A framework for predicting the debonding failure modes of RC beams strengthened flexurally with FRP sheets

This paper presents a unified framework for predicting the flexural behavior of reinforced concrete (RC) beams strengthened with fiber-reinforced polymer (FRP) sheets. The proposed framework model is based on the strain compatibility, force equilibrium, and the nonlinear behavior of materials and considers most of the parameters known to affect the flexural behavior of RC beams strengthened with FRP sheets. In this model, all failure modes of FRP-strengthened RC beams were incorporated with emphasis on the two premature failure modes, i.e., intermediate crack-induced and delamination-plate-end/concrete cover separation debonding. The framework combines the fiber method and several failure criteria that were experimentally established. The proposed framework was then verified against an experimental database of 165 RC beams strengthened in flexure with FRP sheets assembled from previous updated research with various configurations and failure modes. The verification results show that the proposed framework adequately predicts the flexural behavior of strengthened RC beams at different loading levels and gives a good prediction of the load-bearing capacity as well as the failure modes of the FRP-strengthened beams.