Study On Fretting Slip Behavior Of Parallel Steel Wire In Stay Cables

As an important load-bearing member of cable-stayed bridge,the use safety of stay cables is related to the overall operation safety and service life of the bridge.Most of the cable-stayed bridges built in China use parallel steel cable.To study the damage mechanism of parallel steel wires in long-term operation is an important part of long-term operation performance research of cable-stayed bridges.Aiming at the problem of friction damage of parallel steel wires in long-term operation,the fretting slip behavior of parallel steel wires between cables was studied by using fretting slip theory and finite element modeling analysis method on the basis of evaluating the wear condition of the internal parallel steel wires of the old cables replaced by Yinpenling Bridge in Xiangjiang,Changsha.The main research work completed in this paper is as follows:Firstly,on the basis of consulting domestic and foreign research literature,the vibration and bending behavior of stay cables is introduced systematically.The calculation equations of axial force and shear force of micro-section steel wire under bending state are deduced by using the equilibriun state analysis of micro-element body.Secondly,Hertz theory is introduced to analyze the static contact state of parallel steel wire,and the relationship between contact radius and radial extrusion force is obtained.Then the relationship between contact stress,compression and deformation depth is determined.Based on the basic theory of fretting slip,the changes of equivalent contact extrusion force,bending displacement equation and tangential fretting displacement of layered steel wire under bending vibration are systematically analyzed.Thirdly,a finite element analysis model of fine cables with multiple wires is established.The local stress field of the steel wire contact surface and the influence of different bending curvature on the local slip deformation are analyzed by simulating the bending deformation of the cables at the anchorage position.In the simulation of steel wire bundle bending,it is found that the axial micro-strain of steel wire will occur under the shrinkage force of PE sheath,resulting in relative slip of steel wire.Under the action of bending load,the steel wire slips relatively,and the displacement of the contact surface of the bending inner steel wire is larger than that of the outer contact surface.At the same time,different bending radians are applied to the free end of the steel wire bundle to capture the relative slip amplitude of the node at the same position.It is found that the maximum slip value is nonlinear with the bending radian.