Website Banner. John Monash: Engineering enterprise prior to World War 1.

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Davies's Bridge, Creswick
re-decking with Monier plates

Raising and re-decking of bridge over Creswick Creek, Creswick, March-April 1900. Known to Monash & Anderson as Davies Bridge and as Maughan's Bridge. Photo: University of Melbourne Archives, BWP-23883. A larger image has Record ID UMA/I/6361.

In January 1901, Monash & Anderson were part way through construction of Wheeler's Bridge in the Borough of Creswick when Anderson learned that the Borough Engineer, George Maughan, was designing new decking for a road bridge across Creswick Creek. The bridge was situated in a low-lying part of the town, and carried the main road from Ballarat to the region beyond Clunes and Daylesford. Its main structural members were iron girders which supported a timber deck now badly in need of replacement. Anderson pointed out that a Monier reinforced concrete slab would be an ideal solution, with a footpath supported on brackets projecting sideways from the main girders.

Maughan, who was also Town Clerk, called tenders on 20 January for "re-decking road bridge, 56 ft x 33 ft wide, in steel, concrete, or a combination of both", thus opening the way for reinforced concrete. One of the borough councillors complicated the issue by suggesting that the iron girders should be replaced by a Monier arch in order to allow more waterway and relieve the flooding that occurred when water backed up behind the current bridge. However, M&A went ahead with a formal quotation for re-decking at £290.

On 29th Monash, on a visit to the area, heard "local rumour" that M&A's tender had been "reserved for consideration" which usually meant referral to the Department of Public Works for approval. Monash asked Anderson to call on the Chief Engineer of the PWD, Carlo Catani, to press the matter.

Maughan now sent a proposal for a Monier arch bridge to M&A, with a detailed drawing of the existing bridge. M&A expressed surprise that the abutments were less substantial than appeared at first sight, consisting only of four counterforts surrounded by facing. They declared the site unsuitable for a Monier arch and recommended that the Borough adhere to its current plans.

Additional arguments against adoption of an arch are included in the technical notes below.

Nevertheless, the arch proposal maintained momentum. The Creswick Advertiser reported on 10 February that consideration of tenders would be delayed for a month to allow Maughan to refine his proposal. He believed that the arch would cost only £100 more than the re-decking project, and that £50 of this could be recouped by selling the iron girders for use elsewhere. He argued that prior flooding in Albert Street made an arch highly desirable. However, on 24th he telegraphed M&A to say that their tender for re-decking had been accepted. This was officially confirmed on 2 March.

With work on Wheeler's Bridge nearing completion, M&A's foreman James Buick moved to Davies's Hotel at Creswick, conveniently situated at one end of the bridge. Preliminary work commenced on 12 March 1900. After the old deck had been removed, some practical-minded ratepayers living upstream of the bridge presented a petition urging that the iron girders be lifted by a distance of two feet (610mm) in order to provide more waterway beneath them. On 16th, Monash spent the entire day in Creswick, and it was probably then that he agreed to take on this task. He was unprepared to quote a firm figure, but offered to do it for actual cost plus 12.5%. A Council meeting held that evening accepted the petition and approved the additional work. Monash told Buick that P J McGrath, a mason who had proved his worth on other M&A projects, was "a really good man" who would know how to lift and pack the girders.

The Council meeting was reported in the Creswick Advertiser of 20 March 1900.

Monash called at Creswick again several days later, and in mid-April toured the district, calling on J T N Anderson and his brother Jack, who were engaged on a mining project and were very ill with what was suspected to be typhoid. He was present in Creswick on 20 and 21 April for the casting of the reinforced concrete deck. On 8 May, he declared M&A's contract complete. He was in Creswick once more on 13 June for the load test of the bridge deck.

While the M&A team were in Creswick they completed a small dairy at the back of Davies's Hotel.

Creswick Council was unusually generous in giving prominence to M&A on the memorial plaque which read: "Erected in 1869, and re-decked in April, 1900, by Monash and Anderson under the Monier system." Beneath this appeared the names of the Borough Councillors and the Engineer, Geo. Maughan.

Technical notes re Davies's Bridge, Creswick

M&A's main argument against a Monier arch was as follows. Taking the present road level and allowing 2 feet (610mm) for the thickness of the crown of the arch plus the road, and 1'-6" (457mm) clear from the springing to the bed of the creek to allow for centring and wedges, the rise could not exceed 8 feet in a nett span of 50 feet. Although this would be "very proper" for a Monier arch under favourable foundation conditions, in this case the rock was over 19 feet (5.79m) below the crown of the road and the angle of thrust of the resultant on the skewback would mean that the abutments would have to be at least 14 feet (4.27m) thick to keep the thrust within the middle third. To this would be added the cost of removing the existing abutments. Hence the abutments alone would cost £550.

This was still very early days in Monash's and Anderson's acquaintance with reinforced concrete. Gummow Forrest & Co of Sydney, holders of the Monier licence for Australia, sent advice on the design of Monier beams and plates, and reports on tests carried out by themselves for the NSW Railway Department, and by Professor Warren of Sydney University. GF&Co wrote: "Concerning the calculations of beams or plates, it is unnecessary to trouble you with the theories, but [we] forward you a practical formula which we regularly use, and which we find gives results quite accurately enough for all general purposes … If a large area is to be covered, it requires closer consideration and calculation in order to provide a construction which is able to compete with other materials. We find that in the larger construction, the judicious separation of the space into girders and plates is the main point, as that portion of the plate adjoining the girder is then taken into consideration as it very materially assists the girder, and therefore affects the dimensions of the latter." They emphasised that M&A must keep the formula secret.

The road deck was 8" (203mm) thick in the centre and 6" (152mm) thick at the edges, and spanned laterally 7'-6" (2.29m) between adjacent main girders. It was designed for a uniformly distributed load of 25 cwt per lineal foot (40.9 kN per lineal metre) in the longitudinal direction. The cantilevered footpath was reinforced with old railway rails buried in the concrete of the main deck and projecting sideways, bent upwards slightly at their ends to allow the underside of the cantilevered portion to taper. The high relative cost of cement in those days is indicated by the specification which called for a 1:3 mix of cement and sand in the lower 3 inches (76mm) of the slab, and 1:5 in the upper portion. The specification called for a grid of bars ¾" (19mm) above the underside of the slab with 3/8" (10mm) bars in the lateral direction and ¼" (6mm) in the longitudinal direction.

The test load was a 15 ton (15.2 tonne) road roller.

Wallen Road Bridge, Hawthorn
re-decking with Monier slab 1905
(formerly known as "Swan Street Bridge")

Re-decking of bridge over Yarra, Hawthorn, May 1905. Photo: University of Melbourne Archives, GPNB-1095. Another image has Record ID UMA/I/6506.

In October 1904, the City Engineer for the Melbourne suburb of Hawthorn, George Kermode, was preparing to replace the old timber deck on the bridge linking Swan Street (Richmond) with Wallen Street over the River Yarra. Monash suggested the use of a reinforced concrete slab. Kermode's response was positive, but he pointed out that the deck would be required to support the council's 15-ton roller. The bridge had been erected in 1881, and after making calculations, Monash found that it would be "very risky to test with this Roller, so far as concerns cross girders". The problem would not be the new deck, but the strength of the old iron.

For the history of the Wallen Road Bridge, search under that name on the Victorian Heritage Database. To support his case, Monash asked the Engineer of Creswick for a testimonial regarding a similar project carried out at Davies's Bridge, Creswick, in 1900 (see this web page, above).

Kermode called tenders on 4 March 1905, permitting quotations for either timber of reinforced concrete decking. Gummow Forrest & Co, principal representatives for the Monier system in Australia assisted with the calculations. The "Final Calculations" show a deck 6½" (165mm) thick.

Due to an informality, it was necessary to call fresh tenders on 6 April. The contract was awarded to Monash's Reinforced Concrete & Monier Pipe Construction Co, and the deck was ready on 15 May. However, the bridge remained closed to traffic for some time after this, leading to complaints by the adjoining Richmond Council. These were reported in the The Argus as relating to the "Monier Bridge" even though all but the deck was made of iron. RCMPC's managing director, John Gibson, was obliged to write pointing out that RCMPC had completed its contract on schedule (Trove).

Kermode then left his position at Hawthorn to join the Public Works Department and was replaced at Hawthorn by William Parker. Parker persisted with demands for a load test, although Monash remembered explaining the situation to him shortly after the change-over. In September, Monash told Gibson: "I still have an objection to allowing a heavy steam roller on this bridge, because if any injury were done to the cross-girders it is certain that the reinforced concrete work would get the blame". Parker seems to have later agreed to a test with a lighter load, but it appears that it was never carried out. As late as March 1914, RCMPC was obliged to defend its position, telling the Council that they had not opposed a test; that they had been paid for the job; and that if the test had not happened, it was not their fault!


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