Weathering the Storm.
When wind-borne missiles in a hurricane break traditional window glass, the accompanying heavy rains pour in, damaging building interiors and their contents. More catastrophically, the resultant sudden over-pressurization of the building interior from high winds contributes to the failure of roofing components, which often destroys the entire structure.
During Hurricane Georges, the flood damages incurred as the storm pounded the Mississippi Gulf Coast with 25 inches of rain for 16 hours were significant, but again, broken glass was equally culpable for a long, expensive recovery.
Shutters are often used to protect openings from high winds, but they require occupants to deploy them, which often doesn't happen. According to an IIPLR survey in the Miami area, less than half of the commercial and residential buildings had shutters, and of those that did, less than half were in place when Andrew made landfall.
For risk managers responsible for protecting buildings and facilities in hurricane-prone areas, these and other equally convincing statistics make a strong argument for installing laminated glass that can withstand the missile impacts and other damages associated with high winds.
"Georges wasn't as bad as Elena, in 1985, or Camille, in 1979," says Carl Honn. "I've seen hurricanes since before they were named. This building has been hit twice in the 17 years that I've been here." Mr. Honn's store, Gulf Paint and Paper, lost a corner storefront window and was subsequently drenched with rain as Georges parked over Pascagoula. Two days after the storm finally left town, Mr. Honn's friend Joe Westmoreland, owner of Dixie Glass and Trim, replaced the storefront glass to help Mr. Honn get back in business.
Along the Mississippi Gulf Coast hundreds of businesses, from casinos to 10-stool diners, were damaged by Georges. The more fortunate, with windows and roofs intact, had only to mop and clean floors to get back in business. Those with broken windows had to begin major repairs and usually couldn't predict when they would reopen.
Compounding the property losses were the lost use of space and forfeited business and other commercial breakdowns associated with the period after a hurricane. As Mr. Honn points out, businesses that are able to reopen after the storm play a crucial role in helping a community recover, and they have a distinct advantage over competitors that aren't ready to do business. "We'll do an enormous amount of carpeting and paint business as everyone fixes up. Then there will be two years when no one is doing any redecorating because they've all done it. It's really important to open the doors and answer the phone and be ready to help people as soon as the wind quits blowing."
Mr. Westmoreland and his crew were ready to go to work the day after Georges left town. With so much broken glass to repair, Mr. Westmoreland just responded to calls in the order he received them. But some businesses had to wait for replacement glass. "It takes at least 10 days right now to get tempered glass unless it's a broken door in standard size," Mr. Westmoreland notes. Tempered glass can't be cut; every piece must be made to the exact specification of the opening it has to fit.
Tempered glass doesn't perform well in hurricanes, according to Dr. Joe Minor, professor of civil engineering at University of Missouri at Rolla, and arguably the world's foremost authority on small missile impacts during hurricanes. "Anyone who has seen the aftermath of a hurricane knows empirically that quarter-inch tempered glass breaks," says Dr. Minor.
Jim Benney, technical director for the tempering division of the Glass Association of North America, notes that "tempered glass is meant to resist soft body impacts. When hard objects impact it and chip that first surface, it breaks safely." But that "safe" breakage means only that it should prevent personal injury to anyone near the glass, while nonetheless exposing the building and its contents to the wind and rain of the hurricane.
Ask Mr. Westmoreland what the best choice for window and door glass is, where, during the useful life of a building, it is certain to be hit with a hurricane, and he answers, "The same glass that's in your windshield: laminated." Mr. Westmoreland and his son Sean, a third-generation glazier, are unaware of Dr. Minor's research, which confirms their choice, but they have plenty of firsthand observations upon which they base their endorsement; the elder Westmoreland has been replacing glass broken by hurricanes for 30 years.
Just down Pascagoula's Market Street from Mr. Westmoreland's shop, Aaron's Rental, a furniture rental store, survived the storm and an attack by looters, perhaps the second most common cause of broken glass during a hurricane. When power lines go down, burglar alarms are off, and with police and security patrols busy elsewhere, looters are willing to brave the elements. Ricky Carter, the store manager, holds a fist-sized chunk of concrete block and shows where it impacted a laminated glass window five times in an unsuccessful break-in attempt sometime during Georges' 16-hour siege. "It must've surprised the guys who tried to break the window," Carter chuckles. "They made five cracks in the glass but the concrete just kept bouncing off." The laminated glass withstood the attack and held up through the hurricane. "If you want to get through a hurricane, and the looters, it's the only kind of glass to use," says Mr. Westmoreland.
"When Elena blew through in 1985, this furniture store got wrecked," says Mr. Westmoreland. "Every piece of plate glass broke, the roof came off, and essentially the building and everything in it was a total loss." At his suggestion, laminated glass was used to replace all the glass. In a later hurricane, the new laminated glass cracked but kept the building secure from torrential rains and looters. It is the post-breakage performance of laminated glass that distinguishes it from conventional, monolithic glazing.
In fact, it took the Westmorelands, with access to the building interior, and using a razor knife, cordless drill, chisel and screwdriver, 20 minutes to remove the cracked laminated glass lite from the opening.
"There is probably more laminated glass that got cracked during the storm," Mr. Westmoreland says. "We might not hear from those folks right away because their buildings are secure and dry."
Sometime in the later stages of Hurricane Georges, there were reports of tornadoes; brief, violent torsional winds that seemed almost capricious in their targets. One such tornado must have brushed the storefront glass at Aaron's Rental. A four-by-eight piece of laminated glass was sucked out of an opening and landed on the far side of a large van that was parked in front of the store. The piece of glass, folded like a blanket, ended up some 20 feet from the window opening. How one piece of glass along a 30-foot storefront was lost is inexplicable to Mr. Westmoreland, but the fact that just one lite was lost points to a sound job of installing the laminated glass after Elena in 1985.
It is very important to note that laminated glass transfers loads to the window frame, and since the glass can sustain high loads and repeated impacts during a hurricane, the window framing and fasteners must be compatible with the strength of the laminated glass.
Estimating comparative costs among the myriad security glazing options is a pointless exercise--prices can vary widely in different regions--but the specific requirements of a given application will narrow the field. As a rule of thumb for uninstalled glass, laminated glass costs roughly 30 percent more than tempered glass of the same dimensions. "Expressed as a total of the building costs, using quarter-inch laminated glass instead of quarter-inch tempered glass raises the completed costs of a building by roughly one percent," notes Paul Beers, president of Glazing Consultants Inc., in Palm Beach Gardens, Florida.
The best designs for glass under hurricane conditions come from interdisciplinary collaborations between researchers, architects, security experts and structural engineers. Designs for laminated glazing configurations that can withstand the punishment of hurricanes are well-developed and freely accessible through such organizations as the Laminated Glass Information Center, in St. Louis (800.230.4527, lgic.glass-info.com).
As standard practices evolve in response to a threat that virtually the entire Eastern seaboard and Gulf Coast shares, it would be untenable for any risk manager with responsibility for property protection to claim a lack of information on missile-impact resistant glazing. "More than a dozen independent laboratories are testing materials that architects can easily learn about," says Dr. Minor. "Just be sure that the claims made by manufacturers are based on recognized standards developed by credible institutions."
Tom Harpole is a widely published author on the subject if architectural glazing. He lives near Avon, Montana.
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|Date:||Jan 1, 1999|
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