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CIVL 1101

from Reinforced Concrete: Preliminary Design for Architects and Builders

by R.E. Shaeffer, McGraw-Hill, 1992.

Much has been written about the numerous significant buildings of the Roman Empire constructed using concrete as the primary structural material. Many researchers believe that the first use of a truly cementitious binding agent (as opposed to the ordinary lime commonly used in ancient mortars) occurred in southern Italy in about the second century B.C. A Special type of volcanic sand called pozzuolana, first found near Pozzuoli in the bay of Naples, was used extensively by the Romans in their cement. It is certain that to build the Porticus Aemelia, a large warehouse constructed in 193 B.C., pozzuolana was used to bind stones together to make concrete. This unusual sand reacts chemically with lime and water to solidify into a rocklike mass, even when fully submerged. The Romans used it for bridges, docks, storm drains, and aqueducts as well as for buildings.

Roman concrete bears little resemblance to modern Portland cement concrete. It was never in a plastic state that could flow into a mold or a construction of formwork. Indeed, there is no clear dividing line between what could be called the first concrete and what might be more correctly termed cemented rubble. Roman concrete was constructed in layers by packing mortar by hand in and around stones of various sizes. This assembly was faced with clay bricks on both sides, unless it was below grade, and in the case of walls the wythes of bricks served as forms for the concrete (Boethius and Ward-Perkins, 1970). It is known that the bricks had little structural value and were used to facilitate construction and as surface decoration. There is little doubt that the pozzuolanic material made this type of construction possible, as it was used throughout the Rome/Naples area but is not seen in northern Italy nor elsewhere in the Roman Empire.

Most public buildings, including the Pantheon, and fashionable residences in Rome used brick faced concrete construction for walls and vaults. The domed Pantheon, constructed in the second century A.D., is certainly one of the structural masterpieces of all time. It is a highly sophisticated structure with many weight-reducing voids, niches, and small vaulted spaces. The builders of the Pantheon knew enough to use very heavy aggregates at the ground level and ones of decreasing density higher up in the walls and in the dome itself in order to reduce the weight to be carried. The Pantheons clear span of 142 ft dwarfed previous spans and created nothing less than an architectural revolution in terms of the way interior space was perceived (Mainstone, 1975)

Probably due to the lack of availability of similar pozzuolans throughout the world, this type of concrete was not used elsewhere and stone and brick masonry continued to be the dominant construction materials for most of the worlds significant buildings for many centuries. A type of concrete was first seen again in eighteenth-century France, where stuccoed rubble made to emulate true masonry became fashionable. Francois Cointeraux, a mason in Lyon, searched for an economical means of making fireproof walls by using cementitious mortar in combination with the very ancient pise or rammed earth construction technique (Collins, 1959). Pise calls for the use of timber formwork to contain the clay or mud while it is being compacted, but the use of new and stronger cements made the compacting process unnecessary. In 1824 Joseph Aspdin, an English mason, patented an improved cement which he called Portland cement because it resembled a natural stone quarried on the nearby Isle of Portland. It is generally believed that Aspdin was the first to use high temperatures to heat alumina and silica materials to the point of vitrification, which resulted in fusion. Cement is still made this way today. During the nineteenth century concrete was used for many buildings in Europe, often of an industrial nature, as this new material did not have the social acceptability of stone or brick.

Disagreement exists among researchers as to the first real use of reinforcing in concrete. More often than not, the construction of several small rowboats by Jean-Louis Lambot in the early 1850s is cited as the first successful example. Mr. Lambot, a gentleman farmer in southern France, reinforced his boats with iron bars and wire mesh. He had some plans for using this material in building construction because he applied for a patent in France and Belgium in 1856, describing concrete as follows (Cassie, 1965):

An Improved Building Material to be used as a Substitute for Wood in Naval and Architectural Constructions and also for Domestic Purposes where Dampness is to be Avoided.

In 1854 a plasterer, William B. Wilkinson of Newcastle-upon-Tyne, erected a small two-story servants cottage, reinforcing the concrete floor and roof with iron bars and wire rope, and took out a patent on this type of construction in England (Condit, 1968). He built several such structures and is properly credited with constructing the first reinforced concrete building.

In 1867 Joseph Monier, a French gardener, took out a patent on some reinforced garden tubs and later patented some reinforced beams and posts used for guardrails for roads and railways. It was subsequently shown that Monier never understood, as Wilkinson had, the need for the reinforcing to be near the tensile side of a beam.

The first widespread use of Portland cement concrete in buildings occurred under the direction of the French builder, Francois Coignet. He built several large houses of concrete in England and France in the period 1850-1880, at first using iron rods in the floors to keep the walls from spreading, but later using the rods as flexural elements (Farebrother, 1962)

The first landmark building in reinforced concrete was built by an American mechanical engineer, William E. Ward, in 1871-1875. The house stands today in Port Chester, NY. It is well-known because of the diligence with which Mr. Ward conducted all of his business, researching and documenting everything. He desired a concrete house because his wife was terribly afraid of fire and commissioned architect Robert Mook for the design in 1870. Like Coignets buildings, it was made to resemble masonry to be socially acceptable. Mr. Ward handled all technical and construction issues himself, conducting long-term load tests and other experiments. He used the French word for concrete, beton, and in 1883 delivered a paper on the house to the American Society of Mechanical Engineers entitled Beton in Combination with Iron As a Building Material. His audience, by definition, was far more interested in the unique water supply and heating systems, which he had designed, than in reinforced concrete.

In 1879 G. A. Wayss, a German builder, bought the patent rights to Moniers system and pioneered reinforced concrete construction in Germany and Austria, promoting the Wayss-Monier system (Collins, 1959). (Many of these buildings were built in France as well).

The late nineteenth century saw the parallel development of reinforced concrete frame construction by G. A. Wayss in Germany/ Austria, by Ernest L. Ransome in the United States, and by Francois Hennebique in France.

In the 1870s Ernest L. Ransome was managing a successful stone company (producing concrete blocks as artificial stone) in San Francisco. He first used reinforcing in 1877, and in 1884 he patented a system using twisted square rods to help the development of bond between the concrete and reinforcing (Collins, 1959). His largest work of the time was the Leland Stanford, Jr. Museum at Stanford University, the first building to use exposed aggregate. He was also responsible for several industrial buildings in New Jersey and Pennsylvania, such as the 1903-1904 construction of the Kelly and Jones Machine Shop in Greensburg, Pennsylvania.

The Ingalls Building, a landmark structure in Cincinnati, was built in 1904 using a variation of the Ransome system. Designed by the firm of Elzner and Henderson, it was the first concrete skyscraper, reaching 16 stories (210 feet).

On the other side of the Atlantic, Francois Hennebique, a successful mason turned contractor in Paris, had started to build reinforced concrete houses in the late 1870s. He took out patents in France and Belgium for the Hennebique system of construction and proceeded to establish an empire of franchises in major cities. He promoted the material by holding conferences and developing standards within his own company network. Most of his buildings (like Ransomes) were industrial.

When the far-flung company was at its peak, Hennebique was fulfilling more than 1500 contracts annually (Collins, 1959). More than any other individual he was responsible for the rapid growth of reinforced concrete construction in Europe.

If Hennebique was responsible for the acceptability of reinforced concrete as a building material, then it was Auguste Perret who made it acceptable as an architectural material. The works of Ferret include not only factories and apartment buildings, but also museums, churches, and theaters. His better known works are in or around Paris, such as the delicately facaded apartment building at 25 bis Rue Franklin, completed in 1903. Just a few years later he designed the bulky, massive-looking, but spacious Theatre Champs Elysee.

Notre Dame du Raincy, constructed in 1922, represented a significant departure from anything built in concrete before and is generally regarded as a masterpiece of architectural design. The lofty arched ceilings and the slender columns were very convincing statements as to the prowess of this newly accepted building material.

Reinforced concrete permitted the development of an entirety new building form-the thin shell. In 1930 Eduardo Torroja, the brilliant Spanish engineer, designed a low-rise dome of 3.5-in thickness and 150-ft span for the market at Algeciras, using steel cables for a tension ring. Torroja was also responsible for the statically elegant cantilevered stadium roof at the Madrid Hippodrome in 1935.

At about the same time the Italian architect-engineer, Pier Luigi Nervi, began building his famous hangars for the Italian Air Force. At first these were cast in situ, but most of Nervis work, including the Exhibition Hall at Turin and the two sports palaces in Rome, was primarily of precast construction.

The master of the concrete shell, without dispute, would be the Spanish-born mathematician-engineer-architect, Felix Candela. Practicing mostly in Mexico City, he designed the Cosmic Ray Laboratory, with a 5/8 inch thick shell roof, for the University of Mexico City. He adopted the hyperbolic paraboloid form as his trademark and, making use of favorable labor costs, built many factories and churches in and around Mexico City using this form. His most striking building is the restaurant at Xochimilco, built in 1958, consisting of six identical paraboloid vaults.

As a young architect Le Corbusier worked part-time in Perrets office but was always at odds with his employer, having no use for the espoused classical basis for design (Collins, 1959). Le Corbusier was later to become the most highly regarded architect of the modern era, building almost exclusively in reinforced concrete. Among his celebrated works are the Villa Savoye (of flat plate construction, 1931), the housing blocks on pilotis at Nantes and Marseille (late 1940s), the Chapel at Ronchamp (with walls of concreted masonry construction, 1957), the monastery of La Tourette (1959), and the government complex at Chandigarh in India (1961). More so than his contemporaries, Le Corbusier was involved with the play of natural light as a design element, and concrete with its variable surface texture provided an excellent medium for his efforts.

Frank Lloyd Wright declared the prime assets of reinforced concrete to be its formability and monolithic property of construction, but he did not take advantage of this until late in his career. He was the first to exploit the cantilever as a design feature made possible by the continuous nature of reinforced concrete construction. The Kaufman House (Fallingwater), built in 1936, is a tour de force in the use of the cantilever. Thin slabs seem to project beyond the possible, perhaps constructed containing as much steel as concrete!

In 1919 Mies van der Rohe had proposed the idea of a structural core for a high-rise building with cantilevered floor slabs (Drexler, 1960), but it was not until 1947 that Wright brought the idea to fruition with his design for the Johnson Wax Tower at Racine, Wisconsin. The entire Johnson Wax headquarters complex was hailed as being among the best of Wrights creations.

Wrights claim to an organic basis for his designs and the need to exploit the plastic nature of reinforced concrete reached a high point with his design of the Guggenheim Museum in 1956. The monumental spiral form became an overnight New York City landmark.

High-rise construction in concrete progressed slowly forward from the Ingalls Building in 1904. The giants and midgiants of the 1930s were all of steel construction. The Johnson Wax Tower, however, provided the impetus for Bertrand Goldbergs twin towers of Marina City, though on a vastly different scale. The Chicago 60story high-rise, erected in 1962, heralded the beginning of the use of reinforced concrete in modern skyscrapers and with it, competition for the steel frame. Place Victoria in Montreal, constructed in 1964, reached height of 624 ft utilizing 6000 psi concrete in the columns. Concretes of higher strength proved to be the key to increased height, permitting as they do a reasonable column size on the floors below. One Shell Plaza in Houston topped out at 714 ft in 1970 using 6000 psi concrete. The Chicago area, with its plentiful supply of high quality fly ash (which helps to achieve a more workable concrete at lower water/cement ratios), has spawned the greatest concentration of tall reinforced concrete buildings. The 70-story Lake Point Towers used 7500 psi concrete to reach 645 ft in 1968. Water Tower Place reached 859 feet in 1973 with concrete strengths as high as 9000 psi thanks to a superplasticizing admixture (see Section 3.5).

In 1989 the Scotia Plaza Building in Toronto was completed to a height of 907 ft. In 1990 two more towers in Chicago exceeded 900 ft. The taller of these is the building at 311 S. Wacker Drive shown next to the Sears Tower. Even taller buildings are now planned for New York, Chicago, and Tokyo using concretes of 15,000 psi and higher.

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