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 heterogeneous composite, concrete is widely used in the field of civil engineering. The properties of concrete are closely related to the durability and safety of concrete structures. The mechanical properties of various phases in concrete are very wide, and the existence of micro cracks, pores and other initial defects is guided. The basic performance changes of concrete need to be further studied. 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. It is one of the hot spots in the study of the performance of the concrete. At the meso level, it can be seen as a composite material consisting of coarse aggregate, cement paste and various initial defect points. The numerical model of concrete based on the meso analysis method can not only directly reflect the effect of each phase composition of concrete on its performance and the continuous changing load under the reasonable selection of parameters. In this paper, the damage mechanics theory is applied to the numerical analysis, and the damage and damage process of the concrete specimen under uniaxial load is simulated and studied. The concept of equivalent method is introduced in the process of establishing the numerical model, and the rationality of the application of the equivalent method in the meso damage model of concrete is verified through the comparison of the equivalent simulation results before and after the equivalent simulation. The concrete work is as follows: 1. the equivalent method and the basic concepts of the damage fracture mechanics of concrete are expounded, and the equivalence is studied. The concrete application of method in the analysis of concrete meso mechanics.2. uses Monte Carlo method in the numerical software. Through programming language, the random distribution of circular aggregate particles in the specified area and aggregate gradation is realized. Then the generated aggregate coordinate data are processed and the interface unit is added to the final generation. The geometric model.3. of concrete specimen is developed two times for the finite element software, and the double line damage model is introduced to the single axis tension of the concrete specimen and the numerical simulation of the single axis compression. By setting the state variable to judge whether the unit is invalid and deleted, then the law of the expansion of the concrete internal crack is simulated and the corresponding stress is obtained. The strain curve.4. applies the equivalent method to the numerical model, that is, the mortar matrix and the interface transition zone are equivalent to a kind of material. By comparing with the experimental results of the original three phase material model, the reliability of the method is verified and the damage variable output die block is created in the subprogram, which is more intuitively reflected the damage fracture of the equivalent model. The cracking process.5. discusses the interface thickness of concrete, the selection range of aggregate size and the effect of porosity on its performance. In this paper, the establishment process of the model is simplified by using the equivalent method, and the damage variable output module of the model is developed. The concrete can be more truly and intuitively expressed in the same time as the model calculation efficiency is raised. The damage and fracture process under the axial load provides a technical support for the meso analysis of the basic properties of concrete, which lays a theoretical foundation for the structural analysis and optimization of the concrete structure.
【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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