i too thought of the stacked walmart's mentioned
by Michael, and the WTC. it was thought that the
'economies of scale' in the super-sized twin towers
was in part due to reducing of fireproofing or of
some fire code (covering beams or gypsum-board to
cover some structural aspects) -- could this be a
trade-off to get the extra 20-40 stories with the
joists used, and the same floor plate, by reducing
the weight carried by the upper floors, to use the
lightweight structural system to an extreme point
where it's design is the cause of its own failure.
isn't there a calculation for structures (and fire
ratings) which given an buffer for safety and for
give-and-take, and was this safety buffer changed
to a smaller tolerance for failure, using the light-
weight joists at the heights and with the forces of
wind and other movements? is it possible that the
WTC structural failure was only a matter of time?
such as with airplanes and faulty structural or
wiring and taking whole self-similar designs off
for retrofits or decommission, after a disaster--
could extreme weather and high-speed sheer winds
tackle existing skyscrapers of similar structure
because of the lateral issues and severe weakness
to adjust, enough to pop it outside of the zones
of tolerance designed for? is the WTC a time-bomb
bomb, in terms of long-term structural integrity?
wow. i never imagined it could be repeated by time,
that is, slow-motion building implosion, by design.
brian
On Friday, December 3, 2004, at 10:36 PM, John Young wrote:
Recall that the Port Authority elected to increase the towers'
height by 20, then 40, stories because of economies Robertson
introduced with his daring design.
There are photos of models at 70, 90 and 110 stories, with the
floor plate remaining constant. Which means Robertson was
squeezing more potential out of earlier design assumptions.
This squeeze is not uncommon in high design, and it is always
a late decision in the design process to set the number of floors,
with the number riding on how deft the structural designers
are. To be sure, it is done with some ground, air, space and
marine craft to design right against the limits of failure, push
to those limits by financial and legal design.