The Research On Stability Of The Combinational Bridge With Rigid Frame And Single-ribbed Tied Arch

The combinational bridge with rigid frame and single-ribbed tied arch is a kind of new bridge structure form, in which rigid frames and arches are rigidly connected to bear the load together. It combines the rigid frame bridge and the arch bridge harmoniously, not only shows the respective merits of each other, but also makes two kinds of advantages of bridge type get to add mutually. However, for this kind of bridge, the lateral and torsional stiffness of upper structure is limited, the stability problem always exists, especially, the out-of-plane stiffness of the arch rib is far smaller than the in-plane stiffness of that, therefore, the out-of-plane stability problem is more serious. To the stability problem of this bridge type, with Baisha River Bridge which is under construction in Guangzhou for engineering background, the main work in this thesis is as follows:(1) Firstly, this thesis discusses the stability of arch from analytic approach, and theoretical formulas for in-plane and out-of-plane elasticitical stability of parabola single-ribbed arch are deduced. In the out-of-plane case, the effects of directional loads and non-directional loads are considered, and the calculating formulas for stability under transverse wind loads are produced.(2) The finite element methods to analyse stability are summarized, including the nonlinearity theory, and the ways and means to solve nonlinear stability are presented; the criterions to judge buckling and estimate stability are refered; the techniques to analyse stability in ANSYS are introduced.(3) The overall stability is studied. The first sort of stabilities under the combinations of dead loads, wind loads and train loads, and the second sort of stabilities under the dead load taking into account the geometrical nonlinearity and material nonlinearity are analysed, furthermore, the influencing factors to overall stability are studied.(4) The overall-local interactive stability is studied. Firstly the local stability of steel box rib is analysed by ideal stiffened plate local stability theory, then mixed finite element model of whole bridge is established, and the linear elastic interactive stability is analysed, finally, elastoplastic interactive stability is analyised.(5) In the end of this thesis, the aerostatic stability is studied. Firstly, theories about aerostatic stability are reviewed; secondly, static wind load coefficients of bridge sections are numerically simulated by CFD; lastly, the aerostatic ultimate bearing capacity of Baisha River Bridge is analysed not considering and considering aerostatic nonlinearity respectively.