Experimental and numerical investigation of the blast resistance of concrete-filled stainless steel tubular columns

To investigate the damage characteristics, residual axial load-carrying performance, and post-blast axial compression failure modes of concrete-filled stainless steel tubular (CFSST) columns subjected to blast loading, field blast tests, post-blast axial compression tests, and axial compression tests on intact specimens were conducted. The specimens had a square cross-section of 250 mm × 250 mm, a total length of 3000 mm, and a stainless steel tube thickness of 3 mm. In the blast test, a 6 kg TNT charge was detonated at a standoff distance of 300 mm from the mid-height blast-facing surface, while an initial axial compression ratio of 0.2 was applied. An LS-DYNA finite element model based on the multi-material arbitrary Lagrangian-Eulerian method was then established and validated to reproduce blast-wave propagation, fluid-structure interaction, structural damage, and the subsequent axial compression response. The results show that the blast-induced damage was mainly concentrated in the mid-height blast-facing region, where local indentation and lateral outward buckling developed in the stainless steel tube, while the overall integrity of the column was maintained. The maximum indentation depth measured in the test was 37 mm. The validated numerical model reasonably reproduced the damage pattern, displacement response, acceleration response, and post-blast axial load-displacement behavior. The errors between the experimental and numerical peak displacement, peak acceleration, and peak axial load were 1.5%, 5.6%, and 5.0%, respectively. The blast-damaged specimen reached a peak axial load of 1572.2 kN, which was 50.4% lower than that of the intact specimen. As the scaled distance decreased, the failure mode gradually changed from overall flexural failure to a combined failure mode involving local indentation, lateral outward buckling, and overall flexural deformation. The residual flexural deformation generated additional bending moments during subsequent axial compression, while the initial blast damage weakened the composite action between the stainless steel tube and the core concrete. As the initial damage decreased, the axial compression failure mode of the blast-damaged columns gradually changed from mid-height buckling to combined loading-end and mid-height buckling, and ultimately to loading-end buckling in the intact column. These findings provide a basis for the blast-resistant design and post-blast safety assessment of CFSST columns.