Download or read book Improved Shear Reinforcement Details for End Regions of Prestressed Concrete Bridge Girders written by James Harmon Allen and published by . This book was released on 1997 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improved Shear Reinforcement Details for the End regions of Prestressed Concrete Bridge Girders written by John Jacob and published by . This book was released on 1998 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flocculation Treatment Best Management Practices for Construction Water Discharges written by Brian Thomas Mathys and published by . This book was released on 2014 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Minnesota Department of Transportation has typically used epoxy-coated, straight-legged stirrups anchored in the tension zone as transverse reinforcement in prestressed concrete bridge girders. This configuration is readily placed after stressing the prestressing strands. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) specifications require stirrups with bent legs that encompass the longitudinal reinforcement to properly anchor the stirrups. Such a configuration is specified to provide mechanical anchorage to the stirrup, ensuring that it will be able to develop its yield strength with a short anchorage length to resist shear within the web of the girder. AASHTO specifications for anchoring transverse reinforcement are the same for reinforced and prestressed concrete; however, in the case of prestressed concrete bridge girders, there are a number of differences that serve to enhance the anchorage of the transverse reinforcement, thereby enabling the straight bar detail. These include the precompression in the bottom flange of the girder in regions of web-shear cracking. In addition, the stirrup legs are usually embedded within a bottom flange that contains longitudinal strands outside the stirrups. The increased concrete cover over the stirrups provided by the bottom flange and the resistance to vertical splitting cracks along the legs of the stirrups provided by the longitudinal prestressing reinforcement outside the stirrups help to enhance the straight-legged anchorage in both regions of web-shear cracking and flexure-shear cracking. A two-phase experimental program was conducted to investigate the anchorage of straight-legged, epoxy-coated stirrups, which included bar pullout tests performed on 13 subassemblage specimens that represented the bottom flanges of prestressed concrete girders, to determine the effectiveness of straight-legged stirrup anchorage in developing yield strains. Additionally, four girder ends were cast with straight-legged stirrup anchorage details and tested in flexure-shear and web-shear. The straight leg stirrup anchorage detail was determined to be acceptable for Minnesota Department of Transportation (MnDOT) M and MN shaped girders as nominal shear capacities were exceeded and yield strains were measured in the stirrups prior to failure during each of the tests.

Download or read book Computational Modeling of Prestress Transfer End region Cracks and Shear Behavior in Prestressed Concrete I girders Employing Large diameter Strands written by Roya Alirezaei Abyaneh and published by . This book was released on 2016 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prestressed concrete girders are commonly fabricated with 0.5-in. (12.7-mm) or 0.6-in. (15.2-mm) diameter prestressing strands. Recent interest in the use of larger (0.7-in. (17.8-mm) diameter) strands has been driven by potential benefits associated with reduction of the required number of strands and fabrication time, or potential increases in the workable range of prestressed concrete girders (i.e., greater capacities and span capabilities). A limited number of experiments on full-scale specimens with 0.7-in. (17.8-mm) diameter strands have shown that the load-carrying capacity and strand transfer length of specimens with 0.7-in. (17.8-mm) diameter strands can be conservatively estimated using existing AASHTO LRFD provisions. However, performance at prestress transfer requires further investigation to ensure that application of the strands with standard 2-in. (50-mm) spacing and conventional concrete release strength does not increase the end-region cracking that is characteristic of prestressed girders. It must be verified that the development of such cracks does not stimulate anchorage-driven or premature shear failures prior to yielding of the shear reinforcement. Previous research lacks in monitoring of reinforcement stresses and evaluation of end-region cracking which has long been a durability concern. A reliable finite element model that captures the behavior of the specimen at prestress transfer with consideration of performance from construction stages, over the course of the service life, and up to the ultimate limit state can provide key insight into the suitability of using of 0.7-in. (17.8-mm) diameter strands. Further, it could serve as an economical tool for the investigation and proposal of efficient end-region reinforcing details to reduce concrete cracking and enhance durability. Finite element analyses of prestressed I-girder end-regions encompassing cracking and long-term creep- and shrinkage-induced damage, especially in girders fabricated with large diameter strands, have been limited. This research program assessed the limitations of 0.7-in. (17.8-mm) diameter strands at prestress transfer up to limit state response and investigated measures for enhancing the serviceability of the girders through finite element analyses using the commercial software, ATENA 3D. The finite element study was complemented with a full-scale experimental program which was used to validate the numerical results. This paper lays out a validated procedure for modeling the construction stages of prestressed girders and load testing. The model was then used as a tool for investigating alternative end-region reinforcement details for improved end-region serviceability. The most promising options are presented for consideration in further experimental studies and future implementation

Download or read book Evaluation and Repair Procedures for Precast prestressed Concrete Girders with Longitudinal Cracking in the Web written by Maher K. Tadros and published by Transportation Research Board. This book was released on 2010 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report establishes a user's manual for the acceptance, repair, or rejection of precast/prestressed concrete girders with longitudinal web cracking. The report also proposes revisions to the AASHTO LRFD Bridge Design Specifications and provides recommendations to develop improved crack control reinforcement details for use in new girders. The material in this report will be of immediate interest to bridge engineers.

Download or read book Laboratory Tests of Two span Prestressed Reinforced Concrete Bridge Girders Constructed from Three Long Segments written by William Leo Gamble and published by . This book was released on 1979 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tests of two prestressed concrete composite bridge girders which were continuous over two spans are reported. Both were I-section girders with cast-in-place decks, and had spans of about 37 ft (11 m), and were approximately 1/3 scale models of structures spanning 125 ft (38 m). Each girder was constructed from three segments which were joined end-to-end by cast-in-place concrete splices. Modell was post-tensioned after erection of the girders and casting of the deck and splice concrete. The two end segments, each supported on the final abutments and on temporary supports located about 1/3 of the span from the central pier, were pretensioned for their dead loads plus the deck concrete. The central segment, which was supported on the central pier of the structure plus the two temporary supports was precast reinforced concrete, plus a small amount of pre= tensioned reinforcement. Model 2 was externally similar, but was not post-tensioned. The segments were pretensioned for the final moments, and were joined by splicing reinforcing bars which extended into the splice region. Both structures were subjected to a series of loadings to the service load, design ultimate, and high over-load levels. Both had capacities which were significantly higher than the design ultimate values. The capacities were generally predictable on the basis of flexural strength calculations, and shear did not cause major problems. Joint details in Modell lead to difficulties in two tests, and this aspect of the design is discussed in detail.

Download or read book Shear Capacity of in Service Prestressed Concrete Bridge Girders written by Paul Barr and published by . This book was released on 2010 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The design procedure to calculate the shear capacity of bridge girders that was used forty years ago is very different than those procedures that are recommended in the current AASHTO LRFD Specifications. As a result, many bridge girders that were built forty years ago do not meet current design standards, and in some cases warrant replacement due to insufficient calculated shear capacity. However despite this insufficient calculated capacity, these bridge girders have been found to function adequately in service with minimal signs of distress. The objective of this research was to investigate the actual in service capacity of prestressed concrete girders that have been in service over an extended period of time.

Download or read book Carbon Fiber Shear Reinforcement for Prestressed Bridge Girders written by John C. Ward and published by . This book was released on 2017 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Corrosion of reinforcing steel reduces life spans of bridges throughout the United States; therefore, using non-corroding carbon fiber reinforced polymer (CFRP) reinforcement is seen as a way to increase service life. The use of CFRP as the flexural reinforcement in bridge girders has been extensively studied. However, CFRP transverse reinforcement has not been investigated as rigorously, and many of those studies have focused on carbon fiber composite cable (CFCC®) stirrups. The use of C-Grid® or NEFMACTM grid as options for transverse reinforcing has not been previously investigated. This testing program first determined the mechanical properties of C-Grid and NEFMAC grid and their respective development lengths. Five 18-ft long, 19-in deep beams were fabricated to test the C-Grid and NEFMAC, as well as conventional steel and CFCC stirrups. The beams were loaded with a single point load closer to one end of the beam to create a larger shear load for a given moment. Overall beam displacement was measured, and beams were fitted with rosettes and instrumentation to capture initiation of shear cracking. Test results were compared to theoretical shear capacities calculated using four different methods. The design method which provided the best prediction of shear strength was the AASHTO modified compression field theory, using equations for [beta] and [theta]. The manufacturer's guaranteed tensile strength should be used for design, as long as that strength is the average strength, as determined by at least five tests, reduced by three standard deviations. Shear cracks were controlled to a similar width as in beams with steel stirrups when at least two layers of grid were in place. An additional study was undertaken to determine if CFRP grids, either alone or in combination with traditional steel stirrups, could be used to control cracking in the end zones of pretensioned I-beams. Unfortunately, it was determined that, due to its low modulus, the amount of CFRP grid required to control cracking in the end zones was not economically feasible. Nevertheless, this study concluded that C-Grid and NEFMAC grid are both viable shear reinforcement options outside of the end regions. This report presents the initial recommendations for design.

Download or read book Shear Capacity of Prestressed Concrete Beams written by Brian Richard Runzel and published by . This book was released on 2007 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: The shear provisions of the American Association of State Highway and Transportation Officials bridge design code have changed significantly in recent years. The 2004 Load and Resistance Factor Design (LRFD) and 2002 Standard shear provisions for the design of prestressed concrete bridge girders typically require more shear reinforcement than the 1979 Interim shear provisions. The purpose of this research was to determine whether or not bridge girders designed according to the 1979 interim shear provisions were underdesigned for shear and develop a method to identify potentially underdesigned girders. Two shear capacity tests were performed on opposite ends of a bridge girder removed from Mn/DOT Bridge No. 73023. The stirrup spacing in the girder suggested it was designed according to the 1979 Interim shear provisions. The results from the shear tests indicated the girder was capable of holding the required shear demand because the applied shear at failure for both tests was larger than the factored shear strength required by the 2004 LRFD HL-93 and 2002 Standard HS20-44 loading. The results of a parametric study showed that girders designed using the 1979 Interim were most likely to be underdesigned for shear near the support and that the girders most likely to be underdesigned in this region had smaller length to girder spacing ratios.

Download or read book End region Behavior of Precast Prestressed Concrete I girders Employing 0 7 inch Diameter Prestressing Strands written by Jessica Lauren Salazar and published by . This book was released on 2016 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pretensioned concrete girders are currently fabricated using 0.5- or 0.6-in. diameter prestressing strands. In recent years, however, it has become of interest to employ larger-diameter 0.7-in. diameter strands to reduce the number of strands and improve the efficiency of pretensioned concrete members. Such a transition requires a considerable initial investment that needs to be justified based on the benefits obtained. Furthermore, the use of 0.7-in. strands would increase the stresses within the end-region of pretensioned elements, which could lead to undesirable cracking and impact the serviceability of the girders. The work presented in this thesis consists of 1) a comprehensive parametric investigation to evaluate the benefits and limitations of using 0.7-in. strands in pretensioned bridge girders, and 2) a full-scale experimental study to investigate the behavior of pretensioned concrete girders with 0.7-in. strands at the time of prestress transfer. The parametric investigation was accomplished by designing thousands of bridge girders with different span lengths, concrete release strengths, and transverse spacings. The results showed that the most noticeable benefit of 0.7-in. strands over 0.6-in. strands was a reduction of up to 35 percent in the number of strands. However, the difference in the total weight of prestressing steel was insignificant. Increasing the release strength of concrete, at least to 7.5 ksi, was found essential to observe benefits in design aspects other than the number of strands. The experimental investigation involved the fabrication of two Tx46 and two Tx70 specimens at the Ferguson Structural Engineering Laboratory. All specimens employed 0.7-in. strands on a 2- by 2-in. grid and the standard detailing currently used for girders with smaller-diameter strands. The observed crack widths in the specimens upon prestress transfer did not exceed those typically observed in Tx-girders with smaller-diameter strands. Therefore, the use of 0.7-in. strands does not seem to trigger a need to modify the end-region detailing in Tx-girders. However, noticeably greater bursting and spalling forces were observed in the end regions of the specimens compared to the demands predicted by AASHTO LRFD provisions. The measured 24-hour transfer length from the specimens also exceeded estimates by AASHTO LRFD and ACI 318-14 provisions.

Download or read book Design of Prestressed Concrete Girders Without End Blocks written by Rafik Y. Itani and published by . This book was released on 1986 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design Guide for Prestressed Concrete Long segment Bridge Girders written by William Leo Gamble and published by . This book was released on 1979 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shear Reinforcement Requirements for High Strength Concrete Bridge Girders written by J.A. Ramirez and published by . This book was released on 2005-07-15 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design of FRP Systems for Strengthening Concrete Girders in Shear written by Abdeldjelil Belarbi and published by Transportation Research Board. This book was released on 2011 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB's National Cooperative Highway Research Program (NCHRP) Report 678: Design of FRP Systems for Strengthening Concrete Girders in Shear offers suggested design guidelines for concrete girders strengthened in shear using externally bonded Fiber-Reinforced Polymer (FRP) systems. The guidelines address the strengthening schemes and application of the FRP systems and their contribution to shear capacity of reinforced and prestressed concrete girders. The guidelines are supplemented by design examples to illustrate their use for concrete beams strengthened with different FRP systems. Appendix A of NCHRP Report 678, which contains the research agency's final report, provides further elaboration on the work performed in this project. Appendix A: Research Description and Findings, is only available online.

Download or read book Application of Fiber Reinforced Concrete in the End Zones of Precast Prestressed Concrete Bridge Girders written by Nur Yazdani and published by . This book was released on 2002 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transfer Development and Splice Length for Strand reinforcement in High strength Concrete written by Julio A. Ramirez and published by Transportation Research Board. This book was released on 2008 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This report documents research performed to develop recommended revisions to the AASHTO LRFD Bridge Design Specifications to extend the applicability of the transfer, development, and splice length provisions for prestressed and non-prestressed concrete members to concrete strengths greater than 10 ksi. The report details the research performed and includes recommended revisions to the AASHTO LRFD Bridge Design Specifications. The material in this report will be of immediate interest to bridge designers."--Foreword.

Download or read book Macro Synthetic Fiber Reinforcement for Improved Structural Performance of Concrete Bridge Girders written by and published by . This book was released on 2019 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: University of Florida researchers studied the use of fiber-reinforced concrete to control cracking in the end region of concrete girders.