Research On The Reasonable Position Of The Auxiliary Pier Of Long-span Composite Girder Cable-stayed Bridge Based On The Optimization Of Mechanical Performance

Auxiliary pier is an important part of improving the structural stress of cable-stayed bridge,the necessity and reasonable position of its layout have been studied by many scholars in recent years.In order to arrange auxiliary piers more reasonably and accurately,and make the mechanical performance of composite girder cable-stayed bridge better,this paper takes the world’s first steel-mixed composite girder cable-stayed bridge--Chibi Yangtze River Highway Bridge with the main span of 720m as the engineering background to study the influence of auxiliary piers on the mechanical performance of long-span composite girder cable-stayed bridge.On this basis,a comprehensive evaluation method is designed to determine the optimal and reasonable position of a single auxiliary pier,and then calculate the optimal and reasonable position of auxiliary pier,The optimization of the position of the auxiliary pier can be completed.The main research contents of this paper are as follows:(1)Study the effect of setting auxiliary pier on the static performance of composite girder cable-stayed bridge.The difference of stress amplitude of main beam,vertical deformation amplitude of main beam,stress amplitude of stay cable and bending moment of cable tower under live load was compared between the two schemes of composite girder cable-stayed bridge with or without auxiliary piers,and the influence of auxiliary piers on stress amplitude and deformation amplitude of structure was explored.At the same time,the utility of arranging auxiliary piers on the stress of main beam,bending moment of main tower and cable force of cablestayed cable under dead load is studied,so as to judge the necessity of arranging auxiliary piers.(2)Explore the change of dynamic characteristics of composite girder cable-stayed bridge after adding auxiliary piers,and use response spectrum analysis to analyze the similarities and differences of dynamic responses of the structure with or without auxiliary piers under seismic waves,as well as the impact on seismic resistance of the structure.(3)A finite element model containing nine different positions of the auxiliary pier in the original design scheme was established,and then seven key indicators were selected for comparative analysis between the models to obtain the reasonable position interval of the auxiliary pier for a single indicator.On this basis,a comprehensive evaluation method combining coefficient of variation method and standard fraction method is proposed to verify the feasibility of the original design scheme.Then,the linear regression principle is used to fit the relationship curve between different positions and comprehensive evaluation value,and then the optimal reasonable position of the optimized auxiliary pier is obtained through calculation.