Advanced computational approaches to multi-blast scenario analysis: insights into assessing vulnerabilities in multi-span masonry arch bridges

Bridges are critical components of transportation infrastructure and are increasingly vulnerable to intentional or accidental blast events. This study investigates the structural response and damage mechanisms of bridge systems under two distinct blast scenarios: above-deck and below-deck explosions. Using the Coupled Eulerian-Lagrangian (CEL) approach in finite element analysis, the complex interactions between the blast wave and bridge structure are accurately modelled. To enhance the realism of the simulations, a custom VUMAT subroutine is developed to define advanced material properties, including strain rate dependency and progressive failure criteria under high strain rates. The results reveal significant variations in the structural response between above-deck and below-deck blasts, with the latter causing more severe damage to critical load-bearing components, such as the deck slab and all components. Stress wave propagation, localised failure patterns, and overall bridge stability are analysed in detail for both scenarios. This research provides new insights into the dynamic behaviour of bridges under dual blast scenarios and offers a comprehensive framework for improving their safety and resilience against explosive threats. The integration of advanced computational modelling techniques and customised material behaviour codes underscores the potential for more accurate predictions in blast-induced damage assessments.