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OOS Collapse Propagation Model

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ElMondoHummus said:
Waitaminute... how the hell's the core supposed to just stand, let alone withstand forces without the lateral bracing from the floors? And on top of that, how the hell are the floor trusses supposed to separate from the core columns without pulling them in a direction they weren't designed to take stress in?
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I could have sworn somebody here (maybe even yourself) once told me the floor truss connections were the weakest link.


ElMondoHummus said:
Absolutely. I'm just at a loss as to how someone could seriously propose the stripping of the perimeter columns and the floors yet say that the core would somehow resist damage. It's as if they think the core would stand denuded, like some tree who's branches have been stripped off.
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Try stripping the branches from a tree and see if it collapses.
 
bardamu said:
All you need to do is say whether you still believe that, in the particular case of the WTC twin towers, the event of a column to column impact would be the most favorable to arrest.
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What's the alternative?

Columns impacting floors.

I think you just might have had an alternative hypothesis that proposed that this just might be more likely to arrest the collapse.

Care to flesh this out a little?
 
Bell said:
:eye-poppi
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Why is it that we could've predicted that some truther would rise to the bait? You're right, Bell, that deserves little more than a blank stare in response. Trust a truther to compare apples to cartoons; my whole point in bringing up the tree analogy was to point out exactly how truthers misunderstand and misrepresent the Towers construction. You and I know that a tree trunk doesn't depend on branches bracing against something else to keep from falling over whereas the Towers cores did. Wouldn't you know it, some fool walked right into that trap.

Why am I not surprised. :rolleyes:
 
ElMondoHummus said:
Why is it that we could've predicted that some truther would rise to the bait? You're right, Bell, that deserves little more than a blank stare in response. Trust a truther to compare apples to cartoons; my whole point in bringing up the tree analogy was to point out exactly how truthers misunderstand and misrepresent the Towers construction. You and I know that a tree trunk doesn't depend on branches bracing against something else to keep from falling over whereas the Towers cores did. Wouldn't you know it, some fool walked right into that trap.

Why am I not surprised. :rolleyes:
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This thread needs more Keebler Elves. To bad Reality Bites doesn't seem to post here anymore.

avatar9866_3.gif


*high five*
 
Seymour Butz said:
What's the alternative?

Columns impacting floors.

I think you just might have had an alternative hypothesis that proposed that this just might be more likely to arrest the collapse.

Care to flesh this out a little?
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Let's say the energy in the upper block was double that needed to crush the lower block in a column to column impact. Now let's suppose the floor truss connections were by far the weakest link and 80% of the mass of the upper block fell on the floors outside the core. The floors and the perimeter columns would be taken down easily, but only 20% of the total energy would be left to fall on the core.

The point is, Bazant didn't take the design of the structure into consideration.
 
ElMondoHummus said:
Why is it that we could've predicted that some truther would rise to the bait? You're right, Bell, that deserves little more than a blank stare in response. Trust a truther to compare apples to cartoons; my whole point in bringing up the tree analogy was to point out exactly how truthers misunderstand and misrepresent the Towers construction. You and I know that a tree trunk doesn't depend on branches bracing against something else to keep from falling over whereas the Towers cores did. Wouldn't you know it, some fool walked right into that trap.

Why am I not surprised. :rolleyes:
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There was no rising to any bait - just a misinterpretation. I thought you were saying: "It's as if they think a tree stripped of its branches would stand denuded and the core would do the same."

A better analogy would be a mast supported by guy-wires.
 
bardamu said:
Let's say the energy in the upper block was double that needed to crush the lower block in a column to column impact. Now let's suppose the floor truss connections were by far the weakest link and 80% of the mass of the upper block fell on the floors outside the core. The floors and the perimeter columns would be taken down easily, but only 20% of the total energy would be left to fall on the core.

The point is, Bazant didn't take the design of the structure into consideration.
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And what would you expect to see (in reality) when the outer walls, floor spans and some of the core beams were demolished, while exposed core columns that now lack adequate horizontal bracing are being impacted laterally by a mountain of falling debris?

That a section of core would be the last thing to fall. And this is exactly what happened.

Bazant deliberately chose a collapse model that gave the greatest chance of resisting collapse - a 'pure' axial column-to-column impact. Anything else would be even more damaging. He understood the structure perfectly well.
 
GlennB said:
And what would you expect to see (in reality) when the outer walls, floor spans and some of the core beams were demolished, while exposed core columns that now lack adequate horizontal bracing are being impacted laterally by a mountain of falling debris?

That a section of core would be the last thing to fall. And this is exactly what happened.

Bazant deliberately chose a collapse model that gave the greatest chance of resisting collapse - a 'pure' axial column-to-column impact. Anything else would be even more damaging. He understood the structure perfectly well.
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Where does Bazant show the core would collapse as soon as the floors are removed?
 
bardamu said:
Where does Bazant show the core would collapse as soon as the floors are removed?
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<groan> Bazant et al didn't examine a real-life collapse mechanism. They examined the mechanism most favouring collapse arrest. The building still came down in that study. Real life was bound, by definition, to be worse and - golly! - they came down of course.
 
bardamu said:
The point is, Bazant didn't take the design of the structure into consideration.
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Yes, he did.

He made an evaluation and determined that an axial column impact would be the best way to arrest. This is why the Sept 13 paper discusses this. To explain exactly why, once the building initiated collapse, there was no stopping it.

Actually, it sounds like you're the one who's not taking the design into consideration.

You admit that the floors and ext columns would fail. This means the open floors will break apart also. Once that happens, this aspect will continue all the way to the ground, right? And you agree about the ext columns failing due to unspported length.

Inside the core, however, the floors there don't have just floors falling on them. They also have core columns punching through. The core assembly relies on the floor beams for rigidity, which are now gone. So now there's the same condition as with the ext columns. Long unsupported lengths.

Now, explain to me why you accept that the ext columns will fail, due to long unsupported lengths, but not the core columns, when it should be obvious that the now unsupported core columns will be impacted by heavier objects than the ext columns, and from all directions - hat truss, core floors, elevator equipment, HVAC equipment, etc.
 
Didn't take the design of the structure into consideration??!!
(*Facepalm*)

On pg. 3 of Simple Analysis, Bazant and Zhou isolates the column-to-column and column to truss connections when making their argument about buckling and hinge formation. Describing those structural features is specifically addressing a pair of the key design features responsible for the collapse occuring the way it did!

Jesus... do truthers even read the works they presume to criticize?? I mean seriously, that's like saying the Bill of Rights doesn't address citizen's rights! You can only say that if you're completely ignorant of the document's contents!
 
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