Design optimization of 3D printed concrete elements considering buildability

In this paper, we propose an integration of 3D concrete printing buildability requirements into a formal structural optimization problem. The aim is to enable the design of a structural element while balancing between its performance as a load-bearing element and its stability during the printing process. Physical buildability is quantified by stress constraints imposed on the fresh concrete, whose time-dependent strength is determined according to a rheological material characterization. This is complemented by geometric buildability that is achieved by imposing constraints on the overlap between layers. The output of optimization is the shape of the structure and the time instance at which each layer is deposited. Several prototypes were printed for verifying the numerical buildability predictions, showing acceptable quantitative agreement between theory and experiments. A critical trade-off between structural performance and buildability is exposed, that emphasizes the need for further development of holistic methodologies that integrate structural design, material design and tooling limitations.