As you may have read, the nearly finished Bay Bridge near Oakland, California, has run into another problem. After dealing with years of delay caused by design problems and massive cost overruns, giant steel rods are snapping when they are tightened for the final time.
The steel rods, which are 3 inches in diameter and 17 to 24 feet long, connect three critical pieces of the bridge to the pier and are intended to help control side-to-side sway during an earthquake. To say that the steel rods play an important role in the bridge would be an understatement.
Engineers have figured out the rods became brittle after hydrogen atoms invaded the spaces between the steel’s crystalline structure. Metallurgy experts explained that this is a common problem when steel is excessively hardened and galvanized. One rod manufacturer would not bid on this job because it knew galvanizing super-hardened steel like the steel for these rods could cause this very problem.
Interestingly, the bridge design manual prohibits galvanizing this type of steel and the practice is contrary to long-established industry guidelines. Why engineers opted to galvanize these rods anyway has yet to be explained. But, as noted in Engineering News Records’ Bay Bridge article the engineer making this decision may have simply forgotten about hydrogen impact or did not know.
I have no doubt there will be long drawn out finger pointing and perhaps litigation surrounding the decision to galvanize these rods. And, the ultimate question will be why didn’t they just follow the design manual and use the bolts without galvanization.