Vik Pahwa

With the surging demand for office space in downtown Toronto, it was inevitable that developers would begin eyeing the city’s historical stock. Local firm Sweeny &Co Architects literally went above and beyond to increase the floor area ratio of a site in one such neighborhood.

Sweeny &Co Architects Queen Richmond Centre West
Jimmy Wu Queen Richmond Centre West under construction

In 2007, Sweeny &Co saw an opportunity to preserve two adjacent structures built with traditional brick-and-beam construction at the intersection of Peter Street and Richmond Street West. Principal Dermot Sweeny and his team proposed constructing a new 11-story office building on the site—but starting 80 feet in the air. The structure would clear the existing four- and five-story buildings in their entirety, with the exception of an expansive atrium at grade and transitions between the new and old buildings.

The buildings' owner, Allied Properties REIT, agreed. All that was left was how to execute the plan. Initially, the architects considered using box trusses to hold up the proposed 302,000-square-foot Queen Richmond Centre West above the atrium. But the approach would have required hundreds of visually messy cross-bracing members, says principal John Gillanders.

Instead, the architects teamed with local firm Stephenson Engineering to design and develop three mega supports. Dubbed delta frames, the 80-foot-tall frames consist of four upper and four lower legs that converge 40 feet in the air, like giant toy jacks.

Sweeny &Co Architects Queen Richmond Centre West
Sweeny &Co Architects Axonometric section view of the BIM model

Welding the legs to plates at the frames’ midpoints would not be enough to stop them from splaying. As a result, the team decided to secure the legs with more elegant—and much stronger—custom nodes, designed by local firm Cast Connex.

The team used 3D modeling and rapid prototyping to finalize the node’s shape and integration, while eliminating the need for shear studs and reinforcing bars in the node. “We kept working at it backward and forward until everyone believed it was not only beautiful, but that it would work and was manufacturable,” Sweeny says.

Sweeny &Co Queen Richmond Centre West
Node Design Builder/Sweeny &Co Architects The team experimented with different node shapes.

Cast Connex cast the steel nodes in chemically bound sand molds, each of which comprise 22 pieces that lock into a 3D puzzle. Based on fluid-dynamics analyses, the fabricator determined they had to pour nearly 50,000 pounds of molten steel into the molds in less than 60 seconds to achieve uniform nodes. The sand molds disintegrated during the manufacturing process, but the tooling to make future molds remains.

Sweeny &Co Architects Queen Richmond Centre West
Node Design Builder Solidification analysis informed the internal shaping of the nodes and the location of the internal reinforcement. Computational fluid dynamics helped to ensure the laminar flow of molten steel into the mold to minimize air bubbles.
Sweeny &Co Architects Queen Richmond Centre West
Node Design Builder The nodes were cast in sand molds that were destroyed to release the node. However, the tooling can be reused again to make additional molds.

Hamilton, Ontario–based steel fabricator Walters Group used 2-inch-thick rolled steel to form the delta frames’ 40-inch-diameter legs. The legs and nodes were then welded together on site, and the frame was pressure-filled with concrete from the bottom up. Each delta frame can support nearly 18 million pounds—the equivalent of approximately 400 tractor-trailers.
Juror Joyce Hwang said, “This was a well-articulated structural innovation—the way the frames soar above and hold this large mass.” Although juror Steven Rainville thought that the team had other options to achieve its objective, he appreciated its efforts to perfect the frames’ look and behavior. “It’s using methodologies that are progressive in how they resolve the structural solution,” he said. “But the result of it is also quite nice, architecturally.”

Sweeny &Co Architects Queen Richmond Centre West
Sweeny &Co Architects Completed delta frame circa June 2014
Sweeny &Co Architects Queen Richmond Centre West
Sweeny &Co Architects View of the atrium under construction
Sweeny &Co Architects Queen Richmond Centre West
Node Design Builder The 11-story office building clears two historical buildings in their entirety.
Sweeny &Co Architects Queen Richmond Centre West
Sweeny &Co Architects Building exterior circa December 2014

See all the 2015 R+D Award winners here.

Project Credits

Project: Queen Richmond Centre West, Toronto
Client: Allied Properties REIT
Design Firm: Sweeny &Co Architects, Toronto
Structural Engineer: Stephenson Engineering
Fabricators: Cast Connex, Walters Group
Construction Management: Eastern Construction
Electrical Engineer and LIghting Designer: Mulvey & Banani International
Mechanical Engineer: The Mitchell Partnership
Funding: Allied Properties REIT
Special Thanks: Michael Emory, Hugh Clark, John Stephenson, Jeffrey Stephenson, Carlos de Oliveira, Frank DeCaria, Renato Tacconelli, Tim Verhey, and all the skilled people who made this project a reality.

Size: 302,000 square feet