Manufacturers
learn quickly if their products could withstand the real thing
A Category 5 hurricane is a monster of a
storm that most people would want to avoid. But, civil engineer Arindam
Chowdhury actually recreates those monster hurricane force winds in hopes of
helping people better prepare for the real thing.
With support from the National Science
Foundation (NSF), Chowdhury and his team at Florida International University
(FIU) and the International Hurricane Research Center designed a 15-foot-tall
"Wall of Wind," aptly nicknamed WOW. The wall is made up of 12 giant
fans, which can create the intensity of a Category 5 hurricane with 157-mph
winds if the fans are running at full blast.
The goal is to see if low rise
structures and building materials can withstand the same wind forces the
structures and materials would face in a full-blown hurricane. "Based on
our testing of rooftop equipment, such as AC units on building roofs, we made
recommendations that are now in the Florida Building Code," says
Chowdhury.
"Our long-term goal is to prevent
hazardous wind from becoming a disaster," says Kishor Mehta, program
director for hazard mitigation and structural engineering within NSF's
Engineering Directorate. "This facility enables engineers to collect
precise measurements of wind interacting with buildings, in addition to the
visible evidence of the vulnerability of building materials exposed to
hurricane force winds. This combination of basic research and visual evidence
will lead to safer, more cost effective construction."
Manufacturers come to FIU to put some of
their products to the test. During one test, researchers attach a solar panel
manufactured by Power Panel Inc. to the roof of a small building. The building
is secured on a rotating turntable directly in front of WOW. The turntable
allows researchers to rotate the structure and expose the solar panel to wind
from all directions.
In a nearby trailer, researchers huddle
around computers at an informal control center. With the click of a mouse, they
crank up the fans to create a fake hurricane. "I'm going to go up to 60
mph," says the researcher who is at the controls. He uses a walkie talkie
to warn his team members who are outside preparing the building and the solar
panel. Hearing that, they move out of the way as the fans start to blow.
Rob Kornahrens, part owner of Power
Panel Inc., sits in the control room glued to a monitor as the test gets
underway. Fan speed is increased to 90 mph. "We want to make sure the
glass insert stays within the frame," says Kornahrens. "Second thing
we're looking for is that the whole unit stays on the racking itself. Third
thing is the attachment of the racking to the building. We want to make sure
that doesn't come off the structure."
So far, so good, and the fans are now
blowing at 120 mph. The building is swaying. The solar panel is staying on the
roof. Sensors on the building measure the pressures on the panels. Satisfied
with this first round, Kornahrens asks: "Can we flip it around?"
Researchers shut off the fans and rotate the turntable to expose another side
of the panel to head winds.
"Now we can see the effect of the
wind and get the data from all the directions," explains Chowdhury.
"I don't think we'll see any damage
to the panel based on what I saw," says Kornahrens. He is pleased with the
results and with the test itself. "This is great. You can't get this in
any other kind of test!"
Next up, testing roof tiles and a new
adhesive tile foam. "That foam really works with this good tile,"
says Manny Oyola with Eagle Roofing Products. He is with his supplier Riku
Ylipelkonen of 3M, the company that manufactures polyfoam roof tile adhesive.
They, along with another roofing company owner, Tim Graboski, stand in the
control room and watch WOW's forces on the roof tiles and foam.
The fans start to whirl, blowing 90,
then 120, and finally 140 mph. The tiles and foam stay firmly on the roof and
they pass with flying colors. But, does the building itself? Not so much. The
entire structure lets loose from its foundation and flies off the turntable
crashing in a nearby field. "It's a powerful machine," Chowdhury
smiles, "even more powerful than I thought." On a serious note,
Chowdhury says such foundation failures are rare.
Lessons learned on building materials
and structures tested at WOW could help improve design and even save lives.
"The thing we feel good about is
that 2012 is the 20th anniversary of Hurricane Andrew, the Category 5 hurricane
that devastated south Florida, including Homestead," adds Chowdhury.
"Today, we can simulate the hurricane strength of Andrew, learn from the
tests and make changes to mitigate damages." Now, that's a WOW!
The research in this episode was funded
by NSF through the American Recovery and Reinvestment Act of 2009.
Miles O'Brien, Science Nation
Correspondent
Ann Kellan, Science Nation Producer
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