Earthquake Regulations for Seismically Isolated Structures

The first seismically isolated building in the United States was completed in 1985. Although it was publicized in national engineering magazines and visited by a great many engineers and architects from the United States and around the world, it was several years before the next base-isolated building was begun. The acceptance of isolation in the United States as an anti-seismic design approach for some classes of buildings was clearly hampered by the lack of a code covering base-isolated structures. To address this issue the Structural Engineers Association of Northern California (SEAONC) created a working group to develop design guidelines for isolated buildings.