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Investigation and Re-calculation of TL: The Long-period Transition Parameter

In recent years, many changes have been made to the design response spectrum used in ASCE 7, most notably the 22-period response spectrum implemented in 2020 NEHRP Recommended Provisions and ASCE 7-22 (Kircher, 2019). One item that has not been investigated or re-visited since its first appearance in FEMA 450-1/2003 is the long-period transition period parameter, T_L. The long-period transition period parameter was introduced and defined as the corner period that marks the transition from the constant velocity to the constant displacement segments of the response spectrum. The long-period transition period parameter is primarily important for long period structures such as high-rise buildings and bridges.

The most current estimation of T_L used in engineering design standards is loosely based on a correlation between moment magnitude Mw and T_L that does not account for stress drop Δσ or the source velocity β (ASCE, 2016). This project aims to include both Δσ and β in its estimation of T_L. First, inversion of ground-motion models for Central and Eastern United States (CEUS) is used to determine Δσ for CEUS, and we will use the published information for Δσ for Western United States (WUS) and Hawaii. Then the exact definition of the corner period will be used to estimate T_L. The result will be updated national maps of both Δσ and T_L.

Session: 50-State Update of the USGS National Seismic Hazard Models [Poster]

Type: Poster

Room: Evergreen Ballroom

Date: 4/20/2022

Presentation Time: 08:00 AM Pacific

Presenting Author: Christine Assadollahi

Student Presenter: Yes

Additional Authors