A unified bond-slip model for the interface between FRP and steel

The interfacial bond-slip relationship between fiber-reinforced polymer (FRP) and steel plays an important role in analyzing FRP retrofitted steel structures. Different failure modes and epoxy types (i.e., linear epoxy and nonlinear epoxy) lead to various bond-slip relationships. Although several models have been proposed to predict the bond-slip behavior, different models were developed for different emphasis, which may result in inconve nience when being used. This paper proposed a unified bond-slip model by considering different failure modes and epoxy types. A database of bond strength comprising of 400 FRP-to-steel single-/double-lap shear joints was collected. By analytical reasoning, key factors that influence the bond parameters were identified and configu rations of the model were derived. The unknown coefficients in the model were determined subsequently by nonlinear regression analysis using the derived closed-form analytical solutions. Different coefficients were proposed in terms of different failure modes and epoxy types. Furthermore, if the failure modes are unknown before experimental investigation, the proposed model is also capable of giving reasonable predictions. Com parison between theoretical results and test data from the literature was performed to validate the modeling work. Afterward, a parametric study was conducted to further investigate effects of the key parameters on the interfacial behavior.