Experimental Study On Corrosion Charcteristics And Mechanical Properties Of Bridge Cable Wires

Bridge cable is the main bearing and power transmission components of cable supported bridges. It is vulnerable to corrosion by environmental and mechanical factors and the mechanical property deterioration of wires and bearing capacity decrement of wires caused by wire corrosion or corrosion fatigue in the design reference period of bridge. By electro-chemical corrosion test, corrosion characteristics, mechanical tensile tests and fatigue tests, corrosion characteristics and the mechanical deterioration of the wire are studied in the text. The main research process and results are described as follows:1) Firstly, the corrosion mechanism of wires is discussed, and then the interaction of the single factor such as temperature, stress, chlorine ion concentration and pH is researched by electro-chemical corrosion tests. The functional relationship between corrosion rate and each single factor was established. Then, the response surface methodology is used to study temperature, stress, chlorine ion concentration, pH on the corrosion rate of wires, the functional relationship between corrosion rate and multi-factor is established. The study showed that the single factors affect corrosion rate and exist significant interactions between each other.2) Secondly, the three-dimensional size of corrosion pits on corroded wires are detected with established data, and then the distribution characteristics of pits is analyzed by using mathematical and statistical methods. The studies show that the uniform corrosion depth, corrosion pit depth obey generalized extreme value distribution and corrosion pit length, width obey lognormal distribution.3) Thirdly, the mechanical properties parameters of wires are got through the mechanical tensile test, and then the probability distribution of mechanical properties is discussed. The study shows that elongation, yield strength and ultimate strength decrease with the increase of the corrosion degree, and the decline rate of ultimate strength is greater than yield strength. The maximum pit depth used as the parameters to evaluate the degradation of the mechanical properties of the steel wire is more reasonable and accurate than the average corrosion depth.4) Fourthly, fatigue tests are conducted for new wires, uncorroded wires, wires with artificial pits. Based on results of fatigue tests, the wire S-N curves is fitted. The fatigue life and fatigue fracture of wire are discussed. It is found that the fatigue life of new wires decreases little, while the fatigue life of corroded wires decreases more as the corrosion going on. The fatigue life of wires with artificial pits also decreased with corrosion degree and pit depth at low stress amplitude level. There is also a tendency for fatigue life of uncorroded wires and wires with artificial pits decrease even further at high stress amplitude level, the test dates show larger discreteness.