Investigation on lap-joint behaviour of GFRP plates bonded to silica fume and rice husk ash concrete

Abstract Fibre-reinforced plastic (FRP) materials are increasingly being used for the rehabilitation of concrete structures. Various adhesives are being employed for attaching FRP materials to concrete and for creating force-transmitting joints between structural elements. Although various existing models focus on predicting the behaviour of FRP–concrete composites, a fundamental understanding of the lap-joint behaviour of FRP plates bonded to concrete still needs to be gained. In particular, there is a lack of a simple and reliable method that allows defining the stiffness of the adhesive in the FRP–concrete lap-joint area. In this study, GFRP plates were bonded to concrete blocks incorporating various proportions of silica fume and rice husk ash. A test set-up was developed to induce shear stresses in the GFRP–concrete lap-joint area. Specimens were instrumented with strain gauges at key locations to establish local stress–strain behaviour. Three-dimensional solid finite elements were used to model the GFRP plates and concrete block. The adhesive was modelled as a spring system with stiffness kv and kp simulating the shear and peel rigidity of the adhesive, respectively. Although it still needs future developments, the finite element model thus developed coupled with the simple test procedure provide a simple means for calculating the stiffness of the adhesive between the GFRP and concrete. Knowledge of this stiffness is expected to allow a more realistic modelling of the lap-joint behaviour of GFRP–concrete composites.