Moderated Steel structures cannot globally collapse due to gravity alone

Dave Rogers said:
You might want to read up on more recent analysis of the collapse. BLBG refers to the 2008 paper "What Did and Did not Cause Collapse of WTC Twin Towers in New York," by Zdenek P. Bazant, Jia-Liang Le, Frank R. Greening and David B. Benson, which you can find online at http://www.civil.northwestern.edu/p...TC Collapse - What Did & Did Not Cause It.pdf. It gives a more thorough discussion of the mechanics of progressive collapse, including mass ejection.
BLBG page 14

Dave
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On page 4 they describe what "k-out" is. It is the amount of dust and larger fragments expelled by the air pressure of floors collapsing, not the framing sections weighing 4 tons that were ejected up to 600 feet!

"As a refinement of previous analysis, we introduce here a generalization in which we add energy Fs (per unit height) consumed by comminution [pulverization] of concrete floor slabs, energy Fa required to expel air from the tower, and energy Fe required to accelerate the mass of dust and larger fragments ejected from the tower during the impact of upper part; Furthermore, in contrast to previous studies, the compaction ratio will not be assumed as a constant but will be more accurately calculated as _(z) = (1−kout)μ(z)/μc, and kout = mass outside tower perimeter before the end of crush-down (not afterwards). shedding fraction = fraction of mass that escapes"
 
ElMondoHummus said:
They explicitly state that their model is a boundary condition. They explicitly state that it is the best-case scenario for collapse resistence.
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So what? What they state is not relevant. Only what they can prove.

They explicitly state that the upper 10 floors will stay intact while they crush the 95 floors below. That is flat absurd.
 
Christopher7 said:
So what? What they state is not relevant. Only what they can prove.
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Because if the building cannot arrest collapse even with arrest offered a significant favor, the what will allow the structure to arrest collapse under less ideal conditions?


Christopher7 said:
They explicitly state that the upper 10 floors will stay intact while they crush the 95 floors below. That is flat absurd.
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You can yelp about this all you want but this is nothing but ridiculous semantics. It was a simplified model that took into account the most ideal conditions, it was never intended to model the true collapse which clearly did not offer any leeway to this. End of story... If you're not convinced tough luck Nobody can cure incompetence on the level you're playing
 
Christopher7 said:
So what? What they state is not relevant. Only what they can prove.

They explicitly state that the upper 10 floors will stay intact while they crush the 95 floors below. That is flat absurd.
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They explicitly state that they're setting an idealistic scenario that is the most heavily biased towards resisting collapse that is possible. Repeat: The most heavily biased towards tower survival that is possible. They then demonstrate that the energy is indeed available to overcome even that extreme case. That in turn demonstrates that any other scenario, any other realistic model, by virtue of being less favorable to resisting collapse than the ridiculously idealistic one Bazant and Zhou chose, will also result in the collapse of the towers. Because they have less resistance to collapse propogation.

This too has been explained over and over. You refuse to even attempt to comprehend.

And complaining about 10 floors vs. the remainder 1. Only applies to one of the towers, as the other was hit lower and therefore had more mass above the impact and failure zones, 2. Ignores the gravitational potential energy, and 3. Propogates the same mistake as every other truther arguing that detail, which is that the upper segment was not taking on the resistance of the lower segment as a whole, but was doing it floor by floor. The true picture is the upper 10-some stories vs. the single floor immediately below the fire and impact zone. Then, the upper 10-some stories plus the newly accumulated floor vs. the next floor below, with more kinetic energy available since it's now falling faster. And so on until the ground is reached.

This has been explained dozens of times over. Again, your refusal to acknowledge what the correct model is demonstrates an overt willingness to deny the realities of the event.
 
Heiwa said:
1-It seems you do not understand the amount of energy is required to slice a floor. Asssuming a 0.5 m drop of part C (PE = 0.29 GJ) and that part C contacts, say, floor 97 and part A contacts floor 98, i.e. two floors must be sliced for part C to continue descending, in my view the local failures end there! Too little PE available. Just do proper structural damage analysis and you will find out yourself.

If you disagree and suggest there is enough PE available to slice 26 floors (13 in part C and 13 in part A - floors 84-97), after that part C is sliced in two, etc. and two outer walls of part C would have dropped down to ground outside WTC 1.
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No KE would be required to slice through a floor. The concentration of weight on the column ends would punch through even if you gently placed them on the there. Then, all the weight of the upper block, even in such an idealized scenario, would rest on 2 floors, pushing down on one, and pushing up on the other.

The floors can't hold that weight, even starting from a static condition. It's delusional to even suggest it could.

So floors break off, and the scenario repeats.
 
And once again, still no structural calculations from the truthers.

This amazes me as every real structural engineer I've ever worked with is so pernickety about these things that they'd do a quick calc before tying a shoelace.

I wonder why Heiwa and others seem so reluctant to post calcs?

Hmm......
 
KreeL said:
It's totally preposturous to believe the 10-15% of anything can obliterate the remaining 85-90% of itself. Please give us some examples of this phenomenon happening on planet earth.
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KreeL said:
I have looked at Bazant's theory. I am waiting on his model. I want him to drop 15% of something on top of itself and obliterate the remaining 85%. This will be good.
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Coming up with examples of this is absurdly easy. Gravity causing 15% of something to obliterate the other 85%? No problem.








 
Christopher7 said:
~snip~
Most of the mass was ejected outside the buildings.

~snip~.
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How could the most of the mass have been ejected outside the building when the building is said to have fallen within it's foot print?

How could tell with all the billowing dust?
 
KreeL said:
It's totally preposturous to believe the 10-15% of anything can obliterate the remaining 85-90% of itself. Please give us some examples of this phenomenon happening on planet earth.
Originally Posted by KreeL
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KreeL said:
I have looked at Bazant's theory. I am waiting on his model. I want him to drop 15% of something on top of itself and obliterate the remaining 85%. This will be good.
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Cascade failure. look it up
 
Christopher7 said:
BLBG paper? I read Bazant's hypothesis.

He did NOT allow for the material ejected outside the building. He has proven a non-existent event. Big wow.

Most of the mass was ejected outside the buildings.
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Hopelessly incorrect. At the point where the building entered a state where it was already past the point where the collapse would not stop, most of the mass was still within the building footprint.

All it needed was those top sections to fall on the first floor of the lower section and collapse ensues and does not arrest. The fact the top section tipped made it more likely to collapse.

Good of you to post a picture which disproves your claim most of the aluminium was thrown 600 feet from the footprint.
 
Heiwa said:
In 2008 Bazant suggests (the BLGB paper) that upper part C drops and crushes the top storey below of part A, which becomes a layer of rubble - part B. Then part C strangely pushes this layer of rubble - part B - down to crush the next storey of part A that becomes more rubble.
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You think it's strange that part C, devoid of structural support, would fall in the direction gravity pulls on it and take the rubble of floor 97 with it to then impact on floor 96?
 
C7 said:
What they state is not relevant. Only what they can prove.
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Grizzly Bear said:
Because if the building cannot arrest collapse even with arrest offered a significant favor, the what will allow the structure to arrest collapse under less ideal conditions?
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The top section of the south tower was falling down and to the side. Newton's first law says it will continue falling to the side unless an external force is applied.

The leaning side would collapse faster than the other side because of the uneven distribution of weight. This would cause the top section to lean more and fall to the side, not straight down.

C7 said:
They explicitly state that the upper 10 floors will stay intact while they crush the 95 floors below. That is flat absurd.
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It was a simplified model that took into account the most ideal conditions, it was never intended to model the true collapse
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Thank you for noting that critical point.

They have proven a non existent, hypothetical event.

The Bazant theory does NOT model the actual collapse.

Therefore, it cannot be used as proof of how the actual collapse occurred.
 
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Bazant has changed his mind about what happened so many times he might as well be a 'twoofer'. First it was the 'pancake collapse', then it was the 'truss theory', then it was the 'foot of God' theory.

Let me show you the folly of Bazant. He claims that the huge block of 13 stories falls on the lower structure and pulverizes it. That would be a monstrous impact. Yet when you measure the fall of the top block it impacts NOTHING. No impact, it just slips right through a thick cloud of pulverized concrete. No bang, no tremendous jolt, nada, zero, zilch.

He's full of hot air. His papers have been debunked thoroughly, and the most recent is exactly on this topic:

http://www.journalof911studies.com/volume/2008/TheMissingJolt7.pdf
 
KreeL said:
Heiwa's analysis of Bazant's paper is quite correct.

State of grace - the floor trusses weren't the main parts of the towers absorbing the brunt of the falling block. The lattice-work of thousands of steel beams, and the 47 core columns were tremendously more than enough to arrest a 20-30mph impact by the top 15%. Resistance would have been so overwhelming that the top block would have stopped immediately.
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You have no clue what you are talking about. And you produce a paper that used failed engineering to make up false conclusions.

The journal you cite was started to publish false information about 911 by Jones who made up the thermite scenario out of the blue 4 years after 911. Jones told lies to sell his ideas to people who lack knowledge on the subject matter.

There is no support for your ideas past a few fringe nut case 911Truth "experts" like Jones. There are no engineers who support these failed ideas save 0.001 percent of the world's engineers.

So how many engineers have you found to support your ideas on 911? ZERO
 
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