长期服役结构中钢筋的纵向随机锈蚀分布特征

Longitudinal Stochastic Corrosion Distribution Characteristics of Steel Bar in Long-term Service Structure

钢筋在服役结构中的自然锈蚀与试验室人工加速锈蚀存在差异.为研究实际服役工程中钢筋的自然锈蚀特征,从服役50余年的钢筋混凝土桥面板中获取一批钢筋试件,通过三维激光扫描得到精确的锈蚀钢筋剩余表面信息,以锈后剩余截面积直观表征钢筋沿纵向的锈损情况,探究锈蚀程度、钢筋长度对锈蚀纵向不均匀性的影响,经统计分析进行钢筋纵向随机锈蚀的概率分布特征研究,提出相应的概率分布模型.研究结果表明:自然锈蚀钢筋具有多种典型锈蚀形态,锈蚀区域及锈蚀程度沿钢筋纵向随机分布;最大截面积损失率、剩余截面积方差随平均锈蚀率的增大而增大,即平均锈蚀程度越大则锈蚀越不均匀;钢筋长度对纵向锈蚀不均匀性有明显影响,在钢筋来源及平均锈蚀率相同的情况下,随钢筋长度的增大锈蚀不均匀性增大.钢筋的纵向随机锈蚀具有明显的统计规律,多峰正态分布模型可精确描述不同锈蚀程度钢筋的剩余截面积概率分布;Weibull分布及单峰正态分布模型对实测截面积数据拟合优度略低,但其形式简单便于运用,适用于平均锈蚀率低于10%的钢筋.

Natural corrosion of steel bars in service structures differs from experimental artificial accelerated cor⁃rosion.For investigating the natural corrosion characteristics of steel bars in practical engineering,a batch of cor⁃roded steel bar specimens was acquired from reinforced concrete bridge decks that have been in service for more than 50 years.Precise residual surface information of the corroded steel bars was obtained by three-dimensional laser scanning,and corrosion all along the bars was described by residual cross-sectional areas.The effects of corrosion degree and bar length on longitudinal corrosion non-uniformity were studied.The probability distribution characteris⁃tics of longitudinal stochastic corrosion were studied by statistical analysis,and the corresponding probability distri⁃bution models were proposed.Results show that naturally corroded steel bars have various typical corrosion morphology.The corrosion zone and corrosion degree are random along the bars.The maximum cross-section loss ratio and variance of residual cross-sectional areas increase as the average corrosion degree increases,which indicates that the more severe the corrosion is,the more uneven the corrosion is.Bar length influences corrosion non-uniformity significantly.In the case of the same source and average corrosion degree,the non-uniformity increases with the in⁃crease of bar length.The longitudinal stochastic corrosion of steel bars has a statistical law.The probability distribu⁃tion of residual cross-sectional areas of steel bars with different corrosion degrees can be accurately evaluated by the multimodal normal distribution model.In comparison,the Weibull distribution model and the unimodal Normal dis⁃tribution model have a slightly poorer fitness,and are simple in form and easy to apply,which are suitable for steel bars with an average corrosion degree of less than 10%.