Hurricanes may be a force of nature, but high winds and heavy rains
can be engineered — and the engineers are getting good at
That was the impression conveyed earlier this summer at a gathering
of leading hurricane wind engineers from several Florida
universities and better-building advocacy groups in rural central
The engineers were spending a week experimenting on 10 unlucky
vacant homes, with the goal of probing how hurricanes rip apart
houses built before Florida's first statewide building code in 1994
— and figuring out the best retrofits to prevent that damage.
But the tests also showcased the most up-to-date arsenal in the art
of hurricane simulation.
Most visible was a "Wall of Wind" machine. Described by one
researcher as the "mother of all airboats," the business end of the
trailer-mounted rig was equipped with two caged airboat propellers,
each driven by Chevrolet V8 502 motors. Built at Florida
International University and completed this spring, the machine can
generate 120-mph winds. Combined with "rain" sprayed in from a
500-gallon tank, the end product approximates a Category 3
hurricane in a space the size of a car.
"It's not designed to blow down a house," explains Kurt Gurley, an
associate professor of civil and coastal engineering at the
University of Florida. "It's designed to test the components of the
house that are having performance issues."
Shingles and tar paper fly off of the roof of a vacant home in
central Florida as a custom-built wind machine pounds it with
hurricane-force winds. Part of a University of Florida-led
hurricane research project, the experiment was one of several aimed
at learning more about how hurricanes damage homes that were built
before Florida adopted its first statewide building code in
So, too, is another weapon in the engineers' arsenal: the 2x4 air
cannon. Hauled in by engineers at the Tampa-based Institute for
Business and Home Safety (IBHS), the trailer-mounted cannon has a
long PVC barrel "charged" with compressed air.
The cannon can fire a 2x4 at 100 miles per hour, but the engineers
were seeking to mimic flying debris from only a Category 3 storm.
They pounded the homes' windows, covered with Lexan protective
sheathing, with 40-mph projectiles. The clear Lexan bowed severely,
highlighting the need to space it far from glass panes.
One of the odder tools on site was the nail puller. Invented by Tim
Reinhold, vice president of engineering at IBHS, the 2-foot puller
looks like a giant's wine opener — the kind with opposed
handles that yank the cork free when pulled down. But instead of a
corkscrew, the puller has a metal hook that attaches to the nail
and a force transducer that measures the pressure required to pull
Gurley says hurricanes often yank roofing plywood off of homes. The
engineers use the puller to measure the forces involved, with the
goal of specifying the size, number, and distribution of nails to
ensure the plywood stays attached.
That's a bit more complicated than it at first appears, however:
Gurley reports that the vacant home tests revealed nail-pulling
forces ranging from 30 to 200 pounds, depending on the size,
condition, and location of the nail, such as if it was driven into
The wind machine, air cannon, nail puller, and other equipment may
be unusual, but they're all essential to hurricane wind research,
"We have our engineering equations and our assumptions, but there's
nothing quite like breaking something," he explains. —