Post-impact response of rectangular hollow steel tubes: comparative study on partially and fully concrete-filled columns

This research conducts a numerical analysis of the post-impact response of rectangular hollow steel tubular columns with two different filling conditions: partially filled (PF) and fully filled (FF) with concrete. A finite element model was developed in ABAQUS/Explicit and validated against experimental results, successfully replicating the displacement-time history, peak response, and failure mechanism. Based on the validated model, a comprehensive parametric study comprising 64 models was conducted to assess the effects of cross-sectional geometry, the height of the concrete infill, and the impact location on the residual axial capacity. All models are developed with the same slenderness ratio to enable the disassociation of the effects of geometric parameters from those of infill parameters. From the results, wall thickness is the most critical variable across all models. The full-height infill was found to improve residual capacity significantly compared with the partially filled condition. In addition, the impact location was significant, with quarter-span impacts yielding higher residual strengths than mid-span impacts. These findings present valuable insight in support of the use of performance-based design and retrofitting of composite columns subjected to accidental impact.