March 1, 2007 Geometry and mathematical calculations were used to design a next-generation nail for building homes that are twice as resistant to high winds and nearly 50 percent more resistant to earthquake forces. These forces tend to pull wood over the head of nails, so a larger head was designed to reduce this pulling, and flat screw shanks that fit in the grooves made by the nail rings circling the bottom of the nail were added to limit slippage.
- North Anatolian Fault
- Elastic-rebound theory of earthquakes
- Saffir-Simpson Hurricane Scale
Each year millions of dollars are lost to natural disasters. A hurricane tends to push and lift roofs off of homes, while an earthquake rocks a house back and forth.
And when it comes to manufacturing a fastener resistant to nature, engineers at Stanley Bostich say they've nailed it with the HurriQuake Disaster Resistant Fasteners.
"With both [hurricanes and earthquakes], there's a lot of pull through -- meaning that the material you're joining pulls up over the head of the nail. And so that focused our energy on making the head larger," Ed Sutt, Stanley Bostitch's engineer manager of fastening technology, tells DBIS.
Engineers used geometry to design the oversized head. Underneath, flat screw shanks fit in the grooves made by the nail rings circling the bottom of the nail, which creates less slipping. "In order to keep it from coming out of the wood, it has deep rings, which is nothing new, but they're located low on the shank," Sutt says. "There were a lot of mathematical calculations, but at the same time there was a lot of trial and error."
To see if the HurriQuakes are tougher than other nails, he put them to the test. The HurriQuakes survived wind speeds equivalent to a category 5 hurricane, while the wood crumbled.
"The HurriQuake nail ... can provide a structure up to two times the resistance to high-winds and up to 50 percent-more resistance to earthquake-style forces," Sutt says. "A homeowner's gotta understand this is only one piece of making your house more disaster-resistant."
HurriQuake nails exceed standard building codes and add about $15 more to the cost of building an average home. Engineers say the HurriQuake nail can also be used inside your home and will cut down on squeaky floors and stairs.
BACKGROUND: A newly designed nail can withstand hurricane winds and earthquakes. Independent testing showed that the HurriQuake nail can double a home's resistance in high winds and provide up to 50 percent more resistance to earthquake-scale forces. It's also affordable, adding only $15 to the cost of building a new house.
THE DESIGN: The bottom section of the HurriQuake nail is circled with angled barbs that resist pulling out in wind gusts up to 170 mph. This "ring shank" stops halway up to leave the middle of the nail, which endures the most punishment during an earthquake, at its maximum thickness and strength. The blade-like facets of the nail's twisted-top -- the spiral shank -- keeps planks from wobbling, which weakens a joint. The HurriQuake's head is also 25 percent larger than average to better resist counter-sinking and pulling through.
ABOUT HURRICANES: A hurricane is a type of tropical cyclone, a low-pressure system that usually forms in the tropics and has winds that circulate counterclockwise near the earth's surface. Storms are considered hurricanes when their wind speeds surpass 74 mph. Every hurricane arises from the combination of warm water and moist warm air. Tropical thunderstorms drift out over warm ocean waters and encounter winds coming in from near the equator. Warm, moist air from the ocean surface rises rapidly, encounters cooler air, and condensed into water vapor to form storm clouds, releasing heat in the process. This heat causes the condensation process to continue, so that more and more warm moist air is drawn into the developing storm, creating a wind pattern that spirals around the relatively calm center, or eye, of the storm, much like water swirling down a drain. The winds keep circling and accelerating to form a classic cyclone pattern.
WHAT CAUSES QUAKES: An earthquake is a vibration that travels through the earth's crust. It can be caused by any number of things, including meteor impacts, underground explosions or collapsing structures, such as a mine. But most naturally-occurring earthquakes are caused by the movement of the earth's tectonic plates. The earth's surface is made up of large plates that slide over the underlying layer. At the plate boundaries, plates can move apart, push together, or slide against each other.
WHOSE FAULT IS IT ANYWAY: Wherever plates meet, there will be faults at the boundaries: breaks in the earth's crust where the blocks of rock on each side are moving in different directions. There are many different kinds of faults, but in all of them, the various blocks of rock push together tightly and produce a lot of friction. If there is a large enough amount of friction the plates can become locked, increasing the pressure until the plates suddenly give way and snap forward suddenly, sending out a series of seismic waves. These fault lines are the main source of earthquakes.
The American Society of Civil Engineers contributed to the information contained in the TV portion of this report.