Gene Rebeck, first editor of Fabric Architecture magazine, contrasts two major fabric rooves in terms of their tensegrity components. This article ran in the May/June 1992 issue:
The Georgia Dome possesses the world’s largest cable-supported roof, measuring 235m by 186m. Further, it is the world’s first large-scale oval dome. Its cabling system and its shape give the roof a remarkable texture, a tent-like ambience with an almost Arabic air.Designed by engineer Matthys Levy of Weidlinger Associates in New York City, the fabric roof melds Buckminster Fuller’s “tensegrity” concept with the hyperbolic parabola, the “building block” saddle shape of tension structures. Levy calls his design “hypartensegrity.” From Fuller comes the idea of a triangulated membrane in which “islands of compression reside in a sea of tension.” The fused triangular panels of the Georgia Dome are tensioned using cables. These cables also hold aloft a series of three oval-shaped concrete “tension rings,” elliptical about the roof’s two focal points. Each of these rings, along with the cabling, supports numerous steel support posts that provide upward compression. The posts hold up the roof like columns, except that they do not reach to the ground. Thus, spectator views of a speaker or a game are unobstructed.For extra load support, the triangular fabric panels form diamonds that are saddle-shaped (hyperbolic paraboloid). Pulling together the roof’s two foci is a plane cable truss 56m long. The result of all this engineering is a roof distinctive both functionally and aesthetically—this Dome aspires to be not just a dome, but a local architectural landmark.But why fabric instead of something more “solid”? “A solid roof would be no more maintenance-free tha a steel or concrete structure,” says project director Braley. “Given that, the next factor is cost. A fabric roof is simply more economical for these spans.”The Georgia Dome is not the first fabric tensile structure to use the tensegrity concept. The Suncoast Dome in St. Petersburg, Fla., designed by engineer David Geiger, also uses a cable/tension-ring system to hold its fabric roof aloft (FA, Spring 1990.) But in the Suncoast’s round dome, the fabric, although composed of triangular shaped panels, has not been curved into saddles, and its cabling is radian from the central ring. “Mine is totally triangulated,” says Levy. “The stress is completely on the cables, rather than having any on the fabric.”
The Georgia Dome was by three firms—Heery International Inc., Rosser Fabrap International and Thompson, Ventulett, Stainback & Associates.
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