Research On The Stability Of Long-Span Continuous Rigid-Frame Bridge With High Piers At The Construction Stage

Traffic construction is developing rapidly in mountainous areas. Due to restrict of the landform, continuous rigid frame bridges with high piers are widely used in mountainous areas. In construction stage, because of the few restrains of these bridges, the problem of stability is very remarkable. This thesis aims at the stability of Yesanhe Bridge in its construction stage, a long-span continuous rigid frame bridge with high piers in the west of Hubei province, which is situated in the national highway from Shanghai to Chengdu City. The main research work is summarized as follows:(1) The research on stability of double-leg thin-walled high piers: Taking No. 3 piers of Yesanhe Bridge as an example, based on energy principle, the formula of stability coefficient of double-leg thin-walled high piers are deduced. They indicate that the results obtained by the method proposed in this thesis agree well with those obtained by finite element method. Beam-189 finite element in ANSYS being used, the first and second category of stability problems of double-leg thin-walled high piers are analyzed, and the contribution of the nonlinearity to stability is evaluated.(2) The research on stability of long-span continuous rigid frame bridge with high piers during cantilever construction: Aiming at the stability of long-span continuous rigid frame bridge with high piers during its cantilever construction, this thesis investigates the effects of several dominant factors, such as geometric nonlinearity, material nonlinearity and concrete crush, concrete crack, aggregate interlocking, etc, upon the stability by means of the buckling theory, the deflection theory, the elasticity-plasticity theory and the collapse theory. The effects of the construction load type and the rigidity of tied-beam on the stability of long-span continuous rigid frame bridge with high piers during cantilever construction stage are discussed in detail. Analysis and research results show the effect factors of nonlinearity, the relationship between the rigidity of tied-beam and structure stability coefficient, and the unsymmetrical construction loads are really dangerous to the stability.(3) The research on stability of high pier with initial imperfections: Based on the first buckling mode, the stability of single-leg high pier that has both in-plane and out-plane initial geometric imperfections is studied by means of the coherence imperfection mode method. The relationship between stability of high pier and initial geometric imperfections is obtained. Some suggestions about the uprightness of high pier are given. The stability of single-leg high pier that has initial material imperfections is studied, and the most dangerous place where the initial material imperfections appear is found.The results provide the theory instruction for the problem of stability of the Ye- sanhe Bridge and the reference to the research for this kind of bridge's stability and the bridge's stability which considered the initial imperfections.