Maurice Koechlin - The real inventor of the Eiffel tower

portrait Copyright: © deutsche bauzeitung Maurice Koechlin 1886

Though named after a project of Gustave Eiffel, the Eiffel Tower – symbol of Paris – has ist structural concept and form from the responsible chief engineer Maurice Koechlin.

Koechlin was an engineer of outstanding ingenuity and well-versed in the structural techniques of his time. He possessed therefor the best qualifications for evolving such technically innovative conceptions for which Eiffel and his firm were renowned.

Maurice Koechlin was born on the 8th of March 1856 in Bühl (Alsace), offspring of a calm, in the Alsace area and Switzerland living family of industrials and townsmen: the great grandfather Jean Jacques (1789 – 1875) established a foundry in Mühlhausen, which developed into a machine factory that produced steam locomotives since 1839. The father Jean Frederique (1826 – 1914) owned a spinning plant. This way Maurice learned to be familiar with the range of task of the new and upcoming industrial society, from which he chose the work as an engineer for himself.

After a visit at the Lyzeums in Mühlhausen Maurice enwrote at the technical University of Zürich and studied civil engineering. He was a student of Karl Culmann (1821 – 81), who would have great impact on his engineering career.


Karl Culmann

calculation of a pauli girder Copyright: © deutsche bauzeitung calculation of a pauli girder

Culmann was the founder of graphostatics, a new method of statics the time to calculate beams and different frameworks. It is based on the visualizing forces by drawing them as vectors and calculating cutting forces through geometry. Compared to analytical procedures, where often highly complicated integrals are to be solved, graphostatics is based on simple geometrical principals. Are these used consequently complex support structures can be calculated.

Culmann tought his students the use of graphostatics with the help of examples, that were aligned for the geometrical optimization of bridge grinders. The original theories were part of his own studies. The goal was to use the cross section of bridge grinders under pressure in an optimized way – which was also a central quality of the so called “Pauli-Grinder”. This construction, which reduced the amount of used steel, was called the “grinder of equal resistance.


*** Maurice Koechlin - der eigentliche Erfinder des Eifelturms ***

Maria Pia Copyright: © deutsche bauzeitung Maria Pia bridge

Maurice Koechlin left the technical University of Zurich graduating top of his class and began to work 1877 as an engineer at the railway company „Chemin de Fer de l’Est“. Two years later he starts working for the office of Gustave Eiffel (1832 – 1923) in october of 1879. Koechlin was replacing the leading engineer Théophile Seyrig (1843 – 1923), Eiffels Partner, who had provem himself to be an extraordinary and creative Engineer. He designed the steel framework arch bridge „Maria Pia“ cross the Douro near Porto (Portugal, 1875 – 77). This construction (Image 2) brought international recognition to Eiffels firm for the first time, not only because of the exceptional technical Konzept of a 160 meter span round arch, but also because of its economical superiority: the costs of the bridge were almost 40% below the proposal of the nearest favorable provider.

It didn’t take long until others moved up to Eiffel to realize similar constructions. In this context Seyrig asked to be adequate financially included in the merchandise of his construction. Eiffel took the Occasion to terminate his partnership early and to fire Seyrig.


The Garabit viaduct

Copyright: © deutsche bauzeitung The Garabit Viadukt

The steel arch bridge for France is a Garabit- Viadukt (1879 – 84). It bildes an important connection for the marked-out routs of the state train going south and should conquer the 120-Meter-deep gorge of Truyère near St. Flout in the south Auvergne.

A preliminary draft was made by state officials analogous to the Douro-bridge in preparations of the direct commission of Eiffels firm. The pre-planning was edited then by Maurice Koechlin and Emile Nouguier, an engineer of Eiffel specialized on montage and building organization. Koechlin kept the basic principals of the Douro bridge: the sickle-shaped arch, the sort of framework columns and the rectangular carriageway grinder in framework. He adjusted the construction to the new standards of technology, by replacing iron raw cross sections of the columns with rectangular, riveted cross sections made of steel sheets. The connection between the carriageway grinder and the arch was eliminated and instead the grind was led through appropriate columns across the arch apex, without touching it. This change simplified the construction and improved the building process regarding effectivity and velocity. Additionally, it allowed for the arch geometry could be designed freely. Koechlin used this feature for a technical particularity: While the shape of the system axis in the Douro-Viaduct followed a circular arch, the Garabit-Viaduct uses a parabolic curve. Koechlin had obtained this exact shape and its relation between crown height and range by solving an optimization-calculation after minimizing the arch weight.


The Trades Viadukt and the Statue of Liberty

Tardes viaduct Copyright: © deutsche bauzeitung The Tardes Viadukt

Together with Nouguier, Koechlin developed a concept and the construction of the viaduct across the Trades (1881 – 84). The steel-beam-bridge is erected across three spans and one of the first to be built after the cantilever method. This building method reflects in the construction as closed meshed lattice girders, since contrary to them, the Beam bridges by Eiffel had always been cross-struts-frameworks. Because of the lattice girders, the lower brace is evenly supported and the different local pressures caused by shifting of the beam can be handled more easily. Koechlin calculated the different loading conditions of beam and columns through impact curves. The triumph of this project was tarnished, because a winter storm destroyed the bridge during construction.

Less spectacular on technical Terms, however much brighter in its context is the structure of the statue of liberty of the United States of America (1881 – 86), which was design and calculated by Koechlin. The sculpture was a present from France to the Americans in remembrance of their independence. She was originally designed by Auguste Bartholdi, a sculptor from Alsace; Viollet-le-Duc as his consultant. After his early death in 1879 Eiffel and his firm took the project on. Analog to the column construction of the bridge, Koechlin developed a strait framework mast along which the single parts of the sculpture where hung and fastened with bars, cross- and diagonal-pieces. This sub structure was especially designed for pressure under wind power. Its shell is made from policed copperplates, that are connected though rivets and bars. After a test run in Paris in the year of 1884 the statue of liberty was erected outside the gates of New York, on Bedloe’s Island, and unveiled in 1886.


The 300-Meter-Tower

design of the 300m tower Copyright: © deutsche bauzeitung design of the 300m tower

The idea of holding a world exhibition in Paris for the hundredth anniversary of the French revolution in 1889 met high approval in France. In times of defeat and economic depression this sign of confidence and upturn was needed. Beside the proposals to build a colossal statue or a monument, the planning of a high tower was considered, following the examples made in the States and England.

1881 the French engineer Sébillot developed the idea of building a „Tour de Soleil“(„sun tower“), which should enlighten the nocturnal city of Paris with the help of a certain lighting. After the French government had officially announced in May 1884 the world exhibit for the year of 1889, Sébillot designed in cooperation with the Architect Bourdais a 300-meter-high tower made form granite with enormous headlamps on the very top. Even though the project was seen rather skeptical, it was discussed publicly until the first planning competition in May of 1886.

In Spring of 1884 Maurice Koechlin and Emile Nougier had also put thought into the matter. Koechlin developed a design for a so called „Pylone de 300m de hauteur“ construction, a mast of 300-meter hight, build as a framework construction, its silhouette tapering towards the top. This complete different way of designing becomes more obvious, by looking at Koechlins sketches and comparing them to Sébillots and Bourdais, who reminds of a rather oversized and romanticized reconstruction of the seventh world wonder: the extraordinary lighthouse on the island Pharos.

Different from the bridge construction, for the towers the cross operating powers – meaning Wind – play a very important role. Again this was a possibility for Koechlin to start an Optimizationprocess, where the goal is an ideal shape of the tower based on the estimated wind power. The course of the towers pillars equals the “pressure line”, a fictive line, in which the load transfer of cross and lengthway powers all coincide. It’s similar to the moment curve of a vertical cantilever under a given wind power. In the jargon of culmanns or von Paulis teaching one would speak of “a cantilever of equal resistance”. Koechlin determinded the geometry of the world-exhibit-tower under the refined conditions and with help graphostatic methods.

preliminary design Eiffel 1885 Copyright: © deutsche bauzeitung preliminary design Eiffel 1885

When Koechlin and Nouguier presented the sketch of the pylon of 300 meter hight to Eiffel, he responded skeptically, however allowed them to continue their work. Apparently, he had an idea how to sell this rather unusual concept to the exhibition committee. He assigned the architect Sauvestre to edit Koechlins idea. Sauvestre changed the allocation of the floor stages and applicated circular structures at the tower bases. This concept Eiffel presented to the exhibition committee as a first draft and won the project for himself. This way the tower wasn’t only presented as an exhibition building, it also advertised it to be an important tool of scientific research in the area of meteorology, astronomy and aerodynamics. Koechlins initial Partner regarding the idea and construction of the Tower wasn’t mentioned at all and his was put between all the other names of participants. This exceptional construction and shape of the tower was also the main point of criticism at the time. To offend the highly-engaged project engineer, the tower was derogatively called the “Eiffeltower”. This led even more to the connection between name and tower. After a while the critic had turned into general admiration and the tower was finished in time for the exhibition, which gave Eiffel more and more the image of a brilliant engineer – however, on the cost of his employees. Even though, his successful firm is proving his entrepreneurial talent, with a great understanding of the technically possible. His behavior shows though, that his talents as an engineer weren’t as great and he tried to compensate for it by the specific takeover of others ideas.


Koechlin and Eiffel

The Eiffel Tower Copyright: © deutsche bauzeitung The Eiffel Tower

Surely it wasn’t difficult, to differ from Eiffels extrovert personality, however, Koechlin and Eiffel could have not been more different from one another. While Eiffel lived a life in the public, Koechlin preferred to stay rather private, avoid public appearances. Although, he published many scientific pieces and a book regarding the application of graphostatics, he never enjoyed talking about them. This strong understatement surely helped him to accept, that his name was mentioned in the context of the building of the 300 meter tower, but his work was never correctly acknowledged properly and didn’t receive the adequate appreciation.

On the other Hand Koechlin was very aware, that without Eiffels personal und entrepreneurial Engagement, assignments in the quality of a 300-meter-tower would have been unachievable. This particular attitude was an important reason why the cooperation between two such different Characters did not only work very well until Eiffels death in 1923, but was also filled with high mutual respect for one another. Only in the context of the Eiffeltowers 50th anniversary the public began to wonder about the original draft and gave Koechlin more attention. It is said that during that time Koechlin made the only personal statement regarding the 300-meter-tower, in cooperation with Eiffel, in which he states: „Le père de la Tour c’est Eiffel – mais l’idée et les calculs, c’est moi.“ („The Towers father is Eiffel, but the idea and calculation were made by me”). From 1893 on, after Eiffel had stepped down, until 1940 Maurice Koechlin took over the management of the firm. His last years Kochlin lived in his house in Veytaus (Swizerland), where he passed in 1946 at the Age of ninety.

Even though, it sounds paradox: The Eiffeltower as we all know it, would have never been built if it wasn’t for Maurice Koechlin. This shape, developed following only technical aspects, had outshone its competition and fascinates us until today. It illustrates the effect of loads, similar to steel-bridge-constructions in the 19th century, the vaults by Antonio Gaudì or the rope constructions in the sixties by Frei Otto. Koechlin therefore belongs to the group of leading engineers of modern times. Nonetheless, the construction of the 300-meter-tower for the world exhibition in Paris brought mainly the Eiffels name the worldwide renommee. Still, it remains his personal and undebatable accomplishment that his concept enrichened the engineering architecture with another milestone.




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