Bond behaviour of externally bonded FRP under cyclic loading

Abstract

Strengthening of concrete structures through external bonding of fibre-reinforced polymer (FRP) composites has become a popular technique due to its advantages such as strength-to-weight and stiffness ratios, etc. In this investigation, a test method similar to RILEM TC-RC5 (used to evaluate the bond strength of rebars in concrete) is extended to evaluate bond behaviour of externally bonded FRP sheets. In the present study, experimental investigations on two types of FRP composites (with carbon and glass fibres) have been carried out, and the tensile force on the FRP versus bond–slip response has been evaluated. Both monotonic and cyclic loadings have been carried out to study the envelope response and debonding process for the chosen bond length and width. The average ultimate slip for CFRP and GFRP for selected bond length under monotonic loading was 2.28 and 2.03 mm, respectively, and in the case of cyclic loading was 1.95 and 1.76 mm, respectively. The reduction in the bond–slip under cyclic loading is due to partial debonding of FRP during repeated loading and unloading cycles.