A model for the bond-slip of a GFRP bar in concrete

Glass fiber reinforced polymer (GFRP) bars are emerging as desirable alternatives for traditional steel reinforcements in concrete industry. A proper bond between concrete and reinforcement is critical for the performance of reinforced concrete structures. Due to the complexity of modeling the bond action, a perfect bond has been usually considered with the slippage between concrete and reinforcement neglected. The purpose of the present study is to develop a parametric bond-slip model based on pull-out tests performed on sand coated GFRP bars. It included exponential rising, linear descending and residual constant bond stress stages. A sensitivity analysis was performed to determine the bond parameters. Different points along the embedded length of the bar were monitored to illustrate the difference between the average and nodal bond-slip relationships. The proposed bond model was used in a finite element analysis that modeled the cracking in concrete and explicitly simulated the bond action. The model was capable of presenting both concrete splitting and pull-through modes of failure. Simulations were performed on samples with different concrete covers to demonstrate both failure modes.