REMARKABLE STRUCTURE

New Zealand Herald, Volume LXIX, Issue 21136, 19 March 1932, Page 11

REMARKABLE STRUCTURE

MEMORABLE OCCASION. GREAT ENGINEERING FEAT. HISTORY OF THE PROJECT. COST OF £10,000,000. To-day is to be a red-letter day ill the history of the Commonwealth of Australia in general and of Sydney, its greatest city, in particular. With all the pomp and ceremony befitting such an occasion, Sydney's magnificent harbour bridge, tho largest arch bridge in the world, will be opened, and tho dream of over a century, * shaped in steel, concrete and granite, will be realised. The story of Sydney's harbour bridge is far more than a prosaic account of a gigantic engineering undertaking; it is a romance of industry. It has its link with the old pioneering days. Auckland has been debating the proposal of a Waitemata Harbour Bridge for some years new; Sydney discussed the scheme for 100 years before a plan was finally accepted and a start made with the work. A proposal to erect a bridge across Sydney Harbour was first put forward as far back as 1815 by Mr. F. H. Greenway, Government architect. Forty-two years plater, a Sydney engineer, Mr. Peter Henderson, presented the first recorded drawing <if a bridge designed to connect the northern and southern shores. First Definite Action. Th 2re is an interesting historical sidelight on this scheme, as Mr, Henderson had served his engineering apprenticeship in the English workshops of George Stephenson, builder of the first locomotive. It is a far cry from the bridge that he designed to the magnificent structure that now spans one of the finest harbours in tho world —just as far as it is from Stepnenson's first railway engine to the electric locomotives which will soon be pi'ov.ding transport for thousands of people daily across Sydney Harbour. In th 3 years that followed other bridge proposals were put forward, and although all were allowed <to sink into comparative oblivion they played their part in stimu- • lating public imagination and bringing ever nearer the day when a bridge would have to be built in answer to an insistent . public demand. The first definite action was taken by the late Mr. E. W. O'Sullivan, Minister of Works in New South Wales in 1900. He called for competitive designs and tenders, but after mature consideration the 24 schemes submitted were rejected. In the following year, Mr. O'Sullivan appointed an advisory board and from new des:.gn;i and tenders the board recommended the acceptance of that of J. Stewart and Company for a bridge from Dawes Point to McMahon's Point, estimated to cost £1,940,050. A change of Government came shortly after, and the ' scheme died a political death. Authority for Work. Some years later a proposal iwas put forward for the construction of subways, bu > on July 19, 1911, a definite pronouncement was made to the effect that the Cabinet had decided on a bridge for tramway, vehicular and pedestrian traffic and on a subway for railway communication. It w«is at this stage that Di\ J. j. C. Biadfield, designer and chief engineer of th.3 present bridge, first submitted proposals;. He advised the Government that. the bridge, as then proposed, would con-" stituta a menace to navigation and was given permission to forward counter-pro-pcsal.';. Dr. Bradfield looked into the future; ho foresaw the age of mammoth ocean liners ard in his plans took that into consideration. High water clearance was fixed at 173ft.—35ft. more than the clearance upder the Brooklyn and other bridges in New York and 20ft. in excess of the clearances under the Forth Bridge and Canada's great Quebec bridge. In 1913 the Public \\ orks Committee recommended the adoption of one of his three schemes, but the matter became a political bone of contention until September, 1922. when a bill authorising the building of the bridge passed both Houses of Parliament. Great Task Commenced. Preparations for building the bridge now began in earnest. In 1923. tenders were called from all over the world, and on March 24, 1924, the tender of Dorman, Long; and Company, Limited, for a twohinged arch bridge was accepted by the Government. The ceremony of turning the first sod had 1 been performed by the Hon. R. T. Ball at North Sydney on July 23, 1923; in March, 1925, Mr. Ball set the foundation stone of the southern abutment tower at Dawes Point; this morning, at ten o'clock, the Premier, Mr. J. T. Lang, will perform the official opening ceremony on. the southern approach. Those seven years between March, 1925, and March, 1932, saw an industry spring uji which gave employment to thousands of Australian workers. While the preliminary work on the actual site of the bridge was set in train, a host of other matters also engaged the attention of the engineers. A large granite quarry was opened and equipped at Moruya to siupply the 20,000 cubic yards of masonry needed for the facing of the piers and pylons of the bridge. Three ships were built at tho New South Wales Government dockyards to transport the stone to Sydney,. Hugo workshops were Orected near v the bridge site to attend to mechanical and steel work actually on the soot. All this time the preliminary work on the bridge itself was proceeding steadily. By September, 1926, piers were built ready to receive the approach span steelwork. Slowly, this great mass of huge steel girders projected from either side of the harbour, until, on the afternoon of August 4, 1930, the two arms met and the gap was closed. The next problem was the erection of hangers to support the bridge deck. The longest hangers were 193 ft. and weighed 38 tons. Within nine months of the closing of the arch, the steelworl^,.erection of tho deck of the main arch was completed and then, with the roadway concreted and other incidental work rounded off, the bridge was ready for ■ testing. Features of the Bridge. Figures connected with the bridge are of more than passjng interest. There is a span of 1650 ft. and, although this is 25in. shorter than the recently completed Kill Van Ivull Bridge in New York, the Sydney bridge "is 160 ft. wide, as against tho other's 90ft., arid its arch contains 37.000 tons of steel as against 16,000 tuns. Tho Sydney bridge contains in all 52,300 tons of steel and of this over 14.000 tons was supplied by Australian steelworks. Besides being the largest and heaviest arch-type bridge in the world, the Sydney bridge is also the widest bridge of any kind and with the exception of the recently opened George Washington suspension bridge in New York has the highest clearance of any bridge in the world. Inclusive of approaches, the total length is 2J miles. The total cost of the work was approximately £10,000,000, the actual construction cost being £6,250,000. Tho bridge has been designed to carry a tremendous traffic stream. Provision is made for four lines of railway, roadwav for six lines of vehicular traffic anu two footwalks, each 10ft. wide. When the bridge is working at maximum capacity, 128 electric trains, 6000 vehicles and 40,000 pedestrians will be able to cros» in an hour.