The construction of the Eiffel Tower: an exemplary project!

From the agreed upon principle of a Universal Exhibition for 1889 and the idea of a 1,000-foot (300-meter) tower accepted at the end of 1884, Gustave Eiffel had the project studied in detail by his colleagues. When a competition for ideas was launched on May 1, 1886 for the major buildings of the Exhibition, his project was ready and could be integrated into the program. Unsurprisingly, Eiffel was one of the winners and was finally able to sign an agreement with the State and the City of Paris on January 8,1887 to build the Tower, which already bore his name, and which he personally financed. There were just over two years left to complete the construction.

The Tower is relatively light at 7,300 tons, but it still needed a solid foundation. Work began immediately with excavations at the site of the four piers, which resulted in a compact gravel deposit that was sufficiently resistant to a depth of a few meters. On the Seine side, watertight metal caissons had to be used to dig below the level of the water. Sixteen stone blocks, each receiving the base of one of the tower's edges and surrounded by a masonry wall at the level of each pillar, were thus built in five months.

The secret of the Tower: prefabrication

On July 1, 1887, the assembly of the metal part could begin. The incubation time of the project had been put to good use. The project was well along already: the sizes of the 18,000 parts that make up the tower had been precisely calculated and then drawn, with 700 engineer's drawings and 3,600 workshop plans. These parts were composed using a limited range of iron components: flat sheets, L-shaped angles, sometimes I-shaped or T-shaped profiles, all supplied by Forges Dupont and Fould in Pompey in Meurthe-et-Moselle (eastern France). The parts were then traced, cut and drilled in the Eiffel workshops, which were located in Levallois-Perret, four kilometers (2.5 miles) as the crow flies from the Champ de Mars. These parts were all assembled using rivets, a kind of large nail that were hot-drilled into the holes previously drilled into two parts to be assembled together. The rivets were then sledgehammered to fix the parts by cooling them down. Two-thirds of the 2,500,000 rivets in the Tower were thereby inserted at the factory using machines. This principle of very careful prefabrication of the parts is the secret to its super fast construction. All the parts were already pre-assembled on site, in parts a few meters long, on horse-drawn carts. If they had a defect, they were sent back to the factory.

1st floor: the critical moment

On the site, wooden scaffolding was built in the summer of 1887 to support the four pillars that obliquely rose to the sky. Six months later, four new wooden scaffolds were built to support the four large beams that made up the first floor. The critical moment of the assembly took place in late 1887: these beams had to be connected to the four pillars, whose incline had to be adjustable. Two devices were used for this purpose: “sandboxes” on which the edges were supported and which could be gradually emptied to lower them into position, and hydraulic cylinders that could run a few centimeters, inserted at the base of the piers, then replaced by shims once the adjustment had been made.

The work could then continue from the platform on the first floor. The second was built in July 1888 and the 1,000-foot-high (300-meter) summit was reached in March 1889. To assemble the parts, modest steam cranes with a force of three tons were set onto each of the pillars and climbed as they rise. The parts hoisted into position are temporarily bolted, then teams of riveters hammering the final rivets in with a sledgehammer.

A fatal accident unrelated to the construction

Despite this hard work on small platforms without any protection or insurance, and despite the cold and the wind, there were no deaths among the 117 riveters and "chimney sweeps" recruited amongst the carpenters.  A fatal accident nevertheless plunged the construction site into mourning when an Italian worker fell after work hours and whose widow Eiffel would discreetly compensate for her loss. On March 30, 1889, the Eiffel Tower was completed, just in time for the opening of the Universal Exhibition in May. The elevators were almost more complicated to install than the tower itself and would be delivered a few weeks after the opening of the Exhibition.