Finite element investigation of the fatigue performance of FRP laminates bonded to concrete

Abstract The effectiveness of using FRP materials to strengthen existing concrete structures is hampered by the weak bond properties between the FRP and the concrete. Further, very few studies are available on the fatigue performance of FRP-strengthened reinforced concrete beams in bridges. Investigation of the fatigue performance of FRP bonded to concrete is important due to the fact that bridges are subjected to very high levels of cyclic loading throughout their lifetime. This paper focuses on a numerical and experimental investigation of the fatigue life of FRP laminates bonded to concrete. FRP-to-concrete joints were subjected to cyclic loading at various stress ratios and the number of cycles prior to failure was used to generate S-N curves which relate the stress ratio to the number of cycles. Further, numerical simulations using the finite element method were performed using a concrete material model capable of sustaining fatigue damage. The finite element results were found to be in good agreement with the experimental data and were used to provide further insights into the mechanisms of fatigue damage. Both the experimental and numerical results showed that no fatigue degradation occurred when the maximum stress ratio was less than 75% of the ultimate static capacity.