Engineering Wonders of the World
Volume I

STEEL-FRAME BUILDINGS. 5 Fig. 10.—DIAGRAM ILLUS- TRATING COMPARATIVE RAPIDITY OF WALL CON- STRUCTION IN ORDINARY (LEFT HAND) AND STEEL- FRAME (right hand) BUILDINGS. scraper. In building self-supporting walls, they must be reared laboriously stone by stone, or brick by brick, from the foundations upwards. Only one story can be attacked at a time, and the number of men usefully em- ployed is limited strictly by the length of the walls to be built. Therefore, assuming that no more than twenty men can find space on the walls of an ordinary building, and that the con- struction of one story occupies one month, it follows that the building of ten stories would • take ten months. On the other hand, in a steel- cage building of the same size, if twenty men were started simulta- neously on every floor, all the walls would be com- pleted in one month, or in one- tenth of the time required for ordinary con- struction. Assuming the walls to be of equal thickness in both cases, the results of one week’s work would be shown in Fig. 10. But owing to the smaller amount of masonry in the walls of a steel-cage building, the economy of time is actually far greater, although allow- ance must be made for time occupied in erect- ing the steel frame. Moreover, all the floors and partitions of a cage building can be erected on every story as fast as the frame- work is erected, while the execution of similar details in an ordinary building is necessarily delayed by the slow and tedious operations of the stonemasons or bricklayers. Let us now draw a picture of what happens when the erection of a steel-frame building has been decided upon. The site being chosen, an architect is commissioned to i rm , , Erection, prepare plans. These are elab- orated, redrawn, and multiplied. They con- tain masses of figures and calculations, all carefully revised again and again by experts, and their number is legion. No care must be spared here, as human life depends on their absolute accuracy. From the originals are made the photographic prints for the rolling mills and quarries, and to guide the riveter and mason and electrician during the bustling days ahead. This part of the work finished, the columns and girders are rolled at the steel mills, and the contractor starts excavating for the foun- dations. These last must be above all things secure, and foundations, often represent a large proportion of the total cost and labour of the entire edifice. If rock be struck reasonably near the surface, so much the better. If not, the foundation men go down till they reach it, or some stratum sufficiently firm to give a footing for the main columns. In New York the engineers usually go to rock. This may necessitate the use of pneumatic caissons to combat water in quick- !*rFloor basemenr ijllillillill miiirnnU Fig. 11.—TOWER FOUNDATIONS, SINGER BUILDING, NEW YORK. Concrelc sand or fissured rock. In the case of the enor- mous City Investing Building the foundations are rectangular piers formed by sinking caissons to rock at a depth of 80 feet below the surface