Dynamic performance and damage evaluation of a scoured double-pylon cable-stayed bridge under ship impact

摘要

Safety evaluation of a bridge crossing a river under vessel impact is commonly conducted based on the original model of the bridge. However, the bridge may be subjected to local scour within its service time. Therefore, it is necessary to assess the safety of the bridge under multiple hazards: local scour and vessel impact. In this effort, the nonlinear dynamic performance of a double-pylon cable-stayed bridge is investigated by a high-resolution finite-element (FE) method. First, to validate the accuracy of the FE model, a drop-hammer test conducted by previous researchers is simulated, and the numerical results show that the impact force, displacement, and failure modes match with those in the test for each case. Based on the validation, an FE model that constructs a complex colliding system for a double-pylon cable-stayed bridge and a ship is created to conduct nonlinear dynamic analysis. The impact forces, deformation of the pylon and pile foundation, and crush depths of the ship are calculated. The findings indicate that (1) local scour has a small effect on the rising step of ship impact force but affects its descending step; (2) the displacement at the impact point significantly increases with scour depth; (3) scour reduces the crush depth of the ship bow when the ship collides at lower collision velocities; (4) the ship impacts activate the vibration of the high-rise pylon, and the resulting damage severity in the pylon increases with scour depth under the same collision condition. The findings in this study can be used to guide the analysis and design of large-span bridges to resist local scour and ship impact.