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氯离子侵蚀和碳化是影响混凝土结构耐久性的主要因素,各自的理论公式已比较完善,但考虑二者耦合作用的定量分析和模型较少,影响混凝土结构耐久性分析的精度和水平.扩散限制凝聚模型(Diffusion-limited Aggregation,DLA)能够较完善地模拟气体的扩散凝聚,且具有随机性和分形特征,适合细致反映氯离子侵蚀、碳化及二者耦合作用下混凝土性能演变过程.本文基于DLA原理,考虑到扩散深度、混凝土特性及暴露条件等对氯离子扩散的影响,并考虑到混凝土特性及暴露条件等对碳化的影响,以及碳化与氯离子侵蚀的耦合作用,建立DLA模型,可获得任意时刻、任意位置处二氧化碳与氯离子的浓度.针对桥梁耐久性分析需求,提出利用DLA模型预测考虑疲劳效应的混凝土和钢筋性能退化方法.算例表明该方法能够动态细致地模拟桥梁耐久性演变过程.
Chloride ion erosion and carbonization are the main factors that affect the durability of concrete structures. The theoretical formulas have been perfect, but the quantitative analysis and model considering the coupling effect are few, which affect the accuracy and level of durability analysis of concrete structures. Diffusion-limited Aggregation (DLA) can well simulate the gas diffusion and aggregation, with randomness and fractal characteristics, and is suitable for detailed reflection of chloride ion erosion, carbonation and the evolution of concrete performance under the coupling of the two.In this paper, DLA Principle, taking into account the diffusion depth, concrete properties and exposure conditions on the diffusion of chloride ions, and taking into account the concrete properties and exposure conditions such as the impact of carbonation, and carbonation and chloride ion erosion of the coupling effect, the establishment of DLA model available The concentration of carbon dioxide and chloride ions at any position and moment.According to the requirement of bridge durability analysis, a method to predict the fatigue behavior of concrete and steel by DLA model is proposed.Experimental results show that this method can dynamically and carefully simulate the evolution of bridge durability process.