氯盐-荷载耦合作用下混凝土构件耐久性可靠度研究

发布时间：2018-01-07 19:00

本文关键词：氯盐-荷载耦合作用下混凝土构件耐久性可靠度研究　出处：《湖北工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：当今混凝土结构的耐久性问题日益凸显,引起了各国科学界以及工程界的关注。荷载和周边环境是两个影响混凝土耐久性的主要因素,因此研究氯盐环境下受荷混凝土和开裂混凝土中氯离子的传输机理、含量的变化规律以及各因素对构件耐久性可靠度指标的影响,具有较高的实际意义。本文针对这一课题展开了试验研究,研究的主要内容如下:(1)研究受荷混凝土内氯离子的运输机理。采用三分点自锚法,对氯离子在C25混凝土中的扩散性进行研究,分析荷载大小(荷载比为0.3,0.5)和荷载种类(拉应力和压应力)对氯离子扩散速率的影响以及持续荷载作用下混凝土构件中氯离子含量的分布规律。通过对试验数据进行回归分析,建立荷载水平与氯离子扩散系数的函数关系,引入荷载因素进一步完善现有的氯离子扩散模型。(2)研究开裂混凝土中氯离子的传输机理以及裂缝宽度对钢筋锈蚀的影响。采用预制裂缝法制作一批带裂缝的钢筋混凝土小梁,将试件进行70d的氯盐全浸泡侵蚀试验,对裂缝周围区域以及裂缝处不同深度范围内氯离子的含量进行观测分析,发现裂缝以及裂缝宽度对氯盐腐蚀的影响。采用双重孔隙介质模型分析氯离子在开裂混凝土中的传输,建立裂缝宽度与“等效表观氯离子扩散系数”的函数关系,引入裂缝因素进一步完善现有的氯离子扩散模型。通过测量分析裂缝处钢筋的锈蚀长度,拟合得到裂缝宽度与钢筋锈蚀长度的函数关系式。(3)进行了氯盐环境下混凝土结构耐久性可靠度研究。基于改进后荷载作用下氯离子扩散模型以及开裂混凝土中氯离子扩散模型,建立关于氯离子临界浓度和随时间改变的钢筋表面氯离子浓度的极限状态方程;结合算例应用Monte-Carlo方法对钢筋初锈发生的概率进行模拟计算,分析模型中各个参数对钢筋初锈概率的影响,为改善混凝土耐久性提供理论依据。
[Abstract]:Nowadays, the durability of concrete structures is becoming more and more prominent, which has attracted the attention of the scientific community and the engineering community. Load and surrounding environment are the two main factors that affect the durability of concrete. Therefore, the mechanism of chloride ion transport in loaded concrete and cracked concrete under chloride salt environment, the change law of content and the influence of various factors on durability reliability index of members are studied. The main contents of this study are as follows: 1) study the transport mechanism of chloride ions in loaded concrete. The three-point self-anchoring method is adopted. The diffusivity of chloride ions in C25 concrete is studied and the load size (load ratio is 0.3) is analyzed. The influence of load types (tensile stress and compressive stress) on chloride diffusion rate and the distribution of chloride ion content in concrete members under sustained load. Regression analysis was carried out on the test data. The function relationship between the load level and the chloride ion diffusion coefficient is established. Introduction of load factors to further improve the existing chloride diffusion model. The mechanism of chloride ion transport in cracked concrete and the influence of crack width on corrosion of steel bar were studied. A batch of reinforced concrete trabeculae with cracks were fabricated by precast crack method. The samples were subjected to 70 days of total chloride immersion erosion test, and the contents of chloride ions in the area around the fracture and in the different depth range of the fracture were observed and analyzed. The influence of crack and crack width on chloride corrosion was found. The double pore medium model was used to analyze the chloride ion transport in cracked concrete. The relationship between crack width and "equivalent apparent chloride ion diffusion coefficient" is established. The existing chloride diffusion model is further improved by introducing crack factors. The corrosion length of steel bar at crack is measured and analyzed. The functional relation between crack width and corrosion length of steel bar is obtained by fitting. Based on the improved chloride diffusion model and the chloride diffusion model of cracked concrete, the durability reliability of concrete structure under chloride salt environment is studied. The limit equation of state for the critical concentration of chloride ion and the concentration of chloride ion on steel bar surface with time is established. The probability of initial rust of steel bar is simulated and calculated by Monte-Carlo method, and the influence of each parameter in the model on the probability of initial rust of steel bar is analyzed. It provides a theoretical basis for improving the durability of concrete.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU375

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