When M&G Steel Ltd. was awarded a contract that included the design of a 58-foot-long by 36-foot wide elliptical steel ring supported on a 12-foot-long structural frame of sloping diagonal steel leg braces for a large skylight inside a downtown Toronto retail mall, the company knew it had a “challenging and exciting job” ahead of it.
The steel structure and tubular ring supports a large skylight at a two-level interior courtyard known as Oval Square in Hazelton Lanes Shopping Centre in Yorkville.
That ring, which M&G’s Brian Thompson describes as looking like a "flying saucer" you might associate with sci-fi flicks from the 1950s, was tricky to design, fabricate and install.
Using BIM, M&G technicians designed the steel framework and ring as specified to be positioned at an angle in the courtyard.
"Today’s 3D modelling software made the complicated geometry less cumbersome than the historical ways of manual geometry calculations," says Thompson, the company’s vice-president and project manager.
But it wasn’t just the design that was a challenge. Fabrication was no piece of cake, either.
"We had to provide the tube roller (Durose Manufacturing of Guelph) with 12, three quarter-inch pipes to roll to various points to meet the geometry of the elliptical ring," says Thompson.
Getting the steel and equipment on site had its share of scheduling complexities. Neighbourhood residents and businesses within the mall had to be accommodated so there were stringent restrictions on times and days for materials and equipment delivery.
Getting to the mall involved going through laneways. In addition, the site had no laydown space for materials or equipment, so deliveries were scheduled on a just in time basis.
To get materials to the courtyard construction site within the mall, general contractor Traugott Building Contractors Inc. cut an 8×10-foot hole in the mall’s exterior brick wall. This was just big enough to fit materials, but small enough not to undermine the mall wall, says Thompson.
"Old retail space had to be demolished to allow us runway access for materials on buggies from the outside loading dock to the Oval Square," he said.
Some of the elliptical steel elements had to be cut down to fit through the hole and the assembly crane was disassembled before transport. The crane was set up on thick steel plates in four positions for erection of the steel framework.
"We had to do a lot of preparatory work to pull this work off," says Thompson.
Another challenge was the tight schedule — only six weeks because the mall’s interior was open to the elements until the skylight was installed. Novum Structures of Chicago supplied the skylight. About 10 to12 ironworkers erected the steel frame, employed by Stampa Steel Erectors, a sub to M&G.
Thompson says the assembly went smoothly with only one major change specified to wall plates or brackets.
"It caused a bit of a complicated change on the wall," he explains.
The project manager has seen steel designs become more complex since he got into the business in the 1980s, but steady improvements in computer design software have helped steel companies like M&G meet new challenges like Oval Square. "Ten years ago we would have needed a lot more lead time to meet this delivery schedule."
Other work remaining at Hazelton for M&G includes exterior steel for the Avenue Road facade, a mechanical penthouse and steel for glass and curtainwall systems for new offices in the mall including decking work by Vixman Construction.
The contract supplies about 420 tons of steel — small by M&G’s contract standards but big in complexity.
"The design team of Kasian Architects, Entuitive (structural engineers) and Dan Flaminio’s Traugott Construction all co-operatively worked as a team to allow this project to flow smoothly," says Thompson.
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