Thousands of steel tendons used to strengthen the skyway portion of the new eastern span of the San Francisco-Oakland Bay Bridge were exposed during construction to rainfall and salty bay mist, leading to rust and corrosion concerns.
The Sacramento Bee reports that California Department of Transportation engineers in 2006 discovered that ducts containing the tendons had been left unsealed, exposing the steel tendons.
Caltrans examined hundreds of the tendons and said it found little significant corrosion, but experts who reviewed the study for the Bee raised questions about the agency’s testing methods.
The agency reviewed about 1,600 of the more than 5,600 tendons, and nearly half of them displayed rust. Caltrans’ report said only a few suffered from moderate corrosion, and lab tests found no severe damage.
Caltrans’ handling of corrosion protection during the bridge’s construction has also been debated as a possible factor in the failure of 32 seismic safety rods last month.
University of California, Berkeley engineering professor Thomas Devine told the Bee that Caltrans’ tendon tests were inadequate, leading to concerns over the skyway’s durability during a quake.
Others voiced concerns that water trapped in the ducts, or leaky grout work meant to make them water tight, could create pockets of corrosion that would further weaken the tendons.
“There is a very good possibility that you have voids in the grout where corrosion will continue,” said Richard Weyers, a steel tendon expert and emeritus professor of engineering at Virginia Tech.
While most experts agreed the tendon problem would not likely result in the skyway’s collapse during a quake, the corrosion could make portions of the skyway unusable after a temblor.
It could also result in costly maintenance and repairs, making the $6.4 billion project even more expensive.
Bay Bridge spokesman Andrew Gordon said corrosion is an issue on every steel bridge ever built.
“What we learned from this particular challenge six years ago is that we’re never going to be done fighting the battle against corrosion in the San Francisco Bay,” Gordon said in a written response to the newspaper.
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