Global Energy Balance-Based Debonding Modeling of NSM FRP-Strengthened Concrete Beam

An important advantage of the near surface mounted (NSM) technique for concrete beam strengthening over the externally bonded reinforcement technique is its higher resistance to debonding failures. Despite the increased resistance, debonding failures do still occur on NSM strengthened beams. The aim of this paper is to investigate the possibility of using a global energy balance based fracture mechanics model for NSM strengthened beams. The methodology includes determining the available energy for the propagation of the interface flaw. Debonding failure occurs when the available energy for interface flaw propagation reaches the Mode I fracture energy of the concrete, as this is the weakest material of the concrete-fiber reinforced plastic (FRP) composite system. The validation using published experimental results demonstrates that the model is capable of predicting possible modes of debonding failure for NSM FRP strengthened reinforced concrete beams and for any material and geometric properties of concrete beams, adhesive, and FRP. Validation against published experimental results yields a satisfactory performance of the model. The mean ratio between simulated to experimental failure loads for NSM strengthened beams is 0.99 with a standard deviation of 0.09. (C) 2019 American Society of Civil Engineers.