Structural design, fabrication and construction of the Armadillo Vault

Block P., Van Mele T., Liew A., DeJong M., Escobedo D. and Ochsendorf J.
The Structural Engineer
2018

The Armadillo vault, exhibited at the 2016 Venice Architecture Biennale and short-listed for the 2017 Structural Awards, is a doubly-curved, unreinforced, cut-stone funicular vault, constructed from 399 limestone blocks. The thickness of stone varies from 8{12 cm at the supports to 5 cm at the peak. With a height of 4.4m and spans of over 15 m, the structure has a span-to-thickness ratio half that of an eggshell. This paper presents the vault's place among funicular vault design and gives a background to its place in the Venice Biennale exhibit. The form- nding process with Thrust Network Analysis and the use of RhinoVAULT is detailed, as well as the performed detailed structural analysis of the vault through discrete element 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 blocks, or voussoirs, were cut from cream limestone, and tested to determine their design compressive strength. The stone-cutting process for the limestone is outlined, describing the rough-nished inner surface, which was patterned to follow lines of internal force ow, and the smooth at outer surface. Finally, the process of erecting the formwork and falsework on-site is given, talking through the process of de-centering and the use of custom keystone. The entire project was subject to a variety of strict constraints, particularly a tight time schedule, and involved an integrated multi-disciplinary team to deliver the Armadillo vault on-time, using various novel design and construction methods.