Corrosion And Fatigue Life Analysis Of Suspension Bridge Slings

Cable structures are widely used in bridge construction due to their efficient mechanical properties and excellent spanning ability.With the extension of operation time,due to the long-term environmental invasion and various adverse effects,a large number of cable components have corrosion problems.In suspension bridges,the corrosion problem of slings is particularly prominent.In order to maintain the operation performance of bridges and improve the durability and safety of suspension bridges,it is of great significance to study the mechanical properties,fatigue properties and damage identification of slings after corrosion.According to the corrosion status detection of active slings and the existing research,the key factor of corrosion degradation of slings is the corrosion of the cable wire.Therefore,it is particularly important to analyze the mechanical properties and fatigue properties of single slings after corrosion.Based on this,this thesis takes the special detection of a bridge sling as the background,and studies the working performance of the sling after corrosion.This thesis mainly studies the following contents :(1)The parametric modeling of wire rope sling is deduced,and the fine numerical simulation is carried out.The stress characteristics of wire rope sling under axial tension are studied,and the stress distribution law of wire rope sling in elastic stage and plastic stage is analyzed.(2)In order to clarify the corrosion process of slings,the electrochemical accelerated corrosion method was used to simulate the slings under different corrosion degrees.The development of corrosion pits was observed and evaluated from three dimensions:length,width and depth.The curve equation of the pit size with the service time was established,and the finite element analysis method was used to analyze the influence of three pit sizes and different pit directions on the stress concentration factor.It is concluded that the depth of the pit has the most significant effect,and the most unfavorable direction is when the long axis of the pit is perpendicular to the axis of the steel wire.(3)The fatigue test of corroded sling specimens was carried out,and the corrosion rate was established as the corrosion degree index.The finite element simulation analysis of fatigue life of slings under different corrosion rates was carried out.The results show that when the corrosion rate is less than 3%,the fatigue life decreases rapidly with the increase of corrosion rate.When the corrosion rate is greater than 3%,the fatigue life decreases slowly.The exponential function equation of fatigue life with corrosion rate is given.(4)According to the existing calculation theory,the applicability of the refined numerical model in the simulation of the dynamic characteristics of the sling is verified,and the damage identification method with the third-order strain modal difference as the damage index is established,and the curve equation of the index with the corrosion rate is given.