The Tay Bridge (sometimes unofficially the Tay Rail Bridge) is a railway bridge approximately 2.25 miles long that spans the Firth of Tay in Scotland, between the city of Dundee and the suburb of Wormit in Fife.
Proposals for constructing a bridge across the River Tay date back to at least 1854.
The First Bridge
The original Tay Bridge was designed by Thomas Bouch.
Wrought iron lattice girders were supported by cast iron columns on masonry piers, except at the Wormit end, where the Nos. 1- 14 piers were made of bricks. Towards the shore, the rail track ran on top of the girders. At the middle of the river, where clearance was required for tall ships, the track ran on the lower part of the girders (i.e. running through the girders rather than on top of them). For these thirteen girders, the span was considerably larger, and the depth of the girders was also increased. It was also necessary to increase the height of the piers supporting these girders.
1870 July 15th. The North British Railway (Tay Bridge) Act received the Royal Assent
1871 The contract was initially placed with Butler and Pitts. Pitts died and De Bergue and Co became the contractors engineers. Their engineers were Albert Grothe and Edward Robert Austin.
1871 July 22nd The foundation stone was laid.
As the bridge extended out into the river, it shortly became clear that the original survey of the estuary had not been competent. The bedrock, at a shallow depth near the banks, was found to descend deeper and deeper, until it was too deep to act as a foundation for the bridge piers. Bouch had to redesign the piers, and to set them very deep in the estuary bed to compensate for having no support underneath. He also reduced the number of piers by making the spans of the superstructure girders longer than he had originally planned.
1873 After Charles de Bergue was taken ill, Hopkins, Gilkes and Co took over the foundry at Wormit that had been constructed, and completed the contract for the bridge.
1877 September 22nd. The first locomotive crossed the bridge.
1878 June 1st. The bridge was opened. It was the longest in the world at that time. When completed it was 10,395 feet long, was carried on eighty-five piers, with spans ranging from 29ft to 245ft, and accommodated a single line of rails.[1]
Bouch received a knighthood following the bridge's completion.
1879 December 28th. At 7.15pm, the bridge collapsed during high winter gales. A train with six carriages carrying seventy-five passengers and crew, crossing at the time of the collapse, plunged into the icy waters of the Tay. All seventy-five were lost, including Sir Thomas's son-in-law.
The disaster stunned the whole country and sent shock waves through the Victorian engineering community. The ensuing enquiry revealed that the bridge did not adequately allow for high winds. At the time a gale estimated at force ten or eleven had been blowing down the Tay estuary at right angles to the bridge. The engine itself was salvaged from the river and restored to the railways for service.
The original design was ill-conceived. It was further compromised by cost-cutting measures. The detail design was poor, and the standards of foundry workmanship and inspection were unsatisfactory.
Photographs here show the bridge during construction and following failure. The Wormit foundry is also shown.
Salvaged Girders
Portions of damaged original girders are on display at the National Museum of Scotland (NMS) and at The McManus: Dundee's Art Gallery and Museum. Those at the NMS, shown in the above photos, had been recycled for use in a house in Broughty Ferry, while those at Dundee had been used at Panmurefield House, Balmossie, and recovered in 1978. The damage to the beam is consequential, there being nothing to suggest that they were implicated in the cause of the collapse. The angle iron bears the mark J G & Co Middlesbro, presumably relating to Jackson, Gill and Co. Some rows of rivets are countersunk. One photo shows the end of the beam which was riveted to another member. The gap between the vertical angle iron and the web was made up by inserting a plate. The hammer marks may reflect difficulty in driving the plate into the gap. Some other manufacturers favoured 'joggling' the angle iron to step it down onto the web, rather than inserting spacers.
The New Bridge
A Select Committee inquired, during 1880, into the question of replacing the structure that failed in December, 1879, and reported that the bridge should, in the interests of the public and the railway company, be reconstructed. It was also recommended that the North British Railway should obtain approval of its plans by two or three independent engineers of unquestionable standing and experience.
The maximum clearance height was to be reduced from 88ft in the old bridge to 77ft in the new. Girders from the old bridge that were unaffected by the collapse were able to be re-used in the new bridge.
A new double-track bridge was designed by William Henry Barlow and his son [[Crawford Barlow]. It was to be 60 ft upstream of, and parallel to, the original bridge.
William Arrol and Co were the contractors.[2]
After taking extensive soundings and carrying out tests to determine the nature of the ground for the numerous piers, the Barlows deposited their plans towards the end of 1880.
The bridge proposal was formally incorporated in July 1881.
1883 July 6th. The foundation stone was laid.
Fourteen men lost their lives during its construction, most by drowning.
1887 June 20th. The second bridge opened. The structure, 10,527ft long, carries a double line of railways, and its straight portion of 7,397ft lies parallel to the straight portion of the earlier bridge but 60ft away from it.[3]
There are 85 piers, Nos. 28-41 supporting the thirteeen 'high girders' for the 'navigation spans'.
The stumps of many of the original bridge piers are still visible above the surface of the Tay even at high tide.
See Also
Sources of Information
- ↑ The Engineer 1924/12/05
- ↑ The Engineer 1924/12/05
- ↑ The Engineer 1924/12/12
- [1] Wikipedia