Fifty years ago

50 years ago

The finest engineering brains in the country are testing models in a wind tunnel to make certain that the mile-long £15 million Forth Road Bridge will not collapse like the first Tay Bridge, which was destroyed in a storm. Work on the bridge will start this summer.

A look through the Journal and Gazette archives
Queensferry Tooday, UK - Apr 4, 2008

Thirty Year Rule?

A close reading of the history of major bridge failures is contained in a remarkable piece of scholarship by Paul Sibly and his adviser, then at University College London, Alastair C. Walker. Among the conclusions of their work, published in 1977, was the strong temporal pattern that bridge failure had followed from the middle of the nineteenth century. What Sibly and Walker noted was that the collapse of the Tay, Quebec, and Tacoma Narrows bridges, which occurred in 1879, 1907, and 1940, respectively, were very nearly thirty years apart. A less commonly remembered incident, but one that was equally dramatic and in its own time the subject of investigation by a royal commission, was the collapse of Robert Stephenson’s Dee Bridge in 1847—further reinforcing the observation that a thirty-year cycle was associated with bridge failures. To test their hypothesis, which pointed to a major bridge failure about the year 1970, Sibly and Walker looked at incidents from around that time and found that, indeed, in 1970 there were two significant failures of a new type of steel bridge, known as a box girder, then under construction in Milford Haven, Wales, and in Melbourne, Australia.

Bridge Inspection and Testing
U.S. News & World Report – Aug 6, 2007

The observation I quoted from Henry Petroski’s Engineers of Dreams, that major bridge collapses came about every 30 years–the Tay Bridge in 1879, the Quebec bridge in 1907, the Tacoma Narrows bridge in 1940–may turn out to be right, with this caveat: The I-35W bridge collapse in 2007 may turn out to have been caused by mistakes made in 1967.

Barone Blog: The Bridge Collapse
CBS News – Aug 10, 2007