October 8, 2012

Designing for wind remains a challenge

Construction Corner | Korky Koroluk

Alberta has always been a windy place. It's no accident that there are huge wind farms west of Lethbridge, facing the winds as they come a-whooping over the Crowsnest Pass. But, while wind can spin windmills, it can also cause damage.

There have been times lately when two fairly strong storm systems combined to form one big storm. Calgary has been the victim of such combinations a few times in the last two or three years, and the results haven’t been pretty.

In one case a girl was killed by falling debris.

And, last November, the city was swept by two such storms in two days. Then, earlier this month, the city was hit again.

The quiet little town of Hanna in east-central Alberta declared a local emergency when high winds tore roofs off buildings and uprooted trees.

I’m not talking about tornadoes here. These were straight-line blows, similar to the one that swept the United States from Chicago to the Appalachian Mountains a couple of months ago.

All of these storms brought hurricane-force winds with them. They seem to be happening more often as our climate changes.

This year is the 20th anniversary of Hurricane Andrew, the Category 5 hurricane that devastated south Florida and led to stringent provisions in the state building code that are intended to limit wind damage.

Now Florida International University has developed a 15-foot-tall “Wall of Wind,” which has been nicknamed WOW. It’s made up of 12 giant fans which together can recreate the Category 5 winds that Andrew carried.

Those winds hit 157 miles an hour.

The object in building WOW is to see if lowrise structures and building materials can withstand Andrew-like winds. Manufacturers have been bringing in products for testing—solar panels from one, roofing tiles and a new adhesive foam from another.

The products are installed on the roof of a small building anchored to a rotating turntable in front of WOW.

The turntable lets researchers rotate the structure and expose the products to wind from all directions.

When the fans are powered up, the winds they create climb until the product either passes or fails.

However, there are glitches.

In one recent test, the fans were generating winds of 140 mph.

The tiles being tested were holding firm, but then the whole building broke loose from the turntable and was sent flying into a nearby field.

Hurricanes or other big storms occasionally hit the Canadian East coast, but never with the kinds of winds WOW can generate.

Really bad windstorms have become common enough that Canadians are taking notice.

In Calgary’s case, that meant the city called in Rowan Williams Davies and Irwin, Inc., of Guelph, Ont. The firm — usually called simply RWDI — is an internationally known consultant in wind engineering.

The firm has worked all over the world, and has done the wind engineering on many tall buildings. They did the wind work on the Burj Khalifa, in Dubai, presently the world’s tallest building.

They have also done a large handful of other landmark towers in the Mideast and Far East, including the Pearl River Tower in China and Taipei 101 in Taipei.

So, RWDI has developed a system that warns of potential damaging winds as much as 48 hours in advance, based on how the wind is expected to affect specific building locations. Thanks to the warning, the flying glass and other airborne debris in Calgary occurred in largely deserted streets and injuries were few and mostly minor.

Amid all the talk going on about the state of Canadian infrastructure, we should be asking our local officials if they’ve spoken with the folks in Calgary.

Alberta might be more prone to high winds than many places, but that doesn’t mean the rest of us are immune.

Korky Koroluk is a regular freelance contributor to the Journal of Commerce. Send comments or questions to editor@journalofcommerce.com.

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