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The same thing happened at WTC7.
A witness (LT : Graig Bartmer) watching this building heard something like a "thunderclap" that caused the windows to explode outwards, while the base of the burning building gave way a second later, before the whole building followed the movement (Testimony  [LT : on page 13] ), aided by a second explosion, which generated the second Rayleigh wave 6 to 7 seconds later.
Page 18 : In Fig. 6 we show the data set “C,” the respective theoretical trajectories and their accelerations, and SAE.
Here, SAE is calculated over the first 13 points of the data set “C” and the positions predicted by each theoretical model. We note that the free fall has SAE ~= 2.09 m, on one hand side, and on the other, that SAE for the entire three-zone crush-up model over 25 points (~= 3.82 m) is less than SAE for either of the 0-opposition avalanche models (~= 4.69, 4.94 m).
This finding reaffirms our previous conclusion that Phase I is a free fall for H1 ~28 m and not an avalanche that started somewhere in the building (LT : around column 79, as NIST proposed) and propagated for the same distance.
Page 19/24 : It is a reasonable assumption that the seismic signal is excited by changes in the apparent weight of the building, δw, given by δw=fˆ∆W/(M g), where f is the sampling rate, while ˆ∆ is a difference operator acting on a time series of W collected at the sampling rate.
We believe that W', and in particular its time derivative, can be used in interpretation of the seismic signal of the building’s collapse.
As an attempt to connect the two, brings forth numerous additional complications which need to be properly addressed, we leave this topic to future publications.
Different variations of pivots (LT : of trusses) can lead to an inward bowing along the face of the perimeter of about 4 ft (1.22 m) with only about 8 ft (2.44 m) sagging of the (LT : blueprint numbered, number - ) 1000 row columns.
That would be the maximum inward bowing seen on WTC1.
WTC2 had much less inward bowing until the initiation sequence.
These geometrical possibilities were not considered within the NIST reports.
Major_Tom : These columns are interesting but it is the absence of the other 195 core column segments from the steel collection and the investigation, which is much, much more interesting.
It is pretty obvious that for WTC1 careful examination of the 47 column sections spanning floors 98 to 101 and the 47 core column sections spanning floors 98 to 95 would show investigators all they need to know about the collapse initiation processes.
Likewise, for WTC2, careful examination of the 47 core columns spanning floors 80 to 83 and those spanning floors 77 to 80 are very important to understand the WTC2 collapse initiation process. For example, if these columns were pretty straight on the whole, lacking significant signs of visco-plastic creep and buckled hinges, that would tell investigators that there was little collective core buckling.
James G. Quintiere, professor, Dept of Fire Protection Engineering, University of Maryland:
Spoliation of a fire scene is a basis for destroying a legal case in an investigation. Most of the steel was discarded, although the key elements of the core steel were demographically labeled. A careful reading of the NIST report shows that they have no evidence that the temperatures they predict as necessary for failure are corroborated by findings of the little steel debris they have. Why hasn't NIST declared that this spoliation of the steel was a gross error?
""Tony Szamboti wrote:
Ductile steel does not fail catastrophically and quickly. That can only happen with brittle materials. Ductile steel needs time to deform. The immediate, symmetric, and high vertical acceleration is a telltale sign of something unnatural occurring. The steel used for buildings has an elongation of over 20% before it fractures. To put this in perspective that would require stretching a 12 foot tall item about 2.5 feet before it would break. In a buckling situation it would never even get to that, so the ductility would be maintained throughout the buckling and the remaining resistance felt throughout the fall. In addition to that, any heating would have made it even more ductile and even less prone to rapid failure.""
OneWhiteEye : Everything he says is true. However, it's not the entire picture, not by a long shot.
Summary of objections:
1) There is direct evidence "the steel" failed slowly and progressively before catastrophic failure. (LT : only at the Twin Towers, not WTC7)
2) Cascading failure is a well-characterized phenomena and is plausibly applied here. (LT : Charles M. Beck proves it wasn't, at least for WTC7, an avalanche process, by his SAE values he calculated for WTC7)
3) He only considers ductility of the steel members and gives an example using a large member. Other sizes and materials must be considered as well.
4) Buckling occurred, and is also directly observed, but does not represent the dominant global failure mode.
The objections do not dispute the assertions about material properties, rather take a more refined approach to characterizing what could be expected and what was observed, based on existing research and forensic evidence. The problem with Tony's statements is that, while true, these statements do not plausibly have universal applicability to the towers, and the implication that these conditions did not occur at all is simply false. There actually WERE large, slow deformations present but insinuating this should continue indefinitely is unrealistic.
A thermobaric weapon is a type of explosive that uses oxygen from the surrounding air to generate a high-temperature explosion, and in practice the blast wave typically produced by such a weapon is of a significantly longer duration than that produced by a conventional condensed explosive. The fuel-air bomb is one of the best-known types of thermobaric weapons.
And when thermobaric explosives, the disc shaped versions, were used, as I highly suspect they did, you and the video camera microphones would only hear a thunderclap sound if you were near enough
9/11: WTC 7 Collapse (NIST FOIA, CBS video)
originally posted by: LaBTop
That WTC7 collapse really looked exactly as any YouTube video from a demolition job of a high rise.
I posted in this post www.abovetopsecret.com... the AFE Tower demolition, 116 m high, in Frankfurt, Germany, to compare it to.
Listen to the deep low explosions sounds there too, only those from this particular camera position. No high pitch sounds to hear.
Another one from the same building, the same deep sounds first, from the same camera, but now you hear first the high pitched sounds of the warning sirene too. And later on in that video, you hear higher pitched sounds than from the first camera, now however shot in the open air, by another camera.
This shows that different cameras and different positions, like on 9/11, can give totally different explosion sounds from the same demolition event.
That's why I posted this remark at the end of my above linked to post :
Whenever one of these OS Truster wolf-pack members pop-up again with all these repetitive remarks that "no explosions at the WTC complex were heard", post a link to this lengthy post of mine with all the evidence of EXPLOSIONS on 9/11, to stop their annoying -knowingly- LYING.
This is that link full of 9/11 explosion noises and visuals, just copy and paste it in your posting window, with f.ex. this text :
Stop your annoying endless falsehoods posting, of no-explosions on 9/11, here they are :