The New York Rapid-transit Subway

Proceedings.] PARSONS ON NEW YORK RAPID-TRANSIT SUBWAY. 15 60 feet 3 inches, with a total length of 300 feet (Fig. 6, Plate ■>). This arch is semi-circular in form, with a radius of 25 feet and a height from rail-level to key of 25 feet. The minimum thickness of the walls is 6 feet 74 inches, the roof being 2 feet 6 inches thick at the crown, but reinforced with 1-inch square rods running transversely and 12 inches apart, and a double row of 1-inch longitudinal rods 20 inches apart between centres. With but few exceptions, all arches and side walls were constructed of concrete. Use of Reinforced Concrete (Fig. 7, Plate 5). Although the original contracts contemplated the use of steel beams for all portions of the subway where a fiat roof is employed, the successful use of concrete during construction led to the adoption of reinforced-concrete in lieu of beams. A two-track portion was first adopted for such construction where the cover varied between about 5 and 10 feet and the base of the rail averaged about 5 feet below the level of ground-water or high tide. The standard form of bulb-angle column was retained for the row of central columns, except that their tops were not designed to be riveted to cross girders. They were set as usual at the normal distance of 5 feet. In the walls opposite each column, at 5-foot intervals, were placed two angles, 3 inches by 3 inches and 14 feet 2 inches long, riveted together with their legs set parallel to the face of the wall and 2 inches back from it. The tops of these pairs of angles were cross connected, by two 14-inch diameter rods 12 feet 9 inches long, with the sides of the central row of columns. The feet of the angles were embedded in the floor concrete. Between these angles and running from wall to wall were six 13-inch rods in each 5-foot panel where the cover was 6 feet or less, and seven where the cover ranged from 7 to 10 feet. Similar rods 12 inches apart were set vertically in the side walls between the vertical angles. These vertical and cross rods were not connected at either top or bottom, but were simply left embedded in the concrete and set 24 inches back from the face of the wall. In order to form a vertical truss along, and on top of, the row of central columns, four g-inch diameter rods were run from column to column at a mean distance of about 18 inches below the lower surface of the roof concrete, and on the sides of the columns were riveted two small bars 24 inches by 14 inch by % inch, and -to the web of the columns were riveted two angles 6 inches by 4 inches by - inch, the horizontal legs of these angles being 2 feet below the surface of the roof. The roof concrete was then moulded downward at the sides on a curve with a radius of