基于断裂过程区线性位移分布的水工混凝土断裂分析及应用研究

发布时间：2018-06-24 23:24

本文选题：水工混凝土 + 线性分布　；参考：《重庆交通大学》2017年硕士论文

【摘要】：随着水利工程的发展,水工建筑物对于混凝土性能的要求逐步增加,而混凝土出现的裂缝问题也成为本行业关注的焦点之一,对于断裂过程区的研究是混凝土断裂特性研究的基础。本文主要通过使用先进的数字图像相关方法测量技术技术,对试件在三点弯曲实验中的表面应变场进行分析。在目前的断裂力学理论的基础上,通过简化软化曲线模型,利用MATLAB软件编程进行了基于过程区位移线性分布的断裂过程区的特性研究,本文的几个主要工作如下:(1)通过数字图像相关方法观测记录三点弯曲实验中整个试件的全场位移应变变化情况,对比引伸计测量数值,验证了数字图像相关方法的准确性。从全场应变分析,发现随着荷载的增加,全场应变会出现应变集中的现象,主要在裂缝发展过程的周围区域。另外,通过对裂缝尖端切线的不同高度平行线的位移分析,其突变区域也可以判断裂缝存在的区域以及断裂裂缝存在的走向。(2)为了解水工建筑物的断裂过程,分别进行了饱和混凝土与非饱和混凝土试件的三点弯曲实验。通过二者的表现规律,发现二者呈现相同的变化趋势,表明二者的断裂过程发展应该有相同的规律,所以可以将非饱和混凝土的断裂过程区的研究的一些结论运用到饱和混凝土上来。(3)对于断裂过程区发展的研究,主要通过分析断裂过程区与混凝土试件所受到荷载的关系,发现断裂过程区是在荷载达到一定值后才开始发生,产生之后伴随整个受载过程,受边界条件影响,后期到达一定临界值时,断裂过程区长度会下降。(4)对裂缝周边应变进行相关分析,发现裂缝尖端周围不同区域应变值的变化规律与所取分析长度关系不大,但会影响其峰值的大小;所取分析长度的中心距离裂缝的距离会影响应变的变化规律。(5)在前人的断裂理论模型上,假定张开位移呈线性分布,得到一种较为简单、快速软化曲线参数的获取方式。根据本文建立的软化曲线模型,通过对不同强度、不同含水率、不同骨料、不同砂率、不同骨料最大粒径以及不同粗骨料含量进行相关拟合对比,得到相应影响关系。
[Abstract]:With the development of water conservancy engineering, the demand for concrete performance of hydraulic structures is increasing gradually, and the crack problem of concrete has become one of the focal points of the industry. The study of fracture process zone is the basis of the study on fracture characteristics of concrete. In this paper, the surface strain field of the specimen in three point bending experiment is analyzed by using the advanced digital image correlation method. On the basis of the current fracture mechanics theory and by simplifying the softening curve model, the characteristics of the fracture process area based on the linear distribution of the displacement in the process zone are studied by using MATLAB software. The main work of this paper is as follows: (1) the whole displacement and strain changes of the whole specimen in the three-point bending experiment are recorded by the digital image correlation method, and the accuracy of the digital image correlation method is verified by comparing the measured values with the extensometer. From the full-field strain analysis, it is found that with the increase of the load, the full-field strain will be concentrated, mainly in the area around the crack development process. In addition, by analyzing the displacement of parallel lines at different height of the tangent line at the crack tip, the abrupt region can also be used to judge the fracture zone and the strike of the fracture crack. (2) in order to understand the fracture process of hydraulic structures, The three-point bending tests of saturated concrete and unsaturated concrete were carried out respectively. It is found that the two show the same trend of change, which indicates that the fracture process of both should have the same law. Therefore, some conclusions of the fracture process zone of unsaturated concrete can be applied to the saturated concrete. (3) the research on the development of the fracture process zone is mainly based on the analysis of the relationship between the fracture process zone and the load on the concrete specimen. It is found that the fracture process zone does not begin until the load reaches a certain value, followed by the whole loading process, affected by the boundary conditions, and when the critical value is reached at the later stage. The length of fracture zone will decrease. (4) through the correlation analysis of the strain around the crack tip, it is found that the variation of strain values in different regions around the crack tip is not related to the length of the analysis, but it will affect the magnitude of the peak value. The distance between the center and the crack of the analyzed length will affect the variation of strain. (5) in the former fracture theory model, the opening displacement is assumed to be linear distribution, and a simple and fast softening curve parameter is obtained. According to the softening curve model established in this paper, through the correlation and comparison of different strength, different moisture content, different aggregate, different sand ratio, different aggregate maximum particle size and different coarse aggregate content, the corresponding influence relation was obtained.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV431

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