为了准确地模拟混凝土箱梁中氯离子的侵蚀过程,预测截面内任意时刻任意位置的氯离子浓度以及结构耐久性使用寿命。基于2D元胞自动机原理建立了混凝土氯离子扩散的元胞自动机模型(CA模型),模型同时考虑了材料和龄期对氯离子扩散效应的影响。以某箱形截面梁为例,根据箱梁中氯离子扩散的元胞自动机模型,编写了MATLAB计算程序,分析了氯离子在截面内的扩散规律,并根据模型对该结构耐久性使用年限进行了预测。研究结果表明:与氯离子浓度解析解和试验值相比,建立的元胞自动机模型能够有效地模拟混凝土箱梁氯离子扩散过程,且计算精度较高;根据截面倒角形式的不同,氯离子呈现出不同的扩散规律,不同位置氯离子浓度达到钢筋锈蚀临界浓度所需的时间不同;通过与寿命预测解析解进行对比,证明了该模型能有效预测混凝土结构耐久性使用寿命。利用该模型对氯盐侵蚀环境混凝土箱梁耐久性使用寿命进行预测,分析得出服役51 a左右该结构将达到耐久性极限设计状态。
Abstract
A cellular automata (CA) model of chloride ion diffusion in concrete was built based on Fick’s second law to accurately simulate the chloride ion erosion in concrete box girder, obtain the concentration of chloride ion at arbitrary position at any time in cross section, and to predict the durability life of the structure. The effects of material and age on the diffusion effect of chloride ion were taken into consideration. MATLAB calculation program was compiled based on the built CA model. Results of the study demonstrated that compared with the analytical solution and test value of chloride ion concentration, the result of the built CA model is of higher accuracy in simulating chloride ion diffusion in concrete box girder. Chloride ions diffuse in different laws varying with the form of chamfering sections, and the time required for critical concentration of chloride ion for steel corrosion is different. In addition, the model is proved to effectively predict the durability of concrete through comparison with the analytic solution of life prediction. The durability of the studied concrete box girder is around 51 years.
关键词
混凝土箱梁 /
寿命预测 /
氯离子扩散 /
元胞自动机模型 /
数值模拟
Key words
concrete box girder /
life prediction /
chloride ion diffusion /
cellular automata model /
numerical analysis
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参考文献
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基金
国家自然科学基金重大资助项目(11790281);国家自然科学基金资助项目(51878323);中国铁路总公司科技研究开发计划资助项目(2017G010-C)
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