Pins and needles bend and break

Posted on August 04, 2007 by Steve

USA Today is not likely to get a lot of dissent from this op-ed:
'A bridge in America just shouldn't fall down'

Unfortunately, bridges do fall down. In his epic history of bridge builders and bridge failures, Henry Petroski described research published in 1977 showing an eerie pattern of catastrophic bridge disasters roughly every thirty years:

1847 Dee Bridge
1879 Tay Bridge
1907 Quebec Bridge
1940 Tacoma Narrows Bridge

The researchers, Paul Sibly and Alastair C. Walker, found two failures of bridges under construction in 1970, both using a new style of construction known as a box girder. In fact, each of the earlier disasters struck a bridge using a new construction method -- trussed girder, truss, cantilever, suspension, and then box girder. Petroski suggested that engineers behind a new design were more conservative, and later builders had more confidence and took greater risks, until a failure occurred. He warned that a catastrophic failure of a new style of bridge -- perhaps the beautiful and daring cable-stayed bridge -- could occur around the turn of the millennium. So far it hasn't happened, and one can hope that great projects like the Millau Viaduct will be around for a long time.
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