Dynamic responses of long-span road–rail cable-stayed bridge under combined seismic and wave action

Cross-sea–cable-stayed bridges located in earthquake-prone areas can be subjected to earthquakes, wave action, and other dynamic loads of potential threats during their construction and service periods. The dynamic response of a cable-stayed bridge was studied under the combined effects of earthquakes and wave flow. In this study, a cross-sea–cable-stayed bridge is investigated as a prototype. ANSYS software was used to establish a spatial finite-element model, and CFD software was used to simulate the wave loads and calculate the fluid-structure coupling. The peak displacement at each location was determined under different loading conditions during the combined action of earthquakes and waves. The displacement at the top of the tower was the largest, followed by that at the main span. However, when the wave action was severe, the peak displacements of the tower top and main span were comparable, and these two peak displacements occurred simultaneously. The internal-force-response law at the bottom of the tower tended to be consistent, and only the peak values differed. The peak change in the shear force was smaller than that in the bending moment. Earthquakes and waves had a negative effect on bridges; however, they played a dominant role. Nevertheless, the presence of waves alters the dynamic response during joint action; therefore, the effect of waves on the bridge cannot be ignored. The root-mean-square (RMS) under the joint action of earthquakes and waves was evaluated using the RMS of superimposed independent earthquakes and independent waves. However, it can be observed that the joint effect is not a simple superposition effect. Complex interactions exist between the earthquakes and waves. •Using a cross-sea cable-stayed bridge as a background, a spatial finite element model of the bridge was established by ANSYS, and wave loads were simulated by CFD software.•Investigating the dynamic response of bridge key sections under the combined action of earthquakes and waves.•Proving that the combined effects of earthquakes and waves on bridges are not a superposition of dynamic responses, but a complex coupling between earthquakes and waves.