【作者】 孙立国；

【导师】 杜成斌；

【作者基本信息】 河海大学 ， 固体力学， 2005， 硕士

【摘要】 本文在细观层次上把混凝土看作是由粗骨料、水泥砂浆基体和二者之间的界面所组成的三相非均值复合材料,具体针对数值混凝土的关键问题一骨料形状模拟进行了研究,研制了二维、三维任意形状骨料生成的软件。并对大型商业有限元软件MSC.MARC进行二次开发,进行混凝土破坏过程的数值模拟。论文的工作具体可分为以下几个部分:1. 针对大坝等全级配或三级配混凝土骨料含量比较高(0. 60～0. 70) 的特点,研制出一种新的二维任意形状骨料生成软件2D-RAS(TWO DIMENSIONAL RANDOMAGGREGATE SOFTWARE)。主要特点为通过一次性随机投放形成同种骨料的所有三角形基骨料,然后在此基础上随机延凸,生成二维任意形状的随机骨料。2. 采用大型通用有限元软件MARC对东江拱坝三级配混凝土试件的单轴受拉破坏过程进行了数值模拟,比较了骨料形状(多边形、圆形)对混凝土力学性能及破坏的影响。3. 用二维任意形状骨料生成软件2D-RAS和圆形骨料生成程序,在计算机上随机生成了6组具有相同含量和配比的任意多边形骨料和圆形骨料的混凝土随机骨料模型。比较两种类型三点弯曲数值试件的模拟结果,得到了一些重要的结论。4. 建立了以体积为标度的凸型多面体骨料侵入判别准则,并以体积为研究对象建立了凸型骨料的生长模式和骨料“凸性”条件,研制出了三维任意形状骨料生成软件3D-RAS(THREE DIMENSIONAL RANDOM AGGREGATE SOFTWARE)。三维混凝土随机骨料投放算法是二维投放算法的延伸,除了具有二维算法的一切优点外,还考虑了骨料粒径的变化,假定骨料粒径服从正态分布,从而使该软件生成的随机骨料模型和实际结构更为接近。5. 用三维任意形状骨料生成软件3D-RAS,建立三级配混凝土任意多面体三维随机骨料模型,采用投影法将有限元网格投影到已生成的随机骨料模型结构上,自动地识别砂浆单元、骨料单元和界面单元。并对空间的三级配混凝土简支梁的静力学性能进行了初步研究,与球形骨料计算结果进行了比较,得到了一些有价值的初步结论。更多还原

【Abstract】 In this paper, concrete was taken as three-phase composites consisting of mortar matrix, aggregate and the bond between matrix and aggregate. The key issue of numerical concrete-simulation technology of aggregate shape was studied and the program was presented to generate two or three dimensional random aggregate shape. The failure process of concrete is simulated by means of the software-MSC.MARC developed secondly. Main work of this paper includes:1. For the characteristic of three graded or full graded concrete, whose content of the aggregate is higher (0.6-0.7) than that of normal concrete, a more effective method is presented in the paper to generate the random aggregate model, and 2D-RAS(Two Dimensional Random Aggregates Software) was compiled. All the same kind of random triangle aggregate was generated randomly at one time, and then two dimensional aggregate of random shape was generated by the method of random extension.2. Numerical simulations were carried out with nonlinear finite element software Marc, which simulated the whole failure process of uniaxial tension specimen of three graded concrete of Dongjiang arch dam. The comparison between results of simulation of circle aggregate and that of polygon is studied to find out the effect of aggregate shape on mechanical performance and failure process of concrete.3. Six groups of random aggregate models of circle and polygon aggregate were generated by 2D-RAS, with the same content and ratio. Significant results were obtained from comparison of the simulation results.4. Aggregate location conflicting and overlapping criteria in the algorithm were established. Growth pattern and convexity conditions were analyzed for a convex polyhedron aggregate. The 3D-RAS (Three Dimensional Random Aggregate Software) was presented in the paper. The three dimensional generation of random aggregate model is based on two dimensional generation of random aggregate algorithm. Besides merits of the two dimensional generation of random aggregate model, It consider the effect of the radius of the different aggregates, which were assumed to obey normal distribution. Consequently, the numerical model generated is reasonable.5. The 3-D random model of convex polyhedron aggregate was generated with 3D-RAS. The mesh division is auto-performed by the method of projection, which projects finite element mesh onto the random aggregate model generated and assigns different material properties to the respective elements according to the element location in three phases. Numerical results show that the 3-D random aggregate model provides consistent results with these of 2-D.更多还原