Closing San Francisco’s Bay Bridge Is Right Move, Engineers Say

The indefinite closing of the San Francisco-Oakland Bay Bridge after steel rods crashed from a repaired section onto its upper roadway is prudent as authorities assess the structure’s safety, engineers say.

“There’s maybe not a full understanding of what caused that failure in the first place or it wasn’t properly repaired,” said Henry Petroski, a professor of engineering at Duke University in Durham, North Carolina, and author of a 1995 book on the history of bridges. “It could also mean that other parts of the bridge are overstressed, as engineers would put it, or overloaded.”

The Bay Bridge was closed last night after a crossbar and two steel tie rods fell from a section repaired last month, damaging three vehicles and causing minor injuries to one driver. Structural engineers and inspectors are working to determine how long repairs will take, according to a statement from the California Transportation Department, or Caltrans.

“At this time, the bridge is closed until further notice,” Caltrans said in the statement.

About 280,000 vehicles cross the bridge on an average day, compared with 137,500 using New York’s Brooklyn Bridge, according to the Bay Bridge Web site.

The 8.4 mile (13.5-kilometer) span, built in 1936, was damaged during the magnitude 6.9 Loma Prieta earthquake that killed 63 people and caused $7.8 billion of damage around the Bay area in 1989. A $5.49 billion replacement of the eastern span of the bridge is under construction and due to be completed in four years.

Labor Day Fix

The bridge was shuttered during last month’s Labor Day holiday weekend so engineers could replace a 300-foot (91-meter) double-deck section, as part of larger plans to make the structure able to withstand earthquakes.

“Most of these types of problems don’t show up until a few years after they’re installed,” said Jack Moehle, a professor of structural engineering at the University of California, Berkeley. “It’s a little surprising in this case that it happened six weeks after they installed it.”

More than 26 percent of the 600,905 bridges in the U.S. are either structurally deficient or functionally obsolete, the American Society of Civil Engineers said in its quadrennial report on the nation’s infrastructure, released March 25.

The number of deficient and obsolete bridges in urban areas is increasing, and authorities would have to raise spending on bridge repair to $17 billion annually, from $10.5 billion now, to “substantially improve” the state of U.S. bridges, the group said.