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3D Nonlinear dynamic analysis of a square foundation placed on semi-infinite soil
Oral Presentation
Authors
1LMGE Laboratory, Civil engineering department, Faculty of Technology, Badji-Mokhtar-Annaba University, Algeria
2LMGE Laboratory, Badji Mokhtar-Annaba University
3Civil Engineering Department, faculty of Technology, University of Skikda
Abstract
The main objective of this paper is to study the effect of nonlinear soil behavior on the dynamic impedance of a rigid surface foundation, loaded by a harmonic dynamic load. An equivalent linear method of nonlinear soil behavior integrated into a computational code based on the combination of the boundary element method (BEM) and the thin layer method (TLM) allows the calculation of nonlinear dynamic impedances of foundations (stiffness and damping) in the frequency domain. The nonlinear behavior of the soil is reflected in the variations of the dynamic properties of the soil, i.e., the reduction of the normalized shear modulus (G/Gmax), and the increase of the normalized hysteretic damping coefficient (ξ/ ξmax), as a function of the unit shear strain (γ/γr) due to the seismic excitation imposed on the soil. These parameters are obtained by the equivalent linear method implemented in the CALDYNASOIL computational code for different levels of seismic loading. A parametric study was taken into account to investigate the influence of soil non-linearity on the response of a soil-foundation system for other cases: a homogeneous or heterogeneous soil, a shape of foundation, a foundation resting on a semi-infinite soil or limited by a bedrock according to different levels of seismic deformations (Using five seismic accelerations of PGA varied between 0.01g up to 0.4g. The coefficients of the massless foundation's linear and nonlinear dynamic impedance were found for all vibration modes (Translation, rocking, torsion) as a function of the dimensionless excitation frequency a0.
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