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DETAIL
NATURALLY STRONG
FOR THE OPEN-AIR INDOCHINE CAFÉ IN KON TUM, VIETNAM, VO TRONG NGHIA ARCHITECTS TRANSFORMED THOUSANDS OF BAMBOO CANES INTO AN ORGANIC FAN VAULT.
For the restaurant’s nontraditional support structure, Vo Trong Nghia Architects leveraged the mechanical properties of bamboo to create inverted conical columns, which were mocked up and load tested prior to the project’s construction.
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Text by Logan Ward Photos by Oki Hiroyuki BAMBOO MAY BE the ultimate sustainable building material. As one of the world’s fastestgrowing plants, it can sprout up to 4 inches per day depending on variety, soil, and climate. Vo Trong Nghia Architects’ design of the Indochine Café in Kon Tum, Vietnam, proves that the fast-growing grass can look sophisticated—even when it is left in its natural state. Built in 2013 as part of a hotel complex on the Dak Bla River, the 6,000-square-foot open-air restaurant is elegant in its simplicity: 15 inverted cones made of bamboo canes rise 20 feet to create a fan vault of sorts that supports a butterfly roof, also made from bamboo. The columns are arranged in a 3-by-5 grid in the café’s 60-foot-by-100-foot plan. Each one is 20 feet in diameter at the top and tapers to 5 feet at the base, which is anchored into a concrete foundation with steel plates and bolts.
Traditional Vietnamese fish baskets served as the inspiration for the columns. Principal designer Vo Trong Nghia, founding partner of his eponymous firm in Ho Chi Minh City, Vietnam, first worked with the material as a child, helping his family make bamboo tableware. The challenge in designing large structures with bamboo, he says, is respecting its mechanical qualities. Bamboo is dense and hard, but it can bend into strong, curved shapes. Pound for pound, it has three to four times the tensile strength of steel, but its behavior depends on whether it is used in whole, cut in cross-sections, or laminated. Part of the strength of each column comes from the arched geometry of its approximately 400 bamboo canes bound by rope and three steel tension rings inside each cone at 5, 10, and 15 feet above finished floor. An internal central cane bundle and four to eight diagonal crossbraces provide additional support for the roof. Fasteners and conventional construction methods would have ruined the round-cane
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Surrounded by a man-made pond, the restaurant was built as part of a hotel complex along the Dak Bla River in Kon Tum.
Column Section
Roof • 5mm PVC panel • ø35mm–55mm bamboo purlin • 50mm thatch layer • ø35mm–55mm bamboo purlin • Bamboo rafter
Bamboo cross-bracing Bamboo arch Central bamboo bundle
Steel tension ring
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Rope tie
Concrete foundation
texture highlighted in Nghia’s design. Steel-pin joints, for instance, would generate localized point loads that would split bamboo’s hollow hardened cell walls and buckle its joints. The 15 columns were thus prefabricated by means of low-tech joinery—mostly synthetic fiber and a few small nails. Finding structural engineers was difficult, Nghia says. “We based the design on traditional experience, but it follows logical rules of structure. And we always make a mock-up before construction, placing weights on top to test how much the bamboo bends.” Likewise, it’s almost impossible to find contractors experienced in traditional bamboo construction techniques, even in Vietnam. For example, to prevent insect infestation, Nghia knew to soak the bamboo in mud and smoke it dry. As his firm designs more bamboo structures, he has had to hire and train his own construction teams, which now work under a subsidiary company, Wind and Water House. In total, the café contains more than 10,000 bamboo canes, each about 5 years old and costing roughly $1 each. Harvested from Vietnam’s many forests, the bamboo bends into strong, flowing shapes that Nghia loves.