LAUSR

Abstract The primary purposes of this study were to experimentally investigate the influence of the degree of damage in concrete beams on bond behavior of carbon-fiber-reinforced polymer (CFRP) sheets externally bonded to concrete beams. Five concrete beams at different damage levels (evaluated based on flexural stiffness) induced by cyclic loading were externally strengthened with CFRP sheets and were tested under four-point bending load. It was observed during this test that debonding of CFRP sheets appeared for each beam specimen, and propagated from near midspan toward the free end until fracture of CFRP sheets or crush of concrete flange occurred. It was found by comparing the test results and existing bond-slip model that the existing bond-slip model can not exactly predict the bond-slip relationship for CFRP sheets bonded to damaged concrete beams. In addition, the variation of damage parameter, prestress degree and preparation method of concrete surface (notched or non-notched) have little effect on the bond strength and the fracture energy of the CFRP-to-concrete interface, but the interfacial maximum shear stress decreased with an increase in the damage parameter.