Frank Greening submits withering critique of new WTC7 drafts

[funk de fino]

Will you be responding to Frank Greening's criticism of the NIST wtc7 report? Or do you still have the scientist and 911myths contributor on ignore?

Greening is banned here.

 

[mchapman]

Greening is banned here.

Ah so the scientist was banned. Explains it all. Greening doesnt need to be a member here for gravy to respond.

 

[Norseman]

Much ado about nothing

The whole issue of the visual similarity between NIST's WTC 7 collapse simulation and the real collapse goes back to post #10 in this thread. In that post mrbaracuda quoted a critique of the NIST WTC 7 report written by Dr. Greening that was posted on The 911 Forum. The relevant part is this:

Now consider NIST’s version of the final moments of WTC 7 as exemplified by the computer-generated simulacra of Figure 12-69 of NCSTAR 1-9. These images of the final collapse of WTC 7 from the north, west and south show very extensive buckling of the exterior columns especially near the mid-height of the building. It is simply astounding that, even though these computer generated images of a crumpled and severely distorted Building 7 look nothing like the video images of the real thing, NIST nevertheless concludes: “the global collapse analyses matched the observed behavior reasonably well.”

Soruce: The 911 Forum

In connection with this mrbaracuda posted a screenshoot of Figure 12-69 from NIST NCSTAR 1-9 vol 2.

The problem here is that everybody took Figure 12-69 and the claim by Dr. Greening at face value and jumped the gun. And from there everything went downhill with accusations going back and forth about the scale used. I am not going to repeat what has been posted, the interested reader can go back in the thread and find the relevant posts.

Because what nobody here did, as far as I can judge, was to check the context of that figure. Had they done so, they would have found that Figure 12-69 shows the final part of the NIST WTC 7 collapse simulation without WTC 1 debris impact damage. The fact is that the collapse simulation with debris impact damage is quiet similar to what the real collapse looked like in available videos.

On this page NIST has posted a video of the collapse together with animations of the collapse simulations with and without debris impact damage:
http://www.nist.gov/public_affairs/releases/wtc_videos/wtc_videos.html

The following figures from NIST NCSTAR 1-9A should also be relevant:

• Figure 4-43 to 4-45 showing the collapse with debris impact damage.
• Figure 4-61 showing the collapse without debris impact damage.

 

[funk de fino]

Ah so the scientist was banned. Explains it all. Greening doesnt need to be a member here for gravy to respond.

Unhealthy obsession with Gravy. He has already admitted he has not read the WTC7 report so how can he respond?

keep up

 

[Slayhamlet]

Wow. Good call, Norseman. I figured the points Dr. Greening was critiquing would be so far over my head that I didn't even bother to read the report and make sure he was representing it correctly. I'm at a loss as to how Dr. Greening could have made such a fundamental misrepresentation of NIST's work without knowing it.

This should have been caught much sooner. It just goes to show that actually reading the report is the best way to debunk most of the nonsense claims made against it.

The collapse videos are superb, btw. Thanks for linking to them.

 

[rwguinn]

The whole issue of the visual similarity between NIST's WTC 7 collapse simulation and the real collapse goes back to post #10 in this thread. In that post mrbaracuda quoted a critique of the NIST WTC 7 report written by Dr. Greening that was posted on The 911 Forum. The relevant part is this:

Soruce: The 911 Forum

In connection with this mrbaracuda posted a screenshoot of Figure 12-69 from NIST NCSTAR 1-9 vol 2.

The problem here is that everybody took Figure 12-69 and the claim by Dr. Greening at face value and jumped the gun. And from there everything went downhill with accusations going back and forth about the scale used. I am not going to repeat what has been posted, the interested reader can go back in the thread and find the relevant posts.

Because what nobody here did, as far as I can judge, was to check the context of that figure. Had they done so, they would have found that Figure 12-69 shows the final part of the NIST WTC 7 collapse simulation without WTC 1 debris impact damage. The fact is that the collapse simulation with debris impact damage is quiet similar to what the real collapse looked like in available videos.

On this page NIST has posted a video of the collapse together with animations of the collapse simulations with and without debris impact damage:
http://www.nist.gov/public_affairs/releases/wtc_videos/wtc_videos.html

The following figures from NIST NCSTAR 1-9A should also be relevant:

• Figure 4-43 to 4-45 showing the collapse with debris impact damage.
• Figure 4-61 showing the collapse without debris impact damage.

Wow. Good call, Norseman. I figured the points Dr. Greening was critiquing would be so far over my head that I didn't even bother to read the report and make sure he was representing it correctly. I'm at a loss as to how Dr. Greening could have made such a fundamental misrepresentation of NIST's work without knowing it.

This should have been caught much sooner. It just goes to show that actually reading the report is the best way to debunk most of the nonsense claims made against it.

The collapse videos are superb, btw. Thanks for linking to them.

I'll echo that. A lot of cpu time tied up there--and one hell of a lot of manpower in the model. No wonder it took so long to publish.

Having spent 20+ years dealing with people who do not understand a FEA deflection plot, I admit I didn't go directly to the source data. I recognized a normalized plot, and stated it. It is still the case--the deflections are not to scale (that is what "no scale factor was used" means), but are normalized to some max (or min, depending on which absolute is greater), and expressed relative to that. Doesn't matter which model it is.

 

[DC]

The whole issue of the visual similarity between NIST's WTC 7 collapse simulation and the real collapse goes back to post #10 in this thread. In that post mrbaracuda quoted a critique of the NIST WTC 7 report written by Dr. Greening that was posted on The 911 Forum. The relevant part is this:

Soruce: The 911 Forum

In connection with this mrbaracuda posted a screenshoot of Figure 12-69 from NIST NCSTAR 1-9 vol 2.

The problem here is that everybody took Figure 12-69 and the claim by Dr. Greening at face value and jumped the gun. And from there everything went downhill with accusations going back and forth about the scale used. I am not going to repeat what has been posted, the interested reader can go back in the thread and find the relevant posts.

Because what nobody here did, as far as I can judge, was to check the context of that figure. Had they done so, they would have found that Figure 12-69 shows the final part of the NIST WTC 7 collapse simulation without WTC 1 debris impact damage. The fact is that the collapse simulation with debris impact damage is quiet similar to what the real collapse looked like in available videos.

On this page NIST has posted a video of the collapse together with animations of the collapse simulations with and without debris impact damage:
http://www.nist.gov/public_affairs/releases/wtc_videos/wtc_videos.html

The following figures from NIST NCSTAR 1-9A should also be relevant:

• Figure 4-43 to 4-45 showing the collapse with debris impact damage.
• Figure 4-61 showing the collapse without debris impact damage.

this is correct, Figure 12-69 is without the impact damage.

but you can compare it to the other Figure, those with impact damage, and it does still not fit.

 

[DC]

I'll echo that. A lot of cpu time tied up there--and one hell of a lot of manpower in the model. No wonder it took so long to publish.

Having spent 20+ years dealing with people who do not understand a FEA deflection plot, I admit I didn't go directly to the source data. I recognized a normalized plot, and stated it. It is still the case--the deflections are not to scale (that is what "no scale factor was used" means), but are normalized to some max (or min, depending on which absolute is greater), and expressed relative to that. Doesn't matter which model it is.

I have some trouble understanding that.
are you saying that the deflections are not 1:1 ?

NIST wrote:

Thank you for your inquiry regarding the analysis of the collapse of World Trade Center 7. In answer to your questions regarding displacement scaling, there was no displacement scaling in any of the figures shown for the ANSYS analyses (NCSTAR 1-9, Chapter 11) or the LS-DYNA analyses (NCSTAR 1-9, Chapter 12 and NCSTAR 1-9A). With respect to the large deflection (NLGEOM) this was set to to “ON” so that large deflection effects were captured by the analyses. I hope this answers your questions.

When NLGEOM is set ON, then the default settings change, you dont longer have the default deflection scale of 5% of the total length of your model. You have a 1:1 deflection scale, this means, that the deflections will not be amplified NOR normalized. when there is a deflection of 1 meter, ANSYS will display it as 1 meter deflected and not as 2 meter deflected nor as 0.5 meter deflected.

12.3.1. Controlling Displaced Shape Displays
You can control displaced shape displays in two ways:

By superimposing undisplaced and displaced shapes. A display of a structure's displaced shape will often be more meaningful if you can compare the displaced configuration against the original configuration. You can do this by using the KUND argument on the PLDISP command.

By multiplying displacements for distortion displays. In most small-deformation structural analyses, the displaced shape is hard to distinguish from the undisplaced shape. The program automatically multiplies the displacements in your results display, so that their effect will be more readily apparent. You can adjust this multiplication factor, using the /DSCALE command (Utility Menu> PlotCtrls> Style> Displacement Scaling). The program interprets exactly zero values of this multiplier (DMULT = 0) as the default setting, which causes the displacements to be scaled automatically to a readily discernible value. Thus, to obtain "zero" displacements (that is, an undistorted display) you must set DMULT = OFF.
Quote:
/DSCALE, WN, DMULT

Sets the displacement multiplier for displacement displays.

GRAPHICS: Scaling

MP ME ST PR PRN <> <> FL EM <> <> PP <>

WN
Window number (or ALL) to which command applies (defaults to 1).

DMULT

AUTO or 0 — Scale displacements automatically so that maximum displacement (vector amplitude) displays as 5 percent of the maximum model length, as measured in the global Cartesian X, Y, or Z directions. This is the default setting when NLGEOM is OFF.

1 — Do not scale displacements (i.e., scale displacements by 1.0, true to geometry). Often used with large deflection results. This is the default setting when NLGEOM is ON.

FACTOR — Scale displacements by numerical value input for FACTOR.

OFF — Remove displacement scaling (i.e., scale displacements by 0.0, no distortion).

USER — Set DMULT to that used for last display (useful when last DMULT value was automatically calculated).



Command Default
The default value is 1.0 when NLGEOM is ON, and AUTO when NLGEOM is OFF.
Quote:
NLGEOM, Key

Includes large-deflection effects in a static or full transient analysis.

SOLUTION: Nonlinear Options

MP ME ST PR PRN <> <> <> <> <> <> PP <>

Product Restrictions

Key
Large-deflection key:

OFF — Ignores large-deflection effects (that is, a small-deflection analysis is specified). This option is the default.

ON — Includes large-deflection (large rotation) effects or large strain effects, according to the element type.

ANSYS Helpfiles do confirm this, also the mail from NIST confirmed this.
If you have other information that contradicts this, pls feel free to present it.


PS: could someone pls quote me, so he can see my post, as he has me on ignore.

 

[DC]

Using deflections scales in a collapse sim is nonsence....
you would see the floor impacting the lower floor even before the floor actually hits the lower floor. Or the lower floow will collapse do to the impact of the upper floor, but you cannot see it yet impacting that floor, because of deflection scales.

 

[DC]

and you quote like the Loose Change kiddys.

Dear Mr. Kuhn,



Thank you for your inquiry regarding the analysis of the collapse of World Trade Center 7. In answer to your questions regarding displacement scaling, there was no displacement scaling in any of the figures shown for the ANSYS analyses (NCSTAR 1-9, Chapter 11) or the LS-DYNA analyses (NCSTAR 1-9, Chapter 12 and NCSTAR 1-9A). With respect to the large deflection (NLGEOM) this was set to to “ON” so that large deflection effects were captured by the analyses. I hope this answers your questions.



Regards,



Steve Cauffman
Deputy Chief
Materials and Construction Research Division
Building and Fire Research Laboratory
National Institute of Standards and Technology
100 Bureau Drive, Stop 8611
Gaithersburg, MD 20899-8611
Phone: --------*
Fax: --------*
E-mail: stephen.cauffman@nist.gov

but for you, this magically changed to

no scale factor was used

How come?

ETA: removed the phone number, dont know if i am allowed to post thse.

 

[DC]

I'll echo that. A lot of cpu time tied up there--and one hell of a lot of manpower in the model. No wonder it took so long to publish.

Having spent 20+ years dealing with people who do not understand a FEA deflection plot, I admit I didn't go directly to the source data. I recognized a normalized plot, and stated it. It is still the case--the deflections are not to scale (that is what "no scale factor was used" means), but are normalized to some max (or min, depending on which absolute is greater), and expressed relative to that. Doesn't matter which model it is.

Real experts say :

Dear Mr. Kuhn,



Thank you for your inquiry. The results of both the ANSYS and LSDYNA analyses had no normalization, amplification, or any other modification in the analyses or plots showing results in the WTC 7 reports.

Perhaps some of the LSDYNA displacement plots are raising these questions. For instance, in the 1A report, figures 3-10 to 3-14 show the vertical and lateral displacements in a true (1:1) scale and the lateral displacements are further indicated with plot colors where any lateral displacements less than or equal to 0.15 m (6 in.) are colored blue to red and any larger lateral displacement was colored red.

I hope this addresses your question.



Regards,



Steve Cauffman

this speaks for itself......

 

[rwguinn]

http://b.imagehost.org/0813/Clipboard01.jpg

That's the screenshot he's having a problem with. You can find it in NCSTAR 1-9 vol2 on page 255.
And here's the full text:



I can see some deformation in this video:



But I am tired and on my way to bed.

Real experts say :



this speaks for itself......

Yeah, it does.
I've violated my vow not to respond to trolls and know nothings, because I was advised to by a lurker...
the reference was to Figure 12-69 (Which by the way is page 593, not 255, of NIST NCSTAR 1-9, Vol 2). DC, in typical troofer fashion, throws figures 3-10 to 3-14- from Volume 1, no less as proof that I am wrong in my evaluation of Figure 12-69.
Go figure.
Do NOT ever impugn my expertise and integrity by showing me a picture of an F-111, they berate me by quoting F-16 specifications and stating that was what you were talking about all along.
At least if the trolls are attacking me, they are leaving you guys alone...

ETA:
I now question the authenticity of his source. Figures 3-11 to 3-14 deal with fuel loadingdisatribution and generators on floors 7,8 and 9. Figure 3-10 is a floor plan of floor 29...
Why would the authors get that kind of thing wrong?

 

[DC]

Yeah, it does.
I've violated my vow not to respond to trolls and know nothings, because I was advised to by a lurker...
the reference was to Figure 12-69 (Which by the way is page 593, not 255, of NIST NCSTAR 1-9, Vol 2). DC, in typical troofer fashion, throws figures 3-10 to 3-14- from Volume 1, no less as proof that I am wrong in my evaluation of Figure 12-69.
Go figure.
Do NOT ever impugn my expertise and integrity by showing me a picture of an F-111, they berate me by quoting F-16 specifications and stating that was what you were talking about all along.
At least if the trolls are attacking me, they are leaving you guys alone...

you quoted MrBaracuda's post.
to which you answered with this

I am so damn tired of people who have an axe to grind completely misinterpreting FEM and FEA. Dr Greening is an ___ --he KNOWS better!
Yes--the buildings absolutely DID look like that. All you have to do is scale it. Max deflection of a FEM is nearly always distorted--intentionally. Normal procedure is to set the scale such that max deflection is 10% of the available screen.
This is done so that you can actually SEE the Relative deflections. If you used actual scale (1"=1"), it wouldn't even show.
Dr Greening is using HIS authority as a chemist to denigrate the actual authorities in the field he is so totally clueless in.

i just reacted to this post, on your interpretation of Figure 12-69 that was shown in his post. I was very sure that non of the Figures have displacement scaling. For me it played no role on what page the posted figure was.

was your interpretation of the figure wrong because the page mentioned was wrong? Or did you look at another Figure, which has a displacement scaling? and when yes, which figure was that?

 

[DC]

actually it does not mather what Figure you missinterpreted because.

The results of both the ANSYS and LSDYNA analyses had no normalization, amplification, or any other modification in the analyses or plots showing results in the WTC 7 reports.

 

[DC]

....

ETA:
I now question the authenticity of his source. Figures 3-11 to 3-14 deal with fuel loadingdisatribution and generators on floors 7,8 and 9. Figure 3-10 is a floor plan of floor 29...
Why would the authors get that kind of thing wrong?

Oh you are misstaken there, he talks about 1A

For instance, in the 1A report, figures 3-10 to 3-14 show the vertical and lateral displacements in a true (1:1) scale and the lateral displacements are further indicated with plot colors where any lateral displacements less than or equal to 0.15 m (6 in.) are colored blue to red and any larger lateral displacement was colored red.

http://wtc.nist.gov/media/NIST_NCSTAR_1A_for_public_comment.pdf

 

[Norseman]

this is correct, Figure 12-69 is without the impact damage.

but you can compare it to the other Figure, those with impact damage, and it does still not fit.

Of course it does not fit. Just to make this very clear DC, Figure 12-69 is from an simulation that NIST ran to see if WTC 7 could have collapsed from fire induced damage alone, that is without any structural damage from debris impact as a consequence of the collapse of WTC 1. This simulation predicts that the final stage of the collapse would have been visually different than the collapse with structural damage caused by debris impact, as you can see from the figures I referenced and the real world collapse. In other words, due to the lack of impact damage the building would have behaved in a different way in the final stages of the collapse. This what Figure 12-9 shows.

And as I pointed out in my earlier post in this thread, the simulation with impact damage fits the real world collapse. So neither you DC nor Dr. Greening have anything to complain about regarding Figure 12-69.

 

[DC]

Of course it does not fit. Just to make this very clear DC, Figure 12-69 is from an simulation that NIST ran to see if WTC 7 could have collapsed from fire induced damage alone, that is without any structural damage from debris impact as a consequence of the collapse of WTC 1. This simulation predicts that the final stage of the collapse would have been visually different than the collapse with structural damage caused by debris impact, as you can see from the figures I referenced and the real world collapse. In other words, due to the lack of impact damage the building would have behaved in a different way in the final stages of the collapse. This what Figure 12-9 shows.

And as I pointed out in my earlier post in this thread, the simulation with impact damage fits the real world collapse. So neither you DC nor Dr. Greening have anything to complain about regarding Figure 12-69.

can you show me how well they fit?
I will make a colage to draw comparisons this weekend

 

[DC]

Just to make it clear.

The first and only time i refered to any Figures was in my first mail to NIST.

I have a few questions about the "Global Structural Analysis of the Responce of World Trade Center Building 7 to Fires and Debris Impact Damage".

http://wtc.nist.gov/media/NIST_NCSTA...ic_comment.pdf

In particular about the Ansys LS-Dyna FE Analysis.

In Figure 4-18 to 4-35 (Page 80-90) and Figure 4-43 to 4-62 (Page 95-108).

Is there any displacement scaling in those Figures?

I especially provided a link in the mail to prevent any confusion of the documents, As I find it a little confusing with the diffrent documents.

and you also can see that those figures include the analyses with "impact damage" , but also include the "earlier fire induced damage" and the "without impact damage" analyses.

 

[GregoryUrich]

Dr. Greening's response to criticisms here.

 

[DC]

A little bumb for rwguinn, to make sure he realise he was misstaken and not NIST.