Experimental and numerical studies on UHPC-filled Q690 high-strength steel tubular members subjected to axial impact

With the advances in high-performance materials and structures, the impact behavior of ultra-high-performance concrete (UHPC) filled Q690 high-strength steel tubular columns was systematically investigated in this study. A total of 19 axial impact tests on UHPC-filled steel tubular columns were conducted by a drop hammer test apparatus, experimentally obtaining the failure model, impact force and displacement time histories, and energy absorption. The main parameters, including steel strength, steel ratio, impact energy, and specimen length, were considered. The results showed that UHPC-filled Q690 high-strength steel tubular members exhibited excellent impact resistance and could withstand higher energy impacts. As the impact energy increased, the impact force also increased owing to the strain-rate effect, and the deformation was significantly enlarged. Increasing the steel ratio significantly enhanced the impact resistance and energy absorption efficiency of components; the use of high-strength steel and UHPC also improved the impact resistance and energy absorption; the effect of specimen length on the axial impact behavior was limited. Additionally, a finite element model considering the strain-rate effects of high-strength steel and UHPC was established and benchmarked with the test results from the present study and literature. The simulated results were in good agreement with the experimental results, which contributed to the relevant research on UHPC-filled steel tubular components subjected to axial impact.