An improved damage modelling to deal with the variability of fracture mechanisms in FRP reinforced concrete structures

A new way of modelling is developed and proposed to predict different damage scenarios of concrete elements strengthened by externally bonded fibre reinforced polymer (FRP) plates. The bonded assembly is modelled as a three-domain system with concrete, glue and FRP reinforcement assumed as damageable materials being connected together by two interfaces. Interaction between domain and interface damage is introduced. Detachment between FRP reinforcement and concrete in a single lap shear test configuration is analysed by implementing the equations governing the damage model obtained in a finite element code. The damage evolution is characterised through various indexes, which makes it possible to discriminate the failure mechanism when varying properties of the glue or interfacial characteristics. Comparison between simulations and experimental tests shows the accuracy of the damage model prediction and its capability to detect different failure modes; in particular, this new modelling approach allows distinguishing between an adhesive failure at a glue-substrate interface and a cohesive failure of the glue layer.