Stress Analysis Of Herringbone Pylon Of Single Pylon Cable Stayed Bridge During Construction

As an important stressed structure in the whole cable-stayed bridge system,the pylon bears all the live and dead loads from the main girder,and transmits them to the lower piers and foundation through the pylon.Considering the elastic-plastic load on the bridge tower and the cable material,it is quite complicated.Based on the engineering background of Kaixiahe Bridge in Shiqian,Guizhou Province,this paper simulates the key construction stages of the bridge,especially the cable tower construction stage,by using the forward calculated finite element model.It mainly studies the changes of cable tower stress and tower top deflection during the construction process,the influence of construction process on it,the optimization design of cross bracing,the stability analysis of cable tower and the stress distribution of cable tower anchorage zone.The main work and research results are as follows:(1)Through the establishment of MIDAS Civil finite element model of the whole bridge,the measured stress and tower deflection data are compared with the theoretical value,the variation mechanism of the main tower stress and deflection under different working conditions is analyzed,and the influence of system transformation,cable tension series and cable tension sequence on the main tower stress is studied.(2)This paper briefly describes the optimization process of response surface method,and analyzes the shortcomings of the original cross brace scheme,and puts forward the optimization objective of "double control",which takes the cross brace active force,cross brace spacing and cross brace diameter as design variables,and takes the lateral stress at the root of the middle tower and the lateral displacement at the cantilever end as the "double control" when the cable tower is constructed to the maximum cantilever The response surface model and the optimal design variables are calibrated,and the accuracy test and finite element model verification are carried out,and a new transverse bracing scheme is obtained.(3)Combined with the characteristics of Canyon landform at the bridge site of Kaixia River Bridge,a method of calculating static wind load considering the actual topography and landform is proposed by setting up "virtual standard meteorological station".The influence of the inclination angle of the tower and the concrete bulk density on the stability of the tower is also analyzed.(4)Using ABAQUS finite element software,the local structure of cable tower anchorage zone of Kaixiahe Bridge is analyzed in detail,and the stress distribution of steel anchor beam,steel corbel and concrete in the anchorage zone of cable tower under the action of cable force is analyzed.It is found that there is obvious stress concentration near the plate connection part of the steel anchor beam.The analysis of the concrete stress in the anchorage zone of the cable tower shows that there is stress concentration at the connection part with the steel anchor beam and the corner of the inner section of the tower wall,and the stress concentration range is large.