This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The floor-beams were in general 8 inches wide, and the depth below the slab was 18 inches. The amount of reinforcement in the beams varied, depending on the length of the beams. Most of the beams were reinforced with 2 bars 1 inch square, and 1 bar 1 1/8 inches square. The 1 1/8 inch bar was turned up or trussed at the ends, and the 1-inch bars were straight. The roof beams were 6 by 12-inch below the slab, and were reinforced with 2 bars 7/8 inch square, except in the longest beams, in which 2 bars 1 inch square were required. A 3/4-inch bar, 5 feet long, was placed in the top of all floors and roof beams, where they were framed into a girder. The ends of these bars were turned down. The stirrups were made of 3/8-inch round bars, and were spaced as shown in the detail of the beam. See Fig. 190.
The floor girders were 12 by 24-inch below the slab. The span of the girders varied from about 18 feet to about 20 feet; and they were all reinforced with 6 bars 1 inch square, three of the bars being turned up at the ends. Two 3/4-inch square bars were placed in the top of the girders over the supports. These bars were 5 feet long, and they were hooked at the ends. Bars 3/8 inch square, 5 feet long, were placed in the slab near the top, at right angles to the girders. The bars were 12 inches center to center, and were placed over the center of the girders.
The wall beams or lintels on the Fifth Street and Appletree Street sides of the building, are shown in section in Fig. 191. They are 9 inches by 24 inches, and are reinforced with 2 bars 1 inch square. The wall girders in the side of the building opposite Appletree Street are 14 inches by 24 inches, and are reinforced with 6 bars 1 inch square.
The stairs were constructed as shown in Fig. 192. The structural concrete slab was 6 inches thick, and was reinforced with 3/4-inch bars. Safety treads 5 1/2 inches in width, and 12 inches shorter than the width of the stairs, were set in each step.
The concrete for the beams, girders, slabs, and footings was a 1: 2 1/2: 5 mixture; and for the columns, a 1:2:4 mixture was required. The stone used in this concrete was trap rock. The concrete was mixed in a batch mixer, and the consistency of the mixture was what is commonly known as a wet mixture. Square twisted bars were used as the reinforcing steel.
Fig. 193. Structural Floor-Plan of Mershon Building, Philadelphia, Pa.
The first, second, and third floors were finished with l 1/4-inch maple flooring. The stringers, 2 inches by 3 inches, were spaced 16 inches apart, and the space between the stringers was filled with cinder concrete. The other floors were finished with a one-inch coat of cement finish. A cinder fill 2 inches thick was laid on the concrete floor-slab, on which was laid the cement finish. The cinder concrete consisted of 1 part Portland cement, 3 parts sand, and 7 parts cinders. The cement finish was composed of 1 part Portland cement, 1 part sand, and 1 part 1/4-inch crushed granite.