The first AASHTO Guide Specification for Seismic Isolation Design was published in 1991. This guide specification represented a major step in the acceptance of bridge isolation design in the United States. Since adoption of the Guidelines, there has been significant progress in the understanding of isolation technology and the need for updating the document became obvious. A special task group was appointed by the AASHTO T-3 Seismic Design Committee to update this Guide specification. The work was completed by February 1997 and has been balloted by AASHTO. This paper addresses the highlights and issues by the new document.

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