Caltrans downplays latest Bay Bridge rod failure

The new eastern span of the Bay Bridge has a long history of problems:

The new eastern span of the Bay Bridge has a long history of problems: Photo: Paul Chinn, The Chronicle Photo: Paul Chinn, The Chronicle Image 1 of / 54 Caption Close Caltrans downplays latest Bay Bridge rod failure 1 / 54 Back to Gallery

Another steel rod anchoring the foundation of the new Bay Bridge eastern span tower failed a critical strength test, Caltrans officials acknowledged Wednesday, and two sources close to the bridge project told The Chronicle it made a popping noise, suggesting a crack.

Caltrans officials downplayed the failure, stressing that 99 percent of the 407 rods that underwent testing passed, and said that the cause will need to be determined by further tests in a materials lab. But the failure of a second rod leaves the possibility that more rods could eventually fail.

“Hydrogen embrittlement and corrosion occurs over time,” said Steve Heminger, executive director of the Metropolitan Transportation Commission and one of three people on a committee overseeing the east span construction. “They could last 20 years or 50 years, but with this bridge, we want 150 years.”

Caltrans officials cautioned against blaming corrosion for the failure. Dan McElhinney, the Caltrans official overseeing the bridge project, said it could have been caused by threads that were stripped during installation, by corrosion from sitting in water or both.

“We won’t know the cause until the rod is removed and provided for laboratory testing,” said Leah Robinson-Leach, a Caltrans spokeswoman.

That testing is expected to be ordered by the bridge oversight committee at a meeting likely to be held in the next few days, McElhinney said. Initial results could be available in a week to two weeks, Robinson-Leach said, but final results could require more tests and take months.

Caltrans officials said the test results should bolster the public’s confidence in the safety of the bridge. McElhinney said the fact that almost all of the rods passed the mechanical pull test — a test in which a machine yanks at the fastener and detects whether or not it moves — is a sign the bridge tower is well-protected.

“This bridge is safe, and it’s going to perform well in a major seismic event,” he said. “The engineers are saying it’s terrific.”

Some independent experts are not convinced, however.

“That would suggest it did not strip, but that it fractured,” said Bernard Cuzzillo, a Berkeley mechanical engineer. “Because a fracture results in a sudden release of elastic energy, which causes a pop or a bang sound. Stripping is a slower failure and typically does not result in an audible sound.”

Nearly all of the tower’s 424 high-strength rods — intended to provide added seismic protection for the landmark structure — stewed in water for a prolonged period, exposing them to possible corrosion. A botched grouting and sealing job left hundreds of rod sleeves flooded, and recently Caltrans discovered signs indicating that salt water may be leaching into the foundation from the bay.

Caltrans tested all 407 of the rods available for testing and just two failed, McElhinney said. Robinson-Leach said the rod was of normal length and that it failed to hold a load when it was pulled. If overseers choose to remove the newly failed rod for testing, it will be sent to a laboratory for testing with a failed rod discovered about a week ago.

Michael Cabanatuan is a San Francisco Chronicle staff writer. E-mail: mcabanatuan@sfchronicle.com Twitter: @ctuan