Debonding Failures of RC Beams Strengthened with Near Surface Mounted CFRP Strips |
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Authors: | J G Teng L De Lorenzis Bo Wang Rong Li T N Wong Lik Lam |
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Affiliation: | 1Chair Professor of Structural Engineering, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic Univ., Hong Kong, China. E-mail: cejgteng@polyu.edu.hk 2Assistant Professor, Dept. of Innovation Engineering, Univ. of Lecce, Lecce, Italy. E-mail: laura.delorenzis@unile.it 3Postdoctoral Fellow, School of Civil Engineering, Harbin Institute of Technology, Harbin, China; formerly, Research Associate, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic Univ., Hong Kong, China. 4Research Associate, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic Univ., Hong Kong, China. 5Undergraduate Student, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic Univ., Hong Kong, China. 6Senior Research Fellow, Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic Univ., Hong Kong, China.
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Abstract: | This paper presents the results of a series of tests conducted on reinforced concrete (RC) beams strengthened in flexure with near surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) strips. As the main focus of the research is on debonding failure mechanisms, the only test variable investigated was the embedment length of the NSM strip and the NSM strip was extensively strain-gauged to monitor its bond behavior. Load-deflection curves, failure modes, strain distributions in the CFRP strip, and local bond stresses at the CFRP–epoxy interface from the tests are all examined in detail and compared with the predictions of a simple analytical model where appropriate. Of the four embedment lengths investigated, all but the shortest one led to a notable increase in the load-carrying capacity and, to a lesser extent, in the postcracking stiffness of the beam. Debonding was found to be the primary failure mode in all cases except for the beam with the longest embedment length. Also reported in this paper are results from preliminary bond tests used to characterize the local bond-slip behavior of the NSM system. Apart from gaining a better understanding of debonding failures in RC beams with NSM FRP strips, the test results reported in the paper should be useful for future verification of numerical and analytical models. |
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Keywords: | Bonding Fiber-reinforced polymers Flexural strength Reinforcement Concrete beams |
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