The Eiffel Tower in Paris
The Eiffel Tower (in French: la Tour Eiffel) is an iron tower built on the Champ de Mars beside the river Seine in Paris. The tower has become a global icon of France and is one of the most recognizable structures in the world.
Named after its designer, the French engineer Gustave Eiffel, the Eiffel Tower is the tallest building in Paris. More than 200,000,000 people 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. With its 24 m (79 ft) antenna, the structure is 324 m (1,063 ft) high (since 2000), which is the equivalent of about 81 levels in a conventional building.
At the time of completion 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. Today, the tower is the fifth-tallest structure in France and the tallest structure in Paris. The second tallest structure is the Tour Montparnasse (210 m — 689 ft), although it 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.
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. The colour of the paint is occasionally changed; the tower is currently painted a shade of brownish-grey.
The structure was built between 1887 and 1889 as the entrance arch for the “Exposition Universelle” (the Universal Exhibition), 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 the people 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 the people who were responsible for the Universal Exhibition in Paris, where he would build his tower a year later, in 1889. The tower was inaugurated on 31st March 1889, and opened on 6 May. 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 because 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.
Shape of the tower
When the tower was being built, many people were shocked by its daring shape. Eiffel was hugely criticized for the design and accused of trying to create something artistic, or inartistic according to the viewers, 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 14 February 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.
Many people living in Paris had criticized the construction of the Eiffel Tower, stating that it would collapse very quickly!
The Eiffel Tower and the river Seine.
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