Dynamic Response Analysis of Bridge Pier in Deep Water under Combined Loads of Wave, Current and Earthquake

The dynamic equation of a structure under the combined loads of wave, current, and earthquake, was presented based on the nonlinear Morison equation, to reveal the coupling mechanism of water and bridge substructure under the combined action of wave-current and earthquake. The dynamic responses of a pile-cap-bridge pier in deep water were calculated by the finite element method, and the influence of the different wave-current elements on the dynamic response of the structure was analysed. The results show that the wave-current and earthquake interact. The influence of the wave-current on seismic response is between -31.6% to 63.5%. Not only does the wave-current change the amplitude of seismic response, but it also changes the time of its occurrence. Moreover, the excitation frequency of the flow field under the combined action of wave-current and earthquake lies between the seismic excitation frequency and the pure wave-current field excitation frequency. Consequently, it is necessary to analyse the combined action of the wave-current and earthquake. With the increase in wave height, the response of the pier structure is significantly affected by the wave flapping on the cap and above. Therefore, it is necessary to select an elevated pile cap for the sea-crossing bridge.