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TheTrueReview

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Interesting discussion. I feel for the people who live in the path. If the area affected by tornadoes has substantially broadened over the years, there'd have to be many thousands of people living in homes that insurers would refuse to insure. It'd be like living on tenterhooks as to when your home and livelihood could get get wiped out.
 

TrickyPutt

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What is expanded metal Limp? Any other names it goes by?
its that sheet metal they die cut louvers in and pull apart leaving a diamond shape opening. It may not be the best choice above grade, but a heavy gauge of it in a pour vertically to protect from a tornado missile is what i am after, i have seen the poor shear strength of a lot of walls and would try to strengthen that aspect, but even 12" oc #4 rebar wouldnt do what i want orifice wise. Structural steel could help prevent collapse of the roofing structure. I know F2 suggestions for shelters include 3/4 plywood for impact absorption on either side of 1/4 plate steel for toughness. You might see steel simply gone if it wasnt attached to the earth well, and you might see it bent after a big Tornado. You just dont often see heavier steel torn though, and thats a big key for me.
 

nututhugame

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its that sheet metal they die cut louvers in and pull apart leaving a diamond shape opening. It may not be the best choice above grade, but a heavy gauge of it in a pour vertically to protect from a tornado missile is what i am after, i have seen the poor shear strength of a lot of walls and would try to strengthen that aspect, but even 12" oc #4 rebar wouldnt do what i want orifice wise. Structural steel could help prevent collapse of the roofing structure. I know F2 suggestions for shelters include 3/4 plywood for impact absorption on either side of 1/4 plate steel for toughness. You might see steel simply gone if it wasnt attached to the earth well, and you might see it bent after a big Tornado. You just dont often see heavier steel torn though, and thats a big key for me.
OK, up here we use that to form shutoffs and such. NEVER for added strength in a pour. It can really do nothing that isn't being done by the rebar. The minimum wall pour i've ever seen is 8" thick. I know tornados are strong, but a projectile through 8 to 12" of concrete? I just don't think so. If anything could make it through that, the mesh isn't going to do anything the concrete itself wasn't already. A steel roof structure like what i've seen built could withstand basically any storm, it's the decking that would go. The structural (if we're talking I-beam construction) should be fine. So long as you're inside of that structure you shouldn't have to worry about being decapitated by the steel decking. Myself, if I were that worried about it i'd just have a concrete roof.
 
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limpalong

limpalong

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What is expanded metal Limp? Any other names it goes by?
Expanded Metal / Expanded Steel | Direct Metals

The above link gives some photos of expanded metal. It's used for grating, stair treads, etc. Someone may want to use it in a concrete wall. If that's what they want to use, fine. It will substantially reduce the torsion strength of the wall. But...

Most residential walls are 4" thick. A few... very few builders will go to 6". If you use expanded metal in the center of that thin of a wall, you won't even have the torsional strength of a 2" wall on each side of the metal. If the complete concrete mix, aggregate and all, cannot flow uniformly through and around the reinforcing, you lose strength. The mix will "stack" against the metal allowing only the 'paste' through and leaving a 'pile of rocks' on the front side.

First, one really needs to have a Professional Civil Engineer design the structural members... the walls and the reinfocing therein. If they think money will be saved doing the design themselves, they will get what they paid for. One could certainly reduce the reinforcing steel spacing to 6" centers, if fearful of something penetrating the concrete wall through a 12" spacing. Or, go to an 8" wall with two mats of #4 steel. 2" clear, 1/2" bar, 3" between mats, 1/2" bar, 2" clear. The #4 bars on 12" centers could have the mats offset so a foreign object penetrating the wall would need to go through a 6" X 6" space.

I really need to bow out of this discussion. As I said, I love concrete... if designed and placed correctly. I've seen too much concrete in residential applications or in commercial applications without competent on-site observation that has failed. If allowed, contractors will take the cheapest and easiest way out. Builders want the cheapest solution so they can make a profit on sale or rental of the property. I don't know how many sidewalks and slabs I've taken out that are junk. Mesh is walked down to the bottom of the slab as concrete is placed. Workers will attempt to move concrete with a vibrator, separating the aggregate from the cement. If you tell them to use the vibrator for consolidation... keep it vertical and a quick insertion every 18" or so... they want to add water so it will flow. A couple years later, the sidewalk is cracked and looks terrible.

Years ago, we constructed some tank marshalling areas at a local military installation. Not only were they running army tanks on the surface, they were turning and spinning them. We had to place concrete in curbs and bollards that would take a tank running into them and still be standing. Wire mesh or expanded metal wasn't used in any of those structures. They were designed and constructed, using good engineering principles... not a sketch on a napkin.
 

TrickyPutt

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im in the deepest color.
 

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TrickyPutt

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And Limp, what would you guess it would take to stop a 300mph wind with chunks of debris in it?

Given the weight of 27 cubic feet of concrete, I would think my shovel and I were outmatched. I might consider getting my 3 bag mixer out of the shed to help, but too much weight and it trips its thermal breaker. Plus one thing I learned doing some homeowner work is that the soil and foundation surely must be in a particular condition of compaction or the whole shebang will settle, surely inviting some cracking. I dont think my plate compactor is gonna get'r dun so my mind was wondering off toward a hyster vibrating calcium filled drum as it was the last large compacting machine I was ever around. I kinda got the impression that a few folks with that kinda gear might be involved. I thought I might paint it though. If thats ok with you.

It will probably just turn out that a poured shell is too big for the wind load and the thing gets turned into a smaller, infinitely denser structure with a base of weight stuck down into the earth that weighs an unreasonably large amount of tons to prevent it from being plucked from the earth. Too bad the big storms can toss locomotives eh? The entry door design is two L shapes to prevent shrapnel entry even if the door is removed. Im kinda fiquring the costs of that are so high that a below grade shelter is what I would end up with, and a lifetime supply of bug spray for the scorpions and black widows.
 
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nututhugame

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And Limp, what would you guess it would take to stop a 300mph wind with chunks of debris in it?

Given the weight of 27 cubic feet of concrete, I would think my shovel and I were outmatched. I might consider getting my 3 bag mixer out of the shed to help, but too much weight and it trips its thermal breaker. Plus one thing I learned doing some homeowner work is that the soil and foundation surely must be in a particular condition of compaction or the whole shebang will settle, surely inviting some cracking. I dont think my plate compactor is gonna get'r dun so my mind was wondering off toward a hyster vibrating calcium filled drum as it was the last large compacting machine I was ever around. I kinda got the impression that a few folks with that kinda gear might be involved. I thought I might paint it though. If thats ok with you.

It will probably just turn out that a poured shell is too big for the wind load and the thing gets turned into a smaller, infinitely denser structure with a base of weight stuck down into the earth that weighs an unreasonably large amount of tons to prevent it from being plucked from the earth. Too bad the big storms can toss locomotives eh? The entry door design is two L shapes to prevent shrapnel entry even if the door is removed. Im kinda fiquring the costs of that are so high that a below grade shelter is what I would end up with, and a lifetime supply of bug spray for the scorpions and black widows.
Generally foundations are dug down to undisturbed soil. Soil testing done by civil engineers will determine if the soil can carry all intended loads including live loads such as snow, wind, etc... the footings and foundation are designed by an engineer based on the soil findings, bearing points in said structure, etc... That said, you're correct in assuming that structures settle. It's pretty much a sure thing that any structure is going to settle/heave even if only fractionally and over time. That does not mean that there has to be cracking though. There are products and methods out there to account for such movement. Skyscrapers move more than the average person wants to know. Those methods and products are not all 100% full proof, but unless you're driving pilings down to bedrock it's what you get and even if you drove pilings to bedrock when tectonic plates touch your structure will move. I know, that's a bit overboard, but hopefully i'm making my point. The soil a structure is built on combined with the design of the foundation and the back fill will pretty much keep a structure firmly in it's place to the point where in an average persons life they wont actually notice any settling if done correctly.

My house is a 1910 and has minimal cracking in the original plaster. The foundation is a softer cream brick and the floor is 2x8 with the main beam being a 6x8. Shit is stronger than you think. And like Limp has said, they can do wonders with concrete these days so long as it's done how it is intended to be.

As for what it would take to stop a 300mph chunk of debris i'll answer like this... try to shoot a bullet through 8" of concrete and let me know how it works out.
 

TrickyPutt

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As for what it would take to stop a 300mph chunk of debris i'll answer like this... try to shoot a bullet through 8" of concrete and let me know how it works out.

Its an interesting question, but the bullet would splatter. Sometimes slower objects are more dangerous. I can shoot an arrow through a 5 gallon plastic bucket of water, but it stopped my rifle bullet from exiting.

I had forgotten about those soil density tests. When I was younger I was working on a construction of a school in Eagle River, AK. The site was on the lower side of the Mountain range that has Anchorage at one end and Wasilla on the other. Lots of Alluvial soil that turns to Jello during an Earthquake, which happened often. The far end of Anchorage sank into the dirt in 1964, and they left the buildings as a drive through musuem area. Just roofs and corners of buildings sticking up.

The engineers at the school site used a radioactive soil density tester that looked like a yellow highway cone and shot energy into the soil to get a readout. The word was it was crazy expensive, and the USKH firm had a man with it at all times. I guess they would take some core samples also.

One other thing that makes me curious about portland cement crystals is secondary impact. I put a bunch of UL level 4 bullet resistant glass in a military facility, where level 4 stops 3 shots of 30-06 in a 6 inch triangle shot pattern. 12 guage Buckshot was rated by UL as being even tougher to stop, I guess as the first pellets broke through the next pellets didnt lose as much energy and could break through even further. Multiple bricks at 300 mph would be devastating. The Mineral Hardness scale might come into play as if it were a Tornado sandblaster.
 
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