(Reuters) - A little over a year after a section of the San Francisco-Oakland Bay Bridge reopened far behind schedule and over budget, new concerns are being raised about the integrity of steel rods securing the world’s largest self-anchored suspension span.
An independent report released late Tuesday blasted an official California study finding the rods safe and durable against strain and saltwater, calling the state’s analysis erroneous, misleading and unscientific.
“They have to replace the rods with proper materials and get ready to deal with failures of the ones they cannot replace,” said Professor Charles J. McMahon, professor emeritus of materials science and engineering at the University of Pennsylvania, who contributed to the report.
The report’s author, Yun Chung, a University of California, Berkeley-trained retired Bechtel metallurgical engineer, recommended replacing some rods on the bridge’s eastern section.
State transportation officials said they would consider the report, but that for now, no rods are being replaced.
“There should not be concern about the bridge,” said California Department of Transportation spokesman Matt Rocco.
The debate marks the latest chapter in the storied and often tumultuous history of the toll bridge, a critical Bay Area transportation artery that carries 280,000 commuters a day.
Considered an engineering marvel, the original bridge opened in 1936, six months before the Golden Gate Bridge, spanning the bay in two sections; the western end a suspension bridge, the eastern a double-decked cantilever bridge.
The 1989 Loma Prieta earthquake collapsed a section of the upper deck and in 2002 construction began on a new eastern leg.
The new section opened Sept. 2, 2013, six years behind schedule and five times over budget at an estimated cost of $6.4 billion.
But about three dozen of the 2,300 steel rods used to help withstand earthquakes snapped before the bridge’s opening. Those areas were retrofitted, but the rods were not replaced.
Robert Bea, professor emeritus of engineering at UC Berkeley and a contributor to Chung’s report, said in an email that while the suspension section may be safe under normal conditions, it “may not be ‘safe’ for extreme environmental conditions,” including an intense earthquake.
“The conclusions drawn from the (state’s) test data and the analyses of that data are deeply flawed,” he said. “Conclusions regarding ‘safety’ are more deeply flawed.”
Reporting by Michael Fleeman in Los Angeles; Editing by Sharon Bernstein and Eric Walsh