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Bay Bridge anchor‑bolt failures traced to hydrogen embrittlement; retrofit options being evaluated
Summary
Caltrans and the Bay Bridge oversight committee reported that 2,008 anchor bolts at Pier E2 failed due to hydrogen embrittlement. Two retrofit options — a steel collar and a steel saddle — are under evaluation; the 2010 bolts are being tested to determine whether they must be replaced.
Officials overseeing the new Bay Bridge project told the commission that an investigation has attributed the failure of 2,008 anchor bolts at Pier E2 to hydrogen embrittlement and that engineering teams are evaluating retrofit strategies.
A Caltrans representative reported that failed bolts — drawn from components installed and tensioned during the project — show metallurgical evidence consistent with hydrogen embrittlement: sections of the fractured rods displayed the characteristic crescent-shaped smooth region surrounded by rougher fracture surfaces. The presenter said the failures began shortly after tensioning (starting about day three and continuing through day 14) and that detensioning halted further immediate failures.
Two retrofit options under review: the team described two main strategies to address the shear keys where embedded 2008 bolts failed. One alternative calls for a steel collar wrapped around the shear key and anchored into the surrounding concrete; the other uses a fabricated steel saddle bonded into a concrete overlay. The contractor has reportedly ordered steel for both options and fabrication capacity is staged in the region so work could proceed quickly once the oversight committee selects an approach.
2008 versus 2010 bolts: the presenter said the failed (2008‑batch) bolts and the 2010 batch show differences in measured mechanical properties and hardness; the 2010 bolts are marginally more ductile and have lower measured hardness values in preliminary testing. Because the 2008 bolts were embedded and cannot be easily removed, that group will require the selected retrofit; the 2010 bolts pass through the pier and are replaceable if testing determines replacement is necessary.
Testing and responsibility: metallurgical testing and QA/QC desk audits are underway. Officials told commissioners it is not yet possible to say whether hydrogen ingress occurred during fabrication or afterward in the field; additional testing is required to trace the source. Commissioners pressed officials on responsibility and public confidence; the Caltrans representative said the priority is ensuring safety and project performance and that “we are less interested in, in finding blame right now” than in arriving at a durable engineering solution. Officials emphasized the bridge will not open until it meets safety and design performance expectations.
What to expect next: the program oversight committee planned to select a retrofit option imminently and to release the metallurgical report on the 2008 bolts. The 2010 bolts are being subjected to revised test protocols (including accelerated corrosion/tension baths) and a desk audit of QA/QC records for other bolts on the project is underway.
