Local bond stress slip relations for FRP sheets-concrete interfaces

Both increasing FRP stiffness and decreasing adhesive's shear stiffness can enhance the interfacial performance of FRP sheets bonded to concrete. However, in comparison with the former way, the latter one can improve the interfacial fracture energy due to the good toughness and nonlinearity of low shear stiffness adhesives. As a result, the high strength of FRP material can be utilized more efficiently. Depending on the fracture energy and the experimentally obtained strain distributions of FRP, this paper applied an optimum back-calculation method to propose a nonlinear interfacial bond stress-slip model, in which the effects of all interfacial components can be included. All the necessary parameters serving for the model are the fracture energy and two other empirical constants a and P, which govern the ascending and descending parts of the interfacial bond-stress slip curves respectively. Analytical results based on the proposed model show good agreement with the experimental ones.