagnetic (TEM) horn antennae. The TEM horn antenna covers the microwave frequencies. The measurement technique involves a time domain setup that was verified by a frequency domain measurement. Portland cement concrete slabs, 60 by 75 by 14 cm, were cast; defects include delamination, delamination filled with water, segregation, and chloride contamination. In this paper, measurements using the TEM horn antennae and the feasibility of detecting flaws at microwave frequency are presented.

  14. Concrete Mixing Methods and Concrete Mixers: State of the Art

    PubMed Central

    Ferraris, Chiara F.

    2001-01-01

    As for all materials, the performance of concrete is determined by its microstructure. Its microstructure is determined by its composition, its curing conditions, and also by the mixing method and mixer conditions used to process the concrete. This paper gives an overview of the various types of mixing methods and concrete mixers commercially available used by the concrete industry. There are two main types of mixers used: batch mixers and continuous mixers. Batch mixers are the most common. To determine the mixing method best suited for a specific application, factors to be considered include: location of the construction site (distance from the batching plant), the amount of concrete needed, the construction schedule (volume of concrete needed per hour), and the cost. Ultimately, the quality of the concrete produced determines its performance after placement. An important measure of the quality is the homogeneity of the material after mixing. This paper will review mixing methods in regards to the quality of the concrete produced. Some procedures used to determine the effectiveness of the mixing will be examined. PMID:27500029

  15. Fluid flow during slab unbending and dehydration: Implications for intermediate-depth seismicity, slab weakening and deep water recycling

    NASA Astrophysics Data System (ADS)

    Faccenda, Manuele; Gerya, Taras V.; Mancktelow, Neil S.; Moresi, Louis

    2012-01-01

    Subducting oceanic plates carry a considerable amount of water from the surface down to mantle depths and contribute significantly to the global water cycle. A part of these volatiles stored in the slab is expelled at intermediate depths (70-300 km) where dehydration reactions occur. However, despite the fact that water considerably affects many physical properties of rocks, not much is known about the fluid flow path and the interaction with the rocks through which volatiles flow in the slab interior during its dehydration. We performed thermomechanical models (coupled with a petrological database and with incompressible aqueous fluid flow) of a dynamically subducting and dehydrating oceanic plate. Results show that, during slab dehydration, unbending stresses drive part of the released fluids into the cold core of the plate toward a level of strong tectonic under-pressure and neutral (slab-normal) pressure gradients. Fluids progressively accumulate and percolate updip along such a layer forming, together with the upper hydrated layer near the top of the slab, a Double Hydrated Zone (DHZ) where intermediate-depth seismicity could be triggered. The location and predicted mechanics of the DHZ would be consistent with seismological observations regarding Double Seismic Zones (DSZs) found in most subduction zones and suggests that hydrofracturing could be the trigger mechanism for observed intermediate-depth seismicity. In the light of our results, the lower plane of the DSZ is more likely to reflect a layer of upward percolating fluid than a level of mantle dehydration. In our models, a 20-30 km thick DSZ forms in relatively old oceanic plates without requiring an extremely deep slab hydration prior to subduction. The redistribution of fluids into the slab interior during slab unbending also has important implications for slab weakening and the deep water cycle. We estimate that, over the whole of Earth's history, a volume of water equivalent to around one to two

  16. Evaluation of the environmental, material, and structural performance of recycled aggregate concrete

    NASA Astrophysics Data System (ADS)

    Michaud, Katherine Sarah

    Concrete is the most commonly used building material in the construction industry, and contributes to 52% of construction and demolition waste in Canada. Recycled concrete aggregate (RCA) is one way to reduce this impact. To evaluate the performance of coarse and granular (fine and coarse) RCA in structural concrete applications, four studies were performed: an environmental assessment, a material testing program, a shear performance study, and a flexural performance study. To determine the environmental benefits of recycled aggregate concrete (RAC), three case studies were investigated using different populations and proximities to city centres. Environmental modelling suggested that RCA replacement could result in energy savings and greenhouse gas emission reductions, especially in remote areas. Tests were performed to determine if the volumetric replacement of up to 30% coarse RCA and 20% granular RCA is suitable for structural concrete applications in Canada. Fresh, hardened, and durability properties were evaluated. All five (5) of the RCA mixes showed equivalent material performance to the control mixes and met the requirements for a structural concrete mix. The five (5) RAC mixes were also used in structural testing. One-way reinforced concrete slab specimens were tested to failure to evaluate the shear and flexural performance of the RAC members. Peak capacities of and crack formation within each member were analyzed to evaluate the performance of RAC compared to conventional concrete. The shear capacity of specimens made from four (4) of the five (5) RAC mixtures was higher or equivalent to the control specimens. Specimens of the concrete mixture containing the highest content of recycled aggregate, 20% volumetric replacement of granular RCA, had shear capacities 14.1% lower, and exhibited cracking at lower loads than the control. The average flexural capacities of all RAC specimens were within 3.7% of the control specimens. Results from this research

  17. Search for deep slabs in the Northwest Pacific mantle.

    PubMed

    Zhou, H W; Anderson, D L

    1989-11-01

    A residual sphere is formed by projecting seismic ray travel-time anomalies, relative to a reference Earth model, onto an imaginary sphere around an earthquake. Any dominant slab-like fast band can be determined with spherical harmonic expansion. The technique is useful in detecting trends associated with high-velocity slabs beneath deep earthquakes after deep-mantle and near-receiver effects are removed. Two types of corrections are used. The first uses a tomographic global mantle model; the second uses teleseismic station averages of residuals from many events over a large area centered on the events of interest. Under the Mariana, Izu-Bonin, and Japan trenches, the dominant fast bands are generally consistent with seismicity trends. The results are unstable and differ from the seismicity trend for Kurile events. The predominant fast band for most deep earthquakes under Japan is subhorizontal rather than near vertical. We find little support for the deep slab penetration hypothesis.

  18. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-03

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

  19. Abrupt tectonics and rapid slab detachment with grain damage

    PubMed Central

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-01-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  20. Distribution of porosity and macrosegregation in slab steel ingot

    NASA Astrophysics Data System (ADS)

    Tkadleckova, M.; Jonsta, P.; Carbol, Z.; Susovsky, M.; Michalek, K.; Socha, L.; Sviželová, J.; Zwyrtek, J.

    2017-02-01

    The paper presents a new knowledge and experiences with verification and optimization of production technology of heavy slab ingot weighing 40 t from tool steel using the results of numerical modelling and of operational experiments at a steel plant in the company VÍTKOVICE HEAVY MACHINERY a.s. The final porosity, macrosegregation and the risk of cracks were predicted. Based on the results, the slab ingot can be used instead of the conventional heavy steel ingot. Also, the ratio, the chamfer, and the external shape of the wall of the new design of the slab ingot was improved, which enabled to reduce production costs while the internal quality of steel ingots was still maintained at very high level.

  1. Role of Hydrogen in stagnant slabs and big mantle wedge

    NASA Astrophysics Data System (ADS)

    Ohtani, E.; Zhao, D.

    2008-12-01

    Recent seismic tomography data imply that subducting slabs are stagnant at some regions such as beneath Japan and Northeast China [1, 2]. The stagnant slab can have an important effect on the overlying transition zone and upper mantle. A big mantle wedge (BMW) model has been proposed by Zhao [2], in which the stagnant slab in the transition zone could play an essential role in the intra-plate volcanic activities overlying the slab. Water released by the stagnant slab could be important for such igneous activities, such as Mt. Changbai in Northeast China. In cold subducting slabs, several hydrous minerals together with nominally anhydrous minerals accommodate OH and transport water into the transition zone [3]. The effect of dehydration of the stagnant slab has been analyzed by Richard et al. [4]. They argued that warming of the stagnant slab due to heat conduction could play an important role for the slab dehydration, and local oversaturation could be achieved due to decrease of the water solubility in minerals with temperature, and fluid can be formed in the overlying transition zone. We determined the hydrogen diffusion in wadsleyite and ringwoodite under the transition zone conditions in order to clarify the deep processes of the stagnant slabs, and found that diffusion rates of hydrogen are comparable with that of olivine [5]. We also determined the dihedral angle of aqueous fluid between wadsleyite grains and majorite grains under the transition zone conditions. The dihedral angles are very small, around 20-40 degrees, indicating that the oversaturated fluids can move rapidly by the percolation mechanism in the transition zone. The fluids moved to the top of the 410 km discontinuity can generate heavy hydrous melts due to a larger depression of the wet solidus at the base of the upper mantle [6]. Gravitationally stable hydrous melts can be formed at the base of the upper mantle, which is consistent with seismological observations of the low velocity beneath

  2. Efficient Vortex Generation in Subwavelength Epsilon-Near-Zero Slabs

    NASA Astrophysics Data System (ADS)

    Ciattoni, Alessandro; Marini, Andrea; Rizza, Carlo

    2017-03-01

    We show that a homogeneous and isotropic slab, illuminated by a circularly polarized beam with no topological charge, produces vortices of order 2 in the opposite circularly polarized components of the reflected and transmitted fields, as a consequence of the transverse magnetic and transverse electric asymmetric response of the rotationally invariant system. In addition, in the epsilon-near-zero regime, we find that vortex generation is remarkably efficient in subwavelength thick slabs up to the paraxial regime. This physically stems from the fact that a vacuum paraxial field can excite a nonparaxial field inside an epsilon-near-zero slab since it hosts slowly varying fields over physically large portions of the bulk. Our theoretical predictions indicate that epsilon-near-zero media hold great potential as nanophotonic elements for manipulating the angular momentum of the radiation, since they are available without resorting to complicated micro- or nanofabrication processes and can operate even at very small (ultraviolet) wavelengths.

  3. Corrosion control of steel-reinforced concrete

    NASA Astrophysics Data System (ADS)

    Chung, D. D. L.

    2000-10-01

    The methods and materials for corrosion control of steel-reinforced concrete are reviewed. The methods are steel surface treatment, the use of admixtures in concrete, surface coating on concrete, and cathodic protection.

  4. Stress Distribution in the Subducted Slab in the Transition Zone

    NASA Astrophysics Data System (ADS)

    Běhounková, M.; Běhounková, M.; Čížková, H.; Matyska, C.; Špičák, A.

    2006-12-01

    We present the results of numerical modelling of subduction process in a 2-D cartesian box. Our numerical code is based on the method of Gerya and Yuen 2003. We concentrate on the deformation and stress distribution within the slab in the transition zone. Our composite rheological model includes diffusion creep, dislocation creep and power-law stress limiter. The effects of phase transitions at the depths 410 km and 660 km are taken into account. The model is applied to the Tonga subduction region, where the currently subducting plate might face the remnants of the high viscosity subducted material in the transition zone. This material might possibly originate either from a previous episode of the subduction (Chen and Brudzinski, 2001) or from the buoyant detached slab broken off from the active subducting slab (Green, 2001). We prescribe the cold and relatively high viscosity piece of old slab lying above the 660 km interface. The stress distribution in the new subducting place is then investigated as the plate approaches these remnants of old slab. Stress directions and amplitudes are compared to the data available from the analyses of the earthquake mechanisms in Tonga region. Chen W.-P., Brudzinski R, 2001. Evidence for a Large-Scale Remnant of Subducted Lithosphere Beneath Fiji, Science 292, 2475--2479. Gerya T.V., Yuen D.A., 2003. Characteristics-based marker-in-cell method with conservative finite-differences schemes for modelling geological flows with strongly variable transport properties, Phys. Earth Planet. Int. 140, 293--318. Green, H.W., 2001. A graveyard for buoyant slabs?, Science 292, 2445-2446.

  5. Links between fluid circulation, temperature, and metamorphism in subducting slabs

    USGS Publications Warehouse

    Spinelli, G.A.; Wang, K.

    2009-01-01

    The location and timing of metamorphic reactions in subducting lithosph??re are influenced by thermal effects of fluid circulation in the ocean crust aquifer. Fluid circulation in subducting crust extracts heat from the Nankai subduction zone, causing the crust to pass through cooler metamorphic faci??s than if no fluid circulation occurs. This fluid circulation shifts the basalt-to-eclogite transition and the associated slab dehydration 14 km deeper (35 km farther landward) than would be predicted with no fluid flow. For most subduction zones, hydrothermal cooling of the subducting slab will delay eclogitization relative to estimates made without considering fluid circulation. Copyright 2009 by the American Geophysical Union.

  6. Expansion of a cold non-neutral plasma slab

    SciTech Connect

    Karimov, A. R.; Yu, M. Y.; Stenflo, L.

    2014-12-15

    Expansion of the ion and electron fronts of a cold non-neutral plasma slab with a quasi-neutral core bounded by layers containing only ions is investigated analytically and exact solutions are obtained. It is found that on average, the plasma expansion time scales linearly with the initial inverse ion plasma frequency as well as the degree of charge imbalance, and no expansion occurs if the cold plasma slab is stationary and overall neutral. However, in both cases, there can exist prominent oscillations on the electron front.

  7. Slab Driven Mantle Deformation and Plate-Mantle Decoupling

    NASA Astrophysics Data System (ADS)

    Jadamec, M. A.; MacDougall, J.; Fischer, K. M.

    2015-12-01

    Observations of shear wave splitting derived from local sources in subduction zones suggest viscous flow in the mantle wedge is commonly non-parallel to both the subducting plate velocity vector and the motion of the overriding plate. However, far from the subduction zone trench, observations indicate the fast axis of shear wave splitting tends to align with the velocity vector of the surface plates. Similarly, previous 3D geodynamic models show the slab can drive local decoupling of the mantle and surface plates, in both direction and speed. This suggests that there is some distance from the trench over which there is significant decoupling of the mantle flow from surface plate motion, and that this decoupling zone then decays with continued distance from the trench, resulting in far-field plate-mantle coupling. Here we present results from geodynamic models of subduction coupled with calculations of olivine fabric deformation and synthetic splitting to 1) examine the influence of slab strength, slab dip, and non-Newtonian viscosity on the deformation fabric in the mantle wedge and subslab mantle and 2) quantify the spatial extent and intensity of this slab driven decoupling zone. We compare the deformation fabric in a 2D corner flow solution with varying dip to that of a 2D free subduction model with varying initial dip and slab strength. The results show that using an experimentally derived flow law to define viscosity (both diffusion creep and dislocation creep deformation mechanisms) has a first order effect on the viscosity structure and flow velocity in the upper mantle. The free subduction models using the composite viscosity formulation produce a zone of subduction induced mantle weakening that results in reduced viscous support of the slab and lateral variability in coupling of the mantle to the base of the surface plates. The maximum yield stress, which places an upper bound on the slab strength, can also have a significant impact on the viscosity

  8. Investigating the Farallon Slab with Probabilistic Traveltime Tomography

    NASA Astrophysics Data System (ADS)

    Burdick, S.; Lekic, V.

    2015-12-01

    Subduction of the Farallon Plate beneath North America played a key role in its tectonic development. Seismic constraints on the subducted remnants of the Farallon slab provide evidence needed to better understand the polarity and timing of subduction, the structure of the plate, and its relation to tectonic events like the uplift of the Rocky Mountains. Over the course of its deployment, the USArray Transportable Array (TA) has offered ideal data coverage for investigating the Farallon and related slabs in the upper mantle using seismic tomography and converted wave imaging. With its arrival in the east, data from the TA provides the crossing paths necessary to image the upper reaches of the oldest parts of the plate at mid-mantle depths. We perform a global tomographic inversion using the latest P-wave traveltime picks from TA combined with global catalogue data. While the new velocity model resolves upper mantle slab structure at unprecedented detail in the east, a quantitative grasp of model uncertainty is needed to reliably relate velocity variations to the thermal and mechanical properties of the slabs. In order to quantify the uncertainty of our tomographic model, we employ Transdimensional Hierarchical Bayesian (THB) inversion. THB tomography uses Markov chain Monte Carlo to create an ensemble of velocity models that can be analyzed to statistically infer the best-fit velocities, their uncertainties, and tradeoffs. We present and discuss various representations of uncertainty quantified by THB tomography—error bars, model covariance, multimodal distributions of velocity values—and demonstrate its importance for furthering our understanding of the slab fragments beneath North America. We illustrate how we are able to distinguish between spurious slab fragments from those required by the data. By examining bimodal velocity distributions, we put error bars on the spatial extent of the slabs that can then be analyzed using thermal diffusion modeling. By

  9. Seismic Behaviour of Masonry Vault-Slab Structures

    SciTech Connect

    Chesi, Claudio; Butti, Ferdinando; Ferrari, Marco

    2008-07-08

    Spandrel walls typically play a structural role in masonry buildings, transferring load from a slab to the supporting vault. Some indications are given in the literature on the behaviour of spandrels under the effect of vertical loads, but little attention is given to the effect coming from lateral forces acting on the building. An opportunity to investigate this problem has come from the need of analyzing a monumental building which was damaged by the Nov. 24, 2004 Val Sabbia earthquake in the north of Italy. The finite element model set up for the analysis of the vault-spandrel-slab system is presented and the structural role resulting for the spandrels is discussed.

  10. Concrete Operations and Attentional Capacity.

    ERIC Educational Resources Information Center

    Chapman, Michael; Lindenberger, Ulman

    1989-01-01

    To test predictions regarding the attentional capacity requirements of Piaget's stage of concrete operations, a battery of concrete operational tasks and two measures of attentional capacity were administered to 120 first-, second-, and third-graders. Findings concern class inclusion, transitivity of length and weight, and multiplication of…

  11. The Concrete and Pavement Challenge

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2012-01-01

    The modern world is characterized by the extensive use of concrete and asphalt pavement. Periodically, these materials are replaced and the old materials disposed of. In this challenge, students will be asked to develop ways to reuse the old materials. It is important for students to understand how concrete and asphalt are made and applied, as…

  12. Molded Concrete Center Mine Wall

    NASA Technical Reports Server (NTRS)

    Lewis, E. V.

    1987-01-01

    Proposed semiautomatic system forms concrete-foam wall along middle of coal-mine passage. Wall helps support roof and divides passage into two conduits needed for ventilation of coal face. Mobile mold and concrete-foam generator form sections of wall in place.

  13. Technology Solutions Case Study: Insulating Concrete Forms

    SciTech Connect

    none,

    2012-10-01

    This Pacific Northwest National Laboratory project investigated insulating concrete forms—rigid foam, hollow walls that are filled with concrete for highly insulated, hurricane-resistant construction.

  14. Impact analyses for negative flexural responses (hogging) in railway prestressed concrete sleepers

    NASA Astrophysics Data System (ADS)

    Kaewunruen, S.; Ishida, T.; Remennikov, AM

    2016-09-01

    By nature, ballast interacts with railway concrete sleepers in order to provide bearing support to track system. Most train-track dynamic models do not consider the degradation of ballast over time. In fact, the ballast degradation causes differential settlement and impact forces acting on partial and unsupported tracks. Furthermore, localised ballast breakages underneath railseat increase the likelihood of centrebound cracks in concrete sleepers due to the unbalanced support under sleepers. This paper presents a dynamic finite element model of a standard-gauge concrete sleeper in a track system, taking into account the tensionless nature of ballast support. The finite element model was calibrated using static and dynamic responses in the past. In this paper, the effects of centre-bound ballast support on the impact behaviours of sleepers are highlighted. In addition, it is the first to demonstrate the dynamic effects of sleeper length on the dynamic design deficiency in concrete sleepers. The outcome of this study will benefit the rail maintenance criteria of track resurfacing in order to restore ballast profile and appropriate sleeper/ballast interaction.

  15. Investigation into the optimal hydrologic design of porous concrete sites using mathematical modeling

    NASA Astrophysics Data System (ADS)

    Syrrakou, C.; Fitch, J.; Eliassen, T.; Ahearn, W.; Pinder, G. F.

    2011-12-01

    Increase in the amount of paved areas as a result of urbanization in modern societies has lead to the need of stormwater best management practices (BMPs). In that direction, porous pavement has been used successfully in regions of warm climate and application in regions of colder climate is an object of ongoing research with encouraging results to date. The significant cost and effort that accompanies the maintenance of porous pavement facilities calls for a design tool that can be used prior construction to facilitate the design process and also post production to evaluate the site's overall performance. Such a tool is a mathematical model which takes into account the different physical processes that can occur in a porous concrete system including recharge from rainfall, runoff from surrounding conventionally paved areas, vertical flow, storage and finally infiltration into the subsurface. In this research a three-dimensional saturated-unsaturated flow and transport model is modified to account for flow through the porous concrete slab and also evaporation. Runoff is accounted by means of a two-dimensional surface flow model which calculates the infiltration into the perimeter porous concrete area. The mathematical model is used to simulate a porous concrete site which operates as a public parking lot facility in Randolph, Vermont. The subgrade soil in the area of interest consists mainly of dense till deposits typically found in New England. Such deposits can result in small infiltration rates. The specific site is unique not only in terms of the underlying geology but also the heavy instrumentation not usually observed in similar sites. The instrumentation includes a number of groundwater wells which are being monitored continuously through a pressure transducer system, temperature probes installed inside the porous concrete and a detailed underdrain system located in the porous concrete's sub-base accumulating infiltrated water. Laboratory research is also

  16. 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.

  17. Magnetic Launch Assist Experimental Track

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In this photograph, a futuristic spacecraft model sits atop a carrier on the Magnetic Launch Assist System, formerly known as the Magnetic Levitation (MagLev) System, experimental track at the Marshall Space Flight Center (MSFC). Engineers at MSFC have developed and tested Magnetic Launch Assist technologies that would use magnetic fields to levitate and accelerate a vehicle along a track at very high speeds. Similar to high-speed trains and roller coasters that use high-strength magnets to lift and propel a vehicle a couple of inches above a guideway, a Magnetic Launch Assist system would electromagnetically drive a space vehicle along the track. A full-scale, operational track would be about 1.5-miles long and capable of accelerating a vehicle to 600 mph in 9.5 seconds. This track is an advanced linear induction motor. Induction motors are common in fans, power drills, and sewing machines. Instead of spinning in a circular motion to turn a shaft or gears, a linear induction motor produces thrust in a straight line. Mounted on concrete pedestals, the track is 100-feet long, about 2-feet wide, and about 1.5-feet high. The major advantages of launch assist for NASA launch vehicles is that it reduces the weight of the take-off, the landing gear, the wing size, and less propellant resulting in significant cost savings. The US Navy and the British MOD (Ministry of Defense) are planning to use magnetic launch assist for their next generation aircraft carriers as the aircraft launch system. The US Army is considering using this technology for launching target drones for anti-aircraft training.

  18. Importance of bulk states for the electronic structure of semiconductor surfaces: implications for finite slabs

    NASA Astrophysics Data System (ADS)

    Sagisaka, Keisuke; Nara, Jun; Bowler, David

    2017-04-01

    We investigate the influence of slab thickness on the electronic structure of the Si(1 0 0)- p(2× 2 ) surface in density functional theory (DFT) calculations, considering both density of states and band structure. Our calculations, with slab thicknesses of up to 78 atomic layers, reveal that the slab thickness profoundly affects the surface band structure, particularly the dangling bond states of the silicon dimers near the Fermi level. We find that, to precisely reproduce the surface bands, the slab thickness needs to be large enough to completely converge the bulk bands in the slab. In the case of the Si(1 0 0) surface, the dispersion features of the surface bands, such as the band shape and width, converge when the slab thickness is larger than 30 layers. Complete convergence of both the surface and bulk bands in the slab is only achieved when the slab thickness is greater than 60 layers.

  19. Photonic-crystal slab for terahertz-wave technology platform

    NASA Astrophysics Data System (ADS)

    Fujita, Masayuki

    2016-03-01

    Photonic crystals manipulate photons in a manner analogous to solid-state crystals, and are composed of a dielectric material with a periodic refractive index distribution. In particular, two-dimensional photonic-crystal slabs with high index contrasts (semiconductor/air) are promising for practical applications, owing to the strong optical confinement in simple, thin planar structures. This paper presents the recent progress on a silicon photonic-crystal slab as a technology platform in the terahertz-wave region, which is located between the radio and light wave regions (0.1-10 THz). Extremely low-loss (<0.1 dB/cm) terahertz waveguides based on the photonic-bandgap effect as well as dynamic control and modulation of a terahertz-wave transmission in a photonic-crystal slab by the effective interaction between photoexcited carriers and the terahertz-wave trapping due to the photonic band-edge effect are demonstrated. Terahertz photonic-crystal slabs hold the potential for developing ultralow-loss, compact terahertz components and integrated devices used in applications including wireless communication, spectroscopic sensing, and imaging.

  20. Applications of acoustics in the measurement of coal slab thickness

    NASA Technical Reports Server (NTRS)

    Hadden, W. J., Jr.; Mills, J. M.; Pierce, A. D.

    1980-01-01

    The determination of the possibility of employing acoustic waves at ultrasonic frequencies for measurements of thicknesses of slabs of coal backed by shale is investigated. Fundamental information concerning the acoustical properties of coal, and the relationship between these properties and the structural and compositional parameters used to characterize coal samples was also sought. The testing device, which utilizes two matched transducers, is described.

  1. 6. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' ...

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

    6. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' PLATE MILL. FURNACE SHOWING DURING DEMOLITION. C HOOK USED TO CHANGE ROLLS IS VISIBLE IN FRONT OF FURNACE. - U.S. Steel Homestead Works, 160" Plate Mill, Along Monongahela River, Homestead, Allegheny County, PA

  2. Tensor-guided fitting of subduction slab depths

    USGS Publications Warehouse

    Bazargani, Farhad; Hayes, Gavin P.

    2013-01-01

    Geophysical measurements are often acquired at scattered locations in space. Therefore, interpolating or fitting the sparsely sampled data as a uniform function of space (a procedure commonly known as gridding) is a ubiquitous problem in geophysics. Most gridding methods require a model of spatial correlation for data. This spatial correlation model can often be inferred from some sort of secondary information, which may also be sparsely sampled in space. In this paper, we present a new method to model the geometry of a subducting slab in which we use a data‐fitting approach to address the problem. Earthquakes and active‐source seismic surveys provide estimates of depths of subducting slabs but only at scattered locations. In addition to estimates of depths from earthquake locations, focal mechanisms of subduction zone earthquakes also provide estimates of the strikes of the subducting slab on which they occur. We use these spatially sparse strike samples and the Earth’s curved surface geometry to infer a model for spatial correlation that guides a blended neighbor interpolation of slab depths. We then modify the interpolation method to account for the uncertainties associated with the depth estimates.

  3. RAW COPPER SLABS USED IN CASTING OPERATIONS AT BUFFALO PLANT ...

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

    RAW COPPER SLABS USED IN CASTING OPERATIONS AT BUFFALO PLANT OF AMERICAN BRASS COMPANY. MATERIALS STORAGE FOR THE CAST SHOP NOW OCCUPIES A PORTION OF THE ORIGINAL BRASS MILL BUILT BY THE BUFFALO COPPER AND BRASS ROLLING MILL IN 1906-07 AND EXPANDED IN 1911. - American Brass Foundry, 70 Sayre Street, Buffalo, Erie County, NY

  4. Criticality Benchmark Analysis of Water-Reflected Uranium Oxyfluoride Slabs

    SciTech Connect

    Margaret A. Marshall; John D. Bess

    2009-11-01

    A series of twelve experiments were conducted in the mid 1950's at the Oak Ridge National Laboratory Critical Experiments Facility to determine the critical conditions of a semi-infinite water-reflected slab of aqueous uranium oxyfluoride (UO2F2). A different slab thickness was used for each experiment. Results from the twelve experiment recorded in the laboratory notebook were published in Reference 1. Seven of the twelve experiments were determined to be acceptable benchmark experiments for the inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments. This evaluation will not only be available to handbook users for the validation of computer codes and integral cross-section data, but also for the reevaluation of experimental data used in the ANSI/ANS-8.1 standard. This evaluation is important as part of the technical basis of the subcritical slab limits in ANSI/ANS-8.1. The original publication of the experimental results was used for the determination of bias and bias uncertainties for subcritical slab limits, as documented by Hugh Clark's paper 'Subcritical Limits for Uranium-235 Systems'.

  5. 30. VAL LOOKING DOWN THE LAUNCHER SLAB STAIRS AT THE ...

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

    30. VAL LOOKING DOWN THE LAUNCHER SLAB STAIRS AT THE PROJECTILE LOADING CAR AND LOADING PLATFORM ADJACENT TO THE PROJECTILE LOADING DECK AND LAUNCHER BRIDGE. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  6. Electromagnetic fluctuation-induced interactions in randomly charged slabs

    NASA Astrophysics Data System (ADS)

    Rezvani, Vahid; Sarabadani, Jalal; Naji, Ali; Podgornik, Rudolf

    2012-09-01

    Randomly charged net-neutral dielectric slabs are shown to interact across a featureless dielectric continuum with long-range electrostatic forces that scale with the statistical variance of their quenched random charge distribution and inversely with the distance between their bounding surfaces. By accounting for the whole spectrum of electromagnetic field fluctuations, we show that this long-range disorder-generated interaction extends well into the retarded regime where higher order (non-zero) Matsubara frequencies contribute significantly. This occurs even for highly clean samples with only a trace amount of charge disorder and shows that disorder effects can be important down to the nanoscale. As a result, the previously predicted non-monotonic behavior for the total force between dissimilar slabs as a function of their separation distance is substantially modified by higher order contributions, and in almost all cases of interest, we find that the equilibrium inter-surface separation is shifted to substantially larger values compared to predictions based solely on the zero-frequency component. This suggests that the ensuing non-monotonic interaction is more easily amenable to experimental detection. The presence of charge disorder in the intervening dielectric medium between the two slabs is shown to lead to an additional force that can be repulsive or attractive depending on the system parameters and can, for instance, wash out the non-monotonic behavior of the total force when the intervening slab contains a sufficiently large amount of disorder charges.

  7. Slab melting and magma formation beneath the southern Cascade arc

    NASA Astrophysics Data System (ADS)

    Walowski, K. J.; Wallace, P. J.; Clynne, M. A.; Rasmussen, D. J.; Weis, D.

    2016-07-01

    The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO > 7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

  8. Slab Stagnation in the Lower Mantle: A Multidisciplinary Investigation

    NASA Astrophysics Data System (ADS)

    Waszek, L.; Arredondo, K.; Finkelstein, G. J.; Kellogg, L. H.; Lekic, V.; Li, M.; Lithgow-Bertelloni, C. R.; Romanowicz, B. A.; Schmerr, N. C.; Rudolph, M. L.; Townsend, J. P.; Xing, Z.; Yang, F.

    2014-12-01

    Recent tomographic models show that while many slabs seem to deflect or stagnate at the 660 km discontinuity, some slabs continue to subduct deeper and pond at 1000 km below the earth's surface (Fukao and Obayashi, 2013). Only one slab is observed to penetrate significantly deeper into the mantle. Furthermore, some mantle upwellings also appear to be deflected at 1000 km in depth. The radial correlation functions for the low-order spherical harmonics of most tomographic inversions show that while seismic wave velocities are correlated for all depths below ~1000 km, velocities at depths between 400-1000 km are uncorrelated with velocities at any other depth. This implies that there are large scale velocity features coherent from 1000 km to the core-mantle boundary, but no large scale features coherent from the top of the transition zone down to 1000 km. Seismic studies using precursors and receiver functions find evidence for numerous reflectors in the mid-mantle, ranging from 900 km in depth beneath the southern Pacific and southeast Asia to 1200 km beneath Europe and Japan. This range of depths could indicate topography along a single laterally continuous discontinuity or result from multiple unconnected features. Some reflectors are geographically near, and therefore may be associated with, subducted slabs, however the origin of the others is unclear. The 1000 km 'discontinuity' could potentially be explained by an increase in viscosity or density, such as a compositional difference in the mantle below this depth. We use an interdisciplinary approach to investigate the diversity in apparent slab stagnation behavior and which geophysical mechanisms prevent subduction into the lower mantle. The controlling factor may be a function of the slab itself, including subduction rate, trench rollback, composition, or temperature. Alternatively, bulk mantle properties may control slab penetration. We perform 2D and 3D numerical simulations to determine the influence of

  9. Environmental durability of polymer concrete

    SciTech Connect

    Palmese, G.R.; Chawalwala, A.J.

    1996-12-31

    Over the past two decades, polymer concrete has increasingly been used for a number of applications including piping, machine bases, chemically resistant flooring, and bridge overlays. Currently, the use of polymer concrete as a wear surface for polymeric composite bridge decks is being investigated. Polymer concrete is a particulate composite comprised of mineral aggregate bound by a polymeric matrix. Such materials possess significantly higher mechanical properties than Portland cement concrete. However, the mechanical characteristics and environmental durability of polymer concrete are influenced by a number of factors. Among these are the selection of aggregate and resin, surface treatment, and cure conditions. In this work the influence of matrix selection and cure history on the environmental durability of polymer concrete was investigated. Particular attention was given to the effects of water on composite properties and to the mechanisms by which degradation occurs. The basalt-based polymer concrete systems investigated were susceptible to attack by water. Furthermore, results suggest that property loss associated with water exposure was primarily a result of interfacial weakening.

  10. Flood tracking chart, Amite River Basin, Louisiana

    USGS Publications Warehouse

    Callender, Lawrence E.; McCallum, Brian E.; Brazelton, Sebastian R.; Anderson, Mary L.; Ensminger, Paul A.

    1998-01-01

    The Amite River Basin flood tracking chart is designed to assist emergency response officials and the local public in making informed decisions about the safety of life and property during floods along the Amite and Comite Rivers and Bayou Manchac in southeastern Louisiana. This chart is similar in concept to the charts used to track hurricanes; the user can record the latest river stage information at selected gaging stations and the latest flood crest predictions. The latest stage data can be compared to historical flood peaks as well as to the slab or pier elevation of a threatened property. The chart also discusses how to acquire the latest river stage data from the Internet and a recorded voice message.

  11. Flood tracking chart, Amite River basin, Louisiana

    USGS Publications Warehouse

    Callender, Lawrence; McCallum, Brian E.; Brazelton, Sebastian R.

    1996-01-01

    The Amite River Basin flood tracking chart is designed to assist emergency response officials and the local public in making informed decisions about the safety of life and property during floods along the Amite and Comite Rivers and Bayou Manchac in southeastern Louisiana. This chart is similar in concept to the charts used to track hurricanes; the user can record the latest river stage information at selected gaging stations and the latest flood crest predictions. The latest stage data can be compared to historical flood peaks as well as to the slab or pier elevation of a threatened property. The chart also discusses how to acquire the latest river stage data from the Internet and a recorded voice message.

  12. Concrete Dust Suppression System. Innovative Technology Summary Report

    SciTech Connect

    1998-12-01

    The improved technology is a water-based dust suppression system for controlling concrete dust generated by demolition equipment, in this case a demolition ram. This demonstration was performed to assess the effectiveness of this system to (1) minimize the amount of water used to suppress potentially contaminated dust, (2) focus the water spray on the dust-generating source and (3) minimize the dust cloud generated by the demolition activity. The technology successfully reduced the water required by a factor of eight compared to the traditional (baseline) method, controlled the dust generated, and permitted a reduction in the work force. The water spray can be focused at the ram point, but it is affected by wind. Prior to the use of this dust control system, dust generated by the demolition ram was controlled manually by spraying with fire hoses (the baseline technology). The improved technology is 18% less expensive than the baseline technology for the conditions and parameters of this demonstration, however, the automated system can save up to 80% versus the baseline whenever waste water treatment costs are considered. For demolishing one high-walled room and a long slab with a total of 413 m{sup 3} (14,580 ft{sup 3}) of concrete, the savings are $105,000 (waste water treatment included). The improved technology reduced the need for water consumption and treatment by about 88% which results in most of the savings.

  13. Assimilating lithosphere and slab history in 4-D Earth models

    NASA Astrophysics Data System (ADS)

    Bower, Dan J.; Gurnis, Michael; Flament, Nicolas

    2015-01-01

    We develop methods to incorporate paleogeographical constraints into numerical models of mantle convection. Through the solution of the convection equations, the models honor geophysical and geological data near the surface while predicting mantle flow and structure at depth and associated surface deformation. The methods consist of four constraints determined a priori from a plate history model: (1) plate velocities, (2) thermal structure of the lithosphere, (3) thermal structure of slabs in the upper mantle, and (4) velocity of slabs in the upper mantle. These constraints are implemented as temporally- and spatially-dependent conditions that are blended with the solution of the convection equations at each time step. We construct Earth-like regional models with oceanic and continental lithosphere, trench migration, oblique subduction, and asymmetric subduction to test the robustness of the methods by computing the temperature, velocity, and buoyancy flux of the lithosphere and slab. Full sphere convection models demonstrate how the methods can determine the flow associated with specific tectonic environments (e.g., back-arc basins, intraoceanic subduction zones) to address geological questions and compare with independent data, both at present-day and in the geological past (e.g., seismology, residual topography, stratigraphy). Using global models with paleogeographical constraints we demonstrate (1) subduction initiation at the Izu-Bonin-Mariana convergent margin and flat slab subduction beneath North America, (2) enhanced correlation of model slabs and fast anomalies in seismic tomography beneath North and South America, and (3) comparable amplitude of dynamic and residual topography in addition to improved spatial correlation of dynamic and residual topography lows.

  14. Rapid Testing of Fresh Concrete

    DTIC Science & Technology

    1975-05-01

    Cementforenlng, Oslo, 1952). 1.1 Orchard, 0. F., "The Effect of the Vacum Process on Concrete Mix Design ," Symposiwn on Mix Design and Qualify Control...ASTM, Vol 33, Part I (1933), pp 297-307. Orchard, D. F., "The Effect of the Vacuum Process on Concrete Mix Design ," Symposium on Mix Design and... Designed for Use in Determining Constituents of Fresh Concrete," Public floads, Vol 13, No. 9 (1932), p 151. 9 Cook, G. C, "Effect of Time of Haul

  15. Concrete Construction Using Slipform Techniques.

    DTIC Science & Technology

    1982-11-01

    Operations 75 4.1.3 Ramp, Curb, Gutter, Sidewalk and Median Paving "/ 4.1.4 Canal Lining 80 4.2 Cast-in-Place Pipe 82 4.3 Tunnel Inverts 83 4.4...101 APPENDIX B - Bibliography 102 b. -E CHAPTER 1 INTRODUCTION 1.1 BACKGROUND The formwork for concrete structures represents a critical part of...concrete construction, in terms of cost and importance toward getting the job done properly and on time. In fact, concrete formwork frequently costs more

  16. Design and application of a small size SAFT imaging system for concrete structure

    NASA Astrophysics Data System (ADS)

    Shao, Zhixue; Shi, Lihua; Shao, Zhe; Cai, Jian

    2011-07-01

    A method of ultrasonic imaging detection is presented for quick non-destructive testing (NDT) of concrete structures using synthesized aperture focusing technology (SAFT). A low cost ultrasonic sensor array consisting of 12 market available low frequency ultrasonic transducers is designed and manufactured. A channel compensation method is proposed to improve the consistency of different transducers. The controlling devices for array scan as well as the virtual instrument for SAFT imaging are designed. In the coarse scan mode with the scan step of 50 mm, the system can quickly give an image display of a cross section of 600 mm (L) × 300 mm (D) by one measurement. In the refined scan model, the system can reduce the scan step and give an image display of the same cross section by moving the sensor array several times. Experiments on staircase specimen, concrete slab with embedded target, and building floor with underground pipe line all verify the efficiency of the proposed method.

  17. Significance of coplanar macrocells to corrosion in concrete-embedded steel

    SciTech Connect

    Rodriguez, P.; Ramirez, E.; Feliu, S.; Gonzalez, J.A.; Lopez, W.

    1999-03-01

    The influence of microcells and galvanic macrocells on the corrosion kinetics of concrete-embedded steel was investigated experimentally. Nine stainless steel/carbon steel coplanar macrocouples in cathodic-to-anodic ratios of 0.02 to 50 were cast in concrete slabs made from cement, sand, and water in a 1:3:0:5 proportion plus 2% calcium chloride (CaCl{sub 2}) per cement weight. Corrosion potential (E{sub corr}), galvanic current (i{sub g}), polarization resistance (R{sub p}), and impedance measurements from 100 kHz to 0.01 Hz were made for the two metals, coupled and uncoupled. i{sub g} data provided by a zero resistance ammeter led to potentially underestimated corrosion rates for anodic areas, whereas R{sub p} measurements provided fairly reliable corrosion rates. Macrocells polarized anodic areas very slightly at points where an anodic and a cathodic process took place simultaneously.

  18. 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).

  19. Testing of concrete by laser ablation

    DOEpatents

    Flesher, D.J.; Becker, D.L.; Beem, W.L.; Berry, T.C.; Cannon, N.S.

    1997-01-07

    A method is disclosed for testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed. 1 fig.

  20. Concrete density estimation by rebound hammer method

    SciTech Connect

    Ismail, Mohamad Pauzi bin Masenwat, Noor Azreen bin; Sani, Suhairy bin; Mohd, Shukri; Jefri, Muhamad Hafizie Bin; Abdullah, Mahadzir Bin; Isa, Nasharuddin bin; Mahmud, Mohamad Haniza bin

    2016-01-22

    Concrete is the most common and cheap material for radiation shielding. Compressive strength is the main parameter checked for determining concrete quality. However, for shielding purposes density is the parameter that needs to be considered. X- and -gamma radiations are effectively absorbed by a material with high atomic number and high density such as concrete. The high strength normally implies to higher density in concrete but this is not always true. This paper explains and discusses the correlation between rebound hammer testing and density for concrete containing hematite aggregates. A comparison is also made with normal concrete i.e. concrete containing crushed granite.

  1. Testing of concrete by laser ablation

    DOEpatents

    Flesher, Dann J.; Becker, David L.; Beem, William L.; Berry, Tommy C.; Cannon, N. Scott

    1997-01-01

    A method of testing concrete in a structure in situ, by: directing a succession of pulses of laser radiation at a point on the structure so that each pulse effects removal of a quantity of concrete and transfers energy to the concrete; detecting a characteristic of energy which has been transferred to the concrete; determining, separately from the detecting step, the total quantity of concrete removed by the succession of pulses; and calculating a property of the concrete on the basis of the detected energy characteristic and the determined total quantity of concrete removed.

  2. Migrating corrosion inhibitor protection of concrete

    SciTech Connect

    Bjegovic, D.; Miksic, B.

    1999-11-01

    Migrating corrosion inhibitors (MCI) were developed to protect steel rebar from corrosion in concrete. They were designed to be incorporated as an admixture during concrete batching or used for surface impregnation of existing concrete structures. Two investigations are summarized. One studied the effectiveness of MCIs as a corrosion inhibitor for steel rebar when used as an admixture in fresh concrete mix. The other is a long-term study of MCI concrete impregnation that chronicles corrosion rates of rebar in concrete specimens. Based on data from each study, it was concluded that migrating corrosion inhibitors are compatible with concrete and effectively delay the onset of corrosion.

  3. Concrete density estimation by rebound hammer method

    NASA Astrophysics Data System (ADS)

    Ismail, Mohamad Pauzi bin; Jefri, Muhamad Hafizie Bin; Abdullah, Mahadzir Bin; Masenwat, Noor Azreen bin; Sani, Suhairy bin; Mohd, Shukri; Isa, Nasharuddin bin; Mahmud, Mohamad Haniza bin

    2016-01-01

    Concrete is the most common and cheap material for radiation shielding. Compressive strength is the main parameter checked for determining concrete quality. However, for shielding purposes density is the parameter that needs to be considered. X- and -gamma radiations are effectively absorbed by a material with high atomic number and high density such as concrete. The high strength normally implies to higher density in concrete but this is not always true. This paper explains and discusses the correlation between rebound hammer testing and density for concrete containing hematite aggregates. A comparison is also made with normal concrete i.e. concrete containing crushed granite.

  4. Design of SC walls and slabs for impulsive loading

    SciTech Connect

    Varma, Amit H.

    2015-11-11

    Reinforced concrete (RC) structures have historically been the preferred choice for blast resistant structures because of their mass and the ductility provided by steel reinforcement. Steel-plate composite (SC) walls are a viable alternative to RC for protecting the infrastructure against explosive threats. SC structures consist of two steel faceplates with a plain concrete core between them. The steel faceplates are anchored to the concrete using stud anchors and connected to each other using tie bars. SC structures provide mass from the concrete infill and ductility from the continuous external steel faceplates. This dissertation presents findings and recommendations from experimental and analytical investigations of the performance of SC walls subjected to far-field blast loads.

  5. 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

  6. Microstructural investigations on aerated concrete

    SciTech Connect

    Narayanan, N.; Ramamurthy, K.

    2000-03-01

    Aerated concrete is characterized by the presence of large voids deliberately included in its matrix to reduce the density. This study reports the investigations conducted on the structure of cement-based autoclaved aerated concrete (AAC) and non-AAC with sand or fly ash as the filler. The reasons for changes in compressive strength and drying shrinkage are explained with reference to the changes in the microstructure. Compositional analysis was carried out using XRD. It was observed that fly ash responds poorly to autoclaving. The process of pore refinement in fly ash mixes is discussed with reference to the formation of Hadley grains as well as fly ash hydration. The paste-void interface in aerated concrete investigated in relation to the paste-aggregate interface in normal concrete revealed the existence of an interfacial transition zone.

  7. PORTLAND CEMENT CONCRETE FOR ANTARCTICA.

    DTIC Science & Technology

    formulation of recommended procedures for batching, mixing, placing, and curing of portland cement concrete in Antarctica. The pertinent features of the mix and design and related procedures are given. (Author)

  8. 3. NORTH ELEVATION OF THE HOT BAY, SHOWING RAILROAD TRACKS ...

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

    3. NORTH ELEVATION OF THE HOT BAY, SHOWING RAILROAD TRACKS LEADING TO THE MASSIVE STEEL-LINED CONCRETE ENTRANCE DOOR. PART OF THE INTRICATE HVAC SYSTEM IS WEST (RIGHT) OF THE DOOR. - Nevada Test Site, Engine Maintenance Assembly & Disassembly Facility, Area 25, Jackass Flats, Mercury, Nye County, NV

  9. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, J.J.; Elling, D.; Reams, W.

    1990-03-13

    A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

  10. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, J.J.; Elling, D.; Reams, W.

    1988-05-26

    A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt% calcined coke breeze, 40 wt% vinyl ester resin with 3.5 wt% modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag. 4 tabs.

  11. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, Jack J.; Elling, David; Reams, Walter

    1990-01-01

    A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

  12. Detailed slab and mantle structure beneath westernmost Mediterranean

    NASA Astrophysics Data System (ADS)

    Sun, D.; Miller, M. S.; Bezada, M. J.; Humphreys, E.

    2013-12-01

    The geological evolution of the westernmost Mediterranean holds an important piece of the puzzle of how whole western Mediterranean evolved due to the convergence of Africa with Eurasia. Detailed upper mantle seismological images are crucial to test two controversial ideas about the dynamic process of the westernmost Mediterranean during the Cenozoic: slab rollback and lithosphere delamination. Recent tomographic images based on the dense seismic network in Spain and northern Morocco reveal a high-resolution continuous high-velocity anomaly to the transition zone depth under the Alboran domain [Bezada and Humphreys, 2013], which was used to support the slab roll back hypothesis for the westernmost Mediterranean tectonic evolution. However, the slab shape, width, and sharpness of its edges are not well resolved. Furthermore, the deep 2010 earthquake beneath Granada, Spain suggests possible oceanic crust material existing at ~ 600 km depth, which cannot be resolved by current tomography models. The study of multipathing and waveform broadening around sharp features has proven an efficient way to study those features. Here, we use both P and S waveform data from the PICASSO array to produce a detailed image. For the deep Granada earthquake, high frequency second arrivals and long coda after the P and S arrivals are shown on stations in the Rif Mountains of Morocco. By fitting both SH and P waveform data, we suggest that a low-velocity layer (LVL, 2 km thickness, δVs = -10%), possibly old oceanic crust, sits on top of the slab. The seismic waves travel through the LVL as guided waves preserving their high frequency energy. The strength of the second arrivals are very sensitive to the relative location between the deep earthquake and the LVL, which indicates the 2010 deep earthquake was most-likely within the subducted oceanic crust. Using both teleseismic and regional data, we conclude that the width of the sub-vertical slab is ~150 km, which is sharper than the

  13. Concrete waterproofing in nuclear industry.

    PubMed

    Scherbyna, Alexander N; Urusov, Sergei V

    2005-01-01

    One of the main points of aggregate safety during the transportation and storage of radioactive materials is to supply waterproofing for all constructions having direct contact with radiating substances and providing strength, seismic shielding etc. This is the problem with all waterside structures in nuclear industry and concrete installations in the treatment and storage of radioactive materials. In this connection, the problem of developing efficient techniques both for the repair of operating constructions and the waterproofing of new objects of the specified assignment is genuine. Various techniques of concrete waterproofing are widely applied in the world today. However, in conditions of radiation many of these techniques can bring not a profit but irreparable damage of durability and reliability of a concrete construction; for instance, when waterproofing materials contain organic constituents, polymers etc. Application of new technology or materials in basic construction elements requires in-depth analysis and thorough testing. The price of an error might be very large. A comparative analysis shows that one of the most promising types of waterproofing materials for radiation loaded concrete constructions is "integral capillary systems" (ICS). The tests on radiation, thermal and strength stability of ICS and ICS-treated concrete samples were initiated and fulfilled in RFNC-VNIITF. The main result is--ICS applying is increasing of waterproofing and strength properties of concrete in conditions of readiation The paper is devoted to describing the research strategy, the tests and their results and also to planning of new tests.

  14. Protective coatings for concrete

    SciTech Connect

    NAGY, KATHRYN L.; CYGAN, RANDALL T.; BRINKER, C. JEFFREY; SELLINGER, ALAN

    2000-05-01

    The new two-layer protective coating developed for monuments constructed of limestone or marble was applied to highway cement and to tobermorite, a component of cement, and tested in batch dissolution tests. The goal was to determine the suitability of the protective coating in retarding the weathering rate of concrete construction. The two-layer coating consists of an inner layer of aminoethylaminopropylsilane (AEAPS) applied as a 25% solution in methanol and an outer layer of A2** sol-gel. In previous work, this product when applied to calcite powders, had resulted in a lowering of the rate of dissolution by a factor of ten and was shown through molecular modeling to bind strongly to the calcite surface, but not too strongly so as to accelerate dissolution. Batch dissolution tests at 22 C of coated and uncoated tobermorite (1.1 nm phase) and powdered cement from Gibson Blvd. in Albuquerque indicated that the coating exhibits some protective behavior, at least on short time scales. However, the data suggest that the outer layer of sol-gel dissolves in the high-pH environment of the closed system of cement plus water. Calculated binding configuration and energy of AEAPS to the tobermorite surface suggests that AEAPS is well-suited as the inner layer binder for protecting tobermorite.

  15. The slabs for the rutile TiO2 (110) surface

    NASA Astrophysics Data System (ADS)

    Xuechao, Li; Jianhao, Shi; Rundong, Wan

    2016-12-01

    Traditionally, we use a slab to mimic a surface and we constrain the slab to have the bulk-terminated 2D lattice constants. Here we propose a different model in which we impose no constraints, allowing all coordinates including the 2D slab itself to relax. We perform DFT calculations on both models. We find that the unconstrained slabs yield better agreement with experimental results and they have lower total energies. The optimized 2D lattice constants of the unconstrained slabs eventually converge to the attached bulk value. The total energy difference reveals that, with odd number trilayers, the unconstrained slab is much closer to the corresponding constrained slab. The surface energies both converge to the individual values with the number of atomic layers. Project supported in part by the Major Program of National Science Foundation of China (No. 51090385) and the National Natural Science Foundation of China (No. 50974067).

  16. Microwave and THz sensing using slab-pair-based metamaterials

    SciTech Connect

    Kenanakis, G.; Shen, Nianhai; Mavidis, Ch.; Katsarakis, N.; Kafesaki, M.; Soukoulis, Costas M.; Economou, E.N.

    2012-10-15

    In this work the sensing capability of an artificial magnetic metamaterial based on pairs of metal slabs is demonstrated, both theoretically and experimentally, in the microwave regime. The demonstration is based on transmission measurements and simulations monitoring the shift of the magnetic resonance frequency as one changes a thin dielectric layer placed between the slabs of the pairs. Strong dependence of the magnetic resonance frequency on both the permittivity and the thickness of the dielectric layer under detection was observed. The sensitivity to the dielectrics′ permittivity (ε) is larger for dielectrics of low ε values, which makes the approach suitable for sensing organic materials also in the THz regime. The capability of our approach for THz sensing is also demonstrated through simulations.

  17. Mantle–slab interaction and redox mechanism of diamond formation

    PubMed Central

    Palyanov, Yuri N.; Bataleva, Yuliya V.; Sokol, Alexander G.; Borzdov, Yuri M.; Kupriyanov, Igor N.; Reutsky, Vadim N.; Sobolev, Nikolai V.

    2013-01-01

    Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle–slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle–slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content. PMID:24297876

  18. Potato slab dehydration by air ions from corona discharge

    NASA Astrophysics Data System (ADS)

    Chen, Y. H.; Barthakur, N. N.

    1991-06-01

    Space charge (air ions) produced by single corona electrodes was used to enhance drying rates from fresh slabs of potato. The drying path was traced by a beta-ray gauge which provided both sensitivity and reproducibility to the measurements of drying time. The rate of evaporation was increased 2.2 to 3.0 times when subjected to fluxes of 3.02×1012 positive ions alone or in combination with 7.31×1012 negative air ions/cm2 per s compared to that from an air-drying control slab. Electric wind caused by an ionic drag force seems to be the principal driving force for the observed enhancement in drying rates.

  19. Nonlocal microscopic theory of quantum friction between parallel metallic slabs

    SciTech Connect

    Despoja, Vito

    2011-05-15

    We present a new derivation of the friction force between two metallic slabs moving with constant relative parallel velocity, based on T=0 quantum-field theory formalism. By including a fully nonlocal description of dynamically screened electron fluctuations in the slab, and avoiding the usual matching-condition procedure, we generalize previous expressions for the friction force, to which our results reduce in the local limit. Analyzing the friction force calculated in the two local models and in the nonlocal theory, we show that for physically relevant velocities local theories using the plasmon and Drude models of dielectric response are inappropriate to describe friction, which is due to excitation of low-energy electron-hole pairs, which are properly included in nonlocal theory. We also show that inclusion of dissipation in the nonlocal electronic response has negligible influence on friction.

  20. Episodic slab rollback fosters exhumation of HP-UHP rocks

    NASA Astrophysics Data System (ADS)

    Husson, Laurent; Jean-Pierre, Brun; Philippe, Yamato; Claudio, Faccenna

    2010-05-01

    The burial-exhumation cycle of crustal material in subduction zones can either be driven by the buoyancy of the material, by the surrounding flow, or by both. High pressure - ultrahigh pressure rocks are chiefly exhumed where subduction zones display transient behaviors, which lead to contrasted flow regimes in the subduction mantle wedge. Subduction zones with stationary trenches (mode I) favor the burial of rock units, whereas slab rollback (mode II) moderately induces an upward flow that contributes to the exhumation, a regime that is reinforced when slab dip decreases (mode III). Episodic regimes of subduction that involve different lithospheric units successively activate all three modes and thus greatly favor the exhumation of rock units from mantle depth to the surface without need for fast and sustained erosion.

  1. Applying MHD technology to the continuous casting of steel slab

    NASA Astrophysics Data System (ADS)

    Takeuchi, Eiichi

    1995-05-01

    The application of magnetohydrodynamics (MHD) in the continuous casting process started with the electromagnetic stirring of the stand pool with a traveling magnetic field. It has now advanced to the electromagnetic stirring of molten steel in the mold and the control of molten steel flow by an in-mold direct current magnetic field brake. These applied MHD techniques are designed to further improve the continuous casting process capability. They improve the surface quality of cast steel by homogenizing the meniscus temperature, stabilizing initial solidification, and cleaning the surface layer. They also improve the internal quality of cast steel by preventing inclusions from penetrating deep into the pool and promoting the flotation of argon bubbles. Applied MHD technology is still advancing in scope and methods in addition to the improvement of conventional continuously cast slab qualities. The continuous casting of bimetallic slab by suppressing mixing in the pool is one example of this progress.

  2. Modelling matrix diffusion in high-pH infiltration tests in concrete columns

    NASA Astrophysics Data System (ADS)

    Carme Chaparro, M.; Saaltink, Maarten W.; Soler, Josep M.; Slooten, Luit Jan; Mäder, Urs

    2014-05-01

    Tracer tests in concrete columns have been carried out to improve the characterization of the transport properties of the concrete from the Radioactive Waste Disposal Facility at El Cabril (Spain). High entry pressure has been employed in order to perform the experiments in a reasonable time span. Three tests have been performed using different infiltration solutions, with pH 12.6, 7.0 and 13.4, respectively. Lithium, bromide and deuterium have been used as tracers. Experimental results show that permeability decreases with time probably because of mineral precipitation. So, solute transport in concrete cannot easily be decoupled from reactions. A preliminary model of only advection and dispersion could not be fitted satisfactory to the breakthrough curves of conservative tracers. Therefore, we added matrix diffusion between a mobile pore domain, where water can flow, and an immobile zone without any advective flow. Three conceptual models have been compared, considering the immobile zone as (i) slabs, (ii) spheres and (iii) tubes. Porosity of the mobile and immobile zones, size of the immobile zone and a diffusion coefficient are estimated by calibrating the model results to the measured breakthrough curve. The calculated values show that matrix diffusion plays an important role in solute transport. The best fit is obtained with the tube concept: cylindrical diffusion from concrete (large radius) to mobile zone (small radius).

  3. Slab2 - Providing updated subduction zone geometries and modeling tools to the community

    NASA Astrophysics Data System (ADS)

    Hayes, G. P.; Hearne, M. G.; Portner, D. E.; Borjas, C.; Moore, G.; Flamme, H.

    2015-12-01

    The U.S. Geological Survey database of global subduction zone geometries (Slab1.0) combines a variety of geophysical data sets (earthquake hypocenters, moment tensors, active source seismic survey images of the shallow subduction zone, bathymetry, trench locations, and sediment thickness information) to image the shape of subducting slabs in three dimensions, at approximately 85% of the world's convergent margins. The database is used extensively for a variety of purposes, from earthquake source imaging, to magnetotelluric modeling. Gaps in Slab1.0 exist where input data are sparse and/or where slabs are geometrically complex (and difficult to image with an automated approach). Slab1.0 also does not include information on the uncertainty in the modeled geometrical parameters, or the input data used to image them, and provides no means to reproduce the models it described. Currently underway, Slab2 will update and replace Slab1.0 by: (1) extending modeled slab geometries to all global subduction zones; (2) incorporating regional data sets that may describe slab geometry in finer detail than do previously used teleseismic data; (3) providing information on the uncertainties in each modeled slab surface; (4) modifying our modeling approach to a fully-three dimensional data interpolation, rather than following the 2-D to 3-D steps of Slab1.0; (5) migrating the slab modeling code base to a more universally distributable language, Python; and (6) providing the code base and input data we use to create our models, such that the community can both reproduce the slab geometries, and add their own data sets to ours to further improve upon those models in the future. In this presentation we describe our vision for Slab2, and the first results of this modeling process.

  4. Object tracking with hierarchical multiview learning

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Zhang, Shunli; Zhang, Li

    2016-09-01

    Building a robust appearance model is useful to improve tracking performance. We propose a hierarchical multiview learning framework to construct the appearance model, which has two layers for tracking. On the top layer, two different views of features, grayscale value and histogram of oriented gradients, are adopted for representation under the cotraining framework. On the bottom layer, for each view of each feature, three different random subspaces are generated to represent the appearance from multiple views. For each random view submodel, the least squares support vector machine is employed to improve the discriminability for concrete and efficient realization. These two layers are combined to construct the final appearance model for tracking. The proposed hierarchical model assembles two types of multiview learning strategies, in which the appearance can be described more accurately and robustly. Experimental results in the benchmark dataset demonstrate that the proposed method can achieve better performance than many existing state-of-the-art algorithms.

  5. Hydrogen sensor based on metallic photonic crystal slabs.

    PubMed

    Nau, D; Seidel, A; Orzekowsky, R B; Lee, S-H; Deb, S; Giessen, H

    2010-09-15

    We present a hydrogen sensor based on metallic photonic crystal slabs. Tungsten trioxide (WO(3)) is used as a waveguide layer below an array of gold nanowires. Hydrogen exposure influences the optical properties of this photonic crystal arrangement by gasochromic mechanisms, where the photonic crystal geometry leads to sharp spectral resonances. Measurements reveal a change of the transmission depending on the hydrogen concentration. Theoretical limits for the detection range and sensitivity of this approach are discussed.

  6. Slab detachment under the Eastern Alps seen by seismic anisotropy

    PubMed Central

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-01-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian–Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW–NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW–SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW–SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle. PMID:25843968

  7. Slab detachment under the Eastern Alps seen by seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-01-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian-Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW-NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW-SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW-SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle.

  8. Oscillation modes and transmission into a Fibonacci slab

    NASA Astrophysics Data System (ADS)

    Castro-Arce, Lamberto; Molinar-Tabares, Martin; Campos-Garcia, Julio; Figueroa-Navarro, Carlos; Isasi-Siqueiros, Leonardo; Manzanares-Martinez, Betsabe

    In our contribution we developed a study on the behavior of the transmission modes and a Pt / Zn slab of a Fibonacci array of longitudinal and transverse acoustic waves. We have worked with arrangements from n = 1 to10 and has managed to find the energy bands and transmission, filling factor 0.4 observing the appearance of Pseudo-Gaps in the evolution of the study when the arrangement Fibonacci increases. We acknowledge the support of SNI CONACYT.

  9. Slab Detachment Under the Eastern Alps Seen By Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Qorbani, E.; Bianchi, I.; Bokelmann, G.

    2014-12-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian-Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW-NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW-SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW-SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle.

  10. Slab detachment under the Eastern Alps seen by seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-04-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian-Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW-NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW-SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW-SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle.

  11. Slab detachment under the Eastern Alps seen by seismic anisotropy.

    PubMed

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-01-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian-Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW-NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW-SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW-SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle.

  12. On the compensation of geoid anomalies due to subducting slabs

    NASA Technical Reports Server (NTRS)

    Mcadoo, D. C.

    1981-01-01

    Candidate models of the forces which oppose the sinking of slabs are all constrained to produce results consistent with the following observation: relative geoid highs, which one assumes are due to slabs, characteristically occur over subduction zones. Certain models which are otherwise plausible, such as those based on a Newtonian half-space mantle, yield geoid lows instead of highs. This study has extended a published model of viscous corner flow in subduction zones in order to demonstrate that it can, in certain cases, produce the requisite geoid highs. Specifically the relative geoid highs are produced if mantle flow is distinctly non-Newtonian (stress exponent n 2). Results in the form of deflection on vertical (or geoid slope) profiles are computed for typical values of the slab parameters; they are compared with a representative profile of geoid slopes derived from Seasat altimeter data in order to show qualitative similarities. It is concluded that the effect of non-Newtonian flow as opposed to Newtonian, is to spread out the induced surface deformation, thereby stretching out the regional compensation to wavelengths, (transverse to the trench) of several thousand kilometers.

  13. Westernmost Mediterranean Mantle Tomography: Slab Rollback and Delaminated Atlas Lithosphere

    NASA Astrophysics Data System (ADS)

    Bezada, M. J.; Humphreys, E.

    2012-12-01

    We present a new velocity model for the upper mantle in the westernmost Mediterranean including the Iberian Peninsula and northern Morocco. Our imaging improves over previous efforts by taking advantage of the data generated by the PICASSO, IberArray, TopoMed and connected seismograph deployments and by using a new methodology that includes finite-frequency effects and iterative ray tracing, utilizes local earthquakes in addition to teleseismic events and includes constraints from surface wave analyses. We image a subducted slab as a high velocity anomaly located under the Alboran Sea and southern Spain that extends to the bottom of the transition zone. The anomaly has an arcuate shape at most depths and reaches the surface beneath Gibraltar but not under southern Spain. The N-S oriented Gibraltar and E-W oriented southern Spain segments of the slab appear to be separated by a vertical tear or "slab gap". Under the Atlas Mountains in northern Morocco we image low velocities to depths of over 200 km and a high-velocity body at depths of 300-450 km beneath the Middle Atlas, which we tentatively interpret as delaminated lithosphere.

  14. Ionospheric slab thickness and its seasonal variations observed by GPS

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Cho, Jung-Ho; Park, Jung-Uk

    2007-11-01

    The ionospheric slab thickness, the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2), is closely related to the shape of the ionospheric electron density profile Ne (h) and the TEC. Therefore, the ionospheric slab thickness is a significant parameter representative of the ionosphere. In this paper, the continuous GPS observations in South Korea are firstly used to study the equivalent slab thickness (EST) and its seasonal variability. The averaged diurnal medians of December January February (DJF), March April May (MAM), June July August (JJA) and September October November (SON) in 2003 have been considered to represent the winter, spring, summer and autumn seasons, respectively. The results show that the systematic diurnal changes of TEC, NmF2 and EST significantly appeared in each season and the higher values of TEC and NmF2 are observed during the equinoxes (semiannual anomaly) as well as in the mid-daytime of each season. The EST is significantly smaller in winter than in summer, but with a consistent variation pattern. During 14 16 LT in daytime, the larger EST values are observed in spring and autumn, while the smaller ones are in summer and winter. The peaks of EST diurnal variation are around 10 18 LT which are probably caused by the action of the thermospheric wind and the plasmapheric flow into the F2-region.

  15. High Performance Slab-on-Grade Foundation Insulation Retrofits

    SciTech Connect

    Goldberg, Louise F.; Mosiman, Garrett E.

    2015-09-01

    ?A more accurate assessment of SOG foundation insulation energy savings than traditionally possible is now feasible. This has been enabled by advances in whole building energy simulation with 3-dimensional foundation modelling integration at each time step together with an experimental measurement of the site energy savings of SOG foundation insulation. Ten SOG insulation strategies were evaluated on a test building to identify an optimum retrofit insulation strategy in a zone 6 climate (Minneapolis, MN). The optimum insulation strategy in terms of energy savings and cost effectiveness consisted of two components: (a) R-20 XPS insulation above grade, and, (b) R-20 insulation at grade (comprising an outer layer of R-10 insulation and an interior layer of R-12 poured polyurethane insulation) tapering to R-10 XPS insulation at half the below-grade wall height (the lower half of the stem wall was uninsulated). The optimum insulation strategy was applied to single and multi-family residential buildings in climate zone 4 - 7. The highest site energy savings of 5% was realized for a single family home in Duluth, MN, and the lowest savings of 1.4 % for a 4-unit townhouse in Richmond, VA. SOG foundation insulation retrofit simple paybacks ranged from 18 to 47 years. There are other benefits of SOG foundation insulation resulting from the increase in the slab surface temperatures. These include increased occupant thermal comfort, and a decrease in slab surface condensation particularly around the slab perimeter.

  16. Electromagnetic and ultrasonic investigations on a roman marble slab

    NASA Astrophysics Data System (ADS)

    Capizzi, Patrizia; Cosentino, Pietro L.

    2010-05-01

    The archaeological Museum of Rome (Museo delle Terme di Diocleziano) asked our group about the physical consistency of a marble slab (II - III century AD) that has recently fallen down during the transportation for an exhibition. In fact, due to insurance conflict, it was necessary to control the new fractures due to the recent accident and distinguish them from the ancient ones. The sculptured slab (today's size is 1280 x 70 x 9 cm), cut at the ends for a re-use as an inscription in the rear face, was restored (assemblage of different broken parts and cleaning) in contemporary times. We used different methodologies to investigate the slab: namely a pacometer (Protovale Elcometer) to individuate internal coupling pins, GPR (2000 MHz) and Ultrasonic (55 kHz) tomographic high-density surveys to investigate the internal extension of all the visible fractures and to search for the unknown internal ones. For every methodology used the quality of the acquired data was relatively high. They have been processed and compared to give a set of information useful for the bureaucratic problems of the Museum. Later on, the data have been processed in depth, for studying how to improve the data processing and for extracting all the information contained in the whole set of experimental data. Finally, the results of such a study in depth are exposed in detail.

  17. The Green`s function method for critical heterogeneous slabs

    SciTech Connect

    Kornreich, D.E.

    1996-10-01

    Recently, the Green`s Function Method (GFM) has been employed to obtain benchmark-quality results for nuclear engineering and radiative transfer calculations. This was possible because of fast and accurate calculations of the Green`s function and the associated Fourier and Laplace transform inversions. Calculations have been provided in one-dimensional slab geometries for both homogeneous and heterogeneous media. A heterogeneous medium is analyzed as a series of homogeneous slabs, and Placzek`s lemma is used to extend each slab to infinity. This allows use of the infinite medium Green`s function (the anisotropic plane source in an infinite homogeneous medium) in the solution. To this point, a drawback of the GFM has been the limitation to media with c < 1, where c is the number of secondary particles produced in a collision. Clearly, no physical steady-state solution exists for an infinite medium that contains an infinite source and is described by c >1; however, mathematical solutions exist which result in oscillating Green`s functions. Such calculations are briefly discussing. The limitation to media with c < 1 has been relaxed so that the Green`s function may also be calculated for media with c {ge} 1. Thus, materials that contain fissionable isotopes may be modeled.

  18. Non-volcanic tremor and discontinuous slab dehydration

    NASA Astrophysics Data System (ADS)

    Fagereng, Åke; Diener, Johann F. A.

    2011-08-01

    Non-volcanic tremor is a recently discovered fault slip style occurring with remarkable regularity in space near the down-dip end of the locked zone on several subduction thrust interfaces. The physical mechanisms and the controls on the location of tremor have not yet been determined. We calculate the stable mineral assemblages and their water content in the subducting slab, and find that slab dehydration is not continuous, but rather restricted to a few reactions localised in pressure-temperature space. Along geothermal gradients applicable to Shikoku and Cascadia - where tremor has been relatively easy to detect - tremor locations correlate with discontinuous and localised voluminous water release from the breakdown of lawsonite and chlorite + glaucophane respectively. The shape of the pressure-temperature path for subducting slabs prevents fluid release at depths above and below where these dehydration reactions occur. We conclude that abundant tremor activity requires metamorphic conditions where localised dehydration occurs during subduction, and this may explain why tremor appears more abundant in some subduction zones than others.

  19. Application Improvements of Slab-Coupled Optical Fiber Sensors

    NASA Astrophysics Data System (ADS)

    Chadderdon, Spencer Lee

    This dissertation explores techniques for improving slab-coupled optical fiber sensor (SCOS) technology for use in specific applications and sensing configurations. SCOS are advantageous for their small size and all-dielectric composition which permit non-intrusive measurement of electric fields within compact environments; however, their small size also limits their sensitivity. This work performs a thorough analysis of the factors contributing to the performance of SCOS and demonstrates methods which improve SCOS, while maintaining its small dimensions and high level of directional sensitivity. These improvements include increasing the sensitivity by 9x, improving the frequency response to include sub 300 kHz frequencies, and developing a method to tune the resonances. The analysis shows that the best material for the slab waveguide is an electro-optic polymer because of its low RF permittivity combined with high electro-optic coefficient. Additional improvements are based on changing the crystal orientation to a transverse configuration, which enhances the sensitivity due to a combined increase in the effective electro-optic coefficient and electric field penetration into the slab. The transverse SCOS configuration not only improves the overall sensitivity but increases the directional sensitivity of the SCOS. Lithium niobate and electro-optic polymer are both experimentally shown to exhibit minimal frequency dependent sensitivity making them suitable for broad frequency applications. Simultaneous interrogation of multiple SCOS with a single tunable laser is achieved by tuning the resonant wavelengths of KTP SCOS so their resonances overlap.

  20. From stripe to slab confinement for DNA linearization in nanochannels

    NASA Astrophysics Data System (ADS)

    Cifra, Peter; Benkova, Zuzana; Namer, Pavol

    We investigate suggested advantageous analysis in the linearization experiments with macromolecules confined in a stripe-like channel using Monte Carlo simulations. The enhanced chain extension in a stripe that is due to significant excluded volume interactions between monomers in two dimensions weakens on transition to experimentally feasible slit-like channel. Based on the chain extension-confinement strength dependence and the structure factor behavior for the chain in stripe we infer the excluded volume regime typical for two-dimensional systems. On transition to the slab geometry, the advantageous chain extension decreases and the Gaussian regime is observed for not very long semiflexible chains. The evidence for pseudo-ideality in confined chains is based on indicators such as the extension curves, variation of the extension with the persistence length or the structure factor. The slab behavior is observed when the stripe (originally of monomer thickness) reaches the thickness larger than cca 10nm in the third dimension. This maximum height of the slab to retain the advantage of the stripe is very low and this have implication for DNA linearization experiments. The presented analysis, however, has a broader relevance for confined polymers. Support from Slovak R&D Agency (SRDA-0451-11) is acknowledged.

  1. System for loading slab-gel holders for electrophoresis separation

    DOEpatents

    Anderson, Norman G.; Anderson, Norman L.

    1979-01-01

    A slab-gel loading system includes a prismatic chamber for filling a plurality of slab-gel holders simultaneously. Each slab-gel holder comprises a pair of spaced apart plates defining an intermediate volume for gel containment. The holders are vertically positioned in the chamber with their major surfaces parallel to the chamber end walls. A liquid inlet is provided at the corner between the bottom and a side wall of the chamber for distributing a polymerizable monomer solution or a coagulable colloidal solution into each of the holders. The chamber is rotatably supported so that filling can begin with the corner having the liquid inlet directed downwardly such that the solution is gently funneled upwardly, without mixing, along the diverging side and bottom surfaces. As filling proceeds, the chamber is gradually rotated to position the bottom wall in a horizontal mode. The liquid filling means includes a plastic envelope with a septum dividing it into two compartments for intermixing two solutions of different density and thereby providing a liquid flow having a density gradient. The resulting gels have a density gradient between opposite edges for subsequent use in electrophoresis separations.

  2. Water-Moderated and -Reflected Slabs of Uranium Oxyfluoride

    SciTech Connect

    Margaret A. Marshall; John D. Bess; J. Blair Briggs; Clinton Gross

    2010-09-01

    A series of ten experiments were conducted at the Oak Ridge National Laboratory Critical Experiment Facility in December 1955, and January 1956, in an attempt to determine critical conditions for a slab of aqueous uranium oxyfluoride (UO2F2). These experiments were recorded in an Oak Ridge Critical Experiments Logbook and results were published in a journal of the American Nuclear Society, Nuclear Science and Engineering, by J. K. Fox, L. W. Gilley, and J. H. Marable (Reference 1). The purpose of these experiments was to obtain the minimum critical thickness of an effectively infinite slab of UO2F2 solution by extrapolation of experimental data. To do this the slab thickness was varied and critical solution and water-reflector heights were measured using two different fuel solutions. Of the ten conducted experiments eight of the experiments reached critical conditions but the results of only six of the experiments were published in Reference 1. All ten experiments were evaluated from which five critical configurations were judged as acceptable criticality safety benchmarks. The total uncertainty in the acceptable benchmarks is between 0.25 and 0.33 % ?k/keff. UO2F2 fuel is also evaluated in HEU-SOL-THERM-043, HEU-SOL-THERM-011, and HEU-SOL-THERM-012, but these those evaluation reports are for large reflected and unreflected spheres. Aluminum cylinders of UO2F2 are evaluated in HEU-SOL-THERM-050.

  3. On the Right Track.

    ERIC Educational Resources Information Center

    Bieber, Ed

    1983-01-01

    Suggests thinking of "tracks" as clues and using them as the focus of outdoor activities in the urban environment. Provides 24 examples of possible track activities, including: seeds on the ground (track of a nearby tree), litter (track of a litterbug), and peeling paint (track of weathering forces). (JN)

  4. Track Construction Manual.

    ERIC Educational Resources Information Center

    Banke, Ron; Di Gennaro, Guy; Ediger, Rick; Garner, Lanny; Hersom, Steve; Miller, Jack; Nemeth, Ron; Petrucelli, Jim; Sierks, Donna; Smith, Don; Swank, Kevin; West, Kevin

    This book establishes guidelines for the construction and maintenance of tracks by providing information for building new tracks or upgrading existing tracks. Subjects covered include running track planning and construction, physical layout, available surfaces, and maintenance. General track requirements and construction specifications are…

  5. Numerical Modeling of Flat Slab Formation in Central Chile

    NASA Astrophysics Data System (ADS)

    Manea, M.; Perez-Gussinye, M.; Manea, V.; Fernandez, M.

    2009-12-01

    Subduction of oceanic plates beneath large continental masses is a rare process and at present it occurs only along western South America and Central Mexico. Likewise, flat subduction, understood here as where the slab enters at a normal angle and reverses its curvature to flatten at ~70-120 km depth, only occurs at present beneath South America. In general, the angle at which subduction occurs in the depth range of ~100 to ~200 km reflects the balance between negative buoyancy of the slab, elastic resistance of the slab to change the angle of subduction, and non-hydrostatic pressure forces induced by subduction-driven flow within the asthenosphere. The latter force, known as suction force, acts to prevent the slab from sinking into the mantle, and its magnitude increases with increasing subduction velocity, narrowness and viscosity decrease of the mantle wedge [Manea and Gurnis, 2007]. Recent observations show that the upper plate structure varies along the Andean margin, indicating that it is thicker and stronger above flat subduction zones and suggesting a correlation between upper plate structure and subduction angle [Pérez-Gussinyé et al., 2008; Booker et al., 2004]. In this study we use numerical models to explore the extent to which upper plate structure, through its influence on asthenospheric wedge shape and viscosity, can affect the angle of subduction. We test for which upper plate thickness and asthenospheric viscosity repeated cycles of steep and flat subduction are reproduced and compare our results to estimations of lithospheric thickness and the duration of flat and steep subduction cycles hypothesized along the Andean margin. Our models are constrained by realistic plate velocities in hot spot reference frame for both Nazca and South American plates [Muller et al., 2008], the Miocene-Present shortening for the Andes [Schelart et al., 2007] and realistic Nazca plate age distribution [Sdrolias and Muller, 2006]. Using the finite element package

  6. Design of energy efficient building with radiant slab cooling

    NASA Astrophysics Data System (ADS)

    Tian, Zhen

    2007-12-01

    Air-conditioning comprises a substantial fraction of commercial building energy use because of compressor-driven refrigeration and fan-driven air circulation. Core regions of large buildings require year-round cooling due to heat gains from people, lights and equipment. Negative environmental impacts include CO2 emissions from electric generation and leakage of ozone-depleting refrigerants. Some argue that radiant cooling simultaneously improves building efficiency and occupant thermal comfort, and that current thermal comfort models fail to reflect occupant experience with radiant thermal control systems. There is little field evidence to test these claims. The University of Calgary's Information and Communications Technology (ICT) Building, is a pioneering radiant slab cooling installation in North America. Thermal comfort and energy performance were evaluated. Measurements included: (1) heating and cooling energy use, (2) electrical energy use for lighting and equipment, and (3) indoor temperatures. Accuracy of a whole building energy simulation model was evaluated with these data. Simulation was then used to compare the radiant slab design with a conventional (variable air volume) system. The radiant system energy performance was found to be poorer mainly due to: (1) simultaneous cooling by the slab and heating by other systems, (2) omission of low-exergy (e.g., groundwater) cooling possible with the high cooling water temperatures possible with radiant slabs and (3) excessive solar gain and conductive heat loss due to the wall and fenestration design. Occupant thermal comfort was evaluated through questionnaires and concurrent measurement of workstation comfort parameters. Analysis of 116 sets of data from 82 occupants showed that occupant assessment was consistent with estimates based on current thermal comfort models. The main thermal comfort improvements were reductions in (1) local discomfort from draft and (2) vertical air temperature stratification. The

  7. Detecting lower-mantle slabs beneath Asia and the Aleutians

    NASA Astrophysics Data System (ADS)

    Schumacher, L.; Thomas, C.

    2016-06-01

    To investigate the descend of subducted slabs we search for and analyse seismic arrivals that reflected off the surface of the slab. In order to distinguish between such arrivals and other seismic phases, we search for waves that reach a seismic array with a backazimuth deviating from the theoretical backazimuth of the earthquake. Source-receiver combinations are chosen in a way that their great circle paths do not intersect the slab region, hence the direct arrivals can serve as reference. We focus on the North and Northwest Pacific region by using earthquakes from Japan, the Philippines and the Hindu Kush area recorded at North American networks (e.g. USArray, Alaska and Canada). Using seismic array techniques for analysing the data and record information on slowness, backazimuth and traveltime of the observed out-of-plane arrivals we use these measurements to trace the wave back through a 1-D velocity model to its scattering/reflection location. We find a number of out-of-plane reflections. Assuming only single scattering, most out-of-plane signals have to travel as P-to-P phases and only a few as S-to-P phases, due to the length of the seismograms we processed. The located reflection points present a view of the 3-D structures within the mantle. In the upper mantle and the transition zone they correlate well with the edges of fast velocity regions in tomographic images. We also find reflection points in the mid- and lower mantle and their locations generally agree with fast velocities mapped by seismic tomography models suggesting that in the subduction regions we map, slabs enter the lower mantle. To validate our approach, we calculate and process synthetic seismograms for 3-D wave field propagation through a model containing a slab-like heterogeneity. We show, that depending on the source-receiver geometry relative to the reflection plane, it is indeed possible to observe and back-trace out-of-plane signals.

  8. Nanogranular origin of concrete creep.

    PubMed

    Vandamme, Matthieu; Ulm, Franz-Josef

    2009-06-30

    Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium-silicate-hydrates (C-S-H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C-S-H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C-S-H forms: low density, high density, ultra-high density. We demonstrate that the creep rate ( approximately 1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years.

  9. Nanogranular origin of concrete creep

    PubMed Central

    Vandamme, Matthieu; Ulm, Franz-Josef

    2009-01-01

    Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C–S–H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C–S–H forms: low density, high density, ultra-high density. We demonstrate that the creep rate (≈1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years. PMID:19541652

  10. Tomographic imaging of the Cascadia subduction zone: Constraints on the Juan de Fuca slab

    NASA Astrophysics Data System (ADS)

    Chen, Chuanxu; Zhao, Dapeng; Wu, Shiguo

    2015-04-01

    We used 40,343 P-wave arrival times from 1883 local earthquakes and 105,455 P-wave arrivals from 6361 teleseismic events to study the detailed structure of the Cascadia subduction zone. We conducted tomographic inversions using a starting velocity model which includes the high-velocity subducting Juan de Fuca slab as a priori information. A number of such slab-constrained inversions are conducted by changing the slab thickness and the velocity contrast between the slab and the surrounding mantle. Our optimal 3-D velocity model fits the data much better than that determined by an inversion with a 1-D homogeneous starting model. Our results show that the subducting Juan de Fuca slab has a thickness of 30-50 km and a P-wave velocity of 1-3% higher than that of the surrounding mantle. Beneath the northern and southern parts of the Cascadia, P-wave velocity is lower in the slab and along the slab interface, which may reflect a more hydrated slab and more active slab dehydration there. The lateral velocity variations may indicate different degrees of slab dehydration and forearc mantle serpentinization. The segmentation in episodic tremor and slip (ETS) is also spatially coincident with the velocity heterogeneities, indicating that the ETS occurrence and recurrence interval are controlled by fluid activity in and around the mantle wedge corner.

  11. Subducting-slab transition-zone interaction: Stagnation, penetration and mode switches

    NASA Astrophysics Data System (ADS)

    Agrusta, Roberto; Goes, Saskia; van Hunen, Jeroen

    2017-04-01

    Seismic tomography shows that subducting slabs can either sink straight into the lower mantle, or lie down in the mantle transition zone. Moreover, some slabs seem to have changed mode from stagnation to penetration or vice versa. We investigate the dynamic controls on these modes and particularly the transition between them using 2D self-consistent thermo-mechanical subduction models. Our models confirm that the ability of the trench to move is key for slab flattening in the transition zone. Over a wide range of plausible Clapeyron slopes and viscosity jumps at the base of the transition zone, hot young slabs (25 Myr in our models) are most likely to penetrate, while cold old slabs (150 Myr) drive more trench motion and tend to stagnate. Several mechanisms are able to induce penetrating slabs to stagnate: ageing of the subducting plate, decreasing upper plate forcing, and increasing Clapeyron slope (e.g. due to the arrival of a more hydrated slab). Getting stagnating slabs to penetrate is more difficult. It can be accomplished by an instantaneous change in the forcing of the upper plate from free to motionless, or a sudden decrease in the Clapeyron slope. A rapid change in plate age at the trench from old to young cannot easily induce penetration. On Earth, ageing of the subducting plate (with accompanying upper plate rifting) may be the most common mechanism for causing slab stagnation, while strong changes in upper plate forcing appear required for triggering slab penetration.

  12. The Role of Slab Windows in Subduction Cycles

    NASA Astrophysics Data System (ADS)

    Thorkelson, D. J.; Breitsprecher, K.

    2011-12-01

    Active continental margins are enduring features which commonly record a history of subduction spanning tens of millions of years. A subduction history is commonly divisible into distinct intervals of subduction activity separated by periods of non-subduction. The intervals of non-subduction are dominated by transform, transtensional or transpressional regimes. The recognition of subduction cycles as a normal pattern of active continental margins was an essential step forward in the understanding of ancient continental margin assemblages, plate evolution and global tectonics. The causes of interruptions of subduction are varied, and include collision of island arcs or oceanic plateaus, swerves in the motions of large plates, plate deformation and microplate formation, and subduction of oceanic spreading ridges. These processes punctuate subduction that may have occurred unbroken for millions or tens of millions of years, but do not necessarily lead to destruction of the continental margin as fundamentally convergent and active. The intersection of a mid-ocean spreading ridge with a subduction zone brings two distinctive tectono-magmatic systems together at the same location. The style of ridge-subduction zone interaction varies considerably, depending on factors such as the obliquity of ridge-trench intersection, relative plate motions, plate integrity and thermal conditions. Where the ridge intersects the trench, a triple junction exists which, in most cases, migrates along the continental margin. The two oceanic plates that flank the spreading ridge naturally have different motion vectors relative to the overriding plate, and as the triple junction migrates, a given part of the continental margin will be in contact with one plate, and at a later time, the other plate. One or both of the oceanic plates may be convergent with the continent but in all cases a gap in the extent of the subducted slab, termed a slab window, will develop beneath the continent in the

  13. 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

  14. Global Subducting Slab Entrainment of Oceanic Asthenosphere: Re-examination of Sub-Slab Shear-Wave Splitting Patterns

    NASA Astrophysics Data System (ADS)

    Song, T.; Liu, L.; Kawakatsu, H.

    2011-12-01

    Oceanic asthenosphere is characterized as a low seismic velocity, low viscosity, and strongly anisotropic channel separating from the oceanic lithosphere through a sharp shear wave velocity contrast. It has been a great challenge to reconcile all these observations and ultimately illuminate the fate of oceanic asthenosphere near convergent plate margins. Sub-slab shear wave splitting patterns are particularly useful to address the fate of oceanic asthenosphere since they are directly linked to deformation induced by the mantle flow beneath the subducting slab. To address slab entrainment of oceanic asthenosphere through shear wave splitting, it is important to recognize that oceanic asthenosphere is characterized by azimuthal anisotropy (1-3%) as well as strong P wave and S wave radial anisotropy (3-7%) for horizontally travelling P wave (VPH > VPV) and S wave (VSH > VSV), making it effectively an orthorhombic medium. Here we show that entrained asthenosphere predicts sub-slab SKS splitting pattern, where the fast splitting direction changes from predominantly trench-normal under shallow subduction zones to predominantly trench-parallel under relatively steep subduction zones. This result can be recognized by the 90 degrees shift in the polarization of the fast wave at about 20 degrees incident angle, where VSH equals to VSV forming a classical point singularity (Crampin, 1991). The thickness of the entrained asthenosphere is estimated to be on the order of 100 km, which predicts SKS splitting time varying from 0.5 seconds to 2 seconds. After briefly discussing improvement of the millefeuille model (Kawakatsu et al. 2009) of the asthenosphere upon this new constraint and long wave Backus averaging of orthorhombic solid and melt, we will illustrate that, in the range of observed trench migration speed, dynamic models of 2-D mantle convection with temperature-dependent viscosity do support thick subducting slab entrainment of asthenosphere under ranges of

  15. Transition from slab stagnation to penetration beneath the northwestern Pacific and South America (Invited)

    NASA Astrophysics Data System (ADS)

    Fukao, Y.; Obayashi, M.

    2010-12-01

    Subducting slabs tend to once deflect horizontally in the transition zone as stagnant slabs and then to penetrate into the lower mantle across the 660-km discontinuity. Here we present the detailed tomographic images of transition from stagnant-slab mode to penetrating-slab mode, based on the global ISC travel time data to which regional network data and long-term array observation data including ocean bottom data are added. The targets are the subducted slabs beneath South America and the northwestern Pacific. In South America the transition occurs across the northeastward extension of the sharp bend of the Peru-Chili trench. The slab to the south of this extension is stagnant above the 660, and to the north it plunges into the lower mantle across the 660. The transition is sharp as if the originally flat slab in the northern part was rotated into the present configuration by hinge faulting along the extension. We suspect that this hinge faulting either triggered the northward propagation of or truncated the southward propagation of the plunging motion of the slab into the lower mantle. Along the Kurile arc, the slab is flattened above the 660 in the southwest, penetrating in the northeast, with a transitional feature in between. In southern Kurile the flattened part has a deepest bottom near the junction with the dipping part. Such an along-arc change of slab configuration is indicative of a process of transition from stagnant-slab mode to penetrating-slab mode: the flattened part and dipping part of the slab begin to sink into the lower mantle at their junction so that the horizontal part is progressively dragged to and is eventually united to the dipping part as a penetrating slab. Along the Izu-Bonin-Mariana (IBM) arc, the slab is flattened above the 660 in the north (Izu-Bonin) and is penetrating the 660 in the south (Mariana) leaving the horizontal part in the transition zone. In the Izu-Bonin the flattened part has a deepest bottom near the junction with

  16. A Systematic Study on the Formation of South American Flat-Slab Subduction

    NASA Astrophysics Data System (ADS)

    Hu, J.; Liu, L.

    2015-12-01

    The South American subduction zone is characterized by its along-strike variation from flat to steeply dipping slabs. Both formation mechanisms and geometry of flat slabs in South America remain unclear. To evaluate the relative contribution of different mechanisms to flat slab formation, we simulate the post-100 Ma subduction history below South America using 3-D geodynamic models by progressively incorporating key tectonic features including seafloor ages, buoyant oceanic crusts, thickened oceanic plateaus (i.e. the Inca plateau, Nazca Ridge and Juan Fernandez Ridge), continental cratons, as well as deformable trench profiles according to recent geological reconstructions. With a uniform seafloor age of 30 Ma (i.e., the spatial average of the Nazca Plate since 20 Ma), we get steep (>30°, measured at 200 km depth) subduction everywhere except at 25°S -35°S, where the slab dip is affected by earlier subduction at depth. With the actual reconstructed seafloor ages, the slab dip angle is systematically reduced with an average of ~25°; the long-wavelength lateral variation of slab dip angle that resembles the observation results from the spatial variation of slab buoyancy and strength. The addition of a uniformly thick overriding plate, with enhanced dynamic suction in the mantle wedge, further reduces the slab dip angle (<23°) along the entire trench, where the young slab portions are affected more than the old one. Realization of the 3D geometry of cratonic roots enhances along-trench variation of suction force, which results in an additional reduction of slab dip (<20°), especially next to the cratons. While dynamic suction from the overriding plate reduces the long-wavelength slab dip angle, subducting oceanic plateau and aseismic ridges lead to more localized flat-slabs (as low as 15°) as observed. The subduction of aseismic ridges also generates tears within the flat slabs, due to the accumulation of strain at the down-dip end of the ridge. These slab

  17. Dynamic Increase Factors for Concrete

    DTIC Science & Technology

    1998-08-01

    Strain Rate Effects on Fracture, S. Mindess and S.P. Shah, editors, December 1985, pp. 1-13. 35. Weerheijm, J., Reinhardt, H.W., “Modelling of...Out of Anchored Reinforcing Bars,” Transactions of the Japan Concrete Institute, Vol. 15, 1994, pp. 459-466. 50. Bentur, A. S., S. Mindess and N. P...Society Symposia Proceedings Vol. 64 (S. Mindess and S. P. Shah, eds.), Pittsburgh, 1986, pp. 225-234. 51. Banthia, N. P., “Impact Resistance of Concrete

  18. Assessing the concreteness of relational representation.

    PubMed

    Rein, Jonathan R; Markman, Arthur B

    2010-11-01

    Research has shown that people's ability to transfer abstract relational knowledge across situations can be heavily influenced by the concrete objects that fill relational roles. This article provides evidence that the concreteness of the relations themselves also affects performance. In 3 experiments, participants viewed simple relational patterns of visual objects and then identified these same patterns under a variety of physical transformations. Results show that people have difficulty generalizing to novel concrete forms of abstract relations, even when objects are unchanged. This suggests that stimuli are initially represented as concrete relations by default. In the 2nd and 3rd experiments, the number of distinct concrete relations in the training set was increased to promote more abstract representation. Transfer improved for novel concrete relations but not for other transformations such as object substitution. Results indicate that instead of automatically learning abstract relations, people's relational representations preserve all properties that appear consistently in the learning environment, including concrete objects and concrete relations.

  19. Too much slab waving in South America? Wet plumes as an alternative to flat slab steepening as the cause of back arc large volcanic provinces

    NASA Astrophysics Data System (ADS)

    Booker, J. R.; Burd, A. I.

    2013-12-01

    A widely held view is that the Nazca Slab under western S. America acts like a tattered flag waving in the wind: It is segmented and the dip angle of segments flap up and down with time. There are presently two flat segments - one under Peru and the other, the "Pampean" flat slab (centered around 31S) under central Chile and Argentina. Both are correlated with subduction of buoyant crust of oceanic aseismic ridges, complete cessation of Andean arc volcanism and very thick crust. It has been argued that the waxing and waning of flat subduction is responsible for much of the time variations in tectonics and volcanism up to 800 km east of the S. American coast for at least 100 MA. For instance, the back arc Payenia igneous plateau (35-38S) and the Somuncura igneous plateau (40.5-43S) are both thought to follow from the steepening of flat slabs at about 2 and 27 MA. Each flat slab existed for more than 5 MA. However, the case for the existence of these flat slabs rests heavily on volcanism with "arc signature" hundreds of km east of the modern volcanic arc at a time when an asthenospheric wedge would be in its final stages of being squeezed out of the space between the slab and the lithosphere. Arc signature can be summarized as the geochemical consequence of mantle melting in the presence of water. If there is a source of water in the mantle other than a shallow slab, the strongest argument for a flat slab dissolves. We have found two electrically conductive plumes rising from below 350 km near the top of the Mantle Transition Zone (MTZ). One passes through a window in the Pampean flat slab but does not penetrate the lithosphere. The other rises under Payenia. The maximum resistivity at the core of these plumes is less than 10 Ohm-m. Partial melt can explain such low resistivity, but will not be buoyant and rise from below 350 km. We propose that the low resistivity is more likely due to water and that we are seeing "wet plumes" that have been proposed to explain

  20. Cenozoic tectonics of western North America controlled by evolving width of Farallon slab.

    PubMed

    Schellart, W P; Stegman, D R; Farrington, R J; Freeman, J; Moresi, L

    2010-07-16

    Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.

  1. Fabrication slab waveguide based polymethyl methacrylate (PMMA) with spin coating method

    NASA Astrophysics Data System (ADS)

    Andriawan, Alan; Pramono, Yono Hadi; Masoed, Asnawi

    2016-11-01

    Fabrication and characterization slab waveguide based polymethyl methacrylate (PMMA) has been carried out. Slab waveguide fabrication done by the spin coating method. Slab waveguide fabrication process carried out by the rotational speed of 1000, 2000, and 3000 rpm respectively played for 10 seconds. Then the slab waveguides heated using a hot plate. Heating process starting from room temperature then increased 5°C to 70°C with a 5 minute warm-up time interval. From the results of characterization fabricated slab waveguides to determine the film thickness is made. Then made observations on the waveguide by passing the light beam He-Ne laser on the thin layer through a single mode optical fiber. From the results of characterization is known that the fabrication of a slab waveguide with a layer thickness of 166 μm. From this research it is known that polymethyl methacrylate (PMMA) can be used as a waveguide with a spin coating method.

  2. Assessing Workability Complaints in Mass Concrete Construction

    DTIC Science & Technology

    1993-04-01

    up primarily of rigid pipes. It appears that poorly maintained vibrators are frequently proposed for use in consolidating mass concrete . Use of such... vibrators can give the false im- pression of unworkable concrete and result in poorly consolidated concrete . Only vibrators in good operating...units is presented on page vi. 5 Chapt~er 2 Survey Results The survey also indicated that mass concrete is frequently vibrated improp- erly. Improper

  3. Corrosion Behavior of Steel Fibrous Concrete

    DTIC Science & Technology

    1977-05-01

    Crvtaiue wi ,rerse sido it necessaty m’d Identify by block number) steel fibrous concrete corrosion cracked fibrous concrete 20 ABST RACT (Continue...dissolved gas in liq- Although chloride ions affect the rate of steel corro- uids. sion in concrete , corrosion can occur without them. Verbeck has...repcrted that steel subjected to a concrete Corrosion of steel will not occur without water. Not environment normally develops a protective oxide film

  4. Slab optical waveguides in Er3 +-doped tellurite glass by N+ ion implantation at 1.5 MeV

    NASA Astrophysics Data System (ADS)

    Berneschi, Simone; Brenci, Massimo; Nunzi Conti, Gualtiero; Pelli, Stefano; Bettinelli, Marco; Speghini, Adolfo; Bányász, Istvan; Fried, Miklós; Khanh, Nguyen Q.; Lohner, Tivadar; Petrik, Péter; Watterich, Andrea; Zolnai, Zsolt

    2011-07-01

    Slab optical waveguides were fabricated in tung-sten-tellurite glass doped with Er3 + ions by means of nitrogen ion implantation at 1.5 MeV. A wide range of ion doses (from 5.1012 to 8.1016 ions/cm2) was used. Optical characterization, performed by dark-line spectroscopy, revealed that the waveguides were of optical barrier type: the implanted layer exhibited a decrease of the refractive index with respect to the virgin bulk glass, while the region comprised between the sample surface and the end of the ion track acted as an optical guiding structure. It was also demonstrated that a post-implantation annealing process, performed at various temperatures on the samples implanted at higher doses, contributes to the reduction of the barrier region.

  5. Aseismic deep subduction of the Philippine Sea plate and slab window

    NASA Astrophysics Data System (ADS)

    Huang, Zhouchuan; Zhao, Dapeng; Hasegawa, Akira; Umino, Norihito; Park, Jung-Ho; Kang, Ik-Bum

    2013-10-01

    We have made great efforts to collect and combine a large number of high-quality data from local earthquakes and teleseismic events recorded by the dense seismic networks in both South Korea and West Japan. This is the first time that a large number of Korean and Japanese seismic data sets are analyzed jointly. As a result, a high-resolution 3-D P-wave velocity model down to 700-km depth is determined, which clearly shows that the Philippine Sea (PHS) plate has subducted aseismically down to ˜460 km depth under the Japan Sea, Tsushima Strait and East China Sea. The aseismic PHS slab is visible in two areas: one is under the Japan Sea off western Honshu, and the other is under East China Sea off western Kyushu. However, the aseismic PHS slab is not visible between the two areas, where a slab window has formed. The slab window is located beneath the center of the present study region where many teleseismic rays crisscross. Detailed synthetic tests were conducted, which indicate that both the aseismic PHS slab and the slab window are robust features. Using the teleseismic data recorded by the Japanese stations alone, the aseismic PHS slab and the slab window were also revealed (Zhao et al., 2012), though the ray paths in the Japanese data set crisscross less well offshore. The slab window may be caused by the subducted Kyushu-Palau Ridge and Kinan Seamount Chain where the PHS slab may be segmented. Hot mantle upwelling is revealed in the big mantle wedge above the Pacific slab under the present study region, which may have facilitated the formation of the PHS slab window. These novel findings may shed new light on the subduction history of the PHS plate and the dynamic evolution of the Japan subduction zone.

  6. Arc Interrupted: The birth, life, and death of the Peruvian flat slab

    NASA Astrophysics Data System (ADS)

    Wagner, Lara; Knezevic Antonijevic, Sanja; Kumar, Abhash; Beck, Susan; Long, Maureen; Zandt, George; Tavera, Hernando; Minaya, Estela

    2016-04-01

    The Peruvian flat slab is a unique natural laboratory for investigating the temporal evolution of flat slab subduction and its associated thermal, tectonic, and seismic implications. This is because the flat slab has been hypothesized to have first formed further north (at approximately the latitude of Lima, Peru), but broadened to the south over the past 11 Ma. This means that areas further to the north represent an older, more evolved flat slab setting, whereas the southernmost edge of the modern flat slab reflects conditions experienced by a newly formed flat slab. Here we present findings from a suite of recent temporary broadband seismic deployments that spanned this entire region. Results from intermediate depth earthquake locations, surface wave tomography (ballistic and ambient Rayleigh wave), and Rayleigh wave anisotropy all indicate that the flat slab did indeed first form further to the north and broadened to the south, along with the southward migration of the Nazca ridge. Subsequently, a trench-parallel tear developed in the older portions of the flat slab north of the ridge, resulting in a resumption of normal subduction geometry where once a flat slab had existed. This tear allows for an interchange of mantle material from beneath the slab to the south to above the slab to the north. This mantle flow has significant thermal implications, both beneath the flat slab and in the lower continental crust located above the relatively newly formed tear. Our results provide unique constraints on the thermal and tectonic evolution of this unusual subduction geometry that may help us to understand better subduction zone processes everywhere.

  7. Slab Deformation in the Mantle Transition Zone: The Effect of Plate Age and Strength Evolution

    NASA Astrophysics Data System (ADS)

    Goes, S. D. B.; Garel, F.; Davies, R.; Davies, J. H.; Kramer, S. C.; Wilson, C. R.

    2014-12-01

    The deformation encountered by subducted tectonic plates at the base of the upper mantle influences Earth's thermal, chemical, and tectonic evolution. Yet the mechanisms responsible for the wide range of imaged slab morphologies, either stagnating in the transition zone or penetrating into the lower mantle, remain debated. We use 2-D thermo-mechanical models of a two-plate subduction system, modeled with the finite-element, adaptive-mesh code Fluidity. We implement a temperature- and stress-dependent rheology, and viscosity increases 30-fold from upper to lower mantle. Trench position evolves freely in response to plate dynamics. Such an approach self-consistently captures feedbacks between temperature, density, flow, strength and deformation. Our results indicate that key controls on subduction dynamics and slab morphology are: (i) the evolution of slab strength; and (ii) the slab's ability to induce trench motion. We build a regime diagram that distinguishes four subduction styles: (1) a "vertical folding" mode with stationary trench; (2) young slabs that are "horizontally deflected" along the 660-km deep viscosity jump ; (3) an inclined slab morphology, resulting from strong trench retreat (old slabs and thinner overriding plates); and (4) a two-stage mode, displaying bent (rolled-over) slabs at the end of upper-mantle descent, that subsequently unbend and achieve inclined morphologies, with late trench retreat (strong overriding plates). We find that the interplay between trench motion and slab deformation at depth dictates the subduction style, both being controlled by slab strength. We show that all seismically observed slab morphologies in the transition zone can arise just by changing the subducting-plate ages. However, to understand present-day slab morphologies, we have to analyse subduction history rather than just current age at the trench.

  8. The dynamics of double slab subduction from numerical and semi-analytic models

    NASA Astrophysics Data System (ADS)

    Holt, A.; Royden, L.; Becker, T. W.

    2015-12-01

    Regional interactions between multiple subducting slabs have been proposed to explain enigmatic slab kinematics in a number of subduction zones, a pertinent example being the rapid pre-collisional plate convergence of India and Eurasia. However, dynamically consistent 3-D numerical models of double subduction have yet to be explored, and so the physics of such double slab systems remain poorly understood. Here we build on the comparison of a fully numerical finite element model (CitcomCU) and a time-dependent semi-analytic subduction models (FAST) presented for single subduction systems (Royden et. al., 2015 AGU Fall Abstract) to explore how subducting slab kinematics, particularly trench and plate motions, can be affected by the presence of an additional slab, with all of the possible slab dip direction permutations. A second subducting slab gives rise to a more complex dynamic pressure and mantle flow fields, and an additional slab pull force that is transmitted across the subduction zone interface. While the general relationships among plate velocity, trench velocity, asthenospheric pressure drop, and plate coupling modes are similar to those observed for the single slab case, we find that multiple subducting slabs can interact with each other and indeed induce slab kinematics that deviate significantly from those observed for the equivalent single slab models. References Jagoutz, O., Royden, L. H., Holt, A. F. & Becker, T. W., 2015, Nature Geo., 8, 10.1038/NGEO2418. Moresi, L. N. & Gurnis, M., 1996, Earth Planet. Sci. Lett., 138, 15-28. Royden, L. H. & Husson, L., 2006, Geophys. J. Int. 167, 881-905. Zhong, S., 2006, J. Geophys. Res., 111, doi: 10.1029/2005JB003972.

  9. Large negative Goos-Hänchen shift from a weakly absorbing dielectric slab.

    PubMed

    Wang, Li-Gang; Chen, Hong; Zhu, Shi-Yao

    2005-11-01

    It is theoretically shown that the negative Goos-Hänchen shifts near resonance, Re[k(z)d] = m pi, can be an order of magnitude larger than the wavelength for both TE- and TM-polarized beams reflected from a weakly absorbing dielectric slab if the absorption of the slab is sufficiently weak, which is different from the case for a lossless dielectric slab [Phys. Rev. Lett. 91, 133903 (2003)].

  10. Molecular Survey of Concrete Biofilm Microbial Communities

    EPA Science Inventory

    Although several studies have shown that bacteria can deteriorate concrete structures, there is very little information on the composition of concrete microbial communities. To this end, we studied different microbial communities associated with concrete biofilms using 16S rRNA g...

  11. Lightweight concrete with enhanced neutron shielding

    SciTech Connect

    Brindza, Paul Daniel; Metzger, Bert Clayton

    2016-09-13

    A lightweight concrete containing polyethylene terephthalate in an amount of 20% by total volume. The concrete is enriched with hydrogen and is therefore highly effective at thermalizing neutrons. The concrete can be used independently or as a component of an advanced neutron radiation shielding system.

  12. 9 CFR 91.26 - Concrete flooring.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Concrete flooring. 91.26 Section 91.26... LIVESTOCK FOR EXPORTATION Inspection of Vessels and Accommodations § 91.26 Concrete flooring. (a) Pens aboard an ocean vessel shall have a 3 inch concrete pavement, proportioned and mixed to give 2000...

  13. 9 CFR 91.26 - Concrete flooring.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Concrete flooring. 91.26 Section 91.26... LIVESTOCK FOR EXPORTATION Inspection of Vessels and Accommodations § 91.26 Concrete flooring. (a) Pens aboard an ocean vessel shall have a 3 inch concrete pavement, proportioned and mixed to give 2000...

  14. 9 CFR 91.26 - Concrete flooring.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Concrete flooring. 91.26 Section 91.26... LIVESTOCK FOR EXPORTATION Inspection of Vessels and Accommodations § 91.26 Concrete flooring. (a) Pens aboard an ocean vessel shall have a 3 inch concrete pavement, proportioned and mixed to give 2000...

  15. 9 CFR 91.26 - Concrete flooring.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Concrete flooring. 91.26 Section 91.26... LIVESTOCK FOR EXPORTATION Inspection of Vessels and Accommodations § 91.26 Concrete flooring. (a) Pens aboard an ocean vessel shall have a 3 inch concrete pavement, proportioned and mixed to give 2000...

  16. 9 CFR 91.26 - Concrete flooring.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Concrete flooring. 91.26 Section 91.26... LIVESTOCK FOR EXPORTATION Inspection of Vessels and Accommodations § 91.26 Concrete flooring. (a) Pens aboard an ocean vessel shall have a 3 inch concrete pavement, proportioned and mixed to give 2000...

  17. Geometry of the Farallon Slab Revealed by Joint Interpretation of Wavefield Imaging and Tomography Results from the Earthscope Transportable Array

    NASA Astrophysics Data System (ADS)

    Pavlis, G. L.; Wang, Y.

    2015-12-01

    A significant number of P and S wave tomography models have been produced in the past decade using various subsets of data from the Earthscope USArray and different inversion algorithms. We focus here on published tomography results that span large portions of the final footprint of the USArray. We use 3D visualization techniques to search for common features in different tomography models. We also compare tomography results to features seen in our current generation wavefield images. Recent innovations of our plane wave migration method have yielded what is arguably the highest resolution image ever produced of the mantle in the vicinity of the transition zone. The new results reveal a rich collection of coherent, dipping structures seen throughout the upper mantle and transition zone. These dipping interfaces are judged significant according to a coherence metric. We treat these surfaces as strain markers to assess proposed models for geometry of the 3D geometry of the Farallon Slab under North America. We find the following geologic interpretations are well supported by independent results: 1. The old Farallon under eastern North America and below the base of transition zone is universally seen as a high velocity anomaly. 2. All results support a simple, 3D kinematic model of the updip limit of the Farallon slab window that follows a track from Cape Mendocino, across Nevada, and northern Arizona and New Mexico. 3. All models show a strong low-velocity mantle under the southwestern U.S. 4. A low-velocity features is universally seen related to the Yellowstone-Snake River system. Shorter wavelength features observed in different tomography models are inconsistent showing that the theme of this session is very important to understand what features are in current results are real. Isopach maps of the thickness of the transition show a systematic difference in transition zone thickness in the western and eastern US. The transition zone thickens in the eastern US in

  18. Boundary element analysis of post-tensioned slabs

    NASA Astrophysics Data System (ADS)

    Rashed, Youssef F.

    2015-06-01

    In this paper, the boundary element method is applied to carry out the structural analysis of post-tensioned flat slabs. The shear-deformable plate-bending model is employed. The effect of the pre-stressing cables is taken into account via the equivalent load method. The formulation is automated using a computer program, which uses quadratic boundary elements. Verification samples are presented, and finally a practical application is analyzed where results are compared against those obtained from the finite element method. The proposed method is efficient in terms of computer storage and processing time as well as the ease in data input and modifications.

  19. Wave propagation through a random medium - The random slab problem

    NASA Technical Reports Server (NTRS)

    Acquista, C.

    1978-01-01

    The first-order smoothing approximation yields integral equations for the mean and the two-point correlation function of a wave in a random medium. A method is presented for the approximate solution of these equations that combines features of the eiconal approximation and of the Born expansion. This method is applied to the problem of reflection and transmission of a plane wave by a slab of a random medium. Both the mean wave and the covariance are calculated to determine the reflected and transmitted amplitudes and intensities.

  20. Slab dehydration recorded in subducted serpentine sea-mount

    NASA Astrophysics Data System (ADS)

    Okamoto, K.; Fukumura, S.; Ishimori, C.; Jung, H.

    2014-12-01

    It has been considered that there is a correlation between the double seismic zones and metamorphic dehydration reaction in deep slab. The lower seismic plane of the double seismic zone is considered to be located on the 600 oC isotherm in the subducting lithosphere. Antigorite terminal reaction is highly temperature sensitive around 600 oC. Therefore it has been proposed that the oceanic lithosphere was hydrated forming serpentine prior to subduction, then serpentine was decomposed to release fluid causing dehydration embrittlement in the slab. In order to unravel relation between dehydration and seismic deformation, we have investigated dehydration process of natural metamorphic rocks recording very cold geothermal history in the crust and lithosphere in the slab. Metamorphic olivine after antigorite has been described in Italian Alps and also from the Mt. Shiraga, Japan [1]. However, the olivine was formed with talc and fluid by antigorite breakdown reaction in pressures lower than 1.5 GPa. Spinifex olivine with opx in the Cerro del Almirez [2], is the product at pressures (P > 1.5 GPa) relevant to the lower seismic plane beneath Northeast Japan. It clearly indicates the presence of large amount of water facilitate crystallization of elongated olivine with opx. It is also supported by LPO pattern of olivines determined by EBSD. Fine-grained olivine-rich samples shows that Type-C fabric pattern is dominant, suggesting deformation under water-rich condition [3]. With metamorphic olivines, chlorite was also recrystallized, suggesting that water would be transported farther down to deep. The estimated dehydration reaction has a negative P-T slope at pressures higher than 1.5 GPa. The reaction is volume reducing reaction and the olivine-opx spinifex texture was formed under volume reducing reaction. In the warm slab beneath SW Japan, the reaction has a positive slope in P-T space and forms olivine+talc+fluid. From microstrucral and petrological analysis of the

  1. Three-dimensional singularities of a thin plasma slab.

    PubMed

    Pegoraro, F; Bulanov, S V; Sakai, J I; Tomassini, G

    2001-07-01

    The three-dimensional (3D) nonlinear development of the interchange-like (Rayleigh-Taylor) instability of a thin slab of plasma exhibits interesting features with respect to its two-dimensional (2D) limit investigated by Bulanov, Pegoraro, and Sakai [Phys. Rev. E 59, 2292 (1999)]. We show that, contrary to the 2D case, the 3D evolution equations remain nonlinear when Lagrangian variables are adopted. Explicit solutions are found by the use of a generalized hodograph transformation. Both compression and rarefaction singularities are formed. Local solutions in the neighborhood of the singular points have a generic 2D character.

  2. High energy efficient solid state laser sources. [slab geometry laser sources

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1983-01-01

    Slab glass performance studies demonstate 18 J of output at 2 Hz with 2.3% wall plug efficiency. The goal is to achieve 10 J per pulse at 10 Hz and 3% wall plug efficiency during the next annual period. The slab concept was extended to Nd:YAG and to Nd:GGG. To date over 80 W of CW output power at 2% efficiency was generated in slab Nd:YAG. A multiplexed slab Nd:YAG pre-amplifier was invented and a Nd:YAG oscillator was demonstrated with 100kHz linewidth for eventual use in wind velocity measurements.

  3. Leaky unstable modes and electromagnetic radiation amplification by an anisotropic plasma slab

    SciTech Connect

    Vagin, K. Yu. Uryupin, S. A.

    2015-09-15

    The interaction between electromagnetic radiation and a photoionized plasma slab with an anisotropic electron velocity distribution is studied. It is shown that the fields of leaky modes are amplified due to the development of aperiodic instability in the slab, which leads to an increase in both the reflected and transmitted fields. The transmitted field can significantly increase only if the slab thickness does not exceed the ratio of the speed of light to the electron plasma frequency, whereas there is no upper bound on the slab thickness for the reflected signal to be amplified.

  4. Analysis of surface wave propagation in a grounded dielectric slab covered by a resistive sheet

    NASA Technical Reports Server (NTRS)

    Shively, David G.

    1992-01-01

    Both parallel and perpendicular polarized surface waves are known to propagate on lossless and lossy grounded dielectric slabs. Surface wave propagation on a grounded dielectric slab covered with a resistive sheet is considered. Both parallel and perpendicular polarizations are examined. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attenuation and phase velocity are shown for representative geometries. The results are applicable to both a grounded slab with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet.

  5. Calculation and comparison of thermal effect in laser diode pumped slab lasers with different pumping structures

    NASA Astrophysics Data System (ADS)

    Huang, Feng; Jiang, Nan; Wang, Yuefeng; Dong, Wei; Niu, Yanxiong

    2008-03-01

    Laser diode (LD) pumped slab laser, as an important high average power solid-state laser, is a promising laser source in military and industrial fields. The different laser diode pumping structures lead to different thermal effect in the slab gain medium. The thermal and stress analysis of slab laser with different pumping structure are performed by finite element analysis (FEA) with the software program ANSYS. The calculation results show that the face pumped and cooled laser results in a near one-dimension temperature distribution and eliminates thermal stress induced depolarization. But the structure is low pump efficiency due to the small thickness of slabs and the requirement to cool and pump through the same faces. End-pumped slab laser is high pump efficiency and excellent mode match, but its pumping arrangement is fairly complicated. The edge-pumped face-cooling slab laser's pump efficiency is better than face-pumping, and its pumping structure is simpler than end-pumped laser, but the tensile stress on surfaces may initiate failure of the gain medium so it is important to design so that the stress is well below the stress fracture limit. The comparison of the thermal effects with different pumping structure shows that, the edge-pumped slab laser has engineering advantages in high power slab laser's application. Furthermore, the end-pumped slab laser tends to get the best beam quality, so it is fit for the application which has a special requirement on laser beam quality.

  6. Structured mass density slab as a waveguide of fast magnetoacoustic waves

    NASA Astrophysics Data System (ADS)

    Jelínek, P.; Karlický, M.

    Coronal loops are waveguides for magnetohydrodynamic (MHD) waves. These loops are expected to be structured. Therefore, in the present paper, we numerically studied the propagation of the fast MHD waves in the structured density slab (composed from a broad density slab with one axisymmetric narrow sub-slab superposed), and analysed the wave signals. Then, this structured slab was divided into its components, i.e., to simple broad and narrow slabs and the same analysis was made. We compared results of both these cases. For the calculations we adopted a two-dimensional (2D) magnetohydrodynamic (MHD) model, in which we solved a full set of ideal time-dependent MHD equations using the FLASH code, applying the adaptive mesh refinement (AMR) method. To initiate the fast sausage magnetoacoustic waves, we used axisymmetric Gaussian velocity perturbation. Wave signals were detected in different locations along the slab and as a diagnostic tool of these waves, the wavelet analysis method has been used. We found that for the structured density slab with sufficiently sharp boundaries, i.e., for good quality waveguides (without an energy leakage), the guided waves in the structured slab behave similarly as in its separated (simple slab) components.

  7. Tomography of the subducting Pacific slab and the 2015 Bonin deepest earthquake (Mw 7.9)

    NASA Astrophysics Data System (ADS)

    Zhao, Dapeng; Fujisawa, Moeto; Toyokuni, Genti

    2017-03-01

    On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i.e., slightly north of the 2015 deep event hypocenter. In the north the slab becomes stagnant in the mantle transition zone, whereas in the south the slab is directly penetrating into the lower mantle. This deep earthquake was caused by joint effects of several factors, including the Pacific slab’s fast deep subduction, slab tearing, slab thermal variation, stress changes and phase transformations in the slab, and complex interactions between the slab and the ambient mantle.

  8. Tomography of the subducting Pacific slab and the 2015 Bonin deepest earthquake (Mw 7.9)

    PubMed Central

    Zhao, Dapeng; Fujisawa, Moeto; Toyokuni, Genti

    2017-01-01

    On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i.e., slightly north of the 2015 deep event hypocenter. In the north the slab becomes stagnant in the mantle transition zone, whereas in the south the slab is directly penetrating into the lower mantle. This deep earthquake was caused by joint effects of several factors, including the Pacific slab’s fast deep subduction, slab tearing, slab thermal variation, stress changes and phase transformations in the slab, and complex interactions between the slab and the ambient mantle. PMID:28295018

  9. Abnormal seismological and magmatic processes controlled by the tearing South American flat slabs

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun

    2016-09-01

    The influence of flat slab subduction on the formation of intra-slab earthquakes, volcanic activities and mantle seismic velocity anomalies remains unclear. We attempt to better understand these processes by simulating the two flat slabs in Peru and Chile using data-orientated geodynamic models. Our results successfully reproduce the observed flat slabs as mainly due to two subducting aseismic ridges. In contrast to the traditional view of flat-slab subduction, we find that these slabs are internally torn, as is due to the 3D nature of the subducting buoyancy features. This broken slab configuration, confirmed by regional tomography, naturally explains the abnormal distribution of and stress regimes associated with the intermediate-depth earthquakes. We further show that the slab tearing process could also better explain the formation of adakitic and ore-forming magmatism, the evolution of the magmatic arc, and the enigmatic mantle seismic structures beneath these regions. We propose that slab tearing may represent a common result of buoyancy feature subduction and that the resulting mantle processes could affect the long-term geodynamic evolution of continents.

  10. Displacement-based seismic design of flat slab-shear wall buildings

    NASA Astrophysics Data System (ADS)

    Sen, Subhajit; Singh, Yogendra

    2016-06-01

    Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability to punching shear failure. Several national design codes provide guidelines for designing flat slab system under gravity load only. Nevertheless, flat slab buildings are also being constructed in high seismicity regions. In this paper, performance of flat slab buildings of various heights, designed for gravity load alone according to code, is evaluated under earthquake loading as per ASCE/SEI 41 methodology. Continuity of slab bottom reinforcement through column cage improves the performance of flat slab buildings to some extent, but it is observed that these flat slab systems are not adequate in high seismicity areas and need additional primary lateral load resisting systems such as shear walls. A displacement-based method is proposed to proportion shear walls as primary lateral load resisting elements to ensure satisfactory performance. The methodology is validated using design examples of flat slab buildings with various heights.

  11. Meteorological variables to aid forecasting deep slab avalanches on persistent weak layers

    USGS Publications Warehouse

    Marienthal, Alex; Hendrikx, Jordy; Birkeland, Karl; Irvine, Kathryn M.

    2015-01-01

    Deep slab avalanches are particularly challenging to forecast. These avalanches are difficult to trigger, yet when they release they tend to propagate far and can result in large and destructive avalanches. We utilized a 44-year record of avalanche control and meteorological data from Bridger Bowl ski area in southwest Montana to test the usefulness of meteorological variables for predicting seasons and days with deep slab avalanches. We defined deep slab avalanches as those that failed on persistent weak layers deeper than 0.9 m, and that occurred after February 1st. Previous studies often used meteorological variables from days prior to avalanches, but we also considered meteorological variables over the early months of the season. We used classification trees and random forests for our analyses. Our results showed seasons with either dry or wet deep slabs on persistent weak layers typically had less precipitation from November through January than seasons without deep slabs on persistent weak layers. Days with deep slab avalanches on persistent weak layers often had warmer minimum 24-hour air temperatures, and more precipitation over the prior seven days, than days without deep slabs on persistent weak layers. Days with deep wet slab avalanches on persistent weak layers were typically preceded by three days of above freezing air temperatures. Seasonal and daily meteorological variables were found useful to aid forecasting dry and wet deep slab avalanches on persistent weak layers, and should be used in combination with continuous observation of the snowpack and avalanche activity.

  12. Concrete Finisher Program. Apprenticeship Training.

    ERIC Educational Resources Information Center

    Alberta Learning, Edmonton. Apprenticeship and Industry Training.

    This document presents information about the apprenticeship training program of Alberta, Canada, in general and the concrete finishing program in particular. The first part of the document discusses the following items: Alberta's apprenticeship and industry training system; the apprenticeship and industry training committee structure; local…

  13. High temperature polymer concrete compositions

    SciTech Connect

    Fontana, J.J.; Reams, W.

    1985-02-19

    This invention is concerned with a polymer concrete composition, which is a two-component composition useful with many bases including metal. Component A, the aggregate composition, is broadly composed of silica, silica flour, portland cement, and acrylamide, whereas Component B, which is primarily vinyl and acrylyl reactive monomers is a liquid system.

  14. Quick-setting concrete and a method for making quick-setting concrete

    DOEpatents

    Wagh, Arun S.; Singh, Dileep; Pullockaran, Jose D.; Knox, Lerry

    1997-01-01

    A method for producing quick setting concrete is provided comprising hydrng a concrete dry mixture with carbonate solution to create a slurry, and allowing the slurry to cure. The invention also provides for a quick setting concrete having a predetermined proportion of CaCO.sub.3 of between 5 and 23 weight percent of the entire concrete mixture, and whereby the concrete has a compression strength of approximately 4,000 pounds per square inch (psi) within 24 hours after pouring.

  15. Influence of cratonic lithosphere on the formation and evolution of flat slabs: Insights from 3-D time-dependent modeling

    NASA Astrophysics Data System (ADS)

    Taramón, Jorge M.; Rodríguez-González, Juan; Negredo, Ana M.; Billen, Magali I.

    2015-09-01

    Several mechanisms have been suggested for the formation of flat slabs including buoyant features on the subducting plate, trenchward motion and thermal or cratonic structure of the overriding plate. Analysis of episodes of flat subduction indicate that not all flat slabs can be attributed to only one of these mechanisms and it is likely that multiple mechanisms work together to create the necessary conditions for flat slab subduction. In this study we examine the role of localized regions of cratonic lithosphere in the overriding plate in the formation and evolution of flat slabs. We explicitly build on previous models, by using time-dependent simulations with three-dimensional variation in overriding plate structure. We find that there are two modes of flat subduction: permanent underplating occurs when the slab is more buoyant (shorter or younger), while transient flattening occurs when there is more negative buoyancy (longer or older slabs). Our models show how regions of the slab adjacent to the subcratonic flat portion continue to pull the slab into the mantle leading to highly contorted slab shapes with apparent slab gaps beneath the craton. These results show how the interpretation of seismic images of subduction zones can be complicated by the occurrence of either permanent or transient flattening of the slab, and how the signature of a recent flat slab episode may persist as the slab resumes normal subduction. Our models suggest that permanent underplating of slabs may preferentially occur below thick and cold lithosphere providing a built-in mechanism for regeneration of cratons.

  16. ASR damage detection in concrete from ultrasonic methods

    NASA Astrophysics Data System (ADS)

    Gong, Peng; Patton, Mark E.; Greve, David W.; Harley, Joel B.; Junker, Warren R.; Liu, Chang; Oppenheim, Irving J.

    2014-03-01

    Alkali-silica reaction (ASR) is a chemical reaction that can occur between alkaline components in cement paste and reactive forms of silica in susceptible aggregates when sufficient moisture is present. The ASR product, known as ASR gel, can cause expansion and cracking that damages the structure. We pass ultrasonic signals through concrete laboratory specimens and use three different ultrasonic methods to detect the onset of ASR damage, or the presence of ASR damage while still at the microscale. Our test specimens are fabricated with aggregate known to be reactive and are then exposed to an aggressive environment to accelerate ASR development. We use swept-sine excitations and obtain pitch-catch records from specimens that have been exposed to the accelerated environment. From this data, we demonstrate an ultrasonic passband method shows high frequency components diminish faster than low frequency components, and therefore the ultrasonic passband shifts to the low frequency side due to ASR damage. The test results also show that the ultrasonic passband is logically related to specimen size. We also demonstrate a stretching factor method is able to track the progress of ASR damage in concrete very well. These methods are shown to be more reliable than attenuation spectrum or attenuation methods that do not detect the ASR damage in concrete at early stages.

  17. Excitation of ground vibration due to the passage of trains over a track with trackbed irregularities and a varying support stiffness

    NASA Astrophysics Data System (ADS)

    Auersch, Lutz

    2015-01-01

    Train-induced ground vibration can be excited by wheel and track irregularities and by two kinds of irregularities of the soil, by geometric irregularities or by the spatially varying soil stiffness. For both types of irregularities, the effective track irregularity on top of the track is calculated in wavenumber domain and with wavenumber integrals. For a general multi-beam track model, the wavenumber integrals are solved numerically. The irregularities of the soil are filtered by the track when transferred from the bottom to the top of the track. The high-wavenumber irregularities are strongly reduced due to the bending stiffness of the track and the compliance of the support. In addition, soft track elements reduce directly the stiffness variation of the support. Therefore, the mitigation effect of elastic track elements for these excitation components seems to be important. For under-sleeper pads and slab tracks, calculation and measurements are presented including additional excitation components and the dynamic vehicle-track interaction, and the relevance of the excitation mechanisms is discussed based on the dynamic forces which are acting on the ground. Due to the restricted amplitudes, the parametric excitation by the stiffness variation seems to be less important than the geometric irregularities. The calculations yield the correct trends of the measurements and many details of the measured ballast, slab, and under-sleeper-pad tracks.

  18. Repair of the DSS-14 Pedestal Concrete

    NASA Technical Reports Server (NTRS)

    Mcclure, D.

    1985-01-01

    About three years after the Goldstone Deep Space Station antenna was dedicated, grout under the hydrostatic bearing runner was found to be interacting with the runner, causing rust to form between the runner and the sole plates upon which it rests. The rust formed unevenly and the runner could not be kept flat so in 1969 the grout was removed and replaced with a Portland cement and sand dry pack grout that was less likely to produce rust. In the years that followed, oil leaking from the runner assembly caused progressive deterioration of the drypack grout. In 1982 over one thousand hours of spacecraft tracking time were lost due to this deterioration. A plan was developed to rehabilitate the bearing. The plan called for raising the rotating structure free from the concrete pedestal and placing it on three pairs of external support columns. With the weight of the structure transferred to the columns, the pads and runner could be removed and the repair started. The very successful repair included the replacement of a significant portion of the antenna pedestal.

  19. Solar tracking system

    DOEpatents

    Okandan, Murat; Nielson, Gregory N.

    2016-07-12

    Solar tracking systems, as well as methods of using such solar tracking systems, are disclosed. More particularly, embodiments of the solar tracking systems include lateral supports horizontally positioned between uprights to support photovoltaic modules. The lateral supports may be raised and lowered along the uprights or translated to cause the photovoltaic modules to track the moving sun.

  20. Microbiologically induced deterioration of concrete - A Review

    PubMed Central

    Wei, Shiping; Jiang, Zhenglong; Liu, Hao; Zhou, Dongsheng; Sanchez-Silva, Mauricio

    2013-01-01

    Microbiologically induced deterioration (MID) causes corrosion of concrete by producing acids (including organic and inorganic acids) that degrade concrete components and thus compromise the integrity of sewer pipelines and other structures, creating significant problems worldwide. Understanding of the fundamental corrosion process and the causal agents will help us develop an appropriate strategy to minimize the costs in repairs. This review presents how microorganisms induce the deterioration of concrete, including the organisms involved and their colonization and succession on concrete, the microbial deterioration mechanism, the approaches of studying MID and safeguards against concrete biodeterioration. In addition, the uninvestigated research area of MID is also proposed. PMID:24688488

  1. Magnetohydrodynamic stability of natural convection in a vertical porous slab

    NASA Astrophysics Data System (ADS)

    Shankar, B. M.; Kumar, Jai; Shivakumara, I. S.

    2017-01-01

    The stability of the conduction regime of natural convection in an electrically conducting fluid saturated porous vertical slab is investigated in the presence of a uniform external transverse magnetic field. The flow in the porous medium is described by modified Brinkman-extended Darcy equation with fluid viscosity different from effective viscosity. The boundaries of the vertical porous slab are assumed to be rigid-isothermal and electrically non-conducting. The resulting stability equations are solved numerically using Galerkin method. The critical Grashof number Gc, the critical wave number αc and the critical wave speed cc are computed for a wide range of porous parameter σp, the ratio of effective viscosity to the fluid viscosity Λ, the Prandtl number Pr and the Hartmann number M. Based on these parameters, the stability characteristics of the system are discussed in detail. The presence of advective inertia is to instill instability on the flow in a porous medium and found that the magnetic field, porous parameter and ratio of viscosities have a stabilizing effect on both stationary and oscillatory wave instabilities. Besides, the value of Pr at which transition occurs from stationary to oscillatory mode of instability decreases with increasing M ,σp and Λ .

  2. Slab waveguide photobioreactors for microalgae based biofuel production.

    PubMed

    Jung, Erica Eunjung; Kalontarov, Michael; Doud, Devin F R; Ooms, Matthew D; Angenent, Largus T; Sinton, David; Erickson, David

    2012-10-07

    Microalgae are a promising feedstock for sustainable biofuel production. At present, however, there are a number of challenges that limit the economic viability of the process. Two of the major challenges are the non-uniform distribution of light in photobioreactors and the inefficiencies associated with traditional biomass processing. To address the latter limitation, a number of studies have demonstrated organisms that directly secrete fuels without requiring organism harvesting. In this paper, we demonstrate a novel optofluidic photobioreactor that can help address the light distribution challenge while being compatible with these chemical secreting organisms. Our approach is based on light delivery to surface bound photosynthetic organisms through the evanescent field of an optically excited slab waveguide. In addition to characterizing organism growth-rates in the system, we also show here, for the first time, that the photon usage efficiency of evanescent field illumination is comparable to the direct illumination used in traditional photobioreactors. We also show that the stackable nature of the slab waveguide approach could yield a 12-fold improvement in the volumetric productivity.

  3. Trench migration, net rotation and slab mantle coupling

    NASA Astrophysics Data System (ADS)

    Funiciello, F.; Faccenna, C.; Heuret, A.; Lallemand, S.; Di Giuseppe, E.; Becker, T. W.

    2008-07-01

    Laboratory models have been conducted to improve our understanding of the role that the resistance of the slab to bending and its coupling to the ambient mantle play in subduction dynamics over geological time scales. Our models are set up with a viscous plate of silicone (lithosphere) subducting under negative buoyancy in a viscous layer of glucose syrup (mantle). For our study, the lithosphere/upper mantle viscosity contrast has been systematically varied, from ~ 10 to ~ 10 5 in order to explore the parameter space between weak and strong slab dynamics. We found that subduction is characterized by a retreating mode for viscosity ratios > 10 4, by the coexistence of a retreating mode and an advancing mode for viscosity ratios between ~ 10 4 and ~ 10 2, and quasi-stationary, Rayleigh-Taylor like behaviour for ratios < 10 2. By combining our experimental results and kinematic data from current subduction zones in four reference frames which differ in the amount of net rotation, we infer that a lithosphere/upper mantle viscosity contrast of 150-500 is necessary to obtain realistic trench/subducting plate velocity ratios as well as the variability of subduction styles observed in nature.

  4. Descending lithosphere slab beneath the Northwest Dinarides from teleseismic tomography

    NASA Astrophysics Data System (ADS)

    Šumanovac, Franjo; Dudjak, Darko

    2016-12-01

    The area of study covers the marginal zone between the Adriatic microplate (African plate) and the Pannonian segment (Eurasian plate). We present a tomography model for this area, with special emphasis on the northwest Dinarides. A dense distribution of temporary seismic stations in the area of the Northern Dinarides along with permanent seismic stations located in the area, allowed us to construct this P-wave tomographic model. We assembled our travel-time dataset based on 26 seismic stations were used to collect the dataset. Teleseismic events were recorded for a period of 18 months and a set of 76 distant earthquakes were used to calculate the P-wave travel-time residuals. We calculated relative rather than absolute arrival-time residuals in the inversion to obtain depths of 0-400 km. We imaged a pronounced fast velocity anomaly below the NW Dinarides which directly indicates a lithosphere slab downgoing beneath the Dinarides. This fast anomaly extends towards the NW direction to at least 250 km depth, and we interpreted it as a descending lithosphere slab. The thrusting of the Adriatic microplate may be brought about by sub-lithosphere rising movement beneath the Pannonian region, along with a push from African plate. In our interpretation, the Adriatic lower lithosphere has been detached from the crust, and steeply sinks beneath the Dinarides. A lithosphere model of the contact between the Adriatic microplate and Pannonian tectonic segment was constructed based on the tomographic velocity model and results of previous crustal studies.

  5. Ion trap electric field measurements using slab coupled optical sensors

    NASA Astrophysics Data System (ADS)

    Shumway, L.; Chadderdon, S.; Powell, A.; Li, A.; Austin, D.; Hawkins, A.; Selfridge, R.; Schultz, S.

    2014-03-01

    Ion traps are widely used in the field of mass spectrometry. These devices use high electric fields to mass-selectively trap, eject, and count the particles of a material, producing a mass spectrum of the given material. Because of their usefulness, technology pushes for smaller, more portable ion traps for field use. Making internal ion trap field measurements not yet feasible because current electric field sensors are often too bulky or their metallic composition perturbs field measurements. Using slab coupled optical sensor (SCOS) technology, we are able to build sensors that are compatible with the spacing constraints of the ion trap. These sensors are created by attaching a nonlinear crystal slab waveguide to an optical fiber. When a laser propagates through the fiber, certain wavelengths of light couple out of the fiber via the crystal and create "resonances" in the output light spectrum. These resonances shift in proportion to a given applied electric field, and by measuring that shift, we can approximate the electric field. Developing a sensor that can effectively characterize the electric fields within an ion trap will greatly assist in ion trap design, fabrication, and troubleshooting techniques.

  6. Detonation Propagation in Slabs and Axisymmetric Rate Sticks

    NASA Astrophysics Data System (ADS)

    Romick, Christopher; Aslam, Tariq

    Insensitive high explosives (IHE) have many benefits; however, these IHEs exhibit longer reaction zones than more conventional high explosives (HE). This makes IHEs less ideal explosives and more susceptible to edge effects as well as other performance degradation issues. Thus, there is a resulting reduction in the detonation speed within the explosive. Many HE computational models, e. g. WSD, SURF, CREST, have shock-dependent reaction rates. This dependency places a high value on having an accurate shock speed. In the common practice of shock-capturing, there is ambiguity in the shock-state due to smoothing of the shock-front. Moreover, obtaining an accurate shock speed with shock-capturing becomes prohibitively computationally expensive in multiple dimensions. The use of shock-fitting removes the ambiguity of the shock-state as it is one of the boundaries. As such, the required resolution for a given error in the detonation speed is less than with shock-capturing. This allows for further insight into performance degradation. A two-dimensional shock-fitting scheme has been developed for unconfined slabs and rate sticks of HE. The HE modeling is accomplished by Euler equations utilizing several models with single-step irreversible kinetics in slab and rate stick geometries. Department of Energy - LANL.

  7. The influence of temperature on the average number of optical phonons in a polar slab of semiconductors

    NASA Astrophysics Data System (ADS)

    Wang, Xiu-qing

    2017-03-01

    The effects of temperature T, average number of optical phonons N, the phonon frequency ω and slab thickness d in a polar slab were investigated using the linear combination operator and unitary transformation methods. The results showed that the phonon frequency ω increases with increasing temperature T, but the average number of optical phonons N and phonon frequency ω decreases with the increase in slab thickness d. When the slab thickness is <5 nm, N decreases sharply, and when the slab thickness is <10 nm, the phonon frequency ω and slab thickness d changed significantly.

  8. Estimation of Concrete's Porosity by Ultrasounds

    NASA Astrophysics Data System (ADS)

    Benouis, A.; Grini, A.

    Durability of concrete depends strongly on porosity; this conditions the intensity of the interactions of the concrete with the aggressive agents. The pores inside the concrete facilitate the process of damage, which is generally initiated on the surface. The most used measurement is undoubtedly the measurement of porosity accessible to water. The porosimetry by intrusion with mercury constitutes a tool for investigation of the mesoporosity. The relationship between concrete mixtures, porosity and ultrasonic velocity of concrete samples measured by ultrasonic NDT is investigated. This experimental study is interested in the relations between the ultrasonic velocity measured by transducers of 7.5 mm and 49.5 mm diameter and with 54 kHz frequency. Concrete specimens (160 mm diameter and 320 mm height) are fabricated with concrete of seven different mixtures (various W/C and S/S + G ratios), which gave porosities varying between 7% and 16%. Ultrasonic velocities in concrete were measured in longitudinal direction. Finally the results showed the influence of ratio W/C, where the porosity of the concretes of a ratio W/C _0,5 have correctly estimated by ultrasonic velocity. The integration of the concretes of a lower ratio, in this relation, caused a great dispersion. Porosity estimation of concretes with a ratio W/C lower than 0,5 became specific to each ratio.

  9. Diffusion of Radionuclides in Concrete and Soil

    SciTech Connect

    Mattigod, Shas V.; Wellman, Dawn M.; Bovaird, Chase C.; Parker, Kent E.; Recknagle, Kurtis P.; Clayton, Libby N.; Wood, Marcus I.

    2012-04-25

    One of the methods being considered for safely disposing of Category 3 low-level radioactive wastes is to encase the waste in concrete. Such concrete encasement would contain and isolate the waste packages from the hydrologic environment and would act as an intrusion barrier. Any failure of concrete encasement may result in water intrusion and consequent mobilization of radionuclides from the waste packages. The mobilized radionuclides may escape from the encased concrete by mass flow and/or diffusion and move into the surrounding subsurface environment. Therefore, it is necessary to assess the performance of the concrete encasement structure and the ability of the surrounding soil to retard radionuclide migration. The objective of our study was to measure the diffusivity of Re, Tc and I in concrete containment and the surrounding vadose zone soil. Effects of carbonation, presence of metallic iron, and fracturing of concrete and the varying moisture contents in soil on the diffusivities of Tc and I were evaluated.

  10. Durable fiber reinforced self-compacting concrete

    SciTech Connect

    Corinaldesi, V.; Moriconi, G

    2004-02-01

    In order to produce thin precast elements, a self-compacting concrete was prepared. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel-reinforcing mesh were added to the concrete mixture at a dosage of 10% by mass of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40. Compression and flexure tests were carried out to assess the safety of these thin concrete elements. Moreover, serviceability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out in order to evaluate the contribution of steel fibers in counteracting the high concrete strains due to a low aggregate-cement ratio. Secondly, the resistance to freezing and thawing cycles was investigated on concrete specimens in some cases superficially treated with a hydrophobic agent. Lastly, both carbonation and chloride penetration tests were carried out to assess durability behavior of this concrete mixture.

  11. Convective instability of stagnant slabs at the base of the Mantle Transition Zone

    NASA Astrophysics Data System (ADS)

    Motoki, M.; Ballmer, M. D.

    2013-12-01

    Seismic tomography reveals that subducting slabs descend to a depth of about 660 km to stagnate at the base of the mantle transition zone for long timescales. Most of the slab is composed of harzburgite covered by veneers of eclogite and hydrated mantle, a make-up that is positively buoyant overall. Initially, this positive compositional buoyancy is overwhelmed by the negative thermal buoyancy of the cool slab. However, the plate continues to be heated from above and below while it stagnates. Consequently, its thermal buoyancy is expected to slowly increase, turning an initially stable into an unstable thermochemical density stratification, and triggering convective instability. Plumes rising out of stagnating slabs may enhance the transition zone and asthenosphere with compositional heterogeneity, including water, as well as support decompression melting. To study these important processes, we systematically explore the parameters controlling convective instability of stagnating slabs in two-dimensional thermochemical geodynamic models. Preliminary results show that instability occurs at about 50-75 Myr after subduction, a timescale that increases with the age and speed of the subducting plate, as well as Rayleigh number. This timescale is further found to be sensitive to preexisting heterogeneity within the slab, as well as the occurrence of small-scale convection at the base of the overriding plate. The plumes rising out of the slab can deliver only a small fraction of the slab's eclogite to the transition zone, but a larger fraction of the slab's harzburgite and hydrated mantle to the base of the lithosphere, where hydrated lithologies undergo decompression melting in a subset of our models. Most of the slab's eclogite instead settles at the very base of the transition zone. These findings have important implications for the fate of subducted slabs, material transport across the transition zone, the compositional stratification of the mantle as a whole, as well

  12. 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.

  13. Dynamic Subsidence across the Late Cretaceous Western Interior Basin in Response to Farallon Slab Subduction

    NASA Astrophysics Data System (ADS)

    Liu, S.; Nummedal, D.; Liu, L.

    2015-12-01

    The United States Cretaceous Western Interior Basin has long been considered a foreland basin, driven by the Sevier thrust and associated basin sediment loads. However, flexural studies demonstrate that this effect exists only within a narrow band in front of the thrust belt. Most of the basin appears to be due to mantle flow-induced dynamic subsidence associated with Farallon plate subduction. Here we show how the components of evolving long-wavelength dynamic subsidence and flexural subsidence created the accommodation space and controlled the stratigraphy across the western United Sates, based on the correlated stratigraphic sections across central Utah-Colorado and southern Wyoming.These backstripped subsidence data reveal a component of continuously evolving long-wavelength dynamic subsidence, in addition to subsidence driven by the Sevier thrust belt and associated sediment loads. The loci of maximum rates of this dynamic subsidence moved eastward from ~98 to 74 Ma in phase with the west-to-east passage of the Farallon slab, as reconstructed from tomography based on quantitative inverse models. These subsidence data allow testing of existing subduction models and confirm the dynamic-topography driven nature of the Western Interior Basin. The results seem to support that the depocenters track the trough of dynamic subsidence with ca.18 Myr cycles through time and space and the stratigraphic patterns of large-scale progradation, eastward migration of depocenter, and regional clinoform-like downlap are related with the dynamic subsidence. Interpretation of these data also provides more insights into the repeated, ca.2 to 6 Myr cycles of thrust-induced subsidence in front of the thrust belt, which control the local eastward progradation of the sand bodies from the thrust belt. The dynamic, flexural subsidence and eustatic sea level changes interacted and controlled the timing and distribution of unconformities. Our work shows how the stratigraphy precisely

  14. Kinematics of SW Anatolia implications on crustal deformation above slab tear

    NASA Astrophysics Data System (ADS)

    Özkaptan, Murat; Koç, Ayten; Lefebvre, Côme; Gülyüz, Erhan; Uzel, Bora; Kaymakci, Nuretdin; Langereis, Cornelis G.; Özacar, Arda A.; Sözbilir, Hasan

    2014-05-01

    measurements are also consistent with earthquake focal mechanisms suggesting active extension in the region. Thus, the FBFZ is characterized at the surface mainly by extension unlike previously proposed transcurrent deformation. We think, the FBFZ may represent a deep structure that formed at the ancient northern track of the STEP fault that reflected to the surface as a wide extensional zone displaying counter-clockwise rigid body rotation since late Miocene possibly due to fast Aegean slab retreat towards south. This research is supported byTubitak-Turkish National Science Foundation Grant Number 111Y239.

  15. Modelling dielectric-constant values of concrete: an aid to shielding effectiveness prediction and ground-penetrating radar wave technique interpretation

    NASA Astrophysics Data System (ADS)

    Bourdi, Taoufik; Eddine Rhazi, Jamal; Boone, François; Ballivy, Gérard

    2012-10-01

    A number of efficient and diverse mathematical methods have been used to model electromagnetic wave propagation. Each of these methods possesses a set of key elements which eases its understanding. However, the modelling of the propagation in concrete becomes impossible without modelling its electrical properties. In addition to experimental measurements; material theoretical and empirical models can be useful to investigate the behaviour of concrete's electrical properties with respect to frequency, moisture content (MC) or other factors. These models can be used in different fields of civil engineering such as (1) electromagnetic compatibility which predicts the shielding effectiveness (SE) of a concrete structure against external electromagnetic waves and (2) in non-destructive testing to predict the radar wave reflected on a concrete slab. This paper presents a comparison between the Jonscher model and the Debye models which is suitable to represent the dielectric properties of concrete, although dielectric and conduction losses are taken into consideration in these models. The Jonscher model gives values of permittivity, SE and radar wave reflected in a very good agreement with those given by experimental measurements and this for different MCs. Compared with other models, the Jonscher model is very effective and is the most appropriate to represent the electric properties of concrete.

  16. Dual-band infrared imaging to detect corrosion damage within airframes and concrete structures

    NASA Astrophysics Data System (ADS)

    DelGrande, Nancy; Durbin, Philip F.

    1994-03-01

    We are developing dual-band IR (DBIR) imaging and detection techniques to inspect airframes and concrete bridge decks for hidden corrosion damage. Using selective DBIR image ratios, we enhanced surface temperature contrast and removed surface emissivity noise associated with clutter. Our surface temperature maps depicted defect sites, which heat and cool at different rates than their surroundings. Our emissivity-ratio maps tagged and removed the masking effects of surface clutter. For airframe inspections, we used time-resolved DBIR temperature, emissivity-ratio and composite thermal inertia maps to locate corrosion-thinning effects within a flash-heated Boeing 737 airframe. Emissivity-ratio maps tagged and removed clutter sites from uneven paint, dirt and surface markers. Temperature and thermal inertia maps characterized defect sites, types, sizes, thicknesses, thermal properties and material-loss effects from airframe corrosion. For concrete inspections, we mapped DBIR temperature and emissivity-ratio patterns to better interpret surrogate delamination sites within naturally- heated, concrete slabs and removed the clutter mask from sand pile-up, grease stains, rocks and other surface objects.

  17. TrackEye tracking algorithm characterization

    NASA Astrophysics Data System (ADS)

    Valley, Michael T.; Shields, Robert W.; Reed, Jack M.

    2004-10-01

    TrackEye is a film digitization and target tracking system that offers the potential for quantitatively measuring the dynamic state variables (e.g., absolute and relative position, orientation, linear and angular velocity/acceleration, spin rate, trajectory, angle of attack, etc.) for moving objects using captured single or dual view image sequences. At the heart of the system is a set of tracking algorithms that automatically find and quantify the location of user selected image details such as natural test article features or passive fiducials that have been applied to cooperative test articles. This image position data is converted into real world coordinates and rates with user specified information such as the image scale and frame rate. Though tracking methods such as correlation algorithms are typically robust by nature, the accuracy and suitability of each TrackEye tracking algorithm is in general unknown even under good imaging conditions. The challenges of optimal algorithm selection and algorithm performance/measurement uncertainty are even more significant for long range tracking of high-speed targets where temporally varying atmospheric effects degrade the imagery. This paper will present the preliminary results from a controlled test sequence used to characterize the performance of the TrackEye tracking algorithm suite.

  18. TrackEye tracking algorithm characterization.

    SciTech Connect

    Reed, Jack W.; Shields, Rob W; Valley, Michael T.

    2004-08-01

    TrackEye is a film digitization and target tracking system that offers the potential for quantitatively measuring the dynamic state variables (e.g., absolute and relative position, orientation, linear and angular velocity/acceleration, spin rate, trajectory, angle of attack, etc.) for moving objects using captured single or dual view image sequences. At the heart of the system is a set of tracking algorithms that automatically find and quantify the location of user selected image details such as natural test article features or passive fiducials that have been applied to cooperative test articles. This image position data is converted into real world coordinates and rates with user specified information such as the image scale and frame rate. Though tracking methods such as correlation algorithms are typically robust by nature, the accuracy and suitability of each TrackEye tracking algorithm is in general unknown even under good imaging conditions. The challenges of optimal algorithm selection and algorithm performance/measurement uncertainty are even more significant for long range tracking of high-speed targets where temporally varying atmospheric effects degrade the imagery. This paper will present the preliminary results from a controlled test sequence used to characterize the performance of the TrackEye tracking algorithm suite.

  19. Internal deformation of the subducted Nazca slab inferred from seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline M.; Long, Maureen D.; Scire, Alissa; Beck, Susan L.; Wagner, Lara S.; Zandt, George; Tavera, Hernando

    2016-01-01

    Within oceanic lithosphere a fossilized fabric is often preserved originating from the time of plate formation. Such fabric is thought to form at the mid-ocean ridge when olivine crystals align with the direction of plate spreading. It is unclear, however, whether this fossil fabric is preserved within slabs during subduction or overprinted by subduction-induced deformation. The alignment of olivine crystals, such as within fossil fabrics, can generate anisotropy that is sensed by passing seismic waves. Seismic anisotropy is therefore a useful tool for investigating the dynamics of subduction zones, but it has so far proved difficult to observe the anisotropic properties of the subducted slab itself. Here we analyse seismic anisotropy in the subducted Nazca slab beneath Peru and find that the fast direction of seismic wave propagation aligns with the contours of the slab. We use numerical modelling to simulate the olivine fabric created at the mid-ocean ridge, but find it is inconsistent with our observations of seismic anisotropy in the subducted Nazca slab. Instead we find that an orientation of the olivine crystal fast axes aligned parallel to the strike of the slab provides the best fit, consistent with along-strike extension induced by flattening of the slab during subduction (A. Kumar et al., manuscript in preparation). We conclude that the fossil fabric has been overprinted during subduction and that the Nazca slab must therefore be sufficiently weak to undergo internal deformation.

  20. Two-Pass, Diode-Pumped Nd:YAG Slab Laser Head

    NASA Technical Reports Server (NTRS)

    Coyle, D. Barry

    1992-01-01

    Neodymium/yttrium aluminum garnet (Nd:YAG) ring-laser head designed for compactness, simplicity, and increased efficiency for side pumping by diode lasers. Laser head includes two linear arrays of diode lasers, two fused-silica collimating rods, and Nd:YAG slab. Slab mounted on finned copper block, providing good thermal dissipation.