Prediction of the interfacial shear stress of externally bonded FRP to concrete substrate using critical stress state criterion

This research focuses on the development of a fracture mechanics based-model that predicts the debonding behavior between FRP composites and reinforced concrete beams. The maximum transferable load for FRP composite externally bonded to concrete substrate was expressed as a function of material properties and the fracture energy. Fracture energy for FRP pull-off test was determined with the maximum interfacial shear stress and the corresponding slip. The interfacial shear stress and the corresponding slip are predicted based on a proposed criterion that shear stress failure initiates adjacent to the FRP-concrete bond interface. With the application of the elasticity theory, the corresponding slip of FRP bond system and the interfacial shear stress are obtained. Comparison between the experimental FRP pull-off tests and those predicted by the new model showed good agreement.