Dynamic response and failure analysis for urban bridges under far-field blast loads

Abstract

Compared to near/mid-field explosions, the far-field blast generates blast waves with long duration and propagation distance, which will cause distinctly different damage effects. The dynamic response and failure mechanism of urban bridges under far-field blast loads are numerically investigated in this work. To address the excessive model scale caused by the direct simulation and remapping methods, approximate far-field blast waves are input into the air domain through the Autodyn subroutine in the present far-field blast simulations. The reliability of the loading method and the fluid-structure interaction simulation scheme adopted here is then demonstrated by published experimental data. Based on an urban bridge prototype, the refined numerical model of the bridge is established. Eventually, the failure process and damage modes of the bridge under far-field explosions are analyzed, while the effects of impact angles and load parameters are explored. The results imply that (i) the response of the bridge under far-field explosions is global, while the typical features in the response process are the pier tilt and superstructure uplift; (ii) the damage modes of the bridge include crush and twist of piers, damage to shear keys, cracking of bent caps, and movement of the superstructure; (iii) the decrease of impact angle exacerbates the pier displacement and reduces the superstructure uplift; (iv) for peak overpressure, decay parameter and positive phase duration, the bridge structural response is most sensitive to peak overpressure.