Dynamic response modeling of sea-crossing bridge pier under the combined action of earthquakes and ocean waves using high-order time-domain boundary element method

A high-order time-domain boundary element method (TDBEM) for evaluating the combined impact of earthquakes and waves on sea-crossing bridge piers is presented, facilitating a comprehensive simulation of the interactions among seismic activity, wave forces, and structural responses. The proposed method is validated through numerical simulations from existing studies and benchmark model tests. An elliptical pier is used as a case study to analyze these combined effects. Results indicate that water depth significantly influences structural seismic responses due to changes in fundamental frequencies caused by added water mass. The influence of waves in the combined action is contingent upon the dominant seismic frequencies and the structural fundamental frequencies. When the structural fundamental frequency is far from typical ocean wave frequencies, fluid-structure interaction (FSI) effects amplify the peak response by 8 % to 25 %, depending on the ground motion's dominant frequency. When the structural fundamental frequency coincides with typical ocean wave frequency ranges, FSI effects exhibit an uneven influence on the structural response due to the inhomogeneity of wave-induced FSI effects. In such conditions, as the dominant frequency of ground motions increases, the suppression effect induced by wave FSI on the peak response may counterbalance or exceed the influence of earthquake-induced FSI effects.