Concrete beams with externally bonded flexural FRP-reinforcement: analytical investigation of debonding failure

This paper studies the problem of early concrete cover delamination and plate-end failure of reinforced concrete beams strengthened with externally bonded FRP-reinforcement. The accuracy of analytical models and finite element (FE) methods for predicting this type of failure is assessed against published experimental data. Two design approaches based on the maximum concrete tensile strength and the shear capacity of concrete beams were examined first and it was found that linear elastic analysis cannot accurately predict the brittle plate-end concrete failure. It was also found that the extent of strengthening that can be achieved is limited by the shear capacity of concrete beams. The FE analysis is used to examine the effects of internal tensile reinforcement on the magnitude of principal tensile stresses in the critical region. The non-linear behaviour of FRP-strengthened beams is also examined in the FE analysis using the smeared crack model for concrete which is shown to adequately display the inelastic deformation of the beam. Finally, the mixed mode of failure due to the combined shear and concrete cover delamination is addressed through modelling plate-end and shear crack discontinuities using the discrete crack approach.