波流与地震共同作用下深水桥墩动力响应分析

为了揭示深水环境中波流与地震共同作用下桥梁下部结构与水耦合作用机理，基于非线性Morison方程，建立了波浪、水流和地震联合作用下结构动力学方程，通过有限元离散，计算了某深水桩-承台-桥墩结构体系的动力响应，并分析了不同波流要素对该结构体系动力反应的影响.研究结果表明:波流与地震之间存在相互影响，波流对地震响应的影响范围为-31.6%~63.5%，这种影响不仅改变地震响应幅值本身，而且改变幅值出现的时刻，还将使得波流、地震联合作用下流场激励频率介于纯波流场激励频率和地震激励频率之间，因此有必要进行波流与地震的联合作用分析；当波流作用在承台及以上位置时，桥墩的动力响应显著增大，在实际工程建设中须引起重视，有必要选用承台高出水面的高桩承台. 

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.