Impact of initial stress field heterogeneity in dynamic soil–structure interaction

Marc-Denis Rioux,Bertrand Galy,Marie-José Nollet

doi:10.1177/87552930211041640

Abstract

This article covers the impact of soil initial stress field heterogeneity (ISFH) in wave-passage analysis and in prescribed structural acceleration in the context of dynamic soil–structure interaction (DSSI) analysis. ISFH is directly related to the natural behavior of soil where a significant increase in net effective confinement, as is the case in the foundation soil under a building, tends to increase the soil’s modulus and strain. This creates a heterogeneous stress field in the vicinity of the foundation elements, which results in a modification of the dynamic behavior of the soil–structure system. A simple method for considering the impact of ISFH on the value of the soil’s modulus and strain was developed using the direct DSSI approach. The method was used to analyze numerical artifacts and its impact on the surface acceleration values of a nonlinear two-dimensional (2D) numerical soil deposit under transient loading. This analysis was followed by a sample application for a three-story, three-bay concrete moment-resisting frame structure erected on a deep soil deposit. Floor acceleration and relative displacement were used for comparison. The soil deposit was modeled using the typical geotechnical properties of fine-grained, post-glacial soil samples obtained in Eastern Canada from in situ geotechnical borehole drilling, geophysical surveys, and laboratory testing. Ground motion was based on eastern calibrated seismic signals. The results of the soil deposit analysis show that ISFH had a significant impact on surface acceleration values. The effect was found to be period-dependent and to have a direct impact on prescribed acceleration values at the base of structure. Thus, failure to take the effects of ISFH into consideration can lead to errors in calculating prescribed structural accelerations (i.e. over- or underestimation).

Highlights

We have long known that the dynamic behavior of a structure is largely influenced by site effects during an earthquake (Reid, 1906)
In model PIMY-DEP200, initial stress field heterogeneity (ISFH) was considered and a pressure of 200 kPa was applied at the soil surface
A series of wavepassage analyses was carried out to assess the impact of ISFH on the dynamic response of a natural soil deposit located in Eastern Canada

Summary

Introduction

We have long known that the dynamic behavior of a structure is largely influenced by site effects during an earthquake (Reid, 1906). More recent experimental work (Gajan and Kutter, 2008) and post-event reports (Aviles and Perez-Rocha, 1998; Cubrinovski et al, 2011) made it clear that site effects, including dynamic soil–structure interaction (DSSI) (Stewart et al, 1999), play a major role in the dynamic response of a structure. This is true for rigid structures built on deep, loose soil deposits (Stewart et al, 2012). A key element that is seldom considered in the kinematic interaction analysis phase is the total impact of net increases in effective confining stress on supporting soil behavior due to the transferred structural load, which we refer to in this article as initial stress field heterogeneity (ISFH) and which has two major effects

Objectives

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Conclusion