Lessons Learned from the Bay Bridge Bolt Failure
This article discusses the San Francisco-Oakland Bay Bridge in California and the lessons learned when it was found to have structural deficits. The author briefly reviews the history since 1989, when a number of bridges around the San Francisco area were damaged during the Loma Prieta Earthquake. The bridge underwent a complete seismic retrofit in 2004, undergoing modifications to become more resistant to seismic activity and other ground motion. In 2013, the eastern section of the bridge was completely replaced with a new self-anchored suspension bridge (SAS). The author then reviews some of the issues for SAS bridges during seismic events, notably the potential for amplification of stresses on the cables. Topics include the use of shear keys to offset the harmonic amplification of the bridge deck; the preparation and placement of bolts or anchor rods, within the shear keys; early symptoms of problems during pretensioning of the anchor rods; the shear key rod failure investigation, including metallurgical testing, visual inspection, and failure analysis; additional evaluation of the fractured rods; and the mechanism of hydrogen embrittlement. The author reports that conclusion that the Bay Bridge rods installed in 2008 failed because of environmentally-induced hydrogen embrittlement caused by tensioning above their threshold while simultaneously immersed in water. All of the remaining rods on the bridge have been tested and are considered safe. They were also given supplemental measures to prevent corrosion, including dehumidification, paint systems, or grout.
- Record URL:
- Langill, Thomas
- Publication Date: 2017-2
- Media Type: Web
- Features: Photos; References;
- Pagination: n.p.
- TRT Terms: Anchor bolts; Corrosion resistance; Earthquake resistant structures; Embrittlement; Hydrogen; Mechanical failure; Shear properties; Suspension bridges
- Identifier Terms: San Francisco-Oakland Bay Bridge
- Subject Areas: Bridges and other structures; Highways; Maintenance and Preservation; Materials;
- Accession Number: 01643933
- Record Type: Publication
- Files: TRIS
- Created Date: Aug 21 2017 7:42PM