The bad news for the San Francisco Bay Bridge tower just got worse: cracks have been discovered on some of the rods that are part of the tower foundation, according to Caltrans. Caltrans also admitted that one of the four tower anchor rods broke after water exposure made it brittle.
Brian Maroney, Caltrans’ chief engineer on the project, told the San Francisco Chronicle that two rods displayed microscopic cracks, which could indicate similar probelms with some of the 400 other rods.
The general consensus among experts is that the high-strength rods fail from hydrogen exposure from water. Lisa Fulton, a metallurgical engineer and materials scientist at the Berkeley Research Company, told the Chronicle that the crack in the rods “means that there doesn’t have to be a lot of force on those rods for them to break. That could indicate that we don’t need an earthquake for them to snap, that they are unreliable in the service loads that they are under now. The micro-cracking is a sure sign of hydrogen attack. It’s a portent of catastrophe.”
Patrick Pizzo, a metallurgical failure expert, told the Chronicle that he was dubious about the claims from Caltrans that most of the bolts passed pull tests, noting that hydrogen embrittlement in steel can take years to appear. He asked, “That’s one failed rod already in two years. But what about tomorrow? What about 10 years? Fifty years? How many would be left in 150 years?”
In May, a steel rod supporting the 525-foot tower failed an integrity test.
In June, Caltrans director Malcolm Dougherty admitted that the sleeves of 120 of the 400 “high-strength” rods anchoring the tower of were immersed in salt water that could corrode them.
Options for fixing the rods include replacing them rather than repairing them, but Maroney admitted that replacement would raise costs abundantly. He offered the alternative of replacing the grout surrounding the rods with grease. The three-member committee would not approve funding for cleaning and protecting the rods.