May 27, 2010

FEATURE | Steel

Ontario Olympic Pavilion wins CISC innovation award

DON PROCTER

correspondent

Canadian athletes collected a lot of medals at the 2010 Vancouver Olympic Games in February and now one of the structures which served as a backdrop to the event is heading to the podium.

The striking Ontario Olympic Pavilion (Ontario House) — designed, engineered and constructed at a lightning fast pace in less than ideal conditions for the games — is one of the winners of the Canadian Institute of Steel Construction’s steel innovation awards.

The structural steel design was tricky, especially considering that the contract called for the building (roughly 39 by 39 metres) to sit unanchored on an existing asphalt parking lot.

“We weren’t allowed to pierce the asphalt with anything – even a nail,” says Anthony Spick, project engineer, Blackwell Bowick Partnership Ltd., structural engineer.

The unusual restriction was due to environmental regulations concerning industrial waste buried below the site.

BLACKWELL BOWICK PARTNERSHIP LTD.

The Ontario Olympic Pavilion at night

“The problem it created was that the building could slide on the parking lot, tip over in a big wind, or dent/damage the asphalt from its weight,” says Spick.

To prevent catastrophic structural failure in an earthquake or wind storm, the building was engineered like a stiff box, rather than a table with legs (walls) that might buckle under the table top.

For the foundation, engineers designed shallow but wide (800 mm) reinforced concrete grade beams or footings around the perimeter to disperse the building’s weight on the asphalt lot.

To make the structure seismic resistant — a challenge because the building didn’t have enough “surface friction” to stop it from sliding on the lot — engineers designed it to slide without collapsing through “energy dissipation mechanisms,” explains Spick.

“The idea was that frictional energy losses resulting from the sliding would be a way of absorbing the seismic event.”

BLACKWELL BOWICK PARTNERSHIP LTD.

A detail of the facade

To meet that end, extensive bracing was required. and, each wall was engineered as “a large truss.

“We analyzed the movement of the building so the base of the walls could not kick out during back and forth motions. When the structure is moving in the same direction as the walls, everything is tied together but when it is moving in the other direction we wanted to make sure that the base didn’t slide more than four inches during a seismic event.”

The perimeter grade beams were also designed to act as horizontal beams to restrain the potential kick out, he notes. The structural engineer had never done this before.

Blackwell Bowick collaborated extensively with Benson Steel Limited, the steel supplier, on the detailing process. The building required 126 tonnes of steel and took 1,800 hours to draft on Tekla Structures (BIM) 3-D modeling software, says Bob Benson, co-manager of the project for Benson Steel.

BLACKWELL BOWICK PARTNERSHIP LTD.

Framing begins on the Ontario Olympic Pavilion

The extensive bracing specified was unusual, he points out. “Almost every bay in the roof and the walls was braced.” Roof bracing was engineered in various configurations rather than one uniform system because the roof elevation sloped in a ridge-like fashion by at least four feet from front to back.

The roof consists of prefabricated insulated metal panels bearing on 250 mm deep steel purlins which are carried by 610 mm deep roof girders spanning, respectively, in east-west and north-south directions.

To achieve a clean and uniform extension of the wall cladding to the parking lot, columns were installed off-centre in the footings. To speed up the construction process for the project, post-installed anchors were used for the steel columns instead of cast-in anchors, the conventional method.

Also to speed construction the building was bolted (not welded) together. Because the asphalt lot couldn’t take the weight of heavy equipment, materials were transported to site by cranes set up “outside of the building site.” KWH Constructors was retained by Benson Steel for the erection.

“The CNC machinery we have in our shop helped to speed of the process and accuracy of the manufacture of all the plates,” Benson points out.

Spick says that the fast-paced construction schedule meant the engineering details of the building had to be kept simple for erectors. “You could say we tried to use conventional methods to achieve the unconventional.”

The design was by Hariri Pontarini Architects; EllisDon was the general contractor in joint venture with Nussli Special Events (Canada) Ltd. Eric Karsh at Equilibrium Consulting in Vancouver acted as peer review structural engineer.

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