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November 13, 2001

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   Troy Anderson, (858) 822-3075 or

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   Related article in the San Diego Union Tribune.


Structural engineers at the UCSD Jacobs School of Engineering tested the concrete and steel reinforced piers that will support the new San Francisco-Oakland Bay East Span Bridge, displacing a 32 ½ ft. tall, 270,000 lb. model by 20 inches and proving it can withstand earthquakes in excess of those expected from the San Andreas and Hayward faults.

The hollow, four-column rectangular skyway piers have been designed to withstand severe damage during an earthquake, thus protecting other parts of the bridge such as the deck and vertical tower. By designing the bridge to experience damage at strategic locations, engineers can design the "damage zones" for extra deformation or bending capacity, and ensure that the damage is kept under control. This deformation capacity, more than strength, is critical for a structure's survival. When the piers are damaged, they can be simply replaced and the bridge will remain in tact.

Because the bridge is expected to experience seismic forces from all directions, it was important to test the pier in more than the two standard loading directions (longitudinal and transverse). In this test, the pier was loaded "biaxial", which means that it was loaded in both directions at the same time. Hence, the test was called the Diagonal Pier Test. The piers have been designed to withstand 700,000 lbs of seismic force in each loading direction.

UCSD structural engineers have begun a year-long series of proof tests on components for the new San Francisco-Oakland Bay East Bay Span. The single tower, self-anchored suspension bridge and skyway is planned to replace the existing East Bay Spans, which was built after part of the deck collapsed in the 1989 Loma Prieta Earthquake.

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