Engineering Wonders of the World
Volume I

2 ENGINEERING WONDERS OF THE WORLD. and proceeded to incorporate steelwork into their edifices. Modern steel-frame buildings differ essentially from struc- tures of ordinary brick or masonry, and embody two types of construction. As these are often confused the one with the other, it is well that we should have a clear definition of each at the out- set. A “steel-skeleton” building is one with outer walls built up in the usual way, but hav- ing an interior Definitions. „ , r framework oi iron or steel to carry the floors, interior walls, and roof. On the other hand, a “ steel-cage ” building is one in which every ounce of weight is borne by the metal framework, the outer walls being comparatively thin, and inserted like panels in a door or panes of glass in a greenhouse. They are, in fact, nothing but curtains to give protection against the weather, and therefore are known tech- 5.__WALL STREET, IN NEW YORK, SHOWING HOW STEEL- FRAME BUILDINGS OVERTOP EVEN THE TALL STEEPLE OF A CHURCH. nically as “ curtain walls.” Fig. 2.—ORDINARY CONSTRUCTION WITH MASSIVE WALLS CARRYING ALL LOADS. Fig. 3.—SKELETON FRAME CARRYING FLOOR LOADS, SELF-SUPPORT ING WALLS Kg- 4.—CAGE FRAME CARRYING ALL LOADS : CURTAIN WALLS SUPPORTED BY AND ENCASING THE STEEL FRAME. Three simple diagrams will help the reader to understand the case. Fig. 2 represents an ordinary brick building, with walls thick enough to carry their own weight and that of the floors and roof. Fig. 3 stands for a build- ing which has thinner walls, because the floor loads are carried by the steel skeleton. In Fig. 4 we see a “ cage ” edifice, with, the panel walls resting on girders forming part of the cage by which the loads are supported and transmitted to the foundations. These sketches are purely diagrammatic, and are intended merely to make clear the difference between the three forms of construction, and to illustrate the