Dynamic response and performance evaluation of bridges under the combined action of scouring and ship collision

Vessel collision is a critical accidental load in bridge design, while pile scour undermines structural capacity and durability. Limited studies were carried out to investigate scour progression on impact load response. To evaluate the combined action, a safety assessment for a cable-stayed bridge is conducted in this study. Finite element models of three impacted reinforced concrete columns are established and validated. A refined ship-bridge collision model incorporating dynamic pile-soil interaction is developed. The impact force, the dynamic response and the associated damage variations of the bridge tower are examined under different conditions of scour depth, water level, and collision location. The safety of the bridge is evaluated by the vessel collision safety factor determined by the actual resistances of the piers and the internal reaction. Key findings indicate that: (1) water level fluctuation has more significant influence on peak collision force than scour depth; (2) bridge displacement increases substantially with scour depth, while pile head damage exhibits a distinct non-monotonic trend; (3) the pile foundations and pile-cap connections tend to be the first to exhibit insufficient bearing capacity; (4) the critical scour depth according to the original code and the current code is 10.57 m and 0 m, respectively.