Process-informed behaviour of 3D-printed concrete flexural members: A numerical analysis

The structural response of extrusion-based concrete members may retain a measurable imprint of the manufacturing process, yet this process history is rarely incorporated explicitly into structural assessment. This study develops a process-informed numerical framework that links fresh-state deposition history to the hardened flexural behaviour of a 3D-printed concrete beam. Sequential layer activation with age-dependent fresh-state properties is first used to reproduce the as-printed configuration, which is subsequently transferred to a hardened four-point-bending model incorporating time-dependent interlayer degradation. The effects of fresh-state deformation, printing speed, interlayer delay, interface position and concrete strength are examined. A complementary mechanics-based model is also introduced to assess whether the residual interlayer shear-transfer capacity is sufficient to maintain composite action. The numerical results show that interlayer degradation can cause a transition from predominantly flexural behaviour to coupled cracking–debonding and ultimately to non-composite action. The analytical model reproduces this transition by identifying a threshold at which the available interface force becomes insufficient to sustain the longitudinal force required for composite behaviour. The proposed process-to-structure framework and the mechanics-based capacity–demand interpretation constitute the principal conceptual outcomes of the study. The specific peak loads, bond-retention levels and critical delay reported herein are particular to the investigated geometry, material properties, interface formulation and adopted empirical time-gap relationship, including its extrapolation beyond the original calibration range for some cases. The results therefore support process-informed structural assessment in which manufacturing history is treated as an explicit contributor to the mechanical state of printed concrete members.