Near-Crack Debonding in an FRP-Overlaid Steel Plate

Adhesively bonded fiber-reinforced polymer (FRP) reinforcement has been experimentally proven to be effective in extending the fatigue life of cracked structural steel members. While the effectiveness of such repairs depends on the bond behavior between the FRP and the target steel member, debonding of the FRP near the crack from the steel substrate has been observed in most of the reported laboratory tests. Although this debonding is generally expected to reduce the effectiveness of the repair significantly, a method for the accurate assessment of the reduction effect has not been developed. This paper introduces an analytical model recently developed by the authors, which can accurately predict the effect of near-crack debonding on the stress intensity factor as well as other behavioral aspects, such as the crack opening displacement profile and the interfacial response. Numerical results obtained from the analytical model for two series of examples are presented in the paper, which demonstrate that near-crack debonding is not inevitable in the presence of an underlying crack, and, if it occurs, its effect may still be benign. These insights are radically different from the widely accepted understanding.