Reliability-based assessment of bond strength models for near-surface mounted FRP bars and strips to concrete

This article investigates the reliability of three existing near-surface mounted (NSM) fiber-reinforced polymer (FRP) bond strength models including the ACI 440.2R-17 model and two fracture mechanics-based models. Various load combinations and strength reduction factors included in the ACI 440.2R-17 guidelines and the CSA S806-12(17) standard are considered. The uncertainty of the bond models is evaluated using the data gathered from 451 experimental specimens available in the literature with careful consideration of the reported modes of failure and their combinations. A reliability analysis based on the first-order secondmoment (FOSM) method is conducted on the three bond models for both strips and bars against the dead, live, snow, and wind loads accounting for uncertainties due to geometrical and mechanical properties of the NSM FRP-to-concrete joints. This article provides a platform for choosing the proper strength reduction factors for a practical range of target reliability indices. The results show that the strength reliability of the considered bond models with respect to the existing strength reduction factors requires major improvements. The proposed strength reduction factors in this study are able to improve the reliability indices of the bond models significantly for provisions of ACI and CSA when different load combinations are considered.