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Milestone Day and Night

The iconic roof of the New Arena at Seattle Center is now fully supported by temporary steel - and three experts supply reasons to appreciate the feat

by Bob Condor / @NHLSeattle_ /

At 3:56 p.m. Tuesday afternoon, the historic roof of the New Arena at Seattle Center was fully supported by 72 temporary steel columns, plus cross-beams (one per pair of steel columns) and a unique steel reinforcement structure nicknamed the "kickstand." 

Tuesday night, in a perfect bit of planning, three experts walked on the PACCAR IMAX Theater stage at the Pacific Science Center to discuss just how the 44-million-pound roof is staying in position without the 20 original concrete y-columns and four gigantic buttresses. 

The first two speakers, Elliott Veazey, senior director at CAA Icon, a strategic management consulting firm, and Steve Hofstetter, managing principal at Thorton Tomasetti, an engineering consulting firm, hinted at the accomplishment. But both men deferred to third speaker Brent Leiter, project executive at lead construction partner Mortenson working with Oak View Group, the NHL Seattle partner that is building the arena. 

"We're jacked!" exclaimed Leiter with a huge smile, referring to temporary steel lifting. "The load [of the roof] is on the TRS, which is what we call the temporary roof support."

By Wednesday morning, superintendents were handing out "We're jacked" helmet stickers" at the ritual 7 a.m., five-minute "Bend and Stretch" session for workers. 

Like his fellow experts on the PacSci stage, Leiter deflected credit to a team of colleagues (in his case, from Mortenson). He asked a half-dozen or so to stand for applause from a sizable and engaged audience. For the record, Leiter's work on NHL Seattle's soon-to-be home arena is his third National Hockey League project, lining up with three National Football League stadiums and three Major League Baseball venues.  

Veazey noted the Seattle Center campus is a unique location for an urban sports and entertainment facility: "There will 360 degrees of park-like setting" because all loading docks, mechanical equipment and other "back of house" elements will all be built below grade and under the iconic roof. He pledged "thoughtfully designed" concession stands and a seating bowl that will positively "shape and enhance" the hockey fan experience.

Veazey didn't overlook music fans in describing the wonders that will materialize in 2020 and 2021 under the roof and below ground: "This arena will be loud for games yet clear [sound] for concerts."

While promising sustainability of the arena, Veazey assured the total demolition of the previous arena iterations of 1962 and 1995 would right an irregularity for hockey players and fans alike who were part of hockey games following the 1995 renovation. The ice rink will be "centered up" and provide a symmetrical seating bowl. 

Hofstetter satisfied the engineers on hand, citing American Society of Civil Engineers codes and standards for "design loads during construction." Those "historical" codes prove what is reliably supported and are especially critical to holding up the roof during events involving wind, gravity or seismic activity. 

"Because we have temporary steel columns and structures supporting the roof, we even have to allow that a heavy bulldozer or other machinery [accidentally] runs into a steel column," said Hofstetter. "You have to have redundancies to hold these loads."

The redundancies include the so-called kickstand, which is a lever of sorts that runs a steel column angled horizontally (kickstand-like slant) some 230 feet from the southern buttress (aka chevron) to the nearest stable load on Thomas Street. What's happening here is the designers, engineers and steel-erection construction crew are working together transfer the weight of the roof beam to the steel columns. 

In the case of the kickstand, it provides "lateral and gravity" support and helps the New Arena project attain earthquake code during all phases of construction and temporary support of the roof. During a New Arena tour earlier Tuesday, one on-site superintendent likened the kickstand to "holding up a stool if you removed one of four legs, so it doesn't tip over." 

Fun fact from Hofstetter, calculated by one of his Thornton Tomasetti colleagues he was sure to credit: The roof's weight is equally to the body weight of the entire population of Tacoma.

Teamwork was a running theme of the evening's entry in Oak View Group/PacSci's ongoing "Science of Sports & Entertainment" series. Hofstetter, Veazey and Leiter all emphasized the collaboration across their three companies, along with Oak View Group, Populous (architectural firm) and various subcontractors. 

Unlike some projects, designers, engineers and builders have worked together over the last 10 months to determine the right loads for temporary support plus identifying how to build a subterranean arena with all the temporary steel involved. For example, the gigantic buttresses/chevrons have a "lacing" of cross-beams so Mortenson and subcontractors can acutally build arena levels and floors in between what will be four steel laces. 

As usual, the audience questions were smart and prompted the crowd to lean forward for the answers. Sports commentator and the night's host, Ross Fletcher, supplied his usual stellar job of moderating the q-and-a. The first question was more of a thank-you from Seattleite happy for all of the "thoughtful engineering and design." Some audience members wanted to know the biggest advances in sports construction ("4-D computer modeling," said Leiter, "you know the three dimensions, the fourth is time; we can see where the project is going any week or month."

Another knowledgeable questioner inquired about when the temporary steel columns and other structures will be removed because permanent concrete will start being created in December. Leiter noted earlier"I just got my first drawing [Monday] night on how to remove the bracing."

"We will start pouring the foundation around Christmas," said Leiter. "Once we get the first y-column in place, which takes about two weeks, the first temporary steel comes out. It will probably take about six months total."

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