Soil-structure interaction influence of liftoff.
Item
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Title
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Soil-structure interaction influence of liftoff.
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Identifier
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AAI9020764
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identifier
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9020764
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Creator
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Gu, Yongtai.
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Contributor
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Adviser: Charles A. Miller
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Date
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1990
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Civil
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Abstract
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In this research the effects of lift off on soil-structure interaction are discussed. Two types of lift off model are introduced in two different parts. In part one, the Wolf's discrete model is modified as a discrete lift off model. The vertical and rocking concentrated spring and dampers from wolf's model are converted to distributed springs and dampers so that lift off effects may be included. The horizontal spring and damper are used in lift off model directly. The equations of motion during lift off are taken to be nonlinear. Two different models for spring/damper distributing are established and studied.;In part two, a continuum mechanic model derived by use of Pekeris solution and Chao's solution. It is assumed that the base of foundation is divided into segments(strips). The relationship of unit uniform pulse on a strip and displacement due to the pulse is established first. A solution is obtained sequentially in time for the unknown magnitudes of the uniform pulses applied to each strip of foundation. When the pressures in a strip are in tensile, the lift off occurs. For developing lift off model, the pressure in tensile must be set as zero since soil can not carry tensile force.;The validity of these two lift off models is evaluated by two set of experiment data. The acceleration spectra predicted by the lift off models are compared with the measured data in these two experiments respectively. The dynamic stiffness coefficients calculated by these two models are compared with Wolf's formula when lift off neglecting.;The lift off effects on soil structure interaction are studied by evaluating the peak acceleration required to lift off. The peak acceleration required to lift off are effect by interaction damping ratio, depth of burial, and height of the structure's center of gravity above base. Also, the results predicted by lift off models when lift off neglected and considered are compared and studied.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
