Simplified solutions for the stress transfer in concrete beams bonded with FRP plates

Strengthening of concrete beams by the external plate bonding technique has become an important research area over the last two decades, particularly with the increasing applications of the advanced fibre reinforced composites. Unlike the unstrengthened beams, the bonded structure shows an undesirable failure of plate debonding. It has been well recognized that central to this failure mode is the stress concentration at the plate end. This paper reports a novel simplified interfacial stress formulation for the FRP bonded concrete beams subjected to arbitrary loadings. It is featured as a compact closed-form formulation with improved accuracy. The solution satisfies the condition of shear stress free at the plate ends and can predict a non-uniform transverse normal stress over the adhesive layer, as the adhesive is treated as a 2-D medium. Numerical validations are conducted to compare the simplified solutions with those obtained from more rigorous formulations, alternative approximate solutions and experimental results. Adequate accuracy and applicability are achieved. This formulation can be easily incorporated in the strength models to predict debonding loads.