Dynamic Resoponse Analysis For Steel Truss Cable-stayed Bridge Of Combined Highway And Railway Under Earthquake And Wave

Bridge construction in my country extends from the inland to the ocean.Large-scale sea-crossing bridges are increasingly becoming a transportation hub connecting the two places.However,my country’s frequent earthquakes have caused large-scale sea-crossing bridges to be subjected to the combined effects of earthquakes and wave loads.For high-flexibility,low-damping long-span deep-water bridges,its dynamic characteristics make it very sensitive to seismic motion.At the same time,a large number of studies have shown that the force of wave loads on ocean bridges cannot be ignored.Based on the domestic and foreign deep-water bridge seismic-related codes are not yet clear,therefore,the response law of bridges related to cross-sea bridges under the combined action of earthquake and wave loads needs to be further studied and analyzed.Based on ocean engineering wave mechanics theory and bridge seismic code,this paper uses a long-span highway-rail dual-use cable-stayed bridge as the engineering background to construct a multi-flow field numerical flume model,and establish a three-dimensional solid model of a long-span ocean bridge.CFD fluid calculation software simulates and analyzes the wave field.And combined with ANSYS simulation software for secondary development,the transient time history numerical analysis method is used to solve the dynamic response time history of the road-rail dual-use cable-stayed bridge under earthquake and wave action,and the bridge under the combined action of earthquake and wave is studied based on the finite element method.The overall response and internal force change law.The main results are as follows.(1)Based on the finite element theory,a finite element model for road and rail is established,and the structural modal calculations are performed on it.The main vibration modes and dynamic characteristics of the bridge are obtained.The results show that the overall bridge has relative longitudinal stiffness.Stronger,the lateral stiffness of the bridge tower is relatively weak,the torsional stiffness of the main girder is relatively strong,and the advantages of multi-dimensional coupling.(2)A three-dimensional numerical wave flume model of a deep-water solid bridge tower was established,and the fluid-solid coupling numerical calculation between the pier and the wave field was carried out through the FLUENT fluid calculation software,and the wave force time history of the bridge pier under the action of wave loads of different wave heights was obtained.The wave force is applied to the full bridge model of the cable-stayed bridge,and the response law of the bridge structure under the wave load is studied.The results show that with the increase of wave height,the influence range of the displacement response of each position of the bridge structure increases significantly.(3)The seismic response spectrum and dynamic time history analysis were carried out through the secondary development of ANSYS finite element,considering the dynamic response of the overall bridge structure under different seismic intensity conditions,and the artificial wave and the strong earthquake record after amplitude modulation under the same seismic level were carried out El Centro wave calculation and comparison show that the peak response results are relatively close.(4)Considering the combination of working conditions of different wave heights and multiple seismic wave time histories,the dynamic response of a cable-stayed bridge under the combined action of waves and earthquakes is studied.In the calculation example,under the combined action of the earthquake and the wave,the earthquake has a greater contribution to the structure,but the impact of the wave load under the combined action cannot be ignored.From the perspective of this calculation example,considering the combined action of the wave and the earthquake The relative ratio and the influence of the RMS value of the structure response under the action of only the earthquake are in the range of 0.2% to 65.28%.Therefore,it is necessary to analyze the combined effect of earthquake and wave on cross-sea bridges.