While developing their structural systems, the team looked at two steam-bent antecedents: Thonet's No. 14 chair and the bent-wood snowshoes and canoes made by craftsmen in the Great Lakes region. To fully understand the geometries and the bending required, a Thonet chair was deconstructed to its most basic parts.
Deconstructing Thonet
Deconstructing Thonet
Deconstructing Thonet
Deconstructing Thonet
Thonet Deconstructed.
Tests of various regional wood species—including white ash and white cedar—and samples of wood species from further afield, suggested that white oak was the best option for creating the arcing wishbone structural system because of its superior flexibility and weather resistance. But this realization did not come without several failures along the way. Even after white oak was selected, the team continued to move back and forth between digital parametric models and physical models, using the breaking point of the wood to help develop the extent of the curve for the arched structural members.
Several parametric models were created to explore how the severity of the curves of the individual structural components would affect the overall geometry. These models were combined with lessons learned from physical modeling to determine that the best form for the pavilion would be open on one end and closed on the other (shown in red). The parametric model was then run through a series of structural analyses that tested moderate loading, pre-failure, and failure loading to determine how the structure would perform under heavy wind loads.
The team determined that to create the wishbone structure it would have to make each individual piece of white oak achieve a three-axis bend. Each piece of wood is split down the middle, nearly to the ends, then steamed open to form the initial shape, and bent over a barrel-shaped jig developed through parametric modeling. Each piece can be bent to a 1.6-meter radius before breaking. Pieces are then joined together to form the full arch of the structural system.
Once testing was completed and the structural system determined, the team built a full-scale prototype of one half of the potentially fully arched structure. In this partial form, the system can serve as a brise-soleil for an existing building.
Wood is biodegradable, so it can either be composted or used as fuel for wood-burning stoves or heaters once a structure has reached its end of lifebut the complexities of the system are not a great fit for rapidly deployable structures such as disaster housing. However, the team is exploring the idea of using the system for temporary civic buildings, such as outdoor galleries. Covering the structure with a translucent fabric would allow daylight to filter in and create a sheltered space to view artwork.
