Research On Foundation Disturbance And Jacking Construction Technology Of Adjacent Existing Multi-Span Steel Truss Bridge

In recent years,my country’s high-speed railway has developed rapidly.The phenomenon of parallel and adjacent construction of new and old lines is increasing.The construction of multi-span steel truss bridges is difficult to construct.There are few studies on the disturbance of foundation construction of high-speed rail bridges and the jacking construction of long-span girder bridges,so it is of practical significance to study the force,stability control and disturbance of adjacent construction during the jacking construction stage of steel truss girder bridges.Based on this,this paper uses the Madis series software to establish a threedimensional model based on the construction of the third and fourth lines of the Yuyao River Extra Large Bridge in Ningbo Hub.The numerical simulation and field measurement are combined to analyze the impact of the adjacent existing line foundation construction on the existing bridge.Disturbance,dynamic jacking and lateral movement of steel truss girder bridges,changes in displacement and stress in each construction stage,and corresponding construction control and rectification measures are proposed to provide reference for similar bridge jacking projects.The main research contents of this paper are as follows:(1)Considering the positional relationship between the old and new lines,a numerical model was established based on the Midas GTS NX finite element software to analyze the disturbance of the bridge foundation construction to the existing piers.On this basis,the entire process of the existing bridge pier displacement and steel cofferdam construction was carried out.Deformation Monitoring.The comparison results show that the impact of the adjacent construction of the steel cofferdam on the existing high-speed rail bridges is within the safe range,and does not affect the normal operation of the high-speed rail.On the basis of satisfying the overall stability of the steel pipe pile cofferdam,in order to reduce the impact of adjacent construction on the existing bridge,the optimized pile length is 30 m.(2)Based on the three bending moment equations,the fulcrum bending moment formula in the form of "main beam + guide beam" in different jacking stages is deduced,and the fulcrum bending moment coefficients of different spans are calculated and analyzed iteratively by programming.The analysis shows that the bending moment of the fulcrum is greatly affected by the span number of the jacking,and the bending moment coefficient of the fulcrum shows a certain variation law with the increase of the number of spans.(3)By analyzing the construction characteristics of the Yuyao River Bridge,the jacking process is divided into several jacking construction stages,and a three-dimensional jacking numerical model is established based on the Midas civil finite element software to numerically simulate the jacking process.The simulation results show that the displacement changes in multiple construction stages of dynamic jacking of the steel truss girder are all within the safe range,and the axial stress,bending stress and combined stress of each member meet the strength requirements.(4)Through the on-site monitoring of the steel truss girder bridge jacking,the monitoring data and the numerical simulation data are compared and analyzed.The results show that the simulation results are similar to the measured results,the error is small,the simulation calculation results are more accurate,and the corresponding correction measures and jacking construction control measures are proposed for the background project to ensure the smooth progress of the jacking and guide the construction.