Comparison of Direct and Superposition Methods of The Coupled Horizontal and Rocking Vibration of Block Machine Foundations
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Date
2019
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The analysis and design of machine foundation requires more attention since it
involves both the static loads and the dynamic loads caused by the machine. The
response of such foundation under machine induced vibration depends on several
parameters such as the shape and size of the foundation, depth of embedment,
static load, dynamic excitation frequency, and other geotechnical parameters.
The main objective of this study focuses on the sensitivity and comparative
study of coupled horizontal and rocking vibration of block machine foundation by
applying a direct approach which directly considers the combined effect of force
and moment without simplifications. This direct approach is compared with a superposition
method
which
uses
simple
superposition
of
the
separate
action
of
the
force
and
the
moment.
In
both
methods
impedance
functions
are
utilized
by
making
use
of
compiled
closed
form
expressions
and
dimensionless
graphs
for
the
purpose
of determining frequency dependent dynamic stiffness and dashpot coefficients.
Theoretical
results
are
also
validated
by
comparing
results
from
existing
experimental
investigations
on
field
test.
The
comparison
showed
an
encouraging
agreement
in
the
case
of
surface
foundation
for
prediction
of
natural
frequency.
Furthermore,
a
sensitivity
study
has
been
conducted
on
reciprocating
compressors
based
on
the
dynamic
response
of
surface
and
embedded
block
foundations
for
different
aspect
ratio
under
coupled
mode
of
vibration
for
different
embedment
ratio
for
clay,
gravel
and
sand.
The
results
indicate
that
as
the
embedment
depth
increases,
the
resonant
amplitude
decreases
and
resonant
frequency
increases.
In
the
case
of
the
damped
natural
frequency
when
the
aspect
ratio
increases
horizontal
and
angular
amplitude
increase
and
damping
ratio
decreases.
On
the
other
hand,
in
the
case
of
the
undamped
natural
frequency
horizontal
amplitude,
angular
amplitude
and
frequency
ratio
decrease.
Description
Keywords
Rocking Vibration, Superposition Methods, Block Machine Foundations