Tower Collapse Questions for Critical Thinkers

DGM said:
The part he won't get is this "more weight" that he's talking about is the center of gravity that he says should move because of the weight. Anyone else (everyone) see this confusion?:o
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This is confusion?

What does titling a mass do to the distribution of its weight on its support?

That is so difficult to understand. :D :D

psik
 
Sabrina said:
Isn't anyone else wondering why kyle here is using the analogy of a bucket of DIRT to simulate the "approximately 95% hollow and filled with air" Twin Towers?
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My guess is that it's because this major epiphany occured in a sandbox.
 
kylebisme said:
For ease of responding, I'll number the questions below:

1) What is the orientation of the upper portion mass?
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Its tilted

2) How does this orientation relate to the force exerted on the lower portion of mass?
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It barely has any relevence at all. The center of mass of that upper section is still above the lower section which means that it will fall(downwards) on top of the lower section

3) Is that distribution of force reflected in the destruction of the lower portion of mass?
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It actually is although by the time the entire structure has collapsed it had very little effect.

the structure collapsed because enough force was impinged upon the florrspace to fail the floor pans and their trusses thus sending even mor mass down on the next lower floor space. The core simply could not have stood on its own without the lateral support of the perimeter columns via the floor trusses and thus the core too failed. After about half way down though the amount of falling debris and the associated mass loading plus the dynamic loading would have falied the core simply by pummeling it..

Now, having read only the first post I will assume that others have said much the same and that was follwoed by a misuse and misunderstanding of the physics involved by the originator of the thread.
 
psikeyhackr said:
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LOL

Oh, so the tilted upper portion couldn't put more pressure on one side.

Bizarro Physics indeed. :D

psik
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Once the mass is falling it falls straight down. It may rotate but the mass is still falling straight down and all the is required to fail a floor is to impact the floor pan with enough mass and dynamic loading to fail trusses that were designed to accomodate the forces expected for ONE STATIC FLOORSPACE.

In a typical post and beam construction this might have been arrested on the side with slightly less originally falling mass. That is because the columns are spaced apart. In the case of these long span buildings the floors were absolutly required to laterally support the core columns and loads were distributed to perimeter and core via very long trusses. Fail several trusses and one compromises the stability of the structure more dramatically than in a typical post and beam structure (such as WTC 5).
 
psikeyhackr said:
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This is confusion?

What does titling a mass do to the distribution of its weight on its support?

That is so difficult to understand. :D :D

psik
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When the initial collapse began the upper section no longer had a support to pivot on and thus it would have then been rotating about its center of mass to conserve angular momentum. The center of mass was then moving straight downward from where it was at the moment the upper section lost its pivot support.

As initial collapse began the columns on one side were in more compression than they could withstand and buckled. Columns on the other side would have been undergoing a torsion and tension that was they were never designed for and would have bent and snapped or simply folded over as the upper section fell. As all columns were failed and the upper section of those columns no longer lined up at all with their counterparts on the lower section, all mass and dynamic loads would have impinged upon the floor spaces of both the long span areas and the core.

Any rotation the upper section did have was very slow and would have been lost to the upper block as a whole when it came apart as it fell onto the lower portion of the building.
 
jaydeehess said:
Any rotation the upper section did have was very slow and would have been lost to the upper block as a whole when it came apart as it fell onto the lower portion of the building.
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You call this VERY SLOW?

http://www.youtube.com/watch?v=9SSS0DDqfm0

This was 52 minutes after the oscillation from the plane impact had ceased and the plane deflected the building less than 16 inches. So gravity and fire were supposedly the only available influences. So what caused the rotation?

psik
 
psikeyhackr said:
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You call this VERY SLOW?

http://www.youtube.com/watch?v=9SSS0DDqfm0

This was 52 minutes after the oscillation from the plane impact had ceased and the plane deflected the building less than 16 inches. So gravity and fire were supposedly the only available influences. So what caused the rotation?

psik
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Uneven support, caused by the weakening of the structure on the side were the plane hit. There is nothing inherently dubious about that. The problem is the lack of the rotation of the block being reflected in the destruction bellow it.

However, that video does show an curious cloud of dust and debris rising from the upper section of the building after it tumbles off to the side, but before it has a chance to hit the ground.
 
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kylebisme said:
This actually exemplifies my point well, the first illustration that is. With the red block at the angle it is, would you expect the destruction of the blue block below to be horizontal, or match the angle of the red block?
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What part of "the force is straight down as physics dictates" is confusing you?
 
psikeyhackr said:
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You call this VERY SLOW?

http://www.youtube.com/watch?v=9SSS0DDqfm0

This was 52 minutes after the oscillation from the plane impact had ceased and the plane deflected the building less than 16 inches. So gravity and fire were supposedly the only available influences. So what caused the rotation?

psik
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THAT is the best point you find in my post to address?

Yes it would be slow. All things being relative. However no matter what its rotation, the greatest percentage of mass of the upper section still remains above, and therefore falling onto, the lower portion of the structure where it will be impacting the floor of the levels below initial collapse.
 
kylebisme said:
Uneven support, caused by the weakening of the structure on the side were the plane hit. There is nothing inherently dubious about that.
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Yes.

The problem is the lack of the rotation of the block being reflected in the destruction bellow it.
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The rotation of the upper block(approx 15% of the entire building) will have little effect on the distribution of the remaining 85% of the structure. There is no reason for it to do so. The only effect it would have is that the portion of that upper 15% of the structure, which was not still over the lower structure, would likely to come to rest to that side of the tower.

However, that video does show an curious cloud of dust and debris rising from the upper section of the building after it tumbles off to the side, but before it has a chance to hit the ground.
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You mean the expellling of all the smoke within the fire floors as their floors become closer to their ceilings and the thousand square feet of drywall gets crushed in a second or two.? That cloud of 'dust'?
 
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Arus808 said:
Lets see, the top is leaning toward the area that the plane impacted with, meaning that the support columns there have lost its total strength and/or are missing.
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We are writing about the South Tower?

While looking at the OP video. I found this clip

Google Video This video is not hosted by the ISF, the ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
I AGREE


I think it's from a BBC production ("Why The Towers Fell").
During the last few minutes, it discusses the collapse mechanism of the South Tower. It is surmised there that the initial impact was ruled out as the direct cause of collapse and that the building fell (away from the jet impact zone) toward the fire in the NE corner.

Am I confusing something?

Compus

Edited to add. I can't see the clip working full link below,

http://video.google.com/videoplay?d...pX2Mab0qgKTxZWtAw&q#docid=2741743293567850827
 
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jaydeehess said:
The rotation of the upper block(approx 15% of the entire building) will have little effect on the distribution of the remaining 85% of the structure. There is no reason for it to do so. The only effect it would have is that the portion of that upper 15% of the structure, which was not still over the lower structure, would likely to come to rest to that side of the tower.
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Jesus H. Christ!

The plane hit the south tower at the 81st floor. So it was more like 29 stories of 110.

29/110 = 26%
28/110 = 25%

15% would be only 16.5 stories. It was a lot more than that for the south tower.

It was about 13% for the north tower but it did not rotate.

psik
 
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psikeyhackr said:
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Jesus H. Christ!

The plane hit the south tower at the 81st floor. So it was more like 29 stories of 110.

29/110 = 26%
28/110 = 25%

15% would be only 16.5 stories. It was a lot more than that for the south tower.

It was about 13% for the north tower but it did not rotate.

psik
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so you think a 30 story building falling isnt gonna cause a ruckus?
 
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