Numerical analysis of suspension bridges with box girders subjected to detonations

Abstract

This paper focuses on the dynamic behavior of a typical three-span suspension bridge subjected to blast loads. Three-dimensional finite element models were established to simulate the blasting excavation of these structures using the explicit dynamic analysis code LS-DYNA. The explosive charge model was developed using the *LOAD_BLAST_ENHANCED tool in the LS-DYNA software. The accuracy of finite element models was validated against existing experimental and numerical results. The failure patterns and damage process of the bridge under explosive loading on the deck were analyzed, while the effects of mass and location of explosive charge were further explored. Dynamic responses such as displacement, stress, and strain were discussed and compared. Based on the computed results, the most critical location of the explosives was assessed. The results indicated the superior performance of the bridge against near-tower detonation over mid-span detonation. The deck exhibited disproportionate collapse due to very high charges of 5000 kg and 8000 kg TNT detonation at mid-span. The blast outcome generated on the bridge's components due to high charges from 1000 kg TNT to 2500 kg TNT at a standoff distance of 2 m was identified as partial collapse. Moderate charges of 250 kg TNT and 500 kg TNT at standoff distances of 2 m and 3 m led to plastic deformation without fracture of the bridge's component. Very high TNT charges at near-tower detonation caused only partial collapse. The severity of cable relaxation and detachment from the deck due to mid-span detonation exceeded the near-tower one.