SYDNEY BRIDGE.

Hokitika Guardian, 30 January 1929, Page 2

SYDNEY BRIDGE.

BUILDING THE ARCH

SOME CRITICAL WORK. During the year which lias now commenced substantial progress will be made in the construction of the great steel arch of the Sydney Jlarboin Bridge, and by the end of the year both the northern and southern portions of the arch arc expected to be protruding a considerable distance across the water, says the “Sydney Morning Herald.” Already about ICOO tons of the arch steel lias 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 —live oil 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 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 vecliile roadway—and two footways. The latter will overhang each side of the structure and each will bo 10ft in width. The approach spans have almost been completed, even to the placing in position of the steel for the foot way.

The southern abutment tower and pylons have also been completed, the top of the former being 285 ft above mean sea level. The actual building of the arch was commenced some time ago on the southern side of the harbour. but it will be a little while before the work on the northern side reaches the same stage. Operations' on tho Sydney side will shortly he retarded to enable the northern abutment tower and pylons to be advanced to a corresponding degree. AYlien the work on both sides of the harbour reaches the same stage the building of the arch will be proceeded with in earnesef, and the organised scheme of tho bridge builders is that the great arch shall Ih> thrown across the harbour at the same rate from each side. That stage will probably be. reached about file middle of the present year, and by the end of the vear the arch will show definite shape.

The placing in position of the 88.900 tons of steel which will comprise the arch is the critical .portion of the big undertaking, and the bridge engineers make no secret oi the fact that the building of the arch will be the most anxious period of the constructional work. Comparatively the building of the approach spans. and, in tact, all the work up to tho present, is regarded, as “child’s play” compared with the construction of the arch. I p to date about 15,000 tons of steel has been erected, the greater portion of it being in tho. approach spans. The fabrication of the steel for the bridge opened up a new era in industry in the State. At the Milson s Point work-shops of Dorman. Long, and Company. Ltd., the .staff is working two shifts daily turning out pieces of steel weighing from 70 tons each up tq 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 ot steel tor the bridge.

A considerable amount of “spade” work marked flic commencmcnt of operations of the bridge, and that was followed by the interesting work of erecting the groat granite piers and the erection of the approach spans. The building of the arch, will constitute the spectacular part of the big work. Travellers by the ferries, and, in fact the majority of residents of Sydney, will follow with interest the throwing out of the steel arch. Creeper cranes will he used to carry 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 nest piece of steel in its appointed place. Thus the structure will ho erected panel by panel to the oolitic of the span. While the two ends of the arch are being built they will he supported by huge steel erection cables—l2B in num-ber—-secured in tunnels 120 ft deep i" the solid rock. The cables are each 2^in in diameter, and each will bo secured to the top of the end posts of the arch. The tunnels are inclined at 45 degrees, and the cables will remain in position throughout the remainder of the cantilever stages of erection. They will lie removed when the arch lias boon completed and “locked.”

At the present time Dorman. Long, and Company, Ltd., employ about 000 men on the bridge works and its various ramifications, including the M»ruya Quarry, from which all the granite for the bridge is being obtained.