A Tree of Triangles

Akihisa Hirata blends organic inspiration with geometric form for an art pavilion in Tokyo.

Akihisa Hirata Architecture Office

Bloomberg Pavilion
4-1-1 Miyoshi, Koto-ku (81) 3-5245-4111


Obviously influenced by Toyo Ito, with whom he worked for eight years, the Japanese architect Akihisa Hirata has developed a distinctive design methodology based on geometric algorithms. When he was invited to make a temporary pavilion that could showcase contemporary art, and at the same time look emblematic outside the entrance of the Museum of Contemporary Art, Tokyo, the 40-year-old Hirata responded with a complex volume generated from a simple triangle.

From the start, Hirata imagined a treelike object, with walls that seem to grow out of the ground and open up to the sky. This, he felt, would not only create an iconic form but also control incoming light, best displaying the art underneath.

The resulting Bloomberg Pavilion is based on a hyplane, an object that combines geometric shapes to create a saddle-like surface. A flat surface made of identical isosceles triangles would have deformed evenly, but Hirata was looking for a non-uniform branching effect, so he used units of two different sizes to achieve a distorted shape. The walls of the 248-square-foot pavilion gradually break up into 100 triangles, then branch out and fold in on themselves by means of 500 smaller triangles. Until this October, young Japanese artists will display works that bring together concerns about nature, technology, and performance under this crumpled metal canopy.

“A roof is an architectural element that is supposed to be really strong, in order to protect people from the natural elements, but in this pavilion it carries a symbolic meaning,” Hirata explains. “The folds provide shade, and polycarbonate skylights shelter the space from rainfall.” The pleats also have a structural advantage, being much lighter than a conventional roof. The 1.6-millimeter-thick steel triangles, point-welded together for maximal strength, are so light that when the wind blows, the entire roof of the pavilion softly sways, “just like a real tree,” Hirata says.

Such an organic structure would only be possible with precise construction. Parts were prefabricated in a steel factory, then connected on-site and finished off in white, “the natural color of stain-preventing paint,” Hirata says, quipping about the limited budget of the project.

Even at its diminutive scale, the structure investigates how free architecture can be, while still providing a new sense of place. At the Bloomberg Pavilion, Hirata says, “Visitors can simultaneously experience an artificial space and the soft, ambiguous feeling of sitting underneath a tree.”

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