1930 Public Works Department Annual Report.
Sydney Harbour Bridge Branch.
Report for the year ended 30th June, 1930.
I have the honour to submit the following report on the work of this Branch for the year ended 30th June, 1930:-
I. — CONSTRUCTION OF THE NORTHERN APPROACH BY THE SYDNEY HARBOUR BRIDGE BRANCH.
On account of the Curtailment of loan expenditure, very little work was carried out upon the northern approach.
(a) Excavation.
A total of 3,770 cubic yards was excavated, the main item being the south abutment of the 220-feet steel arch bridge.
(b) Concrete Work.
The concrete poured amounted to 11,930 cubic yards, the chief items being the piers and flat top construction for the viaduct fronting Junction-street, between Arthur-street and Alfred-street.
(c) General.
The widening of Broughton-street was carried out, an area of 1,414 square yards being penetrated and seal coated.
Rendering of the concrete arches and retaining walls was continued throughout the year.
Incidental works such as waterproofing, fencing, kerbing and guttering, and the laying of drains were also continued throughout the year.
II. — CONTRACT OF DORMAN, LONG AND COMPANY, LTD.
(a) Concrete and Masonry.
The year ended 30th June, l930, has differed considerably from the previous twelve months in the class of construction which has been carried out.
Previously all substructure efforts had been concentrated on the erection of piers for the approach spans and on the construction of the abutment towers to a height sufficient for that purpose also. During the twelve months just completed, however, the erection of the main arch has been the dominant factor of construction. and substructure work has been intermittent and only carried out at such times as did not interfere either with the drawing of the anchorage cables and their attachment to the arch or with the erection of the arch itself.
At Dawes' Point, the masonry facing on the front of the abutment tower has been completed from R.L. 92.5 to final levels. This had been held up for some months whilst the raking struts from panel points 29 on the arch to the pylon were in position.
Similarly, the masonry facing on the back wall was held up whilst the anchorage cables were being drawn but this now been completed except for a small section which cannot be started until after the cables are removed.
The side walls which were nearing completion at the commencement of the twelve months under review were finished to the main slab level (R.L. 155.50) at the end of 1929, and further construction was held up until all the anchorage cables were attached to the arch, as the cranes were required for this work and could not be released to erect the timber towers on the steel deck and for their transference to these towers for further construction of the pylon.
When the cranes did become available, these towers were started, but further delay was caused as the final approved plans were not completed.
In May, I930, a start was made with the construction of the pylons, i.e., above R.L. 15.5.50, and this work is now progressing well. The work is of cellular construction consisting of masonry walls concrete backed with reinforced concrete slabs tying them together and includes the heavy ornamental masonry balconies corbelled out from the side walls and the masonry arches through which a footway and one railway track pass. The method of construction adopted is to set the masonry before placing the concrete backing so that the erection vertically will not be as rapid as it was below R.L. 155.50 where the concrete shell walls were constructed first and the masonry shell built afterwards.
On the eastern side, construction is now to the level of the top of the balcony and on the western' side it is not quite as far advanced. The anchorage cables do not permit of any construction on one internal corner of each tower for the present, and these sections are being left until the cables are removed in a few months.
At Milson's Point, the construction of the pylon is not as far advanced as at Dawes' Point for the reason that the cranes were required till a later date for work incidental to the arch erection, and at the end of June, 1930, R.L. 155.50 was the limit of construction. The masonry facing has been built to this level with the exception of a small section in the front which until recently was in use for the base of the,
raking struts to the arch.
The timber towers for final construction of the pylon have been erected, and one of the two cranes is in position on top of them. These cranes, which are of the Scotch derrick type, have been, both at Dawes' Point and Milson's Point, converted from steam to electric drive on account of the difficulty of supplying; water and fuel to the high levels.
The following are the quantities for the masonry and concrete work during the year:—
No. 1 concrete 3,107 cubic yards.
Granite masonry 2,216 ,,
Four-cut work on granite masonry 13,819 square feet.
(b) Fabrication of Steelwork.
During the year, 5,074 tons of carbon steel were delivered at Milson's Point, of which 3,521 tons were rolled in England and the balance of 1,553 tons rolled at Newcastle by the Broken Hill Proprietary Co., Ltd. The total silicon steel delivery during the year amounted to 11,409 tons, all rolled in England.
The total steel and bronze delivered to date is 48,900 tons, which is almost the whole of the material required.
There were 4,025 gallons of shop paint and 3,124 gallons of field paint delivered, the totals to date now being, shop paint, 11,760 gallons; and field paint, 3,124 gallons.
The rivet deliveries now total 2,425 tons, of which 633 tons were delivered during the year.
During the twelve months, 17,966 tons of steelwork were fabricated—an average of approximately 1,500 tons per month — comprising practically the whole of the northern half-arch and nine panels of the southern half. In addition, the anchorage link plates for the northern aide were completed and a number of stages for erection and field riveting purposes fabricated.
The first hanger webs were assembled on June 10th, 1930, and riveting of these commenced on June 16th.
The graph herewith shows the quantities of material delivered, fabricated, erected in place and completely riveted since the first steel delivery.
(c) Erection of Steelwork.
At the commencement of July, 1929, erection was proceeding on the third panel on the southern side, whilst preparations were being made for the commencement of the erection of the main span on the northern side when the material for the first length of bottom chord 28-28X was ready for erection.
A start was made with the erection of the main span on the north side on 22nd July, 1929, and by the 30th June, 1930, eleven panels had been erected.
On the south side the erection was carried forward from the third panel to the first triangle of the twelfth panel by the end of June, 1930. A halt was made on the erection when the first triangle of the eighth panel had been erected on 21st January, 1930. and a resumption was not made until 72 days later, when the erection of the southern cantilever was continued.
During the suspension of construction for 72 days at the eighth panel on the south side, the fourth, fifth, sixth, seventh and eighth panels were erected on the north side, thus balancing the progress made up to date on both sides.
The attached diagram shows the progress of construction at each three-monthly period from 30th. September, 1926.
(d) Painting.
South Side. — A start was made with the painting of the first field coat on span No. 1 on 14th August, 1929, and the approach spans were completed up to the first three panels on the fifth approach span on 13th March, 1930, when the painting of the southern half-arch at panel point " 27 " of the first panel was commenced.
By the end of the year, painting was proceeding on the third panel of the arch.
The painting of the outside surfaces of the top and bottom chords has been omitted until such time as the painting cranes are in operation. The inside surfaces of these chords, however, for the first three panels are being painted. i
The top and bottom lateral diagonals, truss verticals and diagonals in these panels have received their first field coat.
No painting was done on the main arch during June 1930 as the painters had been taken back to complete the last three panels of span No. 5, the painting of which at the end of the month was almost completed.
North Side. — A start was made with the painting of the first field coat on the northern approach spans at span No. 6 on 23rd September, 1929, and by 30th June, 1930, the application of the first field coat was completed up to the fifth panel of span No. 10.
The painting of the northern half-arch was commenced during April, 1930, and at the end of June painting was proceeding in the third panel.
The top and bottom lateral diagonals, truss verticals and diagonals in these panels have received their first final coat. The outer surfaces of top and bottom chords have been omitted pending the bringing into use of the painting cranes. The interior surfaces of the top and bottom chords, however, of the first three panels are being painted.
3. CONSTRUCTION OF THE SOUTHERN APPROACH BY THE SYDNEY HARBOUR BRIDGE BRANCH.
As on the northern approach, the work was seriously curtailed on account of reduced loan expenditure.
(a) Excavation.
A total of l5,512 cubic yards was excavated, being chiefly the abutments for Argyle-street arch and the excavation for the railway track tunnels between Grosvenor-street and Argyle-street.
(6) Concrete Work.
The walls, roof, drains and floor, and waterproofing protection constituted the main items of the concrete' work. The 57-feet arch and the western half of the 64-feet arch were also poured during this financial year.
The total quantity of concrete poured was 21,442 cubic yards.
(c) Waterproofing.
A total area of 9,168 square yards was waterproofed, 7,407 being by fabric waterproofing, the remainder by mastic waterproofing.
(d) General.
A total area of 5,710 square yards of protective brickwork was laid for the waterproofing. In addition to the various incidental works, a temporary bridge was erected over the Argyle-street arch abutments and a cable tunnel constructed through the site for the new Scots' Church.
4. FINANCIAL REVIEW.
(a) Land Tax.
To defray one-third of the capital cost of the construction and land resumptions and provide for the maintenance and lighting of the railways and footways of the Sydney Harbour Bridge and approaches from Waverton Station on the northern side of the Harbour to Wynyard Station on the southern side, a land tax of one half-penny 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, Kuring-gai and Willoughby, the shire of Warringah and portion of the shire of Hornsby.
The tax was first imposed in 1923, the rates for the years 1923-30 are as shown on table appended. Of the amount of £1,286,948 15s. 11d. due to 30th June, 1930, a total of £103,368 13s. 8d. was paid to the special deposit fund, leaving a balance of £183.580 2s. 3d. to be paid before 31st December, 1930 Interest upon the amounts received from the rate levy is calculated on the daily balance.
The table shows the details of rates due since the tax was first imposed, the payments to 30th June, 1930, and the balance outstanding at that date.
(b) Expenditure.
The total expenditure to 30th June, 1930, is shown in the following table. The cost to date of the bridge and approaches, including land resumptions and all other charges, is £6,463,943 8s. 7d., of which interest on expenditure is £683,315 1s. 10d.. and resumptions, £1,212,360 10s. 11d., but a large proportion of the latter amount, if not the full amount, will be recouped by the disposal of the residues upon the completion of the bridge.
It will be seen that the wages variation to date on the contract of Dorman, Long & Co., Ltd, is slightly less than 12 per cent, of the amount paid for construction. This percentage is higher than previously on account of the greater margin above ordinary award wages due to the men being engaged up on the main span.
Rate Levy - Payments and Outstanding Amounts at 30th June, 1930
Sydney Harbour Bridge Expenditure to 30th June, 1930.
5. STAFF.
The number of men employed on the Sydney Harbour Bridge and Approaches at 30th June, 1930, was l,654, employed as under:—
Approaches, Public Works Department 390
Civil Engineering, Dorman, Long &, Co., including those at Moruya 219
Workshops at Milson's Point (three shifts) 764
Erection of steelwork {including Painters) 284
Total 1,654
J. J. C. BRADFIELD,
Chief Engineer, Sydney Harbour Bridge
7th November, 1930.
