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Porepunkah Monier arch bridge.

Photo 2008.   Coordinates: -36.697, 146.89393

For historic images see University of Melbourne Archives Image Collection or Picture Australia.
Within UMAIC search under Record ID for: UMA/I/6409, 6410, 6411. Any enquiries to UMA should refer to the Location Numbers for these images, respectively BWP/23958, BWP/23959, BWP/23964. Further images held by UMA, but not online (as at Sept 2011) have Location Nos. BWP/23953 to 23957, and BWP/23960 to 23963.

Preliminary negotiations, 1910.

The Porepunkah Monier arch bridge was built in 1913 to serve the route from Porepunkah to the popular holiday resort of Mount Buffalo, a great favourite of John Monash. The first mention of the bridge in the RCMPC archives dates from May 1910 when the Engineer for the Shire of Bright, H. G. Oliver, wrote asking the firm to provide a quotation for a Monier arch. He noted that the existing timber bridge had become unsafe, and that its "span" (perhaps its length) was unnecessarily large at 72 feet (22m). In the latter half of March 1910 Monash had set out with his wife on an extended world trip, leaving his experienced and dependable lieutenant P. T. Fairway in charge of engineering activities, with John Gibson continuing as General Manager. Although the firm had not built a Monier arch for some years, the necessary calculations for strength and costs were quickly made and resulted in a quotation of £683 for an arch with a single span of 50 feet (15.2m).

The design is interesting from an engineering point of view. In the firm's previous Monier arches, the spandrel walls which contained the earth filling were intended to act as gravity retaining walls, resisting the outward pressure of the earth simply by means of their dead weight. They were made either of unreinforced mass concrete or of brick masonry. However for Porepunkah the walls were designed like modern reinforced concrete retaining walls (with counterforts), resisting the pressure through strength rather than weight (Dossier, p.30). The writer of the covering letter, probably Fairway, noted that they could be made to comprise "a monolithic whole with the arch" and "this not only reduces the cost, but also prevents any possibility of these walls bulging under the pressure of filling, which we have found so frequently occurs with brick walls, unless they are made excessively thick and heavy". A contributing factor may have been the cost of importing bricks from Wangaratta, the nearest source of supply. However, integral walls contribute greatly to the strength and stability of the arch as a whole, and the decision probably represents a major step forward in local design practice.

After a spate of arch-building prior to 1903, in accordance with the Monier patent, Monash had realised that in most situations it is more economic and practicable to build a bridge of horizontal girders, resting on intermediate piers if necessary. After 1903 he always attempted to dissuade clients from adopting an arch unless there was a demand for an imposing ornamental structure and the site was particularly well adapted. Fairway made a mild attempt to dissuade Oliver, pointing out that a girder bridge could be built for £75 less, but he agreed that an arch would look better. Oliver and or the Council must have been dissuaded by the high price, and the proposal was allowed to lapse.

Monash's transition from arches to T-girders is discussed at greater length in the story of the Stawell Street Bridge, Ballarat.

Further negotiations, 1911.

In September 1911 Oliver's successor, A. MacKenzie Tyers, wrote to RCMPC as though unaware of their correspondence with Oliver, and asked for an estimate for a reinforced concrete bridge of one span. Tyers did not specify an arch and the term 'reinforced concrete' was applied at the time to girder bridges as opposed to patent Monier arches. Monash, having returned from his voyage, replied suggesting a girder bridge. However, single spans greater than 40 feet (12.2m) were uneconomic in reinforced concrete when compared with other materials, so he suggested a two-span girder bridge with the pier placed close to the left bank to minimise its effect on the waterway. Although Tyers had written that he did not think floods would be a problem, provision of adequate waterway is an important factor in bridge design. Monash requested his views on this question before proceeding with detailed design. Tyers replied that he preferred the single 40 foot span, as he thought the river would be "rapid in flood" and therefore unsuitable for a pier (presumably fearing the pier would be undermined or struck by debris).

Calculations and estimates for a 40 foot girder bridge were then prepared, initialled by Monash. The quotation was £338 for the bridge itself, excluding demolition of the old bridge and construction of the approaches. As usual Monash presented lengthy arguments in favour of the girder alternative. He also pointed out that half the cost of the bridge lay in the abutments and wing walls. Thus a great deal of money could be saved by lowering the deck by two feet, and there was no need to fear a reinforced concrete bridge might be washed away even if it became submerged. Monash wrote he would be glad to submit a formal tender when appropriate and asked Tyers to keep the price confidential in case tenders should be called. There is no evidence that a drawing was prepared to accompany this proposal. There was no response.

Further negotiations, 1912.

In March 1912 Monash addressed a letter to "The Shire Engineer" at Bright, having noticed in the press that Council was asking for government assistance for re-construction of the original bridge. On the same day, apparently by coincidence, Tyers finally wrote in response to the earlier letter, stating that Council "would like to have more particulars as to what kind of bridge it would be". Monash restated facts already supplied and declared himself mystified as to what more could be wanted. He pointed out that if the project were delayed until winter it would be more costly due to bad roads, bad weather and floods. Tyers's response suggests the Council was reluctant to spend its money on a bridge used mainly by tourists from outside the district, but it had instructed him to obtain a formal tender with specification and drawing from RCMPC, to be forwarded to the Public Works Department. On 18 March Monash promised to prepare the documents, but on 28th he wrote saying that the firm had taken on so many new projects in the intervening days that its resources would be fully stretched and he would prefer to defer construction until the following summer. A few weeks later "The Age" newspaper stepped into the ring, reporting on the parlous state of the existing bridge and the anxiety of road users, who were apparently using a ford which would become unpassable in winter. "The Age" also raised the question of the government subsidy.

There is then a gap of almost four months in the story, until the middle of August 1912 when Monash's old friend George Kermode, a senior engineer with the PWD, rang up to ask if he had heard that the Porepunkah bridge had been let for construction in timber, but that the contractor had thrown up the job uncompleted. This inspired Monash to write yet again to Tyers, stating that the firm was now less busy and was once more interested in the project. Kermode continued to urge a reinforced concrete bridge on the Council, and telephoned the RCMPC office on several occasions to check progress. Monash kept him informed by sending copies of all his correspondence with the Shire. He once again sent Council a design for a girder bridge with tender and specification, this time for £354. On this occasion he did send a drawing, but remained careful not to reveal details of the reinforcement, stating merely that it would be "so disposed as to meet the load conditions … specified". The government joined in by increasing its grant from £150 to £250.

After some urging Tyers responded, stating that he had been instructed by Council to prepare an alternative timber design for comparison with that of RC&MPC and that, as his design provided a roadway four feet (1.22m) wider for about the same cost, he had been instructed to call tenders for the timber version. Monash rapidly calculated that it would cost only £52 extra to increase the width of the reinforced concrete version to 16 feet (4.88m) and argued that the low maintenance costs and long life of a concrete bridge would more than compensate for this. He also appealed to Kermode, who instructed the Council to send all tenders to the PWD. The Council responded by sending only the four tenders for the timber version and proposing to accept the lowest of these at £450. RC&MPC's quotation was not included. Kermode thereupon advised Monash to write to the Secretary of the PWD saying he had learned of Council's intention and enquiring why his own tender of £354 had not been accepted.

Although Tyers had so far maintained that floods would not present a problem, he now wrote saying that the most recent flood had revealed that the waterway between the abutments could not be narrowed to 40 feet. He therefore suggested an arch bridge with a span of 50 feet, and three feet higher than originally proposed. He asked Monash to tender for such a bridge 16 feet wide, in the hope that the government would further increase its contribution. Monash's reply was a design and estimate for a girder bridge of 42 feet (12.8m) span at a cost of £416. He noted that since the PWD had become involved, he had felt able to approach their officers and obtain a cross-section of the river from them. He argued that the waterway provided by the 42 foot girder bridge would be greater than that provided by Tyers's proposed arch.

The ability of the opening beneath a bridge to cater for the discharge of a river depends on many factors, but as a rough measure engineers at this time simply calculated the cross-sectional area of the opening.

Tyers countered by claiming that logs floating on flood waters would be trapped by a flat girder bridge, whereas they could pass beneath the crown of an arch bridge, and claimed that it was he who had first proposed a "Monier" bridge, by which he had meant an arch. He mentioned, however, that Council had decided to call tenders for a Monier bridge to compete with timber. This must have been after a meeting at which the Secretary for Public Works had evidently upbraided the Mayor and a fellow Councillor, who had returned convinced that the PWD was "very sweet on monier bridges". Tyers defended himself at the ensuing Council meeting (Dossier, p.31) by claiming that RCMPC had never submitted a formal tender. Council now resolved to ask the government to pay the full price of the bridge.

Finally, on 20 November 1912, tenders were called for a reinforced concrete bridge only. Monash lodged a tender and a very brief outline specification, but this time it was for an arch of 50 ft span, at a price of £453. As in the 1910 scheme, the spandrel walls appear to be of reinforced concrete, although the counterforts have been omitted (Dossier, p.7). Following normal practice, Council submitted RCMPC's tender to the PWD for consideration. For reasons not evident from the Company's archives, the Department decided to change the location of the bridge, moving it 6 chains 20 feet downstream from the original site. A place was chosen where the cross-section of the creek was very similar to that for which the bridge had been designed, and Monash agreed that there would be no change in price. This was accepted by Council. In an exchange quite at odds with their former relationship, Tyers wrote to ask Monash what length of time he should allow in the contract for the construction period (after which penalties would be incurred for late completion). Monash replied courteously that he thought 12 weeks a fair allowance.

Two lengths of chain have been used in the Imperial system. Gunter's chain of 66 feet was the more common in the UK. The "Engineer's" chain of 100 feet is said to have been more common in the USA and in many former British colonies. Assuming Gunter's chain was referred to in this case, the distance concerned would be 416 feet, or 127 metres.

Construction.

Tyers must have organised the demolition of the old bridge effectively, but there was a little sparring when Monash's works manager Alex Lynch arrived on site, as Tyers proved difficult to meet. Foreman Bendschneider was obliged to start excavating the foundations on 15 March 1913 to a provisional layout provided by an officer of the PWD. However, when Tyers eventually visited the site, Bendschneider reported "he seems a very nice man". Construction proceeded relatively smoothly except that the locations chosen for the abutments proved to be two small prominences of rock jutting out into the creek, surrounded by loosened rock. Bendschneider took the foundations to the wing walls unnecessarily deep into this debris, initiating a contentious claim for extras. The abutments were concreted by the end of the month and work started on the falsework, formwork and reinforcement for the arch. The arch was concreted on 9 April, and by 2 May the structure was complete including the timber handrails. The filling and other earthworks were to be completed by other contractors. Monash put in a claim for £486 (including £33 in extras) and return of the £23 deposit.

In the middle of June, having had no reply Monash requested a progress payment of £400 pending settlement of the claim. Five weeks later, he received a letter from Tyers, saying that one of the wing walls had leaned over by two inches (5cm) and that it should be strengthened by the addition of a return wall. It appears that the lean may have been caused when the formwork moved during casting, and an inspection on behalf of RCMPC showed no signs of cracking or other distress in the wall itself. Further reminders asking for payment of the £56 claimed evinced no action. On 8 December 1913 "The Argus" newspaper reported that Tyers had resigned his position and Monash took the opportunity to write to the Shire President to press his claim. No evidence has been located to show what response he obtained.

The old bridge is still standing and provides access to one farmstead. A prestressed concrete bridge has been built to carry the main road on a new alignment nearby.

Commentary.

The above account, based almost entirely on the Company's records in the University of Melbourne Archives raises several intriguing questions. Fairway introduced a commendable improvement in design in 1910 by introducing reinforced concrete spandrel walls. Why then did he not press the matter more strongly? Was it because he was overloaded with work in Monash's absence, or because he was more of an "engineer's engineer" than a businessman? Histories of other projects suggest that if Monash had been present he would have found out what the Council felt able or willing to pay, modified the design to reduce its cost, and cajoled them into paying a little more to meet him part way. What was the motive behind Tyers's shadow-boxing with Monash over the years 1911 to 1913? Was it due to opposition to reinforced concrete from the local timber industry? Or was the Council playing poker with the State Government in order to extract the maximum subsidy for a bridge whose main benefit was to outsiders? Why did Monash suddenly withdraw his offer in March 1912? It is true there was much activity in the ten days between the 18th and 28th but it was not characteristic of Monash to turn down work in which he had shown an interest. Did he suspect Tyers of attempting to obtain details of the reinforcement prior to a contract, so that Tyers could build the bridge himself? A similar fear is documented in a number of other projects. It is unlikely that the answers to these questions were ever placed on record, but wider research might result in firmer hypotheses.

Footnote

The above history was extracted from our Dossier on the Porepunkah Monier Arch Bridge and edited for presentation here. The Dossier includes details of archival sources, dimensions, a list of personalities, and a 'Timeline' in which all relevant correspondence known to our research team was recorded chronologically in precis or verbatim form.