Experimental Research on the Behavior of UHPC-Encased CFST Composite Columns Subjected to Lateral Impact Loading

A ultra-high super-heavy drop hammer impact test system was employed to conduct lateral impact tests on four UHPC-Encased CFST composite columns (UECC) with fixed axial load ratio. The impact force and displacement responses of the specimens throughout the impact process were studied, and the damage and failure characteristics of the specimens during and after impact under different impact velocities and steel tube diameters were comparatively analyzed. The experimental results showed that the UECC specimens exhibited bending failure at medium to low impact velocities, with only few vertical cracks appearing. At higher impact velocities, the outer UHPC were not spalling, indicating excellent impact resistance of the UECC. Notably, an increase in impact velocity significantly improved the impact force and displacement response of the specimens, accompanied by a proportional rise in impact energy. Furthermore, enlarging the steel tube diameter proved effective in enhancing component stiffness, marginally reducing dynamic displacement response, while exerting minimal influence on impact force responses.