Bridge mired in troubled water

Rob Francis

“The successful engineer is the one who knows not only what has worked in the past but also what has failed and why.”
(Henry Petroski, To Forgive Design: Understanding Failure)

Problems with bridges and similar infrastructure in the USA have largely concerned degradation due to old age. However, one new bridge has been the subject of much discussion because of expensive and high profile failures during construction. A number of critical anchor rods in California’s $US6.5 billion replacement San Francisco–Oakland Bay Bridge, built to last 150 years, fractured in March 2013. As a result, the California Department of Transport (Caltrans) had to install a steel saddle retrofit to provide the required strength at a cost of $US25 million. In addition, the department has suffered bad press and spent significant sums of money on investigations and strategies to prevent further failures.

This failure provides a good case study showing some of the technical issues and problems that can arise in modern steel and concrete structures. The fact that the failure has been played out in public, with most of the documentation freely available on the internet, has made it easy to identify the problems and follow the discussion and arguments by various parties. However, it should be noted that investigations are ongoing, and it is possible that new findings will change some conclusions and recommendations.


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