Influence of elevated temperatures on bond performance between BFRP bars and concrete

The elevated fire temperatures cause the deterioration of the mechanical properties of BFRP bars and concrete. A three-dimensional refined numerical model considering the surface characteristics of ribbed BFRP bars was established to study the effect of high temperature on interfacial bond performance. The "sequence coupling" method analyzes the bonding behavior of BFRP bars and concrete under high temperatures or after natural cooling. The validity of the refined model was verified by reproducing the available test results. Then, the bond behavior was compared and discussed. Based on the simulation results, a constitutive model for predicting the bond performance was developed by modifying the available model at room temperature. The results show that the numerical model can observe the bond failure mechanism between the BFRP-concrete interface. The specimens after natural cooling have better bond performance due to the restoration in material properties. The pull-out failure occurs easier at high temperatures, owing to the various change in the property of BFRP bars and the faster increase in BFRP strain. The influence of temperature rise on peak slip is more significant than that on bond strength. The bond strength and peak slip decrease linearly with the increase in temperature. Finally, the developed bond stress-slip constitutive model considering the effect of temperature, can reasonably predict the bond behavior between BFRP bars and concrete.