We all know a great deal about the Eiffel Tower, which was built in 1887 -1889 to be a lookout tower and magnet during the World’s Fair in 1889. The plan was for it to be inaugurated exactly one hundred years after the French Revolution. The tower, which was built of cast iron, was built in 26 months and met with strong criticism already during the planning process. The tower would be 300 m high and thus by a large margin the world’s tallest structure at that time. This record stood until the Chrysler building in New York City was built in 1930. For cost reasons and since the tower was planned to stand for only 20 years, the construction was built in simple cast iron instead of steel. Steel was at that time available, but it was significantly more expensive than cast iron. Stainless steel, however, was something that became available only about 20 years later. A small part of the cast iron beams in the construction was delivered by Borgvik’s mill in Värmland, Sweden. This mill also manufactured and delivered the approx. 2.5 million rivets that hold the entire tower together. Cast iron is highly prone to corrosion, which means that the tower must be repainted by hand every seven years. The painting work is carried out by 25 painters who for 18 months paint on 160 tons of paint and thereby consume 1,500 brushes and 5,000 grinding wheels. Old paint is scraped off, the surfaces are sanded before the new paint is applied by hand. Each repaint every seven years today costs approx. USD 5 million. This means that maintenance costs are estimated to amount to USD 50 million over a period of 100 years (at today’s price level). A large steel company has calculated that maintenance costs would remain at just over USD 24 million if the tower had been constructed with modern, high-quality stainless steel (of quality 1.4003).
The mass of iron in the tower has a volume that roughly corresponds to a cube with a side of 10 m. Since the wind can pass straight through the truss structure, the tower moves very little even in a full storm.
The construction of the tower was the outcome of the optimism and technological admiration that prevailed during the second half of the 19th century. The engineer had previously been responsible for the construction of a very large truss bridge. Even then, he had perfected the technique he then used for the tower. The Eiffel had first tried to persuade the Barcelona authorities to order a large cast iron tower, but the city’s leading men were not at all interested. The technique was that the Eiffel built the iron elements in a large workshop outside Paris. The elements were first joined with bolts in the workshop and the accuracy then amounted to 1/10 mm. Then the bolts were removed and the elements were heated and riveted together by teams of four men. For the entire construction it took approx. 2.5 million rivets. But only a third of these were put in place at the construction site itself. The others were already in place in the large workshop outside Paris. The construction technology thus consisted of a type of prefabricated approx. 5 m long elements that were transported to the site of the tower and where lifted by steam-powered elevators to the level where they were to be mounted. In addition, the steam engines themselves were hoisted up into the tower as the construction became higher. The tower was built by a workforce that varied between 120 and 200 men at the site of the tower. The entire construction, like a large mechano, consists of approx. 18,000 parts and the tower (excluding the concrete foundations) weighs 10,100 tons, of which the iron weighs 7,341 tons. The construction’s pressure on the ground amounts to only 3.28 kg/cm2. The elevators were designed by the American company Otis.