STUDIES ON THE BOND PERFORMANCE OF FRP-TO-CONCRETE INTERFACES UNDER ENVIRONMENTAL TEMPERATURE DIFFERENCE

To reveal the effect of environmental temperature difference on the interfacial bond behavior of reinforced concrete members strengthened with external bonded fiber reinforcement polymer (FRP) composites, an analytical method for the bond behavior of FRP-to-concrete joints was presented. Based on the cohesive zone model (CZM), a second order differential equilibrium equation was derived. The analytical models of interface slip, bond stress and FRP stress and strain were given by the superposition solution of the boundary condition. Based on the presented theoretical models, the calculation method of the maximum temperature difference that the FRP-to-concrete interface could bear was presented. The effects of the bond length, temperature difference and the number of FRP layers on the interfacial bond behavior was investigated. The results show that the presented theoretical models were in good agreement with the test results. The theoretical models could predict well the bond behavior of FRP-to-concrete interfaces under the temperature difference. When the bond length increased, the maximum temperature difference was increased until reaching an upper limit. With the increase in the environmental temperature, the maximum FRP stress occurred before the maximum temperature difference was reached. The interfacial shear stress was concentrated in the end of the bond interface, which was significantly affected by the temperature difference and the number of FRP bond layers. When the environmental temperature entered the glass transition area of the adhesive, the interfacial shear stress was greatly changed. These results can be helpful to calculate the temperature stress and to assess the interfacial capacity for the strengthened members in bridge or building structures under environmental temperature differences, such as strong sunshine or high temperature environments.