Whistler’s SkyBridge and Cliffwalk takes BIM to a new altitude
When the job site is on a mountaintop a mile high, the need for precision is even higher.
Collaboration and precision are vitally important in any building project. But they take on even more importance when the job site is at 2100 meters (~1.3 miles) above sea level, and so inaccessible that the only heavy equipment used is a heavy-lift helicopter.
That was the challenge facing Canada’s Apex Structural Design, Ltd., as they set about planning and building British Columbia’s SkyBridge at the Whistler Blackcomb ski resort. It’s thought to be the highest pedestrian bridge in North America. The company also built a neighboring structure, the Cliffwalk, a cantilevered observation deck offering breathtaking views of the surrounding mountainscape.
BIM keeps the project team in alignment
Just how important was it that everyone involved in this endeavor was completely aligned throughout the process of building and assembling this demanding project? Take the installation of the final beam in the Cliffwalk as just one example.
With two beams extending over the mountainside, this critical last piece of the structure needed to line up perfectly so it could be bolted into place with anchor nuts. It had to happen in 15 minutes with a Kaman K-Max dual-rotor hoisting it into place, otherwise, the helicopter would have to refuel and try again. This level of necessary coordination across teams is tailor-made for BIM.
“The project team consisted of the owner, contractor, lead design firm, suspension bridge specialist, geotechnical engineer, environmental loading expert, steel fabricator and steel detailer," said Jason Peck, Vice President of Apex Structural Design, Ltd.
“Design-build meetings were hosted with Tekla Structures for all the project team members to visualize the unique structure and it was a very important tool in the overall success of the project.”
The complex design created a challenging task that was made far simpler with the use of Tekla Structures BIM technology. According to Peck, “Tekla was invaluable in quickly providing the project team with alternate connection methods. The compound sloping geometry of the A-frames at each end of the SkyBridge was made possible with Tekla.”
Extreme environments require extreme designs
The Cliffwalk cantilever also required complex geometry due to the curved nature and camber requirements. Lastly, the guardrail system was of the utmost importance for both safety and aesthetics.
Experienced in managing projects in extreme locations, Apex Structural Design understands that successfully managing the extraordinary challenges of such unconventional alpine job sites requires meticulous planning well before construction begins.
“The biggest consideration was the weather in an extreme alpine environment. The design accounted for temperatures as low as -43°C,” explains Peck. “The original autumn installation schedule had to be revised until late spring, as the project could not be rushed from an engineering perspective. The snow was still falling when the first steel cable supports on each end were installed in May. But in the end the SkyBridge opened to the public in the summer of 2018 as planned.”
Engineering to meet unusual challenges
Several challenges unique to this project also needed to be addressed to ensure success. First, each of the deck modules are designed in such a way that they can be removed during the off-season for maintenance. In addition, environmental extremes particular to the alpine climate included accounting for up to 2.25 meters of snow load, 0.2 meters (8 inches) of ice load, and wind speeds upward of 190 km/h – or nearly the equivalent of a category 4 hurricane.
The SkyBridge spans 130 meters from peak to peak across the Whistler Valley, with 101 deck modules secured to four cables. The cables are supported by 14 rock anchors, each driven between six and eight meters into the bedrock. The Cliffwalk is supported with four steel beams that are secured in place by six vertical rock anchors.
Both structures feature open grate steel decking to not only better handle snow load and wind, but to provide guests with a dramatic view to the ground far below.
In recounting the challenges of the project, Peck notes that “Special considerations were made for the 101 deck modules to allow removal for the maintenance in the off-season. There was uncertainty regarding the hazards and effectiveness of snow work during the winter, and we did not want to disturb the skiers and snowboarders descending underneath the SkyBridge.”
Recounting how he, his team and the entire project team succeeded in completing this unique project, Peck describes the feeling of a job well done: “The team at Apex Structural Design pride ourselves on these types of specialty projects, and this one being so close to home for many of us made it extra special. For us, winning the 2019 Tekla North America BIM Awards’ Infrastructure category was an added bonus.”
Watch the interview at Ministry of Bridges: Whistler Sky Bridge - Touching the Sky in Canada
Interested in bridges? Randsilva bridge in Norway is the world’s longest bridge to be designed and constructed using only Bridge Information Modeling, and no traditional paper drawings.