Bali-based architecture firm Ibuku has partnered with bamboo construction expert Jörg Stamm and structural engineering company Atelier One to construct the Arc, an intricate bamboo building at the renowned Green School in Bali, Indonesia. The Arc includes a series of intersecting 14-metre-tall bamboo arches connected by anticlastic gridshells that derive their strength from curving in opposite directions. While the resultant structure is strong and sturdy, its arches still manage to appear delicate and lightweight, as if they were made of fabric.
Ibuku is well-known for their use of bamboo to build homes, hotels, schools, and event spaces around the world. The Arc exhibits their dedication to using bamboo as a construction material. The company uses bamboo for its strength, beauty and flexibility, and also because it is an environment-friendly building material. The enclosure defies convention because of the use of bamboo, which itself is an enigmatic material. “The Arc at the Green School in Bali enters a new era for organic architecture, with its 19-metre-span arches, interconnected by anticlastic gridshells. It is a new community wellness space and gymnasium for the extraordinary campus, in collaboration with Jörg Stamm and Atelier One,” says Elora Hardy, creative director of Ibuku.
The Arc is a unique enclosure, which was constructed after months of research and development, and fine-tuning of tailor-made details. The result is a one-of-a-kind design with delicate beauty that stands as a testament to Ibuku’s commitment to expanding horizons in architecture and design. “The concepted structure for the Arc is totally unprecedented. Embarking on a design never executed before required some bravery and optimism. We were creative and stubborn enough to research and develop the answers needed for the success of the project,” adds Rowland Sauls, the project architect.
Evocative of the Human Ribcage
The Arc uses one of nature’s greatest strategies for creating large spaces with minimal structure. Within a human ribcage, the ribs are held in place by a tensioned flexible layer of muscle and skin. This creates a thin but strong encasement for the lungs. Likewise, in the case of the Arc, arches working in compression are held in place by tensioned anticlastic gridshells. These gridshells seem to drape across the spaces between impossibly thin arches soaring overhead. Although the gridshells appear to hang from the arches, they actually hold them up.
“The Arc operates like the ribs of a mammal’s chest, stabilized by tensile membranes analogous to tendons and muscles between ribs. Biologically, these highly tensile microscopic tendons transfer forces from bone to bone. In the Arc, bamboo splits transfer forces from arch to arch,” states Stamm, design conceptor of The Arc.
The Arc is constructed using minimal structural material. It showcases a counterintuitive orchestration of geometry, which brings the enclosure into a state of equilibrium that results in a dramatically decreased need for structural material. This also creates an unparalleled inner volume with an impossibly thin structure and without any distracting trusses. “The gridshells use shape stiffness to form the roof enclosure and provide buckling resistance to the parabolic arches. The two systems together create a unique and highly efficient structure, able to flex under load allowing the structure to redistribute weight, easing localized forces on the arches,” concludes Neil Thomas, director of Atelier One.