A Three-Dimensional Fully-Coupled Fluid-Structure Model for Tsunami Loading on Coastal Bridges

Abstract

A three-dimensional (3D) fully-coupled fluid-structure model has been developed in this study to calculate the impact force of tsunamis on a flexible structure considering fluid-structure interactions. The propagation of a tsunami is simulated by solving the 3D Navier–Stokes equations using a finite volume method with the volume-of-fluid technique. The structure motion under the tsunami impact force is simulated by solving the motion equation using the generalized alpha method. The structure motion is fed back into the fluid solver via a technique that combines a sharp-interface immersed boundary method with the cut-cell method. The flow model predicts accurate impact forces of dam-break flows on rigid blocks in three experimental cases. The fully coupled 3D flow-structure model is tested with experiments on a large-scale (1:5) model bridge under nonbreaking and breaking solitary waves. The simulated wave propagation and structure restoring forces generally agree well with the measured data. Then, the fully-coupled fluid-structure model is compared with an uncoupled model and applied to assess the effect of flexibility on structure responses to tsunami loading, showing that the restoring force highly depends on the dynamic characteristics of the structure and the feedback coupling between fluid and structure. The maximum hydrodynamic and restoring forces decrease with increasing structure flexibility.