Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 4

were
mined out, and the structure was supported on I-beams and posts, and
ultimately on the transverse girders by using timber bents under the
I-beams, as shown on Fig. 3.
_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.
[Illustration: FIG. 2. (Full page image)
METHOD OF SUPPORTING ELEVATED RAILWAY
STRUCTURE]
[Illustration: 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.
The overhead girders "B" were then put in place, and two of the girders
"C" were used as temporary shoring girders at each column. These, as
shown by Fig. 3, Plate XLVII, were placed parallel to the elevated
railway, with blocking between them and the girders "B." Double bents,
independent of each other, were placed under the ends of these
temporary shoring girders, and these were braced securely to prevent
possible dislodgment during the removal of the rock. The weight of the
structure was then taken by jacking up the girders near the bents until
the column was lifted off the old foundation; blocking was put in
between the girders and the bents during the jacking, so that when the
jacks were released the base of the column was still clear of the old
foundation. One 80-ton jack was used for this purpose, and the general
method is shown by Fig. 1, Plate LII.
[Illustration: FIG. 4. (Full page image)
METHOD OF EXCAVATING NINTH AVENUE PLAN AND
ELEVATION SHOWING VARIOUS STAGES OF THE WORK]

[Illustration: FIG. 5. (Full page image)
METHOD OF EXCAVATING NINTH AVENUE SECTIONS
SHOWING VARIOUS STAGES OF WORK
No. 1
Condition Prior to Commencement of Work
No. 2
East side of Avenue cut down about 20 ft. Beams with Supporting
Posts placed under Surface Railway Tracks. Girders B and Temporary
Shoring Girders C for supporting Elevated Ry. in place.
No. 3
I's in place under Surface Ry. Tracks. Elevated Ry. carried on
Temporary Shoring Girders, and Girders C in place. 24" Water Main
carried on Timber Cradle and