-------- Original Message --------
Subject: WTC CONSPIRACY ANSWERS
Date: Fri, 22 Aug 2008 20:14:10 -0400
From: REAL NEWS thenewsman@ij.net
To: APFN@apfn.org
COLLAPSED WORLD TRADE CENTER BLDG. 7 CONSPIRACY
ANSWERS ON CSPAN-TV PRESS BRIEFING AUGUST 21, 2008
GAITHERSBURG, Md.-The fall of the 47-story World Trade Center
building 7 (WTC 7) in New York City late in the afternoon of Sept. 11,
2001, was primarily due to fires, the Commerce Department's National
Institute of Standards and Technology (NIST) announced today following an
extensive, three-year scientific and technical building and fire safety
investigation. This was the first known instance of fire causing the
total collapse of a tall building, the agency stated as it released for
public comment its WTC investigation report and 13 recommendations for
improving building and fire safety.
"Our study found that the fires in WTC 7, which were uncontrolled
but otherwise similar to fires experienced in other tall buildings,
caused an extraordinary event," said NIST WTC Lead Investigator Shyam
Sunder. "Heating of floor beams and girders caused a critical support
column to fail, initiating a fire-induced progressive collapse that
brought the building down."
"Video and photographic evidence combined with detailed computer
simulations show that neither explosives nor fuel oil fires played a role
in the collapse of WTC 7," Sunder said. The NIST investigation team also
determined that other elements of the building's construction, namely
trusses, girders and cantilever overhangs that were used to transfer
loads from the building superstructure to the columns of the electric
substation (over which WTC 7 was constructed) and foundation below, did
not play a significant role in the collapse.
According to the report, a key factor leading to the eventual
collapse of WTC 7 was thermal expansion of long-span floor systems at
temperatures "hundreds of degrees below those typically considered in
current practice for fire resistance ratings." WTC 7 used a structural
system design in widespread use.
Citing its one new recommendation (the other 12 are reiterated from
the previously completed investigation of the World Trade Center towers,
WTC 1 and 2), the NIST investigation team said that "while the partial or
total collapse of a tall building due to fires is a rare event, we
strongly urge building owners, operators and designers to evaluate
buildings to ensure the adequate fire performance of the structural
system. Of particular concern are the effects of thermal expansion in
buildings with one or more of the following features: long-span floor
systems, connections not designed for thermal effects, asymmetric floor
framing and/or composite floor systems." Engineers, the team said, should
be able to design cost-effective fixes to address any areas of concern
identified by such evaluations.
The investigators also reported that if the city water main had not
been cut by the collapse of World Trade Center towers 1 and 2 (WTC 1 and
WTC 2), operating sprinklers in WTC 7 would likely have prevented its
collapse. "Nevertheless," Sunder said, "we recommend that building
standards and codes be strengthened beyond their current intent to
achieve life safety by preventing structural collapse even during severe
fires like this one, when sprinklers do not function, do not exist or are
overwhelmed by fire."
Sunder identified several existing, emerging or even anticipated
capabilities that could have helped prevent WTC 7's collapse. He
cautioned that the degree to which these capabilities improve performance
remains to be evaluated. Possible options for developing cost-effective
fixes include:
a.. More robust connections and framing systems to better resist
effects of thermal expansion on the structural system.
b.. Structural systems expressly designed to prevent progressive
collapse, which is the spread of local damage from a single initiating
event, from element to element, eventually resulting in the collapse of
an entire structure or a disproportionately large part of it. Current
model building codes do not require that buildings be designed to resist
progressive collapse.
c.. Better thermal insulation (i.e., reduced conductivity and/or
increased thickness) to limit heating of structural steel and to minimize
both thermal expansion and weakening effects. Insulation has been used to
protect steel strength, but it could be used to maintain a lower
temperature in the steel framing to limit thermal expansion.
d.. Improved compartmentation in tenant areas to limit the spread
of fires.
e.. Thermally resistant window assemblies to limit breakage,
reduce air supply and retard fire growth.
The 12 recommendations reiterated from the WTC towers investigation
address several areas, including specific improvements to building
standards, codes and practices; changes to, or the establishment of,
evacuation and emergency response procedures; and research and other
appropriate actions needed to help prevent future building failures.
Determining the probable collapse sequence for WTC 7, NIST found
that the impact of debris from the collapse of WTC 1 ignited fires on at
least 10 floors of WTC 7, and the fires burned out of control on six
lower floors. The heat from these uncontrolled fires caused thermal
expansion of the steel beams on the lower floors of the east side of WTC
7, damaging the floor framing on multiple floors. Eventually, a girder on
Floor 13 lost its connection to a critical interior column that provided
support for the long floor spans on the east side of the building. The
displaced girder and other local fire-induced damage caused Floor 13 to
collapse, beginning a cascade of floor failures down to the fifth floor.
Many of these floors had already been at least partially weakened by the
fires in the vicinity of the critical column. This collapse of floors
left the critical column unsupported over nine stories.
"When this critical column buckled due to lack of floor supports,
it was the first domino in the chain," Sunder explained. "What followed
in rapid succession was a progression of structural failures. Failure
first occurred all the way to the roof line-involving all three interior
columns on the most eastern side of the building. Then, progressing from
east to west across WTC 7, all of the columns in the core of the building
failed. Finally, the entire façade collapsed."
The investigation team considered the possibility of other factors
playing a role in the collapse of WTC 7, including the possible use of
explosives, fires fed by the fuel supply tanks in and under the building,
and damage from the falling debris of WTC 1.
The team said that the smallest blast event capable of crippling
the critical column would have produced a "sound level of 130 to 140
decibels at a distance of half a mile," yet no noise this loud was
reported by witnesses or recorded on videos.
As for fuel fires, the team found that they could not have been
sustained long enough, could not have generated sufficient heat to fail a
critical column, and/or would have produced "large amounts of visible
smoke" from Floors 5 and 6, which was not observed.
Finally, the report notes that "while debris impact from the
collapse of WTC 1 initiated fires in WTC 7, the resulting structural
damage had little effect in causing the collapse of WTC 7."
The investigation team found that the design of WTC 7 was generally
consistent with the New York City building code in effect at the time.
The estimated 4,000 occupants of WTC 7 on the morning of Sept. 11 were
evacuated without any fatalities or serious injuries.
To reach the conclusions in its report, NIST complemented its
in-house expertise with private-sector technical experts; accumulated an
extensive collection of documents, photographs and videos related to the
WTC events of 9/11; conducted first-person interviews of WTC 7 occupants
and emergency responders; analyzed the evacuation and emergency response
operations in and around WTC 7; and performed the most complex computer
simulations ever conducted to model a building's response behavior and
determine its collapse sequence due to a combination of debris impact
damage, fires and a progression of structural failures from local
fire-induced damage to collapse initiation, and, ultimately, to global
collapse.
The NIST investigation of WTC 7 was conducted under the National
Construction Safety Team (NCST) Act, as part of its overall building and
fire safety investigation of the World Trade Center disaster.
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Extensive related documents on
http://www.nist.gov website
a.. Questions and Answers about the NIST WTC 7 Investigation.
b.. CSPAN Opening Statement Press Briefing, August 21, 2008,
Report on the Collapse of World Trade Center Building 7.