OOS Collapse Propagation Model

[Newtons Bit]

My reading is that Tom is concerned with accuracy and honesty.

LOL

Mr B did not explain what happened... (NIST didn't do much better IMSHO) but both of these are repeatedly cited and defended. In fact it appears that many very outspoken people who dominated the discussion and who turned out to be wrong... have "disappeared" and his concern appears to be to

CORRECT the HISTORICAL RECORD.

People make mistakes... no biggie (usually)

And Tom seems to be taking a lot of abuse for all manner of things. But is seems correct about the false narratives which have not been corrected.

LOL

In any event, my comments on page 1 of this thread are still relevant to the latest tripe foisted by Major_Tom onto his gullible followers.

 

[Crazy Chainsaw]

I did not read, nor do I intend to read Mr B's papers because I am not an engineer and his formulas mean nothing to me.

My understanding of this is that Mr B did a study to see if there was enough "energy" in the "tops" to destroy the bottoms. He didn't get into the mechanisms of how that would be so it's not very useful in explaining what happening.... only that what happened did not have to defy the "laws of physics".

Then came the various discussions with supposed models explaining the mechanisms of PARTS / PERIODS of the event/ collapse. None of these made very much sense and described the entire event. Global collapse is not a mechanism. And is no more descriptive of a car accident than calling it a car crash. Kinda.

In 7wtc the NIST model based on a col 79 failure then produces an FEA gif which looks nothing like the real event.... that is the "global collapse phase" post col 79 girder walk off thingy. That looks like a fail by NIST to me.

Then came the discussion that essentially recognized that if the tops of the twins "dropped"... what we could actually see... there HAD to be no axial alignment of columns (which would be the facade as that all we can see). The ASSUMPTION was that the CORE columns had "failed" .. that the entire top was an integrated "whole" and somehow the core columns below could not resist the ones which had rested on them BEFORE fire. "Fail" to some (here) means fire weakened the COLUMNS below service loads OR there was a runaway rapid propagation of "column failures" which I assume to mean "buckling" from being overloaded axially. The problem with this conception is that virtually all 47 core columns should have been found severely buckled or severed from the plane strike.

To make a long story short... NO ONE has actually explained the mechanism of the runaway progressive "failure" of the core due to heat.... other than to reach the conclusion that if the top drop the columns had failed (and the details don't matter).

Since the floors in and outside the core were pretty much rendered to dust and sand... we can tell what was going on there... a threshold mass consisting of floor sections was "freed" from the columns... dropped and became the driver mass for a downward runaway unstoppable avalanche of floor material which ground itself up in the 10-14 seconds of the avalanche as a result of millions or billions of collisions of the slab "chunks".

The take away that (apparently) Mr B didn't see or didn't bother to look for was that: The collapse phase POST initiation had NOTHING TO DO WITH COLUMNS or column strength. The columns COULD have been 100 times stronger and the floors would collapse and the probably those columns would ALSO topple from "Euler" forces. THERE WERE NO BUCKLED (from over loads) COLUMNS BELOW THE PLANE STRIKE ZONE.

Actually JSO you are wrong, Banzant provided a step on the ladder to understanding,
The BLGB paper provided another step to understanding.

Banzant then provided another step to understanding.

Major Tom provided another step to understanding.

Ozeco41 Provided a leap in understanding.

All put work into it and each ones work should be valued.

That's how all science works baby steps even the tumbles can provide incite.

There may be a few more steps, that need to be taken, if we are able.

 

[JSanderO]

Actually JSO you are wrong, Banzant provided a step on the ladder to understanding,
The BLGB paper provided another step to understanding.

Banzant then provided another step to understanding.

Major Tom provided another step to understanding.

Ozeco41 Provided a leap in understanding.

All put work into it and each ones work should be valued.

That's how all science works baby steps even the tumbles can provide incite.

There may be a few more steps, that need to be taken, if we are able.

I don't claim that all of the above added value to the understanding of what happened. I find the contributions on the forums of Ozzie and Tom more valuable to ME. It is settled engineering that if a a too heavy load is presented to a floor... it collapses. That's how ROOSD works and it's almost a no brainer.

Perhaps more esoteric and less comprehensible to non engineers are things like Euler buckling.

We no collisions and "agitation" produce dust and heat in a tumbler. The floor collapse was much like that on a huge scale and the residual heat in the pile comes from this mechanical destruction with a small contribution from persistent fires (I am guessing).

I saw lots of pretty dumb thinking like the top can't possible destroy the bottom because the bottom was stronger or... it had to arrest or it took too fast...

I didn't see too much "work" from most posters (on this forum)... Did you?

 

[WilliamSeger]

I did not read, nor do I intend to read Mr B's papers because I am not an engineer and his formulas mean nothing to me.

Mr B did not explain what happened...

 

[JSanderO]

I continue to find it remarkable some of the posts and responses from presumably intelligent adults such as Mr Seger's above. I find typos and grammar and syntax mistakes more comprehensible that "emoticons". Usually I just ignore them.... because... they don't seem serious.

 

[Newtons Bit]

I continue to find it remarkable some of the posts and responses from presumably intelligent adults such as Mr Seger's above. I find typos and grammar and syntax mistakes more comprehensible that "emoticons". Usually I just ignore them.... because... they don't seem serious.

Ooooooooh burn! You really laid into him there, JSanderO! I'm sure he'll never come back to this thread!

 

[WilliamSeger]

I continue to find it remarkable some of the posts and responses from presumably intelligent adults such as Mr Seger's above. I find typos and grammar and syntax mistakes more comprehensible that "emoticons". Usually I just ignore them.... because... they don't seem serious.

Well, maybe there's a Sherlock Holmes emoji I could use to indicate that I think I spotted a clue.

But as for "serious," some of Jon Stewart's funniest bits were just playing a series of clips from Fox News and then mugging into the camera.

 

[beachnut]

Yes, indeed: Major_Tom's misrepresentations of others' views have continued for four years, and show no sign of ending.

For quite a while now, Major_Tom has been repeating variations of "BV is really, really important to some of you and some of you will stop at nothing to believe in it", ignoring explicit denials by those accused and disregarding specific evidence from forum archives that contradict his claim.

Major_Tom continues to insist that "As of October 20, 2014, only one regular poster, Ozeco, could find and admit to mistakes in BV", even after I quoted posts from two and (almost) four years ago in which I pointed out that BV contains a fairly obvious mathematical error.


Yes, indeed. Major_Tom's entire approach to the topic of this subforum has provided a good example of the "sustained incoherence" David Bohm was talking about:

Where are the differential equations for the book with no conclusion.

 

[tsig]

Originally Posted by JSanderO View Post
I did not read, nor do I intend to read Mr B's papers because I am not an engineer and his formulas mean nothing to me.

Originally Posted by JSanderO View Post
Mr B did not explain what happened...

I continue to find it remarkable some of the posts and responses from presumably intelligent adults such as Mr Seger's above. I find typos and grammar and syntax mistakes more comprehensible that "emoticons". Usually I just ignore them.... because... they don't seem serious.

Since you did not read the papers how do you know they didn't explain what happened?

Are you aware that the first paper was not meant to be an in depth examination of the collapse?

 

[JSanderO]

Since you did not read the papers how do you know they didn't explain what happened?

Are you aware that the first paper was not meant to be an in depth examination of the collapse?

I have read discussions about these papers. AND it would have been well nigh to impossible to explain what happened without some forensic investigation... examining the site, the steel and so on. I believe Mr. B's first papers did not take any of this into consideration other than perhaps some crude raw data about building mass and the presumed "time of collapse".

Investigations of disasters take more time and effort than running some number... n'est pas?

 

[Crazy Chainsaw]

I don't claim that all of the above added value to the understanding of what happened. I find the contributions on the forums of Ozzie and Tom more valuable to ME. It is settled engineering that if a a too heavy load is presented to a floor... it collapses. That's how ROOSD works and it's almost a no brainer.

Perhaps more esoteric and less comprehensible to non engineers are things like Euler buckling.

We no collisions and "agitation" produce dust and heat in a tumbler. The floor collapse was much like that on a huge scale and the residual heat in the pile comes from this mechanical destruction with a small contribution from persistent fires (I am guessing).

I saw lots of pretty dumb thinking like the top can't possible destroy the bottom because the bottom was stronger or... it had to arrest or it took too fast...

I didn't see too much "work" from most posters (on this forum)... Did you?

You have no clue, Read BLGB that would help a lot of it is in simple English.

 

[JSanderO]

You have no clue, Read BLGB that would help a lot of it is in simple English.

I think I have some clues and while I don't have a problem learning new things... I don't think this paper will add to what I am looking for in understanding the collapses. You need to dial back your "style" a bit. Thank you!

 

[tsig]

I have read discussions about these papers. AND it would have been well nigh to impossible to explain what happened without some forensic investigation... examining the site, the steel and so on. I believe Mr. B's first papers did not take any of this into consideration other than perhaps some crude raw data about building mass and the presumed "time of collapse".

Investigations of disasters take more time and effort than running some number... n'est pas?

The paper was not meant as an investigation into the disaster but was a worst case scenario, if you had read it you might understand this and grasp that you are criticizing a Ford for not being a Lamborghini.

 

[tsig]

I continue to find it remarkable some of the posts and responses from presumably intelligent adults such as Mr Seger's above. I find typos and grammar and syntax mistakes more comprehensible that "emoticons". Usually I just ignore them.... because... they don't seem serious.

I don't claim that all of the above added value to the understanding of what happened. I find the contributions on the forums of Ozzie and Tom more valuable to ME. It is settled engineering that if a a too heavy load is presented to a floor... it collapses. That's how ROOSD works and it's almost a no brainer.

Perhaps more esoteric and less comprehensible to non engineers are things like Euler buckling.

We no collisions and "agitation" produce dust and heat in a tumbler. The floor collapse was much like that on a huge scale and the residual heat in the pile comes from this mechanical destruction with a small contribution from persistent fires (I am guessing).

I saw lots of pretty dumb thinking like the top can't possible destroy the bottom because the bottom was stronger or... it had to arrest or it took too fast... I didn't see too much "work" from most posters (on this forum)... Did you?

Well done Tom! WOW just WOW

I assume the questions are rhetorical... these guys are nailed! hahahahaha Oh the hubris of these guys... it's precious.

Or as was asked about a young lawyer's Guild attorney Fred Fisher of Senator McCarthy at his witch hunt hearings? Attorny Welsh said

"When McCarthy tried to renew his attack, Welch interrupted him:

Senator, may we not drop this? We know he belonged to the Lawyers Guild. Let us not assassinate this lad further, Senator. You've done enough. Have you no sense of decency, sir? At long last, have you left no sense of decency?"

hahahahahahahaha

Nothing changes...

I think I have some clues and while I don't have a problem learning new things... I don't think this paper will add to what I am looking for in understanding the collapses. You need to dial back your "style" a bit. Thank you!

Good advice, I suggest you take it.

 

[pgimeno]

I'll bite.

I will formulate 44 separate and highly specific questions on this paper. The specific questions are carefully formulated to help any impartial and honest reader to see the stupidity which most every JREF/ISF regular participating poster has demonstrated within this thread and throughout this forum on the topic of Bazant from 2010 to 2015.

What a set-up. Sounds like you're preparing to call anyone who won't give the answers that you're expecting partial and/or dishonest.

Gregory Szuladzinski begins:

The paper presents a very interesting concept of an accidental demolition, whereby heavy damage sustained by an intermediate
story of a building leads to the upper part of the structure crushing the lower one in a sequence of story collapse steps. The focus of
the paper is on the treatment of equations of motion and very few numbers are quoted; that is, numbers that relate to the physical properties of the structure discussed, namely the World Trade Center (WTC) towers. The following comments are intended to fill that gap as well as to ascertain the likelihood of the applicability of this concept.

Gregory is clearly referring to application of BV equations 12 and 17 to the specific case of the WTC towers. There can be no mistake that he is discussing the specific cases of WTC1 and 2 throughout the discussion.



Question 1: Do you agree or disagree that Greg Szuladzinski is referring specifically to the WTC towers within this quote?

I agree. He specifically says his intention is to test the applicability of the concept to the WTC.

James R. Gourley's opening words are similar:

This discussion describes flaws in the modeling and analysis of the World Trade Center collapses by Bažant and Verdure in their paper entitled “Mechanics of Progressive Collapse: Learning
from World Trade Center and Building Demolitions.” First, the paper’s two-phased approach to the collapse analysis will be considered. The writers will demonstrate that a two-phase collapse analysis is not representative of reality, because it disregards well-accepted laws of physics and therefore is not instructive. Second, the original paper’s summary of the findings of the NIST report will be analyzed.

James is also clearly addressing the application of equations 12 and 17 in BV to the specific cases of WTC1 and 2. He explicitly identifies BV as a modeling and analyzing of the World Trade Center collapses when he states:

This discussion describes flaws in the modeling and analysis of the World Trade Center collapses by Bažant and Verdure in their paper entitled “Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions."

Question 2: Do you agree or disagree that James Gourley is referring specifically to the case of the WTC towers in this quote?

I agree. And he also makes a strawman argument which Bazant is free to ignore:

The writers will demonstrate that a two-phase collapse analysis is not representative of reality, because it disregards well-accepted laws of physics and therefore is not instructive.
​

First, the model does not intend to represent the reality of the WTC collapse, so he's setting up a strawman. Second, he attacks the strawman with the wrong weapons. Bazant's reply ignores the strawman and focuses on the errors, but in order to do so he needs to postulate by hypothesis that the WTC collapse mechanism happened according to his model in order to explain where the commenters' errors reside in the technical sense.

That's the part you and other Bazantophobes seem to fail to understand. It's a technical paper, so he addresses the comments from the technical standpoint of the paper's contents. To do so, he accepts the premise by hypothesis and follows it, even if it's a wrong premise.

Zdeněk P. Bažant opens to Gourley:

Discussion by James R. Gourley

The interdisciplinary interests of Gourley, a chemical engineer with a doctorate in jurisprudence, are appreciated. Although none
of the discusser’s criticisms is scientifically correct, his discussion provides a welcome opportunity to dispel doubts recently voiced
by some in the community outside structural mechanics and engineering. It also provides an opportunity to rebut a previous similar discussion widely circulated on the Internet, co-authored by S. E. Jones, Associate Professor of Physics at Brigham Young University and a cold fusion specialist. For the sake of clarity, this closure is organized into the points listed subsequently and rebutted one by one.

He then argues the 8 points in order, each point being clearly labelled:

1. Newton’s Third Law

2. Are the Internal Forces in Upper and Lower Parts of
Tower Equal?

3. Localization of Energy Dissipation into Crushing Front

4. Can Crush-Up Proceed Simultaneously with Crush Down?

5. Why Can Crush-Up Not Begin Later?

6. Variation or Mass and Column Size along Tower Height

7. Were the Columns in the Stories above Aircraft Impact
Hot Enough to Fail?

8. Steel Temperature and NIST Report

Question 3: Do you agree or disagree that Bazant, when answering James Gourley on each of these 8 points clearly labeled in the paper, is referring specifically to the case of the WTC towers?

I mostly disagree. He's ignoring the strawman argument that his model must be applicable to the WTC literally, and attacking the wrong points of Gourley; he rebuts the points in relation to how his model works (which is not to say it must be applicable to the WTC collapse literally, despite hypothesizing that it can, as discussed above). He does so in points 1 to 6.

In points 7 to 9 (MT forgets point 9, "Were Very High Temperatures Necessary to Trigger Gravity-Driven Collapse?"), he refers to the reality of the towers' weakening and collapse. Note that in none of these points does Bazant refer to his model.

To sum up:

- Bazant's replies to points 1 to 6 refer to his model, and not to the real WTC collapses.
- Bazant's replies to points 7 to 9 refer to the reality of WTC, and not to his model.

Likewise he opens his replies to the G. Szuladzinski discussion:

Discussion by G. Szuladzinski

The interest of Szuladzinski, a specialist in homeland security, is appreciated. After close scrutiny, however, his calculations are found to be incorrect, for reasons explained in the following.

and clearly lists each reply in order:

1. Load-Displacement Curve of Columns and Energy Absorption Capacity

2. Does Excess of over Gravity Load Imply Arrest of Collapse?

3. Is the Equation of Motion for Calculating the Duration of Fall Correct?

4. Could Stress Waves Ahead of Crushing Front Destroy the Tower?

Each discussion by Gourley and Szuladzinski, and each rebuttal by Bazant, can be easily reviewed simply by going to the clearly marked section. Each of the 12 clearly marked objections and rebuttals make specific reference to the case of the WTC towers.



Question 4: Do you agree that Bazant, when answering G. Szuladzinski on each of these 4 points clearly labeled in the paper, is referring specifically to the case of the WTC towers?

Possibly, but not to the case of the real WTC towers' collapses. He's defending his model as attacked by Szuladzinski, not claiming it's directly applicable to the reality of how the towers collapsed. At some points he accepts by hypothesis that the WTC collapsed according to his model, in order to address the points raised by Szuladzinski and Gourley, as discussed above.

This is the Bazant reply to J. Gourley's third point:

"Discussion by James R. Gourley

3. Localization of Energy Dissipation into Crushing Front:
In the discusser's opinion: the hypothesis that "the energy is dissipated at the crushing front implies that the blocks in Fig. 2 may be treated as rigid, i.e., the deformations of the blocks away from the crushing front may be neglected." This is a fundamental misunderstanding. Of course, blocks C and A are not rigid and elastic waves do propagate into them."



But the wave velocity, given by v = ?Et / ? where Et = tangential e modulus of steel in the loaded columns and ? = mass density, tends to zero as soon as the plastic or racturing response is triggered, because in that case, Et ? 0. Therefore, as explained in courses on stress waves, no wave attaining the material strength can penetrate beyond the crushing (or plastic) front. Only harmless elastic waves can. Propagation of the crushing front is not a wave-propagation phenomenon. Destruction of many stories at the rate corresponding to the elastic wave speed, which would appear as simultaneous, is impossible. This is why the collapse is called progressive. Blocks C and A can, of course, deform. Yet, contrary to the discusser's claim, they may be treated in calculations as rigid because their elastic deformations are about 1,000 times smaller than the deformations at the crushing front."

This is the argument Bazant uses to explain to James Gourley that both blocks A (the 'lower block') and block C (the 'upper block') can be treated as 'rigid'.


Question 5: Is Bazant referring to the WTC towers specifically when making this argument about treating 'block A' and 'block C' as rigid?

No. He's discussing how his model works. I don't see him applying it to the WTC, not even by hypothesis.

Question 6: Is he claiming that 'block A' and 'block C' can be treated as rigid because only 'harmless elastic waves' can penetrate them, and that 'no wave attaining the material strength (of the 'blocks') can penetrate beyond the WTC crush fronts'?

That's a loaded question. If the question were formulated like this:

Question 6: Is he claiming that 'block A' and 'block C' can be treated as rigid because only 'harmless elastic waves' can penetrate them, and that 'no wave attaining the material strength (of the 'blocks') can penetrate beyond his postulated crush fronts'?
​

then the answer would be yes, that's what he's claiming.

Bazant continues to answer the points made by James Gourley...

"4. Can Crush-Up Proceed Simultaneously with Crush Down?It can, but only briefly at the beginning of collapse, as mentioned in the paper."

Question 7: Is Bazant claiming that in the case of the WTC collapses, 'crush up' cannot proceed 'crush down' except only briefly at the beginning of the collapse?

No. Again, in his postulated model only.

Bazant continues to explain point 4...

"Statements such as "the columns supporting the lower floors . . . were thicker, sturdier, and more massive,"
although true, do not support the conclusion that "the upper floors (i.e., the floors comprising Part C) would be more likely than the lower floors to deform and yield during collapse" (deform they could, of course, but only a little, i.e., elastically)."

Question 8: Is Bazant claiming that the 'upper floors (i.e., the floors comprising Part C)' would not be more likely than the 'lower floors' to 'deform and yield' during the collapse of the WTC towers?

Not in the real WTC towers collapse. Assuming by hypothesis that the collapse of the towers happened according to his model, which is Gourley's assumption, yes. Note he's making a statement of logic: "do not support the conclusion", i.e. non-sequitur, and he explains why. To do so, he must accept Gourley's assumption as a hypothesis.

Question 9: Is Bazant, when addressing J. Gourley, a known 'truther', about Gourley's specific reference to the WTC towers, talking about the 'lower' and 'upper' floors of the WTC towers, or is he talking about some other building?

He's talking generically, and in order to rebut Gourley's point, to the WTC towers by hypothesis.

Question 10: Why is Bazant writing about the thicker, more massive columns supporting the lower floors of the WTC towers if he was aware of the ROOSD propagation mechanism?

That should be clear by now. He's referring to the context Gourley sets up in order to rebut his point.

Question 11: Why is Bazant talking about the 'upper floors' of the WTC towers only deforming 'a little, i.e., elastically' if he was aware of the ROOSD propagation mechanism?

Same answer as question 10.

Bazant continues on the same point:

"More-detailed calculations than those included in their paper were made by Bažant and Verdure to address this question. On the basis of a simple estimate of energy corresponding to the area between the load-deflection curve of columns and the gravity force for crush down or crush up, it was concluded at the onset that the latter area is much larger, making crush-up impossible."

Question 12: Is Bazant referring specifically to the WTC towers when making this statement?

No. He's saying that he elaborated the model further in order to address Gourley's question in its context (Gourley's belief that it applies literally to the WTC case).

Question 13: Is Bazant claiming that 'crush up' is impossible in the case of the WTC towers?

No. He's claiming that it would be impossible if the towers collapsed according to his model.

Question 14: Does Bazant seem aware of the ROOSD propagation mechanism when making claims such as 'crush-up is impossible' when referring to the WTC towers?

Mooted by the answer to question 13.

Also, loaded question. Do you seem aware that the universe's entropy keeps increasing while you make these questions?

It's not what you're talking about. Likewise, progressive collapse of the floors ahead of the core is not what Bazant is talking about here in order to reply to Gourley.

Bazant continues to explain:

We have now carried out accurate calculations, which rigorously justify this conclusion and may be summarized as follows.

Consider that there are two crushing fronts, one propagating upward into the falling block, and the other down-ward. Denote v1 , v2 = current velocities of the downward and upward crushing fronts (positive if downward); x(t) , z(t)= coordinates of the mass points at these fronts before the collapse began (Lagrangian oordinates); and q(t) = current coordinate of the tower top. All the coordinates are measured from the initial tower top downward. After the collapse of the first critical story, the falling upper Part C with the compacted Part B impacts the stationary lower Part A. During that impact, the total momentum and the total energy must both be conserved. These conditions yield two algebraic equations

Question 15: When Bazant refers to the 'two crushing fronts' and the 'tower top', is he referring to the specific cases of the WTC towers?

Yes.

During impact, ? = 0.2 for the North Tower and 0.205 for the South Tower. For the North or South Tower: m0 = 54.18· 106 or 112.80· 106 kg, m1 = 2.60· 106 or 2.68· 106 kg, m2 = 3.87· 106 or 3.98· 106 kg, and ms = .627· 106 kg for both. For a fall through the height of the critical story, by solving Eq. (2) of Bazant et al. 2007, one obtains the crush-front velocity v0 = 8.5 m / s for the North Tower and 8.97 m / s for the South Tower. The solution of Eqs. (1) and (2) yields the following velocities after impact: v1 = 6.43 or 6.80 m / s, v2 = 4.70 or 4.94 m / s, and vcu = 2.23 or 2.25 m / s for the North or South Tower. These data represent the initial values for the differential equations of motion of the upper Part C and of the compacted layer B. If Lagrangian coordinates x(t) and z(t) of the crush-down and crush-up fronts are used, these equations can easily be shown to have the following forms:

Question 16: When Bazant refers to the 'crush down' and 'crush up' fronts in this quote, is he referring to the specific cases of the WTC towers?

Yes. He's applying the parameters of the WTC towers, in order to address Gourley's point.

"These two simultaneous differential equations have been converted to four first-order differential equations and solved
numerically by the Runge-Kutta method. The solution has been found to be almost identical to the solution presented in the paper, which was obtained under the simplifying assumption that the crush-up does not start until after the crush down is finished."

Question 17: Is Bazant writing about the specific cases of the WTC towers when making these claims?

Same reply as question 16.

Question 18: Is Bazant claiming that these calculations show that the 'crush up' phase of the WTC collapses does not start until the 'crush down' phase is finished?

Same reply as question 16.

Question 19: When Bazant refers to the 'solution presented in the paper', does he mean the 2007 paper by Bazant and Verdure?

Yes. My understanding is that he took the equations and substituted the parameters in order to compare and reply to Gourley. But see also my reply to question 21 below

Question 20: Is Bazant claiming that these more detailed equations show that the original equations in BV were valid when applied to the WTC collapses?

No. As indicated in the answer to question 16, he's applying the parameters of the WTC towers to his equation, in order to address Gourley's point.

Bazant continues to explain:

"The reason for the difference being negligible is that the condition of simultaneous crush-up, x ? 0, is violated
very early, at a moment at which the height of the first overlying story is reduced by about 1%."

Question 21: When making this specific statement is he referring to the WTC towers?

Possibly. There's the possibility of a mistake here, by generalizing crushing direction using WTC parameters to a generic model.

"This finding further means that the replacement of the load-deflection curve in Fig. 3 of the paper by the energetically equivalent Maxwell line that corresponds to a uniform resisting force F? cannot be sufficiently accurate to study the beginning of two-way crush.)"

Therefore, a solution more accurate than that in the paper has been obtained on the basis of Eqs. (3) and (4). In that solution, the variation of the crushing force F? within the story was taken into account, as shown by the actual calculated resistance force labeled F(u) in Fig. 3 of the paper, by the force labeled F(z) on top of Fig. 4 of the paper, and by the resistance curves for the crushing of subsequent stories shown in Fig. 5 of the paper. The precise curve F(u) was calculated from Eq. 8 of Bazant and Zhou (2002). Very small time steps, necessary to resolve the changes of velocity and acceleration during the collapse of one story, have been used in this calculation. Fig. 1 shows the calculated evolution of displacement and velocity during the collapse of the first overlying story in two-way crush. The result is that the crush-up stops (i.e., (x) )_ drops to zero? when the first overlying story is squashed by the distance of only about 1.0% of its original height for the North Tower, and only by about 0.7% for the South Tower (these values are about 11 or 8 times greater than the elastic limit of column deformation)."

Question 22: Is Bazant claiming that the crush up process of WTC1 stops when the first overlying story is 'squashed' by a distance of only about 1.0% of its original height?

No. Only in his hypothetical scenario.

"Why is the distance smaller for the South Tower even though the falling upper part is much more massive? That is because the initial crush-up velocity is similar for both towers, whereas the columns are much stronger (in proportion to the weight carried)."

Question 23: Is Bazant referring to the specific cases of the WTC towers when making this statement?

Yes, within his hypothetical scenario.

Question 24: Why is Bazant referring to the strength of columns if the ROOSD propagation mechanism is independent of column strength?

Because he's not talking about reality. He's talking about his model applied to the WTC towers.

"The load-displacement diagram of the overlying story is qualitatively similar to the curve with unloading rebound sketched in Fig. (4c) of the paper and accurately plotted without rebound in Fig. 3 of the paper. The results of accurate computations are shown by the displacement and velocity evolutions in Fig. 1."

This is figure 1 from the Bazant and Le paper reproduced. The figure shows Dr Bazant's conception of how the "crush up" process compares to the "crush down" process for both WTC1 (north tower) and WTC2 (south tower). According to Bazant, the process of "crush up" in WTC1 will be arrested after it proceeds a mere 1 inch upward. At this point, the "upper block" will be "cushioned" by a region of accumulated rubble which he calls "zone B". The "upper block" of WTC1 and 2 then "survives" until its lower edge makes firm contact with the earth through the completely compacted lower portion of the building. Lastly, the "upper block" is crushed upward and is destroyed.

"So it must be concluded that the simplifying hypothesis of one-way crushing (i.e., of absence of simultaneous crush-up),
made in the original paper, was perfectly justified and caused only an imperceptible difference in the results."

Question 25: Is Bazant referring to the WTC towers when making this statement?

Possibly. See reply to question 21.

Question 26: When Bazant refers to the 'original paper', is he referring to the paper by Bazant and Verdure (2007)?

Yes.

"The crush-up simultaneous with the crush down is found to have advanced into the overlying story by only 37 mm for the North Tower
and 26 mm for the South Tower."

Question 27: Is Bazant referring to the WTC towers when making this statement?

Yes, again in the context of Gourley's point.

Question 28: Is Bazant claiming that the crush up process for WTC1 advanced only 37 mm upward before coming to a stop, at which time only crush-down occurred until the collapse front made contact with the earth?

No. He's claiming that his model predicts that when applied to the towers.

Question 29: Is Bazant claiming that the crush up process for WTC2 advanced only 26mm upward before coming to a stop, at which time only crush-down occurred until the collapse front made contact with the earth?

No. See answer to question 28.

"This means that the initial crush-up phase terminates when the axial displacement of columns is only about 10 times larger than their maximum elastic deformation. Hence, simplifying the analysis by neglecting the initial two-way crushing phase was correct and accurate."

Question 30: Is Bazant referring to the WTC towers when making this statement?

No, but see reply to question 21.

Question 31: Is Bazant claiming that the 'crush up' phase of the WTC towers terminates 'when the axial displacement of columns is only about 10 times larger than their maximum elastic deformation'?

No. See answer to Q28.

Question 32: Is Bazant claiming that it is 'correct and accurate' to ignore the phenomenon of 'crush up' and consider the WTC towers as being only 'crushed down' until the collapse front makes contact wth the earth?

No. See answer to Q28.

"5. Why Can Crush-Up Not Begin Later? The discusser further states that "it is difficult to imagine, again from a basic physical standpoint, how the possibility of the occurrence of crush-up would diminish as the collapse progressed."

This is one of the only intelligent comments made by either 'truther' representative throughout the whole paper. Any logical human being should question why the 'possibility of the ocurance of crush up would diminish as the WTC collapses progressed' But Bazant then proceeds once again to explain why 'crush up' is physically impossible...

"Yet the discusser could have imagined it easily, even without calculations, if he considered the free-body equilibrium diagram
of compacted layer B, as in Fig. 2(f) of the paper."

This is figure 2 from the Bazant and Le paper reproduced. This is how Bazant defines variables for the equations he uses.


Question 33: Is Bazant referring to the specific cases of the WTC towers when making this argument on how 'crush up' cannot occur?

Only in the context of Gourley's question. He's discussing his model, not the reality of the collapses. Again, he switches when addressing points 7 to 9.

As for your comment prior to the question, which seems aimed at biasing the reader's opinion unfairly, Gourley makes the same mistake of understanding that Bazant's models applied literally to the collapses as they happened.

"After including the inertia force, it immediately follows from this diagram that the normal force in the supposed crush up front acting upward onto Part C is

"The discussers' statement that "the yield and deformation strength of . . . Part C would be very similar to the yield and
deformation strength of . . . the lower structure" shows a misunderstanding of the mechanics of failure. Aside from the fact that "deformation strength" is a meaningless term (deformation depends on the load but has nothing to do with strength), this statement is irrelevant to what the discussers try to assert. It is the normal force in the upper Part C that is much smaller, not necessarily the strength (or load capacity) of Part C per se."

"Force F? acting on Part C upward can easily be calculated from the dynamic equilibrium of Part C (see Fig. 2g), and it is found that F? never exceeds the column crushing force of the overlying story. This confirms again that the crush-up cannot restart until the compacted layer hits the ground."

Question 34: Is Bazant referring to the WTC towers when making this statement?

No. See caption of figure 2:

Note the word model. He's talking about his model.

Question 35: Is Bazant claiming that his work has confirmed that the 'crush-up cannot restart until the compacted layer hits the ground'?

In his hypothetical model, yes.

Question 36: Is Bazant writing about the "crush up' of the collase front of the WTC towers, and how it cannot happen until the collapse front hits the earth?

No. But he may have made a mistake, see answer to Q21 again.

"6. Variation or Mass and Column Size along Tower Height:

This variation was accurately taken into account by Bazant et al. (2007). Those who do not attempt to calculate might be surprised that the effects of this variation on the history of motion and on the collapse duration are rather small. Intuitively, the main reason is that, as good design requires, the cross-section areas of columns increase (in multistory steps, of course) roughly in proportion to the mass of the overlying
structure. For this reason, the effect of column size approximately compensates for the effect of the columns’ mass."

Question 37: Why does Bazant consider variation of mass and column size when referring to the collapse propagation of the WTC towers if ROOSD propagation is independent of column strength?

Because he's not addressing real collapse, but accepting Gourley's premise in order to refute his point from the theoretical standpoint. Remember it's a technical journal and Bazant's interests (and the journal's) are technical. It's not a place to discuss conspiracy theories.

Question 38: Does Bazant seem aware of the concept of a ROOSD propagation mechanism when making this statement?

See answer to Q14.

Closing Comments
Although everyone is certainly entitled to express his or her opinion on any issue of concern, interested critics should realize that,
to help discern the truth about an engineering problem such as the WTC collapse, it is necessary to become acquainted with the relevant material from an appropriate textbook on structural mechanics. Otherwise critics run the risk of misleading and wrongly influencing the public with incorrect information."

Question 39: Is Bazant referring to the WTC collapses specifically within this closing comment?

Not outside of Gourley's misunderstanding in that respect.

Question 40: Within every comment quoted above, when addressing two known 'truthers', was Bazant referring specifically to the WTC collapses?

No, as noted.

Question 41: At any time within the quotes given, did Bazant seem aware of the ROOSD mechanism of propagation?

See answer to Q14.

Question 42: Within the multiple references to the 'lower block', the 'upper block', a 'crush down phase', and a 'crush up phase', is Bazant referring specifically to the WTC towers?

Sometimes, by hypothesis.

Gourley, in his opening statement makes the following claim:

...a two-phase collapse analysis is not representative of reality, because it disregards well-accepted laws of physics and therefore is not instructive.

Question 43: Does Bazant, at any time within the paper, give any indication that he does not consider his own 'two-phase collapse analysis' to not be represenative of 'reality' as applied to the WTC towers?

No. That's not what he's set up to do. He's addressing Gourley's and Szuladzinski's claims on their technical merits only.

Question 44: At any time throughout the paper does Bazant deny that BV equations 12 (the 'crush down' equation) and 17 (the 'crush up' equation) can be applied to the specific cases of the WTC towers?

Same answer as in Q43.

These 44 highly specific questions are formulated in such a way that they can be answered by anyone interested in this subject. They are offered so that any interested person does not need to feel that asking and answering these questions is a task outside of their level of education or ability. I strongly encourage any interested reader to not blindly rely on any arguments made by those in positions of technical authority. Papers like the one being currently examined demonstrate that these authors cannot be trusted to represent the WTC collapses accurately to the public. They do not serve the interest of their profession or of the general public as they claim.

 

[Dave Rogers]

Agreed, to all of the above. The discussion is about a specific model which is offered as a useful approximation to the actual collapses. The fact that other models exist, or may exist, isn't the topic of the discussion; indeed, I think a responsible editor would prefer such other models to be excluded from a discussion of a specific paper, because they're not part of the model under discussion.

Dave

 

[WilliamSeger]

So you cannot find any representation of the ROOSD process within published literature?

I have been pointing out the same thing.

How about this:

The likely scenario of failure is approximately as follows.

*snip*

The vertical impact of the mass of the upper part onto the lower part stage 4 applies enormous vertical dynamic load on the underlying structure, far exceeding its load capacity, even though it is not heated. This causes failure of an underlying multifloor segment of the tower stage 4, in which the failure of the connections of the floor-carrying trusses to the columns is either accompanied or quickly followed by buckling of the core columns and overall buckling of the framed tube, with the buckles probably spanning the height of many floors stage 5, at right, and the upper part possibly getting wedged inside an emptied lower part of the framed tube stage 5, at left.

*snip*

The basic question to answer is: Can the fall of the upper part be arrested by energy dissipation during plastic buckling, which follows the initial elastic deformation? Many plastic failure mechanisms could be considered, for example: (1) the columns of the underlying floor buckle locally (Fig. 1, stage 2); (2) the floor-supporting trusses are sheared off at the connections to the framed tube and to the core columns and fall down within the tube, depriving the core columns and the framed tube of lateral support, and thus promoting buckling of the core columns and of the framed tube under vertical compression (Fig. 1, stage 4, and Fig. 2(c));or (3) the upper part is partly wedged within the emptied framed tube of the lower part, pushing the walls of the framed tube apart (Fig. 1, stage 5). Although each of these mechanisms can be shown to lead to total collapse, a combination of the last two seems more realistic (the reason: multistory pieces of the framed tube, with nearly straight boundaries apparently corresponding to plastic hinge lines causing buckles on the framed tube wall, were photographed falling down, "Massive 2001"; American 2001).

B&Z then go on to justify why the limit case analysis answers the "basic question" asked.

 

[JSanderO]

How about this:



B&Z then go on to justify why the limit case analysis answers the "basic question" asked.

It's not (actually) the destruction of the connections... it is destruction and grinding of the floor slabs themselves turning the floor mass (over a very compressed time) into a destructive "FLUID" which flows... in a contained vertical avalanche.

 

[WilliamSeger]

It's not (actually) the destruction of the connections... it is destruction and grinding of the floor slabs themselves turning the floor mass (over a very compressed time) into a destructive "FLUID" which flows... in a contained vertical avalanche.

Then that would appear to be another case where ROOSD is misleading. What do you suppose would happen differently if the floor slabs were mainly broken into big chunks instead of a "fluid?" At what granularity does the "fluid" state arise?

 

[ozeco41]

@Major_Tom your style of asking apparently loaded questions without a clear statement of your claim and passing "burden of research proof" to us has resulted in the usual mix of emotive personal comments and technical partial truths. If that was your intention I deplore it...again.

If you are seeking clear understanding of the technical issues why not state them? Clearly and explicitly?

Let's see if we can get some agreement of the basic technical facts:

I will try to rigorously avoid the personal commantary and focus on the key technical issues.

I will do so in two distinct stages. Stage 1 - Identifying and seeking to resolve any confusions which arise from misunderstanding of or misapplication of the facts of the Bazant and Zhou "Limit Case" paper of 2001/2 and Stage 2 - Extending the clarification to Bazant's thinking as developed in the later papers.

So Stage 1 - Bazant and Zhou.

1) The B&Z paper raised three issues which are key facts for this discussion. They are:

Fact #1a Bazant identified that the real collapse mechanism was complicated and chose a simpler model which was valid for a "limit case argument";

Fact #1b Bazant clearly distinguished the two different mechanisms - the more complicated real event and the simpler version supporting a "limit case" argument;

Fact #1c Bazant's "limit case" argument was conceptually valid, it has not been successfully challenged and he did not confuse the two mechanisms.

2) Major_Tom, myself and others engaged in debate circa 2008-9-10 identified a situation of confusion existing at that time. Others have strenuously argued that there was no confusion. The historic difference of opinion is not relevant NOW. The relevant fact for now is:

Fact #2 Discussion of WTC collapses should not use or rely on confusion of any issues of fact including the facts derived from Bazant's work.

3) Major_Tom OP'd this thread requesting comments on a paper which had this theme:

Careful, detailed observation of the WTC1 and WTC2 core remnants and perimeter motion allow us to understand the probable mechanism by which the towers collapsed. The perimeter was collectively stripped of flooring and fell outward as large, unbuckled, interconnected pieces while most core columns of the building survived the initial collapse.

I agree with that fact. Who disagrees? (Sander as usual you have a different speculation - can we set it aside because I suspect BOTH sides will disagree with you. It will only add more confusion. At this stage. )

Fact #3 - The progression collapse stage for WTC1 and WTC2 was dominated by a mechanism in which material falling down the office space tube stripped floors leaving perimeter columns to fall away.

4) Major_Tom identified that the "real event" mechanism is different to the columns crushing mechanism used in the B&Z "limit case" argument. I agree with that fact - the actual real event mechanism was NOT by column crushing. Who disagrees?

Fact #4 The real event collapse described by Major_Tom in the link from the OP AND restated as Fact #3 is a different mechanism to the column crushing model of the limit case argument.

5) Major_Tom asserted that It was a distinct form of progression collapse - a different mechanism to "column crushing". I agree with that fact. The two mechanisms are different. Who disagrees? (How much different is a pin t for later discussion.)

Fact #5 Reaffirms that the two mechanisms are different.

6) Major_Tom asserted that there was a history of confuion I agree that there was confusion in those earlier days. Others disagree vehemently. The issue which matters is the there should be no confusion. So:

Fact #6 Arguments should not be confused over the two mechanisms and any relationship they may have.

There is an incidental issue - which goes to the use of the label "ROOSD". There are two sub issues which are: (i) Denial that the distinct mechanism needs any label other than "progression"; AND (ii) Resentment at Major_Tom's implied claims as to primacy of and sole discovery.

Neither is important at this stage - (ii) is nonsense and (i) the need for a label - not necessarily Major_Tom's - should flow naturally from agreement that there are different mechanisms of progression. If the mechanism is not different it shouldn't need a label.

Take a rain check on both.

Does anyone have a fundamentally different view of any of those 8 issues of technical fact labelled "Fact #x"?

Are there any other issues of basic fact arising from B&Z that we need to agree?

If we get posted agreement from a few members I will progress to Stage 2 - and take on those later papers one at a time. Prudence suggests that I should not take silence as acquiescence.