Dynamic bond behavior of deformed BFRP bars embedded in concrete subjected to high-temperatures

Abstract

FRP (fiber reinforced polymer) bars have the potential to become an alternative due to their excellent performance. A 3D numerical model considering the effects of strain rates and high-temperatures on material properties was established to investigate the bond behavior between deformed BFRP bars and concrete under the coupled action of dynamic loadings and elevated temperatures. In the model, the surface feature of BFRP bars was explicitly simulated. The model's validity was verified by comparing the simulation results with the experimental records. It was found that the numerical model can characterize the bond behavior of specimens reinforced with BFRP bars, including the cracking propagation, the failure patterns, and the bond stress-slip curves. The failure mechanism for specimens experiencing the dynamic loading and high-temperatures was revealed by analyzing the strain distributions of the concrete and BFRP bars, which indicate that the difference in the mechanical properties of the concrete and BFRP bars subjected to high-temperatures and dynamic loadings ultimately lead to the discrepancies in failure modes. The bond strength increases nonlinearly with the increases in strain rate at various temperatures while decreasing linearly at a higher temperature, regardless of strain rate. The peak slip increases linearly with the increases in strain rate or temperature. The overall bond performance of specimens is worse under high temperatures than after natural cooling. The strengthening influence of strain rate on the bond performance of specimens attenuates at high temperatures, and the weakening influence of temperature is enhanced. Based on the numerical results and mBPE model at ambient temperature, a semi-empirical model was developed by comprehensively considering the enhancement of strain rate and temperature degradation on bond performance. The validity of the semi-empirical model was verified by comparing the prediction results with the simulation and test results.