Residual Life Analysis Of Parallel Wire Cable In Service

Cable-stayed cables are the components that bear the tension force and support the main girder in cable-stayed bridge,and are also the"lifeline"components of cable-stayed bridges.Its main function is to transfer the load from the main beam to the pylon.At present,the cable body of most cable-stayed bridges is a cable that arranges a certain number of high-strength steel wires closely and covers the outer layer with a high-density polyethylene(HDPE)sheath.After the outer HDPE sheath is damaged,the cable steel wire is exposed to a corrosive medium and rust occurs,which affects its mechanical properties,resulting in a reduction in the remaining life of the cable.In order to ensure the service safety of the bridge structure,it is very necessary to analyze the remaining life of the corroded cable.Based on the characteristics of steel wire corrosion and the corrosion detection data,the distribution rule of steel wire corrosion is summarized,and the damage of the steel wire mechanical properties by pitting corrosion is studied.Finally,an analysis model of the remaining life of the cable in service is established with the cable ultimate bearing capacity and fatigue life as the cable failure judgment indicators.The main research contents of this paper are as follows:(1)Mechanical properties of steel wire under pitting stateCorrosion leads to pitting corrosion of high-strength steel wire and its mechanical properties include damage to the ultimate bearing capacity of the steel wire and damage to the fatigue life of the steel wire.The ultimate bearing capacity damage and the fatigue life damage degree of steel wire are described by stress intensity factor K_I and stress concentration factor K_T,respectively.Through numerical simulation,the K_I and K_T of the steel wire under different pit shapes are calculated,and the relationship between the K_Iand K_T and the three-dimensional size of the pit is obtained by fitting,which provides a basis data for the calculation of the ultimate bearing capacity and fatigue life of the steel wire.(2)Bearing capacity and fatigue life calculation of steel wire with pitsThe failure assessment chart method based on J integral and stress intensity factor were used to calculate the ultimate bearing capacity of the steel wire.Based on the theory of cumulative fatigue damage,the fatigue life of corroded steel wire was analyzed using ANSYS n Code Design Life finite element software.Finally,the calculation data was analyzed.After the combination,the quick calculation formulas of the ultimate bearing capacity and fatigue life of the steel wire are obtained respectively.(3)Analysis of remaining life of parallel wire cable in serviceFirst,based on the cable series-parallel model and the equal elongation model,and based on the calculation formula of the ultimate bearing capacity and fatigue life of the steel wire,the calculation method of the cable’s ultimate bearing capacity and residual fatigue life is established.Then use the ultimate bearing capacity and the remaining fatigue life as the two indicators of cable safety assessment to evaluate the cable safety status.Finally,the remaining life calculation process of the active cable was established,and the remaining life of the cable of a long-span cable-stayed bridge was calculated through an example.When the outer PE sheath is damaged,it is the starting point of time,and the residual life is 11.53 years.