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The first of the specific objectives of the NIST study was to
"[d]etermine why and how WTC 1 and WTC 2 collapsed
following the initial impacts of the aircraft
and why and how WTC 7 collapsed."
[3]
These questions are not answered for simple reasons:
Incredibly, the progressive collapse of the Twin Towers
has been left out of the computer models used:
"The global models of the towers extended from several stories
below the impact area to the top of the structure."
[4]
Thus the structurally intact floors 1-91 of WTC 1 and floors 1-77 of WTC 2
were excluded from the so called "global" models of the towers.
Correspondingly, the temporal dimension was cut short as well:
NIST gave itself the task of finding out
"[t]he probable sequence of events from the moment
of aircraft impact until the initiation of global building collapse."
[5]
...
In other words,
"Even without the modeling of the progressive collapse we had to postpone
the publication of the reports four times so we just didn't have time to do that.
And besides, the lower parts of the buildings simply did not slow down the collapse,
as everyone could see on TV, so why bother?"
In summary:
The reports by NIST say nothing about how -- and if! -- the collapse
was able to progress through dozens and dozens of structurally intact floors
without being stopped. If no external energy was available e.g.
in the form of explosives, this would have been the opportunity to show
that no such energy was needed. On the other hand, if some unaccounted-for
energy broke the supporting structures enabling the collapse to progress
with the speed it did, there would have been many good reasons not to try
to model the impossible, ie. a purely gravitation-driven collapse.
Stopping the analysis early enough also saves NIST from trying to explain
the symmetricality of the collapses (despite non-symmetrical impact damage and fires),
the almost complete pulverization of non-metallic materials as well as
the extremely hot spots in the rubble.
These remain as inexplicable by the official story as they have ever been.
One appendix of project 6 includes an interesting analysis of a dropping floor.
[8] According to the results, however, temperatures of
400 to 700 ºC are needed in order for the collapse to be initiated.
Unfortunately, the destruction of evidence at Ground Zero was so complete
that NIST can now only say that the steel components recovered demonstrate
that there was "limited exposure if any above 250 ºC."
[9]
NIST's collapse creed, repeated eleven times with identical wording
(and once with a slightly different one) in the report of project 6 dealing with
the collapse sequences, is this:
"
The change in potential energy due to downward movement of building mass above
the buckled columns exceeded the strain energy that could have been absorbed by
the structure. Global collapse then ensued."
[10]
In other words: "Once the top started coming down,
it was so heavy that the damaged columns could not stop it.
Neither could the undamaged columns of dozens of floors do that, it seems.
But we didn't need to model that for we've all seen that down it came."
Thorough, open, independent?
References:
[1] http://wtc.nist.gov/pubs/semerjian_remarks_62305.htm
[2] http://wtc.nist.gov/pubs/reports_june05.htm
[3] http://wtc.nist.gov/pubs/NCSTAR1ExecutiveSummary.pdf (75 kB), p.3
[4] http://wtc.nist.gov/pubs/NCSTAR1-6ExecutiveSummary.pdf (1.4 MB), p. lxii
[5] Ibid., p. lxiv
[6] http://wtc.nist.gov/pubs/NISTNCSTAR1-6DDraft.pdf (19.4 MB), p. 5
[7] Ibid., p. 169
[8] Ibid., p. 371
[9] http://wtc.nist.gov/pubs/NCSTAR1-3ExecutiveSummary.pdf (52 kB), p. xli
[10] http://wtc.nist.gov/pubs/NISTNCSTAR1-6Draft.pdf (17.5 MB)
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