published in sb 2/2018
Aperture of a camera
Conventional retractable roofs feature utilitarian, sliding panels. For the design of Mercedes-Benz Stadium, the team around HOK found inspiration in the way sunlight passes through the oculus in the roof of the Pantheon in Rome. Made up of eight triangular ETFE “petals” that move together along 16 individual tracks, the semi-transparent roof opens and closes like the aperture of a camera.
The design of Mercedes-Benz Stadium creates an architectural landmark in the heart of Atlanta. The 71,000-seat stadium is home of the NFL’s Atlanta Falcons and the MLS’s Atlanta United FC. Inspired by the oculus in the ancient Roman Pantheon, the stadium’s retractable roof is the centerpiece. Designed as the signature element rather than a utilitarian cover, the roof provides a radical departure from the kinetic roofs of other sports facilities. It features eight triangular ETFE covered petals that move in unison along individual tracks, aiding in passive cooling strategies. The 16 tracks (two per petal) allow the roof to open and close like a camera aperture.
The roof may appear to rotate open but this is an optical illusion: it opens by the movement of the eight “petals” that slide open in a straight line. Four 220-m-long primary steel trusses span between concrete “mega-columns”. These primary trusses are crossed by a series of secondary trusses that align with the movements of the eight petals which glide along the top of the trusses.
Each of the moving petals cantilevers 60 m inwards towards the center of the stadium and provides a roof-covering when the petals are in the closed position. The movable petal structures are powered by eight mechanized “bogies” which drive the petals along an inner rail and are attached to the outer uplift rail by six roller mechanisms. In the closed position the petals lock together to form a water tight seal. Each petal structure is clad with air-inflated ETFE “pillows”, totaling more than 13,350 m² of ETFE in the petals alone.
World’s first halo video board
A first-of-its-kind HD “Halo Board” is built into the roof offering fans a rich, immersive and theatrical 360-degree viewing experience. Wrapping the perimeter of the oval-shaped roof is a high-definition, 360-degree halo video board that gives fans an immersive, theater-in-the round experience. The one-of-a-kind video board is the largest in any of the world’s stadiums (nearly six stories high and 328 m around) and provides clear views from every seat while preserving the beauty of the roof. An additional video display – a 30.5 m-high mega column – is wrapped with a 3D video board, and there are 2,000 TVs throughout the venue. More than 6,438 km of integrated fiber-optic cable supports the technology-driven, interactive game-day experience inside Mercedes-Benz Stadium.
Window to the city
The stadium’s transparent ETFE façade is a continuation of the roof and features angular, wing-like exterior sections, a reference to one of the two home teams – the National Football League’s Atlanta Falcons. The transparency of the façade creates a “window to the city” that provides floor-to-ceiling views of Atlanta’s downtown skyline while connecting fans to the city’s landscape and offering a natural visual impact of the 186,000 m² stadium.
The window to the city is more than 16 stories high and encompasses 2,106 m². The stadium’s transparent ETFE façade, including the window to the city, creates a seamless visual connection from the roof’s ETFE pillows to the building’s structure. There is more than 31,526 m² of ETFE used throughout the project. The design team selected this transparent material because of its highly sustainable nature and the visual connectivity it creates.
Designed to be scalable to host some of the world’s top sports and entertainment events, the stadium is easily reconfigured to accommodate games for the Falcons, matches for Atlanta United, the city’s Major League Soccer franchise, and for world-class events such as Super Bowl, NCAA Final Four, FIFA World Cup matches, and major concerts and performances. Retractable seats surrounding the field and an automated curtain system attached to the roof comes down to bring soccer fans close to the pitch, while an entirely digital stadium platform creates opportunities to customize content for each anchor tenant.
A wide variety of seating options provide fans with different ticket prices, vantage points and levels of service. Amenities include a technology lounge and the 100 Yard Club, a row of concession stands that is bookended by bars and that stretches as long as the field itself.
Designed for sustainability, Mercedes-Benz Stadium is North America’s first LEED Platinum professional sports stadium. A cistern helps recapture and reuse rainwater. This helps protect the neighborhood from flooding and provides rainwater to irrigate trees throughout the city. The site has more than 4,000 solar PV panels. The focus on sustainability extends into the community through connections to public transit and the creation of urban farming areas and open recreation spaces.
In addition to serving as an anchor for the downtown tourist and entertainment district, the stadium will catalyze changes in surrounding neighborhoods. District-scale thinking enables the building to share resources with nearby developments.