Plate end debonding in FRP-plated RC beams—I: Experiments

Abstract

RC beams strengthened with a tension-face FRP plate (i.e. FRP-plated RC beams) often fails by debonding in one of several possible modes. This paper presents an experimental study on plate end debonding failures in FRP-plated RC beams, which was conducted to develop a better understanding of the behaviour and failure mechanisms for the subsequent development of a predictive model. The results of ten four-point bending tests and eleven three-point bending tests conducted on simply-supported FRP- or steel-plated RC beams are presented and discussed in detail. The test beams cover a variety of significant geometric and material parameters over a wide range. In these beams, the critical plate end was subjected to either bending or shear only. Most of the beams failed by debonding in the form of the separation of the concrete cover from the steel tension reinforcement (i.e. cover separation failure), and for both types of plate ends, the debonding failure load depends strongly on the stiffness of the “composite plate” composed of the bonded plate and the concrete cover or the bonded plate alone. For plate ends subjected to a high shear force but a low moment, cover separation failure often occurs following local shear-crack induced interfacial debonding between the plate and the concrete near the plate end. The shear resistance of the beam contributed by the concrete alone provides a lower bound to the debonding failure load of such plate ends, which can be significantly increased by the presence of internal steel shear reinforcement.