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Evaluation of Kinematic Soil-structure Interaction Effects for Vertical Motions at Multiple Instrumented Sites with Large and Deeply Embedded Foundations

The earthquake motion experienced by a building can be affected by the soil-structure interaction (SSI) effects. As a result, motion at the foundation level of a building (FM) can deviate from free-field motion (FFM). Kinematic and inertial SSI effects are two mechanisms that simultaneously cause this deviation, among which kinematic SSI is a result of stiff foundation elements. The kinematic SSI effects can be quantified using procedures that are semi-empirical and were calibrated using earthquake motion databases of multistory buildings in different parts of California. In the design guidelines such as ASCE/SEI 41-17 kinematic SSI is considered by calculating the Ratio of Response Spectra (RRS) between FM and FFM. However, the current simplified methods are limited only to horizontal translational motions for buildings with regular foundation width and embedment depth, and there is a lack of any recommendations for vertical translational motions.

This study presents empirical vertical RRSs based on recorded data at five well-instrumented nuclear facilities in Japan. Recorded data at multiple buildings were used to calculate RRSs for vertical motions from multiple earthquake recordings to evaluate the extent of kinematic SSI in buildings with large and deeply embedded foundations when subjected to vertical earthquake motions. Then a comparison between empirical vertical and code-based horizontal RRSs is made illustrating the need to establish a code-based procedure for vertical RRS. Also, a comparison between empirical vertical and empirical horizontal RRSs is conducted. The overall results of comparisons illustrate that code-based horizontal RRSs tend to overestimate the foundation vertical translational motions. Furthermore, the extent of the overestimation is maximum near the range of fundamental frequency of structures that can be attributed to the inertial SSI effects besides kinematic effects. In future steps of this study, the results will be used to develop a set of empirical equations for estimating vertical RRS which provides a basis for developing new recommendations on kinematic SSI modeling.

Session: Site Response Characterization in Seismic Hazard Analysis [Poster]

Type: Poster

Room: Evergreen Ballroom

Date: 4/22/2022

Presentation Time: 08:00 AM Pacific

Presenting Author: Peiman Zogh

Student Presenter: Yes

Additional Authors