Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 3

at the top; each of the outside
tracks is supported on two longitudinal latticed girders and the central
track on two plate girders; between the columns, transverse girders are
spliced to the outside track cross-frames, and carry the central track
system. It was not thought desirable to put brackets on the columns
near the street level to support the structure temporarily, and, as there is
an expansion joint at each column, and as the transverse girders
carrying the central track system are not rigidly attached to the
longitudinal girders carrying the outside tracks, the central track could
not be supported by supporting the outside tracks; therefore,
independent supports for each track, in the form of overhead girders,
had to be provided. The columns rest on brick piers, each having four
2-in. anchor-bolts. The brick foundations on the west side are wide in
order to allow a 24-in. water main to pass directly beneath the columns.
The foundations are usually on rock.
[Illustration: PLATE XLVII, FIG. 1.--TW 4, P.N.Y. & L.I.R.R.
Terminal Station West. View of 9th Ave. looking Northwest from 32nd
Street, prior to commencement of work. April 23, 06.]
[Illustration: PLATE XLVII, FIG. 2.--TW 17, P.N.Y. & L.I.R.R.
Terminal Station West. View of East side of 9th Ave. looking North
from a point 100 feet south of 33rd St. showing condition of work. July
23, 06.]

[Illustration: PLATE XLVII, FIG. 3.--TW 25, P.N.Y. & L.I.R.R.
Terminal Station West. View showing permanent and temporary
supports of 9th Ave. Structures, looking Northwest from 31st. St. April
24, 07.]
[Illustration: PLATE XLVII, FIG. 4.--TW 28, P.T. & T.R.R. Co.
Terminal Station West. East side of 9th Avenue, North of 32nd St.
looking West, showing rock excavation and supports of 9th Avenue
structures. Aug. 17, 07.]
Fig. 1, Plate XLVII, shows the elevated railway structure and the street
surface prior to the commencement of the work.
The east track is used for north-bound local trains, the west track for
south-bound local trains, and the central track for south-bound express
trains between 7 and 9.30 A.M. and for north-bound express trains
between 2.30 and 7 P.M. It is said that an average of 90,000 passengers
are carried over this structure every 24 hours.
_Surface Railway Structure of the New York City Railway
Company._--This is an electric surface railway of the ordinary type, the
rail and slot being bedded in concrete, with cast-iron yokes every 5 ft.
There are manholes every 100 ft., and cleaning-out holes every 15 ft.
Power conduits are bedded in the concrete on the east side of the east
track.
_Forty-eight-Inch Brick Sewer._--This sewer was in the center of Ninth
Avenue, with the invert about 12 ft. below the surface, and manholes
about 100 ft. apart, and had to be abandoned in this position to allow
the transverse girders to be put in place to carry all structures while the
excavation was being done.
_Twenty-four-Inch Cast-Iron Water Main._--This water main was laid
under the west elevated railway columns, with its top about 3 ft. below
the surface, a space being left for it in the brick foundations, and a large
column base casting being used to span it. Valves were installed, one
north of 33d Street and one south of 31st Street, prior to excavating
near the pipe, so that if it was broken the water could be shut off

promptly.
_Street Surface._--It was the original intention to close and excavate
the east side of the avenue and to erect there a street-traffic trestle
before closing the west side, but, at the contractor's request, both sides
were closed, and all vehicular traffic was turned into the center. A light
trestle on the west side of the avenue provided for pedestrian traffic.
_Other Sub-surface Structures._--There were various gas mains, water
mains, electric conduits, manholes, hydrants, etc., in the avenue, and
most of these were cut out temporarily, at the contractor's request, to be
replaced subsequently.
_Supports for Elevated Railway Structure._--As stated previously, the
central track had to be supported independently.
The overhead girders, known as girders "B", were therefore designed as
shown on Fig. 1, and put in place as shown on Figs. 2 and 3. The
outside tracks were blocked directly on these girders, and the central
track was supported by blocking up the transverse girders on I-beams
placed between the girders "B"; and no blocking was placed between
the girders "B" and the longitudinal girders carrying the central track.
The weight on each column was assumed to be 172,000 lb.
[Illustration: FIG. 1. (Full page image)
DETAILS OF STEEL GIRDERS, ETC. SUPPORTING NINTH
AVENUE STRUCTURES]
_Supports for Surface Railway Structure._--A uniform load of 3,000 lb.
per lin. ft. of single track, with the weight of a car at 39,000 lb., was
assumed. Several feet of earth, between the structure and the rock,