起始点逐层等角度移动时3D打印混凝土圆管可连续打印高度

为研究 3D 打印混凝土圆管可连续打印高度随打印路径等参数变化的规律，开展了打印条带质量测试研究，确定了合适的混凝土材料配合比及打印速度；通过无侧限单轴抗压试验和直接剪切试验，研究了早龄期 3D 打印混凝土本构模型；设计了起始点沿周向逐层等角度移动时圆管的4种打印方案，完成了圆管连续打印高度的试验研究；采用生死单元法对打印过程中圆管的受力进行了有限元模拟。结果表明：建立的基于摩尔库伦屈服准则的早龄期 3D 打印混凝土本构模型与试验数据吻合较好；采用 120°等角度移动方案的圆管可连续打印层数最多，为 24 层，较起始点不移动的方案提高了50%；提出的考虑每层条带结合处薄弱特性的有限元建模方法较为准确，模拟得到的圆管变形、失效模式等结果与试验结果吻合较好，可连续打印层数的模拟相对误差在10%以内。

Continuous printed height of 3D printing concrete circular tube with equiangular movements of starting point

In order to study the law of the continuous printed height with different printing parameters (e.g. printing path) for 3D printed concrete(3DPC) circular tube members, the quality test of the printing strip was carried out to determine the appropriate mixture and printing speed for 3DPC. The constitutive parameters of early age concrete were studied through both unconfined uniaxial compression tests and direct shear tests. Four printing paths of 3DPC circular tube members with equiangular movements of starting point along circle were designed and the continuous printed height experiments were carried out for circular tube members during printing process. And the finite element simulation was carried out by using the birth-death element method for circular tube members. The results show that the constitutive parameters of early age concrete based on Mohr-Coulomb yielding criterion are in good agreement with the measured data. Among the four printing paths in the paper, the path with 120° equiangular movements of starting point layer by layer could build the largest number of continuous printed layers, and the number is 24, which is 50% larger than the member built by the path with no movement of starting point. The proposed finite element modelling method considering the structural weak properties at junction of each layer is built accurately, and the simulation results including deformation and failure mode are in good agreement with the experimental results, and the relative errors of the number of continuous printing layers are all less than 10%.