Description of the Viaduct Erected Over the River Nore, Near Thomastown, in the County of Kilkenny

426 LATTICEVIADUCT. TIMBER which he did not consider to be objectionable; if the bed-plate wad set with reference to this deflection, the girder would be brought levelby the impinging load. At Reedham,he experienced great difficulties in the foundations, owing to the nature of the soil, and he had already described the plan to which he had recourse on that occasion;but in general, he admitted, that roller frames worked with the greatest facility. Mr. R. Stephenson had recently had to consider the principle on which swing bridges should be constructed for t,he railway across the Nile, and he had come to the conclusion, that the roller system was much preferable to the hydraulic principle of support. Mr. C. WAYthought, that on the contrary, there were some practical advantages in adopting the system ofthree tie-bars. He would also point out an important fact, which conld not fail to be useful in practice. It was not generally known, that by casting the rollers in an iron mould, it was possible to obtain a smooth surface, without at all impairing the hardness of the material. There was a class of pig-iron, that would not chill in an iron mould ; the greater part of the Scotch irons had this property: a perfectly solid mass could thus be obtained, which on being turned, would not present a. single speck on the surface. Ile might mention, as an instanceof the facilities now afforded for working metals, that the main rings of the turn-table were jointed and planed by means ofa machine, with as great ease as if they had been of wood. Mr. P. W. BARLOW,through the SECRETARY,said, thatthe successof the Rye Bridge was rather due to the excellent workmanship, than to any novelty in the design, which was derived from Mr. Bidder’s first bridge of thekind. The principal variations from it, consisted inthe use of timber pilesinstead of cast-iron, and in avoiding the employment of the uprightpillar.

NO. 857. ‘‘ Description of theViaduct erected over the River Nore, near Thomastown, in the County of Kilkenny, to carry the Waterford and Kilkenny Railway.” By Captain WILLIAM SCARTHMOORSOM, M. Inst. C. E. . THEWaterford and Kilkenny Railway Company w;t9 incorporated by Act of Parliament in the year 1843, at which time the Author was occasionally consulted by the Company; and upon his taking a more active charge of the works, in the spring of 1846, he found, that it was proposed to deviate from the limits of the line, autho-

Downloaded by [ UNIVERSITY OF CAMBRIDGE] on [23/09/16]. Copyright © ICE Publishing, all rights reserved. LATTICE ‘fIMBEE VIADUCT. 427 rized byParliament, so as to approachnearer to the village of Thomastown, and to erect a viaduct, consisting of several laminated timber arches, npon stonepiers and abutments, similar to those previously built by Nr. Green, (M. Inst. C. E.,) in the neighbour- hood ofNewcastle-upon-Tyne.L Thestructure was to consistof seven arches, each of 130 feet span, and the total height, above the river, was to be about 70 feet. The first points to be considered, were the propriety of deviating from the authorized line of railway, and of erecting a viaduct of the particular characterdescribed. To test these points, specifications wereprepared for contractsto embr’ace two alternative lines of railway, forming a loop in the neighbour- hood of Thomastown ; one line of the loop being that authorized by the Act, and the other, the proposeddeviation. The tenderswere found to be lessexpensive, byseveral thousand pounds, forthe constructionof the authorized line, and as neither presented any peculiar engineering superiority over the other, the authorized line was adopted, and the proposed deviation was abandoned. The tenders sent in, had also embraced two designs for crossing theriver and valley, withviaducts of equal extent, the masonry beingalike for hth designs;but in one design, thearch was proposed to be formed of laminated timber ribs, and in the other plan, alatticed beam of timber was proposed, the clear span in both cases being 200 feet. The tenderssent in for the execution of these designs, showed a difference of cost of about twenty per cent. infavour of thelattice design, as compared withthe laminated arch ; thus confirming- the anticipations expressed in the Engineer’s estimates, whichhad beenpreviously laid before theBoard of Directors. The reason for adopting 200 feet as the span of the arch, was chiefly in order to avoid all question with the Board of Works, in Ireland. The workspreviously constructed on theWaterford and Kilkenny Railway had been subjected, under the provisions of the general consolidated Act of Parliament for railways, to the scrutiny of the Board of Works, in every instance where drainagewas, in the remotestdegree, likely to be affected ; andthe consequence had already been, that delays, veryprejudicial to the finances of the Company, had occurred, before anyapproval was givenby that Board, for commencing each work. In one instance, where a small archof 12 feetspan, was to beformed over a stream,with a _-

l Vide ‘‘Account of theArched Timber Viaducts on theNewcastle and North Shields Itailway, &C.’’ Minutesof Proceedings Inst. C.E., 1841, vol. i., p. 88, and 184G, vol. v., p. 219.

Downloaded by [ UNIVERSITY OF CAMBRIDGE] on [23/09/16]. Copyright © ICE Publishing, all rights reserved. 428 VIADUCT.TIMBER LATTICE bottom of firm limestone rock, the Board of Works required the RailwayCompany to excavate this rock 6 feetbelow the bed of thestream, and to put in foundations of masonry tothat depth, instead of placing the foundations on the rock, at the existing level of therocky bed. Considerationsarising fromthese interruptions, induced the Author to laybefore the Board of Works, such a design fur crossing the River Nore, asshould take away all possible ground of objection, on the score of interference with theriver-way, and for carrying out sucha design, a span of at least 200 feet, was necessary. T&s design also afforded the advantage of working in the foundations on dry ground, without the necessity of having coffer-dams, the piers on each side being so far from the river bed, that ordinary hand-pumps sufficed tokeep down thewater, whichrose through the gravelly strata of the bed of the valley. This bed was found to consist of about 8 feet of gravelly loam, and about 3 feet of strong gravel resting, at depths varying from 9 to 11 feet, on the regular limestone beds of the district. The river, in its ordinary state, was about 9 feet deep in mid-channel, but being subject to floods, the rise of water was, at one time during the construction of theviaduct, as much as 7 feet, giving a total depth of 16 feet of water in mid- channel,and flowing overthe entire valley for a breadth of 180 yards. At the end of April 1846, tenders were sent in for the execution of a portion of the railway, adjoining to both sides of, and including the viaduct: the mean of the amounts quoted in these tenders, for theviaduct alone, was &8,104 11s. 6d. The tender of Messrs. Hammondand Murray, of Dublin, wasaccepted inMay, and a contract having been made with them in the mouth of June, the foundations were got in during the latter part of August and the early part of September, in a favourable season. The masonry was subsequently executed bythe same Contractors, nearly up to the level of thespringing of the cross arches, when the finances of the Company not being adequate to meet the rapid demands of the workmen, and Messrs. Hammond and Murray having finished the other portions of their contract, they retired from the ground, by amicablearrangement, and the work was subsequentlycompleted by smaller contracts, let in separate portions, during part of which ullly, the Author superintended its execution. Owing to these interruptions,it is difficultto give any correct statistical account of the operations, which might serve as a guide for tile future, in similar cases of construction. The labouremployed 011 the masonry of the works, varied at different times during thepro- gre~::ofthe works, from 199 labourers,43 txmsons, 65stone-cutters, and

Downloaded by [ UNIVERSITY OF CAMBRIDGE] on [23/09/16]. Copyright © ICE Publishing, all rights reserved. LATTICE TIMBEZ VIADUCT'. 429 15 horses, down to 15 labourers, 3 masons, 5 stone-cutters, and 1 horse. About 20 carpenters, 20 labourers,and 2 foremen were employed upon the timber work. In ninety working days, (exclusive of Sundays,) during which the works were carried on continuously, there were five holidays, peculiar to Ireland, and eleven other days, on which the work was interrupted either wl~olly, or partially, by storms, rain, or frost. If the progress of the work had been conti- nued at the same rate at which it was carried on, while the funds of the Company were adequate, the masonry would have occupied nine months, and the whole structure would have had its respective parts fitted togetherin place, andcompleted for traffic in eleven months, dating from the laying of the first stone. The complaints of improper workmanship in the masonry were frequent, after the work had been re-let in smaller portions, and several feet in height of the upright work, and the whole of one of the cross arches on the south side of the river were pulled down, before the workmen could be persuaded to execute their task creditably. These instances are noticed, with the desire of impressing upon the younger Engineers who have daily charge of works, the necessity of being themselves on the spot at all hours, early and lace, when the work is going on, as a defect is readily covered up and concealed from view in a few hours, and the result frequentlybecomes apparent, only when it is too late to prevent a disaster. The stone, of which the masonry ofthis viaduct is built, was partlyquarried on the spot intended for the foundations; but the upper courses of these foundations and all the masonry above ground,were quarried out of anadjoining cutting, on theline of railway, about half a mile north from the site of the building. The material is a compact stratified limestone, of dark-grey colour, forming a portion of the extensive beds, of which somevarieties are well known, in England, under the name of Kilkenny marble. The lime for mortar, above water level, was procured from kilns, about a mile distant, situated in quarries of the same stratification, butof a character somewhat moreargillaceous; the lime used below thewater level wits hydraulic lias. The sand was found on the south side of the river, upon the line of railway, and was re- markably clean and sharp. The specifications required, that the masonry should be built, as strong,best, ' coursedwalling,' notinferior to the best samples, (pointed out by the Engineer,) in the bridges on the Great Southern and Western Railway, which had been already finished, ard were near at hand for reference. The voussoirswere tobe dressed on the beds, face, andjoints, and to belaid so its tobreak bond

Downloaded by [ UNIVERSITY OF CAMBRIDGE] on [23/09/16]. Copyright © ICE Publishing, all rights reserved. 430 LATTICE TIMBER VIADUCT. thoroughly well together, throughout each arch. The imposts and springing courses were always to be equal to the full thickness of the arch, and no stone used for such work, was to be less than 30 inches long. The joints of mortsr were not to exceed one quarter of an inch for dressed stone-work, nor half au inch for the coursed walling,’ andin the latter work, there was tobe no difference between inside and outsidework. The timber for the arch, or beam, was specified to be of the best quality of Memeland Archangel fir. SomeAmerican pitch pine was introduced, (by the permission of the Engineer,} in the walings, but experience has shown, thatit should be avoided in future. FJvery part of the timber, within view, was painted with four coats in white lead and oil, and was also specified to be subjected to Sir W. Burnett’s process of saturating with chloride of zinc, but this part of the stipulation was subsequently nlodified. As soon as the masonry had been carried up to the courses, necessary for receiving the iron and timber bands which steady the abutting pieces of the lattice beam, these bands were inserted in the masonry, and the construction of the beam itself was shortly afterwards commenced,on platforms placed onthe shore of theriver and covered with the flooring boards, which were afterwards taken up and used for the flooring of the bridge. Full-sized drawings were made on these platforms, and by these drawingsthe lattice beamswere carefully adjusted. Each piece was cutby a set of irongauges; there was oneset for cutting tllehalvings’ of the lattice bars, and a second set for cutting the intersections of the lattice bars with the waling-pieces, and as the latter are all differently curved to each other, thesegauges were madewith the powerof adjustment to variousangles. There was also a set of ‘ wale-scarf’ gauges, and another set for all the abutting joints of the cross framing, but these were ordinary gauges of sheet- iron. The bands, or waling-pieces were first cutto the proper dimensions, 15 inches by 7 incheseach. The middle, fourth,and bottom bands were laid to a camberof 1 in 100. The topbands were of thesame dimensions, butwere not cambered. The bands were searfed togetherthe full length required; the scarfs of the respective bands being so placed as to divide thejoints equally. The lattices, (which were of best Archangel deals, each 73 inches wide by 23 inches thick,) were then laid down on the bands, at the proper distances apart, and the exact size of the battens was marked on the bands, each in its true place. The bandswere then cut to the depth of 2 inches, leaving the battens,when laid in place, to rise half an inch above the face of the band. The second layer of

lattice battenswas then placed in the sameway as the first, each being laid true to the proper angle, and each crossing of the battens with each other and with the bands, being truly marked. The crossings were then cut out, so that the battens, when driven close together, were reduced to a thickness of 4 inches, The second thickness of bands, or waling-pieces, was then laid in place, and cut in the same way as the first, and over these, the next thickness of battens was placed andcut out as before. Whenthis was completed,the thickness of the entire rib, at the lines of the three bands, became 21 inches, and at the crossings of thebattens, 8 inches. Thh rib was then takento pieces and re-erected on theplatforms before described. The joiststo support the floor, werecut 2 feet longer thanthe widthbetween the ribs, everyfourth joist being G feet Iongerthan its neighbours and resting on the band below it,in order to receive the endsof the struts from the uppermost bands, The joists were clipped to a depth of 1 inch over thebands on which they rested, so asto act as cross ties. Similar ties, 12 inches by 4+ inches, were carried across fmnl each of the three lower bands. Longitudinal crown pieces, 9 inches by G inches, wereplaced directly under the centre of the uppermost joists ; they were scarfed together so as to run the whole length of the bridge, and to brace rtlld supportthe flooring, Diagonal cross struts,in two parallel pieces, each 9 inches by 3 inches, running from the crown piece to the lower waling, were bolted on each side of every alternate cross tie, so as to brace the whole of the cross framing strongly together. Diagonalstruts, G inchesby 43 inches,were alsocarried longi- tudinallyfrom every secondcross tie, on the second tier,to the crownpiece atevery second cross tie, on theupper tier. The third and fourthtiers ofcross ties were diagonallystrutted with pieces, G inches by 4 inches, and bolted to uprights. The floor of each line of way was strutted with diagonals, G inches by 41. inches, tenoned and strapped to the second tier of cross ties, and fitted into cast-iron sockets abutting againsta crown piece, 9 inches by 6 inches, under each alternate top joist, at the centre of each line of way. The flooring was formed of planks 2 inches thick, laid diagonally and spiked tothe joists.Cast-iron shoes wereintroduced atthe butt-end of the struts ; and wrought-iron straps secured the diagonal struts to thehorizontal ties. Angle pieces of wrought-iron con- nccted the ties with the uprights and bands. The ends of thelattice frames were further stiffened bylong wrought-iron straps, bolted to the bottom bearing beams, and carried to the uppermost waling-pieces, so as to bind the extreme bearings of each lattice beamfirmly together, while at the same time, the

openings in the masonry of the abutments were designed to be left clear, for the beams to rest on their bearings, independent of the masonry abovethat level. This intention was not fulfilled in executingthe work, the masonry having been erroneouslybanded in with the upper parts of the lattice beams. It had been designed, thatthe lattices should have beenfastened by oak trenails,but large nails were substituted, at a time when the Engineer-in-Chief had no longer any control over the work. A platform, about 40 feet in width, was laidon the top of the staging for fitting the latticein place, at about 3 feet below the level of the lower wale-pieces. Uprights of half balk were fixed on this, verticallyand fair in line for the outside ofthe wale-pieces, and stayed across the top and diagonally. To these uprights, cleats were spiked, in the lines of' the curves of the lower sides of the several wale-pieces. The outside wale-pieceswere firstlaid along these cleats and fixed, then one row of lattice bars was put in place, then another wale-piece, and so onuntil the wholewas completed. Meanwhile, at every convenient point, cross braces were got in and bolted fast, so as to keep all steady. The inertia of the mass of timber was so great, and the staying of thestage was so firm, thatno inconvenient vibration was felt, duringthe execution of this part of the work,in spite of some heavy gales, which then occurred. The cross framing was all fitted andmarked on a thirdset of platforms, and was rapidlybrought up andput together, as soon as thelattice bars were ready to receive it. All the intersections of every lattice bar werespiked with two large nails, forwhich the holes were previouslybored. The waling-pieces were drawn close with boits, and the joints were made water-tight. Thediagonal flooring plankswere then bolted and spiked down to the cross bearers, and t,he cleats on the uprights were knockedaway. Thearch, or lattice beam now restedon wedges purposelyplaced under the lower wales, whenthese were Srst adjusted. Onthe 1st of Biay, 1850, thesewedges were removed, when the entire beam of 200 feet span subrided, in the course of thesame afternoon, 3 inches inthe centre, and on thefollowing morning, the gauges showed a further subsidence of a quarter of an inch, so thatthe structure with its own weightonly, appeared to reposewith a total deflectionof 3t inches.Between the 3rd and the 10th of May, several locomotive trains of various weights mere passed over the arch, at speeds of from twenty to thirty miles per hour, until it was found, that a further deflection had taken place in the centre, of l&iuch : or in other words, that the deflectiou of the

arch,(without a load,) which on the 2nd of May, was 3B inches had become 5+ incheson the 10th of May. The maximumload which had passed over, appears to have been at1 engine with its train of loaded waggons, estimated at 65 tons. On the 12th of May, the Governnient Inspector tested the arch with various trains and loads, and amongst others, with two engines and a train of loaded waggons, nearly 200 feet in length, extending overthe entire length of thearch, being abol;t 146 tonsweight upon it. The result of allthese tests was, that with the heaviest train, passing at a speedof twenty-six milesper hour, the arch deflected in the centre 23, inches and rose again 12 inch, thus leaving a permanent deflection after the trials were concluded, of about 6% iuches below the level of the centre line of cleats,on which the Iines of the archhad .been laid. The regular traffic of the line has been constantly passing over the viaduct from thatperiod to the present time? and up to the month of ApriI, 1851, a further deflection has been observed of about three- quarters of an inch : this cannot be ascribed to any particular loads thathave passed overthe bridge, nor to any settlement atthe extremities, but to the gradual drying of the whole of the timber, afterbeing so thoroughly exposed to the air, and for the greater part, secured from wet. Thus the total se~tlement intwelve months fromthe date of strikingthe supports, has been 7; idles. The Engineer's expectation of permanent settlement, after ordinary trains should have worked over the arch, was 9 inches ; and the calcula- tion of insistentweight whichrnight be placedupon this beam, withoutfracture, was nearly 600 tons, ifdistributed over its surface. The quantity of solid masonry in the work is 8,984 cubic yards. The timber is about 264 loads. The weight of cast-iron is nearly 4%tons, and of wrought-iron, about 12 tons ; and the total cube of the work measured as one solid mass, fromthe bottom ofthe foundations to the top of the parapet, is 49,268 cubic yards. The width of thearch is 25 feet 3 inchesin the clear between the parapets, and is designed for a double line of railway of 5 feet 3 inches gauge, but onlya single line of way is, at present, laid down. The height of the rails above the ordinary water surface is 68 feet, andthe extreme height from thefoundations to the top of the parapet, is 84 feet. Theextreme length from end to end of the parapet, is 428 feet. The cost of the masonry was about %4,900,and of the arch about &3,300; thus the stoneworkof all kinds, averaged aboutten shillings and eight-pence per cubic yard, and thearch, or beam, came to about [ 1 $51-52.1 2F

Downloaded by [ UNIVERSITY OF CAMBRIDGE] on [23/09/16]. Copyright © ICE Publishing, all rights reserved. 43-4 RAILWAY ACCIDENTS. $15 perfoot of its length,the total lengthbeing 215 feet,including the portions which rest on the piers at each end of the beam. The cost of the whole mass, taken as a solid, averaged three shillings and three-pence halfpenny per cubic yard. The Author has to express his sense of the skill and intelligence exhibited byMr. Robert Mallet, (M. Inst. C. E.,) under contract with whose firm, the woodwork was constructedand erected, and has beenmaintained for twelve monthsafter its completion. He sug- gested some judiciousalteratious of theoriginal design, and he contributedto the details noticedin thisPaper. The work is believed to bethe largest beam both in span andin magnitude, executed in the United Kingdom, on the lattice principle, and Mr. Mallet conducted his portion of it, with a spirit to do justice to one of the greatest ornaments of his native country.

Mr. BIDDERthought, that it would have been both better and cheaper to have erected a tubular bridge. He was not an advocate of the system of lattice bridges, nor could he understand how the conclusion had been arrived at, that the deflection of so complex a structure as that described in the Paper, should be exactly 9 inches. Mr. DOPNEhad erected several large lattice bridges of 100 feet to 200 feet span, and he was convinced that, under certain circum- stances, this system could be employed with greater advantage than any other principle of construction.

April 20, 1852.

JAMES MEADOWS RENDEL, President, in theChair.

NO.877. ‘‘ Railway Accidents ; their cause and means of preven- tion ; detailingparticularly the various contrivances which are it1 use, and have been proposed.” By Captain MARKHUISH, Assoc. Inst. C. E. IN entering upon thesubject of thisPaper, it is unnecessary fo occ~~pytime, in demonstrating the fact, that compared with its results, whether as regards the ease and celerity of transit, or the facility of conveying numbers, railway travelling, even in its present state, is incomparably safer than any previously designed system of locomotion. Contrasting the mere numbers transported from one locality to another, in the present day, by railna!~, with those convejed by