All beams and girders were designed as continuous beams, even where supported on the outside beams. There was twice as much steel over the supports as in the center of the spans. The Building Code of the City of New York requires that the moment for con iV tinuous beams be taken as- 1n at the center of the span, and as 10 a over the support. These %allies are more than twice the theoretical value as computed for continuous beams.
One very interesting feature of this building is that it was constructed dur ing the winter. The first concrete was laid during September, and the concrete work was completed in April. During freezing weather, the windows of the floors below the floor that was being con structed were closed with canvas; and salamanders (open stoves) were distrib uted over the completed floor, and kept in constant operation. Coke was used as the fuel for the salamanders. The con crete was mixed with hot water, and the sand and the stone were also heated. After two or three stories had been erected, and the construction force was fully organized, a floor was completed in about 12 days. Three complete sets of forms were provided and used. They were usually left in place nearly three weeks.
388. Fridenberg Building. In Fig.
206 are shown the plans of stairs con structed 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 con crete.
The concrete was a 1: 2:4 mixture, and was mixed wet. The reinforcing steel consisted of square deformed bars, except the stir rups, which were made of +-inch plain round steel.
389. General Electric Company Building. An interesting feature of a large reinforced-concrete building constructed for the General Electric Company at Fort Wayne, Ind., is the design of the lintels. As shown in Fig. 207, the bottom of the lintel is at the same elevation as the bottom of the slab. The total space between the columns is filled with double windows; and the space between the bottom of the windows and the floor is filled with lintels and a thin wall of reinforced concrete, as shown in the figure.
390. Water=Basin and Circular Tanks. Figs. 208 and 209 illustrate sections of the walls of the pure water basin and the 50 foot circular tanks whiCh have been partly described in Part I under the heading of Waterproofing.
The pure water basin was 100 feet by 200 feet, and 13 feet deep, giving a capacity of 1,500,000 gallons. The counterforts are spaced 12 feet 6 inches center to center, and are 12 inches thick, except every fourth one, which was made 18 inches thick. The 18-inch counter forts were constructed as two counterforts 9 inches thick, as the vertical joints in the walls were made at this point; that is, the con crete between the centers of two of the 1S-inch counterforts was placed in one day. On the two ends and one side of the basin, the counterforts were constructed on the exterior of the basin to support about 10 feet of earth. But on one side it would have been necessary to remove rock 6 to 8 feet in thickness to make room for the counter forts, had they been constructed on the exterior of the basin. There fore they were constructed inside of the basin. If both faces of the vertical wall had been reinforced, the same as the one shown, then the wall would have been able to resist an outward or inward pressure, and the "piers" would act as counterforts or buttresses, depending on ovnether they were in tension or in compression.
The concrete used consisted of 1 part Portland cement, 3 parts sand, and 5 parts crushed stone. The stone was graded in size from +-inch as the minimum to 1-ineh as the maximum size. Square sectioned deformed bars were used as the steel reinforcement. The forms were constructed in units so that they could be put up and taken down quickly.