Tay Railway Viaduct, Perth
in Perth, Scotland
Also known as Perth West Railway Bridge; Friarton Island; Moncrieffe Island; Perth Viaduct; Tay Bridge, Perth.
Leaving the city in an easterly direction, the railway had to cross the River Tay where it was split into two courses with Moncrieffe Island in between. See photo 1. It crossed the island by a masonry viaduct with ten arches, and crossed the river by spans of predominantly timber construction on masonry piers. The piers on the east side are appreciably skewed relative to the railway, due to the great curvature of the route across the river.
The original viaduct was built to carry the Dundee and Perth Railway, on a curve of 15-chain radius. It was replaced in 1864 by a new structure built on a slightly easier curve (of 17 chains). It has five iron plate girder spans over the river to the west of Moncrieffe Island, ten stone arches on the island itself, and seven further girder spans over the river to the east. Engineer: Benjamin Hall Blyth I. Erected by Lee and Freeman. Both(?) river bridges incorporated a swing-span near the west bank of the river, now replaced by fixed spans.[1]
Photographs of the west swing span show bowed-top plate girders, apparently of the Fairbairn box girder type.
A cantilevered walkway is attached to the viaduct.
Press Reports
1864 'THE BRIDGE OVER THE TAY AT PERTH.
For months past many travellers by the Dundee and Perth line have felt a small degree of alarm while passing over the viaduct which crosses the Tay at Perth. In consequence of the erection of a new stone bridge, the half of the old wooden structure had to be cut away, and the traffic carricd on one line of rails. The viaduct therefore seemed anything but secure, and strong opinions were entertained and expressed as to its instability. Indeed, a private representation was made to the Sheriff of the County on the subject, and Lordship, with proper consideration for the safety of the public, promptly remitted to Mr Henry Wyllie, civil engineer, Edinburgh, to examine the bridge and report. The investigation took place a few days ago, and was of the most careful and exhaustive nature. Mr Wyllie was accompanied by the Procurator-Fiscal, and they were met by the officials of the Scottish Central Company, who gave every facility for testing the security the structure. An engine and tender weighing 35 tons - 15 tons more than the locomotive which actually works the traffic over the Bridge — was placed at the Engineer's disposal, in order to allow of his making the trials considered necessary to show the stability of each arch. Mr Wyllie, we learn, has since lodged his report, and though we cannot fully state its contents, it yet gives us much pleasure to say that the result of the inspection was satisfactory, and that Mr Wyllie is of opinion that the bridge is equal to the strain put upon it by the traffic of the Company, not simply because the structure is strong of itself, but also on account the great precautions taken in working that portion of the line which crosses the viaduct.
The construction of the new bridge is being rapidly proceeded with. All the stone piers are nearly completed, except two, and these would also have been far advanced by this time but for unanticipated obstacles which were met with in the foundation of them. These two piers which are still awanting are at opposite ends of the bridge. One of them occupies the first place at the west side, and is meant to bear the end of the draw bridge, while the other is near the east end of the viaduct At the foundation of the western pier piles have been driven to form a coffer-dam, but that erection has not yet been made water-tight, and the building hindered. With the other pier the difficulty experienced is the presence of large boulders in the bed of the river, just where the iron cylinder was to be sunk. Operations are now in prepress, however, to remove these — the aid of divers having been secured — and there is every likelihood of the foundations being speedily laid. When that is done the building of the piers will be rapidly proceeded with. Except those which have to rest on the piers referred to, the iron girders are all in their places. The girders seem fitted to bear an immense strain, and give assurance that the new viadnct will possess great strength and stability. It will be remembered that the Railway Company, with considerable liberality, are to lay down, free of charge, a path for foot passengers on the upper side of the bridge. This roadway is to be thrown out on brackets, and the progress which has already been made in its construction shows that it will be alike comfortable and safe. This road cannot fail be of great value to the residenters in the Barnhill district, and it will also be generally useful in enabling the inhabitants the Fair City to reach, much easier than at present, the many charming walks on the north side of the river. '[2]
1864
'OPENING OF THE NEW RAILWAY BRIDGE AT PERTH.
This immense viaduct is now all but completed, and was opened for general traffic yesterday. It was tested on Saturday with one of the heaviest engines, weighing, including tender, nearly 57 tons, running over at twenty miles an hour, and gave great satisfaction as to strength and firmness. The first train to run over was the 11.30 p.m. mail from Perth the same night, and yesterday, as we have said, it will be in regular use. It has been erected on the north side of the old timber bridge, and occupies partly the site of the north line rails, and partly new ground north of the timber bridge. Owing to its occupying a portion of tbe site of the old bridge, the difficulty of its construction was vastly increaaed, as the northern half of the old bridge had to be sliced off bit by bit as the new one progressed. Notwithstanding this delicate and dangerous process, however, we are glad to say that both the work of construction and demolition has been safely accomplished, and that now the new bridge is complete for running over from end to end. Only one pier remains to built; and as it to be on the identical spot occupied by one of the present timber piers at the river end of the swing bridge, it will only be completed after the timber viaduct is wholly removed. In the bit by bit removal of the northern half of the old structure very great care had to taken to provide for the security of the remaining half, and every arch of it had to be supported and trussed up by enormous piles driven into the bed of the river. In the winter season, too, tbe dangers were multiplied by the ice-floats which descended from the Highlands, and squads of men had to kept breaking the ice as it began to accumulate above the bridge. At this time the channels between the piers were at their very narrowest point, from the new and old piers being both in the bed the river, surrounded by temporary staying, &c. The exertions made to guard against mishaps have been entirely successful; and it will scarcely be believed when we say that, during the whole time the work has been going on - during the time of the sinking of the piers — and during tbe time of the cutting away of the old bridge — not one train, passenger, or luggage, has been delayed, or prevented from crossing. It is particularly creditable to the Contractors that, under such circumstances, they have managed that the traffic of the line has never been interfered with. We should perhaps have mentioned at the commencement that the iron swing bridge put up at the Perth side of the river, and connecting the timber bridge with the land, still remains, and that the new one leads on to it. The only alteration upon it will be a new stone pier in the river for supporting the outer end; and this pier, as we have said, will be on the site of the old one. It will be commenced as soon as the traffic is turned on tbe new line. The new viaduct, including the swing bridge, is of the enormous length of 1350 feet, or about a quarter of mile, is only for one line of rails and formed of stone and iron arches — the stone arches being across Moncreiff Island between the two branches of the Tay, and the Tay with its Willowgate branch being spanned by enormous wrought iron-girders. First, at the west end is the swing bridge of 50 feet span, then four spans of 86 feet each, then ten stone arches of 30 feet span each, and then seven spans of 83 feet each. The iron girders which span the river are of iron plates, 6 feet 3 inches in depth, and 2 in width of line, firmly braced together horizontally and vertically; and these are all set on rollers, to admit of expansion and contraction according to the state of the weather. The cross girders lie on top of main girders, over which lie longitudinally strong timber beams for fixing the rails; and the whole of the top is being covered with strong planking.
There are four piers in the Tay and seven in the Willowgate streams. All of these, except the one supporting the end of the swing, are cylinder piers, sunk from 15 to 25 feet below low water. The cylinders are each in lengths of 7 feet, and brought up to the level of low water, the lower one in each case being conical, 9 feet diameter at bottom, and 7 feet at top. All are firmly bolted together on inside flanges. Great difficulty was found in sinking these cylinders. In some parts the bed of the river was, of course, gravel, so open that it required two pumps and two engines constantly going to keep the water out, and to allow the workmen to get excavated inside. (What would the Dundee Harbour Contractors have said to "quicksand" like this. Much difficulty was also experienced from large boulders, which kept the men cutting and working in the water for weeks at a time. After the cylinders had been got to the proper depth, and the site of the pier excavated, it was weighted with masses of iron weighing 24 tons, and then filled witb concrete, composed of Roman cement, sand, and gravel, which, after being a few days deposited, got as hard as freestone and excluded the water, so as to admit of pumping out and bringing up the circular ashlar work inside and over the tubes. Two of these tubes form one pier, with a small connecting arch between. In the three courses above three circular malleable iron frames, in the form of piers, are let into the beds, to tie the whole together, and are finished on top witb large beam blocks and circular moulding.
On each side of the island there are strong abutments for arches, and for carrying the ends of the girders. These abutments are buUt of ashlar masonry, with circular towers on each corner (to correspond with the piers in the water), carried up and finished with belt and parapet. The intermediate piers are formed of substantial squared masonry — the arches being semicircular, and, with the belt and parapet on each side, all of freestone, the spandrils being of squared rubble. The circular piers and abutment quoins the intermediate piers, arch stones, and parapets are all white freestone, from the quarries of Catcraig, near Bannockburn, and Burntisland; and all the other stones used were from Huntingtower and Carmyllie quarries.
The main girders were made in Glasgow, and sent to Perth, each in one piece, weighing about 17 tons. They were lifted from trucks on the old bridge with strong travelling cranes, and set in their places at night, between trains. The bridge is in the form of a semicircle or long curve of 15 chains radius at each end, and of 20 chains radius in the centre, the whole of which can only be seen at once from the south side, and will be almost hid until the old structure is taken down. One commendable feature in the structure is a footpath which runs along the north side, and formed by the cross girders being carried farther out than on the opposite side, and strong brackets are also built into the masonry over the island to support the footpath, and it is protected by a very neat and somewhat ornamental fence on each side of cast-iron standards and malleable iron tubing. It terminates at the west side with stair leading down to the harbour road, and the stair and footpath will be open to tbe public free of charge. We may mention, for the benefit of those who have a liking for statistics, that we believe there have been used in the construction of this bridge nearly 61,000 cubic feet of ashlar, &c. ; 1030 cubic yards of squared rubble masonry ; 400 cubic yards of concrete; 213 tons of cut iron ; and 520 tons of wrought iron.
The contractors for the whole work were Messrs Lee & Freeman, and the engineers for the whole works were Messrs B. & E. Blyth, civil engineers, Edinburgh. The inspecting engineer for the Railway Company was Mr John Thomson, engineer, Dundee. The total cost of the bridge will be over £25,000 — including the entire removal of the old one. The work throughout is of the most substantial description, and does great credit the contractors — as does the despatch with which they have completed it, seeing that it was only commenced in October 1863.'[3]