The Institution of Structural Engineers released its shortlist for the prestigious international Structural Awards recently and Banff was included on that list.
The international organization has nominated the footbridge over the Bow River from Muskrat Street to Glen Avenue, completed last summer, in the category of pedestrian bridge.
Adrian Field, Town of Banff manager of engineering, said he was thrilled to find out about the nomination, as it is a testament of the hard work and dedication of the whole project team, including the main contractor, StructureCraft.
“StructureCraft have been an excellent company to work with and they have produced an outstanding result here,” Field said. “The quality of the structure was always the foremost consideration in StructureCraft and our view when we conceived this.”
He said the central span of the bridge, at 80 metres, is one of the longest, if not the longest, woodspan bridge in the world and is made using natural materials – making it quite an achievement.
“To achieve that with a slender design and using glulam beams in the way that we have, I’m going to say it is unprecedented in the world of engineering,” Field added.
StructureCraft president Gerry Epp said the Institution of Structural Engineers is the premier organization recognized globally for structural engineers.
Epp was involved closely in the design of the bridge, which took a lot of time and care because of the challenge of designing a pedestrian bridge in the national park.
“It was a wonderful collaboration and a great relationship with the owner and we had to stickhandle through very many things together; it was a great experience for all of us,” he said. “There were huge challenges. There is the fact it is in Canada’s first national park, with huge environmental constraints because we didn’t want to in any way do harm to the beautiful Bow River.”
It was the effort to keep the impact on the waterway at a minimum that resulted in the large span being necessary in the middle of the 113-metre long bridge. With the supports for the bridge being as close to the banks as possible, Epp said the middle section resulted in the 80-metre span and the challenging design.
“We ended up optimizing all of that so the piers are essentially out of the river for most of the year and the river flows in-between,” he said. “It also has to do with the construction of it, because when you are putting the piers in the river you have to drill these piles and that has an environmental effect as well.”
Other challenges, he said, included ensuring the bridge met up with the trail on each side without having to use long ramps and ensuring it meets the 100-year-flood event standard it had to be built to. With last year’s flood being a river flow event of one in one 100, it met those requirements, Epp said.
The development of the $6.8 million bridge also included relocation of utility infrastructure – pipes carrying sanitary waste from the north side of town to the wastewater treatment plant and has been a controversial project in the Banff community, with residents in the neighbourhood adjacent to the bridge on Muskrat Street.
Administration recommended council approve the overall project because by combining the two projects the Town saved $2 million.
“The amount of care and attention to detail that went into the structure was huge. We spent hours and hours and hours deliberating over almost every detail on the bridge and that was because we wanted to build a lasting product and a structure that is befitting of its location in Banff and Canada’s foremost national park,” Field said.
A 1914 report by celebrated landscape architect and planner Thomas Mawson included five pedestrian bridges in Banff, and architect and urban planner H. Peter Oberlander proposed a bridge in the same location in 1961.
In their comments, the Structure Awards website noted its slender timber form was made possible by controlling vibrations with a pair of unique tuned mass dampers that address both walking and jogging frequencies. The thickness of the cables used to suspend the two dampers underneath are aligned to the frequency of the bridge, basically interfering with its natural tendency to vibrate.
“This bridge pushes the boundaries for timber footbridges in a dramatic manner,” was a judge’s comment on the award website. “It responds elegantly and efficiently to its context and delivered ‘everything and more’ than the client expected, coming in under his budget and ahead of schedule. It responded sensitively to the constraints and aspirations for the site to the delight of the town it serves, with sustainability objectives fully met respecting what is a beautiful natural setting.”
Also nominated in the category are the L’Argens Bridge in France and the Muregeya Bridge in Rutsiro, Rwanda built by Bridges to Prosperity Inc.
The awards will be announced Nov. 14 at a ceremony in London, England.
