Stability Simulation Analysis Of Long-Span Continuous Rigid Frame Bridge With High Piers

With the development of the long-span bridge structure, more and more high strength materials are put into application, bridge tower becomes dominant and the wall of the box girder becomes much thinner. As a result, the stability of bridge becomes more important. The bridge stability plays the same important role as the strength especially for high-pier and long-span bridge. In this paper, an engineering case—Long Tan He Great Bridge is considered,the bridge is a long span continuous rigid frame bridge with thin-wall high-piers, built on Hu-Rong national highway in the west of Hubei province. The stability of the high-piers is analysed by using the current FEM software ANSYS. Long Tan He Great Bridge processes the highest pier at present, the stability problem of high pier caused by this is particularly outstanding. Firstly, the paper summarizes the investigation development on stability of bridges with high-piers and some existing process; discuss two kinds of basic theories of stability about bridge structure; further studies the nonlinear FEM compution technique and process of the nonlinear stability problem. By utilizing the current finite element program ANSYS, two types of finite element models, i.e., beam model and shell model, are established for the nonlinear stability comparative analysis in the construction stage and completed bridge stage. Further more, three kinds of analysis are performed, i.e., structure dynamic characteristic analysis, static strength analysis and linear stability analysis. Secondly, the deflection caused by unilateral sunlight is investigated by using thermal-structure coupling analysis method. Nonlinear stability analysis is carried out by regarding the deflection as the initial defect, and two aspects are included in nonlinear stability analysis. The first one, only geometric nonlinearity is considered and the other one, the geometrical and material nonlinearity are considered simultaneously. For geometric nonlinearity, Updated Lagrangian formulations are adopted to derive the tangent stiffness matrix. In order to simulate the nonlinear behavior of plastic hinge in the bottom region of the piers, the multi-curves element COMBIN39 with the Multi-spring model is used in shell model, and the bilinear rotational spring element COMBIN40 is used in beam model. Finally, in order to obtain the effect factor of nonlinearity, the paper compares the result of geometrical nonlinearity and geometrical and matieral nonlinearity. Some important parameters for the design of the thin-wall and high-pier bridge are obtained in these analyses, including critical load and stability safety factor in the construction stage and in all cases of the completed bridge. some problems remain to be solved are put forward.