Analysis Of Seismic Response Of Deck Concrete-Filled Steel Tube Arch Bridge In Deep Cutting Gorge Area

The high mountains and deep valleys in the western region of China are steep,and the construction of bridges is facing the challenge of crossing deep canyons.Under the action of earthquake,the vibration effect of canyon surface is usually greater than that of flat site.Under the influence and control of topography,geotechnical properties,rock structure,vibration characteristics and other aspects,the amplitude of ground motion on canyon surface will produce obvious amplification effect.When the vibration is amplified to a certain extent,the damage of the mountain rock will cause more serious damage to the building structure.The deck concrete-filled steel tube arch bridge has the characteristics of convenient construction,strong span and good structural stability.It has the advantages of light weight and large ductility of steel structure in seismic performance.At present,there is a lack of seismic research on similar structural systems and considering site effects.Based on the actual project,this paper takes a long-span deck concrete-filled steel tubular arch bridge with a total length of 506 meters and a single span calculation span of 330 meters as the research object.Starting from the actual needs of the project,the seismic performance of the structure is analyzed based on the finite element platform,which provides theoretical support for the design.The main contents and achievements of this thesis are as follows:(1)Based on the finite element analysis software Abaqus,a half-space plane strain site model is established according to the real terrain at the bridge site,in which the material properties of the site model,artificial viscoelastic boundary conditions and ground motion input methods need to be considered.The characteristics of ground motion on the canyon surface are analyzed,and the peak acceleration changes along the canyon.(2)Considering the non-uniform excitation of the site effect on the supporting parts of the bridge under the action of earthquake,the amplification effect of the acceleration time history and response spectrum of the arch foot of the bridge is analyzed and studied through the dynamic analysis of the site model.(3)Based on the actual project,the finite element spatial dynamic model of the whole bridge is established by Midas/Civil software.The dynamic characteristics analysis,uniform excitation analysis and non-uniform excitation analysis considering site effect are carried out to obtain the dynamic characteristics and corresponding seismic response of the arch bridge.(4)By comparing the calculation results of the spatial effect of the two ground motions,the seismic response differences of each component of the arch bridge under uniform excitation and non-uniform excitation are analyzed,and the seismic performance characteristics of the deck concrete-filled steel tubular arch bridge across the deep canyon are obtained.The purpose of this paper is to do some basic research work for the promotion and application of long-span concrete-filled steel tube arch bridge across canyon terrain.