The supporting cast isn’t supposed to steal the show, especially when the star attraction is the splendour of Canada’s Rockies.
But despite efforts to make it non-intrusive, the newly completed Glacier Skywalk observation deck, near the Columbia Icefields in Alberta’s Jasper National Park, seems destined for more than a mere walk-on part once tourists start arriving in May.
Simon Brown, of the lead design firm, Read Jones Christoffersen Consulting Engineers (RJC), and others involved with the design of the cantilevered glass walkway 150 metres above the Sunwapta Valley, began work in 2010. The chosen site is near a pull-off on the Jasper-Banff Icefields Parkway, 6 kilometres north of the existing Icefields Discovery Centre.
The client, Brewster Travel Canada (which also operates the site's visitor centre), wanted the skywalk to be safe, functional and cost-effective. The challenge lay in doing so without somehow encroaching upon the magnificent mountain scenery and the nearby Athabasca Glacier. Brown says that through the combined efforts of Sturgess Architects, the contractor PCL Construction Management and others, this objective has been achieved.
The design entailed some challenges – not least of which was the walkway’s glass floor, supported on a structural steel skeleton. The idea of a see-through walkway that allows visitors to look vertically down a precipice is not unique. It is employed on Arizona’s Grand Canyon Skywalk opened in 2007, for example. However, below that structure’s floor there are two large box girders, which limit the vertical sightline straight down into the canyon to one third of the walkway.
In contrast, along the entire length of the 30-metre parabolic deck of the Glacier Skyway, visitors will be able to look straight down. Brown explains that a draped cable, a critical structural element on the inside radius of the curved deck, facilitates this unobstructed “Discovery Vista.” He adds: “We wanted a framing system that kept the view as open as possible.”
The walkway's outermost point is 35 metres from the rock face. It is supported on cantilevered, trapezoidal box girders, secured onto footings rock-anchored some 30 metres into the mountain. With the cantilevered structure, Brown notes, “We had a very large reaction to deal with where it ties into the cliff. A precise understanding of the rock formation and quality was required.” Beyond the weathered surface material, the deeper rock generally was solid and where there was cracking, it was factored into the design.
The deck encounters vibration from two main sources – those walking on it and ambient winds. The first was addressed by tuned mass dampers in the walkway. Following wind-tunnel testing by RWDI of Guelph, the response to crosswinds in the valley was addressed using wind deflectors attached to the outer handrails. The glass floor is fashioned from laminated, tempered and heat-strengthened glass, designed by RJC’s Toronto office. Thinner non-structural glass, which is replaceable when scuffed, overlies the three structural layers (totalling 1 1/4 inches in thickness).
With continuous movement by people on the walkway, the varying load factor was another consideration – though, in fact, the structure will encounter its heaviest loads in the still of winter when it is snow-covered and no-one is aboard.
A 300-metre interpretive pathway leads from the visitor-arrival bus stop. The pathway integrates interactive programs that explain the surrounding geological, hydrological, glacial and biological features.
Even before echoing tourists’ oohs and awes this spring, the Skywalk has garnered international attention by receiving a Future Projects Category Award at the World Architectural Festival in Barcelona, Spain, in 2011.
The design team is: Read Jones Christoffersen ( lead design firm and structural engineers), Sturgess Architecture (architects), PCL Construction Management (project lead and general contractor), Thurber Engineering (geotechnical), Golder Associates (environmental), Urban Systems (civil), RWDI (wind) and SMP (electrical).
Glacier Skywalk in Alberta's Jasper National Park near the Athabascar Glacier. Photograph courtesy Read Jones Christoffersen.