Nonlinear Calculation Program Development Of Self-Anchored Cable-Stayed Suspension Bridge

Self-anchored cable-stayed suspension bridge is a complex structure system with various nonlinear factors coupling, so it's gepmetrically nonlinear problems are relatively outstanding. But up to now, there is no simple, mature and accurate structure analysis method for solving the problems in design and construction of self-anchored cable-stayed suspension bridge, while bridge engineering kingdom urgently need to solve and accurately predict the structure stress and deformation shape. So it is necessary to expand fine study on the nonlinear problems for self-anchored cable-stayed suspension bridge. With the engineering background of Dalian Gulf Bridge to be built, this paper focuses on the geometrically nonlinear analysis in bridge finished state and in bridge construction process of self-anchored cable-stayed suspension bridge. The work mainly covers the following aspects:(1) About using analytic method to calculate cable lineshape of self-anchored cable-stayed suspension bridge. Based on segmental catenary theory, a set of complete analytic method for cable-shape finding is put forward, which can take saddle influence into accurate construction. IP concept for cable finish state is presented, which make the calculation method considering the saddle influence of cable finish state is uniform to the method of bridge finished state and make the calculation method for cable lineshape of cable finish state simple. The formulas for cable-force correction of main span and side span on bridge finished state are deduced. The iterative calculation method for pre-displacement of each saddle is provided with several saddles exit. Analytical method program has properties of good convergence and high calculation accuracy, which can be used in cable lineshape accureate calculation of various forms of suspension bridge and cable-stayed suspension bridge.(2) About geometrical nonlinear analysis of self-anchored cable-stayed bridges. All kinds of solution method of tangent stiffness matrix, nodal loads, effictive nodal forces and internal forces are introduced. CR total formulation method used in nonlinear analysis is provided, the advantages of which included:â‘ The restriction of small rotations in incremental step is removed by using CR coordinate to eliminate the rigid body motion accurately.â‘¡Internal forces are calculated based on the total equilibrium condition but not on incremental equilibrium condition, which avoid accumulative error.â‘¢Make the precision of nonlinear calculation do not depend on the precision of tangent stiffness matrix, leave out the huge workload of deducing accurate tangent stiffness matrix, which not only save calculation time but also ensure the convergence rate and the accuracy of calculation result. Based on cable basic assumption and catenary equilibrium equation, the stiffness matrix and interation scheme of nodal force for catenary cable element of two nodes. The calculation method for complete live-load nonlinearity is given. The nonlinear finite element analysis program FBNL with high accuracy is complied. Proved through a lot of classical examples, this method has extremely high accuracy and efficiency, and its convergence rate is faster than the other methods.(3) About the determination of ideal finished dead state of self-anchored cable-stayed suspension bridge. The synthesis algorithm by combining analytic method with finite element method to determine the ideal finished dead state of self-anchored cable-stayed suspension bridge is put forward. The calculation flow determing the ideal finished dead state by using the program PBNL is described in detail.(4) About the nonlinear analysis of construction process of self-anchored cable-stayed suspension bridge. By introducing CR total formulation into structural analysis of bridges, high precision and efficiency is achieved and analysis of some case become straightforward such as activating or deactivating element, adding or removing support and pretension or retention cable stay. The nonlinear stress-free staus method for construction calculation of self-anchored cable-stayed suspension bridge is established. The calculation methods of erection configuration and stress-free configuration involving the geometrically nonlinearity are given. Based on the synthesis algorithm combing finite element method with analytic method, the nonlinear element program BCNL for finite analysis of construction process is comiled, which can be used to accurately simulate each construction state of self-anchored cable-stayed suspension bridge and can optimize construction scheme. The program has good calculation accuracy and calculation speed. The main features and functions of program BCNL are described in detail.(5) Based on CR formulation method and analytic method, adopting catenary cable element, a refined geometrical nonlinear model is established for nonlinear analysis of finished dead state and construction process of Dalian Gulf Bridge.