When the University of Manitoba required a new student residence that would be closely integrated with existing facilities, the only solution was to go over and up – above the Pembina Hall service centre. A firm student move-in date added to the challenge: design, tendering, construction and certification of the $40,000,000 facility had to be completed in less than 30 months. Location of the structure above a busy occupied building meant essentially no lay-down area for the contractor to work from, as well as unique construction safety issues.
The design concept called for two slender 14-storey towers at each end of Pembina Hall with sufficient strength to support a 10-storey residence block with 36 rooms on each level and a span of 50 metres over the existing structure. The new building would be very slender, rising 57.2 metres above grade, extending almost 80 metres east to west and only 13.3 metres north to south. Given the long span direction, steel was the only solution. The design incorporates four parallel, full-storey-depth, 50-metre-long trusses stacked 10 times.
“The biggest challenge was that this design – a multi-truss span over an existing structure – was really unique and had never been done before,” says Jean-François Leclerc, Vice President Western Division with Supermetal Structures Inc. “We had to think out of the box on how to fabricate and erect [the building]. Deflection was a huge issue. Making sure [the trusses] fit on site. These were the concerns..”
The schedule was tight: one floor per week. Supermetal duplicated the field situation in their shop, making sure that the truss scheduled for the following week fit on the one that came before it in the shop. “We always had three [trusses] in the shop at a time,” Leclerc says.
Each truss had a different camber – largest positive camber on the bottom truss.
“The general contractor was pouring on the lower floors while we were erecting the upper floors gradually reducing the camber. Once we finished stacking [the trusses], the camber was zero! Quite the feat.” added Leclerc.
Lift of the first two interior trusses – which were assembled together as the base for the rest of the structure – was critical. One of the largest steel trusses ever installed in Manitoba, it measured 50 metres long, 5.2 metres high and 2.4 metres wide. It took crews eight days to assemble the 55-tonne truss on the ground and two 300-tonne cranes simultaneously navigating over one building and beside the other to put it into place.
The exterior trusses are fully exposed, creating a dramatic design that provides each room with a “diagonal view”. The minimalist architectural look also required careful attention to the form, fit and finish of the diagonals and connections.
Owner: University of Manitoba
Architect: Raymond S.C. Wan Architect
Structural Engineer: Crosier Kilgour Partners Ltd.
Project Manager / General Contractor: Bird Construction
Fabricator: Supermetal Structures
Detailer: Techdess Inc.
Erector: Supermetal Construction Inc.