From: Ralph Lewis (rlewis10us@yahoo.com)
Date: Tue Sep 11 2001 - 15:24:00 MDT
Hal, thanks, I suspected that building standards for strength have been of
lower priority in favor of wind load or earthquake flexibility leading to
unsafe building design.
The weakling of buildings for open plan office design had not even crossed
my mind.
Look like the old I beam steel framed box design from the 1900's is still
the best for large buildings.
I am not even sure if the Empire State building required insulation around
the I beams. Yet even with the hot aviation gas fed fire, the upper floors
were structurally sound after the accident.
Ralph
At 01:58 PM 9/11/2001 -0700, you wrote:
>Ralph Lewis <rlewis10us@yahoo.com> writes:
>>
>> Interesting that the Empire State Building took a direct hit of an american
>> air force bomber with a much more explosive fuel (aviation gas) than jet
>> fuel and damage was minimal. Makes you wonder about building standards and
>> building permit enforcement today.
>
>John Young, an architect, gave this explanation on another mailing list:
>
>:The WTC towers had a distinctive structural system which utilized
>:the exterior wall framing for lateral bracing -- a so-called lattice
>:framework. This allowed minimization of internal lateral bracing
>:and opened up the floor plans. You can see the effect of that when
>:the buildings collapsed, with the lattice framework crumbling and
>:the interior imploding. The lattice works so long as it remains
>:intact as a system: if a part of it goes, then the whole system
>:goes.
>:
>:The planes punched holes in the lattice, one tower punched
>:on two sides, maybe the other too. Portions of the lattice of
>:the second tower briefly remained standing after the collapse,
>:then fell.
>:
>:The system was considered daring at the time of construction, for
>:it distributed loads more efficiently than legacy column-and-beam-
>:supported systems. Probably the legacy systems would not have
>:totally collapsed due to damage at upper floors, although floors
>:above the damage would have come down if columns were
>:weakened.
>
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