I guess you all have head the claim that the NIST reports are scientifically exceptionally stringent and without fault. We are supposed to be impressed with the number of people involved who has done the research and their objective views.
Well, here is some material from a mainstream guy called James Quintiere with a phd in Fire Engineering, who thinks otherwise. Click on the link below
http://www.nist.gov/public_affairs/ncst ... 112204.pdf
November 22, 2004
To: The National Construction Safety Team Advisory Committee
NCST Advisory Committee
100 Bureau Drive, Stop 8610
Gaithersburg, MD 20899-8610
From: James G. Quintiere
RE: NIST conclusions on the WTC collapse mechanism reported on October 19,
The October surprise in the NIST investigation was the assertion that all of the core
column insulation was knocked off by the airplane impacts. To a lesser extent, reliance
on NYNJPA audit insulation data solidified the NIST assertion that the failure of the corecolumns, and not the trusses, were to blame for the collapses of the South and North towers. That audit information was reported by NIST to have the fire floors of the north tower with truss insulation thicknesses as an average of 2.5 inches up to 4 inches instead of the prescribed 1.5 inches.
NIST needs to produce demonstrable and clear substantive information to support this rationale for its conclusions. The core-damage theory was put forth by the Weidlinger group in the Silverstein civil suit, and I heard it expressed at a local ASME meeting over a year ago by a NIST staffer. Therefore, I think it is incumbent on NIST to explain when and how they came to this conclusion. This collapse mechanism conclusion has profound influence on the recommendations brought from this investigation. The airplane-caused column collapse theory yields significantly, and almost diametrically, opposed recommendations than the fire induced truss collapse mechanism.
NIST needs to validate its conclusion by addressing the following:
1. The NYNJPA North tower insulation data needs to be authenticated. There is a
long saga on the insulation coverage of the truss assemblies, and it should not end
with an audit report that contains data that are extraordinary. The claim that up to
4 inches of insulation was sprayed onto 1-inch diameter truss elements needs
testimony, photographic corroboration, or other tangible evidence to establish the
accuracy of this information.
2. It needs to be clearly demonstrated how the core column insulation was removed.
This cannot simply be based on an assumption or an extrapolation from impact
calculations. It is too important to the conclusions to have modeling as the sole
basis. Sandia has been experimenting with airplane crashes into buildings. Have
they been consulted for supporting information or assistance? NIST needs to live
up to the Daubert-rulling in civil case law, and demonstrate a clear methodology
for their conclusion that the insulation was removed.
Finally, NIST needs to clarify inconsistencies that appear in their public information todate. These inconsistencies and apparent weakness lead me to question their collapse theory, and place the collapse cause more on the lack of sufficient truss insulation.
1. NIST metallurgical analyses show no core columns from the fire floors reached
temperatures above 250 C. It is claimed that this information is consistent with
computer modeling. Moreover, I was pleased to see that after many inquiries for
microscopic analysis of the steel debris, it was done and reported in the October
briefing. The importance of forensic evidence to document the temperatures
reached of the steel cannot be overlooked. First, its consistency with the
modeling has little significance since the modeling cannot have that level of
detailed accuracy precise fire effects around the core columns. Secondly, the core
column theory requires that the columns got sufficiently hot, say 500 C, and
tangible evidence from metallurgical analysis is crucial in supporting the NIST
conclusion. Unfortunately, that evidence has not been found by NIST. Thirdly,
as a consequence, this crucial lack of evidence must indict the selling of the WTC
steel debris before an investigation could be launched. Will NIST speak to this as
they now have future investigative authority?
2. NIST computations show that floor truss assemblies can fail at temperature
measured in the UL tests. UL fire tests showed for ½ and ¾-inch insulation that
steel truss temperatures exceeded 1300 F (704 C) in roughly 58 minutes and 62-
76 minutes, respectively. They reached average temperatures of 1110 F (593 C)
in 66 and 66-86 minutes, respectively. My own data with Isolatek indicate that
individual web elements can reach 593 C in about 35 to 50 minutes, respectively
for ½ and ¾ inches. NIST’s model for a single WTC truss (which is more
accurate than the impact computations), predicts a truss would fail at the column
connections at these temperatures. The NIST model for a single truss and its
connection shows that the truss fails at the interior column seat connection, and
‘walks off” the seat. This occurs at 650 C. The web diagonals begin to buckle at
340 C, and the exterior columns bow inward at 560 C causing the truss to act as a
catenary. Other independent work done by Usmani et al, and Burgess et al., show
similar results. If one floor falls on the floor below while both are heated by fire,
can the impacted floor carry the load? Is this a plausible global collapse
mechanism? To me, this means that truss failure is likely, at least in the South
tower; and in the North if the PA audit data are wrong. Collapses of the floors
were seen in both of the towers well up to 20 minutes before the buildings
collapsed. This indicates the presence of the floor collapse mechanism.
Incidently, the NIST scaling criterion used for the ½-scaling in the UL tests
should be examined, as it is thermally not to scale. The shorter truss members
will cause lower temperatures as the web transfers heat into the concrete floor.
3. NIST has relied on state-of-the-art computer models that are at the forefront of
their technologies. However, these models have not been proven
comprehensively for less complex incidents than the WTC. Will NIST continue
to invest in these modeling technologies, or are they proven and ready for general
use? If they are ready, will NIST advocate their use in design, or will NIST
continue to perform research to improve them? If the latter is true, will NIST
articulate the uncertain aspects of the modeling, and comment on how they bear
on the investigation’s conclusions?
4. NIST has used workstations fire experiments as a basis for their modeling. The
stated fuel load is 4 lbs/ft2 and this loading has been questioned, as it appears very
low in the spectrum of office loadings. Because our students are conducting a
scale model experiment of the 96th floor of the North tower, it forced us to
examine this loading. While we could not pursue our information in depth, I can
relate some major concerns. NIST experimental photographs of the office
modules show little paper, and NIST has told me that the paper load was reported
as light. I was told by a WTC inspector that the load was heavy, storage areas
were overloaded and floors were continually cited for having paper stacked on the
window sills; a furniture installer of the Marsh floors gave me information that
showed extensive file cabinets surrounding the cubicles and these were not
included in the NIST fire experiments – he, too, said that the Marsh office spaces
were heavy in paper; an anonymous Marsh employee said that the Marsh
company were paper “hogs”, and a family member said it was heavy as well. The
fuel loading is crucial to the duration and the temperatures of the fires. A light
fuel load in the modeling will lead to low temperatures and this would affect the
It is imperative that NIST get the cause of the WTC tower collapses correct. The
legacy of its victims bears on future fire safety. The protection of buildings in fire
and terrorists attacks will be impacted by these conclusions, so they need to be right.
The Advisory Panel plays a clear role to sign off on these conclusions. I know of
others that feel the NIST conclusions need, in the least, clarity, and in the main, more
support. However, we are few in number, and it falls on you to insure the public that
they got it right.
Recommendations that should come from this study are submitted in no priority
order as suggestions for your consideration:
1. Experimental studies to establish temperatures and fire duration characteristic of
modern facilities including office large plan spaces, places assembly, and
underground structures should be undertaken to validate models and establish
design methods. The current correlations are incomplete in terms of fuel type and
2. The standard time-temperature structural fire tests should be examined in light of computational methods. Data for the tests yielding temperature and deflection
should be integrated with computations to extrapolate to actual assemblies used in
3. Sensor technologies integrated with alarm monitoring for building performance
should be integrated into the emergency response network for assessing the nature
of the hazard.
4. Forensic techniques and standards should be established to assess failure
information from structural debris. The elimination of the steel structure from the
WTC site should be fully addressed, and its consequences fully stated.
5. Fire and disaster planning should include full and proper analyses for safe egress and effective response. Responders and building planners need to have the
benefit of analyses that quantitatively address these facets. Real time modeling of
the fire effects based on sensor information are possible and should be integrated
into special building designs and response actions.
6. Novel techniques need to be investigated to rescue people and to fight high-rise
7. Current codes weaknesses, in light the WTC collapses, need to be fully addressed. Issues of lightweight construction designs that are vulnerable to catastrophic collapse of a structure need particular attention.
8. A nationally supported infrastructure is needed to insure that objective scientific
input is placed into the code consensus process to bring fire safety to a proper
level of engineering analyses. The current code process is lacking in scientific
underpinning, and the WTC disaster should stand for change in this direction,
especially if the scientific community cannot render a clear and decisive verdict.
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