Purpose

A mesoscopic phase field (PF) model is proposed to simulate the meso-failure process of lightweight concrete.

Design/methodology/approach

The PF damage model is applied to the meso-failure process of lightweight concrete through the ABAQUS subroutine user-defined element (UEL). And the improved staggered iteration scheme with a one-pass procedure is used to alternately solve the coupling equations.

Findings

These examples clearly show that the crack initiation of the lightweight concrete specimens mainly occurs in the ceramsite aggregates with weak strength, especially in the larger aggregates. The crack propagation paths of the specimens with the same volume fraction of light aggregates are completely different, but the crack propagation paths all pass through the ceramsite aggregates near the cracks. The results also showed that with the increase in the volume fractions of the aggregates, the slope and the peak loads of the force-deflection (F-d) curves gradually decrease, the load-bearing capacity of the lightweight concrete specimens decreases, and crack branching and coalescence are less likely during crack propagation.

Originality/value

The mesostructures with a mortar matrix, aggregates and an interfacial transition zone (ITZ) are generated by an automatic generation and placement program, thus incorporating the typical three-phase characteristics of lightweight concrete into the PF model.

中文翻译：

---

相场法模拟的轻质混凝土细观破坏机制

目的

提出了一种细观相场（PF）模型来模拟轻质混凝土的细观破坏过程。

设计/方法/方法

PF 损伤模型通过 ABAQUS 子程序用户定义单元 (UEL) 应用于轻质混凝土的细观破坏过程。并采用改进的单程交错迭代方案交替求解耦合方程。

发现

这些例子清楚地表明，轻质混凝土试件的裂纹萌生主要发生在强度较弱的陶粒骨料中，尤其是在较大的骨料中。相同体积分数的轻骨料试样的裂纹扩展路径完全不同，但裂纹扩展路径均通过裂纹附近的陶粒骨料。结果还表明，随着骨料体积分数的增加，力-挠度（Fd）曲线的斜率和峰值荷载逐渐减小，轻质混凝土试件的承载能力降低，裂缝分支和在裂纹扩展过程中聚结的可能性较小。

原创性/价值

具有砂浆基质、骨料和界面过渡区 (ITZ) 的细观结构由自动生成和放置程序生成，从而将轻质混凝土的典型三相特征纳入 PF 模型。