The Damage Mechanism and Dynamic Response of a Double-layered Portal Pier under Explosion load

• A validated blast-resistance model for double-layer portal piers was established through comparative analysis with experimental data based on actual engineering cases. • Three typical vehicle bombing scenarios aligned with FEMA standards were fabricated to analyze corresponding structural failure modes and conduct dynamic response analyses. • Reinforcement priority in blast-resistant designs for double-layer portal piers should focus on the load-bearing strength and protective capacity of the middle piers. Double-layer bridges are effective in optimizing the usage of urban traffic space, but research on their ability to withstand explosion loads is limited. To clarify the dynamic mechanical response and damage mechanisms of double-layer portal piers under explosion loads, a numerical model was established using LS-DYNA dynamic analysis software, and its accuracy was verified by comparing it with field explosion test data. The damage modes and dynamic response of the double-layer portal pier under three different explosion levels were systematically analyzed. The results indicate significant differences between the overall and local damage of the double-layer portal piers at different scaled distances. Under far-field explosion conditions, no obvious structural damage occurred. Under near-field explosion conditions, the concrete of the pier column peels off as a whole and the maximum crack length of the upper beam reaches 2.13m. When the explosion equivalent reached 445kg, a punching pit of 6.64m in length appeared on the surface of the superstructure beam, significantly weakening the structure’s integrity and overall safety. Under contact explosion load conditions, the concrete was extensively damaged and peeled along the height of the entire middle pier, with the upper bridge deck continuing to bear the risk of collapse. Therefore, the anti-explosion design of double-layer portal piers should focus on enhancing the strength and protective features of the middle pier. This study delivers pioneering insights into double-layer bridge resilience, addressing vital research gaps for urban infrastructure under extreme threats.