The Quebec Bridge Company was formed in 1887 and for the nextthirteen years, very little was done. In 1900, Thomas Cooper, a consultantin civil engineering specializing in bridge building wasappointed the company’s consulting engineer for the duration of thework. The Sixth Street bridge in Pittsburgh, the Seekonk bridge inProvidence, and the Second Avenue bridge in New York werealready part of his portfolio.Conscious of the precarious financial situation of the QuebecBridge Company, Cooper recommended the cantilever superstructureproposed by the Phoenix Bridge Company, of Phoenixville,Pennsylvania as the best and cheapest of the proposals. He also recommendedthat the span of the bridge be increased from 1600 feetto 1800 feet to minimize the cost of constructing the piers supportingthe bridge. The specifications were also modified to allow forgreater unit stresses in the structure. The Quebec Bridge was to bethe longest cantilever bridge in the world.For the next three years, the assumptions underlying the modifieddesign of the most technically ambitious bridge in the world wentunchallenged. After the Canadian government guaranteed a bondissue in 1903, the construction shifted into high gear. In the rush tominimize delays, the assumed weight of the revised bridge was notrecalculated. Instead, work continued with the estimated weight thePhoenix Company had provided with the original proposal. Cooperwas personally offended when the Canadian Department of Railwaysand Canals requested that the plans be independentlyreviewed and approved. With full confidence in his own design andexpertise, Cooper managed to turn the independent review into arubber stamp approval by unqualified individuals.Subsequent warnings were also summarily ignored. In 1906, thePhoenix Company’s inspector of material reported that the actualweight of steel put into the bridge had already exceeded the originalestimated weight. The final weight of the bridge was estimated tobe eleven million pounds higher than originally thought. The alternativebeing to start building the bridge all over again, Cooper concludedthat the increase in stresses was acceptable.In early August 1907, the lower horizontal pieces running thelength of the bridge began to show signs of buckling. The PhoenixCompany insisted that they were already bent when they left theshop in Phoenixville and work continued. They made no effort toexplain why a deflection had increased by an inch and a half in thepast week. On August 29th, the south arm of the bridge collapsedunder its own weight, killing 73 workers.The bridge was eventually redesigned and rebuilt, weighing twoand a half times more than its predecessor. Ironically, it suffered atragedy of its own in 1916 when the central span fell into the riverwhile it was being hoisted into place. The bridge was finally completedin 19181. It is still in use today and it is still the longest cantileverbridge in the world.The parallel with today’s micro-electronic designs is obvious. Thenext design is always more challenging than the previous one and ittakes the designers into previously uncharted waters. A design cannotgo unchallenged simply because it worked in the last implementation.Changes in the specifications or new functionality cannot beassumed to work simply because they were designed by the bestengineers. Errors will be made. It is important that any design beindependently verified to ensure that it is indeed functionally correct.The alternative is to manufacture a non-functional design.Hopefully, no one will get killed. But many could lose their jobs.
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