Stability Study On Arch Bridges With Open Thin-walled Boxes Under The Turning Construction Stage

In addition to the simple design and construction, owing to explicit mechanics states, it's easy to master and develop turning bridges. Comparing with other construction project, such as steel framework, CFST, etc, open thin-walled boxes reduce quite a lot of expense, simplify the construction categories, and have some advantages in view of the turning manipulating. So it's easier to be adopted than others in a mountainous area. At present, in the construction process of light-weight turning, the global stability and local stability problems have some effects on the design theory and method, construction art and construction controlling technology, which have not been researched systematically and have impeded the development of this technology.Firstly, the thesis reviews the history of structure stabilization, in the same time, relates to the real project, points out some problems exist in actual research. Secondly, from the stability theory of long-span bridges, the thesis elicits the basic stability theory and some numerical solution methods about it, enumerates classical buckling of circular arches and deduces the process of discretionary arch axes through the displacement theory. Considering two construction conditions that when breaking away from brackets and when in the second concrete casting stage, the thesis analyzes stability states of half-span arch structure.Relying on the science and technology project from Hubei province transportation bureau [2004]343, according to some reasonable and necessary simplifications, the thesis builds the 3D finite element model of Ping di-ba turning arch bridge which is the largest span turning bridge constructed by the open thin-walled boxes technology at present in Enshi state in Hubei province and submits a model building method for these types of bridges by the finite element software ANSYS. The thesis anticipates structural displacements' change by finite element numerical simulation. Because there are no exterior loads that acting on structures in the stage before the ribs breaking away from brackets, the thesis defines the multiple of structure while the arch ribs lose stability as the stability safety factor. Considering the magnitude of cable force, uniformity of tension, errors from casting concrete, adding the thickness of local sections and the effect of reinforcing steel cage, the thesis provides various stability safety factors of half-span arch which correspond to different conditions. Owing to the structure's symmetry, by using the half-span arch model, the thesis simulates the stability states when the whole bridge under the 2nd casing concrete stage.According to the above research work, the thesis concludes some instable characters and some problems which should be pay more attention to. Considering the theory value and practicability, the research results will be helpful for the western mountainous areas in China.