Moderated Continuation - Why a one-way Crush down is not possible

[BigAl]

Suggest you study the NIST report Fire Protection of Structural Steel in High-Rise Buildings. at http://www.bfrl.nist.gov/pdf/GCR04_872.pdf .

Note that NIST confirms that the WTC destruction was a singular event that has never happened before or after 911 2001, and, not spelled out, has not been explained! That creep would produce a one-way crush down of a structure is not confirmed anywhere.

Edited by Gaspode: 

Edited for civility - moderated thread

Vincent Dunn, FDNY structures expert explains how WTC towers were unique and that fire caused the collapse.

In Report From Ground Zero (pgs 310-311), FDNY structures expert Vincent Dunn describes how the WTC towers had effectively no fireproofing when comparred to the older steel buildings, built to standards that required 2 inches of brick and masonry on all structural steel. Dunn also says that the WTC towers were unique in the minimal fireproofing.

Page 310, Report From Ground Zero;

http://snurl.com/j54ud [books_google_com]

Who is Vincent Dunn?
http://unjobs.org/authors/vincent-dunn

 

[funk de fino]

That local failures due fire in turn can produce a one-way crush down or progressive collapse of any kind of a complete structure, most of it unaffected by the fire, is simply not possible - as explained in post #1 of the original thread.

Edited by Gaspode: 

Edited for civility - moderated thread

lets look at the post he made and change it a bit.

That local failures due to demolition explosives in turn can produce a one-way crush down or progressive collapse of any kind of a complete structure, most of it unaffected by the demolition explosives, is simply not possible.

is that a fair assessment also Anders?

 

[Grizzly Bear]

3. I remember when FEMA published it's initial report, which included a total misrepresentation of the tower structure, claiming "pancake collapse". Where did that go?

FEMA's initial theory concerning a pancake collapse dealt specifically with the initiation process that got it going. The NIST concluded that the floor pancaking wasn't a factor in the initiation, but it was certainly a factor is the collapse progression. The core remnants standing after the main collapse corroborate this.

4. Bazant is flawed for exactly the same modelling simplification reasons that the "Heiwa Challenge" is flawed.
5. It is also flawed because he has to invent an Energy to Work conversion process based upon an accumulation of mass under gravity to justify a "One way crush down" that may not even have happened and may not even be necessary to have happened to cause the collapse!
5. Bazant essentially proposes a pseudo "pancake collapse".
6. Both Bazant and FEMA were clearly influenced by the extensive video coverage of the collapse. They have simplified their models to try explain how the collapse "appears" rather than deal with the complexity of the WTC towers. Bazant is a "God of the Gaps" in the absence of any real hard data.

You're ahead of heiwa... perhaps you could take that as a complement, but you still don't have much of any understanding of what Bazants's model was intended to demonstrate. Bazants' simplification is just that -- a simplification. He reduces the complexity to it's bare minimum and then applies a condition most in favor of collapse arrest which assumes column to column impacts as opposed the the eccentric impacts which really happened. His model was biased heavily in favor of the collapse halting, but his calculations resulted ultimate in the collapse continuing even under the most favorable conditions. Readers who analyze his work start with this basic understanding; that in reality the collapse was not only more complex, but also much less ideal than the controlled conditions Bazant sets for his models.

7. There is an addiction to "pancake collapse" as the overriding reason for the way the towers "appeared" to collapse.

Because as far as the collapse progression is concerned this is exactly what happened. Initial theories - as said earlier - had theorized this in the context of the collapse initiation. The theory went that floors in the fire & impact regions failed over time causing more floors to fail. This then led to long unsupported column lengths which made the columns more vulnerable to buckling. The NIST determined in contrast that creep from the elevated temperatures in combination with the very high loads they were subjected to cause the columns to fail in the impact regions and the "pancaking" occurred later. I'm not quite sure why people have a difficult time understanding this....

Suggest you study the NIST report Fire Protection of Structural Steel in High-Rise Buildings. at http://www.bfrl.nist.gov/pdf/GCR04_872.pdf .

Note that NIST confirms that the WTC destruction was a singular event that has never happened before or after 911 2001, and, not spelled out, has not been explained! That creep would produce a one-way crush down of a structure is not confirmed anywhere.

Since it's well known how structural steel performs complaints about first time in histories are invalid. And you should consider revising what I bolded because it makes no sense whatsoever. Creep behavior was not directly responsible for the progressive collapse of the towers; it led to the the instability in the impact region ultimately to buckling behavior in the columns that started the collapse but the progression to ground level involved a separate set of mechanism dealing with impact and eccentric loading.

Actually, all these models and theories simply confirm that progressive collapse is only possible with rigid mass elements (or complete rigid assemblies of rigid mass elements). As no such elements or assemblies of elements exist in the real world, progressive collapse or, even worse, one-way collapse of a structure by a part of itself (topic) is simply not possible.

Before the towers there was no case that was so severe as to lead to the complete collapse of a skyscraper but progressive collapse has happened both before and after 9/11. The reason why catastrophes like the twin towers, and lesser ones like Ronin Point are so rare, is because most buildings are properly designed to avoid it starting in the first place. Most buildings don't have gaping holes or large multistory fires, or gas explosions... events like those tend to be hazardous for occupant safety. I'm not going to bother with the rest of your post because it's simply incoherent rambling. But this:

As no such elements or assemblies of elements exist in the real world, progressive collapse or, even worse, one-way collapse of a structure by a part of itself (topic) is simply not possible

to remind everyone reading this thread is an example of outright incompetence, and a demonstration that although you use precedents to argue your point, you backtrack on that idea when you claim that collapse mechanisms are impossible. Precedents studies aren't just limited to studying buildings; in many cases they also involve the writer having an intimate understanding of materials and how they are applied, none of which are qualities you possess

 

[tfk]

Heiwa,

There were three issues discussed:

1. You said:

It would appear that normal steel used up top on WTC 1 is pretty unaffected by heat up to 500°C and that the ultimate stress is still > 200 N/mm².

.
Bazant et al said:

Therefore, to decide whether the gravity-driven progressive collapse is the correct explanation, the temperature level alone is irrelevant (Bazant and Le 2008). It is meaningless and a waste of time to argue about it without calculating the stresses in columns. For low stress, high temperature is necessary to cause collapse, but for high enough stress, even a modestly elevated temperature will cause it.

- What Did and Did not Cause Collapse of WTC Twin Towers in New York
Bazant et al, Journal of Engineering Mechanics ASCE, Vol. 134 (2008)

.
My rephrasing of Bazant et al:

The studies by Bazant et al, that demonstrate that unlimited creep (i.e., to catastrophic failure) is a function of BOTH temperature & stress level have been presented numerous times. And those studies have shown that, at high stress levels, runaway creep can occur at temperatures as low as 150°C.

Anyone who ignores those studies and continues to say that "steel will remain unaffected by heat up to 500°C" is incompetent.

.
Your reply:

Suggest you study the NIST report Fire Protection of Structural Steel in High-Rise Buildings. at http://www.bfrl.nist.gov/pdf/GCR04_872.pdf .

Note that NIST confirms that the WTC destruction was a singular event that has never happened before or after 911 2001, and, not spelled out, has not been explained! That creep would produce a one-way crush down of a structure is not confirmed anywhere.

Actually, the whole purpose of fire protection of structural steel in high-rise buildings is just to delay the occurence of local failures allowing people to get out and fire fighters to get in. That local failures due fire in turn can produce a one-way crush down or progressive collapse of any kind of a complete structure, most of it unaffected by the fire, is simply not possible - as explained in post #1 of the original thread.

.
In other words, you have absolutely zero rebuttal to my comment. Figures.

Your original comment is incompetent. Your hand-waving of irrelevant verbiage not withstanding.
___

2. Your comment:

It confirms my little experiment at http://heiwaco.tripod.com/nist1.htm#6 !

.
My reply:

There's no experiment performed here. There is an experiment described. Not performed.

.
Your reply: Silence.
___

3. You said:

... That steel structure suddenly locally explodes as seen on all videos of 911 due to small fires that are burning out is not possible. So somebody pushed the button!

.
I replied:

No video shows any "steel exploding". Absolute nonsense.
Video shows connections rupturing, steel being thrown outward, gypsum being turned into particulates, concrete being crushed and lots of debris being tossed outward.

.
Your reply:

The 911 videos show quite clearly how the complete steel/composite structures explode in a fountain of debris. Sorry - no 'progressive collapse' (sic) of any kind.

.
There is precisely zero evidence of explosives used to throw the steel.
Zero sound.
Zero superplastic high strain rate grain distortions.
Zero exploded steel columns.
Zero exploded connections.

And as you have already claimed, the columns or connections would have to have been blown at every story all the way down.

The world's structural engineering community sees debris thrown in all directions by the crush down of the upper block.

The world's structural engineering community understands that there is plenty of energy available to throw the steel that far from the descending mass.

The world's structural engineering community sees a progressive collapse as the upper block crushes the lower building down to the ground.

Every clear thinking person who is not a structural engineer will listen to, & accept, the consensus of the world's structural engineering community.

The fact that you have excluded yourself from the ranks of "clear thinking people" by virtue of rejecting the opinion of the world's structural engineering community is your business, I guess.


Tom

 

[phunk]

Did Heiwa really just say progressive collapse is impossible?

 

[R.Mackey]

1. The Energy in a mass and it's ability to do useful Work are two entirely different things.

Not really.

2. Simplistic Energy calculations are flawed because we have no real idea how the Energy was ACTUALLY applied within the complexity of the WTC collapse.

The better term to consider, as I've stated here at least 100 times, is momentum. Energy is a bit clumsy. However, it's one fair way to produce an estimate.

3. I remember when FEMA published it's initial report, which included a total misrepresentation of the tower structure, claiming "pancake collapse". Where did that go?

FEMA did not misrepresent as you claim. However, it was discarded on the basis of superior information -- better photography, better access to the original construction documents, analysis of recovered material, and a stupendously complex modeling effort.

4. Bazant is flawed for exactly the same modelling simplification reasons that the "Heiwa Challenge" is flawed.
5. It is also flawed because he has to invent an Energy to Work conversion process based upon an accumulation of mass under gravity to justify a "One way crush down" that may not even have happened and may not even be necessary to have happened to cause the collapse!
5. Bazant essentially proposes a pseudo "pancake collapse".

Wrong on all counts. Dr. Bazant in his 2002 paper with Dr. Zhou is not modeling the collapse. He's presenting a "best case." And he says so quite clearly in the paper itself. The BLGB update is closer to an actual model but still undergoes a number of simplifications.

Dr. Bazant also is not looking at what "caused" the collapse. He's looking at how it progressed. Do you understand the difference? The later stages of collapse are indeed of the "pancake" variety.

6. Both Bazant and FEMA were clearly influenced by the extensive video coverage of the collapse. They have simplified their models to try explain how the collapse "appears" rather than deal with the complexity of the WTC towers. Bazant is a "God of the Gaps" in the absence of any real hard data.

Not really. FEMA had only a few TV news videos to go on. NIST recovered a vastly larger library of video and photographs, some taken by emergency agencies, many by individuals, and had much more detail available to them.

Again, Dr. Bazant presents a limiting case. This is not "God of the Gaps." It's a feasibility study. What it proves is that collapse arrest is basically impossible, once it gets moving. Such an analysis is totally valid and need not be particularly precise.

7. There is an addiction to "pancake collapse" as the overriding reason for the way the towers "appeared" to collapse.

Non sequitur.

I don't agree with Bazant's incredulous "One way crush down" which is essentially a "pancake collapse" plus explanation of video footage. That does not mean that explosives were involved!

Now this, we all agree with. Again, it's a limiting case. It's not accurate nor is it meant to be accurate. In particular, the mechanism of Bazant & Zhou doesn't match the surviving core remnants. However, it proves that explosives are not necessary, since some kind of collapse is inevitable. And that means, unless the make-believe "conspirators" are total dunces, they wouldn't have used explosives in the first place. Why blow up something that's already coming down?

 

[beachnut]

The more I look at it Beachnut the more I think you are wrong about this. I am starting to think that an impregnable case can be made for the reversal of the burden of proof in he case of WTC1.

A one way crush down of WTC1 is just plain impossible and would be easy to demonstrate to any court.

Here it is defferent of course.

I am not wrong the proof of Heiwa's OP must come from him and not talk. There has to be detailed calculations. Where is his paper?

Please show how easy it is to demonstrate. Since the court will see WTC 1 fall due to impact, fire and gravity alone please explain with calculations and engineering terms how you failed to demonstrate in this 1900 post thread your ideas are sound. Show the world the proof you and Heiwa have to demonstrate your point.

You don't have the engineering calculation to support you and you fail to realize gravity is the primary source for the kinetic energy in all building collapse including 911 when impacts and fires initiated the failure, and in controlled demolition.

Where in the thread is the proof? You don't have anything save talk. This is the reason it is not only different here, but in a court of law Heiwa's failed conclusion will be exposed. When will Heiwa provide the detailed calculations to support his ideas?

 

[FineWine]

FEMA's initial theory concerning a pancake collapse dealt specifically with the initiation process that got it going. The NIST concluded that the floor pancaking wasn't a factor in the initiation, but it was certainly a factor is the collapse progression. The core remnants standing after the main collapse corroborate this.


You're ahead of heiwa... perhaps you could take that as a complement, but you still don't have much of any understanding of what Bazants's model was intended to demonstrate. Bazants' simplification is just that -- a simplification. He reduces the complexity to it's bare minimum and then applies a condition most in favor of collapse arrest which assumes column to column impacts as opposed the the eccentric impacts which really happened. His model was biased heavily in favor of the collapse halting, but his calculations resulted ultimate in the collapse continuing even under the most favorable conditions. Readers who analyze his work start with this basic understanding; that in reality the collapse was not only more complex, but also much less ideal than the controlled conditions Bazant sets for his models.


Because as far as the collapse progression is concerned this is exactly what happened. Initial theories - as said earlier - had theorized this in the context of the collapse initiation. The theory went that floors in the fire & impact regions failed over time causing more floors to fail. This then led to long unsupported column lengths which made the columns more vulnerable to buckling. The NIST determined in contrast that creep from the elevated temperatures in combination with the very high loads they were subjected to cause the columns to fail in the impact regions and the "pancaking" occurred later. I'm not quite sure why people have a difficult time understanding this....





Since it's well known how structural steel performs complaints about first time in histories are invalid. And you should consider revising what I bolded because it makes no sense whatsoever. Creep behavior was not directly responsible for the progressive collapse of the towers; it led to the the instability in the impact region ultimately to buckling behavior in the columns that started the collapse but the progression to ground level involved a separate set of mechanism dealing with impact and eccentric loading.




Before the towers there was no case that was so severe as to lead to the complete collapse of a skyscraper but progressive collapse has happened both before and after 9/11. The reason why catastrophes like the twin towers, and lesser ones like Ronin Point are so rare, is because most buildings are properly designed to avoid it starting in the first place. Most buildings don't have gaping holes or large multistory fires, or gas explosions... events like those tend to be hazardous for occupant safety. I'm not going to bother with the rest of your post because it's simply incoherent rambling. But this:



to remind everyone reading this thread is an example of outright incompetence, and a demonstration that although you use precedents to argue your point, you backtrack on that idea when you claim that collapse mechanisms are impossible. Precedents studies aren't just limited to studying buildings; in many cases they also involve the writer having an intimate understanding of materials and how they are applied, none of which are qualities you possess

An excellent post, Grizzly Bear. The "truthers" simply refuse to come terms with Bazant's purpose. He was trying to create conditions favorable to the arrest of the collapse. The "truthers" are forced to pretend that he was modeling what actually happened because the implications of what he was really doing are terribly inconvenient to their nonsense.

 

[Heiwa]

The better term to consider, as I've stated here at least 100 times, is momentum. Energy is a bit clumsy. However, it's one fair way to produce an estimate.

Actually it is almost same thing; momentum = mass times velocity (kg m/s), energy = momentum times velocity divided by 2 (kg m²/s² = Nm = J).

However, in order to do a structural damage analysis, e.g. of an alleged one-way crush down and associated failures and displacements of elements by force, you have to work with energies, as each failure/displacement represents energy.

So when a mass m with velocity v impacts a structure (to produce a one-way crush down?), it has a known momentum and energy. At impact a contact force F develops that m applies on the structure, while the structure applies an equal but opposed force -F on m.

Now, when you apply a force, in this case -F, on a mass m, the mass is accelerated. As the mass m had velocity v prior -F was applied, it means that v is (or should be) reduced after impact, i.e. the momentum is reduced. There should be a jolt of m, prior any one-way crush down of the structure will take place.

If v is very small (say 5 m/s) and the force -F is big, you would expect v to become 0 within a second or even negative (m bounces on the structure).

Another result of -F applied on m is that m may break into small bits. Then the momentum of m becomes irrelevant - m is in bits. But the breakage of m into bits required energy. Thus, a good reason to keep track of the energy after impact and what it produces. That the result would be a one-way crush down of the structure with m intact is not possible.

 

[tfk]

Another result of -F applied on m is that m may break into small bits. Then the momentum of m becomes irrelevant - m is in bits. But the breakage of m into bits required energy. Thus, a good reason to keep track of the energy after impact and what it produces. That the result would be a one-way crush down of the structure with m intact is not possible.

.

Edited by Gaspode: 

Edited for civility - moderated thread

KINETIC Energy is not conserved. It is transformed in to work to deform objects, break objects, hurl objects, etc.

Momentum is always conserved. And is therefore easier to track.

But your statement "m may break into small bits. Then the momentum of m becomes irrelevant - m is in bits" is ludicrously wrong.

Your contention violates fundamental principles of physics & dynamics.

A 50 ton part may be in one solid piece, it may be broken into ten pieces, it may be broken into a million pieces. If the parts are moving at the same speed, then in EVERY ONE of those cases, the 50 tons has precisely the same momentum.

For that matter, 50 tons of water & 50 tons of air, in which the materials are "broken" into individual molecules, moving at the same speed as the original 50 ton object, contains PRECISELY the same momentum as the original object.

The momentum does NOT become "irrelevant because it is broken into bits".

Please do not launch into a "but it takes energy to break it up" misdirection. This is understood. And it negates nothing of what I have stated above.

 

[bill smith]

when an intact item is broken into a million pieces there is then a space between all of those pieces by virtue of them being seperated. So even in the unlkely event that they all struck at the same time it would be over a much wider area.

 

[Heiwa]

.

Edited by Gaspode: 

Edited for civility - moderated thread

Momentum is always conserved. And is therefore easier to track.

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

 

[rwguinn]

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

That, my dear Heiwa, was the stupidest response that could have been made
and it shows you have no clues at all...

 

[tfk]

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

.
You can not POSSIBLY have gotten a technical degree and still be this clueless regarding simple engineering dynamics.

Momentum is ALWAYS conserved. ALWAYS. No exceptions. Not even your "person falling off a bicycle".

Let's see if you can figure out how.

Tom

 

[Dave Rogers]

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

Just checking, Heiwa - are you seriously challenging the validity of the Law of Conservation of Momentum?

Dave

 

[Paulhoff]

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

Now the earth spin has been changed.

Paul

 

[tfk]

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

.
It is bewildering to me that you are this technically incompetent.

Go back & learn some engineering dynamics first principles.

Momentum is ALWAYS conserved. In all collisions.

I KNOW where you are screwing up in your analysis of the bicyclist falling down. Why don't you think REALLY hard on it & see if you can figure it out...

tk

PS. Big hint: Why don't you think about the momentum of the earth for just a second...

 

[Heiwa]

.
You can not POSSIBLY have gotten a technical degree and still be this clueless regarding simple engineering dynamics.

Momentum is ALWAYS conserved. ALWAYS. No exceptions. Not even your "person falling off a bicycle".

Let's see if you can figure out how.

Tom

Hm, you avoid answering the simple question about your own momentum, your mass times velocity, when you drop off your bike, with result that your velocity becomes 0.

I assume your momentum is then also 0. So where did your original, on the bike, momentum end up? How was it conserved?

 

[newton3376]

You're sure? Take yourself! You have a mass. Let's call it m. m goes biking and travels down the road at velocity v! Thus you/m have momentum m times v. Now, m falls off the bike, hits ground and slides on ground. After a while m is at rest, i.e. v = 0. Thus the momentum is now ZERO!

But m/you suggest it was conserved! Pls explain where the momentum is conserved.

OMG....

He is questioning the conservation of momentum....

 

[rwguinn]

OMG....

He is questioning the conservation of momentum....

We've been found out.
Heiwa has proved that you cannot stop a moving car, airplane, bicycle, falling body, or even a ship!
Everything we tried to foist off as science has been shown to be naught but illusion. We are undone!