Hydrodynamic And Seismic Response Analysis Of Complex Piers In Reservoir Area Based On Fluid-Structure Interaction

On October 8,2021,the Central Committee of the Communist Party of China and the State Council printed and distributed "the Outline of the Plan for Ecological Protection and High-quality Development of the Yellow River Basin".With the development of environmental protection and high-quality development of the Yellow River Basin as a national strategy,the demand for transport infrastructure construction along the Yellow River and in the central and western regions has been increasing.Among them,some bridges across the Yellow River and the reservoir areas have been built with deep-water large span and complex system and structural behaviors.To meet the needs of carrying and improving the mechanical behaviors of deep-water bridges,some bridges have complex substructures.Different from common bridges over rivers,deep-water bridges are faced with a more complex and changeable hydrodynamic environment and inevitably suffer from wave,current,scour,and other complex hydrodynamic effects.However,the research on the seismic response of deep-water bridges with fluid-solid coupling effect is not perfect,and there is little research on the hydrodynamic behavior of deep-water complex piers.Given this,based on a 4-column piled frame pier continuous beam bridge in the Xiaolangdi reservoir area of the Yellow River,the paper studies the dynamic response of 4-column piled frame pier and its bridge undercurrent,wave,and earthquake.The main contents and conclusions are as follows:(1)Concerning the 4-column pile-column frame pier,a numerical model of the deepwater bridge pier and bridge is established following the fluid element method to analyze the dynamic response in different water areas and at different water depths.The results show that the natural frequencies of 4-column piled frame piers and the bridges decrease with the increase of water depth,and the amplitude decreases with the increase of water depth.The maximum amplitude of the first four steps of the 4-column piled frame piers is 14.03%,the maximum amplitude of the first three steps of the bridges is 3.34%,and the vertical vibration is unchanged.But the wave is still the main influencing factor in the combined action of wave and current.(2)A three-dimensional flume numerical model shall be established to analyze the dynamic responses of piers in the flow and wave fields.The numerical results show that the dynamic response of piers will be increased with the increase of water depth and velocity under the action of the current.And the dynamic response of piers will also be increased with the increase of wave height and water depth under the action of the wave.Under the combined action of wave and current,the dynamic response of the bridge pier is not the direct superposition of the dynamic response under the action of water flow and wave alone.The flow velocity will increase the dynamic response of the bridge pier under the action of the wave crest,and at the same time will weaken the dynamic response under the action of the wave trough.(3)Considering the fluid-solid interaction effect,the seismic response of the 4column piled frame pier continuous beam bridge under the conditions of anhydrous,still water,wave,and the current environment are analyzed.The results show that the seismic response of piers under a wave and current environment is larger than that under an anhydrous environment.The seismic response of piers in the water is not the direct superposition of the seismic response under the combined action of wave and current and the sole action of an earthquake.