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Showing 1 to 20 of 81 for “"prestress"”.
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Time-Dependent Prestress Losses in Pretensioned Concrete Construction
Made available in DSpace on 2014-12-13T19:31:17Z (GMT). No. of bitstreams: 1 7524318.pdf: 5500784 bytes, checksum: b7563a77f1dac06b42b69502c58ce938 (MD5) Previous issue date: 1975
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Refined Evaluation of Effective Prestress in the Varina-Enon Bridge
… of the bridge. Particular focus has been put on prestress losses which have a significant impact on the strength and serviceability of the bridge. Previous work has been conducted to monitor the behavior of the bridge and to back-calculate effective prestress. This was done using field data from …
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A Mineralocorticoid-Dependent Effect of Prestress on Avoidance Responding in Rats
… avoidance responses if they were given a brief prestress 30 min before the test than if they were undisturbed before the test. This effect of prestress occurred in normal rats whether foot shock, air blast, or simple handling served as the prestress. The effect did not, however, occur in …
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Top Strand Effect and Evaluation of Effective Prestress in Prestressed Concrete Beams
… orientation on bond strength in pretensioned prestressed concrete members. The "top strand effect" was evaluated through transfer and development length tests of prestressed concrete beams. Eight beams were cast with normal orientation, while four beams were cast with inverted orientation so …
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Investigation of Long-Term Prestress Losses in Pretensioned High Performance Concrete Girders
Effective determination of long-term prestress losses is important in the design of prestressed concrete bridges. Over-predicting prestress losses results in an overly conservative design for service load stresses, and under-predicting prestress losses, can result in cracking at service loads. …
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Effects of Prestress Level and Bond on the Behavior of Prestressed Concrete Pavements
Prestressing has long been recognized as a viable method of increasing the flexural capacity of concrete. The early application of prestressed concrete pavements was in the mid 1940's but its progress was slow compared with the other types of rigid pavements. Performance of the early build …
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Computing traction forces, intracellular prestress, and intracellular modulus distribution from fluorescence microscopy image stacks
Cell modulus and prestress are important determinants of cell behavior. This study creates new software tools to compute the modulus and prestress distribution within a living cell. As input, we have a sequence of images of a cell plated on a substrate with fluorescently labeled fibronectin dots. …
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Evaluation of the residual prestress force in aged railway concrete sleepers considered for reuse
… of a conventional railway track is the prestressed concrete sleeper. In South Africa, these sleepers are designed to last for 40 years, and their replacement plan is aligned with their design life. Given the desire to extend the useful life of sleepers, aged concrete sleepers are often …
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Torsion of a thin rectangular beam with axial prestress and ends constrained from warping
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.
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Transfer Length, Development Length, Flexural Strength, and Prestress Loss Evaluation in Pretensioned Self-Consolidating Concrete Members
… development lengths, and flexural strengths of prestressed members. Three small rectangular members were made, two cast with SCC mixes and one cast with a conventional mix, to determine the transfer length of each mix. Transfer lengths of both ends of each member were determined by measuring the …
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Effective Prestress Evaluation of the Varina-Enon Bridge Using a Long-Term Monitoring System and Finite Element Model
… 2012 that prompted concerns regarding long-term prestress losses in the structure. Prestress losses could impact the future performance, serviceability, and flexural strength of the bridge. Accurately quantifying prestress losses is critical for understanding and maintaining the structure during …
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Long-Term Monitoring and Evaluation of the Varina-Enon Bridge
… of a structure, the precise calculation of the prestress losses is very important. In post-tensioned structures, the prestress losses due to creep and shrinkage can cause serviceability issues and can reduce flexural capacity. The Varina-Enon Bridge is a cable-stayed, precast, segmental, …
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Investigation of Transfer Length, Development Length, Flexural Strength and Prestress Loss Trend in Fully Bonded High Strength Lightweight Prestressed Girders
… conducted on two AASHTO Type IV HSLWC prestressed girders, resulted in an average transfer length of 17 inches, well below the AASHTO and ACI guidance. Two girders composed of HSLWC AASHTO Type II girders and a 48" x 8" normal weight 4000-psi concrete deck were produced. The HSLWC Type …
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Shear Strength of a PCBT-53 Girder Fabricated with Lightweight, Self-Consolidating Concrete
… The second goal was to monitor the change in prestress over time (and hence the prestress loss) occurring in the PCBT-53 girder. Prestress losses were experimentally measured by vibrating wire gages (measured changes in concrete strain) and flexural load testing. Measured prestress losses were …
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Investigation of the Time-Dependent Longitudinal Flexural Behavior of the Varina-Enon Bridge
… bridge construction. Over time, the force in the prestressing strands is reduced by delayed strains in the concrete. The accurate estimation of this prestress loss is vital for making good decisions about the remaining capacity of a structure and the infrastructure system at large. The Varina-Enon …
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The effects of various levels of compressive stress fields on the deterioration rate and microcracking of plain concrete subjected to freezing and thawing
… rate in the lateral direction of the uniaxially prestressed members subjected to the deep-seated type of freeze-thaw damage increased as the level of the compressive stress field increased. 2. Under all levels of uniaxial compression, cracks formed parallel to the direction of the applied stress …
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Structural Performance of High Strength Lightweight Concrete Pretensioned Bridge Girders
The use of high compressive strengths in prestressed bridge girders can lower costs by allowing for longer spans, increased girder spacing, and smaller cross-sections. If high strength lightweight concrete (HSLWC) is used, these advantages are further enhanced due to the corresponding reduction in …
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Using Maturity to Predict Girder Camber
… was to determine if differential camber of prestressed concrete girders could be reduced by accurate prediction of initial camber at release of prestress. Maturity at prestress transfer was used to calculate modulus of elasticity for predicting camber at release. The research consists of a …
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Partially prestressed concrete internal square panel
… floor structure, under the influence of various prestressing tendon arrangements. The prestressing effects are studied with the help of a finite element package (PAFEC), representing the prestressing forces by equivalent vertical loads. From a variety of possible spacing arrangements, the …
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