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A Bridge for the Ages - The Firth of Forth Railway Bridge

Jeffrey Syken

On the central coast of eastern Scotland lie two formidable bodies of water that, for many years, stood in the way of efficient rail transportation between England, to the South, and northern Scotland. To the north lay the Firth of Tay (Estuary of the River Tay) and, about thirty miles to the south, the Firth of Forth (Estuary of the River Forth). With the expansion of the UK’s rail transport network as the 19th Century progressed, it became imperative that these water barriers be breached. The man selected to bridge both was an accomplished civil engineer by the name of Thomas Bouch. For the deep waters of the Firth of Forth, he would design a suspension bridge and for the wide but relatively shallow Firth of Tay, a viaduct. The former would never be realized while the latter would meet with disaster.

Opened in July 1878, the Tay Viaduct was a modern wonder-of-the-world. Visiting ex-POTUS U.S. Grant, upon seeing it, said that it was: “A big bridge for a small city.” The longest bridge in the world at the time it opened, the bridge and seventy-five passengers of a Dundee-bound mail train would meet their doom one stormy, windy night in late December 1879. On that fateful night, a gust of wind blew over the train and the long girders of the bridge’s navigation spanned into the icy waters of the Firth of Tay – there were no survivors. The ensuing Court of Enquiry determined that the bridge was: “badly designed, badly built and badly maintained.” As it turned out, Bouch had not neglected but severely underestimated the wind pressure on the bridge. The New Tay Viaduct would run parallel to the first bridge and proper wind pressure design would be included this time around, but Thomas Bouch’s long, distinguished career was over.

With Bouch’s reputation in shatters, his design for the Forth Suspension Bridge was scrapped and a new design by two prominent civil engineers – John Fowler and Benjamin Baker, for a double-span cantilever bridge across the deep waters of the Firth of Forth would be adopted. To reassure a skeptical public that water crossings by rail-bridge were safe, this bridge not only had to BE strong, it had to LOOK strong as well. Fowler and Baker would put all their engineering knowledge and prowess into the design of the Firth of Forth Railway Bridge. It would use the islet of Inch Garvie, conveniently located midway across the Firth of Forth, as a stepping stone for a three tower (battered), six cantilever (two fixed, four free) design (using tubular compression members). The result: A Bridge for the Ages.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

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