Static Analysis And Unitary Stability Research Of The Cable-Stayed Bridge With Single Tower

The cable-stayed bridge with single tower usually includes two types: bilateral symmetry and bilateral asymmetry. In fact, considering the geological condition,terrain condition and hydrological condition, most projects use the later. Being asymmetric, it's more complex to determine the reasonable finished state and the reasonable construction state of the asymmetric cable-stayed bridge with single tower. The Jianning Bridge in Zhuzhou is an asymmetric prestressed concrete cable-stayed bridge with single tower and center-laid cables, which main span is 240 meters long, heading the list at home. Thus its stability should be given prominence. In a word, it's especially necessary to analyze and study the following three aspects of the Jianning Bridge: the reasonable finished state; the reasonable construction state and the unitary stability. The static analysis of the cable-stayed bridge is usually carried through two steps: determining of the reasonable finished state and the reasonable construction state. Firstly the synthesis method is applied to determine the reasonable finished state which integrates the least bending strain-energy method and the stress equilibrium method and the least squares method. This synthesis method calculates the influence of dead load, live load and prestressing force by aiming to restrict the stress of the main beam and by means of adjusting the cable tensile forces. Calculating the cable tensile forces under construction are emphases of determining the reasonable construction state. A "two-step method on the basis of forward analysis"is put forward in this thesis for determining the reasonable construction state. The "two-step method"virtually is to iterate the forward-calculation by aiming to optimize the cable tensile forces. This method is described as the following. The cables are stretched once under cantilever construction ensuring the safety of the main beam. After the main span is closured, taking the cable tensile forces as variables, we can form an optimization model, and apply the least squares method to adjust the cable tensile forces wholly. Finally the forecasting reasonable finished state is attained ensuring the structure safety under construction. The finite element methods for solving the buckling problem of the cable-stayed bridge are expounded in the thesis and two evaluation criterions about the unitary stability are discussed. The author takes the Jianning Bridge as example and adopts the 3-D finite element software ANSYS to analyze its linear and nonlinear unitary stabilities under construction and in the finished state. According to the solutions, its unitary stabilities are evaluated. At last, considering all kinds of nonlinear factors, the buckling types and the most possible destroyed forms of the representative phases are pointed.