AbstractStudying the failure or collapse mechanism of an entire bridge under vehicle–pier collision has engineering demand and practical meaning, while the existing damage assessment work mainly focuses on the impacted pier. This study aims to numerically clarify the collapse mechanism and evaluate the damage level of the entire bridge. First, the previously validated finite-element (FE) model of a simply supported RC bridge with double-pier bent when impacted head-on by a heavy truck. The model improved by incorporating the nonlinear behaviors and damage of the bridge superstructure. According to the truck mass and impact velocity involved in the actual collision accidents, 20 truck–pier collision scenarios are designed and numerically simulated by adopting the nonlinear FE program LS-DYNA. The damage/failure or collapse mechanism of the entire bridge, as well as the vehicular impact force and bridge structural dynamic behaviors, are examined. It shows that (i) the overall collapse of the bridge structure is an impact-successive and damage-accumulative process, which is not completely coincident with the failure of impacted pier; and (ii) the cargo-induced internal forces of the impacted pier have two peaks attributed to the initial contact and the following pushing–drag effect of cargo, respectively. Then, based on the damaged area of concrete and effective plastic strain of reinforcement, the damage levels of the main bridge components, including the pier, bent cap, tie beam, pile, girder, and deck, are qualitatively assessed and classified, followed by the clarifications of their corresponding inner correlations. Furthermore, by proposing two quantitative damage indexes, a feasible on-site approach for assessing the post-collision damage of the bridge structure is established and validated by eight additional collision scenarios, and the dependency of bridge damage level on both the vehicular impact velocity and mass is graphically presented. The proposed approach can be practically generalized to on-site damage evaluation of a bridge structure after actual accidents and can provide useful reference in design and restoration of RC bridges.