Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 6

as shown on Fig. 3, and all temporary
posts under these I-beams were removed. The bents were framed with a
jack, as tightly as possible, and very little settlement of the track
occurred.
A cradle was then built under the 24-in. water main and placed on
girders "C," and, as a temporary footwalk had been constructed on the
west side of the avenue, it will be seen that all structures were thus
carried on girders "C."
All structures were put on the girders "C" before continuing the
excavation on the sides of the avenue because, in case of a slide of rock,
there would be less danger than to individual structures. The outside
piers, on which the girders "C" rested, might even be lost, without
affecting the stability of the structure, and posting could readily be

done beneath these girders in case of necessity.
A very careful record of levels, taken on the elevated railway columns,
was kept, observations being made during each jacking up and at least
twice a week during the progress of the work. The columns were
usually kept about 1/2 in. high so as to allow for compression in the
timber bents.
As a rule, no jacking of the elevated railway structure was done while
trains were passing over, and trains were flagged during the operation.
There was generally very little delay, as all jacking was done between
10.30 A.M. and 2.30 P.M., when the traffic was lightest, and frequently
the jacking was done between trains, causing no delay whatever. Steel
clamps were placed, three on the top and three on the bottom of each
set of the girders "C," to bind them together and cause them to act as a
unit.
All structures then being supported on girders "C," which were carried
on four concrete piers resting on the central rock core, the excavation
on the sides of the avenue was continued down to sub-grade and the
east and west portions of the concrete north abutment were constructed.
The central rock core was about 36 ft. wide on the top and 45 ft. wide
on the bottom, and at the center of 32d Street it was about 42 ft. high.
It was the original intention to excavate a sufficient width of the sides
of the avenue to erect six rows of the permanent steel viaduct, 5 ft.
from center to center, and this was done on the south portion of the
work. On the north portion, however, the rock was of poor quality, and
it was thought best to excavate for only five rows at first, to erect the
five rows of permanent steel and put the timber bents in place under the
ends of the girders "C," in order to give them some support while the
outside concrete piers were being removed and the excavation was
being widened out to permit the erection of the sixth row. Additional
raker braces were put in these bents temporarily, and were removed
when the sixth row of steel had been erected. This is shown on Figs. 4
and 5.
[Illustration: PLATE XLVIII, FIG. 1.--TW 33, P.T. & T.R.R. Co.

Terminal Station West. East side of 9th Ave. looking North from 31st
St., showing rock excavation and supports of 9th Ave. structures. Dec.
28, 07.]
[Illustration: PLATE XLVIII, FIG. 2.--TW 39, P.T. & T.R.R. Co.
Terminal Station West. East side of 9th Ave. looking North from 31st
Street, showing rock excavation and permanent steel work. March 24,
08.]
[Illustration: PLATE XLVIII, FIG. 3.--TW 73, P.T. & T.R.R. Co.
Terminal Station West. West side of Ninth Ave. Jacking up girders "C"
at Elevated Railroad Column 491, showing method of taking weight on
permanent viaduct girders. Nov. 14, 08.]
[Illustration: PLATE XLVIII, FIG. 4.--TW 58, P.T. & T.R.R. Co.
Terminal Station West. East side of Ninth Ave. looking North from
31st St., showing underpinning of Ninth Ave. Structures. Aug. 10, 08.]
Fig. 4, Plate XLVII, and Fig. 1, Plate XLVIII, show the structures
supported on the central rock core and the excavation on the east side to
permit of the erection of the permanent viaduct girders. Fig. 1, Plate
XLVIII, shows also the easterly portion of the concrete north abutment.
Fig. 2, Plate XLVIII, shows five rows of the permanent viaduct girders
erected on the east side of the work.
The excavation of the sides of the avenue having been completed, and
six rows of permanent viaduct girders erected on both sides, timber
bents, as shown on Figs. 2, 4, 5, and 6, were erected on this steel to
support the ends of the girders "C" and carry the structure while the
rock core was being excavated. Fig. 3, Plate XLVIII, shows the method
of taking the weight on these bents. Four 80-ton jacks were used, and
oak blocks were placed on