Free-Form Structural Optimization for Additive Manufacturing in Construction (2024-09)¶

Additive manufacturing (AM) enables the realization of structures with almost unlimited geometrical freedom. In order to fully utilize these capabilities, an optimization methodology that offers the largest possible design space is essential. The so-called vertex morphing approach enables the largest possible design space by allowing each nodal coordinate of the FEM mesh as a design variable. Current extensions of this method aim at the generalization of this extremely rich shape parameterization. For example, material densities are also included in the optimization, which enables the optimization of structural topologies on the one hand and even the determination of an optimal grading of the material on the other hand. In particular, the latter is very promising for AM methods with concrete, as this allows for a further design parameter in structural planning. A spatial distribution and grading of material properties within the structure, which can save on cement, is vital in ecological layout of structures. In this article, the background and possibilities of design using the aforementioned innovative methods in numerical simulation for structural analysis and optimization will be presented, and the necessary extensions to consider the special characteristics of additively manufactured structures in the construction industry will be developed and discussed. For concrete structures, this involves designing of load-bearing structures with compression-dominated load transfer, which must be captured by new suitable optimization formulations. The potential of using a huge set of design variables to enable truly free-form optimization and the combination with digital fabrication is shown in the example of a bridge-like demonstrator structure. This resulted in an outstanding improvement in the strain energy of the structure demonstrating the applicability of the proposed methodology whilst overcoming the pitfalls of the used first order optimization methods. The proposed structure is manufactured with the high-resolution AM technique of Selective Cement Activation which provides the possibility to fully leverage the presented design optimization approach.