Research On Structure Behavior Of Extradosed Cable-stayed Bridge

Extradosed cable-stayed bridge is a new type of hybrid structure., which have been rapidly developed and extensively applied in recent years because of its economy and beauty. By taking an under-constructed extradosed cable-stayed bridge—Lingjiang bridge as the engineering background, this paper researched some problem in construction.This paper reviewed the origin, development and current reseach situation of the scholars in the foreign and domestic, described the phylogeny, status quo, application foreground, base of theory and analysis process of finite element theory briefly and the mechanic characteristic of box-girder detailedly, especially the effect of shear-lag and distortion, considered we could analyze the mechanic property of the broad box-girder exactly by making use of the finite element method and its software.This paper built up its plane beam element model by using a finite element software called MIDAS/CIVIL, analyzed the structural behavior at the stages as follows: longest double cantilevers, fold of half-bridge and load cases of finished phase under dead loads and four-lane of every single-span under moving load, obtained variational law of the internal force and displacement of the box-beam and stress amplitude of cables. Discussed the method of optimal highness of pylon by changing the tensile force of cables adjust to the influence changing highness of pylons.This paper built up its three-dimensional spatial solid element model by using a finite element software called ANSYS according to the specialty of the broad box-girder, analyzed the effect of shear-lag under moving load on four-lane of every single-span, obtained the variational law of the top and the bottom plates of box-girder.Analyzed the structure dynamic response comparing the model of plane beam model to three-dimensional spatial solid model, concluded that the dynamic rigidity of the former is higher than the latter. In order to understand the dynamic property of extradosed cable-stayed, built up its plane continous rigid-frame model and compared with each other, concluded that the former is more complex due to the remarkable coupling effect of cable, pylons and box-girder. The dynamic property of box-girder decide the dynamic property of the bridge, whose whole structure is comparative rigid. This paper indicated that the bridge is not attribute to flexible structure, because its basic free vibration cycle is more shorter than the cable-stayed bridge.