Experimental study on dynamic response of box concrete-encased CFST columns under lateral impact

To study the impact behavior of the box concrete-encased concrete-filled steel tubular (CFST) column, drop hammer test machine based on independent research and development was used to carry out impact experiments on the box composite columns, focusing on the effect of boundary conditions, impact height and axial compression ratio on the time history of impact force, mid-span displacement, time history of the strains and the failure pattern. The experimental results show that the failure of box concrete-encased CFST columns under impact loading belongs to elasto-plastic failure; with the increase of impact height, the time history curve of impact force is developed from two stages to three stages. The failure mode of the column shows that crack and spalling of the outer concrete is obvious, but the steel tube of internal CFST has no local buckling in the middle impact position; with the boundary conditions changing, the impact performance of specimens with fixed ends is better than that supported simply at both ends; and the axial compression has little influence on the dynamic response of the specimens.