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Seeking Shelter From the Storm

Engineers look for ways to help buildings survive hurricanes. Results lead to better building codes.

September 26, 2004|Matt Crenson | Associated Press Writer

GULF BREEZE, Fla. — At first glance, you'd never know what a pounding this place just took.

Three days after Hurricane Ivan, some of the one-story ranch houses in this neighborhood about half a mile from the water have lost patches of shingles. There are a few piles of broken branches dotting the lanes and cul de sacs. But everybody's windows are intact, the spindly trees are upright and kids are playing in their yards.

Then Mary Kort throws open her front door with a flourish, revealing a scene that would render cable TV's perkiest home makeover queen catatonic. Slabs of soggy ceiling sit in the middle of the living room. Pink insulation coats everything. Overhead, slivers of sunlight cut through gaps in the roof.

"I never knew this would happen," Kort said. "It's trashed."

Dave Prevatt smiles ruefully and shakes his head. He's heard words like those before.

A professor of civil engineering at Clemson University, Prevatt is here to see which houses withstood the tremendous forces of Hurricane Ivan and how they differed from the ones that didn't.

Unlike many of her neighbors, Kort stayed put the night that Ivan rolled through. So she can tell Prevatt exactly how this happened.

With her husband and a friend, she watched Ivan's winds accelerate to more than 100 mph. Around that time, the screen enclosure on the back of the house ceased to be.

"It was, like, scooped up," Kort said, her eyes wide. This is clearly a woman who is thankful just to be alive.

Water started leaking through the windows and then the ceiling. Kort and her companions started putting buckets and trash cans under the leaks, but soon there were too many to keep up with.

When pieces of ceiling started coming down, they retreated to the garage, where the former skydiver and self-described adrenaline junkie says she began to pray.

"We thought, 'This is it,' " Kort told Prevatt. "I'm thanking God on my knees I am alive."

When a hurricane makes landfall in the continental United States, Prevatt and his colleagues in the Florida Coastal Monitoring Program are out evaluating which construction methods best protect homes from the tremendous wind forces the storms deliver. The program is sponsored by the Florida Department of Community Development and staffed by scientists from Clemson, the University of Florida, Florida International University, and the Institute for Business and Home Safety, an insurance industry research center in Tampa.

"If we can define the wind forces, then as engineers we believe we can design something that will withstand these forces," said Tim Reinhold, vice president of engineering at the Institute for Business and Home Safety.

Established after Hurricane Andrew socked an unprepared south Florida in 1992 with an estimated $26 billion in damage, the program sets up portable instruments along stretches of coast where hurricanes are poised to come ashore. Engineers erect weather towers that make detailed measurements of the hurricane's winds. They learn about the forces that houses are subjected to by putting pressure sensors on their roofs.

For the research team, the hours before a hurricane are a frenzy of driving and speedy construction. As Ivan's outermost fringes blustered into Mobile, Ala., four researchers were scrambling to put up a portable weather tower along the city's industrial waterfront.

After cruising around looking for a suitable spot, they settled on an open area just outside the chain-link fence surrounding the Mobile airport. For the next hour, they were all socket wrenches and screwdrivers. The men unhitched the trailer they'd been pulling behind a pickup, then extended the four steel legs that can keep the 6,000-pound tower from toppling in 200-mph winds. They tested the instruments and winched the tower up to its full 33-foot height.

Towers like this can measure wind motions in much greater detail than standard meteorological instruments, said Kurt Gurley, professor of civil engineering at the University of Florida. When meteorologists talk about a storm's maximum wind speeds, they're citing readings of the air's horizontal flow taken in a single location at one-minute intervals.

But in a hurricane, the most damaging winds are gusts that last a few seconds or less. They don't come in a smooth horizontal flow, but in localized updrafts, downdrafts or swirling eddies that might demolish one house without touching the one next door.

To capture all that chaotic motion, the engineers mount two sets of gauges on their towers at heights of 16 and 33 feet that measure wind speed and direction in all three dimensions. Three of the program's four portable weather stations also have two smaller towers that are set 50 and 100 feet from the main one in order to determine how much territory sudden gusts cover.

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