Damage And Safety Performance Evaluation Of The Cable-stayed Corrosion

For the modern cable-stayed bridge, the cable system is the main load-bearingcomponents. The old cable-stayed structure in use due to adverse effects, affected byfactors such as stress and corrosion, resulting in the presence of various defects andinjuries. A large number of incidents show that the damage cable will usually cause themechanical properties of the bridge changed, thereby affecting the safety of the bridgestructure, durability and service life. So the damage and safety evaluation of thecable-stayed corrosion is particularly important.This article relying on the national973project Bridge structure evolution theoryand behavior safety monitoring methods study. This paper describes the status of cabledamage detection and assessment of the safety performance. Pointed out that the mainform of steel wire rope damage is stress corrosion and corrosion fatigue damage. Forhigh-strength steel wire rope, unstressed, static stress and alternating stress force by wayof acid salt spray test. Research the cable damage evolution process and the safetyperformance after pitting corrosion, stress corrosion and corrosion fatigue damage.â‘ According to the three injuries status, the process of steel wire damage isdescribed as five stages through salt spray corrosion test, wire intactâ†'galvanizedcorrosion of steel wireâ†'Uniform corrosion of steel wire substratesâ†'steel wire matrixslight pittingâ†'steel wire matrix with a lot of pittingâ†'stress corrosion and corrosionfatigue occurred. And develop â…¤ grade corrosion legend. Put forward a kind ofevaluation method of surface image analysis technique based on the situation ofcorrosion cable through gray analysis. According to salt spray corrosion test and tensiletest data, select the characteristic parameters with good associated, such as corrosionweight loss, tensile strength and elongation rate, give evaluation criteria of steel wire.â‘¡Establishing a hemispherical pits model to calculate the depth of the pits underdifferent weight loss. The formula of point pitting corrosion rate is given. Based on theexperimental parameters, calculate the fracture toughness KIC=117.6MPa mof thewire. Stress corrosion threshold stress intensity factor KISCC=46.8obtainedby fracture toughness. Finally, put forward stress corrosion damage evolution modelbased on injuries mechanics theory. According to the stress intensity factor criterion,calculating corrosion fatigue crack growth threshold K th3.64when the stressratio R=0.â‘¢Introduces the concept of equivalent crack depth, equivalent stress intensity factor calculation based on the crack depth. The transformation of three-dimensionalmodel of steel crack ingenious for plane strain problem, using the straight-lineextrapolation, different values of the crack tip stress intensity factor under the pits depthare simulated by using finite element software ANSYS. Proposed calculation method ofresidual strength based on fracture toughness. Finally, according to breakage securitytheory, given the fail-safe design of corrosion fatigue damage and single wire breakagesafety assessment process.â‘£The single wire corrosion and whole root model under different degrees ofcorrosion are simulation. The results show that: the greater the depth of the pits, thegreater the stress concentration factor at the bottom of the pit. The whole root Lasso rustinto five to simulate the effect of different levels, Maximum stress appears at the contactarea between the outer most wire, with the corrosion levels increasing, stress ofcorrosion Lasso improves overall.