It is pointed out how scaling up existing successful designs can cause latent weaknesses to become dominant, leading to catastrophe. By studying past failures in which this has happened, for example, the 1847 failure of the Dee Bridge designed by Robert Stephenson in Cheshire, England, engineers can guard against overconfidence. The critical flaw in the design process which produced the failed Dee Bridge was the same as the flaw that produced the ill-fated Tacoma Narrows Bridge. The Dee Bridge was geometrically at the outer limits of experience in that design class. Engineer Stephenson employed a trussed girder technique which had been adopted for several other railway bridges. Before the Dee Bridge, the principle had not been applied to trussed girders longer than 88 feet each. The Dee was designed with spans of 98 feet each. This application should have been accompanied by extreme attention and careful observation. The most likely cause of the failure of the bridge was a torsional buckling instability to which the bridge girders were predisposed by the compressive loads introduced by the eccentric diagonal tie-rods on the girder. This case history of engineering failure teaches lessons about the nature of the design process.


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  • Accession Number: 00646376
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 25 1994 12:00AM