FIREPROOF CONSTRUCTION. 64; FIREPROOF CONSTRUCTION. development of fireproof Boor systems. Perhaps the first known example of iron and masonry fireproof floor construction was the cotton-mill of Phillips & Lee, of Manchester, England, erect- ed in 1801. In this mill cast-iron floor-beams were spaced ten feet apart and brick arches were sprung between them. This construction, like the vaulted floor construction previously men tioned, was verj heavy, and no great progress could !"• expected in its extension l immercial and business buildings. In isr>:i the rolled I beam n! wrought iron began to be made in Europe, and a year later its manufacture was begun in Amer ica. In 1885 steel [-beams began to be rolled in was used instead of the furmer plaster filling, to protect i lie bottom flanges of the I beam . U it h these innovations the flat tile arch entered upon its final stage of development. About 1880 at- FlO. '■'>. < I, AY TILE BIDE CONSTRUCTION. tention was tinned In the design of column pro tection, hut it was not until Issii thai -ueh pro tection was generally specified. Xexl to the lad FIG. 1. BRICK-ARCH FLOOR. America. With the rolled I-beam it became possible to develop an I-beam and brick-arch floor system, in which the arches were reduced to such small space that a single thickness of bricks would make an arch of sufficient strength. This brought the weight of the floor down to 75 pounds per square foot, which was a decided im- provement over the cast-iron floor-beam and FIG. 2. CORRUGATED IRON AND CONCRETE ARCH. brick-arch construction. The next attempt to improve upon fireproof floor construction was to spring curved sheets of corrugated iron between I-beams and fill above them with concrete. This construction did not result in any material re- duction in the weight of the floor, and it was further objectionable in that the arches them- selves were not fireproof. Until 1870 the system of fireproof construction consisted of solid ma- sonry walls inclosing a framework consisting of cast-iron columns carrying a system of rolled- iron floor-beams between which were sprung brick arches or arches of corrugated iron and con- crete. The columns were left bare, as were the bottom flanges of the floor-braces. To-day this is recognized as a faulty construction, but in the early days of the art of fireproofing iron, being incombustible, was also regarded as fireproof. The next development in the construction of fireproof floor systems was the invention of the hollow tile, 'flat' arch, which was first applied in the Kendall Building in Chicago in 1872. About the same time a similar but heavier con- struction was used in the New York Post-Office. For the next ten years the development in tile arches consisted of attempts to design a lighter construction and at the same time to obtain a stronger construction. Until about 1883 all tile arches projected about one-half inch below the bottoms of the floor-braces, and the incased spaces thus left under the beam flanges were filled with plaster. All tiles were also made without interior webs. • In 1883, in building the Mutual Life Insurance Building in New York, a 9-inch flat-tile arch was used throughout, where each tile had one vertical and one horizontal web, and a special flat tile FlG. 4. CLAY TILE END CONSTRUCTION. low tile, the most commonly used materials for fireproofing are concrete and plaster compositions. The use of concrete for fireproof Hum- verj prob ably antedates the tile arch, but its active de- velopment as a fireproof material has been vir- FlG. 5. ROEBLING CONCRETE STEEL FLOOR. tually confined to the last decade. Its sudden development was largely due to the invention and perfection of concrete steel construction. Mod- ern concrete fireproof floors consist of concrete arches, either flat or curved, containing an imbed- ded network of steel. Plates of concrete when subjected to bending loads are deficient in ten sile strength, and the purpose of the imbedded network is to supply this deficiency. Plaster composition floors are also usually constructed with imbedded metal network. In 1883 the modern era of tall skeleton build ing construction began in Chicago, and thence spread throughout the United States. The abso- lute necessity of making these enormous struc- tures fireproof has been one of the strongest FIG. 6. EXPANDED METAL CONCRETE STEEL FLOOR. influences in developing the present system of fireproof construction. The modern steel skele- ton building consists of a steel framework or skeleton covered with a skin and integument of masonry and fireproofing. All of this integu- ment is supported by the steelwork except that sometimes the exterior walls are made self supporting. Foundation construction for tall buildings is described in the article on Founda- tions. The steel skeleton consists of a series of steel columns rising from the foundations and surmounted by the roof framework. At each floor the columns are braced together in a horizon-
