Bond strength model for near-surface mounted (NSM) FRP bonded joints: Effect of concrete edge distance

As one of the mainstream topics in the research field of infrastructure application of FRP composites, the near-surface mounted (NSM) fiber-reinforced polymer (FRP) strengthening technique has attracted an increasing attention over the last decade and become an effective alternative to the externally bonded FRP strengthening method. The bond strength (i.e., maximum force that can be developed in the FRP reinforcement) of NSM FRP bonded joints has been extensively studied by worldwide researchers, and several bond strength models have been established. All the existing bond strength models, however, are not able to consider the detrimental effect of insufficient concrete edge distance (i.e., the distance between the groove and the nearer edge of the concrete). To clarify such detrimental effect on the bond strength between NSM FRP strip and concrete, a numerical parametric study, employing a three-dimensional meso-scale model developed by the author for NSM FRP bonded joints, is conducted in the present study. Based on the results from the parametric study, reduction factors are formulated to consider such detrimental effect and a bond strength model incorporating the reduction factors are proposed. The accuracy of the proposed bond strength model is verified with a large test database containing 86 specimens.