Steel Skeleton Construction

Collier's New Encyclopedia (1921)

a form of building construction by which the loads and stresses are transmitted to the foundation by a framework of metal or re-enforced concrete, with girders at each story supporting the walls enclosed. It represents one of the greatest developments in building from the earliest days of architecture. It proves the solution to the problem that arose from the concentration of population in a confined area and it was only natural that the idea should first take shape in what was destined to become the most congested area, in respect to volume of business interests and number of people, in the whole world. The height of buildings had always been determined by consideration of security, utility and cost, and until the advent of the steel skeleton six or seven stories were regarded as nearly as far as the builder could go. In the seventies the rising value of real estate set property owners seeking for a plan of raising more revenue from their investments, and gradually buildings until rose a height of 10 and sometimes 12 stories. The huge quantities of masonry called for in these lofty buildings set property owners and builders under the necessity of seeking out devices that would enable them to economize in material and in the ground occupied. Piers were made thinner and columns were put up to receive the ends of the beams and girders and so relieve the piers of the weight of floor. Finally, in 1889, it was found that the thickness of the piers could be reduced still further by taking from the piers the weight of the walls and placing the four walls on girders set between the wall columns at every floor level. It was thus that the principle underneath Steel Skeleton Construction was revealed. It relegated stone to a subsidiary relation in construction. The essential part of the building became a firmly bound framework of steel able to support not merely the floors and roof, but the walls, interior and external, together with every other part of the building, and constructed on lines sufficient to withstand every condition of STEEL SKELETON CONSTRUCTION 70 wind and weather. In the new type of building the ancient thick supporting walls are known no more. The walls no longer carry loads; they serve merely as a clothing or curtain to the powerful frame of steel which carries the building upward. The first iron girders and beams used in the United States came from Europe about 1840 and their value in the construction of buildings began to become apparent from that time on. Iron beams were used in the floor construction of Cooper Union in New York City in 1860, and steel beams began to be manufactured in 1885. As soon as the principle of steel skeleton construction was perceived steel came to be used throughout the entire building, though cast iron continued to be used in some buildings for columns and bases. As steel grew continually stronger and cheaper a great impetus was given to building construction all over the country, and buildings of great width and height now rose in the course of as many months as formerly it would have taken years for their construction. The height of buildings is now only limited by its relation to the foundation and the service capable of being rendered by a proper system of elevators proportionate to the area of floor space. The amount of space saved by the thinning of the walls has been large. Many buildings are now built in which the amount of stone used is negligible. Even in the central business quarters of large cities the buildings are not a few which are apparently made up of steel and glass. Where formerly a building of 10 stories was regarded as risky, now buildings of over 40 stories are regarded as a moderate development. A building can now be erected at the rate of one story every three or four days, and as the frame directly supports the walls at each story it is not an uncommon sight to see the upper part of a building inclosed by walls while the lower part continues to reveal only the steel frame. The members of the steel skeleton are completed in their construction at the mill and are assembled and riveted together on the site of the proposed building. Angles, plates, channels and other rolled sections are built up into girders and columns. As much as is possible of the riveting is done at the mill, the rest being attended to at the site of the building. In order to distribute the weight of load columns, bases or bearing plates are placed between the column and its foundation. The columns may be of steel or cast iron, hollow circles or hollow squares or H shapes being in use where the strength is sufficient as being the most economical. Slabs or arches of terracotta or concrete laid between steel Ibeams make up the floor construction. The floor area is determined by its division into units of from 15 to 20 or more feet, according to the size of the rooms required. Single or double girders, built up or riveted, placed between the columns, hold up the ends of the floor beams. In high and narrow skeleton buildings cantilever girders are sometimes called for to distribute the weight evenly over the footings. The great height of steel buildings in relation to the area of their site has likewise made methods of wind-bracing necessary, the systems employed being sway-bracing, knee-bracing, and portal-arch bracing, the aim in each case being to hold the steel frame in its several parts more securely to its foundation. While the advantages derived from steel skeleton construction are many and obvious, there are some disadvantages. There is always the liability to corrosion in the metal frame, while the danger to life and limb from their great height and the concentration of population made possible has been often illustrated. While they represent a tremendous development in the art of building, they are erected for convenience rather than for endurance or beauty, though in this latter respect numerous improvements have been made in late years. This disadvantage may be lessened by new rules and devices, but steel skeleton construction has become a necessary adjunct to our material civilization, and greater development may be looked for in the near future.