Fw: Why the Towers collapsed

Xxxx Xxxxxx xxxxxxxxxx at xxxxxxxxx.xxx
Tue Sep 11 18:51:42 MDT 2001

-----Original Message-----
From: Political Science Grad Students Discussion
[mailto:PSGRAD-L at listserv.albany.edu]On Behalf Of Xxxx Xxxxxx
Sent: Tuesday, September 11, 2001 6:13 PM
To: PSGRAD-L at listserv.albany.edu
Subject: Fw: Why the Towers collapsed

> > Mitchell Bomber vs. Empire State Building

The construction of the towers of the WTC is considerably different than
that of the Empire State Building (ESB). The WTC is in essence a box--the
load of the floors and all on them is borne on the outside walls. If you've
been in WTC you've seen how narrow the windows are and how close the
are to each other. These columns bear all the load of the building--both
static load (the weight of the building just sitting there) and the dynamic
load (the wind, people moving around in the building, etc.). This was a
major selling feature of the building when it was opened for leasing:
tenants could arrange each floor (about 42,000 sq ft) any way they wanted,
and the floors could have their partitions rearranged to accommodate
multiple tenants per floor.

In this case, the columns supporting the upper floors probably failed when
the planes crashed into them and burned them. When the columns failed, they
could no longer support the load above them; that load then crashed down
below--this became a dynamic load which the rest of the structure could not
withstand, because it probably wasn't designed for it.

The crash of the B-25 in 1945 did not result in the same sort of fire,
because the plane was not as large, and it did not have as much fuel. The
ESB was also built with a big frame with redundant members that would
protect the building. But one can only speculate what the effect would be
a plane as large as a 757 or larger striking the ESB--if it caused massive
structural failure, it could collapse as well.

Tom Birkland

Xxxx Xxxxx Xxxxxx
Ph.D Student
Department of Political Science
SUNY at Albany
Nelson A. Rockefeller College
135 Western Ave.; Milne 102
Albany, NY 12222

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