基于随机骨料模型的细观混凝土界面特性研究

发布时间：2018-08-26 09:17

【摘要】：混凝土作为一种非均质、多相复合材料被广泛应用于工程实际,混凝土研究的传统方法主要以宏观唯象试验为主,但宏观物理试验需要花费大量的人力、物力、财力,且试验结果往往受到许多环境因素的影响,有些情况下甚至难以进行。随着计算机技术的高速发展,混凝土损伤与断裂过程的研究已经从宏观尺度转向细观尺度,运用数值模拟方法探究混凝土的宏观层次力学问题已成为一种发展趋势。本文立足于细观层次,将混凝土视为由骨料、砂浆与界面层组成的三相复合非均质材料,将几何与统计理论相结合,基于蒙特卡罗方法建立混凝土随机骨料模型,以MATLAB软件为基础编写了圆形、椭圆形和多边形三种不同形状的二维随机骨料模型程序,提出以“面积占有率”来控制模型中骨料的投放,分别生成骨料含量为40%、50%和60%的模型,结合AUTOCAD软件提取骨料边界。考虑到界面层作为混凝土三相材料中最薄弱的环节,为研究界面特性对混凝土的力学性能影响,分别建立不同形状、不同界面层厚度、不同骨料含量的骨料模型,以ANSYS为计算平台,对建立的模型进行单轴压缩数值试验,经分析计算后得到:骨料含量对混凝土的抗压强度会有重要影响;在同一骨料含量下,多边形骨料的抗压强度最高,比圆形和椭圆骨料高出18.4%和8.0%左右;在同一骨料含量条件下,当界面层厚度增大时,混凝土的抗压强度有一定程度的降低;混凝土破坏形态数值试验验证了混凝土的破坏是从界面层开始,裂缝不断延伸扩展直至最终形成宏观裂缝。
[Abstract]:As a kind of heterogeneous and multiphase composite material, concrete is widely used in engineering practice. The traditional method of concrete research is mainly macro phenomenological test, but macro physical test needs a lot of manpower, material and financial resources. The test results are often affected by many environmental factors, and in some cases it is even difficult to carry out. With the rapid development of computer technology, the study of damage and fracture process of concrete has changed from macroscopic scale to mesoscale scale. It has become a developing trend to use numerical simulation method to explore the macroscopic mechanics of concrete. Based on the mesoscopic level, the concrete is regarded as a three-phase composite heterogeneous material composed of aggregate, mortar and interfacial layer. Based on Monte Carlo method, the random aggregate model of concrete is established by combining geometry with statistical theory. Based on MATLAB software, a two-dimensional random aggregate model program with circular, elliptic and polygonal shapes is developed. It is proposed that "area occupancy" is used to control the aggregate delivery in the model, and a model with 40% aggregate content and 60% aggregate content is generated, respectively. Aggregate boundary is extracted with AUTOCAD software. Considering that the interfacial layer is the weakest link in the three-phase concrete material, in order to study the influence of interfacial characteristics on the mechanical properties of concrete, the aggregate models with different shapes, different interfacial layer thickness and different aggregate content are established, respectively. On the basis of ANSYS, the uniaxial compression test of the established model is carried out. The results show that the aggregate content has an important effect on the compressive strength of concrete, and the polygonal aggregate has the highest compressive strength under the same aggregate content. Under the same aggregate content, the compressive strength of concrete decreases to a certain extent when the thickness of interfacial layer increases. The numerical test of concrete failure pattern verifies that the failure of concrete starts from the interface layer and the cracks extend and eventually form macroscopic cracks.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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