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| The Tay Bridge today, courtesy of The Tay Bridge Disaster web page. |
Thomas Bouch was the engineer responsible for the design, construction, and maintenance of the Tay Bridge. He completed the bridge in February of 1878 and was knighted by Queen Victoria. Sir Thomas Bouch proceeded to design the Forth Bridge. The Tay Bridge collapsed 19 months after completion. Consquently, he was removed from his current project, the Forth Bridge. Sir Thomas Bouch died on October 30, 1880 (10 months after the Tay Bridge collapsed)(3).
Bridge Background
Structural design was based solely on experience. No codes had been written for Sir Thomas Bouch to follow. He designed most of his bridges with “lattice girders supported on slender cast iron columns braced with wrought iron struts and ties.”(5) The Tay Bridge, a bridge over the Firth of Tay in Scotland, was close to two miles in length. It consisted of 85 spans, 72 spans were supported on deck spans and 13 were navigation spans. Averaging about 235 feet in length, these navigation spans were about 27 feet high and about 88 feet above the water surface.
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| The fallen Tay Bridge, courtesy of Andrea French's web page. |
Failure and Aftermath
On December 28, 1879, there was a great storm with gale force winds topping 70 mph at right angles to the bridge. It was 7:15 PM when the Tay Bridge collapsed into the Firth of Tay at Dundee. Also falling into the river was a 6 carriage train and 75 people. The collapse claimed all of the lives on the train. However, the engine, given the name “the diver”, was recovered and used for many years after.(3) A Court of Inquiry set out to determine the reason for the failure. “The Court of Inquiry report concluded that, 'The fall of the bridge was occasioned by the insufficiency of the cross bracing and its fastenings to sustain the force of the gale.'”(5) It was found that Bouch designed the Tay Bridge for a 10 lb/sq.ft. wind load, which is significantly underdesigned. Some of the iron used was very poor in quality. In turn, the iron was cracking due to the very cold weather. It was also determined that the lugs holding the bracing were snapping off from being “too tight.” Sir Thomas Bouch was held fully responsible for the disaster and, consquently, was removed from his Forth Bridge design.
1. Cook, P. Now and Then: Nunthorpe man ruined by Tay Bridge Disaster. Accessed May 2, 2001 at 10:05 PM. The Now and Then Magazine
2. Crawford, E. Tay Bridge and associated lines. 1998. Accessed May 2, 2001 at 9:45 PM. www.railscot.co.uk/Tay_Bridge_and_associated_lines/frame.htm
3. French, A. The Tay Bridge Disaster, 1879. Accessed May 2, 2001 at 9:30 PM. Andrea French's Web Page
4. Koerte, A. Two Railway Bridges of an Era, Firth of Forth and Firth of Tay. Basel; Boston: Birkhauser Verlag, 1992.
5. The Tay Bridge Disaster. Accessed May 1, 2001 at 9:00 PM. www.tts1.demon.co.uk/tay.html
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