TUESDAY, APRIL 2, 2013
Construction on the east span of California’s new Bay Bridge has hit a snag after workers discovered over 30 broken bolts on the new eastern span, state transportation officials announced.
Heavy-duty bolts, installed for seismic stability, popped loose and damaged the bolts just days after crews tightened started tightening them, the Metropolitan Transportation Commission said.
In early March, workers started tightening nuts on both ends of 96 bolts, also called anchor rods; a total of 288 rods have been installed on the span. The bolts range from 9 to 24 feet long and are three inches in diameter.
Only a few days later, the crew returned to discover that 32 of the bolts had broken loose.
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| Photos: Caltrans Bay Area Toll Authority California Transportation Commission |
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One-third of anchor rods, or bolts, installed on the easternmost part of the Bay Bridge popped loose just days after crews started tightening them, transportation officials announced. |
MTC, which oversees the Bay Bridge project with Caltrans, held a meeting on March 27 to present information on the broken bolts.
Assessing the Problem
Tony Anziano, Caltrans Toll Bridge Program Manager, presented information on the busted bolts.
"This is certainly something that merits briefing," Anziano said, explaining that the large rods connect two columns that rise from the underwater foundation to the concrete pier cap.
In some cases, the rods go entirely through the concrete cap, or are embedded into it, limiting access to rods in the middle portion of the cap.
The rods were tensioned between March 1 and 5; broken rods were discovered between March 8 and 15, Anziano said. Bolts were originally installed in 2008.
"Within a week, we started seeing evidence that these rods were breaking in place. At this point in time, we are still in the process of assessing the situation," said Anziano.
So far, testing has shown that hydrogen has caused the problem, explained Anziano.
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The bolt in the foreground is lifted about the area that it should be flushed with, giving a "pretty clear indication" that the rod is broken, Caltrans officials explained. |
Possible Repairs
Caltrans is still looking into possible solutions, which they expect to develop within a matter of weeks.
"We have actually done a fair amount of laboratory and materials testing. We've taken some of these rods out. They're not easy to get out," Anziano said.
"They actually have to be extracted as far as you can pull them out, then you have to cut a piece off, extract a little bit further, cut a piece off," he said. There are only five feet of clearance to work with, and the rods are at least nine feet long.
According to Anziano, three of the rods have been sent for metallurgical testing and hydrogen was found, which often causes the type of fracture found on the rods.
"Hydrogen is one of those things that works its way in in ways that you don't always typically see. And that's why hydrogen is an issue when you're dealing with steel. Even with the most rigorous inspection practices, hydrogen somewhow sneaks its way in and manifests itself in situations like this," Anziano explained.
While some of the rods can be replaced, an alternate design solution may be implemented where rods cannot be accessed.
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A solution and timetable for the fix have not yet been determined, and some of the rods might not be accessible, requiring a second solution for repairs.   |
'Greater Challenges'
The new Bay Bridge is scheduled to open this Labor Day weekend, and officials remain optimistic that the bolt problem won't delay the opening.
"We have surmounted far greater engineering challenges than this one in getting this bridge constructed, and I have no doubt that we will get through this one as well," Steve Heminger, executive director of MTC, said at the meeting.
Heminger said that they are "certainly mindful" that someone will have to be responsible for the extra cost.
"I think the cost will end up being a rounding error in terms of this project," Heminger told KQED. "We're talking about a $6 billion bridge, and I can't conceive of a solution that's even going to cost a fraction of that amount."
Randy Rentschler with MTC said there are $300 million in contingency funds built into the original budget, and fixing the bolts won't even make a dent in that amount, local CBS affiliate Channel 5 KPIX reported.
The bridge has been under construction for over a decade, and the bolts aren't the first problem.
Sections of the steel deck that were fabricated in China delayed work for months when microscopic cracks were found and further inspections delayed work when the integrity of welds on the piers of the new skyway section were questioned.
And then there were accusations that an inspector faked seismic inspection reports on another, unrelated project.
Tagged categories: Bridges; Concrete; Construction; Department of Transportation (DOT); Galvanized steel; Performance testing; Program/Project Management; Retrofits; Steel
