Debunked: NIST computer simulation of Building 7 collapse is inaccurate

Marc Powell

Active Member
Conspiracy theorists claim that the NIST computer simulation of the collapse of Building 7 is inaccurate because it shows walls folding in as the interior of the building crumbles away. And since the NIST simulation looks nothing like videos of the actual event where the building walls remained relatively vertical as they fell, it is asserted that the NIST hypothesis for the collapse mechanism must be wrong. In the 2014 David Hooper film, The Anatomy of a Great Deception, (viewable in its entirety at youtube.com/watch?v=l0Q5eZhCPuc ), the NIST computer simulation is presented several times. The first is at the 20:37 mark, where it is speeded up for comic effect, and the second is at the 32:34 mark where it is repeated several times interspersed with a repeated video clip of the actual global collapse. Below is a screen capture of the NIST simulation from the video clip presented in Hooper’s film:


NIST Sim Per AOAGD.jpg


The narrator (David Hooper) presents a list of presumably provable issues denied by NIST and then says, “Even the NIST computer animation of Building 7's collapse was inaccurate showing the outer structural walls crumpling in instead of coming straight down.” However, that is not true at all. NIST conducted two collapse simulations for Building 7, one that included damage due to debris impact from the collapse of the WTC North Tower and one that did not include such damage. The simulation with debris impact damage closely resembles the actual observed collapse event. The simulation shown in Hooper’s film is the other simulation that differs significantly from actual observations. Below is the NIST simulation with impact damage that Hooper should have presented:





For comparison, below is the NIST collapse simulation without impact damage (the one Hooper chose to present):





By presenting the wrong computer simulation Hooper’s film leaves its audience with the false impression that either, (1) NIST scientists are incompetent and their report unscientific or, (2) that the report is a fantasy produced strictly for political purposes. One would expect that, with all their exhaustive research, sincere seekers of truth and justice like David Hooper and his Technical Director, Richard Gage, would know about the two NIST computer simulations and make an effort to present the correct one.
 
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Thomas B

Active Member
NIST conducted two collapse simulations for Building 7, one that included damage due to debris impact from the collapse of the WTC North Tower and one that did not include such damage.
Thanks for this. It's a very good point. Do you have a reference to the part of the NIST report (or a FAQ) where this is explained?
 

Marc Powell

Active Member
Thanks for this. It's a very good point. Do you have a reference to the part of the NIST report (or a FAQ) where this is explained?
Chapter 12 of the NIST Building 7 investigation talks about the collapse simulations. The simulation with debris impact damage is covered in Section 12.4.4 and the one without impact damage is covered in Section 12.4.6. Section 12.5 compares the two simulations with actual observables and Section 12.6 summarizes findings.
 
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Landru

Moderator
Staff member
Chapter 12 of the NIST Building 7 investigation talks about the collapse simulations. The simulation with debris impact damage is covered in Section 12.4.4 and the one without impact damage is covered in Section 12.4.6. Section 12.5 compares the two simulations with actual observables and Section 12.6 summarizes findings.
Perhaps you can provide links.
 

Marc Powell

Active Member
Perhaps you can provide links.
I was referencing NIST NCSTAR 1-9. It can be downloaded at https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=861611. Section 12.4.4 starts on page 571 and Section 12.4.6 starts on page 591. In Section 12.5, Table 12-2 on page 599 compares the two simulations with actual observed events. Section 12.6, starting on page 603, summarizes findings for the collapse simulations NIST performed.

This information is also presented in a more abbreviated form in Section 3.4.6 of NIST NCSTAR 1A, available at https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1a.pdf .
 
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Mendel

Senior Member.
Thanks for this. It's a very good point. Do you have a reference to the part of the NIST report (or a FAQ) where this is explained?
Googling for "nist wtc7 collapse simulation version" gives you the FAQ, and answer 29 adresses this issue.
 

Oystein

Senior Member
Googling for "nist wtc7 collapse simulation version" gives you the FAQ, and answer 29 adresses this issue.
As per no-click policy:

29. The simulation of the collapse modeling of WTC 7 does not match the video footage of the collapse. In particular, the large inward deformations of the upper exterior walls after the beginning of global collapse are not visible in the video footage. Can NIST explain the difference between the results of its computer model of the collapse and the available video evidence?

NIST conducted two global collapse analyses, one that included damage due to debris-impact from the collapse of WTC 1, and one that did not include any debris-impact damage. These two analyses were conducted to determine the influence of the debris-impact damage on the response of WTC 7 when subjected to the effects of the fires that burned on floors 7 to 9 and 11 to 13. In its comparison of the two analyses (see NIST NCSTAR 1A Section 3.5), NIST showed that the analysis with the debris-impact damage better simulated the sequence of observed events, and it is this simulation that is considered here.

NIST believes that the simulation of the collapse, based on the analysis with debris-impact damage, does capture the critical observations derived from the digital video recording. The critical observations and corresponding failures identified in the structural analysis include: 1) east-west motion of the building beginning at approximately the same time as failure of floors 6 through 14 around Column 79, 2) the formation of the "kink" in the roofline of the east penthouse approximately one second after Column 79 was found to buckle, 3) window breakage on the east side of the north face as the buckling of Column 79 precipitated the failure of upper floors, and 4) the beginning of global collapse (vertical drop of the building exterior) within approximately one-half second of the time predicted by analysis. Both measured time and analytically predicted time, from the start of failures of floors surrounding Column 79 to the initial downward motion of the north face roofline, was 12.9 seconds (see NIST NCSTAR Report 1A, Table 3-1). The collapse observations, from video analysis of the CBS News Archive video, are covered in detail in NIST NCSTAR Report 1A Section 3.5 and NIST NCSTAR Report 1-9, Section 8.3. Only in the later stages of the animation, after the initiation of global collapse, do the upper exterior wall deformations from the NIST analysis differ from the video images.

Uncertainties associated with the approach taken by NIST are addressed in NIST NCSTAR Report 1A, Section 3.5, where it is noted, "Once simulation of the global collapse of WTC 7 was underway, there was a great increase in the uncertainty in the progression of the collapse sequence, due to the random nature of the interaction, break up, disintegration, and falling debris." The contribution to stiffness and strength of nonstructural materials and components, such as exterior cladding, interior walls and partitions, was not considered in the analyses conducted by NIST. It is well known that such non-structural components can increase the stiffness and strength of a structural system, but their contribution is difficult to quantify. Given these factors, disparities between the video and the animation in the later stages of collapse would be expected.
Source: https://www.nist.gov/topics/disaster-failure-studies/faqs-nist-wtc-7-investigation
 

econ41

Senior Member
Isn't the problem even more simple and fundamental. Two problems actually:

First the type of simulation NIST presents exaggerates the magnitude of strains to show the direction of movements. It is not intended to "look like" the real event rather to allow further engineering analysis. It is a class of simulation which intentionally does NOT "look like" the real event. That is not its purpose.

Second truthers, esp those influenced by AE911, have been taught that simulations MUST visually "look like" the actual. That is not true of all engineering modelling - some types of simulations "look like". Many dont. Both are legitimate.

THEREFORE the reason for the trickery with the Hulsey "simulations". They were deliberately "fudged" to meet the pre-set expectation of the AE911 audience. Viz Simulations which "look like" are correct - simulations which do not "look like" are wrong.

So in the broader picture "Simulations must look like the real event" is merely another of those handful of false premises which underpin much of truther lore. Other ones being "Free fall proves CD" >> it doesn't. "Falling in own footprint proves CD" >> it doesn't. "Symmetry proves CD" >> It doesn't - whatever is meant by "symmetry". And setting aside that for all three the core claim (free fall, footprint et simile) is usually false.
 
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Mendel

Senior Member.
As per no-click policy:
I was hoping to "teach a man to fish", since Thomas seemed to be aware that the NIST FAQs exist, but also appeared unable to find them. That's why I didn't provide a direct link.
I wasn't discussing the information, I was discussing how to find it.
 

Mendel

Senior Member.
First the type of simulation NIST presents exaggerates the magnitude of strains to show the direction of movements. It is not intended to "look like" the real event rather to allow further engineering analysis. It is a class of simulation which intentionally does NOT "look like" the real event. That is not its purpose.
Well, there's the simulation and the visualization of the simulation.
The simulation itself is calculating the physics and the movement that results from it, and that should reflect the event.
The visualization aims to make the results of the calculations apparent.

The problem is that when the simulation results that interest you are too small to notice, you need to exaggerate them. Kinda like all maps that show "profile" (or even all profile graphs, like for a mountain section of the Tour de France) scale height more because otherwise you wouldn't really notice the hills that much.
The profile is still based on real data, it's just visualized in a distorted way because that's more useful that way.

Is that what you're referring to?
 

econ41

Senior Member
The problem is that when the simulation results that interest you are too small to notice, you need to exaggerate them. Kinda like all maps that show "profile" (or even all profile graphs, like for a mountain section of the Tour de France) scale height more because otherwise you wouldn't really notice the hills that much.
The profile is still based on real data, it's just visualized in a distorted way because that's more useful that way.

Is that what you're referring to?
Exactly. There are broadly two main classes of simulations or modelling viz "look like" or "exaggerated to facilitate an engineering analysis purpose".

The gross distortions of the NIST model grossly exceed the ductility limits of the materials. Engineers and others familiar with the methodology are not confused. But whether intended or not the failure to "look like" the real event has been used by truther advocates to mislead followers. So that is a fundamental problem - the other details are probably of less importance.
 

Oystein

Senior Member
...the type of simulation NIST presents exaggerates the magnitude of strains to show the direction of movements. ...
I am fairly certain that this is NOT the case for the two global collapse animations in question here.
Could you please provide a citation for your claim?
 

econ41

Senior Member
I am fairly certain that this is NOT the case for the two global collapse animations in question here.
Interesting. Given the level of ductility needed to allow the large distortions.
Could you please provide a citation for your claim?
None. Other than general engineering understanding. Since that doesn't meet the criteria for this forum I won't pursue the issue. ;)
 

Oystein

Senior Member
Interesting. Given the level of ductility needed to allow the large distortions.
Right.
Which would (if I am correct and you are wrong) mean that your "general engineering understanding" fails you in this regard, or that this NIST simulation is "wrong" (a point I have seen some Truthers make: "Look at how unrealistically distorted this is, how can you believe this? And in extrapolation: How can you believe anything NIST published?" (<- obviously a paraphrase, not actual quote)) - or both.
None. Other than general engineering understanding. Since that doesn't meet the criteria for this forum I won't pursue the issue. ;)
Should be in the sub-sections of Chapter 12 of NIST NCSTAR 1-9 that @Marc Powell referenced above.
I won't pursue it either - your claim, your burden of proof.
 

econ41

Senior Member
Right.
Which would (if I am correct and you are wrong) mean that your "general engineering understanding" fails you in this regard,...
A rare but real possibility. ;)
.... or that this NIST simulation is "wrong" (a point I have seen some Truthers make: "Look at how unrealistically distorted this is, how can you believe this? And in extrapolation: How can you believe anything NIST published?" (<- obviously a paraphrase, not actual quote)) - or both.
NIST is only "wrong" in the minds of truthers who are looking for a "look like" simulation. Yes I agree (have done many times over quite a few years) that the NIST modelling does not "look like" the real event.

f course if I am wrong then the whole field of argument is open for debate....
I won't pursue it either - your claim, your burden of proof.
I have no interest in proving it. If I'm right it only adds one more example to the history of identifying fundamental issues which are rarely picked up in debates which are focused on details. If I'm wrong - I'm wrong. Add one more to the list. :confused:

By the way can I take it that you don't disagree with my starting premise - that there are two broad types of simulations/models viz "look like" and "not intended to look like"?
 

Jeffrey Orling

Senior Member
I think in this day of computer animation many assume that an animation can be created which is accurate and faithful in the details to the actual collapse. This IS possible with adequate and accurate input variables and enough computing power and time. Lots of things these days use computer simulations. Even film simulates and mixed the simulations with real "footage".
So the input variables require accuracy. I don't think this is / was available. Whomever builds these simulations has to limit the number of variables and make a lot of assumptions. Lot of hit or miss and with such complexity the desired result may elude.

So what is the purpose of such a simulation?
 

JarJar

Member
Does NIST specify if the simulation was created with a particular piece of software or engine? Or maybe by a contractor? I don't see that info anywhere.

Companies like Dassault Systèmes have used design/testing simulations without the need for a physical prototype for more than 30 years. Any variables can be programmed.

Edit: at least part of it was done with ANSYS who has a similar history of simulations. They even list the model details for the different materials in the appendix of their report.
 
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Marc Powell

Active Member
So what is the purpose of such a simulation?
My understanding is that the NIST computer simulations were intended merely to demonstrate the plausibility of the premise that a single connection failure (resulting from the effects of fire) could initiate a progressive collapse that could bring down the entire structure. The detailed discussion about beam A slipping out of connection B and slamming into floor C, causing buckling of column D, etc. is only in reference to what the model did, not to what actually happened. There were far too many assumptions made and much too much chaos in the collapse for the model representing it to provide anything more than a general idea of what may have been possible. And the farther into the collapse the simulations were carried, the more unreliable the results became. That is why NIST cut them off when they did… a few seconds into the beginning of the global collapse. And that is also why any simulation that looks exactly like the actual events (Hulsey) should be suspect. Please forgive me if I am stating the obvious. Computer modeling of building failures is not my forte.
 

Oystein

Senior Member
... And the farther into the collapse the simulations were carried, the more unreliable the results became. ...
If there is anything of real value to be learned from NIST's two LS-DYNA runs, it is this:

The outer appearance of the collapse progresses is significantly dependent on (changes significantly with varying) starting conditions.

It is very much apparent to both the amateur and the expert viewer that the collapse simulations a) with, b) without structural damage to the South face from the North Tower collapse are quite different.

Next step to understand: NIST (nor anyone else) did not know the exact extent and severity of that initial structural damage.
Also, there is of course a real degree of uncertainty about the exact extent and severity of damage accrued by the many hours of fire progression.

It follows that we must expect the collapse simulation to differ from reality, given that it is more likely than not that real damage differed from model input damage.
I would expect (and a close reading of Chapter 12 no doubt will reveal this) that NIST's assumptions for the with-initial-damage run were rather on the conservative side - that they input only the damage which has sufficient evidence from observation going for it; there may have been more damage, or more severe damage, in reality.

The with-initial-damage run still did a decent job of recreating a number of the observed significant collapse features - more than the silly Hulsey model. Such as:
  • early collapse of EPH, with correct kink in EPH itself (Hulsey has the bottom of the EPH's sides swinging outward, instead of the corners sinking inward)
  • East-to-West progression of WPH collapse
  • the kink in the Eastern portion of the North wall
  • the building twisting counter-clockwise
 

Jeffrey Orling

Senior Member
Seems to me that there were way too many variables especially as failure progresses through the structure to produce a simulation which closely resembles real world other than in gross ways.
NIST felt they had to demonstrate that a local failure at a column in the NE quadrant could produce a total collapse. They did.
 

Marc Powell

Active Member
It follows that we must expect the collapse simulation to differ from reality, given that it is more likely than not that real damage differed from model input damage.
I would expect (and a close reading of Chapter 12 no doubt will reveal this) that NIST's assumptions for the with-initial-damage run were rather on the conservative side - that they input only the damage which has sufficient evidence from observation going for it; there may have been more damage, or more severe damage, in reality.
According to firefighter reports, Building 7 had been popping, creaking and showing external deformations as the un-fought fires spread that afternoon. These were indications of internal failures that NIST had no way of quantifying and so, were not considered in its modeling of the initial damage conditions.
The with-initial-damage run still did a decent job of recreating a number of the observed significant collapse features - more than the silly Hulsey model. Such as:
  • early collapse of EPH, with correct kink in EPH itself (Hulsey has the bottom of the EPH's sides swinging outward, instead of the corners sinking inward)
  • East-to-West progression of WPH collapse
  • the kink in the Eastern portion of the North wall
  • the building twisting counter-clockwise
The Hulsey model also did not include the east-west swaying of the building that NIST determined to have started six seconds before the falling of the EPH and continued until the beginning of global collapse. The swaying, which NIST referred to as "vibration," can actually be seen in the CBS video of the collapse taken from West Street.
 

Jeffrey Orling

Senior Member
According to firefighter reports, Building 7 had been popping, creaking and showing external deformations as the un-fought fires spread that afternoon. These were indications of internal failures that NIST had no way of quantifying and so, were not considered in its modeling of the initial damage conditions.

The Hulsey model also did not include the east-west swaying of the building that NIST determined to have started six seconds before the falling of the EPH and continued until the beginning of global collapse. The swaying, which NIST referred to as "vibration," can actually be seen in the CBS video of the collapse taken from West Street.
The observations you note WERE the signs of the fire warping the frame which eventually failed. NIST sims are the collapse phase one the frame went past the point of no return structurally. Their models "begin" with the beam / girder drop on floor 13.
 
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