Bond performance of FRP bar reinforced concrete under monotonic load and fatigue effect

To investigate the bond properties of concrete reinforced with fibre-reinforced-polymer bars (FRPBs) under different loads, FRPB-reinforced concrete specimens were subjected to pull-out tests. Three types of FRPBs were used in the experiment – ordinary steel rebars, carbon-fibre-reinforced polymer (CFRP) bars and glass-fibre-reinforced polymer (GFRP) bars. Pull-out tests were first conducted under monotonic load to determine the effect of concrete strength and reinforcement diameter on the bond performance of FRPB-reinforced concrete and steel-reinforced concrete. The variation in bond performance for the different reinforcements was investigated. Fatigue tests were then performed, followed by further pull-out tests to determine the bond stress–slip curves between concrete and reinforcements, and the influence of fatigue action on the bond stress–slip curve was then examined. Formulae to calculate the stress were developed, which can be applied to determine the bond failure pattern, bond strength and bond–slip curve.