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Atlanta’s Georgia Dome establishes a number of new fabric-roof records
By Gene Rebeck
Call the 70,500-seat Georgia Dome a domed stadium, according to its designers, and you miss the point. To understand how, you first need the answer to a key question: Why a dome in Atlanta?
Although many domed stadia have been built in warm climates —Houston’s Astrodome, New Orleans’ Superdome— most have been built in colder or rainier areas (Minneapolis, Detroit, Seattle), where inclement conditions can cost unprotected sports teams cash-paying fans. But why would warm, sunny Georgia need a domed stadium of its own?
Because in a very real sense, the Georgia Dome is not a domed stadium. “The Georgia Dome is a building, not just a stadium with a roof,” asserts Scott Braley, AIA, the structure’s project director. “It’s a building with a stadium inside.” The Georgia dome doesn’t look like any other domed stadium. The typical “dome,” however ingenious its engineering indoors, tends to present a utilitarian, almost Brutalist face to the public. Come in, stay outside, don’t matter to me, these exteriors seem to say. This probably isn’t the architects’ fault: Design money, like hot air, seems to float up to the ceiling, leaving a façade that is little more than an ugly precast-concrete blank.
Not so the Georgia Dome. Attached to the Georgia World Congress Center in downtown Atlanta (the Omni Center and Cable News Network tower are nearby), the Dome will play a key part in an exhibition and convention complex. Housing sporting events is only one of the Dome’s purposes. The stadium will play host to Atlanta Falcons football games and the Peach Bowl; however, it also can accommodate other functions where its big seating capacity can be put to use—concerts, exhibitions and big conventions. A huge unattractive football stadium would work against the surrounding buildings and against its magnetic pull for big events.
Instead of concrete, the dome’s rectangular, 25-story exterior is clad in composite metal panels, whose electrostatically applied palette of plum, blue-green and white pick up tones from the surrounding structures and the dome’s white roof. Curtain walls of green glass appear at the truncated corner entrances. Inside, rings of restaurants and pedestrian concourses also help underplay the structure’s sporting function.
But the project’s distinctiveness doesn’t end there. 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.”
Even the Georgia Dome’s architectural team, Heery/RFI/TVS, has a distinctive structure. Various members of three firms—Heery International Inc., Rosser Fabrap International and Thompson, Ventulett, Stainback & Associates—combined to form a ‘mini-firm’ autonomous in its separate office. Duties were not divided between members of each firm but overlapped holistically, cooperatively.
When completed, the Georgia Dome cost more than $200 million and covers about 6 hectaires. About 10,000 parking spaces are located within three blocks, with MARTA, the local mass-transit system, serving the Dome at two stations.
Besides the Falcons games and the Peach Bowl, the structure housed events for the 1996 Summer Olympics. Not bad work for a building that isn’t a stadium.