Dynamic response and failure mechanism for urban continuous beam bridges under far-field blast loads

In modern society, urban bridges often encounter blast threats caused by accidents and terrorist attacks. Moreover, the research on the response of bridges under blast loads is insufficient, especially for far-field blast loads. To investigate the dynamic response and failure mechanisms of urban continuous beam bridges under far-field blast loads, this study established a method for simulating far-field blast loading and a fluid-structure interaction method implemented using the LS-DYNA explicit dynamics code. Subsequently, the refined numerical model of a typical continuous beam bridge was set up to analyze the response processes and typical failure modes under different blast scenarios. Further studies were conducted on the effects of stand-off distance, charge weight and impact angle on structural responses and failures. The computational results explicitly show that continuous beam bridges exhibit a unique set of characteristic deformation features throughout the dynamic responses, including superstructure uplift, substructure bending, and piers tilt. The pressure differential caused by the evolution of blast waves at the front and back surfaces of the bridge, combined with the integrality of the bridge structure, are the key factors influencing the dynamic response process. Under far-field blast, continuous beam bridges typically appear wet-connectors shear failure, piers penetrating damage, and bent caps bending failure. Parametric analyses revealed that both the magnitude of superstructure uplift displacement and the degree of pier tilt undergo a significant decrease as the blast impact angle and scaled distance progressively increase. Moreover, for scaled distance and impact angle, the bridge structural response (the superstructure uplift and pier tilt) is more sensitive to variations scaled distance. The research obtained the response and failure results of continuous beam bridges under far-field blast loads with different blast quantity, blast distances and impact angles. This study provides valuable analytical methods and failure mechanism references for blast response analysis of bridge structure and anti-blast design.