Changes in Seismic Design Criteria and Design Ground Motions in IBC 2018 and ASCE 7-16, and Recommendations for Seismic Design Practice in Utah
by Travis Gerber, Wind & Seismic Committee
Members of SEAU and other Utah professional design organizations recently released a white paper entitled “Changes in Seismic Design Criteria and Design Ground Motions in IBC 2018 and ASCE 7-16, and Recommendations for Seismic Design Practice in Utah.” This paper may be of interest to many readers, being a follow-up to the July 2019 seismic design workshop co-sponsored by SEAU. The abstract is as follows:
“The 2018 International Building Code (IBC 2018), and by extension referenced provisions of ASCE 7-16, was adopted July 2019 by the State of Utah. ASCE 7-16 introduces significant changes to prescribed seismic forces for the design of structures when compared to IBC 2015 and ASCE 7-10. These changes include updated mapped B/C boundary seismic values Ss and S1 as well as revised site coefficients (with the coefficients typically being larger). Most notable are new requirements to perform site-specific ground motion hazard analyses (GMHA, which is comprised of both deterministic seismic hazard analysis [DSHA] and probabilistic seismic hazard analysis [PSHA]) for areas of moderate to high seismicity and softer soil sites (Site Classes D and E). This site-specific study requirement is the result of deficiencies which are now more widely recognized in the shape and magnitude of the code-based (“standard”) design response spectrum. In some cases, exceptions exist where an otherwise required GMHA may be omitted; however, these exceptions together with the other changes in ASCE 7-16 can increase design base shears by as much as 70%. In early 2019, a group of individuals from several professional societies formed an ad-hoc committee to develop a workshop whose purpose was to help inform fellow engineering and geological professionals in Utah about these changes. In preparing for the workshop, various design practice issues not explicitly addressed in IBC 2018 or ASCE 7-16 were discussed. The outcome of these discussions were consensus recommendations which are believed by committee members to represent good seismic design practices. This document presents several of those recommendations, including minimum qualifications for those performing site-specific seismic studies as well as the typical content of such reports.”
The full paper may be found here.
Welcome to New Members
New SEAU Members
The following individuals have submitted applications to the SEAU membership committee for new members or have advanced their SEAU membership.
David Dunn, Structural Engineer
Jaxon McCloy – Professional Engineer
Scott VanderDoes, Professional Engineer
Adam Lambert - Student
Emily Diedrich - Student
Emma Black – Student
Jeffrey Lebaron – Student
