Folded assembly methods for thin-walled steel structures

•A parametrised crease geometry is developed for folding steel sheet by hand.•A comparison between geometrical imperfection measured by 3D scan and 3D digital image correlation is shown.•An experimental and a numerical study are conducted on steel columns assembled by the proposed method.•A numerical study shows fold-line influence can be predicted with an exact crease geometry.•This is the first investigation into the structural performance of folded steel structures.

There has been significant recent interest in origami-inspired foldable structures for applications in which transportability and rapid construction are primary design drivers, for example, emergency shelters and staging structures. However, widespread application is not yet seen due to complexities in folded geometry and modelling the structural behaviour of folded sheet material. This paper proposes a fundamentally new approach whereby folded assembly methods are developed for conventional thin-walled steel construction and benchmarked in terms of their assembly effort, manufacturing accuracy, and structural performance. Manufacturing accuracy was benchmarked with 3D digital image correlation and 3D scanning and showed a folded assembly method to be accurate to within ± 50% of plate thickness with assembly by unskilled persons. Structural performance under uniaxial compressive load was assessed with experimental and numerical analyses, with consistent predictions showing that conventional thin-walled steel analysis techniques are sufficient to model folded structure behaviours. Modelling of the novel folded steel structures is therefore also shown to avoid much of the complexity normally encountered in folded structure analysis, such as characterisation of fold-line rotational stiffness or folding plasticity behaviours.