Dynamic behavior and residual performance of CFDSTCs under coupled collision and blast loads

Bridges can suffer partial or even total collapse when bridge piers, as crucial load-bearing bridge components, are hit by vehicles or ships. Concrete-filled double-skin steel tubular columns (CFDSTCs) offer high bearing capacity and good fire resistance, exhibit excellent mechanical properties under separate collision or blast load, and have broad application prospects in bridge structures. However, in extreme cases, CFDSTCs can be subjected to coupled collision and blast (CCB) loads, initiating coupling effects. In this study, the dynamic behavior and residual performance of CFDSTCs under CCB loads were investigated. First, the reliability of the numerical model was validated on the basis of existing experimental results. Second, the damage propagation process of CFDSTCs subjected to the separate collision and CCB loads was investigated, and the patterns of damage, deflection (D), and impact force (F) time histories were comparatively analyzed. The performance level of CFDSTCs after the CCB loads was determined based on the damage index thresholds. Finally, the primary determinants affecting the dynamic behavior and residual performance of CFDSTCs were investigated. The results showed that compared with the sum of the deflections under the separate collision and blast loads, the maximum deflection and residual deflection under CCB loads increased by 6.1 mm and 7.8 mm, respectively.