Eden Project uses a hybrid between a geodesic dome and spaceframe, interlocking three domes of varying size to create a series of climate-controlled greenhouses. The base structure is created from hexagonal units, rather than the smaller equilateral triangles as more typically used by Buckminster Fuller. The poles and nodes were fabricated off site and arrived in flats to be fully site-erected. A substantial scaffold was required to erect the domes, which are 125m/410ft across and 60m/197ft high. ETFE cladding was chosen for its durability and very high level of solar transparency as this would help to ensure good light for the plant specimens to be housed within.
The exterior of Eden Project in St. Austell, UK by Nicholas Grimshaw shows the pillow nature of the ETFE cladding as it pinches together at the sides and presses out at the center of each panel.
Larger steel truss arches were required at the intersection points of the domes in order to resolve the geometry and stabilize the structures.
The steel structure closely resembles the system used to create spaceframe structures. The opened sections show the level of visual transparency of the ETFE material. The relative sizes of the steel tubes and rods that comprise the outer structure of the dome can be seen against the smaller members that create the three-dimensional bracing layer on the interior. Services such as wiring, fire protection and air to maintain the pressure in the skin run tightly along the hexagonal steel grid to conceal the systems.
IRREGULAR MODULES The National Aquatics Center for the 2008 Beijing Olympics was the first structure in China to use an ETFE membrane. The idea for the structure was based upon the geometry of soap bubbles. This transformation of the combination of a spaceframe and geodesic structure into one that included large variations in the relative sizes of the units added significant complexity to the design, fabrication and erection of the structure. The polyhedral spaceframe is comprised of 22,000 individual elements and 12,000 joints. Its form is highly earthquake-resistant. Whereas earlier uses of this sort of structure worked with spherical geometry for the shape of the building, the Watercube creates an orthogonal building with an irregularlooking, three-dimensional polygonal steel framework of uniform thickness. The framework is clad on the exterior and interior with ETFE membrane bubbles. The 197x197x35m/ 646x646x115ft building was digitally “carved” out of a theoretical 3D model of a solid block of Weaire-Phelan Foam. The geometry of foam, seen as a perfect array of soap bubbles, served as a model to subdivide the three-dimensional space of the frame into a continuous bubble-like structure that could be transformed into a steel-framed system. Because of this means of form generation, the roof and wall structures are continuous. This also led to a decision to site-weld the steel components. Rectangular HSS steel members are used on the interior and exterior faces of the wall to provide the proper geometry for the attachment of the ETFE membrane. Round HSS are used between the faces to work more easily with ball-joint-type connectors.
– TENSION SYSTEMS AND SPACEFRAMES