Sharp Centre for Design, OCAD
October 1, 2005
By Canadian Consulting Engineer
The structural engineering design of the Sharp Centre for Design in downtown Toronto directly reflects the architects' vision to create a bold structural form....
The structural engineering design of the Sharp Centre for Design in downtown Toronto directly reflects the architects’ vision to create a bold structural form.
The structural engineers undertook the project out of a desire to do work that was unique and required a broader design approach than the projects they typically undertake. In the beginning the design team had no idea what the project would look like. Architect Will Alsop introduced the project to the firm by placing a model on a table, consisting of a black rectangular shape that appeared to be supported by a series of randomly oriented slender circular legs. He simply asked if the engineers could make it work. They studied the model for a few moments and said yes. Eighteen months later it was complete.
The project had been initiated when the 50-year old Ontario College of Art and Design (OCAD) in downtown Toronto decided it needed additional space to support its growing student population. Any building expansion was extremely limited by the surroundings. It was not structurally feasible to build vertically on top of the existing building, and the only open land available was a small 1,225 square metre parking lot south of the existing building.
Furthermore, the college’s neighbours, a condominium apartment complex on one side and the Ontario Art Gallery on another, had their own opinions as to the nature of any expansion. They were particularly concerned about how any new building might affect Grange Park adjacent to the college.
The design solution developed by the architects and engineers was the “tabletop,” a two-storey building 30 metres wide by 80 metres long, supported on slender steel columns high above the existing building. By floating the structure 28 metres above the street, the effect on the neighbours is surprisingly minimal. The new building allows them to have views to the park through the gap between the existing building and the floating structure. And they have improved pedestrian access to the park at the south end.
Because the tabletop structure was constructed above the existing building there was little disruption to the school activities. All the support for the new structure is outside the existing building, although almost half the tabletop sits above it.
The tabletop is designed as a rigid box form using transverse trusses, perimeter bracing and internal bracing. Two-storey trusses span both transversely and longitudinally but are detailed to allow easy access within the building. Classrooms and studios are located between the trusses and the corridors pass through the trusses. The vertical stair core acts as a primary vertical and lateral stabilizing element.
The most pronounced design feature is the sloping steel columns that allow the tabletop to “float” over the existing buildings. Architecturally the columns were intended to be located in a random fashion. Randomness could have been accommodated in the steel superstructure but the foundation conditions required a balanced arrangement to resist horizontal forces created by the sloping columns. The solution was to provide the columns in six pairs, each pair with its own axis of symmetry, while achieving the effect of randomness by having no two pairs aligned identically. In this fashion the lateral forces at the base of each column are counterbalanced by tie beams below grade.
The round columns are slender, only 914 millimetres in diameter and 28 metres long. To further enhance their slenderness, the ends are tapered down to 450 millimetres at both ends.
High-strength structural steel that is normally used in the petroleum industry was used for the support legs. The project also involved the first full-scale lateral load test on a caisson foundation to be done in Toronto in decades. It confirmed the actual foundation characteristics.
A highly integrated team design approach was used, with active participation by the owner, the architects, the steel fabricator and the builder.
A boost for morale
This is a building with a highly visible structural form that works. Over 3,000 tonnes of recyclable structural steel remain suspended 10 stories above the ground, providing over 4,000 square metres of studio and design space. The project has significantly enhanced the scale and scope of the teaching facilities at the college. The location, the exterior windows and the elevation of the building provide exceptional views of the city for students and staff.
The building has, in the words of the college president: “changed the way OCAD is doing what they do and what they plan on doing.” Since the project was completed in the spring of 2004, it has been highly publicized in print, radio and television media and has boosted morale at the college. The design has also raised the profile of architecture and design in Toronto and internationally.
For a design institute the building represents an appropriately strong and bold image. The structural design is highly visible as part of the architectural expression. People are drawn to the presence of the building and made to think about and respond to the building.
Name of project: Ontario College of Art & Design, Sharp Centre for Design, Toronto
Award-winning firms: Carruther & Wallace (Chris Andrews, P.Eng., Paul Sandford, P.Eng., Li Ming Tang, P.Eng., Sha Zhu) and MCW Consultants, Toronto.
Owner: Ontario College of Art & Design
Architects: Alsop Architects; Robbie Young + Wright Architects, in joint venture
Geotechnical consultant: Shaheen & Peakes
Other key players: PCL (general contractor), Walters (steel fabricators)
Suppliers: Dufferin Concrete (concrete)