Residual performance and damage mechanism of prestressed concrete box girder bridge subjected to falling heavy object impact

Extreme vertical impact loading from dropped heavy cargo or falling rocks threatens the safety of bridge structures. The impact behavior and post-impact performance of a multi-piece prestressed concrete (PC) box girder bridge were investigated through numerical simulation. The moment-curvature analysis was performed to explain the damage mechanism and to predict the residual capacity of the girder under impact. The results demonstrate that the impacted girder suffers the most severe flexural failure whereas the other un-impacted girders exhibit flexural-torsional combined damage type. The impacted girder suffers from flexural failure to shear failure if the impact position on the girder transfers from mid-span to support. The increased impact energy deteriorates the damage of impacted girder while has little influence on the un-impacted girder. When the impact area decreases due to the varying impact angle, the displacement and impact force of the impacted girder reduce whereas local damage becomes more severe. The residual stiffness and resistance decrease significantly as the impact energy raises. It is concluded that severe concrete damage of top plate diminishes the flexural capacity of impacted girder.