Location

San Diego, California

Session Start Date

5-24-2010

Session End Date

5-29-2010

Abstract

Strong ground motions generally lead to both a stiffness reduction and a larger energy dissipation in the soil layers. Thus, in order to study such phenomena, several nonlinear rheologies have been developed in the past. However, one of the main difficulties of using a given rheology is the number of parameters needed to describe the model. In this sense, the multi-surface cyclic plasticity approach, developed by Iwan in 1967 is an interesting choice since the only data needed is the modulus reduction curve. Past studies have implemented this method in one-directional SH wave-propagation (1D-1C). This work, however, aims to study the local site effects by considering one-directional (1D) seismic wave propagation accounting for their three-dimensional nonlinear behavior. The three components (3C) of the outcrop motion are simultaneously propagated into a horizontal multilayer soil for which a three-dimensional constitutive relation is used. The rheological model is implemented using the Finite Element Method. The alluvial site considered in this study corresponds to the Tiber River Valley, close to the historical centre of Rome (Italy). The computations are performed considering the waveforms referred as the 14th October 1997 Umbria-Marche earthquake, recorded on outcropping bedrock. Time histories and stress-strain hysteretic loops are calculated all along the soil column. The octahedral stress and strain profiles with depth and the modulus of acceleration transfer function (surface/outcrop spectral ratios) are estimated in the cases of combining three 1D-1C nonlinear analyses and of 1D-3C conditions, evidencing the influence of threedimensional loading path.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fifth Conference

Publisher

Missouri University of Science and Technology

Publication Date

5-24-2010

Document Version

Final Version

Rights

© 2010 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 24th, 12:00 AM May 29th, 12:00 AM

Nonlinear Site Effects: Interest of one Directional - Three Component (1D - 3C) Formulation

San Diego, California

Strong ground motions generally lead to both a stiffness reduction and a larger energy dissipation in the soil layers. Thus, in order to study such phenomena, several nonlinear rheologies have been developed in the past. However, one of the main difficulties of using a given rheology is the number of parameters needed to describe the model. In this sense, the multi-surface cyclic plasticity approach, developed by Iwan in 1967 is an interesting choice since the only data needed is the modulus reduction curve. Past studies have implemented this method in one-directional SH wave-propagation (1D-1C). This work, however, aims to study the local site effects by considering one-directional (1D) seismic wave propagation accounting for their three-dimensional nonlinear behavior. The three components (3C) of the outcrop motion are simultaneously propagated into a horizontal multilayer soil for which a three-dimensional constitutive relation is used. The rheological model is implemented using the Finite Element Method. The alluvial site considered in this study corresponds to the Tiber River Valley, close to the historical centre of Rome (Italy). The computations are performed considering the waveforms referred as the 14th October 1997 Umbria-Marche earthquake, recorded on outcropping bedrock. Time histories and stress-strain hysteretic loops are calculated all along the soil column. The octahedral stress and strain profiles with depth and the modulus of acceleration transfer function (surface/outcrop spectral ratios) are estimated in the cases of combining three 1D-1C nonlinear analyses and of 1D-3C conditions, evidencing the influence of threedimensional loading path.