Blast effect zones and damage mechanisms of concrete bridges under above-deck car-bomb attacks

Above-deck car-bomb attacks cause significant effects on engineering structures from those of explosive blasts in the free air. In this paper, a post-disaster investigation for an existing bridge under above-deck car-bomb blast loading is presented. The crack distribution and damage deformation of the blast loaded girders are systematically investigated, and the blast effect zone is proposed to describe the blast loading distributions on girders and to characterize the girder structural behavior. The girder failure is dominated by one of the three typical damage mechanisms: shear, flexural-shear, and flexural, depending on the blast effect zone where the girder is located. The study also indicates that the isolation effect of the vehicle can significantly affect the blast loading distribution on structures, even though the isolation effect is localized in a region with a small standoff distance. It is gradually attenuated by the increase of the standoff distance. Numerical analysis is conducted to verify the findings by simulating the truck isolation effect with a steel plate.