Wonders Of Welding

Vikings’ U.S. Bank Stadium Throws Open Its Doors

By Charles McChesney

Bank Stadium, the new home of the U Minnesota Vikings, boasts a. number of new features – luxury boxes at field level, locally-sourced food, a roof that is mostly clear plastic, and a modern interpretation of a Viking ship in the plaza in front of the 66,655-seat stadium.

But the most eye-catching feature of U.S. Bank Stadium may be its doors. They’re big. According to Viking officials, they are bigger than any doors you have ever seen swing open. Other places have huge doors – Marlin Park, the home of the Florida Marlins: AT&T Stadium, home of the Dallas Cowboys: Kennedy Space Center and many Air Force bases – but those doors slide or roll to the side to open. The doors at U.S. Bank Stadium swing open. like a door at your house or business. What makes these unique is that each of the five doors on the west face of U.S. Bank Stadium is as big as the side of a building. Creating such big doors was a big project, says David Doss, operations manager and chief engineer at Industrial Door Contractors in Columbia. Tenn. It was a design challenge and not one his company initially was eager to undertake, he says. The 60-employee company, which has been in business since 1983, specializes in hangar doors and bunker doors.

Stadium doors didn’t land in the company’s portfolio until the Miami Marlins chose to build giant doors into their new stadium in 2012. Doss remembers talking with the construction manager then about the project, and having to explain why he referred to what they wanted as “hangar doors.” To them it was an “operable wall,” he says. “It looks like a hangar door to me,” he told them, “it just sits 40 feet up in the air.”

M.A. Mortenson was a contractor Industrial Door had worked with on past projects. When Mortenson was named contractor on the U.S. Bank Stadium project, the company turned again to Industrial Door. Doss says his company hadn’t built anything like the pivoting doors being called for — nobody had.

Tighter Tolerances

What designers and architects came up with were doors built of grade 50 structural steel, MIG welded and built to a tighter tolerance standard than the building itself. The doors have a core truss at the pivot point and cantilevered wings that span out to the tips of the doors. The structure was required to carry its own cantilevered weight plus the significant weight of the aluminum and glass curtain wall system. It also was required to resist the design wind loading. Hollow structural steel tubes were chosen as the primary framing material to provide the necessary strength, and because they would make an aesthetically pleasing structure. Welded construction was specified to make the connections blend into the structure. Compensation for the weight of that glass was integrated into the erection of the doors, Doss says. Sixteen-inch square steel-plate weights were used to simulate the weight of the glazing and frames.

On-Site Fitting

To facilitate assembly on site, the main truss tubes were fitted with tapered alignment guides that also served as backing bars for the full penetration welds which joined the sections. Locating plates were provided on the main truss chords to ensure proper location of the wing members during on-site assembly. Each door structure was assembled into two smaller sections on the ground. The lower section was then lifted into position and secured before the upper section was positioned atop it and the sections welded together.

At the top of the doors, engineers had to compensate for different building tolerances. “The general AISC (American Institute of Steel Construction) erection tolerances for the building columns (about which the doors pivot) allowed for the columns to be out of position by almost 2 inches at the top of the doors and still be considered totally acceptable,” Doss says. “Since it was not economically feasible to have the building erected to the tighter tolerances, the pivot door top-bearing journals were designed to be adjustable, to permit it to be centered with the door base bearing.”

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The original specifications only required that the giant doors open one at a time. But Doss said he knew someone would want to see the five doors swing open at once. Before work was done, a Vikings official asked if it would be possible to do a choregraphed opening of the five doors. It was. “I felt vindicated,” Doss remarks. (You can see a quick video of the doors opening on Instagram:

Member Connection

Construction of U.S. Bank Stadium provided a lot of jobs in the building trades, according to GAWDA Member Kevin Falconer, vice president and general manager at Minneapolis Oxygen Company. Falconer says his business supplied about a half-dozen contractors who were involved in the project. It didn’t hurt that Minneapolis Oxygen has a storefront less than 5 miles from the stadium. “Any general contractor that was in need of something for welding or gases could come to us,” Falconer says.