Page:Popular Science Monthly Volume 23.djvu/635

Rh half inches. It will he observed that for the same reason as in beam construction, and as before explained, the iron rods for re-enforcing were placed near the bottom of the work, so as to resist the tensional stresses due to the load, while that due to compression in the upper



 [sic]-inch iron rods; b, same sized rods running at right angles with a a a; c, lateral openings through the beams for the circulation of heated air; d d, flanges supporting ceilings; e e, re-enforcing beam of wrought-iron.

portion would be sustained by the béton alone. In this manner, and by this process, over thirteen thousand square feet of flooring and roofing were constructed in the building.

The only test of any consequence upon the combined strength of the floors and beams together was made on a section of the widest floor in the house, where the beams are eighteen feet span and six feet between centers. Casks of plaster were placed upon the floor over the beam, forming a triangular load of thirty tons, which was sustained without any injury to the floor, or measurable permanent deflection. The dimensions of the beam that sustained this load were, seven by sixteen inches, and eighteen feet span, re-enforced in its lower portion with a seven-inch I-beam, weighing fifty-five pounds to the yard.

This test indicates that in addition to its admitted fire-resisting qualities, the re-enforced system of construction challenges comparison with other methods of building in matters of strength and of cost, whether for buildings requiring long or short floor-spans.