OOS Collapse Propagation Model

[TheRedWorm]

How much less?

Well, I could tell you, but I'd have to be dead.

 

[rwguinn]

I was asleep under a rock for the past 100 years... Who said you boys are all wrong and Tom is always right? I believe I wrote that the ROOSD was the best fit explanation I was aware of.

You did.

I find this "discussion" hysterical. It appears to me that Tom has produced a pretty well documented and accurate depiction of the collapse mechanism(s)... he's called it ROOSD. It hardly matters what it's actually called... but I think giving it the acronym is perfectly reasonable... But it also seems that all the big guys with alphabets attached to the name seemed to NOT identify the mechanism and.... are too proud (hubris???) to admit it. And who the eff cares that Mr B could run some number proving X mass could destroy the tower.... it's not what happened so it's a waste of time essentially... it sheds no light on the actual mechanisms.

Of course what seems to drive these guys mad is that they perceive Tom to be a truther or a liar about something and it certainly seems that on the matter of the collapse he seems to be the one telling the "truth" here not the other fellas in the JREF club.

I don't dispute that there are some very intelligent people... who participated in the discussion... they just happened to have been wrong. Frankly as ROOSD has nothing to do with initiation.... and it only the collapse process... why does the initiation matter? Maybe Tom was a "truther" and maybe he still believes that CD kicked off ROOSD... THAT is another matter and has nothing to do with the veracity of ROOSD. And as a side note I don't see any truthers jumping on the ROOSD bandwagon either.... not a one.

I'd also like to know what Tom lied about? Maybe he changed his opinion? or evolved his understanding? I know my thinking on this matter has evolved... but it has never really accepted the illogical and sloppy (bad) thinking that truthers seem to display. I don't consider myself to be a liar... perhaps a bit dumb and dense at times.

But in the end these battles of personalities just seem childish to me... egos seem to driving this not rational thinking.

What was yours mr guinn? And how did you arrive at it?

The same as NIST, and eventually Major Tom. Back in Late September 2001.
It's all in the archives at JREF, somewhere...

 

[ozeco41]

I wonder if anyone has been able to read through the whole thing, I've tried a few times. I've determined that it's un-readable in its entirety.

Maybe ozeco has.

I haven't. And given the continuing confusion of the main issues in this thread here is my full reasoning. Stay with me or ignore the post as you wish - because I will explain exactly where I disagree with M_T.

When reading posts/papers I look first for things which I agree with or which appear to be correct. And check out the apparent validity of the evidence adduced and the supporting reasoning. And I do that without regard to whether the poster/publisher is a truther or alleged truther. THEN I look at the errors of argument and very quickly lose interest - especially if the errors are fatal to the claim e.g. the false starting premises for "Missing Jolt". My interest wanes whether or not the errors come from a debunker, a truther or - rare these days - an uncommitted sceptic. I will often attempt to explain correct reasoning for 'truthers' - I rarely bother with errant debunker logic - reasons don't matter here.

SO I tried reading Major_Tom's "book" but it was after I had multiple interactions with TOM on this forum and others.

I have not wavered over 3-4 years in my stance on M_T viz:
a) He gets some technical bits right. And his supporting research is of the highest quality. Plus I loathe the style of the dishonest debunker counter that says "his research is of no value (to me - but they omit the qualifier to support the implied lie) THEREFORE his research is faulty/wrong/unnecessary etc etc" - Dozens of different versions of that form of slightly disguised personal attack.
(b) His style is offensive and has become increasingly so - his motive clearly is to goad people rather than support his technical claims. He has explicitly admitted his intent on several occasions. So pure trolling IMO; AND
(c) His logic is false and dominated by two major and persistent errors. The big one - mostly in his pseudo psychology - is that he makes an assertion which could well be true for a minority of anomalous examples THEN claims it is global truth. So 'false generalisations'. The second one - more relevant to technical argument - is that he denies that factors in argument MUST be both relevant to and significant in the conclusion reached. That one not of interest here BUT vital to countering his false technical claims which I have done many times. (Remember the "NIST errors in Key Areas" debacle).

And I have spent kilowords explaining the logic errors plus advising him to abandon his offensive style. Both on this forum and on another forum. And about three time separated series of posts for each forum.

So when I came to try to read the book I immediately recognised:
1) the same few valid technical points which I did not need to re-think; AND
2) And a whole load of cobblers pseudo psychology
3) The same major errors of logic structure mainly false generalisations - bits of claims based on a truism which could apply to a minority which is falsely globalised into a claimed general truth; AND
4) and all framed in the obnoxious style of self aggrandising arrogance whilst implying that the rest of "us" are wrong and mentally deficient for not seeing it.

However, its becoming apparent that those are the parts of the paper he is most interested in over technical discussion.

Interesting because he doesn't actually make any clear point in that regard. I have no problems with his physical observations.

...A pointless step in my opinion. Why would he need agreement? Does he think his knowledge is so superior that we need to agree in order to keep up?

Those are two of the key points where I am in full agreement - trolling and personal attacks take preference AND arrogant self aggrandisement built on a poor foundation.

 

[ozeco41]

Well, in this thread, on this forum, I get it, ozeco41 gets it, JSO gets it, DGM gets it, Newton's Bit gets it, rwguinn gets it, pgimeno gets it and beachnut gets it.Obviously FEMA gets it, and so does NIST

Where's the beef? just tfk?....

Who is conspicuous by his absence after precipitating this recent surge of interest.

NOW - FOR THE RECORD

I have stated my position clearly on two areas of discussion viz:
1) The technical matters; AND
2) The personal aggression aspects of much current discussion.

..plus hinted that we would be better served by discussing one or the other BUT not mixing both.

Thanks jaydeehess for listing me as one who "gets it" - I think I do.

On the two technical issues:
(1) The mechanism NOT the label - we seem to be agreed that whatever we called it "ROOSD" is a valid explanation of the main element of the progression collapse mechanism. [AFAICS only tfk and beachnut being holdouts on that aspect and beachnut's "OOS=BS" could be read ambiguously as referring to the label when the rest of us were (should have been) discussing the mechanism, not the label.]

(2) Whether there was or was not (including "is or is not") confusion over the boundary of Bazant's works including but not limited to the valid limit case application of B&Z 2001-2.

So, for the record only, I hold to this position:
1a) B&Z 2001-2 as a limit case was taken as valid, served its purpose, is no longer of much significance BUT has been challenged in maths by the recent Sz, Sz and J paper. That challenge unresolved AFAIK. I do not need B&Z limit case for any of my arguments therefore the status of the challenge is not relevant to my needs. And - if Bazant was wrong on the maths - it simply leaves NIST in the position of apparently having reached the right conclusions for the wrong reason. Global collapse was inevitable. With or without support of B&Z.

1b) The limit of applicability of B&Z was subject to much confusion in forum discussions whether or not some engineers understood the distinction before all the lesser mortals like me. And current discussions are not clarifying that aspect - rather rebuilding the historic confusion. And I'm not interested in further discussion at this stage. Some people were confused whether others were or were not.

2) Bazant's later papers do not employ limit case modelling. They apply column crushing models in the stated goal of developing a generic approach to collapse analysis. So far so good. So explicitly they are NOT intended to be WTC 9/11 collapses. Several of us therefore agree on that point but from opposite perspectives. THEREFORE any attempt to "back engineer" later Bazant work onto WTC "real event" collapse will be wrong. Whether within the papers OR in external commentary. OR - a potentially worse situation - will be right for the wrong reasons. And we have seen several of those over the years. I'm in agreement with M_T on that and anyone who can show it wrong is welcome to do so in an appropriate thread. I will not object to being proved right OR shown where I am wrong.

 

[WilliamSeger]

I don't dispute that there are some very intelligent people... who participated in the discussion... they just happened to have been wrong.

If you misunderstood the purpose of Bazant's analysis, then it seems likely that you also misunderstood a lot of the defense of it, too.

 

[Major_Tom]

R Mackey's posts from the first 8 pages of this thread are reproduced below. They are a wonderful example of how a person can reason in order to not perceive any shortcomings in the atter Bazant papers on the WTC collapses.

The whole line of investigation is ridiculous. What unanswered question does this paper purport to examine? None. Existing, reliable, reviewed scientific literature covers it quite thoroughly. All the made-up acronyms and appeals for attention are no more than fatuous Truther narcissism.

Newtons Bit and R Mackey claim that the study provides no new information that was not known before.

Unless participants in the JREF forum have abandoned Bazant's opinions stated in BV and BL, this is provably false.

>>>>>>>>>>>>>>>>>>>>>>>>>


CRUSH DOWN FOLLOWED BY CRUSH UP, 2006-2010, R. I. P.

BAZANT AND VERDURE EQUATIONS OF MOTION, EQS 12 AND 17, 2006-2010, R. I. P.


If we accept the ROOSD study as accurate, one logical consequence is that the claims in the papers BV and BL are incorrect.

...


Let's ask R Mackey and NB the following questions and see what they have to say:

1) In BL, can you explain why Dr Bazant insists that crush down must be complete before crush up occurs. Does he mean this literally?

2) Do you consider the equations of motion in BL, equations 12 and 17, to be accurate considering the information in the ROOSD study?

3) Is the following statement true or false:

Dr Bazant believes that a crush-down phase must continue to completion before a crush up phase can begin.

If you answer false, please provide evidence to the contrary.

4) Is ROOSD consistent the claims of crush down preceding crush up in BV and BL?

Personally, I like how he seems to think Bazant and Le (2002) is supposed to be an accurate description of the collapse rather than a limiting case, or that he thinks that plus Bazant and Verdure (2006) cover the entire scope of the literature. As if we hadn't explained this to practically every Truther who ever lived a million times each.

Ah well. I guess it keeps them occupied, at least.

These questions were carefully chosen to expose fundamental weaknesses in Dr Bazant's papers. They also can help us understand the papers better. This is important because there are many false beliefs about what the papers say and do not say.



What we have seen in the first 5 pages of this thread is there are many misconceptions about the papers.

It's much worse than that. Bazant and Le Zhou was written within 48 HOURS of the incident.

I talked about this in my discussions on Hardfire. Basically, Bazant and Le Zhou present a simplified model to illustrate certain features and phenomena relative to the actual events. The Truthers, casting about in desperation for a windmill to tilt at, seize not upon the phenomena nor on providing an alternate conclusion, but instead bitch about the model.

We know the model isn't precise. That's the whole point.

It's like watching reviewers in another country critique Shakespeare despite not understanding the language, going off what they get from the Google translator. The Truthers simply do not understand what they're talking about, and wind up criticising their own misapprehensions. That, plus being totally ignorant of the many other journal papers on the subject. Is it any wonder there's no point talking to them?

I also don't think the simple model is a perfect representation of reality. In fact, going back to Hardfire, I presented my own model (a cartoon, really, but it could be expanded on) of the collapse initiation and progression. It's in these slides. Reading this, the Truthers will probably crow that I've "refuted" or I "discount" Dr. Bazant, but of course that's not true at all.

On the fifth page of the thread R Mackey finally realized he was confusing the papers BZ (2002) and BL (2008).

Oops. You are correct. Fixing now...

Too many acronyms!

ETA: I wonder what Major_Tom meant by "BL" then? There is no relevant article with only Dr. Bazant and Jia-Liang Le. I just assumed he meant Bazant & Zhou.

Seeing as how there is no paper by Bazant and Le that is relevant here, and you've ignored requests to clarify what you mean, I think you should cool it a bit.

Do you mean Bazant, Le, Greening, and Benson (2008), sometimes known as BLGB? Or are you even more confused than we thought?

Just so everyone knows, BV and BL are......

BV:

Mechanics of Progressive Collapse: Learning from World
Trade Center and Building Demolitions
Zdenfk P. Bažant, F.ASCE; and Mathieu Verdure
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/466.pdf


BL:

Bazant & Le
Closure to "Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions"
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25 WTC Discussions Replies.pdf

We have a basic misunderstanding on how to read the BV and BL papers linked in my last post.

Each is only a few pages long so it shouldn't be difficult to to see if R Mackey, Dave, NB and Myriad are right or wrong. We need to clear this up before the thread can progress.

My suggestion is that the readers learn to distinguish between Bazant and Zhao, published in 2002, and BL and BV, published in 2008.

If this is where you're going, I'll save you the trouble. This line of inquiry goes nowhere.

Originally it was claimed by the Truth Movement that the character of the WTC collapses could only be caused by explosives. This, of course, was utter nonsense. Dr. Bazant's first paper was out before there ever was a Truth Movement, and the early Truthers were totally ignorant of his findings.

Dr. Bazant's later papers are a refinement of his initial work, partly in response to Truthers who remained ignorant even after learning of his findings, such as Mr. Gourley. They prove exactly what they set out to prove, namely that this style of collapse is not only possible, but in fact predicted, and that no explosives or thermite or space beams or anything are needed.

What you are asking is whether Dr. Bazant's results rule out explosives. That was not their intent, but in fact, they do. Not because an explosive demolition would perform differently with respect to the effects modeled, though. Instead, Dr. Bazant rules out explosives by attacking the "evidence" for explosives -- the only "evidence" there has ever been in support is the claim that it couldn't have happened any other way. That claim is refuted by Dr. Bazant's work, and therefore, there is no evidence of any kind, including the circumstantial for explosives.

What you're doing, typical of the more inane Truthers, is performing an extremely slow, dull-witted, and well-telegraphed Shifting the Burden of Proof and Begging the Question logical fallacy. Dr. Bazant's papers do precisely what they were intended to do. You are trying to show they are inadequate for a purpose they were never intended, and is not needed in the first place. What a waste of time.

There is no evidence yet that he ever read the papers BV, BL or BLGB and quite a bit of evidence he never read them.

Either logic or the English language escape you -- I answered you in the post you responded to. That was the whole point of the post!

Tell you what. I'll try again, and I'll use small words and simple sentences.

1. There is no evidence for explosives. None.

2. The closest there has ever been was a belief that only explosives would cause collapses like that.

3. This belief is false. Dr. Bazant's papers prove this.

4. Therefore, his papers rule out a controlled demolition.


Don't respond yet, just read the above until you understand.

Now that you understand, it's my turn to ask a question. You're interested in "controlled demolition" of WTC 1 and 2. Will you follow the scientific method in your study? Yes or no?

I don't see an answer to my question anywhere in there.

In typical Truther fashion, you answer my question with a question, and your question is nonsense to boot. You may as well say the paper used Newton's Second Law, so is Newton's Second Law just meant as a limiting case or does it really apply to WTC 1. Your logical fallacy this time is the Fallacy of Many Questions, which is slightly more interesting than your previous dodges, but still just plain stupid.

I'm not inclined to explain any further without some reciprocity from you. Third time: You're interested in "controlled demolition" of WTC 1 and 2. Will you follow the scientific method in your study? Yes or no?

You have no good reason for not answering. It's a simple question.

1) R Mackey, in a post on page 3 you wrote: " Personally, I like how he seems to think Bazant and Le (2002) is supposed to be an accurate description of the collapse rather than a limiting case, or that he thinks that plus Bazant and Verdure (2006) cover the entire scope of the literature. As if we hadn't explained this to practically every Truther who ever lived a million times each."

Of course you were confusing Bazant and Le with Bazant and Zhao. Do you agree with Dave and Myriad that the crush up, crush down model developed in BV and BL was meant as just a limiting case, or does Bazant believe it really applies to WTC1?


and another...

2) R Mackey, does Dr Bazant believe WTC1 experienced crush down, then crush up as he explains or is the idea of crush down, then crush up just a "limiting hypothetical case in which the structure is best able to resist collapse".
>>>>>>>>>>>>>

Dave, Myriad and NB have made their opinions clear already. You have not. I need a clear answer from you before I can respond to them.

R Mackey posted in another thread on this same subject a bit later in response to this OP comment by pgimeno:

I'm trying to understand Bazant's crush-down/crush-up model, which I know is widely accepted. I am not questioning it, I merely want to understand it, and hopefully the explanation will be useful for someone else too.

In these comments he demonstrates how he understands the latter Bazant papers very clearly.



R Mackey is refering to me as being a 'denier' for pointing out that the arguments in BZ (2002) and BV (2007) are quite different.

Maybe if we all write it a thousand times, the denier will get it.

Bazant and Zhou's "crush down / crush up" model is a model. It represents the best case from the standpoint of structural survival. It is not an accurate representation of the precise blow-by-blow collapse, nor could it be. It was written on September 13, 2001!

Bazant and Zhou's model shows that even the limiting case of collision is expected to totally collapse. Therefore, no matter what the details are, the structure is expected to collapse. There is no mystery in the total collapse of either WTC 1 or WTC 2.

Bazant and Zhou's model also shows that the dominant factor in the timing of collapse is the momentum transfer between moving portions. Not the strength, not how the structure was hit, not its failure modes. The momentum transfer is pretty much the same regardless of the details of collapse. Therefore, the collapse timing they estimate is also close to reality (provided one doesn't include the core remnant in the collapse time).

That's it. The Truthers have nothing, so they're going for the semantic argument and trying to create a false dichotomy. This in no way simulates a legitimate controversy. The matter is settled.

There is no such thing as a 'crush-up, crush-down model' in BZ. Once again, he is talking about the wrong paper and ascribing arguments to it that do not exist.

I attampted to point out this simple fact many times but I was called a 'liar' and a 'denier'.

David Benson to me, 2008:

"One dimensional homogenous structure crush down is indeed what Newton's laws require. This was first briefly explained in Bazant & Verdure and elaborated more fully in Bazant's 'reply to comments' in a more recent issue of J. Engg. Mechanics.

Of course, the collapse of WTC 1 only begins to approach the assumption of homogeneity after about three floors are crushed. After that, the layer of crushed materials does the damage to the portion below and protects the part above (ideally) from further damage. In the actual event, we know that the spire punched through the top portion; after that the top portion began to fall apart. It seems that it fell completely off before the crush down was complete, but not much before.

If this detail is of sufficient importance, find the video showing the antenna tower flying away at about a 70 degree angle. Do the timing analyss to determine how long after initiation this was and, if possible, how high up the antenna tower was at that time.

My claim of not much before the end of crush down is based on the excellent timing fit of BLGB. Some adjustment, of course, can be made, but not having the top portion fall off the crushed zone at, say, 4 seconds into the collapse.n the following quote David Benson is explaining to me that the WTC1 "spire" must have punctured through the roof of the famous upper block."

From this post:

http://the911forum.freeforums.org/post763.html#p763


In this post he is trying to explain to me why the WTC1 "spire" is consistent with the Bazant crush down, crush up idea and an "upper block". He explains that the 60+ story columns must have "punctured" the famous upper block.


Do you see how he applied specific features of the stick model in BV to WTC1?

I could probably find 50 different examples in his posts.

Why don't you read what he posted before lecturing me on what he intended?

In the next post R Mackey is describing how an 'upper block' is 'cushioned' by rubble and

It's the latter.



This is not the only factor, but it too is partially correct.

Think of it in terms of impulse -- the total change of momentum at a particular impact. Impulse is equal and opposite, by conservation of momentum. Impulse is equal to F delta-T (force times the time over which the force is applied), or M delta-V (the raw change of momentum in its familiar definition P = m V).

When we look at the "upper block," it's delta-V is smaller than the delta-V experienced by the newly broken part of the lower block. As you say, the upper block decelerates by an average 1/3 g, while the lower block accelerates by an average 2/3 g. This is because the participating part of the lower block masses less than the participating part of the upper block -- it really is the compacted mass and upper block versus a small number of floors at a time, not the entire lower block.

The reason only part of the lower block participates at any given time is because the lower block is still a mostly intact sparse structure of braced columns. When it's hit, the columns lose bracing, get loaded eccentrically, shear their welds and bolts, and in some cases are totally overwhelmed and fracture entirely. These pieces break at a stress much too low to actually support the descending mass. This also has nothing to do with the strength of the perfectly intact building -- the descending rubble heap isn't contacting the lower structure at its strongest points, and it's introducing brand new failure modes, so the effective opposing strength of the lower structure is far lower than its ideal carrying capacity. Furthermore, where the lower structure does resist at or near its ideal strength, it can only do so for a very brief delta-T -- until reaching its failure strain, which takes only about ten milliseconds at the speeds of collapse -- and this is not enough to amount to all that much total impulse.

The upper chunk, in contrast, is cushioned by a thick layer of rubble. This is compacted about as far as it can, thus it doesn't have those complex failure modes and it doesn't suffer much more "damage" even at much higher stresses. So the rubble pile remains, and the lower structure gives way. This is for the same reason you don't sink into the ground, even though you can push your finger easily through a cupful of soil.

The "upper block," what remains of it, rides on top of this cushion of debris. It is supported pretty well. It also only decelerates at that lower rate, thanks to the much greater inertia of the upper block + debris. So the only real force it suffers is the inertial force, i.e. its own self-weight times its deceleration, again about 1/3 g. It can be expected to survive this deceleration. It's only when the rubble pile has nowhere else to go and the upper block has to suddenly stop, dissipating all of its momentum in mere milliseconds, that it totally fails.

Again, this is slightly idealized, but you get the point. Unless you're a Truther.

So, roughly it's just that the transmission speed of the wave is not fast enough, and the material yields before transmitting most of it. I think it must be related to the speed of sound in steel, which is about 6,000 m/s, and that is not fast enough... wow. Kind of shocking.

Anyway, I think that the answers to this question have produced results. I've found a key part that makes me understand how a crush-down only can be justified. It comes from an explanation I was given in another forum:

​

(source). I also think it matches this sentence from Ryan Mackey, but I didn't fully understand its implications before:

​

Ok, I think I am now in the position to elaborate a theoretical scenario that justifies crush-down only based on the assumptions.

The starting point of my assumed scenario is two sections of a building, a top section which is hanging and a bottom section fixed to the ground. No columns in between; the first impact is assumed to be floor slab against floor slab. The top is assumed to be able to produce a progressive collapse, so I don't care much about height, weight, etc.

The top is dropped until it impacts the bottom. What will happen on the first impact?

Wait, there's a little detail, in strict application of the above principle. A column cannot transmit more force than its yield force. But that principle must apply in both directions for each of the sections. That is, the action force that makes the column yield, is accompanied by a reaction force that is exerted against the other column.

There can be negligible differences, e.g. the weight of a column (it must be able to support itself) plus the weight it supports are forces that will only be acting on the bottom part, thus in a perfect setup the stress on the bottom will be slightly greater than that on the top. But let's not be that picky. I'll assume that both floors are crushed at the same time.

So, right after impact we have a top with one less floor and a bottom with one less floor, and between them there's a layer of rubble consisting of two floors, which is initially equidistant to both.

But gravity pushes only in one direction. The rubble layer is attracted by gravity and starts to accelerate downwards. The top plus the rubble will push down on the bottom. Assuming that the rubble arrives first (due to gravity, otherwise they would arrive at the same time), the bottom will be able to arrest the impact of two floors, but then comes the top.

What happens now is the key. The bottom columns are supporting their own weight and the corresponding floor, plus a two floor rubble layer. That's three times the weight that we neglected to consider before. We can no longer neglect the stress that those three floors exert on the bottom. Now the top impacts. The stress on the bottom columns is that of the top columns, plus that of the rubble. They can't transmit back more reaction force than their yield strength, and the rubble layer keeps pushing down due to gravity and thus subtracting from that force, so the force on the top will now be clearly less (and no longer negligibly so) than the yield stress that broke the bottom columns. The top will resist.

If it's still considered negligible, repeat a second time. That means two top floors crushed. The amount of rubble is now 4 floors, plus the floor the bottom columns are already holding, makes 5 floors inducing stress on the bottom structure. Now there's little excuse to say it's negligible.

Also, the rubble layer will soon gain enough mass as to be able to crush the bottom by itself without the need for the top.

Now I may have screwed up somewhere. If so, I'd like to know where.

Plus, I'd like to know if this explanation holds any relationship with the way Bazant explained it. For what I remember, Bazant always started at a point where there was already a rubble layer in between.

The comments by R Mackey are not much different from the comments by Dave Rogers and Myriad, which will be reproduced next.


But the R Mackey posts show how a person can revise the written history to perceive no contradiction between Bazant's latter papers on the WTC collapses and the OOS model.



At least the earlier comments by TFK recognize that the OOS propagation model and the information on crush up, crush down in BV, BL and BLGB are not compatible. R Mackey could not perceive or recognize that fact.

 

[rwguinn]

If you bothered to reat those quotes, M_T, you would find they do not support your case ( nor JsanderO)-- in fact, they rather serve as evidence you have finally arrived at the conclusion many others arrived at years ago...
That Bazant is not, nor was it intended to be an accurate description, rather a limiting case;
That progressive collapse, rather than buckling was the most likely case,
and that that progressive collapse was rubble led, among other things.
As described by R. Mackey and others, in the quotes you provided

 

[beachnut]

...
You will recall my code expression over many years "Blue Sky Syndrome"

Still.... This is the JREF we seem to love.....

...

What blue sky?

OOS is blue-sky

 

[jaydeehess]

R Mackey's posts from the first 8 pages of this thread are reproduced below. They are a wonderful example of how a person can reaso......

No one cares about your pseudopsych musings!

Do you have a discussion about the collapses in mind any time soon?

 

[Newtons Bit]

If you bothered to reat those quotes, M_T, you would find they do not support your case ( nor JsanderO)-- in fact, they rather serve as evidence you have finally arrived at the conclusion many others arrived at years ago...
That Bazant is not, nor was it intended to be an accurate description, rather a limiting case;
That progressive collapse, rather than buckling was the most likely case,
and that that progressive collapse was rubble led, among other things.
As described by R. Mackey and others, in the quotes you provided

Like Heiwa, he is an expert at ignoring what people write, then substituting in his own reality.

 

[Newtons Bit]

Major_Tom, we're perfectly capable of going back to the beginning of this thread. I did it a couple of days ago and got quite a laugh at your foundering. The fact that you think that it was some part of victory for you is baffling to me. Perhaps you'd like to clearly explain what you think all of us are missing.

 

[pgimeno]

The comments by R Mackey are not much different from the comments by Dave Rogers and Myriad, which will be reproduced next.

So, you're menacing us with boredom to death by showing everyone here how you misunderstand the quoted text and make claims about the people writing them that the quoted comments themselves prove wrong.

Time to unsubscribe from this thread, I guess.

 

[carlitos]

Perhaps you'd like to clearly explain what you think all of us are missing.

If he does, I'll eat my hat.

 

[Newtons Bit]

So, you're menacing us with boredom to death by showing everyone here how you misunderstand the quoted text and make claims about the people writing them that the quoted comments themselves prove wrong.

Time to unsubscribe from this thread, I guess.

It's a true talent of his.

 

[MileHighMadness]

Remember...the book is written as a monument to T_M ego. Nothing more, nothing less...

 

[Major_Tom]

Comments by Dave Rogers and Myriad in the first 8 pages of this thread:

A summary of my questions concerning the Bazant papers asked thus far:


1) In BL, can you explain why Dr Bazant insists that crush down must be complete before crush up occurs. Does he mean this literally?

2) Do you consider the equations of motion in BV, equations 12 and 17, to be accurate for WTC1 considering the information in the ROOSD study?

3) Does Dr Bazant believe crush down, then crush up applies literally to WTC1? (or as just a "limiting hypothetical case in which the structure is best able to resist collapse")

4) Are the findings in the OOS study consistent with the claims of crush down preceding crush up in BV and BL?

5) Where in the BLGB arguments is the possibility of a CD based on ROOSD, exploiting the natural weaknesses of the building with minimal explosives, addressed?

If it is not, is it not true that the the arguments in BLGB are largely irrelevant when considering this type of controlled demolition?

6) When Bazant makes the following statement in BL, what does he mean?:

"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. 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. 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."

Is he applying this to WTC1, or to just a hypothetical extreme case?
>>>>>>>>>>>>>>>>>>>>>>>

These questions were carefully chosen to expose fundamental weaknesses in Dr Bazant's papers. They also can help us understand the papers better. This is important because there are many false beliefs about what the papers say and do not say.



What we have seen in the first 5 pages of this thread is there are many misconceptions about the papers.

Bazant's model is a limiting case representing the most favorable assumptions for collapse arrest. Among those assumptions is that all the weight of the falling mass -- even the already crushed and broken rubble -- somehow lands squarely on columns.

In that model, meaning under those assumptions, crush-down precedes crush-up. Bazant shows how and why.

The extent to which crush-down did not precede crush-up in the actual collapse indicates only that those favorable assumptions for collapse arrest were not true, so collapse arrest was even more impossible.

Try this analogy, Major Tom: suppose you're skydiving and your chute fails to open. Bazant, who happens to be looking on, quickly assesses the situation and says, "His best chance to survive is if he lands on that giant pile of mattresses over there. But even then, my calculations say the landing will kill him." You respond (since you have nothing better to do whilst plummeting earthward), "Ha! I'm landing nowhere near those mattresses! In fact, I'm heading right for that Upright Steel Spikes Inc. storage yard 1000 feet west instead. You believe I'm going to land on the mattresses but the facts contradict you. So your prediction that I'm going to die has no validity!

At that point Bazant rightly figures that there's no point in saying anything further. Why bother to argue with someone who thinks that proving a situation is worse than the best-case scenario somehow means that one should expect better than the best-case outcome?

Respectfully,
Myriad

Dave is writing to a different poster:

If you were to actually read Bazant's papers for comprehension, rather than deciding what strawman you want to attribute to them, you would see that the analysis predicts that crush-up and crush-down will initially both occur, but that the rate of crush-up will quickly decay to zero while the rate of crush-down increases. This is an idealised case, and the presence of damage to the structure above or below the collapse initiation zone will modify the precise amount of crush-up initially observed, but at no point is Bazant claiming that there is no crush-up until crush-down is complete; he's determining that a very small amount of initial crush-up occurs, but that it self-terminates until the upper block contacts the ground. As a result, a small proportion of the rubble comes from the upper block, and the majority from the lower.



Funnily enough, no, the rest of us can't see that, because the dust ejected by the collapse obscures vision of the upper block part way into the collapse. Since we can't tell what happens to things we can't see, we can either make up something that fits our prejudices or model the physics of the collapse mathematically and draw provisional conclusions. The first approach seems to be working very nicely for you, to the extent that you've convinced yourself you can see something that's hidden in a dust cloud. For the rest of us, we'd rather start from what we can see then decide on a conclusion, than start from a conclusion then decide what we can see.

Dave

You're changing your story now, are you? You were claiming that the top block was smashed into rubble; now you're saying that 'a big part' was smashed into rubble, and that you only saw the first two seconds. At the end of that two seconds, there was still a large part of the upper block intact, and you don't know what happened to it after that because you couldn't see it. So your observation - now you've admitted to what you actually observed, rather than what you initially claimed you observed - is in fact completely consistent with an initial limited amount of crush-up, followed by primarily crush-down.



I suggest you look up the meaning of the word 'only'. Myriad is pointing out that some or all of the rubble could come from the lower block, which you've now admitted, and that therefore the existence of rubble doesn't imply crush-up, which is elementary logic.



This is from Bazant's papers, which I suggest you re-read (I forget which one, but it won't hurt you to re-read them all).

Dave

I am being sarcastic in the next sentence. I had no idea at the time that people would still be defending them in this same forum and thread 4 years later.

I'm very glad other posters have came out to defend the BV and BL papers.

Dave, In BL, can you explain why Dr Bazant insists that crush down must be complete before crush up occurs. Does he mean this literally?

R Mackey seems to be saying he doesn't mean this to apply to WTC1 literally.

What do you think?



That is in BL and I suggest all of you who wish to participate reread it carefully. You'd save me some time if you do.

Bazant showed that initial crush-up would arrest very quickly, and that in effect the upper block would ride down on the intervening rubble block as it destroyed the lower structure. This is for the specific case of a perfectly level collapse with axial column-on-column impacts of a previously undamaged structure, which is the limiting case Bazant used to determine whether it was possible for the structure to resist collapse.



That's correct. As everyone keeps pointing out ad nauseam, Bazant is considering the limiting hypothetical case in which the structure is best able to resist collapse, and finding that it cannot.



Neither. Without some kind of modelling the only rational assumption would be that we don't know whether the crush-up of the upper block continued, and anything more would be a guess. Since the only case that's been analysed indicates that crush-up is expected to arrest, then it's reasonable to assume that that was the case in reality.

Let me point out, though, that your two alternatives are highly misleading. The two possible assumptions are in fact:
- that the rest of the upper block stayed intact and smashed the block underneath it.
- that the rest of the upper block was destroyedsmashed to rubble, too, which was then able to smash the block underneath it.

I'm sure you didn't mean to suggest that the upper block ceased to exist and that the rubble couldn't have destroyed the lower structure, but it's best to clear these things up in advance.

Dave

Myriad, when Bazant makes the following statement, what does he mean:

"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. 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. 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."

Is he applying this to WTC1, or to just a hypothetical extreme case?

I'm pretty sure he means that 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. This, he explains, is because 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. Which, he goes on to explain, 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, he concludes, simplifying the analysis by neglecting the initial two-way crushing phase was correct and accurate.




He is applying it to his model of a WTC tower, which incorporates best-case assumptions for the possibility of collapse arrest. That he is analyzing a model is indicated by the methodology used -- which is performing mathematics on the model, as opposed to, say, running up and down the tower with a tape measure as it was collapsing.

In other words, complete crush-down preceding significant crush-up is not an arbitrary assumption imposed on the best-case model to simplify the calculations, it is also a result derivable from analysis of the best-case model.

If it could be shown with actual evidence that crush-down did not in fact precede crush-up in the real event, all that would mean is that the real case was far worse, in terms of the likelihood of collapse arrest, than the assumed best case. (Which we already knew, because for most of the collapse, the load sheared floors from the columns instead of buckling the columns, reducing the actual amount of energy absorbed in inelastic strain to only a small fraction of the maximum theoretically possible).

Again: if your goal is to show that there should have been a better than best-case outcome, showing that there was a worse than best-case event won't get you there, or even move you in the right direction. You're basically pushing on a rope here.

Respectfully,
Myriad

Another cautionary word, though: Bazant and Verdure's model is a simplified one-dimensional homogeneous approximation to the behaviour of a real building, which is intended to reproduce gross features of collapse behaviour. Any attempt to apply it to the detailed features of collapses of specific, three-dimensional, inhomogeneous and (most importantly) already locally damaged buildings is absolutely certain to fail.

Having said that, would you like to repeat your enquiry about the model's predictions as applied to the detailed features of the collapse of a specific, three-dimensional, inhomogeneous and already locally damaged building, if you think it's a topic worth pursuing?

Dave

ETA: And also, since you've stressed the importance of not confusing Bazant & Zhou with Bazant & Verdure, could you please clarify which one you're referring to as BL?

Once again:

"A simplified one-dimensional analytical
solution of the collapse front propagation will be presented. It
will be shown how this solution can be used to determine the
energy absorption capability of individual stories if the motion
history is precisely recorded. Because of the shroud of dust and
smoke, these histories can be identified from the videos of the
collapsing WTC towers only for the first few seconds of collapse,
and so little can be learned in this regard from that collapse."

you see, he would like to apply it to the WTC1 if the motion history was precisely recorded. That was his intention as he states, but he cannot because of all the dust and smoke.

The intention of these equations is to map the actual propagation front, just as he states.

Myriad, please show where Dr Bazant intends the equations to be used only as a best case scenario, rather than to map the actual collapse front of the actual building.

>>>>>>>>>>>>>>>>>>

I watched Dr Benson apply it to the first few seconds of data over many, many posts. He tries to match real data of the real building to the equations, not some "best case scenario".

>>>>>>>>>>>>>>>>>

I asked: Myriad, in BL, can you explain why Dr Bazant insists that crush down must be complete before crush up occurs.

He answered:

Here y'go:

Abstract: This paper presents a simplified approximate analysis of the overall collapse of the towers of World Trade Center in New York on September 11, 2001. The analysis shows that if prolonged heating caused the majority of columns of a single floor to lose their load carrying capacity, the whole tower was doomed. The structural resistance is found to be an order of magnitude less than necessary for survival, even though the most optimistic simplifying assumptions are introduced. [emphasis added]

Clever of Bazant, wasn't it, to hide his intentions in the abstract. I mean, who reads those, right?

Respectfully,
Myriad

Myriad, in your last post, when asked a question about BL, you quoted an abstract from the wrong paper.

Once again: Myriad, please show where Dr Bazant intends the equations to be used only as a best case scenario, rather than to map the actual collapse front of the actual building.

Remember he gives the equations in BV. The intention of BV is different than that of BZ, as anyone can see by reading the introduction of the correct paper.

Can you answer this without citing the wrong paper?

I cited the paper that contains the answer to the question you asked regarding whether Bazant intended the assumptions made in his collapse model of the WTC towers to represent a limiting best (most favorable to collapse arrest) case. In the paper in which he introduced that model and first applied it to the WTC collapses, he clearly stated that it was (using the phrase "most optimistic.") That paper is cited in "BV" so presumably Bazant still stands by its claims; nor does he need to repeat that information in "BV," having cited it.

What is this bizarre game you're playing with "answer my question using only the paper I tell you to?" Can I play too? What's the capital of Michigan, and please back up your answer using only passages from Shakespeare's prime numbered sonnets. Thanks!

Respectfully,
Myriad

ETA: Actually there's a misstatement in the above that I'll gladly own up to. I did not actually cite the paper containing the answer, I merely quoted the answer itself from the paper. However, since you had no difficulty discerning which paper I was quoting from, no harm done I trust.

Just so everyone knows, BV and BL are......

BV:

Mechanics of Progressive Collapse: Learning from World
Trade Center and Building Demolitions
Zdenfk P. Bažant, F.ASCE; and Mathieu Verdure
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/466.pdf


BL:

Bazant & Le
Closure to "Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions"
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25 WTC Discussions Replies.pdf

...


A good discussion of BV and BL is possible in view of the study presented in the OP, for there is much to say.

Unfortunately, I cannot do that here because most every poster who is defending BV has shown they have no capacity to distinguish between the argument in BZ and BV (only Dave has shown he may understand the difference). Consider the last post by Myriad. If that makes sense to you, I'm speechless.

I didn't realize that such a misunderstanding is so widespread among people who post here regularly. The barrier created by those who imagine that the BV argument is just a continuation of the BZ argument appears way too high to overcome, though discovering this barrier has been useful for me and, I hope, for you too.

If there are a few of you who can actually distinguish between the two arguments, please let me know and I can show you how BV and BL are proven wrong by the study.

Of not, the few readers that do understand the difference in the two arguments must be just as amazed as I am. Your comments can tell them much more about your own level of understanding than it does about the study.
>>>>>>>>>>>>>>>>>>>>>>>>>>>

Just to verify, do you really believe the following comments are true?

R Mackey: "Personally, I like how he seems to think Bazant and Le (2002) is supposed to be an accurate description of the collapse rather than a limiting case, or that he thinks that plus Bazant and Verdure (2006) cover the entire scope of the literature."

You mean Bazant and Zhao.

Myriad: "Bazant's model is a limiting case representing the most favorable assumptions for collapse arrest."

Different papers, different arguments. That was pointed out a few times but he still seems to believe it is true.

David James: "It was written within a few days doesn't represent a full analysis, Why not critique the NIST report?"

Wrong paper. These are from 2007-2008 and still believed to this day.



I asked: R Mackey seems to be saying he doesn't mean this to apply to WTC1 literally.

What do you think?

To which Dave answered:
"That's correct. As everyone keeps pointing out ad nauseam, Bazant is considering the limiting hypothetical case in which the structure is best able to resist collapse, and finding that it cannot."


That is the center of our disagreement. He actually does believe this literally, that crush down happens before crush up. This is pretty clear in the papers themselves (as long as you don't confuse their purpose and intent with BZ), but it became much clearer through long conversations with David Benson, who communicates with Dr Bazant.

You think I'm joking? I wish I was.

One of my favorite posters on another forum summed it up thus:

"I've said it before, it's worth saying again. I'm not at all confused where the model ends and reality begins, but I'm not so sure about the author. There is acknowledgement that the real affair was quite different in various ways, but then there's the insistence that significant early crush-up could not occur when it sure as hell looks like it did. Almost certainly did. I don't understand how that did not merit even a mention; perhaps he doesn't even know! It strongly suggests the author is wedded to theory such that the lines between theory and reality are blurred. Incredible intellect, without a doubt, wish I had a piece of that, but... It really becomes academic to the point of 'how many angels can dance on the head of a pin' - if there were angels, the argument might be worth double-checking!"

As stated in the (correct) papers in question, BV equs 12 and 17 are meant to be taken quite literally according to the author himself, as long as 4 simplifying assumptions are satisfied. Dr Bazant truly believes his 1-D model can be used to to measure the actual trajectory of the crush front for WTC1 and that the 4 simplifying assumptions apply to WTC1, including a slight lean.

We have a basic misunderstanding on how to read the BV and BL papers linked in my last post.

Each is only a few pages long so it shouldn't be difficult to to see if R Mackey, Dave, NB and Myriad are right or wrong. We need to clear this up before the thread can progress.

My suggestion is that the readers learn to distinguish between Bazant and Zhao, published in 2002, and BL and BV, published in 2008.

Anyway, of the 4 only Myriad has tried to justify his opinion with an actual quote. He simply quoted the wrong abstract from the wrong paper presenting a different argument published 6 years earlier.

But that's cool, at least he tried.

So, I'll offer one last chance for those posters to reconsider their views before proceeding.

ANd in a different thread cmcaulif comments on the Bazant crush down, crush up concept:

We are discussing Bazant's model, which is a theoretical exercise. In this model, as you mention, the actual failure mechanism of the WTC towers is not considered. On the other hand, Bazant was trying to create a scenario which could represent an upper bound of the towers' resistance. Whether or not he is correct in that depends on the validity of his assumptions. In particular, the assumption that there is no energy dissipated outside of the collapse front. In other words, dissipation is localized to the front.

Again, this is reasonable if there is plastic straining in the collapse front only. Plastic straining could occur outside of the collapse front if a plastic wave were allowed to propagate through the impacted column to the column below. Bazant claims this is not possible because the impacted column will buckle plastically and form hinges which fracture, preventing the transmission of the plastic wave. The paper shows that, depending on the column slenderness and the strain rate, buckling can be delayed significantly, resulting in a response dominated by the propagation of the axial plastic wave, i.e. a scenario in which the rationale for the localization assumption is not valid. On the other hand, in loading regimes closer to the tower collapses early on, the response is dominated by buckling, which is the scenario Bazant's assumption relies on. Since the columns studied were less slender that those in the towers, I would expect also, that these, under the axial impact proposed by Bazant, would buckle similarly. For this reason I think the localization assumption is valid.

In yet another example, these participating posters are incapable of perceiving that there is any contradiction or inconsistency between BV, BL, and BLGB (2007-2008) and the OOS collapse progression model.

 

[BrianH]

Is this a conspiracist equivalent of the "All work and no play makes Jack a dull boy" thing?

 

[beachnut]

Yes, math is in the engineering models ...

 

[carlitos]

M_T is posting comments from folks who haven't participated in the JREF forum for years, because ___________?

 

[Newtons Bit]

Damn, Major_Tom, you're bringing this up again?

Anyway, of the 4 only Myriad has tried to justify his opinion with an actual quote. He simply quoted the wrong abstract from the wrong paper presenting a different argument published 6 years earlier.

You even retracted that lie years ago, but now you're using it again.