Engineering Wonders of the World
Volume I

14 ENGINEERING WONDERS OF THE WORLD. must be enormous when a gale is raging ; and as the architect is prevented by the presence of many window openings from using diagonal ties such as could be incorporated into, say, a bridge, the problem of stiffening a building is no easy one to solve. Nothing illustrates the efficiency of wind- bracing and the ingenuity of the architect better than the Flat-Iron Building, New York. This structure, 285 feet high, is 171 feet long, and tapers from a mere 86 feet of depth at one end to a knife edge at the other—“ the sharpest thing any architect ever perpetrated,” as an American said. The isolated position of the “ Flat-Iron ” and its disproportionately small depth required the amplest wind-bracing. Figs. 57 and 58 will explain “ how it was done,” with, the aid of deep plate girders arranged horizontally and strutwise. Figs. 57 AND 58.— WIND-BRACING IN THE “flat-iron” BUILDING, NEW YORK. Another system is that employed for the Old Colony Building, Chicago. Here sets of portal arches (Fig. 59) were built between and riveted securely to the main columns on The Singer every floor. The wind-bracing of the tower of the Metropol- itan Life Assurance Building is shown in Fig. 61 ; that of the Land Title Building in Fig. 62. The Singer Tower, 65 Tower Bracing. stiffened by a very in- Each side is divided into feet square in plan, is genious method, five vertical panels. Of these, the cen- tral three were kept quite free of bracing, in order to obtain a maximum of win- dow space ; and it was decided to con- sider the structure as being built up of four square corner towers and a cen- tral tower forming the elevator well, all stiffened by bracing running c o ntinuously through each wall of each tower from top to bottom. In this manner was provided on each face of the tower a Fig. 59.—SECTION OF THE OLD COLONY BUILDING, SHOWING PORTAL ARCH WIND-BRACING. vertical open space 36 feet across. This system has proved to be very efficient. We may now turn from general features to a few structural details of various build- ings which deserve special attention, äs illus- trating what one may call the r , i p n_________ Other Details versatility of steel-frame con- J of Interest, struction. It will be understood that, under ordinary conditions, the pier supporting a column must approach nearer to the boundary of the build- ing site than does the column itself. In the case of the Land Title Building, Philadelphia, the architect wished to bring one set of columns right up to the boundary, and effected his purpose in the manner illustrated by Fig. 60. The columns were supported by overhanging cantilever girders, and balanced by a second set of columns in such a way as to throw the