By Stephen Budiansky
THANKS TO HURRICANES LIKE CHARLIE,
FRANCES, AND IVAN, ENGINEERING STUDENTS IN FLORIDA ARE GETTING
REAL-WORLD RESEARCH EXPERIENCE—AND HELPING TO MAKE HOUSES
SAFER IN THE PROCESS.
"We sit in classrooms and teach students about structural
analysis and draw little pictures on the board and say here
are the forces and can you calculate the stresses,"
says Kurt Gurley, associate professor in the Department of
Civil and Coastal Engineering at the University of Florida.
"But there's enormous benefits in seeing the enormous
complexity of what goes on in real life—and getting
a sense of how little we really do know."
you live in Florida and are looking for a lesson in reality
and complexity, nature can oblige. There are few things more
real than a hurricane—and few things more complex than
the pattern of destruction one leaves in its wake. For the
past five years Gurley and his students have taken advantage
of what nature has provided to carry out an innovative research
project on hurricanes and the damage they do. This year there
has certainly been no shortage of educational opportunities.
Every time a storm approaches Florida, the engineers set
out in a caravan of trucks and trailers to set up portable
wind-monitoring towers and install pressure sensors on pre-selected
houses close to the storm's predicted path. Not only
does this project provide a hands-on lesson in real-world
research for engineering majors and graduate students, it
also answers some fundamental questions about how houses stand
up to the destructive forces of a full-blown hurricane.
research has already yielded practical recommendations on
how building codes and construction practices need to be revised
for hurricane-prone areas. Along the way, they have also provided
meteorologists with a wealth of detailed data on how hurricane
winds behave at ground level—data that simply has not
been available to researchers before.
When surveying the damage wrought by a hurricane, the most
difficult—and most basic—thing that needs to be
determined is whether the damage that occurred to houses was
caused by local, extreme wind gusts that exceeded the design
specifications of the structures, or by a flaw in the building
codes or workmanship that left the building unable to meet
its design specifications.
One of the difficulties in making that determination is that
although meteorologists have become proficient at measuring
and forecasting the maximum sustained winds in a hurricane,
they still have almost no way of predicting the gusts that
typically appear in local, short-lived, and chaotic patterns
and cause the most damage. A gust might last just a few seconds,
but reach speeds 50 to 60 percent higher than the maximum
sustained winds. In a typical suburb, which is filled with
obstacles that chop the wind up into turbulent patterns, the
gusts become even more extreme and localized.
Gurley and his co-workers in the Florida Coastal Monitoring
Project (FCMP) realized that the first challenge was to establish
"ground truth": determining what actual, local
wind speeds were responsible for the observed damage that
occurred in a storm.
at Clemson University—where the project was initiated
in 1999—designed the portable towers used in the project.
They are sturdy enough to withstand 200 mph winds but light
enough to be towed on a regular trailer behind a van or pickup
truck. They are easy enough to set up that a crew can assemble
them in about 20 minutes and leave well before the storm strikes.
"This is a safe operation, I should stress," Gurley
says. "We retreat to a safe location during the storm.
We will not sacrifice safety to get a piece of data."
The towers are instrumented with anemometers and computers
that record wind speed data at 5 and 10 meters above ground
level every 1/100th of a second—providing an astonishingly
detailed look at wind gusts in one precise location. It's
vastly more detailed data than is provided by the National
Oceanic and Atmospheric Administration's (NOAA) fixed
weather stations at airports, or by the radiosondes that hurricane
chasers drop by parachute into a storm. And because the FCMP's
towers are mobile, specifically designed to withstand high
winds, and provided with backup power, they are more likely
to avoid destruction or having their power knocked out—the
typical fate of airport weather stations that have the fortune,
or misfortune, of ending up in a hurricane's path.
Still, mishaps do occur. During Hurricane Charley this year,
the engineers set up two towers along the stretch of Florida's
east coast where landfall was predicted. The eye of the storm,
as Gurley ruefully puts it, "used our towers as goal
posts" and passed right between them, causing them to
miss recording the maximum winds. And during Hurricane Frances,
flying debris took out some of the instruments on one of the
towers, though the tower itself survived.
both graduate and undergraduate, are directly involved in
everything from designing the computer equipment, to analyzing
the data afterwards, to the hands-on work of setting up the
towers and instruments. With four full-blown hurricanes hitting
Florida this season already—the first time that has
happened in 40 years—it's been a busy time for
all. "This project couldn't exist without the
students," Gurley says. "It's driven entirely
by the dedication of the students I work with. They have to
know everything from details of computer architecture and
instrumentation to how to drop a diesel fuel tank out of a
Ford F250 to drain water out of it. So we need people who
are mechanically inclined, electronically inclined—and
people who are just gung-ho."
A recent graduate student of Gurley's, Forrest Masters—now
an assistant professor at Florida International University—designed
and created a system that has been added to the tower instrumentation
package to transmit real-time data over a cellular telephone
connection. The data is relayed directly to a website where
meteorologists, utility companies, and emergency management
agencies (and anyone else, too: http://grove.ufl.edu/~fcmp/)
can access it in the middle of a storm. The five to six undergraduates
who work on the project get paid an hourly wage and "it's
a great thing to have their résumé to show they've
participated in actual research," Gurley notes.
While the instrument towers provide ground truth on actual
wind speeds that impinge on houses in the path of the storm,
a second set of instruments is used to fill another void in
data that has long vexed building engineers. To calculate
how a given wind speed relates to a given structural load
that a house has to be able to resist, engineers involved
in setting building codes use wind tunnel studies. They place
a miniature of a house in a wind tunnel and measure the pressures
that result on various parts of the house. The trouble with
that, Gurley observes, is that wind tunnel studies are always
an approximation and involve a lot of simplifying assumptions.
And there have been almost no data collected to validate or
calibrate the wind tunnel results against those from the real
To fill that void, the FCMP team has pre-selected 32 houses
located at 10 mile intervals along the coastal regions that
lie in the major storm paths. The houses have been equipped
with cables and connections for computer equipment and stainless
steel brackets on the roofs to hold pressure sensors. When
a storm is approaching, the engineers and student teams put
the sensors in place and hook up the computers. (In exchange
for their cooperation, the homeowners receive an analysis
of their home's structural vulnerabilities and free
upgrades to make them more wind-resistant.)
"This gives us the actual forces on a building as the
wind flows over," Gurley explains. And then "every
time we take data from one of our houses, we build a miniature
of it and put it in a wind tunnel to validate what we see
in the wind tunnel. So now we have a bridge between the building
code and the real world."
The final step in the process is to go back once the storm
has passed and see what damage has been done to nearby houses.
Overall, Gurley says, the more stringent building codes put
in place after Hurricane Andrew in 1994 have been noticeably
effective in reducing damage, especially in the case of mobile
homes. After Hurricane Charley, he says, "we could see
the 1994 and later [mobile] homes a mile away, literally,
because they were the only ones left standing." Newer,
site-built homes also fared well. The researchers did, however,
find problems. For example, clay roof tiles that had been
mortared in but not fastened with screws tended to come loose
and "started flying around like little 10-pound missiles."
Tim Reinhold, who helped start the project when he was an
engineering professor at Clemson, is now vice-president of
the Institute for Business & Home Safety, a nonprofit
research organization funded by insurance companies. Reinhold
emphasizes that this kind of real-world data and analysis
is essential to setting effective—and cost-effective—building
codes for new houses, and especially in trying to decide what
retrofits need to be made to older houses. Given the current
rate of new construction, he notes, "We're able
to address only about 2 percent of the housing stock a year
through the building codes. So you've got this vast
number of older structures built to a variety of older standards,
and with poorer enforcement in the past. So there are a lot
of very vulnerable structures."
Being able to compare the performance of retrofitted houses
with unimproved houses around them, and with actual wind and
pressure data as a reference point, can point directly to
what steps are effective in making older houses more hurricane-resistant.
The FCMP has been run on something of a shoestring budget
that includes some funding from NOAA. The Florida state government
has helped pay for equipment development, but Gurley says
it's always a scramble to cover the operational costs
of meals, lodging, fuel, and student pay. But it's a
great example of how innovative thinking can both fill a real-world
need for engineering expertise and provide students an experience
Stephen Budiansky is a freelance writer based in Leesburg,
Va. He is the author, most recently, of Air Power: The Men,
Machines, and Ideas That Revolutionized War, From Kitty Hawk
to Gulf War II (Viking).