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RE: Nova program on World Trade Tower Collapse

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>Drew Morris wrote:
>Can you post your response to NOVA on the SEAINT
>list?  I have briefly looked at the NIST report
>and would welcome your viewpoint.

Since you asked, I've pasted the email with my comments below.

Charlie


-----Original Message-----
From: Carter, Charlie
Sent: Sunday, November 14, 2004 11:07 AM
To: Larry Klein
Cc: Gaia Remerowski
Subject: RE: "Why The Towers Fell" Corrections

Mr. Klein,

Thank you for the opportunity to provide the following suggestions of
corrections for the NOVA program "Why the Towers Fell". I've grouped my
comments by subject into four major focus areas and one list of
miscellaneous items to make the suggestions less repetitive. I used the
video tape version and reset the counter on my VCR as the FBI warning
screen faded out (for another reference, the NOVA intro and music began
at 3:30 on my VCR counter. The counter numbers are probably approximate
anyway.

I think you did an excellent job in conceiving and creating the program.
In fact, most of the corrections I suggest are the result of knowledge
that only came to be after you would have created it.

Thanks again. I'd be happy provide additional information or answer any
questions this email might generate.

Charlie Carter
AISC Chief Structural Engineer

**********
Suggested Correction #1:
The truss connections to the tower wall were welded, not just bolted.
The bolts were there to facilitate erection. Later during construction,
thick plates and welding were used to permanently attach the trusses to
the tower wall. NIST has extensive pictures that show limited areas of
floors sagging and ruptured connections in areas of impact, but the
global failure was not initiated until the items discussed in correction
#2 occurred. Related to this:

1:20 the illustration shows the bolts, but not the plates or the welds

11:50 welded connection is verbally acknowledged (GOOD!)

34:10 the illustration and verbal testimony of Charles Thornton
indicates that the connections were bolted. As stated above, this is now
known to be incorrect.

47:10 it is stated that the truss to wall connections failed. NIST
studies have concluded that this could not have happened (see correction
#2).

Correction #2: The tower wall buckling that initiated the global
collapse of each tower was an inward bow, not an exterior bow. Also,
NIST studies conclude that the core of the building was sagging and
pulling on the exterior wall through the trusses and their connections
to the exterior wall. Related to this:

34:10 The depiction of trusses dropping one by one could not have
happened. Rather, the core columns began to deflect in the heat of the
fire and dragged the floors down. The floors dragged the outer walls in
until the global collapse occurred. The truss connections turned out to
be very robust in order to go through this action. Thus, the statement
by Thornton is incorrect that the truss connections were not capable of
taking the tension forces.

37:50 There is a statement made that the core of the tower remained
standing for some time period after the perimeter fell. NIST says the
core went first in both towers.

39:00 The depiction of the outside wall bowing out as the truss
connections failed and rupturing along a line is not correct. With the
trusses connections intact, the wall was dragged inward.

39:52 Depiction of core as remaining in place as exterior fell is not
correct as stated above.

45:00 The implication is given that the North and South Tower failed in
different ways. NIST has failure scenarios that differ slightly, but not
in the ways presented in the program. They now say the cores in both
towers began to collapse first and pulled the exterior walls down with
them.

45:30 The depiction of the core falling as remainder of building stood
in place is not correct in view of the above.

Correction #3: The floor truss system was a two-way truss system. The
depictions show it as a one-way truss system. That is, in addition to
the trusses shown in the illustrations, there was a system of secondary
trusses running perpendicular to those shown. These bridging trusses
would not have permitted an individual truss to fall as the
illustrations show. This affects the depictions shown at 34:10 and
38:40. Maybe elsewhere?

Other miscellaneous correction:

19:24: It is stated that the aircraft shattered on impact. You might
want to cover the NIST study of the wings. If they had been empty, the
shattering of the aircraft wings would have been guaranteed. But full of
fuel, NIST showed that the wings would cut the steel at the speed and
mass they possessed at impact prior to shattering. Perhaps this is what
you meant and I am just reading too finely into it.

50:00 I suspect the original focus on the connections led to the FEMA
report conclusion that connection fire protection was an issue. NIST
studies have since shown that the connections remained intact and were
not as affected by the fire as first assumed. Essentially, connection
fire protection is on the verge of becoming a red herring issue (my
opinion, anyway).

1:55 and 50:39: Criticisms made by Charles Thornton about the floor
system are based upon the erroneous information that was assumed correct
in late 2001. We now know from the NIST studies that the floor system
was extremely resilient. On this basis, I think it is inappropriate to
retain the criticisms provided by Thornton.

2:20 Matthys Levy says that steel softens and melts. I don't think it
can be shown that the temperatures in the fire were hot enough to melt
steel. Later, at 26:45, he says it perfectly -- steel softens, buckles,
fails. Perhaps this comment can be addressed simply by eliminating the
"melts" part.




-----Original Message-----
From: Gaia Remerowski [mailto:gaia_remerowski(--nospam--at)wgbh.org]
Sent: Wednesday, October 13, 2004 9:39 AM
To: Carter, Charlie
Cc: Larry Klein
Subject: "Why The Towers Fell" Corrections

Hello,
We just spoke on the phone - I work with Larry Klein at WGBH television
in Boston. Larry produced the NOVA program "Why The Towers Fell" and he
has asked that you e-mail him the corrections you spoke of in your
letter. Larry's e-mail is:
larry_klein(--nospam--at)wgbh.org

Thank you,
Gaia
--
Gaia Remerowski
Special Projects Assistant
Global Health Project
WGBH/NOVA Science Unit
125 Western Ave.
Boston, MA 02134
Tel: 617-300-4364
Fax: 617-300-1003

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