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JONATHAN H. COLE, P.E.
914 Palomino Trail
Englewood,
FL 34223
September 11, 2008 Sent Via E-Mail To: wtc@nist.gov
WTC Technical Information Repository
Attention: Mr. Stephen Cauffman
National Institute of Standards and Technology
Stop 8610
Gaithersburg, MD 20866-8610
Re: Public Comments of NIST Reports NCSTAR 1A – “Final Report on
the Collapse of World Trade Center Building 7”, and
NCSTAR 1-9 Volume One and Two, “Structural Fire Response and
Probable
Collapse Sequence of World Trade Center 7”
Dear Mr. Cauffman:
Pursuant to the instructions
contained on the NIST website, I offer the attached public comments
relating the referenced documents.
Please recognize that
due to the limited three week time-frame for public review of the reports,
it’s entirely possible that some of my concerns may be readily answered
in the documents. However, even if some can be reasonably answered,
I believe all comments must be adequately resolved in order to put this
issue to rest, as it has far reaching implications for the future of
structural design.
Thank you for allowing
the public to offer this input.
JHC:pec
Attachment
PUBLIC COMMENTS
For
THREE
DRAFT REPORTS – WTC 7
NIST NCSTAR 1A: “Final Report on the Collapse of World
Trade Center Building 7”
NIST NCSTAR 1-9: “Structural Fire Response and Probable
Collap
Center Building 7” - Volume
1
NIST NCSTAR 1-9: “Structural Fire Response and Probable
Collap
Center Building 7” - Volume
2
Prepared and Submitted
By:
Jonathan H. Cole, P.E.
614 Palomino Trail
Englewood, FL 34223
September 11, 2008
WTC Technical Information Repository
Attention: Mr. Stephen Cauffman
National Institute of Standards and Technology
Stop 8610
Gaithersburg, MD 20866-8610
Name: Jonathan Cole, P.E.
Affiliation: N/A
Contact: JC@jonsbarn.com
Report Number: NCSTAR 1A, NCSTAR
1-9 Volume One and Volume Two.
Comment 1:
Report Number: NCSTAR 1-9 Volume 2, Chapter 10
Page Number: Graphics of floor temperatures on Pages 400 through Page 410
Paragraph/Sentence:
N/A Graphics only.
Comment:
The building collapsed just before 5:21 P.M. (NCSTAR 1A page xxxi, first
paragraph), yet all these graphics indicate floor temperatures at 5:30
p.m. and 6:00 p.m., or well after the structure collapsed.
Reason for Comment:
Since the floors as a whole didn’t even exist after 5:21 P.M., it’s
unusual that the graphics would indicate predictions of floor and beam
temperatures well after the collapse event.
Recognizing that the
temperatures are only estimates based on a computer model simulation
extrapolated beyond the collapse, it is misleading to show graphics
with the hotter floor temperatures that we know are impossible because
the floors themselves simply did not exist as a unit after the global
collapse.
Suggestion for
Revision: If the above assessment is true, suggest the graphics
indicating predicted fire spread and temperatures of the floors after
the global collapse of the structure, be deleted on these pages and
other pages.
Comment 2:
Report Number: NCSTAR 1A
Page Number: 10
Paragraph/Sentence:
Last paragraph; the following sentence: . . .
“On the 11th and 12th floors, which will be seen later to have been
the sites of significant and sustained fires, the mass of additional
paper materials was described as very high.”
Comment:
It is unclear how the mass of paper loading of these floors was ascertained
and additional information as to the type and volume of material stored
on these particular floors would be helpful, because the material loading
of these floors was used as a basis for causing bigger and hotter fires.
This appears to conflict with the prior Page 9 last sentence which states:
. . . “Presumably there were a variety of amounts and locations
of paper, both exposed on the work surfaces and contained within the
file cabinets.”
And the unknowns by NIST
about the details of these floors such as NCSTAR 1-9 Page 48: . . .
“However, despite the quality of the drawings and verbal descriptions
obtained by NIST, there was some uncertainty regarding the nature of
some spaces. Notably, the US Securities and Exchange Commission
and American Express occupied all but the east side of the 13th floor,
and NIST was unable to find people who recalled the nature of the unoccupied
space.”
And NCSTAR 1-9 Page 60
(for floors 11 and 12): . . . “The mass of the furnishings per
office was not known; the mass of additional paper materials was described
as very high. As indicated in
Section 9.3.1, the Investigation Team began with an initial estimation
of the combusted fuel load of approximately 32 kg/m (cubed).
Simulations of the fires with a lower combusted fuel load (Chapter
9) resulted in poor agreement with the observed spread of rates.”
And (same page) for floor 13: “There was little information regarding
the combustibles on this floor, and there was little visual evidence
for estimating the effect of different combustible mass loadings on
agreement with the observed fire growth patterns. NIST assumed
a combusted mass similar to that on the 11th and 12th floor.”
Reason for Comment:
“Very high” appears to be subjective and difficult to quantify.
In addition NIST uses the word “presumably” as if it’s just a
rough estimate at best, since there is no way of knowing the true volume
of combustibles. And if people didn’t even know what occupied
some of the spaces, then how could NIST assume that the “very high”
estimation of material creating the larger fire that caused the eventual
collapse (based on the NIST simulations) is even reasonable? Moreover,
it appears that NIST is not even very certain of the fire intensities.
(NISTNC STAR 1A, Page 28 states: “There were far fewer photographs
and videos of WTC 7 than the towers; and, thus, the details of the WTC
7 were not as precise as for the fires in the towers.”
Because the simulation did not match observed fires and associated heat needed for “thermal expansion”, it appears that NIST used a predetermined conclusion to arrive at the necessary initial assumption. In other words, since NIST needed hotter fires to later cause the simulated first ever “thermal expansion” type of global collapse, and also assumed the fires were only from burning office material, then NIST assumed that there must have been more combustible mass then normal for an office to create the fire.
But what if the fires
that were observed were from some other fuel source? Is it possible
that an incendiary such as thermite was used to weaken the heavier core
columns so they would be easier to blast later with a smaller shape
charge, and could that be the source of the observed hotter fires?
Or what if smaller explosions witnessed earlier that day (refer to eyewitness
testimony by Mr. Barry Jennings and Mr. Michael Hess, who were
inside WTC 7), weakening the internal network of columns and beams before
the global collapse at 5:21 P.M. were the cause of the observed fires?
Regardless, it would
be helpful to know why NIST believed these particular floors contained
a very high paper mass to reinforce the assumption that these floors
burned more intensely causing thermal expansion and the ultimate global
failure of the entire structure.
Suggestion for
Revision: “On the 11th and 12th floors, which will be seen
later to have been the sites of significant and sustained fires, the
mass of additional paper materials was described as very high, however
this was just an assumption made on the part of NIST to produce the
fires observed that was eventually used in the NIST model simulation.
Comment 3:
Report Number: NCSTAR 1A
Page Number: 16
Paragraph/Sentence:
Section 2.2.3, second paragraph, second sentence: “With the
collapses of the towers fresh in their minds, there was concern that
WTC 7 too might collapse, risking the lives of additional firefighters.”
Comment:
Prior to this particular day, no steel structure ever globally collapsed
due to fire, and firefighters know this, which is why they rush in to
burning skyscrapers without concern. If there was no historical
precedent, how would the firefighters at the time have known this?
Moreover, according to NCSTAR 1-9 Section 6.6 Page 299
“Between 11:00 a.m. and 12:00 noon approximately 40 FDNY members arrived
at WTC 7 with orders to put the fires out.
Inside they reported seeing small fires in debris in the core area
and on the west side of the same floor of the building.
A chief officer inside the building ran into other firefighters who
had searched the upper floors and they reported that no one was inside
the building. When the chief officer reached approximately the 9th
or 10th floor, he had been inside the building about 20 minutes to 25
minutes. He received a radio call from another Chief Officer outside
the building ordering him out of WTC 7.
The Chief Officer was ordering everyone out of the building.
The Chief Officer left the building and went to the FDNY Command Post
and reported to the Command Post Chief that he believed the fires inside
WTC 7 could be extinguished. Thus the Chief assigned to the firefighting
tasks was sent back to extinguish the fires.”
Reason
for Comment: Typically, scientific research papers
rely on the known facts and not assumptions of what individuals might
have been thinking.
Suggestion for
Revision: Suggest NIST deletes the sentence in its entirety
as it could be construed by some as being unscientific.
Comment 4:
Report Number: NCSTAR 1A
Page Number: 16 Section 2.3 “General”
Paragraph/Sentence:
Second paragraph: “Most likely, the WTC 7 fires began as
a result of the impact from the collapse of WTC 1 at about 10:29
a.m.”
Comment:
It appears that in addition to not really knowing the mass of combustibles
on the floors, NIST is also uncertain of how the fires even started.
For example, NIST NCSTAR 1-9 Page 194 states: . . .
“Since fires were observed on the ground surrounding WTC 7, it is
possible that potential ignition sources might have entered WTC 7 through
openings created in the south and west face of the building during the
collapses of the towers. NIST found no evidence to confirm this
possibility, but the available data suggest that this was highly likely.”
And NCSTAR 1-9 Chapter
9, Section 9.1.1: . . . “Chapter 3 showed that there were no pathways
for the flames and heat to pass from one floor to another, aside from
the debris damaged area in the southwest of the building.”
Because of the tremendous uncertainty, other fire initiation scenarios
should be investigated. For example, the intentional setting of
independent fires is possible or setting of fires due to incendiaries
weakening critical columns in the hours before the global collapse,
particularly since the fires appear to jump from location to location
on certain floors.
It is also very possible
that fires were started by explosions inside the structures well before
collapse, and is consistent with the eyewitness accounts of people inside
hours before the collapse. Moreover, an explanation of exactly
how steel beams and columns thrown from the exploding WTC 1 could start
a fire would be a benefit, since we know of several other adjacent structures
at about the same radius as WTC 7 with steel impacts from the towers
did not start any fires.
Reason for Comment:
All possible explanations and reasons as to how the fires actually started
should be addressed.
Suggestion for
Revision: The exact source for the ignition of the fires
is unknown, and it is unclear if it was from the impact from WTC 1 or
possibly from some other ignition sources inside the structure.
Comment 5:
Report Number: NCSTAR 1-9 Vol 1.
Page Number: 245 last paragraph and 246 first paragraphs
Paragraph/Sentence:
. . . “The next time that flames were observed on the 13th floor
was around 5:00 p.m., when intense burning was observed between windows
13-53D and 13-54D, to the west of the center of the north face.
A couple of minutes prior to the collapse of the building at
5:20:52 p.m., a jet of flames was pushed from windows in the same area.
NIST found no evidence regarding the cause of this unusual behavior,
but the behavior is similar to smoke and flame expulsions in the
WTC towers prior to their collapses that were attributed to pressure
pulses associated with structural changes (e.g. a partial floor collapse)
occurring within the tower.”
Comment:
There is a very good explanation for this unusual behavior that NIST
should investigate; and that is, the pulses were caused by blasts of
exploding charges, cutting the internal core columns just prior to the
global collapse. This is far more logical and fits precisely with
all the other evidence of a controlled demolition, than a “partially
collapsed floor” pushing the flames out.
Reason for Comment:
Although technically outside the scope of this report, the comparison
by NIST to the twin towers for similar pulses of flames can also be
explained with the following hypothesis that matches all known evidence
for WTC 1 and WTC 2: The expulsions of flame and concrete dust
in the WTC towers just prior to collapse were not at every floor but
rather from about each third floor. Because of this, the expulsions
could not be from a “pancake” or “piston” effect of collapsing
floors, but rather were very likely the result of high explosives placed
in the core columns at the weld points.
The tremendous energy
from the blasts from the core columns not only pulverized the concrete
floors (a gravitational collapse in the initial stage simply does not
have the necessary energy to pulverize the floors), but also pushed
out flames in the initial seconds.
In addition, those high
explosives placed in the core of the towers threw out huge segments
of steel hundreds of feet away into the adjacent structures, including
WTC 7; something an “office fire” has never done.
And because the pulses
of concrete dust from the explosive charges in the towers were at roughly
30 foot intervals, one would expect that the resulting debris at ground
zero would indicate similar lengths of cut core columns. This
is precisely what was found at ground zero (not “pancaked” floors
at all) further confirming this scenario.
The fact that the destruction
of the corners of the towers lagged significantly behind the center
portion of the floors as the structure exploded also proves that the
pancake or piston type of collapse was impossible.
In addition, no block
of upper floors could be seen “sledge hammering” down on the structure,
as they too were vaporized on the way down to ground zero.
Moreover, the initial
collapse of the 353 ton antennae in WTC 1 that was supported with a
hat truss on the core columns fell several feet first, before
the perimeter walls collapsed, confirming that the core columns had
to have been cut first, all at the same time. The fact that the
antenna accelerated into the path of most resistance (the core columns),
rather then slow down, indicates that the core columns were being cut
at a rapid rate, generating the necessary energy to pulverize the concrete
and allowing the towers to fall very close to free fall speed.
Finally, the fact that
some of the inner core was seen momentarily standing after the floors
fell, cut at about the 60th floor level (well below the airplane strike),
indicated that the tower collapse simply could not have been from a
“pancake or piston type” crushing effect. NIST did not investigate
any of this evidence, stopping their investigation of the towers at
“collapse initiation”, rather than having the burden of explaining
all the above phenomena.
Only pre-planted, rapidly
timed explosives can explain all the known events of the collapses that
day, and those same explosives also easily explain the unusual behavior
of the flames and pressure pulses just prior to the global collapse
of WTC 7.
Suggestion for
Revision: “NIST will look into the possibility that internal
explosives detonating just before collapse could be the source of the
observed unusual behavior.”
Comment 6:
Report Number: NCSTAR 1-9 Vol. 1
Page Number: Section 5.7.3 Distortion of North Façade Page 271
Paragraph/Sentence:
“Since the majority of the window
glass in the area of the movement was still intact, it is probable that
the lighter area was the result of changing light reflections due to
distortions of the façade, similar to those discussed earlier.
Such distortions could be due to physical movement
of the face or perhaps to pressure changes within the building.
Whatever the cause, it seems clear that some type of disturbance began
to move downward in the building at the same time as the east penthouse
started descending.”
Comment:
NIST should investigate another very likely cause of the distortions
noticed. A controlled demolition with internal explosions can
create pressure waves distorting the facade of glass. The disturbance
moving downward could have been created by well timed explosions, severing
the columns and bringing the building down.
Reason for Comment:
Only a controlled demolition easily explains all the evidence and events
of the day. This shock wave is one more piece of evidence that
is explained by a controlled demolition.
Suggestion for
Revision: “This downward moving distortion may be the
result of a controlled demolition. NIST will investigate this
scenario further.”
Comment 7:
Report Number: NCSTAR 1A
Page Number: 19 Section 2.4
Paragraph/Sentence:
Second paragraph: The phrase: “.
. . because water was not available.”
Comment:
Better corroboration is needed for this statement, because it appears
that there is some evidence that water was available in the NIST Report.
Reason for Comment:
Almost immediately after the total collapse virtually into its own footprint,
there is a picture of several fire hoses spraying water on the cut up
wall segments. If fire trucks are in the photo it is difficult
to determine and yet, there appears to be a full stream of water spraying
the debris pile. If there was no water in the mains, where did
the firefighters get the water to spray the pile shortly after collapse?
In addition there is a photo of a fire stream hosing down the area in
front of WTC 7 before the collapse on Page 141 NCSTAR 1-9 Chapter 5
with what appears to be ample water pressure, at 1:30 p.m.
Suggestion for
Revision: “ . . because of reports
that water may not have been available, however, photographic evidence
does not corroborate the report.”
Comment 8:
Report Number: NCSTAR 1A
Page Number: 19
Paragraph/Sentence:
Sixth paragraph: ”This buckling process that occurred at
temperatures at or below approximately 400º C (750
ºF), which are well below the temperatures considered in current practice
for determining fire resistance ratings associated with significant
loss of steel strength.”
AND
Fifth paragraph:
“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.”
Comment: While heat does indeed expand steel and concrete, the primary method for deducing that the heat generated in WTC 7 was enough to “damage the floor framing on multiple floors” was based on model simulations where inputs could be easily “tweaked” to produce the desired results. Is there any physical evidence of the steel from WTC 7 to corroborate this model? Equally important, did NIST conduct any laboratory analysis, with a full scale beam–column set up in a furnace in an effort to replicate the simulation results? Since the model input can significantly affect the output and the conclusions are so remarkable; and since it the first time in history that a building globally collapsed allegedly due to “thermal expansion”, a full scale fire test simulation is definitely in order.
Reason for Comment:
Was there any specific physical evidence of distorted beam-column connections?
Was there any physical evidence of damaged floor framing due to heat
found?
It appears that this
was a result based on a model simulation only, but not based on any
physical evidence or testing whatsoever.
Suggestion for
Revision: “One hypothesis is that 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. However, because the temperatures did not
last for the minimum time necessary to generate the heat on the beam–column
system for the model to predict that thermal expansion could have occurred,
no physical evidence was found indicating beam joint failures; no testing
was done to confirm the simulation; and the fact that thermal expansion
never caused a global collapse on any steel structure, it is very highly
unlikely that thermal expansion could possibly be the real cause of
the structures global collapse.”
Comment 9:
Report Number: NCSTAR 1A
Page Number: 19
Paragraph/Sentence:
Last paragraph: “This movement (from thermal expansion) was
enough to lose its connection to Column 79.”
Comment:
Thermal expansion of floor beams breaking its beam seat connection and
then causing a global collapse has never happened before, and very highly
unlikely. Structural engineers do not design connections for lateral
forces from thermal expansion because it is so rare. No structure
before or after 9/11 has ever globally failed due to “thermal expansion”
and it’s very doubtful if it was the cause of the collapse of WTC
7.
Reason for Comment:
Structural engineers do not design connections for lateral forces for
thermal expansion because it is so rare. Thermal expansion for
a 53 foot beam with a delta “T” of 654 F (752 – body temp) is
less then 2.7 inches.
Other pages in NCSTAR
1-9 indicate sag in the floor system due to the heat. (NCSTAR
1-9 Vol. 1 Chapter 8, Page 323: “Elevated temperatures in
the floor elements led to thermal expansion, with or without thermal
weakening and sagging, . . ”)
The sagging effect is
also indicated graphically in NCSTAR 1-9 Vol. 2 Page 56.
Any sag effects need to be subtracted from the lengthening effects
of thermal expansion. In addition any warping of the flange or
web will also consume some distance and must be subtracted from any
elongation and assumed forces of the thermal expansion. NIST is claiming
that girders “walked off” their beam seats at the major connections
with Column 79 (and others). But the elongation from thermal expansion,
even if the sagging effects are ignored, is only a couple of inches
at most; yet the beam seats are longer. How can the girders “walk
off” their beam seats if the seats are longer then the possible expansion?
Finally, any residual
expansion distance, once the sag, warping, and torsion effects are subtracted
is shared between each end of a beam and any lengthening or sagging
is incrementally re-distributed throughout the network of adjacent beams
and columns rendering elongations at any one particular location to
be almost negligible; or well within the elastic limits of the connections.
Steel structure beam
to beam, or beam to column connections have been riveted, bolted, welded
or a combination thereof for over a hundred years, with no significant
“thermal expansion” sheering problems during much hotter fires,
which is one reason it’s simply not necessary to include in any structural
design analysis.
Because no steel structure has ever failed globally due to fire, and this fire was a cool office fire when compared to historical fires, the suggestion that thermal expansion of the floor beam system was the trigger for global collapse is highly suspect and definitely should not be considered the leading hypothesis; given the overwhelming evidence for a hypothetical blast scenario.
Suggestion for
Revision: Delete sentence and all related (thermal expansion
causing global collapse) conclusions in its entirety and dismiss this
cause of failure, due to the fact that it is so highly improbable as
to render it not credible to scientific scrutiny.
Comment 10:
Report Number: NCSTAR 1-9 Chapter 13 13.3 (16)
Page Numbers: 606
Paragraph/Sentence:
Section 13.3, Paragraph (16) -
“Hypothetical blast events did not cause the collapse of WTC
7. NIST concluded that blast events could not have occurred and found
no evidence of any blast events.”
Comment:
Contrary to the above opening statement, it is apparent that adequate
effort was not expended or was intentionally overlooked when compiling
the evidence for a blast scenario. There are many layers of evidence
for a controlled demolition and some of the issues that were overlooked
include:
Note:
an office fire will not cause a eutectic state
for the steel found by FEMA. Sulfur, from a thermite reaction,
could very well cause this eutectic state.
Reason for Comment:
All of the above evidence linking explosives appears to have been grossly
overlooked or intentionally ignored.
Without discussion of
the above items, all of Section 2.3 as well as the entire NIST report,
analysis and conclusions are incomplete and simply not credible to scientific
scrutiny.
Suggestion for
Revision: “Hypothetical Blast Events are
the primary cause the collapse of WTC 7.
NIST concluded that blast events must have occurred because no other
hypothesis can explain all the known events, all the known evidence
and all the testimony from eye witness accounts.
Only a blast scenario addresses 100% of all known evidence, and
therefore is our leading hypothesis.”
Comment 11:
Report Number: NCSTAR 1A
Page Number: 32
Paragraph/Sentence:
Section 3.4.5 Second to last paragraph. “Figure 3-9 shows
an example of the extent of structural damage from the fires, in this
case for the 13th floor. At both 3.5 h and 4.0 h, connections, floor
beams, and girders were damaged or had failed at steel temperatures
that were approximately 400º C or less, primarily due to the effects
of thermal expansion. After 4 h of heating, there was substantially
more damage and failures in the WTC 7 structural system than at 3.5
h of heating.” And in the next paragraph: “However,
it appeared likely the critical damage state occurred between 3.5 h
and 4 h.”
Comment:
Exact input details of the NIST model were not provided for review.
However, based on the above, it appears the modeling effort to reach
failure mode of the connections required was at least a time of 3.5
hours at a temperature of approximately 400º C., or to put it another
way, any time less then 3.5 hours or 4 hours would not cause
a failure.
Reason for Comment:
Based on Figure 3.6, Page 30 (NCSTAR 1A) temperatures near the floor
system of Column 79 did not sustain temperatures of 400º C for a time
in excess of 3.5 hours. Rather, this indicated a time of perhaps
2 hours.
In addition, according
to Page 330 Section 8.4.1 (NCSTAR 1-9 Vol. 1): “Prediction and
growth of building contents fires (Chapter 9) indicated that such fires
did not persist at any one location for more then about 20 min to 30
min., which is consistent with observations of fires in the windows
(Chapter 5).”
Finally, Floors 12 and
13 (the SEC floors) were determined to be the hottest, yet:
“Fire was first observed on the 12th floor, on the south side of the
east face, at about 2:10 p.m.”
(Page 381 NCSTAR 1-9 Vol 2), and didn’t even begin to heat up the
areas near Column 79 until around 3:00 p.m.
NCSTAR 1-9 Page 243 for
the 8th floor: “As late as 3:22 p.m., there was no indication
of fire in this area but about 17 min later a substantial fire spreading
to the east was visible between windows 8-47C and 8-53C.”
NCSTAR 1-9 Pages 244
and 245 state: 11th floor: “A fire was first observed
at 2:08 p.m. on the east face.”, and for the 12th floor, a similar
time.
For the 13th floor:
“The first visual evidence for burning on the 13th floor was
seen on the east face around 2:30 p.m.”; less then 3 hours before
the collapse.
And even more importantly,
the floor temperatures predicted (Figure 3-8 Page 31 NCSTA 1A) indicate
temperatures colder then 200º C as late as 4:00 p.m. in the area of
Column 79, and not until about 5:00 p.m. (20 minutes before collapse)
does only a small portion of the floor area theoretically approach temperatures
of 400 C. But the building collapsed at about 5:21 p.m. in the
afternoon, about a half hour later, far less time than the critical
3.5 hour time used in the model.
If the entire analysis of the initial failure event is dependent on temperatures approaching 400º C that must exist over 3.5 hour period, and/or the fires did not last that long in the critical Column 79 area, then the entire foundation of the simulation appears flawed. And if the input of the model is flawed, the output results and conclusions are also flawed.
Suggestion for
Revision: Add the sentence: “Because the time of
heating was not sufficient or near the necessary time of 4.0 h to cause
sufficient thermal expansion in the connections, this hypothesis for
global collapse was abandoned.”
Comment 12:
Report Number: NCSTAR 1A
Page Number:
34 NCSTAR 1A Section 3.4.6 Global Analysis using LS-DYNA - third to
last paragraph: “The first
was based on NIST’s best estimate of both debris impact damage
form” (sic from) “WTC 1 and the fire-induced damage as
developed using the ANSYS modeling. This occurred at 4 h in the
ANSYS computation.”
AND
Paragraph/Sentence:
Page 35 NCSTAR 1A - Paragraph
2: “The global analysis with fire-induced damage at 4.0 h
most closely matched the observed collapse
events, and the following discussion begins with the results
from this analysis.”
Comment:
The heat applied for four hours to the floor system and floor beams
did not last that long in the critical area.
Reason for Comment:
If the heat did not last four hours in the area of Column 79, then
there is no collapse initiation by “thermal expansion” and no trigger
to start the global collapse due to fire.
If the above is true,
the entire model, analysis summary and conclusions are wrong.
Suggestion for
Revision: “The global analysis with fire induced damage at
4 h most closely matched the observed events and the following discussion
begins with the results of the analysis. However, since the office
fires in WTC 7 did not have duration of 4 hours in any one area, although
the model results may have matched the observed events, the model input
was not valid and therefore the entire model results were dismissed.”
Comment 13:
Report Number: NCSTAR 1A
Page Number: Page 35
Paragraph/Sentence:
Last paragraph: “With no fires on the west side of
Floors 10 through 14, the intact floor framing pulled the exterior columns
inward and the interior columns fell downward. Loads from the
buckled interior columns were redistributed to the exterior columns,
which, in turn, buckled the exterior columns between
Floors 7 and 14 within approximately 2 s. At that point the entire
building above the buckled-column region moved downward as a single
unit, resulting in the global collapse of WTC 7.”
Comment:
There are several problems with this hypothetical collapse sequence.
Reason for Comment:
First, if the interior floors under the penthouse and surrounding Column
79 collapsed first, there is very little floor load to be redistributed
to the exterior walls, particularly on the northwest, southwest and
west side. If anything, the loads would become significantly reduced
on the perimeter walls as there is no dead loading from the internal
floors, nor of course any live loads imposed by occupants, wind or snow
loads. The steel structures, in addition to being able to carry full
loadings, are also designed with a factor of safety of at least double
the maximum rated loadings, acting simultaneously. Probably this
particular structure has a higher factor of safety since it was a reinforced
emergency command center.
Secondly, Figure 3-14,
indicates the most buckling on the westerly face with a severe kink
between Floors 7 -14. Any buckling of the perimeter wall columns
by increased loading above, must by definition, shorten the distance
between the top of the roof and the ground along the westerly wall,
compared to the easterly wall. If the “top block of floors” remains
fixed and level, then there can be no increase in vertical loading and
no buckling of the lower walls. This shortening due to the buckling
would be reflected in a roofline that would not be parallel to the horizon
as it fell, but rather a tilted roof line relative to the horizon.
We know from video that the roof fell parallel to the horizon and was
definitely not tilted or at an angle.
In addition the twist
of the entire easterly portion of the structure, indicated in Figure
3-14 as representative of the model, is not supported by the videos
or photographic evidence of the collapse.
NIST then claims that:
“At that point the entire building above the buckled-column region
moved downward as a single unit, resulting in the global collapse of
WTC 7.” But to remain as a unit, one would expect to see a stack
of pancaked floors in the final debris pile; with concrete floors stacked
on each other crushed but intact, and furniture crushed between the
floors. But that was not observed at the debris pile. Rather,
steel wall W sections were cut up (not bent, but cut), and there were
no stacks of floors as predicted by the NIST account of events, with
the upper floors falling as a single unit. The concrete floors
were pulverized and the debris pile looked exactly like that of a controlled
demolition, and definitely not a collapse of a single block of upper
floors. And to fall vertically as a single unit, the underlying perimeter
supports would all have to fail at the same time. But the NIST analysis
indicates the bucking of the walls on the south westerly side first,
followed later by failure on the north and easterly sides.
The evidence simply does
not match the conclusion presented in the global collapse analysis presented,
and is, therefore, fatally flawed.
Suggestion for
Revision: Delete “thermal expansion leading to global collapse”
as your leading hypothesis. It is fatally flawed. Re-focus
on the blast scenario which addresses all known evidence.
Comment 14:
Document: NCSTAR 1-9 WTC 13.3(16)
Page Number: 606
Paragraph/Sentence:
“The minimum explosive charge (lower bound) required to fail a critical
column (i.e. Column 79) would have produced a pressure wave that would
have broken windows on the north and east faces of the building near
Column 79.”
AND
NCSTAR 1A Pages 22-23
Paragraph/Sentence:
“Nearly all the windows on the northeast section of the blast
floor would have been broken, even by the smaller charge. Simulations
for open landscaped floors led to more extensive window breakage.”
The actual window
breakage pattern on the visible floors on September
11, 2001 (NIST NCSTAR 1-9 Chapter 5) was not at all like
that expected from a blast that was even 20 percent of that needed to
damage a critical column in WTC 7. The visual evidence did not
show showing such a breakage pattern on any floor of WTC 7 as late as
about 4:00 p.m. or above the 25th floor at the time
of the building collapse initiation. Views of the northeast corner
at the time of the collapse were obstructed by other building.”
Comment:
I believe the inference from NIST can be summarized as follows:
Since the windows would have been broken with a blast event, and we
didn’t notice any broken windows, we conclude that there was no blast
event. This logic is flawed for many reasons:
Reason for Comment:
Window breakage is a very poor method to conclude that explosives were
not used, especially since there is overwhelming evidence that explosives
were used to bring the building down.
By NIST’s own admission,
there is not sufficient evidence to support this rationale whatsoever.
Suggestion for
Revision: “Unfortunately the
visual evidence did not show showing such a breakage pattern on any
floor of WTC 7 as late as about 4:00 p.m. (which was well over an hour
before the building collapsed), or above the 25th floor at the time
of the building collapse initiation. Views of the northeast corner
at the time of the collapse were obstructed by other buildings.
Accordingly, we cannot rule out a blast scenario based on available
window data, since we do not have data at the time a blast would have
occurred, or within seconds of the collapse at about 5:20 P.M.”
Comment 15:
Report Number: NCSTAR 1A
Page Number: 23
Paragraph/Sentence:
“The calculations showed that all the hypothetical blast scenarios
and charge sizes would have broadcast significant sound levels from
all of the building
faces.” AND
“. . . the sound level . . . would have been approximately 130
dB to 140 dB at a distance of 1 km . . .”
AND (Page 24 NCSTAR 1A): “However, the soundtracks from
videos being recorded at the time of the collapse did not
contain any sound as intense as would have accompanied such a blast
event. Therefore, the Investigation Team concluded that there
was no demolition-type blast that would have been enough to lead to
the collapse of WTC 7 . . .”
Comment:
I believe the NIST position can be summarized as follows: Since
our model predicted explosive sounds in excess to what we have known
recordings of the event, we conclude that explosives were not used.
This logic is flawed for many reasons:
Reason for Comment:
To conclude that explosives were not used based only on sound
is not realistic, in light of all the other evidence that the use of
explosives were used to take the building down, that has not been addressed
in this report.
All the known evidence
of explosions need to be addressed in order to be valid. Relying
on video sound tracks and a simulation model is simply not appropriate
or sufficient to dismiss the use of explosives in light of the overwhelming
unaddressed evidence for the use of explosives.
Suggestion for
Revision: “However, the soundtracks from videos being recorded
at the time of the collapse did not contain any sound as intense as
would have accompanied such a blast event.
NIST recognizes that video sound tracks are not accurate enough to
dismiss the use of explosives, and given all the other evidence (time
of fall, symmetry of fall, eyewitness accounts, cut up wall segments
contained debris field, evidence of thermite, evidence of molten metal,
pyroclastic flow of dust, etc), NIST recognizes that dismissing the
blast hypothesis based on only one method (model predicted sound levels)
is inappropriate, and not accordance with the scientific method.
Comment 16:
Report Number: NCSTAR 1A
Page Number: 22
Paragraph/Sentence:
Section 3.3 Paragraph 4: “The other scenarios would have required
more explosives or were considered infeasible to carry out without detection.”
Comment:
To dismiss a very high probability of global collapse due to explosives,
which easily explains all known evidence and eyewitness accounts
because NIST examiners didn’t “think” that planting of explosives
could be carried out without detection, is totally unscientific.
Rather, it’s very plausible that explosives could have been planted
since many of the floors were controlled by governmental entities and
much of the prep work could have been placed on the core columns accessed
undetected inside the elevators shafts, similar to the twin towers.
Moreover night work and the fact that the owner of the structure gained
financially by the collapses that day would point to access issues not
being problematic at all.
Reason for Comment: To dismiss placement of explosives because those placing it “might be detected” is not a good scientific reason to dismiss the likelihood and only increases the potential ridicule of the official investigation.
Suggestion for
Revision: “The other scenarios would have required more explosives,
which is entirely within the realm of possibility. Moreover, NIST
bases the conclusions solely on scientific evidence and research, and
leaves how the potential explosives could have been placed to
other agencies having jurisdiction.”
Comment 17:
Report Number: NCSTAR 1A
Page Number: xxxi Executive Summary
Paragraph/Sentence:
“This was the first known instance of the total collapse of a tall
building due to fires.”
Comment:
This very conclusion, regardless of how extensive the modeling simulations
were, is cause for deep concern and is highly suspect. Since there
have been thousands of fires, several of which were discussed in the
“Lessons Learned” Chapter (NCSTAR 1-9 Chapter 8.5 pages 331 –
336), that burned hotter and longer and never globally collapsed; it
is very improbable that this is the first and only structure to-date
that experienced global collapse in all of world history.
Reason for Comment:
A far more likely rationale is that the structure was taken down by
a controlled demolition. It has all the attributes of a
controlled demolition, and the evidence collected all point to a controlled
demolition. And almost anyone who watches the collapse and compares
it to other controlled demolitions concludes the same thing. However,
NIST ignored all the evidence and dismissed this cause on very questionable
model results and video noise levels; the determination that in NISTS
opinion, anyone planting explosives would have been detected,
and a flawed window analysis.
Suggestion for
Revision: “Since no structure has ever experienced a global
collapse due to a simple office fire, before or after 9/11, any conclusion
that suggests “thermal expansion” as the cause of the collapse of
WTC 7 would be remarkable and highly suspect. Accordingly, the
finding of NIST does not support the following explanations for the
global collapse: diesel fire, damage due to impact from WTC 1,
column heating beyond its strength carrying capability,
“thermal expansion” of beams breaking their connections, or global
collapse due to the relatively cool and short duration of office fires.
Rather, the only explanation for the global collapse that matches all
known evidence is that WTC 7 collapse is due to a
controlled demolition. Who placed the explosives and when
they were placed, is outside the jurisdiction
of this agency, and scope of this report.
Comment 18:
Report Number: NCSTAR 1-9 Chapter 11
Page Number: 534 and 535
Paragraph/Sentence:
The entire summary of findings, including bolt failures, weld failures,
beams buckling, girders “walking off” beam seats, sheer studs breaking,
at relatively low temperatures ultimately leading of loss of lateral
support of Column 79; and then to a global collapse needs to be confirmed
by something besides a computer “simulation.”
Comment:
Not having the computer inputs, the models or the necessary time to
evaluate, due to the deadline for public input, there was no way to
verify the simulations that NIST performed. Therefore, one must
rely on logical deductions as to the validity and probability of the
results.
The entire analysis of
the global collapse in Chapter 12 is based upon the collapse initiation
simulation of Chapter 11, which is based on the assumptions of temperatures
models in prior chapters, which is based on the fuel loading of a prior
chapter, and based on fire initiation of an even prior chapter. Each
module is dependent on the results of a prior simulation. Yet,
all of it is just a computer simulation that has not been verified in
a laboratory and the end results are so fantastic as to be totally unbelievable.
Never in all history has a building collapsed this way, and there have
been hundreds of if not thousands of fires in steel framed structures
with hotter temperatures and with no global collapse at almost free
fall speed.
Reason for Comment:
Having worked with many computer simulation models, the output results
can be very sensitive to the input assumptions, and those results can
be dramatically different based on the input. Results from model
simulations, for example, the weather service predicting “projected”
hurricane paths can be very questionable. In this particular
case, any errors or wrong assumptions are compounded because each subsequent
simulation is dependent on the cumulative assumptions and results from
prior simulations. Recognizing this reliance of assumptions and
the multiplying effect of incorrect assumptions, resulting in a conclusion
that has never happened in the real world, places the entire modeling
simulations into the realm of the unbelievable without corroborating
evidence. The results from the NIST simulation would be like NOAA
predicting an Atlantic hurricane travelling from the Caribbean to Africa,
spinning clockwise, opposite to all historical precedence.
Suggestion for
Revision: “Because the simulation results are so astonishing,
only thermal expansion leading to global collapse based only
on computer simulations simply cannot be believed unless it is confirmed
with actual historical examples of structures that acted in a similar
way.”
Comment 19:
Report Number: NCSTAR 1A
Page Number: 41
Paragraph/Sentence:
Second Paragraph, First Sentence:
“The elevation of the top of the parapet wall was +925 ft. 4 in.”
Comment:
This elevation needs to be clarified. Was this NGVD or AGL?
In other words, is the top of the parapet wall 925 feet above mean sea
level or above the ground level?
Reason for Comment:
The datum should be clarified because according to Page 5 NCSTAR 1A,
the height of the building was 610 feet tall.
Suggestion for
Revision: “The elevation of the parapet wall was [+925
feet 4 inches above the ground] OR [+925.33’ NGVD.]
Comment 20:
Report Number: NCSTAR 1A
Page Number: 38
Paragraph/Sentence:
“Figure 3-14 Buckling of the lower exterior columns within 1 s of
Figure 3-13.”
Comment:
This graphics indicates the buckling anticipated from the NIST model
simulation on the westerly side of WTC 7, and a predicted twist on the
easterly side. The top of the graphic is truncated horizontally,
almost inferring that it is the roof top. Recognizing that this is a
section cut through at a lower level, a continuation of the graphic
up to the parapet walls on the roof would indicate that the roof could
not be parallel to the horizon because of the predicted buckling and
twisting action. This can be seen viewing the yellow horizontal
(yet uneven) floor lines of Figure 3- 14.
Reason for Comment:
Since we know the roof of the actual collapse event did remain
virtually horizontal or parallel with the horizon and the graphic on
Figure 3-14 would indicate a roof line that is NOT parallel with the
horizon; the predicted global collapse from the model is false, and
the model must be discarded. In addition, the graphic indicates that
the sides of the structure would be twisted and not vertical.
Yet, we know that the sides fundamentally remained vertical. According
to NIST NCSTAR 1-9 Page 277: “Thus, well into the building collapse,
the northeast corner of the building fell either straight down; directly
toward, or directly away from the video camera.”
AND
Near the end of the next
paragraph, same page: “The northwest edge initially tilted in
a similar manner, but then settled back to its original line and fell
nearly vertically, (or directly toward or away from the camera).”
Other videos from differing perspectives indicate the same thing, eliminating
the “directly toward or away” from the camera
comment. The building fell straight down, and to fall straight
down without the roof line tilting, all 58 perimeter 14” W shape columns
had to be cut at the same time.
Suggestion for
Revision: Show the entire structure all the way to the
top to indicate the roof and wall lines of position that the NIST
model predicts just before collapse and it will indicate how the simulation
simply does not follow the observed collapse geometry.
Comment 21:
Report Number: NCSTAR 1A
Page Number: 40
Paragraph/Sentence:
3.6 Last paragraph, about halfway through it: “Assuming that
the descent speed was approximately constant, the two quantities needed
for the determinations were (1) a length of some feature of the building
descended and (2) the time it took to fall that distance.”
Comment:
The first phrase of the sentence “Assuming that the descent speed
was approximately constant…” is a poor assumption.
The speed of a falling body is not constant. It’s accelerating
at a rate of 9.8 m/s (squared). The rate of acceleration is constant…not
the speed.
Reason for Comment:
The assumption by NIST is incorrect, or rather defies all known Newtonian
physical laws of free falling bodies.
Suggestion for
Revision: “Assuming that the descent speed was accelerating
at the rate of gravitational attraction . . .”
Comment 22:
Report Number: NCSTAR 1A
Page Number: 40
Paragraph/Sentence:
3.6 Last Paragraph, first sentence:
“NIST was interested in estimating how closely the time for WTC
7 took to fall compared with the descent time if the building were falling
freely under the force of gravity (NIST NCSTAR 1-9 Chapter 12).
Comment:
The time that the structure fell may not have been precisely at free
fall speed in a vacuum, but was certainly close to free fall speed which
is remarkable given the fact that it was supported by 24 core and 58
perimeter columns. Saying that the actual rate of fall for the selected
feature was 1.5 seconds longer (5.4 seconds vs. a fall in a vacuum of
3.9 seconds), or “40 percent longer”, is misleading and not
significant. Regardless, all 58 exterior supporting columns
had to be severed at virtually the exact same time in several places
at various levels, in order for the roof to fall parallel to the horizon
at almost free fall speed.
Reason for Comment:
What would be far more significant is to compare the actual time
of collapse vs. the NIST simulation that was done, including the time
delay for the natural inertial effects of impact and acceleration of
each internal floor. In addition the time to buckle the interior
and exterior southwest columns and the twist of the faces predicted
by the NIST model graphically indicated on Page 38 needs to be calculated.
If all the inertial effects
are summed, the time for each floor to cascade and the time to bend
and buckle all the columns as predicted in the NIST model was determined
vs. the actual the time to fall, it would be far more beneficial to
determine if the NIST simulation is even valid. If the model time
does is not corroborated by the actual time, then the model is fatally
flawed.
Suggestion for
Revision: “NIST compared the time predicted in the model that
accounted for all buckling time and the inertial effects of accelerating
each floor and compared it to the measured time of the event.”
(Then expand on the results.) The “40% greater”
comment is of little value.
Comment 23:
Report Number: NCSTAR 1A
Page Number: 58 through 66
Paragraph/Sentence:
All the recommendation for stricter design codes including recommendations
such as (Page 55-4.6) “Structural systems expressly designed to
prevent progressive collapse. The current model building codes do not
require that buildings be designed to resists progressive collapse.”
Comment:
A global collapse has never happened with any steel structures in the
way that WTC 7 fell, unless it was a controlled demolition.
Like tornadoes, designing for the loadings imposed by a controlled demolition
is simply out of the question due to cost. The conclusion of NIST
that this building fell due to thermal expansion does not fit the evidence,
and even if it somehow did (which defies all probability and does
not pass the straight face test); if it only has happened once in
the last 100 years, and never since that day, then a recommendation
of an overhaul in fire and structural design codes is irresponsible.
At a minimum, a cost/benefit study should be conducted prior to making
such recommendations based on a singular event in the last 100 years.
Reason for Comment: The reason that engineers and codes do not require thermal expansion analysis of structures globally failing due to fires, is because it never happens, and any small thermal expansion that does happen is negligible or local relative to the entire structure. NCSTAR 1A Executive Summary Page xxxi states: “This was the first known instance of the total collapse of a tall building primarily due to fire.”
NCSTAR 1A Section 4.5.2
states: “The structural design did not explicitly evaluate fire
effects, which was typical for engineering practice at that time and
continues to remain so today.”
NCSTAR 1A Page 44 states:
“This is the first known instance where fire-induced local damage
(i.e. buckling failure of Column 79; one of 82 columns in WTC 7) led
to the collapse of an entire tall building.”;
AND
NCSTAR 1A Section 5.1 Page 57 states: “The partial or total collapse of a building due to fires is an infrequent event.” By the many admissions of NCSTAR 1A, it is such a highly improbable event (in fact NEVER has a steel structure collapsed globally due to thermal expansion) as to render the entire NIST simulation process, its conclusions and the recommendations for even more stringent codes based on a flawed analysis of a singular event, totally unacceptable.
Suggestion for
Revision: “Since the global collapse of a steel structure
never occurred before or after the collapse of WTC 7, without the use
of explosives, code changes based on one single event is not prudent,
and no code changes whatsoever are recommended.”
Comment 24:
Report Number: NCSTAR 1A
Page Number: Cover Page of Report
Paragraph/Sentence:
N/A
Comment:
This report and analysis has far reaching implications, since it is
a structural analysis with associated conclusions and recommendations.
Accordingly due to its importance, Professional Engineer(s) in responsible
charge should sign, date and seal all documents in accordance with ASCE
and State Statutes. As such, that engineer is responsible for
its content, and any falsification of content would be subject to disciplinary
action if it was found that facts were intentionally overlooked, or
conclusions intentionally skewed, in accordance with the Code of Ethics
for Engineers.
Reason for Comment:
All engineering documents, studies and analysis should be signed and
sealed by the professional engineer(s) in responsible charge, to lend
credibility to the entire report.
Comment 25:
Report Number: NCSTAR 1A
Page Number: Page xxxi of the Executive Summary
Paragraph/Sentence:
Paragraph 3 states: “However, the reader should keep in mind
that the building and the records kept within it were destroyed, and
the remains of all the WTC buildings were disposed of before congressional
action and funding was available for this
Investigation to begin.”
Comment:
Due to the problem of having key evidence destroyed, which puts a real
burden on the analysis team at NIST, and realizing that the computer
models could not be verified by field evidence, places the entire modeling
process, calibration and conclusions of that model into serious question.
Reason for Comment: To protect NIST staff, you may wish to put a bold disclaimer on the cover of the entire report. As mentioned several times (NCSTAR 1A Page 38): “Independent assessment of the validity of the key steps in the collapse of WTC 7 was a challenging task.”
Suggestion for Revision: “KEY EVIDENCE RELATING TO THE COLLAPSE OF WTC 7 WAS IMMEDIATELY AND SYSTEMATICALLY DESTROYED BEFORE THE INVESTIGATION INTO THE CAUSE OF THE COLLAPSE COMMENCED. THE NIST COLLAPSE SCENARIO HEREIN IS BASED IN PART ON A COMPUTER MODEL UTILIZING NUMEROUS ASSUMPTIONS THAT COULD NOT BE FIELD VERIFIED. INPUTS, EQUATIONS AND ASSUMPTIONS USED IN THE COMPUTER SIMULATIONS AND THE TECHNICAL ANALYSIS HAVE NOT BEEN PEER REVIEWED. NIST RESERVES THE RIGHT TO MODIFY THE CONCLUSIONS OF THIS REPORT IF ADDITIONAL INFORMATION AND EVIDENCE IS FOUND WHICH MAY DRAMATICALLY ALTER THE RECOMMENDATIONS.”