Parking Structure at Fairview Mall- Don Mills Subway Station, Toronto

Earth Tech Canada Inc.

Category: Buildings and Structures

The terminal station on the Toronto Transit Commission’s new Sheppard Subway line is at the intersection of Don Mills Road with Sheppard Avenue. Earth Tech Canada is prime consultant providing engineering services for both the new passenger train station still under construction and the 1,200-space parking structure that was completed last November. The four-level parking structure serves both mall shoppers and future subway commuters, and is jointly owned by the transit commission and Cadillac Fairview.

Safe and sound

The engineers used a traditional building system in an innovative way in order to extend the structure’s life and durability, and to resolve difficult constraints with the site layout. The primary structural system consists of a 17-metre x 17-metre post-tensioned folded flat slab. The engineers do not know of any other project that has achieved such long spans in this way. They developed their own models and spreadsheets to analyze and design for the configuration.

Another key aspect was the use of high-performance concrete. Earth Tech specified a state-of-the-art concrete mix to provide a design strength of 45 MPa (6500 psi). This material will minimize cracking and decrease future maintenance costs. The specifications included a defined combination of Portland Cement, ground granulated blast furnace slag cement, silica fume, air entrainment and high rate superplasticizer. They also stipulated a minimum total cementitious content and maximum water cement ratio.

A big concern of both clients was that the facility would be secure and feel safe for the users. The design addressed these issues in several ways. The long span structure meant there were few columns to cause visual obstructions, and 50 per cent of the perimeter could be open, thus making it more inviting and safe. The structure is well lit using high intensity white light. Stairwells and elevator landings have glazed walls, are equipped with surveillance cameras and are positioned close to the mall and subway entrances.

Aesthetically, the structure echoes elements of the mall’s architecture, using brick and precast concrete balustrades and facades. It blends into the surroundings and yet is recognizable as a parking facility.

Construction scheduling was complex in order to minimize disruption to the mall’s operations and maintain the number of parking spaces available to shoppers. The engineers prepared detailed construction staging drawings month by month, showing access routes and temporary facilities erected to maintain pedestrian and vehicular circulation routes.

The engineers also had to detail for an “upside down” construction sequence. The 15,000-m2 bus terminal over which the parking structure was superpositioned was only partly excavated when the first phase of the parking structure was built in November 1998. The columns common to both facilities were designed to allow double and triple floor free heights in the first stage, enabling the bus terminal roof to be built into these supports later.

The design and detailing also had to anticipate that alternating light and heavy columns would have differential settlement over the time of the staged construction approach. The engineers required special monitoring at these points, and jacks were built into the column bearings to keep the bus terminal’s roof supports at a constant elevation while the columns were settling.CCE

Project name: Toronto Transit Commission/

Cadillac Fairview Joint Use Parking Facility

Award winner: Earth Tech Canada Inc., Toronto

(prime consultant)

Project team: Doug Whitney, P.Eng, Jay Climenhaga, P.Eng., Dave Lampman, P.Eng., Ian Sherman, William Priestner, P.Eng., James Dixon, P.Eng.

Client/owner: Toronto Transit Commission/ Charles Wheeler, Carlos Laborde-Basto, P.Eng. and Cadillac Fairview/John Doyle, P.Eng.

Other key players: Otter Brown Engineering (construction scheduling), Golder Associates, Thurber Engineering (geotechnical), Cole Sherman URS/Scott Thorburn, P.Eng. (utilities), Richard Stevens Architects, Hanscombe Consultants (costing)

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Parking Structure at Fairview Mall-Don Mills Subway Station