In Fig. 206 are shown the plans of stairs constructed in the Fridenberg building at 908

Chestnut Street, Philadelphia. This building is 24 feet by 60 feet, and is seven stories high. Structurally the building was constructed of reinforced concrete. The stair and elevator tower is located in the rear of the main building.

The plans of the stairs are interesting on account of the long-span

(about 16 feet) slab construction. The stairs were designed to carry safely a live load of 100 pounds per square foot; and in the theoretical calculations the slab was treated as a flat slab with a clear span of 16 feet. The shear bars were made and spaced as shown in the details. The calculations showed a low shearing value in the concrete, but stirrups were used to secure a good bond between the steel and concrete.

Fig. 207. Detail of Lintel.

Fig. 207. Detail of Lintel.

The concrete was a 1:2:4 mixture, and was mixed wet. The reinforcing steel consisted of square deformed bars, except the stirrups, which were made of 1/4-inch plain round steel.