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OEM Report: Heavy Equipment/Construction

Season opener

By Gretchen Salois

Above: Four 720-ft.-long primary steel trusses span concrete “mega-columns” that are crossed by a series of secondary trusses that align with the movement of eight petals that glide along the top of the steel trusses.

Fabricators go to great lengths to construct fan-focused sporting facilities

October 2017 - Meeting your future in-laws is a big deal. I remember the exact date: Nov. 26, 2006, the tail end of Thanksgiving weekend. I awoke early to see a thin veil of frost covering my bedroom window.

“Layer up,” warned my future father-in-law as he patted his pocket containing coveted NFL season tickets. It gets cold up in the steep-angled upper stands at Gillette Stadium.

I watched as he ceremoniously packed up the pork chops and portable grill, pots for simmering baked beans—two New England dinner staples—and Tupperware cradling potato salad made faithfully the night before. Add a cooler full of Molson beer and we were geared up for a 3.5-hour ride south from Augusta, Maine, to Foxborough, Massachusetts. My new family and I tailgated before their New England Patriots bested my beloved Chicago Bears 17 to 13.

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Nearly 250 workers poured concrete and 400 ironworkers manned the steel, contributing to the roughly 18,000 construction workers who labored on Mercedez-Benz Stadium over the course of the project. Photo: Hales

Fans join together to rally their teams. FFJournal delves into the latest designs in steel that house the NFL Atlanta Falcons, MLB Atlanta Braves, NHL Detroit Red Wings and NBA Detroit Pistons.

Upgraded

In May 2010, the Atlanta Falcons announced they wanted to demolish the Georgia Dome in favor of a new stadium. In August, the team played its first preseason game in the new Mercedes-Benz Stadium. The stadium is girded by 27,500 tons of structural steel, compared to its predecessor’s 8,300 tons. The fixed roof is 17,000 tons of steel with 5,000 tons for the façade, 4,000 tons for the retractable roof petals, and 1,500 tons of structural steel used for other parts.

Nearly 250 workers poured the concrete and 400 ironworkers manned the steel, among roughly 18,000 construction workers over the course of the project, according to Mercedes-Benz Stadium.

The retractable roof is the standout element. Four 720-ft.-long primary steel trusses span concrete “mega-columns” that are crossed by a series of secondary trusses that align with the movement of eight petals that glide along the top of the steel trusses. Each petal cantilevers approximately 200 ft. inward toward the center of the stadium. The weight of a single roof truss is more than 1.6 million lbs.

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“SunTrust Park features some of the longest, column-free cantilever seating areas in the MLB, reaching up to 55 ft. in some areas,” says Adam Karabenli, Walter P Moore. Photo: Ryan Linton

“It features eight triangular ethylene tetrafluoroethylene (ETFE) covered petals that move in unison along individual tracks, aiding in passive cooling strategies,” says a stadium spokesperson. “The tracks allow the roof to open and close like a camera aperture.”

The grand roof is also practical. Rainwater will be captured and reused to mitigate flood issues in the neighboring community. “Solar panels are integrated and the roof and façade allows for substantive daylighting.”

By land and by sea

Materials for Mercedes-Benz Stadium came from all over the country and maneuvering each piece to the job site required astute attention to detail. Bennett International Group LLC in McDonough, Georgia, orchestrated the more than 4,000 flatbed truckloads of material that caravanned from the Port of Savannah through Atlanta’s city streets. Coordinators surveyed the area to map out travel routes more than a year before the first piece of steel arrived.

“We worked with Mercedes-Benz Stadium designers and engineers to calculate how large pieces could make it through the city,” says Kyle Wilckens, business development manager at Bennett. “Half the truckloads were oversized either by width, length, weight or height.”

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Roughly 130,000 sq. ft. of roof surface can accumulate over 3 million lbs. of snow. Photo: Olympia Development of Michigan

Eleven vehicles synchronously traveled the streets for each load leading to the job site. The succession included the truck carrying the steel, licensed private escorts equipped with sirens traveling along each corner of the truckload, police escorts, and a truck carrying a maintenance crew.

“There are legal ramifications and safety considerations with every leg of the transport,” Wilckens says. “We had to work within a busy city during heavy traffic hours to safely move material while also being mindful of pedestrians and school schedules.”

“Transport and design become a collaborative discussion,” says Charles Phillips, president of Bennett International Logistics. The company informs manufacturers if they must alter designs or sizes to account for obstacles such as hanging traffic light wires or tight turn angles.

“[A customer] may have a small 0.06-in. component sticking out on one of their pieces that—while tiny compared to the overall piece—could result in thousands of additional transport dollars instead of removing it and fabricating it on-site later,” Phillips continues.

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During construction of Mercedes-Benz Stadium, prefabricated sections were kept in a laydown yard.

Unobstructed views

Approximately 13 miles away, SunTrust Park puts Atlanta Braves fans closer to the game than any other park in Major League Baseball—a view unobstructed by massive columns. “Columns are a structural engineer’s best friend—but they’re not so great for the fan experience,” says Adam Karabenli, graduate engineer at Walter P Moore (WPM), an engineering and consulting company. “SunTrust Park features some of the longest, column-free cantilever seating areas in the MLB, reaching up to 55 ft. in some areas.”

American Builders—a joint venture between Brasfield & Gorrie, Mortenson Construction, Barton Malow Co. (which also worked on Little Caesars Arena in Detroit), and New South Construction Co.—provide construction management and general contractor services, specializing in sports construction. During peak manpower, American Builders had 1,400 people working on SunTrust Park per day; and 11,110 people completed safety orientations over the course of the project. The construction team and its subcontractors completed the stadium in 29 months, logging more than 5.6 million work hours, says Brasfield & Gorrie Division Manager Chris Britton, who serves as American Builders’ 2017 project director.

Connections were welded on site. “All of the reinforcing steel was fabricated off site [in Georgia, Texas and Minnesota] and delivered to the project,” says Brasfield & Gorrie Operations Director Mark Granger. Torches were used for field modifications for the reinforcing steel. Connections were a combination of both welding and bolt-ups.

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The grand roof of Mercedes-Benz Stadium is also practical. Rainwater will be captured and reused to mitigate flood issues in the neighboring community. Photo: Hales

SunTrust Park was designed in 10 months—the fastest design turnaround in MLB stadium history, from a structural engineering standpoint. Cantilevers reaching 70 ft. long make SunTrust Park’s sunscreen canopy the largest in MLB. “Early on during the design phase, a shading analysis was performed to determine the most structurally efficient canopy that would share a predetermined percentage of seats,” says WPM’s Karabenli. “WPM performed this optimization using parametric modeling techniques that ultimately helped drive the canopy shape.”

Round hollow structural sections and seamless API pipes were used to simplify connections in a sleek design. Many connections were field bolted and concealed with cover plates. “Similar to the four light towers, the canopy was delivered to the site in prefabricated pieces to simplify and accelerate steel erection,” Karabenli says.

“The most prominent of these elements is the sunscreen canopy over the seating bowl,” says Brad Albers, Populous associate principal and lead project architect for SunTrust Park. Populous has had a hand in 22 of the 30 MLB ballpark design or renovations done in recent years. Metal fabricators were used on both exterior and interior building elements.

At over 100,000 sq. ft., SunTrust Park’s roof is the largest in American baseball. Because the roof “is a dominant feature of the building’s appearance, we chose a prefinished metal deck with dovetail ribs. The deck was mechanically fastened to the structural steel frame,” says Albers.

Familiar with baseball stadium geometry, the team at Populous had to be creative with seating design. “Nothing is orthogonal or simple, and virtually every section of the ballpark is unique,” adds WPM’s Karabenli. “This emphasizes the importance of coordination between all design disciplines.”

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9,500 lbs. of structural steel was used during the construction of Little Caesars Arena in Detroit. Photo: Olympia Development of Michigan

The seating bowl massing model was imported from Populous and modified by WPM’s internally developed software programs to auto-generate custom precast seating unit profiles and the supporting steel frame, as well as other parts of the project such as the canopy, scoreboard and light towers.

Delicate balance

In Detroit, the Little Caesars Arena roof had to be structurally prepared to handle Michigan’s harsh winters. The roof area is approximately 130,000 sq. ft. of roof surface that can accumulate over 3 million lbs. of snow, according to Magnusson Klemencic Associates (MKA), the structural engineering firm.

The arena roof structure spans over the arena seating bowl 440 ft. in the long direction and 325 ft. in the short direction, according to MKA. A two-way “super truss” structural system features pairs of 40-ft.-deep trusses spanning in both the long and short direction of the roof. As a result, eight columns (one on each end of the pair of two direction trusses) support the majority of the roof loads. The remaining roof structure are much smaller and lighter.

Architectural and structural engineering teams matched systems and spaces to make each part of the arena work for the NHL Red Wings and NBA Detroit Pistons. While it appears there is an abundance of space in arenas housing hockey and basketball teams, Mike Rogers, professional engineer at Smith Seckman Reid Inc. in Nashville, says spacing can be restrictive.

“Multiple layers are being pulled in close to the seating bowl,” Rogers says. “Having the fans close to the action is a goal for most seating bowls and this compresses the levels, creating tight floor-to-floor spaces.”

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Maneuvering took precise planning as half of Bennett International's truckloads moving steel to the Mercedes-Benz Stadium work site were oversized either by width, length, weight or height. Photo: Bennett International

For example, designers and engineers have to approach arenas with ice rinks differently from a football stadium or baseball field because hockey requires tight temperature and humidity control. “Hockey is by far the most restrictive due to the ice sheet and problems encountered with humidity in these buildings,” Rogers says.

He notes that 9,500 tons of structural steel was used to complete the stadium. “Once we get the basic systems fitted, we then integrate the needs of all the sub-systems within the building, such as food service, audio visual, telecom, security, ice floor, etc.”

Designers dealt with major changes during the process, including the Pistons moving in while construction was already under way. “We designed the addition of the Pistons’ training and locker room areas separately,” Rogers says.

Manpower ebbed and flowed with more than 20,000 hours spent to complete the project. Just-in-time installation during arena construction required the majority of sheet metal and piping systems to be prefabricated in local shops and transported to the job site.

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The majority of sheet metal and piping for Little Caesars Arena was prefabricated in local shops and delivered to the job site for installation. Photo: Olympia Development of Michigan

“I’m always amazed at how organized and precise the mechanical subcontractors are with their off-site fabrication,” Rogers says. “The use of 3D modeling, job site laser scanning and materials tracking have come a long way over the last few years. On-site installation is quick and precise.”

Virtually no on-site storage was used during the building process. “Fabricators wheeled in the sections with all the necessary hangers, installed [them on each section] and then went back to the shop for the next section,” Rogers says.

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70-ft.-long cantilevers make SunTrust Park’s sunscreen canopy the largest in MLB. Photo: Mortenson Construction

Lining the exterior walls of Little Caesars Arena are “Spirit Murals” celebrating Detroit legends including hockey great Gordie Howe and basketball’s Isiah Thomas.

Much like the teams that rigorously train for competition, the architects, engineers and fabricators behind stadium, park and arena projects synchronize their work—coupling smart design and boots on the ground to achieve results. Each task is carried out with the same discipline athletes bring to game day, to ensure they do right by their devoted fans. FFJ

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