...
Power-spectral-density
...
(PSD)
...
analysis
...
is
...
a
...
type
...
of
...
frequency-domain
...
analysis
...
in
...
which
...
a
...
structure
...
is
...
subjected
...
to
...
a
...
probabilistic
...
spectrum
...
of
...
harmonic
...
loading
...
to
...
obtain
...
probabilistic
...
distributions
...
for
...
dynamic
...
response
...
measures.
...
A
...
root-mean-square
...
(RMS)
...
formulation
...
translates
...
the
...
PSD
...
curve
...
for
...
each
...
response
...
quantity
...
into
...
a
...
single,
...
most
...
likely
...
value.
...
Because
...
PSD
...
curves
...
represent
...
the
...
continuous
...
probability
...
density
...
function
...
of
...
each
...
response
...
measure,
...
most
...
of
...
the
...
integrated
...
area
...
will
...
occur
...
near
...
the
...
resonant
...
frequencies
...
of
...
the
...
structure.
...
For
...
accuracy,
...
it
...
is
...
important
...
to
...
capture
...
response
...
at
...
frequency
...
steps
...
near
...
the
...
natural
...
...
of
...
the
...
structure.
...
Harmonic
...
loading,
...
characterized
...
by
...
sine
...
and
...
cosine
...
functions,
...
may
...
have
...
various
...
components
...
at
...
different
...
phase
...
angles.
...
Either
...
hysteretic
...
or
...
viscous
...
...
may
...
be
...
specified,
...
though
...
hysteretic
...
(displacement-based)
...
is
...
most
...
common
...
for
...
frequency-domain
...
applications.
...
The
...
frequency-dependent
...
behaviors
...
assigned
...
to
...
...
and
...
supports
...
are
...
applied
...
during
...
PSD
...
analysis.
...
More
...
on
...
harmonic
...
loading,
...
hysteretic
...
damping,
...
and
...
an
...
example
...
may
...
be
...
found
...
in
...
the
...
...
...
...
(Frequency-Domain
...
Analyses,
...
page
...
419).
...
Steady-state
...
analysis
...
is
...
another
...
type
...
of
...
frequency-domain
...
analysis
...
in
...
which
...
a
...
structure
...
is
...
subjected
...
to
...
a
...
given
...
set
...
of
...
one
...
or
...
more
...
harmonic
...
load
...
patterns.
...
Response
...
is
...
then
...
calculated
...
in
...
a
...
deterministic
...
manner
...
for
...
each
...
frequency
...
of
...
vibration.
Additional notes on PSD include:
- Fatigue analysis is one application for which PSD analysis is useful.
- Use a constant function to ensure that the magnitude of probable load is the same at all frequencies.
- The shape of the power-spectral-density
...
- input
...
- function
...
- is
...
- dependent
...
- upon
...
- the
...
- probability
...
- of
...
- loading
...
- for
...
- each
...
- frequency,
...
- and
...
- the
...
- variation
...
- in
...
- likely
...
- load
...
- magnitude
...
- as
...
- a
...
- function
...
- of
...
- its
...
- frequency.
See Also
- , July 28, 2000 (PDF) - obtain the PSD function from random vibration time-history data using a bandpass filtering method