基于等效化方法的混凝土细观损伤断裂研究
发布时间：2018-08-04 11:21
【摘要】：混凝土作为一种典型的多相非均质复合材料,在土木工程领域有着非常广泛的应用,其材料性能与混凝土结构的耐久性和安全性等有着密切的联系。混凝土内部各相材料的力学性能差距很大,加之微裂纹、孔隙和其它初始缺陷的存在导致混凝土的基本性能变化规律有待进一步研究。数值分析方法作为研究混凝土劣化机理的重要手段,可以在各项试验数据和理论研究的支持下对混凝土的各项力学性能进行模拟和预测,是当下混凝土材料性能研究的热点之一。混凝土在细观层次上可以看作是由粗细骨料、水泥浆体和各种初始缺陷点等组成的复合材料。基于细观分析方法的混凝土数值模型,在参数选择合理的情况下不仅可以直观的反映出混凝土各相组成对其性能的影响以及持续变化荷载作用下的整个损伤断裂过程,而且可以避免实体试验中环境因素和人为失误等客观原因对试验结果的影响。本文基于混凝土细观随机骨料模型,将损伤力学理论应用到数值分析中,模拟研究了混凝土试件在单轴荷载作用下的的损伤破坏过程,并在数值模型的建立过程中引入等效化方法的概念,通过等效前后模拟结果的对比验证了等效化方法在混凝土的细观损伤模型中应用的合理性。具体工作如下:1.阐述了等效化方法及混凝土损伤断裂力学的基本概念,并研究了等效化方法在混凝土细观力学分析中的具体应用。2.在数值软件中运用蒙特卡洛方法,通过编写程序化语言实现了圆形骨料颗粒在指定的区域和骨料级配范围内的随机分布。然后对生成的骨料坐标数据进行处理,添加界面单元最终生成二维混凝土试件的几何模型。3.对有限元软件进行二次开发,将双折线损伤模型引入到混凝土试件的单轴受拉、单轴受压的数值模拟中去,通过设置状态变量判断单元是否失效删除,进而模拟出混凝土内部裂纹的扩展规律,并得到相应的应力应变曲线。4.将等效化方法应用到数值模型中去,即把砂浆基质与界面过渡区等效为一种材料,通过与原三相材料模型的试验结果进行对比,验证方法的可靠性,并在子程序中创建损伤变量输出模块,较为直观地反映等效后模型的损伤断裂过程。5.讨论了混凝土的界面厚度、骨料粒径选取范围和孔隙率对其性能的影响。本文运用等效化方法简化了模型的建立过程,而且开发出了模型的损伤变量输出模块,在提高模型计算效率的同时可以更真实和直观地表达混凝土在单轴荷载作用下的损伤断裂过程。为进行混凝土基本性能的细观分析提供技术支持,为对混凝土结构进行结构分析与优化设计奠定理论基础。
[Abstract]:As a typical heterogeneous composite material, concrete has been widely used in civil engineering. Its properties are closely related to the durability and safety of concrete structures. The difference of mechanical properties between different phases of concrete is very large, and the existence of micro-cracks, pores and other initial defects lead to the further study of the basic performance of concrete. As an important means to study the deterioration mechanism of concrete, numerical analysis method can be used to simulate and predict the mechanical properties of concrete under the support of experimental data and theoretical research. At present, it is one of the hot spots in the research of concrete material performance. At the meso level, concrete can be regarded as a composite composed of coarse aggregate, cement paste and various initial defect points. The numerical model of concrete based on the mesoscopic analysis method can not only reflect the effect of each phase composition of concrete on its performance but also the whole damage and fracture process of concrete under the action of continuous changing load under reasonable selection of parameters. Moreover, it can avoid the influence of environmental factors and human error on the test results. Based on the concrete meso-random aggregate model, the damage mechanics theory is applied to the numerical analysis, and the damage and failure process of concrete specimen under uniaxial load is simulated. The concept of equivalent method is introduced in the process of establishing the numerical model. The rationality of the application of the equivalent method in the meso-damage model of concrete is verified by the comparison of the results of the simulation before and after the equivalence. The work is as follows: 1. This paper expounds the basic concept of equivalent method and concrete damage fracture mechanics, and studies the concrete application of equivalent method in concrete meso-mechanics analysis. The Monte Carlo method is used in the numerical software to realize the random distribution of the circular aggregate particles in the specified area and the aggregate gradation range by programming language. Then, the data of aggregate coordinate are processed, and the geometric model of two-dimensional concrete specimen is generated by adding interface element. The double broken line damage model is introduced into the numerical simulation of uniaxial tension and uniaxial compression of concrete specimens, and the state variables are set to determine whether the unit is invalid or not. Furthermore, the propagation law of internal crack in concrete is simulated, and the corresponding stress-strain curve. 4. The equivalent method is applied to the numerical model, that is, the mortar matrix is equivalent to the interfacial transition zone as a kind of material, and the reliability of the method is verified by comparing the experimental results with the original three-phase material model. The damage variable output module is created in the subprogram to reflect the damage fracture process of the equivalent model. The influence of interfacial thickness of concrete, selection range of aggregate particle size and porosity on its performance is discussed. In this paper, the process of establishing the model is simplified by using the method of equivalence, and the output module of the damage variable of the model is developed. The damage and fracture process of concrete under uniaxial load can be expressed more realistically and intuitively while improving the efficiency of model calculation. It provides technical support for the mesoscopic analysis of the basic properties of concrete and lays a theoretical foundation for structural analysis and optimum design of concrete structures.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528
本文编号：2163820
[Abstract]:As a typical heterogeneous composite material, concrete has been widely used in civil engineering. Its properties are closely related to the durability and safety of concrete structures. The difference of mechanical properties between different phases of concrete is very large, and the existence of micro-cracks, pores and other initial defects lead to the further study of the basic performance of concrete. As an important means to study the deterioration mechanism of concrete, numerical analysis method can be used to simulate and predict the mechanical properties of concrete under the support of experimental data and theoretical research. At present, it is one of the hot spots in the research of concrete material performance. At the meso level, concrete can be regarded as a composite composed of coarse aggregate, cement paste and various initial defect points. The numerical model of concrete based on the mesoscopic analysis method can not only reflect the effect of each phase composition of concrete on its performance but also the whole damage and fracture process of concrete under the action of continuous changing load under reasonable selection of parameters. Moreover, it can avoid the influence of environmental factors and human error on the test results. Based on the concrete meso-random aggregate model, the damage mechanics theory is applied to the numerical analysis, and the damage and failure process of concrete specimen under uniaxial load is simulated. The concept of equivalent method is introduced in the process of establishing the numerical model. The rationality of the application of the equivalent method in the meso-damage model of concrete is verified by the comparison of the results of the simulation before and after the equivalence. The work is as follows: 1. This paper expounds the basic concept of equivalent method and concrete damage fracture mechanics, and studies the concrete application of equivalent method in concrete meso-mechanics analysis. The Monte Carlo method is used in the numerical software to realize the random distribution of the circular aggregate particles in the specified area and the aggregate gradation range by programming language. Then, the data of aggregate coordinate are processed, and the geometric model of two-dimensional concrete specimen is generated by adding interface element. The double broken line damage model is introduced into the numerical simulation of uniaxial tension and uniaxial compression of concrete specimens, and the state variables are set to determine whether the unit is invalid or not. Furthermore, the propagation law of internal crack in concrete is simulated, and the corresponding stress-strain curve. 4. The equivalent method is applied to the numerical model, that is, the mortar matrix is equivalent to the interfacial transition zone as a kind of material, and the reliability of the method is verified by comparing the experimental results with the original three-phase material model. The damage variable output module is created in the subprogram to reflect the damage fracture process of the equivalent model. The influence of interfacial thickness of concrete, selection range of aggregate particle size and porosity on its performance is discussed. In this paper, the process of establishing the model is simplified by using the method of equivalence, and the output module of the damage variable of the model is developed. The damage and fracture process of concrete under uniaxial load can be expressed more realistically and intuitively while improving the efficiency of model calculation. It provides technical support for the mesoscopic analysis of the basic properties of concrete and lays a theoretical foundation for structural analysis and optimum design of concrete structures.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528
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