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The Bendigo Monier Arch Bridges.
Contract acquisition, planning, design and construction.

Turning the arch at Booth St. BWP/23798. Testing the Booth St Bridge. BWP/23797.
University of Melbourne Archives Image Collection

Historic images (including the above) may be found on the internet at: UMAIC or Picture Australia
Within UMAIC search under Record ID as follows: King's Bridge Collapse: UMA/I/6203, 6245, 6246, 6248, 6390, 6391, 6402. Second King's Bridge: UMA/I/6395. Booth St Bridge: UMA/I/6247, 6286, 6292, 6293. Myrtle St Bridge: UMA/I/6397. Wade St Bridge: UMA/I/6211. Any enquiries to UMA concerning these images should refer to their Location Numbers. See Note 3 below.

For GPS coordinates of the extant Bendigo bridges, see Note 4.

Introduction.

The Monier system of construction was patented in 1867 by Joseph Monier, a French manufacturer of garden ware. He used a grid of small-diameter iron bars embedded in a coarse mortar especially for the construction of planter pots. The technique and patents were gradually extended to cover, amongst other things, arch bridges. The technique was forcefully developed and promoted in the German-speaking world by a number of licensees, amongst whom Gustav A. Wayss became dominant. It was formally introduced to Australia in the early 1890s through the efforts of W. J. Baltzer, a German immigrant who joined several businessmen to obtain licences through Wayss to cover the Australian Colonies. The firm of Carter Gummow & Co was formed in Sydney and built two important arched sewage aqueducts and a number of smaller structures.

In 1894 Monash had founded a partnership with J. T. N. Anderson. While Gummow was on a visit to Melbourne in September 1897, Anderson persuaded him that the partners should act as his agents in Victoria. They provided minor assistance to the Sydney firm with Victoria's first Monier arch bridge across the Yarra at Anderson Street in Melbourne, and were largely responsible for the planning, design and construction of two further such bridges at Fyansford near Geelong and at Lawrence near Creswick (Wheeler's Bridge). There was mutual recognition that any inadequacies in design and construction might bring the new technique into disrepute. The partners therefore sought advice from Gummow and Baltzer, while the latter tended to specify rather than advise. Monash was away in Perth on an extended legal case from July 1898 to July 1899 and missed much of the action regarding the first three bridges. The Bendigo project was thus the first Monier contract in which Monash was able to thoroughly immerse himself.

In winning and executing the contracts for construction of the Monier concrete bridges the partners found themselves engaged in a battle of wits with local interests: the brick industry, local contractors, and particularly the City Surveyor (or Engineer) J. R. Richardson. It seems that Richardson was sympathetic to local interests and suspicious of the new technology. He may have resented the fact that his own designs - for conventional bridges with iron girders resting on brick piers - were superseded by the Monier system.

Although I have tried to avoid bias, the following account is based largely on the Monash & Anderson archives, and it may give insufficient weight to the viewpoints and motives of Richardson and regional business interests.

2. Initial planning and winning of the contract.

In the 1890s Bendigo Creek, which runs through the centre of the city, was subject to sudden floods and carried large amounts of tailing sludge from nearby mines. The City obtained a loan from the government of the then Colony of Victoria to assist with work which included straightening and lining the creek and the reconstruction of seven bridges over the creek itself and one over its tributary, Back Creek. In August 1899 Monash & Anderson proposed that the bridge carrying High St (Calder Highway) should be built as a Monier arch. It was to be a grand affair with a span of 55 ft and a width of 99 ft. Monash estimated that a somewhat ornate Monier version [drawing p.28 of the Dossier] could be built for £2897, compared with £4359 for a conventional iron girder bridge.

After successfully presenting this proposal to the Council, the partners prepared designs for the other seven bridges. However one of them, King's Bridge, was so heavily skewed that its oblique span would be 92 feet and the partners feared that a Monier version would in this case not compete with a simpler iron alternative.

The skew angle initially specified for King's Bridge was 53° off square. A drawing dated 23 October 1900 is reproduced on page 32 of the Dossier. King's Bridge was referred to initially as the bridge on White Hills Road. The road it carries is now named Weeroona Avenue.

It was therefore agreed that they would submit draft specifications and a blueprint [Dossier, p.29] for the other seven bridges, with the option of tendering for King's Bridge at a later date. Richardson visited the partners' Melbourne office and demanded certain modifications to their proposals, while providing details of his own designs for iron girders resting on brick piers. The partners took advantage of this information to ensure that their Monier prices were lower than those likely to be offered by other contractors for iron and brick. On 29 October the first computation for the profile of a bridge (Oak St) arrived from Gummow Forrest & Co., initialled by Baltzer. In the meantime, Richardson demanded further amendments to the Monier designs and the partners made a quotation of £5317 for all seven bridges, indicating that considerable economies had been made in the High St design.

On the death of Carter in 1899, Gummow operated briefly as F M Gummow & Co, then joined with his Construction Manager to form Gummow Forrest & Co.

In calling formal tenders, Richardson failed to notify the partners that he was inviting prices for King's Bridge to his own design. When the tenders were opened, the prices were found to exceed the amounts estimated in the government loan schedule. The allocation for King's Bridge was £1200 and the lowest tender for Richardson's design had been £1600. Monash objected strongly, claiming that by using a cast iron parapet and lime concrete in the foundations, a Monier arch could be built for £1200. He wrote to a friend in Bendigo that if Monier were adopted, the City would get a great bridge at a 25% saving over Richardson's design. He asked his friend to put him in touch with the most influential Councillors so that he could pull a few strings. After submitting a drawing of a £1200 Monier version, he met the Mayor and some Councillors and offered a £25 reduction on each bridge if all eight were let to the partnership. The Mayor inspected Wheeler's Bridge and was suitably impressed. The Council decided to call fresh tenders for construction of the eight bridges as either Monier or iron-and-brick, using Monash & Anderson's designs for the Monier versions. Late in July 1900 the partners submitted plans and specifications for the eight bridges, embodying extensive modifications demanded by Richardson. Other contractors could bid to build the Monier alternatives, paying a royalty of 20% to the partnership. At some stage the oblique span of King's Bridge was changed to make it about 100 feet. Richardson expressed concern that the partners had underestimated the depth necessary to take the foundations to rock or firm ground. They replied that if it were found necessary to go down another foot or two, Richardson could always order this, but the bearing pressures were so low that even an "indifferent" clay would suffice, as had been demonstrated at the Fyansford Bridge.

On 31 August 1900 Monash and Anderson met in Bendigo for the public exhibition of the contract drawings and specifications, prior to the submission of tenders. They were horrified to find that Richardson had greatly reduced the cost of his own designs by major changes, some of which undoubtedly reduced the quality of the work. Monash later charged that Richardson had reduced the span of several bridges by reducing the skew; reduced the waterway provided; substituted rows of cast iron columns for solid brick piers, and in some cases omitted one pier entirely (thus obliging the girders to span further); had reduced the thickness of the timber deck from five to four inches; omitted certain masonry components; and entered parapets and copings as schedule items of unspecified quantity, thus removing them from the contract price. These changes had been entered on the original drawings so that they were no longer to scale and in parts "almost unreadable".

Nevertheless, the partners prepared tenders with a total price of £7245 if the contracts were let separately, or £6842 if all were granted to Monash & Anderson. These were submitted and opened within a week. The Council's decision was then deferred because the prices for the alternative versions were close. Monash weighed in with an argument that maintenance on the iron girders and timber decks of the conventional bridges, when capitalised, would add a further £1000 to their cost, and pointed out that the Monier arches required no intermediate piers obstructing the waterway. On 15 September 1900 he travelled to Bendigo for an animated meeting with the influential Councillor and former Mayor, S. H. McGowan, at which he set out his accusations against Richardson. He also managed to extract a few hints as to whether the partners were high or low in their prices for individual contracts.

Monash's account of this meeting, addressed to Anderson, is reproduced in Appendix D of the Dossier.

Following this the Council arrived at a shortlist of two: Monash & Anderson and Pickles & Smith. Monash offered a £25 discount on six of the bridges even if all were not let together, and a few days later made it unconditional. Local interests argued that the Monier contracts would involve the use of large amounts of "foreign" material and little local labour. Monash replied that the Monier alternative would in fact use more local labour and local materials (sand and stone for concrete and bricks for masonry). Only 1800 casks of cement and nine tons of reinforcing rods would come from outside the district at a total cost of £1500. In the case of the girder bridges, 125 tons of iron, 69000 super feet of timber, and 600 casks of cement would come from outside at a total cost of £3500. Little unskilled labour would be involved.

A super foot was a measure of volume equal to 12" × 12" × 1".

On 5 October 1900 Council decided to award the contract for all eight bridges to Monash & Anderson for a total price of £6967. On the 23rd Monash travelled to Bendigo to meet Mayor McColl and the next day signed the contracts. At Richardson's insistence these contained extra provisions which were to prove burdensome - and one which was to have a disastrous consequence. It was normal to test new bridges by running a 15 ton steam roller over them. Richardson argued that this was insufficient to represent the effect of heavy boilers likely to cross the Bendigo bridges in transit to nearby mines, and that the roller should be accompanied by a traction engine of similar weight. Monash must have agreed to this to secure the contracts, but he was to argue later that the boilers would have no such effect. Both machines were to be "run over every part of the roadway as often as the City Surveyor may direct". A provision that "the contractor shall take responsibility for the bridge sustaining the specified test" was printed in bold letters. The abutments of King's Bridge and High St Bridge were to be carried down to depths of seven and eight feet respectively unless rock were struck earlier. The terms of payment were somewhat stringent. Progress payments were to be monthly and based on 90% of work below springing level and 50% of work above springing level. If a bridge tested satisfactorily, an additional 40% of work above springing level was to be paid for. The final 10% was to be paid on completion of the entire project. Advances were to be made on materials delivered to site at 75% of their value. The materials were then to become the property of the City Council.

Commencement of design and construction.

Throughout October, the partner's assistant engineer, J. S. Gregory, produced simple outline drawings for the bridges. The drawing of Booth St [Dossier, p.30] is typical of those square to the creek, while that of Thistle St [p.31] is typical of skewed bridges. On 26 October 1900, a team under the direction of foreman J. Buick commenced work on dismantling the old timber bridge at Oak Street, followed by excavation for the new foundations. It appears the depth to rock was greater than anticipated and minor problems were experienced with water. Monash & Anderson attempted to modify the level of the springing to their own advantage, telling Buick not to worry about Richardson, as he was not familiar with the details of Monier bridge construction and "it should be very easy to bluff him". The partners took advantage of an option to build the wing walls in brickwork rather than mass concrete above ground level. A disagreement over the exact level of the change-over led to further sparring and they wrote to Buick "It is unfortunate that Mr Richardson should interfere in points which he evidently does not understand … if he continues to persist … you had better carry out his wishes rather than offend him … We would sooner run this expense than absolutely defy Mr Richardson, if we cannot persuade him quietly."

By 10 November the abutments were concreted and ready for the 'centres' [the timber framework that would support the wet concrete of the arch]. The partners abandoned their attempt to lower the springings, but when Monash inspected the works he declared Richardson "extremely fidgety" about the quality of cement and inclined to interfere in matters he did not understand. As preparations for the arch progressed, Richardson condemned the grids as being too widely spaced. He wrote that concrete should not be poured if the weather was hot or windy, demanded that the small blocks (or 'pats') of mortar used at regular intervals to support the reinforcing grids 3/4" above the surface of the formwork be removed afterwards, and made reference to the amount of ramming to be applied to the "compo". Monash & Anderson told Richardson they knew he had been in contact with their old sparring-partner from the Fyansford Bridge project, A. L. Campbell, Engineer for the Shire of Corio, who was "on the side of our declared enemies in a pending litigation". They told Buick "please take as little notice as possible of Mr Richardson's absurd and vexatious interferences". On 18th came the first of the many sudden floods which were to bedevil the project, in this case fortunately without consequences. On 23 November, Monash travelled from Melbourne to supervise the casting of the first Monier arch in Bendigo.

Although the haunches, spandrel walls, filling and parapets at Oak St were still to be completed, attention now turned to King's Bridge. The partners pressured Richardson to alter the road alignment slightly to reduce the skew from 53° to 50° off square.

Monash & Anderson and their colleagues defined the skew angle of a bridge as the angle between the longitudinal centreline of the bridge and that of the stream, so that a bridge square to the stream had a skew angle of 90°. The definition adopted in the dossier is more common today and is the angle by which the longitudinal centreline of the bridge diverges from that of a square bridge.

One reason for reducing the skew was that it was considered essential that a Monier arch be cast (or "turned") from end to end in one day without interruption to the concreting process which might cause a weak joint across the width of the arch. As the dry, coarse mortar (or "compo") used was mixed by shovel and conveyed to its destination by the barrow-load on a narrow runway of boards, the quantity of concrete that could be placed in one day was limited. It was therefore necessary to turn large bridges in a number of parallel strips. Reducing the skew at King's Bridge would reduce the number of strips necessary from four to three. Perhaps more importantly, it would improve the stability of the arch. Richardson obtained a £45 reduction in price on the grounds that the length of the bridge would be reduced, the span along the edge becoming 93'-4" instead of 101 feet. GF&Co were asked as a matter of urgency to provide a new profile and check the thicknesses of the arch and abutments. Baltzer was away from the office and it was agreed that Monash & Anderson should simply "project the curve from the old". This presumably meant reducing all horizontal distances proportionally so that the new curve had a length of 93'-4". At the end of November a start was made on removing the old timber bridge and excavating the foundations.

Meanwhile on the Oak St Bridge, Buick had had trouble finding bricklayers to work on the spandrels. Anderson reported "the trades have seriously boycotted us … but [Buick] has now got two good men (black legs)". The excavations at King's Bridge soon struck "troublesome quicksand material". Anderson probed downwards with an eight-foot iron bar and could feel no rock. Just after he arrived the sides of the excavation caved in and one workman narrowly escaped being trapped. It appeared that it would be necessary to install an expensive wall of sheet piling around the excavation. The partners' trusted senior foreman C. Christensen was brought in to help. On 21st Buick was told that as soon as he reached material that was "at all presentable" as a foundation he should make sure that Richardson saw it and approved the pouring of concrete. This point was reached around Christmas Day which, with Boxing Day, was taken as a public holiday. There was, however, confusion over the adequacy of the foundation material, the foremen wishing to pour concrete and Richardson insisting on going deeper with the excavation. In this case Anderson agreed with the City Surveyor. The records do not provide a clear picture, but it appears that after further excavation one end of the right abutment was founded on rock and the other on pipe clay. ['Left' and 'right' as seen looking downstream.] Anderson hoped for healthy 'extra' payments on the left abutment and wrote to Monash "I will try to bluff Richardson into some order for further strengthening the abutment if I find I can frighten him by protests, but I feel the position will need very careful handling, as probably Christensen is set[?] on concreting at our risk". The attempt appears to have failed, as Richardson wrote in reply that the stability of the work was entirely Monash & Anderson's responsibility.

While concreting continued on the right abutment, a wall of sheeting was completed around the left abutment and excavation below the waterline commenced. Major problems occurred with seepage of water and appeals were made for more pumps. The battle continued for days, with the crew working at all hours, and Anderson making heroic efforts to get the steam plant and pump functioning properly. Monash came to Bendigo to take over while Anderson travelled to check progress on the partnership's other projects. After some 12 days, concluding with all-night work, the excavation reached bottom on a bed of stratified pipe clay described by the partnership as a "thoroughly sound and satisfactory" foundation. However, on this occasion, concrete was poured without the approval of Richardson. Monash & Anderson claimed they had waited all day while their messengers searched for him and that his Assistant Engineer and Clerk of Works, though present, had refused to take responsibility. During the delay, silt was washing through cracks in the sheeting, loosening the ground around the future abutment. Workmen therefore commenced concreting at 4.20 pm without Richardson's permission and continued throughout the night. (Richardson later refused to believe that serious efforts had been made to find him.) Within days, the left abutment was concreted to skewback level. The muck was sluiced out from under the bridge, and soon the centres and lagging (formwork surface) were being installed and the reinforcement grids tied and placed.

In the meantime, an attempt had been made to strike the centres at Oak St; but shrinkage or sag of the arch had caused them to jam, and to Christensen's consternation, they had been released by cutting the bolts in the connections between the timbers. Progress on the upper parts of this bridge had been steady, though interrupted by disputes with Richardson and problems in finding bricklayers. On the 8 January 1901, the first horse-and-trap passed over the first Monier arch to be completed in Bendigo. Oak St bridge was duly tested by steam roller on 5 February and certified for acceptance. On the 12th February plant and gear were moved to commence work at the High St site. Although the span there was only 50 feet square to the creek, the bridge was over 90 feet wide and it was necessary to cast it in four strips. The two inner strips were made square to the creek, while the outer strips were of varying width to accommodate the skew of 26°. Construction of the bridge was carried out in two stages, the upstream half being completed before excavation commenced for the downstream half.

Sketch plan. Strips 1 to 4 run from abutment to abutment. Strip 1 is at the upstream side of the bridge. It narrows. Strips 2 and 3 are rectangular in plan. Strip 4 widens out.

Excavation of the first half of the left abutment occupied about two weeks until it hit bottom on a bed of awkward, vertically stratified rock. The depth required to reach reasonably firm rock varied from 4 feet to 9 feet: slightly over the eight feet limit of the contract. Within a few days the abutment was concreted to springing level. On the right abutment excavation proved more difficult than expected. Although the record in unclear, it seems it was necessary to drive sheeting and use a pump. Monash emphasised to Christensen the need to record depths of excavation and make sure "the City people" were aware of them, "because we are sure to get extras here". On 4th March the partners realised that Buick had made a slight error in the orientation of the first strips. Later in the month Richardson set a springing level lower than originally specified, presumably aiming to reduce the amount of concrete needed for the abutments.

In mid-January, Monash & Anderson had decided to modify the design for the arch of King's Bridge by a slight reduction in its cross-section. On 8 February, both partners were present for the major operation of turning the first of the three arch strips, about nine feet wide on the downstream side. The following day workmen began to build, along the edge of the arch strip, the concrete bases for the downstream spandrel walls. The centres were removed on 27 February but it appears that this arch also had sagged. It was necessary to cut the centres to remove them, causing delay in their re-use for casting the second strip, which was achieved on 7 March. On 31 March a serious row broke out between Christensen and Buick. After mutual recriminations, Buick resigned on the spot and left Bendigo. As he had looked after the local paperwork and finances it was necessary for Monash to cancel appointments and travel to Bendigo to sort out the mess. He declared himself disgusted with Buick, and wanted nothing more to do with him, but Anderson advised restraint, as they might need him as foreman on future projects. A new man was engaged as full-time clerical assistant to Christensen.

April was a busy month with the third strip of King's Bridge being cast on 1st, work commencing at Booth St on 17th, and the first strip of High St cast on 18th. Soon after this the second strip must have been cast, but the profile was evidently not in accordance with the design. The actual profile was surveyed and on 3 May drawings were prepared to allow Gregory to make check calculations. These showed that the arch was just stable, the thrust line passing within two inches of the lower surface. Monash and Richardson made plans to celebrate the opening of High St with costs shared between Monash & Anderson and the Council. Monash was keen to get traffic on to King's Bridge to consolidate the fill, but this necessitated completion of the spandrels. Again the bricklayers were slow.

There are references to construction of the spandrels in both concrete and brickwork. The drawings available to the authors do not throw any light on the matter. It is possible the lower portions were in concrete and the upper parts in brick.

Disaster at King's Bridge.

On 14th May 1901, King's Bridge was tested with Monash present. At Richardson's insistence the steam roller and traction engine were run repeatedly over the bridge and brought back-to-back to ensure that their heavily-loaded back axles were as close as possible. Monash believed the entire test was grossly in excess of any load the bridge might experience in service but was unable to persuade Richardson that this was so. Towards the end of the test, a crack developed in the arch, but the participants were not unduly concerned, as it appeared to be confined to the surface of the arch. They may have remembered that in German tests to destruction the first cracks had occurred at about one-third of the final collapse load. Richardson insisted that for one final test the engines should be manoeuvred closer to the edge of the bridge. The major participants, who had gone under the bridge to examine the crack drew back only a short way. A. E. Boldt, business partner of the driver of the traction engine, leant against the balustrade looking over the edge. With little warning, the downstream strip of the bridge collapsed, tearing away from the adjacent strip, and the traction engine was projected into the creek.

Wreckage of King's Bridge
University of Melbourne Archives BWP/23802
Reinforced Concrete & Monier Pipe Construction Co. Collection

Boldt fell beneath the engine and was killed instantly. Monash assembled survivors on the bank to check who was missing, while messengers went for assistance. When opportunity occurred he wired asking Anderson to come to Bendigo as soon as possible, but when his wife offered to join him, he replied in undiplomatic terms: "Thanks, but you no good here". He spent the evening in the Shamrock Hotel drafting a letter to Council expressing sorrow over Boldt's death and promising that, as a demonstration of their faith in the Monier principle, Monash & Anderson would rebuild the bridge at their own expense.

The inquest convened the following day and at weekly intervals thereafter. Monash & Anderson expressed their mystification. Calculations had been made according to accepted theory and indicated that, despite the severity of the test load, the stresses were not high. They were confident that the materials and workmanship were of adequate quality. To look for possible causes and to assist them at the inquest, they secured the services of W. C. Kernot, Professor of Engineering at the University of Melbourne. On 22 May, Gregory double-checked the strength of the arch using conventional theory and on 28th he again checked the High St profile as it had been built [Dossier, p.35]. Richardson found himself in a difficult position because he had approved the Monier design, even though he was unfamiliar with the technique and had been suspicious from the first. At the inquest on 29 May there was disagreement about the location at which the collapse had initiated. Some observers said the central portion of the crown had given way first and collapsed into the stream, leading to rupture at the abutments. Monash insisted that the abutments had crushed under excessive outward pressure, allowing the crown to descend into the enlarged opening. However, the decisive evidence was given by Kernot whose investigations suggested that established theory, as set out in a respected contemporary text, underestimated the maximum stresses in a highly-skewed arch by a factor of about four. On 30 May the coroner recorded a verdict of accidental death, including the statement that "no blame can be attached to anyone". After the verdict, Monash & Anderson, Baltzer and Kernot continued attempts to find precise values of stresses. However, the problem was beyond the range of theoretical techniques likely to be found in practical design offices of the time.

A comprehensive analysis of such a highly skewed arch, including its complex abutments and foundations (partly clay and partly rock) would challenge the skills of a present-day engineer armed with the power of modern computer packages. The story of King's Bridge is told in greater detail in a companion Dossier which has two parts intended for the general reader and a third mainly for engineers.

The collapse provided ammunition for opponents and doubters. Some Councillors called for termination of the Bendigo contracts, while municipalities which had been contemplating orders for Monier bridges considered suspending negotiations. Monash instituted a public relations campaign to counter these effects. However, he and his own staff were unsettled. Christensen wrote expressing concern about soft patches in the arch of an un-named bridge, probably Oak St. In turn, he was warned by the Melbourne office to take great care in striking the centres of Booth St, and to be sure that no sag occurred in the arch. Similar instructions were later given to Anderson's brother Jack who was supervising construction of the three-arched bridge across the spillway of the Upper Coliban Reservoir. [Dossier.] The partners' already desperate financial situation was worsened. They had completed considerable extra works on their Fyansford Bridge project near Geelong, with the approval of the supervising engineer, but the client Councils had refused to honour an amount of some £2100. A bitter court battle had ended with Monash & Anderson hopeful of success, but the judge had delayed for several months and the judgement was still outstanding. Deprived of the progress payment which would have been theirs if King's Bridge had withstood the test, they were now faced with the cost of paying for its reconstruction.

It was eventually favourable to Monash & Anderson, but their clients, the Shire Councils of Corio and Bannockburn, appealed. The Appeal verdict recognised the ethical validity of Monash & Anderson's claim but, on the basis of a technicality, awarded them only a fraction of the amount claimed. Details of the court proceedings and transcipts of the two judgments are provided in Volume 2 of the Fyansford Dossier.

Continuation of work.

Despite the set-back, work continued on the other bridges. On 17 June a flood displaced the centres prepared for the Booth St arch, but the arch was successfully turned on 22nd (see photo at top of page). Two strips of High St Bridge were now complete, with traffic passing over them, and excavations started for the downstream side. As the construction of Wade St Bridge neared, the partners continued their sparring with Richardson who suggested that as rock was so deep at this site and covered by "slum" from the mines, the abutment block should rest on piles driven through the slum, rather than being carried right down to the rock. A similar method had been adopted at one end of the Anderson St (now Morell) Bridge across the Yarra in Melbourne. There were technical objections to this, but the scheme would also rob the partners of large extras for concrete. When they objected, Richardson proposed to call in other contractors to carry out the piling. Monash wrote a stinging letter calling the suggestion an "injustice" and an "infringement of our rights". With the aid of Christensen he finally persuaded Richardson to back down: a process which was becoming an established pattern.

A serious dispute was now developing over the partners' claim for extras in the High St foundations. The abutments were so extensive that the depth to rock varied from 4 feet to 12 feet. Richardson argued that because the average depth was 8 feet, the figure specified in the contract, Monash & Anderson were entitled only to the contract price for the bridge. The partners argued they should be paid the contract price plus extras for whatever work had been carried out below 8 feet. The dispute was complicated by disagreements over measurement of levels and accuracy of calculations. On 10 August Richardson declared the clay exposed at Wade St at a depth of 7 feet a satisfactory foundation implying that he would not pay for further excavation or concrete at this site. Monash instructed Christensen that as long as safety was assured, stopping on a clay foundation would provide a useful precedent for doing the same thing when constructing the new pier to be provided for King's Bridge, even though it would lose the opportunity for a big extra at Wade St. Christensen was therefore to play it by ear, while trying to frighten Richardson by inviting him to take responsibility for the safety of the foundations. The outcome was an extra of about 25.5 cubic yards. In August the remaining strips of High St Bridge were cast and on the 18th or 19th, Booth St was successfully tested. (See photo at top of page.)

Booth St Bridge photographed c1997

On 17 September Wade St arch was turned but was destroyed the next day when a flash flood began to sweep away the centres. The partners' opponents took the opportunity to renew their attacks on the Monier system. On 18 September Richardson pointed out that the abutment and downstream spandrel wall of High St were out of line and demanded rectification. A few days later Anderson became convinced that Richardson had been moving the level pegs at Abbott St to gain a reduction in the amount of earthworks. On 3 October Monash and Anderson were both present for the load test of High St. With some reason, Monash noted in his diary: "Heavy anxiety re Bendigo test …" There were troubling inaccuracies in the profile as constructed, and Richardson was insisting that a roller and traction engine be used and a heavily loaded wagon pulled across. It was futile to protest that if any such load had been applied to Richardson's own iron girder designs they would undoubtedly have failed. The Monier bridge withstood the test successfully, though some Councillors argued that only the roadway had been tested and demanded that loads be driven over the footpaths! After some discussion, Richardson was persuaded that this would be unnecessary.

The battle of wits continues.

The tortuous nature of the battle over extras is illustrated by the case of Abbott St. At the time they prepared their schedule of prices, Monash & Anderson expected that rock would be found close to the surface at this site. In this, they seem to have depended on Richardson's estimates of rock depth supplied in the early stages of planning. There is no indication that either party conducted proper site investigations. Presumably because they saw no chance of gaining extras in the foundations, the partners ensured that "according to the levels shown on the contract drawing" the approach embankments would contain several hundred cubic yards more earth than shown on the schedule. As Richardson would be obliged to authorise payment for this excess they had adopted the common practice of weighting the unit prices. They increased the price of earthworks per cubic yard and lowered that of concrete, maintaining the same overall tender price for the project, but allowing themselves to make the most of the excess earthworks. Christensen was warned to block any attempt Richardson might make to cut down the quantity of earthworks, which he could only do by reducing their width or making the grades steeper.

However, when excavation commenced in late October it turned out that the rock level was much lower than expected. The low price the partners had quoted for concrete meant that, for once, oversize foundations were not to their advantage. Richardson, apparently in an effort to reduce the height of the embankments, delayed in providing a bench mark level, then negotiated with Christensen a level 2'-5" lower than shown on the plan. The partners told Christensen the consequences would be: less excavation and concrete in the foundations (this was "not too serious because our price is not very 'fat' on this"); less room for the centres; and a big reduction in the earthworks, where all their profit was concentrated. He was told to take whatever steps were possible to induce Richardson to raise the springing level, preferably to that shown on the plan. "Every possible expedient must be tried to get as much stuff into the embankment as possible … Richardson has been very smart indeed in trying to make up for the extra cost of the foundations … and we want to be just as smart in trying to block him."

In mid-November Monash found himself forced to buy earth for the embankments from the Council, as he was unable to find other sources of sufficiently high quality to satisfy Richardson. He must have felt the City Surveyor was adopting unnecessarily high standards, as he told Anderson he was "boiling over" as a result of Richardson's "obstructionism". When he protested to the Mayor he was told that Richardson was only responding to pressure from Councillors still strongly opposed to the partners. The position was now reversed, with the partners wishing to minimise rather than maximise the earthworks. They now told Christensen "Richardson will certainly try to increase the quantity as much as he can. Please report every instruction he gives, so that we can checkmate him if he comes too strong … Should he decide to widen the bank at any point, you can do this … by keeping the slopes as steep as ever they will stand … The game to play is to get the approaches done as soon as possible and then knock the drays off and then object later on, to going over the work a second time …" As it turned out, Christensen built quite healthy embankments and Monash was furious with the resulting cost to the partnership. This was one of several instances in which Christensen appears to have supported local interests at the expense of the partners'.

On 7 October the Wade St arch was turned for the second time and on this occasion was not carried away. A week later Monash gave Richardson a lecture when claiming for extra work at Booth St. "We point out that you are in a judicial position, in which it is your duty to decide fairly, and it is no part of your duty to endeavour to strain the provisions of the specification against us. The question really is, whether we could fairly have anticipated this extra work, so as to include it in our tender." About this time the partners applied for a 50 per cent progress payment on High St. and asked for an advance payment of the money promised to them on completion of the new King's Bridge. (It had been agreed that they should receive the money which would have been paid to them had the first bridge withstood the test.) After some delay, the Council agreed to the advance and Monash finally saw some hope of pulling through financially in the Bendigo contract. He wrote a private letter to the Town Clerk frankly setting out the partners' financial situation in an attempt to obtain settlement of the claim on the High St foundation extras, but achieved no further progress.

Reconstruction of King's Bridge.

King's Bridge reconstructed with a central pier (barely visible) and two spans
University of Melbourne Archives BWP/23803
Reinforced Concrete & Monier Pipe Construction Co. Collection

Throughout June, Council had been pushing Monash & Anderson for action on the repair of King's Bridge, but there had been difficult decisions to make. Kernot's investigations suggested that if the arch were rebuilt in its original form the abutments would have to be strengthened - possibly involving demolition and reconstruction - at considerable expense. Eventually they decided that the safer and cheaper alternative was to build a completely new pier in mid-stream and build two arches of approximately half the span of the original. This reduced the thrust on the abutment considerably and meant that the width of each arch was a much greater proportion of its span than had been the case with the original.

Specifications and drawings were presented to Council in mid-July, supported by Baltzer's calculations [Dossier, p.36], and the matter was referred to Kernot for advice. He agreed with the proposals, but suggested the replacement of the stone parapet by a light steel lattice balustrade on the grounds that it would lighten the load on the bridge. This was economically advantageous to Monash & Anderson as it allowed them to build a narrower arch and save on concrete.

Clearance of the remains of the failed bridge had been commenced in the first half of July and completed by the end of September. After a battle with water, the pier had been constructed in mid-stream and the centres erected. Monash found inaccuracies in the geometry of the centres which had a rise 3" less than specified, but work went ahead with the turning of the right hand arch on 20 November. It was supervised by Anderson, who recorded that the temperature was 95°F (35°C) and the wind rose to gale force over the day. This could not have pleased Richardson who, early in the project, had forbidden concreting in such conditions. However, he objected mainly about the use of large aggregate (stones) in the compo, and perceived inadequacies in the thickness and width of the arch. The partners had proposed the use of aggregate in accordance with the latest techniques observed by Gummow while on a trip to Europe, but Richardson had not replied. Anderson thus had some reason for forcing the issue, but Richardson appears to have been justified in complaining about the size of the stones (2") and their quality. The difference over thickness occurred because the specified thickness was measured in a plane parallel to the edges of the arch, while Richardson had measured it in a vertical plane orthogonal to the abutments and obtained a lower figure. The reduction in width of the arch was justified by the adoption of steel lattice balustrades. Monash & Anderson sent a strongly-worded letter asserting that they had every desire to work on friendly relations, but could "only regard such groundless complaints … as imputations of dishonest attempts to provide less than is proper" and hoping to be spared "further unnecessary irritation". Richardson compromised as usual, agreeing to the use of stone in future bridges, as long as it was of good quality and finer than that used at King's Bridge. Before the bridge was tested Monash carried out a detailed check on the stresses, though still using traditional theory. The test took place on 28 January 1902, using a 15 ton roller only. Reconstruction had cost the partners an extra £1000.

Completion.

Work on the remaining bridges had been continuing relatively smoothly. On 2 December Wade St had been tested with a steam roller only. On 29 January the arch of Myrtle St bridge was turned. Monash recorded in his diary: "Very trying day. Home by last train." Sparring continued, with Richardson refusing to sanction the re-use of stone from the abutments of the former bridges in the spandrels of the new ones. When it was discovered that the centres of Thistle St bridge had an average span two feet longer than specified (the two sides being of different lengths) Richardson wrote that it did not greatly concern him, as long as Monash & Anderson did not try to claim an extra! On 8 March, Monash brought his wife to Bendigo for a visit of several days, during which the arch of the Thistle St bridge was turned. Yet again, the fresh concrete was threatened by flood waters, but Christensen had the presence of mind to strike the centres a little early, as soon as heavy rain set in. On 3 March Myrtle St was tested successfully.

The partners' financial difficulties continued and in late April, they were not sure whether they would be able to pay the men's wages. This inspired yet another appeal to Council for settlement of the claim for extras in the High St foundations. On 22 April Anderson, who had been trying to find a salaried position to relieve the situation, learned that he had obtained a post in Dunedin, New Zealand. The last bridge in the series, Thistle St, was tested successfully on 12 May, the day before Anderson was due to sail. As the project drew to its close, Monash had been trying hard to obtain more work in the municipality, offering Monier versions of several proposed bridges and Monier pipes for a large drainage project. Once again, these schemes had been designed by Richardson in conventional materials and this time Monash's efforts proved fruitless, Richardson informing him briefly that Council had decided to adhere to the existing designs. After the acceptance of the Thistle St bridge, Monash made a last attempt to settle the outstanding claim on the High St foundations. After a brief search for an arbitrator, Council made a compromise offer of £50 instead of the £128 claimed. In notifying his acceptance, Monash wrote to the Town Clerk: "This closes our present transactions with the City of Bendigo. Thank you for your unfailing courtesy."

Authorship of design.

The major technical matters to be determined in Monier arch bridges were the form and dimensions of the arch and its abutments. These included the profile and thickness of the arch and the thickness and shape of the mass concrete abutment blocks required to resist its outward thrust. Monash & Anderson had the ability to compute the required dimensions, but there are no calculations in the files relating to the early stages of design of the Bendigo arches. Gregory's drawings of October 1900 show the profiles of the Booth, Oak and Wade St bridges with three circular segments: a central portion of radius 55 feet and two outer portions of radius 29 feet. No radii were shown on drawings produced later in the month and it is possible that pressure of work persuaded Monash & Anderson to rely, from then on, on the advice of Gummow Forrest & Co. As soon as they received news of the Council decision to award the contract, the partners asked Gummow Forrest & Co. to provide "definite particulars" for the Oak, Wade, Booth, and High St bridges. The partnership's letters give the impression of a request for instructions and the Sydney firm's replies have a prescriptive tone. Their profiles differ from Gregory's in having five segments and different values of radius. There is little direct evidence to show which versions were adopted, but it appears that advice from Sydney was taken seriously. A letter to Buick at the start of the Oak St project in late October 1900 told him that if the profile for the centres were not received from Gummow Forrest soon, Monash & Anderson would supply their own. They also wrote: "We are sorry to tell you that Gummow's views on the Monier are slightly more conservative than ours, and it will no doubt end in our having to make the Monier a little heavier than we at first intended". The October drawings show the abutment as a relatively thin wall with stepped counterforts, or buttresses, at each end to counteract the overturning effect of the thrust from the arch. Gummow Forrest's design was for a simple, thicker wall rendering the counterforts unnecessary. Buick was told to adopt the thicker wall, but that he must still include the counterforts as they were shown in the contract drawings. However, he was to not to worry too much about them and was not to take the "elaborate pains" foreshadowed by Monash.

The general picture is thus of Monash & Anderson agreeing, somewhat reluctantly, to follow the more conservative dimensions advised by Gummow Forrest. However, in the case of King's Bridge they showed more independence. In June 1900 they had told Richardson the arch thickness would be 11" at the crown and 15" at the springings. In a hurried request for a new profile after the skew was reduced, they showed an awareness of current theory, noting that it required the arch to be designed as though it were square, but with a span equal to the length along the edge, approximately 100 feet. (As we have seen, the actual behaviour of a highly-skewed arch was not that simple.) Late in October, Gummow Forrest & Co. had recommended 17" and 22" for the crown and springings. In mid-January 1901, Monash & Anderson decided to modify the cross-section and informed Buick that the middle strip should have thicknesses of 16" and 20", and that the upper surface of the outer strips should have a 3" cross-fall, to give thicknesses of 13" and 17" at their outer edges. There is no record in the files of the calculations on which this was based, but there is reference to "careful investigation" and "mature consideration". Anderson mentioned a check on stresses using the "method of virtual velocities" which led him to believe the arch was equivalent to a square arch with a span of only 68 feet. There is thus a hint that he realised the special nature of the problem, but that established methods of calculation led him in the wrong direction.

Note 1: The account given above was extracted from our spiral-bound Dossier on the Bendigo Monier Arch Bridges and has been lightly edited for presentation here. The Dossier includes details of archival sources, dimensions, and a 'timeline' in which all correspondence known to our research team is recorded chronologically in precis or verbatim form.

Note 2: An error in quoting William Julius Baltzer's first name has been carried over into several dossiers. It appears on page 38 of the Bendigo Monier Arch Bridges dossier.

Note 3: For enquiries to University of Melbourne Archives concerning historic images of the Bendigo Bridges, please quote Location Numbers (BWP/xxxxx) as follows:
King's Bridge Collapse: UMA/I/6203 = BWP/23792; UMA/I/6245 = BWP/23786; UMA/I/6246 = BWP/23789; UMA/I/6248 = BWP/23791; UMA/I/6390 = BWP/23800; UMA/I/6391 = BWP/23801; UMA/I/6402 = BWP/23806.
Second King's Bridge: UMA/I/6395 = BWP/23803.
Booth St Bridge: UMA/I/6247 = BWP/23790; UMA/I/6286 = BWP/23796; UMA/I/6292 = BWP/23797; UMA/I/6293 = BWP/23798.
Myrtle St Bridge: UMA/I/6397 = BWP/23804.
Thistle St Bridge: UMA/I/6400 = BWP/23805. Wade St Bridge: UMA/I/6211 = BWP/23795.
Further images, not appearing on UMAIC (as at Sept 2011) are:
High St Bridge: BWP/23799.
Oak St Bridge: BWP/23793, BWP/23794.

Note 4: GPS coordinates of the extant Bendigo Monier arch bridges are: Wade St -36.77042, 144.26082; Booth St -36.769847, 144.261839; High St -36.769628, 144.263867; Abbott St -36.758347, 144.289917; Second King's -36.74364, 144.29165; Thistle St -36.76837, 144.2671.

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