Dynamic Response Analysis Of Deep-water Bridge Piers Considering Fluid-structure Interaction

In recent years,countries around the world have been working to improve transportation infrastructure.So a number of deepwater Bridges were built.But since some or all of the lower structures of such bridges are in deep water,the presence of water will affect the dynamic characteristics of the structure itself,thereby affecting its dynamic response during earthquakes;in addition,the interaction of water flow and wave in the environment will also affect the dynamic response of the structure.However,there are still few correlation researches,especially on the deep-water hollow bridge piers.Therefore,it is of great value to study the fluid-structure coupling effect of deep water pier under the action of earthquake,water flow and wave.The main research contents include:(1)Based on the finite element method of potential fluid,the finite element numerical analysis model of single circular hollow pier is established.The dynamic characteristics and seismic responses of hollow piers with different water depths,wall thickness and with or without internal water in the hollow bridge piers are analyzed.The results show that the natural vibration frequency of the bridge piers decreases due to the existence of water,and decreases with the increase of water depth.The thinner the wall thickness of the bridge piers,the more the natural vibration frequency is affected by the water depth,and the exist of water in the hollow bridge piers increase the influence of water depth on the natural vibration frequency.Under the action of earthquake,the dynamic response of the brige piers increases with the increase of water depth,and the thinner the wall thickness of the bridge piers or the inner water will increase its influence.(2)A three-dimensional numerical model of pier-current and flow field coupling was established to study the dynamic response of bridge piers under the action of water flow and waves.The results show that the dynamic response of the bridge piers increases with the increase of flow velocity and wave height.The dynamic response of wave to bridge piers decreases with the increase of wave period.The existence of water in the inner of the hollow bridge piers will reduce the dynamic response of water flow to the bridge piers,but will slightly increase the dynamic response of wave to the bridge piers.When multiple piers are continuously affected by water flow,the stability value of the dynamic response of the firstpier in the flow direction is the maximum,and the maximum value of the dynamic response of the last pier is the maximum.(3)On the basis of considering the action of water flow and wave at the same time,the finite element model of pier-wave and current combined action is established,and the dynamic response of deep water bridge pier under the action of wave and current combined action is studied.The results show that the dynamic response of the bridge piers is not the direct superposition of the action of water flow and wave alone.The influence of wave load on the bridge piers is the main one in the combined action.Water flow strengthens the effect of wave crest on bridge pier s and reduces the effect of wave trough on bridge piers.