| The suspension bridge has a large span capacity and beautiful shape,and is one of the preferred bridge types for extra-large span bridges.The mountainous area is rich in groundwater resources,and the anchor room of the main cable of the suspension bridge is in harsh conditions.Tunnel anchors often have the phenomenon of surrounding rock seepage and river water backfilling,and the humidity in the anchor room is high.Under the coupling of environment,constant load and live load,the main cable strand is susceptible to corrosion fatigue damage,which poses a hazard to the safe operation of the suspension bridge.Therefore,studying the corrosion fatigue damage behavior of the main cable strands of the suspension bridge has important theoretical significance and engineering application value for ensuring the operation safety of the suspension bridge.With the support of the National Natural Science Foundation of China,Research on the Corrosion Fatigue Damage Mechanism and Long-term Performance of Cable-stayed Cable Anchoring System under Coupling of Stochastic Load and Environment(No.52178273),this paper focuses on the corrosion fatigue damage behavior of the main cable strands of suspension bridges,and discusses the long-term performance of cable strands in the anchoring section of the main cable under service conditions.The main work and research conclusions are as follows:Firstly,through the constant current accelerated corrosion experiment of the main cable stranded steel wire,the corrosion damage mode and evolution mechanism of high-strength galvanized steel wire and anti-corrosion coated galvanized steel wire were studied,the inhibition mechanism of anti-corrosion coating on corrosion damage was revealed,the degradation law of mechanical properties and fatigue life of corroded steel wire was analyzed,and the fatigue experimental results of steel wire were statistically analyzed through Weibull theory,and the P_f-S-N curve of steel wire with different failure probabilities under different corrosion degrees was obtained.Experimental studies have found that the evolution process of steel wire corrosion is divided into five stages:stage I:intact stage;Stage II:the galvanized layer corrodes,and white products are generated on the surface of the steel wire;Stage III:the iron matrix begins to corrode,forming yellow corrosion products;Stage IV:moderate corrosion of iron matrix,formation of red corrosion products;Stage V:the surface of the steel wire is covered with red corrosion products,and there are erosion pits.The corrosion evolution process of anti-corrosion coated steel wire is manifested as aging and damage of the anti-corrosion coating on the surface of the steel wire,and then the same corrosion process occurs as galvanized steel wire.The maximum weight loss rates of galvanized steel wire and anti-corrosion coated steel wire were 3.31%and 2.29%,the maximum yield load reduction rates were 4.73%and 2.38%,and the maximum ultimate load reduction rates were 4.83%and 2.36%,respectively.The anti-corrosion coating has an obvious inhibitory effect on the corrosion damage of steel wire.Secondly,through Abaqus finite element simulation analysis,the spatial stress distribution law of corroded steel wire in different sizes and depths of pits is simulated,and the influence of pit size and depth on the stress concentration effect is revealed,and it is found that the depth of the pit determines the degree of stress concentration of the steel wire,and the smaller the size of the pit at the same depth,the more obvious the stress concentration effect.The results of Fe-safe finite element simulation of corroded steel wire show that the fatigue life of steel wire decreases rapidly when the pit is just generated,but with the deepening of the corrosion degree,the decline trend of steel wire life gradually slows down,and the sensitivity of wire fatigue life decline gradually decreases with the increase of corrosion degree.The theoretical model of fatigue life prediction of rusted steel wire was further established.Thirdly,through Abaqus finite element simulation,combined with the mechanical properties of rusted steel wire and P_f-S-N curve,the spatial stress distribution law and fatigue life of rust cable strands and tie rods in the anchor section were analyzed,and the corrosion fatigue damage mode and evolution mechanism of the main cable strands and tie rods in the anchor section were revealed,and it was found that the area above the anchor head of the cable strands was the area with the lowest fatigue life and the most prone to corrosion fatigue damage fracture.By comparing and analyzing the influence of the rust part of tie rod on the spatial stress distribution and fatigue life,it is found that the corrosion damage under and inside the middle of the tie rod bolt has a great influence on the fatigue life of the tie rod.Finally,the long-term performance index system of cable stocks in the anchoring section of the main cable of the suspension bridge was established by the analytic hierarchy method,and the key indicators to determine the long-term service safety of the cable stock in the anchoring section of the suspension bridge are:mechanical properties(tensile strength of steel wire,corrosion fatigue performance of steel wire),protective performance(coating adhesion,coating aging performance).Based on the long-term performance research and experimental simulation results of bridges at home and abroad,as well as the methods of regular inspection,health monitoring and special testing of bridges,the long-term performance monitoring and evaluation method of the anchoring section of the main cable of the suspension bridge is preliminarily established,which provides technical support for the safe operation of the suspension bridge. |
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