BAY BRIDGE: Welds crack on main tower of S.F.-Oakland Bay Bridge

Caltrans has no idea how latest mishap happened; no timetable on repairs set yet

Bridges News Sacramento Bee May 02, 2013
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Construction milestones are being replaced with bad days at the new San Francisco-Oakland Bay Bridge—too many of them.

 

Weeks after rods snapped after post-tensioning, officials discovered about 20 cracked welds on the signature tower of the span. Caltrans was not ready to comment on the problem, and nobody knows the timetable of the repair at this time.

 

The welds connect giant steel plates between the four legs of the 525-ft tower at its base just above water. Welding is supposed to make the bridge more flexible in case of an earthquake. Workers used the electroslag method, and inexpensive process that uses long, thick welds that take half the time as the traditional method. The damaged welds are 33 ft long and 4 in. thick.

 

Karl Frank, a professor emeritus at the University of Texas and a recipient of a Lifetime Achievement Award from the American Institute of Steel Construction, said the process of welding produces shrinking which can sometimes cause cracks. Frank said the San Francisco-Oakland Bay Bridge job offered unique challenges with its unusual scale and environment. Still, he said mockup test went well and it was all being handled by an experienced group of engineers.

 

“I’m not exactly sure why, or if anybody knows why, the problems occurred,” he told the Sacramento Bee.

 

In 1977, the Federal Highway Administration prohibited the practice of electroslag welding on federally funded bridge projects due to the crack threat, but lifted it in 2000 on certain spans.

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