Tay Rail Bridge

Proposals to build a bridge across the Tay date to 1854 but it was not until 15 July 1870 that the (33 & 34 Vict. c. cxxxv) received royal assent. On 22 July 1871, the foundation stone of the bridge was laid. The bridge was designed by engineer Thomas Bouch, who received a knighthood following the bridge's completion. The bridge was a lattice-grid design, combining cast and wrought iron. The design had been used by Thomas W. Kennard in the Crumlin Viaduct in South Wales in 1858, after the use of cast iron in the Crystal Palace. The Crystal Palace was not as heavily loaded as a railway bridge. An earlier cast-iron design, the Dee bridge collapsed in 1847, having failed because of poor use of…

The engineering details on the Tay Bridge were considerably simpler, lighter, and cheaper than on the earlier viaducts. The machined base of each column section docked securely into a machined enlarged section of the top of the section below. The joint was then secured by bolts through matching holes on lugs (Crumlin The bottom connection was to two sling plates bolted to the base of the equivalent section on an adjacent column. The bar and sling plates all had matching longitudinal slots in them. The tie bar was placed between the sling plates with all three slots aligned and overlapping. A gib was driven through all three slots and secured. Two cotters, metal wedges, were then positioned…