Research On Hoisting Construction Method Of Steel Truss Girder Of Super-large Span Suspension Bridge In Mountainous Area

Since the 1950s,China has made great efforts to develop transportation,with remarkable achievements in transportation construction.The transportation network covers a wide range and is of high quality.However,there are differences in the quantity and quality of traffic in different places,and the east is dense and the west is sparse.Therefore,the development center and site of China’s traffic and transportation will be transferred from the eastern and central regions to the western regions to build long-span Bridges across deep valleys.Suspension Bridges occupy an important position in long-span Bridges because of their beautiful linear shape,reasonable stress,integration with the environment and strong spanning ability.In addition,the mountainous terrain environment and climate conditions and other factors restrict the bridge construction,so the construction methods of stiffening girders of suspension Bridges in mountainous areas are required.Relying on the engineering background of Jinshajiang Bridge in Jin ’an,this paper has carried out the following work from four aspects: construction scheme selection of the main girder of the mountainous long-span suspension bridge,structural design of the specific scheme,proposal of corresponding calculation theory,and analysis of relevant influence parameters:1.This paper investigates the main girder construction method of suspension bridge at home and abroad,analyzes the examples of each erecting method,makes a qualitative analysis from the working principle,structural characteristics and site requirements,and excludes the construction scheme that is not suitable for mountainous area and long-span suspension bridge.Then jin Yangtze river bridge as the engineering background,the bridge cantilever erection,cable assembly,rail line moving beam erection was proposed to formulate the construction steps,from the similarities and differences in site,personnel,time limit for a project and aerial work time,equipment management,quality control,six aspects of quantitative analysis,through the time and the number of cable hoisting scheme is chosen as the final advantage.2.The parameters and specifications of the cable hoisting system are determined,and the initial sag of the main cable and the connection form at the bottom of the tower are calculated.The influence of the side span should be considered for the initial sag,and it is suggested to fix the tower to the cable tower of the suspension bridge.3.By analyzing the working process of the cable hoisting system,the internal force adjustment of the midspan cable with the influence of the cable and the tower when the pulley on the top of the tower participates in the load change is considered.In this paper,a nonlinear iterative method is proposed to simulate the pulley boundary with the same length of the three spans of the load-bearing rope and the same tension on both sides of the pulley as the constraint conditions.Finally,combined with the actual project,the data verification is carried out,and the calculation results are verified with the tension equation considering the influence of side span.It is believed that the nonlinear iterative analysis and calculation method is suitable for the long-span cable hoisting system,and it is feasible and accurate.4.Through the influence parameter analysis,it is found that when the vertical span ratio changes,the deflection value will appear a rule similar to the minimum value of a parabola.It is determined that the Angle of back cable has no effect on the stress-free length and maximum tension of the middle span main cable.However,the force transmission efficiency of side span main cable can be improved by choosing a larger Angle of back cable,which reaches the maximum at 45°.The method of single amplitude series fixation is proposed.The calculation results show that the initial installation error exists but has little effect on the maximum tension of main cable.It is found that the influence of the wind load on the maximum tension and deflection of the main cable is stable,but the influence on the transverse displacement is large.