Study On Seismic Performance Of High-speed Railway Bridge With Functional Separation Bearing Considering Soil-structure Interaction

Since the reform and opening up,China's railway construction has developed rapidly,and high-speed railway construction has entered a period of rapid development.In railway construction,the bridge structure has the characteristics and advantages of saving land and making full use of the upper space.Like other countries that build high-speed railways,bridges are widely used in the construction of high-speed railways.The proportion of bridges in some high-speed railways is even 90%.However,China is a country with a vast territory,complex terrain and frequent earthquakes.The construction of high-speed railway bridges can not avoid the influence of site conditions and earthquake hazards.At present,in the application of bridge structure,the technology of isolation seismic has become one of the ways to replace the traditional seismic mode.The effectiveness of seismic isolation technology has been fully verified in earthquakes at home and abroad.Because of the characteristics of high-speed railway bridge structure and the influence of rails,most of high-speed railway bridges have not yet adopted seismic isolation technology,except for some special high-speed railway bridges.Therefore,in the construction of high-speed railway bridges,it is necessary to study the application of isolation technology and the influence of site conditions on isolation technology in order to improve the seismic performance of high-speed railway bridges.At present,the main function of bridge bearings is the normal use of bearings.It includes the functions of vertical bearing,rotation and horizontal displacement.On the basis of this normal function,the bearings with seismic isolation technology add the seismic isolation function,which can only play a role in the event of earthquakes.In this study,the support system for high-speed railway bridges is divided into the normal functional support system to ensure the normal operation of trains and the subsidiary functional support system to ensure the isolation effect during large earthquakes.The two systems are organically combined to establish a complete and effective support system for high-speed railway bridges.The basic idea of the seismic isolation technology system for high-speed railway bridges proposed in this paper is to maintain the seismic performance of bridges by relying on the stiffness of bridges under small and medium earthquakes.Under the action of large earthquakes,when the pier enters the plastic state,the bearing system enters the isolation state to ensure the safety of the bridge.Furthermore,considering the soil-structure interaction,the seismic isolation performance and control effect of high-speed railway bridges with functional separation bearings are compared and analyzed,and the experimenta l verification is carried out.This paper does the following research contents:(1)The theory and calculation method of soil-structure interaction are summarized.SR model is used to calculate the parameters of soil spring when the actual site is converted into spring model.(2)Taking Zhangjiatian Bridge as a prototype,the finite element model of a standard 6-span high-speed railway bridge with equal height is established.Fixed connection model and soil spring model are adopted at the bottom of pier.In finite element analysis,9 degree rare earthquake with peak input acceleration of 0.64 g.Through linear elastic time history analysis,the effects of different earthquake input directions and soil-structure interaction on seismic response of bridge structures are studied.(3)Elastic-plastic time history analysis of the two models is carried out by setting plastic hinges at the bottom of piers.By inputting seismic waves with different peak accelerations,the peak accelerations of the piers in the yielding state of the two models are determined respectively.Nonlinear time history analysis of isolated bridges with functional isolation bearings is carried out to analyze the effect of soil-structure interaction on the elastic-plastic properties and isolation performance of structures.(4)The form and working principle of the function-separated bearing are summarized in detail,and the shaking table test of the isolated high-speed railway bridge specimen with reduced ratio of single span is carried out to fully verify the rationality of the working principle of the function-separated bearing and its good isolation performance.