Photo: Tom Sawyer for ENR
Image courtesy of Odell Associates
Photo: courtesy of iBHS
A hurricane is rising in the farmland of northwestern South Carolina, and it is going to stay there for the foreseeable future, ripping off roofs, driving rain through walls, shattering windows and shredding buildings.
That’s the purpose of a $40-million building materials and assemblies test facility nearing completion in Chester County, S.C. It is designed to attack full- scale test structures with the swirling winds and rains of hurricanes, the pounding hail of severe thunderstorms, or the wind-driven embers of wildfires.
The owner is the Institute for Business and Home Safety (IBHS), a Tampa, Fla.-based insurance industry group whose member companies are sick of paying for losses to buildings that fail in heavy weather.
“This is such a critically important, game changing initiative,” says Julie Rochman, IBHS president and CEO. “There really—at least to me—was no other choice but to try and do it right, the best way it could be done.”
Rochman, who was at the Insurance Institute for Highway Safety prior to joining IBHS in late 2007, says she saw a huge advance in automobile safety arise from data collected at the highway group’s crash-test lab. As a result, she threw her energy into convincing the IBHS board to move ahead with its sputtering plans to build a similar facility to test the ability of construction materials and building techniques to survive strong storms.
“How can you not pursue something like our lab with vigor?” Rochman says. “There is no doubt that millions of people will benefit from what we are doing.”
The IBHS says its member companies make the country’s largest purchases of roofing materials for re-roofing storm-damaged homes. Reducing these payments is expected to cover the cost of the lab and its operations.
The plan makes perfect sense, but it doesn’t prepare a visitor, rounding a curve on a country road about 45 minutes south of Charlotte, N.C., for the view along the curious, curving, 20-ft-high sound-attenuation berm and the sight of the building with its massive bank of fans.
The main structure is a nearly 42,000-sq- ft wind instrument. It is tuned to channel the programmable blasts of 105 electric fans that are 300 hp, have 16 blades, and are 5½-ft in diameter. The fans blast wind through a stack of curving tunnels and into a chamber designed to accelerate a wall of wind to about 140 mph as it hits test subjects on a 55-ft-dia turntable in the 21,000-sq-ft test chamber. With some slight future additions to the tunnels and exit portal, top winds should hit 175 mph.
If everything goes as planned, when all the fans crank up to 100% velocity for the first time on the week of July 4, the device will roar like an army of chain saws, suck 30 MW of electricity off the 100 kVh transmission line running past the rear of its 90-acre site and send the roiling winds of a Category 3 hurricane through the room.
Each fan can push 230,000 cu ft of air per minute. Together, they can push 24 million cu ft per minute, which is an airflow volume equivalent to 20 times the flow of water at Niagara Falls, says IBHS spokeswoman Allison Dean Love.
The roof and walls are more heavily braced against lift and internal wind pressures, at 35 psf, than external ones. The back wall, which has four massive doors that subtly shape the exit portal to maximize wind velocity, is hardened to withstand the impact of flying debris expected to sail into the open field beyond.
Two engineers will guide the research: Timothy A. Reinhold, senior vice president of research and chief engineer, and Anne D. Cope, director of research.
The facility is Reinhold’s dream. Formerly a civil engineering professor at South Carolina’s Clemson University, he has been researching storm damage to structures for decades. But in the wake of 1992’s Hurricane Andrew, he began to scheme for the creation of a hurricane that he could capture and turn on and off to test the assembled components in buildings that all too often fail—even when they individually carry heavy- weather ratings.
“We need to get rid of all the smoke screens that come up after these events,” he says, describing how the material manufacturers and installers invariably start blaming each other’s work whenever building systems fail. Rather than performing forensic analysis on piles of wreckage, scientists using the new facility will measure the loads and methodically create that wreckage, in the presence of sensors and high-speed video cameras, for scientific analysis.
“One goal is to get data we can’t get any other way,” says Cope, who also studied storm damage under Reinhold at Clemson. “The other goal is to get compelling video,” she says. It was car-crash test videos that slapped the auto industry into a higher state of safety, she notes. She hopes videos of buildings being destroyed by storms will lead to similar results.
The campus includes an 11,000-sq-ft office and conference building, built of precast concrete and heavily insulated against sound, but finished to resemble a local farmhouse. Tommy Dew, project architect with Odell Associates, Charlotte, says the office building is styled to evoke the purpose of the facility—to lead the way to building stronger, safer homes.
Then there is the nearly 42,000-sq-ft test facility itself, including its 145-ft square test chamber with 60-ft-tall clear span and a turntable that lets test subjects be rotated to simulate shifts in wind. The early involvement during design development of construction manager Holder Construction Co., Atlanta, is credited with influencing the decision to go with precast construction, rather than the steel, Quonset hut-style-enclosure originally envisioned.
A fire pit that runs the length of the windward side will permit the generation of a rain of flying embers. Four remotely operated water cannons on the floor and a high-volume sprinkler system on a retractable grid provide fire protection. There is an observation area and control room behind glazing rated for 180 mph winds.
The fan array and its stack of tunnels is structurally independent of the main building. The fan tower is designed to support 8,000 lb of thrust from any one fan, as well as overall maximum thrust of 400 kps, according to structural engineer John Lyons, a principal of Walter P. Moore Associates’ Atlanta office.
The tower is made of precast concrete, which was selected as a durable substrate for mounting the 9,130-lb fans. The mass also “mitigates vibration,” Lyons says. Stability along the axis of the chamber is provided by the load-bearing walls. Transverse stability is provided by external 12-in.-deep precast buttress walls. Smooth interior surfaces reduce air turbulence.
The control systems include a heavily air-conditioned, 3,413-sq-ft electrical building to house banks of Rockwell variable-frequency drives to modulate electrical current frequency and control fan speeds. A Duke Power substation crouches just outside the door.
Finally, there is a 750,000-gal water tank with a supporting pump room for the fire-suppression system and for delivering torrential rains during testing..
The project is so special that the head of its mechanical-electrical and controls engineer, United Engineering Group Inc., Charlotte, decided he would serve as project engineer rather than hand the task to another senior staff member. “It was such an unusual project I did it myself,” says Don Pettigrew, United’s president.