Torsional buckling usually spells disaster in buildings. In nature, however, bending and buckling are regular—and even desired—occurrences in the evolved anatomies of plants and animals. For example, the vivid petals of the bird-of-paradise flower torque open in response to the weight of a bird landing on it, exposing its precious nectar and pollen, which covers the bird’s feet in the hopes it will be carried onward to another flower.
A variant of this behavior is used to operate the kinetic façade of the Theme Pavilion at Expo 2012, the world fair that opened in May in Yeosu, a coastal city in South Korea. Named One Ocean, the pavilion shepherds visitors through exhibitions areas and a theater presenting a multimedia show on this year’s expo theme, “The Living Ocean and Coast.” In the pavilion’s winning design by Vienna architecture firm Soma, dynamic, wavelike movements wash across the eastern face of the 74,000-square-foot structure, capturing with it the attention and awe of fairgoers.
But how to create the active façade? Eschewing virtual animation and conventional hinged louvers, Soma worked with German engineering consultant Knippers Helbig Advanced Engineering to develop a kinetic outer skin that uses low-tech hardware and materials to produce innovative, bioinspired mechanics.
The façade moves by elastically deforming its 108 louver fins, each of which measures between 10 and 42 feet tall and 0.35 inch thick. Made out of glass fiber-reinforced polymer, each fin—or “lamella” to borrow the anatomical term for gill tissue—is compressed at its top and bottom by actuators attached to the pavilion structure. As it gets squeezed, the lamella begins to buckle longitudinally along one of its side edges, which creates an opening in the building skin. Meanwhile, the lamella’s remaining side edge—which is reinforced by a stiffening rib to hold its fixed shape—pivots on a bearing, widening or narrowing the louver opening.
When choreographed as a whole, the lamellas create a rippling surface, visible from the Expo’s main fairgrounds across a causeway. Throughout the day, the 450-foot-long façade behaves as a giant architectural gill that breathes in natural light instead of air. As it opens, the façade allows daylight to filter into the non-theater areas of the pavilion. Four computers control the façade’s operations, which consume a maximum of 80 kilowatts; about one-third of the mechanical energy used to open the louvers is recovered by the actuators when the louvers relax into the closed position. Once closed, the fins are imperceptibly stretched into tension to form a fixed, unbroken surface to limit infiltration by natural elements. A glass curtainwall stands behind the façade. At night, the façade becomes a choreographed display whose movements are enhanced by LEDs.
Sited on a manmade island in a formerly industrial harbor, the pavilion must withstand typhoon winds, humid summers, and freezing winters. Its sea-facing west elevation is a bulwark of hollow concrete cones, designed to withstand the elements. The kinetic east elevation is also engineered to last 25 years, according to Knippers Helbig, thanks to the actuators’ simple spindle mechanisms and maintenance-free radial bearings.
Though Expo 2012 closes on Aug. 12, Soma’s One Ocean Theme Pavilion was commissioned as a permanent exhibition structure that will become a centerpiece for Yeosu long after the fair moves on to its next destination—Milan—in 2015.