混凝土断裂破坏过程及尺寸效应研究

发布时间：2018-05-04 16:44

本文选题：混凝土 + 裂缝扩展　；参考：《辽宁工程技术大学》2015年硕士论文

【摘要】：尺寸效应作为准脆性材料的固有属性,在混凝土中表现尤为明显,如何准确、合理的通过研究小尺寸试件的断裂参数来分析大尺寸混凝土结构的断裂破坏是广大科研工作者需要解决的问题。而研究混凝土的断裂参数建立混凝土断裂破坏准则首先要研究混凝土断裂过程中裂缝扩展规律。目前对于混凝土裂缝扩展路径规律的研究很少涉及而且大多数只是从混凝土试件的表面观测裂纹的扩展。因此混凝土断裂破坏过程中裂缝扩展规律以及其断裂参数的尺寸效应问题仍具有重要的研究价值。针对以上问题本文通过数字图像相关方法研究了混凝土楔入劈拉试件的断裂全过程,分析混凝土裂缝的扩展全过程并在对得到的荷载—裂缝张开口位移曲线尾部进行拟合分析的基础上计算分析了混凝土断裂能和断裂韧度的尺寸效应。在对比物理试验的基础上进一步做了数值模拟研究,通过Matlab建立反映混凝土内部结构的随机骨料模型并在Ansys中进行网格单元的划分,并最终导入FLAC3D对数值模型进行计算分析。通过物理实验和数值模拟的对比进一步研究了混凝土裂缝扩展规律和断裂参数的尺寸效应规律。通过物理试验和数值模拟结果的对比研究发现：(1)数字图像相关方法能真实的反映混凝土断裂破坏中裂缝的扩展过程,混凝土破坏时其裂缝尖端附近存在应变局部化带,裂缝的扩展过程中存在着亚临界扩展。数字图像相关方法研究混凝土裂缝的扩展对评价混凝土构件的稳定性和控制裂缝扩展方向具有指导意义。(2)在混凝土断裂过程中其断裂能和断裂韧度存在着尺寸效应,混凝土的断裂能和断裂韧度有随着混凝土试件高度的增大而增大的趋势,但当试件高度超过500mm时,混凝土的断裂韧度与试件尺寸无关。(3)数值试验结果与物理试验的结果具有一致性,因此数值试验为解决土木、水利等工程中由于实验室中大尺寸试件制作及实验困难这一难题提供了一个有效途径。
[Abstract]:As the inherent property of quasi-brittle material, the size effect is especially obvious in concrete. It is necessary to solve the problem of analyzing the fracture failure of large size concrete structures by studying the fracture parameters of small size concrete structures. In order to establish the fracture failure criterion of concrete, it is necessary to study the crack propagation law in the process of concrete fracture. At present, the research on crack propagation path of concrete is seldom involved, and most of them are only observed from the surface of concrete specimen. Therefore, it is of great value to study the crack propagation law and the size effect of fracture parameters during the fracture failure of concrete. In view of the above problems, the whole fracture process of concrete wedge wedge tensile specimen is studied by digital image correlation method. The whole process of crack propagation is analyzed and the size effect of fracture energy and fracture toughness of concrete is calculated and analyzed on the basis of fitting and analyzing the load-crack opening displacement curve. On the basis of comparing the physical experiments, the numerical simulation is done. The random aggregate model reflecting the internal structure of concrete is established by Matlab, and the mesh element is divided in Ansys. Finally, the numerical model is calculated and analyzed by introducing FLAC3D. Through the comparison of physical experiment and numerical simulation, the law of crack propagation and size effect of fracture parameters of concrete are further studied. By comparing the results of physical test and numerical simulation, it is found that the digital image correlation method can truly reflect the crack propagation process in concrete fracture failure, and there is a strain localization zone near the crack tip of concrete. There is subcritical propagation in the process of crack propagation. The digital image correlation method is helpful to evaluate the stability of concrete members and control the crack propagation direction.) there is a size effect on the fracture energy and fracture toughness of concrete in the process of fracture. The fracture energy and fracture toughness of concrete increase with the height of concrete specimen, but when the height of concrete specimen is higher than 500mm, The fracture toughness of concrete has nothing to do with the size of the specimen.) the results of the numerical test are consistent with the results of the physical test, so the numerical test is to solve the problem of civil engineering. In water conservancy engineering, an effective way is provided because of the difficulty of making large scale specimen in laboratory and the difficulty of experiment.
【学位授予单位】：辽宁工程技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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