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Dear Debbie:
What happened when the World Trade Center towers collapsed
after those jetliners
hit them? I saw the video and I still don't really under-
stand why they
fell in the way they did!
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The
buildings that you see every day, even the house or apartment building
you live
in are mechanisms
whose basic function
is to support a considerable
amount of
weight. The amount
of work the mechan-
ism foes in moving
the weight of the struc-
ture to the ground
is a function of the
the size of the structure.
The load in
downward motion follows
a path. Once
the load path is corrupted,
the mechanism
must seek alternate
routes to transfer
the load downward,
which results in work.
The North Tower succeeded
in this for
more than 1.5 hours;
the South Tower
accomplished this
for almost a half an
hour.
The subsequent thermal
effects of
the fire resulted
in the steel melt-
ing and those new
paths could no
longer transfer the
load to the
|
ground, which resulted
in the col-
lapse of the structuresm
as gravity
pulled the unsupported
load straight
downward. |
The
Numbers::
-
The outside walls of the
Twin Towers supported most of the structures' total weight. Within the
walls were 18-inch tubular steel columns positioned 22 inches apart.
Each wall had a width
of 209 feet with more than 60 columns on each side.
Each floor had an area
of 40,000 square feet; the towers stood 110 stories.
Each floor was separated
by a reinforced concrete honeycomb approximately 3 feet in thickness.
The weight of nearly an entire acre of concrete fell onto the barrier below,
which iniated a sort of domino effect; this resulted in the weight
of nearly two acres of concrete descending on the third bsrrier,which resulted
in the weight of three acres of concrete descending to the fourth barrier,
and so on. After 110 times, within a matter of seconds, eachtower collapsed
to the ground This result in an ashe and smoke cloud so large,it was detected
by orbiting satellites.
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| Debbie
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