Impact behavior of a strengthened bridge substructure under scour and vessel collision

When subjected to a vessel collision in the presence of scour induced by wave-current or flood, a bridge can sustain more severe damage compared to the pristine bridge undergoing the same impact. Scouring diminishes the ultimate capacity of pile foundations and can result in local damage to piers and pile foundations post-collision. This study aimed to mitigate impact damage on a scoured steel reinforced concrete (RC) bridge by employing a concrete-filled steel tubular pier and increasing the pile foundation section area. Pendulum impact tests were conducted on four concrete-filled steel-tubular pier-pile foundation systems to study their impact behaviors with scour depth effects. Experimental results show that while the displacement at the top of the pier increases with scour depth, there is no observed local damage to the impacted pier, even at deep scour depths. Subsequently, an FE model of the steel RC bridge was developed to assess the local dynamic behavior and damage based on the validated model. The impact performance of the scoured bridge, reinforced with a concrete-filled steel tubular pier and an increased pile section area, was then evaluated. Compared to the pristine bridge, the pile foundation with scour is prone to yield under the same impact condition, especially at deep scour depths. The increased section area method significantly enhances impact performance and reduces potential local damage to pile foundations, even under deep scour conditions. Additionally, a concrete-filled steel tubular pier markedly improves impact behavior compared to a conventional RC bridge pier. These findings underscore the efficacy of structural enhancements in bolstering the resilience of bridges against vessel collisions in scour-prone environments.