Effect of temperature variation on the plate-end debonding of FRP-strengthened steel beams: Coupled mixed-mode cohesive zone modeling

Fiber-reinforced polymer (FRP) strengthened steel beams may experience significant temperature variation during their service life. Because of the different coefficients of thermal expansion (CTEs) of FRP and steel materials, thermal stresses can be generated by temperature variation at the FRP-to-steel interface and consequently influence the plate-end debonding mechanism. Therefore, an accurate prediction of the debonding failure of FRP-strengthened steel beams under combined mechanical and thermal loading is of great importance for the strengthening design. This paper proposes a closed-form analytical solution based on a coupled mixed-mode cohesive zone model (CZM) (i.e., with the consideration of Mode-I and Mode-II mixity), to analyze the effect of thermal stress on the debonding failure of FRP-strengthened steel beams. An excellent agreement has been achieved between the analytical solution and the finite element (FE) modeling in terms of interfacial full-range debonding behavior. Further parametric studies were conducted and indicated that the thermal stresses induced by elevated temperatures tend to reduce the plate-end debonding load and such effect becomes more significant when a thicker FRP plate is adopted.