Why developable surfaces in the construction industry?
Over the past twenty years, the democratization of the 3d modeling tools induced a growing emergence of architectural free-form design. These shapes are widely represented as curved surfaces, perfectly smooth and with no thickness. The constructive reality is much different even though the manufacturing of double curvature surfaces is technically practicable: it is generally not a financially viable solution.
In the beginning, the constructive answers focused on a strong technological rationalization (planar triangular or quadrangular panels, use of standard profiles and repeatability of the connecting nodes…) by limiting the choice to geometries with obvious constructive advantages (spheres, cylinders, cone… translation, rotational and homothetic surfaces). Then, thanks to advances in geometrical optimization and better understanding of intrinsic constructive properties of free form surfaces, technological rationalization could be preserved while going beyond the classical geometrical primitives.
Today, two new issues question the constructive rationalization and may widen its spectrum.
First, the advances of digital fabrication tools for which the repeatability is no more an absolute necessity revolutionizes in shop fabrication and begins to appear on site. In the field of steel construction, these tools already operate within three categories of fabrication:
- additive fabrication (welding, casting, 3d printing, …)
- subtractive fabrication (milling, drilling, …)
- formative fabrication (bending, stamping, folding, …)
The last one (formative fabrication) is massively used since it allows the transformation of commercial products with moderate energy and limited material cut-off.
Second, the regain of interest in the theory of developable surfaces could widen the range of constructive rationalization. Indeed, developable surfaces are isometric transformation of planes, which relates them precisely to a formative approach. A forming process by pure bending is thus able to transform ‘off-the-shelf’ building products sold in the form of plates or sheet coils into three-dimensional complex shapes.