Bond-slip model for interfaces between externally bonded FRP reinforcement and concrete at elevated temperatures

This paper presents a nonlinear bond-slip model for fiber reinforced polymer (FRP) plates/sheets externally bonded to concrete at elevated temperatures as an extension of the two-parameter bond-slip model previously proposed by Dai et al. [1] for ambient temperature responses. The two key parameters of the model, the interfacial fracture energy and the interfacial ductility index , were determined from the existing shear test data of FRP-to- concrete bonded joints at elevated temperatures. During the interpretation of the data, the effects of temperature-induced thermal stresses and temperature-induced bond degradation are appropriately isolated and dealt with. It is shown that the interfacial fracture energy remains almost constant initially and then decreases as the temperature increases; the interfacial ductility index exhibits a similar trend. The proposed bond-slip model is shown to compare well with the test data upon which it is based, in terms of both the ultimate load and the strain distribution in the FRP, demonstrating that the model closely represents bond behavior of FRP-to-concrete interfaces at elevated temperatures.