Damage to the San Francisco-Oakland Bay Bridge (Again)

By ThinkReliability Staff

In a previous blog, I wrote about the impressively quick repairs to the San Francisco-Oakland Bay Bridge.  These repairs allowed the heavily-traveled bridge to reopen only an hour and a half late from scheduled repairs, despite unexpectedly finding a cracked eyebar during that time.

However, during evening rush hour on October 27, less than 2 months after the eyebar repair had been completed, two metal rods and a 5,000 pound metal beam fell onto the roadway.  The items that fell were part of the previous repair, which was supposed to have lasted until the new bridge opened in 2013. Although only one motorist was injured, other injuries or even fatalities were possible, and the damage to the bridge necessitated repairs and closing the transportation route for 280,000 cars a day for more than 5 days.

The “cause” given for the failure of one of the rods (which snapped, leading to the falling of the other rod and the beam) was fatigue caused by high (over 30 mile per hour) winds.  However, an adequate repair would have been able to withstand less than 2 months of traffic and 30 mile per hour winds, so the rod failure must have been caused by the combination of the high winds and an inadequate repair.

Given the speed with which the repair was completed (see our previous blog), it’s possible that the repair job was rushed.  Additionally, the Federal Highway Administration did not inspect the bridge after the repairs were completed, instead relying on state inspection reports.  Had another agency inspected the repairs, it’s possible the problems with the repair would have been noticed and fixed before the bridge was re-opened.

A summary of the investigation to date can be found on the downloadable PDF.  (To open, click on “Download PDF” above.)  The investigation includes a timeline, which can aid in the understanding of this issue, the problem outline, and the Cause Map (visual root cause analysis).  A thorough root cause analysis built as a Cause Map can capture all of the causes in a simple, intuitive format that fits on one page.  As with any investigation, as more information becomes known, more detail can be added to the Cause Map.