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SAN DIEGO — A major earthquake would cause only minor damage to the massive concrete and steel columns that will support a portion of the new eastern span of the San Francisco-Oakland Bay Bridge, a seismic test showed Friday. 

Engineers at the University of California, San Diego, placed a quarter-scale model of one column in the equivalent of a giant vise to simulate the pressure of a magnitude 8 earthquake on the nearby San Andreas fault or a magnitude 7.5 on the Hayward fault. 

A spider web of cracks appeared on a thin layer of exterior concrete near the base and top of the column as chunks the size of dinner plates fell to the ground. But scientists and state Department of Transportation officials dismissed the damage and called the column’s performance a success. 

“The column is still in perfect condition structurally,” Frieder Seible, chairman of the UCSD department of structural engineering, said as he stood by the 32-foot-tall model. 

The test at UCSD’s seismic lab was one in a series to be performed on components of the new span, which is being replaced to make it safer in an earthquake. 

Construction on the $1.5 billion project is scheduled to begin in late summer and to be completed in 2005. 

The seismic test also has implications beyond the Bay Bridge project because Caltrans plans to use the same type of column when it replaces the Carquinez  

and Benicia bridges northeast of  

San Francisco. 

The new type of column, also called a pier, consists of four solid columns of reinforced concrete surrounding a box-like concrete structure with a hollow center. About 14 piers will support two miles of the eastern span. 

Each pier is a coated in a thin layer of chalk-colored concrete to prevent corrosion and to improve the aesthetics of the support.  

This exterior layer at the base and top of the column cracked and flaked off during the test. 

But the damage doesn’t harm the structure of the column, is easily fixed and could be prevented with a minor architectural adjustment, said Bay Bridge project manager Brian Maroney. 

“I’m going to feel perfectly comfortable driving over this,” Maroney said. 

During the 7.1 Loma Prieta earthquake in 1989, a 30-foot span of the upper deck of the Bay Bridge collapsed.  

Caltrans later determined it would be cheaper to replace the eastern span than to retrofit it to modern safety standards. 

The 64-year-old bridge, crossed by 280,000 motorists a day, presents a major challenge because it straddles the Hayward and San Andreas faults.  

But engineers hope to minimize the risk with tests such as Friday’s, which exerted 700,000 pounds of sideways pressure on the column. 

“We have every confidence that it will hold,” Andy Budek, a UCSD research engineer, said as he observed the test of the column.