SYDNEY BRIDGE

Evening Post, Volume CVII, Issue 21, 25 January 1929, Page 3

SYDNEY BRIDGE

BUILDING THE ARCH

SO'iJH CI!ITJGAL "WORK

During the year which has now commenced substantial progress will be made in the construction, of the great steel arch of the Sydney Harbour Bridge, and by the end of tliu year both tho northern and southern portions of the arch are expected to be protruding a considerable distance across the water, says the "Sydney Morning Herald." Already about 1000 tons of the arch steel has been placed in position on the Sydney side of the bridge, but the work on the northern side is not so far advanced. The ten approach spans—five on either side of the harbour —have been virtually completed, and a cross sectional view of the decks of the approach spans now discloses the lay-out' of the traffic arrangements on the bridge. A vehicle roadway 57ft wide, to accommodate six lines of vehicle traffic, will occupy the centre of the deck. There will be four railway tracks —two on either side of the vehicle roadway—and two footways. The latter will overhang each side of the structure and each will be 10ft in width. The approach spans have almost ■ been completed, even to the placing in position of the steel for the footway.

The southern abutment tower and pylons have also been completed, the top< of the former being 235 ft above mean sea level. The actual buildiug of the arch was commenced some time <igo on the southern side of the harbour, but it will be a little while before the work on the northern side readies the same stage. Operations on tlie Sydney side will shortly be retarded to eur.blc the northern abutment tower and pylons to be advanced to a corresponding degree. \ When the work on both sides of the harbour reaches the same stage the building of ' the arclf will be proceeded with in earnest, and the organised scheme o£ the bridge builders is that the great arch shull be thrown across the habour at tho same rate from each side. That stage will probably bo reached about the middle of (.lie present year, and by the end of the year tho arch will show definite shape. The placing in position of the 38,000 tons of steel which will comprise the arch is tho critical portion of the big undertaking, and the bridge engineers make no secret of the fact that the building of the aroli will be the most anxious period o£ the constructional work. Comparatively the building of the approach spans, and, in fact, all the work up to the present, is regarded as "child's play" compared with tho construction of tho arch. Up to date about 15,000-tons of steel has been erected, tho greater portion of it being in the approach spans. The fabrication of the steel for the bridge opened up a new era in industry in the Stale. At tho Milson's I'oint workshops of Dorman, Long, and Company, Ltd., the staff is working two shfits_ daily in turning out pieces o£ steel weighing from 70 tons each up to 220 tons. Nothing of the kind had ever before been attempted in Australia, and the bridge contractors have also established a world's record in fabricating the 220-ton pieces of steel for tho bridge. A considerable amount of "spade" work marked the commencement of operations on the bridge, and that was^ followed by the interesting work of erecting the great granite piers and the erection of the approach spans. The building of the arcli will constitute tho spectacular part of the big work. Travellers by the ferries, and, in fact, the majority of residents of Syd--ney, will follow with interest the throwing out of the steel arch. Creeper cranes will be used to ••arry the street "members" of the arch over, the water, and as each portion of the arch is placed in position the cranes will move forward, on the top of the chords of the arch ready to place the next piece of steel in its appointed place. Thus the structure will be erected panel by panel to. the centre of the span. 1

While the two ends of the arch are being built they will be supported by huge steel erection cables—l2B in number —secured in tunnels 120 ft deep in the solid rock. The cables are each. 2%in in diameter, and each will be secured, to the top of the end posts of the arch. The tunnels are iiicliued at '45 degrees, and the cables will remain in position throughout the remainder of the cantilever stages of erection. They will be removed when the arch has been completed and "locked."

At the present time Dorman, Long, and Company, Ltd., employ about 900 men on the bridge works arid its various ramifications, including the Moruya Quarry, from which all the granite for the bridge is being obtained.