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Many state, county, and local agencies are faced with deteriorating bridge infrastructure composed of a large percentage of relatively short to medium span bridges. In many cases, these older structures are rolled or welded longitudinal steel stringers acting compositely with a reinforced concrete deck. Most of these bridges, although still in service, need some level of strengthening due to increases in legal live loads or loss of capacity due to deterioration. Although these bridges are overstressed in most instances, they do not warrant replacement; thus, structurally efficient but cost-effective means of strengthening needs to be employed. In the past, the use of bolted steel cover plates or angles was a common retrofit option for strengthening such bridges. However, the time and labor involved to attach such a strengthening system can sometimes be prohibitive. This project was funded through the Federal Highway Administration's Innovative Bridge Research and Construction program. The goal is to retrofit an existing structurally deficient, three-span continuous steel stringer bridge using an innovative technique that involves the application of post-tensioning forces; the post-tensioning forces were applied using fiber reinforced polymer post-tensioning bars. When compared to other strengthening methods, the use of carbon fiber reinforced polymer composite materials is very appealing in that they are highly resistant to corrosion, have a low weight, and have a high tensile strength. Before the post-tensioning system was installed, a diagnostic load test was conducted on the subject bridge to establish a baseline behavior of the unstrengthened bridge. During the process of installing the post-tensioning hardware and stressing the system, both the bridge and the post-tensioning system were monitored. The installation of the hardware was followed by a follow-up diagnostic load test to assess the effectiveness of the post-tensioning strengthening system. Additional load tests were performed over a period of two years to identify any changes in the strengthening system with time. Laboratory testing of several typical carbon fiber reinforced polymer bar specimens was also conducted to more thoroughly understand their behavior. This report documents the design, installation, and field testing of the strengthening system and bridge.
The repair of deteriorated, damaged and substandard civil infrastructures has become one of the most important issues for the civil engineer worldwide. This important book discusses the use of externally-bonded fibre-reinforced polymer (FRP) composites to strengthen, rehabilitate and retrofit civil engineering structures, covering such aspects as material behaviour, structural design and quality assurance. The first three chapters of the book review structurally-deficient civil engineering infrastructure, including concrete, metallic, masonry and timber structures. FRP composites used in rehabilitation and surface preparation of the component materials are also reviewed. The next four chapters deal with the design of FRP systems for the flexural and shear strengthening of reinforced concrete (RC) beams and the strengthening of RC columns. The following two chapters examine the strengthening of metallic and masonry structures with FRP composites. The last four chapters of the book are devoted to practical considerations in the flexural strengthening of beams with unstressed and prestressed FRP plates, durability of externally bonded FRP composite systems, quality assurance and control, maintenance, repair, and case studies. With its distinguished editors and international team of contributors, Strengthening and rehabilitation of civil infrastructures using fibre-reinforced polymer (FRP) composites is a valuable reference guide for engineers, scientists and technical personnel in civil and structural engineering working on the rehabilitation and strengthening of the civil infrastructure. Reviews the use of fibre-reinforced polymer (FRP) composites in structurally damaged and sub-standard civil engineering structures Examines the role and benefits of fibre-reinforced polymer (FRP) composites in different types of structures such as masonry and metallic strengthening Covers practical considerations including material behaviour, structural design and quality assurance
This report presents the details of research study on the use of Carbon Fiber Reinforced Polymers (CFRP) sheets to strengthen the Pre-stressed concrete TxDOT Tx-28 bridge girders in flexure and shear. Four girders were subjected to destructive test in this research. First girder as control specimen without any CFRP applied on it, Second and third girders were flexural strengthened for one and two layers of CFRP and the forth girder is shear strengthened with one layer CFRP. Experimental phases along with the comparison of test results in terms of flexural and shear capacity of bridge girders, strains and deflections are discussed with reference to control and CFRP strengthened specimens. The CFRP strengthening was designed based on the ACI 440 recommendations. The report details the installation process as well as a load-testing program utilized to assess the effectiveness of the strengthening system. The installation process was found to be rapid and simple. The bonding between the FRP installed and the concrete surface is verified by pull off test. Adding to this in order to monitor the strain and displacement, we had strain gages on the surface of FRP at the tension and compression zones of the girders and two transducers near the supports and two more transducers at the center. Good agreement was obtained with the experimental and theoretical findings of strength, strains and deflections. Overall, the strengthened girders behaved as predicted when subjected to the design loads. The detailed design of FRP strengthening is system is reported in this report.
The use of fiber-reinforced polymer (FRP) composite materials has had a dramatic impact on civil engineering techniques over the past three decades. FRPs are an ideal material for structural applications where high strength-to-weight and stiffness-to-weight ratios are required. Developments in fiber-reinforced polymer (FRP) composites for civil engineering outlines the latest developments in fiber-reinforced polymer (FRP) composites and their applications in civil engineering. Part one outlines the general developments of fiber-reinforced polymer (FRP) use, reviewing recent advancements in the design and processing techniques of composite materials. Part two outlines particular types of fiber-reinforced polymers and covers their use in a wide range of civil engineering and structural applications, including their use in disaster-resistant buildings, strengthening steel structures and bridge superstructures. With its distinguished editor and international team of contributors, Developments in fiber-reinforced polymer (FRP) composites for civil engineering is an essential text for researchers and engineers in the field of civil engineering and industries such as bridge and building construction. Outlines the latest developments in fiber-reinforced polymer composites and their applications in civil engineering Reviews recent advancements in the design and processing techniques of composite materials Covers the use of particular types of fiber-reinforced polymers in a wide range of civil engineering and structural applications
This book presents the analysis and design of fiber-reinforced polymer (FRP) bridge decks, which have been increasingly implemented in rehabilitation projects and new construction due to their reduced weight, lower maintenance costs, and enhanced durability. It compiles the necessary information, based primarily on research by the authors, to facilitate the development of standards and guidelines for using FRP decks in bridge designs. The book combines analytical models, numerical analyses, and experimental investigations, which can be applied to various design formulations. It also, for the first time, offers a complete set of design guidelines.
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.
The in situ rehabilitation or upgrading of reinforced concrete members using bonded steel plates is an effective, convenient and economic method of improving structural performance. However, disadvantages inherent in the use of steel have stimulated research into the possibility of using fibre reinforced polymer (FRP) materials in its place, providing a non-corrosive, more versatile strengthening system. This book presents a detailed study of the flexural strengthening of reinforced and prestressed concrete members using fibre reinforces polymer composite plates. It is based to a large extent on material developed or provided by the consortium which studied the technology of plate bonding to upgrade structural units using carbon fibre / polymer composite materials. The research and trial tests were undertaken as part of the ROBUST project, one of several ventures in the UK Government's DTI-LINK Structural Composites Programme. The book has been designed for practising structural and civil engineers seeking to understand the principles and design technology of plate bonding, and for final year undergraduate and postgraduate engineers studying the principles of highway and bridge engineering and structural engineering. Detailed study of the flexural strengthening of reinforced and prestressed concrete members using fibre reinforced polymer composites Contains in-depth case histories
Most of the recent highway bridges built in California have post-tensioned, cast-in-place, concrete box-girder superstructures rigidly connected to bridge columns. However, methods provided in the current (2007 and 2010) AASHTO LRFD Bridge Design Specifications for estimating long-term prestress losses are essentially based on research focused on pretensioned members and are not adequate for post-tensioned bridge girders. Long-term prestress losses in post-tensioned members are expected to be smaller than those in pretensioned members due to two main factors. One is the higher amount of mild reinforcement present in posttensioned bridge girders, which provides a higher restraint to the creep and shrinkage of concrete, and the other is that post-tensioning could take place a long while after the girders have been cast and the concrete has reached a more mature age, which results in a lower creep. The main objectives of the study reported here were to assess the accuracy of the long-term prestress-loss estimation methods given in the current AASHTO LRFD Specifications for post-tensioned bridge girders, and to develop more suitable analysis methods for these members.