Analysis Of The Influence Of Main Cable Arrangement On The Three-tower Suspension Bridge Stress

In recent years,multi-tower suspension bridges with strong crossover capabilities and low overall costs have attracted much attention from the bridge community.However,under the most unfavorable load conditions,the main girders of multi-tower suspension bridges have too large deflections,complex forces in the center tower,and main cables.The lack of anti-sliding coefficient at the middle tower saddle limits the further development of the multi-tower suspension bridge.To solve these problems,this paper starts with the layout of the main cable of the three tower suspension bridge.Analytical calculation and numerical simulation are combined to analyze the effects of different main cable layouts on the overall stiffness,static bridge formation and structural deformation of the three tower suspension bridge.Specific analysis and research work are as follows:This paper summarizes the evolution process of the existing main cable layout of suspension bridges,and summarizes and analyzes the complex solution to the force of the middle tower of the three-tower suspension bridge,and proposes the structural system of three towers and four cable plane suspension bridges.According to the existing main cable shape calculation theory of suspension bridge,the calculation method of the main cable shape suitable for the three tower suspension bridge is explored.Finally,the three-tower suspension bridge with large flexibility,long span,and overhanging booms was used to calculate the main cable alignment.The results of the pitch calculation method,the parabola method,and the catenary method were within a millimeter range.All three methods can provide coordinate data when establishing a finite element model for a three-tower suspension bridge,and improve the three-tower suspension bridge in Midas/civil that cannot be modeled with a suspension bridge modeling assistant.The relevant theory of suspension bridge analysis is expounded,and the expression of load redistribution between high and low cables is deduced and optimized when the load is evenly distributed,and the calculation accuracy of the change of the main cable sag caused by the load is improved.According to the principle of equivalent spring stiffness,the spring loaded across the main cable is equivalent to the spring,and the static mechanical model of the multi-tower suspension bridge is established.According to the force transfer mechanism of the vertical bridge of the three-tower suspension bridge,the load-spanning main cable of the three towers and four cable-stayed suspension bridges is analyzed.The equivalent spring stiffness calculation method at both ends was used to analyze the displacement of the tower and the deflection formula of the stiffened beam.The finite element model was used to compare the numerical solution with the analytical solution.The results show that the calculation results of the two methods are basically consistent.The relevant theories and specifications for the stiffness analysis of the mid tower of a three tower suspension bridge are described.The calculation method and reasonable value of the mid tower stiffness of a multi-tower suspension bridge with different main cable layouts are analyzed under the most unfavorable load conditions.Based on the value of the stiffness of the middle tower,it has a great influence on the stress and deformation of the suspension bridge structure.Then the structural parameters of the three tower suspension bridges with two different cable surfaces are studied to explore the changes in the span,the span ratio and the bridge surface stability.The influence of the main design parameters,such as load,on the variation of the extreme value range of the middle tower stiffness provides a theoretical basis for design and construction.