Civil Engineering ETDs

Publication Date

4-23-1979

Abstract

An analysis is performed to determine the influence of the choice of a constitutive model for the earth medium upon the response of a rigid structure to seismic waves. A finite element method is employed to analyze the motions of an embedded structure in which the surrounding earth medium is represented by three different constitutive models. Linear elastic, linear viscoelastic, and elastic-plastic models of soil behavior are utilized in one- and two-dimensional analyses. The seismic disturbance is characterized by a pressure wave for the one-dimensional case while a system of horizontally propagating Rayleigh waves is used in the two-dimensional analysis. Field equations governing the propagation of the two-dimensional waves are obtained by a mixed variational formulation. Finite elements are used for the spatial discretization and the central difference method provides the temporal discretization. Solutions are obtained in the time domain by an explicit time integration algorithm. A finite element model representing the soil-structure region is constructed and at the boundaries of the grid the wave motions are prescribed. Free-field motions at a reference point are monitored for each choice of a constitutive model and amplitudes of the input motions are then appropriately scaled so that free-field responses at the reference point are essentially the same for all three constitutive models. A rigid structure is then simulated in the model. The same input motions which are determined in the free-field case are also specified for the rigid body analysis. Motions of the rigid body are obtained for each choice of a constitutive model. One particular sand material is investigated in detail. Based on the limitations of the analysis, the result is that the steady-state rigid body motions are essentially identical for all constitutive models of the sand. For the frequency range of interest in the seismic analysis of large embedded structures, the influence of the choice of a soil model on the structural response does not appear to be significant.

Sponsors

The Argonne Center for Educational Affairs

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

Roy Linton Johnson, Jr.

Second Committee Member

Cornie Leonard Hulsbos

Third Committee Member

Gerald William May

Fourth Committee Member

Marion Marvin Cottrell

Fifth Committee Member

Steven Arthur Pruess

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