Seismic engineering built into critical Bay Area facilities

The Bay Area is at the forefront of the need and in rapid catch-up mode when it comes to seismit retrofitting.
March 15, 2011 7:15:22 PM PDT
Last week's earthquake in Japan underscores the need to make sure critical facilities, such as hospitals and airports, are able to function after a high-magnitude event. The Bay Area is both at the forefront of that need and in rapid catch-up mode.

Mills-Peninsula Medical Center in Burlingame is set to open on May 15, replacing an aging and seismically vulnerable hospital. It has been engineered to withstand a major earthquake with little to no damage with the use of base isolators underneath. The base isolators allow the hospital building to move 30 inches in any direction. On the assumption that roads and streets will be passable, Mills-Peninsula should be operational to handle medical emergencies and treatment of earthquake victims.

"This building will actually lift a few inches in a seismic occurrence because the puck will ride up the concave dish, and as the building moves, the weight of the building will drive that puck back to center and back and forth," Senior Project Manager Larry Kollerer said.

The new $620 million facility is expected to sustain little to no damage, allowing it to function when medical emergency care will be a critical need.

Similar technology was built into the new International Terminal at San Francisco International Airport, which opened in 2000 at a cost of nearly $1 billion. The facility processes about 20,000 arriving and departing passengers per day. SFO would be a critical gateway for supplies and relief workers in the event of a devastating earthquake.

ABC7 Aviation Consultant Ron Wilson says 269 base isolators allow the structure to move.

"When the earth moves, it rolls on a stainless steel 15-inch ball in a trough and takes up all of the shock of the movement of the earth, and the building itself sits on top of it, gets very little of that shock transmitted to it," he said.

Over 200 base isolators are installed below the terminal, allowing for movement of 40 inches. The International Terminal is actually three structures -- a main check-in terminal with a soaring ceiling and two wings to either side where aircraft gates are located.

Airport spokesman Mike McCarron, who oversaw the construction of the terminal, showed ABC7 the three-foot wide section that joins the main terminal to the gate wing that serves as a kind of circuit breaker.

"To have a building this big and be able to move that much, is quite revolutionary," he said.

It is designed to help allow for the independent movement of the structures during violent ground movement. There is are two seams in the floor to allow for that movement. Some glass skylights above this section might fall, but the integrity of the buildings should withstand the seismic activity.


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