Moore Oklahoma Tornado 20May2013

[Huntn]

I imagine most of you have seen the images. Tornadoes seem to be the most dangerous weather events I know of and scare me the most. Hurricanes do more overall damage to a larger area, but nothing can match the intensity and focused damage of a twister. In 1999 the highest winds every recorded was associated with an F5 twister, 318 mph, in the same vicinity near Oklahoma City.

I wonder what happens to the population count after an event like this. I'm not talking of the deceased, but the number of people who say they've had enough and move away?

 

[justperry]

Your video shows this:

 

[GoCubsGo]

I'm not sure if there is a state you can move to where you won't experience something. It is terrible for sure and I think I fear tornados more than earthquakes. I spent 90% of my life in So. Cal. so perhaps that is just my ignorance of the unknown. The devastation in Moore is horrible. I did read at least a little news where they had the death toll at 91 and figured out they double counted some so the number when down to 24. (source)

For me, I would say that was enough and get the F out. Moving may not be that easy for some depending upon their job/family situation. I do wish the best for those affected as well as anyone ever affected by any natural disaster.

 

[justperry]

I don't understand one thing here, this is already the 3th time this happens in the same area yet these houses are still built out of wood.
Not only there but in the whole Tornado ally, where I am from houses are built out of brick (solid) and double walls with insolation in between, so much stronger.

Sadly, as long as these houses are not built stronger we will see this happening again and again.

 

[bradl]

I'm not sure if there is a state you can move to where you won't experience something. It is terrible for sure and I think I fear tornados more than earthquakes. I spent 90% of my life in So. Cal. so perhaps that is just my ignorance of the unknown. The devastation in Moore is horrible. I did read at least a little news where they had the death toll at 91 and figured out they double counted some so the number when down to 24. (source)

The hard part for me: 7 of that 24 were children.

As far as equating it to experiences you may know, picture a Ludlow earthquake on Saturday, followed by Northridge on Sunday, followed by Loma Prieta on Monday (The one that took out the Bay Bridge). All of those back to back to back within 72 hours. That's what happened here.

For me, I would say that was enough and get the F out. Moving may not be that easy for some depending upon their job/family situation. I do wish the best for those affected as well as anyone ever affected by any natural disaster.

this is a tough one for me, as all of my family were born/raised in Oklahoma. I wasn't, but lived in Tornado Alley all my life. For this to surprise and shock storm chasers says enough.

I'll post more thoughts after I get to work or the airport, depending on which may be needed (may be taking a flight to OKC to help with cleanup).

BL.

 

[SMDBill]

I don't understand one thing here, this is already the 3th time this happens in the same area yet these houses are still built out of wood.
Not only there but in the whole Tornado ally, where I am from houses are built out of brick (solid) and double walls with insolation in between, so much stronger.

Sadly, as long as these houses are not built stronger we will see this happening again and again.

You're right about them being wood homes on a block foundation or slab. I used to live in Moore, very close to where this took place (right off of Broadway if you look at a map of the path). I left in 1997 and 2 years later Moore was hit with the strongest winds ever recorded on earth. Many friends still live there and I hope they are all safe.

Everything was destroyed in the path so building the homes out of brick or block and brick would not have saved the homes. Tornadoes are not like hurricanes where sustained winds can be tolerated. They're incredibly violent and usually destroy everything in their path. Look at photos of that school. They're built out of heavy block and it was still destroyed. While it would stand up better to it, block homes would still not be able to remain standing through a tornado after a direct hit and the cost would probably be prohibitive. Many there choose to build a storm shelter beneath the home for times like that. Fortunately, when I lived there my next door neighbor had an underground shelter that we never had to use.

 

[Huntn]

Your video shows this:

I figured it out. Got the link from Youtube: http://youtu.be/xTpceWd8UE4. For use in this forum and Youtube tags, it's [youtube]and just the video designator in this case xTpceWd8UE4, followed by the ending youtube tag.

I don't understand one thing here, this is already the 3th time this happens in the same area yet these houses are still built out of wood.
Not only there but in the whole Tornado ally, where I am from houses are built out of brick (solid) and double walls with insolation in between, so much stronger.
Sadly, as long as these houses are not built stronger we will see this happening again and again.

My guess they are building them with wood cause wood is less expensive. If you are referring to cinderblock, or better yet poured concrete walls, that might make a difference. Brick veneer while in some less intense cases might help a little, but with an F4/5, just provides more projectiles. I suggest storm cellars. Having lived with a basement all my life until the last 3 years, makes me feel insecure, however I live in an area with infrequent tornadoes (Houston, Tx).

The hard part for me: 7 of that 24 were children.

As far as equating it to experiences you may know, picture a Ludlow earthquake on Saturday, followed by Northridge on Sunday, followed by Loma Prieta on Monday (The one that took out the Bay Bridge). All of those back to back to back within 72 hours. That's what happened here.

I can imagine the terror they experienced, utter sadness.

 

[justperry]

You're right about them being wood homes on a block foundation or slab. I used to live in Moore, very close to where this took place (right off of Broadway if you look at a map of the path). I left in 1997 and 2 years later Moore was hit with the strongest winds ever recorded on earth. Many friends still live there and I hope they are all safe.

Everything was destroyed in the path so building the homes out of brick or block and brick would not have saved the homes. Tornadoes are not like hurricanes where sustained winds can be tolerated. They're incredibly violent and usually destroy everything in their path. Look at photos of that school. They're built out of heavy block and it was still destroyed. While it would stand up better to it, block homes would still not be able to remain standing through a tornado after a direct hit and the cost would probably be prohibitive. Many there choose to build a storm shelter beneath the home for times like that. Fortunately, when I lived there my next door neighbor had an underground shelter that we never had to use.

Saw on CNN they used hollow cinderblocks, those are not strong, solid bricks or concrete would be much better.

I figured it out. Got the link from Youtube: http://youtu.be/xTpceWd8UE4. For use in this forum and Youtube tags, it's [youtube]and just the video designator in this case xTpceWd8UE4, followed by the ending youtube tag.



My guess they are building them with wood cause wood is less expensive. If you are referring to cinderblock, or better yet poured concrete walls, that might make a difference. Brick veneer while in some less intense cases might help a little, but with an F4/5, just provides more projectiles. I suggest storm cellars. Having lived with a basement all my life until the last 3 years, makes me feel insecure, however I live in an area with infrequent tornadoes (Houston, Tx).



I can imagine the terror they experienced, utter sadness.

No, solid bricks

 

[GoCubsGo]

The hard part for me: 7 of that 24 were children.

As far as equating it to experiences you may know, picture a Ludlow earthquake on Saturday, followed by Northridge on Sunday, followed by Loma Prieta on Monday (The one that took out the Bay Bridge). All of those back to back to back within 72 hours. That's what happened here.

No, I understand that my equation of personal experience may not be even, but I did say that a tornado terrifies me more than any earthquake. I'm not young so my time in CA did span across all three of the earthquakes you mentioned. Even still, justperry makes mention of something relevant and that is how buildings are manufactured. With the earthquakes come updated codes and mechanisms to help reduce destruction. (San Francisco library is on base isolators for example) Why haven't they looked at rebuilding in ways that could help reduce some of the damage?

 

[Huntn]

No, I understand that my equation of personal experience may not be even, but I did say that a tornado terrifies me more than any earthquake. I'm not young so my time in CA did span across all three of the earthquakes you mentioned. Even still, justperry makes mention of something relevant and that is how buildings are manufactured. With the earthquakes come updated codes and mechanisms to help reduce destruction. (San Francisco library is on wheels for example) Why haven't they looked at rebuilding in ways that could help reduce some of the damage?

There is much I don't know about home construction other than to say when it comes to a residential home, and an F4/5 if you are not willing to build underground, the focus is probably on just having a safe place to weather the storm, but not save the house. I'm thinking of a storm cellar or storm closet (link, link2).

I believe that a tornado proof house would require building codes that would make houses unaffordable, but I might be talking out my arse on that. One of the keys to safer construction would be a design that keeps the roof on. Once it comes off, the walls no longer have anything reinforcing their upright position and most likely they will collapse.

 

[Tomorrow]

I wonder what happens to the population count after an event like this. I'm not talking of the deceased, but the number of people who say they've had enough and move away?

As you said, tornadoes are not like hurricanes in many ways - one being that they're much smaller. They affect a dramatically smaller area than a hurricane. Which means that very few people ever actually have two tornadoes sail over their home in their lifetimes.

I had the misfortune to get caught out in a tornado once (Fort Worth/Arlington in 2000). I wouldn't want to go through that again, but knock on wood, I haven't.

Saw on CNN they used hollow cinderblocks, those are not strong, solid bricks or concrete would be much better.

Homes are very, very rarely made out of brick (I'm not talking brick veneer), and I don't think I've ever seen one made from poured concrete - it just isn't done. There's no upside to it (because PIP or tilt-up concrete walls can simply be knocked over), and there's a tremendous expense associated with it. Plus, they're just plain fugly.

You would also still need to build an interior stud wall for insulation, so there's that to consider as well.

 

[SMDBill]

It would be too cost prohibitive to use solid stones of any kind to build every structure in areas prone to tornadoes. We have them in so much of the country that it just wouldn't be possible. Best bet is make them as strong as possible within cost reasonability and create shelters for the few events one may face in a lifetime that could threaten lives directly. Predicting Mother Nature has proven impossible.

 

[Huntn]

No, solid bricks

I believe they can run reinforcing rod through cinderblocks. I lived in a cinderblock house with a flat concrete roof (I think) on Navy Housing on Guam and it seemed to be Hurricane proof. However, I think poured concrete walls, similar to what they do with basements/foundations would be a better method.

 

[rhett7660]

Some of the before and after pictures. The page has been updated a couple of times now.

Just wow...

http://photoblog.nbcnews.com/_news/...o-cuts-devastating-path-through-oklahoma?lite

Some places it looks like a bomb went off.

 

[Huntn]

Some of the before and after pictures. The page has been updated a couple of times now.

Just wow...

http://photoblog.nbcnews.com/_news/...o-cuts-devastating-path-through-oklahoma?lite

Some places it looks like a bomb went off.

Seconded. I saw some pics on USA Today mobile, where houses were intact on one side of the street, but gone only foundation slabs left on the opposite side.

 

[bradl]

No, I understand that my equation of personal experience may not be even, but I did say that a tornado terrifies me more than any earthquake. I'm not young so my time in CA did span across all three of the earthquakes you mentioned. Even still, justperry makes mention of something relevant and that is how buildings are manufactured. With the earthquakes come updated codes and mechanisms to help reduce destruction. (San Francisco library is on base isolators for example) Why haven't they looked at rebuilding in ways that could help reduce some of the damage?

That is a good question, and I am not sure on the building standards for it, as the last time I was anywhere over there seriously was when I was a child.

But what I do know is this: a lot of the reinforcements of the land is limited because of how rich in oil the land is. The red dirt that makes up the area there is so rich that it causes the land to be rather soft. That was the main reason why a lot of the homes there didn't have any basements (and that was odd to me being from Nebraska, where every house has a basement). It does explain the storm cellars and why they are underground, as they can handle it. I can't reconcile the high rise buildings though.

It would be interesting to see if they do make changes to building codes and standards.. if HUD has the funding for it.

BL.

 

[Tomorrow]

That was the main reason why a lot of the homes there didn't have any basements (and that was odd to me being from Nebraska, where every house has a basement). It does explain the storm cellars and why they are underground, as they can handle it. I can't reconcile the high rise buildings though.

Other factors with basements are the high water table here and the shallow frost depth (only 6") makes a basement an unnecessary expense for a house. For a large building like a high rise, the basement becomes more natural since you have to excavate pretty deep to get a solid enough footing for the added weight.

 

[Don't panic]

Homes are very, very rarely made out of brick (I'm not talking brick veneer), and I don't think I've ever seen one made from poured concrete - it just isn't done. There's no upside to it (because PIP or tilt-up concrete walls can simply be knocked over), and there's a tremendous expense associated with it. Plus, they're just plain fugly.

You would also still need to build an interior stud wall for insulation, so there's that to consider as well.

I am no expert, but i really don't think you are right here.
for what I have read, and experiences in other countries, poured concrete houses are much better than wood-frame house by almost any metric, including cost.
the problem in the US is that there is a lack of demand, and therefore the skills, technology and equipment are not readily available. that is why they result more expensive, not because they intrinsically are.
a properly built poured-concrete is obviously stronger, but is also much better insulated, lasts longer and is cheaper to maintain (plus mostly fireproof and no termites)
as far as the look of it, it can be made in any shape, with the same exterior trimmings, so it can look exactly the same as a traditional house, or completely different, it's up to the builder.

also, while some structure might not be enough for an EF5 events, they would be much better in storms not as severe or not in the very worst path, so the overall damages would be greatly diminished. not to mention the reduction of projectiles and thus indirect damages.

In any case, i think building code should mandate at least that any new house should be equipped with a EF5 storm shelter. they are really quite inexpensive (2-5K), and they would be even cheaper with an enlarged market if they became mandatory.

Finally, the lack of proper storm shelters at the schools is nothing short of criminal, IMO.

 

[Tomorrow]

I am no expert

That's okay, I am.

Poured concrete homes - particularly single-family - are not common at all.

Don't confuse concrete with cement. And don't confuse poured concrete with precast concrete or concrete block.

Commercial construction is a completely different matter; poured concrete (including tilt-up) is very common, so there's a ton of expertise. But that's not what we're talking about here.

a properly built poured-concrete is obviously stronger, but is also much better insulated, lasts longer and is cheaper to maintain (plus mostly fireproof and no termites)

There's very little insulation in poured concrete; it's one of the worst-insulating materials used in construction (6" of concrete has roughly the same R-value as 3/8" plywood). And good luck getting the fire marshal to accept it as "fireproof" - I've never been able to do it.

as far as the look of it, it can be made in any shape, with the same exterior trimmings, so it can look exactly the same as a traditional house, or completely different, it's up to the builder.

Sounds like you're describing EIFS, which looks and feels like concrete, but it can be molded - and is not a structural material.

 

[Don't panic]

That's okay, I am.

Poured concrete homes - particularly single-family - are not common at all.

Don't confuse concrete with cement. And don't confuse poured concrete with precast concrete or concrete block.

Commercial construction is a completely different matter; poured concrete (including tilt-up) is very common, so there's a ton of expertise. But that's not what we're talking about here.

There's very little insulation in poured concrete; it's one of the worst-insulating materials used in construction (6" of concrete has roughly the same R-value as 3/8" plywood). And good luck getting the fire marshal to accept it as "fireproof" - I've never been able to do it.

Sounds like you're describing EIFS, which looks and feels like concrete, but it can be molded - and is not a structural material.

i know they are not common in the US, but it seems mostly out of tradition than any other reason. I have seen plenty in europe.
I am talking about reinforced concrete homes, at least for the structural elements. And insulation can be provided as separate layers, like it is now. ICFs make houses very energy efficient.

I am not sure why you'd think that concrete is limited in terms of what forms/shapes can be constructed. it's extremely versatile, and pretty much any any house plan that you can design in traditional construction style can also be made in concrete, but not viceversa, although i suppose that with concrete you can't easily change your mind after it's poured
and concrete is fireresistant. it's better then most material both because it is non combustible but also because it retains its structural integrity longer in heat. in a fire i would certainly rater be in a concrete home than in a wooden one. same for a tornado.

 

[Huntn]

Enlightening USA Today article: Saftey Experts Say Okla. School Was Ready For Tornado

Oklahoma has reinforced tornado shelters in hundreds of schools across the state, but the two that were hit this week, Plaza Towers Elementary and Briarwood Elementary, did not have them, emergency officials said Tuesday. Albert Ashwood, director of the Oklahoma Department of Emergency Management, told reporters a shelter would not necessarily have saved more lives at the Plaza Towers, where seven children sheltering in above-ground classrooms were killed. He said each jurisdiction sets priorities for which schools will get limited funding for safe rooms. He says no disaster mitigation measure is absolute.

The first bolded statement is wishful excuse making imo. Limited funding for safe rooms? Man...
My summary of the article is that the school staff was ready but the school structure was not. Inexcusable for this area that a school would be allowed to be built without one. I heard yesterday that the Tornado has now been categorized as F5 (winds 261-300+mph).

Other factors with basements are the high water table here and the shallow frost depth (only 6") makes a basement an unnecessary expense for a house. For a large building like a high rise, the basement becomes more natural since you have to excavate pretty deep to get a solid enough footing for the added weight.

But I grew up with a basement and now that I'm in a house without one, I miss it primarily for storage and other uses. I assume there are cases where builders pour a slab cause it's faster for them to build. As far as excavating to find solid footing, my understanding in the places I've lived Maryland, Tennessee, Minnesota, that is not the primary reason for basements (excavating so deeply), although in Minnesota you do have to get the foundation below the frost line which if I remember correctly is about 30" deep. The primary reason I've heard why an area does not have basements is due to high water table, but sometimes I wonder about that excuse.

I am no expert, but i really don't think you are right here.
for what I have read, and experiences in other countries, poured concrete houses are much better than wood-frame house by almost any metric, including cost.
the problem in the US is that there is a lack of demand, and therefore the skills, technology and equipment are not readily available. that is why they result more expensive, not because they intrinsically are.
a properly built poured-concrete is obviously stronger, but is also much better insulated, lasts longer and is cheaper to maintain (plus mostly fireproof and no termites)
as far as the look of it, it can be made in any shape, with the same exterior trimmings, so it can look exactly the same as a traditional house, or completely different, it's up to the builder.

also, while some structure might not be enough for an EF5 events, they would be much better in storms not as severe or not in the very worst path, so the overall damages would be greatly diminished. not to mention the reduction of projectiles and thus indirect damages.

In any case, i think building code should mandate at least that any new house should be equipped with a EF5 storm shelter. they are really quite inexpensive (2-5K), and they would be even cheaper with an enlarged market if they became mandatory.

Finally, the lack of proper storm shelters at the schools is nothing short of criminal, IMO.

I agree. As far as concrete insulation values, I believe concrete walls would need additional insulation on the walls. But this would not eliminate concrete as an outstanding building material in a tornado prone area.

Don't confuse concrete with cement. And don't confuse poured concrete with precast concrete or concrete block.

So which would best be suited to resist high winds?

Commercial construction is a completely different matter; poured concrete (including tilt-up) is very common, so there's a ton of expertise. But that's not what we're talking about here.

When my house was built in Minnesota, for the basement to foundation, they set up forms and poured concrete. It seems like the perfect solution for an entire house as long as the roof can be constucted to hold the structure together and not blow off. I assume a flat, not gabled roof, such as used in commercial buildings would be a better solution.

There's very little insulation in poured concrete; it's one of the worst-insulating materials used in construction (6" of concrete has roughly the same R-value as 3/8" plywood). And good luck getting the fire marshal to accept it as "fireproof" - I've never been able to do it.

I did not realize concrete had that low of an insulation value. Why would the fire marshall have an issue with concrete walls when it comes to fire?

 

[rdowns]

Seems to me you can never build to withstand tornadoes of that magnitude and certainly not in any cost effective way. It would make sense to require all new construction to have underground shelters as code.


EDIT: The Mayor agrees with me.

Moore, Oklahoma (CNN) -- The mayor of tornado-ravaged Moore, Oklahoma, will push for a law requiring storm shelters or safe rooms in new housing projects, he told CNN Wednesday.

"We'll try to get it passed as soon as I can," Glenn Lewis said.

http://www.cnn.com/2013/05/22/us/oklahoma-tornado/index.html

 

[Huntn]

Seems to me you can never build to withstand tornadoes of that magnitude and certainly not in any cost effective way. It would make sense to require all new construction to have underground shelters as code.


EDIT: The Mayor agrees with me.



http://www.cnn.com/2013/05/22/us/oklahoma-tornado/index.html

I agree with you and the mayor! Speaking of an alley, I'd think twice about living in this area:

 

[Tomorrow]

As far as excavating to find solid footing, my understanding in the places I've lived Maryland, Tennessee, Minnesota, that is not the primary reason for basements (excavating so deeply)

No, not for a house - I was talking about a commercial building, which is much heavier (depending on the height) and needs a more solid footing than simply building on top of soil.

although in Minnesota you do have to get the foundation below the frost line which if I remember correctly is about 30" deep. The primary reason I've heard why an area does not have basements is due to high water table, but sometimes I wonder about that excuse.

The frost depth is a huge part of it. Remember, when water freezes, it expands - same with soil. The frost depth here in the south is only six inches, so you don't need to build your foundation any lower than that to keep it from freezing underneath.

As for the water table, it was explained to me that it's very much like an old swimming pool; after so many years in the soil with the weight of the water holding it down, if you were to drain the pool, it could quite literally float up from water in the soil. Same thing could happen if you build a basement where the water is near the surface.

I don't deny the convenience of a basement, but it IS an added expense during construction. Think of the cost of a 1-story vs. a 2-story house with the same size footprint. They won't cost the same.

I agree. As far as concrete insulation values, I believe concrete walls would need additional insulation on the walls. But this would not eliminate concrete as an outstanding building material in a tornado prone area.

Remember what a tornado is: wind. Wind blowing against a wall exerts a force, regardless of what the material is made of. And regardless of what the wall is made of, you're more likely to knock it over than to break it.

Tornadoes also create very low pressure; this causes all the walls to want to spring outward. Considering that the only thing holding up a wall is another wall, you can see why this might be bad.

This tornado had sustained winds of over 200 mph; that's a velocity pressure of just over 100 pounds per square foot. (The concrete floors of an office building are typically built to around 75 pounds per square foot.) On a wall ten feet high and twenty feet long, that's 20,000 pounds of force. That's a lot for any wall, concrete or not.

I did not realize concrete had that low of an insulation value. Why would the fire marshall have an issue with concrete walls when it comes to fire?

It's not combustible, but it's greatly weakened by the heat. Same with steel. Look on the underside of a concrete slab in a multistory building, you'll often see spray-on fireproofing on the steel and the deck.

Here's an example:

 

[Huntn]

Remember what a tornado is: wind. Wind blowing against a wall exerts a force, regardless of what the material is made of. And regardless of what the wall is made of, you're more likely to knock it over than to break it.

Tornadoes also create very low pressure; this causes all the walls to want to spring outward. Considering that the only thing holding up a wall is another wall, you can see why this might be bad.

This tornado had sustained winds of over 200 mph; that's a velocity pressure of just over 100 pounds per square foot. (The concrete floors of an office building are typically built to around 75 pounds per square foot.) On a wall ten feet high and twenty feet long, that's 20,000 pounds of force. That's a lot for any wall, concrete or not.

I agree, the wall in combination with the roof structure holds it all together. As a rule commercial buildings tend to hold up better than the blocks of splintered piles of rubble that used to be houses.