Assessing Structural Failure in Extrusion-Based 3D Concrete Printing Using a Plasticity Model with Non-Linear Hardening (2026-03)¶

3D concrete printing (3DCP) brings automation to construction, reduces material usage, increases design flexibility, and eliminates the need for formwork. However, it is a complex process governed by numerous interdependent parameters that are often tuned through trial-and-error. This can lead to unforeseen failures during printing, such as instability or plastic collapse of the material. Computational modeling offers a means to predict and prevent such failures by enabling virtual design assessment, process optimization, and evaluation of how variations during printing influence the final structure. The structural failure during printing is primarily governed by the material response of fresh concrete, making the choice of constitutive model critical. Plasticity-based models are commonly employed to assess buildability, yet most approaches neglect the nonlinear behaviour observed experimentally for fresh concrete before failure. This simplification often leads to underestimation of deformations and overprediction of structural stability. In this work, a numerical framework is developed to investigate how nonlinear isotropic hardening influences the failure behaviour of printed structures. The model is based on a von Mises plasticity formulation with a saturation-type hardening law and is implemented in an updated Lagrangian finite element framework with the Jaumann stress rate to capture geometric nonlinearity. The printing process is simulated through a pseudo-density -based layer activation method, while time-dependent material parameters are incorporated to account for structural buildup and aging. A systematic parameter study is performed on printed cylinders with varying diameters and hardening parameters to investigate how geometry and material hardening jointly influence buildability. The results show that the number of printed layers before failure depends strongly on the hardening rate, particularly for slender, instability-prone geometries, while stable configurations are largely unaffected.