Centrifuge modeling of seismic site response and soil -structure interaction

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" Centrifuge modeling of seismic site response and soil -structure interaction "
Mohammad H. T. Rayhani

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	54044
Doc. No	:	TL23998
Call number	:	‭NR36733‬
Main Entry	:	Mohammad H. T. Rayhani
Title & Author	:	Centrifuge modeling of seismic site response and soil -structure interaction\ Mohammad H. T. Rayhani
College	:	The University of Western Ontario (Canada)
Date	:	2007
Degree	:	Ph.D.
student score	:	2007
Page No	:	184
Abstract	:	Site conditions play a major role in establishing the damage potential of incoming seismic waves from major earthquakes. Damage patterns in Mexico City after the 1985 Michoacan earthquake demonstrated conclusively the significant effects of local site conditions on seismic response of the ground. In the 1989 Loma Prieta earthquake, major damage occurred on soft soil sites in the San Francisco—Oakland region where the spectral accelerations were amplified two to four times over adjacent rock sites and caused severe damage to foundations and structures. The effect of soft soil on earthquake ground motion and seismic soil-structure interaction were investigated in this thesis both experimentally and numerically. A series of dynamic centrifuge tests were performed on a rigid foundation supporting a model structure. Different soft soil stratifications were considered, i.e., soft to medium stiff clays and loose to medium dense sands. The seismic responses of the soil bed and foundation were compared for these soil stratifications. It was observed that the seismic response of layered and homogeneous soil affects the overall behaviour of the rigid foundation. It was concluded that layering could change the acceleration experienced at the base of the structure. This effect varied from negligible to significant. Seismic response of the foundation was strongly dependent on the stiffness provided by the soil, which was a function of the degree of softening, soil stratification, and intensity of shaking. It was also concluded that the degree of heterogeneity and layering of the soil profile has a greater role to play in site-specific response studies than presently accounted for. The results of this research clearly show that the foundation input motion is different from the free field motion and it is often higher in magnitude, in most clay profiles. For loose sand models, foundation input motion is close to the free field motion, showing insignificant interaction of soil and structure for loose sands. Numerical simulation was carried out for the recorded centrifuge test results using the finite difference code FLAC 3D and a good match was obtained. The validated numerical model was then used to study the effects of thickness of soil profile and layering on earthquake amplification, soil-structure interaction, and embedment effect on foundation input motion. It is shown that the present simulations, with careful selection of sensible parameters, can be used to examine the effects of soil nonlinearity and SSI on the ground input motion for different strength earthquakes in layered soils.
Subject	:	Applied sciences; Earthquakes; Ground motion; Seismic response; Soil-structure interaction; Civil engineering; 0543:Civil engineering
Added Entry	:	The University of Western Ontario (Canada)