The 9/11 Forum

Mpg (compressed)
http://rapidshare.com/files/144493904/WTC7.mpg

Avi (21mb)
http://rapidshare.com/files/144493988/WTC7.avi

and thanks for the tools einsteen.

Comments on the Draft Report NIST NCSTAR 1-9: “Structural Fire Response and Probable Collapse Sequence of World Trade Center Building 7”, issued by NIST August 21st, 2008

(Revised and Extended Version of Comments Issued September 11th 2008)

By F. R. Greening

1.0 Introduction

A preliminary (draft) version of NIST’s final report on the collapse of WTC 7 was issued on August 21st 2008 together with a call by NIST’s Investigation Team for the submission of comments on the Draft Report from interested parties within the general public. First I wish to thank NIST for producing such a detailed technical report on the collapse of WTC 7 and secondly, I applaud NIST for allowing researchers from around the world to offer technical feedback that hopefully will be duly considered by NIST before a final version of the report is issued.

In reading the Draft WTC 7 Report a number of issues emerge that are crucial to the credibility of NIST’s proposal as to how and why building 7 collapsed on September 11th, 2001. These key issues center on the narrative surrounding the ignition of the fires in WTC 7 and the spreading of these fires within the building prior to its collapse. The accuracy of NIST’s account of what transpired within the confines of building 7 during 9/11, is vital to NIST’s entire WTC 7 Report because it provides the basis for the computer modeling/simulation of the heating of structural elements on the fire-affected floors, which in turn, leads to NIST’s proposed collapse initiation and propagation mechanism.

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Administrator wrote:Comments on the Draft Report NIST NCSTAR 1-9: “Structural Fire Response and Probable Collapse Sequence of World Trade Center Building 7”, issued by NIST August 21st, 2008

(Revised and Extended Version of Comments Issued September 11th 2008)

By F. R. Greening
...
Read more

Excellent. Thanks for putting that up.

In 'Comments...' Greening wrote:While there may be some questions regarding the scaling of the maximum
deflections shown in Figure 12-69, Figures 4-46 and E-4 use lateral and vertical
displacement contours that span 2 meters, a level of building distortion that
should have been visible in the WTC 7 collapse videos, but was in fact not seen.

Dr. G wrote:This means the collapse of WTC 7 is still VERY fast, and WAY FASTER than NIST says, but certainly NOT at free fall!

No doubt about it. Fascinating post and interesting conclusions.

Dr. G wrote:I think David Chandler has done some good work with his little video but I do have one complaint. This is with his selection of t(zero). Even looking at the velocity plot he displays in his video I would move his t(zero) cursor a tad to the left which would slow his acceleration significantly ......

I agree with you about Chandler's work and this underscores the need for caution and due diligence. There is some good work there but not enough to carry it to a conclusion, which is often the case in the best of situations.

Dr. G wrote:This has prompted me to do some sensitivity tests on some of my own collapse plots.

My long winded comment about this has been placed here (http://the911forum.freeforums.org/technical-notes-on-video-motion-analysis-t55.html#526) so as not to further derail this thread.

In 'Comments...' Greening wrote:I would therefore ask NIST to reconsider the analysis presented in Section 12.5.3 of the Draft Report, and hopefully adjust its findings to be in better agreement with the vast majority of existing studies of the collapse time of WTC 7.

Bravo!

Dictator Cheney wrote:what is the "exact" gravity in New York?

Dr. G wrote:DC:

From "Fundamentals of Astrodynamics and Applications" by D.A. Vallado:

Because the earth is not exactly spheroidal, g varies with latitude.

g at the equator is 9.780325 m/s^2
g at the pole is 9.832185 m/s^2

For NYC you need to use:

g(NYC) = {(1 + k.sin^2(lat))/(Sqrt(1 - e^2.sin^2(lat))}

with e = the earth's eccentricity = 0.006694

and k a constant = 0.00193185

From this mess I get g(NYC) = 1.8167 m/s^2 but you may want to check my math!

Anyway, I always use g = 9.81 m/s^2 which I think is plenty good enough for the present debate!

Are you gentlemen accounting for the fact that New York sucks?


(Now Max, is that really the best joke on 9/11?)

Max!

So you, (like Einsteen), want to factor in some kind of negative air resistance, or what I would call "air assistance" to the collapse?

Interesting if true, ......

and interesting anyway!

But I don't buy it.

Fear not; the humor is free.

Plus, we all know nature abhores a vacuum (which explains all the cosmic dust).

My mistake; New York does not suck.

Max Photon wrote:

My mistake; New York does not suck.

aaah i see, i found the source of my weight problems.
Switzerland sucks i dont need a diet, i need a ticket to Canada or China.

DC, thanks a lot, I'll d/l it tonight and look at it

Dr. G,
Thanks for the new comments, as before it is no critique but sweeping the floor with the draft! Yesterday I did a small error analysis of the parabole I've pasted, as you know it gave 9.80 m/s^2. When I take a pixel error of 3 in both directions and assume the building is 173 meter then the absolute absolute minimum I get is 8.50 m/s^2, but I want to try DCs movie tonight.

einsteen wrote:DC, thanks a lot, I'll d/l it tonight and look at it

Dr. G,
Thanks for the new comments, as before it is no critique but sweeping the floor with the draft! Yesterday I did a small error analysis of the parabole I've pasted, as you know it gave 9.80 m/s^2. When I take a pixel error of 3 in both directions and assume the building is 173 meter then the absolute absolute minimum I get is 8.50 m/s^2, but I want to try DCs movie tonight.

ur welcome

i think my clip is of no real use. i tryed to get as good quality and a not changing framerate (25 frames/sec). but the clip itself is not very good.

i have the impression on the DVD it is already a lower quality than the rest of the movie, and it is cut.

i took from the first WTC7 frame to the last one, but i have the impression the roofline is in frame 1 already moving, not sure.

Einsteen and OWE:

Thanks for the positive reviews of my latest Comments to NIST.

Einsteen, it is indeed interesting that you also find that a small shift in t(zero) gives the significantly lower acceleration of 8.5 m/s^2, (but still pretty fast!). By the way, what time interval would 3 pixels correspond to?

I would add that 8.5 m/s^2 is close to my lower limit on the acceleration of WTC 7 which makes its collapse faster than WTC 1 or WTC 2. This is predicted by energy transfer calculations because the mass of the "hammer" is highest for WTC 7 if we assume the mass of one floor in WTC 7 is similar to one floor in the Twin Towers. Then we have the descending masses in the ratio 39:30:15 for WTC 7, WTC 2 and WTC 1, respectively.

Dr.G,

It was a quick and dirty calculation, normally if A is value a with an error e_a and B is value b with an error e_b then A-B has absolute error e_a+e_b, measuring horizontally then gives 2pixels, I added one extra. 3 pixels horizontally is 0.1 secnods in time, if we assume the framerate is fixed, I don't know if the error margin a a camera's framerate

Dictator Cheney,

You mpeg2 is pal 25 fps, BUT interlaced and that is great! This means that lines 1,3,5,7,... and lines 2,4,6,8,... are different, you can make a new 50 fps movie from it!

einsteen:

i can upload the VOB part from the WTC7 clip so you can cut it on your own. if that would help