Performance analysis of various bond-slip models in finite element modelling of reinforced concrete beams strengthened with FRP sheets

The purpose of this study is to analyze the performance of various bond-slip models in modelling of reinforced concrete beams strengthened with FRP sheets. A comprehensive finite element model based on the concrete damage-plasticity behavior has been constructed. The cohesive element is used to model the bond-slip behavior and existing experimental results were used for verification. By comparing the results of the finite element model with the experimental results, the capability of the selected model in predicting beam behavior has been proven. The indent distribution of strains in FRP plates was due to the occurrence of cracks in concrete. With an increase in the loading, both the crack opening and the number of cracked sections in the beam are increased and the indentation state of the strain curves is intensified. On the other hand, the yielding of tensile rebars increases the strain in the FRP sheet. The interfacial shear stress values between FRP sheets and concrete shows high fluctuation at the final stages of loading due to the development of cracks and release of stresses at the crack tip. Maximum slip values between concrete and FRP surface occur near the loading points in which bending moment and shear force are maximum. The obtained load-displacement results showed that Lu-Bilinear and Lu-Simplified models have the best performance in modeling the bond between concrete and FRP sheets and in predicting the failure load of beams, they had On average 3.8% and 6.1% error with respect to experimental results, respectively.