Irish Railway Record Society

Irish Railway Bridges-Part 1

NIALL V. TORPEY C.Eng, F.I.Struct.E, F.IEI

Public railways for the transport of passengers and freight have existed in Ireland since the 1830s, when in December 1834 the Dublin & Kingstown Railway commenced its services between Westland Row and its then terminus near the West Pier at Kingstown . At this time, Westland Row was one of the first city termini of what would later be called a commuter railway. Four years later in 1838, the Ulster Railway opened its line between Belfast and Lisburn and this line was also an early commuter railway in a European context. These lines introduced the civil engineering infrastructure, which we have today, and we can therefore say that the stations, bridges and earthworks are now, anything up to about 170 years in service.

This paper begins with the building of our first railways and will end at about the late 1960s, except for information, which is in the public domain. I would also note that many topics will not be touched on at all, such as the matter of telescopic railway bridges, or the insistent bridge at Broadstone harbour.

It may be noted that the original construction of the railways in Ireland was carried out by private enterprise companies, functioning in a laisse faire economy in which the satisfaction of the shareholders by way of share values and dividends was the primary concern of the direc-tors and managers of the various companies.

  THOMAS DRUMMOND

The railways in Ireland were not however initially intended to be so laisse faire. A much neglected figure nowadays, Thomas Drummond, Under Secretary for Ireland between 1835 and 1840, was seriously concerned for the plight of the poor of Ireland , and the poor were, not surprisingly the largest proportion of a population which in 1834 was estimated at almost 8 million. Drummond proposed and largely prepared the Report of the Irish Railway Commissioners, which was published in July 1838. The Report envisaged the construction (by a combination of Government and private funding) of trunk railway lines between Dublin and Cork and Dublin and Belfast and to many other places throughout Ireland . One purpose of this proposal was to provide gainful employment in the hope of encouraging the emergence of working and middle classes from among the Irish population, most of whom lived at subsist- ence    levels  on   tiny   agricultural    holdings.

  Drummond died in April 1840 at the early age of 42 after a life of some considerable hardship. His death was a blow to the peaceful development of Ireland and to the prospects for the implementation of the Report. His grave in Mount Jerome cemetery is a mark of the loss felt by the society of his day. The story of his work in Ireland should be told.

The Report included a proposal for Dublin , which involved the construction of a line connecting the D&KR with the GS&WR on a series of bridges over the streets of the city. Such a facility, if it existed today, would surely be intensively used.

  EARLY BRIDGES

The earliest bridges on Irish railways were built from masonry, cast iron, wrought iron, and timber, and combinations of these materials. Stone was however the noble material and has proved itself to be the most durable and strong of the several materials with which it competed in those days. Indeed in its own terms its strength and durability is still proved today with the numerous stone arches carrying today’s service loads which are very much greater than those envisaged at the time of their construction.

  DEVELOPMENT 1845-1865

The period of twenty years between 1845 and 1865 was the one in which almost the entire current railway network was built. Dublin was connected by rail to Belfast , Derry , Sligo , Castlebar, Galway , Limerick , Tralee , Cork , Waterford and Enniscorthy. In addition, Belfast was connected to Bangor , Downpatrick, Cavan and Derry , while Cork had railways to Passage, Kinsale and Bandon, Youghal and Cobh .

The longest stretch of line to open on a single day in this period was the 76 miles from Mullingar to Galway on the MGWR, which opened on Friday, 1 August 1851 .

All of this construction included railway stations, and the facilities for the construction and maintenance of locomotives, carriages and wagons. Some of the principal stations and not a few wayside ones may be regarded as an important part of our architectural heritage. The Dublin stations at Heuston (Kingsbridge) and Broadstone merit a mention in this respect, as do the stations at Cahir, Bagenalstown, Ballinasloe, Portlaoise and many other places.

Tunnels were built near Cork ( Blackpool and Ballinhassig), Down Hill, Co. Derry , Bray and Lissummon, Co. Armagh . Substantial earth-works of both embankments and cuttings were made on many of these lines, but particularly on the main GS&WR line between Mallow and Cork and on the main line to Belfast between Dundalk and Poyntzpass.

Many significant railway bridges were built for these railways and some of them are still in service as originally built examples being at Athlone, Cahir, Craigmore, Kilnap and Monard. Lines now closed also had significant bridges, such as at Ballyvoyle, Borris, Fermoy, Cappoquin, Chetwynd and Innoshannon [sic].

In order that the global picture should not be lost sight of, it may be remarked that on the line for example from Dublin to Cork , well over 400 bridges were built in the construction period 1844-49. Most of these were small public road or farm accommodation bridges. An overview of the topic of bridges, particularly over rivers and sea inlets, may be had by reference to Across Deep Waters¹.

  RAILWAY BRIDGE MATERIAL - ENGINEERING

I have noted that the materials used in bridge construction were masonry, iron, timber, and combinations of these materials. The quality of such materials was in the case of the GS&WR in Contract No. 1 of 31 March 1845 and also the Waterford & Central Ireland Railway (for its bridge at Thomastown, completed in May 1850) specified to be:

Stone Masonry GS&WR The stone to be used for rubble and hammer dressed work is the limestone of the country (commonly called calp).

For ashlar work, copings etc., the stone to be from the purer limestone or granite quarries, and such as can be chisel dressed. It is to be taken from such quarries as the … Engineer … may approve…

Arch   The face of the abutments and outside spandril walls to be coursed work, with close square joints. No course in the abutments shall be less than eight inches thick, and to be of the same thickness throughout… None of the arch quoins to be less than 21 inches long, nor less than 11 inches deep, and their beds neatly dressed to radiate to that part of the arch where laid. When the bridge is askew the courses of the arch are to be laid in spiral lines, and the quoins must be dressed to the proper twist of the spiral…

The face of all wing walls to be of hammer squared and punched stones in random courses…

The parapet wall to be 1½ foot thick, of best hammer squared work, with a thorough tie in every course, at every six feet. The cope of the parapet walls to be 20 inches broad, and nine inches thick at the centre, and weathered off 2½ inches on the outer side. No stone to be less than 18 inches long, and to be connected with each other by cast iron dowels, 4 inches long and one inch square, run with cement.

The other parts of the building not here described to consist of substantial rubble masonry, and all the stones to be laid on their natural bed, and well packed and pinned and pointed. The back of the abutments and space behind the wing walls to be made up with hard dry materials in courses not more than one and a half foot thick, and beat up hard and firmly placed behind the walls.

Stone Masonry W&CIR  The specifications required, that the masonry should be built, as strong, best 'coursed walling' not inferior to the best samples (pointed out by the Engin-eer) in the bridges on the GS&WR, which had been already finished, and were near at hand for reference. The voussoirs were to be dressed on the beds, face, and joints, and to be laid so as to break bond thoroughly well together, throughout each arch…

Timber GS&WR The timber used in the main ribs, struts, braces, and hand rails to be of the best grown memel, the cross bar, King and Queen posts of red pine, and the sheeting and flooring to be of red pine, or larch of the country. All the timber to be squared, smoothly wrought and closely jointed and painted with two coats of best oil paint, after being in place; the priming coat to be laid on before the work is put in place; all the joints are to be carefully filled with white lead. All tenons to fit the mortices, and to be well pinned, and no … unsound timber to be used.

Iron Work GS&WR The iron in the straps, stirrups and plates to be of the best English iron. The tie rods to be of the best cable iron, and all the bolts, nuts, screws and pins, of the best Welsh iron. All cast iron to be of the best quality and the workmanship well and carefully executed. All iron work to receive two coats of oil paint, before it is oxidised. All girders to be subject to such test as the Company’s Engineer may direct.

GS&WR Concrete The concrete shall consist of good coarse gravel, perfectly free of loam or clay, and  unslaked lime, from or other quarries equally good, in the proportion of five measures of gravel to one of lime, to be beat up with a proper quantity of water, but it is not to be mixed up until wanted for use. It must be thrown into place from a height of ten feet at least…

GS&WR  Brick Work The bricks made use of in  any  arch  or  culvert  shall  be  sound, well shaped, thoroughly burnt, and of uniform colour in the face or exposed work. No broken bricks shall be used, and no joint of mortar shall exceed a quarter of an inch in thickness…

  ENGINEERING KNOWLEDGE

Engineers  The construction of the railways in the period up to late in the 19^th century was carried out by engineers and others who were the product of their age. It might be appropriate to name at least some of these and to try to assess the range of their knowledge.

The ordinary knowledge of the engineers of that day would have included a familiarity with the strength of the commonly used materials of stone and brick masonry, wrought and cast iron and timber. In addition, the analysis of structural sections by calculation would have been well known to engineers concerned with assessment of bridges and their components. Engineers resident and working in Ireland had their technical work published to the English speaking world, of which Stoney’s The theory of stresses¹⁹ and Mills’ work Railway Construction²⁰ were examples. A not inconsiderable source of information and useful technical support came from the learned societies such as the ICE, ICEI, IMechE, and the various Railways and Mechanics’ Institutes in their current papers and other publications presented by practising engineers. The British Standards Institution²¹ was not established until 1901, and for some years thereafter its standards related to steel (steel at that time being a vital strategic material on which armies and navies depended). Many of the earliest publications of the fledgling BSI related to rails, locomotives and other railway and tramway topics.

  BRIDGE LOADING

On the matter of railway bridge loading, Stoney noted¹⁹ in the 1880s that the 16 ton axle load resulting from three 0-6-0T locomotives on a triple headed train would be the heaviest load to which a railway bridge might be exposed. In the case of road bridges, Stoney noted that the effects of running cattle or men marching in step across a suspension bridge will strain a such a bridge far more than any other form of passing load. In the absence of standards or codes, Stoney describes his own experiments to determine the weight of people on a bridge as he goes on to say:

A crowd of people constitutes the greatest distributed load on a public bridge, and 15 adults are generally estimated to weigh one ton, which gives an average of 149.3 lbs to each adult. … In order to test this I packed 29 Irish artisans and 1 boy, … weighing collectively 4,382 lbs, or averaging 146 lbs per individual on a weigh bridge of 29.4 square feet, resulting in a UDL of 149 lbs per square foot.

It can, perhaps, be assumed that few engineers then would have had the freedom to carry out such experiments with artisans and a boy! On a more serious point, the average weight of the employees today would almost certainly be greater than 146 lbs, or somewhat less than 10½ stones.

  GOVERNMENT INVOLVEMENT

THE BOARD OF TRADE etc.

Government involvement in the day-to-day business of railway operation emerged only slowly and usually as the result of difficulties or disasters. Legal matters involving the fledgling railway companies required them in having Acts of Parliament passed giving them the powers to construct their lines. When the lines were built and before their opening for public use, Inspecting Officers examined the line and its construction. In a more general way, the matter of the track gauge was decided on, in the case of Ireland , as the result of the disparity of gauges in the railways when they were first built. The gauge of 5’ 3” was fixed in the Act of 1846²².

A further source of difficulty, particularly in the area of bridge building, was the influence of river and maritime navigation exercised by the Board of Works and the Admiralty. Many railway bridges were built having opening spans for navigation to waters, which were rarely if ever used for the purpose. It is believed for example that the Lough Atalia Bridge at Galway was never opened for water traffic. Another aspect of this problem was at Thomastown; Captain Moorsom’s experiences with navigation problems caused him to decide on a single span between abutments, which were built clear of the river Nore, resulting in a span of 200’, but needed no discussion on river navigation.

A topic, which came forcefully to the attention of bridge engineers, would have been the matter of wind forces acting on bridge superstructures particularly in exposed locations. The collapse of the bridge over the estuary of the river Tay in Scotland in on 28 December 1879 gave rise to a Board of Trade enquiry, which reported in 1881. In the report, it was stated that a maximum wind pressure of 56 lbs/ft² should be assumed for the purposes of calculation. Before the collapse, a pressure of from 25 to 40 lbs/ft² was considered an ample allowance. When one considers that almost all of the larger railway bridges in Ireland were built long before 1881, and that almost all of them are still in service today, the foresight of the engineers who built them and the innate toughness of their construction must impress the engineers of today. Examples of such bridges are those over the Shannon at Athlone (1850-1), over the Suir at Cahir (1852), over the Nore at Thomastown (1877), Craig-more (1852), Monard and Kilnap (both 1849).

In the 1880s the Board of Trade rules for railway bridges (see Annex) included such matters as:

Cast iron must not be used for railway under bridges except in the form of arched ribbed girders, where the material is in compression…..

It is desirable that viaducts should, as far as possible, be wholly constructed of brick or stone…

Where iron is made use of for the construction of … piers of high bridges,… it must be distinctly understood that these piers should not consist of cast iron columns of small size, such as 12, 15 or 18 inches in diameter.

The last of these rules may well have had its origin in the collapse of the Tay Bridge . The high girders of the bridge were supported by such columns and were suspected of being at least partly responsible for the disaster.

EDUCATION & TRAINING

We can record that the formal education of engineers in Ireland commenced in the 1840s at TCD, the first Professor of Engineering being John Macneill. Up to that time the knowledge of structural analysis would have been limited, and the building of bridges and other construction would have been based on tradition and having an experienced based feeling for the correctness of what should be done. Before the start of formal education at TCD and for many years thereafter, the training of engineers was regarded as a practical matter deeply dependent on the experiences of the engineer in training. Engineers trained in this practical manner who are today rightly regarded as leaders of excellence, include Abraham Darby, George and Robert Stephenson, Isambard Brunel, and in an Irish context, John Macneill. Indeed, even today, engineering institutions in their qualifying functions regard practical training as an essential part of the experience of their chartered members. 

IRON BRIDGES

The late eighteenth and early nineteenth centuries were notable for the development of cast iron, particularly in useful structural sizes and quantities. Abraham Darby at Coalbrookdale, Shropshire , established the usefulness of cast iron as a material for bridge building with his use of the material in the construction of the bridge there in 1779. In Ireland , the Darby Company was responsible for the Halfpenny Bridge over the Liffey completed in 1816. Within the following few years, a further Liffey bridge (called King’s Bridge for many years and now known as Seán Heuston bridge and now being rebuilt to carry the Luas) was built upstream, this time, as reported by de Courcy², from castings made by the Royal Phoenix Iron Works situated directly across the Liffey from the GS&WR’s Kingsbridge (now Heuston) Station and beside the site of the bridge. An early railway bridge of cast iron members was the Lough Atalia Road Bridge in Galway , built in 1850-1, whose cast iron members, made in Galway , are still in situ and in service.

At about the same time in the middle of the nineteenth century, wrought iron made its appearance, and a most useful material it was. Offering strength in tension and compression together with a substantial degree of resistance to corrosion, its usefulness was quickly recognised. Early railway bridges built using this material included the Dublin & Drogheda Railway bridge over the Royal Canal at Dublin in 1844. A remarkable, distinctive and pleasing use of a combination of stone masonry and cast and wrought iron was the Chetwynd viaduct completed in 1851 on the Cork & Bandon Railway. However, the largest Irish wrought iron railway bridge of this period, much examined by engineers from abroad, was the Boyne Viaduct at Drogheda .

  The remainder of this article appears in IRRS Journal number 153, published February 2004.

Copyright © 2004 by Irish Railway Record Society Limited
Revised: March 08, 2004 .