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

[Introduction.]   [Main JM Index.]  [Bridges Index.]  [People Index.]
[Abbreviations.] [Units & Currency.] [Glossary.]

Maribyrnong Bridge (1911-1967)

Caption. Maribyrnong Bridge, linking the City of Essendon to the Shire of Braybrook, 1911. University of Melbourne Archives, Image No. GBNP-1107. I believe this shows the north side, looking east. For details of other images of this bridge and its predecessor, see Appendix A below.

Overview

This bridge was built across the Maribyrnong River (formerly the Saltwater River) to link the City of Essendon and the Shire of Braybrook. The route was named Maribyrnong Road on the Essendon side and Raleigh Road on the Braybrook side. Monash's bridge replaced a timber structure dating from 1870 that had been in a dangerous condition for years. The new bridge had five spans, each nominally 40 feet (12.2m) in length. The Councils were willing to pay for more styling and ornamentation than is to be seen on most of Monash's bridges. Essendon Council took responsibility for running the project through its Engineer, W Murray Pullar.

Monash was asked in November 1906 to provide a preliminary estimate of cost, but some councillors thought the old bridge should be repaired, and debate dragged on until March 1909. Proposals for replacement in reinforced concrete firmed early in 1909. By mid-year, Monash and his staff had prepared a design with four spans and an estimated price of £3566. The drawings were submitted to the Councils under Pullar's name, and after renewed debate accepted. The Minister for Public Works promised to contribute half the cost provided the Councils supplied the rest. The design and computations were approved by the engineers of the Public Works Department, and tenders called. No serious competition was offered, and RCMPC was appointed as contractor in December 1909.

As usual, Monash had planned to sink the foundations of the river piers during low water in the summer months (January and February 1910). However at this stage the Chief Engineer of the PWD, Carlo Catani, was appointed acting Inspector General. He was concerned that, despite serious flooding in 1906, people had since been allowed to erect buildings on the river flats. In order to increase the opening available for the passage of flood water, he ordered that an extra span be added to the bridge and that the deck should be higher. This resulted in further debate within the councils, while Monash prepared a new design under his own name, and the PWD produced an alternative design in steel.

With all parties anxious to get the project under way before the winter rains, the councils sent deputations to Parliament and Monash arranged with Pullar to see Catani. They hammered out a scheme in which Monash trimmed his own design in several ways, one of which was to use timber rather than reinforced concrete piles under the western abutment. He and John Gibson appeared at a joint conference of both Councils, at which this proposal was accepted at a price of £3806. It was agreed to align the piers with the flow of the river, as a result of which they were no longer square to the deck of the bridge.

There was a initial confusion over the exact placement of the bridge, but Monash's view triumphed. In March 1910, as materials were being ordered, he sailed from Melbourne for a long-planned overseas tour to last six months. Construction work was therefore supervised by his senior assistant engineer, P T Fairway. There was further, serious delay when it was found that the rock surface, which occurred at reasonable depth below Piers 1 and 2, dipped steeply away under Pier 3. The foundations for this pier were taken down to extra depth, then flared (belled) out at the bottom to rest on hard clay. The first spans were cast in July, and the last in October. The Councils agreed to extend the contract deadline by a total of four months, to allow for the difficulties experienced. Monash returned to Melbourne in November 1910 when only the finishing touches remained to be done. Yet more delay was caused by a strike of plasterers, and Monash broke ranks with other employers in order to have the bridge finished. Pullar conducted a heavy load test in February 1911, and the bridge was opened to traffic with a simple ceremony on 16 March.

Monash's bridge and an adjacent tramway bridge were demolished when the alignment of the road was improved in the 1960s. The co-ordinates of the Monash bridge were approximately -37.769850, 144.901557.

Detailed History

Initial concept, November 1906

The first contact regarding this bridge between Pullar and Monash recorded in the RCMPC files was in November 1906. Pullar sent a sketch plan of the old timber bridge and his suggestions for aligning the new bridge so as to improve the approach curves. Monash proposed five spans of 37'-6" (11.43m) at an estimated cost between £2500 and £3000. This was subject to investigation of strata below the river bed. Monash assured Pullar that reinforced concrete would compete with timber or iron, as long as the ornamentation was minimized - "as it would have to be if building in timber or in plain metalwork plate girders or trusses". He concluded with his established sales pitch about the advantages of reinforced concrete compared with competing materials.

Pullar met with his Essendon councillors and announced that he had the matter "in trim". He asked Monash for a preliminary drawing of the proposed bridge, and photographs of the Lancefield and St Kilda St bridges, to present to the next meeting of the Braybrook Council.

Municipal deliberations, 1906

The two councils formed a Maribyrnong Bridge Conference for the purpose of reaching joint decisions. In his written report to this body, Pullar condemned the present timber bridge, which had been built in 1870 with the financial assistance of the local meat company. It was not safe for the heavy traffic that now used it. It had a distinct permanent sag and high deflection under load. The large number of piers and their cross-bracing reduced the flood discharge and interfered with boating. A new bridge on a different alignment would improve the approach curves. Pullar advised that a new timber bridge with three Howe trusses would cost about £1500. However, he argued against this option because of expected heavy quarry traffic, and the possibility that the tramway system might be extended over the new bridge. Under these circumstances a timber bridge might last 20 years. Assuming maintenance to cost £25 per year, the capitalized cost would be £3000. A steel lattice girder bridge with stone abutments would cost between £6000 and £8000, assuming typical foundation conditions. In contrast, a reinforced concrete bridge with three spans of 50 feet each would cost between £2500 and £3000. Pullar cited Monash's existing bridges at Elsternwick and Lancefield, and recommended the latter as a suitable model.

The joint conference adopted Pullar's suggestion. It recommended that the State of Victoria be asked to contribute two-thirds of the cost and that, as the North Melbourne Electric Tramway Company would benefit from the project, it should also be asked to contribute. The Shire of Braybrook, at its December 1906 meeting agreed to this, provided the full width of the bridge was increased from 25 feet (7.62m) to 35 feet (10.7m).

Municipal deliberations, 1907-1908

In March 1907, matters had moved little further. Cr Spong of Braybrook deplored the fact that Essendon had not shown more interest. The nearby Maribyrnong settlement had been subdivided, and all blocks allotted. Many people would settle there, and each house built would cost at least £300. Rateable benefits would accrue to Braybrook only, but Essendon would share in the general advantage. Cr Walden regretted that council had not taken up an offer by the Railway department to sell several girders for bridge construction which would have been suitable. It was resolved, on the motion of Crs Spong and Collins, that the Essendon council be asked to report on its progress.

There was a surge of interest in January 1908, when the Councils of Footscray and Williamstown asked Braybrook to co-operate in a push to have the electric tramway extended from Ascotvale over the River at Maribyrnong, on through Maidstone to Footscray, and then on to Williamstown. This would necessitate a substantial bridge over the river.

In February, the Braybrook and Essendon councils proposed to approach Premier Sir Thomas Bent and the Minister for Public Works, to offer to pay £500 each, if the State Government would provide £2,000 towards the £3,000 cost of a Monier bridge. They argued it was unlikely that the Electric Tramway Company would help, as its headquarters were in far-away London. However, the City of Footscray was prepared to invest heavily in the tramway corporation. Cr Caldecott predicted the tramway would popularise closer settlement at Maribyrnong, and cause the long stretch of uninhabited country between Maribyrnong and Footscray to be converted into an immense residential area, housing thousands of families. Cr Mullenger was in favour of borrowing £10,000 to invest in the scheme. However, further consideration was deferred pending the deputation to the Premier. A certain W. Pullar, jun., described as ex-acting secretary of the Shire of Braybrook, was disparaged for having said that the scheme was a "wild cat one".

Negotiations dragged on. In October 1908, the proprietors of sand pits at Maribyrnong complained that pieces of planking falling from the old timber bridge had hit one of their barges, seriously injuring the bargeman. However, the Braybrook secretary and shire engineer, P Lingford countered that the timbers had probably been dislodged by the barge striking the bridge.

Municipal deliberations, early 1909

At their March 1909 meeting the Braybrook Council, reminded once again of the condition of the old bridge, agreed to contribute £875 towards the £3000 cost, if Essendon agreed to contribute the same amount, and the State Government agreed to provide £1500. Alert to occasional reports in the press, Monash asked Pullar what was happening. Pullar replied that the Braybrook Council had "come into line", but he thought "the Maribyrnong Bridge is still a dream". On the other hand, Essendon Council had bought a quarry on the far side of the river, and all their stone traffic would come from there. This might push things along.

By this time, a 5-ton limit (5.08 tonnes) had been put on the bridge, although contractors moving wooden houses on trucks had been known to remove the handrail posts and take 15-ton loads across. The Essendon Gazette of 8 April reported that the timbers were rotten, and the bridge was a danger to life and limb. Quoting Scripture, it declared that constant repairs were like putting new wine in old bottles. The deck deflected an inch under the weight of one man. Two carts caused it to "sink" by one to two inches (25 to 51 mm). "It may be argued that this 'spring' is advisable, and a necessary buoyant safety valve", but one day it would not spring back. "Then probably there will be a holocaust of human beings, horses, loads of stone and falling timbers in the deep waters beneath." Continued neglect was foolhardiness, and tempting Providence. Lives should no longer be imperilled.

The Gazette also reported that a deputation to the State Treasurer, W A Watt, had proposed that the councils share half the cost, and the State the other half. It appears that a simultaneous deputation called on Bent, whose government had recently been defeated. Bent was encouraging but pointed out that other councils would benefit from the bridge, and should be expected to contribute. Stone from the quarries would be conveyed to the City of South Melbourne and for export to South Australia. The bridge also led from Essendon to land allocated for the closer-settlement scheme and to the Federal Government's cordite factory. The deputation included representatives of several of these interested councils, but they offered only moral support. Pullar showed 'his' drawings to Watt, and "suggested that one of the latest Monier bridges be erected". The estimated cost had by now become £3500, for a version with only two piers, and spans of 50 feet (15.2m).

Commencement of detailed design, May 1909

At last, in May 1909, the Minister of Public Works and the Treasurer gave Pullar the signal to prepare drawings. Typically, after almost two-and-a-half years of deliberation, the drawings were expected to be ready within a month. Although Monash, with his assistants, was to carry out the actual work of design, he allowed Pullar to publish the drawings under his own name, so that he would not be deprived of the normal fee as a consultant. However, the contract documents were drawn up in such a way that competing contractors could tender upon them. The cylinder piles that supported the piers (see drawing below) could be formed from either cast-iron or Monier pipe cylinders. Only the position and arrangement of reinforcement was indicated on the drawings - it was up to contractors, or whatever consultants they might employ, to calculate in detail how much reinforcement was required. (Their submissions would be subject to the approval of the PWD.)

Design was delayed while Monash waited for Pullar to make sub-surface investigations. On 10 June he announced "I have practically decided to adopt four spans". He asked Pullar to set out the bridge on the ground, take levels in the vicinity of the abutments and wingwalls, and drive bores in the river at the sites of the piers. Layers of silt, blue clay, and yellow clay were found, with a rock surface lying apparently at a reasonable depth. By the end of the month Monash had sketch drawings ready, and an estimate of £3566. It is possible that Pullar drew the contract drawing following sketches prepared in Monash's office. The PWD approved the drawing, on condition that details of reinforcement be submitted later.

When the Braybrook Council saw the drawing, they protested that it did not show the proposal agreed upon by the joint conference. They objected to an awkward curve in the approach road on the west bank, and suggested the bridge be located 20 feet (6.1m) further downstream. Monash, through Pullar, responded that this would place the south-west corner of the bridge in deep water, requiring much more concrete and the use of a cofferdam. It would increase the cost by between £200 and £300. Braybrook gave way. This cleared the way for the calling of tenders.

Tenders, late 1909

Tenders were called on 28 October, returnable on 22 November, so that work could start in the early summer. By this time, the Minister had authorised a grant of £1,750 to each of the two Councils, subject to ratification by Parliament, with the two Councils each expected to contribute a similar sum.

Monash was so confident that his was the only firm capable of delivering top quality design and construction in reinforced concrete - and that Pullar knew this - that he offered the city engineer a few hints on how he should answer queries from potential competitors. As the deadline neared, Pullar told Monash that few people had looked at the plans, and "the only ones worthy of attention" were Minahan Bros, who seemed uninterested in tendering, and H R Crawford, whom Monash described in his notes as "the Engineer who poses as a Reinforced Concrete expert, and who has recently put up Sniders and Abrahams Building in Drury Lane". Crawford had spent several hours studying the drawings and asked some questions. He thought the time allowed for completion was too short, and saw the sinking of the cylinders as a challenge. He had seemed to seriously consider tendering, but had not returned. Monash noted: "So far as I know, Mr Crawford has not access to any capital, but his possible competition ought not to be ignored". However, he resolved that if Crawford had not returned by the morning of 22nd, he would not reduce RCMPC's tender from £3566.

The Sniders & Abrahams building is still extant at 7 Drewery Lane, Melbourne.

A joint Conference of the two councils decided to award the contract to RCMPC, pending formal ratification. Pullar duly asked Monash to supply full details of the reinforcement, to be forwarded to the PWD for approval. Monash furnished a confidential list, rather than a complete working drawing. He explained: "As we are adopting the plain round bar reinforcement, as already shown upon your drawings (but not figured) it will not be necessary to supply fresh drawings, but merely to state the dimensioning of the rods in the several parts of the structure. It is to be understood that these data are supplied for the confidential use of yourself and the Public Works Department in checking the design, and are not to be used otherwise. The particulars given hereunder are the minimum quantities proposed to be used, but we reserve the right to use larger diameters, or closer pitch, if the market supply or other conditions make such a change desirable."

Ratification

It was not until 14 December that Pullar sent official confirmation of RCMPC's success. Reports in The Age and Argus newspapers on 15th show that his claim to have prepared the drawing was tested in the Braybrook Council meeting. Cr. McKay complained also that lack of reinforcement details had made it practically impossible for more than one contractor to tender. He successfully moved that Pullar's fee of £87 for preparation of plans and supervision of construction be struck out of the estimates. However, he was to be compensated for "incidental expenses". The Council also refused to accept the tender until the PWD had sanctioned the entire process. Additional items had by now brought the contract price to £3750, with each council expected to contribute £1000. McKay proposed the money be borrowed, and repaid by a rate of fourpence in the pound.

Monash wrote in reply (via the Town Clerk of Essendon) that RCMPC had never promised to provide precise details of reinforcement on the drawing. These had been left open to allow contractors to insert whatever patented form of reinforcement they had at their disposal. "The information furnished in these plans and specifications was in every way sufficient, both for the purposes of tendering, and for the execution of the work on the part of all persons or firms who are accustomed to this class of construction."

While all awaited the approval of the PWD, the Braybrook Council evidently demanded that it be a party to the contract. Monash protested that "it would involve very serious complications for us to enter into a contract with two separate Councils, as there would be divided control and responsibility". The contract should be with one Council only and RCMPC thought it should preferably be Essendon. (Nevertheless, the contract document preserved in the RCMPC files carries the seals of both councils and the signatures of both sets of principal officers.)

Late in December, Monash ordered the first material to be used in the bridge, and strengthened the deck to support a 24" (610mm) water main for the Melbourne & Metropolitan Board of Works, adding a further £46 to the price.

Unexpected intervention by the PWD

At this stage, January 1910, came a surprising intervention from the PWD. Approval for the current scheme had been granted under the direction of its elderly Inspector General, William Davidson, who had just commenced six months' leave of absence. Chief Engineer Carlo Catani, now Acting IG, took the opportunity to make improvements. As reported in the Argus, his first objection was that the new bridge would be little longer than the existing structure, which had been a serious obstruction to the record flood of 1906. Damage to property would be much greater in future, as the Government had sold off much of the river flat, and buildings had been erected. Catani required the addition of at least one more span, to widen the gap between the abutments by at least 40 feet (12.2m). Secondly, the proposed level of the bottom of the girders would have been two feet below the 1906 flood. In a future flood, floating debris striking the girders could damage the layer of concrete covering the reinforcement, permit rusting, and perhaps even rip out the steel rods. Catani required the deck to be raised by the necessary amount. Thirdly, the bridge was planned to cross the river at a skew of about 20 degrees, with the piers aligned at right angles to the deck. This meant they presented an unnecessarily large impediment to flood discharge, as well as to pleasure craft. Catani wanted the piers aligned with the flow of the river. In a move which may have been intended to push deliberations in a certain direction, Catani had his PWD engineers produce designs conforming to his requirements in both concrete (at an estimated cost of £4,166) and steel (with three spans, at a cost about the same as Monash's proposal).

Note. This summary of Catani's objections is based on a report in The Argus of 26 January, p.9.
A photograph showing the 1906 flood at the site of the bridge may be seen on Picture Victoria. If Catani's design in steel was like the one he prepared for the Anderson St Bridge, it would not have been injurious to Monash's hopes. In that case the steel design was based on inelegant trusses, and obviously less preferable than the Monier design.

At the next meeting of the Essendon Council it was claimed that Monash's current proposal would in fact provide twice the waterway of the timber bridge; and that renegotiation of the contract would mean that work could not start before the winter rains set in. An extra span on the Braybrook (west) side would place the abutment further back than the Anglers' Arms hotel frontage and subject it to the full force of any flood waters. The mayor, town clerk, and Pullar were deputed to contact State Treasurer Watt and urge prompt action to resolve the issue.

At a hastily organised meeting with Pullar and Catani, Monash proposed two compromise schemes. The first was to add an extra span of 40 feet to the east end. The east abutment, thus placed further from the river, could be built without a pile foundation. To further minimise cost, the piles to support the west abutment could be of timber rather than reinforced concrete. The architectural treatment of the handrails, newels and parapets could be simplified; and a cheaper road surface applied. With these savings, a five-span bridge would cost only £219 more than the present proposal, making a total of £3785. Monash also offered, without cost, to introduce an upward curvature to the deck, thus raising the level in the centre by 2 feet (610mm). His second proposal was to make provision for the addition of an extra span on the east end at a later date. With the same savings as above, the price would be £3400. Monash noted in a private memorandum that these estimates included an item "General Savings", which was "based upon the promise of Mr Pullar that in view of the hasty manner in which these estimates were prepared, and the matter negotiated, we would have an entirely free hand to make whatever savings we could throughout the whole of the structure, by cutting down proportions wherever we liked, provided we did not impair the efficiency and appearance of the structure".

Catani proved reluctant to abandon the "aesthetic adornment", which was part of a beautification scheme for the locality. (See also Anderson St Bridge.) Monash therefore suggested that a compensating saving be made by increasing the upward curvature of the deck to three feet. With this concession, the increase in price would be kept to £240. Catani committed the PWD to grant £120 and Pullar agreed to approach the Councils for £60 each.

Note. The increase in upward curvature of the deck partially (and only nominally) met the requirement for greater waterway beneath the deck without raising the level of the tops of the abutments, thus saving a considerable amount of concrete in the associated retaining walls.

Further deliberation ends in sealing of the contract

With this understanding, Monash reminded the Essendon council that it was almost two months since his tender and deposit had been lodged, and two months of fine summer weather had been lost. He warned them that if the contract was not settled within a further two weeks, he would be compelled to withdraw the tender, or insist on extra money and time to allow for river work in autumn and winter. The town clerk replied that it would be necessary for a joint meeting of the two councils to ratify the new proposal, and this could not happen before 16 January 1910. On 14th, the Braybrook council passed unanimously a motion declaring "That this council is in favour of the construction of an iron bridge as recommended by the Public Works department and agrees to tenders being invited for same, or for alternate tenders being invited for a concrete bridge, subject to a suitable waterway and alignment."

Both Monash and Gibson attended the joint conference. According to the Argus, it was Catani who overcame the reluctance of Braybrook, and "eventually broke down all objection". The drawing showing the revised alignment of the piers carries the same date of 16th, and the signatures of Pullar and the respective council officials. The tender was accepted with an increase in price of £240, making a total of £3806. It included all the cost-saving modifications previously agreed. The piers and abutments were to be set at a skew fixed by Pullar. The upward curvature was to be only two feet, but the abutments were to be one foot higher than in the original tender. The alignment was also to be slightly altered. The Mayor of Essendon and the President of Braybrook assured Monash that he could start work without fear of further changes and that Pullar was to be in complete and sole charge of construction.

Note. Argus, 18 February 1910, p.5.

The official contract, incorporating the amendments, was signed by both Councils on 21 February 1910.

First steps in construction

Caption. Half-elevation of the final scheme for the bridge, as shown in a drawing prepared on 15 April 1910. The view is taken at right-angles to the deck. The piers, which are aligned with the direction of flow, are seen at an angle. Both pillars and the cross-beam are revealed. (See also sketch plan below, showing alignment of girders and piers.) J Thomas Collection.

Monash's assistant engineer J A Laing met Pullar at the bridge site to set out the plan; but found they were working to different notions of alignment and level. Monash won the ensuing debate, and took the opportunity to choose an angle of skew whose cotangent was exactly 3. This made the measurements much simpler for the workmen building the formwork. On the strength of this verbal understanding he signed the contract documents.

Note. Monash calculated the resulting angle of skew as "about" 18°-26'-10".

Turning to detailed design, he noted that the superstructure would be very similar to that of his Benalla bridge which had just been tested on 18 February. He therefore contemplated increasing the number of main girders to six, on five-foot (1.52m) centres, with a 2'-6" (762mm) overhang. "As the Benalla girders … have proved satisfactory, adopt these in toto as the circumstances are practically identical … Location of cylinders can be arranged thus:-"

Caption. Monash's sketch showing the benefit of his choice of angle of skew. The girders are indicated by dotted lines. The distance between the centres of the piers, measured at right-angles to the deck, is 18 feet (5.49m). The piers are offset by exactly 6 feet (1.83m) in the direction of the girders. (University of Melbourne Archives, Reinforced Concrete & Monier Pipe Co. Collection, File 830.)

"Length AB will be nearly 19'-0" [5.79m]. If Pier Shaft measures 2'-6" [762mm] along line of pier, the net span of Transverse Girder will be 16'-6" [5.03mm], & it will be loaded thus:-"

Caption. Monash's sketch to calculate the bending moment in the pier cross-head, due to the weight carried by the girders. Although this sketch models the cross-head as having zero depth - a limitation of the hand-calculation methods of the time - he took advantage of the curved "corbels" (see drawing below) to reduce the theoretical span. (University of Melbourne Archives, Reinforced Concrete & Monier Pipe Co. Collection, File 830.)

Having settled the dimensions of the transverse girder, Monash noted: "care must be exercised, in concreting same, to get monolithic connection with deck-system; it is the Benalla case again, but much more critical". He then calculated the loads exerted on the two pillars and decided that 2% reinforcing would be adequate, but "the Pillars of the piers require rather careful design". Next day he issued a requisition to the factory for materials for the bridge.

By now Monash was getting ready to leave Melbourne for a six-month round-the-world tour combining business and pleasure. His senior Assistant Engineer, P T Fairway prepared to step into his shoes.

Fairway contacted H Hyatt, of Blakeville, who tendered successfully to supply 96 stringybark piles about 30 feet (9.14m) long for temporary staging. Another source was found for 17 ironbark piles, "of superior quality for permanent work", 18 to 20 ft long (5.49 to 6.10m).

The stringybark piles were required to have a minimum diameter of 8" (203mm) at the toe, and 12" (305mm) at the head. For the ironbark piles, the requirements were 12" and 15" respectively (305 and 381mm).

The final scheme adopted for the bridge is slightly different from Monash's, involving five main girders and two smaller outer girders, as shown below. It was probably adopted by Fairway while revising the computations.

Caption. The final scheme for the cross-section of the bridge, as shown in the drawing prepared on 15 April 1910. Also shown is the architectural treatment of the edge of the pier. (J Thomas Collection.)

Work begins on site

Work was already underway early in April, when Pullar observed that a pile being driven for the western abutment was not showing the resistance required by the specification. A hammer drop of five feet (1.52m) had caused it to penetrate 2 inches (51mm). Fairway replied that the pile in question had not yet reached its full depth, and he was sure that the penetration per blow would decrease to the specified figure by the time it was fully driven.

On 15 April 1910, J A Laing completed what seems to have been the definitive (working) drawing of the bridge.

By June the cylinder piles were being sunk, with a diver employed to excavate under water. Pullar asked what steps would be taken to assure him that they had reached a sufficiently firm base. It was agreed that it would be RCMPC's responsibility to ensure that they reached rock; but that Pullar would be free to check for himself. According to RCMPC's 'as built' drawing, the cylinders for Piers 1 and 2 met rock earlier than expected. However, the cylinders for Pier 3 were taken to a depth of 32'-6" (9.91m) below Low Water, meeting only hard clay. Probing with steel rods showed no sign of rock, so the excavation was belled out below the end of the cylinder to a diameter of 7'-0" (2.13m) and filled with concrete. Computations showed this would limit the pressure below the footing to 2.8 tons per square foot (300 kPa) with crowd loading on the deck and 2.2 (236 kPa) without. It was assumed that the rock surface must dip steeply away at that side of the river, and Pier 4 was treated similarly, though less excavation was necessary to find suitably hard clay.

Caption. Edited extract from a drawing dated 9 September 1910, entitled "Maribyrnong Bridge. Depth of Pier Cylinders." This appears to be an 'as built' drawing, with longitudinal- and cross-sections showing the strata found in the river bed and the actual depth of the piers. The eastern abutment was not included in this drawing. (J Thomas Collection.)

By the end of June, the western abutment was complete, sitting on 340 lineal feet (104m) of timber piles. The vertical plate facing the river, with its integral columns to support the girders, was in reinforced concrete. A total of 148 lineal feet (45m) of cylinders had been completed. RCMPC valued the work done and materials delivered to site at £1979 and requested a progress payment of at least £1200. It was expected that the first two spans would soon be concreted, implying that Piers 1 and 2 were by this time complete and the necessary formwork was ready.

In July, Fairway must have suggested that it would not be necessary to excavate for the eastern abutment as deeply as shown on the drawings. This would have been consistent with Monash's understanding that RCMPC was allowed to make any savings possible so long as they did not affect the quality of the work. Pullar agreed to meet Fairway at the site, but emphasised that "no variation or allowance can be made in respect of the depth of the eastern abutment, which must be of the depth originally designed". He added: "There was never any suggestion … that this should be otherwise, and this fact is clearly borne out by the wording of the amended Contract agreement submitted to and signed by your Company".

Early in August, Pullar reported that there had been "adverse comment" on the quality of the sand used for the concrete. Fairway consulted Gibson, who replied that tests at the University had shown that it produced concrete of unusually high strength. However, it contained a high proportion of iron, which could have given the concrete in the abutments an unusual colour. He recommended substitution of an "excellent creek sand" in the neighbourhood, which could be used in the deck.

It was about this time that Braybrook Shire decided how to finance its contribution to the bridge, floating a loan of £1,000 at 4%, repayable in half-yearly instalments over three years. There was the usual dispute amongst the councillors as to how much each riding of the shire should contribute. It was resolved that each should contribute an equal amount, regardless of population. The Council accepted an offer from the MMBW to contribute £100 towards the cost of the bridge because they intended to use it to carry a 24" (610mm) water main to Braybrook.

Time allowed by contract is exceeded

On 29 August, Fairway wrote to Pullar stating that the time allowed in the contract for completion of the bridge had been exceeded. He attributed this mainly to the "considerable and unexpected difficulties" with the work in the river, but also to early confusion over its exact placement and level. An extension of three months was granted.

During this time, drawings had been completed showing the architectural embellishment of the piers, balustrading, and wing walls. The files and drawings give no indication of who was responsible for this styling.

A summary issued on 7 September showed the eastern abutment and two deck spans were now complete. The total value of work done, plus materials and plant on site, was £3199-15-0. The first progress payment had been £1350, and Fairway requested a further £800. About this time the foundations were finished, and the 'as built' drawing of cylinder depth was issued.

As work neared completion early in October, Fairway calculated the likely profit as £906, on a total price of £3906 (which included small extras and provision for the water main). He contemplated making a claim for £85 for the greater-than-expected depth of Pier 3, but decided against it. Pullar might counter that Piers 1 and 2 were less deep than expected; it might raise awkward questions about the depth of the eastern abutment; and it would be hard to justify within the terms of the contract.

In a copy of the Specification, someone has marked a sentence which reads: "The cylinders shall be sunk into the bed of the river until rock is reached, or until a penetration is reached which is satisfactory to the Engineer".

Finishing touches

On 31 October, Fairway reported to Pullar that the whole of the structural work was complete. All that remained to be done was fixing of the handrails, paving of the deck, building small wingwalls, and minor plastering. The total value of work done was now about £3700. RCMPC had received £2150, so he requested a payment of £600 or £700.

On 3 November, Monash returned to Melbourne at the end of his overseas trip.

A fortnight later, Pullar reported a "fairly large" crack in the western abutment, approximately level with the underside of the girders. He asked for quick action, as the council was tipping filling behind the abutment to make the approach road. After inspection, Fairway replied "We … find that the crack is merely a thermal one and does not in any way affect the strength or stability of the bridge. It is a crack which is always likely to occur during the setting of large masses of concrete, and no importance need therefore be attached to its presence."

In December there was a strike of concrete plasterers. RCMPC initially stood by other contractors in refusing to give them a pay rise. However Monash, eager to wind up the contract, confidentially asked Pullar to write him a stern letter pointing out the inconvenience to the municipalities due to the delay in completion of the bridge. Pullar obliged, making "a most emphatic protest against the delay" and threatening to "advise the Councils concerned to impose the penalties as provided under the General Conditions of Contract". The plasterers were engaged at the higher rate, and the councils granted a further one month extension to the deadline.

By 10 February 1911 there was only a small wing wall to be completed, and this could not be done until the old bridge had been closed. Pullar arranged to test the bridge on 15th. He invited P Lingford, Shire Engineer for Braybrook, and a Mr Nolan from the MMBW. The test load consisted of a 14-ton (14.2 tonne) road roller and six one-horse drays weighing about 3 tons each. These were crowded together, so that all 32 tons (32.5 tonne) would fit onto a single span. Measurements of deflection were taken and the load was then shifted to the next span. For most of the spans the deflection was too small to measure with the instruments available, but on one span a deflection of 1/100 of a foot (3mm) was recorded.

Official opening

The new bridge was officially opened on 16 March 1911. According to the Argus, the Mayor of Essendon (Cr Showers) and the president of Braybrook (Cr Spong), simultaneously cut red ribbons at each end of the bridge. The "large assemblage of councillors and representative people" then adjourned to Spong's Hotel for toasts. Spong proposed a toast of "Parliament", of W A Watt the State Treasurer, and of W J Evans the local Member of the Legislative Council. Watt stated that the State intended to establish "closer settlement" on government land in the neighbourhood. Evans expressed the hope that the bridge would assist in promoting that settlement. Cr Young proposed "The Contractors," and eulogised the way in which the work had been carried out. Lieut.-Colonel Monash responded.

On 3 April Monash reported to Pullar that the small wing wall had been completed, and requested payment of the last money remaining with the council: the original contractor's deposit of £180, plus the remainder of the account for construction, £135-1-06.

Postscript

In September 1915, Pullar expressed concern about the safety of the bridge, owing to the number of cracks that had developed since construction. In addition to the old one in the abutment, Fairway noted: "There are about 8 or 10 of the main girders of the bridge which show very decided cracks exactly where shear failure would occur. These cracks are exactly similar to those which have occurred in the Benalla and Laanecoorie Bridges and are just beyond where the vertical shear reinforcement was placed."

He continued: "Previous to meeting Mr. Pullar we had examined the design and find same is very ample everywhere, the stresses on both steel and concrete being very conservative. I consider that the cracks are due to a great extent to thermal movement as no expansion joint is constructed in the total length of the bridge [200 ft or 61 m]. Added to this, there is, of course the tendency for a crack to appear where there is no vertical steel to bind the concrete. I explained my views to Mr. Pullar and Mr. Andrew [presumably Engineer for Braybrook] and told them I considered the bridge perfectly safe and would be pleased to do anything possible to convince them of same. During the discussion several drastic methods were suggested, both in regard to possible repairs and examination, Mr. Andrew almost insisting on the cutting away of the concrete to enable an examination of the main steel bars to be made. Finally, however, at my suggestion, it was arranged that we should test these girders with the steam roller on Wednesday next at 3 o'clock, and that when the result of this test had been carefully observed, further discussion could take place and the matter be finally dealt with. Both Mr. Pullar and Mr. Andrew agreed that any repair work necessary would be carried out at the cost of the Council."

Fairway promised Pullar a copy of the original drawings and calculations, and J A Laing double-checked the shear stresses. Unfortunately, he and his colleagues were using the same text-book methods as used in the original design. It was realised in the 1920s that these resulted in insufficient shear reinforcement, especially where rolling loads occurred.

Laing computed the maximum shear stresses occurring at the ends of the girders, at mid-span, and at points eight feet (2.44m) from the centre, due to two rolling loads of 8500 lb each, 10 feet apart (37.8kN each, 3.05m apart). Currently accepted theory suggested shear stresses carried by the concrete of 45 psi, 20 psi, 48.5 psi respectively (0.31, 0.14, 0.33 MPa).

Appendix A: Images of the 1911 bridge and its predecessor.

At University of Melbourne Archives:
Views of construction work on Monash's bridge: GPNB-1115, 1116, and 1117.
Views of the completed bridge: Image Nos. NN-713, NN-714, GPNB-1105, GPNB-1106.

On the State Library of Victoria website:
Partial view of Monash's bridge completed: Accession No: H90.160/866, Image No. a02460.
View of the previous timber bridge: Accession No. H90.160/865, Image No. a02459.