On the Juniper Street side, balconies were constructed nearly the full length of the house. They are 4 feet wide. Structurally they were constructed as cantilever beams, and consist of slabs of concrete 6 inches thick and reinforced with I-inch round bars spaced 6 inches center to center. These balconies are constructed at each floor level. In Fig. 204 is shown a cantilever beam with a span of 6 feet. It is 12 inches wide and 26 inches in depth, and is reinforced with 4 bars b inch in diameter. This cantilever supports the ex terior wall and one end of a simple beam of a span of about 16 feet.
The exterior and interior columns were constructed of concrete, and reinforced with plain round bars. The roof construction was similar to the floor construction.
The concrete consisted of a mixture of 1 part Portland cement, 3 parts sand, and 5 parts stone. The stone was trap rock, broken to pass through a 4-inch ring, dust screened out; and the sand is known as Jersey gravel, which is a bank sand. The reinforcing bars were plain round bars of medium steel.
3S6. The McNulty Building.* The columns used in the con struction of the McNulty Building, New York City, are a very interest ing feature in this building. The building is 50 feet by 96 feet, and is 10 stories high, and was one of the first small-column reinforced-con crete buildings erected in New York. The plan of all the floors is the same. A single row of interior columns is placed in the center of the building, about 22 feet center to center.
The columns are of the hooped type, and were designed from the formula approved by the building laws of New York City. The formula used was P = 1,600 + (160,000 Alt ÷ p ) X r + 6,000 As,. in which P — the total working load, r = radius of the helix, As = the total area of the vertical steel, Alt = sectional area of the pooping wire, p = the pitch of the helix.
The interior columns are .cy:udrical in form, except those sup porting the roof, which are 12 by 2-inch and are reinforced with 4 bars inch in diameter. In all tie other stories except the ninth, they are 27 inches in diameter. BeJcw the fifth floor the reinkrce ment in each of these columns consists if 2-inch round vertical bars, ranging in number from seven in the fifth floor to thirty in the base ment, and banded by a 24-inch helix of 1,-inch wire with a pitch of 11 inches. The vertical bars were omitted between the sixth and tenth floors; and the diameter of the helix was gradually decreased, while the pitch was increased. In the ninth floor the diameter was reduced
to 21 inches.
The wall columns are in general 30 by 26 inches, and support loads from 48,000 pounds in the tenth floor to 719,750 pounds in the basement. In the sixth story, the reinforcement in these columns consists of 3 round vertical bars 2 inches in diameter; and in each of the floors below, the number of bars was increased in these columns there being 24 in the basement columns. These are spirally wound with -h-inch steel wire forming a helix 23 inches in diameter, with a pitch of 2,1 inches. Above the seventh floor, the columns are rein forced with 4 bars inch in dameter, and tied together by A-inch wire spaced 18 inches apart. The columns rest on cast-iron shoes, which are bedded on solid rock about 21 feet below the base ment floor.
The main-floor girders extend transversely across the building, and have a clear span of 21 feet. The floor-beams are spaced about 6 feet apart, and have a span of about 20 feet 6 inches. The sides of the beams slope, the width at the bottom being two inches less than the width at the under surface of the slab. The reinforcement con sists of plain round bars. The bars for the girders and beams were bent and made into a. truss (the Unit System) at the shops of the con tractor, and were shipped to the work ready to be put in place. The stirrups were hot-shrunk on the longitudinal bars. The helices for the columns were wound and attached to some of the vertical rods at the shop, to preserve the pitch. The vertical rods in each co:umn project 6 inches above the floor line, and are connected to the bar placed on it, by a piece of pipe 12 inches long.
The concrete was a 1: 2: 4 mixture. Giant Portland cement was used, and i-inch trap rock. The placing of concrete was begun about the middle of August, 1906, and the building was completed December 20.
387. The McGraw Building. The McGraw Building, New York City, completed in 1907, is a good example of a reinforced concrete building. The building has a frontage of 126 feet and a depth of 90 feet, and is 11 stories in height. The height of the roof is about 150 feet above the street level. The building was designed to resist the vibration of heavy printing machinery. The first and second floors were designed for a live load of 250 pounds per square foot; for the third floor, 150 pounds per square foot; for the fourth floor and all floors above the fourth floor, 125 pounds per square foot.