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

[Main Index] [Projects Overview] [Bridges] [Buildings] [Tanks] [Walls] [Wharves etc] [People] [Localities] [Abbreviations] [Units & Currency] [Glossary]

Marine and Riverine Projects:
Reinforced Concrete Pontoon and Barge projects

On this page:
1. Pontoon for SA PWD Port River works (built)
2. Barge for Mt Lyell Co (proposal)
3. Barges for SA PWD River Murray Works (unsuccessful tender)

1. Reinforced Concrete Pontoon for Govt of South Australia

University of Melbourne Archives
Reinforced Concrete & Monier Pipe Co Collection BWP-23725

The story in brief.

In 1909, South Australia's Chief Engineer asked Monash if he could supply reinforced concrete "pontoons" for river work, of the type being built in Europe. Monash admitted that he and his workforce had no experience in this type of construction; but he was keen to open up a new line of business and negotiated to build a prototype with others to follow if the first was successful. Design of the hull, and stability calculations, were carried out in the Melbourne office under Monash's direction. His Resident Engineer in Adelaide worried about the problems of building and launching the vessel. Their calculations for flotation and for slipway friction involved principles of high-school physics, so have been covered in some detail below, in the hope that they will be of educational value. The prototype hull was floated on 16 March 1910 and was afterwards worked for some time equipped with a Priestman steam crane as shown in the drawing below. However, no further orders were made and there is evidence that the crane was removed within a year, and the hull used as a simple barge.

The concept.

Illustration based on a drawing in the J Thomas Collection.

The idea of concrete ships has excited the imagination of many an engineer. Joseph Louis Lambot built concrete boats in France from 1848 onwards. Monash's first and only venture was inspired by A B Moncrieff, Chief Engineer of South Australia, who wrote in November 1908 that he needed pontoons for work on the Port Adelaide River. He knew they had been built of reinforced concrete in Europe, and thought this might be inexpensive and require less maintenance than wood or steel. He asked Monash whether he had a suitable design available. Moncrieff sent a sketch showing a length of 50 feet (15.2m) and a beam of 22 feet (6.71m), specified a maximum draught of 2'-6" (762mm), and suggested a shell thickness of two inches (51mm). The vessel would be equipped with a Priestman steam crane, with the necessary coal bunker and water tank.

Displacement and draught

After initial investigation, Monash set J A Laing to work on calculations. The displacement (and thus total weight) of a pontoon with Moncrieff's plan dimensions and draught would be 71 tons. Assuming it could be made with a 2" shell, the dead weight exclusive of crane, gear, tools and stores would be 44 tons. This would leave 27 tons for the rest. But Monash reasoned that the shell thickness could not be less than 3 inches, because such a vessel would be subject to rough handling. For the same plan dimensions, this would mean a dead weight of 66 tons. Allowing 24 tons for the crane etc, the draught would be increased to 3'-2". The only way to keep it at 2'-6" would be to increase the plan to 63 ft × 27 ft. The dead weight would then be 85 tons and the total weight, fully equipped, about 110 tons.

A special contract

Assuming three pontoons would be ordered, Monash informally quoted £400 each for the 50 ft × 22 ft version with 3'-2" draught, or £500 each for the 63 ft × 27 ft version with 2'-6" draught. Moncrieff preferred to keep to the original plan dimensions, and decided to live with the 3'-2" draught. In February 1909, JM submitted a formal proposal with reservations. He wrote: "Although a considerable amount of work has been successfully carried out in this field elsewhere, we have so far had no direct experience of pontoon construction; and therefore feel some hesitation in taking indefinite responsibility at the present stage. We are, however, most desirous of embarking upon this class of work, and consequently beg to submit the proposal in a form which, while fully safeguarding your Department, will not impose upon us a serious responsibility, either as regards the efficiency or the cost of the work. In the event of your ordering one pontoon only, we desire that in the event of the work not proving successful, our liability shall be limited to loss of payment only, and that we should be under no ulterior liability, as under the usual form of contract. In the event of your ordering three or more pontoons, we desire that, in the event of the first pontoon not proving successful, we may have the option of not proceeding further with the order. Under above conditions our price for a single pontoon 50 ft long 22 ft beam will be £460, and our price for each of three such pontoons will be £400."

Moncrieff then issued blueprints showing the agreed dimensions. The details, method of construction, and reinforcement were left to SARC. However, workmanship and materials were to be "of the best quality" and delivery was required as soon as possible.

Finalisation of design

Stress calculations were carried out by the Melbourne office in the middle of May 1909. The structure of the pontoon was treated as an inverted building floor, with the ribs of the pontoon acting like beams, and the shell like a floor slab; but subjected to upward pressure from the water. Monash decided at this stage to check what would happen to the pontoon when the crane picked up a load. His memorandum to Laing reads like an exam question - he had recently been acting as an external examiner for the Faculty of Engineering at the University of Melbourne.

"Mr Laing. Please work out following problem:-

ABCD is a pontoon 46' long × 22' wide, weighing, empty, 62½ tons. Assuming this weight to be uniformly distributed along its length, the displacement (in fresh water) will be 2'-2.6" (check this) i.e. EB = FC = 2'-2.6". Now, suppose that a concentrated load W is brought upon the pontoon, at point H, on centre line, 9' from one end. Find the values of EB and FC if W be taken respectively as 12, 18, & 24 tons. Rough solution required as soon as possible, subject to any urgent work in hand. JM 16/5/09."

The results were somewhat alarming, as the expected freeboard for the bare hull was less than 2'-6".

[load]EBFC
no crane load:2'-2½"2'-2½"
12 tons:1'-9½"3'-5½"
18 tons:1'-8½"4'-0"
24 tons:1'-6"4'-72/3"

However, the SA Engineer for Harbors, J B Labatt, assured JM that the pontoon would not sink, as the figures were "undoubtedly wrong". "The utmost concentrated load down the central pillar of the crane would not exceed 10 tons, while the utmost load hanging from the end of the jib would not exceed 2 tons."

Computations for the strength of the pontoon resumed at the end of July and continued into August. Laing calculated the strength required of the cross-rib under the crane, treating it as a beam of span 6'-8", carrying a load of 12 tons. After calculating the bending moment and shear force, he decided to provide small tertiary ribs directly below the crane. The volume of concrete in the pontoon would be 964 cubic feet. Without the crane, fuel, etc, it would displace 2'-6" of water, giving a freeboard also of 2'-6". It would be able to take more than 60 tons uniformly distributed load "without losing buoyancy". Monash sent these details and a copy of the calculations to his Resident Engineer in Adelaide, W W Harvey and asked him to finish off the design by sorting out details of the fender beams, bollards, and manhole covers.

Practicalities of building and launching.

Harvey had started to think about how the pontoon could best be constructed. His first idea had been to build temporary walls in the river to enclose a makeshift dry-dock, running parallel to the bank. The water would be pumped out, and the pontoon built on a portion of the river bed. Water would then be let back in to float the pontoon, and the walls removed. However, locals had told him the land surrounding the Port Adelaide River was so sandy that the dock would never be dry. They claimed that water in pits dug one mile from the river had been seen to fluctuate 4 feet with the tide. Foreman Suffren assured him this story was true. Harvey therefore suggested making a slipway and building the pontoon either inclined at the angle of the slip, or on a launching platform. The first method would be cheaper, but would induce bending of the hull during launching because one end would start to float while the other was still on the slipway, leaving the middle unsupported. As the pontoon was intended for use in quiet water, this effect had not been catered for in design. The second method, suggested by Monash, would ensure the pontoon floated off the platform evenly supported by water along its full length. However, powerful jacks would be needed to move the assembly, and abutments would be required for them to thrust against. This option was chosen. Monash approved Harvey's sketch for the platform and agreed it would be best to launch the barge sideways.

Optimum slope for slipway.

Then followed much discussion of the optimum slope for the slipway. A steep slope would minimise the force required to move the assembly, but there would be a risk that it might get out of control. A gentle slope would need greater force and a longer slipway, extending further out into the water. The vertical descent of the pontoon to obtain flotation would have to be about 4 ft, even at high tide. Laing had calculated that with a slope of 20 degrees, a force of 10 tons would be needed just to get the platform and pontoon moving. He based this on coefficients of friction he found in texts by Rankine (0.25 to 0.5 for wood moving on wood) and Molesworth (wet wood 0.68, dry wood 0.5, at repose). The platform would need to move 11 ft horizontally to achieve flotation. However, Monash was concerned that the 20 degree slope would be dangerous and suggested a flatter angle, implying a horizontal movement of about 30 ft.

RCMPC's Managing Director John Gibson promised to "have enquiries made from some practical men in Melbourne". In Adelaide, Foreman Pratt obtained advice from a Mr Fairweather of the South Australian Tug Co. that the usual grade of slipways for launching ships was between ½" and 1" per foot [2.4 to 4.8 degrees]. The Tug Company's own slip was reckoned to be steep at 7/8" to the foot. Fairweather suggested that SARC's slip could be set at 1" to 1¼" to the foot - or more if they chocked the ends to prevent the platform running away.

Harvey's summary of the problem was as follows:
[skip summary]
He used T as the symbol for tons.

University of Melbourne Archives, Reinforced Concrete & Monier Pipe Construction Co Collection

 
W = weight of Pontoon and launching Platform - say 70T
R = W cos θ and F = μ R = μ W cos θ = μ × 70 × 0.94 = μ × 66T
Resolved part W down plane = W sin θ = 70T × 0.342 = 24T
Therefore additional force reqd to keep [platform] in motion = μ × 66T = 24T = P
If μ = 0.5, P = 33 - 24 = 9 tons.
If μ = 0.5 critical angle = θ' where tan θ' = 0.5      θ' = 26.5 degrees
Above would apply with perfectly true ungraded skids wood to wood with planed surfaces clean and dry. In case of Pontoon it is intended to use planed oregon [Douglas fir] lubricated thoroughly with tallow. So above cannot be applied.
Coeff of kinetic friction for these conditions = say 0.075 (Trautwine p.415).
tan θ = 0.075      θ = about 4° only.
or a batter of nearly 1" in a foot.
Slope of 1 inch in a foot agrees fairly well with practice (see Pratt's memo of 11/8/09).
But these slopes of 1 inch to 2 inch per foot assume:
(a) Planed surfaces dry and
(b) Well tallowed
In our case however the tender slip will be alternately wetted and tried with salt water for perhaps 3 months before it is required to use it. Must study and enquire re:
(a) effect of continual wetting and drying on timber
(b) [ditto] on tallow (sea water)
(c) What is the 'ultimate' or 'static' friction of tallowed oregon under these conditions as distinguished from 'kinetic' friction (to determine force required to start)
(d) Whether ultimate friction is likely to increase between surfaces so long in contact under these conditions.
Consider
whether in view of uncertainty on above should not build on an angle which would permit launching supposing lubricant failed to act (taking precaution against sliding during construction)
whether should not build at flat angle with lubricated surfaces; and skids on which built above (or protected from) High Water.
 

After wrestling with the problem for several days, Harvey told Monash he agreed that a 20 degree slope was too steep, recommending 4 degrees, but suggesting further recourse to "practical men". However, he continued to propose new schemes. One was to face the skids with iron and use 1¼" bars as rollers, though the slope would have to be very low for safety reasons, and the length of the slipway correspondingly long. Finally, he came up with the method that was to be adopted: to use timber skids, but have them separated by wedges, "as done in the ship building industry". The timbers would not be greased until the pontoon was ready to launch. The platform would have to be stiffened to avoid distortion of the pontoon as the wedges were gradually removed. Harvey ended: "There are so many details in connection with this whole matter which are new to me that I will be glad of your brief advice on the various schemes mentioned".

Internal stiffness and strength.

An incomplete drawing in the J Thomas Collection (JTC) suggests that at some stage in the design process, the Melbourne office had decided to simplify the system of internal stiffening walls suggested by Moncrieff's team by providing only two, longitudinal, wall-girders. Stiffness in the transverse direction would be achieved by adding ribs to both the deck and bottom plates. However, Harvey was worried that this would not provide sufficient resistance to racking effects. "Regarding the general design, there is one modification which I strongly recommend viz the introduction of three cross stiffening walls."

Harvey stated that the advantages of his scheme were:

Harvey pointed out that parts of these walls already existed in the Melbourne scheme to provide a water storage tank for the crane engine. The weight of the walls would increase the displacement by only one inch - less, if the advantage were taken of the stiffening walls to reduce the ribs in places. For a while, he was worried that the concrete might absorb up to one third of its volume in water, thus increasing its weight and the displacement of the vessel. However, after "Calculations and Experiments" he decided the absorption would be only about 8%.

Final arrangements

A reinforcement drawing initialled by Harvey was issued by SARC on 19 August 1909. The first requisition for materials followed the next day. On 23rd, Monash approved Harvey's choice of site for the slipway and suggestion for increasing the lateral stiffness of the pontoon. Launching should be by means of a platform with a horizontal top, a slipway with a grade of 5 to 7 degrees, and skids separated by wedges as suggested, the whole being chocked for safety. For launching, preventer ropes should be attached on the land side to limit movement, the skids greased, the wedges removed, and the assembly lowered away using the jacks to assist.

Harvey now negotiated with Labatt a number of modifications to simplify construction. The latter agreed that the ends of the barge, instead of being semi-circular in plan, could be formed from five straight sections. However, he insisted that the lower edge of the hull, where the sides met the bottom, should be rounded, arguing that this would make it easier to refloat the pontoon if it became grounded. The contractors naturally preferred a simple right-angle. It seems that Labatt tried to convince Harvey by showing him a copy of the Scientific American of 5 Sept 1908, containing European examples of concrete vessels. Monash tried to hunt up a copy in Melbourne, but his approach to Gibson and Mitchell was unsuccessful. He suggested as a compromise that the corner be made as a double bevel to simplify formwork.

By 6 September, Harvey was having doubts about the wisdom of the project. "I cannot help thinking that we are working on a wrong basis by trying to mould the pontoon. I fear that if this were the right method of construction for floating craft, that there would be very little field for the application of Reinf. Concrete owing to high price of timbering and complicated nature of the work. Also the heavy nature of the work when done."

Construction.

On 3 November, Harvey reported the slipway and launching platform complete. Work had started on the formwork, and on 11 December the 'floor' of the pontoon was concreted. Monash became concerned about the high cost as work proceeded, and learned that the Government Inspector was insisting on giving directions to SARC's foreman, Suffren, about details of construction. Monash declared this "unsupportable" - SARC had guaranteed to supply a barge and had agreed to get no payment until the thing was finished and afloat. The pontoon was a product, like in a shop - the Government should not be involved. By this time H G Jenkinson had taken over from Harvey as SARC's Resident Engineer. He assured JM there would be no more interference, and on 26 January 1910 reported that the concrete work had been finished and stripped, and looked excellent.

Launching.

The first attempt at launching took place towards the end of February 1910. It was only with great difficulty that the platform was induced to move, although two 10 ton jacks were employed. The pontoon was slid to the end of the skids; but the tide proved not high enough to lift the pontoon. A small local tug named the Wallace was hired to pull it off, but could move it only 6 inches (15cm). During a wait for higher tides, someone realised that the platform had skewed and become jammed. Jenkinson tried to hire a more powerful tug, the Wato, but its owners were unwilling to risk its running aground. On 16 March, someone at SARC took drastic action, and removed two end principals from the platform substructure. The remaining principals then "slowly collapsed sideways" and the pontoon floated off at peak tide. Jenkinson reported that the draught was about 2'-10" with no load. The sides were "sweating a little", but no more than was expected and would "doubtless take up soon". The pontoon's water tank (for the steam engine) would be filled and kept full until its walls became water-tight.

Outcome.

About a fortnight after the launch, the pontoon was put on a slip for inspection. The SA Government Inspector declared it satisfactory and it was formally delivered to the Way & Works Department. SARC was paid £473-10-0d. Although Labatt had said he might order six more pontoons after the first had been tried out, Jenkinson doubted that SARC could supply them for a price acceptable to the Department. A photograph of the vessel in the RCMPC records [top of this page] carries the inscription: "Port Bridge, Adelaide. Reinforced Concrete Pontoon at work in canal, Oct 1910, with steam crane and grab". However, a photograph published in the Adelaide Register in May 1911 shows only the bare hull, apparently being used as a barge.

Footnote.

In mid-1917, the Adelaide Register reported that Monash's rival in reinforced concrete, E G Stone, was promoting the idea of concrete ships of 4000 tons and would guarantee them seaworthy. He stated "We [Stone & Siddeley] built the biggest pontoon in the world. It was 180 ft long with a beam of 80 ft. It is now in use in the Sydney Harbour."

spacer

2. Reinforced Concrete Barge for Mount Lyell Co (Project?)

Late in May 1910, Jenkinson informed Monash that the Mount Lyell Company had asked SARC to quote for a reinforced concrete barge to be used for loading superphosphate at Port Adelaide. He continued: "Details are given in the enclosed estimate concerning which I wish you to confer with Mr Gibson. I have a scheme in mind, which will avoid a great deal of the difficulty experienced in launching the Pontoon recently completed for the Government [above]. Should we obtain the work, I will have a cradle cheaply made which will run on old rails like an ordinary slip right into deep water."

Jenkinson emphasised the simplicity of the vessel, compared with the pontoon. It would be an open, flat box 70 feet long, 30 feet wide, and 6'-6" deep (21.3 × 9.14 × 1.98 m). Floor and walls would be strengthened and stiffened by internal ribs. The walls would be 4" (102 mm) thick and the bottom 3" (76 mm). It would displace 108 tons and have a draft empty of 1.85 feet (0.56 ) and full less than 4 feet (1.22 m). He estimated the basic cost at £520, and allowed £60 for constructing a slipway and launching, £60 for "Commission etc", and £110 for margin, giving a total price of £750.

Monash commented to Gibson that: "The general design appears to be both suitable and simple from a constructional point of view, but it seems to me that the owners may probably require some amendment. No deck has been provided, nor even combings and there would surely be some considerable risk of the loaded craft being swamped, particularly in the exposed water at Port Adelaide. The responsibility of this point should certainly be fixed before the matter is settled. I find from Mr Jenkinson's figures that the barge just finished [i.e. the Pontoon] cost (including launching &c) 11/2 per cubic foot of concrete, but that was a very complicated construction with division walls &c. so that the works can hardly be compared. I cannot see that the design proposed by Mr Jenkinson should cost a great deal more than an ordinary floor construction, and his estimated cost of 6/6 per c. ft. I consider very ample indeed. The addition of a partial deck or combings would not complicate the construction to any great extent. However, if the price of £750 can be obtained for the work I would not suggest any alteration, as the margin allowed - £110 - on a cost of £640 - is not a large one. At the same time, I think that should the necessity arise, the quote could safely be somewhat reduced. Subject to the above remarks, I quite concur with Mr Jenkinson's design and estimate."

We have found no further information on this project, so conclude that it probably did not proceed.

spacer

3. Reinforced Concrete Barges for Murray River Works, S.A. (unsuccessful tender)

In April 1914, Jenkinson obtained blueprints from the South Australian Department of Public Works showing a design for wooden barges intended for use on its River Murray Works. The design had been prepared under the direction of a Captain Johnson, an "American Consultant" [Capt E N Johnston(?), US Army Corps of Engineers]. Jenkinson intended to offer an alternate design in reinforced concrete. He told Monash that he had based this on the design of the Port River Pontoon (see above) but had given it sloping ends as in the Department's timber design. He presumed the idea was to allow the barges to run up on the bank. The barges were required to carry "stone &c".

The Department was willing to accept delivery anywhere on the Murray River, and Jenkinson proposed to build them at the town of Murray Bridge. He explained that pressure of work had prevented him from putting a great deal of thought into the proposal, but wanted to suggest a rough price to the Department and test their reaction. He thought the timber barges as designed by "Johnson" would cost at least £1300. It was likely that six would be ordered.

Jenkinson's barge would be 24 feet wide and 6 feet deep. The reinforced concrete plate forming the bottom would be 68 ft long and 3" thick. The deck would be 90 ft long and only 2¾" thick. The sides and sloping ends would be 3" thick. There would be two longitudinal stiffeners, like full-height internal walls. Lateral ribs 6" × 6" would stiffen the bottom, walls, and deck. The hopper opening in the deck would be furnished with a "railing" 2'-6" high and 3" thick.

The Port River Pontoon was a poor guide to the probable cost of construction. "Certain circumstances enhanced cost of pontoon greatly - chiefly the fact that the work was done under the supervision of a foreman who, while an excellent man at directing pile driving and other awkward operations was not used to economical construction of forms and placing of concrete. Also, Port River Bridge, being current at same time as Pontoon, engaged the foreman for the bulk of his time - so Pontoon suffered. I have now several foremen who have become skilled in country work, principally tanks, and the actual construction of the Barge should cost very little more than tank work. I would engage a man specially to arrange launching matters." Keeping this in mind, Jenkinson's estimate was:

Labour£239
timber including fenders175
concrete materials107
reinforcement76
sundries, bollards &c30
launching, including labour200
freight to Murray River 60
 887
Standing Charges 70
 957
Clear Margin  200
Total£1150

Monash basically agreed with Jenkinson's ideas, but thought the margin was not enough for "critical work of this kind". There would be no competing tenders in reinforced concrete, and with an anticipated price for timber barges of £1300 plus; a margin for concrete of £250, and a tender price of £1200 would be appropriate.

In June, Jenkinson advised that the Engineer-in-Chief had decided to call tenders, this time specifically for reinforced concrete barges. He added "I fancy the presence in S.A. of Stone & Siddeley, the contractors for the Glenelg Breakwater, has influenced the Chief in deciding on the above procedure". Notices appeared in the Melbourne newspapers on 12 June. They called for pairs of barges, up to a maximum of six pairs (12 total), with a variety of deadlines.

The advertisement in the Melbourne Age did not mention the material, or the possibility of submitting alternative tenders.

Jenkinson calculated prices for 10 possible cases, assuming that fixed charges per barge would be £536. To supply 2 or 4 barges before the end of the year would require two sets of formwork and two launching platforms. To supply six within this deadline would require three sets.

SchemeNo. of
barges
No. of
sets
No. to be
delivered
by end of 1914
Deadline for
completion
Price £Margin £
121all32 weeks1962400
242allearly 19153924800
3624Apr 191554961100
462allJan 191558861200
5824end July 191570681400
6826end Apr 191574581500
71024end Oct 191586401700
81036end July 191590301800
91224end Jan 191610,212??
101236July 191510,602??

Jenkinson noted: "The Chief considers reinforced concrete barge building still in experimental stage and is not likely to order all the barges in reinforced concrete".

Monash was not able to reply until 26 June, four days before closing date for tenders. "Although I have had these papers before me since the 18th inst, I have, partly through a severe cold, and partly through a great congestion of other business, been able to give this matter only intermittent and rather superficial attention until yesterday …" He agreed with most of Jenkinson's proposals, but the question of profit had caused him the most thought. He would not insist, but felt that the margin could be raised on Case 1 from £400 to £500, and on Case 2 from £800 to £850.

On 17 July, word came that fresh tenders were to be called for timber barges only. The Engineer-in-Chief's main reason for rejecting concrete barges was that their draught, when empty, would have been 2'-11" compared with less than 18" for a timber barge. This was significant in the shallow waters for which they were intended. Jenkinson reported that "Mr Stewart also thought our prices were pretty stiff", but he had been "very well satisfied with our proposed design." Monash returned all the drawings to Adelaide, so they are presumably lost.