1928 Public Works Department Annual Report.
Sydney Harbour Bridge Branch.
Report for the year ended 30th June, 1925.
I have the honor to submit the following report on the work of this Branch for the year ended 30th June, 1928:—
I.— CONSTRUCTION OF THE NORTHERN APPROACH.
(a) Tunnels.
The excavation had been completed previously and work was confined to completing the concrete lining of the Down Mosman tunnel flyover, 771 cub. yds. of concrete being poured.
(b) Open Cut Excavation.
The principal excavation works were the abutments for the Burton-street and Fitzroy-street Arch Bridges, foundations for retaining walls, &c.
The total quantity of excavation work carried out on the Northern Approach was 21,832 cub. yds-
(c) Concrete Work.
A large amount of concreting was carried out, the chief items being the completion of the Arthur-street Arch, Fitzroy-street Arch, abutments of Burton-street Arch, pier foundations near Kirribilli Station and several large retaining walls.
The arch ring of the Fitzroy-street Arch contained 2,122 cub. yds. of concrete, and was poured in nine working days.
The total quantity of concrete placed in position was 31,680 cub. yds, and the number of bags of cement used was 112,420.
(d) Demolition of Property.
Practically all resumed property has now been demolished; during the year thirty-seven properties were sold for demolition, the total receipts being £1,799.
(e) General.
There were many incidental works carried out, the chief items being 2,861 lineal feet of fencing, stone crushing, erection of poles for power lines, rehandling and placing in permanent position spoil from tunnels not required for stone crushing, quantity estimated to be 59,561 cub. yds.
The average number of men employed throughout the year was 214.
II. — CONTRACT OF DORMAN, LONG & Co. LTD.
(a) Excavation, Concrete and Masonry.
The construction of the Southern Approach spans was completed, and on the northern side of the Harbour the whole of the Approach Spans, except the steelwork for Span No. 10.
The Moruya Quarry has been the deciding factor in the construction of the main abutment towers. The output of masonry and concrete aggregate was not sufficient to carry on the construction of both towers simultaneously at full speed, consequently Dawes Point abutment tower was taken to R.L. 155-50 before the wails of Milson's Point tower were commenced.
The level R.L. 155-50 is as high aa the towers can be built until the main arch span is nearing completion. At this level a reinforced concrete floor has been constructed between each outside and adjacent inner wall which will be utilised for the erection of the steel ramp and creeper crane, and also as a platform for the placing of the cable anchorages.
The granite facing has: progressed steadily as supplies came forward from the Quarry, and as cranes could be made available, and on 30th June had reached R.L. 73-00. This work will be carried to R.L. 155-50 whilst the arch is being constructed across the Harbour. The granite facing is 12 inches thick and is fixed to the concrete walls by steel cramps spaced at 6 feet centres in each course, the space between the concrete and the granite being filled with concrete.
Very little work had been done on the Milson's Point abutment tower during the latter part of 1927 on account of the whole output of aggregate from the Quarry being required at Dawes Point. Since the Dawes Point abutment tower has been completed to R.L. 155-50 good progress has been made with the abutment tower at Milson's Point. The remainder of the wall foundations were taken out and concreted, and the walls at the back are now only a few feet below where the sliding bearings for Span No. 10 will be placed. To set the bearings as soon as possible so that Span No. 10 may be completed, the back wall has been advanced ahead of the front wall, and as soon as the bearings are placed, the front, side and internal walls will all be brought to the same level and then carried up together, as was done with Dawes Point abutment tower.
The main bearings at Milson's Point, each weighing 296 tons, were concreted in position towards the end of 1927, thus completing the bearings on both sides of the Harbour.
No masonry had been set on the Milson's Point abutment tower prior to July, 1927, but during the year under review all the large stones to R.L. 41-50 have been placed in position.
At Dawes Point the anchorage tunnel has been concreted and the reinforced concrete saddles for the change of direction of the anchorage cables at the entrances are in course of construction. At Milson's Point the tunnel is completed and shortly the concreting will be commenced.
The following are the quantities of excavation, concreting and masonry carried out during the year:—
Earth excavation 805 cubic yards.
Rock excavation 1,826 „
No. 1 concrete 36,791 „
No. 2 concrete 666 „
Granite masonry 3,639 „
Four cut work on granite masonry 22,215 square feet.
The piers and abutments of the approach spans have now been completed, and the final quantities at schedule rates show a saving of £91,439 19s. 8d. on the contract.
The retaining wall around Hickson-road on the eastern side of the Southern Approach spans was completed during the year. This was not in the contract, but was carried out at the contract schedule rates.
(b) Fabrication of Steelwork.
During the year there were 6,295 tons of carbon steel delivered at Milson's Point, of which 4,061 tons were rolled in England and 2,234 tons at Newcastle by the Broken Hill Pty. Co. Ltd., and in addition there were delivered 3,084 tons of silicon steel rolled in England.
To the end of June, 1928, there were 19,300 tons of material delivered to the workshops.
During the year 650 tons of rivets and 3,288 gallons of paint were delivered to the workshops.
The fabrication of the first arch member was commenced on 13th March.
The largest rivets in the main arch are 1⅜ in. diameter, the shanks being 15 in. long. The holes for these rivets are 17/16 in. diameter and the maximum grip 12 in. These rivets arc the largest ever used in bridge construction and are driven with an 80-ton hydraulic riveting machine. These large rivets are heated to a bright orange colour, viewed in direct sunlight, then carefully scaled and dipped in water to a depth of about 4 inches until the ends of the rivets were a dull red and then driven.
To expedite the fabrication of the steelwork of the main span, a second shift was commenced in the fabricating shops on 7th May, and at the end of June 58 men were engaged on the second shift, while 407 were employed on the day shift.
The total weight of steelwork fabricated during the year was 8,096 tons, bringing the total to 13,049 tons. The highest monthly output was 1,117 tons for August, 1927, when fabrication of the Northern and Southern Approach spans was being carried out. More recently the shop output has decreased owing to the commencement of the fabrication of the main arch members. This work is of a much heavier nature than that previously encountered and the amount of preparatory work before the complete assembly of the finished member involves much time and labour.
The graph herewith shows the quantities of material delivered, fabricated, erected in place and completely riveted since the first delivery.
(c) Erection of Steelwork.
The erection of the five Southern Approach spans was completed on the 9th February with the exception of deck riveting.
The erection of the Northern Approach was continued, and during the year Spans 6, 7, 8 and 9 were completely erected and three panels of Span No. 10 had been completed up to 25th May, when work on the Northern Approach was temporarily suspended. It was not possible to proceed further with the erection of this span until the back wall of the pylon had reached the proper level for the sliding bearings.
The total tonnage erected during the year on the North and South Approaches amounted to 8,822 tons.
The attached drawing shows the position of the construction of the main bridge at intervals of three months from 30th September, 1926, up to 30th June, 1928.
On 14th March, 1928, a commencement was made with the erection of the South Pylon steelwork, which was completed ready for the creeper crane ramp on 28th April.
During the year the main bearings on the Northern side were completely erected, the four main bearings now being complete.
III. — CONSTRUCTION OF THE SOUTHERN APPROACH.
During the year work has been augmented and is now proceeding over the whole section from the south end of Dorman, Long & Co.'s contract to the north end of Wynyard Station.
(a) Tunnels.
The double track tunnel for the Shore local tracks under Jamieson-street was completed, while the double track tunnel for the Shore tracks was partly excavated and a commencement made with the concreting.
Both of these tunnels are in poor rock, having little cover, consequently heavy timbering was necessary.
During the year 5,699 cubic yards of excavation and 749 cubic yards of concrete lining were completed.
(b) Excavation.
The total quantity of excavation was 86,136 cubic yards, the principal items being the Jamieson-street to Grosvenor-street cutting, 11,6.32 cubic yards, the Grosvenor-street to Essex-street cutting, 26,083 cubic yards, and between Argyle-street and the end of the contract, 35,658 cubic yards.
(c) Concrete Work.
The cut and cover work on the new Scots Church site was completed, and the site was ready for the Scots Church authorities on 30th June, 1928, as promised. Excluding the tunnel lining there were 5,488 cubic yards of concrete poured and the number of bags of cement used being 26,228.
(d) Alterations to Existing Services.
Several water mains, including the 12-inch and 10-inch mains in Grosvenor and York streets, were deviate and capped clear of the cuttings.
Telephone cables in conduit across Grosvenor-street were replaced by aerial lines.
Several gas mains were deviated and removed from Grosvenor-street.
Electric light aerial and underground cables were deviated.
Where thought desirable the Sydney Harbour Bridge Branch collaborated with the various authorities and carried out excavation work, back filling of trenches, recovery of old mains, &c.
(e) Demolition of Property.
During the year 190 properties were sold for demolition, the total receipts being £5,218.
(f) General.
The whole of the girder reinforced roof under the new Scots Church site was waterproofed with bituminous sheeting, total area 1,123 square yards.
A considerable amount of temporary fencing was carried out, total length 3,870 feet.
Around the Hickson-road retaining wall the kerbing and guttering was completed.
A drinking fountain, erected by the City Council in 1857, was removed to the grounds of the Fort-street Girls' High School.
The average number of men employed during the year was 184, while at the end of June there were 248.
IV.—FINANCIAL REVIEW.
(a) Land Tax.
To defray one-third of the capital cost of the land resumptions and construction of the Sydney Harbour Bridge and Approaches, a land tax of one halfpenny in the pound was imposed upon the unimproved capital value of all rateable land within the city of Sydney, the Municipalities of North Sydney, Mosman, Manly, Lane Cove, and Willoughby, the Shires of Warringah and Ku-ring-gai and portion of the Shire of Hornsby.
The tax was first imposed in the year 1923; the rates for the years 1923-28 are as shown on table appended. Of the amount due to 30th June, 1928, £720,683 8s. 7d. was paid to the Special Deposit Fund, leaving a balance of £183,098 2s. 7d. to be paid before 31st December, 1928.
Interest due is calculated on the daily balance, and from 1923 to 30th June, 1928, a total of £64,478 27s. 5d, has been credited to the rates account as interest.
The table shows the details of the rates due since the tax was first imposed, the payments to 30th June, 1928, and the balance outstanding at 30th June, 1928.
(b) Expenditure.
The total expenditure up to 30th June, 1928, is shown in the following table. The total cost of the Bridge and Approaches, including land resumptions, interest on construction, and all expenditure prior to 1st July, 1923. is £3,348,908 6s 5d.
It will be seen that the wages variation to date on the contact of Dorman, Long & Co. for the main bridge and ten steel approach spans is slightly greater than 9 per cent. of the total amount paid to the contractors for construction.
V. — SCHEME FOR IMPROVEMENT OF TRAFFIC AVENUES.
With the consent of the Minister, I gave evidence before the Traffic Advisory Committee and submitted various schemes for the improvement of the existing traffic avenues and for the establishment of additional ones to provide for the increased traffic consequent upon the completion of the Sydney Harbour Bridge. All the schemes submitted were favourably reported upon by the Traffic Advisory Committee.
Among the schemes was the provision of a roadway above the Quay Station to carry traffic from the Bridge Highway to Macquarie-street, thus providing a direct outlet from the Bridge to the eastern side of the City. This scheme was strongly recommended by the Traffic Advisory Committee.
VI. — STAFF.
The number of men directly employed on the Sydney Harbour Bridge and Approaches as at 30th June, 1928, was approximately 1,450. Dorman, Long & Co. employ 240 at Moruya Quarry, and in transporting material from Moruya to Sydney; about 700 are employed in placing concrete and masonry, fabricating steelwork in the workshops and in erecting the steelwork, whilst some 500 men are employed on the construction of the Approaches under the Public Works Department.
As reported at various times, great difficulty has been experienced in obtaining suitable draftsmen. During the year there have been several resignations, draftsmen leaving to get higher salaries.
Applications have been repeatedly called, but it was found not possible to obtain suitable men in New South Wales because of better salaries offering elsewhere, whilst Graduates in Engineering of the University of Sydney can apparently do better outside the Public Service. The result has been that draftsmen have been brought from Victoria, South Australia, and in one case from Tasmania.
I desire to thank the Superintendent of Stores, Mr. Peterson, and his staff for their co-operation and assistance in the work of this Branch, whilst the work of the Bridge Branch Staff has been carried out thoroughly and efficiently, and I wish to place on record my appreciation of their work during the year.
J. J. C. BRADFIELD,
Chief Engineer, Sydney Harbour Bridge.
16th October, 1928.
