The design of the Eiffel Tower was originated by Maurice Koechlin and Emile Nouguier, who had discussed ideas for a centrepiece for the 1889 Exposition Universelle. In May 1884 Koechlin, working at his home, made an outline drawing of their scheme, 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".[23] Initially Eiffel showed little enthusiasm, although he did sanction further study of the project, and the two engineers then asked Stephen Sauvestre to add architectural embellishments. Sauvestre added the decorative arches to the base, a glass pavilion to the first level and the cupola at the top. The enhanced idea gained Eiffel's support for the project, and he bought the rights to the patent on the design which Koechlin, Nougier and Sauvestre had taken out. The design was exhibited at the Exhibition of Decorative Arts in the autumn of 1884, and on 30 March 1885 Eiffel read a paper on the project 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 that the tower would symbolise[24].mw-parser-output .templatequoteoverflow:hidden;margin:1em 0;padding:0 40px.mw-parser-output .templatequote .templatequoteciteline-height:1.5em;text-align:left;padding-left:1.6em;margin-top:0
Little happened until the beginning of 1886, but with the re-election of Jules Grévy as president and his appointment of Edouard Lockroy as Minister for Trade decisions began to be made. A budget for the Exposition was passed and on 1 May Lockroy announced an alteration to the terms of the open competition which was being held for a centerpiece for the exposition, which effectively made the choice of Eiffel's design a foregone conclusion: all entries had to include a study for a 300 m (980 ft) four-sided metal tower on the Champ de Mars. On 12 May a commission was set up to examine Eiffel's scheme and its rivals and on 12 June it presented its decision, which was that only Eiffel's proposal met their requirements. After some debate about the exact site for 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 one and a half million francs toward the construction costs. This was less than a quarter of the estimated cost of six and a half million francs. Eiffel was to receive all income from the commercial exploitation during the exhibition and for the following twenty years.[25] Eiffel later established a separate company to manage the tower.
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The tower had been a subject of some controversy, attracting criticism both from those who did not believe it feasible and from those who objected on artistic grounds. Just as work began at the Champ de Mars, the "Committee of Three Hundred" (one member for each metre of the tower's height) was formed, led by Charles Garnier and including some of the most important figures of the French arts establishment, including Adolphe Bouguereau, Guy de Maupassant, Charles Gounod and Jules Massenet: a petition was sent to Jean-Charles Adolphe Alphand, the Minister of Works, and was published by Le Temps.[26]
"To bring our arguments home, imagine for a moment a giddy, ridiculous tower dominating Paris like a gigantic black smokestack, crushing under its barbaric bulk Notre Dame, the Tour Saint-Jacques, the Louvre, the Dome of les Invalides, the Arc de Triomphe, all of our humiliated monuments will disappear in this ghastly dream. And for twenty years ... we shall see stretching like a blot of ink the hateful shadow of the hateful column of bolted sheet metal"
Work on the foundations started on 28 January 1887. Those for the east and south legs were straightforward, each leg resting on four 2 m (6.6 ft) concrete slabs, one for each of the principal girders of each leg but the other two, being closer to the river Seine were more complicated: each slab needed two piles installed by using compressed-air caissons 15 m (49 ft) long and 6 m (20 ft) in diameter driven to a depth of 22 m (72 ft)[27] to support the concrete slabs, which were 6 m (20 ft) thick. Each of these slabs supported a limestone block, each with an inclined top to bear the supporting shoe for the ironwork. These shoes were anchored by bolts 10 cm (4 in) in diameter and 7.5 m (25 ft) long.Work on the foundations was complete by 30 June and the erection of the iron work was started. Although no more than 250 men were employed on the site, a prodigious amount of exacting preparatory work was entailed: the drawing office produced 1,700 general drawings and 3,629 detail drawings of the 18,038 different parts needed.[28] The task of drawing the components was complicated by the complex angles involved in the design and the degree of precision required: the positions of rivet holes were specified to within 0.1 mm (0.004 in) and angles worked out to one second of arc. The components, some already riveted together into sub-assemblies, were first bolted together, the bolts being replaced by rivets as construction progressed. No drilling or shaping was done on site: if any part did not fit it was sent back to the factory for alteration. The four legs, each at an angle of 54 to the ground, were initially constructed as cantilevers, relying on the anchoring bolts in the masonry foundation blocks. Eiffel had calculated that this would be satisfactory until they approached halfway to the first level: accordingly work was stopped for the purpose of erecting a wooden supporting scaffold. This gave ammunition to his critics, and lurid headlines including "Eiffel Suicide!" and "Gustave Eiffel has gone mad: he has been confined in an Asylum" appeared in the popular press.[29] At this stage a small "creeper" crane was installed in each leg, designed to move up the tower as construction progressed and making use of the guides for the elevators which were to be fitted in each leg. After this brief pause erection of the metalwork continued, and the critical operation of linking the four legs was successfully completed by March 1888. In order to precisely align the legs so that the connecting girders could be put into place, a provision had been made to enable precise adjustments by placing hydraulic jacks in the footings for each of the girders making up the legs.
The main structural work was completed at the end of March 1889 and, on 31 March, Eiffel celebrated by leading a group of government officials, accompanied by representatives of the press, to the top of the tower. Since the lifts were not yet in operation, the ascent was made by foot, and took over an hour, Eiffel frequently stopping to make explanations of various features. Most of the party chose to stop at the lower levels, but a few, including Nouguier, Compagnon, the President of the City Council and reporters from Le Figaro and Le Monde Illustré completed the climb. At 2.35 Eiffel hoisted a large tricolour, to the accompaniment of a 25-gun salute fired from the lower level.[30]
His first aerodynamic experiments, investigating the air resistance of surfaces, were carried out by dropping the surface to be investigated together with a measuring apparatus down a vertical cable stretched between the second level of the Eiffel Tower and the ground. Using this Eiffel definitely established that the air resistance of a body was very closely related to the square of the airspeed. He then built a laboratory on the Champ de Mars at the foot of the tower in 1905, building his first wind tunnel there in 1909. The wind tunnel was used to investigate the characteristics of the airfoil sections used by the early pioneers of aviation such as the Wright Brothers, Gabriel Voisin and Louis Blériot. Eiffel established that the lift produced by an airfoil was the result of a reduction of air pressure above the wing rather than an increase of pressure acting on the under surface. Following complaints about noise from people living nearby, he moved his experiments to a new establishment at Auteuil in 1912. Here it was possible to build a larger wind tunnel, and Eiffel began to make tests using scale models of aircraft designs.[38]
Eiffel had meteorological measuring equipment placed on the tower in 1889, and also built a weather station at his house in Sèvres. Between 1891 and 1892 he compiled a complete set of meteorological readings, and later extended his record-taking to include measurements from 25 different locations across France.
The tower is 330 metres (1,083 ft) tall,[5] about the same height as an 81-storey building, and the tallest structure in Paris. Its base is square, measuring 125 metres (410 ft) on each side. During its construction, the Eiffel Tower surpassed the Washington Monument to become the tallest human-made structure in the world, a title it held for 41 years until the Chrysler Building in New York City was finished in 1930. It was the first structure in the world to surpass both the 200-metre and 300-metre mark in height. Due to the addition of a broadcasting aerial at the top of the tower in 1957, it is now taller than the Chrysler Building by 5.2 metres (17 ft). Excluding transmitters, the Eiffel Tower is the second tallest free-standing structure in France after the Millau Viaduct.
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 centerpiece 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.[6] 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".[7] Eiffel initially showed little enthusiasm, but he did approve further study, and the two engineers then asked Stephen Sauvestre, the head of the 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.
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