Bazant's progressive collapse math is bogus.

[eomer]

I'm rescuing this subthread from a parent thread that got locked for reasons having nothing to do with this content.

The topic is Dr. Bazant's conclusion in a Journal of Engineering Mechanics article, http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/466.pdf">Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions that claims to demonstrate that progressive collapse was inevitable once collapse was initiated.

Here is the discussion we were having in that subthread:

eomer
Bazant's math is bogus. Anybody can learn to construct equations that don't conform to reality.

Discussion of “Mechanics of ProgressiveCollapse: Learning from World TradeCenter and Building Demolitions” byZdene˘k P. Bažant and Mathieu VerdureMarch 2007, Vol. 133, No. 3, pp. 308–319.DOI: 10.1061/(ASCE)0733-9399(2007)133:3(308)James R. Gourley11B.S. Chemical Engineering; Attorney, Carstens & Cahoon, LLP, Dallas,TX 75240. E-mail: [e-mail] -snip- The first problem with the original paper is that throughout it,the collapse is assumed to occur in two phases. As a result, allequations that purport to model the collapse are developed separatelyfor the first phase and for the second phase. In the firstphase, which the paper calls crush-down phase, the section of thetower above the aircraft impact zone (called Part C in the originalpaper; see Fig. 2 of the original paper) remains essentially intactas it progressively crushes down through the entire section of thetower structure below the impact zone called Part A in the originalpaper; see Fig. 2. The second phase, called the crush-up phase,starts when the entire lower structure of each tower (Part A) hasbeen completely destroyed by the upper part (Part C), and Part Callegedly impacts the dense pile of debris created during thecrush-down phase at high speed, thereby destroying Part C fromthe bottom up. Initially, this two-phase collapse mode may seemplausible, but after careful examination, it is clear that this twophasecollapse scenario is scientifically implausible, which callsinto question the veracity of all equations developed in the originalpaper. The paper appears to justify this collapse mode by making akey assumption that the authors do not support with any explanationor analysis. This key assumption, which is one of what theauthors call “reasonable . . . simplifying hypotheses” is that, duringthe building collapse, “(e)nergy is dissipated only at thecrushing front (this implies that the blocks in Fig. 2 may betreated as rigid, i.e., the deformations of the blocks away from thecrushing front may be neglected . . .)” In other words, the paperassumes that Part C of each tower is treated as a rigid block whileit crushes down through and destroys the lower structure. Althoughthis assumption may have had the intended effect of simplifyingthe paper’s collapse analysis, it also rendered the collapseanalysis at odds with the reality of the physics at work during thecollapse. It should be noted here that no lateral forces are consideredin this discussion in accordance with another simplifyingassumption made by the paper, namely, that the “only displacementsare vertical” (p. 312 of the paper). This simplifying assumptionis flawed (e.g., steel members and dust were spreadacross a wide area surrounding the location where the towersstood) but is beyond the scope of this discussion.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25%20WTC%20Discussions%20Replies.pdf

Once you realize that Bazant's math is based on gross simplifications, all persuasive power is sucked out of it (if you're paying attention). I don't claim that progressive collapse would not have occurred. I do claim that Bazant has not proved that it would.

Bolo Boffin
That's amusing - quoting Gourley's paper to refute Bazant.

You should know that Gourley's paper was only published so Bazant could demonstrate the gross simplifications presented by Gourley and other 9/11 CD advocates. Bazant ends his response with a recommendation that the writer take a class in basic structural engineering before trying to contribute to the subject further. JEM printed that. OUCH.

Please stop failing all over the place.

eomer
Here is visual proof that Bazant and his equations are wrong.

The top Part C of the tower (as Bazant refers to it) did not remain intact as a rigid block. The frames in this video are the proof:

http://911research.wtc7.net/wtc/evidence/videos/st_nbc1.html

1. First look at frame 6:03:00 and note the height of the intact Part C by measuring the height of the corner that is toward us. The distance you are looking for is from the very top of the corner of Part C down to the apparent bottom of Part C at the collapse zone.¹ This is the height of the top Part C that has started to move as an intact unit at collapse initiation.
   
2. Now look at frame 13:06:15 and note the distance from the top of Part C down that same corner. See if you can fit an intact Part C that is the same size as it was at collapse initiation before you run out of space at the intact lower Part A. You cannot.

The original Part C that we saw moving together as a unit at initiation cannot fit in the remaining space 7 seconds later. Crush-up has clearly occurred, causing the top Part C to be crushed to a size significantly smaller than it was at initiation. Bazant claimed that his equations demonstrate that the top Part C would remain intact as a rigid block and that crush-up would not occur. He and his equations are clearly wrong.


¹ The collapse zone can be determined in frame 6:03:00 by the point at which the corner has an obtuse angle due to the lean of the top Part C. I copied the frame into a photo editor and drew a straight line that I could line up with the lower part of the corner to determine where the angle occurs and therefore where both the collapse zone and the bottom of Part C are. I concluded that it occurs just above the point where the corner of the bottom intact building (Part A) becomes obscured by smoke. You may also need to alternate between watching the video in motion a number of times and watching it frame by frame to interpret where the top Part C is at each point and where the collapse initiation zone is.

eomer
More visual proof that Bazant's equations are wrong.

Bazant's equations assume that all the mass of Part A is incrementally added to that of Part C as the collapse works its way down.

Clearly from the video you can see, if it weren't already obvious, that some of the mass of Part A and/or Part C is ejected horizontally out of play and cannot be part of the mass that is crushing Part A. In addition, the horizontal momentum represents energy that Bazant erroneously counted in the downward force in his equations.

Further, you can see that portions of Part A remain standing after the collapse zone has passed well below them. In frame 17:08:15 you can see columns still standing when the collapse zone has moved quite a ways below them. There is also a significant chunk of structure that remains well above the collapse zone in frames 21:10:15 through 24:12:00 and then drops out of view.

All of the mass that was ejected horizontally out of play and all of the mass that remained standing above the progressing collapse zone represent undeniable error in Bazant's equations. This mass cannot be part of the mass that is (allegedly) crushing Part A as Bazant's formulas assume. All of the horizontal momentum represents energy that Bazant erroneously counted as part of the crushing force.

Rather than taking a conservative position on each of these points in order to demonstrate his assertion, Bazant does the opposite: he errs obviously in a direction that overstates his case. He goes so far as to assume that all the mass and all the momentum will count in his favor, a grossly false assumption. He therefore leaves us (and him) not knowing whether his assertion is true or not. Is the sum of his errors, a sum that obviously subtracts from his case, enough to have flipped the result he was going to get from collapse=false (if he had properly accounted for the mass and momentum) to collapse=true? No one knows, including Bazant. But what we do know for sure is that his equations are wrong.

[AZCat]

1. Gourley is an idiot.

It would not be wise to accept his arguments at face value. Have you ever taken an advanced physics course - say, dynamics or mechanics of materials?

[procopia]

2. Gourley described his JEM publishing experience

here:
http://www.911blogger.com/node/18196

He was limited to a 2000 word response, but Bazant was allowed to far exceed that limit in his response to Gourley.

[Bolo Boffin]

3. He was given just enough rope. n/t

[procopia]

4. So JEM provides "rope"???

What is its motivation?

[Bolo Boffin]

5. JEM's motivation

The Journal of Engineering Mechanics covers activity and development in the field of applied mechanics as it relates to civil engineering. Research on bioengineering, computational mechanics, computer-aided engineering, dynamics of structures, elasticity, experimental analysis and instrumentation, fluid mechanics, flow of granular media, inelastic behavior of solids and structures, probabilistic methods, properties of materials, fracture mechanics, stability of structural elements and systems, and turbulence is reported. Typically, published papers describe the development and implementation of new analytical models, innovative numerical methods, and novel experimental methods and results.

[procopia]

9. This is its motivation

for publishing Gourley's paper?

[Bolo Boffin]

6. LOL.

Doubling down on a demonstration of your inability to understand what Bazant is doing - priceless.

ETA: Or is "rescuing" your "analysis" from a locked thread in order to call me out better described as "trebling down"? You decide.

[OnTheOtherHand]

11. I don't see eomer calling you out here

I hadn't seen the JEM critiques and response before (there's a lot I haven't seen). To me it seems perfectly reasonable for eomer to repost his discussion so that it's open to comments.

[Bolo Boffin]

16. What need did eomer have to repost my response to him?

His posts read just fine on their own. The only reason to reproduce my post is to call me out.

[OnTheOtherHand]

18. shrug

I agree that his posts read fine on their own, but it doesn't follow that his only reason to reproduce your post is to call you out. It could be construed as a good-faith effort to reproduce both sides of the discussion, not just his own.

Full disclosure: I like eomer. We rarely agree about the subjects in this forum, but I generally find his posts thoughtful and engaging, as well as mercifully short on personal invective.

[Algorem]

45. you're so veddy veddy important.

[BeFree]

61. Oh

Bolo was cut and pasted, verbatim. Is that fair? Doesn't bolo have every right to be upset?

[whatchamacallit]

7. Bazant is a tool

The right man for the right job at the right time. Mission Accomplished!

[Bolo Boffin]

8. lol

http://www.civil.northwestern.edu/people/bazant.html

Education

* C.E., Czech Technical University, Prague, Civil Engineering (Structural Engineering) 1960
* Ph.D. (in mechanics)., Czechoslovak Academy of Sciences, Prague 1963
* Postgraduate diploma in Physics, Charles University, Prague 1966
* Docent habil., Czech Technical University, Prague 1967
* S.E. 1970, Illinois Registered Structural Engineer


Research

Prof. Bazant's interest spans mechanics of materials and structures, structural safety, response uncertainty, and engineering applications. The current investigations include some fundamental problems in the field of quasibrittle fracture and damage mechanics, fracture scaling and its asymptotics, size effects, probabilistic mechanics and extreme value statistics, micro- and nanomechanics, constitutive models, progressivecollapse of buildings, missile impact, seismic response, interfaces with chemo-mechanics, chemical reaction kinetics, diffusion, thermodynamics, poromechanics, landslides and geo-mechanics. His research team has been developing material models for fiber composites, concrete, rocks and soils, sea ice, snow, tough ceramics, sandwich shells, rigid foams, cellular materials, bone, and shape memory alloys. Applications have covered structural and aero-space engineering, building codes, ship design, automotive crashworthiness, arctic engineering, earthquake engineering and nuclear safety. Although the emphasis is theoretical, his team also conducts specialized fracture testing of composites, concretes and rocks. Computational modeling is a heavy component in each problem, but Bazant's attitude is to seek first analytical solutions and asymptotics-based approximations. The current and recent research sponsors include NSF, ONR, DoT, WES, ARO, DoE, AFOSR, Sandia N.L., Chrysler, Boeing, Cirrus Aircraft, and Argonne National Laboratory.

Teaching Activities

* CIV_ENG-422 Inelastic Analysis of Structures
* CIV_ENG-424 Stability of Structures
* CIV_ENG-430 Cohesive Fracture and Scaling


Honors and Awards

* Elected to: National Academy of Sciences; National Academy of Engineering; American Academy of Arts and Sciences; Austrian Academy of Sciences; Accademia Nazionale dei Lincei (Rome); Spanish Royal Academy of Engrg.; Engrg. Academy of Czech Rep.; Academia di Scienze e Lettere (Milan); European Academy of Sciences and Arts.
* Six Honary Doctorates (Boulder, Prague, Karlsruhe, Milan, Lyon, Vienna).
* Prager Medal from Society of Engineering Sciences; von Karman Medal; Newmark Medal; Lifetime Achievement Award; Croes Medal; Huber Prize and TY Lin Award from ASCE; Honarary Member ASCE; Nadai Medal and Warner Medal from ASME; L'Hermite Medal from RILEM; Exner Medal, Austria; Humboldt Prize, Germany; Torroja Medal, Spain; Solin Medal, Prague; Z. Bazant (Sr.) Medal, Prague; Stodola Medal, Slovakia; Roy Award, Am.Ceramic Soc.; ICOSSAR Award; Czech Soc. for Mech. Medal; Outstanding Contribution Award, IACMAS; Guggenheim, NATO, JSPS, Humboldt, Ford and Kajima Fellowships; National Winner, 1958 Math.Olympics, Czechoslovakia; ISI Highly Cited Scientist in Engrg. (among top 100, www.ISIhighlycited.com). >9300 citations and H-index=43, up to Aug. 2008.
* Former President of SES, IA-FRAMCOS (founder) and IA-CONCREEP (founder); Former Editor, Journal of Engineering Mechanics, ASCE.


Selected Publications
(selected among 490+ journal articles and 6 books)

* Bazant, Z.P., and Cedolin, L. (1991). "Stability of Structures: Elastic, Inelastic, Fracture and Damage Theories", Oxford University Press, New York (textbook and reference volume, 984 + xxiv pp.).
* Bazant, Z.P., and Planas, J. (1998). "Fracture and Size Effect in Concrete and Other Quasibrittle Materials". CRC Press, Boca Raton and London (textbook and reference volume, 616 + xxii pp.).
* Bazant, Z.P. (2002). "Scaling of Structural Strength." Hermes Penton Science, London (French transl. with updates, Hermes, Paris, 2004).
* Bazant, Z.P. (2004). "Scaling theory for quasibrittle structural failure." Proc., National Academy of Sciences 101 (37), 13397-13399 (inaugural article).
* Bazant, Z.P., Cusatis, G., and Cedolin, L. (2004). "Temperature effect on concrete creep modeled by microprestress-solidification theory." J. of Engrg. Mechanics ASCE 130 (6) 691--699.

[whatchamacallit]

10. Smells like bias-laced idol worship in here

:loveya:

[Bolo Boffin]

14. lol

Just a more accurate description than the smear I responded to, that's all.

[procopia]

13. Being a tool has nothing to do with one's credentials.

Obviously.

[Bolo Boffin]

15. Just letting the people know the person you're smearing. n/t

[procopia]

17. No one has questioned his credentials.

:eyes:

[AZCat]

12. Link to previous discussion --->

Previous discussion of this topic

[OnTheOtherHand]

19. thanks, I guess I missed this back in October '08

I don't remember growing older....

[AZCat]

23. Neither do I.

It must have happened, though - these grey hairs came from somewhere.

[William Seger]

20. That reminds me...

Didn't Gourley promise he was going to have a rebuttal to the humiliating ass-kicking he got served? Been a year now... Which also reminds me: If Bazant is so wrong, why have those "952 architectural and engineering professionals" over at AE911truth been so useless to the cause -- are they too busy?

[thepeopleunited]

21. Thanks, that really an eye opener.

Shocking isn't it? And "bogus" is much too kind. "Criminal" is the word that comes to my mind, and that applies not just to the authors but to every JEM editor, referee, and advisory board member who allowed this idiocy to be published without vigorous public protest and resignation.

[William Seger]

22. "Bogus" is too kind a word to use for the "truth movement's" lame attempts to refute Bazant

"Pathological" is the word that comes to my mind.

[Realityhack]

24. The ignorance it BURNS!!!

It would be best for you if you avoided calling large groups of professionals criminals because you don't have the first clue as to the details of their profession, and do not agree with the implications of their conclusion. In general you will find that you are in fact just as wrong as the creationists who call biologists criminal conspirators or Holocaust deniers who yell at historians.

The fact that you can not understand the JEM article and do not like it's conclusion in no way makes it invalid, weak, or criminal. Your statement that the authors etc. are criminal just makes you look stupid.

[thepeopleunited]

25. Meaningless ad hominem fallacy.

You don't know the first thing about me. On the other hand, the Bazant article is patently and offensively ridiculous, and there is every reason to seriously question the credentials and/or honesty of anyone endorsing it, including all the above mentioned.

[William Seger]

26. Of course we know something about you

We know that you post slander on the internet with no apparent basis except your own ignorance, don't make even a minimal effort to justify accusing a huge number of people of "criminal" behavior, then when called on it you whine about "meaningless ad hominem fallacy" -- a term you also apparently don't understand, since your post was completely devoid of any actual argument.

[thepeopleunited]

27. Who is "we"?

And you know as much about me as you know about law and engineering, which is very little. I don't mean that personally, but every one of your statements reveals an absence of basic information, not to mention basic courtesy.

[OnTheOtherHand]

28. "basic courtesy"?

At the risk of simply repeating others' comments, it seems pretty precious to smear a group of people as "criminal" -- without any support whatsoever -- and then lecture another poster on "basic courtesy."

[thepeopleunited]

29. I believe you're trying to change the subject.

Fine, but why?

[OnTheOtherHand]

30. I'm responding to your posts

If you'd like to go back and make substantive points, please do.

[thepeopleunited]

31. The substantive point is that Bazant is lying.

There was no "progressive collapse," no "snap-down," no "crush down," and no "crush up." Those are preposterous terms explaining an impossible event and I cannot believe that Bazant, his coauthor, the JEM editor, referees, and members of the advisory board, if it has one, are not fully aware of that fact.

[OnTheOtherHand]

32. OK, I can hardly believe that you believe all that

Are we done?

[procopia]

33. But you have no trouble believing

that Bazant could write a complex paper explaining the collapse of the WTC towers and present it only 2 days after 9/11, and all without the benefit of physical evidence. Okay...

[whatchamacallit]

34. Insanity

When did he start it anyway? The day of 9/11? Before?

I guess Bazant woke up and said "Hey I know what happened to (both) towers"... "Ye old (never before seen) crush down/crush up!". "Yea, that's the ticket..."

I'm pretty certain the OCT will ultimately regret putting their eggs in that basket.

[OnTheOtherHand]

35. seriously?

You seem to be verging on a classic self-swallowing CT argument. If it was impossible for Bazant and Zhou to write the paper -- or, rather, the roughly 1 1/2 pages that they apparently submitted on 9/13 -- in that amount of time, then why would it make any sense for them to submit the manuscript then? Was the act of submitting a journal manuscript somehow supposed to stop the Truth Movement in its tracks? Maybe they did it just to signal to attentive observers that they were part of the cover-up?

Then again, just how long do you think it takes to write a page and a half? Granted, it can take a long time depending on the specific content, but it seems pretty darn doable.

[whatchamacallit]

36. Seriously!

But here's a question for you; why would any reasonable person blindly accept a theory formulated in such a ridiculously short period of time, and without the benefit of relying on any physical evidence? I'll tell you why, it's because you're not reasonable. You are OCT-religious, and will cleave to any dogma that supports your beliefs, no matter how supernatural.

[OnTheOtherHand]

37. funny, that

You've formulated your own theory based on no evidence whatsoever -- starting from the premise that I "blindly accept" Bazant and Zhou.

Why would you accept your own theory? I won't try to answer that. I don't even know if you do accept your own theory.

[William Seger]

53. Simple answer: You are wrong.

> But here's a question for you; why would any reasonable person blindly accept a theory formulated in such a ridiculously short period of time, and without the benefit of relying on any physical evidence?

There was absolutely nothing new about the "theory" of progressive vertical collapse, and there's nothing "ridiculous" about an expert like Bazant being able to write a page-and-a-half about it in a couple of days. You just don't know what you are talking about.

[whatchamacallit]

54. You OCT myna birds only seem to know what you are talking about

William want a cracker? Sure lots of academics CAN write and publish a technical paper in a couple of days, but SHOULD they? What motivated (or directed) Bazant to proffer this particular theory so quickly? The dust hadn't even settled on the wtc, and within two days we are treated to an extremely speculative theory, that (surprise!) supports what *will be* the official account. And yes it is just a theory. There has never been a "progressive vertical collapse" that remotely resembles what we witnessed on 9/11. Not before or since. No William, this one belongs in the same category as the patriot act. The "where the fuck did that come from and why?" category.

[William Seger]

62. LOL, you're a trip, whatcha

I don't believe I've ever seen anyone who offers quite so many arguments based on what he doesn't know. But I don't think you quite grasp the concept that others are not as impressed with your ignorance as you seem to be.

There's absolutely nothing "extremely speculative" about Bazant's paper. It's based on principles that were already well known, and once again you are simple wrong to assert that "there has never been a 'progressive vertical collapse' that remotely resembles what we witnessed on 9/11." Do some research. As I've mentioned here many, many times, the case I'm personally very familiar with is the Skyline Towers collapse in 1973. I'm sure Dr. Bazant could cite many more (in fact, I believe he did somewhere), but I don't feel like wasting time right now doing your research for you.

[procopia]

63. This?

The Skyline Tower collapse caused by insufficient wooden shoring for concrete, not by fire, hardly resembles what we witnessed on 9/11.

[William Seger]

71. "hardly resembles what we witnessed on 9/11"

To you, perhaps, but again, why do you attach such significance to your lack of understanding? You don't see the similarity because you don't understand how the top couple of floors could crash all the way through the building, down into the subbasements. Bazant does, and I'm pretty confident that virtually every structural engineer in the world does, with the possible exception of a tiny handful of crackpots over at AE911truth. (And in fact, it's possible that they do, too, but signed Gage's petition for unrelated reasons.) And I am myself the proof that you don't need to be structural engineer to understand it, because it's basically very simple: Skyline Towers and the WTC towers collapsed because falling masses can deliver impulse forces that are many times their weight, and buildings are not typically designed to take that kind of abuse.

[procopia]

73. No, it doesn't resemble the WTC tower collapses--

It wasn't even a completed building. It partially collapsed because wooden shoring for concrete was removed too quickly. How you can equate that to WTC is remarkable, even for you. It could possibly resemble a controlled demolition where supports are intentionally removed, however.

[William Seger]

74. It totally collapsed...

... up to an expansion joint, which in reinforced concrete buildings creates structurally separate and independent buildings to avoid cracks from thermal stresses. Yes, the initiating events were completely different from the WTC, but you said you understood Bazant's paper, which is concerned with what happened after that. What happened after that is completely similar to the section of Bazant's paper that I quoted in post #66: There was more kinetic energy in the falling mass than the structure could absorb.

It had nothing to do with the top of the structure remaining rigid, so that part of Bazant's model is simply not relevant, whether or not it's accurate. As I said before, he explained what and why he was doing, and you apparently haven't even read it. Your claiming that you have x-ray vision to see what's happening inside the debris cloud at the WTC collapse is not evidence of anything. What is evidence, however, is that we can see plenty of evidence of the Bazant model at work, including "crush down/crush up," in the videos of the vérinage type of demolition:

http://www.youtube.com/watch?v=NwFHEoiUZ7o

I don't have any hope of making you understand this, but that simply doesn't matter. I can assure that these kinds of arguments against Bazant's paper will repeatedly fail, because you simply don't know what you are talking about.

[procopia]

123. Except for the part that didn't,

it totally collapsed. The building partially collapsed and does not resemble the WTC total collapse, regardless of your word games.

"There was more kinetic energy in the falling mass than the structure could absorb."

Never proven. If it had been proven, NIST would have applied Bazant's theory to explain the WTC collapse, rather than having to admit,

"We are unable to provide a full explanation of the total collapse".

[OnTheOtherHand]

124. do you realize how wildly you're misrepresenting that NIST letter?

Quite possibly not, as most people who quote that part of a sentence don't put it in context.

In the case of the WTC Towers, NIST has established that the failures initiated in the floors affected by the aircraft impact damage and the ensuing fires resulted in the collapses of the towers. This conclusion is supported by large body of visual evidence collected by NIST. Your letter suggests that NIST should have used computer models to analyze the collapse of the towers. NIST carried its analysis to the point where the buildings reached global instability. At this point, because of the magnitude of the deflections and the numbers of failures occurring, the computer models are not able to converge on a solution.

Your letter contends that NIST's report violates the Information Quality Standard of "utility." NIST believes that the report has utility. In fact, the codes and standards bodies are already taking actions to improve building and fire codes and standards based on the findings of the WTC Investigation. As we mentioned previously, we are unable to provide a full explanation- of the total collapse....

...With respect to the second request for change, it was most critical for NIST to explain why the collapse initiated. Once the collapse initiated, it is clear from the available evidence that the building was unable to resist the falling mass of the upper stories of the towers....

http://www.911proof.com/NIST.pdf

Whether or not one construes that as "apply(ing) Bazant's theory," there isn't a heck of a lot of difference there. NIST is saying that it can't accurately simulate the collapses all the way down, not that it's unsure why the buildings collapsed.

[procopia]

125. Thanks for providing the context...

"the computer models are not able to converge on a solution" is just fancy rhetoric for "We are unable to explain the total collapse."

NIST is saying that it can't accurately simulate the collapses all the way down, not that it's unsure why the buildings collapsed.

NIST is saying it is unable to prove its hypothesis.

[OnTheOtherHand]

126. I stand by my statements, and you offered no substantive response

I have no confidence in your capacity to interpret NIST's "fancy rhetoric." But if you are hell-bent on believing that NIST is making some excruciating concession here, I'm sure you will.

ETA: I'll try one more appeal to reason. Do you really, truly, honestly believe that "because of the magnitude of the deflections and the number of failures occurring, the computer models are not able to converge on a solution" means that NIST can't explain why the buildings collapsed? What meaning, if any, does the part of that quotation before the comma convey to you?

[procopia]

128. Does "not able" mean "can't"?

NIST apparently can't explain, because it didn't.

NIST did not even attempt to explain the actual collapse, or why WTC buildings collapsed at nearly free-fall speeds when no steel frame building have ever collapsed before 9/11 due to fire, even though they burned hotter and longer.

[OnTheOtherHand]

129. do you really not get it?

Yeah, NIST explained it. What NIST didn't do was to model it from beginning to end. We've been over this, and over this, and over this. It's not that you have any arguments, as far as I can tell; all you have is the dogged insistence that NIST's arguments don't actually exist.

ETA: Care to explain your failure to answer my question about the portion of the quotation before the comma?

[procopia]

132. Do you not?

NIST did not model it, nor did NIST explain it.

http://www.911proof.com/NIST.pdf (p. 4, paragraph 1):

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."

[OnTheOtherHand]

133. you still refuse to answer my simple question

You refuse even to acknowledge it.

Here, let's try another question. In your proof text of choice -- the one in which you pretend that the context is irrelevant -- how do the words "full" and "total" modify the meaning?

[procopia]

134. Your question is irrelevant

and posed for the purpose of distracting from NIST's clear admission:

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."

[OnTheOtherHand]

135. no, it's crucial to understanding NIST's meaning

and I fear that is why you are committed to ignoring it. A pity, that.

Unless you have another candidate, "As we mentioned previously" must refer to the sentence I quoted -- and you refuse to try to figure out what that sentence means. That's your privilege, but there's no reason for anyone else to follow you down that rabbit hole.

[procopia]

147. I don't have to "figure out" what the sentence means

and neither do I feel obliged to respond to your questioning, an obvious ploy designed to distract from the original point, which was this:

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."

[OnTheOtherHand]

150. you don't need to know what NIST meant in order to know what NIST meant?

Can you possibly be that confused?

[procopia]

152. I know what the fricking sentence means, OK?

Why do you think I'm obliged to prove that to you?

Are you still trying to distract from this admission?

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."--NIST

[OnTheOtherHand]

153. no, you don't

If you knew what it meant, you wouldn't insist that the questions you refuse to answer are irrelevant.

Frankly, procopia, you're pwned. I guess it isn't painful for you, only for me.

[procopia]

154. Why would you think

that sentence would be difficult for someone to understand? Do you think those are big words or something? I said your question was irrelevant because it was obviously intended to distract from NIST's admission:

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."

[OnTheOtherHand]

155. "because of the magnitude of the deflections and the numbers of failures occurring"

I don't think it's difficult to understand. Apparently you've chosen not to understand it. You've already whiffed on about ten chances to demonstrate otherwise. But you can change your mind at any time.

[procopia]

156. NIST admits it is unable to explain the total WTC collapse

http://www.911proof.com/NIST.pdf (page 4, paragraph 1)

[Bolo Boffin]

157. because the stated objective is much too complex for computer modeling

[procopia]

158. NIST neither modeled nor explained the total collapse

and admitted it was unable to.

http://www.911proof.com/NIST.pdf

[Bolo Boffin]

161. because such a task was impossible as they explained. n/t

[procopia]

162. Impossible to explain? nt

[Bolo Boffin]

163. No, impossible to model and thus produce the kind of explanation you've set up as the goalpost.

Explain, NIST has done.

Met your impossible criteria, NIST has not done.

[OnTheOtherHand]

160. do you ever find yourself getting really annoyed with other posters?

Yes, that was a rhetorical question. ;)

[OnTheOtherHand]

137. with apologies to Gary Larson:

What NIST Said to Jones, Ryan, Gage et al.:

In the case of the WTC Towers, NIST has established that the failures initiated in the floors affected by the aircraft impact damage and the ensuing fires resulted in the collapses of the towers. This conclusion is supported by large body of visual evidence collected by NIST. Your letter suggests that NIST should have used computer models to analyze the collapse of the towers. NIST carried its analysis to the point where the buildings reached global instability. At this point, because of the magnitude of the deflections and the numbers of failures occurring, the computer models are not able to converge on a solution.

Your letter contends that NIST's report violates the Information Quality Standard of "utility." NIST believes that the report has utility. In fact, the codes and standards bodies are already taking actions to improve building and fire codes and standards based on the findings of the WTC Investigation. As we mentioned previously, we are unable to provide a full explanation- of the total collapse....

...With respect to the second request for change, it was most critical for NIST to explain why the collapse initiated. Once the collapse initiated, it is clear from the available evidence that the building was unable to resist the falling mass of the upper stories of the towers....

What They Heard:

blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah not able to converge on a solution.

blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah unable blah blah blah blah explanation blah blah blah collapse....

...blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah....

cf. Larson

[procopia]

139. You totally misrepresented NIST's admission

which should be:

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."

As for the rest, "blah blah blah," that's fairly accurate.

[OnTheOtherHand]

140. riiiiight, I totally misrepresented it by quoting it in context

Hey, don't ever change. We like you just the way you are.

ETA: If you're criticizing me for leaving "full" and "total" out of the blah-blah version, you might need to review the questions you've refused to answer.

[procopia]

143. You left out this part:

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."

This is the admission most commonly quoted, the part you are attempting to ignore.

[OnTheOtherHand]

146. OK, you've veered into self-parody n/t

[procopia]

148. OK, so you included the admission, even though

you tried to trivialize it. At least you did finally acknowledge it. :bounce:

[OnTheOtherHand]

149. oh, brother n/t

[procopia]

151. I know it was difficult for you

"As we mentioned previously, we are unable to provide a full explanation for the total collapse."--NIST

[OnTheOtherHand]

159. as I mentioned previously, you've veered into self-parody n/t

[AZCat]

164. There's really no point in engaging posters like this.

I like to call them on their bullshit, but a prolonged discussion doesn't serve any purpose other than highlighting how clueless they are.

[OnTheOtherHand]

165. well, it also sears the cluelessness into my memory, perhaps

The first two or three rounds, I can easily forget. After the first dozen rounds or so, I'm likely to remember that a given poster is frozen in place.

But not always. And even when I do remember, it's hard for me to accept.

[AZCat]

166. It is difficult, because they mostly claim to value the pursuit of knowledge.

Unfortunately it seems to be a surface thing, and knowledge is only valuable to them if it can support their predetermined conclusions.

[procopia]

168. haha

I'm pretty sure OTOH is not Socrates.

[procopia]

170. Maybe you learned something then.

Remember saying this? "Yeah, NIST explained it"

Now you know that NIST itself admits:

"...we are unable to provide a full explanation of the total collapse."

[OnTheOtherHand]

172. since "full" and "total" are meaningless, that makes perfect se-- oh, wait

How unfortunate. Even out of context, your proof text still doesn't say what you want it to say.

[procopia]

173. Actually

It doesn't say what YOU want it to say.

[OnTheOtherHand]

174. actually

what matters is what it means -- and that's why one ought to pay attention to the context. I'm sorry you can't find it within you to agree.

[procopia]

178. Actually, there is no reason to believe it means anything other than what it says

I do agree that context is important, not only the context of the NIST letter to WTC family members, but the context of the portion of the letter NIST responded to, which says:

"NIST was statutorily tasked with telling the American people, the 9/11 victims’family members, independent researchers, and the U.S. government how and why the WTC Towers collapsed...

...Requesters further request that NIST revise the WTC Report so that the
information presented therein is “useful” in that it is “helpful, beneficial, or
serviceable to its intended users” in accordance with applicable information quality
standards. To comply with this request, NIST must revise section 6.14.4 by adding a
detailed computer simulation or physical structural simulation detailing the behavior of
the structure after “collapse initiation.” NIST’s implication that total and complete
structural collapse and the destruction of the entire building was inevitable following
“collapse initiation” is unsupported by the laws of physics, logic, history, data,
calculations, science of any kind, computer models, or physical models. Again, NIST is
advised that using circular logic (ie. trying to use the fact that the Towers did, in fact,
totally and completely collapse “as seen in videos” to prove that total and complete
collapse was imminent following “collapse initiation”) is wholly inadequate to satisfy
NIST’s burden of explaining how and why the buildings collapsed. Even if a collapse
event were initiated as NIST has suggested, NIST still has the burden of explaining why
the Twin Towers suffered total collapses, when all other high rise fires in modern steelframed
structures have resulted in no or only very limited and partial collapses.
Furthermore, it is clear that, under the NCST Act, NIST was required to explain why and
how the entire building completely failed to stand, not just how “collapse initiation” was
reached."

http://www.journalof911studies.com/volume/200704/RFCtoNISTbyMcIlvaineDoyleJonesRyanGageSTJ.pdf

Family members wanted to know why the buildings collapsed as they did, so quickly and symmetrically, the first steel framed buildings ever to totally collapse because of fire when others have burned longer and hotter. But the NIST report did not address the collapses beyond initiation. That is why NIST was forced to admit,

"...we are unable to provide a full explanation of the total collapse."

[OnTheOtherHand]

180. you're flat-out wrong

Of course the NIST report addressed the collapses beyond initiation. Read 6.14.2-6.14.4 again. Even the letter addresses the collapses beyond initiation: "Once the collapse initiated, it is clear from the available evidence that the building was unable to resist the falling mass of the upper stories of the towers."

It's one thing to argue that NIST's explanation of the collapses is wrong. But it's a giddy height of denialism to aver that NIST doesn't have an explanation of the collapses.

Now, if you intend to get this right, here is something you can say about NIST's approach, from the footnote on page xxxvii: NIST's investigation of the probable collapse sequence "includes little analysis of the structural behavior of the tower after the conditions for collapse initiation were reached and collapse became inevitable." If you can marshal the intellectual courage to confront the NIST report on its own terms, this statement will actually make sense to you -- even if you decide to disagree with the NIST report. It dovetails neatly with the point about model convergence that you presently feel compelled to argue isn't actually a point at all. Hence my Gary Larson parody.

[procopia]

181. Speaking of veering...

You accused me of taking NIST's statement out of context to change its meaning. I provided the context to show the statement meant exactly what it says:

"...we are unable to provide a full explanation of the total collapse."

Now you want to change course and argue whether the NIST report addressed the collapse after initiation. It did, but it was very limited and not useful or supported "by the laws of physics, logic, history, data, calculations, science of any kind, computer models, or physical models."

[OnTheOtherHand]

187. this precisely supports my point that you complained about below

"I provided the context" -- no, you did not. You continue to wrench this sentence fragment out of the context in which it appears; see your post #178. Your posts fully support my paraphrase: "yes, context matters -- but only the context of the letter to NIST, not anything else from NIST itself."

Now you want to change course and argue whether the NIST report addressed the collapse after initiation. It did....

I'm not changing course at all, except to point out that when you wrote,

But the NIST report did not address the collapses beyond initiation.

, you were wrong. Thanks for conceding your mistake, sort of.

[AZCat]

127. No, it isn't.

Thanks for proving you don't understand simulations of complex systems.

[William Seger]

176. Wrong, and wrong again

> The building partially collapsed ...

As I already pointed out to you, the part that collapsed totally was an independent structure. The part still standing is really a structurally separate building -- separated by an expansion joint. Your misunderstanding of that point does not change the significance of the total collapse.

> Never proven.

The same kind of math that's used to design buildings was used to prove that the structure could not possibly absorb that kinetic energy, and your uninformed concurrence is not required.

> If it had been proven, NIST would have applied Bazant's theory to explain the WTC collapse...

NIST did "appl(y) Bazant's theory to explain the WTC collapse." Bazant's paper is the first cited reference in section 9.5 of the NIST NCSTAR 1-6 document.

> ...rather than having to admit, "We are unable to provide a full explanation of the total collapse".

Typical "truther" out-of-context quote-mining. The part of the quote that your "truther" propaganda source left out was that the sentence actually began with "As we mentioned previously, ..." That's a reference to the previous paragraph of the same letter which said, "NIST carried its analysis to the point where the buildings reached global instability. At this point, because of the magnitude of the deflections and the number of failures occurring, the computer models are not able to converge on a solution." They were "unable to provide a full explanation of the total collapse" using their computer model. And both paragraphs are contained in a section of the letter entitled "The Goal of the WTC Report and Its Overall Analysis," in which NIST was simply responding to Gourley's misunderstanding of the NIST charter: It was tasked with determining the most probable cause of the collapse, not with coming up with "a full explanation of the total collapse" with a computer simulation. Unlike you, NIST and the vast majority of the structural engineers in the world understand why that would be completely unnecessary: Like most buildings, the structure was not strong enough to withstand the collapse after it got started, and Bazant's cited analysis explains why that's so.

Fail. Better look for another straw.

ETA: LOL, I guess I should have read all the other responses before responding. I see you've already been chewed out for your out-of-context quote-mining. I also see that it just bounced off your shield of invincible ignorance. Oh, well, I trust that no sensible person here has any real hope of convincing you that you are wrong. I'll settle for the much more achievable objective of demonstrating that you don't know what you're talking about.

[OnTheOtherHand]

182. there are interesting moments

For instance, I loved it when procopia said, "As for the rest, 'blah blah blah,' that's fairly accurate." It's also interesting when she says that yes, context matters -- but only the context of the letter to NIST, not anything else from NIST itself. You'd think someone would notice that that is leaving out a lot!

But I have to admit that even after all these years, Morton's demon still amazes me.

[procopia]

183. Interesting moments, like when you misquote me?

"It's also interesting when she says that yes, context matters -- but only the context of the letter to NIST, not anything else from NIST itself.

I actually said:

"I do agree that context is important, not only the context of the NIST letter to WTC family members, but the context of the portion of the letter NIST responded to,"

It is obvious why you are trying to divert this thread and make it about me, but I don't have time for your games, diversions, and dishonesty.

[OnTheOtherHand]

184. that isn't quoting you at all

This is just another misrepresentation on your part, and I'm sick of your wandering and blundering. Procopia, it's long past time for you to do some intellectual work. Long past time.

If you think my paraphrase is inaccurate, you could try to demonstrate that by pointing to your explanation of how "full" and "total" modify the meaning of your proof text, and what the statement in the preceding paragraph means.

ETA: Or you may prefer to offer a sensible response to Seger, since for whatever reason you seem incapable of according me that iota of respect. Yeesh.

[procopia]

186. You didn't "paraphrase"

You changed the meaning of my words completely.

[OnTheOtherHand]

188. this is just another unsupported assertion on your part

As far as I remember, your most extensive discussion of the context of your proof text is as follows:

As for the rest, "blah blah blah," that's fairly accurate.

I thought I was done being surprised by you, but I haven't an effing clue what you are complaining about here.

[Realityhack]

57. Unfortunately you are as poor at logic as you are at physics.

Pointing out that you clearly have no idea what you are talking about is not an ad-hominem attack. It is a comment on the understanding displayed in your post about a specific subject.
And I do not need to know the first thing about you to point out the fact that your arguments are bogus.

[procopia]

38. Still photo proof

It's even more obvious in still photos that the upper block of floors does not remain a rigid structure as Bazant/Zhou theorized. Compare photos of WTC 1--one second into collapse, 2 seconds into collapse, and 2.6 seconds into collapse:

http://www.scienceof911.com.au/the-argument/introduction

[Bolo Boffin]

39. You and eomer are making the same mistake as Tony Szamboti. n/t

[procopia]

41. Bazant's mistake (one of them)

was to claim the upper block remained whole and rigid. The photos show it did not.

[Bolo Boffin]

42. You do not understand Bazant's paper. n/t

[procopia]

43. Explain it to me then.

Specifically, what is it that I don't understand?

[Bolo Boffin]

44. Bazant/Zhou is not an exact modeling of the WTC towers' collapse. It's a limiting case.

It's meant to start the discussion.

It does show that there was no stopping the upper section once it got momentum. Bazant/Zhou considers an best-case-scenario for the survival of the towers' structure. However, what happened on 9/11 is not the best case scenario.

If the towers' structure could not survive a best case scenario, there is no way they could have survived what actually did happen.

You betray your lack of understanding (as does Szamboti) by exterpolating from Bazant/Zhou things that you think you should see in the videotape. It's a rookie mistake.

[procopia]

46. Then probably NIST shouldn't have used it as a basis

for its reports explaining what caused the WTC collapse.

[Bolo Boffin]

47. You continue to misunderstand Bazant's report. n/t

[procopia]

48. Oh I understand it

better than you think. :eyes:

[Bolo Boffin]

49. No, and your continued mangling of it demonstrates that amply.

You would not be expecting to see Bazant's description in the video if that were the case.

You would not be discarding the truth Bazant Zhou demonstrates mathematically if that were the case.

You are wedded to the religious belief, against all evidence, that the buildings were controlled demolitions, and you insist on misunderstanding very clear, scientifically valid, and peer-reviewed papers that demonstate the truth - that these buildings simply fell down.

[procopia]

50. No one could mangle it more than Bazant himself

but you are a close second.

[Bolo Boffin]

52. No. n/t

[William Seger]

51. Really? If you really understand it but still disagree with it...

... you should be able to offer some cogent reason for that disagreement, i.e. explain where you think Bazant went wrong. Eomer at least made an attempt to do that, but unfortunately only demonstrated that he hasn't read it very carefully (if at all). You have not even made the attempt. Why is that, if you understand it so well?

I'll even help you get started by explaining what you need to do: Bazant clearly states what he is doing (and not doing) with his analysis. The simplifications he makes are to make the problem tractable. The justification -- common in physics -- is that often a simple model is all you need to make "yes or no" decisions. If you use a simple model and come up with a close call, then you can't trust that model to give you the right answer; you need to develop it in more detail. But if your simple model comes up with, say, a "yes" by an order of magnitude, then all you need do is determine if a finer model could possibly change the result. If you claim you understand Bazant's analysis but have valid reasons for disagreeing with his conclusion, then you need to explain where his model makes something like an order of magnitude error. Problem is: while it's certainly true that some of Bazant's simplifications favor a collapse, most do not.

So cut the pretense and get on with it.

[procopia]

58. I've already stated my reason

Photos show the upper floors are disintegrating before impact with the bottom floors, and not behaving as a "rigid body" as Bazant suggests.

Beyond that, I understand Bazant's hypothesis starting with the never-proven 800 degree C temperatures. It isn't that difficult to grasp.

[William Seger]

72. (Post #66 applies to you, too.)

Please respond there, if you have anything to say.

[eomer]

60. Bazant assumes the worst case, not best.

So it is not a limiting case, or not a useful one anyway.

He assumes that:

1. the upper part of the tower remains intact as a rigid block,
   
2. all of the mass of the upper part therefore is brought to bear on the lower part,
   
3. all the mass of the lower part stays within the footprint after the crushing collapse passes by it and is therefore brought to bear on the lower part,
   
4. all the momentum imparted by gravity stays on board with the crushing effect rather than shooting off outside of it.
   
   These assumptions are all grossly untrue. These assumptions all make the model skew toward collapse.
   
   A skewed model produces a useful limiting case only if you skew your inputs in favor of one outcome and then see the model produce the opposite one.
   
   By skewing these inputs in a direction that made the model more likely to collapse and then seeing the model collapse, what the skewing did in reality was to render the model meaningless and irrelevant - we already knew that we could make a model collapse if we skewed it far enough away from physical reality in the direction that would make it collapse.
   
   

[William Seger]

66. Good examples...

... of exactly what I called "bogus" and "lame attempts to refute Bazant."

I suppose that we'll have to go through your list, but please let's start with a very important quote from the article that Gourley attempted to respond to. There is no point in going on until you understand the significance of this:

Inabsorbable Kinetic Energy

First, let us review the basic argument (Bazant 2001; Bazant and Zhou 2002). After a drop through at least the height h of one story heated by fire (stage 3 in Fig. 2 top), the mass of the upper part of each tower has lost enormous gravitational energy, equal to m₀gh. Because the energy dissipation by buckling of the hot columns must have been negligible by comparison, most of this energy must have been converted into kinetic energy K = m₀v₂/2 of the upper part of tower, moving at elocity v. Calculation of energy Wc dissipated by the crushing of all columns of the underlying (cold and intact) story showed that, approximately, the kinetic energy of impact K > 8.4 Wc (Eq. 3 of Bazant and Zhou 2002).

It is well known that, in inelastic buckling, the deformation must localize into inelastic hinges (Bazant and Cedolin 2003, sec. 7.10). To obtain an upper bound on Wc, the local buckling of flanges and webs, as well as possible steel fracture, was neglected (which means that the ratio K/Wc was at least 8.4). When the subsequent stories are getting crushed, the loss m₀gh of gravitational energy per story exceeds Wc exceeds 8.4 by an ever increasing margin, and so the velocity v of the upper part must increase from one story to the next. This is the basic characteristic of progressive collapse, well known from many previous disasters with causes other than fire (internal or external explosions, earthquake, lapses in quality control; see, e.g., Levy and Salvadori 1992; Bazant and Verdure 2007). {emphasis added.}

Merely to get convinced of the inevitability of gravity driven progressive collapse, further analysis is, for a structural engineer, superfluous. {emphasis added.} Further analysis is nevertheless needed to dispel false myths, and also to acquire full understanding that would allow assessing the danger of progressive collapse in other situations.

Do you understand what Bazant is saying there? No, you do not -- you apparently do have not the first clue. Otherwise, you would understand that if you want to criticize Bazant's paper, this is where you need to start -- not a handful of insignificant details -- and if you can't do that, then as Bazant said "further analysis is superfluous" to overcome your invincible ignorance. You clearly don't understand what Bazant is saying in that paragraph, but you think you can parrot a bunch of insignificant details that you picked up from websites that, like you, desperately need to disbelieve Bazant's conclusions, to protect delusions that you have developed for perfectly irrational reasons. Then, you feel justified in smearing and slandering not only Bazant but the huge number of people who do understand what Bazant is saying in that paragraph. It's beyond pathetic, and you don't seem to understand it well enough to understand why that's so.

So, eomer, prove me wrong and talk to me like you understand what that paragraph says, or please do everyone a favor and stop wasting our time.

[thepeopleunited]

75. Is this a joke?

Seriously. I'm laughing. It doesn't even make grammatical sense. What kind of fool would put their name on this horseshit and what kind of half-baked outfit would publish it? You couldn't self publish this at a vanity press unless maybe it was Kinko's.

[William Seger]

76. LOL

Strike one.

[thepeopleunited]

77. I'm glad you're laughing.

And the Bazant comedy team struck out long ago. Having read my share of engineering textbooks and journal articles I can assure you that this is pure junk.

[AZCat]

79. Pardon me if I don't depend on your overwhelming engineering experience...

to determine what is and what isn't pure junk. I guess having a license and actual experience can't hold a candle to your superior knowledge of all things engineering. :eyes:

[thepeopleunited]

80. "Credentials are somewhat irrelevant"

quoth thee directly below (reply #65), and in this case, I concur.

[OnTheOtherHand]

81. but so are unilateral declarations of competence

If you offer an argument, we can assess it without reference to anyone's credentials. When you brag about the textbooks and journal articles you've read, you just invite comparisons that are unlikely to break in your favor.

[AZCat]

82. Exactly.

If someone's going to brag, they should probably have something worth bragging about.

[thepeopleunited]

83. You have an agenda, I have experience.

It's a buyer's market.

[SDuderstadt]

84. What "experience" do you have...

exactly?

[AZCat]

86. He already told us...

He's read some books and journal articles, and now he's an expert!

[thepeopleunited]

87. Professional experience too, on high-rise steel frame projects.

How about you?

[SDuderstadt]

89. I seriously doubt that, dude...

you would have mentioned that the first time around.

[AZCat]

92. Uh-huh.

I don't care what you claim to have done - I care about the quality of your arguments. So far, it has been poor.

[thepeopleunited]

94. Likewise. n/t

[AZCat]

97. Except I haven't been basing my arguments...

on soi disant expertise.

[thepeopleunited]

101. What arguments?

So far, soi disant expertise is all I've seen you offer. Just an observation, nothing personal.

[AZCat]

103. That hasn't been the basis of any of my arguments.

Whereas you made it the basis of yours. Perhaps you've forgotten already? It's right here ----> post #77, this thread

[AZCat]

85. That's really quite amusing.

Too bad your knowledge and experience don't match your ego.

[thepeopleunited]

88. I'm not the one bragging.

But since you seem to want to know whether I'm speaking from experience, the answer is yes.

[AZCat]

90. Actually, yes - you were.

You claimed your reading of textbooks and journal articles was sufficient to qualify you as experienced.

[thepeopleunited]

93. Incorrect. I don't brag about my experience

and I put little stock in words of those who do.

[AZCat]

95. Now it's just pathetic.

Why don't you try for a little consistency, thepeopleunited - you're less likely to look foolish. You could try reading up on logical fallacies like the appeal to authority - avoiding them might improve the quality of your posts.

[SDuderstadt]

98. Dude...

no one in a serious discussion of this sort would initially leave out their direct experience with steel frame highrise buildings, but tell us all about "textbooks and journals" they have read. More bullshit.

[AZCat]

99. Notice he doesn't describe what KIND of experience that was. n/t

[SDuderstadt]

102. Exactly....

this guy is probably one of those "citizen investigators" and thinks of himself as working on a "case".

[OnTheOtherHand]

104. naw, that could be true

I have no clue what experience tpu has with high-rises, and I don't really care much. But he is reacting to a manuscript, so it makes some sense to compare it with other things he has read.

Also, it's true that this particular article has some low-level writing problems that are unlikely to have made it through journal review. That isn't to say anything about the content, although tpu apparently thinks it does.

[AZCat]

105. Some sense - yes...

but such a comparison cannot replace a substantive argument about the technical aspects.

[OnTheOtherHand]

106. certainly it can't

I thought Seger's "LOL" was pretty much on target.

ETA: I've encountered people who think they can rule out non-response bias in exit polls because they once interviewed people, or once taught research methods, etc. -- so I'm inclined to suppose that tpu is not so much exaggerating his experience as its relevance. (Of course, for all I know, he might be understating it. Hard to tell in the absence of substantive arguments.)

[SDuderstadt]

91. I call bullshit...

dude.

[thepeopleunited]

96. You call lots of things I've noticed.

Fine. Enjoy your stay.

[SDuderstadt]

100. I call bullshit when I see it...

dude, and it's just oozing out of you.

[eomer]

78. Address my subtantive point.

The fatal flaw in Bazant's article is contained in that excerpt. It assumes that all the kinetic energy after a fall of one story (K) must be dissipated in the lower Part A and that none of it will be dissipated in the upper Part C. It assumes, in other words, that the upper Part C is a magic cube that defies the laws of physics.

The result of this flaw manifests itself in the disparity between the model's lack of crush-up and the visual evidence that crush-up did in fact occur.

[William Seger]

107. That's easy

You are simply misunderstanding Bazant's argument. But before going into that, it's interesting to note that even if you were correct, that would not support the conclusion you would like to reach, that the collapse should not proceed. Even if you were correct, then there would "only" be 4.2 times more kinetic energy than the lower part of the structure could absorb, rather than 8.4.

But you are not correct, and the problem is really with your logic, not the math. Bazant certainly does not "assume that all the kinetic energy after a fall of one story (K) must be dissipated in the lower Part A." His calculation of Wc is simply the maximum of energy that the lower part could absorb. By noting that the kinetic energy available was 8.4 times larger than that, Bazant is simply pointing to the futility of hoping that the collapse could be arrested. That is, for the collapse to be arrested by those columns, something else would need to absorb almost 90% of the kinetic energy. He most certainly does not assume or claim that all of that energy could or did go into crushing those columns.

Refuting your own misunderstanding of Bazant's argument is obviously insufficient. To refute Bazant's conclusion in that paragraph, you need to show that either:

A) his calculation of the total kinetic energy is incorrect;
B) his calculation of the energy that could be absorbed by the top columns in the lower block is incorrect; or
C) you've found another energy sink that could absorb 90% of the available kinetic energy

... or some combination. As I said before, you need to find something like an order of magnitude error in Bazant's simple model before you can argue that the building should not have experienced total progressive collapse.

Until you can do that, the only people likely to be impressed with your "refutation" are those like thepeopleunited. And until you do, it's pretty danged obvious that you and he are not really basing your opinions on reason, but rather grasping at straws to defend an irrational speculation. You are so desperately hoping that someone will prove that the collapse would not be possible without demolition that you even find Gourley's "Newton's Third Law" nonsense to be impressive.

[eomer]

109. No, it's not easy.

If it were that simple then simultaneous, symmetrical crush-down and crush-up would have occurred. Instead, on at least one of the towers, only crush-up occurred until at least half of Part C was crushed-up. Obviously Part C was not able to impart 4.2 times the force necessary to crush Part A because Part A was not crushed (at first ).

By the way, I do not claim that progressive collapse would not have occurred. I claim that it's an unknown.

[William Seger]

116. Utter nonsense

Your imaginary description of what happened has no bearing on the issue.



Up until the time that dust and smoke obscure the view, what we see is what Bazant described: some crush-up, after which the debris itself is exerting impulse forces on the lower part, so the forces on part A and part C are nowhere near equal. But for confirmation, we can see the exact same thing happening more clearly in the Vérinage demolition videos:

http://www.youtube.com/watch?v=NwFHEoiUZ7o

Furthermore, the whole "crush-down/crush-up" pseudo-controversy is nothing but a red herring, tossed out by people with a pathological need to deny Bazant's analysis but incapable of finding any substantive flaw. Even if the entire top section were torn apart in the collapse, most of its mass would still be falling and bashing the lower part. (By the way, you inaccurately asserted that Bazant didn't consider mass lost over the side. He didn't in the original short paper of 2001, but that proves that you didn't actually read the JEM article Gourley was attempting to refute, since that paper has a discussion of the effects of "mass shedding".)

> By the way, I do not claim that progressive collapse would not have occurred. I claim that it's an unknown.

Only among the willfully ignorant. "956 architectural and engineering professionals" over at AE911truth.org, and not a one of them has managed to put a dent in Bazant's analysis, nor any of the http://www.ae911truth.info/tiki-index.php?page=Scholarly+Papers">several other analyses that reach the same conclusion using different methods. At some point, perhaps you ought to objectively consider why that's so.

[eomer]

131. Conceded that Bazant does reflect some ejection from Part A.

I had in fact noticed that on re-reading Bazant a couple of days ago and was waiting for someone to notice.

My other points stand, including that there was mass ejected from Part C that, along with its kinetic energy, Bazant is erroneously including in the crushing force.

See my post further down for my response to your other points.

[William Seger]

171. Nonsense. Mass can ONLY be ejected from part B

Parts A and C are the intact bottom and top sections at any point in time -- part B is the debris -- and the "mass shedding" that Bazant considers does get subtracted from the kinetic energy.

I'll make one more attempt in the other subthread to explain why your other points are either invalid or irrelevant to Bazant's conclusion.

[eomer]

177. Semantics.

All mass that is ejected originated in either Part A or Part C because no mass originates in Part B (its mass comes originally from A or C). The adjustment that Bazant makes is (correctly) to subtract the ejection mass from Part B. But whether you want to think of that mass has having become categorized as Part B at the instant that it is liberated from A or C and then subtracted from B as it is ejected or, alternatively, as having never being categorized as Part B is just an irrelevant naming issue. It has nothing to do with the calculations. Either way the ejected mass needs to not be included in A, B, or C in the calculations.

Bazant does adjust for some mass that originated in A and then gets ejected. He does not adjust for any mass that originated in C being ejected. He assumes that C remains a rigid and intact unit that loses no mass. This is obviously incorrect based on the visual evidence. Bazant takes credit in the crushing force for mass and kinetic energy that in fact was ejected.

[William Seger]

185. More nonsense

In calculating the effect on A, the falling mass is taken as the sum of B and C. It does not matter if the mass ejected from B originally came from A or C: It is no longer in the B + C sum, so Bazant excludes it in the adjusted calculation of the kinetic energy available. You are the one who is "obviously incorrect."

[eomer]

196. Bazant insists that Part C remains intact.

Can Crush-Up Proceed Simultaneously with Crush
Down? It can, but only briefly at the beginning of collapse,
as mentioned in the paper. 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). 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. We
have now carried out accurate calculations, which rigorously
justify this conclusion and may be summarized as follows.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25%20WTC%20Discussions%20Replies.pdf

It seems strange that he would continue to insist that Part C remains intact even when challenged but would simultaneously be adjusting the mass and energy of Part B for ejections that came out of Part C. It seems much more likely to me he is adjusting for mass ejections that originate from Part A. In any event, I do agree with your statements if the amount of his adjustment is enough to cover the ejections that originate from both A and C. To be honest I don't know what amount he assumes or how he arrives at it so this question is probably floundered unless or until someone knows that.

[eomer]

110. Please allow an actuary to assist all you amazing engineers.

Your best argument is that after some initial phase of crush-up, the give in Part C was exhausted enough so that its now condensed (though chaotic) mass became sufficient to begin crushing Part A.

As long as you keep insisting that your equations prove that crush-down would begin immediately after the one-story drop, you are obviously disproved by the visual evidence.

[eomer]

113. And to state it more correctly,

It would be the force imparted on Part A by the combined kinetic energy of Parts B and C that you need to demonstrate exceeds what is needed to crush Part A.

I doubt you can do that math and even if you could you've blown your credibility defending an obviously erroneous model.

[Bolo Boffin]

115. Could you do a force diagram of what you're proposing here?

It would be an interesting contribution to the discussion at this point.

[eomer]

136. No, it's too complex.

One of my points that I guess I haven't made sufficiently is that it is a complex system. Bazant's reduction of Part C to a magic cube is totally unjustifiable. Anyone who reduces it to a force diagram of just a few vectors is committing a similar mistake. Another mistake such an exercise would make would be ignoring the distribution over time for the application of the total kinetic energy into force imparted against Part A.

[Bolo Boffin]

138. How amusing. n/t

[eomer]

141. You disagree? You think it can be reduced to a simple diagram at a single instant of time? n/t

[Bolo Boffin]

142. Force diagrams are a standard way of getting your mind around a problem.

Your refusal to attempt one tells me you know just exactly the amount of bullshit you're shoveling.

And that amuses me.

[eomer]

144. Utterly worthless in this case.

Just like magic cubes, it could only give an unwarranted impression.

[Bolo Boffin]

145. No, much too revealing in this case.

A force diagram would reveal your bullshit for what it is. It would show us the man behind the curtain.

So keep up the farce, O Great and Powerful Eomer.

[eomer]

167. Your suggestions makes no sense to me.

If you think it makes sense then draw it up and present it, if you wish.

One of my main points is that Bazant's solution is oversimplified. In fact I think that is why his solution failed to produce a simulation that came even close to what is seen in the video. How you can make any analysis at a single instant of time and with just a few force vectors escapes me. It seems to me you will have to assume magic cubes, which is what I object to. Show me, if you can.

[Bolo Boffin]

169. You guys are SO predictable.

The shift of burden of proof is SO 2004, guy. Get a new act.

[William Seger]

118. WTF? That's exactly what Bazant has done.

This is becoming more and more pointless. You start a thread claiming Bazant's math is "bogus" yet you don't even know what's in the papers.

[eomer]

130. No, you missed the distinction I'm making.

That's probably my fault because I clumsily split it over two posts.

Bazant asserts that only crush-down will occur during the first phase. He says that Part C will remain rigidly intact during this phase, which will last until the intact Part C reaches the ground. Only then, he asserts, will a distinct phase of crush-up of Part C occur.

My improved version of Bazant is an initial phase of crush-up of Part C followed by crush-down of Part A, with or without simultaneous crush-up of Part C continuing.

No way can the same model be used for these two versions. Demonstrating that the second phase (crush-down of Part A) will ever actually commence is something that Bazant has not yet done.

[William Seger]

175. Please throw that red herring back, it's under the legal limit

> Bazant asserts that only crush-down will occur during the first phase.

Correction: Bazant asserts that in his simplified model, under the clearly stated assumptions and qualifications, there would be very little crush-up during the first phase, and he provides the math for making that assertion. He also provides the math that shows an accurate prediction of the collapse time using that simplified model, which demonstrates that the model is fundamentally sound despite the simplifications. The title of your OP is "Bazant's progressive collapse math is bogus," yet you persist in a bait-and-switch tactic of arguing something completely different: that Bazant's model doesn't match what you believe you see in the videos, so therefore, as a matter of pure personal opinion, you don't see any value to his model. But you have yet to address the actual logic of Bazant's argument. In an attempt to get you back on track, let me call your attention to this, from the paper you linked to:

In broad terms, this scenario was proposed by Bažant (2001), and Bažant and Zhou (2002a,b) on the basis of simplified analysis relying solely on energy considerations.
...
The kinetic energy of the top part of the tower impacting the floor below was found to be about 8.4 x larger than the plastic energy absorption capability of the underlying story, and considerably higher than that if fracturing were taken into account (Bažant and Zhou 2002a). This fact, along with the fact that during the progressive collapse of underlying stories the loss of gravitational potential per story is much greater than the energy dissipated per story, was sufficient for Bažant and Zhou (2002a) to conclude, purely on energy grounds, that the tower was doomed once the top part of the tower dropped through the height of one story (or even 0.5 m).
{Emphasis added.}

A falling mass has kinetic energy. In order to arrest the fall, that energy must be dissipated somewhere. The fundamental logic of Bazant's argument for using a simplified model is that even if you were to do a detailed analysis of where energy went other than crushing the lower structure, there would still be much more than could possibly be absorbed by plastic deformation of that lower structure. As noted in the section I quoted, he only considered plastic deformation even though fracturing would have dissipated less energy. Elsewhere, he notes that he has assumed that the connections between columns and the floor beams were strong enough to hold while the columns were being crushed, although it's a virtual certainty that in many cases, those connections were broken and columns were merely pushed aside, again dissipating less energy than his simplifying assumptions. His analysis is of a one-dimensional, straight-down force on the columns, even though we do know from the videos that both tops tilted, and we know that columns cannot sustain as much asymmetric, off-center loading as they can symmetric, centered loading, so even Bazant's estimate of plastic deformation energy is on over-estimate.

You persist in side-stepping this critical energy argument and instead keep pointlessly arguing that his model is not a realistic representation of what you believe actually happened, completely ignoring that Bazant himself says that it is not intended to be. You repeatedly claim that his crush-down/crush-up hypothesis is a major flaw in the analysis and conclusion, yet you have failed to establish that it's even a minor flaw: First, you have not demonstrated that the hypothesis is wrong, but much worse, you have not offered even a ghost of a rebuttal for how it could possibly refute the conclusion in Bazant's energy argument, even if you were right. Neither the available kinetic energy nor the ability of the lower structure to absorb energy are affected in any substantial way by when the upper section was destroyed!

All of this has been pointed out to you before in the original thread that you dredged up and again here, and yet you just keep making the same failed arguments. Unless you intend to actually address the actual Bazant argument at some point, I do believe we are finished.

[eomer]

179. I'm not the one sidestepping -- Bazant is.

What he sidesteps is the distribution over time of the application of that "critical energy".

If I am traveling down the highway at 100 MPH then my car has enough kinetic energy to tear my tires to shreds, but only if that "critical energy" could somehow be applied to my tires all at once. If on the other hand the application of that energy to my tires is distributed over time then they will not be shredded. Luckily for me the complex system consisting of my car and the road is incapable of delivering all that energy to my tires at a single instant. No matter how I drive the car the application of the energy to my tires is going to get distributed over time and they are likely not going to get shredded. The energy is "critical" only in theory.

Bazant takes all the kinetic energy that exists at time of impact of C against A, which is all in C (B does not yet exist), and assumes that all of that energy is applied against A at a single instant. But C is incapable of applying all that kinetic energy at a single instant. The actual distribution over time of the application of that energy against A is going to be drastically different than Bazant's magical "all in a single instant".

So I am not ignoring that the "critical energy" exists, I'm just not conceding Bazant's conclusion that it is critical. It is critical if you make an assumption that goes magical and abandons the application of the laws of physics. But if you consider the question in the real world where the laws of physics insist on being followed, we don't know the answer yet because no one has worked through it.

And the fact that the model more or less matches the fall time is clearly due to Bazant backing into a model that makes it so. It proves nothing other than how modeling works.

[William Seger]

189. You're wrong about what Bazant calculated, and you are the one trying to use magic

In order for the top columns in the impacted structure to bring the falling mass to a halt, they would need to do so before they buckle and can no longer provide any sensible resistance. That means they would need to decelerate the falling mass back to 0 within that time. The time cannot be magically spread out over an arbitrarily long time or distance, the way a car can be decelerated by the brakes. In fact, you can use that observation to make a rough estimate of the strength that would be required in those columns to arrest the falling mass. Since it's really a deceleration problem, you can use either the time or the distance involved to do that.

Structural steel can only compress "elastically" about 0.2% before it starts permanently deforming "plastically." The energy expended in plastic deformation, down to the point that the columns are bent completely in half, is actually the energy that Bazant calculates. But the resistive strength of a column drops off drastically at the point a column first begins to buckle and three "plastic hinges" form, as shown by the diagrams in Bazant's paper. At the point of first buckling (or actually, even before then), the columns would no longer be able to support even the dead load of the mass, even if its velocity had been reduced to 0 exactly at that point, so the weight alone would continue crushing the column. So, the buckling point is the limiting case: The columns must stop the fall before they buckle.

The buckling point of a steel column depends on its geometry, specifically its "slenderness ratio" which takes into consideration it's cross-sectional shape and total area, and its unsupported length. We can, therefore, estimate the necessary deceleration by estimating how much the length of the column could be compressed before buckling sets in. That would actually be somewhat different for each different column. However, we can work the deceleration problem backwards to see why there is no logical reason to expect the WTC columns to be able to stop the falling mass.

And the calculation is actually very simple if you use distances. If a mass falls with an acceleration of g for a distance of X feet, and then its velocity is smoothly brought back to 0 over a distance of Y feet, then the deceleration expressed in terms of a ratio to g is simply X/Y. For example if it falls 12 feet and the fall is smoothly arrested over a distance of 6 feet, that would be a deceleration of 2 "Gs" -- twice the acceleration of gravity. To stop it within 4 feet, you would need to apply a deceleration of 3 Gs. Being generous, let's say that the WTC columns could have supported (on average) 3 times the weight of the structure above, as a dead load. An impulse force is not exactly equivalent to a static weight, but as a first approximation, we can therefore estimate that the columns would need to stop the falling top of a WTC tower within a distance of roughly 4 feet. Since all we're looking for is a "yes or no" answer, let's be very conservative and estimate that the columns could provide a 4 G deceleration to the falling mass, so they have 3 feet to do it.

So, let's stop there for a minute and see where we are: Do you think the WTC columns could be shortened from 12 feet to 9 feet without buckling?

[OnTheOtherHand]

190. I think you lose some people at "the falling mass"

Not speaking for eomer, but I think it's a common intuition that what "should" happen is that the falling portion of each tower should be reduced to rubble, bit by bit, with very little impulse force on the lower part at any given moment.

[eomer]

192. That speaks for me.

I think you said the same as my reply, more succinctly.

[OnTheOtherHand]

193. no, wait, we need to curse at each other for 10 or 20 posts...

:)

[eomer]

195. I know.

Well, we always did agree occasionally. Maybe one of us is a broken clock? Wouldn't be me, of course. :)

[Bolo Boffin]

194. What On The Other Hand is describing is a common misperception.

He knows it's a common misperception. You plead guilty to having it. I continue to be amused.

[OnTheOtherHand]

197. well, here's what interests me

As far as my own physical intuitions, I can find either version plausible. That's excellent, because I can't help but be skeptical about my physical intuitions when they are mutually contradictory! And of course it helps me to understand why people can disagree about this issue for reasons other than political predispositions (which certainly play in as well).

This gets me nowhere near eomer's position on Bazant, but at least I feel that I can understand it.

[eomer]

198. Oops, reading it again I find I may disagree.

We knew it wasn't going to last long. :)

Your description overstates what I say, I think. I don't necessarily claim almost no force exerted on the Part A below. I just claim what is implied by the visual evidence, which is that it was not always enough to buckle Part A. At least to some degree and/or for some time Part C buckled before Part A. Bazant strongly insists this is not possible according to his equations and yet there it is in the video.

[William Seger]

199. Which weighs more...

... 50,000 tons of intact building or 50,000 tons of building debris? Of course they would have the same mass, so they have identical kinetic energy when moving at a given velocity.

For simple physics calculations, in the equation for force due to acceleration (or deceleration) F = ma, the mass m is generally taken as a single point-like object. In that simple formulation, it would not matter if the falling mass was intact building or debris. However, it is true that they would not really deliver quite the same impulse force, because the impact would be spread out somewhat in time rather than all at once. But Bazant does not use that simplified formulation: His calculations include a term to distribute both the velocity and the "momentum density" linearly through the compacted debris layer. That improve the precision of the differential formula he derives, but it's still important to note that Bazant's primary argument is that the kinetic energy of the falling mass was much larger than the structure could absorb.

[eomer]

200. Bazant's primary argument

Bazant's primary argument is that the kinetic energy of the falling mass was much larger than the structure could absorb.

Yes, but that argument cannot be tested until you specify the distribution over time for the attempted absorption. If the time interval is virtually instantaneous as Bazant assumes then the test will tell us it cannot be absorbed and the structure will fail. If the time interval is extremely long then the test will tell us it can be absorbed and the structure will hold up. Somewhere in between those two extremes is a threshold between structure failure and structure holding up.

How do you know where that threshold is? And how do you know what time interval the application was spread over (or more precisely, how it was distributed over time)?

[William Seger]

202. Last time for this

Bazant does analyze the "distribution over time for the attempted absorption" and does not assume "time interval is virtually instantaneous."

Where do you get the chutzpah to start an OP entitled "Bazant's progressive collapse math is bogus" when you don't understand his math?

Furthermore, I just gave you an extremely simple way to at least estimate what the columns would need to do in order to halt the collapse: They would need to decelerate the falling mass to 0 before they buckle. For smooth deceleration -- i.e. the case that produces the least impulse -- you can use either time or distance, because the are intrinsically correlated. Where is your answer to the question I asked in that post? Nowhere. Apparently you do not understand extremely simply math, either.

[eomer]

205. No, it is you who does not understand Bazant's calculations.

Bazant makes it quite clear that he treats Part C as though it is a rigid block. A rigid block transfers all of its kinetic energy at once when it collides with another object.

Here is one place where Bazant makes that clear (emphasis mine):

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 {formula omitted} where Et=tangential
modulus of steel in the loaded columns and p=mass density,
tends to zero as soon as the plastic or fracturing 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.

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/D25%20WTC%20Discussions%20Replies.pdf

Bazant takes credit in his calculations for 100% of the kinetic energy being applied against Part A at the instant that Part C collides with it. That is what "rigid" means.

Bazant's justification for treating the blocks as rigid might be valid if it weren't for the fact of crush-up of Part C. Given crush-up, the rigid assumption is completely invalidated.

[William Seger]

207. As near as I can tell, you haven't understood a single word I've said to you

... and I really don't think I write all that poorly that what I've said is that incomprehensible. I'm trying to think of some good reason to take the time to repeat it, and I can't think of any. Your inability to respond cogently to what I've said does not necessarily mean that I'm right, of course, just as your inability to come up with any valid criticism of Bazant's analysis to back up the bold claim in your OP does not necessarily mean that Bazant is right. It does, however, indicate that further argument with you is a complete waste of time.

[eomer]

208. No, I've understood your words. Let me try to rephrase my point more in the way you think of it.

You say that the Part A columns have to decelerate the Part C mass to zero before buckling. But, again, decelerate it to zero over what time interval? If Part C is a rigid block as per Bazant's assumption then that deceleration has to be accomplished over a very short (virtually instantaneous) time interval. This is the calculation that Bazant makes. With no give (assumed) in Part C, the time it would take (theoretically) before the Part C columns fail or accomplish deceleration has got to be a small fraction of a second.

If, on the other hand, Part C is not a rigid block and the Part C structure fails before the Part A structure does then the time interval over which the deceleration must occur is drastically different. If, hypothetically, the leading one-story structure of Part C fails before the leading one-story structure of Part A does then the result of the first such contest is that Part A fends off collapse for a time interval and a partial deceleration has been accomplished during that interval. Now there is a Part B in existence and a new leading one-story structure of Part C. If Part C wins again in this second collision then another interval has occurred during which Part A fends off collapse, partial deceleration has occurred and we have to keep going to see what happens. An iterative process ensues of successive Part C one-story structures failing before the leading one-story structure of Part A does. During all these iterations the deceleration of Part C is occurring gradually. The time for this process to occur may be at least several seconds based on the visual evidence.

Between Bazant's assumption and my hypothetical, there is a drastic difference in the time that the deceleration of Part C must occur. Bazantts interval would be a small fraction of one second; mine would be at least several seconds. It seems there could easily be an order of magnitude of difference, perhaps more.

I'm not claiming that collapse will not occur under my alternative explanation. I'm just claiming that we do not know whether collapse will occur until we do the calculations correctly. Bazant's calculation clearly requires the deceleration to occur within an unrealistically (erroneously, in other words) short period of time and therefore does not demonstrate what it claims to demonstrate.

[OnTheOtherHand]

203. well, it makes sense to me

I guess if I were convinced (as eomer apparently is) that I saw the upper floors substantially disintegrating on contact, I might take a different view -- although I can't quite figure out what the different view would be. That most of the mass is going over the side? I can't make that jibe with other things I know. That the upper block doesn't have a "compacted debris layer" at all, but rather is falling in a low-density cloud, while some sort of explosive chain progressively destroys the floors beneath it? Not So Much.

I hope all involved can agree that it doesn't necessarily matter whether the upper block is intact. To take your question one step further, 50,000 tons of sand would pack quite a wallop if it fell all at once.

[eomer]

191. You miss my point.

You continue to miss the point that crush-up did occur. It is impossible, therefore, for Part C to have imparted all the kinetic energy onto Part A in either an instant of time or a short interval up to the time at which the Part A columns would buckle.

If you take the hypothetical case of only crush-up initially then you can see the point more clearly.

In this hypothetical, the Part C leading edge begins applying some of the kinetic energy to Part A but the Part C leading edge buckles before the Part A leading edge does. Clearly Part C applied some of the kinetic energy to Part A during this time interval, but not all of it. Now a new leading edge of Part C continues impact with Part A (and a Part B that is piled on top of Part A). The new leading edge of Part C again buckles first before that of Part A does and a second time interval has occurred during which some but not all of the kinetic energy was applied to Part A. Continue with additional similar time intervals until at least half (and maybe more) of Part C has crushed-up. Now there has been a significant period of time during which the kinetic energy was gradually applied to Part A at a rate that Part A was able to resist.

I admit that the hypothetical is a bit too neat, but it is essentially what is seen in the video referenced elsewhere in this thread. Part A resists whatever energy Part C is able to apply against it for a significant time period during which Part C is crushing-up to half its original size or less. Obviously, therefore, Part C was not able to apply all the kinetic energy at once or even during the time interval it took to crush-up one floor. The application of a limited portion of that kinetic energy was spread over at least the time (and then some) that it took to crush-up at least half of the Part C floors. At the end of that time the remaining kinetic energy that wasn't already applied to Part A had been dissipated in various ways, ejected outboard, or was still oncoming in whatever part of Part C remained intact.

To claim that all the kinetic energy can be counted in determining whether the Part A columns will buckle in the initial impact is clearly false. No way is the leading edge of Part C able to deliver all that energy in that time interval.

Bazant's entire approach depends on the premise that crush-up will not occur. In that case you can count all the kinetic energy because it will keep being poured on by the unbuckled Part C until Part A buckles. But if Part C buckles first then all bets are off and Bazant's entire approach is flawed. Part C does appear to buckle first in the video, so Bazant's entire approach is flawed.

[William Seger]

201. No, I have answered that point more than once, and you've just ignored what I said

First, you still have not demonstrated that your impression of the "crush up" is an accurate observation. I'll post this once more (since you seem to have missed it the first time (:eyes:) :



I put those green lines on there to show you why I do not accept your description of what is happening. What I see is very little "crush up" relative to the distance that the top falls. It is not possible to tell much about what's happening after those frames because of the cloud of debris and smoke, and as I've said several times now, I'm not willing to accept imaginary descriptions as an argument.

Second, you still have not demonstrated why it matters. You merely claim that "Bazant's entire approach depends on the premise that crush-up will not occur." That is simply not true. It is not any kind of "premise"; it is a result of the differential equations he derives from first principles. He explains both mathematically and logically why it happens, and in case you also missed this (:eyes:), I'll give you the logical explanation again, which is completely absent from your description of what you believe is happening: The forces on part A and part C are not equal, because the momentum of the moving part B is applying a force to part A that it cannot apply to part C, because part C is moving in the same direction with the same velocity as part B. Furthermore, as I just said in a response to OTOH, Bazant does take into consideration that the debris layer does not really act as a solid object, so again you have an imaginary criticism of Bazant's analysis, due to not really knowing what's in there.

Bazant makes sense to me; you do not.

In addition to failing to respond to my objections to your arguments, you have completely ignored several other points that I've made. It's getting harder to justify the time it takes to respond to you.

[eomer]

204. My OP discussed my visual evidence but here it is again, packaged better.

The above frames (and others that are before, between, and after) can be seen here:
http://911research.wtc7.net/wtc/evidence/videos/st_nbc1.html

The frames I excerpted are:
4:02:00 / 6:03:00 / 8:04:00 / 10:05:00 / 12:06:00

And the video version of the same frames can be played here:
http://911research.wtc7.net/wtc/evidence/videos/docs/south_tower_collapse.mpeg

I lined the outline up with Part C in the first two frames and then with the top of Part C in the remaining frames. You may need to click through frame-by-frame to confirm that I've placed it correctly. In some cases the frame before or after helps determine where the top corner is. The continuity of the animation formed by the outlines in sequence is also an indication that they are placed correctly.

You can see that the bottom of the original Part C extends (theoretically) well beyond the crush zone by the end of this sequence. Therefore there is a portion of Part C that is missing from the bottom. It has crushed-up.

[Bolo Boffin]

206. 2002

[whatchamacallit]

112. Goalposts on the move

As I said before, you need to find something like an order of magnitude error in Bazant's simple model before you can argue that the building should not have experienced total progressive collapse.

Oh is that the accepted scientific threshold for "refutation"? Must of missed it... :rofl: So much effort to buttress such lameness.

[William Seger]

117. Not surprising

... you have no idea what's even being discussed. Yes, since Bazant's simple model analysis shows that there was approximately an order of magnitude more kinetic available than was necessary to crush the columns, you need to find an order of magnitude error to refute the conclusion: that the total collapse was inevitable after it got started. You probably should stay out of threads that involve a modicum of reasoning, whatcha.

[whatchamacallit]

119. heh, maybe so... (nt)

[Bolo Boffin]

108. Relying on disparity between Bazant Zhou's model and visual evidence is your flaw. n/t

[whatchamacallit]

111. Why rely on real visual evidence when you have totally theoretical numbers?

:crazy: The mind of the OCT...

[Bolo Boffin]

114. You also have misunderstood the purpose of Bazant Zhou.

It is fallacious to accuse Bazant Zhou of not doing something it was never intended to do. It's like blaming a Rothko for a lack of perspective drawing.

It is fallacious to dismiss what Bazant Zhou actually does because it does not do something you think it should be doing.

It is your assumptions that prevent you from understanding what Bazant Zhou does.

It is your own problem that you cannot understand how Bazant Zhou puts the visual evidence into a proper context.

The numbers don't lie. Bazant Zhou began the process of putting numbers to the visual evidence. In the course of doing that, Bazant Zhou demonstrated a simple numerical fact about those buildings - that the structure below had no ability to arrest the force of the descending upper section. Further work has refined that demonstration and gotten the numbers closer to the visual evidence, but this does not deny the validity of what Bazant Zhou demonstrated.

And you can be flippant about things you don't understand all the live-long day. You're only fooling yourself.

[whatchamacallit]

120. You missionaries are doing a great job of proselytizing

but it's still mumbo jumbo. Let's get one thing straight; he demonstrated nothing. He modeled a collapse mathematically. This does not constitute proof at all. Pretty much anything you can dream up can be simulated with the right inputs. Even more annoying is your "superior grasp of the subject". You're pimping calculations you don't even really get. But continue on with your charade if it makes you feel good. Didn't you mention you were/are an actor?

[OnTheOtherHand]

121. comparing his post to yours

I have to suspect that he does have a superior grasp of the subject. However, you're pretty good at personal attacks. (ETA: In fairness, he can deliver some zingers too.)

[SDuderstadt]

122. Our side has better and more sophisticated...

zingers.

[RUMMYisFROSTED]

40. Entertaining thread.

[Realityhack]

55. This thread is a perfect example of why non-engineers / physicists / etc. are not...

normally included in technical discussions. The posters criticizing Bazant don't even understand the purpose of the paper. They do not understand it much less are equipped to analyze it on a technical level.

It honestly is exactly like watching creationists try to talk about DNA when they don't even know the difference between a gene and a genome. In both cases the 'critics' are simply not equipped to even enter the discussion never mind make any meaningful contribution to it.

[whatchamacallit]

56. I forget, what is your field of expertise, hack?

Obviously YOU belong in technical discussions of this nature. Please present your credentials or kindly STFU.

[AZCat]

65. Credentials are somewhat irrelevant.

Judy Wood has a PhD. in ME, yet she still has shown a horribly poor understanding of basic dynamics. I knew people like her in school and have worked with a few others (although they tend to get pushed into management or sales).

[whatchamacallit]

67. We agree AZ

Some people in here like to pretend they gain expertise and authority by virtue of their beliefs. Bona fides by association if you will. Sort of infuriating...

[AZCat]

68. I was talking about something similar with my girlfriend last night.

Sometimes people get so used to credentials carrying an argument that they forget how to make a cogent one if someone doesn't necessarily accept them as an expert on the issue. Some of the other professional engineers I work with are this way, and it can come across as condescending. I know I've done it before, but I try to avoid it.

Regarding expertise and authority on account of someone's beliefs, we see that all the time in the political arena. How often is someones opinion dismissed because of their ideology? It's wrong, but easy to do.

[whatchamacallit]

69. You are wise (nt)

[AZCat]

70. I make lots of mistakes.

Best damn way to learn, in my oh-so-very humble opinion!

[procopia]

59. The purpose of the paper,

non-evidence-based and rushed to submission on 9/13/01, is questionable at best. Do you actually believe the purpose of the paper was to "start the discussion"? Like there would be no discussion otherwise?

[eomer]

64. Bazant's slip is showing.

His calculations predict zero crush-up. Crush-up clearly occurred in significant amount. Apparently the engineers are too busy admiring each others' equations to notice.

[spooked911]

209. well said-- the Bazant refutation is a joke

this thread is fun, but as is typical, the OCTists stubbornly cling to the notion that mathematical models PROVE something even when they have no similarity to actual data.

Good job, Eomer.

[OnTheOtherHand]

210. ROFL

So, you show up two years later to declare that eomer won the thread. Oh-kay.

[ryan_cats]

211. Like a Zombi

Like a Zombi, this story keeps popping up. What up?

[spooked911]

214. Just found it the other day. Sorry I missed it when it first came around.

It's still good, though.

Still trying to make time to do a thorough study and write-up on Bazant.

[OnTheOtherHand]

215. fair enough -- but there is a big problem in the OP

eomer, whom I like a lot, wrote in part:

Once you realize that Bazant's math is based on gross simplifications, all persuasive power is sucked out of it (if you're paying attention).

I guess that might make sense for a suitable definition of "gross," but the truth is that even back-of-the-envelope analyses can be legitimately highly persuasive -- or unpersuasive -- to people who know how to evaluate them.

It would make about as much sense to write, "Once you realize that the physics of climate change is based on gross simplifications, all persuasive power is sucked out of it (if you're paying attention)." The fact is: really simple climate models predict warming on average; really complicated models (albeit with severe simplifications) predict warming on average; we're actually observing warming on average; it takes some heroism worthy of a better cause to conclude that the models are utter crap, and it should be downright embarrassing to infer that from the mere fact that they use "gross simplifications."

[eomer]

216. That's a gross simplification of my argument.

OTOH, whom I like a lot, wrote in part:

I guess that might make sense for a suitable definition of "gross," but the truth is that even back-of-the-envelope analyses can be legitimately highly persuasive -- or unpersuasive -- to people who know how to evaluate them.

Yes, that's pretty much the point I was trying to make but apparently didn't word well enough.

Gross simplifications are neither inherently true nor inherently false. They are neither inherently safe nor inherently unsafe. But in the context of a paper that purports to demonstrate something mathematically their credibility starts at zero. You can't demonstrate something using a gross simplification unless you also demonstrate that the gross simplification is safe to make in the context in which it is used. Bazant's gross simplification starts at zero credibility and then stays at zero credibility because he never demonstrates why it is a safe simplification in the context.

Edit to add: in the case of meteorology the simplifications of the models are vetted empirically over time. Same thing with the simplifications of economic models. Paul Krugman wrote a blog entry recently pointing out that his models continue to hold up through the recent financial disasters while those that insist on supply-side solutions failed to correctly predict the behavior of the real-world system. Obviously this is all stuff you know, just pointing it out for the record.

[OnTheOtherHand]

217. well, you stuck around and offered better arguments

However, your assertion that Bazant's gross simplification "starts at zero credibility and then stays at zero credibility" is either false or equivocal. Many people have found it suitable for first-order analysis.

Yes, climate models are tested against reality over time. In this case, Bazant "predicts" that the towers should have collapsed, as indeed they did. Of course that isn't much of a feat, since the outcome was known in advance. But I don't see much analogy to supply side economics.

[eomer]

218. Here is the blog entry by Krugman that I was remembering:

...

I think this is an acceptable practice, as long as you keep your perspective. The models clearly aren’t literally true, and in no sense are you testing your theory. What you’re basically doing is elaborate thought experiments that are somewhat disciplined by the data, and which you hope are more informative than just plain guesses.

The point is that if you have a conceptual model of some aspect of the world, which you know is at best an approximation, it’s OK to see what that model would say if you tried to make it numerically realistic in some dimensions.

But doing this gives you very little help in deciding whether you are more or less on the right analytical track. I was going to say no help, but it is true that a calibration exercise is informative when it fails: if there’s no way to squeeze the relevant data into your model, or the calibrated model makes predictions that you know on other grounds are ludicrous, something was gained. But no way is calibration a substitute for actual econometrics that tests your view about how the world works.

Yet the freshwater guys have in large part exalted calibration into a substitute for econometrics. (I recall a story about one freshwater department that wanted to eliminate econometrics from the graduate curriculum and replace it with analysis, on the grounds that the models weren’t yet ready for testing. If anyone knows more about this, can you let me know?)

...

http://krugman.blogs.nytimes.com/2011/10/18/calibration-and-all-that-wonkish/

His point describes better than I could what I think about the Bazant model: it's an interesting thought experiment but gives very little help in deciding whether you are more or less on the right analytical track.

[OnTheOtherHand]

219. I don't think the analogy is very close

As I understand it, the rational expectations school turned to calibration because conventional econometric approaches weren't "working" with their models. They offered some justifications or rationalizations for this turn, but I don't think anyone disputes that it was a turn.

Bazant's various models of the WTC 1/2 collapses look like standard-issue engineering models to me -- and, as far as I can tell, to most engineers. It's true that they can't be tested against the collapses (or non-collapses) of other buildings like the Twin Towers, so in a sense we're all stuck without the equivalent of "actual econometrics." Maybe that is about as far as you intend the analogy to go.

ETA: Of course I'm not claiming to be an economist or an engineer!

[eomer]

220. Yes, that was as far as I intended the analogy to go.

The rational expectations school created a model. Their next step was to check whether that model worked. It didn't. They then threw in some tweaks to force it to work in some dimensions but there is no guarantee that it will then work in other dimensions.

Bazant created a model. His next step would be to check whether that model works. He has no way to do that. So he is stuck with a model that may be interesting but with no way to check against "actual econometrics" whether it does or doesn't work.

And I don't think the parts of the model I'm objecting to are standard-issue. If they are then Bazant (or someone on his behalf) should be able to point to lots of cases where they've been used before. Specifically, when in the past has a large section of a building falling onto a lower section of a building been assumed to be a rigid cube. What was the justification for that assumption or how was it checked against the real world to see whether it works. Or, alternatively, when was such an assumption made in some other engineering problem that can be demonstrated to be functionally equivalent to this problem.

[OnTheOtherHand]

221. wait, hang on a second

Are you saying that there are "lots of cases" in which a large section of a building has fallen onto the lower section? If so, then indeed we ought to have a useful baseline.

If not, then even the phrase "section... falling" strongly suggests to me that "rigid cube" (or cuboid) is a reasonable starting point. And, for heaven's sake, practically every physics problem I've ever done (the introductory ones, of course!) has made much that sort of simplifying assumption. Of course the question immediately arises: what makes the falling section more like a rigid cuboid than the section it is falling on? I think Bazant has answers to that (which include "look, if you don't like that model, here's a more complicated one that gives similar results"). Of course those answers are subject to debate.

It may not be facially obvious -- especially to non-engineers, but in some cases even to engineers -- whether a simple model is fatally flawed. But the mere assertion that the simple model might be fatally flawed isn't enough to render the model utterly unpersuasive.

[zappaman]

213. I agree spooked

science is stupid!

[spooked911]

222. science isn't stupid but apparently Bazant thinks we are stupid

certainly he's gotten away with extremely specious arguments-- because it suits a powerful constituency, people have lapped it up.

[William Seger]

223. Depending on who you mean by "we"...

... you could be right, but no, he has not "gotten away with extremely specious arguments." His analysis has not had any serious challenge from the engineering community but you refuse to consider the possibility that it's not because thousands of engineers have "lapped it up," but rather because people who understand have found it to be very solid in what it actually does. You and Eomer simply persist in misunderstanding Bazant's arguments and then disparaging the analysis on the basis of nothing but that misunderstanding and imaginary physics.

Try to prove me wrong by stating in your own words what you think Bazant claims to be demonstrating in his analysis, what the calculations are actually analyzing, and why it matters. One would think that would be a starting point for any critique, but you and Eomer seem to have skipped that step.

[deconstruct911]

212. Reminds me of a Nikola Tesla quote

"Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality. " ~ Nikola Tesla