Robert Maillart's Bridges

The Art of Engineering

David P. Billington

• Editore: Princeton University Press
• Anno: 2020
• ISBN:
  9780691216072
• Argomento: Architecture
• Categoria: Architecture Essays & Monographs

The description for this book, Robert Maillart's Bridges: The Art of Engineering, will be forthcoming.

1 Family and School (1872-1894)

Robert Maillart was born on February 6, 1872 of a long line of professionals, businessmen, and artists. The family was originally from Belgium and descended from a certain Jean Coley dit Maillart, who was recognized in 988 for valor in battle under the Bishop of Liege. His loss of sight on the battlefield is supposed to have been the origin of the French version of Blind Man’s Buff, which is known in French as “Colin-Maillard.”¹

Robert Maillart’s great-grandfather, Philippe Joseph Maillart (1764-1856), had a distinguished career, first as an engraver and later as a landscape painter.² His works are to be found in Belgium, and his landscapes still belonging to the Swiss Maillart family depict charming scenes of small houses and countrysides. Maillart’s grandfather, Hector, married a Protestant, Petronelle Hubertine Schirmer, in 1833. They eventually settled at Carouge, near Geneva, in 1852 and Hector acquired Swiss citizenship in 1858.³ The older of their two children, Edmond (1834-1874), was Maillart’s father, about whom very little is known.⁴ In 1866, he married Bertha Küpfer (1843-1932), the daughter of a prominent family of Bern. Edmond and Bertha Maillart had six children, of whom Robert was the fifth.⁵ When Robert was two, his father died, leaving the family with little money.

From 1885 until 1889, Robert Maillart attended the Bern Gymnasium, where he excelled in mathematics and drawing, both artistic and technical. In 1889, he passed his state examinations with a grade average of 4.8 out of 6.0. His best subjects were descriptive geometry and his weakest, language and natural history.⁶ At seventeen, he qualified for admission to the Swiss Federal Technical University, the Eidgenössische Technische Hochschule (ETH), in Zurich. But since the entrance age had been fixed by law at eighteen, Maillart spent the next year at the municipal school of watchmaking in Geneva. Finally, in October 1890, he entered the ETH, then as now one of the finest technical institutes in Europe.

Founded in 1855 as the Polytechnische Schule, the institute began with five departments; architecture, civil engineering, mechanical engineering, chemical engineering, and forestry, all under a corps of professors chosen from Switzerland and neighboring countries. For Maillart’s education, the two most important initial appointments were the Germans Gottfried Semper (1803-1879) and Carl Culmann (1821-1881), each probably the most influential European academic in his field during the middle of the nineteenth century.

Fig. 1-1 a. Diagram taken from Graphic Statics by Carl Culmann, 2nd ed., 1875, p. 594.

Semper had been a practicing architect and director of the School of Architecture in Dresden from 1834 to 1849, when he had to leave Germany following the abortive revolution. His completed works and his writings exerted a strong influence,⁷ promoting the “rationalist” or structural approach to architecture in German-speaking Europe. Called to the ETH from London in 1855 at the suggestion of Richard Wagner, who was then living in Zurich, Semper was the first professor appointed in the architecture department (then called the building school). He left his imprint not only by designing the main Institute building, but also through his ideas.⁸

Maillart, coming to the ETH after Semper’s death, absorbed this influence largely in his courses on building construction under the architect Benjamin Recordon (1845-1938), who had been appointed professor in the architecture department in 1890. In class notes that Maillart kept to the end of his life there appear some beautiful sketches of structures about which Recordon had lectured. Engineering students at the ETH continued to be taught by visually oriented architects within the school founded by Semper.⁹

Even more important was the influence of Carl Culmann of the Rhenish Palatinate, the first appointment made in the Institute’s department of civil engineering.¹⁰ Culmann had studied engineering at the Polytechnical School in Karlsruhe, had worked in building and bridge construction in Germany, and had traveled for two years through the British Isles and the United States studying bridges, railroads, and steamship construction. Although well trained in mathematics, Culmann brought to Zurich in 1855 the idea that structural calculations could be made graphically, and immediately began writing his great work Graphic Statics, which strongly influenced all engineering education and practice for the next half century. It is interesting to compare Culmann’s arch moment diagram (from the 1875 edition, Fig. 1-1 a) with Maillart’s design for the Bern railway bridge competition sixty years later (Fig. 1-1 b). The visually suggestive nature of Culmann’s diagram indicates the design potential inherent in his methods.¹¹ While there is no evidence that Maillart copied this diagram for his Bern design, he did learn at the ETH the habit of connecting force diagrams to design forms.

Fig. 1-1b. Maillart’s design for the railroad bridge competition, Bern, 1935

When Culmann died in 1881, he was replaced by his student Wilhelm Ritter,¹² who not only took over his courses on the graphical analysis of structures and on bridge design, but also continued his work in graphic statics. Maillart took Ritter’s courses, and his class notes clearly show his early interest both in the graphic analysis of bridges and in the wide variety of bridge forms described by Ritter, who like Culmann had traveled to the United States for study.¹³

Ritter used to end lectures on wooden bridges with a brief section on arch bridges, in which he named four systems, each described essentially in terms of stiffening. Maillart’s class notes reveal not only Ritter’s ideas but also something of Maillart’s own reactions: Swiss bridges were “very complicated”; “to be noted [were] the elegant American examples of braced truss work”; and finally at the very end, after writing down Ritter’s description of the fourth system—which is the only one that could be called fully deck-stiffened—Maillart added the note, “marvelous bridge.”¹⁴

Maillart saved these class notes and a few others and, like most Swiss structural engineers of his generation, was influenced by Wilhelm Ritter all his life. In Maillart’s first set of calculations for a deck-stiffened arch, his basic computations contained only one reference, which read as follows: “See Prof. W. Ritter. Collections of the complete technical writings, under stiffening beams.”¹⁵ The technical foundation of deck-stiffened arches, is to a large extent, the work of Ritter.

The ETH civil engineering curriculum of 1890-1894 was far more visually oriented than that of engineering schools in the mid-twentieth century, and probably more so than that of any other school in the 1890’s. It is perhaps no accident that the two most outstanding bridge designers in the first half of the twentieth century—one using concrete (Maillart) and the other steel (Othmar Ammann)—were both graduates of the ETH, where they had studied under essentially the same faculty.¹⁶

Maillart’s academic record shows him to have been proficient in mathematics and drawing, poor in theoretical machine studies, and only fair in bridges and the theory of structures. His highest grades were in the theory of ordinary differential equations and descriptive geometry. When he received his diploma on March 17, 1894, he was probably as well trained as any engineering student in Europe; in fact, the only two courses in basic civil engineering taught today that Maillart did not have then were on reinforced concrete and statically-indeterminate structural analysis, just the two areas in which he was to make revolutionary contributions. To appreciate the nature of his work, it is essential first to understand the properties of reinforced concrete and its development up to the 1890’s when Robert Maillart began his career.

2 Reinforced Concrete in the 1890’s

Figs. 2-1a and 1b. (a) Tension cracks in a gravity-loaded concrete beam (b) Reinforcing bars to carry the tension in a concrete beam

Concrete is a building material consisting of gravel or crushed stone, sand, cement, and water. Because it is a fluid mass when mixed, it can be cast into forms of any shape desired before hardening. Reinforced concrete is made by casting the concrete over a cage of steel bars. An unreinforced concrete beam will bend downward under its own weight, especially at the center, causing the top to compress together but stretching the bottom apart in tension. Concrete carries compression easily, but under very low tension it cracks (Fig. 2-1 a). However, if reinforcing steel bars are embedded along its bottom inside, the bars can carry tension while the concrete in the top part of the beam can carry the compression (Fig. 2-1 b).

When Robert Maillart graduated from the ETH in 1894, reinforced concrete was little used in Switzerland. The ETH taught no course in it, and no Swiss engineer had ventured to design a major structure in such a material.¹ Masonry, wood, and metal were still the basic materials of engineering construction, as they had been since the Roman Empire, although unreinforced concrete was known even then.

Joseph Monier, a French gardener, was one of the first to think of reinforcing concrete. Around 1867 he strengthened concrete tanks and pipes by casting the concrete over a skeleton of iron, and patented the idea. But lacking technical training, Monier never fully realized why such reinforcing worked and so was partly unaware of engineering applications for his invention. It was a civil engineer, G. A. Wayss of Berlin, who recognized the potential of reinforced concrete as a large-scale building material when he saw some of Monier’s work at the Antwerp Exhibition of 1885. After purchasing the patent rights from Monier, Wayss established in Berlin a “Corporation for Concrete and Monier Construction,” which built reinforced concrete structures all over Germany in the 1880’s. Sadly, Monier himself gained nothing from Wayss’s subsequent success, having sold the rights for a block sum instead of for a royalty.²

The use of reinforced concrete became widespread only after 1894, however, and the leading Eu...