Origins and Construction of the Eiffel Tower

The Design of the Eiffel Tower

The plan to build a tower 300 meters high was conceived as part of preparations for the World's Fair of 1889.

Bolting the joint of two crossbowmen.(c): Collection Tour Eiffel

The wager was to "study the possibility of erecting an iron tower on the Champ-de-Mars with a square base, 125 meters across and 300 meters tall". Selected from among 107 projects, it was that of Gustave Eiffel, an entrepreneur, Maurice Koechlin and Emile Nouguier, both engineers, and Stephen Sauvestre, an architect, that was accepted.

Emile Nouguier and Maurice Koechlin, the two chief engineers in Eiffel's company, had the idea for a very tall tower in June 1884. It was to be designed like a large pylon with four columns of lattice work girders, separated at the base and coming together at the top, and joined to each other by more metal girders at regular intervals.

The tower project was a bold extension of this principle up to a height of 300 metres - equivalent to the symbolic figure of 1000 feet. On September 18 1884 Eiffel registered a patent "for a new configuration allowing the construction of metal supports and pylons capable of exceeding a height of 300 metres".

In order to make the project more acceptable to public opinion, Nouguier and Koechlin commissioned the architect Stephen Sauvestre to work on the project's appearance.

A quite different first edition

Sauvestre proposed stonework pedestals to dress the legs, monumental arches to link the columns and the first level, large glass-walled halls on each level, a bulb-shaped design for the top and various other ornamental features to decorate the whole of the structure. In the end the project was simplified, but certain elements such as the large arches at the base were retained, which in part give it its very characteristic appearance.

The curvature of the uprights is mathematically determined to offer the most efficient wind resistance possible. As Eiffel himself explains: "All the cutting force of the wind passes into the interior of the leading edge uprights. Lines drawn tangential to each upright with the point of each tangent at the same height, will always intersect at a second point, which is exactly the point through which passes the flow resultant from the action of the wind on that part of the tower support situated above the two points in question. Before coming together at the high pinnacle, the uprights appear to burst out of the ground, and in a way to be shaped by the action of the wind".

The construction

The assembly of the supports began on July 1, 1887 and was completed twenty-two months later.

All the elements were prepared in Eiffel’s factory located at Levallois-Perret on the outskirts of Paris. Each of the 18,000 pieces used to construct the Tower were specifically designed and calculated, traced out to an accuracy of a tenth of a millimetre and then put together forming new pieces around five metres each. A team of constructors, who had worked on the great metal viaduct projects, were responsible for the 150 to 300 workers on site assembling this gigantic erector set.

The rivet workers

All the metal pieces of the tower are held together by rivets, a well-refined method of construction at the time the Tower was constructed. First the pieces were assembled in the factory using bolts, later to be replaced one by one with thermally assembled rivets, which contracted during cooling thus ensuring a very tight fit. A team of four men was needed for each rivet assembled: one to heat it up, another to hold it in place, a third to shape the head and a fourth to beat it with a sledgehammer. Only a third of the 2,500,000 rivets used in the construction of the Tower were inserted directly on site.

The rivet workers. Copyright : Collection Tour Eiffel

The uprights rest on concrete foundations installed a few metres below ground-level on top of a layer of compacted gravel. Each corner edge rests on its own supporting block, applying to it a pressure of 3 to 4 kilograms per square centimetre, and each block is joined to the others by walls.

On the Seine side of the construction, the builders used watertight metal caissons and injected compressed air, so that they were able to work below the level of the water.

 

The tower was assembled using wooden scaffolding and small steam cranes mounted onto the tower itself.

The assembly of the first level was achieved by the use of twelve temporary wooden scaffolds, 30 metres high, and four larger scaffolds of 40 metres each.

"Sand boxes" and hydraulic jacks - replaced after use by permanent wedges - allowed the metal girders to be positioned to an accuracy of one millimetre.

On December 7, 1887, the joining of the major girders up to the first level was completed. The pieces were hauled up by steam cranes, which themselves climbed up the Tower as they went along using the runners to be used for the Tower's lifts.