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The Eiffel Tower is an iron
tower built on the Champ de Mars beside the Seine River in
Paris. The tower has become a global icon of France and is one
of the most recognizable structures in the world.
Introduction
Named after its designer, engineer Gustave Eiffel, the Eiffel
Tower is the tallest building in Paris. More than 200,000,000
have visited the tower since its construction in 1889, including
6,719,200 in 2006, making it the most visited paid monument in
the world. Including the 24 m (79 ft) antenna, the structure is
325 m (1,063 ft) high (since 2000), which is equivalent to about
81 levels in a conventional building.
When the tower was completed in 1889 it was the world's tallest
tower — a title it retained until 1930 when New York City's
Chrysler Building (319 m — 1,047 ft tall) was completed. The
tower is now the fifth-tallest structure in France and the
tallest structure in Paris, with the second-tallest being the
Tour Montparnasse (210 m — 689 ft), although that will soon be
surpassed by Tour AXA (225.11 m — 738.36 ft).
The metal structure of the
Eiffel Tower weighs 7,300 tonnes while the entire structure
including non-metal components is approximately 10,000 tonnes.
Depending on the ambient temperature, the top of the tower may
shift away from the sun by up to 18 cm (7 in) because of thermal
expansion of the metal on the side facing the sun. The tower
also sways 6–7 cm (2–3 in) in the wind.As demonstration of the
economy of design, if the 7300 tonnes of the metal structure
were melted down it would fill the 125 meter square base to a
depth of only 6 cm (2.36 in), assuming a density of the metal to
be 7.8 tonnes per cubic meter. The tower has a mass less than
the mass of the air contained in a cylinder of the same
dimensions, that is 324 meters high and 88.3 meters in radius.
The weight of the tower is 10,100 tonnes compared to 10,265
tonnes of air.
The first and second levels are accessible by stairways and
lifts. A ticket booth at the south tower base sells tickets to
access the stairs which begin at that location. At the first
platform the stairs continue up from the east tower and the
third level summit is only accessible by lift. From the first or
second platform the stairs are open for anyone to ascend or
descend regardless of whether they have purchased a lift ticket
or stair ticket. The actual count of stairs includes 9 steps to
the ticket booth at the base, 328 steps to the first level, 340
steps to the second level and 18 steps to the lift platform on
the second level. When exiting the lift at the third level there
are 15 more steps to ascend to the upper observation platform.
The step count is printed periodically on the side of the stairs
to give an indication of progress of ascent. The majority of the
ascent allows for an unhindered view of the area directly
beneath and around the tower although some short stretches of
the stairway are enclosed.
Maintenance of the tower includes applying 50 to 60 tonnes of
paint every seven years to protect it from rust. In order to
maintain a uniform appearance to an observer on the ground,
three separate colors of paint are used on the tower, with the
darkest on the bottom and the lightest at the top. On occasion
the colour of the paint is changed; the tower is currently
painted a shade of brownish-grey.[8] On the first floor there
are interactive consoles hosting a poll for the colour to use
for a future session of painting. The co-architects of the
Eiffel Tower are Emile Nouguier, Maurice Koechlin and Stephen
Sauvestre.
History
The structure was built between 1887 and 1889 as the
entrance arch for the Exposition Universelle, a World's Fair
marking the centennial celebration of the French Revolution.
Eiffel originally planned to build the tower in Barcelona, for
the Universal Exposition of 1888, but those responsible at the
Barcelona city hall thought it was a strange and expensive
construction, which did not fit into the design of the city.
After the refusal of the Consistory of Barcelona, Eiffel
submitted his draft to those responsible for the Universal
Exhibition in Paris, where he would build his tower a year
later, in 1889. The tower was inaugurated on March 31, 1889, and
opened on May 6. Three hundred workers joined together 18,038
pieces of puddled iron (a very pure form of structural iron),
using two and a half million rivets, in a structural design by
Maurice Koechlin. The risk of accident was great, for unlike
modern skyscrapers the tower is an open frame without any
intermediate floors except the two platforms. However, because
Eiffel took safety precautions, including the use of movable
stagings, guard-rails and screens, only one man died.
The tower was met with much criticism from the public when it
was built, with many calling it an eyesore. Newspapers of the
day were filled with angry letters from the arts community of
Paris. One is quoted extensively in William Watson's US
Government Printing Office publication of 1892 Paris Universal
Exposition: Civil Engineering, Public Works, and Architecture.
“And during twenty years we shall see, stretching over the
entire city, still thrilling with the genius of so many
centuries, we shall see stretching out like a black blot the
odious shadow of the odious column built up of riveted iron
plates.”[10] Signers of this letter included Messonier, Gounod,
Garnier, Gerome, Bougeureau, and Dumas.
Novelist Guy de Maupassant — who claimed to hate the tower —
supposedly ate lunch in the Tower's restaurant every day. When
asked why, he answered that it was the one place in Paris where
one could not see the structure. Today, the Tower is widely
considered to be a striking piece of structural art.
One of the great Hollywood movie clichés is that the view from a
Parisian window always includes the tower. In reality, since
zoning restrictions limit the height of most buildings in Paris
to 7 stories, only a very few of the taller buildings have a
clear view of the tower.
Eiffel had a permit for the tower to stand for 20 years, meaning
it would have had to be dismantled in 1909, when its ownership
would revert to the City of Paris. The City had planned to tear
it down (part of the original contest rules for designing a
tower was that it could be easily demolished) but as the tower
proved valuable for communication purposes, it was allowed to
remain after the expiration of the permit. The military used it
to dispatch Parisian taxis to the front line during the First
Battle of the Marne, and it therefore became a victory statue of
that battle.
Shape of the tower
At the time the tower was built many people were shocked by
its daring shape. Eiffel was criticised for the design and
accused of trying to create something artistic, or inartistic
according to the viewer, without regard to engineering. Eiffel
and his engineers, as renowned bridge builders however,
understood the importance of wind forces and knew that if they
were going to build the tallest structure in the world they had
to be certain it would withstand the wind. In an interview
reported in the newspaper Le Temps, Eiffel said:
“ Now to what phenomenon did I give primary concern in designing
the Tower? It was wind resistance. Well then! I hold that the
curvature of the monument's four outer edges, which is as
mathematical calculation dictated it should be (...) will give a
great impression of strength and beauty, for it will reveal to
the eyes of the observer the boldness of the design as a whole.
”
—translated from the French newspaper Le Temps of February 14,
1887
The shape of the tower was therefore determined by mathematical
calculation involving wind resistance. Several theories of this
mathematical calculation have been proposed over the years, the
most recent is a nonlinear integral differential equation based
on counterbalancing the wind pressure on any point on the tower
with the tension between the construction elements at that
point. That shape is exponential. A careful plot of the tower
curvature however, reveals two different exponentials, the lower
section having a stronger resistance to wind forces.
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