Dynamic Stability Of High Piers Structure Of Bridge And Its Influence Factors Analysis

The stability of bridge structure is one of the main problems in the safety and economy. It has the same importance with the strength. With the rapid development of modern science and technology, more and more high strength materials and thin wall structures are used in the piers. Therefore the stability of bridge structure is becoming increasingly prominent. Especially the pier structure slenderness ratio of modern very high-pier bridge is being larger and larger, so analysis of its stability is particularly important.For the stability of pier structure, the current popular method is to focus on the most unfavorable state, for example, to calculate stability coefficient under cantilever construction state. This is a static analysis method. Relatively, dynamic analysis is still in the theory stage.This paper first derives the dynamic equilibrium equation of pier structure under axial loads, then based on the Lyapunov stability theory, according to different boundary conditions, chooses different trial functions to imitate the deformation curve, deduces the boundary of stable and unstable regions, and analyses the influence of material constants, section forms and boundary conditions. Then the nonlinear terms are introduced, and the multi-scale method is used for qualitative analysis. The nonlinear problem of fundamental parametric resonance and principal parametric resonance are discussed respectively, and both will lead to the Hopf bifurcation.In addition, this paper tries to break the original weak parametric excitation limitation, and looks for new methods to solve the parametric excitation problem. With the traditional method, using small parameter, the approximate solution and the transition curve are obtained. Then, to replace small parametric excitation amplitude with another small parameter by equation transformation, the stable and unstable regions under arbitrary excitation amplitude can be determined. Moreover, compared the calculation results of the traditional method and the improved method, the advantage of the improved method is advisable. At the case study, taking the current first high pier bridge in Asia—Hezhang super large bridge as an example, whose piers are195m high, different from the static analysis in the existing literature data, this paper transforms reasonably loads from the code to dynamic loads, compares the influence of the related factors according to the dynamic response of fundamental parametric resonance and principal parametric resonance. Especially aiming at finished bridge state, converting the boundary conditions of pier bottom to different support stiffness in digital test, analysing respectively the linear and nonlinear problems, some useful conclusions for engineering design are obtained.