Investigation of damage mechanisms in NRC box girder bridges subjected to above-deck contact explosions

Abstract

Amid frequent global conflicts and terrorist attacks, normal concrete reinforced (NRC) box girder bridges are increasingly vulnerable to contact explosions, underscoring the necessity of thoroughly investigating their damage mechanisms. This paper presents the results of a 6 kg TNT above-deck contact explosion test conducted on a bridge model, scaled down to ¼ of its original size. A numerical model was developed using LS-DYNA, and its accuracy was validated by comparison with experimental results. By analyzing the interaction between shock waves and the structure, as well as stress wave propagation, the damage mechanisms were comprehensively revealed. Further parametric analysis explored the effect of blast intensity and concrete strength on the damage. Results indicate that within a specific range of blast intensities, localized damage is the predominant damage mode for the bridge. As blast intensity increases, the severity and complexity of these localized damages also intensify. When the blast intensity exceeds the critical level, shear failure of the bottom slab emerges as the dominant mode. Concrete strength can influence both the extent of localized damage and the critical blast intensity.