The concrete-filled double steel tube (CFDST) has been more and more widely used in infrastructure due to its greater moment of inertia compared to the ordinary concrete-filled steel tube (CFST). With the increase in collision accidents occurring in recent years, the research on CFDST under impact needs more attention. To study the dynamic responses of CFDST columns under lateral impact, the finite element package ABAQUS was used to simulate the impact force and mid-span deflection of the column under the coupling action of axial force and lateral impact based on the comparison of experimental data in the literature. The influence of hollow ratio, axial compression ratio, slenderness ratio, impact energy, and material strength on the dynamic responses of the CFDST column are studied. The results show that with the increase in the hollow ratio from 0.3 to 0.8, the residual mid-span deflection of the CFDST column decreases by 77.9%. The mid-span deflection shows an increasing trend following a decreasing one with the axial compression ratio increasing. With the increase in the slenderness ratio from 30 to 60, the plateau impact force decreases by 62.5%, and the residual mid-span deflection increases by 240.5%. The practical formulas for the impact-bearing capacity and residual mid-span deflection of the CFDST column are suggested with high accuracy.

Square in square concrete-filled double-skin steel tube (CFDST) columns are widely preferred on account of their convenient nodal structural form and efficient construction process. In order to investigate the axial compression behavior of the columns after lateral impact, a precise numerical model for the post-impact axial compression of square in square CFDST columns was established using the finite element package, and was validated by existing experiments and studies. The residual axial compression bearing capacity of the columns after lateral impact has been analyzed. The typical vertical load–axial displacement curve, the failure mode and stress distribution of the columns have been studied. The parametric analysis has been also carried out to explore the influence of key parameters. Lastly, based on the parametric analysis, a simplified formula has been proposed to estimate the residual axial compression bearing capacity of the columns. The results show that under lateral impact, the columns generally exhibit a flexural failure mode. Local indentation occurs at the impact location, and buckling also appears at the bottom of the fixed support section. The coefficient of residual axial compression bearing capacity decreases with the increase of impact energy, slenderness ratio, and concrete strength, and increases significantly with the increase of steel strength.