Midspan shear debonding of CFRP-laminated reinforced concrete beams

Fibre composite strengthening presents a very attractive option for dealing with the current need to rehabilitate infrastructure in this country and around the world. However; the materials' behaviours have yet to be conveniently and accurately modelled in many situations. The research presented herein investigates a particular failure mechanism that results in the separation of the FRP laminate from the remainder of the beam. Debonding is usually initiated directly under the load point. This particular failure mechanism has not been found to occur in beams strengthened with steel plates. The objective was to develop a better understanding of the materials' behaviour and develop simple design methods similar to conventional techniques for predicting a beam's capacity when failing as a result of this mechanism. The experimental program investigated the effect of concrete compressive strength and amount of shear reinforcement on the occurrence of this failure mode. A shear friction technique is shown to provide a simple design procedure.