Water Mains and Sewer.—Cradles were designed for the support of the 48-in. and 24-in. water mains, resting on the transverse girders, and the 48-in. cast-iron sewer on the east side of the avenue was carried on I-beams bracketed to the ends of the transverse girders, as shown on [Figs. 1] and [2].
Fig. 2. (full page image)
METHOD OF SUPPORTING ELEVATED RAILWAY STRUCTURE
Fig. 3. (full page image)
METHOD OF SUPPORTING TRACKS OF NEW YORK CITY RAILWAY CO.
Girders "C."—The transverse girders below the street surface, referred to above, were known as girders "C," and they were put in place at first resting on concrete piers on the central core; the weight of all structures was placed on them while the sides of the avenue were being excavated, and the sides of the viaduct were being built. The ends of these girders were then picked up on the sides of the viaduct, and, spanning the central rock core, carried all structures while the core was being excavated and the viaduct completed. New foundations were then placed on the deck of the viaduct to carry all structures.
Fifty-four of these girders were required, each weighing about 19,000 lb. The bents carrying the ends of these girders on the sides of the viaduct are shown on [Fig. 2]. They were of long-leaf yellow pine. These girders were located so that a cradle could be laid on them east of the elevated railway structure to carry a proposed 48-in. cast-iron water main.
Girders "B."—Eighteen of these girders were required, each weighing about 6,000 lb. The timber bents supporting these girders, shown on [Fig. 2], were of long-leaf yellow pine.
The total weight, including the elevated railway structure, surface railway structure, pipes, etc., supported during the work, amounted to about 5,000 tons.
Details of the Work.—The method in general is shown on [Figs. 4] and [5]. At first the east side of the avenue was closed and excavated down to rock, the earth was mined out under alternate yokes of the surface railway structure, and temporary posts were placed under the yokes to support the structure while the remainder of the earth was being removed. Then needle-beams and posts were placed under each yoke. The concrete forming the track structure was then enclosed with planking to prevent it from cracking and falling. I-beams were then placed under the needle-beams carrying the structures, and these were carried on posts; they were changed alternately until the excavation had been taken out to a depth of about 16 ft. below the surface. In placing these I-beams, heavier blocking was used in the center of the span than at the ends where the bents would come, to prevent the subsidence of the track owing to the sag in the I-beams. As much excavation, to a depth of about 20 ft., was taken out adjoining the elevated railway foundations as could be done with safety. [Fig. 2, Plate XLVII], shows this condition of the work. The 48-in. brick sewer was broken, and the sewage was pumped across the excavation.