| Self-anchored cable-stayed suspension composite system bridge is a new type, with obvious characteristics of suspension bridge and cable-stayed bridge. It has novel structure, the unique model and exquisite linear. But as a new kind of bridge system, the structure is so complex that the mechanical properties are not very clear. What’s more, during the construction process, it has been complex and nonlinear, which has made the design and construction of bridge in trouble. With the background of Dongtiaoxi Bridge Project in Huzhou, Zhejiang Province, this thesis researched the construction control method of main girder with the stress-free status method and geometry control method, compared and analyzed the differences of some schemes hoisting main girder, verified the feasibility of "Erecting Cable before Constructing Girder" hoisting construction method of this bridge system by a test of the whole bridge model. The main research contents include:1. Concluded the structure analysis theories for suspension bridge and summarized the finite element analysis method for the hoisting process of stiffening girder. Based on the stress-free status method and geometry control method, this thesis has established a set of forward calculation method that could be used in the analysis of hoisting construction of main girder of self-anchored cable-stayed suspension composite system bridge. In this method, unstressed dimensions and geometric relations of the structural members has been used as control quantities to determine whether each structural state is ideal in the construction process.2. As a numerical example of Dongtiaoxi Bridge, this thesis has verified the correctness of the forward analysis method based on the geometry control method. Some influencing factors, such as temporary load and connection mode of girders, have been considered and analyzed contrastively. It has shown that the structure could be always in the ideal state when using the forward analysis method based on the geometry control method; and temporary load, the position of temporary connections and the opportunity of temporary connections converted to rigid connections had no impacts for the final state of the structure.3. According to the practical engineering of Dongtiaoxi Bridge, this thesis selected six hoisting schemes of stiffening girder to simulate the whole construction process, analyzed the influences of the construction intermediate state when temperature changing, discussed closure and construction conditions of a variety of hoisting schemes, and proposed suitable scheme for the practical construction by summing up the advantages and disadvantages of each scheme.4. Considering the complex structure of self-anchored cable-stayed suspension composite system bridge, a total bridge model (Dongtiaoxi Bridge) test had been taken, for inspecting the differences of structure’s stress state and cable-curve state between theoretical calculation and practical construction, and supporting for the final determination of the practical construction scheme. And then based on similarity theory, a test model was designed with the structural parameters of Dongtiaoxi Bridge.5. Aiming at two hoisting sequences, from the towers to the middle of the span and the opposite direction, the total process simulating model tests were conducted respectively. Besides, this thesis has compared and analyzed the results of the model tests and theoretical calculation, verified the correctness of theoretical calculation, and provided theoretical and experimental basis for the actual construction of stiffening girder.6. Based on the total bridge model of Dongtiaoxi Bridge, the static and dynamic performance tests were made respectively, which had got the static and dynamic performance indexes of Dongtiaoxi Bridge-a self-anchored cable-stayed suspension composite system bridge, and provided basis for understanding the mechanical properties of this new type bridge. |
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