← Back to Sessions

A Seismological Method for Estimating the Long-Period Transition Period Tl in the Seismic Building Code

Description: 

The design response spectrum in the ASCE 7 Standard has undergone numerous changes in recent years. Despite these updates, one crucial parameter, the long-period transition period parameter (T_L), has remained unchanged since its inception in FEMA 450-1/2003. T_L represents the corner period signifying the shift from constant velocity to constant displacement segments within the design response spectrum. This parameter holds particular significance for structures with longer periods, like high-rise buildings and bridges. Presently, the estimation of T_L utilized in engineering design standards is primarily based on a correlation between modal magnitude (Mw) and T_L, overlooking factors such as stress drop (Δσ) or crustal velocity in the source region (β). This study seeks to integrate both Δσ and β into the TL estimation process. Modal magnitude data is derived from disaggregation data from the 2018 National Seismic Hazard Model (NSHM) for the contiguous United States (CONUS) and the 2021 NSHM for Hawaii (HI). β values are obtained from existing literature. To calculate Δσ for events in the Central and Eastern United States (CEUS), ground motion models are inverted. For events in the Western United States (WUS) and HI, published information is utilized to determine Δσ. The T_L is then determined using the definition of the corner period. The outcomes of this study indicate a generally more conservative or longer estimation of TL compared to the current approach employed in engineering design standards.

Session: The 2023 USGS National Seismic Hazard Model and Beyond [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Shahram

Student Presenter: No

Invited Presentation: 

Authors