A rate dependent cohesive model for the analysis of concrete-FRP bonded interfaces under dynamic loadings

Reinforced concrete structures, strengthened with fibre-reinforced polymers materials (FRP), are frequently subjected to dynamic loadings, due to, e.g., earthquake, blast, or impact events. The definition of proper cohesive laws to model the bond between the fibre-reinforced polymer sheet and concrete, under high deformation rates, is a crucial issue because the typical failure mode of these joints is debonding of the composite from the concrete substrate. Although numerous studies have already investigated the quasi-static interface response, experimental and numerical investigations, concerning the effect of deformation rate on the bond behaviour between a fibrereinforced polymer sheet and concrete, are still few. This paper presents a cohesive law for the modelling of interfaces under mixed-mode dynamic loadings, considering the effect of deformation rate. The formulation is based on the decomposition of the discontinuity displacement vector across the interface into elastic and viscoplastic components, with the evolution of the latter being governed by a viscoplastic law formulated according to the overstress approach. Experimental results available in literature, related to double- and single-lap shear tests, performed on FRP reinforced concrete specimens, are exploited to validate the proposed model and to show its capacity to simulate closely the experimental behaviour.