Stochastic model of seismic torsional ground motion: Application to Lotung soft site |
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Authors: | Email author" target="_blank">Nasser?LaouamiEmail author Pierre?Labbé Ramdane?Bahar |
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Institution: | (1) CGS, National Center of Applied Research in Earthquake Engineering, Rue Kaddour Rahim, BP 252, Hussein Dey, Algiers, Algeria;(2) EDF-SEPTEN, 12-14, Avenue Dutriévoz, 69628 Villeurbanne Cedex, France;(3) Laboratory of Geomaterials and Environment, University of Tizi Ouzou, BP, RP 17, 15000 Tizi Ouzou, Algiers |
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Abstract: | The purpose of this paper is to present a stochastical approach, which analyse the torsional ground motion, induced by the
spatial variability of seismic motions. For this purpose, a torsional ground motion analytical model is proposed and a normalised
differential motion parameter is introduced. The approach regards the seismic motion as the combination of a travelling wave
on the site (coherent component) and a zero mean randomizing factor that introduces a loss of correlation effect. The soil
parameters as fundamental frequency and damping coefficient are integrating by modeling the coherent component with the commonly
used Kanai-Tajimi power spectral density. The parametric analysis of the model shows an increase of the induced torsion with
both the soil frequency and the motion scattering parameter, and a decrease with the separation distance, the apparent wave
velocity and the correlation length. Finally, in order to test the proposed torsional ground motion model prediction, it is
compared to the experimental results recorded by the EPRI LSST array in Lotung, Taiwan (Laouami and Labbé, 2002). The comparison
leads to the identification of the model parameters for the Lotung soft site. |
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Keywords: | spatial variability torsion analytical model stochastic free field seismic motion |
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