Designing elastically formed steel hollow sections for free-form reticulated gridshells

This paper presents a design to manufacturing methodology for large-span grid shells constructed from elastically formed flat sheet steel components. By leveraging computational engineering and laser-cutting technology, the approach optimizes material use and structural efficiency. This enables the precise fabrication of curved rectangular hollow sections. Unlike traditional discrete segmentation in reticulated shells and continuous smooth segmentation in elastic gridshells, this research optimizes the cross-sectional members for sequential assembly. The method uses digital form-finding to unroll bent and twisted sheets, improving scalability and simplifying construction. A computational design workflow is developed through a systematic formulation of geometric and structural strategies on both global and local scales. The global geometric strategy extracts extrinsic parameters of smooth segmentation from the free-form surfaces. The local geometric strategy develops shell modeling for elastically deformed plates based on differential geometry principles. Structural strategies are based on both analytical and numerical models for determining optimal cross-section dimensions. The analytical strategy follows Eurocode 3 for approximating the cross-section dimensions for plate buckling resistance and member length. Numerical models assess structural performance through non-linear analysis. The global model analyzes the structure without prestress under external loads to identify the critical member. This member will undergo local simulations to validate the geometries of the curved plates and analyze their residual stresses, ensuring even load distribution and structural integrity under expected loads. The proposed methodology was tested and refined through the design and construction of a demonstrator for the ZukunftBau POPUP campus exhibition. This provided practical insights into the application of elastically formed laser-cut flat steel components for complex geometries. A cross-section comparison demonstrates a 62 % improvement in material efficiency compared to the Mitoseum 2017 reference project of a steel grid-shell.