Study on Impact Resistance of All-Lightweight Concrete Columns Based on Reinforcement Ratio and Stirrup Ratio

All-lightweight concrete (ALWC), using non-sintered fly ash ceramic pellets and pottery sand as coarse and fine aggregates, is a novel energy-efficient and environmentally friendly building material that has emerged in recent years. However, its structural behavior under impact loading remains to be thoroughly studied. This paper examines the dynamic response of four ALWC columns with different longitudinal reinforcement ratios and stirrup ratios under lateral impact loading using drop hammer tests. The effect of stirrup densification on the impact resistance was analyzed, focusing on the failure modes, impact forces, acceleration, and midspan displacement time history curves. Results showed that increasing the reinforcement and stirrup ratios shifted the column failure mode from shear to flexural failure, significantly enhancing peak impact force and reducing both midspan and residual displacements. Densifying the stirrups in the column ends resulted in localized flexural failure, with first and second peak forces increasing by 7.43% and 55.98%, respectively, thereby improving impact energy absorption and reducing impact damage.