悬索桥主缆钢丝腐蚀速率计算方法

A Method for Calculating Corrosion Rate of Main Cable Steel Wires of Suspension Bridge

悬索桥主缆钢丝的腐蚀严重影响着主缆的安全服役,缆内钢丝的腐蚀与其所处的缆内微环境有密切的关系,为预测悬索桥主缆内各区域中钢丝的腐蚀发展和剩余承载力,需建立主缆钢丝区域化腐蚀环境与腐蚀速率之间的计算关系。采用正交试验原理将影响钢丝腐蚀的:温度、相对湿度、Na Cl浓度、p H值、钢丝拉力5个主要因素分为两组,分别采用极化电阻腐蚀传感器和电化学工作站三电极体系两种测量手段对正交工况下的钢丝腐蚀速率进行测量。试验分析数据表明:在试验因素的取值范围内相对湿度和p H值各为两组因素中的主要因素,Na Cl浓度和p H值两个因素之间存在交互效应,温度、相对湿度、钢丝拉力之间相互独立;通过最小二乘法分别拟合得到5个因素与钢丝腐蚀速率之间的拟合计算关系;将实测的主缆内各区域的腐蚀环境统计为腐蚀环境年谱,并代入腐蚀速率与环境因素的计算关系,得到主缆各区域内钢丝的腐蚀速率和直径损失,其中主缆顶部区域腐蚀速率最高为0. 010 8 mm/a,服役20年后直径损失约为0. 02 mm即镀锌层耗损完毕,与实际桥梁检测情况吻合,服役100年直径损失将达到约1. 1 mm,将不能满足主缆的设计要求。建立的腐蚀速率计算方法为计算钢丝腐蚀量提供参考。

The corrosion of the main cable of suspension bridge seriously affects the safe service of the main cable,the corrosion of the steel wire inside the cable is closely related to the inside microenvironment. In order to predict the corrosion stage of steel wires in different parts of the main cable of suspension bridge,it is necessary to establish the calculation relation between the corrosive environment and the corrosion rate of the main cable steel wires. Dividing the 5 main factors affecting steel corrosion,including temperature,relative humidity,NaCl concentration,p H value and steel wire tension into 2 groups by orthogonal test principle,the corrosion rates of steel wires are measured by polarization resistance corrosion sensor and electrochemical workstation 3-electrode system. The analysis of experimental data shows that( 1) the main factors among the 2 groups within the range of experimental factors are relative humidity and pH value respectively;( 2)there is an interaction between NaCl concentration and pH value,while temperature,relative humidity and steel wire tension are independent of each other. The fitting calculation relationships between the 5 factors and the corrosion rate of steel wire are obtained by least squares fitting. The corrosion environment of each part in the measured main cable is counted as the corrosion environment aging spectrum,which is put into the calculation relationship between the corrosion rate and the environmental factors. Thus,the corrosion rate and the diameter loss of each part of the main cable are obtained. The corrosion rate in the top part of the maincable is up to 0. 010 8 mm/a,the diameter loss after 20 years of service is about 0. 02 mm,i. e.,the galvanized layer is worn out,which is consistent with the actual bridge detection. After 100 years of service,the diameter loss is about 1. 1 mm,which will not meet the design requirements. The established corrosion rate calculation method provides a reference for calculating the corrosion amount of steel wire. The proposed calculation method of corrosion rate will provide a reference for calculating corrosion amount of steel wire.