Wed May 22, 2013
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Can Anything Be Done To Tornado-Proof A House?



As you heard, repairing the physical damage to Moore, Oklahoma will take a long time. Reducing that time and the damage these storms cause is something Andrew Graettinger is working on. He's a civil engineer, a professor at the University of Alabama, and he was part of a study that looked at the structural impact of the 2011 tornados that ripped through Joplin, Missouri and Tuscaloosa, Alabama. He joins us now. Good morning, Dr. Graettinger.


WERTHEIMER: Now, it's hard to imagine more thorough destruction than occurred when that tornado plowed up Moore, Oklahoma. Houses are reduced to shards and shreds. Should something be done? Can anything be done to tornado-proof a house?

GRAETTINGER: Well, when we looked at what happened in Tuscaloosa and then unfortunately had the opportunity to go right back and do the same study in Joplin just a month later, we looked at the path that the tornado took and we kind of walked across it and saw that the damage level on the edges was much lower than in the center.

And when we started to understand the wind speeds that would cause the damage on the edges, we found out that about 85 percent of that area in both Tuscaloosa and Joplin we could engineer to protect those homes and reduce the amount of damage that was occurring in those homes.

WERTHEIMER: What would you have to do?

GRAETTINGER: Well, we can leverage some of the technology that they're using along the Gulf Coast in hurricane regions so we could hurricane clips which are at the top of the wall and they connect to the roof, and that would hold the roof on. And then, if you hold your roof on, you need to hold - you need to continue that path down into the foundation so at the bottom of the wall you need to put a hurricane strap on, which then straps the bottom of the wall to the foundation.

WERTHEIMER: Would this be very expensive to do?

GRAETTINGER: They're not very expensive. These hurricane clips and straps, they're maybe about a dollar apiece or even a little bit less than that. You'd need several hundred of them for a house, and then, of course, installation costs. Now, you'd do this on new construction. Trying to retrofit an existing home with these clips and straps is very expensive, so that wouldn't be an option.

But remember, we've got two levels of damage. We've got this level of damage we can engineer for at the lower wind speeds, but then in the center of that storm it's complete destruction. Even the wood is breaking. And so what you need to have in those areas is a safe room to go to. So it's kind of a dual objective.

At the lower wind speeds, we try and keep your house together and protect it with those hurricane clips and straps, and at those higher wind speeds we're looking for life safety and that means a safe room in your house.

WERTHEIMER: What would a safe room have to be? What would it need to be safe?

GRAETTINGER: Well, FEMA has designs out for safe rooms and storm shelters, and so these are well-designed. They're reinforced. Typically it's concrete. It could be made out of steel and you could even make it out of wood with steel reinforcing in it. So there's a number of ways you can design a safe room, and you can even put them underground and build them that way.

So there's a number of different designs and they're designed to handle those EF5 kind of wind speeds.

WERTHEIMER: I gather that nothing could really protect property against a storm like Moore, Oklahoma, but you think you could protect people. What about those old-fashioned storm cellars like my grandmother who lived in Oklahoma had one in her backyard. I remember lots of nights waking up in that thing.

GRAETTINGER: Yes. It's a great place if that's where you have to go. And of course safe spots in your house, like in the bathroom or something in the center of the house or the basement, if that's all you have, those are the best places to go. But you want to make sure that something like a root cellar or something like that has a proper tornado door on there also because you don't want any impacts to get in, like a flying piece of debris to break through the door or the door to be pulled off.

But any one of those locations that we had talked about, those are all good places to go if that's where you have to go.

WERTHEIMER: Andrew Graettinger is a professor at the University of Alabama. Thank you very much for joining us.

GRAETTINGER: Oh, you're welcome. Transcript provided by NPR, Copyright NPR.

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