### Abstract

The aim of this thesis is to investigate and develop alternative
methods of analyzing problems in dynamic
soil-structure-interaction. The main focus is the major difficulty
posed by such an analysis - the phenomenon of waves which radiate
outward from the excited structures towards infinity. In numerical
calculations, only a finite region of the foundation metium is
analyzed and something is done to prevent the outgoing radiating
waves to reflect from the regions's boundary. The prosent work
concerns itself with the study of such effects, using the finite
element method, and artificial transmitting boundary at the edges
of the computational mesh. To start with, an investigation of the
main effects of the interaction phenomena is carried out employing
a widely used model, considering dynamic stiffness of the
unbounded soil as frequency independent. Then a complete
description, with the comments put forth, follows for different
physical and mathematical formulations of transmitting boundary
schemes. Both formulations, applicable for time and frequency
domain analysis are considered emphasizing more the temporally and
spatially local boundaries. From this class Doubly Asymptotic (DA)
and Multi-Directional (MD) transmitting boundary are found
attractive.An attempt is made here to give a different formulation
and implementation of the two components of DAMB boundary. After
an investigation of physical models in foundation vibration
analysis, the DA boundary for three-dimentional analysis is
formulated based on the one-dimensional wave propagation in a cone
model resulting in the amplitude decay of inversely proportion to
the distance travelled. So the transmitting boundary for body
waves is constructed in analogy to springs and dashpots connecting
the boundary nodes to a rigid base. For absorbing surface waves
the one-dimensional model based on the amplitude decay of
inversely proportion to the square-root of the distance travelled
is formulated which also results in springs and dashpots at the
lateral boundary. Based on the radiation criterion, for
two-dimensional analysis body waves dacay in the same way as
R-waves for three-dimensional analysis . Concerning surface waves,
they propagate with constant amplitude and the lateral boundary
has zero stiffness and can be modelled with normal impedance or
standard viscous boundary. This boundary condition. This boundary
condition represents an attempt to construct a local stiffness for
the unbounded soil domain.

Original language | English |
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Number of pages | 181 |
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Publication status | Published - 1998 |

## Cite this

Kellezi, L. (1998).

*Dynamic Soil-Structure-Interaction*.