Buildings that Use Base Isolation Technology

Q: How many structures in the United States currently employ base isolation technologies?

A: According to the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, Part 2: Commentary (FEMA 450-2/2003 edition), "The potential advantages of seismic isolation and the recent advancements in isolation-system products already have led to the design and construction of over 200 seismically isolated buildings and bridges in the United States."

The 8 structures listed below employ base isolation technologies, either as the original construction or a retrofit.

Oakland City Hall, California (retrofit)
Oakland City Hall
This 18-story building with full basement, central rotunda, council chambers, and administration offices was the first high rise government office building in the United States when it was completed in 1914. The original structure of the building is a riveted steel frame with infill masonry walls of brick, granite, and terra cotta, and is supported on a continuous concrete mat foundation. This 1994 retrofit utilized 42 lead rubber bearings and 69 natural rubber bearings.
Oakland City Hall
San Francisco City Hall, California (retrofit)
San Francisco City Hall
The two-block-long building was cut from its foundation and made to "float" on 530 isolators, shock absorbers designed to dissipate earthquake motion and allow the building to sway horizontally up to 26 inches without shaking apart.
San Francisco City Hall
Los Angeles City Hall, California (retrofit)
L.A. City Hall
City Hall has been placed atop a mechanical system of isolators, sliders, and dampers employing base isolation technology that will dampen the violent movements of the earth during a seismic event.
L.A. City Hall
San Francisco International Airport, International Terminal, California
San Francisco 	
						International Airport
The International Terminal is among the largest base-isolated structures in the world. It is supported on 267 Friction Pendulum isolators which are placed between the building and the building's foundation. The bearing is very stiff and strong in the vertical direction, but flexible in the horizontal direction. The building is designed to remain functional under almost any size earthquake.
San Francisco International Airport
Mackay School of Mines, University of Nevada - Reno, Nevada (retrofit)
MacKay School of Mines
During a $10-million remodel, engineers recently improved the 1908 building's resistance to earthquakes by lifting the foundation off the ground, installing a moat, and placing 44 Teflon slider plates and 64 base-isolation columns in the sub-basement. Mackay Mines is just the second historic building in the United States with base-isolation retrofitting.
Mackay School of Mines
References & Additional Sources

The source listed below provides a building description, project dates, and details regarding the type and number of isolators used for most of the projects listed above. Many contain photos as well.

Naeim, F and Kelly, J.M. (1999). Design of seismic isolated structures. New York: John Wiley & Sons. (pp. 6-17).

The following Web sites list projects each company has been responsible for:

This 2001 article profiles a base isolation project employed by Immunex Corp., a Washington State–based company with laboratory equipment exceeding $50 million.

For more information on base isolation, please visit our FAQ, What are some advanced earthquake resistant techniques?

This source provides a list of seismically–isolated buildings and other structures in the United States (developed by the Protective Systems Research Group of the Earthquake Engineering Research Center at the University of California at Berkeley). Please note that this list was last updated May 1997.