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Carbon fiber reinforced polymer (CFRP) materials are emerging as an effective means of strengthening and rehabilitating bridges. Near surface mounting (NSM) is a newer technique for application of CFRP for retrofitting of bridge members that provides advantages over conventional strengthening techniques. The technique is still new and uncertainties remain regarding design including the influence of member proportions, flexural reinforcing steel, and CFRP spacing. Further, retrofitted girders may also be exposed to millions of cycles of loading after rehabilitation. It is not known if the effects of fatigue loading will affect the service life of the retrofitted member. To address these issues, laboratory tests were performed on eight full-size reinforced concrete girders, representative of in-situ bridge girders, to determine the performance of NSM-CFRP retrofitting for shear. Two of the specimens were exposed to fatigue loading. Results indicated that NSM-CFRP retrofitting provides significant shear capacity increases and exposure to fatigue cycling did not affect the strength or behavior of the specimens.
During the interstate expansion of the 1950s, many conventionally reinforced concrete deck girder bridges were built throughout the country. These aging bridges commonly exhibit diagonal cracking and rate inadequately for shear, thus they are candidates for shear strengthening to extend their useful life. Carbon fiber reinforced polymers (CFRP) are emerging as effective materials for strengthening and rehabilitating such bridges. Near surface mounting (NSM) is a newer technique for application of CFRP for retrofitting bridge members that provides advantages over other strengthening techniques. The technique is still new and uncertainties remain regarding strength, long-term durability, and design including the influence of member proportions, flexural reinforcing steel, and CFRP spacing. Bridge girders retrofitted with NSM-CFRP may be exposed to millions of load cycles and environmental conditions and the influence of these exposures on performance are not established. To address these issues, laboratory tests were performed on ten full-size reinforced concrete girders, representative of in-situ bridge members, to determine the performance of NSM-CFRP retrofitting for shear strengthening. One of the specimens was exposed to fatigue loading, two were subjected to environmental exposures, and one was subjected to combined environmental exposure and fatigue loading. Results indicated that NSM-CFRP retrofitting provided significant shear capacity increases, and the high-cycle fatigue and environmental exposures considered did not adversely affect the strength or behavior of the girders. Environmental exposures of some of the adhesives considered did show somewhat reduced performance; therefore, careful selection of materials is important to ensure performance over the expected lifetime. Recommendations for shear strength design with NSM-CFRP are made.
During the interstate expansion of the 1950s, many conventionally reinforced concrete deck girder bridges were built throughout the country. These aging bridges commonly exhibit diagonal cracking and rate inadequately for shear, thus they are candidates for shear strengthening to extend their useful life. Carbon fiber reinforced polymers (CFRP) are emerging as effective materials for strengthening and rehabilitating such bridges. Near surface mounting (NSM) is a newer technique for application of CFRP for retrofitting bridge members that provides advantages over other strengthening techniques. The technique is still new and uncertainties remain regarding strength, long-term durability, and design including the influence of member proportions, flexural reinforcing steel, and CFRP spacing. Bridge girders retrofitted with NSM-CFRP may be exposed to millions of load cycles and environmental conditions and the influence of these exposures on performance are not established. To address these issues, laboratory tests were performed on ten full-size reinforced concrete girders, representative of in-situ bridge members, to determine the performance of NSM-CFRP retrofitting for shear strengthening. One of the specimens was exposed to fatigue loading, two were subjected to environmental exposures, and one was subjected to combined environmental exposure and fatigue loading. Results indicated that NSM-CFRP retrofitting provided significant shear capacity increases, and the high-cycle fatigue and environmental exposures considered did not adversely affect the strength or behavior of the girders. Environmental exposures of some of the adhesives considered did show somewhat reduced performance; therefore, careful selection of materials is important to ensure performance over the expected lifetime. Recommendations for shear strength design with NSM-CFRP are made.
During the interstate expansion of the 1950s, many conventionally reinforced concrete deck girder bridges were built throughout the country. These now vintage bridges commonly exhibit diagonal cracking and rate inadequately for shear, thus they are candidates for shear strengthening to extend their useful life. Near-surface mounted (NSM) retrofitting is a promising new strengthening technique, but limited test data are available for carbon fiber reinforced polymer (CFRP) in shear strengthening making the long-term durability of NSM-CFRP unknown. This paper provides experimental results from realistic full-scale specimens strengthened with NSM-CFRP. Specimens were tested for shear strength and subjected to environmental exposures to assess long-term durability. Small cylinder specimens were tested to investigate relative performance of different adhesives on bond strength under different environmental exposures. Test results provide a better understanding of the NSM-CFRP shear behavior and strength. Recommendations for shear strength design with NSM-CFRP are made.
Strengthening Design of Reinforced Concrete with FRP establishes the art and science of strengthening design of reinforced concrete with fiber-reinforced polymer (FRP) beyond the abstract nature of the design guidelines from Canada (ISIS Canada 2001), Europe (FIB Task Group 9.3 2001), and the United States (ACI 440.2R-08). Evolved from thorough cla
The Concrete Solutions series of International Conferences on Concrete Repair began in 2003 with a conference held in St. Malo, France in association with INSA Rennes. Subsequent conferences have seen us partnering with the University of Padua in 2009 and with TU Dresden in 2011. This conference is being held for the first time in the UK, in association with Queen’s University Belfast and brings together delegates from 36 countries to discuss the latest advances and technologies in concrete repair. Earlier conferences were dominated by electrochemical repair, but there has been an interesting shift to more unusual methods, such as bacterial repair of concrete plus an increased focus on service life design aspects and modelling, with debate and discussion on the best techniques and the validity of existing methods. Repair of heritage structures is also growing in importance and a number of the papers have focused on the importance of getting this right, so that we may preserve our rich cultural heritage of historic structures. This book is an essential reference work for those working in the concrete repair field, from Engineers to Architects and from Students to Clients.
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.
Vols. 29-30 contain papers of the International Engineering Congress, Chicago, 1893; v. 54, pts. A-F, papers of the International Engineering Congress, St. Louis, 1904.