Structural design, fabrication and construction of the Armadillo vault

The Armadillo vault, exhibited at the 2016 Venice Architecture Biennale and commended at the 2017 Structural Awards, is a doubly curved, unreinforced, cut-stone, compression-only vault, constructed from 399 limestone blocks. The thickness of the stone varies from 8–12cm at the supports to 5cm at the peak. With a height of 4.4m and spans of over 15m, the structure has a thickness-to-span ratio half that of an eggshell. This paper describes the form-finding process and detailed structural analysis. Steel supports were designed to take the reaction thrusts of the vault and transfer them safely to both the ground and the internal steel tie system. The stone-cutting process for the limestone is also outlined, describing the rough-finished inner surface, which was patterned to follow lines of internal force flow, and the smooth flat outer surface. Finally, the process of erecting the formwork and falsework on site is also set out, including the process of decentring and the use of custom keystones.