Building 7 didn't collapse
symmetrically (the East Penthouse fell first...and then the rest of the
building was pulled down). It also didn't collapse into it's own
footprint - because the debris significantly damaged 2 other buildings
nearby.
As far as technical complexities, here is what the NIST report concluded about WTC7: -
The initiating local failure that began the probable WTC 7 collapse
sequence was the buckling of Column 79. … When steel (or any other
metal) is heated, it expands. If thermal expansion in steel beams is
resisted by columns or other steel members, forces develop in the
structural members that can result in buckling of beams or failures of
connections. (p. 21)
Fire-induced thermal expansion of the floor system surrounding Column 79
led to the collapse of Floor 13, which triggered a cascade of floor
failures … down to the 5th floor (which … was much thicker and
stronger). … This left Column 79 with insufficient lateral support, and
as a consequence, the column buckled eastward, becoming the initial
local failure for collapse initiation. (p. 22)
http://www.america.gov/st/webchat-english/2009/April/20090428110108atlahtnevel0.7957117.html
There are arguments made that the debris from WTC1 and WTC2 was a factor
in the collapse of building 7 (along with the fires). However, this is
countered by the fact that other buildings in the same (or closer)
distance from towers 1&2 were equally hit with debris (or more so).
NIST's analysis deals with this by their discussion of Column 79 and how
the debris initiated fires that initiated collapse.
The claims about an apparent symmettry in the collapse of the building
(by "controlled demolition" theorists) are also addressed by NIST: -
There were clues that internal damage was taking place, prior to the
downward movement of the exterior frame, such as when the east penthouse
fell downward into the building and windows broke out on the north face
at the ends of the building core. The symmetric appearance of the
downward fall of the WTC 7 was primarily due to the greater stiffness
and strength of its exterior frame relative to the interior framing.
http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.cfm
NIST does not say that the debris was the main factor. The structural
design of the building is emphasised as the main flaw (which does give
some legitimacy to some claims that there should be further
investigation into WHY such structural flaws existed).
The collapse of the East Penthouse (before the rest of the building)
also complicates the argument. It means that after the East Penthouse,
we have the vast majority of the building still standing - BUT, the
collapse is still not technically a global or total collapse. It is
assymmetric. In this video of a steel-framed university building
partially collapsing from fire; we can see it looks rapid and almost
explosive: -
http://www.liveleak.com/view?i=ff1_1210707903
Now, some may respond by saying it looks different to how Building 7
fell. That is true, but both buildings are differently designed on the
exterior frame (albeit both are steel-framed high-rise buildings) and
the fire-dynamics and nature of partial ASSYMETRIC collapse are
obviously different.
Claims of molten steel in building 7? NIST has this to say on the molten steel issues: -
Under certain circumstances it is conceivable for some of the steel in
the wreckage to have melted after the buildings collapsed. Any molten
steel in the wreckage was more likely due to the high temperature
resulting from long exposure to combustion within the pile than to short
exposure to fires or explosions while the buildings were standing.
http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm
If people wish to refute NIST's position on molten steel causality, then
they have to get into technical arguments regarding certain conditions.
There are a lot of debates on the internet (albeit mostly by
unqualified people) as to the authenticity of the molten steel citings
and whether what was seen was actually molten steel. Things like
eutectic melting and sulfidation (as observed in WTC7) have also been
discussed and debated with certain people claiming that thermite-based
controlled demolition is not the only hypothesis ( e.g. the length of
time that heat was sustained in the rubble may not neccessarily be from
thermite according to some). The nano-thermite paper that was published
by Harrit et al has its shortcomings. There has not been enough
independent analysis of the dust samples, and there are problems with
the chain of custody regarding the acquisition of the samples. There are
problems with the fact that some of the people who wrote the paper,
know how to make nano-thermite themselves (e.g. Kevin Ryan). The paper
may have been peer-reviewed, but it was published in a journal in which
the editor famously resigned out of indignation over the publication. No
conventional explosive residue has been found, and some people (namely
on forums like JREF and SCIFORUMS) have questionned whether
nano-thermite was used as an explosive or an incendiary/trigger.
Other "explosive" claims have been rebutted by physicists like Dave Thomas at NMSR. His analysis can be found here: -
http://www.nmsr.org/nmsr911.htm
I hope those points make it clear that the WTC7 argument is NOT the
"smoking gun" of 9/11 Truth. This is because it is hard to keep the
argument simple. While my points are just for the sake of argument; they
do actually illustrate the COMPLEX implications of pursuing the
physical-evidence argument. This then puts off a lot of people, and
makes the argument weaker in the light of counter-claims or other
possibilities.
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