Elastoplastic Stability Analysis Of Long Span Steel Box Tied-Arch Bridge

Because the tie bar can afford horizontal thrust of the arch foot, tied-arch bridge has lower requirement on the pier and foundation, which greatly increases the application scope. Compared with the traditional arch bridge, with the obvious advantage of mechanics and aesthetics, Tied-arch bridge is a good choice in the design and construction of bridges. With the increase of the span of steel box tied arch bridge, the stability problem becomes one of the main control factors of design.Development process and research status of arch bridge stability analysis theory were reviewed in this thesis. The main factors that affect the stability of arch bridge were determined, which are compression-bending effect, large displacement effect and material non-linear factor. The geometric nonlinear theory and material nonlinear finite element theory of bridge structure were introduced. The comparison of TL, UL and CR formulations was carried out firstly considering the geometric nonlinearity. Then the concept, coordinate system and rotation of CR formulation were introduced emphatically. The concept of the plastic hinge method and the plastic zone method were introduced considering the material nonlinearity. Based on the ideal elastoplastic constitutive relation, the solution process of the elastoplastic stiffness matrix of the element was introduced. Stability function, CR formulation and the meshed section method were introduced to consider three factors affecting the stability.The finite element analysis method for first stability problem and the second stability problem was introduced. C++ language was used to develop the program of stability analysis of arch bridge, elastoplastic static problem, first stability problem and the second stability problem could be solved in the program. The double nonlinearity is realized in the stability calculation of arch bridge. The accuracy of the program was verified by examples.The program was used to analyze the second elastoplastic stability problem of a through steel box tied-arch bridge. The development process of the plastic zone, instability mechanism and the effect of the material nonlinear factors on the stability of tied arch bridge were analyzed and the results showed that the bridge met the stability requirements.