Lightweight Structures
Fabric and Shells

By 'lightweight structures' we mean those which use their form, or shape, to resist loads. Typically they form a three dimensionally curved surface which can resist transversely applied forces by arching compression or 'in plane' tension. This three dimensionality also greatly enhances their capacity to resist concentrated loading and reduces the tendency to buckle out of plane. Typically, because of their high structural efficiency, they have low self weight and hence the lightweight categorisation.

Shell structures in concrete have been around for many years; the works of Torroja, Candela, Samuelly, and Arup are well known. However the high costs of formwork have made their price prohibitive. The development of the grid shell has removed this problem by creating similar arching structures from simple and cheaply manufactured 'sticks'. The approximately square network can be formed either from initially straight components, such as aluminium extrusions, or from pre-curved components of laminated timber or steel.

The structural 'inverse' of a shell is a tensile membrane, where the double curvature is used to resist transverse forces by tension in the fabric. These ultra lightweight forms however require significant anchorages from which to 'spring' from.