Dynamic Characteristics And Seismic Response Analysis Of Long-span Tied-rod Steel Box Basket Arch Bridge

At present,China’s economic development and infrastructure show a trend of rapid growth.After entering the 21 st century,China’s steel output and steel smelting technology are becoming more and more mature.With the continuous improvement of arch bridge construction technology in China,more and more long-span and high-strength arch bridges have been built.Steel arch bridge is used in many cities in China with its beautiful and diverse structural forms,high strength ratio and bearing capacity.In recent years,earthquake disasters occur frequently all over the world,and steel arch bridges are affected by earthquakes.Therefore,many experts and scholars have carried out seismic research on steel arch bridges and obtained many important results.Based on the engineering background of a Fujiang bridge project in Mianyang,this paper establishes the whole bridge model of the arch bridge by using Midas civil finite element simulation software,and analyzes the seismic response of the steel arch bridge around the model.It mainly includes the following aspects:（1）Firstly,it introduces the development process of steel arch bridges at home and abroad,collects the data of typical steel arch bridges at home and abroad,introduces the stress characteristics and seismic research status of steel arch bridges,expounds three theoretical methods of seismic response of steel arch bridges,namely static method,response spectrum method and time history analysis method,and compares the advantages and disadvantages of the three methods,so as to make a theoretical basis for the later seismic example analysis.（2）Taking a Fujiang bridge in Mianyang as the engineering background,according to the theory of structural vibration mechanics,the finite element model of the whole steel arch bridge is established,the natural vibration characteristics of the arch bridge are analyzed,and the natural vibration frequency and formation of the steel arch bridge are found out,which lays a foundation for the subsequent seismic response analysis and research of the steel arch bridge.The natural vibration performance of steel arch bridge is studied by adjusting the parameters such as the inclination angle of arch rib,the stiffness of arch rib and the number of transverse braces.（3）Based on the seismic response spectrum theory and the site conditions of Fujiang bridge,the response spectrum analysis of the long-span steel arch bridge model is carried out to explore the internal force and displacement response relationship of the arch rib section of the steel arch bridge under the transverse,longitudinal and vertical one-way seismic waves and the transverse + vertical and longitudinal + vertical combined seismic waves in the seismic response spectrum,Finding out the most unfavorable position of internal force and displacement in the seismic response spectrum should be paid more attention in the design of steel arch bridge.（4）Based on the theory of seismic time history analysis,the finite element simulation software is used to analyze the seismic time history response of long-span steel arch bridge model,and analyze the internal force and displacement response law of steel arch bridge under transverse seismic wave,vertical seismic wave,longitudinal seismic wave and combined seismic wave.Considering the response of long-span steel arch bridge under seismic traveling wave effect,the seismic response law of steel arch bridge does not show a monotonous change law under different wave speeds.With the increase of traveling wave speed,the internal force response of each section of steel arch bridge first decreases,then increases,then decreases and then increases.