**7.1 Pittsburgh bridge collapse**

On Jan 28, 2022, at 6:45 am a 52-year old steel-framed bridge, **Figure 7**, which spans a deep ravine in Frick Park, collapsed, sending six cars and a metro bus down with it. Fortunately no one was killed. Six people had minor injuries. According to the mayor, an inspection of the bridge was performed in September. The bridge has been described as in "poor" condition in previous reports from 2011 to 2017. A structural evaluation described the bridge meeting "minimum tolerable limits to be left in place as is."

*Failure analysis*: The root cause of the bridge failure was a single point of failure in a corroded structural element. The bridge was non-redundant and fracture critical, meaning a single point of failure will cause the bridge to collapse. Contributing factors were a failure in the inspection process to assess and accurately determine the structural capacity of the corroded steel elements and the decision to keep the bridge open despite a poor condition.

**Figure 7.** *Collapsed Pittsburg bridge January 2022. CC BY-SA 3.0.*
