Impact responses of precast hollow reinforced concrete beams with prestress tendons using high-fidelity physics-based simulations

This study investigates the dynamic response, damage mechanisms, and residual capacity of precast hollow reinforced concrete beams with prestress tendons (HRCBPT) under impact loads by using High-Fidelity Physics-Based (HFPB) finite element (FE) models. The accuracy of the numerical model developed in this study has been fully calibrated against two different dropweight impact tests available in open literature, including a scaled hollow reinforced concrete beam (HRCB) and a full-scale reinforced concrete (RC) beam. The results in this study show that under low to moderate impact loads, the flexural cracks and global deformation of the HRCBPT are similar to the hollow beam with normal reinforcement. Under high impact loads, although these beams exhibit similar diagonal shear cracks near the impact location, the HRCBPT experiences more local concrete spalling damage on the bottom flange, higher residual capacity index, and smaller reaction force at supports owing to the contribution of the initial prestress force. The results also suggest that the maximum compressive stress at the bottom flange of the section should be smaller than 17.6% of its compressive strength in order to maximise the beam's impactresistant capacity, while the prestress level in the tendon should be lower than 65% of the tendon yield strength to prevent premature failure under moderate impact conditions. Furthermore, different combinations of the impact velocity and impact mass would generate different impact force profiles on the beam resulting in dissimilar impact responses and residual capacity. In the design analysis, together with the critical impact location at the mid-span, the impact location close to the supports which may cause critical shear response of the beam, also needs be considered. In this study, the impact in the vicinity of the support yields the most severe damage to the beam resulting in the lowest residual capacity.