As a thin layer surrounding aggregates, the interfacial transition zone (ITZ) has a significant influence on the mechanical performance of concrete, a large number of small elements is required to discretize the ITZ and its vicinity owing to its small thickness. In this contribution, the mesostructure of concrete is explicitly built by a novel method named improved random walking algorithm (IRWA), with which the grading, content, shape of aggregates and the thickness of ITZs, can be conveniently controlled by users, and high volume fraction of aggregate and remarkable efficiency can be achieved. In the framework of the scaled boundary finite element method (SBFEM), the image-based quadtree decomposition is employed to automatically generate the multi-level mesh for the concrete composites, with no trouble in dealing with hanging nodes or the dramatically changing element size in the vicinity of the material interface. The nonlocal damage model in integral format is extended to simulate progressive damage of concrete at mesoscale with good mesh independence. Four benchmarks are modelled to demonstrate the performance of the proposed approach, and the effects of model parameters on the structural responses are also discussed.

作为围绕骨料的薄层，界面过渡区（ITZ）对混凝土的机械性能具有重大影响，由于厚度小，需要大量小元素来离散化ITZ及其附近区域。在此贡献中，混凝土的介观结构是通过一种名为改进的随机游走算法的新方法显式构建的（IRWA），用户可以方便地控制骨料的等级，含量，形状和ITZ的厚度，并且可以实现骨料的高体积分数和显着的效率。在比例边界有限元方法（SBFEM）的框架中，基于图像的四叉树分解被用于自动生成混凝土复合材料的多层网格，而无需处理悬挂节点或单元中尺寸急剧变化的问题。材料界面附近。扩展了整体格式的非局部损伤模型，以模拟具有良好网格独立性的中尺度混凝土的渐进式损伤。对四个基准进行了建模以证明所提出方法的性能，并且还讨论了模型参数对结构响应的影响。