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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

A Bridge to the Future

By Kevin Wilcox

Designers and engineers develop an innovative solution to cross a busy street in downtown Edmonton as part of a new hockey arena that anchors a major revitalization effort.

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The Winter Garden serves as a lobby, a performance space, and a bridge over the highway that links the arena to the community. Courtesy ICE District JV

March 15, 2016—The sleek, new, glass-and-stainless-steel arena taking shape in downtown Edmonton, Alberta, Canada—home to the Edmonton Oilers hockey team for the next 35 years—is the stunning centerpiece of a revitalization effort known as the ICE District. There is already $2.7 billion of private-sector development under way in the city's urban core near the arena, including 1.3 million sq ft of new office space, 1,000-plus residential units, 300,000 sq ft of retail space, and a new J.W. Marriott Hotel.

"The downtown used to be a place where people came to hang out and have a good time—work, play, everything. That started to go away, and it just became a place to work," says Rick Daviss the executive director of the Edmonton Arena District for the City of Edmonton, who cites the effects of suburbanization as a chief cause. "The idea was, how do we bring people back downtown, not just to work? You need to serve the population with amenities," he says. "An arena, done right, in downtown, can do great things for a city."

The arena is being developed in a public-private partnership between the City of Edmonton and the Katz Group of Companies, a privately held corporation headquartered in Edmonton that develops real estate and that owns the Oilers, as well as a chain of pharmacies, health care clinics, and entertainment venues.

"In order to make the downtown competitive, we felt that we had to make [it] a more attractive place to live, work, and play. We had to create great sports and cultural infrastructure in the downtown [because] those things have such an impact on the quality of life," says Bob Black, the executive vice president of the Katz Group.

"From the beginning we had an inspiration to create a truly great arena. We felt that for the arena to be a critical mass in driving a broader private-sector revitalization, [it] had to be a great piece of architecture," Black says. "We were intent on finding someone who could think outside the box and produce a genuinely significant piece of architecture."

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The facade of the arena, which anchors a larger revitalization effort in Edmonton’s urban core, is made of sleek, unpainted stainless steel. Courtesy of ICE District JV

After reviewing concepts from many top sports arena architecture firms, the development team chose HOK, with offices and a Sports + Recreation + Entertainment practice in Kansas City, Missouri. The team assembled by HOK includes structural engineering by a partnership of Thornton Tomasetti, headquartered in New York City, and the Edmonton office of DIALOG.

"We ended up with a team that I think is a compelling combination of substantial expertise from the United States in arena construction [and] great local companies with substantial expertise in local construction," Black says. "There are some unique factors [related to] constructing in Edmonton—one of the northernmost cities in North America."

The design that HOK developed features dynamic flowing lines, evocative of snow drifts and the dynamism of hockey. The development team was able to assemble a 26-acre parcel for the project, displacing just four small buildings—a considerable feat in an urban core. Much of the site is a former railyard immediately north of 104 th Avenue, just outside the traditional demarcation point for downtown.

According to Ryan Gedney, a vice president and senior project designer for HOK,  "104th Avenue is a very distinct divider between our site and the rest of downtown as it currently exists. The challenge was how do you connect the venue to the future [ICE District] in a way that is meaningful?"

That connection was vital. A pedestrian movement analysis indicated that somewhere between 70 to 75 percent of arena goers would arrive from the south. "It's a busy street. Nobody was really comfortable with shutting down traffic on 104th Avenue to take people across the street," says George Heinlein, AIA, the principal in charge of the project for HOK. "That was when we agreed that everybody would come up and over 104th Avenue."

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The Winter Garden bridge gives the visual impression that a snow drift has blown off the mass of the arena and across the busy street. Courtesy of ICE District JV

"From our perspective, the opportunity was how might you solve that very practical need in a way that is good for the arena identity, architecturally," Gedney says. The idea of a bridge came up very early in the process but what evolved from those discussions is the Winter Garden, a wide, elevated pedestrian crossing that is meant to give the visual impression that a snow drift has blown off the mass of the arena and across the busy street.

"The beauty of [the design that] Ryan came up with is that it is as if the entire arena bridged across the street," Heinlein says. "It is one unique form that linked the north side of that street to the south." The Winter Garden thus becomes an iconic grand entrance at the south face of the arena, serving not only as a bridge but also as an exterior lobby and an event space in its own right.

Although the Winter Garden is one of the most visible parts of the project, the engineering team was able to design it so that the expansion joints required to relieve thermal stresses in its 200 m long spans are invisible, according to Jesse Chrismer, P.E., LEED AP, an associate of Thornton Tomasetti, who provided written answers to questions posed by Civil Engineering online.

"With this extreme length, and the location of our lateral cores, it was necessary to allow movement," Chrismer said. "We ended up with a bridge that lands on a podium on the south side of the street, which rigidly supports it vertically and laterally in the east-west direction but allows translation in the north-south direction. The expansion joints were then completely concealed under the bridge deck at the interface with this podium so that there are no joints in the facade itself.

"The roof of the bridge rises up to 27 meters above the bridge deck below," Chrismer added. "The roof is supported on major north-south running trusses on the perimeters. The west truss runs straight, departing from the curved facade, while the east truss is built integrally into the facade wall's support framing. The facade itself is supported by wind girts that are hung from the roof framing and allowed to slide vertically at the deck."

The arena itself is supported on a pile foundation, many bearing upon an upper clay till deposit, but some on lower, cohesive layers based on foundation geometry and differential deflection concerns, Chrismer said. The structural system is a concrete flat plate at the event level and below grade parking levels with a steel superstructure for the above grade framing.

Even so, the greatest engineering challenge of the project was the roof of the main arena, which is supported by two primary queen-post trusses spanning in the short direction across the ice, Chrismer said. The top chords are made of box trusses to help with erection stability. "Other major trusses span from an interior column ring to these trusses, following the radius of the roof on the ends," he explained. "Between the main trusses we utilized paired joists to minimize weight and enhance erection speed."

The facade of the arena is unpainted stainless steel cladding, chosen both because it is exceptionally durable and it imparts a sleek, dynamic aesthetic that fits with the architectural goals. "It is neutral and sleek, … reflecting the different qualities of the light at all times of day," Gedney says. "It takes on many different characteristics depending on what is going on around it."

The arena is scheduled to open in the fall; the Oilers have signed a 35-year lease on the facility, which Black and Daviss agreed made the facility a win-win proposition for the public-private partnership and is generating excitement among city residents. "It has already become apparent that the arena will be a genuinely great facility," Black says. "It's one that we believe will set new paradigms in many regards." 

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