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

Mendel

Senior Member.
I don't have a dog in this race, but does this count?

The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse:
  • Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall).
  • Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
  • Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity
Content from External Source
https://www.nist.gov/pao/questions-and-answers-about-nist-wtc-7-investigation
NIST continues:
This analysis showed that the 40 percent longer descent time—compared to the 3.9 second free fall time—was due primarily to Stage 1, which corresponded to the buckling of the exterior columns in the lower stories of the north face. During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below. This is consistent with the structural analysis model which showed the exterior columns buckling and losing their capacity to support the loads from the structure above. In Stage 3, the acceleration decreased as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below.
Content from External Source
So it's "essentially in free fall" after the support has buckled, not while it is buckling.
 

Henkka

Banned
Banned
Hope you don't mind that I don't respond to every single thing, I feel like the discussion could become really unwieldy if I did that. I try to respond to things that I think would make for most interesting discussion.
Do you accept as fact that the video record shows the core collapsing first? << If you don't we need to go back and establish that fact.
I would say that the video shows the penthouse collapsing first. Then about 7 seconds later, the rest of the roof structures start going down. And then a fraction of a second after that, the perimeter walls start going down. Just from the videos, it would be hard for me to say that the entire core collapsed during those 7 seconds, since we can't see inside the building.
but that doesn't need answering. We already know that wTC7 looks different to others because it was different. The challenge is to understand why WTC7 el the way it actually did fall. NOT to review dozens of different and irrelevant other collapses.
You questioned me a lot on why I'm doing these comparisons at all. I guess to put it simply, I'm not counting out the possibility that the actual reason for the 99% g acceleration was because the building was intentionally blown up in a controlled demolition. So to suss out that possibility, the only thing you can really do is compare it to other collapses, either actual or virtual. But unfortunately there's very little to go on, really only the Plasco in terms of actual collapses.
No, we are not! The debate is about 'How Buckling Led to "Free Fall" acceleration for part of WTC7's Collapse.' And the recent discussions focused on what could have caused the period of near "g" acceleration that did in accepted fact occur with the perimeter shell of WTC7.

"We" are not discussing "soda can" crushing which is a side track you introduced and I and some other members have cautioned you against taking it. We need to comprehend why the WTC shell fell at that "speed".
I think we might be splitting hairs here... The point is the weight on top is causing the columns to buckle. If you think "crush" is the wrong term for that, sure. But it gets a bit confusing considering this thread started off with multiple demonstrations involving crushing soda cans. I'm not sure what you mean when you say I introduced that into the thread.
Why accept NIST as authoritative? Why accept Bazant as authoritative? Or any other academic? What position do you take when they are wrong?
This would make for a really interesting thread imo
 

Jeffrey Orling

Senior Member
It is my belief... that the initial floor collapse around col 79... brought 8 or more floors crashing on Transfer Truss 1 and 2. Yes or no?
If yes this led to displacement of the E-W girder across the north row of core columns Yes or no?
The MG 27 girders collapsed and the north side of the moment frame lost axial support Yes or no?
With the collapse of the MG27s the floor north of core collapsed Yes or no?
The failed north girder running from columns 62 - 79 collapse Transfer truss 3 Yes or no?
The collapse of TT3 led to the collapse of the west quadrant slabs. Yes or no?
The core columns COLLAPSED (no buckled) from the falling slabs at the west north east and south. Yes or no?
Column buckle when the load increases... or bracing is removed, Did this happen to the core columns? Yes or no?
Is it likely that the column end to end connections failed and the columns came apart... Yes or no?
 

Jeffrey Orling

Senior Member
.......

I think we might be splitting hairs here... The point is the weight on top is causing the columns to buckle. If you think "crush" is the wrong term for that, sure. But it gets a bit confusing considering this thread started off with multiple demonstrations involving crushing soda cans. I'm not sure what you mean when you say I introduced that into the thread.

This would make for a really interesting thread imo
so the columns supported the building loads (including a factor or safety)... and then something made them buckle? Without changing the load condition if the bracing is removed the column loses strength... but it also is unload because the bracing is where the floor loads transfer to the columns.
If all the core columns buckled NIST would have the buckled columns to show. Have you seen any?

Most columns did not buckle.
The perimeter columns were pushed outward from the debris accumulated from 47 floors
Core columns support few floor loads as they were framing for the elevator shafts
Collapsing floors tore apart the steel frame.
 

Edward Current

Active Member
Wasn't most of the steel quickly cleaned up and shipped off to be melted down?
No, that's a false CT talking point. All of the debris was inspected piece-by-piece by forensics experts at Fresh Kills landfill. Consider this minor beam that was found with interesting erosion characteristics (which is also a CT talking point, probably discussed in some old thread):

Screen Shot 2022-06-05 at 5.50.28 PM.png

(From https://www.fema.gov/pdf/library/fema403_apc.pdf)

I'm not counting out the possibility that the actual reason for the 99% g acceleration was because the building was intentionally blown up in a controlled demolition.
Twenty years on, you probably should, for many reasons beyond the scope of this thread.
 

Henkka

Banned
Banned
No, that's a false CT talking point. All of the debris was inspected piece-by-piece by forensics experts at Fresh Kills landfill. Consider this minor beam that was found with interesting erosion characteristics (which is also a CT talking point, probably discussed in some old thread):

Screen Shot 2022-06-05 at 5.50.28 PM.png

(From https://www.fema.gov/pdf/library/fema403_apc.pdf)

Well, I did say "most of". I've seen a clip of Jonathan Barnett being interviewed about this, but I'm not sure what documentary it's from. He says they were unable to thoroughly investigate the rubble pile as they normally would. This is the exact quote:

"When you have a structural failure, you carefully go through the debris field, looking at each item, photographing every beam as it collapsed, and every column where it is in the ground, and you pick them up very carefully and you look at each element. We were unable to do that in the case of tower 7."

I could link the video I got that from, but it's a really long CT video that's 99% other stuff. Does anyone know what documentary that quote is from? I'm not sure what he said before or after that, it's a very short clip in a random Youtube video. Either way, I'm pretty sure he's referring to how quickly the site was cleaned up.

And yeah some of the steel was examined by FEMA, but not much was left by the time NIST got started on their investigation. In fact, I think they say in their FAQ they didn't look at a single piece of physical evidence. Here is that part:

22. NIST's entire investigation included no physical evidence. How can the investigators be so sure they know what happened?

In general, much less evidence existed for WTC 7 than for the two WTC towers. The steel for WTC 1 and WTC 2 contained distinguishing characteristics that enabled it to be identified once removed from the site during recovery efforts. However, the same was not true for the WTC 7 steel. Certainly, there is a lot less visual and audio evidence of the WTC 7 collapse compared to the collapses of the WTC 1 and WTC 2 towers, which were much more widely photographed.
That part is confusing to me. It seems like they're saying they probably have WTC 7 steel still lying around somewhere, but it can't be identified? That being the case, it's strange they didn't ask to examine that eroded piece of steel, especially considering FEMA didn't come to any conclusions on what could have caused it, and called for a "detailed study" into it. They even state it's possible the erosion started "prior to collapse", weakening the building. It feels like NIST would have been in an ideal position to run physical experiments to replicate this effect on steel.
 

Edward Current

Active Member
"When you have a structural failure, you carefully go through the debris field, looking at each item, photographing every beam as it collapsed, and every column where it is in the ground, and you pick them up very carefully and you look at each element. We were unable to do that in the case of tower 7."
Who is "we" in this case? Several teams (notably Yanuzzi Demolition) were responsible for the handling at various stages. Is he saying nobody was able to look at every piece, or just his team?

This is an assumption, but I'm pretty sure the debris was photographed heavily along the way, especially anything that was anomalous. I would agree with Jeffrey that there probably wasn't much inelastic buckling going on at the individual-column scale. Most buckling (if you want to call that) refers to the entire assembly failing laterally at its connections. IIRC those were every two stories in WTC7.
 

Mendel

Senior Member.
I guess to put it simply, I'm not counting out the possibility that the actual reason for the 99% g acceleration was because the building was intentionally blown up in a controlled demolition.
how would free fall in phase 2 allow you to draw conclusions on how phase 1 was initiated? there's no logical connection, this approach cannot help you make that decision!
 

Abdullah

Active Member
@Jeffrey Orling The collapse in the east was responsible for a global loss of bracing against rotation. And the shift in center of mass caused an impulse which caused the rotation to occur. Hence buckling.Screenshot_2022-04-04-16-38-39-473_com.microsoft.office.word-01.jpeg
Notice the caption "Northward shift of interior structure spread to buckling of north exterior"
 

econ41

Senior Member
Hope you don't mind that I don't respond to every single thing, I feel like the discussion could become really unwieldy if I did that.
Agreed. So why don't we focus on ONE topic at a time? The comments from various members are drifting onto other topics in attempts to respond to your concerns. And your remaining concerns about possible cd could be holding you back from clear understanding. Let's avoid two topics being unnecessarily overlaid or conflated:

Topic #1 - The OP - "How Buckling Led to "Free Fall" acceleration for part of WTC7's Collapse." Which refers specifically to the observed and measured near FFA when the perimeter column shell fell through about 7 or 8 storeys. << THAT is the topic of this thread.

Topic #2 - which @Henkka is your remaining concern that there may have been CD involved in the WTC collapses.

It would be better if you understood why there was no CD. Two main reasons viz: (1) It was not needed - all three WTC Towers collapsed as a result of a combination of initial damage in two of the towers and unfought fires larger than the buildings were designed to withstand in all three cases. AND (2) No "truther" has ever presented valid hypotheses ("proof" if you use layperson language) that CD help was needed or that CD was performed.

SO - if you cannot set aside your concerns about CD - it would be preferable that you resolve your doubts first before adding unnecessary confusion to this discussion.

I try to respond to things that I think would make for most interesting discussion.

that is Topic #3 - take a rain check. And your response to my comment about accepting NIST, Bazant et al as "authorities"
This would make for a really interesting thread imo
... could be Topic #4. ;)

My brief responses to your comments on this thread's topic:
I would say that the video shows the penthouse collapsing first. Then about 7 seconds later, the rest of the roof structures start going down. And then a fraction of a second after that, the perimeter walls start going down. Just from the videos, it would be hard for me to say that the entire core collapsed during those 7 seconds, since we can't see inside the building.
Agreed "Penthouse" went first - that should be all we need. because it means that the internal structure under the core had failed for whatever reason. All we need to accept is that the perimeter shell fell substantially separated from the core. And, if you cannot accept that, we need to go into more reasoning. Remember - we are NOT debating the whole building collapse. Just seeking to explain why the perimeter shell had 7-8 storeys of near FFA.
You questioned me a lot on why I'm doing these comparisons at all. I guess to put it simply, I'm not counting out the possibility that the actual reason for the 99% g acceleration was because the building was intentionally blown up in a controlled demolition.
Off-topic as per previous comments.

So to suss out that possibility, the only thing you can really do is compare it to other collapses, either actual or virtual. But unfortunately there's very little to go on, really only the Plasco in terms of actual collapses.
False assumption. We can engage in reasoned analysis of the collapse physics. Remember my multiply repeated advice - First Step >> Understand the mechanism.
I think we might be splitting hairs here... The point is the weight on top is causing the columns to buckle. If you think "crush" is the wrong term for that, sure. But it gets a bit confusing considering this thread started off with multiple demonstrations involving crushing soda cans. I'm not sure what you mean when you say I introduced that into the thread.
The can is a "whole structure" We are looking at part of the WTC7. Equivalent as far as the analogy allows to a one-inch square portion of the lower part of the can. Yes, the can crushing can illustrate basic principles. In this example, it will cause more confusion >> Another derail if we need to dispose of the issue.

Is the possibility of CD still causing you confusion? Can you set it aside or do you need to go to an appropriate thread to resolve the CD issue?
 

Abdullah

Active Member
@econ41 I used to accept that the "perimeter fell substantially separated from the core". No more. According to NIST, the global collapse started at 6.9 seconds, whereas the west penthouse disappeared at 9.3 seconds. That is, it remained above the roofline well past the moment (8.65 seconds) at which freefall was achieved, and only disappeared after the roof had fallen 2m
 

Henkka

Banned
Banned
Who is "we" in this case? Several teams (notably Yanuzzi Demolition) were responsible for the handling at various stages. Is he saying nobody was able to look at every piece, or just his team?

This is an assumption, but I'm pretty sure the debris was photographed heavily along the way, especially anything that was anomalous. I would agree with Jeffrey that there probably wasn't much inelastic buckling going on at the individual-column scale. Most buckling (if you want to call that) refers to the entire assembly failing laterally at its connections. IIRC those were every two stories in WTC7.

I think he was part of the FEMA team that did the initial investigation. So that would be the "we". And there he's talking about examining the rubble pile of building as it had fallen, not so much the steel after it had already been removed.

Idk, if such photography existed, I think we would know about it? And it could be potentially acquired through FOIA.
 

Henkka

Banned
Banned
Topic #1 - The OP - "How Buckling Led to "Free Fall" acceleration for part of WTC7's Collapse." Which refers specifically to the observed and measured near FFA when the perimeter column shell fell through about 7 or 8 storeys. << THAT is the topic of this thread.

Topic #2 - which @Henkka is your remaining concern that there may have been CD involved in the WTC collapses.

It would be better if you understood why there was no CD. Two main reasons viz: (1) It was not needed - all three WTC Towers collapsed as a result of a combination of initial damage in two of the towers and unfought fires larger than the buildings were designed to withstand in all three cases. AND (2) No "truther" has ever presented valid hypotheses ("proof" if you use layperson language) that CD help was needed or that CD was performed.
I think these are largely the same topic. :D

There's two different things... 1) Could the building collapse without CD, and 2) could the building collapse in the observed manner without CD? If we take the NIST report and its simulations at face value, 1) is a yes, they performed various simulations of the building collapsing without CD. But they don't resemble the observed collapse very well, so I'd say 2) is still unknown.

Then I'm not sure if we should take the NIST report at face value. The fact that they withheld data regarding the simulation due to "public safety" concerns me.
Agreed "Penthouse" went first - that should be all we need. because it means that the internal structure under the core had failed for whatever reason. All we need to accept is that the perimeter shell fell substantially separated from the core. And, if you cannot accept that, we need to go into more reasoning. Remember - we are NOT debating the whole building collapse. Just seeking to explain why the perimeter shell had 7-8 storeys of near FFA.
Yeah clearly some internal failure led to the fall of the penthouse. But it's unclear from the videos how far it fell, and if it triggered an east-to-west chain reaction of failures. I've seen a video done by Mick that shows a kind of "wave" going all the way down across the building, so it's possible the entire internal structure below the penthouse collapsed, as seen in the NIST simulation. But imo there is no video evidence of the entire core progressively collapsing east-to-west. During those 7 seconds, the remaining roof structures don't budge, until they suddenly fall as one unit:

Jun-06-2022 11-01-53.gif

If there was an east-to-west collapse of the core, I would maybe expect them to fall more like this:

Jun-06-2022 11-14-38.gif

So I think calling it just the "perimeter shell" requires us to make assumptions about things we can't see... We can't see inside the building. So it's hard to say what's going on there exactly. So I would maybe say the observed roofline was in FFA, rather than "perimeter shell".

And even if I agree it was just the perimeter shell, why would it go straight down at 99% of g? Rather than becoming floppy and then falling one way or another.
 
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econ41

Senior Member
@Henkka I have tried to help you. But your evasions continue. Please focus on a reasoned sequence of logical explanations.

I think these are largely the same topic. :D
They aren't for reasons I have outlined and which you could discuss if you stop the obstructive comments.

There's two different things... 1) Could the building collapse without CD,
It did. That is both the staus of debate and the true situation as any honest person competent in physics and logic could explain if you ever stop the obstructive comments.
and 2) could the building collapse in the observed manner without CD?
It did. Same comments as above.
If we take the NIST report and its simulations at face value,
Why accept NIST or any other authority - reason from the basic facts and available evidence.
1) is a yes, they performed various simulations of the building collapsing without CD. But they don't resemble the observed collapse very well,
Then YOU need to learn why engineering simulations come in two main varieties -
(a) Those that "look like" the real event; and
(b) Those that don't "look like' because they need to provide quantifiable engineering data and therefore need to deal with the issues of "scaling".

Remember AE911Truth sp[ent $330k "buying" a faked report to fool supporters - and one of its main tricks was pseudo "simulations" manipulated to meet the expectations of gullible supporters who wanted "look like" graphics.
so I'd say 2) is still unknown.
It isn't but if you need that false assumption... your call.
Then I'm not sure if we should take the NIST report at face value.
Fully agreed. So stop using NIST as the absolute authority. I made that choice back in 2007 within two weeks of first joining on-line discussions.
The fact that they withheld data regarding the simulation due to "public safety" concerns me.
OK. So you have conspiracy theorist biases.
Yeah clearly some internal failure led to the fall of the penthouse. But it's unclear from the videos how far it fell, and if it triggered an east-to-west chain reaction of failures. I've seen a video done by Mick that shows a kind of "wave" going all the way down across the building, so it's possible the entire internal structure below the penthouse collapsed, as seen in the NIST simulation. But imo there is no video evidence of the entire core progressively collapsing east-to-west. During those 7 seconds, the remaining roof structures don't budge, until they suddenly fall as one unit:
So what? I"ve already challenged you to address the real issue - and the issue that is "on-topic" - Something removed the supports from under the perimeter shell. Whether to not you agree that there was a perimeter shell. Only three possibilities for removing that support are "on the table for debate". They are (1) Column buckling alone - the implicit claim of the thread OP; (2) Column buckling in some combination with Transfer Truss failures OR (3) Some form of CD for which no one has EVER presented a viable hypothesis of how it was done or proof that it was done or rebutted the physics which says it wasn't needed.
So I think calling it just the "perimeter shell" requires us to make assumptions about things we can't see...
Hogwash. Giving something that exists is valid. Denying that it exists is dishonest.
We can't see inside the building. So it's hard to say what's going on there exactly.
Yes. That is why the truth movement switched focus to WTC7 to support its nonsense claims for CD. All the necessary evidence was visible for Twin Towers. It's hidden for WTC7 so it needs a bit of engineering physics proficient intelligence to work out some of the bits of mechanism.
So I would maybe say the observed roofline was in FFA, rather than "perimeter shell".
So bleeding what? The topic issue is what caused the observed FFA of what was seen falling on 9/11. That question does not depend on, is not affected by your denials of reality.
And even if I agree it was just the perimeter shell, why would it go straight down at 99% of g? Rather than becoming floppy and then falling one way or another.
At last, you get to the point. Sadly you just repeat the question without adding value. Here for the umpteenth time are the answers you are pretending have not been given:
(1) It went down because support had been removed.
(2) I've now several times advised you what the options are for "removing support". Here we go again: (a) Column buckling; (b) Column buckling was somehow assisted by transfer truss failure OR CD which did not happen. Take your pick out of the other two. My position hasn't shifted in years.
(3) It didn't "[become] floppy and then falling one way or another".It fell straight down because something removed the support. we are supposed to be discussing what removed the support. I've identified three options. Which one do you prefer? Why? Do you want to suggest something else?

Let's stop the going round in circles and discuss the topic.
 
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Jeffrey Orling

Senior Member
So we "know" some things:
EPH was the first movement and it seems to drop right down through the tower. This likely means that support was destroyed well below the columns below the roof level.
For the facade and moment frame to "drop together more or less intact" it lost support all around the perimeter most likely around the 7th or 8th floors. Why? Because its motion shows a de-acceleration above dropping 7 or 8 floors...
A good hypothesis that there was a something that undermined the columns at the base of the tower up to the 3 story belt truss at floors 5-7. Likely cause was collapsed debris from the 40 stories above this location which the bottom "perimeter" could not contain... and which caused the 27 columns at the base to buckle/fail/be displaced
Seems likely that this was a entire footprint wide event... collapsed floors destroyed the entire perimeter support of the building.
Maybe
 

Jeffrey Orling

Senior Member
So... the moment frame, by design was very stiff/rigid and was a structural tube which supported the outer side of the slabs. There were no columns on the floors outside the elevator or except cols 79, 80 & 81. So it was a largely "column free floor space".
No one will dispute that something led to a "total failure" of column 79-80 and maybe 81 because the entire EPH lost support and dropped down through the building. It was above those three columns. Along with the failure of these 3 columns was the entire floor area of the east / north east side of the tower over the entire height of the building.
Though we can't see inside the base, it's more than likely that a pile up of 47 stories of floors and contents would exert outward force at the base of the facade "tube".... The rigid moment frame went from floors 5 to the roof with a 3 story belt truss around its base at floors 5-7... and one at floors 22-24. These made the tube quite rigid and when the 27 columns supporting the tube failed/buckled... the tube, without axial support dropped straight down... 100' + the height where the moment frame essentially "began".

It is a reasonable assumption that the collapse of 47 floors of materials onto transfer trusses 1 and 2 would cause them to fail and impart a westward impulse to the core and especially the girder joining and supported by the core's north columns. This girder also supported the MG17 cantilever girders. The moment frame's north side was on those cantilevers.

So the "sequence" may have been:

1. Failure at column 79 (80 & 81)
2. EPH collapses
3. Beams and Girders framed into those columns and the moment frame collapsed
4. Floor slabs supported the these girders lost support and they too collapsed (min entire east side floor system plus the floors north of the core.
5. Falling floor mass destroyed the transfer trusses at floors 5-7 East of (and framing into) the core
6. A westward moving wave of destruction is set off by the collapse of the East transfer trusses involving the north side of the core and the MG17 girders supported there.
7. Transfer truss 3 on the west side of the core collapses
8. The floor areas west of the core collapse including the WPH
9. North slabs collapse with the failure of the MG17s
10. Core which is mostly elevator shafts collapses
11. When the core collapses the floors areas to the south lose support and collapse
12. East, North, South and West of the floor systems collapse
13. The tower has been "hollowed out" and all the floor and contents pile up at the base inside the facade tube
14. The massive debris pushes outward in all directions and undermines the 27 columns supporting the moment frame.
15. The "hollow" moment frame then collapses 8 stories (100+ feet) with no support at close to FF in 2.25 seconds
16. Parts of the tube lay atop the massive debris of the collapsed building

As with the twin towers... floor collapse destroyed the entire building
As with the twin towers... over heated, expanded, warped lateral steel led to buckling of axial structures (columns)
As with the twin towers - loss of lateral structure (failure) led to local floor collapse which "grew" to involve entire foot print.
Unlike the twin towers... the floor collapse in 7WTC was a "crush down" at the bottom
The twin towers failure high in the structures freed a mass (floors) which drove a runaway floor collapse to the bottom bypassing columns
All floor collapses bypassed columns.. but led to the failure of columns robbed of lateral bracing.
 
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Henkka

Banned
Banned
OK. So you have conspiracy theorist biases.
I don't think NIST withholding their simulation data is evidence they're part of some conspiracy... The most likely explanation in my opinion is that they don't feel very confident that they got it right. At the very least, I don't believe their reasoning for saying the release of the data would "jeopardize public safety". Here was that reasoning:
This information was exempt from public disclosure under Section 7d of the National Construction Safety Team Act because it was determined by the Director of NIST that release of the files might jeopardize public safety. The withheld information contains detailed connection models that have been validated against actual events, and therefore, provide tools that could be used to predict the collapse of a building. The information contained in the withheld files is sufficiently detailed that it might be used to develop plans to destroy other, similarly constructed, buildings.
It's totally farfetched, I would even say ludicrous, to believe that some terrorist could dig through these files and use them to develop plans to destroy some other building. Terrorists are generally content to blow stuff up, shoot people, drive cars into crowds etc. They're not doing advanced engineering analysis to cause the total collapse of buildings. Now you could say this is conspiracy theorist thinking, and yeah many truthers have made this argument, but isn't this also what a skeptic should do? Be skeptical of government authorities when they make claims that don't make sense?
Then YOU need to learn why engineering simulations come in two main varieties -
(a) Those that "look like" the real event; and
(b) Those that don't "look like' because they need to provide quantifiable engineering data and therefore need to deal with the issues of "scaling".
I would definitely like to see a simulation that "looked like" the real event. I don't think that's too much to ask.

Also, what is the basis for saying NIST did not intend to create a simulation that "looked like" the real event? Here's what Shyam Sunder said about it at the press conference:
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
(2) I've now several times advised you what the options are for "removing support". Here we go again: (a) Column buckling; (b) Column buckling was somehow assisted by transfer truss failure OR CD which did not happen.
I don't believe that it has been sufficiently demonstrated, through real world experiments or computer simulations, that (a) or (b) would result in the observed collapse.
 

Abdullah

Active Member
@econ41 the relative displacements are so small as to suggest that the floors were still connected, and providing lateral bracing, when the north wall buckled. This suggests that the notion of a hollow tube crumpling is incorrect.

@Jeffrey Orling thinks he had an explanation, but it's too speculative for debunking. And it is not needed, as NIST has another, backed up by analysis.
 

Abdullah

Active Member
@econ41 and I forgot to mention the second reason. You mentioned load redistribution, but I'm not sure that the floor connections could redistribute significant load, especially given what haf happened not 7 seconds esrlier
 

Jeffrey Orling

Senior Member
I don't think NIST withholding their simulation data is evidence they're part of some conspiracy... The most likely explanation in my opinion is that they don't feel very confident that they got it right. At the very least, I don't believe their reasoning for saying the release of the data would "jeopardize public safety". Here was that reasoning:

It's totally farfetched, I would even say ludicrous, to believe that some terrorist could dig through these files and use them to develop plans to destroy some other building. Terrorists are generally content to blow stuff up, shoot people, drive cars into crowds etc. They're not doing advanced engineering analysis to cause the total collapse of buildings. Now you could say this is conspiracy theorist thinking, and yeah many truthers have made this argument, but isn't this also what a skeptic should do? Be skeptical of government authorities when they make claims that don't make sense?

I would definitely like to see a simulation that "looked like" the real event. I don't think that's too much to ask.

Also, what is the basis for saying NIST did not intend to create a simulation that "looked like" the real event? Here's what Shyam Sunder said about it at the press conference:

Source: https://www.c-span.org/video/?280569-1/investigation-world-trade-center-building-7 @ 16:30

I don't believe that it has been sufficiently demonstrated, through real world experiments or computer simulations, that (a) or (b) would result in the observed collapse.
There sim looks poor because NIST ignored the role that the transfer structures played in what they called - global collapse. Any engineer can see that the failure of the transfer structure would be fatal and cause footprint wide destruction unlike any local floor collapse would.
I believe the building's engineer Cantor asserted that the transfer structures failure is what "did in" the tower. And he recognized correctly that TRANSFERS move loads laterally and this is how the entire building was rapidly involved. NIST's global collapse sounds like something caused all the columns to fail without suggesting how that might work.
One could argue that it was actually the failure of the transfer structure which was the proximate cause of collapse.
And the proximate cause of the truss failures was the massive dynamic loading from collapse of 40 stories on them.
It took a lot of force to move those trusses.... and 40 stories of collapsing floors was that force.
Would/could the collapsing floors destroy the columns if there has been no transfer trusses?
Maybe yes but likely no. We saw stunning evidence that floor collapses BYPASS the columns which support them - the "spires"... And that remaining columns topple without the bracing the floors provided.
An interesting study would be to determine with more precision/certainty how the local floor collapse turns into a floor wide global one. Happened in the twins and happened in 7WTC.
My hunch for the twins is that the fall top blocks wrecked the entire floor footprint...
My hunch for 7WTC is that the transfer structure failures caused the entire footprint involvement

So historically FEMA was aiming blame at the truss system in 7WTC which did not have light long span steel web bar trusses. In the twins NIST aimed the blame at the floor trusses... but they were likely wrong for multiple reasons.
The cores dropped because the columns failed... likely buckled related to fires in the core destroying bracing. The perimeter was less affected by the fires and certainly the fire was not throughout the entire footprint as it would be required for NIST's truss pull in theory. But once the tops were free and dropping... it was settled engineering which explains the runaway floor destruction called pancaking rather than the more accurate vertical avalanche.
7's demise was more like a CD which targets key columns low down causing the top to drop and the building is destroyed in a crush up.
@econ41 the relative displacements are so small as to suggest that the floors were still connected, and providing lateral bracing, when the north wall buckled. This suggests that the notion of a hollow tube crumpling is incorrect.

@Jeffrey Orling thinks he had an explanation, but it's too speculative for debunking. And it is not needed, as NIST has another, backed up by analysis.

All explanations are speculative... including NIST's. There is very little data to work with aside from the design of the existing structure.
 

Jeffrey Orling

Senior Member
I don't think NIST withholding their simulation data is evidence they're part of some conspiracy... The most likely explanation in my opinion is that they don't feel very confident that they got it right. At the very least, I don't believe their reasoning for saying the release of the data would "jeopardize public safety". Here was that reasoning:

It's totally farfetched, I would even say ludicrous, to believe that some terrorist could dig through these files and use them to develop plans to destroy some other building. Terrorists are generally content to blow stuff up, shoot people, drive cars into crowds etc. They're not doing advanced engineering analysis to cause the total collapse of buildings. Now you could say this is conspiracy theorist thinking, and yeah many truthers have made this argument, but isn't this also what a skeptic should do? Be skeptical of government authorities when they make claims that don't make sense?

I would definitely like to see a simulation that "looked like" the real event. I don't think that's too much to ask.

Also, what is the basis for saying NIST did not intend to create a simulation that "looked like" the real event? Here's what Shyam Sunder said about it at the press conference:

Source: https://www.c-span.org/video/?280569-1/investigation-world-trade-center-building-7 @ 16:30

I don't believe that it has been sufficiently demonstrated, through real world experiments or computer simulations, that (a) or (b) would result in the observed collapse.
There sim looks poor because NIST ignored the role that the transfer structures played in what they called - global collapse. Any engineer can see that the failure of the transfer structure would be fatal and cause footprint wide destruction unlike any local floor collapse would.
I believe the building's engineer Cantor asserted that the transfer structures failure is what "did in" the tower. And he recognized correctly that TRANSFERS move loads laterally and this is how the entire building was rapidly involved. NIST's global collapse sounds like something caused all the columns to fail without suggesting how that might work.
One could argue that it was actually the failure of the transfer structure which was the proximate cause of collapse.
And the proximate cause of the truss failures was the massive dynamic loading from collapse of 40 stories on them.
It took a lot of force to move those trusses.... and 40 stories of collapsing floors was that force.
Would/could the collapsing floors destroy the columns if there has been no transfer trusses?
Maybe yes but likely no. We saw stunning evidence that floor collapses BYPASS the columns which support them - the "spires"... And that remaining columns topple without the bracing the floors provided.
An interesting study would be to determine with more precision/certainty how the local floor collapse turns into a floor wide global one. Happened in the twins and happened in 7WTC.
My hunch for the twins is that the fall top blocks wrecked the entire floor footprint...
My hunch for 7WTC is that the transfer structure failures caused the entire footprint involvement

So historically FEMA was aiming blame at the truss system in 7WTC which did not have light long span steel web bar trusses. In the twins NIST aimed the blame at the floor trusses... but they were likely wrong for multiple reasons.
The cores dropped because the columns failed... likely buckled related to fires in the core destroying bracing. The perimeter was less affected by the fires and certainly the fire was not throughout the entire footprint as it would be required for NIST's truss pull in theory. But once the tops were free and dropping... it was settled engineering which explains the runaway floor destruction called pancaking rather than the more accurate vertical avalanche.
7's demise was more like a CD which targets key columns low down causing the top to drop and the building is destroyed in a crush up.
 

Jeffrey Orling

Senior Member
@Jeffrey Orling thinks he had an explanation, but it's too speculative for debunking. And it is not needed, as NIST has another, backed up by analysis.
This is actually humorous. NIST's analysis is based on what they think (no one could see) happened to the beams and girders around col 78 and likely 80 and 81... over several floors. Their assumption begins with failures of multiple beams and girders leading to local floor collapse in that region.

Their analysis then asserts / concludes that global collapse ensued. Quite a leap there
I make no detailed claims... rather try to show a progressive of likely failures based on visual evidence and the nature of the steel frame.

Debunk that 40 stories of floors falling in the NE would destroy the transfers or cause them to displace enough to cause further destruction/failures to the west low down in the tower. Collapsing floors don't bypass lateral members like beams, girders and transfer trusses
fig-5-6A.gif

WTC 7 support.jpg
EPH_page1.jpg
 

FatPhil

Senior Member.
Here you can see that the roof and penthouse move nearly at the same timeezgif.com-gif-maker (8).gif
Personally, I'd describe it the exact opposite way. There are at least 3 frames of that sequence where the penthouse is in motion and the rest of the roof that we can see isn't.
 

Abdullah

Active Member
@Jeffrey Orling

1. How could NIST havr ignored the transfers?

2. NIST did not do s good job of explaining the mechanism for failure progression. I have asserted this elsewhere, as @econ41 will be aware. But their simulations may contain enough information to find it.

3. That we take NIST as an authority is essential because conspiracy theorists will not budge otherwise
 

Jeffrey Orling

Senior Member
@Jeffrey Orling

1. How could NIST havr ignored the transfers?

2. NIST did not do s good job of explaining the mechanism for failure progression. I have asserted this elsewhere, as @econ41 will be aware. But their simulations may contain enough information to find it.

3. That we take NIST as an authority is essential because conspiracy theorists will not budge otherwise
I don't care about the conspiracy nuts...
Few are informed enough to even discuss the matter.
My interest was basically I wanted to understand how these massive buildings collapsed. There may be multiple ways it could happen. But all I need a one sensible explanation and I am satisfied. I doubt we will ever know for sure and precisely what happened... how it progressed in anything but a "gross" way.
 

Abdullah

Active Member
NIST very specifically discusses the fate of Truss 1 and 2. Truss 1 is shown to not collapse, whereas Truss 2 does. So we can't say they completely ignored the transfers.

Moreover, they state that the collapse of Truss 2 was not essential to the failure of it's columns.
 

Jeffrey Orling

Senior Member
NIST very specifically discusses the fate of Truss 1 and 2. Truss 1 is shown to not collapse, whereas Truss 2 does. So we can't say they completely ignored the transfers.

Moreover, they state that the collapse of Truss 2 was not essential to the failure of it's columns.
Yea sure... TT1 is standing when the dust settles.... hahahahaha
 
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benthamitemetric

Senior Member
I don't think NIST withholding their simulation data is evidence they're part of some conspiracy... The most likely explanation in my opinion is that they don't feel very confident that they got it right. At the very least, I don't believe their reasoning for saying the release of the data would "jeopardize public safety". Here was that reasoning: ...
It's totally farfetched, I would even say ludicrous, to believe that some terrorist could dig through these files and use them to develop plans to destroy some other building. Terrorists are generally content to blow stuff up, shoot people, drive cars into crowds etc. They're not doing advanced engineering analysis to cause the total collapse of buildings. Now you could say this is conspiracy theorist thinking, and yeah many truthers have made this argument, but isn't this also what a skeptic should do? Be skeptical of government authorities when they make claims that don't make sense?
The decision to withhold the data was not even made by NIST. It was made by the Office of the General Counsel to the Department of Transportation, which is the agency that oversees NIST. There is absolutely no reason to believe that this decision was made based on a concern with the quality of the work product. That is pure speculation based on your bias towards believing there was some sinister conspiracy afoot. Instead, the Office of the General Counsel to the Department of Transportation relied upon public safety as the reason for its denial and, importantly, the FOIA filer chose not to exercise such filer's right to appeal that determination.

Perhaps the Department of Transportation's decision was too risk averse, but it's not absurd or farfetched, and it's certainly not surprising if you understand that, fundamentally, governmental agencies will be risk averse in general and here, while the risk may be very remote, the potential damage would be very high and, on other hand, the benefit to releasing those files would be very low. It is also worth pointing out that the statutory framework for adjudicating a FOIA request has no bearing on whether other researchers who would actually use that data for legitimate purposes could receive it from NIST; it only governs requests that are made via a FOIA request. As the chief findings of the NIST report survived a prolonged period of actual peer review by the Journal of Structural Engineering, it seems that actual experts on this topic were able to receive from the NIST authors everything they felt they needed to see in order to evaluate those findings.

(Sorry to others for the aside, but the FOIA denial is constantly misunderstood.)
 
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