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.
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.
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 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."
