So, remember last week when I shared some good news about the Bay Bridge? Well, the Bay Bridge Bolt Botch is back in the news, and this time it’s good news and bad news! So much more interesting than that unending diet of sweetness and light we had for a whole week!
Let’s start with the good news. The actual Bolt Botch is officially history. Not only are the saddle and the grease caps in place to relieve our fears about the bolts, but the new troll is also in place! Caltrans moved him into his new home on the bridge a couple of weeks ago and positioned him on the very same pier as the broken bolts. That should make it as easy as possible for him to protect the bridge from further bolt breakage.
For the record, the troll’s location is not visible from the roadbed, so whatever antics he gets up to shouldn’t disturb traffic. The location is visible from the water and partly visible from the bike path, so we hope he’ll keep the wild parties to a minimum to avoid distracting bikers and upsetting boaters.
So the troll is the good news. The bad news? Nothing less than a whole new reason to worry about the bridge’s seismic safety. Yes, the Bay Bridge’s new east span–built because the old one was deemed unlikely to survive a major earthquake–may not be able to survive a major earthquake.
I’m sure at this point many of you are thinking, “What, another failure to follow standards or test?” You’re right! Well, half right, anyway.
Stick with me on this. Remember that the bridge is a suspension design. That means that the entire weight of the roadbed rests on those huge cables that swoop so gracefully through the air. At each end of the bridge, those cables separate into 274 strands, each of which is anchored to the roadbed. The connection is made with a steel rod (yes, more steel rods) which runs through a hole in the steel chamber under the road. Yes, the same steel chambers that leak.
Oddly enough, the potential problem has nothing to do with the leaks, nor has there (yet?) been any indication that the rods are galvanized and/or embrittled. The problem is that the rods run through holes in the steel chamber. If the rods come into contact with the edges of the holes, the rods can be bent. That puts additional strain on the system, leading to the possibility that the rod or cable could break.
Wasn’t that possibility accounted for in the design? Well, yes. The design is for the holes to be slightly larger than the rods and for the rods to run through the center of the holes. That way, there’s a small amount of space around the rods to accommodate a little slippage. Unfortunately, Caltrans allowed the builder to make the last holes larger than the design called for, which means there’s more room for the rods to move around.
And they did indeed move. According to a recent inspection, 209 of the 274 rods are off center to the point that they’re in danger; two of them are actually in contact with the edge of their holes. Either the rods will need to be readjusted, or the holes will need to be enlarged.
“A recent inspection?” Yup. Nobody had checked the position of the rods since they were installed, even after the temporary support scaffolds were removed and the entire weight of the bridge went onto the cables (a critical moment that Caltrans engineers think may have been when the shifting occurred.) The problem was found as part of the ongoing inspection of all rods and bolts that started when the bolt botch was discovered.
So that’s why I said you were half right. As far as I can tell (and, as usual, I’m indebted to our buddy Jaxon at the Chron for most of my information here), the enlarged holes don’t violate any standards. But they do represent a design change, and one which was apparently not adequately thought through. When combined with the apparent decision to omit testing–a decision we’ve seen over and over again in the accounts of the bridge’s problems–and we’re left with yet another failure for the bridge in meeting its seismic stability targets.
So far, all of the problems can be traced back to a culture that encouraged cost-saving design and materials changes with limited analysis, combined with what seems to be a single decision to limit testing. It doesn’t take malice to explain the string of problems that have surfaced, but as they accumulate, it gets harder to ignore the possibility.
Somebody, whether the primary contractor or not, is going to be paid to fix all of the problems. Somebody else controls who gets those jobs. Food for thought, no?
In the meantime, the bridge is at risk, and with it, people’s lives and livelihoods. That’s an awful lot to place on the shoulders of one small troll.