Finite element modelling of RC beams strengthened in flexure with NSM FRP and anchored with FRP U-jackets

Abstract

Reinforced concrete (RC) beams flexurally-strengthened with near-surface mounted (NSM) fibre-reinforced polymer (FRP) bars/strips have been frequently found to fail by debonding at the end of NSM FRP. Such end debonding failures significantly limit the performance of the strengthened beams and the utility efficiency of FRP material. To mitigate/prevent the debonding failures of NSM-strengthened beams, the adoption of FRP U-jackets is an attractive option. A systematic experimental study on RC beams flexurally-strengthened with NSM carbon fibre-reinforced polymer (CFRP) strips and anchored with FRP U-jackets have been conducted and presented by the authors in a previous study. In order for a better and in-depth understanding of the behaviour of such RC beams and for the development of reliable design code/guideline in the future, an accurate finite element (FE) model for such RC beams is proposed in this paper. In the proposed nonlinear FE model, the material properties and bond-slip relationships were properly defined. The failure modes, load–deflection responses and strain development of the beams obtained from FE predictions and test observations were carefully compared. It was shown that the proposed FE model is capable of providing accurate predictions to the test results.