Page:Forth Bridge (1890).djvu/41

Rh {| cellpadding=4
 * +| All Figures for Concrete and Rubble in Cubic Yards—for Granite in Cubic Feet


 * rowspan=2 colspan=5 |—
 * colspan=2 |Foundations.
 * colspan=4 |Granite Masonry Piers.
 * rowspan=2 |—
 * rowspan=2 |—


 * |Concrete.
 * |Rubble.
 * |Concrete.
 * |Rubble.
 * |Granite.
 * |Freestone Bond Courses.
 * |Freestone Bond Courses.


 * colspan=5 |South Viaduct.
 * rowspan=10 |
 * rowspan=10 |
 * rowspan=10 |
 * rowspan=10 |
 * rowspan=10 |
 * rowspan=10 |
 * rowspan=10 |
 * rowspan=10 |


 * Pier No.||1|| ... || ... || ...
 * |246
 * |nil
 * |42
 * |314
 * |5526
 * |not stated
 * |not stated


 * 2|| ... || ... || ...
 * |176
 * |nil
 * |322
 * |318
 * |5591
 * |1793
 * |1793


 * 3|| ... || ... || ...
 * |151
 * |nil
 * |413
 * |607
 * |10002
 * |3425
 * |3425


 * 4|| ... || ... || ...
 * |73
 * |nil
 * |540
 * |607
 * |10002
 * |3392
 * |3392


 * 5|| ... || ... || ...
 * |72
 * |nil
 * |622
 * |607
 * |10002
 * |3513
 * |3513


 * 6|| ... || ... || ...
 * |80
 * |nil
 * |685
 * |607
 * |10002
 * |5912
 * |5912


 * 7|| ... || ... || ...
 * |228
 * |nil
 * |936
 * |607
 * |10002
 * |5993
 * |5993


 * 8|| ... || ... || ...
 * |320
 * |nil
 * |973
 * |607
 * |10002
 * |5946
 * |5946


 * 9|| ... || ... || ...
 * |706
 * |nil
 * |973
 * |607
 * |10002
 * |5987
 * |5987


 * colspan=4| South Cantilever End Pier || ...
 * | 2167
 * | 295
 * | 1753
 * | 3420
 * | 43984
 * | 39078
 * | 162 of blue brick
 * | 162 of blue brick


 * colspan=5 |North Viaduct.
 * colspan=5 |North Viaduct.


 * colspan=4| North Cantilever End Pier || ...
 * | 205
 * | nil
 * | 774
 * | 2320
 * | 32944
 * | 17305
 * | 37 of blue brick
 * | 37 of blue brick


 * Pier No.||10|| ... || ... || ...
 * |69
 * |nil
 * |90
 * |598
 * |11610
 * |not stated
 * rowspan=4 |
 * 11|| ... || ... || ...
 * |52
 * |nil
 * |130
 * |611
 * |11814
 * |611
 * |11814


 * 12|| ... || ... || ...
 * |273
 * |nil
 * |304
 * |508
 * |11756
 * |1954
 * |1954


 * 13|| ... || ... || ...
 * |340
 * |nil
 * |419
 * |610
 * |11789
 * |1019
 * }
 * }

other end were used. When the girders had been raised to a point above the cantilever pier and the abutment (as far as these had by then been built) the two ends were joined on, and the completed girders raised up to their final position. The first lift of these girders was made about the middle of October, 1885, to level 42 ft. above high water, and the last lift to level 130 ft. 6 in. above high water on February 15, 1887.

The connections of the permanent way on this viaduct with that on the cantilever at one end and with that on the masonry arches at the other end are made by means of expansion joints, identical with those used at the fixed ends of the Fife and Queensferry central connecting girders, and fully described in connection with the latter.

On the Queensferry shore, owing to the rising ground between pier 3 and the south abutment, the girders had also to be built at different levels, and were only joined when the various portions had arrived at the same level. The seven spans from pier 3 to south cantilever end pier were all built on staging erected between the piers, and rising to a few feet above the masonry, in order to allow the lifting rams and lifting girders to be placed between piers and viaduct girders.

Piers 3 to 5 had been brought up to level 18 ft. above high water early in January, 1884, pier 6 in March, 1884, pier 7 in October, 1884, pier 8 and cantilever pier in February, 1885, and pier 9 in June, 1885. The delays which occurred were due to difficulties and to a larger amount of work in connection with the construction of the cofferdams and the building of foundations and lower portions of these piers; but so soon as any of them were completed, the staging between was built, and a start made with the erection and rivetting of the viaduct girders. Thus it was possible to have everything ready and to commence lifting early in the month of May, 1886.

Piers 2 and 1 had in the mean time had their foundations laid and their masonry raised to about 43 ft. above high water, while the abutment on top of the hill was raised to 115 feet above high water.

For the purpose of raising the viaduct a box girder of great strength, about 22 in. deep; 2 ft, 6 in. wide, and some 24 ft. in length, was placed directly under the girder end-posts—that is, along the centre of the piers. During the raising of the girders temporary connections had been made between girders at those places where expansion and contraction could take place. Immediately under each main girder a hydraulic ram, 14 in. in diameter and 16 in. stroke, was inserted in the box girder, and was made a fixture in it. There was thus a length of girder of about 3 ft. outside each cylinder for packing. All the cylinders were connected with force-pumps, which could produce a pressure of 35 cwt. per square inch, the pumps being placed within the bottom booms of the viaduct girders, which were completely decked over and used as a road, being fenced on each side, and having two narrow-gauge lines laid down on it, during the time of lifting. Round each pier a timber platform was suspended from the girders, so arranged that its planking could be brought up close to the masonry as the piers diminished in size with the ascent. On this platform—which is clearly shown in Plate VIII.—were also stowed the hardwood packings and other necessaries for the lifting work. All these things put a great deal of extra weight on the girders, but as neither buckle-plates nor wind-fence had been put on as yet, the weight did not greatly exceed that of the finished girders. The mode of procedure was as follows: Hardwood packing in slabs of varying thickness, from 1 in. up to 12 in., was placed under the girders in two or three places, and by means of long wedges, one worked from each side, every lift was closely followed up to prevent sudden drops, should the hydraulic presses give way. When a lift of 1 ft. had thus been made, the girder was packed and the ram was fleeted—that is, drawn back into the cylinder—and a hardwood block with a strong steel plate on top was underlaid and a further lift made.

At first it was attempted to raise the whole mass of over 1400 tons at once on all points, but this was not found to work very well, and it was then arranged to work 3 in. at the time only, and lift on each pier in succession. No accumulator was used,but the pumps were just kept going until the girders were up. As a rule the lifts were of 3 ft. 6 in. at the time for two courses of masonry, but at times a foot more or so was done, according to requirements.

With the last lift on each occasion the packing was so arranged as to occupy the least room upon the masonry last done, and the masons then at once proceeded to set the granite facing and build the rubble backing in every place that they could get at, taking good care to leave the work so as to make sufficient bond with the remainder. After allowing forty-eight hours for the setting of the new work, the weight of the girders was shifted on to packings laid on the new work, and the remaining of portions the two or three courses, as the case might be, were then built in. After due allowance for the setting of this work also—another forty-eight hours generally—a fresh lift was made.