Dynamic Response Of Long-span Continuous Composite Bridge With Corrugated Steel Webs Under Strong Earthquakes

In recent years,composite continuous bridge with corrugated steel webs has a rapid development in China,the main span exceeding 160 m.The static problems have been increasingly improved in the field.With the popularization and application of this kind of bridge in mountainous and high intensity earthquake areas,the dynamic characteristics especially seismic performance begins to attract attention.Ambient vibration test,model modification and dynamic time history analysis method are adopted in this thesis,taking BR-06 Bridge of Iran Tehran North Highway as background.The study calculated the dynamic responses of the bridge under strong earthquakes and explored effective seismic mitigation and absorption methods.The main contents and conclusions of this thesis are listed as follows:(1)The dynamic characteristics of BR-06 Bridge was obtained by ambient vibration test.The FEM was established based on ANSYS and then it was updated and verified using third-order response surface method to determine the baseline FEM of BR-06 Bridge.It was proved that the dynamic characteristics of updated FEM have much higher correlation with test results.(2)Based on updated FEM,nonlinear time history analysis of BR-06 Bridge was carried out to investigate coupling effect of multi-direction excitation.The findings show that the effect of vertical excitation is considerable for long-span composite bridge with corrugated steel webs,especially when checking the longitudinal capacity of piers.(3)The seismic response was simulated under E1 and E2 earthquake,and compared with design values.The analysis reveals that: under E1 earthquake,the concrete of beam and pier remains elastic;the bearings and dampers absorb the vibration within their capacity;under E2 earthquake,the RC piers work with cracks which still meet the capacity requirements;seismic mitigation and absorption system controls horizontal vibration effectively;but the transverse deformation of B4 in abutment exceeds the limit,the bridge may slightly damage here.(4)In comparison with fixed bearings and pot bearings,friction pendulum bearings make two piers work coordinately instead of the fixed pier resisting vibration alone,which solve the problem of asymmetrical force caused by asymmetric height of piers.However,the displacement of beam will be incontrollable when only using friction pendulum isolation technology.(5)Parameter analysis were conducted,including curvature radius and friction coefficient of friction pendulum bearings,damping constant and velocity index of viscous fluid dampers.Their influence to structure seismic response were studied and the reasonable value ranges were assessed based on efficiency coefficient method.The results support the idea that the isolation system combining friction pendulum bearings and viscous fluid dampers reduces structural response of internal force and displacement at the same time under strong earthquakes,and significantly improves the seismic performance of this kind of bridge.