| The extradosed cable-stayed bridge is a combination system, its geometry andmechanics characteristic between the cable-stayed bridge and continuous beam. In ourcountry, Research and analysis of the extradosed cable-stayed bridge compared to othercountries lagged, beginning construction was also relatively late. Also, study of extradosedcable-stayed bridge in the earthquake and seismic research is still very lack. In this regard, theSanduiz Jinsha River extradosed cable-stayed bridge is in the design stage, and do research onseismic respons and isolation Analysis of the bridge. So as to provide reference for theseismic design of the bridge later. In this paper, by using the finite element softwareMidas/civil established Sanduizi Jinsha River extradosed cable-stayed bridge model, and hascarried on the following research:(1)In the simulation of cable, first determine whether the cable for the bridges need toconsider the sag effect, the calculation it is found that difference between the equivalentelastic modulus and the elastic modulus of cable of cable materials is only0.437‰, thedifference is small.So in the process of modeling the cable sag effect can be neglected.(2) In order to simulate seismic response more accurate, effect pile soil of theextradosed cable-stayed bridge were considered. In the model the pile-soil interaction wascalculat by the "m" method. In the study of the dynamic characteristics of the bridge, it wasfound that the result of considering the elastic foundation pile-soil interaction or not haddifference. Elastic foundation vibration cycle was longger than the rigid foundation vibrationcycle, but the frequency of Elastic foundation was lower. And the change in the mode shapewas also difference. In the calculation of self vibration characteristic, the200th modalparticipation mass can satisfy the accuracy requirement to total mass more than90%. In Xdirection (in longitudinal bridge), Y (transverse), Z (vertical direction of the bridge) of the200th modal participation mass rate were99.69%,98.99%,91.83%.(3) In the seismic response spectrum analysis, respectively considering whenearthquake force acting on the longitudinal, transverse and vertical direction caused thereaction of internal force and displacement. By reference to earthquake combination methodof European standard, To research the changes which caused by the combined action, includinternal force, displacement and stress(4)In the elastic seismic time history analysis, according to the site type, seismicintensity and characteristic period of Sanduizi Jinsha River Extradosed Cable-stayed Bridge,select the three records of seismic wave in Midas.To input the three wave respectively fromlongitudinal, transverse and vertical of the bridge.Than the internal force and displacementseismic response are obtained respectively, and draw the curve of the displacement and internal force of special parts. By comparison selected maximum among the three waveresults,than the results were compared with the response spectra. It was found that timehistory response results larger than response spectra’s(5) After the introduction of the principle of isolation, the isolation design method basedon displacement. The author designed the lead rubber bearing for piers and abutments ofbridge. To input yield load, elastic stiffness, yield stiffness ratio and the hysteresis parameterof lead rubber bearings, in Midas.Among nonlinear time history analysis of the bridge, withisolation measures is compared with the result of time history response without isolationmeasures. Results can be obtained by the time history response with isolation measuressmaller than non isolation measures. While the basic cycle of this bridge was1.7times longer,effectively avoid of seismic energy, thereby reducing the seismic response of the bridge. Sowe can illustrate that the lead rubber bearing which designed has better shock-absorbing effect.Lead rubber bearing displacements was in the design range, the lead rubber bearing design isreasonable. |
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