6. Reinforced Concrete.—In the early use of concrete, it was commonly employed as a filler in heavy construction, and was not possessed of great strength. Walls of concrete were usually protected by facings of stone or brick masonry. In recent years, however, the availability of cementing materials of high grade has made possible the use of concrete in many classes of construction for which stone or brick masonry- was formerly employed. The facility with which concrete may be applied to many uses makes it highly desirable material, and since the introduction of Portland cement its use has rapidly increased. This use has been further extended in the past few years by the development of reinforced concrete construction. In 15.50 Lambot, in France, constructed a boat of reinforced concrete, and in 1555 patented his invention in England. Francois Coignet, in 1S61, applied reinforced concrete to the construction of beams, arches, pipes, etc.
In 1S61 Joseph _Monier, a gardener of Paris, constructed tubs and small water tanks of concrete in which a wire frame was imbedded. In 1567 Monier patented his reinforcement, which consisted of a mesh formed of wires or rods placed at right angles to each other. He also exhibited some work at the Paris Exposi tion in the same year. Nothing came of this invention for a number of years, but in 1857 Wayss and Bauschinger published, in Germany, the results of an investigation showing the value of the Monier system, and giving formulas for use in design.
The next few years saw considerable development of this type of construction in Austria, and Melan, an Austrian engineer, invented a system of reinforcement for arches in which I-beams were bent to the form of the arch and enclosed in concrete. Hennebiyue, in France, began making reinforced concrete slabs about 1880, and patented his system of slab reinforcement in 1892.
The first use of reinforced concrete in the United States seems to have been by Ernest L. Ransome, in 1874. The next year W. E. Ward constructed a building in New York, in which reinforced concrete walls, roof, and floor beams were used. In 1877 H. P. Jackson used reinforced concrete in building construction in San Francisco. About 1884 Ransome began applying reinforced con crete to important work in California, and in that year took out a patent for the first deformed bar.
In 1S94 the Melan system of arch-bridge construction was intro duced into the United States by Mr. Fr. von Emperger, who built the first important arch bridges. At about the same time Mr. Edwin Thacher began the construction of arch bridges using bar reinforcement.
During the period from 1890 to 1900 the use of reinforced con crete steadily increased, while the dpplications of plain concrete had been extending rapidly, as the increasing supply of cement provided material for a better grade of construction.
Since 1900 the use of reinforced concrete has rapidly increased. The use of massive slab construction for railroad bridges was intro duced by the C. B. & Q. Railroad at Chicago. Fireproof building construction of concrete has become common, and concrete has become the standard material for short-span highway bridges. Many investigations have been made concerning the properties of the materials and the strengths of various structural forms; the work of Consideere, in France, and of Talbot at the University of Illinois, being specially notable. Principles for rational design have been established and recognized standards of practice are rapidly forming.