This is stunning:
They discovered the problem after massive steel bolts were tightened to anchor part of the bridge's seismic safety system. Of the 96 that were tightened, 32 broke.If I recall, in the process of hardening steel, you can use carbon monoxide. But the process for making carbon monoxide produces hydrogen as well. If you don't remove the hydrogen it can make the steel brittle at high temperatures. So, at first glance (and I am no expert), this looks to be what happened.
The broken bolts, which measure 3 inches in diameter, had "hydrogen embrittlement," the project's engineers say. When the bolts were produced in 2008, excess hydrogen was present, making them "susceptible due to the steel being harder on the outside than in the middle, or a lack of uniformity in the steel's microstructure," according to the California Department of Transportation.
Just another issue in the ongoing debacle of the Bay Bridge. I just can't believe it's taken this long to build it.