FC: Pat Farrell on "architectural implications" of WTC attack

[Declan McCullagh <declan () well com>]

[Also see John Young's note below. --DBM]

***********

Date: Tue, 11 Sep 2001 17:31:48 -0400
To: Declan McCullagh <declan () well com>
From: Pat Farrell <pfarrell () pfarrell com>
Subject: Architectural implications of WTC attack

Hi Declan,

I've written up a small article on politics and technology of architecture
relating to today's WTC destruction. I wrote it because I see all the
mass media hand wringing and wailing as missing the key point.
A pointer to it in politech, or feel free to take it all if you think 
anyone would be
interested.

URL is http://www.pfarrell.com/rants/archtower.html
I'll paste the whole text in the postscript, it isn't too long.

Thanks
Pat




Pat Farrell                     pfarrell () pfarrell com
http://www.pfarrell.com

  ============ pasted article =============


<p>
The attack and destruction of the NYC World Trade Centers
was clearly a political act, and it used a technical approach unique to the
construction of the World Trade Center buildings.
This article deplores this act of terrorism, but will leave
analysis of the politics and techniques of the attacks alone, and focus on the
impact of the attack on architecture and cities themselves.

<p>

Cities exist where they do for any of a number of reasons,
but their site usually owes a large amount to trading and transportation.
Traders stopped in New York because of its central location in the colonies and
its wonderful port. Consumers, merchants, and manufacturers liked the proximity
of each other, and a great city grew. Similarly, office buildings sole purpose
is to facilitate human interaction. Office buildings allow easy walking and
communications between parts of an organization or business. Transportation for
goods, workers, and consumers, is easier when they are located in close
proximity. Prior to the acceptance of personal cars, the only way to accomplish
this was central locations. The natural result is great cities with lots of
transportation, offices, markets tightly packed together. Getting the required
density requires that the city grow upwards.

<p>

Very tall buildings are hard to build, not only for the
obvious strength and safety reasons, but also because needed services (i.e.
elevators, plumbing, wiring, stairs, air-conditioning ducts) require increasing
amounts of overhead as the building gets taller. In addition to bigger beams
and columns, tall buildings need more elevators, bigger pipes, etc. than short
campus-style buildings. As building height increases, these overhead items grow
faster more quickly than the usable floor space, making very tall buildings
hard to justify economically. Making very tall buildings make business sense
requires a significant architectural and engineering effort.

<p>
The World Trade Centers existed because of their architecture and the
supporting engineering. Unlike other skyscrapers, the exterior walls of the
World Trade Centers were load bearing.
[See <a href="http://www.enr.com/new/A0816.asp";>for a brief discussion</a>].
The whole building was a vertical truss, and
the interior was column free. Without this design, it is unlikely that the WTC
could have been built on that site. The architecture enabled the existence of
the building.

<p>

As we saw in the painful to watch news footage of September
11, 2001, when the load bearing walls were damaged, the whole structure became
unstable and collapsed.

<p>

Simply telling the engineers to make the building stronger
is not a viable answer. Of course they could make it stronger, add redundancy,
or both. But at the cost not only of the material and labor to add the
strength, but at the cost of substantially increasing the overhead of the
building itself. If the building's internal overhead becomes larger, the
economics of the project quickly disappear. There are hard numbers of dollars
behind the decisions not to build buildings bigger than the Empire State
Building up until the WTC towers, and if the WTC architecture is not feasible
or acceptable, then the density it enables will not be possible.

<p>

The implications for the city are huge. Successful public
transportation requires that large numbers of commuters go to the same place at
about the same time. Similarly, the density of people is what enables the
wonderful shops, markets, theaters and clubs of New York. The lack of density
is a direct cause of the decline in quality of life.

<p>

<p>The attacks on the World Trade Centers caused a horrible
loss of individual human lives today, and there is a significant chance it will
cause a significant loss of life of the city in the future.

<p>

***********

Date: Tue, 11 Sep 2001 13:25:30 -0700
From: John Young <jya () pipeline com>

The '45 Empire State Building crash is oft studied in architectural
and structural engineering to learn why the building withstood the
hit. The plane was a B-24, I believe, but in any case a much smaller
craft than the ones which hit the WTC and the Pentagon. The '45
plane's engines did penetrate the building, shooting out the far side
and falling to the ground and killing passersby, but most of the plane
remained inside the structure for it was made of far more fragile
materials than a building. A relative small amount of damage was
done to the structure of the building though fire was devastating,
especially from flaming gasoline cascading inside.

The fireball that shot from the second WTC tower hit, opposite
where the jetliner penetrated, blew out windows and perhaps part
of the latticework exterior structure. Flaming fuel probably
cascaded down the shafts of elevators and ductwork and
stairwells whose fire-protection enclosures would have been
destroyed by the explosive crash and ballistic heavy plane
parts. These fuel flames, and fires started from them,
would have weakened interior structural support beyond
protection provided by code-required fireproofing. Once
the interior structural supports were weakened, and
the exterior lattice lost its integrity collapse was inevitable.

I modify my first evaluation to speculate that the interior
supports appear to have given way before the exterior lattice
(whose girdle of closely-space columns and thin vertical
windows between gave the buildings a unique look compared
to use of large panes of glass elswhere)  The lattice amazingly
contained the interior collapse and the whole mess dropped
vertically, almost, as newscasters report, as if executed by a
demo expert.

I did not expect the Twin Towers to collapse. To suffer terrible
fires and localized interior damage but not total collapse. The
first was unbelievable, and as I said, I thought only the portion
above the crash fell. Then the smoke cleared momentarily
to show the totality. Then the second tower, collapsing in a
near-perfect copy of the first. The sudden dropping of the
floors above the crash, that impacting load overpowering
the remaining system, and the straight drop collapse, neither
tower falling much to the side, indicated what had happened.

Close-ups of the exterior show the latticework bridging the
crash penetrations, reminding of sales pitches from the
19th Century when cast-iron manufacturers promoted
their architecture with structural compoments missing
with no apparent destabilization -- the load automatically
shifting to remaining components. Their prognostications
failed at the first intense fire which overheated and cracked
the cast iron, sometimes collapsing more quickly than
predecessor masonry bearing wall and wood floor system
composites.

Humbling news: My daughter is safe and sound. She heard the
first crash and saw the tower blazing on the way to work and
thought it was merely (!) a fire. Her office remained at work
unaware of what had happened, and was happening, without
TV or radio, until telephoned from overseas headquarters
which ordered everyone home. At first the office dismissed
the alarm, saying, hey, this is New York, no problema, we
have work to do, our customers come first, sure that would
impress the venal bastards. Then someone was sent
outside to check reality.

***********




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