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Bay Bridge retrofit plan addresses failed bolts

Transportation officials say a steel saddle will take the place of massive bolts that failed on the San Francisco-Oakland Bay Bridge's eastern span. A Labor Day opening is uncertain.

May 08, 2013|By Lee Romney, Los Angeles Times
  • Explaining why Caltrans went against its own standards in using certain galvanized bolts on the Bay Bridge, Brian Maroney, deputy toll bridge manager, noted that “every single project has special provisions.”
Explaining why Caltrans went against its own standards in using certain… (Laura A. Oda / Bay Area News…)

OAKLAND — State and regional transportation officials announced plans Wednesday for a retrofit to the new eastern span of the San Francisco-Oakland Bay Bridge that will cost up to $10 million and effectively do the job of nearly 100 massive bolts that failed earlier this year.

Questions remain, however, about whether the world's largest single-tower, self-anchored suspension span will open on Labor Day weekend as planned. The new span will replace the one that partially collapsed in the 1989 Loma Prieta earthquake.

"We believe the work can get done by Labor Day, but it will require extra shifts and perhaps a 24-hour-a-day operation and that will cost more money," Steve Heminger, executive director of the Metropolitan Transportation Commission, told the Bay Area Toll Authority Oversight Committee.

The thick steel bolts — which are 17 feet to 24 feet long — connect the bridge deck to so-called shear keys, which are designed to control movement during an earthquake. They were part of a batch manufactured and galvanized in 2008 and installed on the span, which has been in the works for years and has ballooned in cost to $6.4 billion.

When the 96 bolts, which were embedded in concrete and impossible to remove, were tightened earlier this year, a third of them broke, leaving the seismic safety of the massive endeavor in question.

That batch of bolts has been deemed too compromised to rely on.

The wild card, Heminger said, is whether bolts made from similar steel in 2010 — some equally large and some much smaller — will also have to be replaced before the bridge opens or simply monitored after the fact.

Commissioners were filled in Wednesday on the planned retrofit as well as a battery of tests being conducted on the bolts made in 2010.

Those bolts, which are accessible and can be swapped out for others, have not yet broken. "The longer they are not doing that, the more daylight we are seeing between the 2008 bolts and the 2010 bolts," Heminger said. A decision will probably be made by month's end on the bolts and the opening date.

In addition to Heminger, presenters included Andre Boutros, executive director of the California Transportation Commission, and Malcolm Dougherty, director of the California Department of Transportation. Their three organizations jointly oversee the bridge project.

Boutros said the group had opted for one of two finalists for the retrofit — a steel saddle that must be fabricated and will be clamped down on top of the shear key plates with tensioned cables. Another option, for a larger steel collar, would have cost as much as $20 million.

Caltrans has come under fire for using the galvanized steel bolts. U.S. industry standards and Caltrans' own guidelines warn against galvanizing the specific grade of steel used due to its hardness and tendency to break under extreme tension.

The massive bolts failed due to a phenomenon called hydrogen embrittlement, in which hydrogen atoms invade the spaces between the steel's crystalline structure and weaken it. That may have occurred during galvanization, or when the bolts sat for years untightened in casings that filled with water.

Caltrans has said that it asked the manufacturer to use a galvanization process less likely to cause hydrogen embrittlement but that in retrospect it should have tested the bolts more thoroughly in the lab before installing them.

When asked why Caltrans deviated from its own specifications, which warn against galvanizing this type of steel, Brian Maroney, deputy toll bridge manager at Caltrans, said that in his 25 years of bridge engineering, "every single project has special provisions, because those standards don't really fit and you have to come up with a technical solution.

"The Bay Bridge," he added, "has many, many, many special deviations away from the standard."

lee.romney@latimes.com

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