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These guidelines are written as supplemental to the AASHTO Standard Specifications for Highway Bridges, 16th Edition, Division I-A: Seismic Design and incorporate the generic requirements for seismic isolation design. Isolating structures from the damaging effects of earthquakes is not a new idea. The first patents for base isolation schemes were obtained nearly 130 years ago, but until the past two decades, few structures were built using these ideas. Early concerns were focused on the displacements at the isolation interface. These have been largely overcome with the successful development of mechanical energy dissipators. When used in combination with a flexible device such as an elastomeric bearing, an energy dissipator can control the response of an isolated structure by limiting both the displacements and the forces. interest in seismic isolation, as an effective means of protecting bridges from earthquakes, has therefore been revived in recent years. To date there are several hundred bridges in New Zealand, Japan, Italy, and the United States using seismic isolation principles and technology for their seismic design.

Seismically isolated structures such as the University of southern California Hospital in Los Angeles, and the West Japan Postal Savings Computer Center in Kobe, Japan, performed as expected in recent earthquakes. Records from these isolated structures show good correlation between the analytical prediction and the recorded performance.