Robert Maillart
continued
Maillart & Cie
Maillart turned 30 in February 1902, and his future seemed full of possibilities. He had just started his own engineering design and construction company, Maillart & Cie, with two colleagues, Max von Müller (c.1876-1927) and accountant Adolph Zarn.
However, he was working 12-hour days at the office, trying to win contracts. Perhaps unwisely, the firm had been launched without the promise of work. Finding no immediate creative outlet, he sometimes gave way to outbursts of temper.
Maillart decided to apply for a patent for the ideas behind the engineering design he had used for the Zuoz Bridge in 1901 when he was working for Frôté & Westermann. On 18th February 1902, he submitted patent No. 25712 Bogenträger aus armiertem Beton (arched beams of reinforced concrete) to the Swiss Federal Office for Intellectual Property in Berne. It would be granted by May of the next year, although destined not to stand for very long.
In March 1902, Maillart's wife Maria announced that she was expecting a child, their first. This momentous news was immediately followed a bout of gall bladder trouble for Maria — an illness from which she would suffer for the rest of her life.
Maillart & Cie struggled on, project-less, financed largely by von Müller and to some extent by Zarn. In late May 1902, Maillart took part in a contract bid for the construction of cylindrical reinforced concrete water cisterns for two large gas tanks at St Gallen, south of Bodensee (Lake Constance). Rather than use the massive retaining walls suggested by the city engineers, he went with the option of offering an alternative, and developed a design for thin-walled tanks strengthened with buttresses.
To evaluate the idea of retaining water using circumferential forces in a thin wall, Maillart used the graphical analysis techniques he had learned from (Karl) Wilhelm Ritter (1847-1906), his professor at the Eidgenössische Technische Hochschule (ETH) in Zürich. By successive plots of wall deflections and hoop stresses for differing water pressures, he showed that the bending and circumferential forces within the wall worked together, like the staves and bands of a barrel. This is the first correct analysis of thin shell behaviour.
Maillart's idea was a new concept and the St Gallen authorities wanted the opinion of an academic — it was common practice for public works designs to be vetted by a third party. The city engineers hired François Louis Schüle (1860-1925), professor of construction analysis at ETH 1901-24, to review the tenders. It's likely that they would have appointed Ritter, a director at ETH 1891-1904, but he was unwell.
On 13th June 1902, Schüle recommended Maillart & Cie's bid. This was the company's first project, and the St Gallen cisterns were the largest reinforced concrete tanks attempted to date. The steel reinforcement alone cost three times the total amount spent constructing the Zuoz Bridge.
On 28th June, just as work on the tanks was getting under way, bids were invited for a bridge over Steinach Brook in St Gallen. Maillart decided he could better the city's specified design, and produced plans for an arch of precast concrete blocks. On 7th July, he confidently described his alternative in a letter to the director of the municipal building department, Leonhard Kilchmann (1852-1926), as "a more rational and a more beautiful solution".
The proposed arch design consisted of two concentric layers of concrete blocks. Maillart thought that using blocks would minimise cracking, which was an issue for hingeless concrete arches of the period. He also returned to the construction technique of providing centring for the first ring, with the second ring supported by the first once it was up to strength.
Schüle was again the city's design reviewer but this time he wasn't about to give Maillart an immediate endorsement. Whereas Maillart and Ritter looked at the overall performance of a structure, using graphic analysis with load testing for verification, Schüle insisted on full stress calculations, especially for construction conditions, and compliance with regulatory codes. Maillart & Cie was awarded the contract but arguments over structural stresses and the final dimensions of the bridge dragged on until late August 1902, delaying completion until 1903 as work was halted in winter.
On 3rd October 1902, Maillart and Maria's first child, a son, was born. They named him Edmond Benedetto Maillart (1902-62) after their respective fathers. Maillart's mother, Bertha, stayed at their Rigiplatz apartment to help care for the baby with Maria, a nurse and a maid.
By this time, Maillart was beginning to appreciate that his business had both benefits and drawbacks. As a designer of innovative structures he had no peer, which gave him a leading position but also meant he couldn't delegate work. The paradox extended further. Although he railed against the strictures of Swiss authorities on engineering issues, he adhered firmly to traditional conservative Swiss views on family life and hard work.
In May 1903, Maillart & Cie tendered for another bridge in the St Gallen canton, a two span structure — the Thur Bridge at Billwil. His design drawings are annotated "Bogenträger System Maillart" to indicate his patented hollow-box method.
Ritter, still in poor health, compared the two lowest-cost designs — by Maillart (three-hinge arches) and Jaeger & Cie (two-hinge arches). On 26th June 1903, Maillart & Cie was awarded the contract. In August, Ritter scrutinised Maillart's calculations and pointed out that the Zuoz Bridge had suffered cracking at the crown, prompting Maillart to add/increase crown reinforcement for Billwil. This was Ritter's last work. He died in 1906, after two years in a sanatorium.
The Thur Bridge (Billwil) marked a watershed for Maillart as it was the first bridge that the company financed and built as well as designed. He spent much of his time on site. During construction of this bridge, Frôté & Westermann objected to Maillart's patent on the grounds that his hollow box ideas had been developed while he was in their employ. On 2nd October 1903, the courts agreed and the patent was voided.
The bridge was completed in April 1904 and is still standing. It is 84m long, 4m wide and has two 35m spans with a single pier.
After failing to win the contract for the Uto Bridge over the River Sihl with a four-compartment box arch, Maillart took a fresh look at his hollow box design. He realised he could either combat cracking by increasing the quantities of steel and concrete, making the structure much heavier, or he could modify the form completely to avoid cracks forming. This radical thinking was to fashion a masterpiece over the River Rhine in Graubünden canton, eastern Switzerland — Tavanasa Bridge.
In August 1904, Maillart visited Tavanasa to see the proposed site. The single-span three-hinge arch he designed for it had an open hollow box cross-section. To alleviate cracking in the spandrels adjoining the abutments, he removed most of the spandrel walls. The only abutment connections were now with the bridge deck and the lower pin joints of the arch. The most heavily stressed parts of the arch — at the quarter-span points — were the most substantial parts of the structure.
Maillart & Cie submitted a tender on 1st October 1904, and it was accepted as the lowest price bid shortly afterwards. This time, the design was reviewed by Emil Mörsh (1872-1950), professor at ETH, who endorsed it with minor modifications. Construction of the Tavanasa Bridge was soon underway.
Meanwhile, Maillart & Cie was struggling financially. Cash flow was an issue as no money was forthcoming on the projects until the end of the contracts. However, the company was ready to take on all kinds of work. In 1904-5, among other projects, Maillart worked on the design of avalanche protection structures for the Rhätische Bahn (Rhaetian Railway), transmission poles in Zürich, extensions to two sanatoriums in Davos, the Queen Alexandra Sanatorium in Davos-Platz (opened 15th November 1909) and the four-storey Pfenninger cloth factory in Wädenswil, south of Zürich.
At Wädenswil, Maillart acted as architect as well as engineer for the first time. The factory, which still stands though no longer Pfenninger & Cie, features a much lighter and more spacious interior than was usual, thanks to Maillart's slender structural frame, which would become his trademark.
On 28th September 1905, the Tavanasa Bridge was successfully load tested. Maillart's radical design had no precedents. However, it also had little immediate effect on other bridge designers and, unfortunately, it was destined to be destroyed by a rock avalanche on 25th September 1927. Not until the 1950s, long after Maillart's death, would his influence on structural reinforced concrete design be widely acknowledged.
In November 1905, better business prospects enabled Maillart & Cie to open an office in St Gallen. It was an astute move that led in March 1906 to a contract for construction of the Tonhalle (St Gallen concert hall). As ever, Maillart couldn't resist proposing improvement's to the official scheme. Though the concrete frame was to be completely covered by decorative façades, Maillart made slabs and columns thinner but stronger, and replaced the stage support by a thin arch fused in the centre to the deck of the stage floor — a bridge inside a theatre.
Maillart and his family had left the apartment on Rigiplatz in January 1906 and moved some 15km south to Kilchberg on the west bank of Zürisee (Lake Zurich). More good news was to follow. On 13th August 1906, Maria gave birth to their daughter Marie Claire (1906-2009).
In 1907, Maillart designed a reinforced concrete siphon tube as a conduit to divert the Reihenteich, a stream in the city of Basel (Basel-Stadt canton) on Switzerland's northern border. Completed in October, the project was unusual in that the tube was elliptical in section, and because his tender was not the cheapest, though less than the city engineer's estimate.
Now 35 years old, Maillart was gaining a reputation in Switzerland for tackling difficult design problems and offering original, and sometimes challenging, solutions. In the years ahead his innovative thinking was also to be put to good use far beyond his native country.
All items by Robert Maillart  •  All items by Maillart & Cie  •  All items by Ingenieurbureau Maillart  •  Everything built ... 1872 - 1940
main reference  RM
1901 portrait of Robert Maillart  by A Wicky, copyright ETH-Bibliothek Zürich, Bildarchiv

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Biography
Robert Maillart in 1901
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François Louis Schüle
François Louis Schüle (1860-1925), professor at ETH, 1901-24. Schüle was hired by the St Gallen city engineers to assess the tenders for the design of large concrete water cisterns. He recommended Maillart & Cie's bid, which proposed a thin shell solution. This was the the company's first project and in delivering it, Maillart made the first correct analysis of thin shell behaviour.
Photo: copyright ETH-Bibliothek Zürich, Bildarchiv
Fact file : Load testing
In 1823, army officer and engineer Guillaume-Henri Dufour (1787-1875) carried out scientific load calculations and testing on the two-span Saint Antoine wire cable footbridge in Geneva. This was probably the first scientific load test done on a bridge in Switzerland.
guideline development
The Eidgenössische Materialprüfungs- und Forschungsanstalt (Swiss Federal Laboratories for Materials Science & Technology) was founded in 1880 to test materials and develop testing guidelines. By 1892, load testing was commonly used for small bridges, as shown by the controversy between Ritter and Engesser described in the main text.
use by Maillart
Maillart used static load tests to verify the structural integrity of his work. For example, in 1904, the Thur Bridge at Billwil was loaded with containers of water to replicate snow loading. In 1908, his first experimental beamless slabs were loaded with sandbags at Maillart & Cie's yard in Zürich. In 1913-14, further testing and deflection monitoring led Maillart to derive reinforcement patterns for the beamless slabs.
recent use
Load testing is still in use. The 1987 Swiss Codes recommend dynamic load testing for any new bridge with a span exceeding 20m. The test load imposed is about 80% of the characteristic design load, which should not cause cracking. The loading is often achieved by driving a number of loaded trucks over the bridge to be tested.
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Thur Bridge, Billwil
The Thur Bridge, Billwil (completed April 1904). A hollow-box reinforced concrete bridge with three-hinged arches and one river pier — pictured under construction. This project marked a watershed as it was the first bridge that Maillart & Cie financed, designed and built.
Photo: copyright ETH-Bibliothek Zürich, Bildarchiv
Tavanasa Bridge
Tavanasa Bridge under construction in 1905. In his search for ever more-pared back solutions, Maillart developed the hollow box idea into an open box.
Photo: copyright ETH-Bibliothek Zürich, Bildarchiv
Tavanasa Bridge
The completed Tavanasa Bridge in 1905. This radical design, which could pass as contemporary today, had no precedents. The bridge was destroyed by a landslide in September 1927. A replacement was completed in 1928, using a design influenced by Maillart's approach.
Photo: copyright ETH-Bibliothek Zürich, Bildarchiv
Tavanasa Bridge
The Tavanasa Bridge from below, 1905.
Photo: copyright ETH-Bibliothek Zürich, Bildarchiv
former Pfenninger & Cie cloth factory
The Pfenninger & Cie cloth factory complex at Wädenswil on Zürisee (Lake Zurich). The 1906 building designed by Maillart, as architect and engineer, is in the foreground. The photo was taken between 1918 and 1937. The peninsular is now a commercial and residential complex.
Photo: copyright ETH-Bibliothek Zürich, Bildarchiv
Tonhalle, St Gallen
Maillart & Cie undertook structural engineering and acted as contractor for the Tonhalle (concert hall) in St Gallen. Despite appearances, an innovative slender reinforced concrete frame is concealed behind its Art Nouveau façades. The building was refurbished in 1993.
Photo: Andreas Praefcke [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons