Seismic anchor rods used for the $6.4-billion San Francisco-Oakland Bay Bridge are once again under scrutiny. Inspectors' discovery last month of stripped threads, loss of protective coatings and micro-indicators in three galvanized-steel units—installed in 2007 at the base of the bridge's 525-ft-tall east self-anchored suspension span (SAS) tower—have triggered a new probe.
Although the investigation is ongoing, Caltrans believes the presence of water in the 3- to 4-in.-dia, 26-ft-long rods' steel casings may have contributed to the problem. One rod fractured, with characteristics typically associated with hydrogen embrittlement, a condition that arises when nonuniform metal is exposed to excess hydrogen and tension. Similar fractures occurred in 2013, when 32 of 96 galvanized-steel rods used for the east tower's shear keys failed during tightening after being exposed to salt water.