Structural Performance Of Texas U Beams At Prestress Transfer And Under Shear Critical Loads
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Structural Performance Of Texas U Beams At Prestress Transfer And Under Shear Critical Loads
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Author : Catherine Grace Hovell
language : en
Publisher:
Release Date : 2011
Structural Performance Of Texas U Beams At Prestress Transfer And Under Shear Critical Loads written by Catherine Grace Hovell and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
The Texas U-Beam standard designs were released in the 1990's and have been used increasingly in bridges across the state since. While prototypes of the 54-in. deep prestressed concrete beam were built during the design phase, no full-scale load tests were performed. This study of the U-Beam had five goals: (i) determine the magnitude and location of stresses induced in reinforcing bars in the end region of the beam at prestress transfer, (ii) measure concrete curing temperatures in square and skewed end blocks, (iii) establish the vertical shear capacity of the standard section, (iv) evaluate interaction between behavior at prestress transfer and performance under shear-critical loads, and (v) identify design and detailing improvements and make recommendations. Eight full-scale Texas U54 prestressed concrete beams were fabricated to achieve these goals. Load testing of the first four of these beams revealed a critical weakness along the bottom flange-to-web interface of the beam. The weakness caused failures that occurred at loads well below the calculated shear capacity. Given the horizontal sliding observed, the failure mode was called horizontal shear. The next two beams were fabricated to test three modifications to the end-region design, two of which were deemed successful. The final two beam sections tested contained the recommended new standard reinforcement and concrete geometry. A method to evaluate the horizontal shear demand on and capacity of the bottom flange-to-web interface of prestressed concrete beams was developed. The calculations were formulated using the theories of beam bending and shear friction. This method was calibrated and verified using the U-Beam test data, a series of small-scale specimens, and results of shear tests in the literature. Stresses induced in reinforcing bars at prestress transfer met expectations set by existing codified equations. No modifications to the current U-Beam standard design are needed to manage these stresses. The induced stresses did not influence vertical shear behavior, and no interaction between the two is believed to exist for U-Beams. This dissertation contains the specifics of the beams tested and the data collected, and provides the details of recommended changes to the Texas U-Beam standard drawings.
Performance Of Precast Prestressed Concrete I Girders Employing 0 7 In Diameter Prestressing Strands Under Shear Critical Loading Conditions
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Author : Alex Tyler Katz
language : en
Publisher:
Release Date : 2016
Performance Of Precast Prestressed Concrete I Girders Employing 0 7 In Diameter Prestressing Strands Under Shear Critical Loading Conditions written by Alex Tyler Katz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
The majority of precast, pretensioned concrete elements are currently fabricated using 0.5- or 0.6-in. diameter prestressing strands. However, in recent years, potential benefits such as reduced fabrication costs and extended span capabilities have led to an interest in using larger-diameter 0.7-in. strands in the pretensioning industry. Such an increase in the diameter of strands might impact the shear strength of pretensioned girders due to the possibility of atypical failure modes that are not considered in current design provisions. An experimental program was conducted to study the effects of using 0.7-in. prestressing strands on the performance of precast, prestressed concrete I-girders under shear-critical loading conditions. Four full-scale pretensioned Texas bulb-tee girders (Tx-girders) employing 0.7-in. strands were fabricated and tested at Ferguson Structural Engineering Laboratory at the University of Texas at Austin. The mild steel reinforcement in the specimens was detailed according to standard drawings by the Texas Department of Transportation for girders employing 0.6-in. strands. The test program investigated the shear failure in girders with different concrete release strengths, overall member depths, shear span-to-depth ratios, and strand patterns. Analysis of the results revealed clear signs of atypical shear failure mechanisms in all specimens. Considerable strand slip was recorded at both ends of the specimens prior to peak load. In three of the specimens, the shear failure resulted in prominent horizontal cracks at the interface between the web and the bottom flange. However, all specimens demonstrated significant diagonal cracking prior to failure. Yielding of the stirrups was also confirmed in all specimens, indicating a shear-tension failure. The capacities of all specimens were conservatively estimated using the general procedure in AASHTO LRFD Bridge Design Specifications and the detailed method in ACI 318-14. The findings of this study reveal no concerns regarding the performance of existing design provisions in predicting the shear strength of Tx-girders that employ 0.7-in. diameter prestressing strands.
Shear Behavior Of Prestressed Concrete U Beams
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Author : Andrew Michael Moore
language : en
Publisher:
Release Date : 2010
Shear Behavior Of Prestressed Concrete U Beams written by Andrew Michael Moore and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
An experimental study was conducted at the Ferguson Structural Engineering Laboratory in order to investigate the shear behavior of 54-inch deep prestressed concrete U-beams. The primary goal of this research was to improve the design and detailing of the skewed end-blocks commonly used in these beams. As U-beams had been in service for several decades without incident, it was anticipated that there would be little need for change in the design, and the findings of the research would involve a slight tweaking to improve the overall performance. Unfortunately, during the first phase of shear testing (testing of the current design standard) it was found that the U-beam was not reaching the code calculated shear capacity. During this phase of testing the premature failure mechanism was isolated as the breakdown of the web-to-flange interface in the end region of the girder. Therefore, the second phase of testing sought to prevent the breakdown of this boundary by three options: (1) increasing the web width while maintaining current levels of mild reinforcement, (2) increasing the web width while also increasing the amount of reinforcement crossing the web-to-flange boundary, or (3) by increasing the amount of reinforcement at the boundary while maintaining the current web width. Two acceptable solutions to the premature failure method were developed and tested during this phase both of which included an increase in the amount of mild reinforcement crossing the web-to-flange interface (with and without an increase in web width). The research into refining of these new details is ongoing as part of the Texas Department of Transportation's Research Project number 0-5831.
Shear Behavior Of Steel Fiber Reinforced Prestressed Concrete Beams Without Shear Reinforcement
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Author : Jae-Sung Cho
language : en
Publisher:
Release Date : 2011
Shear Behavior Of Steel Fiber Reinforced Prestressed Concrete Beams Without Shear Reinforcement written by Jae-Sung Cho and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Fiber-reinforced concrete categories.
The ACI 318-08 building code allows to use the steel fiber reinforcement as alternative shear reinforcement with satisfying certain criteria when a beam is required minimum shear reinforcement. However, this provision applies to a nonprestressed and prestressed concrete beam such that it could be conservative since the shear strength of prestressed concrete beam is generally enhanced due to the prestressing force. This is due partially to the fact that the provision has been accepted based on researches, mostly conducted in nonprestressed concrete beam. Most of experiments conducted for prestressed concrete beam in small scale tests, with a height of specimens were less than 10 in. A larger scale of experiment is required due to concerns of size effect. In addition, in order to evaluate the qualification of a Steel Fiber Reinforced Concrete (SFRC) mixture used for structural applications, such as increasing shear resistance, a material evaluation method is essential. Currently ASTM or ACI Committee 544 (Fiber-Reinforced Concrete) does not recommend any standardized test method for evaluating shear performance of a particular SFRC material. This study addresses the research gaps described above by testing large-scale Steel Fiber Reinforced Prestressed Concrete (SFRPC) beams as well as developing a simple laboratory test techniques. A total 13 simply-supported beams for large-scale test with a shear span to effective depth ratio of 3.0 and a height of 24 in. were subjected to monotonically-increased, concentrated load. The test parameters were mainly included compressive strength, volume fraction of steel fibers, compressive reinforcement ratio. The results of large-scale test showed that the use of hooked steel fibers in a volume fraction greater than or equal to 0.50% volume fraction of steel fibers (67 lb per cubic yard), which is less than requirement by ACI 318-08 (0.75%, 100 lb per cubic yard), led to substantial enhancement of shear behaviors including the first cracking, the ultimate, and ductility. High compressive strength of SFRC, greater than 9000 psi, which is higher than ACI 318-08 requirement (less than 6000 psi) could be used as well. However, there was no significant effect from compressive reinforcement ratio. A simply shear test method for SFRC was proposed in this study. The test apparatus is almost exactly the same as the conventional ASTM bending test with only minor modification, in addition, it could simulate a pure shear stress by adjusting loading and support positions. By introducing a proper reinforcement for bending stress, it was possible to evaluate shear performance of SFRC with clear and uncomplicated shear stress field in the critical section.
Pretensioned Box Beams
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Author : Alejandro Raul Avendaño Valderrama
language : en
Publisher:
Release Date : 2011
Pretensioned Box Beams written by Alejandro Raul Avendaño Valderrama and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Pretensioned concrete box beams have been used in highway bridges for more than half a century. Due to their geometry, they have often been used as a viable alternative to the classic I-shaped girders. Box beams are highly effective in cases where speed of construction is a priority. However, the detailing and design of box beams are more complicated than that of I-shaped girders. The flow of forces at the beam's end blocks must be understood in order to detail reinforcement adequately. The following were the objectives of this research study: (i) quantify the demands placed on box beam end blocks upon prestress transfer, (ii) characterize the demands placed on box beam end blocks upon the application of superimposed loads, (iii) evaluate the effects of alternative void geometries at skewed ends of box beams on curing temperatures, (iv) based on the knowledge gained in (i), (ii) and (iii), improve the box beam end blocks, (v) test the improved end block under worst case scenario demands at prestress transfer and under extreme loading conditions, and (vi) validate currently used shear strength design methodologies in their application to pretensioned box beams. In order to achieve these objectives, an experimental program was conducted. The experimental program included the load testing of ten 4B28 and five 5B40 box beams, for a total of twenty nine load tests. The influence of several factors that distinguish box beam behavior from the better-understood I-shaped girder behavior was studied. Additionally, the experimental program included the fabrication, instrumentation and early-age behavior study of five 5B40 box beams. The first three beams were used to vii assess the behavior of box beams fabricated with the current TxDOT standard details (from December 2006). The fourth beam incorporated modifications to the standard reinforcement details based on the observations made through the study of the first three 5B40 box beams. The last specimen corresponded to a new box beam cross section (5XB40) optimized to be used in a spread-box beams configuration.
Pretensioned Box Beams
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Author : Alejandro Avendaño
language : en
Publisher:
Release Date : 2013
Pretensioned Box Beams written by Alejandro Avendaño and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Box beams categories.
Pretensioned concrete box beams have been used in highway bridges for more than half a century. Due to their geometry, they have often been used as a viable alternative to the classic I-shaped girders. Box beams are highly effective in cases where speed of construction is a priority. However, the detailing and design of box beams are more complicated than that of I-shaped girders. The flow of forces at the beam's end blocks must be understood in order to detail reinforcement adequately. The following were the objectives of this research study: (1) quantify the demands placed on box beam end blocks upon prestress transfer, (2) characterize the demands placed on box beam end blocks upon the application of superimposed loads, (3) evaluate the effects of alternative void geometries at skewed ends of box beams on curing temperatures, (4) based on the knowledge gained, improve the box beam end blocks, (5) test the improved end block under worst case scenario demands at prestress transfer and under extreme loading conditions, and (6) validate currently used shear strength design methodologies in their application to pretensioned box beams. In order to achieve these objectives, an experimental program was conducted. The experimental program included the load testing of ten 4B28 and five 5B40 box beams, for a total of twenty nine load tests. The influence of several factors that distinguish box beam behavior from the better-understood I-shaped girder behavior was studied. Additionally, the experimental program included the fabrication, instrumentation and early-age behavior study of five 5B40 box beams. The first three beams were used to assess the behavior of box beams fabricated with the current Texas Department of Transportation (TxDOT) standard details (from December 2006). The fourth beam incorporated modifications to the standard reinforcement details based on the observations made through the study of the first three 5B40 box beams. The last specimen corresponded to a new box beam cross section (5XB40) optimized to be used in a spread-box beams configuration.
Time Dependent Deformation Behavior Of Prestressed High Performance Concrete Bridge Beams
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Author : Kenneth Arlan Byle
language : en
Publisher:
Release Date : 1997
Time Dependent Deformation Behavior Of Prestressed High Performance Concrete Bridge Beams written by Kenneth Arlan Byle and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with categories.
Dissertation Abstracts International
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Author :
language : en
Publisher:
Release Date : 2004
Dissertation Abstracts International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Dissertations, Academic categories.
Construction And Design Of Prestressed Concrete Segmental Bridges
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Author : Walter Podolny
language : en
Publisher: Wiley-Interscience
Release Date : 1982-05-11
Construction And Design Of Prestressed Concrete Segmental Bridges written by Walter Podolny and has been published by Wiley-Interscience this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982-05-11 with Technology & Engineering categories.
An extensively illustrated handbook summarizing the current state of the art of design and construction methods for all types of segmental bridges. Covers construction methodology, design techniques, economics, and erection of girder type bridges; arch, rigid frame, and truss bridges; cable-stayed bridges; and railroad bridges.
Reinforced Concrete Deep Beams
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Author : F K Kong
language : en
Publisher: CRC Press
Release Date : 1991-05-01
Reinforced Concrete Deep Beams written by F K Kong and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991-05-01 with Architecture categories.
The contents of this book have been chosen with the following main aims: to review the present coverage of the major design codes and the CIRIA guide, and to explain the fundamental behaviour of deep beams; to provide information on design topics which are inadequately covered by the current codes and design manuals; and to give authoritative revie