Wind tunnel speeds along hurricane research

Clemson, S.C. — Researchers at Clemson University's wind-load test facility are among the innovators striving to learn more about the impact of hurricanes on homes.

Clemson's wind tunnel was among the first to be dedicated to research on damage to single-family homes.

"When you started looking at damage itself, the smaller structures were not well engineered, and you have hundreds of thousands in vulnerable areas," Scott Schiff, director of wind and structural engineering at Clemson, said.

An air cannon shoots out projectiles to test at what speeds they will puncture a structure. At an impact speed of 39 mph, cracks appeared in a brick wall. At 45 mph, a 2x4 board took a chunk out of the wall, but the interior of the structure would still be OK.

Researchers have also determined which nails best secure a home. Schiff tested two types of nails: one with a traditional smooth nail and the other, developed by Clemson graduate, with ridges and a larger head.

The new nail required 50 percent more force to remove it and, therefore, better secured a home against high winds. The ridged nails were also cost effective at approximately $50 more per house, Schiff said.

Clemson University researchers maintain test homes along the North Carolina coast. The homes have been pre-wired to collect data when a hurricane passes over.

The wind tunnel also tests wind pressure on scale models of homes. Schiff's plexiglass models have been able to give builders accurate details on how roofing material should be attached to a home in order to survive a storm.

"(Roofing) may be fine for 20 years, because you don't have a high-wind event," Schiff said. "Then, all of a sudden, you have a high-wind event, then find out they didn't attach the sheeting correctly, or they didn't attach attach a roof frame to the wall.

"It's a bad time to find out."