Study of Structural Behavior of 7-Pylon PC Extradosed Bridge

The finite element method is used to analyze the structural behavior of the multi-pylon prestressed concrete(PC) extradosed bridge.Like a cable-stayed bridge,the rational completion status of the extradosed bridge can be determined through optimizing the initial tensioning force of stay cables and the safety and rational force conditions of the structure can be ensured through optimizing the construction schemes.The dead load of the extradosed bridge is mainly carried by the stay cables while the live load is carried by the main girder.The maximum stress amplitude of the stay cables under the action of live load is at the outmost cables at side span,which is quite close to that of the stay cables of the cable-stayed bridge and the mutual influence between the horizontal displacement at the top of a pylon and the deformation of the adjacent pylons is little.By way of example of Kaifeng Huanghe River Bridge on Daqing-Guangzhou Expressway and by changing the structure into the continuous girder and cable-stayed bridge,the structural behavior of three types of the structural systems under the action of live load is comparatively analyzed.It is known from the analysis that from the continuous girder to the extradosed bridge to cable-stayed bridge,the global rigidity of the structure gradually increases,the bending moment carried by the main girder and the structural displacement gradually decrease while various orders of the natural vibration frequency of the structure gradually increase.