Robert Maillart
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Robert Maillart (February 6, 1872 - April 5, 1940) was a Swiss civil engineer who revolutionized reinforced concrete with such designs as the three-hinged arch, the deck-stiffened arch, and the mushroom slab.
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[edit] Education
Maillart attended the Federal Institute of Technology in Zurich. He studied under Wilhelm Ritter, who was another accomplished Swiss civil engineer. Maillart did not excel in academic theories, but understood the necessity to mate assumptions and visualize when analyzing a structure. A customary train of thought prior to the 1900’s was to utilize shapes that could be analyzed easily using mathematics. This overuse of mathematics annoyed Maillart, as he greatly preferred to stand back and use common sense to predict full-scale performance. Also, as he rarely tested his bridges prior to construction, only upon completion would he verify the bridge was adequate. The testing of Maillart's designs were often performed by Ritter himself. This attitude towards bridge design and construction was what provided him with his innovative designs.
[edit] Development and use of reinforced concrete
The first use of concrete as a major bridge construction material was in 1865. It was used to form a multiple-arch structure on the Grand Maître Aqueduct in France. The concrete was cast in its crudest form, a huge mass without reinforcement. Later in the nineteenth century, engineers explored the possibilities of reinforced concrete as a structural material. They found that the concrete carried compressive forces, while steel bars carried the tension forces. This made concrete an even better material for structures.
Joseph Monier, from France, is credited with being the first to understand the principles of reinforced concrete. He embedded an iron-wire mesh into concrete. However he was a gardener, not a licensed engineer, and sold his patents to contractors who built the first generation of reinforced concrete bridges in Europe. He also perfected the technique of pre-stressing concrete, which leaves permanent compressive stresses in concrete arches.
By the early twentieth century reinforced concrete became an acceptable substitute in construction for all previous structural materials, such as stone, wood, and steel. People like Joseph Monier, had developed useful methods for design and construction, but no one had invented new forms that showed the full aesthetic nature of reinforced concrete. Robert Maillart had an intuition and genius that could entirely exploit the aesthetic of concrete. He designed three-hinged arches in which the deck and the arch ribs were combined to produce closely integrated structures that evolved into stiffened arches of very thin reinforced concrete and concrete slabs. The Schwandbach Bridge (1933) and the Salginatobel Bridge (1930) are classic examples of Maillart’s deck stiffened arch bridges and three-hinged arch bridges. in 1991, the American Society of Civil Engineers (ASCE) declared the Salginatobel Bridge a world monument, which is a tremendous achievement. Only 30 other structures in the world have received this award, including the Eiffel Tower, the Statue of Liberty, and the Panama Canal. Also, in 2001, the British Trade Journal, “Bridge – Design and Engineering,” voted the Salginatobel Bridge the most beautiful bridge of the century; which alone displayed the bridges tremendous achievements and only furthering the greatness in which Robert Maillart strived for.
These designs went beyond the common boundaries of concrete design in Maillart’s time. Both of the bridges mentioned above are great examples of Maillart’s ability to simplify design in order to allow for maximum use of materials and to incorporate the natural beauty of the structure’s environment.
[edit] Analytical methods
By the second half of the nineteenth century, major advances in design theory, graphic statics, and knowledge of material strengths had been achieved. As the nineteenth century neared its end, the major factor contributing to the need for scientific design of bridges was the railroads. Engineers had to know the precise levels of stresses in bridge members, in order to accommodate the impact of trains. The first design solution was obtained by Squire Whipple in 1847. His major breakthrough was that truss members could be analyzed as a system of forces in equilibrium. This system, known as the “method of joints,” permits the determination of stresses in all known members of a truss if two forces are known. The next advance in design was the “method of sections,” developed by Wilhelm Ritter in 1862. Ritter simplified the calculations of forces by developing a very simple formula for determining the forces in the members intersected by a cross-section. A third advance was a better method of graphical analysis, developed independently by J.C. Maxwell (UK) and Karl Culmann. (Switzerland).
Robert Maillart learned the analytical methods of his era, but he was most influenced by the principles developed by his mentor, Wilhelm Ritter, mentioned above. Maillart studied under Ritter, who had three basic principles of design. The first of these was to value calculations based on simple analysis, so that appropriate assumptions could be made based on common sense. The second was to consider carefully the construction process of the structure, not just the final product. The last principle was to test a structure always with full-scale load tests. All these principles are an adaptation of the available techniques, but with an emphasis on the careful study of previously built structures.
At the time of Maillart and Ritter, other designers preferred that their designs evolve from previously successful structures and designs. German engineers and scientists had developed elaborate mathematical techniques, and were confident that they did not need practical load tests of their designs developed using those techniques. However, these techniques did not encourage designers to think of unusual shapes, because those shapes could not be completely analyzed using the available mathematical techniques. Ritter’s principles did allow for uncommon shapes.
[edit] Other bridges
- Tavanasa Bridge
- Zuoz Bridge
- Stauffacher Bridge
[edit] References
- ASCE, History and Heritage of Civil Engineering, [1].
- Bill, Max, Robert Maillart Bridges and Constructions, Fredrick A. Praeger Publishers, 1969.
- Billington, David P., Robert Maillart: Builder, Designer, and Artist, Cambridge University Press, 1997.
- Billington, David P., Robert Maillart’s Bridges: The Art of Engineering, Princeton University Press, 1978.
- Billington, David P., Robert Maillart and the Art of Reinforced Concrete, Architectural History Foundation, 1991.
- Billington, David P., The Art of Structural Design: A Swiss Legacy, Princeton University Press, 2003
- DeLony, E. (1996). Context for World Heritage Bridges. ICOMOS and TICCIH http://www.icomos.org/studies/bridges.htm#20
- Molgaard, John, The Engineering Profession,
[2].
