If buildings were contestants on TV make-over programs, the transformation of the Capital Health Centre entrance in downtown Edmonton from mousy to elegant would steal the show. When Capital Health purchased the 1970s office complex for use as its headquarters, the two concrete towers were connected by a dark, uninviting, one-storey entry.
“A new entry was needed to improve the level of the building, reflecting its status as the headquarters of one of the biggest employers in Alberta,” says Gene Dub, principal of Dub Architects. “The entry was low, hidden, and located in mid-block. We angled and extended the roofline to make it more prominent.” The structure also had to interface with the existing buildings and integrate with the underground parkade.
The new entry features a dramatic cantilevered steel and glass canopy that gives the impression of an open raft floating above the interior and exterior spaces. The design maintains the same footprint as the original structure but uses a single span, allowing for a vast column-free space. The steel frame also allows generous natural light to penetrate the atrium between the towers.
“We wanted an enclosure that would appear both light and substantial,” Dub says. “We chose steel because it gave us these qualities. The canopy is designed much like a suspension bridge, with few vertical supports.”
The structure consists of four primary beams supported by two primary mast columns in hollow structural steel. The primary beams are supported at mid-span by tensile rods that splay outward from the mast columns. Stepped skylights provide a transition between the steel slope and the existing precast buildings.
“The natural tendency of a sloped structure is to sag,” says Jason Collins, General Manager of Collins Industries Ltd., steel fabricators on the project. “The tensile rods were used to support the huge cantilevers and counter that.”
The project presented some construction challenges, including limited site access. “We had to sequence the work precisely,” Collins says. “There was no room to store materials on site. The components were prefabricated and pre-painted so we could just back up to the site and unload them as needed for assembly.”
Connecting the new steel structure with the existing concrete buildings was another challenge. The new structure is designed to be structurally independent of the existing buildings and is connected through slotted holes that allow for movement between structures. “We had to work closely with the glazing contractor to make sure we worked within the tolerance of the glazing,” Collins says.
All of the steel is exposed in the final construction, Collins says. “Because it was open for all to see, we used a special finishing involving a three-coat intense and durable paint system.”
“All in all, it was a very complex project, but the design made it simple to execute with proper planning. The simplicity of it is what makes it neat. It’s an elegant, beautiful structure.”
Owner: Alberta Health Services
Architect: Dub Architects
Structural Engineer: Protostatix Engineering Consultants Inc.
Project Manager / General Contractor: Aman Building Corporation
Fabricator: Collins Industries Ltd