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Caltrans testing 2010 Bay Bridge bolts

May 9, 2013 8:20:20 PM PDT
Caltrans has settled on a plan for dealing with the 32 broken bolts on the new Bay Bridge, but they still have a lot of testing to do on the ones that haven't broken.

What started out as a 22-foot rod has been sliced and diced down to smaller pieces in a Sacramento Caltrans lab. The specimens are from a batch of 192 rods delivered and installed on the new self-anchored suspension span in 2010. Eight of them have been removed and brought to Sacramento for testing because similar rods, from 2008, failed when tensioned and now Caltrans wants to make sure the 2010 bolts are not prone to the same problem, called hydrogen embrittlement.

These rods were already tested before being installed, but Caltrans didn't know hydrogen embrittlement was a threat at the time.

"Now we know that it was hydrogen embrittlement to cause those 32 rods to break out of that initial batch of 96; we now have a little bit of evidence, that gives us a little more information to work with," Caltrans spokesperson Andrew Gordon said.

The lab is gathering data on how hard the steel is. A diamond-tipped indentor penetrates a a slice of the rod; another test measures how the metal withstands forceful impact, and another measures its strength when pulled with force at a rate of one-half-inch per minute.

So far the testing data is encouraging ? it seems to indicate that no more bolts will crack.

Data collected at the lab will be sent elsewhere for analysis. Independent labs are testing as well, and the Federal Highway Adminsitration will do an "arm's length review" to satisfy those who have lost faith in Caltrans, like state Sen. Mark De Saulnier, who's called a hearing on the bolt debacle next week.

"It's $6.3 billion for the safest bridge, supposedly, in the world, in a seismically active area, so trust is really important to the general public," he said.

Wednesday, Caltrans announced it had settled on a plan for dealing with the bolts already trapped in concrete on the bridge.

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