Analysis And Research On Secondary Tension Cable Force Of Railway Low Tower Cable-stayed Bridge

Low-tower cable-stayed bridge is a transitional bridge between continuous girder bridge and cable-stayed bridge.It has the advantages of both.It has the characteristics of large main beam stiffness,concentrated cable stays,rigidity and flexibility,and good economic benefits.In recent years,it has developed rapidly at home and abroad.The tension of the stay cables of the low-tower cable-stayed bridge is comprehensively considered from the perspective of construction convenience,construction period and structural stress,and the method of secondary tension is usually adopted,that is,each stay cable is carried out during the pouring of the main beam.Initial tension,after the main beam is closed,the second phase of the dead load is applied,and then the secondary tension of the stay cable is performed.The secondary tension can not only optimize and adjust the internal force of the structure but also determine whether the secondary tension effect meets the ultimate bridge formation goal.Therefore,the secondary tension of the low-tower cable-stayed bridge is theoretically analyzed and analyzed.Construction control is crucial.This paper takes the Panzhihua Jinsha River Bridge on the Chengkun Double Line as the engineering background,theoretically analyzes the secondary tension of the Jinsha River Bridge and controls the on-site secondary tension construction stage.The main work and conclusions are as follows:(1)The finite element software midas Civil was used to simulate and analyze the Jinsha River Bridge during the construction phase,and the internal force,stress,deformation and cable force calculation results of the structure used for the dead load of the bridge were obtained,which was the subsequent secondary tension cable force analysis and construction The monitoring work provides a research basis.(2)Introduced the method of calculating the secondary tension of low-stayed cable-stayed bridges,and selected the iterative method of the difference in positive installation as the method of calculating the secondary tension of Jinshajiang Bridge.The six groups of initial iterative cable forces were calculated.Through comparative analysis,reasonable initial iterative cable forces with fast convergence speed and high calculation accuracy were obtained.The final calculation determined the Jinshajiang Bridge secondary tension cable force.The reasonable initial iterative cable force can be calculated before the second tension and near the minimum value of the difference between the cable force and the dead load cable force designed for the bridge.(3)Reduce the secondary tension cable force by 5%,10%,increase 5%,10% into the calculation model,and compare with the design of the bridge state,the impact of secondary tension construction error on the structure Parameter analysis.The linear change of the secondary tension cable force has a linear relationship with the structural displacement and internal force changes caused by the same change.The secondary tension cable force of thesame change has the largest change in the displacement of the main beam,followed by the main tower offset,indicating that the low tower is diagonally pulled.The main tower of the bridge contributes greatly to the safety of the structural system.Select four kinds of tension sequential schemes,and use the formal difference iterative method to obtain the secondary tension force corresponding to each scheme.By comparing the tensile force of the stay cable,the stress displacement of the main beam,the stress and the deviation of the main tower,the program that meets the structural stress and is convenient for the actual construction operation on site is selected.For low-tower cable-stayed bridges with symmetrical structure,the more reasonable secondary tensioning sequence is symmetrical tensioning from long cable to short-span mid-span.(4)Conduct construction monitoring on the secondary tension of Jinsha River Bridge and the adjustment of cable strength of the completed bridge,and obtain the cable force of the diagonal cable,the vertical displacement change of the main beam,the structural control section stress after the construction is completed,and the error between the actual measured value and the theoretical calculated value To meet the accuracy requirements of the control error system,the Jinsha River Bridge finally meets the requirements of being designed into a bridge state.