Corrosion Fatigue Analysis Of The Stay Cables Under The Combined Effect Of Random Wind-vehicle Load And Iced Accretion

In actual service,cable-stayed bridges are vulnerable to wind-vehicle loads,together with icing accretion and exposed to corrosive environments for a long time,cables are prone to corrosion and fatigue damage.And its essence is the corrosion fatigue fracture of the wire inside the cable,which reduces the bearing capacity of the cable.Studies have shown that the life of cable-stayed bridges generally depends on the life of the stay cables.Therefore,to study the corrosion fatigue of cables under wind-vehicle load and icing accretion can ensure the safety and reliability of cables during service period,and also predict the corrosion fatigue life of cable,the best time for cable change is to maximize the service life of the cable.This paper uses a cable-stayed bridge in Wuhan as the engineering background,establishes the finite element model of cable-stayed bridges,and applies random wind load,vehicle loading and icing accretion to obtain the actual stress state of the cable.Then the finite element model of the cable wire is established,the corrosion fatigue life of cable wires under pitting and cracking was analyzed.An accelerating corrosion test of cable wires was designed,fatigue tests were performed on the cable wires after corrosion,and he results were compared with the finite element results.The specific contents are as follows:(1)This paper summarizes the cable replacement projects due to the corrosion in recent years.It also summarizes the corrosion tests of cables at domestic and international,the corrosion fatigue life status of cables,and the corrosion fatigue life of stay cables.(2)The corrosion fatigue mechanism of stay cables is elaborated in detail.The model of pitting corrosion of steel stay cables and the nucleation model of cracks are analyzed.The crack propagation models of cables are mainly explained.The results provide the basis for calculating the corrosion fatigue life of cables.(3)Based on an actual cable-stayed bridge,the finite element model of the cable-stayed bridge was established.Firstly,the node dynamic load of random vehicle is excited on the model according to vehicle load spectrum;Then the wind speed time history is generated through the harmonic superposition method,the chattering effect caused by wind load is applied to the model;Finally galloping effect of icing accretion cable is taken into considered using the principle of transverse galloping.Based on the cumulative damage theory,the fatigue reliability of cable stays under random vehicle load,random wind load,and icing accretion is obtained in a non-corrosive environment.The stress time history of the cable is taken as forced state of finite element model of cable wires.(4)Accelerated corrosion tests were conducted on cable stay cables to calculate the corrosion rate of cable wires.The corrosion of steel wires after corrosion was analyzed,and the finite element model of steel wire containing pits was established to analyzed the influence of the pit depth,width to depth ratio and the spacing on the equivalent stress of the steel wire and the degree of stress concentration,and the pitting propagation life of the steel wire is obtained.(5)Fatigue tests were performed on corrosion-resisting cable wires to obtain S-N curves with different corrosion times and different stress amplitudes.In combination with finite element analysis results of cable wire crack propagation,the crack propagation life of cable wires was obtained,and the corrosion fatigue life of the cable steel wire is obtained.