Study On Mechanical Property Of Reinforced Concrete Box Arch With Stiffness Frame Of Minor Steel Tubes During Construction

Using steel tube truss arch as stiffness frame, we can realize arch bridge construction without support, which provides a new direction of arch bridge development. Reinforced concrete box arch bridge with stiffness frame of steel tubes is consistent with the requirements ,and built of the new combination of materials. This kind of arch bridge gives full play to the advantages of high strength material and construction without support.Steel tubes of reinforced concrete arch bridge with stiffness frame are primarily used for the efforts of the crutch during contruction. Firstly, fill with concrete within the steel tubes;Secondly, set formwork and wrap concrete-filled steel tubes with concrete.The main arch ring is gradually formed by pouring concrete of separate layers and separate segments. During construction, load and structure are changing.Arch ring is time-varying structure of mechanical property. Steel tubes participate in effort of completed bridge, not designed for the service stage, but designed for the construction stage. The main subjects are summayized as follows:(1) Firstly,the thesis discusses the basic theory of non-linear finite element method and mechanics analysis methods during construction. The mechanical state of overall structure formed for only one time is regarded as mechanical state of dead load in traditional design method. The impact of the construction method on mechanical state of structure is considered in stress superposition method, and different construction methods lead to different internal force states of completed bridge. The stress superposition method should be used for mechanics analysis of arch bridge with stiffness frame.(2) Secondly,the space finite element model for main arch ring of Changyang Huanglingdong Bridge is established by general FEM programme ANSYS. Mechanical analysis of nude arch is carried on by stress superposition method and traditional method. Stress superposition method is validated more accurate by comparing stresses and deflections of some sections. (3) Again,the construction process of reinforced concrete arch bridge with stiffness frame is discussed. Twelve different concrete pouring paths of separate layers and separate segments are planned,and mechanical analyses of nude arch in different paths are carried on by stress superposition method. The sixth path and eighth path are verified more reasonable through comparing deflection and stress of nude arch during construction.(4) Finally,the changes of sectional characteristics , including section area, moment of inertia and neutral axis,are compared.It is discussed that influences from the number and location of separate layers and separate segments on mechanical analysis of arch-box during construction. According to the influences,reasonable and feasible concrete pouring path of arch-box is planed by mechanical analysis.