【作者】 邢立坤；

【导师】 王立成；

【作者基本信息】 大连理工大学 ， 结构工程， 2011， 硕士

【摘要】 根据内部结构组成和研究的需要,混凝土材料从分析尺度上可分为宏观、细观和微观三个不同层次。混凝土的力学性能可以通过宏观和细观两个层次下的模型来进行预测。在细观层次上,通常将混凝土看作由粗骨料、硬化水泥砂浆和界面粘结带组成的三相非均质复合材料,其中,硬化水泥砂浆或骨料可分别视为各向同性材料。细观刚体弹簧元法是在细观层次上应用刚体弹簧元法的原理对混凝土进行力学分析的方法。本文采用细观刚体弹簧元法模拟分析了混凝土试件及钢筋混凝土构件在静态加载下的力学性能,并与试验结果进行了对比分析,验证了该方法在钢筋混凝土结构力学性能模拟上的有效性和可行性。具体开展工作及结论如下：(1)系统总结了细观刚体弹簧元法的理论框架,包括粗骨料的生成过程(方法)、细观刚体单元的划分原理、刚体弹簧模型的确定方法、细观本构关系的建立过程等,并评述了国内外细观刚体弹簧元法的最新研究进展及研究成果。(2)考虑劈裂试验的加载特点,对劈裂试件刚体单元的划分方法进行了局部调整,建立了适用于劈裂分析的数值模型。模拟了不同尺寸混凝土试件的劈裂抗拉试验,与试验结果的对比表明：试件破坏形态和劈裂抗拉强度均与试验结果保持良好的一致性,其中小尺寸试件所表现出的尺寸效应要明显于大尺寸试件所表现出的尺寸效应。对不同垫片宽度混凝土劈裂抗拉数值模拟结果表明,垫片宽度对混凝土的劈裂抗拉强度有重大影响,但当垫片宽度b与试件宽度D的比值(b/D)小于0.04时,垫片宽度对混凝土的劈裂抗拉强度影响不大,劈裂强度基本不变；当b/D为0.058时,劈裂抗拉强度与轴心抗拉强度近似相等。(3)砂浆-骨料界面是混凝土的薄弱环节,在细观数值模拟中,界面本构模型对混凝土力学性能的数值模拟结果有重要影响。本文将不同的界面拉伸软化本构模型以及界面剪切本构模型用于细观刚体弹簧元模型的数值模拟中。通过数值模拟结果和试验结果的对比表明,在断裂能相同的情况下,不同软化曲线下的数值模拟结果差别不大；各界面剪切本构模型均可用于混凝土的细观数值模拟中。(4)在混凝土细观刚体弹簧元模型的基础上,钢筋采用梁单元模拟,进行了配有箍筋的钢筋混凝土受弯构件正截面和斜截面承载力的细观数值模拟研究。并与试验结果进行了对比分析,结果表明：数值计算结果与试验结果吻合较好,本文建立的模型能够较为合理地描述钢筋混凝土梁的破坏形态、荷载位移响应及加载过程中钢筋的应力变化过程。另外,对不同尺寸钢筋混凝土梁弯曲破坏过程的计算分析表明,随着梁有效高度的增加,梁的名义弯曲强度整体上呈现降低的趋势,但当试件有效高度大于240mm时趋于稳定。更多还原

【Abstract】 In terms of the composites of concrete material and researching consideration, there are several different levels:macrolevel, mesolevel and microlevel. All the mechanical properties of concrete are available to be predicted through the levels of macro or micro. On mesoscale, concrete is usually regarded as a three-phase composite, consisting of coarse aggregates, mortar and the bond zone between these two compositions. Among them, the mortar or aggregate can be regarded as isotropic materials, respectively. Mesoscopic Rigid Body Spring Model (RBSM) is an approach to analyze the properties of concrete by the method of RBSM on mesolevel. In this paper, the mesoscopic RBSM is used to simulate the behavior of concrete and reinforced concrete members under static loading. By comparing the simulation results with experimental data, the mesoscopic RBSM is confirmed to be effective and feasible for simulating the mechanical properties of reinforced concrete members. The main contents are summarized as follows:(1) This paper systematically summarizes the theoretical background of the mesoscopic RBSM, covering the generation process of coarse aggregates, the meshing technique of elements, the construction of the mesoscopic RBSM and the development of constitutive law of the springs. In addition, the latest research advances and results on the application of mesoscopic RBSM are reviewed.(2) Regarding of the loading characteristics of splitting test in simulation, the adjustment of element meshing is adopted for the sample in order to be able to represent the test condition. The article simulates the concrete splitting tensile tests under different sample sizes, which is compared with the results from the experiments. It is shown that both the failure modes and splitting tensile strengths are similar with those from test results, and the size effect is more evident in small size samples. The influence of bearing widths on splitting tensile strength of concrete is also analyzed. The results show that ratio of bearing width b to sample width D has a significant impact on splitting tensile strength of concrete, but if the ratio b/D is less than 0.04 that splitting tensile strength of concrete is not obvious; if b/D equals to 0.058, splitting tensile strength is almost the same with axial tensile strength of concrete.(3) Mortar-aggregate interface is the weak zone in concrete. The constitutive model of the interface has an important effect on the mechanical properties of concrete for the mesoscopic simulation. In this thesis, different tensile softening constitutive models and shear constitutive models for interface are used in the mesoscopic RSBM. Compared with test results, it is shown that the difference among different constitutive models is not to much when the fracture energy is kept constant; different shear constitutive models are all effective in mesoscopic simulation of concrete.(4) Based on the mesoscopic RBSM, and reinforcing bars are modeled as beam elements. Both the flexure and shear bearing capacity of reinforced concrete members are simulated. Compared with the experimental results, it is shown that RBSM on mesoscale can be sucessfully applied to the simulation of the failure mode, load-displacement response and the stress variation of reinforcement subjected to loading. In addition, the results from the failure progress of reinforced concrete beams under different sizes show that the nominal compressive strength goes lower with the growth of effect depth of beams, and the strength does not change if the effect depth of beam is larger than 240mm.更多还原