October 3 2007

Tensairity Structure! Kongsberg's Tubaloon Band Stand

This summer, Norway's Kongsberg Jazz Festival was home to a large fabric cochlear shaped band stand affectionately named the "Tubaloon." The structure was designed by Norwegian architecture firm Snohetta and was was inspired by Le Corbusier and Zenakis's Philips Pavilion at the 1958 world exposition which used cables, rods and fabric in a similar fashion to create a volume.

The fascinating aspect of this design is that it uses an innovate structural technique called a "Tensairity." The technique was developed by a Swiss engineer named Mauro Pedretti and is now being fabricated by his company Airlite. According to the literature, the patented technology can create large-span beams that "minimize strut material by using low pressure air to prevent compression elements from buckling."

"In its most basic form, a Tensairity beam consists of simple airbeam (a cylindrical membrane filled with pressurized air), a compression element tighly connected to the airbeam, and two cables running (wrapped) in a helical form around the airbeam."


Here are two diagrams comparing the structural qualities of a Tensairity (above) to a truss girder (below). As you can see they function similarly even though the Tensairity can forego the vertical struts.


For a detailed description of the technology  and exact engineering information please refer to the article "Tensairity" published by Dr. Mauro Pedretti.

The following image shows a remarkable study Dr. Pedretti completed as a proof of concept. In the test a car was supported by two identical parallel tensairity beams with a 50 cm diameter each. The bridge was capable of supporting 3.5 tons of weight. Fascinating is when Dr. Pedretti notes that the weight of each tensairity beam is 40kg. An HEB steel girder designed to support the same load would weigh 370 kg! And an airbeam without the tensairity compression rib and tension cables would be pressurized to 15 bar (compared to 400mbar in the tensairity beams).


It is fascinating to see the application of ancient structural principles to new materials and technologies. Personally I believe that many great works of architecture have not only a well-conceived plan and section, but a novel use of a material or design process. Think of Corbusier = Concrete / Gehry = CATIA / Mies = Steel and Glass

The following slideshow shows the Tubaloon in action and has a few more shots of Tensairities...


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October 20th, 2007 at 11:11 PM