Survey on the interface behaviour in reinforced concrete beams strengthened with externally bonded FRP reinforcement

The use of FRP materials to strengthen reinforced concrete elements has gained more and more popularity in the last decades, for their relevant properties such as the high strength to weight ratio and the excellent corrosion resistance. However, debonding of FRP lamina from the substrate may prevent the achievement of the full load bearing capacity of the reinforced element. In the present study, a novel numerical method recently proposed by the authors is adopted in order to model 25 experimental tests available in literature. The numerical approach, able to follow the complete equilibrium path of a reinforced concrete beam externally strengthened by means of FRP sheets, let shedding further light on the behaviour of the interface between concrete and FRP lamina, during the different stages in the loading process from the service behaviour to the ultimate limit state. A comparison with the approach proposed by the codes shows that the error committed when adopting the hypothesis of perfect bond is still acceptable.