A Study On Several Key Techniques Of Long-span Flexible Suspension Bridge

Long-span flexible suspension bridge is a structure with obvious nonlinear effects.Since bridge of such type has been in wide use,it is crucial to offer detailed analyses on its design and construction.Taking Daqingshan Pedestrian Glass Suspension Bridge in Zhangjiakou City as an example,this dissertation focuses on the determination of reasonable finished state of the long-span flexible suspension bridge and the control during construction stage.The major contents of this research are as follows.(1)The segmental catenary theory is used to calculate the shape of plane and spatial cable system of the suspension bridge with the method of analytical calculation.On the basis of the segmental catenary theory proposing a method to find the shape of main cable with the given IP,suspender force and mid-span sag,the calculation program of plane cable shape is extended to spatial one,proposes a method to find the spatial cable shape with the known IP,component force of the suspender and sag,which features quick calculation and high accuracy.In addition,this method can also be used in the determination of main cable shape and wind-resistant cable shape of the finished state of suspension bridge.(2)The CR total formulation is used to compile a nonlinear finite element program for the bridge structure.With the CR total formulation,the displacement and rotation of the structure are accurately deducted,which transforms the problem of large displacement and rotation into the small one in local element coordinates,making the accuracy of program results independent of the precision of tangent stiffness matrix.In other words,the tangent stiffness matrix only functions as a configuration predictor,while the exact force of end point is worked out according to the stability function method.Adopting the iterative method to solve the nonlinear equations is effective in avoiding the error accumulation in the calculation process.This program is used to calculate and analyze beam element,truss element,cable element,etc.,verifying its computing ability.(3)The analysis method of bridge construction process is elaborated.The zero displacement assembly method and the tangent assembly method are used to simulate the cantilever casting and segmental precast in the construction process.The CR formulation is applied into the analysis in the construction stage,simplifying the calculation and analysis of increase or decrease of the element and support,as well as the adjustment of cable force in the construction process,contributing to no need to compile additional calculation program.(4)The determination of reasonable finished state of the long-span flexible suspension bridge and the control during the construction are discussed.Targeted at Daqingshan Pedestrian Glass Suspension Bridge in Zhangjiakou City,this paper combines the finite element analysis program of the skeletal structures with the analytical method for cable system analysis program,the shape of the main cable,the design of wind-resistant cables and the whole bridge finite element analysis are demonstrated,and influences of crowd and temperature load are analyzed in the reasonable finished state.From the aspect of construction process,programs mentioned in this paper are beneficial to precisely analyzing and controlling several procedures such as main truss hoisting,cable saddle predeflection and pushing.