Fern Hollow Bridge Collapse

Fern Hollow Bridge collapsed due to ‘extensive’ corrosion, inability to carry load, NTSB says

PITTSBURGH — The National Transportation Safety Board said the Fern Hollow Bridge should have been closed prior to its collapse in January 2022.

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The Forbes Avenue Bridge collapsed 100 feet down into Fern Hollow on Jan. 28, 2022. Six cars were on or near the bridge when it collapsed and four people were hurt.

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“On behalf of the NTSB, we are so sorry you experienced such a terrifying event,” NTSB Chair Jennifer Homendy said. “The Fern Hollow bridge collapse should have never happened, your injuries should have never occurred.”

The NTSB determined the bridge collapsed due to extensive corrosion, section loss and inability to carry the load at the time of the collapse, all of which resulted from the City of Pittsburgh’s failure to act on repeated maintenance and repair recommendations from inspection reports.

Poor quality of inspections, incomplete identification of fracture-critical pieces and poor oversight also contributed to the collapse, the NTSB said.

Several failures allowed the Fern Hollow Bridge to remain open when it should have been closed, including overestimation of each leg’s load capacity and section loss of each leg.

Investigators found three main aspects of the load rating calculation that were inaccurate: how holes and section loss on portions of the bridge legs were handled, the effective length factor used to estimate the bridge legs’ ability to resist buckling and the amount of asphalt wearing surface on the bridge at the time of the collapse.

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The bridge was inspected every two years, with yearly inspections starting in 2014. However, the NTSB said between 2005 and 2021, there’s documentation for maintenance that never happened. The last time the bridge was inspected was four months before the collapse.

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The NTSB said 2015 into 2021 showed drains filled with leaves, which allowed water to run down the legs which led to major corrosion and section loss. The Fern Hollow Bridge was built with weathering steel, which was expected to resist corrosion.

There were holes in the metal on all four of the bridge’s legs, which were first noted in 2007, per the NTSB. In 2009, steel cables were added until cross bracing was replaced but that was never completed. A rust-inhibiting coating was supposed to be completed but never happened.

Steel legs were in bad condition in reports from 2019 to 2021 and should have had a structural review. The legs were identified by PennDOT as fracture-critical members, so the city didn’t do a review.

There was a repeated lack of action on recommendations that came from inspections, bridge inspection program failures and insufficient overnight at the city, state and federal levels that contributed to the collapse.

“There were a lot of failures there, lack of documents, inspectors relying on faulty engineer analysis, maintenance that wasn’t conducted,” Homendy said.

>> NTSB issues national bridge recommendations following Fern Hollow collapse

In total, the NTSB said the Fern Hollow Bridge inspections failed to:

  • Clean corrosion before measuring
  • Accurately quantify remaining material
  • Accurately rate the general bridge superstructure condition
  • Recommend a structural review of the bridge legs

Inspectors also failed to perform the inspections in compliance with national standards which led to the overload of the bridge.

The NTSB reported the City of Pittsburgh was responsible for inspection and maintenance of the bridge, PennDOT was responsible for ensuring all state bridges comply with federal policies and the Federal Highway Administration was responsible for oversight of all bridge state programs.

As a result of these findings, the NTSB is issuing 11 new recommendations. Those can be found here.

Furthermore, the NTSB said that had the city taken appropriate action, the collapse could have been prevented. They also said PennDOT’s insufficient oversight of the city’s inspection program led to the collapse.

“The Fern Hollow catastrophe was a serious wake-up to the City and PennDOT and I hope it serves as a serious wake-up call to every other bridge owner,” Homendy said.

The NTSB said 6.9% of bridges in the country are in poor condition and that people in cars cross the bridges 167 million times a day. Pennsylvania ranks sixth in the nation for poor bridges.

The NTSB said the City of Pittsburgh needs to update paving records.

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