Optimization Of Longitdinal Aseismic System Of High Tower And Combined Beam Cable-Stayed Bridge In High Earthquake Area

With the western development strategy and the implementation of "The Belt and The Road",the traffic infrastructure of our country is booming.Accordingly,the aseismic design problem of long-span cable-stayed bridges has attracted more and more attention.At present,for the aseismic research of large-span cable-stayed bridges,the theoretical analysis based on finite element method was mostly adopted.There are few model tests of the whole or local member to further verify the accuracy of the theoretical analysis.To seek reasonable,effective and reliable shock absorption measures for long-span cable-stayed bridges in high earthquake area,the optimization design of the longitudinal aseismic system for the cable-stayed bridge in high earthquake area is studied by using element analysis and model test.And the research is based on the Xigu Yellow River Bridge in Lanzhou where the basic intensity is VIII degree.The main research contents and corresponding results are as follows:(1)The mechanism of bridge damage is analyzed,and the research status quo of seismic design for long-span cable-stayed bridges at home and abroad was summarized.The key problems and innovations of this article are pointed out.(2)Based on the basic theory of seismic response analysis,the SAP2000 finite element model of Xigu Yellow River bridge in Lanzhou was established.And the self-vibration characteristic analysis was carried out.(3)By using the spatial finite element model,the influence of pile-soil interaction and non-uniform earthquake excitation on the seismic response of the cable-stayed bridge in high earthquake area in Northwest China was discussed.The results show that pile-soil interaction has different effects on the internal force and displacement response of key positions of cable-stayed bridge in high earthquake area.Studying the seismic performance of the cable-stayed bridge,it is more reasonable to consider pile-soil interaction.When the seismic wave velocity is less than a certain value,the influence of the traveling wave effect on the seismic response of the long-span cable-stayed bridge can not be ignored.(4)By using the nonlinear time history analysis method,the seismic response characteristics of different longitudinal structure system of cable-stayed bridge were compared and analyzed.The relationship among the internal forces,the displacements response of key positions of the bridge and the damping parameters of the 6500 kN longitudinal viscous dampers was emphatically studied.The results show that the semi floating system connected by the damper is more reasonable,and the system can take account of the displacements and internal forces response of the cable-stayed bridge at the same time.The two element function can be obtained by fitting the relationship among the internal forces,the displacements of the key position and the damping parameters.The optimal damping parameters can be obtained by finding the extreme value of the two element function under the constraint conditions.(5)A viscous damper with 6500 kN large tonnage in 1:1 full scale were designed and fabricated.Low velocity test,constitutive relationship test and damping coefficient test were carried out in the experimental laboratory TREES Lab,at EUCENTRE(Pavia,Italy).The experimental results show that the viscous damper has good mechanical properties and strong energy dissipation capacity and the stability of energy dissipation reaction is good.The experimental results of constitutive relations are consistent with that of the damping parameters obtained by the optimization method,which further validates the correctness of the damping parameter optimization method.