钢筋混凝土力学性能的细观数值模拟研究

Mesoscopic Simulation of Mechanical Properties of Reinforced Concrete

作者: 专业:结构工程 导师:王立成 年度:2010 学位:硕士  院校: 大连理工大学

Keywords

Rigid Body Spring Model (RBSM), Random aggregate model, Numerical simulation, Mesoscale, Bilinear softening curve, Reinforced concrete, Bond-slip relationship, crack

        随着计算机技术的不断发展,近些年来数值分析方法已经越来越多的应用于高耸、大跨等大型结构工程的分析计算中。在众多数值分析方法中,刚体弹簧元法以其在模拟混凝土裂缝发生、扩展以及计算裂缝宽度上的优势,成为一种发展潜力巨大的数值分析方法。本文采用刚体弹簧元法,模拟分析了混凝土及钢筋混凝土构件在静态加载作用下的力学性能及裂缝扩展特征,并将模拟结果与实验数据进行对比,验证了刚体弹簧元法应用于钢筋混凝土力学性能模拟上的有效性和可行性。本文开展的具体工作如下:1.提出了一种以改进面积判别准则和凸多边形生长方式为基础的二维混凝土骨料随机生成算法。在骨料生成过程中,通过对骨料延伸条件的改进和定点位置条件的限定,改进了程序的可执行性,提高了随机多边形骨料的生成效率。通过对轴向拉压计算实例,对比分析了不同骨料形状(圆形和多边形)对于混凝土试件单轴抗压、抗拉力学性能的影响。结果表明,圆形骨料试件抗拉、抗压能力略高于多边形骨料试件,骨料形状对于混凝土试件拉压力学性能数值模拟结果的影响很小。2.分析了三种不同软化本构关系(无软化、线性软化、双线性软化)对于混凝土力学性能数值计算结果的影响。结果证明,由于混凝土是非理想脆性材料,软化段的设置可使混凝土破坏的模拟过程更接近于实际情况。通过对立方体试件受拉、受压以及混凝土梁三点受弯破坏过程的数值分析,对比数值模拟结果与实验数据可以得出,在适当取值的情况下,双线性软化本构关系可以较为精确地模拟混凝土的破坏过程,所得荷载、位移值也与实验值较为接近。3.提出了一种改进的描述钢筋混凝土破坏行为的细观数值方法。在该方法中,混凝土材料采用细观刚体弹簧元模型,钢筋采用梁单元模拟,混凝土与钢筋之间的连接采用弹簧单元以模拟二者之间的相对变形。通过对钢筋混凝土受拉及三点受弯试件受力过程的细观数值分析,系统研究了混凝土斜截面破坏的开裂过程和裂缝分布规律。通过与试验结果的对比表明:该方法可较为准确的模拟钢筋混凝土破坏的开裂趋势和裂缝的分布情况,模拟结果与实验值拟合良好。
    With the development of computing technology, in recent years numerical methods have been widely used in high-rise, large-scale structural design. Because of the advantages on simulating the generation and propagation of cracks in concrete, as well as on prediction of crack width, the Rigid Body Spring Model (RBSM) has become a kind of important numerical method on the structural design and durability analysis. In this paper RBSM is used to simulate the behavior of concrete and reinforced concrete under static loading in terms of the mechanical properties and cracking characteristics. Through comparing the simulation results with experimental data, the RBSM has been confirmed to be effective and feasible for simulating the behavior of reinforced concrete. The major contents are summarized as follows:1. An improved method of generating random convex aggregates in two-dimensional area is proposed with help of the area index and convex polygon criteria. The methods of extending the aggregate or locating the special points are improved on the basis of previous findings. The new methods are able to accelerate the generation process of random polygon aggregates and subsequently improve the computational efficiency. Examples of uniaxially loading specimen are presented in the paper with the purpose to show that the mesoscopic simulation method can provide us with effective information to understand the effect of concrete performance of aggregates with different shapes. The calculated results illustrate that the concrete sample with circular aggregates has slightly higher strength and than that with polygon aggregates, which also indicates that shape of aggregate has little effect on the compressive and tensile mechanical properties of concrete in terms of the numerical simulation technique.2. By using different kinds of softening relationship (i.e., no softening branch, bilinear softening relationship and linear softening relationship), in this paper the mechanical properties of concrete specimens is simulated on the basis of RBSM. The results show that, since concrete is not a pure brittle material, by choosing an appropriate softening relationship the failure procedure of concrete can be simulated well to match the actual situation. It is concluded that the bilinear softening relationship can simulate the failure of concrete well when the parameters are set appropriately.3. Finally, this thesis proposes an improved method to analyze the failure of reinforced concrete structures by numerical simulation. In this method, concrete is represented by the RBSM, which can randomly mesh the spcimen. Reinforcing bars are modeled by beam elements. Link-springs are used to simulate the reaction between reinforcement and concrete. By means of the analysis of two-dimensional reinforced concrete specimens under three points bending load, the cracking process and distribution of cracks, as well as the load-deformation curve are investigated and compared with come available experimental results. The computed results give a good agreement with test findings.
        

钢筋混凝土力学性能的细观数值模拟研究

摘要4-5
Abstract5-6
1 绪论10-20
    1.1 概述10
    1.2 钢筋混凝土结构数值模拟国内外研究现状10-11
    1.3 混凝土细观力学研究方法11-12
        1.3.1 混凝土多尺度研究基本概念11-12
        1.3.2 细观力学研究方法12
    1.4 几种常用的基于细观损伤的混凝土数值模拟模型12-14
        1.4.1 微平面模型12
        1.4.2 二维格构模型12-13
        1.4.3 随机粒子模型13
        1.4.4 随机骨料模型13-14
        1.4.5 随机力学模型14
    1.5 混凝土本构关系软化曲线研究14-15
        1.5.1 线性软化本构关系14-15
        1.5.2 双线性软化本构关系15
        1.5.3 非线性软化本构关系15
    1.6 网格划分方法15-16
        1.6.1 Delaunay三角剖分15-16
        1.6.2 推进波前法16
    1.7 数值方法16-18
        1.7.1 有限元法16-17
        1.7.2 离散元法17-18
        1.7.3 刚体弹簧元法18
    1.8 本文的主要工作18-20
2 刚体弹簧元基本理论介绍20-29
    2.1 引言20
    2.2 刚体弹簧元基本力学模型介绍20-22
    2.3 细观本构关系模型22-26
        2.3.1 砂浆模型22-25
        2.3.2 骨料模型25
        2.3.3 界面模型25-26
    2.4 单元划分26-28
    2.5 材料参数设定28-29
3 混凝土细观分析中随机多边形骨料生成方法研究29-42
    3.1 引言29
    3.2 骨料生成方法29-34
        3.2.1 随机多边形骨料的生成步骤29
        3.2.2 生成随机四边形基骨料29-31
        3.2.3 随机多边形延伸方式31-32
        3.2.4 凸多边形判定方法32-33
        3.2.5 程序实现流程图33-34
        3.2.6 随机多边形骨料生成实例34
    3.3 算法特点分析34
    3.4 多边形骨料单元划分34-36
    3.5 不同形状骨料试件实例计算分析36-40
        3.5.1 单元尺寸的选择36-38
        3.5.2 模拟计算实例38-40
    3.6 小结40-42
4 混凝土细观分析中软化曲线形状对于计算结果的影响42-53
    4.1 引言42
    4.2 线性、双线性软化曲线本构关系公式中参数的确定42-44
        4.2.1 线性软化曲线本构关系42-43
        4.2.2 双线性软化曲线本构关系43-44
    4.3 混凝土立方体受拉试件在不同软化关系下计算实例分析44-47
        4.3.1 计算模型设置44-46
        4.3.2 受拉试件模拟结果分析46-47
    4.4 混凝土立方体受压试件在不同软化关系下计算实例分析47-49
        4.4.1 试件破坏形态研究47-48
        4.4.2 不同软化关系对于混凝土受压结果影响48-49
    4.5 不同软化关系对于混凝土三点受弯计算结果影响49-52
    4.6 小结52-53
5 钢筋混凝土构件受力过程的细观分析53-75
    5.1 引言53
    5.2 混凝土材料基本力学模型设置53-56
        5.2.1 受弯构件混凝土刚体弹簧元模型53-54
        5.2.2 细观与宏观力学参数转换关系54-56
    5.3 钢筋材料基本力学模型设置56-59
        5.3.1 钢筋单元模型56-58
        5.3.2 钢筋材料模型58-59
    5.4 钢筋混凝土轴心受拉构件细观数值模拟59-63
    5.5 钢筋混凝土受弯构件斜截面破坏细观数值模拟63-74
        5.5.1 无腹剪压63-67
        5.5.2 无腹斜压67-70
        5.5.3 无腹斜拉70-74
    5.6 小结74-75
结论与展望75-77
    本文结论75-76
    展望76-77
参考文献77-82
攻读硕士学位期间发表学术论文情况82-83
致谢83-85
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