Oded Amir

We present a novel body-fitted iso geometric topology optimization framework for fluid–structure interaction problems. Using a spline-based parametric representation of the fluid and solid domains as well as their interface, the method enables consistent evaluation of flow and structural quantities on geometrically accurate boundaries throughout the optimization process. When verified on various benchmark problems, the underlying iso geometric analysis exhibited higher accuracy and superior convergence rates in comparison to standard finite element methods. A shape optimization stage is introduced after the optimized topology is obtained, alleviating geometric artifacts arising from trimming and untrimming operations and reducing computational effort while preserving geometric smoothness and convergence. Several numerical examples demonstrate the capabilities of the framework to optimize fluid–structure interactions involving challenging functionals such as lift, drag, pressure drop, interfacial stress and fluid-to-solid traction distribution. Overall, the framework provides an accurate and physically consistent approach for shape and topology optimization in fluid–structure interaction systems.

We present a novel framework for the direct optimization of continuous, non-intersecting toolpaths in extrusion-based additive manufacturing. The toolpath parameterization serves both as an explicit representation of the geometry and as the optimization design variables, eliminating the need for intermediate design representations and post-processing for generating a manufacturable toolpath, thereby closing the gap between design and fabrication. The toolpath is represented by a continuous piecewise-linear centerline that is controlled by shape design variables. Finite element analysis for evaluating structural and thermal responses is achieved by a distance-based embedding technique within a fixed grid. Physical manufacturability is enforced throughout the optimization using differentiable geometric constraints that ensure minimum filament spacing, prevent self-intersections, control local toolpath angles, and preserve prescribed material-free regions. Inspired by potential applications in 3D printing of cementitious materials, the efficacy of the framework is demonstrated primarily by applications in cross-section layout design of masonry blocks and walls, considering structural and thermal performances. The numerical examples show that the proposed approach generates toolpath-based layouts that are straightforward to manufacture, while providing systematic control over structural stiffness and thermal insulation.

In this paper, we present an integrated computational framework for the optimal design of post-tensioned concrete structures, assembled from segments that are composed of printed formwork and complementary casting. The framework hinges upon shape optimization of B spline surfaces that parameterize castable concrete members, and accounts for both the load-balancing stage and the service stage, commonly referred to in prestressed concrete design. Buildability of the formwork is guaranteed by separating the geometry of the printed toolpath and imposing a set of stress constraints according to the material properties of the fresh concrete. Numerical results show how the capacity of the fresh concrete and fabrication parameters affect the outcome of shape optimization, and how the optimizer successfully finds geometrical forms that are buildable. This paves the way towards a holistic, seamless design-for-manufacturing approach in 3D concrete printing.

We present a novel body-fitted iso geometric topology optimization framework for fluid–structure interaction problems. Using a spline-based parametric representation of the fluid and solid domains as well as their interface, the method enables consistent evaluation of flow and structural quantities on geometrically accurate boundaries throughout the optimization process. When verified on various benchmark problems, the underlying iso geometric analysis exhibited higher accuracy and superior convergence rates in comparison to standard finite element methods. A shape optimization stage is introduced after the optimized topology is obtained, alleviating geometric artifacts arising from trimming and untrimming operations and reducing computational effort while preserving geometric smoothness and convergence. Several numerical examples demonstrate the capabilities of the framework to optimize fluid-structure interactions involving challenging functionals such as lift, drag, pressure drop, interfacial stress and fluid-to-solid traction distribution. Overall, the framework provides an accurate and physically consistent approach for shape and topology optimization in fluid–structure interaction systems.

In this paper, we present an integrated computational framework for the optimal design of post-tensioned concrete structures, assembled from segments that are composed of printed formwork and complementary casting. The framework hinges upon shape optimization of B-spline surfaces that parameterize castable concrete members, and accounts for both the load-balancing stage and the service stage, commonly referred to in prestressed concrete design. Buildability of the formwork is guaranteed by separating the geometry of the printed toolpath and imposing a set of stress constraints according to the material properties of the fresh concrete. Numerical results show how the capacity of the fresh concrete and fabrication parameters affect the outcome of shape optimization, and how the optimizer successfully finds geometrical forms that are buildable. This paves the way towards a holistic, seamless design-for-manufacturing approach in 3D concrete printing.

In this study, we investigate and compare formulations for computing shape derivatives in bi-material level-set optimization with precise modeling of the interface. The level-set function is parameterized using B-splines, whose coordinates serve as design variables. A precise mechanical model is obtained every design cycle, replicating the exact geometry of the bi-material design, using untrimming techniques and IGA on unstructured meshes. Design sensitivities are formulated by either a "discretize-then-differentiate" or a "differentiate-then-discretize" approach. A detailed comparative study shows the limitations of the latter in terms of accuracy, specifically when stresses near the material interface dominate the stress field. The precise representation of the interface facilitates an accurate evaluation of interfacial stresses, and the consistent discretized sensitivities enable to minimize them directly -- highlighting the main advantage of our framework. Furthermore, reducing the discretized approach by considering only interface control points and a selective set of adjacent control points provides an ideal trade-off between accuracy and numerical efficiency. This lays the foundations for multi-material shape and topology optimization procedures, considering accurate responses on the interface.

Three-dimensional printing of cementitious materials for construction has been extensively investigated in recent years, with several demonstration projects successfully carried out. These efforts aim to leverage the printing process to achieve more efficient production of components compared to conventional concrete technologies. This includes both the process itself (eliminating the formwork stage) and the flexibility in producing complexly shaped elements. To maximize the potential of 3D printing in the construction industry, additional steps must be taken, grounded in a holistic view of the entire process. This involves integration of the production chain, including design, materials, and manufacturing of components, to create elements with optimal performance, encompassing structural, environmental, and architectural aspects. Such multi-functionality requires the viewing of 3D printing not just as a production technology but as a platform enabling the integration of all these components. To advance this approach, quantitative tools are developed to optimize the following three key components: material composition; manufacturing parameters to ensure buildability; and design tools to optimize multiple performance criteria, particularly structural and architectural shape. A demonstration component, namely a post-tensioned beam, featuring two multi-functional characteristics—structural and architectural—is designed, produced, and evaluated. The scientific concepts and research tools used to develop these quantitative design tools are multidisciplinary, including rheological characterization, control of the internal structure and composition of granular materials, simulation of the mechanical behavior of green material during printing, and the hardened properties of the components, all utilizing structural optimization to enhance performance.

In this paper, we present a new parameterization and optimization procedure for minimizing the weight of ribbed plates. The primary goal is to reduce embodied CO₂ in concrete floors as part of the effort to diminish the carbon footprint of the construction industry. A coupled plate-beam finite element model and its computational mesh enable simultaneous topology, shape and sizing optimization of ribbed plate systems. Using analytical sensitivity analysis and gradient-based optimization, we achieve significant weight reductions in the range of 24–57%, in comparison to reference designs with regular ribbing patterns. The results strengthen the argument in favor of ribbed plates as a structural system that can serve the environmental goals of the construction industry. While our focus is on ribbed concrete plates in buildings, the proposed mesh-based design parameterization is applicable in the general case of optimizing stiffened shells—with potential contributions also to automotive and aerospace applications. All computer codes used in this study are freely available through a public repository, https://zenodo.org/records/11489996.