基于初始缺陷试验的混凝土强度数值模拟
发布时间:2018-03-20 06:04
本文选题:初始缺陷 切入点:混凝土 出处:《郑州大学》2017年硕士论文 论文类型:学位论文
【摘要】:混凝土作为一种准脆性材料,其在受到荷载作用之前,内部就已存在微裂纹及孔隙等初始缺陷,这些初始缺陷的存在对混凝土力学性能和失效破坏有着较大的影响。目前对于混凝土初始缺陷对混凝土强度的影响研究多是基于数值模拟,数值模型中关于初始缺陷的结构参数选取多是基于定性的假设,因此本文基于微观结构试验获得的初始缺陷结构参数建立混凝土数值模型,研究初始缺陷对混凝土强度的影响。主要工作和结论如下:(1)确定了混凝土试验方案和混凝土配合比。根据拌合物坍落度及混凝土强度确定了混凝土试件配合比,研究了水灰比、骨料种类对混凝土初始缺陷及强度的影响。混凝土微观结构试验主要包括真空环氧浸渍技术及图像处理技术两个部分。(2)试验研究了混凝土微观结构,定量分析了混凝土初始缺陷分布。混凝土初始缺陷定量分析技术通过对荧光图像进行处理获取了混凝土初始微裂纹的总面积、长度、宽度以及孔隙含量等结构参数。结果表明:随着水灰比的减少,混凝土界面中初始微裂纹面积占混凝土总面积的百分比及初始微裂纹平均宽度随之减少,初始微裂纹总面积及总长度随之增大。(3)分析了初始缺陷对混凝土强度的影响。通过混凝土细观结构试验及宏观强度试验分析了初始缺陷与混凝土强度的关系:平均宽度、孔隙含量、界面区微裂纹含量、总缺陷含量的减小,混凝土抗压及抗拉强度均表现出增大趋势。分析得到:界面的力学性能对混凝土力学性能影响较大。(4)建立了由粗骨料、砂浆基体、界面过渡区和初始缺陷组成的混凝土数值模型。运用混凝土细观数值模型模拟了混凝土单轴受压试验,并与宏观强度试验结果对比。结果表明:混凝土细观数值模型能较好的模拟混凝土单轴受压强度试验以及混凝土破坏机理。(5)采用上述模型分析了骨料含量对混凝土强度的影响。建立粗骨料体积含量分别为40%、35%、25%的混凝土细观数值模型模拟混凝土单轴受压强度。模拟结果表明:在粗骨料体积含量为35%时数值模型的受压强度达到最大值。
[Abstract]:As a kind of quasi-brittle material, concrete has some initial defects, such as microcracks and pores, before it is subjected to load. The existence of these initial defects has a great influence on the mechanical properties and failure failure of concrete. At present, most of the researches on the effects of initial defects on the strength of concrete are based on numerical simulation. In the numerical model, the structural parameters of the initial defects are mostly based on the qualitative hypothesis. Therefore, the numerical model of concrete is established based on the structural parameters of the initial defects obtained from the microstructure test in this paper. The effects of initial defects on concrete strength are studied. The main work and conclusions are as follows: 1) the concrete test scheme and concrete mix ratio are determined. The mix ratio of concrete specimens is determined according to the slump and strength of concrete, and the water-cement ratio is studied. The effect of aggregate types on the initial defects and strength of concrete. The microstructure test of concrete mainly includes two parts: vacuum epoxy impregnation technology and image processing technology. Quantitative analysis of initial defects in concrete. The total area and length of initial microcracks in concrete are obtained by processing fluorescence images. The results show that with the decrease of water-cement ratio, the percentage of the initial micro-crack area to the total area of concrete and the average width of the initial micro-crack decrease with the decrease of water-cement ratio. The influence of initial defects on concrete strength is analyzed by increasing the total area and total length of initial microcracks. The relationship between initial defects and concrete strength is analyzed by meso structure test and macro strength test: average width. The decrease of pore content, microcrack content and total defect content in the interface area, the compressive strength and tensile strength of concrete all show an increasing trend. It is concluded that the mechanical properties of the interface have a great influence on the mechanical properties of concrete. The concrete numerical model composed of mortar matrix, interface transition zone and initial defect is used to simulate the uniaxial compression test of concrete. The results show that the meso-numerical model of concrete can simulate uniaxial compressive strength test of concrete and failure mechanism of concrete. (5) the above model is used to analyze the effect of aggregate content on coagulation. Under the influence of soil strength, a mesoscopic numerical model for simulating uniaxial compressive strength of concrete with 40% and 35% volume content of coarse aggregate was established respectively. The simulation results show that the compressive strength of the model reaches the maximum when the volume content of coarse aggregate is 35.
【学位授予单位】:郑州大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TU528
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