The International Information Center for Structural Engineers

Friday, 12 June 2015 00:00cat

More Structural Problems for the Bay Bridge

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More Structural Problems for the Bay Bridge

The San Francisco-Oakland Bay Bridge was completed in 2013, took 12 years to build and cost $6.4 billion. It is the largest and most ambitious public works project in California history, in large part because it is designed to withstand a massive earthquake. Since shortly before its completion, however, the bridge has been plagued with questions about its sturdiness.

Last week Caltrans revealed that 120 of the 400 galvanized steel rods that anchor the bridges tower to its foundation are in leaky sleeves flooded with saltwater.   This presents a key vulnerability in the event of a large earthquake.

Caltrans Director Malcolm Dougherty said that while a completely watertight bridge is impossible, the degree of infiltration is a serious dilemma.

“We need to protect this. We need to come up with a solution,” he said.

The massive threaded rods are up to 24 feet long and two to three inches thick and keep the bridge from bucking off its bearings in the event of a quake.

Previous vulnerabilities were discovered 2 years ago when workers found that 32 steel bolts intended to stabilize the structure during an earthquake were brittle and cracked because the steel had been contaminated by hydrogen, either during manufacturing or from being left in holes that filled up with rainwater. It cost Caltrans millions of dollars to put protective metal saddles over the bolts.

It is critical to remedy the bridges defects because the structure connects two major fault lines, the San Andreas and Hayward faults.

“The city is going to need this bridge after a big event, because a bid even will bring San Francisco to its knees,” said Brian Maroney, the bridges chief engineer.


Sources: Discovery News, Wired

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