Column_1: Shelling & Fluting (part 1 out of 9 from New Orders)
The architectural investigation for this prototype proposes a sequence of semi-public outdoor spaces within the shaft of a column through perforations while aiming for a high degree of structural integrity. To achieve this, a structural knuckle made of a maximum of air was conceived with minimum material. Column 1 draws on the history of thin shell structures, specifically by revisiting Felix Candela’s work on Hyperbolic Paraboloid also known as Hypar. Warped surfaces, efficiently described by a series of rotating lines (ruled geometry) and in close proximity with its resulting formwork procedure (lines materialized by straight timber sections), serve as the principal spatial and structural element for the void description.
Instead of considering saddle structures as single storey, the prototype instigates their potential to stack up into a vertical compound of interchanging vaults. 4 rotating hypars of varied amplitudes interlock to describe 3 successive voids within a vertical shaft. The first tested hypar composite comprises of 87 percent of air and of 13 percent of structural mass.
Following a series of incremental formwork design and casting tests, a final 1to1 scale prototype was built to assess its loading resistance. The concrete shaft consists of three parts; a bottom support, the middle hypar composite of 12mm thick, weighting 5kgs and a top loading element of 30kgs. The ceiling planes of each of the saddle surfaces were structurally amplified by protruded ribbed beams connecting the ruled lines of the successive hypars. Those same lines were extended out as flutes along the surface of the shaft in an effort to accentuate the column’s vertical reading.
Upon completion, the prototype was assessed to be properly performing under dead load and deemed successful as initial proof of concept. Further analysis through computational simulations need to be conducted to evaluate more accurately the stresses distribution from hypar to hypar under various loading scenarios.
The fabrication of the formwork took into account the issue of formwork decentering known in thin shell structures. This was accounted for through a two-step casting process; by first producing the 3 positive voids in rubber as part of the final mould for the concrete hypar composite. The rubber plugs were used for their ductile property in demoulding to prevent any concentration of stresses on the shells.