NIST (National Institute for Standards and Technology) was given a budget
tens of millions of dollars to study the collapses of the World Trade Center
skyscrapers. Yet it avoided that charge in any meaningful sense. Its final
report admits that it didn't even attempt to model the collapses.
The first critique to thoroughly expose NIST's evasion of its task of
investigating the collapses was provided by Sami Yli-Karjanmaa on July 14, 2005.
The following excerpt includes more that half of the brief critique.
e x c e r p t
title: NIST and the WTC: 'Science' at the Service of an Empire
authors: Sami Yli-Karjanmaa
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."  These questions are not answered for
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."  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." 
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.
 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." 
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." 
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?
 http://wtc.nist.gov/pubs/NCSTAR1ExecutiveSummary.pdf (75 kB), p.3
 http://wtc.nist.gov/pubs/NCSTAR1-6ExecutiveSummary.pdf (1.4 MB), p. lxii
 Ibid., p. lxiv
 http://wtc.nist.gov/pubs/NISTNCSTAR1-6DDraft.pdf (19.4 MB), p. 5
 Ibid., p. 169
 Ibid., p. 371
 http://wtc.nist.gov/pubs/NCSTAR1-3ExecutiveSummary.pdf (52 kB), p. xli
 http://wtc.nist.gov/pubs/NISTNCSTAR1-6Draft.pdf (17.5 MB)
Later, Jim Hoffman wrote a critique of NIST's report, which, although far more
detailed than Yli-Karjanmaa's, makes essentially the same central point.
e x c e r p t
title: Building a Better Mirage: NIST's 3-Year $20,000,000 Cover-Up of the Crime
of the Century
authors: Jim Hoffman
To shield the reader from the evidence of controlled demolition, NIST fills
hundreds of pages with amazingly realistic plane crash simulations, tedious
details about fire tests and simulations, and long lists of recommendations for
improving building safety. It calls its event narrative of each Tower, which
starts with the jet impact and ends at the point that "collapse ensued," the
"probable collapse sequence," but it is neither probable nor a collapse sequence.
NIST's misleadingly named "probable collapse sequence" is a mirage, masking the
explosive reality of the collapses with a cinematic account of the crashes and
fires. NIST's theory stops at the moment that the "upper building section began
to move downwards," thus avoiding the longer timeline of the truss-failure
theory and any overlap with the time span in which the demolition-like features
appear. Despite NIST's theory being even more incredible than its predecessors
(with spreading "column instability" triggering "global collapse" in an instant)
it works better as a mirage because its timelines stop short of the collapses.
NIST's Report states that its first objective is to "determine why and how WTC 1
and WTC 2 collapsed." The Report does not fulfill that objective, and hides that
failure with misleading headings and disproportionate, misapplied technical
detail. Its authors should admit that they have failed to explain why and how
the Towers collapsed, and should call for an investigation that will address
rather than avoid the issue.
net page: http://911research.wtc7.net/essays/nist/
Hoffman's critique points out that NIST's Report, while avoiding even claiming
to model the collapses, implies but does not show that it modeled the onsets of
the collapses. The Report's section entitled Results of Global Analysis"
describes the tops of the Towers first tilting and then moving downward as
intact blocks, but there are not images in the Report of its computer models
showing this behavior. The New Civil Engineer (NCE), an engineering trade
journal based in the United Kingdom, published an article highlighting NIST's
failure to publish visualizations of its alleged analysis of "collapse initiation."
e x c e r p t
title: WTC Investigators Resist Call for Collapse Visualization
authors: Dave Parker
WTC Investigators Resist Call for Collapse Visualisation
WORLD TRADE Center disaster investigators are refusing to show computer
visualisations of the collapse of the Twin Towers despite calls from leading
structural and fire engineers, NCE has learned.
Visualisations of collapse mechanisms are routinely used to validate the type of
finite element analysis model used by the investigators.
The collapse mechanism and the role played by the hat truss at the top of the
tower has been the focus of debate since the US National Institute of Standards
& Technology (NIST) published its findings (NCE 22 September 2005).
NIST showed detailed computer generated visualisations of both the plane impacts
and the development of fires within WTC1 and WTC2 at a recent conference at its
Gaithersburg HQ. But the actual collapse mechanisms of the towers were not shown
University of Manchester (UK) professor of structural engineering Colin Bailey
said there was a lot to be gained from visualising the structural response.
"NIST should really show the visualisations, otherwise the opportunity to
correlate them back to the video evidence and identify any errors in the
modelling will be lost," he said.
University of Sheffield professor Roger Plank added that visualisations of the
collapses of the towers "would be a very powerful tool to promote the design
code changes recommended by NIST."
NIST told NCE this week that it did not believe there is much value in
visualising quasi-static processes such as thermal response and load
redistribution up to the point of global collapse initiation and has chosen not
to develop such visualisations.
But it said it would 'consider' developing visualisations of its global
structural collapse model, although its contract with the finite element
analysis subcontractor was now terminated.
A leading US structural engineer said NIST had obviously devoted enormous
resources to the development of the impact and fire models. "By comparison the
global structural model is not as sophisticated," he said.
"The software used has been pushed to new limits, and there have been a lot of
simplifications, extrapolations and judgement calls. This doesn't mean NIST has
got it wrong in principle, but it does mean it would be hard to produce a
definitive visualisation from the analysis so far."