Wednesday, July 4, 2007

Maillart’s bridges

The Swiss engineer, architect, and artist Robert Maillart (1872–1940) exploited the structural strength and expressive potential of reinforced concrete to generate a modern form for his bridges. By using simple construction concepts he developed graceful structures based on flat or curved reinforced concrete slabs. Amongst his radically innovative ideas were the mushroom slab, the deck-stiffened arch, the open three-hinged arch, and the hollow-box arch. Maillart’s biographer David Billington (1997, 2) asserts that the engineer’s “elegance arose from structure itself and not from an extraneous idea of beauty.”

Taken singly or together, Maillart’s bridges are engineering and architectural feats that elegantly demonstrated, as Le Corbusier claimed in Vers une Architecture (1923), that engineers recognized (long before architects) that beauty could be achieved through thoroughly defining and solving problems. That new approach to design lay at the foundation of modem architecture.

Maillart studied civil engineering at Switzerland’s Federal Technological Institute in Zürich under Wilhelm Ritter, an expert on reinforced concrete. Graduating in 1894, he worked in private and government engineering offices, mostly on railroad, road, and bridge projects.

Unreinforced concrete was first used in 1865 for a multiple-arch bridge on the Grand Maître Aqueduct between the River Vanne and Paris. The invention of reinforced concrete is credited to Joseph Monier, a French gardener who in 1867 patented molded planters made of cement mortar reinforced with iron-wire mesh. Over the next decade there followed several bridge patents. Because French law prevented him from building bridges, Monier sold the patents to contractors Wayss, Freitag, and Schuster, who built Europe’s earliest reinforced concrete bridges in Germany and Switzerland.

Around the turn of the century the French engineer François Hennebique built reinforced concrete bridges at Millesimo, Italy (1898), and Châtellérault, France (1900). Therefore, while his designs were probably the most elegant, Maillart was not the pioneer of reinforced concrete bridges. In 1902 he established his own firm, specializing in reinforced concrete design and construction. By then he had already built a 100-foot-span (30-meter) bridge over the River Inn at Zuoz; its innovative slenderness and flatness created a stir in professional circles. There followed the 115-foot (35-meter) Thurbridge near Billwil (1903) and another single 167-foot (51-meter) arch across the Rhine near Tavanasa (1905, since demolished), identified by some scholars as marking the birth of a modern architecture that reintegrated art and technology.

Maillart moved his practice to Russia in 1912 and produced a number of factories, warehouses, and office buildings in Riga, Charkov, and Kiev. Following the October 1917 Revolution, he returned to Switzerland and in 1919 set up a consulting design practice in Geneva, later opening branch offices in Bern and Zürich.

From 1925 he built several remarkable bridges in Switzerland of two principal structural types: stiffened-slab arches, such as the 140-foot (43-meter) span over the Val-Tschiel near Donath, of 1925; and three-hinged arches in which the arch, roadway, and stiffening girder were integrated into a monolithic structure, exemplified by, among others, the Schwandbach Bridge (1933) in Bern Canton and the Salginatobel Bridge (1930) over the Salgina Valley in Graubunden Canton. The latter is a hollow, box-concrete arch bridge with a span of 295 feet (90 meters) and a rise of 43 feet (13 meters). The slender arch rib deepens from the supports to the quarter-span points, at which it becomes integral with the concrete road deck and tapers again to the midspan hinge. Salginatobel Bridge is widely regarded as an exceptional monument of modern architecture, a piece of structural art. In 1991 the American Association of Architects and Engineers designated it an International Historic Civil Engineering Landmark. It has also been called “the most spectacular and classic example of [its] type in the world.”

Ritter had urged his students to think of shapes and forms that could not be analyzed easily by mathematical calculation. Clearly, Maillart had learned that lesson, and his visual imagination and intuition were a major part of his approach to engineering; just as clearly, his subtly beautiful bridges evidence a thorough comprehension of the nature of forces in a structure. His deep appreciation of the properties and behavior of reinforced concrete permitted him to develop innovative, light sculptural forms. Through his bridges, Maillart, virtually unknown and unacknowledged before about 1930, became internationally famous as a designer of sophisticated concrete structures.

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