The design of the Eiffel Tower is attributed to Maurice Koechlin and Émile Nouguier, two senior engineers working for the Compagnie des Établissements Eiffel. It was envisioned after discussion about a suitable centrepiece for the proposed 1889 Exposition Universelle, a world’s fair to celebrate the centennial of the French Revolution. Eiffel openly acknowledged that inspiration for a tower came from the Latting Observatory built in New York City in 1853. In May 1884, working at home, Koechlin made a sketch of their idea, described by him as “a great pylon, consisting of four lattice girders standing apart at the base and coming together at the top, joined together by metal trusses at regular intervals”. Eiffel initially showed little enthusiasm, but he did approve further study, and the two engineers then asked Stephen Sauvestre, the head of company’s architectural department, to contribute to the design. Sauvestre added decorative arches to the base of the tower, a glass pavilion to the first level, and other embellishments.
The new version gained Eiffel’s support: he bought the rights to the patent on the design which Koechlin, Nougier, and Sauvestre had taken out, and the design was exhibited at the Exhibition of Decorative Arts in the autumn of 1884 under the company name. On 30 March 1885, Eiffel presented his plans to the Société des Ingénieurs Civils; after discussing the technical problems and emphasising the practical uses of the tower, he finished his talk by saying the tower would symbolise:
[n]ot only the art of the modern engineer, but also the century of Industrand Science in which we are living, and for which the way was prepared by the great scientific movement of the eighteenth century and by the Revolution of 1789, to which this monument will be built as an expression of France’s gratitude.
Little progress was made until 1886, when Jules Grévy was re-elected as president of France and Édouard Lockroy was appointed as minister for trade. A budget for the exposition was passed and, on 1 May, Lockroy announced an alteration to the terms of the open competition being held for a centrepiece to the exposition, which effectively made the selection of Eiffel’s design a foregone conclusion, as entries had to include a study for a 300 m (980 ft) four-sided metal tower on the Champ de Mars. (A 300-meter tower was then considered a herculean engineering effort). On 12 May, a commission was set up to examine Eiffel’s scheme and its rivals, which, a month later, decided that all the proposals except Eiffel’s were either impractical or lacking in details.
After some debate about the exact location of the tower, a contract was signed on 8 January 1887. This was signed by Eiffel acting in his own capacity rather than as the representative of his company, and granted him 1.5 million francs toward the construction costs: less than a quarter of the estimated 6.5 million francs. Eiffel was to receive all income from the commercial exploitation of the tower during the exhibition and for the next 20 years. He later established a separate company to manage the tower, putting up half the necessary capital himself.
The puddled iron (wrought iron) of the Eiffel Tower weighs 7,300 tons, and the addition of lifts, shops and antennae have brought the total weight to approximately 10,100 tons. As a demonstration of the economy of design, if the 7,300 tons of metal in the structure were melted down, it would fill the square base, 125 metres (410 ft) on each side, to a depth of only 6.25 cm (2.46 in) assuming the density of the metal to be 7.8 tons per cubic metre. Additionally, a cubic box surrounding the tower (324 m x 125 m x 125 m) would contain 6,200 tons of air, weighing almost as much as the iron itself. Depending on the ambient temperature, the top of the tower may shift away from the sun by up to 18 cm (7 in) due to thermal expansion of the metal on the side facing the sun. Interior View of Eiffel Tower, Paris (July 2018)
When it was built, many were shocked by the tower’s daring form. Eiffel was accused of trying to create something artistic with no regard to the principles of engineering. However, Eiffel and his team – 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 sure it could withstand them. In an interview with the newspaper Le Temps published on 14 February 1887, Eiffel said:
Is it not true that the very conditions which give strength also conform to the hidden rules of harmony? … Now to what phenomenon did I have to 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.
He used graphical methods to determine the strength of the tower and empirical evidence to account for the effects of wind, rather than a mathematical formula. Close examination of the tower reveals a basically exponential shape. All parts of the tower were over-designed to ensure maximum resistance to wind forces. The top half was even assumed to have no gaps in the latticework. In the years since it was completed, engineers have put forward various mathematical hypotheses in an attempt to explain the success of the design. The most recent, devised in 2004 after letters sent by Eiffel to the French Society of Civil Engineers in 1885 were translated into English, is described as a non-linear integral equation based on counteracting the wind pressure on any point of the tower with the tension between the construction elements at that point.
When originally built, the first level contained three restaurants — one French, one Russian and one Flemish — and an “Anglo-American Bar”. After the exposition closed, the Flemish restaurant was converted to a 250-seat theatre. A promenade 2.6-metre (8 ft 6 in) wide ran around the outside of the first level. At the top, there were laboratories for various experiments, and a small apartment reserved for Gustave Eiffel to entertain guests, which is now open to the public, complete with period decorations and lifelike mannequins of Eiffel and some of his notable guests.
In May 2016, an apartment was created on the first level to accommodate four competition winners during the UEFA Euro 2016 football tournament in Paris in June. The apartment has a kitchen, two bedrooms, a lounge, and views of Paris landmarks including the Seine, the Sacre Coeur, and the Arc de Triomphe.
The arrangement of the lifts has been changed several times during the tower’s history. Given the elasticity of the cables and the time taken to align the cars with the landings, each lift, in normal service, takes an average of 8 minutes and 50 seconds to do the round trip, spending an average of 1 minute and 15 seconds at each level. The average journey time between levels is 1 minute. The original hydraulic mechanism is on public display in a small museum at the base of the east and west legs. Because the mechanism requires frequent lubrication and maintenance, public access is often restricted. The rope mechanism of the north tower can be seen as visitors exit the lift.
Gustave Eiffel engraved on the tower the names of 72 French scientists, engineers and mathematicians in recognition of their contributions to the building of the tower. Eiffel chose this “invocation of science” because of his concern over the artists’ protest. At the beginning of the 20th century, the engravings were painted over, but they were restored in 1986–87 by the Société Nouvelle d’exploitation de la Tour Eiffel, a company operating the tower.
The tower is painted in three shades: lighter at the top, getting progressively darker towards the bottom to complement the Parisian sky. It was originally reddish brown; this changed in 1968 to a bronze colour known as “Eiffel Tower Brown”.
The only non-structural elements are the four decorative grill-work arches, added in Sauvestre’s sketches, which served to make the tower look more substantial and to make a more impressive entrance to the exposition.
A pop-culture movie cliché 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 seven storeys, only a small number of tall buildings have a clear view of the tower.
Maintenance of the tower includes applying 60 tons of paint every seven years to prevent it from rusting. The tower has been completely repainted at least 19 times since it was built. Lead paint was still being used as recently as 2001 when the practice was stopped out of concern for the environment. Source : wikipedia