Study On Corrosion Properties Of Stainless Steel Wire For Cable Use And Assessment Of Time-Variant Reliability Of Stay Cable Of Bridge

Corrosion of cable is considered on bridge design and construction, especially for the bay bridge. At present, most sling material is high strength carbon steel wire or steel strand, which is in high stress state in the actual operation and sensitive to the outside environment attack. The anticorrosive coating aging, corrosion and broken wire of cable are exposed as the years growing, which need a lot of human resources to replace. Otherwise the broken cable will make the bridge collapse. With this reason, the idea of using the stainless steel wire instead of the traditional material comes into being. Combined with the project of the ministry of science and technology "The development and study of whole life stainless steel cable" and the national basic project’ The fundamental research of extra long-span bridge safety design and evaluation", corrosion property of stainless steel wire was studied and the time-variant reliability of stay cable of bridge was analyzed, on the basis of the theory of corrosion, which includes the following major contents and conclusions:(1) Corrosion environment and morphology were discussed to study corrosion mechanism and influencing factors, which provided theoretical basis for the analysis of steel wire corrosion.(2) To study the corrosion property of stainless steel wire cable, every single stainless steel wire was applied four levels of stress of 0,20%,30%,40%, using the zero stress common galvanized steel wire as comparison. Neutral salt spray test was established for three periods of 7d,20d and 40d, after which comparative analysis was done on the changes in quality loss rate of stainless steel wire and load-deformation curves under different stress levels and the zero stress common galvanized steel wire. Degradation coefficient was fitted by the data of neutral salt test. SEM was conducted to analyze the fracture surface topography after tensile test. The results showed that he weight loss rate of ordinary steel wire was more than 30 times that of stainless steel wire under the zero stress, which showed that the corrosion protection property was far better than ordinary steel wire. The weight loss rate of stainless steel wire gradually increased with stress, so the stainless steel wire was easier corroded under high stress. In the short term corrosion, the effect on the ultimate tensile strength was not very big. With the increase of corrosion, the tensile fracture of galvanized steel wire and stainless steel wire presented brittleness increasing trend. The fracture surface topography of galvanized steel wire developed from micro cracks to wide cracks, of which the stainless steel wire developed micro cracks by no cracks because of lighter corrosion.(3) One cable-stayed bridge was modeled and cable force was calculated using ANSYS. Stainless steel wire and ordinary steel wire were applied to cables of the bridge. Degradation coefficient was used to establish functions. Using a second moment method, the reliability indexes of cables were calculated and analyzed. The results showed that the reliability indexes of stay-cables near the cable tower were bigger than that of away from the cable tower. The reliability index didn’t change if cables were not corroded. Nevertheless, if cables began to corrode after being exposed 20 years, the reliability indexes of ordinary galvanized steel declined faster than that of stainless steel.