NISTian black boxes - Oh, let me count the ways

[metamars]

The purpose of this thread is to cast light on what I'll call NISTian black boxes, as well as (what I believe) is the blindness of the NIST fan base regarding these black boxes. A NISTian black box is an insufficiently documented procedure, wherein a 'plan B' was pursued instead of an intial 'plan A', which affects the outcome of NIST's analysis in ways that can't be determined by the reader of the NIST docs. Indeed, I don't even think NIST knows - it's not just a question of documentation. Be that as it may, certainly the NIST apologists should be able to readily explain to us what's inside these black boxes, if their faith is of the scientific rather than religious type.

I should admit, from the beginning, that I haven't done my homework, in that the person to put the questions regarding the NISTian black boxes (NBB hereafter) should be somebody who understands the modeling technology. However, as nobody else has stepped forward to do this (including the now numerous engineering and architect professional members of ae911truth), I guess that I will plunge in where angels fear to tread! I have taken a graduate course in numerical methods, many years ago, but that in no way makes me suitable for the task at hand - even if I actually remembered most of what I had learned, which I don't.

The algorithm for producing the NBB's is pretty simple - load the NIST pdf file, search for the string "converge" (ignoring it in executive summaries), and record in this thread those instances where the plan B workaround for making the hitherto un-converging model converge. This will be followed by two question per incident, viz.,
Q1) what is the physical (as in "inherent physics captured in the software") difference in the two approaches, in general? The preferred form of this answer is in terms of list of various properties/behavior over a domain large enough to encompass the WTC scenario to which it is applied. I will guess that graphs are probably the best way to convey the information, though they'd ideally be accompanied by the equations from which they were derived.
Q2) what was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied? In particular, what was the quantitative effect of using the convergent method on the overall modeling behavior?

Some variation in this routine is expected, depending on the text, which I just happen to come across while using the "converge" string process. I don't recall NIST using the term "workaround", but it should be clear that I am talking about the computational method that was actually used, since the first method(s) contemplated either did not converge, or converged too slowly.

Now, 2) seems like a trick question, even to me. For if the first method, presumably involving the best guess of software widgets/algorithms/approximations that could be made by the NIST engineers, would not converge, how is answering 2) even possible? I don't know, but the answer may well be that it is never possible. OTOH, it may be possible to compute formulas for converging deltas between the two methods, some or all of the time.

It may turn out (I haven't looked at the NIST documents in a long time, I'm about to now) that even 1) is a trick question, of sorts. And the reason is that it may often be the case that even the convergent methods are not adequately documented. If the reader of NIST's 10,000 page report still cannot determine which elements of the toolbox were used at a given step in the modeling process (as well as whatever ancillary info was used), they sure as heck can't tell us what the deltas are with the (presumably) less documented non-converging methods.

I plan on only adding to this thread on weekends. This is not my life's work, even if this has proven to be a huge life diversion....

Also, I will not be going in order through the NCSTAR documents. I start with 5 examples in NCSTAR 1-6C.

OK, NIST apologists, this is your chance to really shine! Otherwise, some "twoofers" may come to the conclusion that proclaiming the NIST documents as an explanation was mostly an exercise of faith in NIST, rather than a fair (and of necessity, knowledgeable) evaluation of their work.


NBB #1: p. 12 / acrobat p.60
=======================
"To improve convergence in analysis, the negative slope in the stress-strain relationship after cracking or crushing in compression was removed, and the concrete was assumed to be plastic after cracking or crushing"

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?


NBB #2: p. 73 / acrobat p.121
========================
"To improve convergence in analysis, the negative slope in the stress-strain relationship after cracking or crushing in compression was removed, and the concrete was assumed to be plastic after cracking or crushing"

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?


NBB #3: p 77 / acrobat p. 125
===================
Gravity Plus Thermal Loading: The analysis of the truss model subjected to temperature time history was carried out statically; however, when the solution process did not converge, to overcome the convergence problem, the problem was solved dynamically with a 5 percent Rayleigh damping. The static analysis was then resumed when the acceleration and velocity became small.

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?


NBB #4: p. 84 / Acrobat p. 132
=========================
Creep in shell was included in the simplified truss model; however, it was not included when the simplified truss model was incorporated in the full floor model, because of convergence problems inherent in BEAM188 elements.

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?


NBB #5: p. 84 / Acrobat p. 132
========================
The concrete slab was modeled by SHELL181 elements with a temperature-dependent bilinear material model that had the same yield stength in both tension and compression. The yield strength was set to the compressive strength.

Q1) What is the physical difference between these two approaches, in general?

Comment Even a non-engineer like me knows that concrete does much better in compression than tension!

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?

[beachnut]

You need to explain why you are posting SPAM. Why not explain this to where it makes sense. I think you failed to read and understand NIST to make a rational post.

[metamars]

You need to explain why you are posting SPAM. Why not explain this to where it makes sense. I think you failed to read and understand NIST to make a rational post.

And I think that the religious faith of NISTian apologists is being challenged. I am not criticizing the report, per se, as much as I am criticizing the lack of information needed to determine the quatitative effects of numerous 'plan B' procedures undertaken by NIST, to escape convergence problems. Fortunately, NIST was honest enough to document the existence of numerous convergence problems.

It's not so much the information that is present in the report that (for the purposes of this thread) bothers me, it is the information not in the report which makes it impossible to figure out if and where NIST has gone wrong.

I have little doubt that most NIST apologists that post on debunker forums don't have the expertise to understand and explain the logical holes (NBB's), even if they were adequately documented. (In which case, we should rename them to NIST Decision Trees :) ). However, I also have little doubt that there is not even enough documentation presented by NIST to allow an individual with sufficient expertise to do this.

Even so, I invite others to prove me wrong.

[twinstead]

metamars do you REALLY think that nobody on this forum is capable of addressing your OP and will all run away when 'challenged'?

[pomeroo]

And I think that the religious faith of NISTian apologists is being challenged. I am not criticizing the report, per se, as much as I am criticizing the lack of information needed to determine the quatitative effects of numerous 'plan B' procedures undertaken by NIST, to escape convergence problems. Fortunately, NIST was honest enough to document the existence of numerous convergence problems.

It's not so much the information that is present in the report that (for the purposes of this thread) bothers me, it is the information not in the report which makes it impossible to figure out if and where NIST has gone wrong.

I have little doubt that most NIST apologists that post on debunker forums don't have the expertise to understand and explain the logical holes (NBB's), even if they were adequately documented. (In which case, we should rename them to NIST Decision Trees :) ). However, I also have little doubt that there is not even enough documentation presented by NIST to allow an individual with sufficient expertise to do this.

Even so, I invite others to prove me wrong.


And when Mackey, Newton's Bit, Rwguinn, beachnut, Gumboot, and other super-bright posters prove you wrong, you will...

LEARN ABSOLUTELY NOTHING AND CONTINUE SPOUTING THE SAME RUBBISH.

[metamars]

And when Mackey, Newton's Bit, Rwguinn, beachnut, Gumboot, and other super-bright posters prove you wrong, you will...

LEARN ABSOLUTELY NOTHING AND CONTINUE SPOUTING THE SAME RUBBISH.

Hopefully they will answer my questions on this very thread, so that others that have the same questions regarding the NBB's can see the answers, eloquently explained. In which case, nobody will care how I interpret their answers, right?

Most of my posts on this thread will not be of the scolding type, but rather quotes from the NIST docs, followed by a couple of very rational questions.

Or are the NIST docs some sort of Bible, that we have to accept without question, in fear of our soul being lost if we do not? That's certainly not my view.

Or are the quotations from NIST "spam"? Is that the problem? If so, that would suggest that we are only supposed to pay attention to the conclusions, and you should take up the question with NIST, itself, of why 10,000 pages, at a cost of $20 million, consists of so much "spam".

[twinstead]

The point is, metamars, that you will categorically reject ANY explanation of the points in your OP that don't point to an 'inside job'.

It's not like we aren't familiar with your tactics or anything, right?

[Quad4_72]

So basically metamars is saying that he is smarter than the hundreds of scientists and engineers who wrote the NIST report. He is also saying that he has somehow discovered some flaw in NIST's methods that no one else has ever discovered. The thousands of people in the scientific community who agree with NIST's work are clueless. Is this correct what you are implying metamars? And if so, how logical does this seem?

[DGM]

Metamars:
Do you believe that the reason for the NIST report was to convince laymen that the towers should have collapsed the way they did? It sure seems that way.

[metamars]

metamars do you REALLY think that nobody on this forum is capable of addressing your OP and will all run away when 'challenged'?

I'm expecting some serious answers (probably of a general "this is how we do things" type), a lot more of "who do you think you are?" type of responses, and at the end of the day, the NBB's will remain, by and large, NBB's.

Note that, in the case of NCSTAR 1-6C, while there are references, there are no footnotes. The conundrums inherent in the quotations either have no explicit explanation, or those explanations are hidden well. (Or I'm too dumb to see them. Let's not forget that logical possibility!)

[rwguinn]

T......
I should admit, from the beginning, that I haven't done my homework, in that the person to put the questions regarding the NISTian black boxes (NBB hereafter) should be somebody who understands the modeling technology. However, as nobody else has stepped forward to do this (including the now numerous engineering and architect professional members of ae911truth), I guess that I will plunge in where angels fear to tread! I have taken a graduate course in numerical methods, many years ago, but that in no way makes me suitable for the task at hand - even if I actually remembered most of what I had learned, which I don't.

.....l
NBB #1: p. 12 / acrobat p.60
=======================
"To improve convergence in analysis, the negative slope in the stress-strain relationship after cracking or crushing in compression was removed, and the concrete was assumed to be plastic after cracking or crushing"

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?

Conservative approach. Plastic assumes it will still carry load. Fractured/cracked/crushed= won't carry load. Bias in favor of collapse arrest

<<Duplicate question removed>
NBB #3: p 77 / acrobat p. 125
===================
Gravity Plus Thermal Loading: The analysis of the truss model subjected to temperature time history was carried out statically; however, when the solution process did not converge, to overcome the convergence problem, the problem was solved dynamically with a 5 percent Rayleigh damping. The static analysis was then resumed when the acceleration and velocity became small.

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?
when the equations don't converge in a non-realistic analysis, generally, more closely simulating reality will unstick the analysis


NBB #4: p. 84 / Acrobat p. 132
=========================
Creep in shell was included in the simplified truss model; however, it was not included when the simplified truss model was incorporated in the full floor model, because of convergence problems inherent in BEAM188 elements.

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied? sEE ABOVE



NBB #5: p. 84 / Acrobat p. 132
========================
The concrete slab was modeled by SHELL181 elements with a temperature-dependent bilinear material model that had the same yield stength in both tension and compression. The yield strength was set to the compressive strength.

Q1) What is the physical difference between these two approaches, in general?

Comment Even a non-engineer like me knows that concrete does much better in compression than tension!

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?
Conservative approach, and avoids non-linear modeling. The concrete should not go into tension under the load conditions given anyway

Now, go do your homework. Obvious to me you have never had to model and correlate with reality

[twinstead]

I'm expecting some serious answers (probably of a general "this is how we do things" type), a lot more of "who do you think you are?" type of responses, and at the end of the day, the NBB's will remain, by and large, NBB's.

Note that, in the case of NCSTAR 1-6C, while there are references, there are no footnotes. The conundrums inherent in the quotations either have no explicit explanation, or those explanations are hidden well. (Or I'm too dumb to see them. Let's not forget that logical possibility!)

False dilemma. An additional possibility is you are perfectly smart enough, in fact, you think you're smarter than the contributers to the NIST as well as any scientist who thinks that the NIST, while not perfect, is pretty much the best explanation.

Right?

[beachnut]

Even so, I invite others to prove me wrong.
Your own post, proves you wrong. You have failed to understand the NIST report and the goal of NIST on 9/11. What is new? You are making up things to argue about on the NIST report, and not doing a good job of it.

I'm expecting some serious answers (probably of a general "this is how we do things" type), a lot more of "who do you think you are?" type of responses, and at the end of the day, the NBB's will remain, by and large, NBB's.

Note that, in the case of NCSTAR 1-6C, while there are references, there are no footnotes. The conundrums inherent in the quotations either have no explicit explanation, or those explanations are hidden well. (Or I'm too dumb to see them. Let's not forget that logical possibility!)
I was serious; your post does not make sense if you really understand NIST and the overall topic. But you have some answers; good luck

[metamars]

Conservative approach. Plastic assumes it will still carry load. Fractured/cracked/crushed= won't carry load. Bias in favor of collapse arrest


NIST didn't concern itself with arresting (or not arrresting) global collapse. The questions concern the (undocumented) quantitative effects of their 'plan B' s on their models in the period before collapse initiation.



when the equations don't converge in a non-realistic analysis, generally, more closely simulating reality will unstick the analysis
sEE ABOVE

Please explain how they "more clearly simulated reality"? I read NBB #1 and NBB #2 just the opposite - they ended up using a less realistic analysis. In fact, I was assuming that's generally the case. If not, we may have an even less clear situation, overall. If NIST's 'plan A's' were generally the less realistic approach even theoretically possible (in terms of whatever computational tools they had at their disposal), they were that much more likely to 'miss', irregardless of any quantitative determination of just how much they missed.

In this case, NBB #3, I'm not sure. So, please also explain how, in NBB #3, they "more clearly simulated reality".


SEE ABOVE

The fact that NIST even mentions creep wrt floor elements means that it's a real and expected phenomena, no? So, even if floor element models with creep are present in a simplified truss model, but absent in the full floor model doesn't mean that creep, itself, was a simplification. Quite the opposite, correct?



Conservative approach, and avoids non-linear modeling. The concrete should not go into tension under the load conditions given anyway

Wouldn't a horizontal shell, loaded from the top, be in compression in it's inner (topmost) arc, and tension in it's lower arc? I'm assuming it undergoes catenary flexing.


Now, go do your homework. Obvious to me you have never had to model and correlate with reality

No, I intend to allow those people who have already know this stuff to illuminate the rest of us.

[metamars]

False dilemma. An additional possibility is you are perfectly smart enough, in fact, you think you're smarter than the contributers to the NIST as well as any scientist who thinks that the NIST, while not perfect, is pretty much the best explanation.

Right?

False dilemma. Another possibility is that NIST apologists, being human beings, are psychologically predisposed to overlook it's flaws, while those who are antagonistic to it, are more likely to see (and sometimes overestimate) it's flaws. Likewise qualified scientists, who may not really care that much about whether NIST is right or wrong, are nonetheless predisposed (one way or other) via their feelings towards the larger picture of possible government culpability in 911.

Read The Trouble with Physics, if you really believe that physicists are perfectly adequate at rising above tribalism. I can assure you, the author comes to the opposite conclusion, and I concur completely.

[1337m4n]

metamars, when you are trying to be friendly and polite, it helps if you don't make subtle accusations of "religious faith" in your OP.

Either be mean, or be nice. Don't try to go halfway; that's just being a poser.

[Apollo20]

Metamars:

Very interesting questions .... met with typical Nistian apologist responses!

Pomeroo:

I await with great anticipation the answers from "Mackey, Newton's Bit, Rwguinn, Beachnut, Gumboot, and other super-bright posters...."

Oh, that's right, Beachnut and Rwguinn did respond already .... but unfortunately I am not illuminated by their alleged "super-brightness".

[boloboffin]

Ryan Mackey has already spoken to this in his whitepaper:

Considering Mr. Douglas’s whitepaper, the author believes that many of his concerns are based on incomplete or mistaken readings of the NIST Report itself. Some of these are exacerbated by unusual or unclear wording within the Report. Other issues raised here echo limitations acknowledged by NIST itself. Having said this, a number of objections are valid, and a few others are not quite correct but instead lead one to additional fine points of valid criticism. In the author’s opinion, the following list of items should have been included, clarified, or explored in the NIST Report, as suggested directly or indirectly by Mr. Douglas:

*Completeness of Fire Data: NIST should have included all of its thermocouple data from the workstation tests. While this presents no reason to doubt NIST’s conclusions, given the 10,000 page bulk of the Report, there should be no objection to adding a few dozen additional charts.
* Completeness of Fire Testing: NIST’s single workstation fire tests would be more valuable if the effect of the hood on ventilation could be quantified. A seventh test without the hood active would provide this.
* Heat Content of Furnishings: NIST’s own experiments indicate about a 25% discrepancy in total heat content between different types of workstations, but the Report does not discuss the potential impact on fire behavior. If NIST explored the impact of this on the larger fire model, this could partially explain mismatches in burning time between model and reality, or resolve challenges regarding the total volume of combustibles levied by other researchers.
* Choice of Jet Fuel Load: NIST assumed and conducted experiments with 4 L of fuel per workstation, where a cursory analysis suggests that the actual distribution was closer to 12 L per workstation. While we do not expect this to make a large difference overall, at the very least a better explanation should have been given.
* ASTM E 119 Truss Tests: NIST’s tests of the as-built truss structures, with intact fireproofing, reflected the original design, and are of limited value when considering the upgraded SFRM applied as a retrofit. Additional testing would permit a better assessment of hypothetical fire situations. NIST should also have considered tests in this series that incorporated damaged SFRM or fire sprinklers in order to better quantify the range of expected responses.
* Verification of SAP2000 Models: The ASTM E 119 tests, particularly the surprise difference between restrained and unrestrained tests, also could have been used as an excellent verification of the floor system structural models. Given the expense of full-scale experiments in general and wealth of data provided by these tests, it is unclear why this opportunity was overlooked.
* Full Factorial Analysis: NIST’s population of different cases is not a full factorial analysis, but rather a more typical sensitivity analysis, ultimately pared down to an “incompressible list” of four cases. NIST should have better explained its choices in restricting itself to four cases. The author also suggests that additional cases, focused on varying the amount and placement of combustible material after impact, would greatly strengthen NIST’s hypothesis.

As noted in the main text, the author does not expect NIST to revisit its report at this time. It remains to be seen if other ongoing investigations resolve these questions, and whether there is any effect on the collapse hypothesis as a result. The author anticipates no impact on the core NIST hypothesis, but surmises that these questions, if resolved, will help to reconcile differences between NIST and other scientific studies.

Set that to There Is A Fountain Filled With Blood and we've got another hymn for the NISTian choir book.

[Max Photon]

Metamars:

Very interesting questions .... met with typical Nistian apologist responses!

Pomeroo:

I await with great anticipation the answers from "Mackey, Newton's Bit, Rwguinn, Beachnut, Gumboot, and other super-bright posters...."

Oh, that's right, Beachnut and Rwguinn did respond already .... but unfortunately I am not illuminated by their alleged "super-brightness".


No, Apollo, that's "superb-rightness."

[metamars]

metamars, when you are trying to be friendly and polite, it helps if you don't make subtle accusations of "religious faith" in your OP.

Either be mean, or be nice. Don't try to go halfway; that's just being a poser.

OK, I may have carelessly gone over the top. In point of fact, I consider it part of the human condition to be subjective, and furthermore consider this subjectivity to arise largely due to evolution. And this subjectivity is behaviorally (and likely biologically) related to religious behavior.

While I (nevertheless) believe in spiritual reality, to get a handle on what the heck I'm talking about, you can read the chapter on religion in E.O. Wilson's On Human Nature. No offense was meant, though I can see how somebody would take it that way. There used to be a tee-shirt, quoting bigot Archie Bunker, saying "There's a little bit of me in all of yous." Likewise, we're all subjective to one degree or another (including myself), and this has a religious aspect to it, understood from a socio-biological point of view.

[metamars]

Metamars:

Very interesting questions .... met with typical Nistian apologist responses!

Pomeroo:

I await with great anticipation the answers from "Mackey, Newton's Bit, Rwguinn, Beachnut, Gumboot, and other super-bright posters...."

Oh, that's right, Beachnut and Rwguinn did respond already .... but unfortunately I am not illuminated by their alleged "super-brightness".

Thanks. To be fair, rwguinn did make an initial stab at addressing the questions I posed.

[Jonnyclueless]

I love this whole creationist mindset:

"If we can just find some way of casting doubt on the scientific community, it will prove God exists"

Only in this case God = insidejob.

[rwguinn]

Thanks. To be fair, rwguinn did make an initial stab at addressing the questions I posed.
Actually, I spent 37 seconds trying to explain what is obvious to an engineer to someone who has no clue...
And who truthfully declared his incompetence at understanding modeling and modeling assumptions in the IP

[twinstead]

I love this whole creationist mindset:

"If we can just find some way of casting doubt on the scientific community, it will prove God exists"

Only in this case God = insidejob.

You mean all you have to do is create some doubt, no matter how small, in a prevailing theory, and you can insert any crazy alternative theory in the gap and declare it true by default without having to provide any evidence to support it at all?

That ROCKS!

[boloboffin]

You mean all you have to do is create some doubt, no matter how small, in a prevailing theory, and you can insert any crazy alternative theory in the gap and declare it true by default without having to provide any evidence to support it at all?

That ROCKS!

Knowing this will definitely increase my chances of hooking up tonight. SWEET!

[milesalpha]

You mean all you have to do is create some doubt, no matter how small, in a prevailing theory, and you can insert any crazy alternative theory in the gap and declare it true by default without having to provide any evidence to support it at all?

That ROCKS!

Also a popular tactic with Holocaust revisionists. No gas at x camp = no systematic program against the Jews. They never seem to get the idea that the odd small anomaly does not change the overall story.

[twinstead]

Knowing this will definitely increase my chances of hooking up tonight. SWEET!

Works for me every time, baby!

[pomeroo]

Metamars:

Very interesting questions .... met with typical Nistian apologist responses!

Pomeroo:

I await with great anticipation the answers from "Mackey, Newton's Bit, Rwguinn, Beachnut, Gumboot, and other super-bright posters...."

Oh, that's right, Beachnut and Rwguinn did respond already .... but unfortunately I am not illuminated by their alleged "super-brightness".


Okay, Frank, I deserved that. You are indeed "super-bright" and my omission of your name is inexcusable. I am truly ashamed of myself.

I may have overlooked you because you have not responded to the flood of idiotic e-mails we've both received lately. If you want to ignore them, I will gladly remove your address when I reply.

[pomeroo]

No, Apollo, that's "superb-rightness."



Not bad, Max: I'll give you that.

[tsig]

False dilemma. Another possibility is that NIST apologists, being human beings, are psychologically predisposed to overlook it's flaws, while those who are antagonistic to it, are more likely to see (and sometimes overestimate) it's flaws. Likewise qualified scientists, who may not really care that much about whether NIST is right or wrong, are nonetheless predisposed (one way or other) via their feelings towards the larger picture of possible government culpability in 911.

Read The Trouble with Physics, if you really believe that physicists are perfectly adequate at rising above tribalism. I can assure you, the author comes to the opposite conclusion, and I concur completely.

How do you know you are not succumbing to tribalism?

[tsig]

Metamars:

Very interesting questions .... met with typical Nistian apologist responses!

Pomeroo:

I await with great anticipation the answers from "Mackey, Newton's Bit, Rwguinn, Beachnut, Gumboot, and other super-bright posters...."

Oh, that's right, Beachnut and Rwguinn did respond already .... but unfortunately I am not illuminated by their alleged "super-brightness".

Compared to your brilliant genius all else are but a candle in the dark.

[metamars]

Actually, I spent 37 seconds trying to explain what is obvious to an engineer to someone who has no clue...
And who truthfully declared his incompetence at understanding modeling and modeling assumptions in the IP

Ah-h-h, I would say that it's almost obvious that there was something wrong with each of your answers. (Well, I'm not yet sure what to make about the one about unsticking the analysis via more realism.)


Certainly, you've provided no answer regarding quantitative differences between a single NBB 'plan A' and 'plan B', either in a general or WTC-specific case.

[1337m4n]

No, Apollo, that's "superb-rightness."

Max you are awesome; why do you not post more?

[Profanz]

metamars do you REALLY think that nobody on this forum is capable of addressing your OP and will all run away when 'challenged'?

metamars might if you don't address it. You do know that just posting just anything isn't necessarily addressing it don't you?

Oh sure you do.

[metamars]

How do you know you are not succumbing to tribalism?


Actually, I belong to the Tribe of Stop Shopping (http://www.revbilly.com/index.php). (We call it a "Church", but that's just for tax purposes. Clever, eh?) I've been trying, for years, to get into Max Photon's tribe, instead, but he/they won't let me. Something about me being cloaked in mildew. I just don't get it....

In any event, my tribe's subjectivity mostly has to do with materialism, not buildings falling down. E.g., you wouldn't want to ask us what we think a Cartier watch is worth, because we wouldn't give you a bag of pulverized concrete for it.

[beachnut]

Metamars:

Very interesting questions .... met with typical Nistian apologist responses!

Pomeroo:

I await with great anticipation the answers from "Mackey, Newton's Bit, Rwguinn, Beachnut, Gumboot, and other super-bright posters...."

Oh, that's right, Beachnut and Rwguinn did respond already .... but unfortunately I am not illuminated by their alleged "super-brightness".
Far from interesting, Metamars’ questions prove one thing. He has limited understanding of NIST’s goals, and work. Sorry for being too concise; his single page critique in the form of questions lacks merit. I guess I could be wrong;

… no, I was correct. (what would jesus say/I know he would not buy it)

Darn, you could have posted some super bright stuff, but you fell into my trap with me... (reminds me of a coldplay song)

Are only the anti-NISTian quibblers in need of NIST to understand or not understand 9/11?...

[Apollo20]

Beachnut:

I know you think you understand 9/11, but the rest of us un-illuminated types need help.

Have you read the NIST Report Beachnut?

I thought parts of it were ok,......

but the plot line was rather weak, ......

and the ending .......

Well, what can I say!

[chillzero]

Please - the first thing to do is to respond to the OP, and not the poster. Please keep the thread civil and on topic, without resorting to bickering.

[Sizzler]

Can someone laymanize OP for me? Generally speaking, what is this all about anyway?

[DGM]

Can someone laymanize OP for me? Generally speaking, what is this all about anyway?
The fact that the NIST report is not written for laymen. "Truthers" don't like that. Maybe it should be made into a youtube video.

[metamars]

Can someone laymanize OP for me? Generally speaking, what is this all about anyway?

You might say that it's about the difference between mathematics and physics. Numerical methods are iterative, and in order to claim you've solved some equations on a computer, you have to show that an error term can be made small enough to suit you, after having performed however many iterations it has taken to achieve this.

What if you run your computer for a week, through zillions of iterations, and your error term is still not suitably small? In other words, what if your numerical method won't converge?

Well, instead of buying a faster computer, waiting another week, trying to find a more efficient algorithm, etc., one thing you could do is to solve a similar problem, using equations that are similar, but still not the same.

In so doing, you are actually making different physical (as in physics) assumptions - i.e., you have changed the physics.

I am essentially putting NIST, and NIST'ians, on the spot by challenging them to quantify the differences between what the oiginal physics approach taken by NIST - which I believe is generally more realistic (contrary to what rwguin seems to believe) - and the one settled upon ('plan B', so to speak). Those that cannot be so quantified, I will continue to refer to as NBB's. These are analogous to religious "mysteries of the faith".

It seems apparent that such quantitative determinations don't exist - I don't recall them being convincingly demonstrated anywhere, though there may be some handwaving assertions that all is well. As I noted above, there's no footnotes in NCSTAR 1-6C, so the NBB's of 1-6C surely are not documented there.

I expect that, before all is said and done, there will be scores of instances of NBB.

Even "realistic" physics equations can (and generally will) have assumptions 'hidden' therein, that physicists are likely to forget about. Case in point - the basic wave equation for ideal stretched string! If your equation or equations are realistic 'enough', then they will have predictive power when experimentally tested. In the case of a WTC model, since so little of the forensic evidence was kept, just how are we supposed to know that there's any significant correlation between reality and NIST's models? (For floor elements, there wasn't much to keep. :-) But for columns, I will guess that creep was measurable or estimable. I'd appreciate it if knowledgeable engineers would inform us as to whether or not this is correct.)

Another point - which I don't particularly want to get into in this thread - is how do you know that even NIST'ian first choices which converged were adequate for the job? As sophisticated as it may have been, the computer modeling software still could not be used to predict the wall getting pulled in - it had to be added as an ad hoc assumption. That raises serious questions in my mind as to what other deficiencies were inherent in the entire NISTian enterprise.

[Jonnyclueless]

In other words, it's really easy to be critical of others work, but much harder to do it better yourself.

[beachnut]

Read The Trouble with Physics, if you really believe that physicists are perfectly adequate at rising above tribalism. I can assure you, the author comes to the opposite conclusion, and I concur completely.
String theory and NIST. Not the best analogy. The cool thing, people can use simple models to confirm NIST conclusions.




Goals of NIST, notice they do not address 9/11 truth fantasy ideas on 9/11
improvements in the way buildings are designed, constructed, maintained, and used;
improved tools and guidance for industry and safety officials;
revisions to building and fire codes, standards, and practices; and
improved public safety.Tools, like string theory, were not needed to help with these goals. The NIST report process does not share the quagmire of sorting out string theory. That quagmire only exists in your mind and others. If you have some far out fantasy just present your case and stop bringing up a report that has nothing to do with the implications of CT produced by your imagination.

Please don't explain the string theory book, I understand what you are trying to say; but you were wrong. You can’t mention the string theory junk and wave your hands and say the same problems are found in NIST; in the real world you present the evidence of the interaction similar to the things you are saying NIST is guilty of. And then show how this dynamic made NIST to miss the actual goals. Good luck presenting evidence instead of your fantasy ideas about how NIST interaction did not live up to your CT ideals.

[metamars]

The fact that the NIST report is not written for laymen. "Truthers" don't like that. Maybe it should be made into a youtube video.

The problem for this particular Truther is that the NIST report is not verifiable. It is not verifiable in two senses.

Firstly, even assuming that we had $20 million dollars to throw at the problem, NIST won't share evidence. (I think you can get the video and photographic evidence for a price, but I'm mostly thinking of metal samples.)

Secondly, most of the evidence is gone. In the case of the columns, which should show the creep that NIST claimed, this seems unforgivable.

Furthermore, as discussed in this thread, it has 'black boxes' of unknown, quantitative implications. While the cause for 'plan B's' arising is probably not NIST's fault, in general, they illustrate an uncertain degree of uncertainty, which should raise questions in everybody's mind regarding just how much explanatory power the NIST report really has.

By "uncertain degree of uncertainty", I mean that they can't quantify differences between the specific model they settled on, versus the specific model they would have chosen had all it's constituent pieces converged.

BTW, I'd guess that in many instances (maybe most), their plan B's were good enough. Unfortunately, I don't know that, and I don't think that NISTian apologists know that, or that even NIST knows that.

[Alt+F4]

I am essentially putting NIST, and NIST'ians, on the spot...

You are in no way, shape or form putting NIST on the spot. You are posting on an educational Internet forum. If you want to "give it" to NIST then file a compliant in federal court, protest in front of their headquarters, and/or contact each of the 300+ people who wrote the report and discuss your findings with them.

I am a fan of the New York Mets, does that make me a Metian?

[metamars]

[COLOR=black][FONT=Verdana]String theory and NIST. Not the best analogy.


The subject of the book is in large part the string theory community. Not only does Smolin, the author, speak of tribalism amongst physicists, he also relates the story of him writing about such problems, submitting to a journal, getting rejected, and then, upon inquiry, being told that it is nothing new to the journal readers. (I think it was a journal of education, but I don't remember.)


And just like physicists have told Smolin that they fear for their jobs and career if they buck the string theory parade (and thus they remain anonymous), I've heard reports of engineers not buying the NIST story at all, but keeping their mouths shut (and requesting anonymity). (BTW, it appears that there's been a backlash, and current job openings of particle theorists include no string theory positions. Looks like Smolin and Woit have partially succeeded in trying to get some balance of research foci.)

Not all, though. When I did my survey of civil engineers, one of them asked me what I thought had brought down the WTC towers. When I told him "CD", he laughed. OTOH, another engineer in my survey hadn't even heard of the collapse of WTC7, and since engineers in an academic department socialize on a regular basis (after seminars, and such), that suggests that nobody else in the department knew, either.




The cool thing, people can use simple models to confirm NIST conclusions. produced by you.

Using gross approximations to confirm a sophisticated analysis which, nevertheless, I am saying was lacking clarity and almost certainly capacity to nail down the collapse, is hardly the way to go. Gross approximations are what you use when you can't do any better, or don't care to.

[beachnut]

- i.e., you have changed the physics.

You make this up as you go?

[metamars]

You are in no way, shape or form putting NIST on the spot. You are posting on an educational Internet forum. If you want to "give it" to NIST then file a compliant in federal court, protest in front of their headquarters, and/or contact each of the 300+ people who wrote the report and discuss your findings with them.


Fine. I am putting the NIST report on the spot. When I have gone through the NIST report, I will create a summary document containing all of the NBB's I find, and send it off to NIST. I don't expect to hear back from them.

If I thought that filing a complaint in federal court, protesting in front of their headquarters, and/or contacting each of the 300+ people who wrote the report would do any good, I might consider it.

I think a better idea is to do what Smolin and Woit did regarding lemming-like, unscientific behavior in the string theory community, viz., write popular books. Maybe Dr. Greening would care to write such a book. I've got better things to do.

I didn't even want to do this thread, but nobody else stepped forward. I suggested this topic at physorg (http://www.physforum.com/index.php?showtopic=19501&st=330&#entry306600) back in January.


I am a fan of the New York Mets, does that make me a Metian?
The word "fan" is from the Greek "fanaticos". Guess what that means?

It's extraordinarily unlikely that, being a fan of a particular sports club, allows you to more objectively view their strengths and weaknesses. In fact, I claim that generally the opposite is true (with the fan skewing his/her "analysis" in favor of the home team), and that this is a testable hypothesis. To test it, you could study the betting record of fan vs. non-fan bettors, obviously in a game where the fan's team is playing.

As for those fans who become completely fanatical, some of them end up killing others at sporting events. Think "soccer", here.

So, yes, you are a "Metian", understood as somebody who is not likely to be an objective critic of the Mets, due to your attachment to them. If you read On Human Nature be E.O. Wilson, you may agree with me that this is not completely bad, and, in fact, may have allowed humans to survive! Unfortunately, whatever the survival value of subjective adherence to the group mythology may be, it is also antithetical to the scientific process and ethic.

[metamars]

You make this up as you go?

Do you understand the difference between substituting a more efficient algorithm for solving the same set of equations, vs. changing the equations themselves that you are trying to solve?

[beachnut]

The problem for this particular Truther is that the NIST report is not verifiable. It is not verifiable in two senses.

Firstly, even assuming that we had $20 million dollars to throw at the problem, NIST won't share evidence. (I think you can get the video and photographic evidence for a price, but I'm mostly thinking of metal samples.)

Secondly, most of the evidence is gone. In the case of the columns, which should show the creep that NIST claimed, this seems unforgivable.

Furthermore, as discussed in this thread, it has 'black boxes' of unknown, quantitative implications. While the cause for 'plan B's' arising is probably not NIST's fault, in general, they illustrate an uncertain degree of uncertainty, which should raise questions in everybody's mind regarding just how much explanatory power the NIST report really has.

By "uncertain degree of uncertainty", I mean that they can't quantify differences between the specific model they settled on, versus the specific model they would have chosen had all it's constituent pieces converged.

BTW, I'd guess that in many instances (maybe most), their plan B's were good enough. Unfortunately, I don't know that, and I don't think that NISTian apologists know that, or that even NIST knows that.
You seem to be paranoid. Why? You analytical skills may be suffering from the very thing you try to pin on NIST; some tribal string theory political mayhem. Are you leading a new dark ages type of anti-intellectual extremism movement.

You need to back up your allegations with claims that are not so transparently wrong. The only people you fool maybe PhDs in chemistry who hold giant grudges against NIST. Once again, NIST is not needed to explain 9/11. Read the goals of the NIST report on 9/11. Relax, pursue your own independent CT, all you lack is evidence. Stop wasting time on NIST; this is a tangent; Got math?

Your post illuminated someone's bias against some unknown ... good job

[TexasJack]

The word "fan" is from the Greek "fanaticos". Guess what that means?

It's extraordinarily unlikely that, being a fan of a particular sports club, allows you to more objectively view their strengths and weaknesses. In fact, I claim that generally the opposite is true (with the fan skewing his/her "analysis" in favor of the home team), and that this is a testable hypothesis. To test it, you could study the betting record of fan vs. non-fan bettors, obviously in a game where the fan's team is playing.

As for those fans who become completely fanatical, some of them end up killing others at sporting events. Think "soccer", here.

So, yes, you are a "Metian", understood as somebody who is not likely to be an objective critic of the Mets, due to your attachment to them. If you read On Human Nature be E.O. Wilson, you may agree with me that this is not completely bad, and, in fact, may have allowed humans to survive! Unfortunately, whatever the survival value of subjective adherence to the group mythology may be, it is also antithetical to the scientific process and ethic.

Well, your analogy falls flat on its face. I'm willing to bet that the average "fan" of a sports team is more critical of their team and the decisions that they make than that of opposing teams. Have you ever been at a game where the home team fans booed? Every read a sports blog when a team management makes a poor decision?

[beachnut]

Do you understand the difference between substituting a more efficient algorithm for solving the same set of equations, vs. changing the equations themselves that you are trying to solve?
I understand if you had something on NIST to show they did not live up to their goals you could replace the entire NIST team with your methods and expertise at computer modeling.

Yet, when I ran algorithms in the lab, they were experimental. And since we knew the outcome, changing the algorithm to arrive at the correct answer was actually a good idea. Then testing, apply the new algorithm across data sets was the hard part. I am starting to think you missed something when you post your ideas on math/physics and computer modeling. When I see your posts, I see someone, like me, who sometimes has problems grasping large systems, and making faulty analogies and error filled questions.

You make allegation about NIST and your ideas are full of errors. Someone who has more time and knowledge on this subject at their fingertips, will show, and have shown you the errors you ignore, and continue to make.

To simplify your position for me: you think NIST failed in meeting goals, you fail to show which goal they have failed at. But you are caught up in the details you do not understand. Then you try to compare this to a book by someone on string theory, who actually acknowledges the work in string theory has made important math advances, and thinks it is time to move on with no theory in sight. Your convoluted comparison is flawed. If you have no need of NIST goals; move on, you have NO valid theory in sight~!

[Heiwa]

I think the NIST report is crystal clear. After 10 000 pages of analysis NIST suggests that some local strucural failures developed up top in the 240-280+ columns on the 4 000 m² large initiation floors due to the heat which resulted in sudden release of a lot of potential energy, PE, (the upper block suddenly dropped down as a solid hammer) which in turn exceeded what the structure below could absorb. Global collapse ensued. Brilliant. How much PE we are talking about is not given and there is no calcuations what the structure below could absorb. Normally not very much PE is released due to local failures and in most cases any local collapses are quickly arrested by intact structure that may just cause some further local failures, but NIST does not consider that. The report stops at "Global collapse ensued"! There is no evidence that global collapse ensued due to some local failures due to heat.

I see that Apollo20 is back in action. Apollo 20 suggests, if I understand correctly, that the upper block, apart from providing a lot of PE, had a very solid bottom that pushed down the structure below. The upper block was the strongest part of the whole building and when it got loose - the building below collapsed while the upper block was intact. Fantastic. Seen on all videos, of course. I wonder why NIST missed that? Such an obvious answer. Why complicate the analysis like NIST when Apollo20 in a short article, with Bazant, explains everything?

[Jonnyclueless]

So any study where the physical evidence isn't freely distributed among anyone who wants it is unreliable?

Perhaps someone could list some research that does what metamars wants. What's an example of a study on a disaster where all the components were freely sent to any and everyone ho wants them? How about some plane accidents? Does the NTSB just send the plane parts to anyone who asks? And does this mean that their studies are farce?

[metamars]

Well, your analogy falls flat on its face. I'm willing to bet that the average "fan" of a sports team is more critical of their team and the decisions that they make than that of opposing teams. Have you ever been at a game where the home team fans booed? Every read a sports blog when a team management makes a poor decision?

I agree that some fans have a pre-disposition to boo the home team - especially New Yorkers. :) Nevertheless, the "critical" I'm concerned about is in the sense of "objective". I'm arguing that a fan will be less objective (with skewing in favor of the home team). I suppose, though, that a better way of testing a hypothesis of non-objectivity is to simply study the difference between fan vs. non-fan betting records (on games in which they've both bet), regardless of whether the fan votes for or against his team. In fact, I'll bet .25 cents that such a study has been done by somebody, somewhere. :)

As for whether the negative (boo-likely) fans outnumber the positive (cheer-likely) fans, I doubt it. On a bad day/steak/season, cheer-likely fans have nothing much to cheer about! If 1% of the crowd boos loudly, that's what people will remember.

Certainly, as applying these notions to the NISTians, I see almost no evidence of boo-likely fans. Mackey has, at least, made technical criticisms of the report. Otherwise,....... On this thread, aside from rwguinn, who only took an initial stab at answering my questions (and seems to have most everything wrong), nobody else has attempted answering directly. Also, the ratio of non-technical to technical comments is extremely high. Which sort of comment do you think is more prone to be shaded by emotions and genes?

As for the dissonance between a fan being less critical of the team, while more critical of individuals comprising that team, both of these subjective attitudes makes sense, to me, ito evolutionary biology. A chain is only as strong as the weakest link, get rid of the weak link, blah, blah. I have to admit, though, that I don't think EO Wilson ever said this, nor any other evolutionary biologist (not that I've read much in the field.)

[EventHorizon]

In any event, my tribe's subjectivity mostly has to do with materialism, not buildings falling down. E.g., you wouldn't want to ask us what we think a Cartier watch is worth, because we wouldn't give you a bag of pulverized concrete for it.

I'm curious. How many bags of pulverized concrete do you not pay for your internet connection?

[Spud1k]

This is exactly analogous to what us atmospheric scientists have to put up with when you have climate change sceptics criticising global climate models - their problem isn't that they've found a legitimate problem with the model, they simply find somewhere where an assumption is made and build up the strawman from there. The point is that their issues don't come from having an informed opinion, they come from ignorance.

At least metamars is upfront in saying he doesn't understand the ins and outs of the model, but it still doesn't make his questions a valid criticism. All models have to make assumptions and simplifications; if one wants to make the case that these would significantly affect the outcome and the conclusions, someone has to show - not speculate - this to be the case.

[Apollo20]

Spud1k:

As intimated by Jean-Francois Lyotard in his book "The Postmodern Condition: A Report on Knowledge", science has always been in conflict with narratives. Judged by the yardstick of science, the majority of these narratives (as with NIST's spin on the collapse of WTC 1 & 2) prove to be fables.

But to the extent that science claims to seek the truth, it is obliged to legitimate the rules of its own game.....

[metamars]

This is exactly analogous to what us atmospheric scientists have to put up with when you have climate change sceptics criticising global climate models - their problem isn't that they've found a legitimate problem with the model, they simply find somewhere where an assumption is made and build up the strawman from there. The point is that their issues don't come from having an informed opinion, they come from ignorance.

At least metamars is upfront in saying he doesn't understand the ins and outs of the model, but it still doesn't make his questions a valid criticism. All models have to make assumptions and simplifications; if one wants to make the case that these would significantly affect the outcome and the conclusions, someone has to show - not speculate - this to be the case.

Do you have good reasons to prefer one model, run into convergence issues which you can't solve, and then say "the heck with it, we'll just change the model, to something less realistic but more solvable, and trust that it's good enough, even though we don't have a clue how much it'll change our model's predictions."?

[B3LYP/CEP-31G(d)]

Do you have good reasons to prefer one model, run into convergence issues which you can't solve, and then say "the heck with it, we'll just change the model, to something less realistic but more solvable, and trust that it's good enough, even though we don't have a clue how much it'll change our model's predictions."?


If a model encounters convergence issues, do you actually believe there will even be any predictions against which to measure their change on switching models?

More importantly, do you even understand the concept of convergence within computational models?

[H'ethetheth]

Do you have good reasons to prefer one model, run into convergence issues which you can't solve, and then say "the heck with it, we'll just change the model, to something less realistic but more solvable, and trust that it's good enough, even though we don't have a clue how much it'll change our model's predictions."?Yes, of course you have good reasons to do that. The engineers also had a good clue how the changes affect the outcome, namely on the side of safety.
The facts are that the buildings collapsed; erring on the side of safety in a model means erring on the side that will disprove your hypothesis (in this case collapse initiation).
To clarify even more: Say you simplify the model without thinking about erring on the safe side. You can then get either collapse arrest, in which case you know you've made a modelling error, or you get collapse initiation, in which case you've either done it right or created a model that has nothing to do with reality but just happens to create the right outcome.
If you err on the side of collapse arrest you do no thave this problem.
Does that make sense to you?

[Spud1k]

Spud1k:

As intimated by Jean-Francois Lyotard in his book "The Postmodern Condition: A Report on Knowledge", science has always been in conflict with narratives. Judged by the yardstick of science, the majority of these narratives (as with NIST's spin on the collapse of WTC 1 & 2) prove to be fables.

But to the extent that science claims to seek the truth, it is obliged to legitimate the rules of its own game.....

...which is all just a fancy way of speculating that in this case, the science might not be right in an objective sense. Seeing that this speculation originates purely from a lack of understanding, it's doesn't really carry much weight.

The truth movement has had quite a while now to come up with a more convincing and substantiated argument against the NIST model, but hasn't done so yet. This just leads me to suspect that it never will.

[Spud1k]

Do you have good reasons to prefer one model, run into convergence issues which you can't solve, and then say "the heck with it, we'll just change the model, to something less realistic but more solvable, and trust that it's good enough, even though we don't have a clue how much it'll change our model's predictions."?

A model that doesn't converge is useless. If you have to make simplifications to make it do so, you generally go for the most conservative scenario.

But anyways, you kind of miss my point. The truthers try to make the case that the tower couldn't have collapsed from the impact and fire damage but haven't done anything nearly as thorough as what NIST have. Their case is based on guesswork only and the onus is on them to show, not speculate, where NIST went wrong.

[GregoryUrich]

A model that doesn't converge is useless. If you have to make simplifications to make it do so, you generally go for the most conservative scenario.

But anyways, you kind of miss my point. The truthers try to make the case that the tower couldn't have collapsed from the impact and fire damage but haven't done anything nearly as thorough as what NIST have. Their case is based on guesswork only and the onus is on them to show, not speculate, where NIST went wrong.

I think you may be missing the point Spud. It doesn't really matter that some truthers try to make any particular case. This thread is about whether NIST has proved their case scientifically (as many JREF regulars like to claim) more specifically whether the simplifications were in fact more conservative. It is clearly NIST's responsibility to describe and justify their simplifications. Otherwise, no one can possibly validate or invalidate their results.

So how are we doing...are we having fun yet? I have only seen one attempt on this thread to actually deal with the topic. Rwguinn has provided some answers and metamars has pointed out his issues with the answers provided at which point Rwguinn resorts to insults. That is our current status...until of course metamars adds some more NBBs.

Excellent topic metamars!

[Hokulele]

So, yes, you are a "Metian", understood as somebody who is not likely to be an objective critic of the Mets, due to your attachment to them. If you read On Human Nature be E.O. Wilson, you may agree with me that this is not completely bad, and, in fact, may have allowed humans to survive! Unfortunately, whatever the survival value of subjective adherence to the group mythology may be, it is also antithetical to the scientific process and ethic.


Bit of a derail, but I have read On Human Nature, and while there may be some interesting ideas, there are several major flaws in socio-biology. It certainly doesn't support your points regarding group behavior. You may want to take this up in the Science sub-forum.

[Spud1k]

I think you may be missing the point Spud. It doesn't really matter that some truthers try to make any particular case. This thread is about whether NIST has proved their case scientifically (as many JREF regulars like to claim) more specifically whether the simplifications were in fact more conservative. It is clearly NIST's responsibility to describe and justify their simplifications. Otherwise, no one can possibly validate or invalidate their results.

I can't claim to know much beyond the basic physics and how finite element models work in general, but all the statements quoted in the OP (except for the dynamical modelling of the trusses - I'm a bit rusty on that) immediately strike me as the way of taking the assumption that would make a collapse least likely. For instance, modelling concrete as plastic after it gives would mean it would offer more strength than is realistic.

Also, it is worth pointing out that a lack of convergence doesn't necessarily mean that there is a question of the ultimate outcome; this means that there is most likely ambiguity as to exactly how the collapse took place, not whether it would take place. This is especially true of the assumptions regarding dynamics, which would only come into effect once stuff started moving.

[H'ethetheth]

I think you may be missing the point Spud. It doesn't really matter that some truthers try to make any particular case. This thread is about whether NIST has proved their case scientifically (as many JREF regulars like to claim) more specifically whether the simplifications were in fact more conservative. Seriously? It's pretty clear they're more conservative if you know a little about mechanics of materials.


So how are we doing...are we having fun yet? I have only seen one attempt on this thread to actually deal with the topic. Rwguinn has provided some answers and metamars has pointed out his issues with the answers provided at which point Rwguinn resorts to insults. That is our current status...until of course metamars adds some more NBBs.

Excellent topic metamars!
That means you haven't payed a lot of attention. The only issue I could see with rwguinn's first post is his ambiguous "see above" remark. So if I may recap:
Issue 1: The negative stress-strain relation mentioned means that in that region, the more elongation you impose on the material, the less it will resist. Remove this area of the stress strain graph and the modelled concrete becomes stronger in the plastic region.
Issue 2: identical to issue1.
Issue 3: Static analysis (all velocities and accelerations assumed negligible) is replaced by dynamic analysis (velocities and accelerations allowed) at times where accelerations are significant. This is more accurate physically.
Issue 4: No creep in the floor shells means no plastic deformations until yield stress. This makes the modelled slab more rigid than the real thing.
Issue 5: Concrete is indeed stronger in compression than in tension, therefore the modelled slab is stronger than the real thing.

As for this:

Wouldn't a horizontal shell, loaded from the top, be in compression in it's inner (topmost) arc, and tension in it's lower arc? I'm assuming it undergoes catenary flexing.
Take a look at the floor's construction. The concrete is only on top of the whole truss + floor pan thing; the thing bends as a whole.
In other words, you would have a point if the whole floor truss were made of concrete which is, incidentally, why it isn't.

[Lurker]

I do Finite Element Analysis for a living so I'll have a go at this.


NBB #1: p. 12 / acrobat p.60
=======================
"To improve convergence in analysis, the negative slope in the stress-strain relationship after cracking or crushing in compression was removed, and the concrete was assumed to be plastic after cracking or crushing"

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?


Hmm, to be honest, I don't do FEa on concrete so am unfamiliar with the specific material behavior of concrete. A negative slope for modulus causes convergence problems in FEA codes. What I do, typically, is to add damping in to model. A quick check of the enegy due to the artifical dampers can minimize error. But your quote indicates they changed the material model to get rid of the negative slope and instead made it a plastic area. The use of an elastic-plastic model would certainly help convergence. As to the error, I don't think it would be significant as long as they assumed perfect or nearly perfect plasticity.



NBB #3: p 77 / acrobat p. 125
===================
Gravity Plus Thermal Loading: The analysis of the truss model subjected to temperature time history was carried out statically; however, when the solution process did not converge, to overcome the convergence problem, the problem was solved dynamically with a 5 percent Rayleigh damping. The static analysis was then resumed when the acceleration and velocity became small.

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?


It sounds like they changed from an implicit code to an explicit code for a portion of the analysis here. Again, this is very typical for FEAs as explicit can be used to solve specific types of problems that an implicit code will choke on. For explicit, damping is almost always used to damp the result as otherwise you get a lot of noise in the solution. A 5% damping does not seem excessive but any FEA engineer worth his pay would check the energy of the damping versus the total energy of the system and ensure it is not too high. 5% would be kind of high but not terribly so.


NBB #4: p. 84 / Acrobat p. 132
=========================
Creep in shell was included in the simplified truss model; however, it was not included when the simplified truss model was incorporated in the full floor model, because of convergence problems inherent in BEAM188 elements.

Q1) What is the physical difference between these two approaches, in general?

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?

I can't answer this one without looking at the results more closely.


NBB #5: p. 84 / Acrobat p. 132
========================
The concrete slab was modeled by SHELL181 elements with a temperature-dependent bilinear material model that had the same yield stength in both tension and compression. The yield strength was set to the compressive strength.

Q1) What is the physical difference between these two approaches, in general?

Comment Even a non-engineer like me knows that concrete does much better in compression than tension!

Q2) What was the physical, quantitative difference which accrued by using the workaround in the specific WTC scenarios to which this workaround was applied?
[/quote]
Good point about concrete in tension vs compression. I'd assume they lazily set the tension value like they did because the concrete in the model was not in tension. If the concrete did undergo a tensile load then the material model would be wrong.

Lurker

[rwguinn]

I....

So how are we doing...are we having fun yet? I have only seen one attempt on this thread to actually deal with the topic. Rwguinn has provided some answers and metamars has pointed out his issues with the answers provided at which point Rwguinn resorts to insults. That is our current status...until of course metamars adds some more NBBs.

Excellent topic metamars!
Actually, not an insult, unless you consider that he insulted himself by pointing out that I should admit, from the beginning, that I haven't done my homework, in that the person to put the questions regarding the NISTian black boxes (NBB hereafter) should be somebody who understands the modeling technology. However, as nobody else has stepped forward to do this (including the now numerous engineering and architect professional members of ae911truth), I guess that I will plunge in where angels fear to tread! I have taken a graduate course in numerical methods, many years ago, but that in no way makes me suitable for the task at hand - even if I actually remembered most of what I had learned, which I don't.
It is very nearly impossible to explain what the assumptions mean to someone who doesn't know what modeling is actually intended to accomplish.
Negative slope on the stress-strain curve makes FEM programs belch and give up in the non-linear calculation. So, what they did was make it flat-line at the inflection point, which actually increases the stiffness value, allowing energy absorption. That is what is meant by making it plastic.

This was a non-linear solution in two ways:
1) The material (S) were non-linerar (concrete tension/compression), Steel at or above the yield point (and I would assume they also got rid of the "knee" where the slope goes negative also)
2) the geometry changed radically as failure was initiated.
In order to reach failure initiation, simplifying assumptions had to be made due to the non-linearities. Allowing fracture brings us to the same problem as modeling Failure to completion--many more unknowns than equations to describe them. So, they simplified by not allowing fracture--a conservative assumption.

[Spud1k]

Good point about concrete in tension vs compression. I'd assume they lazily set the tension value like they did because the concrete in the model was not in tension. If the concrete did undergo a tensile load then the material model would be wrong.

Whatever their reasons, I think the point regarding the OP is that the model would overestimate the strength of the concrete and therefore make collapse initiation, if anything, less likely.

[Lurker]

This was a non-linear solution in two ways:
1) The material (S) were non-linerar (concrete tension/compression), Steel at or above the yield point (and I would assume they also got rid of the "knee" where the slope goes negative also)
2) the geometry changed radically as failure was initiated.
In order to reach failure initiation, simplifying assumptions had to be made due to the non-linearities. Allowing fracture brings us to the same problem as modeling Failure to completion--many more unknowns than equations to describe them. So, they simplified by not allowing fracture--a conservative assumption.

I would add that there was probably a third nonlinearity in teh model - contact. So the model hit the trifecta of nonlinearities;

1. Material
2. Large Scale deformation
3. Contact

[Lurker]

Whatever their reasons, I think the point regarding the OP is that the model would overestimate the strength of the concrete and therefore make collapse initiation, if anything, less likely.

Agreed. My saying it could be wrong was in regards to providing an inaccurate solution but still provide a conservative estimate as you say.

[rwguinn]

I would add that there was probably a third nonlinearity in teh model - contact. So the model hit the trifecta of nonlinearities;

1. Material
2. Large Scale deformation
3. Contact

Which is likely why they went with plastic rather than fractured in the concrete material properties. Eliminates a non-linearity and provides a conservative approach

[GregoryUrich]

Which is likely why they went with plastic rather than fractured in the concrete material properties. Eliminates a non-linearity and provides a conservative approach

Good work gentlemen. Thanks for the focus on the OP. I think you have provided reasonable explanations.

[beachnut]

Good work gentlemen. Thanks for the focus on the OP. I think you have provided reasonable explanations.
I think this thread can be used as a trap to snare people who agree with the OP author and expose they know less about NIST than the author's error filled questions.

[rwguinn]

Good work gentlemen. Thanks for the focus on the OP. I think you have provided reasonable explanations.
I guess we can all hang up our guns, folks. The battle is over and won.
GregoryUrich approves:rolleyes:

[H'ethetheth]

I guess we can all hang up our guns, folks. The battle is over and won.
GregoryUrich approves:rolleyes:Now now, I think this is a very un-trutherlike reaction from Gregory Ulrich. I was pleasantly surprised, in fact.

[Whiplash]

I am a fan of the New York Mets, does that make me a Metian?


No, that would simply make you irrational.

;)

[twinstead]

I thought a metian was just a really selfish person?

[GregoryUrich]

I guess we can all hang up our guns, folks. The battle is over and won.
GregoryUrich approves:rolleyes:

Max Photon is rolling over in his futon. Save us with something poetic Max.

By the way, my teenagers have the same reaction to my approval. Does that say something about you or me?:)

[rwguinn]

Max Photon is rolling over in his futon. Save us with something poetic Max.

By the way, my teenagers have the same reaction to my approval. Does that say something about you or me?:)
It's gotta be you.:D
All my folks just curse...

[Max Photon]

Max Photon is rolling over in his futon. Save us with something poetic Max.





Nonscience

By: Max Photon

Can't you all see
That mathematical modeling
Of the WTCs
Is but for coddling
Those who are waddling
Away from reality?

Finite element analysis
Of overdriven systems
Is mental paralysis
Or at best toddling
In the face of such
Ambiguous complexity.

[Apollo20]

Max, rwgwinn et al. must face the facts!
FEA is most drear
Its cost is too dear
Its results unclear
Even Bazant
Cant
Stand to use it
And is prone to disabuse it!

P.S. I got this info from the estimable professor himself!

[Max Photon]

...so banish math off the shelf!

[Max Photon]

Oops...I forgot...since many of you can't read, here is the gist of this thread in picture-form:

Model Over the Limit - Modeling Wipeouts (http://www.youtube.com/watch?v=6O9qAyjGDLs)

[pomeroo]

Nonscience

By: Max Photon

Can't you all see
That mathematical modeling
Of the WTCs
Is but for coddling
Those who are waddling
Away from reality?

Finite element analysis
Of overdriven systems
Is mental paralysis
Or at best toddling
In the face of such
Ambiguous complexity.


(With apologies to Ogden Nash)


There is a term for those obstinate, agenda-driven folk who can't understand, or simply ignore, the effects of extensive fires;
They are called, Conspiracy Liars.
They don't much like reason, and they lack evidence.
Frankly, they enjoy making no sense.
One problem that causes them to rack what passes for their brains
Is what to make of those damned, #$&*%^, inconvenient planes!
Colorful crackpots have tried to vanish them away with claims of video fakery,
Which, for sheer stupidity, is take-the-cakery.
Stick with the thermite, dear Maxie, for while it is true
That it's a silly myth, so are you!

[Apollo20]

Pomeroo, it's true
Your verse
Goes from bad
To worse...........

[pomeroo]

Pomeroo, it's true
Your verse
Goes from bad
To worse...........



Hey, don't complain to me. I was merely channeling the master.

[pomeroo]

For you, Frank:

The firefly's flame
Is something for which science has no name.
I can think of nothing eerier
Than flying around with an unidentified glow on a person's posterior.

--Ogden Nash

[Max Photon]

Don't you mean on flyash
My dear inferior?

[metamars]

You guys are strictly amateur. For a real 911 poem, look here (http://www.physforum.com/index.php?showtopic=12383&st=1830&#).


If you can't handle more than 4 lines of fine art at a time, you can settle for:

Improbability multiplied upon improbability
Faze not "debunkers", still
The warmongers' evil serendepity
Means the public foots the bill

[Heiwa]

Shakespeare described the deceit early 1600 - Othello (Act V):

Oth.
Soft you; a word or two before you go.
I have done the state some services, and they know't.
No more of that. I pray you in your letters,
When you shall see these unlucky deeds relate,
Speak of me as I am; nothing extenuate,
Nor set down aught in malice: then must you speak
Of one that loved not wisely but too well;
Of one not easily jealous, but, being wrought,
Perplex'd in the extreme; of on whose hand,
Like the base Indian, threw a pearl away
Richer than all his tribe; of one whose subdued eyes,
Albeit unused to the melting mood,
Drop tears as fast as the Arabian trees
Their medical gum. Set you down this;
And say besides, that in Aleppo once,
Where a malignant and a turban'd Turk
Beat a Venetian and traduced the state,
I took by the throat the circumcised dog
And smote him, thus. [Stabs himself.

[Max Photon]

Perhaps it is more accurate to say, "NISTian grey boxes."

[pomeroo]

Perhaps it is more accurate to say, "NISTian grey boxes."


Max, I was wondering why you haven't erased that silly signature of yours. Every word of it has been bashed flat, smoked, blasted out of existence, refuted, rebuked, rebuffed, reamed, steamed, and dry-cleaned. In short, it's wrong.

Maybe you just like the sound of it.

[Max Photon]

Underpowered Rotary Drill,

What does your quote have to do with your post?