Many commercial developers along the Atlantic and Gulf coasts use high-tech modeling software to gauge how their buildings would fare against hurricane-force winds. But Minneapolis-based development firm Opus Group, an active high-rise developer on both coasts, has melded that regimen with a lower-tech flourish: wind tunnel testing.
Unlike computer-generated models that crunch scores of meteorological variables to predict an outcome, tunnel tests apply real gusts to Fisher-Price-scale models. The result, say engineers, is an incredibly accurate glimpse of how a given property will fare against violent winds.
Another advantage: Wind tunnel tests on new projects can give insurers added confidence that the structure won’t get blown away or split apart during a storm. That assurance can only help policyholders when it comes time to renew their already-pricey property & casualty policies, too.
“In general, any kind of discretionary engineering [such as wind tunnel testing] that is completed by a developer is definitely viewed favorably by insurers when they go to set pricing,” says Matt Walsh, managing director at Chicago-based insurance brokerage Aon Construction Services.
Wind tunnel testing isn’t exactly new — the first trials on commercial properties were conducted more than twenty years ago — but the recent spate of hurricanes has opened many developers’ eyes to its value. It’s easy to forget that stucco ledges and satellite dishes can become projectiles when they are blasted by hurricane-force 155 mph gusts.
“All buildings receive certain loads from the wind. This enables us to gauge how much load our building can absorb, plus how the adjacent buildings will affect the wind pattern,” says Darren Azdell, manager of design at Opus.
The $1.4 billion company had 35 million sq. ft. of commercial space in either planning or construction phase as of this month. Ten of the company’s projects are being built between coastal Alabama and Fort Lauderdale.
Later this summer, Opus plans to complete its 29-story Parkshore Plaza project in St. Petersburg. The high-rise condo was originally slated to front the Gulf, but Opus decided to build it to the east along the bay instead. Azdell says that wind-tunnel tests of a scale model revealed the need for impact-resistant laminated glass in the entire building.
Here’s how the wind tunnel tests work: Small-scale replicas of the buildings are placed on a detailed grid that also features adjacent structures (and even trees) located within a quarter-mile radius of the building. Dozens of tiny sensors are glued to the building model, which is summarily blasted by simulated hurricane force winds.
This simulation, which can take place in tubes as narrow as three feet wide, allows engineers to pinpoint any structural weakness in the building. Azdell remembers one tunnel test years ago that involved a high-rise condo with a rooftop cooling tower. The tower was nearly blown off the roof by 155 mph winds. A computer-generated model of this scenario might not have predicted that outcome, says Azdell, adding that wind-related “torque” (defined as a twisting or turning force) is much easier to determine through tunnel testing versus relying solely computers models.
“We see a lot more firms are using the wind tunnels now, especially if they are building on the coast,” says Azdell, who has put his buildings through these tests since the 1980s.
Boca Raton-based Procacci Development Corp., which builds office properties along Florida’s Eastern coast, is constructing Class-A buildings that can withstand 185 mph winds thanks to solid concrete roofs and steel reinforced wall panels (among other measures). Wind tunnel testing is also part of their design process.
Earlier this year, Procacci broke ground on Phase I of two 90,000 sq. ft. office and warehouse buildings in Miami. Procacci bills the Crossroads at Dolphin Commerce Center as a “hurricane resistant” property. Both buildings also feature a 20,000-gallon underground fuel tank that offers back-up electrical service in the event of a blackout. Like Opus, Procacci substituted fortified glass for standard panes.
Florida’s stringent building code requires that high-rise developers install reinforced glass at least 60 feet or above on a building. Wind intensity typically increases at greater heights. Opus, however, elected to use this expensive glass from from top-to-bottom. The wind-tunnel test also helped Opus determine how many window braces are needed to ensure that the glass remains in place during a storm.
“It does cost more, but it does two things for us,” says Azdell of Opus. “One, it benefits the condo owners and, two, it can help us reduce our insurance costs.”