June 26, 2008

HALCROW YOLLES

An existing parking garage at Toronto’s prime real estate corner offered challenges to builders as they expanded the site.

Steel lends flexibility to Toronto Life Square

PETER KENTER

correspondent

Toronto Life Square is 500,000 square feet of prime real estate located at the corner of Toronto’s Yonge and Dundas streets, one of the busiest areas of the city in terms of both vehicle and foot traffic. The complex houses 24 theatres, stores and restaurants.

The biggest catch in building it is that part of the project’s footprint was already occupied by a parking garage belonging to Ryerson University.

“Ours was a stand-alone structure and had to be kept separate from the parking building,” says Brent Lodge, an engineer with Halcrow Yolles, the company providing structural engineering services for the downtown project.

“We chose structural steel because of its light weight, high strength, versatility and fast construction time frame. With steel construction you can basically erect the framework without the requirement for any shoring, unlike the concrete system.”

With two levels of theatres overhanging the parking garage, steel provided a solution to minimize impact on the existing structure. “We used a steel truss system that required only six new columns to be inserted right through the centre of the parking garage, carefully located near that structure’s central wall,” says Lodge. “That allowed the parking facility to maintain the existing parking spots.”

At the same time, the design of the theatres required unobstructed sight lines, so a structural steel grid was laid out along the theatre walls.

By placing unique support structures through the garage, the builders were able to add two dozen restaurants, shops and movie theatres.

A complex system of composite steel beams, transfer trusses, hangers and four-storey columns achieved the effect of opening up the theatres while maintaining a lightweight structure. “We had transfer trusses supporting trusses, but we were able to hide all of the columns inside the walls of the theatres of various sizes,” says Lodge. The largest truss weighed in at 60 tonnes.

The use of structural steel also allowed for a careful sequencing of construction by general contractor PCL Constructors Canada Inc., with activity moving slowly northward from Dundas Street, while eliminating the need for temporary shoring of the garage during construction.

“Good old PCL carefully timed the lane closures on Victoria Street, parallel to Yonge,” says Lodge. “That minimized the blocking of access at two important locations for people in the area — the front of the garage and the entrance to Tim Hortons.”

Steel construction also allowed for a top-down construction sequence whereby trusses were located at roof level instead of directly above the parking garage.

Steel, again, was used to create a structure to house 20,000 square feet of outdoor signage, including Canada’s largest high-definition video board. Steel stubs at floor level projected from the exterior cladding to provide an anchor for sign boxes.

The design provided versatility to accommodate future tenants as well.

“Structural steel frame is conducive to alterations in interior design, so as tenants took possession of their spaces, we were easily able to add new stairs, plumbing cores and large mechanical restaurant units,” says Lodge.

“We were able to build flexibility into the project with steel.”

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