Pole buildings can be easily designed to withstand hurricane and tornado wind loads. The article below is from www.technewsdaily.com May 26,2011 and speaks to housing design under high winds.
Redesigned Roofs Withstand High Wind Events
The tornado that stormed through Joplin, Mo., on May 22 shredded an estimated 8,000 buildings and stranded desperate families that now must decide whether to rebuild or find a new home. For those choosing to rebuild, Rima Taher, an expert on wind-resistant structures, has a bit of advice: don’t do it the old way.
“You wonder why we keep doing the same things, making the same buildings,” Taher told Innovation News Daily.
By analyzing debris from hurricanes, Taher has come up with a set of guidelines for building new homes in areas prone to extreme weather.
“There are similar problems. So, what usually works for tornadoes would work for hurricanes,” Taher said.
When wind hits, the roof provides the most critical defense. But during a hurricane or a tornado, the roof is often the first to go. Taher found that increasing the number of slopes on a roof improves the aerodynamics of the structure and greatly reduces the amount of pressure exerted on it. She recommended building a roof with at least four slopes, rather than a traditional gable roof that has only two.
As wind swirls around a house, it can push on the roof from both the inside and outside. Taher suggested installing a moveable flap close to the seam of the roof. During hurricanes and tornadoes, the flap would open, stabilizing the air pressure. In hot weather, the flap would provide ventilation.
Taher also recommended spending a bit of extra money on hurricane clips that attach the roof more firmly to the walls than nails or staples alone.
Researchers at the Center for Building Science and Technology in France tested the recommendations by placing wooden models in a wind tunnel and used the results to design a “cyclonic home” that has twice the wind resistance a traditional home.
Moreover, most of the suggestions are simple to execute and well worth the investment.
“A lot of the things we suggest don’t really cost a lot of money. The expense is really minimal compared to the benefits,” Taher said.
Applying modern technology to pole building design, the roof trusses are directly connected to the columns, which are embedded in the ground. Rather than even depending upon light gauge “hurricane” clips for wind uplift resistance, seven gauge steel plates, attached with 5/8 inch diameter through bolts can create a positive anchorage between the roof and the walls. Low cost ventilated ridge caps help to equalize internal and external pressures, to relieve some of the uplift forces. Pole buildings can also be easily designed with roof systems having gables or hips in multiple directions to improve aerodynamics.
Hansen Buildings provides custom designs, including multiple gables, hips or other features to increase wind uplift resistance. Alternate designs, using T’s, L’s, gables and just about any design you can think of is possible. My feeling is, if a pole building can be structurally designed to meet code, we will find a way to produce the pole building kit!
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