Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 7

the top of each jack to transmit pressure to a
temporary oak cap under the girders "C" independent of the bents; all
four of these jacks were operated simultaneously, and the girders "C"
were lifted off the bents and clear of the concrete piers. Oak filling
pieces were then inserted between the bents and the girders "C," so that
when the jacks were released the girders "C" were clear of the concrete
piers. Fig. 3, Plate XLVIII, shows that the girders have been lifted off

the piers. Elevations were taken on each set of girders during each
operation, and careful observations were made on the elevated railway
columns. Where the rock was very close to these bents, the open space
between the posts was filled with blocking so that there would be less
danger of the bent shifting if struck by blasted materials. Fig. 3, Plate
XLVIII, shows one of these bents filled with blocking.
All structures being carried on girders "C," which, in turn, were carried
on the sides of the permanent viaduct, the central core was excavated.
Fig. 4, Plate XLVIII, and Figs. 1, 2, 3, and 4, Plate XLIX, show various
views of the work at this stage.
The central portion of the viaduct was then erected, and, using concrete
piers and timber bents, all structures were placed on its deck. Fig. 3,
Plate XLIX, shows the piers under the elevated railway columns prior
to the removal of girders "C."
[Illustration: FIG. 6. (Full page image)
GENERAL ARRANGEMENT OF TEMPORARY AND
PERMANENT STRUCTURES]
During the latter part of 1908 a 48-in. cast-iron water main was laid by
the city on a cradle built by the Railroad Company on girders "C" on
the east side of the avenue. This is part of the high-pressure system, and
the location and elevation of this water main were taken into
consideration when the underpinning was designed. This main, and the
48-in. cast-iron sewer bracketed to girders "C," are shown on Fig. 4,
Plate XLVIII.
Elevations had been taken on marks on the elevated railway columns
between 30th and 34th Streets at the time the original surveys were
made, in 1902, and these marks were used to test the level of the
structure during the progress of the excavation.
At the extreme south end of the work the procedure was changed. The
east side was excavated down to sub-grade, the east portion of the south
abutment was constructed, and six rows of the permanent steel viaduct

were erected. Very little excavation had been done on the west side of
the avenue at the south end of the work, and it would have delayed the
completion of the work to have waited for the excavation for and the
construction of the west portion of the south abutment and the erection
of the steel; therefore, instead of supporting the girders "C" on the
central rock core, the east ends were taken up on the permanent viaduct
girders, and the west ends were supported on a concrete pier on the
rock. The central portion of the avenue was excavated in advance of the
west portion. The permanent viaduct girders were put in place from
east to west across the avenue, and the girders "C" were supported on
the deck of the permanent viaduct approximately under the west
elevated railway columns before the west portion of the avenue was
excavated, the central portion of the south abutment having been
constructed before the west portion. This procedure was adopted only
at the north girders "C" at elevated railway column No. 488, the south
set of girders "C" being on the rock immediately south of the south
abutment. Figs. 2 and 4, Plate XLIX, and Fig. 2, Plate LII, show
various stages of the work at the south end.
[Illustration: PLATE XLIX, FIG. 1.--TW 60, P.T. & T.R.R. Co.
Terminal Station West. Under Ninth Ave., looking South from North
abutment, showing underpinning and excavation of rock core. Aug. 13,
08.]
[Illustration: PLATE XLIX, FIG. 2.--TW 84, P.T. & T.R.R. Co.
Terminal Station West. View looking toward Ninth Ave. from South
side of 31st St., 200 feet West of Ninth Ave. Jan. 28, 09.]
[Illustration: PLATE XLIX, FIG. 3.--TW 88, P.T. & T.R.R. Co. N.R.
Div. Terminal Station West. Center line of 32nd St., looking East from
Sta. 183+50, showing excavation under Ninth Avenue, permanent
concrete piers under Elevated Railway Columns and removal of
temporary shoring girders "C". April 8, 09.]
[Illustration: PLATE XLIX, FIG. 4.--TW 95, P.T. & T.R.R. Co. N.R.
Div. Terminal Station West. View under Ninth Avenue looking
Southward from 100 feet South of center line, showing underpinning of
Ninth Avenue structure taken at sub-grade. May 25, 09.]

It was made a practice all through the work to transfer the weight of the
structures very positively from one support