Shear-bending interaction in debonding failures of FRP-plated RC beams

Fibre reinforced polymer (FRP) plates can be bonded to the tension face of a reinforced concrete (RC) beam to increase its flexural capacity. Many studies have reported premature failure by debonding of the FRP plate before the ultimate flexural capacity of the plated section is reached, and the most commonly reported debonding failure mode occurs at or near the plate end. This paper presents the results of an experimental investigation into the interaction between shear force and bending moment at the plate end at debonding for FRP plated beams by varying the length of plate. The experimental results are compared with a plate end debonding strength model recently proposed by the authors in which this interaction is ignored. A bi-linear approximation is then proposed to describe the interaction between the shear force and the bending moment at the plate end at debonding based on the present results. The effect of U strip end anchorage, used to delay or prevent plate end debonding, is also assessed in this study but it is shown that U strip end anchorage provides only limited strength enhancement.