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Author Topic: It's hard being a building block...sooooo much pressure !!..or is there ?  (Read 4936 times)

Offline neilep

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Sirs, Madams, Others !

This is a Skyscraper:




Nice isn't it ? Notice how scraping of the sky it is ?

Sky Scrapers are great...they are like really small buildings but are really really big ....DOH !!


I think I might actually know the answer to my question but I'll ask it anyway because I don't know for sure.

Is the pressure acting on the lower blocks really taking on the weight of all above them ?

If so, does this mean that the nature of the block is different than the ones at the top ?..ie: stronger mix ?..more absorbent of pressure mix ?

Is there compression involved ? ie: do the blocks ' give  ' under the weight !

...or is there a way to evenly distribute the weight of the entire building ?

I realise there are foundations involved but am just interested in the construction and weight distribution



A trip up the Empire State to all those who assist me here. ;)

THANKS ALL

Hugs

neil
xxxx

 


 

Offline iko

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Sirs, Madams, Others !


Is the pressure acting on the lower blocks really taking on the weight of all above them ?

If so, does this mean that the nature of the block is different than the ones at the top ?..ie: stronger mix ?..more absorbent of pressure mix ?

Is there compression involved ? ie: do the blocks ' give  ' under the weight !

...or is there a way to evenly distribute the weight of the entire building ?




Dear Neilengineer,
of course the pressure is acting
on LOWER BLOCKES!!!

ikod   :D
« Last Edit: 26/08/2007 21:15:35 by iko »
 

Offline neilep

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LOL !!..Thanks Iko-nographer...

If it was me at the top of that pile those guys below would have sand in their eyes !!! :D
 

Offline Bored chemist

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If that's true then you wouldn't have been able to climb up.

It's true that the stone at the foot of a skyscraper is holding a pretty large pressure but don't worry too much. The rocks at the foot of a mountain are holding a lot more and have been doing so for a long time (the tapered shape of mountains helps a lot, but the point's still valid.)
 

Offline neilep

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If that's true then you wouldn't have been able to climb up.

It's true that the stone at the foot of a skyscraper is holding a pretty large pressure but don't worry too much. The rocks at the foot of a mountain are holding a lot more and have been doing so for a long time (the tapered shape of mountains helps a lot, but the point's still valid.)

THANK YOU BC...I was going to mention the tapering of mountains  whilst reading your post....but you finalised your post by mentioning it !!...leaving me without the opportunity to look as if I know stuff !! ;)

I agree though...your point is most valid...and your post most welcome !!
THANK YOU BC
 

Offline eric l

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If it were so that the bottom stones had to support the whole weight of the building, you should worry more about the cement between the stones than about the stones themselves.
But you shouldn't worry about the cement either :  sky scrapers are built with a frame (steel in most cases) which takes up most of the load, and the stones and cement only have to carry up to the next horizontal beam above.
This "framing" is not a recent invention, it is just a modern version of what is known in England as the Tudor style with "timbered" and "half timbered" buildings.  In those days (15th century) it was current practice all over Europe, but in England relatively more of those buildings have survived.
 

Offline lightarrow

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If that's true then you wouldn't have been able to climb up.
I can't understand what you mean. If the building weighs x tons and the basement has an area of a, the pressure on the basement is x/a.
So, certainly all the weight of the building is on the basement. Or you intended something else?
 

Offline eric l

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Alberto, he was reffering to Neil's reaction on that picture in message 117265 (the human pyramid) where the lower blocks (or rather blokes in this case) have to carry all the load.
 

Offline lightarrow

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Alberto, he was reffering to Neil's reaction on that picture in message 117265 (the human pyramid) where the lower blocks (or rather blokes in this case) have to carry all the load.
Ah! Ok, sorry!
 

lyner

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Materials Science has been a big help, lately.
In mediaeval times, they built several cathedrals which just crumbled under the load after a short while. Then - back to the drawing board.
The flying buttress - that was an invention and a half. That was the two guys - bottom left and bottom right on the photogaph.
 

Offline JimBob

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Then there is the fact that most concrete basements are now done in one pour so there will be no separation between slabs and everything will be interconnected by the structural steel (rebar) in the concrete.

I might also mention that many skyscrapers float.

 

Offline Bored chemist

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A flying butress didn't stop the masonry being crushed by the weight of the stuff above it. It stopped the walls being pushed out by the roof. I doubt anyone has  built a building where the stonework failed in compression.
Most skyscrapers don't float, but only because they are not on water. They have a density less than that of water so they would float. On the other hand, the windows would probably burst  so don't try it at home.
(Hmm, problem with windows; that sounds familliar)
 

Offline JimBob

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A flying butress didn't stop the masonry being crushed by the weight of the stuff above it. It stopped the walls being pushed out by the roof. I doubt anyone has  built a building where the stonework failed in compression.
Most skyscrapers don't float, but only because they are not on water. They have a density less than that of water so they would float. On the other hand, the windows would probably burst  so don't try it at home.
(Hmm, problem with windows; that sounds familliar)

May I please ask you to take no umbrage at what I am about to point out? Any skyscraper that is not cemented into the bed rock floats. It must as if it did not it would slowly sink into the soil. When an architect (or rather a firm of them) design a skyscraper they must consult Archimedes's “On Floating Bodies — Book I". There are two significant "Laws" in this tome. The “Law of Buoyancy” for example. If not on bedrock, all of the skyscraper is heavier than the soil underneath it. - steel concrete, etc. and has a lot more weight. So it is not buoyant in soil. Soil also has other problems. It has water in it. This lowers its density even further. I stole the following in quotes "Take “the Toppling Structure” model, which depicts an object with a flat base topped by a mass rising above the supporting surface. Think of a skyscraper. An earthquake has liquefied the soil under it, and now it’s sinking. Archimedes’ equation “proved” that, even when the surface becomes a liquid, “this structure cannot topple until its base is partially exposed above the soil level” " In other words, until the building floats above the soil.

Buoyancy calculations, making sure the skyscraper - or even a 10 story building - will float in the medium in which it is constructed are absolutely necessary for skyscrapers not firmly fixed to bedrock.
« Last Edit: 22/08/2007 23:37:54 by JimBob »
 

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