Energy-Based Reliability Analysis against Progressive Collapse of a Multi-Span Bridge under Dual Risks of Vessel Impact and Scour

Bridges spanning busy coastal or inland waterways are exposed to high risks of accidental vessel collisions. When a multi-span bridge is impacted, progressive collapses may develop within the bridge system, which can be aggravated by the decrease of pile embedment depth due to riverbed scour. Yet the system responses of a multi-span bridge supported on pile foundations under vessel collisions are not well addressed. In this study, a series of advanced centrifuge model tests on vessel-bridge collision under the normal and scoured condition was performed and interpreted from an energy perspective. Based on centrifuge tests results, an innovative energy-based limit state function is proposed and applied to the system reliability analysis of a multi-span bridge subjected to dual risks of vessel impact and scour. The reliability analyses show that, when the vessel energy is 3 times of the energy consumption capacity of the bridge, the probabilities of 3-span progressive failure with scour depths of 1, 3 and 5 times the pile diameter are 0.38, 0.94 and 1, respectively.

Keywords: Vessel-bridge collision, Progressive collapse, System reliability, Energy analysis, Centrifuge modelling