Research On Design Problems Of Self-anchored Cable-stayed-suspension Bridges

The self-anchored cable-stayed-suspension bridge is a new type of cable supported bridges, originating from modern self-anchored suspension bridges and cable-stayed bridges. It takes a lot of advantages, i.e. reasonable mechanical behaviors, strong foundation adaptability, saving cost. One of this bridge type was accomplished and several other bridges were in scheme design. In this paper, some problems about the bridge design are studied. The main research work covers the following aspects:1. Problems and shortages about accurate solution of geometric nonlinear analysis in self-anchored cable-stayed-suspension bridges are studied. C.R. method is used to study the rigid body rotation of beam element. The axial deformation is calculated by shape function and stability function method to take second-order effects into account. A displacement reduction and multi-cycle method are proposed to improve the nonlinear solution convergence of beam element. The element resistance vectors of axial and cable elements are calculated by total lagrange method. The cable element may exists multiple solutions is put forward. In order to solve the problem, a double bars element method is derived to obtain a good initial value and a multi-initial values method is proposed to prevent divergence and abandon spurious results. Meanwhile, a damping stiffness matrix is introduced in the cable element solution to improve the nonlinear analysis robustness. The elements are verified by the representation examples to prove the convergence and precision, which offer guarantee for the further analysis of self-anchored cable-stayed-suspension bridges.2. The permanent load state is investigated for the self-anchored cable-stayed-suspension bridge. Design variables, constraint conditions and objective functions are then determined, where the load and non-load factors are considered. A quadratic programming method for constraint relaxation is used to solve the optimization problem, and a method about how to reduce structure reanalysis by the global stiffness matrix is presented to improve the solution speed. Finally, a two stage cycle method is proposed to obtain the permanent load state of self-anchored cable-stayed-suspension bridges, and Zhuanghe Jianshe Bridge is studied to verify the effectiveness.3. A hybrid algorithm is adopted to fit the creep coefficient power function introduced in China standard of 2004 highway PC bridge appendix F into exponential function, from which can obtain the successive expression of the creep. The curve of creep coefficient is firstly fitted by the genetic simulated annealing algorithm to estimate the initial data, and then based on the Levenberg-Marquardt method and Gauss-Newton method, the curve is exactly fitted by the nonlinear least square method. The exponential function is determined by the result analysis at last. Based on the exponential function and age-adjusted effective modulus method, the successive expression of the creep is derived. According to the corresponding program, the influences of creep to a self-anchored cable-stayed-suspension bridge are analyzed.4. Compared with several steel-concrete joints of usual bridge type, the advantages and disadvantages are analyzed and the steel-concrete joint of Jinzhou Bay Bridge is trial designed. A multi-convergence criterion is proposed by material nonlinearity. In order to analyze the connection modes of steel-concrete joints, a space finite element model that contains solid elements and shell elements is built by ANSYS. The bond-slip behavior of steel and concrete is taken into account, which aims to study the problems of transfer mechanism, stress distribution, local stability and so on. Finally, the joint is analyzed by two main load cases and the stress distribution of contact surface, internal force of shear connectors and shear-lag effect of steel girder are discussed, from which the multi-stability coefficient of joint are obtained. Ways to increase stability coefficients are also put forward. The method can be applied to design and estimate the steel-concrete joint performance of self-anchored cable-stayed-suspension bridges.5. The problem about low computational efficiency during the structural design of self-anchored cable-stayed-suspension bridges is studied. The development and evolution of bridge design process is reviewed and the modern design methods are introduced. In order to take modern design methods into bridge engineering, the cooperative design method is used to integrate other modern design methods to bridges design. The bridge analysis softwares are divided by functions and the cooperation method is studied. The structure description way is discussed and parallel computation is inducted to improve the analysis efficiency. Tcl/Tk is used to develop the graphic display module. Based on cooperative analysis, the software system is realized and the frame rudiment of self-anchored cable-stayed-suspension bridges is established by modern design methods.