Bond of NSM systems in concrete strengthening – Examining design issues of strength, groove detailing and bond-dependent coefficient

Research on the strengthening technique using near-surface mounted (NSM), fiber-reinforced polymer (FRP) composites has substantially advanced the knowledge on the bond-related issues such as bonded length, failure mechanisms, groove and bar dimensions, and local bond-slip behavior. In this study, several important design-related parameters that deserve more attention are carefully examined, including average bond strength, groove detailing, and bond-dependent coefficient. The accuracy of the existing analytical and semi-empirical models for average bond strength is assessed using the experimental data available in the literature. Optimum groove dimensions and a new empirical model for the bond-dependent coefficient are also proposed to complement the existing design guide for the NSM FRP technique used in concrete strengthening.