The Research On Structure Parameters Of The High Speed Railway Extradosed Cable-stayed Bridge

The extradosed cable-stayed structure was first proposed in1988by a French engineer.The mechanical characteristics of the structure are between continuous beam and cable-stayedbridge, and the main girder stiffness is bigger, the tower is shorter, and the cables are arrangedrelatively concentrated. Because of the good mechanical properties and unique style, thestructure was developed vigorously abroad in the later, especially in Japan, however, the riseof the structure is relatively later in our country.The development of cable-stayed bridge onrailway in our country is slow, and so far only three railway cable-stayed bridges has beenbuilt. Two are combined bridge and Wuhu Yangtze River Bridge（180+312+180）m is a railextradosed cable-stayed bridge. Therefore, the research on the mechanical properties of therailway extradosed cable-stayed bridges is not deep enough.Base on the high speed railway extradosed bridge (96+176+96) m, the whole bridgefinite element model is established by adopting the finite element software Midas/Civil. Aseries of static and dynamic models are generated by modifying the boundary conditions orgeometric parameters (the average stiffness of main girder, the height of tower and the cablesectional area).First of all, the stress of the extradosed cable-stayed bridge is analyzed, and it is reachedthe stress of the whole bridge structure after construction meets the specification requirements.Determining the cables strength is for all the cables, determining the maximum ratio betweenthe cable force under the dead load and the cable force under the dead and live load. So thequantitative analysis of cable force of the railway extradosed cable-stayed bridge can be taken.By introducing the concept of the cables effect, the girder internal force (bendingmoment,axial force) and deflection of the continuous beam are compared with the extradosedcable-stayed bridge, and the cable performance on the girder is analyzed.Second, when the structure system is changed or one of the geometric parameters (theaverage stiffness of main girder, the height of tower and the cable sectional area) is changed,under the live load，the internal force and the maximum deflection of the changed bridge arecompared with the original bridge. When the structure system and the geometric parametersare changed, the influence on the structure internal force and maximum deflection of thegirder is studied, and it is obtained that under the live load, the stress of the rigid frameworksystem is better than that of column beam consolidation, and beam pier separation system.Finally, the structure support conditions and geometric parameters (the average stiffnessof main girder, the height of tower and cable sectional area) are changed, that is to say thesupport conditions are only changed and the geometry parameters are unchanged, or one of the geometric parameters is just changed and the structure support conditions and othergeometrical parameters are unchanged. The frequency corresponding to the first mode of thedifferent structure is obtained and when the structural support conditions and geometricparameters are changed, the influence on the structural natural vibration is analyzed. Theresearch methods and conclusions in this paper have some reference value for the design ofthe similar bridge.