Saturday, 16 January 2010

Eiffel Tower


At 300 metres (320.75m including antenna), and 7000 tons, it was the world's tallest building until 1930. Other statistics include:

* 2.5 million rivets.
* 300 steel workers, and 2 years (1887-1889) to construct it.
* Sway of at most 12 cm in high winds.
* Height varies up to 15 cm depending on temperature.
* 15,000 iron pieces (excluding rivets).
* 40 tons of paint.
* 1652 steps to the top.




It was almost torn down in 1909, but was saved because of its antenna - used for telegraphy at that time. Beginning in 1910 it became part of the International Time Service. French radio (since 1918), and French television (since 1957) have also made use of its stature.

During its lifetime, the Eiffel Tower has also witnessed a few strange scenes, including being scaled by a mountaineer in 1954, and parachuted off of in 1984 by two Englishmen. In 1923 a journalist rode a bicycle down from the first level. Some accounts say he rode down the stairs, other accounts suggest the exterior of one of the tower's four legs which slope outward.


Design of the tower
The third floor of the Eiffel Tower, at night, seen from Trocadéro.


Material

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 (7.1 in) because of thermal expansion of the metal on the side facing the sun. As demonstration of the economy of design, if the 7300 tonnes of the metal structure were melted down it would fill the 125 metre 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 metre. The tower has a mass less than the mass of the air contained in a cylinder of the same dimensions,[22] that is 324 metres high and 88.3 metres in radius. The weight of the tower is 10,100 tonnes compared to 10,265 tonnes of air.




Wind considerations

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, however, as renowned bridge builders, 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.





Maintenance

Maintenance of the tower includes applying 50 to 60 tonnes of paint every seven years to protect it from rust.

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