Experimental and numerical study on impact resistance of external prestressed reinforced concrete beams

Abstract

Externally prestressed reinforced concrete (RC) beams demonstrate considerable potential for enhanced structural performance under impact loading. However, a comprehensive understanding of how key factors such as initial prestress, partial prestressing ratio (PPR), and reinforcement ratio influence the failure modes and structural response of these beams under impact loading remains limited. Drop hammer impact tests were performed on externally prestressed concrete beams subjected to varying levels of initial prestress. The influence of initial prestress on the dynamic response and failure modes was assessed through measurements of impact force, support force, and mid-span displacement. The commercial finite element software LS-DYNA was utilized to investigate the effects of key parameters, including initial prestress, partial prestressing ratio, and non-prestressed longitudinal reinforcement ratio, on the impact resistance of externally prestressed beams. Empirical relationships were established via curve fitting based on simulation results. Experimental findings indicate that, under identical impact conditions, higher initial prestress leads to greater peak impact forces and reduced mid-span displacements. As the initial prestress increases, the dominant failure mode shifts from flexural-shear to shear failure. Numerical simulations further demonstrate that mid-span displacement decreases progressively with increases in initial prestress, PPR, or non-prestressed longitudinal reinforcement ratio. Among these, the displacement reduction effect of the non-prestressed longitudinal reinforcement ratio diminishes most rapidly, followed by initial prestress, while the effect of PPR attenuates at the slowest rate.