Experimental and numerical study of damage mechanism of steel box girders under external blast loads

Abstract

Steel box girders are commonly utilized in bridge construction, particularly in continuous bridges and long span cable-stayed and suspension bridge. The bridges are vulnerable to blast loads induced by accidental explosions and terrorist attacks. Moreover, these types of explosions always occur above the bridge decks. Hence, the steel box girders subjected to blast loads were investigated in this study. A field blast experiment on a steel box girder was carried out. Furthermore, a finite element model (FEM) was developed and validated by the experimental results. And the FEM yielded the same results as the experiment. The damage mechanism of the experimental specimen was revealed by the numerical model. The results showed that the damage of the steel box girder concentrated on the top plate, and the experimental specimen can be simplified to the analysis of stiffened plate. Based on the validated finite element model, parametric analysis was performed. The maximum displacement responses of the top plate, the damage modes and mechanisms, and the energy dissipation mechanism were discussed. The blast load parameters and the transverse web thickness were all found to have significant influences on the displacement responses of the top plate. Three main damage modes were observed in the steel box girder subjected to blast loads. The transverse web thickness has a substantial impact on the damage modes. Moreover, the damage mechanisms of the damage modes were revealed. When considerable plastic damage occurs, most of the energy is absorbed by the top plate and transverse web components, according to an examination of the energy absorption mechanism. The strength of the blast loads and the transverse web thickness significantly influence the energy absorption ratio of the top plate and transverse web components. The types of damaged components should be reduced from the standpoint of repairability. Hence, through the analysis, it is advised to increase the transverse web thickness to improve the repairability of the steel box girder after explosions.