South Esk Viaduct (Montrose)
in Montrose
Introduction
Built between 1881 and 1883 for the North British Railway, replacing the original viaduct designed by Thomas Bouch.
The viaduct has masonry (brick) approaches leading to sixteen spans having wrought iron lattice truss girders, supported by pairs of braced cast iron columns filled with concrete.
A short distance to the south is the brick-built Rossie Island Viaduct.
Refurbished in 2018 by Network Rail and Taziker Industrial.
See Canmore entry.
The First Viaduct
Thomas Bouch was responsible for the design of the viaduct. It was condemned by Colonel Yolland following the failure of Bouch's Tay Bridge.
The Tay Bridge was of fundamentally unsatisfactory design, largely in respect of the cast iron pipe-type piers. While the South Esk Viaduct also had piers constructed from cast iron pipe-type members, the piers were much shorter than on the Tay Bridge, and, importantly, many of them were stabilised by raking supports. Why, then was the bridge condemned in 1880?
Clearly there was a serious loss of confidence in this sort of pier, despite the fact that many bridges with similar piers were giving good service. In fact, some of the faults with the Tay Bridge piers had been addressed during the construction of the South Esk Bridge. However, the decision to condemn the bridge was made easier by evidence of poor standards of construction, and in particular by appreciable sinking of the piers.
Colonel Yolland's 1880 Report on the First Viaduct [1]
'COLONEL YOLLAND'S REPORT ON THE SOUTH ESK VIADUCT.
The following is the text of Colonel Yolland's report to the Board of Trade, giving the result of his examination of the South Esk Viaduct :
Board of Trade (Railway Department),
5 New Street, Spring Gardens,
London, S.W.,
29th Nov., 1880.
Sir, I have the honour to report, for the information of the Board of Trade, that, in compliance with the instructions contained in your minute of the 1st inst., I have examined the viaduct over the Southesk river, near Montrose, on the Arbroath and Montrose Railway, now in course of construction by the North British Railway Company. I was met at Montrose, as previously arranged, by Mr Galbraith, C.E., who had been called in by the North British Railway Company to advise them on the subject of this viaduct, and also by the contractors for the construction of this line and the viaducts, as well as by Mr Patch., C.E., who had been employed under the late Sir Thomas Bouch, who was the engineer for the Arbroath and Montrose Railway ; but I understand that Mr Peddie was not specially charged with the supervision over the erection of this viaduct while it was in hand. It is right to state that I received every information which I desired from the whole of these gentlemen, and was made acquainted with the circumstances under which the stability of this structure is questioned.
‘This viaduct of 30 spans, each of 47 feet from centre to centre of the piers, &c., is carried on cast-iron columns or piles supporting wrought iron continuous girders placed on the tops of the columns, screwed or driven from 7¼ to 15 feet into the bed of the river Esk, composed of mud, sand, and gravel. The viaduct is straight, and on a steep incline of 1 in 88, falling towards Montrose or the north. At the highest pert of the viaduct, above the bed of the river, there are three or four tiers of cast-iron columns, each about 12 feet 8½ inches in length, and various short lengths of similar columns are introduced to make up the requisite height for the incline.
'The permanent way is placed above the wrought-iron continuous girders, and the level of the rails at the lower end of the viaduct is 13 feet 4 inches above high water of ordinary spring tides and about 29 feet 4 inches at the higher end of the viaduct, and at the highest part about 46 or 47 feet above the bed of the river. The piers, with the exception of three, consist of four cast-iron columns, two vertical (the centre ones), and the outside columns are raking columns, starting from about the level of low water and joining the centre ones at the top of the latter. These four columns are placed at right angles to the line of the viaduct, at the following distances apart : Pile, 11 feet (pile, 9 feet, pile, central piles) 11 feet pile from centre to centre of each column, and making up a total breadth of 31 feet between the centres of the outside columns. There are 26 of these piers altogether, and 3 before referred to, which are each formed of eight columns or piles, four vertical and four raking where the fixed bearing of the continuous wrought-iron girders are placed. These are the 6th, 14th, and 22d piers reckoned from the south. The 1st continuous girder is fixed on the 6th pier from the south, and it extends over three spans to the south and four to the north of the pier. The second and third continuous girders are fixed on the 14th and 22d piers, and these extend over the spans on each side of the fixed bearings on these piers. The first three spans from the south and the last four spans from the north end of the viaduct are virtually the halves of two continuous girders respectively covering six and eight spans of 47 feet. The abutments are of brick.
'Five piers at each end of the viaduct are built on cast-iron screw piles 15 inches in diameter and 1 or 1½ in thickness, of metal, and having blades 30 in. in diameter. These were screwed into the bed of the river, but the remaining 19 piers have had the lower tier of cast-iron piles all driven by a pile engine having a falling weight of 35 cwt. and a drop of from 4 to 5 ft. These piles of 1¼ in. in thickness, of metal with pointed ends, it is stated, were all driven until they ceased to drive as much as a quarter of an inch with each drop of the hammer or "monkey”. But it is now questioned whether this was actually enforced.
'The iron columns have a projecting piece or spigot at the lower end of each column, which fits into a recess or faucet on the upper end of the column below it. The spigots and faucets are said to have been turned so as to ensure their fitting, and there are also raid [raised] surfaces about 2½ or 3 inches in width adjacent to the spigots and faucets above the general surface of the ends of the columns, so that the whole surface of the flange of one column does not fit and rest on the whole surface of the flange of the top of the one blow it. The end of the two columns are fastened together by eight wrought iron bolts ¼ [1¼ ?] inches in diameter passing through the flanges at the ends of the columns, and secured by screw nuts. The holes through the flanges are stated to have all been drilled. The cast-iron columns in the 29 piers were all secured by wrought iron diagonal bracing transverse to the line of the viaduct, fastened to lugs cast on the outside of the cast-iron columns, except in a few instances that I noticed where the lugs had been bolted on to the cast-iron columns. The two central vertical columns in each pier, which are immediately under the wrought iron continuous girders on each side, were, I was told, all filled with concrete after they were erected. Two bolts, one on each side, pass through the upper flange of the two topmost central columns in each pier, which flanges have a diameter of about 22 inches, and through a slotted hole in the bottom booms of the wrought iron continuous girders, which are about 6 feet in height, thus providing for a certain amount of sliding of the girders on the tops of the columns, caused by an expansion or contraction of their length ; but there are no rollers under the continuous girders to facilitate this movement, and it was stated that no movement of the continuous girders on the tops of the columns had been noticed, and it is probable that the columns moved as the girders expanded or contracted.
'Transverse timbers of 12 inches by 9 inches scantling, and about 14 feet in length, are fixed on the tops of the wrought iron continuous girders at intervals of about 3 feet apart, and longitudinal timbers 16 inches by 7 inches are laid and fastened on to the transverse beams. These longitudinal timbers carry the 75 lb. double-headed Bessemer steel rails, with check rails on each side inside the stocks rails, both rails being secured in cast-iron chairs by means of wooden keys. There is no reason, I understand, to question the strength of the wrought-iron continuous girders, and I may state that the quality of metal in the cast-iron columns appeared to be good, and the columns seemed to be free from those defects which were so apparent in many of the columns of the Tay Bridge.
'This viaduct was practically completed in Oct. 1879, some months preceding the fall of the Tay Bridge, and after that happened I understand that this viaduct was carefully overhauled by the directions of the late Sir Thomas Bouch, the engineer of the line, and it was then determined to cause the cast holes in the lugs on the cast-iron columns to which the diagonal bracing of the piers was secured to be bored out or drilled so as to make the sides of the boles parallel to each other, and to insert larger bolts, those originally used being 1½ inches in diameter, and these were increased to 1¾ inches in diameter. It was also decided to alter and strengthen the diagonal bracing throughout, and additional cross bracing was introduced for the continuous girders.
'After some time, and before all the raking piles had been erected, when the contractor's engines had been running over this viaduct with materials, it was found that the permanent way on it got out of order and sank in various places, and, on examination, it was discovered that at intervals some of the wrought-iron girders no longer rested on the tops of the columns on which they had been placed, and the columns appeared to have sunk under the effects of this rolling load. Steps were then taken to test some of the piers by loading them with a certain weight of rails laid at the side of the line for a distance on each side of a pier, still continuing to run loads of material over the viaduct. An experiment was made on the 24th pier from the south end, which consisted of two upright and two raking columns. It was loaded with from 105 to 110 tons weight of rails over a length of about 48 feet, and when a rolling load, consisting of a locomotive weighing 22 tons, and nine trucks each weighing 7 tons, together making up a rolling load of about 85 tons, continued to run over the viaduct, and in 36 hours this pier went down bodily about 2 3/8 inches. It then considered that the foundations were insecure where the piles had been driven, but one of the five piers at each end of the viaduct, where screw piles had been used, stood the same test very well, and did not give way. It was thought that placing iron cylinders outside the piles which had been driven, filled with concrete, would be sufficient to secure stability, and arrangements were made for carrying this into effect. Subsequently to this Mr Galbraith was called in to advise the Directors of the North British Railway Company, who were most anxious that this viaduct should be made thoroughly reliable, but nothing has as yet been absolutely determined upon as to what should be done.
'The work in this viaduct produces the impression that a sufficiently strict supervision of it was not exercised while it was in progress. The line and viaduct were intended to be straight, but care was not taken to place the piles in straight lines nor to fix them truly at right angles to the line of the viaduct. Many of them are not vertical, and the contractor has been engaged in drawing some of these piles for the purpose of placing them in their proper position and truly vertical, encased in cylinders 5 feet in diameter, and embedded 8 feet in the ground. In one instance I noticed that the pile sunk in the ground was not in the same line as the column above it, and thus the flanges on the two columns which were bolted together were not parallel to each other. One obvious defect of the structure as erected is the insecurity of the foundations; but that in my opinion is of far less importance than its general design and the nature of the material (cast-iron) with which the piers have been constructed. The evidence brought before the Court of inquiry that investigated the causes that produced the fall of the Tay Bridge piers, of about the same diameter as those used in this viaduct, stated that they broke without any special cause for their fracture being established, and other evidence proved that it was by no means an unusual occurrence. I have no positive knowledge as to the nature of the future structure intended to be erected across the estuary of the Tay ; but it is generally understood that the piers are not to be made up of cast-iron columns of small size, and that the line is intended to be made double. The Court of Inquiry were unable to state positively what was the actual cause of that accident, or to say for a certainty that it was not caused by the fracture of one of the cast iron columns in one of the piers which fell; and so in this viaduct fracture of one of the vertical columns to any one of the piers might possibly cause the viaduct to fall, and on that ground I am of opinion that piers constructed of cast-iron columns of the dimensions used in this viaduct should not in future be sanctioned by the Board of Trade. The project for an overhead railway at Liverpool proposed a viaduct of nearly six miles in length and about 20 feet in height, the railway to be carried on cast-iron columns of small diameter, but I objected to that material, and the engineer at once assented to the substitution of wrought-iron uprights, instead of cast-iron columns.
'There is also another very grave objection to the viaduct as now constructed, similar, in fact, to that which is to be seen in the standing portion of the Tay Bridge, in the placing of the permanent way on which the traffic is carried above the wrought-iron girders with nothing but a mere hand-rail of gas-piping 2½ inches in diameter at the outer edges of the railway, so that in the event of a vehicle getting off the rails from any cause whatever—the fracture of an axle or tyre of a wheel, &c.—the hand-rail would not suffice to keep the vehicle from being thrown over the side of the viaduct, and probably dragging other vehicles after it. The check rails which have been placed inside the rails, like those on the Tay Bridge, become a positive source of danger in the case of any foreign substance getting in between the stock rails and the check rails. An instance of this kind occurred at Southall, on the Great Western Railway, last February, when several trucks were thrown off the rails and ran foul of the up main line immediately in front of an express train travelling at the rate of 60 miles an hour, and a collision ensued, owing to a piece of chain getting in between the check rail and the stock rail, and causing the trucks to leave the rails.
'Again, this line is intended to be a part of a main line of communication for the North British Railway Company, and as such it should, I think, at once be made a double line. From its proximity to Montrose Station, it would be of material advantage as regards the working of the traffic, and its construction as a double line would certainly add to its stability as a structure. I cannot think there need be any difficulty in substituting substantial piers for this viaduct across the Esk river (judging from the success which apparently attended the screw piles), either of brick, or of wrought or cast-iron cylinders of considerable dimensions filled with concrete. In connection with this part of the subject you are aware that in the reconstruction of sundry long and high viaducts with more durable materials than they were originally built the Board of Trade has recently requested the Company concerned to provide a good parapet wall not less than four feet or four feet six inches in height above the level of the rails, and not less than 18 inches thick.
'As the result of my examination I should therefore recommend that this viaduct should be reconstructed, and for a double line of railway, with the permanent way placed inside plate, lattice, or bowstring girders, so as to obtain some security against a train, or portion of a train, being hurled over the edge of the viaduct, if an accident occurred on it ; and that these girders should be supported on substantial piers, not constructed of small and slight cast-iron columns.-- I have the honour to be, &c., W. YOLLAND, Colonel. The Secretary the Railway Department, Board of Trade.'
Construction of the First Viaduct
John Rapley provides interesting information in his biography of Thomas Bouch [2]. Thomas Bouch had delegated most of the work to his Resident Engineer, Alexander C. Raff. Thomas Bouch appointed his son William Bouch as Resident Engineer for the viaduct, nominally under Raff's supervision.
The team involved in constructing the Tay Bridge had dispersed, and the men sent by Edgar Gilkes to construct the South Esk iron bridge were described by Rapley as incompetent, and William was too inexperienced to control them.
Raff was well aware of problems with the piles, and wanted them withdrawn and re-driven. Some of the piers showed signs of sinking, and Thomas Bouch hd 5 ft diameter cylinders cast and fixed round those piers, and sunk onto piles and filled with concrete. Misalignment of piers was blamed for the girder assembly being 4 ft too short. Gilkes addressed this problem by cutting a pair of girders in half and inserting ironwork to increase the length by 4 ft.
As in the case of the Tay Bridge, the structural design of the girders was satisfactory. The rails were on top of the girders, which allowed the piers to be made shorter, but Yolland objected to this arrangement, preferring the security of having the trains running between the girders.
Pending reconstruction, limited running was permitted on the viaduct from 1 February 1881, for goods trains only, and at no more than 3 mph.
The Present Viaduct
The Board of the NBR appointed William Robert Galbraith to design a new viaduct. William Arrol and Co was the successful bidder to construct the ironwork. The first trains ran in May 1883.
Designed by Mr W. R. Galbraith, C.E., London, the bridge , which is 475 yards in length , is carried on 15 double cylindrical piers 13 of the openings being 96 feet , one on the south side 63 feet, and two on the north side 64 feet and 57 feet 6 inches respectively. The cylinders which form the piers are sunk into tho bed of the river to an average depth of 18 feet , and rest either on hard sand and gravel or on a clay foundation ; In the latter case, ' the- water was pumped out, and a base of concrete wider than the diameter of the cylinder introduced, so as to guard against any tendency of the clay to settle on a heavy weight being placed upon it. The lower sections of the piers, extending from the foundation up to low-water mark, are of cast iron, 7 feet 6 inches in diameter. Cast in lengths of 6 feet, they have been strongly bolted together; and for greater security have straps of wrought iron around them. At low-water mark, the piers taper to 5 feet, and at that diameter are carried up to the underside of the longitudinal girders. The tapered cylinders are heavy castings; while those reared above them to meet the girders are of-wrought iron. The cylinders have all been filled with concrete, made with the finest Portland cement. In sinking the cylinders, a pontoon, similar to those now being employed at the Tay Bridge for a like purpose, was used — Messrs Arrol, Glasgow, having been the contractors also for this; viaduct . On tho top of each pier, and embedded in the concrete, is a massive coping of Aberdeen granite; and upon this the bed-plates of the main longitudinal girders, which are of wrought iron and of lattice construction, are laid. Between these longitudinal girders, wrought-iron transverse girders are placed , 5 feet 6 inches apart from centrea to centre, and on these heavy longitudinal timler beams, for carrying the rails, are fixed. The sides of the longitudinal girders, which are of an arched form, rise above the permanent way to a height varying from 4 feet 6 inches to 7 feet, and form an efficient parapet to the 'bridge. It may be stated that before the wrought-iron superstructure was placed in position, two of the cast-iron cylinder piers were subjected to a severe test. Upon each 200 tons of rails were placed, and allowed to remain for eight or ten days, with results which are said to have satisfactorily demonstrated the stability of the foundations. The viaduct was completed in February last, and on the 1st of March Colonel Yolland made an official inspection on behalf of the Board of Trade. ......'[3]
Some settlement of the 6th and 8th piers counting from the south end, just visible by dips in the line of girders in photo 1.
In 1957-8 the bridge was strengthened, the timber deck being replaced by steel sections. See photos 4 & 5.
See Also
Sources of Information
- ↑ Transcribed from the Montrose Standard - Friday 24 December 1880, via British Newspaper Archive (www.britishnewspaperarchive.co.uk)
- ↑ 'Thomas Bouch - The Builder of the Tay Bridge' by John Rapley, Tempus Publishing, 2007
- ↑ Transcribed from The Scotsman - Saturday 28 April 1883, via British Newspaper Archive (www.britishnewspaperarchive.co.uk)