The Applicability of "Depthscrapers"

[Skgoa]

How high is the chance to be hit by a tornado anyways? Comparing that versus the cost of a tornado-proof building might explain why its done this way.

(P.S. Skoga, you have a small typo in that sig quote)

Thanks, but that was in the original post.

[Akhlut]

Individual buildings have a relatively low chance of being hit, but, if you happen to be in, say, Oklahoma during a monster storm, very bad things can happen. That storm I linked to caused nearly $2billion worth of damage (in 2007 money). And Oklahoma is prone to a lot of tornadoes, and regularly receives millions of dollars in damage due to tornadoes. The main problem would be the initial capital in building a depthscraper; while it might be more expensive to have to rebuild numerous buildings once or twice, no one wants to put the money upfront to build a structure of that nature, I'd assume.

[Broomstick]

How high is the chance to be hit by a tornado anyways? Comparing that versus the cost of a tornado-proof building might explain why its done this way.

Even if you live your whole life in "tornado alley" the odds are that you will never take a direct hit - most people never do. However, the chances of getting hit are not zero. Tornadoes are incredibly violent, but relatively small, localized, and of short duration. If you look at a street of homes after one goes through you can have one house completely destroyed and the one next to it only having minor damage.

It makes more economic sense to build for normal weather (which around here can still be pretty intense), install a shelter of some sort, and insure the house/possessions. The main goal is to protect the people.

[Sky Captain]

How expensive it would be to build tornado proof house comparad to normal house of similar size? For example large freighters are bigger than most buildings and have to regulary surwive storm waves which create far more stress on the hull than even the most extreme tornado would cause. And a ship doesn't cost orders of magnitude more than skyscraper of similar size.

[General Zod]

How expensive it would be to build tornado proof house comparad to normal house of similar size? For example large freighters are bigger than most buildings and have to regulary surwive storm waves which create far more stress on the hull than even the most extreme tornado would cause. And a ship doesn't cost orders of magnitude more than skyscraper of similar size.

It's not just a matter of stress on the body, freighters are in motion in a fluid medium while houses are fixed in place thanks to their foundations. You have to account for a completely different environment with houses than you do a ship.

[Broomstick]

How expensive it would be to build tornado proof house comparad to normal house of similar size? For example large freighters are bigger than most buildings and have to regulary surwive storm waves which create far more stress on the hull than even the most extreme tornado would cause. And a ship doesn't cost orders of magnitude more than skyscraper of similar size.

Well, you'd have to build something capable of withstanding winds up to 500 kph, plus withstand any debris launched by those winds including entire other buildings. It's not just the wind, you see, it's also the debris flying around. That's why even masonry buildings can be knocked down by tornadoes.

Not sure how you'd go about calculating that. For something like a nuclear power plant building to that extreme makes sense, and they do that, but that's part of the reason such facilities are enormously expensive. The cheapest way to build a tornado proof house would, in fact, be to put in under ground.

[Simon_Jester]

How expensive it would be to build tornado proof house comparad to normal house of similar size? For example large freighters are bigger than most buildings and have to regulary surwive storm waves which create far more stress on the hull than even the most extreme tornado would cause. And a ship doesn't cost orders of magnitude more than skyscraper of similar size.

It's not just a matter of stress on the body, freighters are in motion in a fluid medium while houses are fixed in place thanks to their foundations. You have to account for a completely different environment with houses than you do a ship.

Counterintuitively, being anchored to a rigid foundation is actually a disadvantage. A ship can get slapped around by wave action enough to tip it a few degrees away from its 'proper' orientation, bounce back, and be just fine.

Tip a building a few degrees away from the vertical, and you rip it off its foundations and it falls over.

Being nailed down is a disadvantage when your structural integrity depends on those nails holding in place

Also, buildings are very often made of masonry and ceramics- brick, glass, stone, concrete. Those are substances that do not take tensile forces well. Which makes them vulnerable to being torn or shaken apart by forces much smaller than the ones it would take to crush them flat.

Steel and wood both handle tension pretty well*, but wood is far too weak to stand up to tornado-force winds, while steel construction for a whole building is liable to be impractical... and even then you'd need a lot of it to make the building tornado-proof. Given the fact that tornados can exert forces of (I'd expect) at least a pound per square inch or more over a structure with hundreds of square feet of surface area, you're looking at the equivalent of tens or hundreds of tons of weight pushing on the side walls of the house.

It's just not worth it.

If it's any consolation, ships don't take tornadoes very well either, not on a direct hit. It's just that there are more houses per square mile than ships, so houses get ripped up by tornadoes more often.

*(relative to their compressive strengths, not in absolute terms; wood is after all much weaker than steel).

[General Zod]

Counterintuitively, being anchored to a rigid foundation is actually a disadvantage. A ship can get slapped around by wave action enough to tip it a few degrees away from its 'proper' orientation, bounce back, and be just fine.

It actually seems pretty intuitive to me. A ship can roll with its punches while a house doesn't have any choice but to take them head on with the full impact.

[Sky Captain]

Not sure how you'd go about calculating that. For something like a nuclear power plant building to that extreme makes sense, and they do that, but that's part of the reason such facilities are enormously expensive.

Wouldn't the tornado proof part come by default for such structures. If a reactor dome can survive full speed impact by fully loaded A380 then tornado should be minor problem.

If it's any consolation, ships don't take tornadoes very well either, not on a direct hit.

How severe damage would be there if say 20 000 ton cargo ship were dirctly hit by F5 tornado? I'd guess most windows and stuff like radars, antennas would be gone and some damage to superstructure from flying debris. If it is container ship then many containers blown overboard. But the main structure should remain intact, IIRC ship hulls are designed to take loads up to 15 - 20 tons per square meter without damage.

[LadyTevar]

If it's any consolation, ships don't take tornadoes very well either, not on a direct hit.

How severe damage would be there if say 20 000 ton cargo ship were dirctly hit by F5 tornado? I'd guess most windows and stuff like radars, antennas would be gone and some damage to superstructure from flying debris. If it is container ship then many containers blown overboard. But the main structure should remain intact, IIRC ship hulls are designed to take loads up to 15 - 20 tons per square meter without damage.

The ship would be lifted up out of the water, and if it's lucky just flipped over. If it's unlucky, the tornado will carry it for several meters, and it will get thrown by the winds into whatever happens to be nearby.

[Sea Skimmer]

Building underground fucking sucks unless you have ground which is completely dry, all the time. Water is the utter bane of underground construction, and quite often precious little can be done but to pump it out. Even massive facilities you'd think were awesomely thick and totally sealed like ICBM silos still need sump pumps to stay dry. Concrete isn't waterproof, and steel rusts.

So out in the desert, when safe from flash floods, sure underground depthscraper living might work, but it would accomplish nothing that you couldn't do protection wise with a surface bunker banked in earth that was far cheaper. Indeed a giant hollow center depthscraper would be absurdly poorly protected, as well as being absurd less safe in the event of a fire. Smoke goes up.. the exits are up... life is not good.

[Gil Hamilton]

The problem with the notion of the Depthscraper is that earthquakes are large vibrations acting on the Earth. Solid rock transmits vibrations very well. Thus, embedding your building into that solid rock is probably a bad idea if one of your design requirements is not killing everyone inside the structure in the event of an earthquake.

What's interesting is that the Japanese have building "earthquake-proof" buildings down to an art, by making buildings that sway under large vibrations without themselves having vibrations transmitted terribly much through them, in addition to mass dampers, base isolators, and carefully surveying the land to put your buildings in places where they'll avoid the worst of tectonic activity. The last one is particularly important, as the best way to have buildings not be destroyed by earthquakes is not to have them where the earthquake is likely to be centered. The other thing the Japanese do is combine this with excellent training for citizens in what to do in case of natural disasters.

[Sea Skimmer]

The problem with the notion of the Depthscraper is that earthquakes are large vibrations acting on the Earth. Solid rock transmits vibrations very well. Thus, embedding your building into that solid rock is probably a bad idea if one of your design requirements is not killing everyone inside the structure in the event of an earthquake.

What's interesting is that the Japanese have building "earthquake-proof" buildings down to an art, by making buildings that sway under large vibrations without themselves having vibrations transmitted terribly much through them, in addition to mass dampers, base isolators, and carefully surveying the land to put your buildings in places where they'll avoid the worst of tectonic activity. The last one is particularly important, as the best way to have buildings not be destroyed by earthquakes is not to have them where the earthquake is likely to be centered. The other thing the Japanese do is combine this with excellent training for citizens in what to do in case of natural disasters.

Burying is not that bad, it can even be protective if you go down 100-200ft or more. One other thing Japan is doing as we speak is burying its infrastructure like that. Absolutely huge water and power tunnels are being dug under Tokyo to move all the utilities underground’s the reason is simple, almost all the actual movement of the ground in an earthquake takes place near the surface. Go down a significant depth and the ground doesn’t move and thus vibrate human structures the same way. The movements are dampened by the pressure of the ground. A depthscraper would need a heavily reinforced neck, but the rest of it would not be badly off relative to the costs of earthquake proofing in the surface. A vertical building that sways in the wind as well as being subject to ground motion is just awful. This is also Tokyo can get away with having such an extensive subway system, without it being an automatic death trap everyone fears. In fact in an earthquake you want a firm foundation, solid rock with some real integrity is actually good. Soft material is not because it will liquefy or extensive shift.

[madd0ct0r]

going back to the tornado risk, it seems I misjudged them pretty badly.

I really hadn't considered the debris damage, so it makes sense you'd need to ensure everybody built their homes tough enough to not fly off, and hope a lorry isn't parked near
We'd be looking at devastating damage over a very small area, while the tropical storms (or north sea storms) that i do know how to design for are less intense but can take out entire cities. by.

hence building tougher is worth it - in Vietnam nearly all new construction is concrete; slabs, columns and roofs. God knows how badly it'll perform in a Earthquake but the storms are 1-2 a year.

Most skyscrapers have/need extensive basements. Because these hollow concrete rooms are below water level, they actually want to float, lowering the total load on the foundations. Impossible to balance the forces perfectly, but the Victorians were having a good stab at it 100 years ago.
The depthskrpaer will need several dozen meters of mass concrete at the bottom, or tension piles (rock bolts?) to avoid popping up like a cork. We have enough trouble with manholes doing that.

[Gil Hamilton]

That's interesting stuff and somewhat counterintuitive to me. Solid rock is excellent at transmitting vibrations; the closer you get to a dense, crystal system, the easier it is to transmit energy through the system without the vibration being damped by lattice irregularites and gaps. This is physically demonstratable. That's why anti-earthquake buildings have damping systems built into them. You want a strong foundation that won't shift... but then you need something to damp the vibration delivered to your building that got transmitted with little loss through your foundation.

I don't doubt your facts, it just strikes me as embedding your building in a medium that propagates vibrations significantly better than air does is a bad idea. However, if the weight the system acts to dampen the vibrations, that's useful.

[Sea Skimmer]

That's interesting stuff and somewhat counterintuitive to me. Solid rock is excellent at transmitting vibrations; the closer you get to a dense, crystal system, the easier it is to transmit energy through the system without the vibration being damped by lattice irregularites and gaps. This is physically demonstratable. That's why anti-earthquake buildings have damping systems built into them. You want a strong foundation that won't shift... but then you need something to damp the vibration delivered to your building that got transmitted with little loss through your foundation.

Its okay if things shift, if they all shift together. That's why underground stuff will work. You move, the earth around you moves too because pressure binds you together. As long as what you build is nice and strong it will hold together as it does so, and you would only have damage at places in which the earth permanently shifts right along a fault line. A building in the open air has nothing to support it so its far more vulnerable to shaking apart.

[Enigma]

Wouldn't a decent way to build a tornado-resistant (you can't proof it and I find it silly to build an underground house or building in the style shown in the OP for if the iris doesn't close and an F5 tornado goes over it, I see it coming down and trashing the building. ) would be to build one that resembled a mound? Nothing for the tornado to "grab" onto? Just a reinforced concrete mound (obviously with windows and door. ).

[Broomstick]

Doesn't have to b a "mound" - a blocky but sufficiently reinforced concrete block building would probably do as well, it's just that cost of building houses to that standard is prohibitive. Not to mention fugly.

This is the principal behind "storm rooms" for mobile homes and pre-fab buildings these days - you have one massively overbuild room to duck into that can stand up to an F5. When not in use as a storm shelter they usually double as a closet or store room of some sort, though some people report sleeping in them as with the door shut they are extremely quiet. You have to be sure and anchor such a thing sufficiently to the ground so a tornado can't pick it up and make it airborne, but that's certainly within the scope of modern technology.

[Enigma]

Doesn't have to b a "mound" - a blocky but sufficiently reinforced concrete block building would probably do as well, it's just that cost of building houses to that standard is prohibitive. Not to mention fugly.

This is the principal behind "storm rooms" for mobile homes and pre-fab buildings these days - you have one massively overbuild room to duck into that can stand up to an F5. When not in use as a storm shelter they usually double as a closet or store room of some sort, though some people report sleeping in them as with the door shut they are extremely quiet. You have to be sure and anchor such a thing sufficiently to the ground so a tornado can't pick it up and make it airborne, but that's certainly within the scope of modern technology.

But would one built like a mound be more aerodynamic and would have less pressure pressed against it by high winds and tornadoes?

[Sea Skimmer]

How expensive it would be to build tornado proof house comparad to normal house of similar size? For example large freighters are bigger than most buildings and have to regulary surwive storm waves which create far more stress on the hull than even the most extreme tornado would cause. And a ship doesn't cost orders of magnitude more than skyscraper of similar size.

Semi tornado proof houses rated for 140mph winds with steel frames and steel walls are gaining ground slowly; the cost is about 5% greater then wooden framing but some people don't like the way they look for whatever reasons. If you want total F5+ tornado proofing, then lots of different material will work because the easiest way to do that is mound up earth around the walls and on the roof. This will also vastly reduce heating and cooling bills, though it does mean you need very good water proofing. At this point resisting 300mph atomic blast isn't that big a deal.

[Gil Hamilton]

Its okay if things shift, if they all shift together. That's why underground stuff will work. You move, the earth around you moves too because pressure binds you together. As long as what you build is nice and strong it will hold together as it does so, and you would only have damage at places in which the earth permanently shifts right along a fault line. A building in the open air has nothing to support it so its far more vulnerable to shaking apart.

My concern is the contents on the building surviving. I can shake an aluminium can violently without damaging it at all due to it's geometry and materials, but if something was inside the can, it would be severaly banged around. I suppose though the big killer in earthquakes is things collapsing on people inside the buildings and putting it in solid rock transmits more energy to the interior the building such that the internal structure of the thing can be damaged.

I'm not saying you are wrong, naturally, I'm just trying to wrap my head on this.

[madd0ct0r]

no, you are right.

the tin can that is the dethscraper's exterior wall would be fine, as long as all of it is moving the same amount.

inside the can, the occupants and their belongings would be rattling about. but not as much as you might think.
I'm going to assume you'd sensibly use vertical steel restraint for internal walls (or really light walls plasterboard)

http://www.youtube.com/watch?v=iRzK6JIvlPw

watch it twice, preferably with a ruler against the screen. Notice how much more the top moves then the base?
the entire depth scraper would be moving the same amount as the base.
Possibly enough to knock your wardrobe over (assuming you hadn't tied it to the wall with a steel bracket, which is what i do to my bookcases as a matter of course). not much more.

this vid shows internal movement, but dosen't state at that floor height. I'm going to assume the top as it's a promo vid.

Quakes can include vertical components to the movement, which might affect the depthscraper more then a regular building.
http://www.youtube.com/watch?v=GCBRBxBL1Dc but I can't find a good vid for a buildings test.

[Sea Skimmer]

Nuclear bunkers do use base isolation systems or chains suspended from the ceiling and buffered with hydraulic shock absorbs to protect the occupants of the facility from intensive shockwaves. They also in some instances have seats with seat belts, such ICBM launch control facilities. But that's to protect against a nuclear groundburst, which would be similar to a earthquake directly under your structure. I can’t internal shaking this being a serious problem in an earthquake in a depthscraper, for the reason madd0ct0r has well illustrated in that video.

[Master of Cards]

That's interesting stuff and somewhat counterintuitive to me. Solid rock is excellent at transmitting vibrations; the closer you get to a dense, crystal system, the easier it is to transmit energy through the system without the vibration being damped by lattice irregularites and gaps. This is physically demonstratable. That's why anti-earthquake buildings have damping systems built into them. You want a strong foundation that won't shift... but then you need something to damp the vibration delivered to your building that got transmitted with little loss through your foundation.

I don't doubt your facts, it just strikes me as embedding your building in a medium that propagates vibrations significantly better than air does is a bad idea. However, if the weight the system acts to dampen the vibrations, that's useful.

What makes underground safer is that solid rock shakes as one and stops at once. The soil and non solid bedrock on the surface will keep going for a bit after the earthquake has finished which means more force acting on the building. Also the underground thing has all the ground supporting which the above ground structures do not. (dampening systems are because earthquakes have a nasty habit of finding the frequency of the building and destroying it.

[Kreller1]

Decent idea until a tsunami washes a huge wave over the opening and floods the entire thing.