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Seismic Stabilization Bolts Snap On New Bay Bridge

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SAN FRANCISCO (CBS) – Dozens of bolts used for seismic stabilization have snapped on the new span of the Bay Bridge.

Caltrans told CBS San Francisco what they’re doing to fix the problem.

“There are challenges in every large project like this,” said Toll Bridge Program Manager Tony Anziano.

This is a cross-section of the bolts location, tying the roadway decks onto the east pier of the new Bay Bridge. They range from 9 to 24 feet in length with a 3-inch diameter. The broken rods were discovered last week.

This photo shows where the bolts snapped. (credit: CBS)

This photo shows where the bolts snapped. (credit: CBS)

“When these rods do snap, they pop up basically. And this is exactly what you see out in the field. This was what was observed by our inspectors, which gave a clear indication that we do have an issue that we have to deal with,” said Anziano.

About one-third of bolts tested were found to have snapped. The MTC and Caltrans will be evaluating whether or not all 288 need to be replaced or if they can make an exterior collar for the structure instead.

“The goal is to find a retrofit strategy so that the specifications of holding these shear keys down on the concrete can be met,” said Metropolitan Transportation Commission Director Randy Rentschler.

Either way, the whole mechanism is about seismic safety. There’s no danger to the bridge structure itself, but seismic safety is the whole reason we’re getting a new Bay Bridge.

“Any solution that we put in place will cause this to perform as its designed to perform, so all of these factors are taking into consideration in developing the ultimate design,” said Anziano.

The MTC says it looks like hydrogen got into the steel making the bolts brittle. Crews removed three of them and sent them away for testing to figure out what went wrong.

Who has financial responsibility and how much will it cost to replace the bolts is still unknown.

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