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Last Updated: Monday, 26 June 2006, 07:17 GMT 08:17 UK
Hurricane machine to flatten home
By Jonathan Fildes
Science and technology reporter, BBC News

A house destroyed by Hurricane Katrina
Category five hurricanes are the most destructive storms
A family home in Canada will be deliberately destroyed by scientists to understand how buildings react to hurricane force winds.

The two-storey structure will face the equivalent of 200mph (320km/h) gusts to simulate a category five storm, like Hurricane Katrina at its peak.

The tempest will be created by a new computer-controlled simulator.

The University of Western Ontario team hopes its work will inform building plans in areas such as New Orleans.

"We're hoping our work here will have an impact on future building codes and public policy with regards to the safe construction of homes," said Professor Greg Kopp, one of the members of the team.

Destructive force

The damage caused by hurricanes to housing, other property and services is huge.

Last year, hurricanes Wilma, Rita and Katrina alone cost the global insurance industry $60bn (34bn).

It's the equivalent of trying to co-ordinate 100 people dancing on a trampoline at the same time
Eric Wilkinson, Cambridge Consultants
In addition, poorly constructed buildings often result in significant loss of life.

In 1998, Hurricane Mitch led to at least 11,000 deaths when it came ashore in Central America.

As a result, there is great interest in making buildings safer and more resilient to the damaging effects of extreme weather.

Close attention

The new tests will be carried out at a hangar near London International Airport in Ontario, known as the "three little pigs" facility, after the children's story.

Construction workers have built a two-storey, four-bedroom family home in the hangar for the purposes of the test.

The test hangar with the house inside
Tests on the full-size house will begin in autumn

To make sure that the building is structurally sound before they start the demolition, the researchers have gone over the house in fine detail.

"We know where every single nail is in the house," said Professor Kopp.

"Nails often miss trusses. If a nail hits the edge of a truss its holding strength is much less than if it hits the middle, so we had to document them all."

If the house does not conform to current building standards, the researchers cannot make recommendations to change them based on their experiments.

Giant machine

To test the strength of the building, the team is fitting it with an advanced wind simulator.

The scientists are unable to use a standard wind tunnel. To do so - to simulate real hurricane conditions around a structure as large as a house - would require a tunnel with a cross section 20 times the size of the building.

Satellite image of Hurricane Alberto

"It's just too expensive," said Professor Kopp.

Instead, the researchers asked technology company Cambridge Consultants to come up with a system that would replicate the effects of a hurricane without the need for a tunnel.

"That's the biggest challenge," said Professor Kopp.

"Either you do that in a hurricane area and wait for the winds to come to you, or try to do it in a lab."

Huge pressures

The giant machine will consist of 100 units, each made up of an actuator and fan, strapped across the outer surface of the house.

Each unit operates like a hovercraft. A flexible skirt from each unit is attached to the building.

The fans create the airflow and the actuators increase or decrease the pressure inside the skirt.

"The advantage of this system is that each test is perfectly repeatable.
Professor Gregg Kopp
"It's not the wind speed we're simulating; it's the actual force the wind exerts on the building," said Eric Wilkinson of Cambridge Consultants.

This is relevant because most of the damage to houses occurs in places where there are sudden changes in pressure, such as at the corners and edges of the building.

"You get swirling and rapid changes from positive to negative pressure," Mr Wilkinson explained.

"If you were going to pull a panel off a roof you wouldn't just heave on it, you'd try to waggle it; and that's the most destructive thing for the wind to do."

Complex winds

These complex pressure patterns are controlled by an automatic system that can vary the speed and direction of the airflow up to seven times a second.

An actuator
100 actuators will be able to simulate 200mph (320km/h) winds

"It's the equivalent of trying to co-ordinate 100 people dancing on a trampoline at the same time," said Mr Wilkinson.

Once the facility is up and running in the autumn, the researchers will be able to start testing the house in different wind conditions up to the equivalent of 200mph (320km/h) gusts.

They will also be able to make modifications to the design of the house, such as varying the shape of the roof, to see how each change affects the resulting damage.

"The advantage of this system is that each test is perfectly repeatable," said Professor Kopp.

After two years of tests, modifications and constant repairs, the house will be ready for its final experiment.

"In 2008, we expect to break it in a way that will make it unusable any further," said Professor Kopp.




SEE ALSO
'Above normal' hurricanes in 2006
22 May 06 |  Science/Nature
'Warming link' to big hurricanes
15 Sep 05 |  Science/Nature
Model predicts hurricane activity
21 Apr 05 |  Science/Nature

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