Damage mode and dynamic response of RC girder bridge under explosions

Abstract

During the whole service life, bridge structures potentially suffered from the threats from military conflicts, terrorist attacks and accidental explosions. The related studies on the damage modes and dynamic responses of entire RC girder bridges subjected to the explosion loadings is very limited, which is addressed through high-reliability numerical simulations. Firstly, by comparing with the experimental overpressure- and acceleration-time histories, as well as the damage modes from the explosion tests on 1/5 scaled two-span girder bridges, the validities of the material models and corresponding parameters, as well as the numerical simulation algorithms are verified sufficiently. Then, three levels of potential explosive threats, i.e., suitcase, sedan, and small moving van (the corresponding equivalent cubic TNT explosive masses are 23 kg, 454 kg and 4536 kg) specified by Federal Emergency Management Agency (FEMA) were selected to analyze the damage modes and dynamic responses of a typical four-span prototype RC girder bridge under both below- and above-deck explosion scenarios. Furthermore, the blast resistance of both simply-supported and continuous girder bridges were examined, and the minimum safe distances were proposed. It derives that, (i) for the below-deck explosion scenarios, total nine damage modes exist from small-scale spalling of concrete at the bottom of pier to the total collapse of the bridge; (ii) for the above-deck explosion scenarios, eight damage modes can be induced, including cratering and opening in deck, flexural failure of the T-girder, etc.; (iii) the continuous bridge exhibits obvious and slight enhanced blast resistance for below- and above-deck explosions than simply-supported girder bridges; (iv) small moving van can lead to the destruction of the entire bridge, the minimum safe standoff distances for suitcase and sedan bombs are 0.5 m and 3.0 m.