Spatial Cable System Calculation Method And Static Wind Stability Analysis Of A Self-anchored Suspension Bridge

Special as it is, self-anchored suspension bridge has become more and more popular with engineers because of its highly aesthetic view, good economy performance and striving adaptability of geology and topography feathers. It has become a highly competitive bridge type for the urban bridge within span from 100m to 400m. Stone-marked by Konohana Bridge in Japan and Yeongjong Bridge in South Korea, self-anchored suspension bridge has strived both abroad and within the country. However, there is not a full understanding of the self-anchored suspension bridge, not only of the theory on research field of static and dynamical performance, but also of the bridge design and construction process. Relying on the project of Youcha Bridge in Nanjing, this thesis carried out researches on non-linear shape finding analysis, erection shape of cable and pre-displacement of saddle without loads, amendatory method of cable's unstressed length and static wind stability analysis. Main work in the thesis are as follows:(1) The thesis firstly made an general introduction on the phylogeny and application actuality inland and abroad, summarizes the basic construction and forcing characteristic, and indicates the existing problems and developing trend of self-anchored suspension bridge.(2) Theories of the main cable of suspension bridge includes mainly the analytical calculating method and finite element method. Analytical calculating models consist of parabolic theory, catenary theory and segmental catenaries theory. Bar element and flexible cable element for finite element method and their respective tangential stiffness matrix are introduced at last. The thesis also gives spatial expression of the cable element.(3) Chapter 3 introduces systemically the theory for main cable and total bridge system calculation of self-anchored suspension bridge, including calculating design line shape and internal force, erection line shape of cable and pre-displacement of saddle without loads, the fixed position for erecting cable and amendatory method of cable's unstressed length.The total bridge cable system calculating methods can be divided into analytical calculating method and finite element method. The analytical method is based on the analytic calculation method of the cable's line shape in chapter 2. It is only applicable for earth anchored suspension bridges whose main girder is constructed by segmental articulation method. The thesis combines the analytical and the finite element method together. On the groundwork of preliminary line shape using the linear.for by FORTRAN, the thesis programmed catenary.m using Matlab on the bases of segmental catenaries theory and the related force balance and deformation consistency to calculate the cable shape. The results of which were used in the next step where ANSYS were used to calculate the total bridge system. According to the deformation of the bridge deck, we adjust the suspenders'force and calculate the cable shape again. After several times the rational internal force and shape of the total bridge is converged. Calculation of cable only system and saddle pre-displacement were then carried out and the amendatory of the saddle on line shape was also calculated.(4) The static wind collapsing structure destabilized by static wind load which induced the bending and twist rotation that leads to the change both on stiffness and the relating static wind loads. The effects together results in the increment of both the deformation and the load, finally they lead to the collapse of the bridge. This mutual-exciting effect has been tested in the wind tunnel test. Static wind stability analysis is necessary therefore, especially for a new type of bridge.The thesis introduced a plane linear static model and a 3D static model of the beam of bridge. Then calculation was carried out based both on the 2D and 3D model. The results of -3°,0°and +3°of critical wind velocity for twist rotation indicates that the Youcha Bridge satisfies the static wind stability demands. Meanwhile, the comparison of the plane result and spatial results indicates that the critical static wind velocity formulation on the code is not suitable for self-anchored suspension bridge, which has a relative small span.