The Eiffel Tower from below
The puddled iron[37] (wrought iron) structure of the Eiffel Tower weighs 7,300 tonnes, while the entire structure, including non-metal components, is approximately 10,000 tonnes. As a demonstration of the economy of design, if the 7,300 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 the density of the metal to be 7.8 tonnes per
cubic metre. 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.
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 experienced 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.[38]
Researchers have found that Eiffel used empirical and graphical methods accounting for the effects of wind rather than a specific mathematical formula. Careful examination of the tower shows a basically exponential shape; actually two different exponentials, the lower section overdesigned to ensure resistance to wind forces. Several mathematical explanations have been proposed over the years for the success of the design; the most recent is described as a nonlinear integral equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point.[39][40] As a demonstration of the tower's effectiveness in wind resistance, it sways only 6–7 cm (2–3 in) in the wind.[5][39][40]
Accommodation
When built, the first level contained two restaurants: an "Anglo-American Bar", and a 250 seat theatre. A 2.6 m (8 ft 6 in) promenade ran around the outside.
On the second level, the French newspaper Le Figaro had an office and a printing press, where a special souvenir edition, Le Figaro de la Tour, was produced. There was also a pâtisserie.
On the third level were laboratories for various experiments and a small apartment reserved for Gustave Eiffel to entertain guests. This is now open to the public, complete with period decorations and lifelike models of Gustave and some guests.
Engraved names
Main article: List of the 72 names on the Eiffel Tower
Gustave Eiffel engraved on the tower seventy-two names of French scientists, engineers and other notable people. This engraving was painted over at the beginning of the twentieth century but restored in 1986–1987 by the Société Nouvelle d'exploitation de la Tour Eiffel, a company contracted to operate business related to the Tower.
Maintenance
Maintenance of the tower includes applying 50 to 60 tonnes of paint every seven years to protect it from rust. The height of the Eiffel Tower varies by 15 cm due to temperature.
Aesthetic considerations
In order to enhance the impression of height, three separate colours of paint are used on the tower, with the darkest on the bottom and the lightest at the top.[41] On occasion the colour of the paint is changed; the tower is currently painted a shade of bronze.[42] On the first floor there are interactive consoles hosting a poll for the colour to use for a future session of painting.
The only non-structural elements are the four decorative grillwork arches, added in Stephen Sauvestre's sketches, which served to reassure visitors that the structure was safe, and to frame views of other nearby architecture.[43][44][45]
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 storeys, only a very few of the taller buildings have a clear view of the tower.
( From Wikipedia )
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