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08.18.2014
In Detail> Atlanta Falcon's Stadium
360 Architecture and BuroHappold have designed a stadium with a retractable, petal-like roof for the Atlanta Falcons.
Courtesy 360 architecture

As the home viewing experience has become much better, NFL owners have grown concerned about ensuring attendance at their stadiums on game day, especially if their teams are not perennial championship contenders. While in part this has been seen in an increased mediation of the game by way of jumbo screens and the like, teams building new facilities have looked for the architecture itself to become part of the draw. The result has been the introduction of formal adventurousness to a typology that was previously rather utilitarian and straightforward.

The most recent team to follow this trend is the Atlanta Falcons, which has unveiled a new stadium to replace the Georgia Dome (1992). Designed by Kansas City–based 360 Architecture, the 1.8 million-square-foot, 71,000-seat facility is an eight pointed star in plan and features a unique retractable roof with eight triangular panels, or petals, that slide diagonally apart much in the manner of a camera aperture mechanism.

   
The Atlanta Falcons’ new stadium design is topped by a unique retractable roof made up of eight, ETFE-clad triangular petals that open and close along dedicated rails. While each petal moves in a straight line, diagonal to the others, the coordinated movement creates the impression of circular motion, resembling that of a camera aperture mechanism.
 

The architects derived the stadium’s angular geometry from the Falcons’ logo. To design the structure and moving apparatus of the roof, 360 worked with BuroHappold, kinetic architecture consultant Uni-Systems, and Chuck Hoberman, inventor of the Hoberman Sphere—an isokinetic structure capable of folding down to a fraction of its normal size by way of scissor like joints. Hoberman convinced the team to abandon an initial scheme that had the roof opening with circular motion because circular motion is difficult to pull off in large structures. Instead, the team went with a scheme that has the petals moving together along dedicated rails in diagonal lines to each other, which creates the illusion of circular motion.

 

The fixed portion of the roof is made up of a mix of primary, secondary, backspan, and gutterbox trusses. There are four primaries, each 70 feet deep with a 12-foot deep top chord, which span 715 feet between 179-foot-tall, reinforced concrete megacolumns. The petals of the retractable roof are clad in transparent ETFE and are each framed by three main trusses, which taper from 30 feet deep to four feet deep at the tip. Between 196 feet and 236 feet long and 128 feet and 160 feet wide, the petals cantilever between 156 feet and 192 feet from their rails, which they overlap by 40 feet. Each petal runs on two rails, an inner rail that handles compression forces with eight two-wheel bogies, and an outer that handles uplift with six roller assemblies. The tracks are between 225 feet and 375 feet long and 12 7.5-horsepower traction drive wheels propel each petal.

 

RESOURCES:
Architecture Consultants:
BuroHappold
MEP Engineer:
WSP
Geotechnical Engineer:
Langan
Kinetic Architecture Consultants:
Hoberman
Uni-Systems

 

The kinetic nature of the stadium does not end at the roof. 360 envisioned the building as primarily open-air with the ability to become an indoor, air-conditioned facility in exceptionally hot weather. As a result, when the roof opens so do the louvers and operable glass curtain walls that make up the stadium’s envelope, providing ample cross-ventilation for the concourses and seating bowl. And, of course, video mediation is part of the design in the form of a 58-foot-tall, 360-degree, high-definition video halo that hangs from the roof’s primary trusses. This screen will show each fan a magnified view of the game from the perspective of their seating area, a serving of video content unavailable to those watching at home on the couch.

Aaron Seward