Influence Of Corrosion On Mechanical Properties Of Galvanized Steel Wire For Bridge Cable

After bridge cable steel wires corrosion, the mechanical properties and fatigue properties of steel wires will be reduced which bring the hidden danger for bridge safety operation. To make better and more safety operation for bridge, the reasonable maintenance measures shall be formulated combining the change features of mechanical properties after steel wires corrosion to ensure the service life of bridge cables. This article makes the analysis and assessment on the surface of the corrosion condition, the static and dynamic mechanical properties and corrosion fatigue life of bridge cable steel wires, specific as follows:Statistic analysis of the bridge cable galvanized steel wire corrosion dimension found that actual corrosion depth and average corrosion depth use generalized extreme value distribution fitting, and the corrosion depth and length adopt logarithmic normal distribution fitting. After fitting the actual statistical data can be controlled within the scope of the fitting of distribution, and obtained good fitting effect. There is no definite function relation between the Actual corrosion size and average corrosion depth. Due to zinc sacrificial anode protection, small temperature changes impact on the corrosion potential slightly and almost no effect on the corrosion current.Through limited atoms model analysis, based on the stress intensity factor analyses for the corrosion of steel wires with surface crack, fitting obtain the expression of stress intensity factor correction coefficient of bridge corrosion steel wires. Based on the linear elastic theory, estimate the residual strength of corrosion steel wire and conclude that the expression of corrosion pit being equivalent to the stress intensity factor of corrosion steel wire after surface crack and the expression of corrosion residual strength of steel wire.Through a large number of fatigue tests, we get the S-N curve of different state steel wires, and fitting out the fatigue curve equation by Basquin equation. The prediction results of steel wire fatigue life show that without regard to other factors,the fatigue life of a new steel wire is about 25.5 years in the case of 125 MPa auto load amplitude and 3.5 Hz cable vibration. Keep fixed stress ratio unchanged, carry on fatigue testing for the fatigue crack steel wires with the prefabricated different dimensions and obtain that when the sizes of corrosion pit depth are same, the length of the corrosion pit is directly proportional to the number of fatigue; when the sizes of corrosion pit length are same, corrosion pit depth is inversely proportional to the number of fatigue. The emergence of bridge steel wire surface corrosion willsignificantly shorten the producing time of steel wire corrosion fatigue, and greatly reduce the corrosion fatigue life of bridge steel wires. So enhancing the ability of resistance to bridge steel wire corrosion is the key to improve resistance to corrosion fatigue of the whole bridge cable system.