In this work, the lattice model is applied to study the printing process and quantify the buildability (i.e., the maximum height that can be printed) for 3D concrete printing (3DCP). The model simulates structural failure by incorporating an element birth technique, time-dependent stiffness and strength, printing velocity, non-uniform gravitational load, localized damage, and spatial variation of the printed object. The model can reproduce the plastic collapse failure modes reported in the literature. In this research, three main contributions for 3DCP modeling work can be found. A new failure criterion is proposed and adopted to improve the estimation of critical printing height; the element birth technique is utilized to mimic the continuous printing process and study the impact of non-uniform gravitational load; variability of a printed structure is modeled through the inclusion of disorder during mesh generation and Gaussian distributions of material properties. Using this model, parametric analyses on non-uniform gravitational load and material variation are conducted to assess their impact on the failure–deformation response and the critical printing height. Finally, the model is validated by comparison with two 3D printing experiments from the literature. The proposed lattice model can reproduce the correct failure-deformation modes of two types of structures commonly used for buildability quantification: A 3D-printed hollow cylinder and a square wall layout. Lattice modeling of the square structure yields a relative difference of around 10% with the experimental printing height. For the cylinder structure, the predicted radial deformation and corresponding height show good agreement with the experimental data; the model yields a 41.38% overprediction of the total number of printing layers, compared with the experimental data. Possible reasons for the quantitative discrepancy are discussed.

中文翻译：

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用于评估3D打印混凝土可建造性的离散晶格模型

在这项工作中，将使用点阵模型来研究打印过程并量化3D混凝土打印（3DCP）的可构建性（即，可以打印的最大高度）。该模型通过结合元素生坯技术，随时间变化的刚度和强度，打印速度，不均匀的重力载荷，局部损坏以及打印对象的空间变化来模拟结构破坏。该模型可以重现文献中报道的塑性塌陷破坏模式。在这项研究中，可以发现3DCP建模工作的三个主要贡献。提出并采用了一种新的失效准则，以改善对临界印刷高度的估计。利用元素诞生技术模拟连续印刷过程，研究重力载荷不均匀的影响。通过包含网格生成过程中的无序和材料特性的高斯分布，可以对印刷结构的可变性进行建模。使用该模型，对不均匀的重力载荷和材料变化进行了参数分析，以评估它们对失效-变形响应和临界印刷高度的影响。最后，通过与文献中的两个3D打印实验进行比较来验证该模型。所提出的晶格模型可以重现通常用于可建造性量化的两种类型结构的正确失效-变形模式：3D打印空心圆柱体和方墙布局。正方形结构的晶格建模与实验印刷高度产生约10％的相对差异。对于圆柱结构，预测的径向变形和相应的高度与实验数据吻合良好。与实验数据相比，该模型对总印刷层数的预测为41.38％。讨论了数量差异的可能原因。