AASHTO GSID-4-I1

The parent publication, Guide Specifications for Seismic Isolation Design, 4th Edition (GSID-4), published in 2014, addresses major changes in the state of the art of seismic isolation design for highway bridges and reflects changes in the way seismic hazard is defined in the AASHTO LRFD Bridge Design Specifications, 9th Edition, and the AASHTO Guide Specifications for LRFD Seismic Bridge Design, 2nd Edition. The specifications include industry trends in the design and construction of isolators, and provisions in the design specifications that impact the design and testing of isolation bearings.

These new 2023 interim revisions update the guide specifications to include a risk-targeted approach for the development of a design spectrum and the adoption of the 2018 United States Geological Survey (USGS) National Seismic Hazard Model (NSHM). This approach provides for a uniform risk throughout the country. It differs from the uniform hazard approach used previously, which resulted in a non-uniform risk, due to the variance in the shape of hazard curves with location.