How Buckling Led to "Free Fall" acceleration for part of WTC7's Collapse.

Jeffrey Orling

Senior Member
I agree this is somewhat veering off-topic, but I don't want to not reply to something I find interesting to talk about just because it's technically off-topic. And it is still related... The thread is about NIST claiming that buckling explains why the roofline of the building appeared to be in free fall acceleration for about 2.25 seconds. They base this on their simulations, stating:

My question was, how do we know the simulations to be accurate? As with anything, trust should be proportional to transparency. And my trust that NIST got it right would be greatly increased if all their simulation files were publicly released. Because they're not, we depend on their say-so.
NO! "they don't base" this FFA on anything but the OBSERVATIONS. The simulations are not explanations of WHY the frame / building did what it did... but supposedly the sequence of the "behavior" of the frame....with no explanation given explaining the movements.

++++

It's basic engineering or physics that something such as a facade of a building falls DOWN because it loses axial support.

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The NIST simulation seems incorrect... but it does show total destruction. NIST showed a total collapse... something that people thought could not happen. We know it collapsed because we saw it. NO ONE NEED a simulation.

What would be more useful would be a series of force diagrams showing the forces in the frame in small increments of time from static to collapsing.
 

Mendel

Senior Member.
This seems contradictory?

If the simulation does not match the real collapse, how can you be sure the simulation explains why the collapse occurred? Just because you can get a virtual replica of WTC 7 to collapse one way inside a computer, that doesn't mean that's what actually happened on September 11th around 5:20PM.
The simulation matches a potential sequence leading to the real collapse because NIST did some research and made it match.

Now the value of science is that you can bypass all the effort of finding out what works and what doesn't if you can go to the library and read up on it. That's why you can find textbooks on nuclear physics, but the "how to build an atom bomb" texts are highly classified.

The NIST model would be analogous to a how-to textbook on turning a building stability simulation into a working, validated building demolition simulation. The value and the danger of the NIST data is exactly that.

And yes, obviously we lack data to verify that this was 100% accurate. There's still some uncertainty as to the exact sequence—maybe truss #2 failed before column 79 did instead of the other way around? But we know that the NIST sequence is a good effort to establish what could possibly have happened given the observations they collected. The simulation supports the idea that it's reasonable to think that the fires caused this collapse.
 

Henkka

Active Member
And yes, obviously we lack data to verify that this was 100% accurate. There's still some uncertainty as to the exact sequence—maybe truss #2 failed before column 79 did instead of the other way around? But we know that the NIST sequence is a good effort to establish what could possibly have happened given the observations they collected. The simulation supports the idea that it's reasonable to think that the fires caused this collapse.
This kind of circles back to something I said earlier... That if we take it at face value that the NIST simulation is accurate and done correctly, it shows that fires could cause a collapse. But it doesn't show that fires could cause the observed collapse. To accomplish that, the simulation would have to match the observations more closely in my opinion. But I'm not asking for perfection. If NIST produced a simulation that showed for example 1.8 seconds of FFA instead of 2.25 seconds, I think it would be pretty unreasonable for me to still whine about it. I would say that would be pretty damn good and convincing. But it's ultimately arbitrary when you think the simulation is "close enough" to be satisfactory.
 

Thomas B

Active Member
But Feynman was the scientist on this commission, and he talked to the engineers at NASA, and thus the report was not a whitewash, and not the precedent that I asked for.

Also, the Rogers Commission was a political commission (Presidential, even, so you had the "supreme boss" of NASA order an investigation about NASA)
How much do you know about the Rogers Commission? I don't consider myself an expert, but Feynman doesn't seem to been "the" (sole?) scientist on it, and it certainly seems to present its findings as scientific ones. In fact, this sort of language can surely also be found in the NIST report:
In arriving at this conclusion, the Commission reviewed in detail all available data, reports and records; directed and supervised numerous tests, analyses, and experiments by NASA, civilian contractors and various government agencies; and then developed specific failure scenarios and the range of most probable causative factors.
Content from External Source
https://history.nasa.gov/rogersrep/v1ch4.htm

How are you distinguishing this investigation (which included "numerous tests, analyses, and experiments by NASA, civilian contractors and various government agencies") from an "engineering" investigation?

Again, I'm not an expert, and it's been a while since I looked at it last, but it's my understanding that many committee members (including Sally Ride) felt that they were participating in a whitewash but lacked power to call it out. If Feynman hadn't pressed the point, there is good reason to think the report would have been much less conclusive about the cause in order to avoid assigning (or even insinuating) blame. In fact, one version of the story (which made it in the movie version) has it that Rogers would have rather reported that the disaster had "no known cause" than that NASA had made a mistake.

(As I've mentioned before, I think this discussion should be moved to a separate thread. I'll PM @Landru to see if that can be arranged.)
 
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Thomas B

Active Member
If argument by incredulity is acceptable to you, let me be incredulous that such an investigation has ever been subverted. It's your claim anyway, so it's your onus to support it.
The coverage back in 1986 certainly supposed that it's possible that investigations like this might be subverted. I don't think my skepticism of NIST is any stronger than the mainstream media's skepticism of NASA and the Rogers Commission we find here:

Commission sources say that Chairman William Rogers read [Feynman's] chapter and was furious. He called Feynman to Washington Wednesday and urged him to tone down his criticism of NASA because [Feynman's] chapter threatened to destroy public confidence in the space agency. (0:36-0:51)
It's interesting to see Feynman relate this story at the end as diplomatically as he could (9:07ff).*

This is basically what I was talking about when I said that government sometimes
uses official investigations to sweep problems under the rug and gloss over controversies that might cause public anxiety or civil strife.
_____
*EDIT: It's described in much greater detail (with less punches pulled) in What Do You Care What Others Think? Including his trouble with the media. Interesting stuff.
 
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Edward Current

Active Member
it shows that fires could cause a collapse. But it doesn't show that fires could cause the observed collapse.
Yes it does. The goal of the simulation was to find out what interior event could have caused the EPH to crumple as it did, which was the first obvious sign that something catastrophic was about to happen. And, the simulation did exactly that. The last part of the simulation is irrelevant. You have to recognize that nobody in the world except for layperson CT believers, and laypersons sympathetic to them, have any issue with the last part of NIST's simulation — there's a reason for that.

The analogy I use is this: Suppose a car lost control due to some manufacturing defect, flipped, and spun and landed upside down on its roof. There is a video of the crash, and the first thing that happens is that the front-right wheel suddenly rotates 45°. Engineers build a simulation of the transmission and find that if they make a particular connection fail, then with the car going at the same speed as observed, the front-right wheel rotates the same way. They hypothesize that the failure of this connection is what caused the crash. The simulation does not need to reproduce how the car subsequently spun out. If the simulated car does not land on its roof, that's completely irrelevant. The simulation did its job.
 

benthamitemetric

Senior Member
This kind of circles back to something I said earlier... That if we take it at face value that the NIST simulation is accurate and done correctly, it shows that fires could cause a collapse. But it doesn't show that fires could cause the observed collapse. To accomplish that, the simulation would have to match the observations more closely in my opinion. But I'm not asking for perfection. If NIST produced a simulation that showed for example 1.8 seconds of FFA instead of 2.25 seconds, I think it would be pretty unreasonable for me to still whine about it. I would say that would be pretty damn good and convincing. But it's ultimately arbitrary when you think the simulation is "close enough" to be satisfactory.
It would be a tremendous waste of effort to try to achieve such accuracy in a simulation of the later stages of the collapse because no one even knows for sure exactly how the internal stages of the collapse progressed and that cannot be known. NIST very painstakingly and carefully describes the limitations of its model given the limitations of its knowledge of the exact conditions of the building pre-collapse and the simplifying assumptions the software must make in simulating the structure and its failures. After millions and millions of calculations based on such simplifications and given imprecise starting conditions, of course the simulation will significantly diverge from the real event. It's amazing, frankly, that NIST and Weidlinger Assocs. were able to build the robust collapse models that they did that showed some significant aspects of the collapse that matched real world observations (even though they both started from differing initial assumptions). (ARUP didn't go that far (but didn't pretend to) and Hulsey couldn't go that far but flat-out faked that he did with misleading, hand-animated graphics.)

The fact that NIST's simulation ultimately did show a massive buckling event across the north face that corresponded with "Stage 1" of the north face collapse, and then a period of little resistance that corresponded with "Stage 2" of that collapse, is even more amazing, whether or not it perfectly synced up to the observations (which no reasonable person in their right mind should expect it to, given the limitations). Taken in the context of everything else we know about the collapse, NIST thus presented a reasonable enough explanation (which is consistent with first principles) of how it could likely have happened.

It feels like this type of conversation always just circles endlessly because, at the end of the day, truthers like you and @Thomas B, are just grasping endlessly for reasons to not believe that fire caused the collapse, so you hold the NIST report up to some arbitrary and ridiculous standard that has nothing to do with what the NIST report even claims (if you actually read it after all these years), as if its failure to meet that standard is the thing that's preventing you from looking at the preponderance of the evidence across all the available reports, public testimonies, photographs, videos, etc. and realizing that, at this point, it is beyond obvious that fire, and not some still-undefined controlled demolition methodology, brought the building down. In the chaotic noise of the collapse, truthers misinterpret the short period of near free fall acceleration of a portion of WTC7 as a signal of controlled demolition. Unsurprisingly, they are just "finding" the only signal they are looking for in the noise. But it's not a signal; it's just noise.

And, think about it, if NIST were trying to bamboozle the public on this point, wouldn't they just artificially build this period of acceleration perfectly into their model like Hulsey did? (And I know that's not fair to Hulsey--he didn't even have a model; he only had an animation. ;))
 
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Henkka

Active Member
Hulsey couldn't go that far but flat-out faked that he did with misleading, hand-animated graphics.)
And, think about it, if NIST were trying to bamboozle the public on this point, wouldn't they just artificially build this period of acceleration perfectly into their model like Hulsey did? (And I know that's not fair to Hulsey--he didn't even have a model; he only had an animation. ;))
Might respond to other stuff later, but I was wondering about some stuff regarding this specifically. I don't know that much about the Hulsey study, other than glancing through it. I've also seen Mick's video criticizing it, and I do agree the way the penthouse folds in looks odd.

But didn't he use an engineering program called SAP2000 to make the videos? Does a program like that even have tools for hand-animation, like keyframing in Blender? And didn't he also release everything in a big .zip file, so someone with SAP2000 could open the files and see if they were animated by hand? Or did he not release everything?
 

Thomas B

Active Member
no one even knows for sure exactly how the internal stages of the collapse progressed and that cannot be known.
The words "exactly" and "for sure" are doing a lot of work there. Personally, I think this idea that the internal progression isn't known, is an unnecessary concession to make. If NIST's theory is correct then we do know how the collapse progressed internally.

Yes, we need to qualify that, as NIST does, with the word "probably," and we can't know precisely how each and every column, beam, and connection moved. But not knowing "for sure exactly" is as good as knowledge gets in science.

I'm happy to say to truthers that we know that there were no bombs in the buildings and fires caused a progressive series of structural failures. I just don't know how to explain the process to them in a credible way (i.e., one that I understand myself). And I find that frustrating.
 

benthamitemetric

Senior Member
Might respond to other stuff later, but I was wondering about some stuff regarding this specifically. I don't know that much about the Hulsey study, other than glancing through it. I've also seen Mick's video criticizing it, and I do agree the way the penthouse folds in looks odd.

But didn't he use an engineering program called SAP2000 to make the videos? Does a program like that even have tools for hand-animation, like keyframing in Blender? And didn't he also release everything in a big .zip file, so someone with SAP2000 could open the files and see if they were animated by hand? Or did he not release everything?
Hulsey did release some (but not all) of his files. For example, he withheld the input to the report he received from his sponsor, AE911Truth, which was only mistakenly revealed because one of his research assistants accidentally included in the released files a screen shot of his desktop with a folder set aside for comments from Tony Szamboti (which comments were not included in the released files). I downloaded all of the files and confirmed there were two types of global models: gummy, rubber-like models that did not allow for connection failures and thus could not dynamically model anything with any degree of accuracy (which Hulsey typically used as the basis for some of the pictures in his report because showing them in action produces ludicrous results) and the models from which he released videos which were animated by hand (and also didn't include any connection failures other than those that were artificially forced). None of the models even has any collision detection built in, as any failed piece flies through the rest of the building unhindered. I was ready to pony up for SAP2000 but ultimately didn't even need the program as the files included excel spreadsheets with handrigged displacement instructions that showed how the animations were achieved. There's a whole thread on the nonsense contained in those files here. Isn't it somewhat ironic, by the way, that it seems so very few of the truthers who tell us every day that they need NIST's files have even downloaded Hulsey's, let alone looked at them or Hulsey's report critically? Suffice to say, NIST provided a far better explanation for the observed fall of the north wall of WTC7 than did Hulsey (who, in fact, provided none).
 
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benthamitemetric

Senior Member
I'm happy to say to truthers that we know that there were no bombs in the buildings and fires caused a progressive series of structural failures. I just don't know how to explain the process to them in a credible way (i.e., one that I understand myself). And I find that frustrating.
:rolleyes: Back to that schtick, eh? Can you provide a link to one of these discussions you have had with truthers where you need some help? (Hint: In reality, people don't generally devote themselves to casually educating others about concepts they themselves do not understand and find to be frustrating.)
 
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Henkka

Active Member
I was ready to pony up for SAP2000 but ultimately didn't even need the program to do it as the files included excel spreadsheets with handrigged displacement instructions that showed how the animations were achieved. There's a whole thread on the nonsense contained in those files here. Isn't it somewhat ironic, by the way, that it seems so very few of the truthers who tell us every day that they need NIST's files have not even downloaded Hulsey's, let alone looked at them or Hulsey's report critically?
That is pretty damning if true. You mention a "timed sequence of gravity multipliers" used. That seems to be the answer to my question, I was thinking there's no way there's like a timeline and keyframing tools in engineering software.

How do you think Hulsey would defend his work if accused of this? I mean, it seems pretty stupid to animate the collapse and then release the files showing you animated it. Like can you imagine some "steelman" argument for doing the visualization in that manner?
 

benthamitemetric

Senior Member
That is pretty damning if true. You mention a "timed sequence of gravity multipliers" used. That seems to be the answer to my question, I was thinking there's no way there's like a timeline and keyframing tools in engineering software.

How do you think Hulsey would defend his work if accused of this? I mean, it seems pretty stupid to animate the collapse and then release the files showing you animated it. Like can you imagine some "steelman" argument for doing the visualization in that manner?
Just watch the videos. You can see they are not dynamic simulations. The only connection failures are artificial and clearly externally induced and then the behavior of the structure that follows makes no sense as there are no collisions between any of the parts of the building as it falls. I suspect Hulsey knows the report is garbage, which is why, after 3 years of burning Ed Asner's money (RIP), he didn't even have the guts to submit his findings for peer review by any reputable third party, such as an engineering journal (or, if he did, they quietly rejected it and he never disclosed that fact); instead, he assembled a group of like minded conspiracy theorists on a "peer review panel". He'll never face those questions because he is content to travel around in his retirement on AE911Truth's dime and speak only to likeminded conspiracy theorists.

Anyway, I don't want to stray to far off topic as @econ41 will come lay down the law at some point, but the point of this particular detour is that modeling something so complex is very hard, involves path dependency and uncertainty, and NIST still managed to get a lot of it right. Attacking the NIST report for not being perfect rings hollow when you look at what they produced versus what others were able to accomplish and the difficulties anyone is up against in such an endeavor. The NIST report at least supports the idea that a buckling event could lead to the observed Stage 2, whereas no other extant research has ruled that out and no one has presented a cogent alternative hypothesis.
 
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Thomas B

Active Member
In reality, people don't generally devote themselves to casually educating others about concepts they themselves do not understand and find to be frustrating.
Right, they would come to a place like this first for help and, until they've figured out how to explain it, they'd stay out of discussions with truthers on the engineering issues.
 

Henkka

Active Member
Just watch the videos. You can see they are not dynamic simulations. The only connection failures are artificial and clearly externally induced and then the behavior of the structure that follows makes no sense as there are no collisions between any of the parts of the building as it falls. I suspect Hulsey knows the report is garbage, which is why, after 3 years of burning Ed Asner's money (RIP), he didn't even have the guts to submit his findings for peer review by any reputable third party, such as an engineering journal (or, if he did, they quietly rejected it and he never disclosed that fact); instead, he assembled a group of like minded conspiracy theorists on a "peer review panel". He'll never face those questions because he is content to travel around in his retirement on AE911Truth's dime and speak only to likeminded conspiracy theorists.

Anyway, I don't want to stray to far off topic as @econ41 will come lay down the law at some point, but the point of this particular detour is that modeling something so complex is very hard, involves path dependency and uncertainty, and NIST still managed to get a lot of it right. Attacking the NIST report for not being perfect rings hollow when you look at what they produced versus what others were able to accomplish and the difficulties anyone is up against in such an endeavor. The NIST report at least supports the idea that a buckling event could lead to the observed Stage 2, whereas no other extant research has ruled that out and no one has presented a cogent alternative hypothesis.
Yeah, let's maybe leave it... But it would be interesting to hear an opinion on from someone who works professionally with SAP2000 and is able to open the files. I've watched some SAP2000 tutorial videos, it's pretty clear it's a very abstracted program that does not put out realistic or "sexy" looking simulations like the NIST one or Kostack. Like everything is just lines that seem to bend and stretch infinitely. I'm sure it's a great program for whatever it's used for, but I've no idea if it's appropriate for simulating the collapse of a skyscraper or if Hulsey's approach was justifiable.
 

benthamitemetric

Senior Member
Right, they would come to a place like this first for help and, until they've figured out how to explain it, they'd stay out of discussions with truthers on the engineering issues.
No, they wouldn't. And did you forget that you once told me that you've been hanging around forums like this and talking to truthers for more than 10 years? In all those years of talking with truthers you somehow avoided "engineering issues"? I'd love to see what you have been discussing. Or you could just drop the schtick already.
 

Henkka

Active Member
The analogy I use is this: Suppose a car lost control due to some manufacturing defect, flipped, and spun and landed upside down on its roof. There is a video of the crash, and the first thing that happens is that the front-right wheel suddenly rotates 45°. Engineers build a simulation of the transmission and find that if they make a particular connection fail, then with the car going at the same speed as observed, the front-right wheel rotates the same way. They hypothesize that the failure of this connection is what caused the crash. The simulation does not need to reproduce how the car subsequently spun out. If the simulated car does not land on its roof, that's completely irrelevant. The simulation did its job.
I don't think this is very analogous... Like obviously in this analogy, all anyone cares about is why the wheel suddenly rotated 45 degrees. The exact manner in which the car spun out afterwards is completely irrelevant, and there's nothing surprising or unexpected about a car spinning out in that circumstance.

A steel-framed skyscraper entering free fall as the result of fires is surprising, even shocking. A computer simulation of that collapse should absolutely seek to replicate the observed FFA. If you can't replicate any amount of FFA with those simulations, let alone several seconds, then you should consider alternative explanations other than fire.
 

Edward Current

Active Member
I don't think this is very analogous
Of course.

... Like obviously in this analogy, all anyone cares about is why the wheel suddenly rotated 45 degrees.
And in the case of WTC7, all anyone in the structural engineering community cares about is what initiated the failure of the building structure, i.e., why the EPH crumpled.

If you know of anyone in the structural-engineering community who cares why 2.25 seconds of FFA (within the margin of measurement error) was measured on the north roofline in the last moments of the sequence, please cite them.
 

Mendel

Senior Member.
How much do you know about the Rogers Commission? I don't consider myself an expert, but Feynman doesn't seem to been "the" (sole?) scientist on it, and it certainly seems to present its findings as scientific ones.
Eugene Covert was another scientist/engineer on it, and he teamed up with Feynman to get a lot of the analysis done as he actually had experience with rocket engines.

But as you point out, the chairman was a politician, many other members were administrators with an interest in the outcome, and while e.g. Sally Fields was an astrophysicist, that education didn't really help.

How are you distinguishing this investigation (which included "numerous tests, analyses, and experiments by NASA, civilian contractors and various government agencies") from an "engineering" investigation?
I've not been distinguishing the investigation, the Rogers commission did a good job, and that's why I don't accept it as evidence for the general insinuation you've been using to discredit the intentions of the NIST report in lieu of lacking actual evidence you could use to discredit it.

I'm distinguishing the composition of NIST (engineers) from the composition of the Rogers commission, and I've also talked about the bias inherent in the job.

I don't really want to talk about the Rogers commission, much less in a separate thread; what I want to do is make it absolutely clear that your distrust in NIST is apparently not based on evidence or precedent, but in conspiracy theorist thinking. Now I'm not forcing anyone to trust NIST, but when you tell others to distrust it, you should be honest about the (lack of) foundation for that distrust.

Plus, who else is more trustworthy than NIST?
 

Henkka

Active Member
And in the case of WTC7, all anyone in the structural engineering community cares about is what initiated the failure of the building structure, i.e., why the EPH crumpled.
Interesting:

1.gif

Not that interesting:

5.gif

Like, what? I guess I don't have much of an argument to make here, I'm just kind of gobsmacked. What you're saying would make sense if everyone already agreed that any partial collapse of a building will always lead to a total collapse in FFA. So in that case, we would only need to find out the cause of the initial failure, with the total collapse being a mundane inevitability that doesn't require much study. But we can see from examples like the Murrah building that obviously you can have a partial collapse without a subsequent total collapse, let alone a total collapse in FFA.
 

econ41

Senior Member
Anyway, I don't want to stray to far off topic as @econ41 will come lay down the law at some point,
;) Nah!! I'm not a moderator on this Forum. But I prefer to respect the forum rules. So I have been trying to get some evasive members to focus on the topic whilst resisting the temptations to rebut their multiple side tracks and evasive derails.

Answering the actual topic is straightforward and simple depending on how deep we need to go into details. None of our three evasive would be conspiracy theorists are prepared to debate the actual topic. I've outlined the answer several times with no reasoned response...


;)
but the point of this particular detour is that modeling something so complex is very hard, involves path dependency and uncertainty, and NIST still managed to get a lot of it right. Attacking the NIST report for not being perfect rings hollow when you look at what they produced versus what others were able to accomplish and the difficulties anyone is up against in such an endeavor. The NIST report at least supports the idea that a buckling event could lead to the observed Stage 2, whereas no other extant research has ruled that out and no one has presented a cogent alternative hypothesis.
The irony is that we don't even need to refer to NIST for answers to either of the two current issues:
(1) The OP is "How Buckling Led to "Free Fall" acceleration for part of WTC7's Collapse." NOT "Was NIST's Explanation of Buckling Correct".

There is zero doubt that buckling was a major factor. There is a prima facie case that Transfer Truss failure was involved to some extent.. that aspect has NOT been eliminated/falsified and therefore MUST be considered in any discussion of to what extent buckling was the cause of observed FFA. And for legitimate argument, the question of CD has to be addressed.

It is that simple. THEN - we need to reject the attempted derails into irrelevancy or outright dishonesty. (a) the free fall was of a facade measured at the roofline. It was not freefall of the whole structure. (b) It involved the "perimeter shell" despite efforts of one of our claimants to deny the existence of the perimeter shell (and the subset - the strong moment frame which helped maintain the shell together as it fell) I won't repeat the full list of evasive tricks. All of them are easily answered BUT preferably in separate threads as per this Forum's guidelines. Which is another reason why I have been firm in challenging members to address the topic and stop evasive derailing.

(2) One other issue which is resulting in much sidetrack discussion is the unreal appearance of the NIST model. The reasons have been posted many times over the years and several times in these current discussions. Yet "both sides" continue to ignore the distinction.

Simulations are of two broad types: (i) Sims that "LOOK LIKE" the real event and (ii) Engineering sims that account for scaling by distorting some values. The NIST sim is one of that form. It does not "Look Like" the real event. (Except possibly to a professional who understands what is being done with the simulation.)

Truthers have been indoctrinated for many years in the belief that the NIST sim is wrong because it does not "look like" the real event. The Hulsey Report was commissioned to produce a "look like" pseudo sim to meet the expectations of the gullible audience of truthers.

It is disappointing that even at this late stage some debunkers still seem to be unaware of that fundamental difference in simulation types.
 
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econ41

Senior Member
And in the case of WTC7, all anyone in the structural engineering community cares about is what initiated the failure of the building structure, i.e., why the EPH crumpled.
Whilst I understand the truth of your statement it may be too "global" to satisfy a dedicated Conspiracy Theorist. (EDIT: Too late - I see that @Henkka has already "bitten". :rolleyes:)

I regard myself as a member of the "structural engineering community" and I've been interested in more. BUT my interest is in explaining WTC collapses to persons who do not understand. Laypersons, fellow professionals, and any truthers who honestly want to learn. That means I need to understand a lot more than the general run of professionals who would be fully satisfied with the part you identify. Viz: (a) What started it? and maybe (ii) Why didn't it stop? But "what started it" is the #1 issue for most professionals.
If you know of anyone in the structural-engineering community who cares why 2.25 seconds of FFA (within the margin of measurement error) was measured on the north roofline in the last moments of the sequence, please cite them.
You wouldn't even need to explain to "anyone in the structural-engineering community" why FFA is irrelevant. BUT the Truth Movement has put a lot of effort into persuading its gullible followers that "Free Fall" is significant. Specifically, the mantra "Free Fall proves CD" which is an outright lie but 99.9% of truthers believe it. Cd is one way of starting - triggering - a collapse. Free Fall Acceleration, if it occurs, is a feature of the collapse mechanism. Not what started the collapse. The start Barrier doesn't win the Horse Race. It just releases the horses to gallop.
 

Henkka

Active Member
Simulations are of two broad types: (i) Sims that "LOOK LIKE" the real event and (ii) Engineering sims that account for scaling by distorting some values. The NIST sim is one of that form. It does not "Look Like" the real event. (Except possibly to a professional who understands what is being done with the simulation.)

Truther have been indoctrinated for many years in the belief that the NIST sim is wrong because it does not "look like" the real event. The Hulsey Report was commissioned to produce a "look like" pseudo sim to meet the expectations of the gullible audience of truthers.
I linked you earlier a statement by Shyam Sunder on whether or not they intended it to be a "look like" simulation:
Here's our structural model, showing the building collapsing, which matches quite well... with the video of the event.
Source: https://www.c-span.org/video/?280569-1/investigation-world-trade-center-building-7 @ 16:30

They also have a question in the FAQ where they list everything they got right. But then they say there was "a great increase in the uncertainty in the progression of the collapse sequence", which is why they seem to think the simulation differs from the videos. I'm not really seeing anything in the answer (Question #25), about them not intending to create a simulation that "looked like" the real event.

I do kind of agree the Hulsey simulation is also sketchy. It's also maybe unnecessary? From what I gather, he's running a pretty simple and abstracted simulation of what would happen if the core and perimeter columns were all cut near-simultaneously by "something". Well, you don't have to be Sherlock Holmes or Isaac Newton to figure that out... The building would fall straight down.

And fundamentally, they are both limited by being computer simulations. Just because you can make something happen in a computer, that doesn't it mean it happened in reality. We wouldn't be poking in the dark if there had been a more thorough examination of the physical evidence. For example, did the "perimeter shell" fall on top of everything else? A detailed study of the rubble pile could've told us that.
 

econ41

Senior Member
I linked you earlier a statement by Shyam Sunder on whether or not they intended it to be a "look like" simulation:
I'm not an apologist for NIST. Merely pointing out a simple fact that seems to get lost in these discussions. And the reality is that truthers have been indoctrinated to judge a simulation on the basis of "looks like".

The sim is of zero importance to discussing the OP if "we" ever stop chasing derails and going round in circles.

The free fall occurred because something removed the support from under the perimeter shell. That is step #1. Do you agree?

If you don't we have nowhere to go. If you do we can discuss what was removed. Then, if necessary, explain why removal of some or most support can result in near "G" FFA. THAT is the topic whether we recognise the faulty presumption in the OP and deal with it OR go along with @Abdullah's "split the topic in two" derail... which for reasons which should be obvious will have to deal with how much was buckling and if any of it was transfer truss failure.
Source: https://www.c-span.org/video/?280569-1/investigation-world-trade-center-building-7 @ 16:30

They also have a question in the FAQ where they list everything they got right. But then they say there was "a great increase in the uncertainty in the progression of the collapse sequence", which is why they seem to think the simulation differs from the videos. I'm not really seeing anything in the answer (Question #25), about them not intending to create a simulation that "looked like" the real event.
I'm well aware that NIST wasn't writing to close all the holes of opportunity that could be exploited by determined conspiracy theorists. As I've explained many times - I decided in 2007 to not regard NIST (or Bazant) as authoritative. Too many "truthers" kept changing the objective, as you are now, from "Explain the Event" TO "Was NIST's explanation correct"

The facts are as I have commented, independent of any derail into "NIST said". There are two broad classes of simulations. NIST's was a technical engineering sim. Hulsey was charged with producing a "look like" (pseudo) sim to fool the gullible. (And, yes, there are legitimate valid "look like" sims. AND it is possible in some circumstances to produce a sim that does both "look like" and is engineering accurate. AND NO I won't chase that derail further in this thread.
I do kind of agree the Hulsey simulation is also sketchy. It's also maybe unnecessary?
The aim of the Hulsey project was to drag out time for AE911 making it look that the Truth Movement was still active and going somewhere. It cost ~$330k from memory. It was a failure post-release but it did serve to give 4-5(??) years of "debate". Tony Szamboti's "Missing Jolt" paper had far more success and cost AE911 nothing... But Szamboti was early in the game - before the debunker "movement" understood the collapse physics. Remember lots of academics and far too many debunkers do not, even now, comprehend the real collapse mechanisms for the WTC Twin Towers.
From what I gather, he's running a pretty simple and abstracted simulation of what would happen if the core and perimeter columns were all cut near-simultaneously by "something". Well, you don't have to be Sherlock Holmes or Isaac Newton to figure that out... The building would fall straight down.
Don't miss the irony. That is EXACTLY the big picture reality I've posted what -- 5 or 6 times?? - about the bit of free fall.
And fundamentally, they are both limited by being computer simulations. Just because you can make something happen in a computer, that doesn't it mean it happened in reality. We wouldn't be poking in the dark if there had been a more thorough examination of the physical evidence.
We don't need the sim to answer the questions currently before us. (Other than the derails into questioning the sim - which is a bit circular ;) )
For example, did the "perimeter shell" fall on top of everything else? A detailed study of the rubble pile could've told us that.
Now you are going Conspiracy THeorist looking for evidence to back a false presumption. (And the answer is "No!" for two fairly obvious reasons. The core fell inside the perimeter shell.. and probably took out those dreaded transfer trusses - CAUSING -- next step - the perimeter to drop. So SOME debris got there first can may have been under the perimeter shell as it dropped and broke up.)

And remember my oft-repeated advice... understand the collapse mechanisms. Most of these little nit-picking questions either answer themselves OR are easily understood - IF you understand the mechanism.
 
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econ41

Senior Member
Large print image which says "Kostack agrees with what econ41 has been saying for many posts.
Now @Abdullah do you understand why your attempt to split the topic into two threads is wrong?

Can we go back and discuss the OP which says: "How Buckling Led to "Free Fall" acceleration for part of WTC7's Collapse."

... Now Mr Kostack has agreed wioth what I have been saying??? We have to deal with the proportion and sequencing of the two sub-mechnaisms. Buckling and transfer truss failure. (And, of course, how they interacted..)
 

Henkka

Active Member
The free fall occurred because something removed the support from under the perimeter shell. That is step #1. Do you agree?
Yeah if any part of the building is in free fall, that would mean the support is zero. Or maybe one could say "negligible", like NIST says in their FAQ.
The aim of the Hulsey project was to drag out time for AE911 making it look that the Truth Movement was still active and going somewhere. It cost ~$330k from memory. It was a failure post-release but it did serve to give 4-5(??) years of "debate". Tony Szamboti's "Missing Jolt" paper had far more success and cost AE911 nothing... But Szamboti was early in the game - before the debunker "movement" understood the collapsed physics. Remember lots of academics and far too many debunkers do not, even now, comprehend the real collapse mechanisms for the WTC Towers.
They also did modelling of the girder connection to column 79, right? And in their opinion, it was not physically possible for the girder to be pushed off by thermal expansion. I think that part is a bit more interesting than the SAP2000 model of the whole building. Showing that the building will fall straight down if the columns are cut is just kind of obvious.
 

econ41

Senior Member
Yeah if any part of the building is in free fall, that would mean the support is zero. Or maybe one could say "negligible", like NIST says in their FAQ.
Good. So that is step #1. Remember I'm not impressed by NIST - either way. It is simple fact that "nearly FFA" means negligible support whether or not NIST agrees. NIST saying it doesn't make it any truer.

So - Step #2 - what removed the support? Buckling, TransferTruss failure, a combination of those two or CD?

And take care - the building was measured as (near enough) Free Fall ACCELERATION i.e. not necessarily "Free Fall" ["FF"].

No matter how many persons confuse the two or are loose with terminology FFA is not FF. The measured "average FFA" of the point/zone disputed by D Chandler is near certain proof that the FFA was not Free Fall >> another sideline for another time but the distinction between FFA and FF can often be critical.
They also did modelling of the girder connection to column 79, right? And in their opinion, it was not physically possible for the girder to be pushed off by thermal expansion. I think that part is a bit more interesting than the SAP2000 model of the whole building.
Just start the argument from the right end. EPH fell therefore Col 79 and associated structures must have failed.

There are three ways to fail Col 79:
(a) Gross overload >> no evidence of hundreds of tonnes of extra load being imposed - eliminate that one;
OR
(b) remove horizontal bracing so that the column goes into overload failure due to exceeding critical unbraced length; << Which is what NIST says but even that is bleeding obvious without needing NIST to say it. And despite all the silly arguments about "pushing off". If something happens it is futile arguing that it couldn't.
OR
(c) Explosive CD (It is far too big for thermXte.) 20 years on and no one has ever proved it was needed or that it was done.

So it is a two way choice either overload with existing loads due to exceeding critical length OR CD by explosives. And nobody has ever proved or even presented a plausible hypothesis for CD. Whilst loss of bracing >> exceed critical length is plausible despite all the trivial noise from AE911 and followers.
Showing that the building will fall straight down if the columns are cut is just kind of obvious.
Again the point I've been making for some weeks in recent discussions.
 

Thomas B

Active Member
Plus, who else is more trustworthy than NIST?
Like I say,
I don't think my skepticism of NIST is any stronger than the mainstream media's skepticism of NASA and the Rogers Commission
back in 1986. In fact, I think I trust NIST about as much as Feynman trusted NASA. Feynman thought the engineers were mostly doing a good job but were constantly undermined by "management". The history of science since the mid-1980s is one of increasing politicization and commercialization, so I'm not inclined to think that either organization has become more objective.

Government agencies sometimes make mistakes and often cover them up when they do. So do scientists (see https://retractionwatch.com).
 

Thomas B

Active Member
Just start the argument from the right end. EPH fell therefore Col 79 and associated structures must have failed.
As I understand the Hulsey report, in their model the failure of column 79 low in the building did not cause the EPH to fall. They had to introduce that damage much higher up, to the columns directly under the penthouse. And when they did this, the failure of the penthouse did not then cause a total failure of the buidling.

It would be interesting to see a frame by frame comparison of the NIST and UAF simulations that identifies where they diverge and explains why. (I think the reason is that the models specify different connection strengths between the elements. Someone has suggested that Hulsey gerrymandered -- lightened -- the loads above the failure. That would certainly also explain it.)

Bascially, I agree with Jeffrey that we need some diagrams.
What would be more useful would be a series of force diagrams showing the forces in the frame in small increments of time from static to collapsing.
If someone can make some simplified load path diagrams (just a few columns and floors) that capture the difference between the models (in terms of loads, connections, yield strength, etc.) this would become much clearer.

If something happens it is futile arguing that it couldn't.
But this is exactly the truther's argument. The main evidence for CD (after the destruction of most of the physical evidence) is that a plausible steel-framed building couldn't collapse (especially in free fall) without the simultaneous (not progressive) collapse of its columns. They argue that you can't get from the removal of lateral support around one column to the total collapse of the building.

So they are arguing that the "something" didn't "happen". And their evidence is that it couldn't in a reasonable model of the structure. The question is whose model is (whose initial conditions are) more reasonable. And this is where NIST's withholding of its data is a bit frustrating. We can't compare the parameters that the two investigations assumed. We have to trust NIST that their model is a reasonable representation of the WTC in its initial state.
 
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Henkka

Active Member
So - Step #2 - what removed the support? Buckling, TransferTruss failure, a combination of those two or CD?
I guess I don't know. NIST says it was buckling. I don't know enough about transfer truss failure to comment on that at all.

But as I've said, it is hard to imagine columns buckling causing the observed collapse. I know I've been spamming gifs in this thread, but just one more time:

Jun-08-2022 09-05-51.gif

It just looks like one second the building is holding just fine, and then the next it's in basically symmetrical FFA across its entire width. It happens so abruptly, the columns would have to buckle basically simultaneously, which I don't understand how that could be possible.
 

Mendel

Senior Member.
Government agencies sometimes make mistakes and often cover them up when they do.
[citation needed], especially for the 'often'. Also, you're back to overgeneralizing again.
The Federal Register lists over 100 agencies, you really feel justified to tar them all with the same brush? Or are you simply trying to cover up that you can't really support your claim?
Covering up that you have no evidence to distrust NIST? That you simply don't want to accept their results? (And again, you don't have to, but please don't cover up that it's unjustified.)

I could argue, "people sometimes lie, therefore Thomas B lies", and say that I distrust you; and that distrust might be appropriate or not; but the argument is still bunk.
Another point of yours that contradicts your own argument: a retraction is not a coverup, but rather the public acknowledgement of a serious mistake.
 
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Thomas B

Active Member
a retraction is not a coverup, but rather the public acknowledgement of a serious mistake.
You should probably read some of the stories. The process of getting a paper retracted in science is not simply one of the scientist admitting the mistake. Even journal editors usually take the side of the author until the evidence against them is overwhelming.
 

Mendel

Senior Member.
[citation needed], especially for the 'often'. Also, you're back to overgeneralizing again.
The Federal Register lists over 100 agencies, you really feel justified to tar them all with the same brush? Or are you simply trying to cover up that you can't really support your claim?
Covering up that you have no evidence to distrust NIST? That you simply don't want to accept their results? (And again, you don't have to, but please don't cover up that it's unjustified.)

I could argue, "people sometimes lie, therefore Thomas B lies", and say that I distrust you; and that distrust might be appropriate or not; but the argument is still bunk.
You should probably read some of the stories. The process of getting a paper retracted in science is not simply one of the scientist admitting the mistake. Even journal editors usually take the side of the author until the evidence against them is overwhelming.
See, that's why the Metabunk link policy prohibits you from just throwing a link out instead of making your point explicitly, with quotes.

Even our criminal justice system usually takes the side of the accused until the evidence against them is overwhelming. That's how the system is intended to work.

Your claim was about coverups, not about arguing the evidence. You're shifting the goalposts.
Your unsupported claim was that NIST not releasing some files constitutes a coverup on their part.
 

Thomas B

Active Member
Your claim was about coverups, not about arguing the evidence. You're shifting the goalposts.
The question is whether covering your mistakes is something that happens often enough in science and politics to justify skepticism when someone refuses to share their data or records. If a politician refuses to release their tax records, we don't assume that there's probably nothing to see.

In science, it's disturbingly common to hear, long after a study has been widely promoted in the media ("Eat this simple thing and live to 100!"), that the data, when closely examined, doesn't justify the published conclusions (let alone the overblown hype). Sometimes the problem is big enough to warrant a retraction. But that usually only comes after a tough fight with the scientists who did the study. Sad but true.

I could argue, "people sometimes lie, therefore Thomas B lies", and say that I distrust you
Yes, if I say something surprising or implausible and claim to a have a source that backs me up but I refuse to share that source with you, you have a reason to be suspicious. If I say, "If you can't show me cases of people lying in the past, you have to assume I'm telling the truth," that's just weird isn't it?
 

econ41

Senior Member
Just start the argument from the right end. EPH fell therefore Col 79 and associated structures must have failed.
As I understand the Hulsey report, in their model the failure of column 79 low in the building did not cause the EPH to fall. They had to introduce that damage much higher up, to the columns directly under the penthouse. And when they did this, the failure of the penthouse did not then cause a total failure of the buidling.
Remember the point I keep repeating - start with "What Really Happened" NOT "the authority" whether NIST or Hulsey.

"EPH fell" is an assertion of observable fact. Nothing to do with what NIST or Hulsey said. It is a fact independent of the protagonists of either side. And the consequence is undeniable: "...therefore Col 79 and associated structures must have failed." Why make the argument more difficult than it needs to be?
It would be interesting to see a frame by frame comparison of the NIST and UAF simulations that identifies where they diverge and explains why. (I think the reason is that the models specify different connection strengths between the elements. Someone has suggested that Hulsey gerrymandered -- lightened -- the loads above the failure. That would certainly also explain it.)
Whether it serves any useful purpose or not a "Frame by Frame" comparison won't prove anything. NIST's simulation is an engineering sim that, for legitimate reasons, grossly exaggerated the deformations. Most of which are an order of magnitude outside the ductile limits of structural steel. AND - the fatal problem - Hulsey's pseudo simulation is a bit of fudged graphic art intended to fool gullible truthers. The two are not able to be compared.
But this is exactly the truther's argument.
Not really unless you are very generous with truther illogic.
The main evidence for CD (after the destruction of most of the physical evidence)
Destruction of physical evidence is a red herring. Claims for CD must have a reasoned hypothesis and there has never been one. The physical evidence is only support. If the truther argument was valid the lack of alleged "evidence" could be of some interest.
is that a plausible steel-framed building couldn't collapse
Which is utter hogwash. It is well known and accepted fact that steel frames are vulnerable to fires. No honest person can claim otherwise unless they claim total ignorance. In which case they are not qualified to comment.
(especially in free fall) without the simultaneous (not progressive) collapse of its columns.
and you are wrong to insist on simultaneous. Your ignorance of physics is not proof. What appears to be simultaneous actually can only arise from "progressive" or "sequential" processes. Sure they are faster but must be sequential. Yet another issue where understanding of basic physics can save a lot of confusion and false arguments.
They argue that you can't get from the removal of lateral support around one column to the total collapse of the building.
Nor is their ignorance of physics any sort of proof. BTW they cannot "argue" nonsense - they may "attempt to argue".
So they are arguing that the "something" didn't "happen".
And they have never presented a valid hypothesis as "proof" of their false claim. Why don't you follow my advice and try arguing from reality. "Arguing" from false presumptions will never achieve anything.
And their evidence is that it couldn't in a reasonable model of the structure.
They are, of course, wrong. So their argument fails.
The question is whose model is (whose initial conditions are) more reasonable. And this is where NIST's withholding of its data is a bit frustrating. We can't compare the parameters that the two investigations assumed.
Why bother comparing them? Just examine the evidence. Yes, I know, you aren't qualified. So either believe those who are qualified OR don't support those who are not qualified and make false claims.
We have to trust NIST that their model is a reasonable representation of the WTC in its initial state.
Utter nonsense. Join me and those other honest persons who refuse to accept "authorities" as the peak of truth finding.
 

Jeffrey Orling

Senior Member
The facade... a curtain wall bolted to the moment frame appears to essentially drop as a tube with a kink north of column 70 (inward fold). It also appears to rotate anti clockwise around some point on the west side. It also seems to come down as a "whole". There is little evidence that the insides came down at the same time. The drop of the EPH and the WPH is a tell that the inside destruction preceded the drop of the exterior frame. The kink is a tell that there likely was not much interior on the north side... that is whole floor slabs.
The mass if the penthouses... mech equipment... is a tell that once they loose support... no slab below will likely be able to stop their collapse.
There a few ways for the perimeter frame to behave as it did is:
1 - support was removed beginning at floor 7 - 8
2 - moment frame was moved laterally off the 27 columns which supported it at floor 7 - 8
3 - a combination of 1 & 2
7wtc rotation.JPG

Note:
all the transfer structures TT1, TT2, TT3, MG 27s, MG 53 and the magenta girder were on floors 5-7
There was a perimeter 3 story truss under the perimeter frame at floor 5-7
the kink "corresponds" to the location of the east side of the core
The facade "spans" over Con Ed on the north side.

Reasonable assumptions:
The floor collapse of 47 stories would produce a debris pile of up to 5 stories high
The debris would extert a lateral force on the inside of the columns below floor 5
collapse of floors would "undermine" the 27 columns below floor 5
If the east side collapsed first, the west side could rotate (like 2WTCs top block)
the 2.25 seconds is a tell that the drop was 7 story heights
 

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