Use of Scale Model or Full Sized models for investigating 9/11 collapses

Seriously? I don't buy that for a second. How could any engineer designing the construction of a sky scraper not seriously discuss a plane hitting it, or a bomb going off in the basement or on a floor.
Post 9-11, they wouldn't, back in the 60's though? The considered crisis scenarios would have been very different.
 
they wouldn't, back in the 60's though? The considered crisis scenarios would have been very different
I looked for the documentary a few weeks back, but they kinda all look the same so I didn't find it... so all I got is memory...

the one i saw one of the guys in charge of that aspect of the building said they did think about planes but 1. they were thinking smaller planes and didn't really consider the fuel because they didn't really think such a thing would ever happen. They thought about small planes though.
 
The floor pans of the common wtc towes floors were all constructed the same way. Iirc, 4 inch of lightweight concrete on steel pans, with web trusses partially embeded in the concrete.
The COLUMNS varied in size, heavier lower down.
 
I looked for the documentary a few weeks back, but they kinda all look the same so I didn't find it... so all I got is memory...
the one i saw one of the guys in charge of that aspect of the building said they did think about planes but 1. they were thinking smaller planes and didn't really consider the fuel because they didn't really think such a thing would ever happen. They thought about small planes though.
Prior to 9/11 the biggest plane that had hit a building was the B-25 Mitchell that hit the Empire State building in 1945. The maximum possible takeoff weight of a B-25 is less than the weight of fuel in either plane used in 9/11. Note: I can't find the weight of a few other planes that hit buildings, so this might not actually be the heaviest, but the point is none of them were airliner sized.

The planes that had hit buildings before were all small, and most were either civilian planes (which often got away with breaking the rules), and military planes (bound by a less restrictive set of rules), usually during fog. Big commercial planes were just too well regulated and monitored, even then.

Hijacking probably never occurred to them, either. To that point, every attempt to hijack a plane had been for reasons like ransom, defection, hostages, etc. Even today that's way more common than trying to crash one into a building. It would have been a hard sell to get anyone to fund a building built to withstand something that nobody had even attempted on purpose and was incredibly unlikely on accident, and that accident would be somebody else's liability anyway.
 
found an hour to post.

I was wondering....

If a group were to build an exact full scal model of ONE floor of the towers, supported on columns 12 feet long, details as seen fit, and then dropped 10 times the dead + live load onto it from a height of 6 feet, to be conservative with impact velocity, and the floor connections failed. Would truthers accept this as validating the progressive floor failure scenario as very probable (ie. true)?
I apologise for my recent absence from this thread: I have a young family, demanding job and other stuff on at the moment, but that doesn't mean I'm not still interested in discussions like these going on in dusty corners of the internet :)

Anyhow, I'm not a "truther" and certainly can't speak for those who claim they are. One of the more predictable, disappointing and yet at the same time fascinating aspects of the discourse around 9/11 is the way the discussion has been polarised into these camps, allowing people on both "sides" to ignore and vilify the other when they have reasonable or valid points to make. Thus no common ground is found and reasonable skepticism is scorned.

Now, I am certainly skeptical about aspects of the official narrative, and to illustrate my point about "truthers" vs "debunkers": it is merely a statement of fact to observe that the NIST model of the WTC7 event stops, in terms of timeline, long before the onset of the freefall "fascia collapse" it purports to explain. Similarly, I would suggest it is almost impossible to defend or justify NIST's explanation for hiding the input data for its model from independent verification. No-one who claims to have a skeptical perspective and understands elementary principles of the scientific method and what is known in general terms about structures should unquestioningly accept the suggestion that NIST's model represents dangerous, transferrable knowledge of any kind.

And yet by making these observations I predict I will be attacked by members of this forum a "truther", and have the term "conspiracy theory" applied to these relatively banal and uncontroversial points. Should any of you wish to cast mud at me for making these remarks, or demand I present a complete alternative theory because of them (or even debate them sensibly) I'm sure you can do that in other threads: but in my opinion the only rational response to such basic criticism of the official position on the model of WTC7 is collective agreement.

Anyway, to answer your question: no, I don't think a single floor model would be sufficient validation of the progressive collapse scenario, as much Jeffrey and others may feel it is unnecessary. This progressive collapse theory is continually presented as being essentially simple, and yet the fact remains that a simple, representative multi storey model that accurately reproduces the phenomenon of the most catastrophic building failures in history has yet to be successfully demonstrated.
 
yet the fact remains that a simple, representative multi storey model that accurately reproduces the phenomenon of the most catastrophic building failures in history has yet to be successfully demonstrated.
And what is the significance of that fact? Is there an inference you would like us to take from this?
 
Now, I am certainly skeptical about aspects of the official narrative, and to illustrate my point about "truthers" vs "debunkers": it is merely a statement of fact to observe that the NIST model of the WTC7 event stops, in terms of timeline, long before the onset of the freefall "fascia collapse" it purports to explain. Similarly, I would suggest it is almost impossible to defend or justify NIST's explanation for hiding the input data for its model from independent verification.

NIST's job wasn't to explain the fall of the North face of WTC 7; their job was to explain how fire caused the whole building to collapse. On 9/12/2001, nobody expressed the slightest doubt that fire had caused the collapse. (This is important.)

The computer model of the collapse stops with the fall of the North face because at that point, computations are completely chaotic; but more importantly, they're pointless since the complete destruction of the building is now inevitable.

Elements of the explanation for the collapse can be physically demonstrated, such as thermal expansion of long span girders; but building a scale model is pointless, for reasons already discussed.

As for the NIST inputs into their computer model, I"m pretty sure that one will get the same results with the same inputs. The issue is, can one come up with a better model? There's nothing to stop any rival group of competent engineers from doing their own computer model. And with the growth of computational power in the 6 years since NIST did their mode, any rival group could do more iterations and variations of their model than NIST did with theirs.
 
The issue is, can one come up with a better model? There's nothing to stop any rival group of competent engineers from doing their own computer model. And with the growth of computational power in the 6 years since NIST did their mode, any rival group could do more iterations and variations of their model than NIST did with theirs.
Agreed - but the framing question is "better for what purpose?" and that means both "What technical purpose?" and "For the benefit of what class of persons?"

Technically this series of recent discussions has been around three aspects of WTC collapses viz "Twin Towers" progression stage as distinct from initiation stage and the WTC 7 collapse mechanism in total.

As for the "who benefits" question - the main reason for raising the question in recent posts - has been a genuine concern by some non-engineer members that he (they?) need a better model so they can understand. I don't think it is a practical way to help them understand. Here is an outline of why.

From the engineers perspective - my opinion - there is no need for a better model for Twin Towers progression. The mechanism is simple enough to understand and no model would validate the reasoning better. The model would not be more rigorous - almost certainly less rigorous - than explanations which can be given based on available real event evidence. So I would prefer the path of better explanation for those who don't yet understand or lack sufficient confidence in their current level of understanding. IMO building a better model is not the best away to achieve that understanding or level of confidence. And that applies to "Twin Towers - Progression Stage".

I would dismiss modelling as a way to better understand Twin Towers initiation and WTC overall explanation because both of them far too complex for physical models. Arguably also too complex for computer modelling for Twin Towers - or better computer modelling than NIST did for WTC7. I comprehend and agree with Redwood’s comments that current technology could potentially do more precise mathematics but the precision of the outcomes is probably already limited by the layers of necessary assumptions. Any apparent better precision could well be insecure.
 
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On 9/12/2001, nobody expressed the slightest doubt that fire had caused the collapse. (This is important.)
Apart from major media anchors like Dan Rather, who said it looked like controlled demolition (at 0.40s in the video below)



In any case, an appeal to popularity on your part does not bring a successful model any closer to becoming a reality.

The computer model of the collapse stops with the fall of the North face because at that point, computations are completely chaotic;
In other words, the model is no longer representing the event it purports to explain, within reasonable parameters: in short, it fails.

Your argument here is quite absurd. If, for example, an experimental model of an aeroplane fails to perform as predicted in a virtual windtunnel, you cannot claim that the computation was too chaotic for accuracy and insist the design of the model was sound. That would be ridiculous.
but more importantly, they're pointless since the complete destruction of the building is now inevitable.
This is mere bare assertion, as the model you refer to has totally failed to demonstrate that the way the building collapsed with freefall acceleration has been understood.
building a scale model is pointless
You can't hand-wave away the fact that no successful models of the most catastrophic structural disasters in history have ever been made.
As for the NIST inputs into their computer model, I"m pretty sure that one will get the same results with the same inputs.
If you hand-wave any harder you might take off! What you're sure of is irrelevant. Whether or not other models can be made is irrelevant.

The point here is that the inputs are not available for independent verification, and without independent verification there is no scientific credibility to NIST's model.

What I expect now is general agreement that NIST's argument for hiding those inputs from independent verification is indefensible.
 
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Apart from major media anchors like Dan Rather, who said it looked like controlled demolition...

"Looked like" is a commonly used term to explain what was viewed.

It is merely a convenient way to describe an event, using what is called a 'comparison'.

Slightly 'OT', but I've dealt with the phrase "looked like" in other "conspiracy theory" genres...such as the Apollo Moon missions (where some people say it "looked like" the Astronauts in Apollo EVA video footage are "suspended by wires").

As I warned, 'OT' but used as a "comparison" for the term "looked like".....
 
If someone decided to bomb the towers on lets say the 75th floor, and used enough explosives to cause the structure to fail (in the way 911 happened) then the towers probably would've come down in a similar fashion. Right?
This is a good point, and it could be investigated. We already have models such as these being made: as its creator notes, they'll be worth running again in a few years' time when computing power has increased.

 
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"Looked like" is a commonly used term to explain what was viewed.

It is merely a convenient way to describe an event, using what is called a 'comparison'.

Slightly 'OT', but I've dealt with the phrase "looked like" in other "conspiracy theory" genres.

Congratulations on being the first to fulfil my prediction that the term "conspiracy theory" would be applied to the remarks I'm making on this thread, Weedwhacker. Not only that, but you're dealing only with petty semantics. I was responding to Redwood's false assertion that no-one at the time expressed doubt that fire had caused the collapses.

What Rather says in the video I posted is that "...it's reminiscent... of those pictures we've all seen... when a building was deliberately destroyed by well-placed dynamite to knock it down."
 
....but you're merely dealing with petty semantics.

I tend to think of myself as more pedantic, actually. Just trying to clarify terms....words can be misinterpreted so very, very easily.

Also, it seems that there is a discernible time-lag between posts...meaning, this is often, in such Internet venues, a cause for unnecessary conflict and mis-communication.

What Rather says in the video I posted is that "...it's reminiscent... of those pictures we've all seen... when a building was deliberately destroyed by well-placed dynamite to knock it down."

....yes...this somewhat bolsters my earlier opinion in posted comments. KEY word there..."reminiscent". That is all I meant.
 
What Rather says in the video I posted is that "...it's reminiscent... of those pictures we've all seen... when a building was deliberately destroyed by well-placed dynamite to knock it down."
Well then perhaps it should have been couched in terms such as, " after study of the collapse, no competent engineering organization believed it was a demolition".
ASCE doesn't, AIA, the organization Gage touts his membership in, doesn't, the CTBUH explicitly states that they give no credence "whatsoever" to any conspiracy theory, which would certainly include demolition.
 
I apologise for my recent absence from this thread: I have a young family, demanding job and other stuff on at the moment, but that doesn't mean I'm not still interested in discussions like these going on in dusty corners of the internet :)
Not a problem. Most of use do have other interests and responsibilities.
Anyhow, I'm not a "truther" and certainly can't speak for those who claim they are. One of the more predictable, disappointing and yet at the same time fascinating aspects of the discourse around 9/11 is the way the discussion has been polarised into these camps, allowing people on both "sides" to ignore and vilify the other when they have reasonable or valid points to make. Thus no common ground is found and reasonable skepticism is scorned.

OK, however one must note that the vast bulk of "questions" concerning 9/11 events is driven by the so called truthers. They are by far the loudest as well.
Now, I am certainly skeptical about aspects of the official narrative, and to illustrate my point about "truthers" vs "debunkers": it is merely a statement of fact to observe that the NIST model of the WTC7 event stops, in terms of timeline, long before the onset of the freefall "fascia collapse" it purports to explain
Where do you get the idea that NIST ewas tasked with explaining the 2.25 second period of facade apparent free fall in an otherwise 16-20 second progressive collapse? NIST did model the vertical and horizontal progression of collapse. Their animation based on the FEA ends at a point where it is patently obvious the structure's collapse will not arrest. Details beyond that point are completely irrelevant to the tasks NIST was assigned.

.
Similarly, I would suggest it is almost impossible to defend or justify NIST's explanation for hiding the input data for its model from independent verification.
What independent verification, and by whom?
The only org I know of claiming to wish to do that is not a professional engineering organization, AE911T. Secondly, they do not explain what they mean by "verify". Reading their releases on this matter though, it seems apparent that all they wish to do is re-run the same computer programs using the data NIST used , to see if the same results come out the other end. There is no engineering, and no research involved in doing that. Its a complex equivalent to entering 2+2 into a hand calculator, twice, to see if it arrives at the same answer both times. It is clear in many AE911T postings that they claim the results were simply made up. That's not engineering, its witch hunt.
There is some implication by AE911T that they would examine the quantified inputs. This is really all they could do and it would easily devolve into nitpickery with AE911T demanding that NIST change their inputs and do the FEA again, shifting the burden of proof as they are so won't to do.
Third, NIST determined that public safety trumps release of that data, though it appears that some groups such as the ASCE might have been given access. Simply detailing how such info could be used would also jeopardize public safety.
An anecdote: I was a civilian tech at a military base for several months. I worked in a non-secret area of the base. I became friendly with a few military personnel including one who worked in the secure area. I once asked him what he did. " I type", was his answer. "Type what?", I asked. No reply. Thinking he didn't hear me I asked again. He just looked me in the eye and said nothing. I got the message.
See the connection?
No-one who claims to have a skeptical perspective and understands elementary principles of the scientific method and what is known in general terms about structures should unquestioningly accept the suggestion that NIST's model represents dangerous, transferrable knowledge of any kind.
I fit into both of those categories, yet I accept the finding. I do so because I have an understanding of the progression of collapse that serves to satisfy me and does not require any " verification" of the details.
And yet by making these observations I predict I will be attacked by members of this forum a "truther", and have the term "conspiracy theory" applied to these relatively banal and uncontroversial points
the post of mine that you quoted made no reference to you at all. OTOH this thread also includes demonstrations by psikeyhacker, who definitely falls into that category. (If memory serves)


Anyway, to answer your question: no, I don't think a single floor model would be sufficient validation of the progressive collapse scenario, as much Jeffrey and others may feel it is unnecessary. This progressive collapse theory is continually presented as being essentially simple, and yet the fact remains that a simple, representative multi storey model that accurately reproduces the phenomenon of the most catastrophic building failures in history has yet to be successfully demonstrated.
Aye, there's the rub.
It is essentially simple, at least for WTC towers, that once it is shown that the first intact lower floor space would be vastly overwhelmed, that there existed no mechanism by which progression of floor collapse could be arrested.
The computer modeling of WTC7 ends at a point that has the building in such a state of destruction that only the most egregious of skeptics could deny that its complete collapse is inevitable.
As for modeling that progression it seems you wish to model the entire destruction of 110 storeys of each tower. Anyone with an understanding of this would know that this would require an extreme amount of approximation and simplification, in either a computer or physical model. So, to what end would this be done? If such model did arrest progression you would have no way to know if it is the result of one of those approximations/simplifications, and if it doesn't arrest you will face opponents who will attack your approximations and simplifications and demand more.

Furthermore, it has been pointed out that many of those who have attempted very simple small scale models have consistently modeled something other than the mechanism put forth by NIST.
 
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What Rather says in the video I posted is that "...it's reminiscent... of those pictures we've all seen... when a building was deliberately destroyed by well-placed dynamite to knock it down."
Dan Rather is most certainly not an engineering expert. His musing on this matter is that of a definitely nontechnical person. In addition, these musings, one cannot even describe them as truly an opinion, are arrived at within minutes of the event, with no study, no contact with an engineering expert. In fact no possibility of a sober minded examination of the events. He is a journalist, a pretty good one. However, if asked I would expect that he does not, and never did, believe that these structures(3 of over double that number, that were destroyed that day in Manhattan) were brought down by anything other than the direct and indirect effects of having very large aircraft moving very fast smashing into the towers and igniting multilevel fires.
 
But all he said was that it was reminiscent.
At no point does he say, " I think there must have been explosives in that building and the fire and damage alone could not have caused that" or anything along those lines.
He might well have been THINKING it, but unless you ask Dan Rather what he was thinking, then currently Redwood's assertion has not been proven false.
 
On 9/12/2001, nobody expressed the slightest doubt that fire had caused the collapse. (This is important.)

Apart from major media anchors like Dan Rather, who said it looked like controlled demolition (at 0.40s in the video below)




In any case, an appeal to popularity on your part does not bring a successful model any closer to becoming a reality.


Rather did not express any doubts that WTC 7 collapsed from fire! He said it resembled a controlled demolition, which it superficially does, especially if you ignore that it was on fire, and that no sound of demolition charges was heard. Look up "simile".

It is not “an appeal to popularity” to note that nobody expressed surprise that it collapsed from fire, and that nobody reported anything suspicious. It’s an empirical fact, and shows why NIST was asked to explain how the fire caused the collapse, not to hunt about for some mysterious cause. In other words, we have a Level One explanation: Fire caused the collapse, just as USS Arizona was sunk by a bomb, and RMS Titanic sank from hitting an iceberg. The rest is details, and NIST was asked to provide the details.

The computer model of the collapse stops with the fall of the North face because at that point, computations are completely chaotic;


In other words, the model is no longer representing the event it purports to explain, within reasonable parameters: in short, it fails.

Wrong! The model has done everything asked of it. It has provided an explanation for the collapse. It’s purpose was never to explain every last detail of the collapse itself. That’s ridiculous. You can model a Jenga Tower and explain when it collapses from removing elements, but no model is ever going to predict where every last tile lands. Build 100 Jenga Towers and collapse them, and you’ll never get two that are exactly alike. Collapses are chaotic; small changes at the beginning make big changes in the details at the end. But unless you have good reason to explain some detail, it pointless to go past the initiation of the collapse.

Your argument here is quite absurd. If, for example, an experimental model of an aeroplane fails to perform as predicted in a virtual windtunnel, you cannot claim that the computation was too chaotic for accuracy and insist the design of the model was sound. That would be ridiculous.

Don’t know much about computer modeling, do you? Airplanes are largely designed on computers nowadays, and the computations do go to completion. If an experimental airplane built to design specs were to fail, it wouldn’t be from the computations being too difficult; it would be that the computations omitted some significant factor, as in the famous case of the square windows in the pioneering DeHavilland Comet. And no computer model of its failure would ever predict every last detail of the failure.

but more importantly, they're pointless since the complete destruction of the building is now inevitable.

This is mere bare assertion, as the model you refer to has totally failed to demonstrate that the way the building collapsed with freefall acceleration has been understood.

Wrong again! It’s easy to show from a static model that once the building has suffered internal collapse, collapse of the exterior columns is inevitable from lack of lateral support. A certain Mr. Leonhard Euler could explain it to you, or any engineer. A static model won’t give the details of the collapse, but unless you think it’s really, really important to do so, there’s no reason to model it, except perhaps as an intellectual exercise.

building a scale model is pointless

You can't hand-wave away the fact that no successful models of the most catastrophic structural disasters in history have ever been made.

Calling it unsuccessful is unsupported personal opinion. If a group of structural engineers were to express dissatisfaction with NIST’s results, and give a reason why the model should have predicted the details of the last stages of the collapse, it would be expert opinion. But none has done so.
 
ASCE doesn't, AIA, the organization Gage touts his membership in, doesn't, the CTBUH explicitly states that they give no credence "whatsoever" to any conspiracy theory, which would certainly include demolition.
At no point does he say, " I think there must have been explosives in that building and the fire and damage alone could not have caused that" or anything along those lines. He might well have been THINKING it
Dan Rather is most certainly not an engineering expert. His musing on this matter is that of a definitely nontechnical person. In addition, these musings, one cannot even describe them as truly an opinion, are arrived at within minutes of the event, with no study, no contact with an engineering expert.
Rather did not express any doubts that WTC 7 collapsed from fire! He said it resembled a controlled demolition, which it superficially does, especially if you ignore that it was on fire, and that no sound of demolition charges was heard. Look up "simile".
I'm not going to respond further to the assertion that there were no people at the time who said the collapses were "suspicious", and I'm certainly not going to respond to patronising insinuations that I don't understand what similes are, or any other off-topic insults. I provided that footage of Dan Rather to show that there were people at the time who commented to the effect that it looked like a controlled demolition: if you want to discuss semantics, what you think you thought he really meant by "resemble", what was actually "thinking", whether or not his technical background has a bearing on the point, appeals to authority like the CTBUH or "engineering experts", or the presence or absence of explosive sounds or the effect of fire: do it on another thread.

The model has done everything asked of it. It has provided an explanation for the collapse.
As I've already pointed out, and will not point out again: the model does not even approach, in terms of timeline, the part of the collapse that shows the building falling freefall acceleration and a remarkable degree of external symmetry [please note I'm not going to discuss degrees of symmetry in this thread either]. If it answers the question you'd ask -- and that question is not "how did that building fall with freefall acceleration?" then my observation is that your question is not apposite to the problem.
Airplanes are largely designed on computers nowadays, and the computations do go to completion. If an experimental airplane built to design specs were to fail, it wouldn’t be from the computations being too difficult; it would be that the computations omitted some significant factor
Precisely my point. The significant factor missed in the modelling of the WTC7 event was running it even close to completion. Your assertion is apparently it was too complex a scenario to be modelled to the free-fall acceleration stage, but that doesn't change that fact that it has not been demonstrated or explained by a model, even in simplified terms: which is my point -- although I am actually most interested in models of the collapse sequence of the Towers.
You can model a Jenga Tower and explain when it collapses from removing elements, but no model is ever going to predict where every last tile lands.

Just one of many, many examples. Please don't drive this thread into some black hole of irrelevances or semantics in response to that fact that you've been shown to be wrong, as you were with the assertion I put the lie to by using the Dan Rather example.

Mick, I've been getting untold JavaScript errors on this site across all platforms. It makes it quite difficult to use.
 
I'm not going to respond further to the assertion that there were no people at the time who said the collapses were "suspicious", and I'm certainly not going to respond to patronising insinuations that I don't understand what similes are, or any other off-topic insults. I provided that footage of Dan Rather to show that there were people at the time who commented to the effect that it looked like a controlled demolition: if you want to discuss semantics, what you think you thought he really meant by "resemble", what was actually "thinking", whether or not his technical background has a bearing on the point, appeals to authority like the CTBUH or "engineering experts", or the presence or absence of explosive sounds or the effect of fire: do it on another thread.
The one point of fact in dispute seems to be whether or not it "looked like a CD" at the time or shortly after. I have no doubt that to many people it looked like a CD. I'm not even interested in whether those persons meant it was a CD or some lesser assertion about resemblance. Lets take the topic discussion forwards. You say it looked like CD - I agree that it looked like CD. The topic is about Scale or Full Sized Models - therefore use of physical models. And whether or not such models offer advantages over other analytical or explanatory methods.

You have some things you don't want to keep discussing:
As I've already pointed out, and will not point out again: the model does not even approach, in terms of timeline, the part of the collapse that shows the building falling freefall acceleration and a remarkable degree of external symmetry [please note I'm not going to discuss degrees of symmetry in this thread either]. If it answers the question you'd ask -- and that question is not "how did that building fall with freefall acceleration?" then my observation is that your question is not apposite to the problem.
So you don't want to discuss degree or extent of some factors - I'm comfortable with that.

You restate or clarify your concern:
Precisely my point. The significant factor missed in the modelling of the WTC7 event was running it even close to completion. Your assertion is apparently it was too complex a scenario to be modelled to the free-fall acceleration stage, but that doesn't change that fact that it has not been demonstrated or explained by a model, even in simplified terms: which is my point -- although I am actually most interested in models of the collapse sequence of the Towers.
I'm OK with put to one side for now your interest in the "Towers" - however the "Twins" are IMO a better starting point for building explanations and understanding. Your call.

The facts you assert include:
1) Modelling did not continue to completion of collapse; AND
2) That modelling did not extend to the free fall stage (Or I assume - correct me if I'm wrong) through the free fall stage.

Both those facts are IMO true and not in dispute.

So the next question is "Why does that issue concern you?" I am approaching this as a professional engineer who will try to see your point of view and, if necessary, explain some aspects for you. My own initial perspective is that I cannot see any realistic advantage by extending the modelling into that stage. You appear to think that you could benefit from extended modelling. So our viewpoints are some distance apart - we need to bridge the gap. If that is the situation we can progress discussion. Otherwise show me what I have misunderstood and I'll try again.

Just one of many, many examples. Please don't drive this thread into some black hole of irrelevances in response to that fact that you've been shown wrong, as you were with the Dan Rather example.
Agreed that we should avoid side tracks etc
 
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NIST recognises a 2.25 second period of free-fall but as we agree econ41 the model does not proceed to this point in the collapse sequence. For now I will suggest that it concerns me because freefall acceleration is without doubt a feature of the collapse that has raised questions and is a frequent focus of objections to NIST's conclusions; it cannot be disputed that this aspect of the collapse is not explained by the model. The "realistic advantage" as you put it would be to demonstrate with a model (to the "layperson", if you will) that this controversial and unique aspect of the collapse has indeed been fully understood, as is claimed.

However, I would prefer to focus on the collapse sequence of the Towers, as there are no successful models of this of any kind, to my knowledge.
 
http://www.wai.com/project.aspx?id=1817&type=600
These guys did a model, it cost money. They found impacts and fire did it - and agree with the full up models of the tower, how they collapsed. As an engineer, I find the full up models are best for the impact fire gravity collapse confirmation of what happened. This study/model confirms the real event, as seen, gravity collapse. There are more studies, more models. I have a momentum model. With all the models done up to collapse, and a few of the collapse; with the evidence, there was no CD, and gravity collapse as seen confirms itself, as do all rational engineers - and the models.

Perdue did some work too.

Is this the kind of model wanted, but of the collapse, a computer model of the collapse. Once started the collapse would continue, not sure it is practical to study something already known to be true.

Why does the lead structural engineer for the WTC not need a model of the collapse?
HOST: Glad to have you with us. Leslie Robertson, I’d like to begin with you. The federal research center, the National Institute of Standards and Technology (NIST), did an extensive study of the collapse of the Twin Towers, concluding that the planes hitting the towers essentially caused fire and trauma to the structure that resulted in their collapse. I want to ask if you support the conclusions of the NIST report, and if so, why?
ROBERTSON: Yes, I do. I support the general conclusions of the NIST report. It was prepared, by the way, not just by NIST, but by a series of engineering firms around the country who provided advice and assistance to NIST in their investigations. It was reasonably thorough, amounting, as I recall, to about $16 million of effort. And our firm participated in a small way in providing information about the basic structure that was in fact constructed. It's a little more complicated than one might suppose, because there were a lot of modifications made to the structure as it was being built. That's rather normal – tenants have individual requirements – and so there was strengthening done for the most part here and there to achieve the needs of the individual tenants.
The project was designed for the impact of a, what we call a low-flying, slow-flying Boeing 707, that was the largest aircraft of its time, actually the intercontinental version. We envisioned it much as was the case for the aircraft that struck the Empire State Building in the Second World War, the same condition, lost in the fog, i.e. an accidental impact of an aircraft into the building. It was not designed for high-speed impact from the jets that actually hit it.

When you design a system, you can model it in your head.
ROBERTSON: But the collapse mechanism of the Trade Center is as we had anticipated it would be when we first designed it. It was not – please don't misunderstand me – it was not designed to collapse. But any prudent engineer looking at the future has to think about, what are the mechanisms that cause collapse, and how to go about strengthening the building so as to minimize that circumstance. So sure, we spent time looking at that kind of event, and that which was observable from the photographs and so forth is reasonably consistent with that which we thought would be the case.
Lead engineer agrees with full up models.

http://www.nae.edu/Publications/Bri...ecurity/ReflectionsontheWorldTradeCenter.aspx

But the model these guys did, is it good enough.
http://www.wai.com/project.aspx?id=1817&type=600http://www.wai.com/project.aspx?id=1817&type=600
 
NIST recognises a 2.25 second period of free-fall but as we agree econ41 the model does not proceed to this point in the collapse sequence. For now I will suggest that it concerns me because freefall acceleration is without doubt a feature of the collapse that has raised questions and is a frequent focus of objections to NIST's conclusions; it cannot be disputed that this aspect of the collapse is not explained by the model. The "realistic advantage" as you put it would be to demonstrate with a model (to the "layperson", if you will) that this controversial and unique aspect of the collapse has indeed been fully understood, as is claimed.

Regarding the free-fall though, this is something where there is simply no justification for modelling it besides (partially) satisfying Truthers. The models went as far as showing that the interior of the building was gone, and that the exterior skin had buckled across the lower levels. At that point full collapse is inevitable, and since there is nothing supporting the exteriors, then near free-fall is an expected result.

Like with a can being crushed by my weight, once it has started to be crushed, there's no need to model if the crush is going to continue, or exactly how fast it is.


The same applies to the WTC Towers. If you've determined that progressive collapse is inevitable, then there is little point in analyzing how it actually progresses - especially since we have the two real-world examples to study.

Just one of many, many examples.

The point was not that you can't run a model to completion, but that the complexity of the model makes duplicating the exact real-world outcome impossible. Basically chaos theory.
https://en.wikipedia.org/wiki/Chaos_theory
Chaos theory concerns deterministic systems whose behavior can in principle be predicted. Chaotic systems are predictable for a while and then appear to become random. The amount of time for which the behavior of a chaotic system can be effectively predicted depends on three things: How much uncertainty we are willing to tolerate in the forecast; how accurately we are able to measure its current state; and a time scale depending on the dynamics of the system, called the Lyapunov time.
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A computer model of a Jenga tower can be run again and again and will get the same result. But change the position of a block 1mm and you will get a radically different final result.

Build a physical Jenga tower and collapse it in the exact same way, and you will NEVER get the same result twice.

But the final placement of the girders on the ground is not really what is being discussed. The questions are more:

1) Was total progressive collapse possible?
2) How fast would it be?

Again here, these are questions that are only raised by Truthers. Question #1 has been answered many times with a resounding YES. The floors could not support the weight, so they would be stripped away. The outer walls would peel outwards, the central columns would remain for a period but would eventually (after a random, chaotic amount of time) fall due to buckling. These things seem self evident. They match exactly what we saw that day.

As for the speed of collapse, the objections that are raised here are frankly silly. Appeals to the laws of motion, which don't apply to a complex system, and models which don't reflect the actual mode of collapse.

If AE911 thinks a better model was needed, then they should build one. They can start with a computer model that actually models the real mode of collapse.
 
Mick, you're the first to fulfil my prediction that this discussion would be reduced to an artificial, antagonistic/adversarial opposition of "debunkers" vs "truthers" to the purpose of trivializing another's argument. If you're going to support the NIST WTC7 model I think you should explain why anyone should accept a computer model for which the input parameters are not available for independent verification, and if you're going to suggest an organisation like AE911 could produce a model I'd ask you what your response would be if they did so but refused to supply the input parameters for verification for the same reasons NIST has given.

Without independent verification there's really no defence against the suggestion that, say, NIST's model was manipulated to support a pre-established hypothesis and the progression of the model was arrested at the point it became plain it was deviating too far from the video evidence to be capable of supporting anything.

Seriously: if it's your view that the period of freefall acceleration in the collapse of WTC7 was due to factors that are simply too complex to model, and that's why it wasn't attempted, you may as well say so. You'll just have to accept that the model doesn't demonstrate what you claim is nevertheless well understood.

Your collapsing can is certainly an excellent illustration of how asymmetric one might expect such events to be.

Keith, I can't believe that you're still persisting with this claim that the towers were somehow "full up" models of themselves. How can I explain this to you? A volcano erupting is not a model of a volcano erupting. A plane crashing is not a model of a plane crashing. An asteroid strike is not a model of an asteroid strike. These are all events that can be modelled, but they're not of themselves models. Once we get past this bit of confusion, I'm sure we can proceed.

econ41, I look forward to your response to my post replying to your question as to why issues like this might concern me, as you least have offered to bridge the gap.
 
Mick, you're the first to fulfil my prediction that this discussion would be reduced to an artificial, antagonistic/adversarial opposition of "debunkers" vs "truthers" to the purpose of trivializing another's argument. If you're going to support the NIST WTC7 model I think you should explain why anyone should accept a computer model for which the input parameters are not available for independent verification, and if you're going to suggest an organisation like AE911 could produce a model I'd ask you what your response would be if they did so but refused to supply the input parameters for verification for the same reasons NIST has given.

Without independent verification there's really no defence against the suggestion that, say, NIST's model was manipulated to support a pre-established hypothesis and the progression of the model was arrested at the point it became plain it was deviating too far from the video evidence to be capable of supporting anything.

Seriously: if it's your view that the period of freefall acceleration in the collapse of WTC7 was due to factors that are simply too complex to model, and that's why it wasn't attempted, you may as well say so. You'll just have to accept that the model doesn't demonstrate what you claim is nevertheless well understood.

Your collapsing can is certainly an excellent illustration of how asymmetric one might expect such events to be.

Keith, I can't believe that you're still persisting with this claim that the towers were somehow "full up" models of themselves. How can I explain this to you? A volcano erupting is not a model of a volcano erupting. A plane crashing is not a model of a plane crashing. An asteroid strike is not a model of an asteroid strike. These are all events that can be modelled, but they're not of themselves models. Once we get past this bit of confusion, I'm sure we can proceed.

econ41, I look forward to your response to my post replying to your question as to why issues like this might concern me, as you least have offered to bridge the gap.

I am trying to understand YOUR motives, here.

You seem to be NOT advocating CD, in regards to WTC 1, WTC 2 or WTC7.

So, "what". exactly, IS your assertion?
 
Mick, you're the first to fulfil my prediction that this discussion would be reduced to an artificial, antagonistic/adversarial opposition of "debunkers" vs "truthers" to the purpose of trivializing another's argument.
That's not what I'm saying at all. I'm saying there is no point in simulating after collapse initiation. And the only people interested are truthers.

Seriously: if it's your view that the period of freefall acceleration in the collapse of WTC7 was due to factors that are simply too complex to model, and that's why it wasn't attempted
Absolutely not. You could just let the model run. There's just no point. It has started to collapse, it's going to collapse, you can see the column have buckled, they are not going to offer any resistance. What is the purpose of continuing the simulation? The only reason would be to satisfy truthers.

This isn't a criticism of truthers. It's simple reality.

Your collapsing can is certainly an excellent illustration of how asymmetric one might expect such events to be.
If the building was three inches across, maybe.

Keith, I can't believe that you're still persisting with this claim that the towers were somehow "full up" models of themselves. How can I explain this to you? A volcano erupting is not a model of a volcano erupting. A plane crashing is not a model of a plane crashing. An asteroid strike is not a model of an asteroid strike. These are all events that can be modelled, but they're not of themselves models. Once we get past this bit of confusion, I'm sure we can proceed.

But the point there is in what you want the model for. If you simply want to see what happens, then studying the actual events is the best you are going to get. Sure they are not "models", they are better than models.
 
A volcano erupting is not a model of a volcano erupting. A plane crashing is not a model of a plane crashing. An asteroid strike is not a model of an asteroid strike. These are all events that can be modelled
really? let's see your model of a volcano erupting. and we'll compare it to the real deal.
 
NIST recognises a 2.25 second period of free-fall but as we agree econ41 the model does not proceed to this point in the collapse sequence. For now I will suggest that it concerns me because freefall acceleration is without doubt a feature of the collapse that has raised questions and is a frequent focus of objections to NIST's conclusions; it cannot be disputed that this aspect of the collapse is not explained by the model.
How does NIST explain the 2.25 seconds of free fall? For free fall to have taken place in a structure there would need to be "0" interference below the portion that was falling at free fall. Meaning the entire floor(s), exterior columns, and core columns would've had to fail simultaneously. Right?

But the point there is in what you want the model for. If you simply want to see what happens, then studying the actual events is the best you are going to get. Sure they are not "models", they are better than models.
The problem with studying the actual events in the collapse of the WTC bldgs is the collapse was hidden behind a veil of dust and debri. I also believe the dust and debri have allowed CT's to propagate as long as they have.
 
The problem with studying the actual events in the collapse of the WTC bldgs is the collapse was hidden behind a veil of dust and debri.
But the crucial part of the collapse, the initiation, is visible, and is what interests investigators. The complete collapse all the way to the ground is less so and doesn't really justify massive investigation.
 
I'm not going to respond further to the assertion that there were no people at the time who said the collapses were "suspicious"..... I provided that footage of Dan Rather to show that there were people at the time who commented to the effect that it looked like a controlled demolition....

{deep sigh} The reason I mentioned that nobody expressed any surprise that the building fell, or expressed any suspicions about it, was to explain why NIST was given the task of explaining the collapse in engineering terms, and why law enforcement wasn't asked to do an arson/murder/insurance fraud investigation. Capisce?

Clearly, there are now individuals who do claim such. It shouldn't be hard for you to look up the first time such allegations were made, and who made them, if it's that important to you.

As I've already pointed out, and will not point out again: the model does not even approach, in terms of timeline, the part of the collapse that shows the building falling freefall acceleration and a remarkable degree of external symmetry... If it answers the question you'd ask -- and that question is not "how did that building fall with freefall acceleration?" then my observation is that your question is not apposite to the problem.

We agree! (Except for the "symmetry" part - if you look closely at videos of the collapse, you'll see that structural columns were still falling after the North Facade was completely down. I think they're probably exterior columns from the East Facade, which were heavily cross-braced at the bottom to take the load delivered by the transfer trusses. But no structural engineers - and no Truthers - really care about that, either.) The point is, that no structural engineers care about the period of freefall, because it's only a detail of the inevitable total collapse after the fall of the East Penthouse. If you think it's a problem, it's unsupported personal opinion and nothing more.


Precisely my point. The significant factor missed in the modelling of the WTC7 event was running it even close to completion. Your assertion is apparently it was too complex a scenario to be modelled to the free-fall acceleration stage....

Again, it is your unsupported personal opinion that the period of freefall is somehow significant. It's not really that you can't continue the calculation - it's that it's meaningless, and sucks up a lot of computer time. Vary your inputs even slightly at that point, and you'll get different results, possibly wildly different results. That's what Chaos Theory is all about. Think of the simple equation, y=1/x. As x => 0, slight changes is x make for big differences in y. The equations in an FEA are much more complex; they're differential equations with no exact solution that require lots of computer time to converge on a solution for a particular value.

....but that doesn't change that fact that it has not been demonstrated or explained by a model, even in simplified terms: which is my point -- although I am actually most interested in models of the collapse sequence of the Towers.


You don't need computer models for the collapse of the Twin Towers; simple calculations show that the force exerted on the top floor of the lower section as the upper portion falls exceeds the yield strength of the connections of the floor assemblies to the columns. Rinse and repeat as the collapse continues.

If you want to show that the collapse should have arrested, you'll need a dynamic model whereby the upper section loses more mass by falling over the side at each floor impact than it gains by breaking loose one more floor. Perhaps you could befriend an engineering student and persuade him/her that it would be a fine thesis to do. Or persuade AE911T to do it as a project. They have nothing to lose, and everything to gain, at this point.

Just one of many, many examples. Please don't drive this thread into some black hole of irrelevances or semantics in response to that fact that you've been shown to be wrong, as you were with the assertion I put the lie to by using the Dan Rather example.

{deep sigh} Why don't you contact Dan Rather and ask him if he's ever entertained any suspicions that WTC 7 or the Twin Towers were brought down by more than mere fire and airliner impact? He's probably a lonely old man and he'd probably enjoy hearing from you.

Again, modeling details of a failure are more difficult even than modeling failure itself. The best "models" are real-world examples, such as the failures of the WTC buildings. As they say, you learn more from studying why a structure failed than why it stays up.
 
maybe you can think of it like an avalanche? once it lets go, its going.
I agree somewhat, but I think the puzzling thing about free fall has to do more with the fact that in order for an entire bldg to fall at free fall, all of the core and exterior columns, and flooring would have to fail at the exact same time. If one area of the bldg weakened before the other, the bldg probably would've leaned over as it fell. I believe things happened exactly as NIST explained, but the whole free fall thing has always rubbed me the wrong way, and that's probably due to my lack of engineering knowledge. And for something to fall for 2.25 seconds at free fall, when it took 8 or 9 seconds for it to collapse completely, that means the bldg fell a 1/4 of the the way without any resistance from beneath. Thats the part I have a hard time understanding or getting around it.
 
I agree somewhat, but I think the puzzling thing about free fall has to do more with the fact that in order for an entire bldg to fall at free fall, all of the core and exterior columns, and flooring would have to fail at the exact same time. If one area of the bldg weakened before the other, the bldg probably would've leaned over as it fell. I believe things happened exactly as NIST explained, but the whole free fall thing has always rubbed me the wrong way, and that's probably due to my lack of engineering knowledge. And for something to fall for 2.25 seconds at free fall, when it took 8 or 9 seconds for it to collapse completely, that means the bldg fell a 1/4 of the the way without any resistance from beneath. Thats the part I have a hard time understanding or getting around it.

No, it just means there was very little resistance from beneath.

The key to understand this is "buckling".

Columns are incredibly strong, but only as long at they are straight and vertical. Once a column bends a bit, or deviates from vertical, then the amount of weight it can support is greatly diminished, the bending or deviation increases, and BAM, the column collapses. It gives very little resistance, just as if it had been blown away.


Once it has started, there is relatively little resistance. Sure, a bent column still offers vast resistance if you were jumping up and down on it - but add a few thousands tons of falling building on top, and it's little better than paper.

As for them failing at the same time - an individual column failure cascades to the next in a fraction of a second. The failure will rip around the building like a zipper.
 
No, it just means there was very little resistance from beneath.

The key to understand this is "buckling".

Columns are incredibly strong, but only as long at they are straight and vertical. Once a column bends a bit, or deviates from vertical, then the amount of weight it can support is greatly diminished, the bending or deviation increases, and BAM, the column collapses. It gives very little resistance, just as if it had been blown away.


Once it has started, there is relatively little resistance. Sure, a bent column still offers vast resistance if you were jumping up and down on it - but add a few thousands tons of falling building on top, and it's little better than paper.

As for them failing at the same time - an individual column failure cascades to the next in a fraction of a second. The failure will rip around the building like a zipper.
So the claims of "free fall" aren't correct. It could never be exactly free fall due to minimal resistance, more like "almost" free fall, right?
 
So the claims of "free fall" aren't correct. It could never be exactly free fall due to minimal resistance, more like "almost" free fall, right?

It's "essentially" freefall. If the difference is less than 0.1 seconds, then you can't really detect it from video. Read #11 here:

http://www.nist.gov/el/disasterstudies/wtc/faqs_wtc7.cfm
During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below
Content from External Source
Negligible is not zero, but close enough as to make no real difference.
 
NIST recognises a 2.25 second period of free-fall1​ but as we agree econ41 the model does not proceed to this point in the collapse sequence2​ . For now I will suggest that it concerns me because freefall acceleration is without doubt a feature of the collapse that has raised questions and is a frequent focus of objections to NIST's conclusions3​ ; it cannot be disputed that this aspect of the collapse is not explained by the model4​ . The "realistic advantage" as you put it would be to demonstrate with a model5​ (to the "layperson", if you will6​ ) that this controversial and unique aspect of the collapse has indeed been fully understood7​ , as is claimed8​ .

However, I would prefer to focus on the collapse sequence of the Towers,9​ as there are no successful models of this of any kind, to my knowledge10​.
My apology for the delay - pragmatics of real life intruded. Some preliminary points - we are mostly in agrement so far.
1, 2, 3, 4 - Agreed
5, 6 - Agreed - "layperson" however my aim is to explain to you and to show why a model is not the best way of doing it. In fact it may not be possible AND the objective is to address your concerns which I assert can be best done by explanation rather than model.
7 - understood by who? there is a lot of confusion - my aim is to clear up any confusion you may have NOT solve all the confusions for everybody involved. (Not at this satge - that may come later :rolleyes:)
8 - false claim I suggest.
9 - that is what I will focus on.
10 - My understanding also.

OK, now my offer was specific and focussed:
You appear to think that you could benefit from extended modelling. So our viewpoints are some distance apart - we need to bridge the gap. If that is the situation we can progress discussion. Otherwise show me what I have misunderstood and I'll try again.
...other members are continuing discussion on a range of related issues. I could contribute to those discussions but to facilitate our discussion I will stay focussed on the issues we are discussing. And since our discussion is dead centre on the topic of this thread - use of models - I don't think we need to shift to another thread. Guidance welcomed - and we could relocate if appropriate.

So the issues I will explore with you Cube Radio are:
1) The relevance of free fall as a factor in explaining the collapse mechanisms of the Twin Towers collapses which actually occurred on 9/11 (your preferred starting point)
2) The suitability of modelling as a tool of explanation for lay persons AND whether modelling can fulfil that purpose better than well structured explanation. I will come from the position that it cannot and will explain why as we progress.
3) The possible involvement of Malicious Human Interventions ("MHI") (other than planes and unfought fires) AKA "CD". The approach I will take is strictly neutral to the CD factor - I will comment explicitly on CD if and when it becomes necessary OR assists the explanation.

So lets see if we can agree the context for discussions.

A) The Setting is Collapse of Either "Twin Tower" - we can distinguish 1 from 2 if and when we need to.
B) I will treat the collapse initially as three distinct phases viz:
(i) "Initiation" - what happened from impact to "Top Block" starts to fall. (And not discounting CD as a possible factor at this stage.)
(ii) "Transition" - How the collapse changed from (i) "Initiation" to (iii) "Progression".
(iii) "Progression" - the rapid falling of the Global collapse of each tower. (Again not discounting CD as a possible factor at this stage.)

IMO (iii) is the one we need to focus on - it is the one with fall rates arguably approaching or a large proportion of "free fall" - without me getting all pedantic about "acceleration' v "velocity" OR getting lost in all the confusions we see posted on forums.

So - process check - have I adequately described the "start line" for further discussion?

1) Do you agree with my outline of the context?
2) Are you comfortable with the "three stages" of collapse as I have defined them?
3) Do you agree that "(iii) Progression" is the stage for which I need to explain free fall and modelling as per your expressed concerns?

Then - so I know where to start fleshing out explanations:
Are you familiar with the acronym "ROOSD" and what it refers to? Do you object if I use it? If you do I will avoid it. Otherwise it is useful "shorthand".

Are you familiar with my "Three Mechanisms" explanation of the progressive collapse stage for WTC1 ans WTC2? If not I will summarise. It has been posted on other forums but not here where I am a "newbie"

Those two are the foundations for understanding the collapse progression mechanism - therefore they are the foundations for understanding free fall related concepts in this setting AND for deciding whether modelling is a better tool than "explaining".

Cheers
Econ41
 
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