Abstract This paper presents mesoscale thermo-mechanical analyses of plain (unreinforced) concrete based on the discrete element method (DEM). The proposed discontinuum modelling strategy represents the aggregates and matrix as a system of deformable polyhedral blocks, interacting along their boundaries. The nodal velocities of each block are calculated via the explicit integration scheme of DEM, and contact stresses are computed based on the relative contact displacements of the adjacent blocks. To better predict the thermo-mechanical behaviour of concrete, fracture energy-based contact constitutive models are implemented by considering temperature dependency at the zone and contact properties. First, the discrete meso models are tested under uniaxial compression loading at room temperature. Then, transient thermo-mechanical tests are performed considering different load levels. The results of the computational models are compared with the macroscopic response quantities of concrete obtained from the available experimental studies in the literature. The results indicate that the developed DEM framework predicts the complex mesoscale thermo-mechanical response history and the typical damage progression observed in concrete. Furthermore, the fracture patterns, crack propagation with temperature, and the differential thermal expansion phenomena are studied in detail.

中文翻译：

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模拟高温下混凝土热机械破坏的中尺度离散元方法框架

摘要 本文介绍了基于离散元法（DEM）的素（无钢筋）混凝土的中尺度热力学分析。所提出的不连续建模策略将聚合体和矩阵表示为一个可变形的多面体块系统，沿着它们的边界相互作用。通过DEM的显式积分方案计算每个块的节点速度，并根据相邻块的相对接触位移计算接触应力。为了更好地预测混凝土的热机械行为，基于断裂能的接触本构模型通过考虑区域的温度依赖性和接触特性来实现。首先，离散细观模型在室温下在单轴压缩载荷下进行测试。然后，瞬态热机械测试是在考虑不同负载水平的情况下进行的。计算模型的结果与从文献中可用的实验研究中获得的混凝土的宏观响应量进行了比较。结果表明，开发的 DEM 框架预测了复杂的中尺度热机械响应历史和在混凝土中观察到的典型损坏进展。此外，还详细研究了断裂模式、裂纹随温度的扩展以及不同的热膨胀现象。结果表明，开发的 DEM 框架预测了复杂的中尺度热机械响应历史和在混凝土中观察到的典型损伤进展。此外，还详细研究了断裂模式、裂纹随温度的扩展以及不同的热膨胀现象。结果表明，开发的 DEM 框架预测了复杂的中尺度热机械响应历史和在混凝土中观察到的典型损坏进展。此外，还详细研究了断裂模式、裂纹随温度的扩展以及不同的热膨胀现象。