Effect of transverse groove on bond behavior of FRP-concrete interface: Experimental study, image analysis and design

Abstract This study conducts a comprehensive investigation into the effect of transverse grooves on the bond behavior of fiber-reinforced polymer (FRP)-concrete interface. Twenty-seven concrete block specimens were tested under single shear to experimentally evaluate the effect of groove characteristics (such as clearance, width, and depth) on bond behavior. The ultimate load increased when a larger ratio (i.e., larger width and smaller clearance) of groove was used. As the groove depth increased, the ultimate load first increased and then decreased. The transverse groove yielded several peak bond stress distributions and higher bond strength. The following image analysis reveals that transverse groove enhanced the bond strength of the concrete-epoxy interface and switched the fracture surface from the concrete-epoxy interface to other interfaces, improving bond strength. Finally, a design method is proposed to predict the ultimate load of externally bonded (EB)-strengthened concrete structures using transverse groove. The contributions of different failure fracture surfaces are considered, and the empirical relationship between the percentage of each failure mode and groove characteristics is established. The comparison between the experimental and predicted ultimate load shows that the proposed design method provides close prediction of ultimate load.