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Events / Evening Meeting / New Site Classification Procedures for Seismic Design for US Building Codes with Applicability to New Zealand

New Site Classification Procedures for Seismic Design for US Building Codes with Applicability to New Zealand

Date / Time
May 22, 2024 @ 5:30pm - 7:00pm
Organizer
NZGS
Branch
Christchurch
Website
N/A
Downloads
Christchurch 22.5.2024_tr

Presented by   Jon Stewart (UCLA)

Free Registration HERE

A joint  NZGS and Canterbury University Event

The procedures used to classify sites were revised in the 2020 NEHRP Provisions and the 2022 ASCE 7/22 documents, which form the basis for U.S. building codes. This presentation reviews the historical procedures used for site classification, problems with those procedures, and revised site classes intended to address those problems. A key feature of the revised procedures is their requirement that a site shear wave velocity profile be developed. Various ways of developing shear wave velocity profiles, either through measurement or estimation from other parameters, are described. A seemingly benign detail of the site classification is that it is based on a time-averaged velocity over a depth interval of 0 to 30 m. The NEHRP and ASCE documents have added a specific definition of that depth interval due to practices for some recent projects where engineers have redefined the parameter to apply over a deeper depth interval for applications to embedded structures. The speaker will explain why this practice is unconservative, which motivated the specific depth range definition in the code documents. Alternative procedures to derive ground motions for the foundation levels of structures that are allowable in the code are described.

 

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