|
| |
 |
New York Architecture
Images- Gone World
Trade Center 5- Towers of Innovation
(2) |
WTC
0-Main
Commentary
1-why
did it collapse?
2-images
from September 11th, 2001.
3-more
images
4-Timeline:
World Trade Center chronology
5-Towers
of Innovation
6-The
work of Minoru Yamasaki
7-images
of reactions from around the world |
The
towers' pioneering "skylobby" system, which separated
express and local elevators, maximized efficiency of transport and
economy of space. |
 |
Part 2 | Back to Part 1
Elevators like subways
The second problem that Tozzoli's team addressed concerned elevators.
Ironically, while the invention of elevators had made skyscrapers
possible, elevators were thought to limit how high skyscrapers could go.
The more floors you have, the more people you have; the more people you
have, the more elevators you need; the more elevators you need, the less
space you have to rent to pay for all those floors. This conundrum was one
of the reasons, if not the chief one, why skyscrapers rarely reached
beyond 80 floors.
Undaunted, Tozzoli's group devised a solution. They would design the
elevator system to mimic a subway system, with express and local
elevators.
In the World Trade Center, giant express elevators, each capable of
carrying 55 passengers and rising at 1,600 feet per minute, zipped up to
"skylobbies" on the 44th and
78th floors. Here passengers exited on
the side opposite from where they had entered and crossed the lobby to
pick up local lifts. Each tower also had a single express elevator that
went all the way to the top. The one in the South Tower went to the
observation deck, that in the North Tower to the Windows on the World
restaurant.
The beauty of this system lay in its economy of space. Local elevators for
the lower, middle, and upper zones of the building sat one atop the other
in the same shafts. And since the express elevators to the skylobbies
traveled no farther than the 44th and 78th
floors, respectively, the higher one ascended in the building, the less
space had to be given over to elevator shafts.
It was, as Angus Kress Gillespie, author of the book Twin Towers,
put it, "a pioneering translation into the vertical of horizontal
mass transportation." The result: 75 percent of the floor space in
each tower was rentable, a significant improvement over 62 percent, the
highest yield achieved in earlier skyscrapers.
A tube of a tower
That 75 percent was also made possible by another innovation. Previous
high-rises had relied for their structural integrity on a forest of
supporting columns on each floor. Typically, architects spaced these 30
feet apart throughout the interior. The exterior walls of such buildings
were merely curtain walls, which let light in and kept weather out but
provided little support.
The
World Trade Center's tube-style construction, with steel columns
found only along the exterior wall and within a central core,
freed up nearly an acre of space on each floor for offices. |
|
 |
Such was not the case in the World Trade Center. Consulting engineers
Leslie Robertson and John Skilling invented an entirely new method of
construction. The forest of interior columns vanished; such columns only
appeared in and around the central core of elevator shafts, stairwells,
and bathrooms. Then it was nothing but open space -- 60 feet of it on two
sides, 35 on the other two sides -- before one reached the outside walls.
These were not curtain walls but cages of steel columns spaced just over a
yard apart, with 22 inches of glass in between. (Minoru Yamasaki, the
building's architect, designed it this way in part because he was insecure
with heights and felt more comfortable with such narrow windows.)
The shafts of steel in the exterior walls shouldered not only gravity
loads pressing down from above but also lateral loads caused by gusty
winds nudging the building from the side. Such tube-style architecture
relied on high-strength steel, which was only then becoming available. It
resulted in up to an acre of rentable space on each floor, and it became
the pioneering style of frame for a whole new generation of buildings.
Damping the sway
As sturdy as these towers would be, Robertson and Skilling knew they would
still be flexible in high winds. Indeed, they designed them to be so. But
they realized the swaying effect, especially in strong gusts, might bother
tenants high in the building. So they fashioned yet another innovation, a
state-of-the-art damping system. Like door closers or car shocks, the
dampers absorbed the wind's punch, easing the towers one way or the other
so smoothly that office workers hardly noticed the movement.
|
Each
of the Twin Towers had 11,000 built-in shock absorbers to lessen
the buildings' sway in strong wind. |
 |
The dampers were made of visco-elastic material. "These are materials
that are partially viscous, that is, partially flowable like oil, and also
elastic, which means they act somewhat like steel, in that if you strain
them they return to their original shape," Robertson says. "So
the material is in between those two materials -- it's not like oil, it's
not like steel, it's visco-elastic."
Robertson's crew placed the dampers, 11,000 of them in each building,
between the bottom of the floor trusses and the columns -- two parts of
the building that tended to move with respect to each other when the
edifice swayed. When it did so, those two parts would shear the visco-elastic
dampers. This shearing caused the material to heat up, and that heat was
transferred to the building. "So we take the energy of the wind, and
we heat the building with it," Robertson says with a note of pride in
his voice.
Reactions
Such innovations meant nothing to the tower's critics, however. Both
before and after the World Trade Center's official dedication in April
1973, certain vocal members of the American intelligentsia went after it
as assiduously as those who let their feelings about the Eiffel Tower be
known by signing a petition against its construction. (These included the
writers Guy de Maupassant and Emile Zola.)
The philosopher Lewis Mumford, a noted architectural critic who died in
1990, railed against the building's "purposeless gigantism and
technological exhibitionism." The architect Charles Jencks went so
far as to liken the use of redundancy in the towers' design to fascist
methods. "Repetitive architecture can put you to sleep," he
wrote. "Both Mussolini and Hitler used it as a form of thought
control knowing that before people can be coerced they first have to be
hypnotized and then bored."
The jabs came not just from architects. New York Times columnist
Russell Baker noted that the towers "seem to go on and on and on
endlessly in the upward dimension, as though being constructed by
battalions of exuberantly unstoppable madmen determined to keep building
until the architect decides what kind of top he wants."
Yamasaki
saw the World Trade Center, here memorialized in light, as a
monument to peace. |
|
 |
Yamasaki, the architect, must have been stung by such comments. He saw his
creation in a completely different light. In his book Architects on
Architecture, the author Paul Heyer quotes Yamasaki as saying,
"World trade means world peace, and consequently the World Trade
Center buildings in New York ... had a bigger purpose than just to provide
room for tenants. The World Trade Center is a living symbol of man's
dedication to world peace."
Tragically, since the heinous attacks of September 11th,
2001, the towers have become instead a symbol of international terrorism.
Apart from the loss of life, Yamasaki would surely have been appalled and
horrified if he had had any idea that such a fate awaited his
"monument to peace," as he once called it. Had he lived to
witness that awful day, he might have gone on to design differently in the
future, for such Eiffelesque grandeur was not his natural inclination. As
he once wrote, "As an architect, if I had no economic or social
limitations, I'd solve all my problems with one-story buildings. Imagine
how pleasant it would be to always work and plan spaces overlooking lovely
gardens filled with flowers."
Fortunately, Yamasaki did not have to watch his beloved towers fall. He
died in 1986 at the age of 73, with his best-known work still standing
tall above Manhattan, "grand in its own right."
Peter Tyson is editor in chief of NOVA Online.
|
|