基于细观力学方法的水分对混凝土力学性能影响研究

发布时间：2018-03-27 18:06

本文选题：混凝土　切入点：细观力学　出处：《西北农林科技大学》2015年硕士论文

【摘要】：混凝土结构经常处于水环境中,水就会渗入到混凝土的微裂纹和孔隙中,使混凝土材料的静动力学性能发生一系列的改变,对混凝土结构的强度和耐久性产生一定影响。在水环境工作的混凝土建筑物不可避免地会承受地震荷载、波浪荷载、冲击荷载甚至爆炸荷载等动力荷载,混凝土在动态荷载下的力学特性有别于其在静荷载下的力学性能。因此为保证在水环境工作的混凝土建筑物的安全运行,就有必要开展水环境影响下的混凝土强度、弹性模量等力学性能的变化规律和破坏机理的研究。基于宏观唯象学的研究模型并不能揭示混凝土材料复杂的细观特征和力学性能的变化机理,因此本文基于细观力学方法,以不同含水量混凝土在静动力荷载下的力学性能为主要研究对象,分析了C20和C30两种强度等级混凝土的抗压强度随含水量及加载速率的变化规律和破坏机理,所做工作及取得的成果如下:(1)从混凝土材料的细观结构出发,将混凝土视为由骨料、砂浆和两者之间的粘结界面组成的三相复合材料,基于蒙特卡罗方法和瓦拉文公式,生成了与真实混凝土结构相似的二维随机骨料模型。以ANSYS/LS-DYNA有限元分析软件为平台,引入弹脆性细观损伤本构对混凝土试样单轴压缩断裂过程进行了数值模拟,分析了混凝土的破坏机理。(2)在随机骨料三相复合材料模型的基础上,通过随机改变单元的材料属性的方法生成了6种不同含水量的混凝土细观数值模型,对不同含水量混凝土的单轴压缩破坏过程进行了数值模拟,研究了水分对混凝土静力力学性能的影响规律。通过将数值模型计算结果和夹杂理论结果比较,验证了本文所建模型的合理性和计算结果的可靠性。研究表明:混凝土的静抗压强度随含水量的增加而降低,初始弹性模量随含水量的增加有所提高。(3)设计了不同含水量混凝土的动态加载数值试验方案,综合分析了强度等级、含水量及加载速率三种因素对混凝土抗压强度的影响规律。研究表明:含水量是影响混凝土动态抗压强度的一个重要因素,高含水量混凝土的率敏感性比干燥和低含水量混凝土更为显著;高强度等级混凝土的率效应比低强度等级混凝土的率效应小。
[Abstract]:The concrete structure is often in the water environment, the water will seep into the microcracks and pores of the concrete, and make a series of changes in the static and dynamic behavior of the concrete material. Concrete buildings working in water environment will inevitably bear dynamic loads such as earthquake load, wave load, impact load and even explosion load. The mechanical properties of concrete under dynamic load are different from those under static load. Therefore, in order to ensure the safe operation of concrete buildings working in water environment, it is necessary to carry out concrete strength under the influence of water environment. The research model based on macrophenomenology can not reveal the complex meso-characteristics and the mechanism of mechanical properties of concrete, so this paper bases on the method of meso-mechanics. Taking the mechanical properties of concrete with different moisture content under static and dynamic loads as the main research object, the variation law and failure mechanism of compressive strength with water content and loading rate of concrete of two strength grades C20 and C30 are analyzed. The work done and the results obtained are as follows: 1) starting from the mesoscopic structure of concrete materials, the concrete is regarded as a three-phase composite composed of aggregate, mortar and the bond interface between them, based on Monte Carlo method and Varavan formula. A two-dimensional random aggregate model, which is similar to the real concrete structure, is generated. Based on the ANSYS/LS-DYNA finite element analysis software, the elastic brittle meso-damage constitutive model is introduced to simulate the uniaxial compressive fracture process of concrete samples. The failure mechanism of concrete is analyzed. (2) based on the three-phase composite material model of random aggregate, six kinds of meso-numerical models of concrete with different moisture content are generated by randomly changing the material properties of the element. In this paper, the uniaxial compression failure process of concrete with different moisture content is numerically simulated, and the influence of moisture on the static mechanical properties of concrete is studied. The numerical model results are compared with the inclusion theory results. The rationality of the model and the reliability of the calculation results are verified. The results show that the static compressive strength of concrete decreases with the increase of water content. The initial modulus of elasticity increases with the increase of water content. The dynamic loading numerical test scheme of concrete with different water content is designed, and the strength grade is analyzed synthetically. The effects of water content and loading rate on the compressive strength of concrete are studied. The results show that water content is an important factor affecting the dynamic compressive strength of concrete. The rate sensitivity of high water content concrete is more obvious than that of dry concrete and low water content concrete, and the rate effect of high strength grade concrete is less than that of low strength grade concrete.
【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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