Caltrans announced Wednesday that it has chosen a steel saddle system to retrofit and reinforce three dozen faulty bolts that snapped earlier this year after they were installed on the new span. The cracked steel rods are enclosed in concrete, so they can't simply remove them and replace them with new ones. So, the plan is shore up the structure the rods are a part of.
The fix could take months to complete.
Caltrans engineers used a scale model Wednesday to explain their plan for dealing with the 32 broken rods. The cracked rods are inside a seismic safety feature called bearing which allows the bridge deck to move without breaking in an earthquake. Two steel saddles will house 430 extremely strong steel cables that will wrap around and underneath the bearing. There will be perpendicular strapping as well and all of it will be housed within a concrete sheath.
Caltrans says this fix is the best choice because it's the least difficult to install and retains the same clamping force of the original bolt design. "What you see here is already something the contractor has looked at, commented on, and said yes, I can do this and I feel more comfortable with this alternative than the other alternatives, so that I can have a better chance of making Labor Day," explained Caltrans structural engineer Marwan Nader.
As far as opening the bridge on schedule, John Goodwin with the Metropolitan Transportation Commission says, "It's still an outstanding question. I think that there's going to be a real close race, either way."
"There are no promises. This is going to require an unbelievable amount of hard work and we need to get it right the first time," Caltrans bridge engineer Brian Maroney said.
The broken bolts were delivered in 2008. Caltrans is now testing another 192 of the same kind that were delivered in 2010. So far, the later batch has proven stronger in testing. "The data we're seeing is showing a divergence between the 2008 bolts that failed and the 2010 bolts that have not," MTC Executive Director Steve Hemminger said.
There is an independent peer review panel taking a look at Caltrans plans for the repair and bolt testing going forward. Also, the bridge oversight committee has sent a letter to the Federal Highway Administration asking them to take a look. That move is recognition of the fact that public confidence in Caltrans has recently been shaken.
Caltrans will be working with a contractor to firm up an opening date but ultimately, Gov. Jerry Brown will have the final say on when the new span opens. There is money available in the budget for the bridge for cost overruns like this one, but it is still a big setback and there is no quick fix.