Simplified finite element modelling of end cover separation in RC beams flexurally-strengthened with bonded FRP reinforcement

The flexural performance of RC beams can be improved using externally bonded (EB) or near-surface mounted (NSM) fibre-reinforced polymer (FRP) reinforcement. One of the commonly observed failure modes of such FRP-strengthened RC beams is the end cover separation failure mode which involves the detachment of the bonded FRP reinforcement together with the cover concrete along the level of the longitudinal steel reinforcement. This paper presents a simplified finite element (FE) model for end cover separation failure in RC beams flexurally-strengthened with either EB or NSM FRP. In this simplified FE model, only the part of the RC beam between the two cracks near the critical end of the FRP reinforcement is simulated. This model leads to the determination of the FRP debonding strain at the cracked section in the strengthened region nearest to the critical end (excluding the one at the end), which can then be used to determine the moment acting on the section at debonding failure through conventional section analysis. The validity of the proposed FE model is verified using laboratory test results.