Debate! What debate?
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Crazy Chainsaw
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I thought One of the rules here was you have to provide proof of a claim, or retract the claim.
But being from the UK I will except your claim to be the best in the UK, second best in the world.
I didn't....
The Greening paper relies on energy dissipation figures gleaned, in part, from the Bazant Zhou paper. The Bazant Zhou paper has no experimental evidence for it. The Greening paper is well written, and a real contribution to serious efforts in understanding the collapses. However, it is also wrong.
We know it's wrong because of it's reliance on Bazant and Zhou. (OK, to be fair, he also compared to figures obtained from researchers who studied the effects of the plane impacts.) Both theory and experiment describing the effects of impacting masses on thin metal plates (via a vertical strike), were done back in 1984, in (what I believe was) a seminal work by Calladine and English. This was in an attempt to develop scaling laws, which would allow engineers to accurately extrapolate the effects of impact from small models onto real life (i.e., full scale) models.
Ultimately, the Bazant Zhou paper relies on energy dissipation figures for quasi-static bending of metal columns, while simultaneously assuming an initial drop of a "rigid" top portion of the WTC of 1 floor height ("h", in their paper). However, an impacting velocity of about 8 meters/second (as posited in BZ) is just outside the regime tested experimentally by Calladine and English. In Calladine and English's work, none of the metal samples broke. Instead, all of them fully absorbed the effects of the vertical blow, with various degrees of bending.
I should note that I have not worked out the exact case relevant to the Bazant Zhou scenario, though I remember enough of my physics to know that it can't be that hard for a working physicist to do. However, even if breakage were to occur between h and 2h, it seems intuitively clear that so much of the energy would have been dissipated, that at most 1 more floor would break.
My intuition and 85 cents will buy you a cup of coffee. I am not posting this to sell anybody on my intuition, nor to try and get Greening to update/correct his work. Almost certainly, he was aware of the mention of Calladine and English that I made on physorg, and that was a few weeks ago.
The reason I am posting this is to see if there are any other individuals with the requisite technical background who can digest Calladine & English, Greening, and Bazant Zhou, and make the necessary corrections to the latter two. It will then be interesting to see if global collapse is even possible (under the Bazant Zhou conditions), and, if it is, whether it could possibly take less than 17 seconds.
Note that the Bazant Zhou paper was cited in the NIST report as justification for their belief in inevitable global collapse. Thus, the unraveling of the Bazant Zhou paper has more at stake than just casting doubt on the Greening paper. It also casts doubt on the NIST report, itself. And, indeed, on NIST itself. Bazant and Zhou may have dashed off their paper within a few days of 9/11, but NIST had plenty of time to do a literature search to see if the Bazant Zhou paper was credible, and what engineers who study impacts (there's at least one engineering journal devoted to the study of impacts) might have to say about Bazant Zhou specifically, or the collapses in general.
What does this say about NIST? Nothing very postive, I'm afraid. If there's ever a serious investigation by the government into 911, I would hope that they subpoena some NIST'ians and get answers to this - and numerous other - questions.
I have posted info re Calladine and English on two other forums, and have directly appealed to two structural engineers (including Calladine) to take a look. Also, I've asked that the members of upcoming "Architects and Engineers for 911 Truth" (AE911Truth.org ) examine the paper. I've been told that they will post my request, but they are not slated to be fully online until May.
N.B.: I wrote an email to Calladine, asking him to comment on the applicability of the paper he co-authored to Bazant Zhou, but I've received no reply.
N.B. #2: I congratulate Greening in showing the character it takes to not walk in lock-step, like a lemming, with the NIST'ian orthodoxy. (This is not the same as saying that anybody who believes in the NIST report as credible must be a lemming.)
N.B. #3: Correcting Bazant-Zhou and Greening, ala dynamic effects as worked out by Calladine and English, does not, by itself, spell the doom of global collapse theories, even if a global collapse in their scenarios turns out to be forbidden. However, it would allow us to dispense with the notion that this is a solved problem (in terms of it's "inevitability"), and also focus attention on joint failure, fracturing, etc.
I've believed for a long time that only a credible computer model of collapse can constitue something akin to proof of the US government's notions of global collapse - or the converse. Science may be guided by intuition, but it's certainly not decided by same.
N.B. #4: Gordon Ross' paper attempted to calculate the effects of energy loss beyond the topmost impact floor approximation used by Bazant Zhou. Kudos to him, though I think his paper also needs to be compared to Calladine and English, and probably corrected or refined. My expectation is, though, that unlike Bazant Zhou and Greening, Ross' basic conclusion regarding the "inevitability" of global collapse, will need no correction.
N.B. #5 I am not interested in participating in this forum in any significant way. If somebody has something to say that is credible and rational regarding the applicability of Calladine and English, well and good. If they can put together a coherent paper on the subject, even better. My goal is to facilitate serious research (the results of which are likely to be beyond me), not waste time in exhausting, handwaving arguments. I will check this thread for the next couple of weeks to see if anybody posts anything of value. After that, should somebody do so, please PM me.
=========================
Reference:
Calladine, C. R. and English, R. W., "Strain-rate and Inertia Effects in the Collapse of Two Types of Energy-Absorbing Structure", Int. J. Mech. Sci., Vol. 26, No. 11/12, pp. 689-701, 1984.
Summary:
(The relevant structure in CE is their Type II ).
You can purchase a copy of CE from sciencedirect.com for about $30. But be forewarned, there was a page missing in my copy. You're better off getting it from a technical library.
Last edited:
Crazy Chainsaw
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The plates in the Calladine and English paper of course absorbed the impact, it had no welds.
It is clear from the photos that the welds and joints in the twin towers were what broke, the Bazant-Zhou and Greening papers I believe deal more with the energy necessary to cause weld fracture not fracture of the unwelded parts of the beams.
The welds are the weakest parts, they are what fail first.
If you know the tension strength of the welds then you will have a issue to debate.
Also did not Calladine and English use flat plates, which were not Hollow square steel beams, which use leverage for strength? That same leverage can be their undoing.
I wonder if applying the Calladine and English paper to this model might be misleading I will ask an engineer friend of mine about this he should be able to help me answer that question.
I enjoyed your posts on physorg, but I do have some disagreements with some of your ideas based on experience.
Pardon me if this makes no sense, because I haven't yet read Calladine and English, but if their work conforms to normal testing:
If I'm not mistaken, whether or not the samples broke has more to do with the existence (as in the WTC cases) or not (as in their tests) of a static load after the impact. No point testing to fracture, since after that happens you can't measure how much energy the steel absorbed. In such a case, this observation isn't really relevant.
I also don't understand why you're using impact velocity alone, since that is hardly the only relevant factor in the WTC collapses.
It's not intuitively clear at all! If the first floor breaks, life will be worse for the second floor -- at least the same distance, more mass, more initial momentum. In the absolute best case where the impact stops the upper block dead before breaking, the second floor still suffers a harder impact than the first floor did.
Don't confuse -- as so many have -- the initial floor collapse conditions with the successive floor collapses.
The B&Z collapse mechanism isn't the correct one for the initial floor collapse, which is precisely what Dr. Greening and I have been discussing in this thread. However, for the following collapses, it's probably the right model. You seem to be yet another person who's mixed them up.
A simple energy argument will show that, if the collapse happens at all, it is highly likely to occur in less than 17 seconds. Especially since the end of the collapse is not a well-defined event.
Rubbish. Just because NIST cites that as one of their supports, doesn't mean -- even if B&Z are totally wrong -- that the initial collapse model in NIST is flawed. As for successive collapses, the energy surplus is quite large, large enough to make it a non-issue.
Your expectation is wrong. Both Dr. Greening and I reviewed Ross's paper independently, and we both concluded it was full of holes (my reviews are here and here).
If you start with Ross's paper, accept his numbers, then simply correct the linear strain sink with the correct number of floors and remove the sinks that aren't relevant for first-floor collapse (viz. the concrete crumbling energies), you get an energy surplus for the second floor collapse of > 100%. And since the four lower floors have already been stressed, the energy needed to collapse the next floor is less.
And that's before you compensate for the fact that the first floor to collapse and its neighbors were heavily damaged by impact, missing numerous structural members, and had lost most of their material strength due to heating. Or take into account the significant lateral stresses that Ross doesn't treat at all.
Even a ham-handed analysis will conclude that a global failure was inevitable, unless that first floor collapse was extremely gentle (quasi-static vertical displacement ~ 3 m), which NIST's models showed was impossible.
While Dr. Greening's model, B&Z's paper, and the NIST report could probably all use refinement -- that's precisely what we were talking about -- there's no way in the world you're going to get the answer you apparently believe in. Give it a try if you don't believe me.
What? You've put forth a very strange request.
Are you claiming that you lack the training to reach your own conclusion, and you're asking someone else to do it for you?
How does that work? If you don't have the skills to do this yourself, why do you think that you're right? Lucky guess?
Next time I'm at the library, I will take a look for Calladine & English. Thanks for the reference.
Actually, they not only didn't calculate wrt fracturing, but Bazant has pooh-poohed the Cherepanov fracture wave paper. However, in his rebuttal, Bazant notes that fractures in welds "greatly reduce energy absorption capacity". Also, from BZ, it's clear that they are ignoring fracturing in their calculations, though they don't deny it's importance:
No I don't know the tension strength of the welds. I agree that a thorough investigation into the global collapse question has to look at this, plus a bunch of things that I am doubtless clueless about. However, as a first step, I would like to see Bazant Zhou and Greening corrected as per Calladine and English. (And I do mean rigorously.) Afterwards, more work can be done in correcting the corrections.
The Bazant Zhou paper has inhibited serious inquiry by the engineering community into post -collapse initiation investigations and questioning. Or so it would seem. Nobody is pretending that merely correcting it via Calladine and English will be the end of the story.
If you, or somebody else, wants to simultaneously correct it for fracturing as well as dynamic effects ala Calladine and English, go for it.
Yes, CE Type II was flat plates (slightly prebent). I have no idea what you mean by "use leverage for strength".
The WTC columns also consisted of I beams and box (rectangular cross section) columns.
Please do, thanks.
Oh, don't feel bad about that! I have some disagreements with some of my prior ideas, also!
Gravy
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Hello, metamars. Welcome to the JREF forums.
Exactly how does it "seem" that the Bazant paper has prevented anyone from questioning or studying the collapses? Was there an edict I missed? Threats made?
How about Bazant's June, 2006 paper on progressive collapse: do you feel that it has also "inhibited serious inquiry"?
Calladine and English used a vertical drop hammer apparatus. After impact, the load most certainly stayed on top of the impacted plate - thus becoming static - until if was removed.
I mention the closeness of the velocity to show that their results should be able to be extrapolated to the Bazant Zhou scenario. In that scenario, after collapse initiation, there is a free fall through a height equal to 1 story, which they symbolize as "h".
The scaling rules of concern to Calladine and English were not just for velocity, but also kinetic energy.
In the Bazant Zhou paper, the period of time immediately after collapse initiation is modeled as a free fall - as though one of the floors had no structural integrity, whatsoever. If one accepts this part of the Bazant Zhou scenario (as an approximation), the question then becomes what happens after the first impact?
If you want to argue that some of the premises of the Bazant Zhou paper cannot be accepted, aside from those that the Calladine and English paper call into question, be my guest. However, at the end of the day, one would like to see a complete treatment, incorporating whatever objections one might have to the Bazant Zhou paper. If I were able to do that with the Calladine and English paper, I would have done so, already. Instead, I am calling on others, better equipped than myself, to do so.
If you assume that, post collapse initiation, a free fall of height h occurs, does that favor a global collapse? (as opposed to meeting resistance during the initial descent of height h) Answer: it favors a global collapse.
But again, I am interested in seeing BZ and Greening corrected ala Calladine and English as a first step.
This post is interesting, and makes a powerful argument why the phrase "near free fall" is problematic in the least, and perhaps misleading. Adding 6 seconds to free fall time implies an enormous amount of energy.
However, the argument is half-baked not only in a discussion of how legitimate the phrase "near free fall is", but even moreso in terms of this thread. Without calculating, from first principles, how much energy you need to collapse the structures, of what significance is this calculation? Let us say that the collapse takes 15 seconds (BTW, I personally put most stock in Hoffman's estimates, which IIRC are in the 12 - 14 second range or thereabouts; however, I haven't paid much attention to this particular debate in a long time) From your calculations, we conclude that this requires the structure to absorb the energy equivalent of 99.1 tons of TNT. However, if our calculation from first principles shows that the energy equivalent of 100 tons of TNT are required to collapse the structure, and not a joule less, then you have an indication that something was done to the building to lower the threshold required for complete collapse.
Of course, if calculations from first principles showed that the energy equivalent of 1,000 tons of TNT are needed to collapse the structure (absent CD), then you you have a much bigger problem to explain. In this scenario, CD is certainly the first thing that would pop into my mind. However, this argument simply underscores the need to not make a half-baked argument, but instead to flesh it out by doing the hard work required to complete it.
Perhaps, like me, you will try and get somebody else to do the heaving lifting for you.
Strictly speaking, you are correct. However, I said this "casts doubt" on the NIST report, and NIST itself.
I don't want to quibble about this, because the degree to which one takes the $20 million NIST report's giving credence to the quarter-baked BZ paper as a sign of their - ahem - doubtfulness, depends on one's predispostion towards trusting governmental agencies in general, and NIST in particular.
Thus, my comment should be understood as an expression of personal mistrust more than a necessary logical inference.
I rather doubt that a correction of the Bazant Zhou would allow a collapse to get underway, even after a free fall drop of distance h, as posited in BZ. I look forward to somebody actually doing the work that I am calling for, and showing me correct or incorrect, on this point.
Even if the Ross paper is "full of holes", I specifically referred to his conclusion as what I expected to remain unchanged, if his paper was refined or corrected as per Calladine and English.
I'm sorry, but I don't have time or inclination to get into the Ross paper. If you are correct, then any amount of corrections via Calladine and English will likely not matter, anyway.
I don't believe you, but please believe me when I tell you that it's been over 20 years since I got my degree in physics, have never used it professionally, and to get the corrections I am calling for done, there have to be literally tens of thousands of individuals in the US who are quite capable of doing so. We will have to wait and see what conclusions they come to.
I am optimistic that somebody will do so in the near future, but I am trying to hasten that day along.
Even if you are not interested in doing so, perhaps you know somebody who is both capable and interested?
To tell you the truth, it's been so long since I took my degree, I'm not even sure whether or not I could have fully digested the CE paper, and then figured out it's implications for BZ and Greening, or not, at the time of my graduation.
However, I remember enough of my physics to know that the paper is quite relevant. Remember, too, CE's purpose was to develop scaling rules. The fact that they didn't test the BZ scenario exactly (not that they could) is irrelevant. The real questions are: can their results be extended into the domain relevant to the BZ/WTC, and what does doing so tell us?
I suppose it wouldn't have hurt if I had mentioned the following:
Finally, one learns by asking questions of people who do know, or know enough to figure out. Back in the day, I was quite impressed with the knowledge and smarts of all my physics profs. I see nothing wrong with continuing that practice, especially now that it's more necessary with the passage of time.
You're welcome.
Sorry, but these are exactly the sorts of questions I have no interest in debating.
In fact, I'm not interested in verbally debating CE's relevance and application to BZ or Greening, per se. I'm am interested in seeing it's implications worked out, mathematically, the same way one would do in college if one was presented this problem by one's professor.
If a professor assigns a homework assignment: "What are the implications of the CE paper for BZ and Greening?", what would a good physics or engineering student turn in to his professor? Of course, some calculations with logical arguments.
That is what I'm looking for.
Gravy
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What steps have you taken to determine if your mistrust is justified? For example, with which engineers who worked on the NIST report have you corresponded?
Gravy
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That's fine, but I'd like to suggest that you not make claims if you're not interested in discussing them, this being a discussion forum. It's your belief that the B&Z paper inhibited questioning and investigation. Is that belief based on facts, or is it due to your inherent mistrust of...something?
Belz...
Fiend God
I stopped reading here.
Gravy
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Why?
Belz...
Fiend God
That's because all of them use the same arguments; and all of them show the same disdain for logic, and lack of critical skills.
That's because the lot of us already understand it. We don't need to resort to magic konzpiraciez.
This, however, is not new, and I'm still looking for a term I'll have to invent for that particular fallacy.
If you're a scientist, then you should understand why.
Again, of course. Why would they bother ? Once the collapse begins, what's there to stop it ? And please don't go all Judy Woods on me.
What about the sighs of collapse, visible several minutes before it happened ?
Then what the hell are you babbling on about ?
Ah! So basically, you have no idea what happened. You don't like the "official story" and so you're just trying to replace it. Will that make you feel better ?
Well you don't HAVE a story, so I don't see how you could possibly be going on about NIST's hypothesis beign wrong.
Belz...
Fiend God
I'm allergic to the words "molten steel", now. Overused, I guess.
Crazy Chainsaw
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Originally posted by metamars
Cherepnov's paper has more to do with the way the geometry of the Columns transfer load stress though the beams than with facture wave fromation durring collapse.
One of the reason I believe that Bazant plays down Cherepnov's theory is because the building falls to slowly for a fracture wave model, the building in a fracture wave model would have fallen at 7/8th the speed of free fall, that is just too fast since the building fell at 3/4th the speed of free fall.
Here are some interesting papers on welding fracture that I have been going over since the debate on Physorg about fracture waves. I have no doubt that fracture waves did play a part in the collapse, but the question is can it ever be modeled to know the true perimeters.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXD-4177HXB-14&_user=10&_coverDate=11%2F30%2F2000&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6a1a91d8a77f688ddc43ef330346c226
http://www.scientific.net/0-87849-413-8/543/
http://www.scientific.net/3-908451-29-9/21/
http://www.mt.luth.se/division/dmk/publications/publications.html
http://www.material.tohoku.ac.jp/~fukugo/elab.html
http://www.shipstructure.org/list_reports.pl
http://www.reliability.com/articles/article56.htm
I hope that this is not too confusing, I tried to keep it as simple as possible.
Cherepnov's fracture wave paper is based on the shape of the Columns being tapered causing a fracture wave that destroys the weld joints.
Cherepnov's paper has more to do with the way the geometry of the Columns transfer load stress though the beams than with facture wave fromation durring collapse.
One of the reason I believe that Bazant plays down Cherepnov's theory is because the building falls to slowly for a fracture wave model, the building in a fracture wave model would have fallen at 7/8th the speed of free fall, that is just too fast since the building fell at 3/4th the speed of free fall.
Calladine and English are meaningless in this instance, as they test they preformed was on steel plate, do to the geometry of the steel in the world trade center and its ability to form fulcrums in the structure and tear the weld joints Calladine and English do not apply.
NO it most certianly has not it is just that no one else has come up with a better model.
I agree there are minor corrections to Bazant but not from Calladine and English, as they are not testing in any comparable way the structure or the integrity of hollow steel columns that work on in a different manor that flat plate steel.
Then you do not understand Cherepnov's fracture wave paper. Columns acquire their strength from leverage, the ability to resist Buckling flat plate is easy to bend but Columns are not. Columns actually absorb more impact energy than flat plate which will dissipate it though oscillations faster. That is why Calladine and English are meaningless you would first have to correct Calladine and English for hollow square Columns before it would have relevancy.
Exactly my point they are not steel flat plate, I work with steel all the time I have to take this stuff into consideration. The shape of the material drastically effects the way it is effected by stress. Before you can use Calladine and English, to correct Bazant, you must first correct Calladine and English for the shape of the materials in question. I believe that Bazant wrote a paper or an editorial on it some time back with the calculations to correct mechanical stress analysis for different shapes. IN a journal of fracture mechanics , though I am not sure when it was published or what volume it is in. I will try to find it though.
Here are some interesting papers on welding fracture that I have been going over since the debate on Physorg about fracture waves. I have no doubt that fracture waves did play a part in the collapse, but the question is can it ever be modeled to know the true perimeters.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXD-4177HXB-14&_user=10&_coverDate=11%2F30%2F2000&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6a1a91d8a77f688ddc43ef330346c226
http://www.scientific.net/0-87849-413-8/543/
http://www.scientific.net/3-908451-29-9/21/
http://www.mt.luth.se/division/dmk/publications/publications.html
http://www.material.tohoku.ac.jp/~fukugo/elab.html
http://www.shipstructure.org/list_reports.pl
http://www.reliability.com/articles/article56.htm
I hope that this is not too confusing, I tried to keep it as simple as possible.
BELZ, GRAVY, ENIGMA, PARDALIS:
Since all of you appear to believe/support the NIST Report, I am interested in your qualifications and/or experience in the fields of ENGINEERING, PHYSICS, CHEMISTRY, or MATERIALS SCIENCE.
If you do indeed have a background in chemistry, metallurgy or materials science, could you please tell me: what is your scientific understanding of the significance of micron sized iron spheres in the WTC dust.
But if you lack credentials or hands-on experience in any of the areas of scientific enquiry noted above, I wonder why you consider your OPINIONS on the collapse of WTC 1 & 2 of interest or value to anyone......
R. MACKEY:
I am still thinking about those lateral forces.....
Since all of you appear to believe/support the NIST Report, I am interested in your qualifications and/or experience in the fields of ENGINEERING, PHYSICS, CHEMISTRY, or MATERIALS SCIENCE.
If you do indeed have a background in chemistry, metallurgy or materials science, could you please tell me: what is your scientific understanding of the significance of micron sized iron spheres in the WTC dust.
But if you lack credentials or hands-on experience in any of the areas of scientific enquiry noted above, I wonder why you consider your OPINIONS on the collapse of WTC 1 & 2 of interest or value to anyone......
R. MACKEY:
I am still thinking about those lateral forces.....
I am not a scientist and I freely admit that, yet micron sized iron spheres would imply they have formed and cooled without significant contact with materials which would distort a sphere. This implies molten metal right? So in what situations do you think these would be created? I'm just trying to get an idea of the possibilities for explanation of this, as I am not a scientist.
Scientists are not the only people who can think critically.
Belz...
Fiend God
Abysmal.
About as much as modifying the phase variance.
Because thousands of experts and specialists around the world consider this a non-issue, I find one person barking at their conclusions somewhat puzzling.
"Because thousands of experts and specialists around the world consider this a non-issue."
Oh, really!
Most people apparently don't even KNOW about this.
"A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring."
Alexander Pope
Oh, really!
Most people apparently don't even KNOW about this.
"A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring."
Alexander Pope