*RANDOM RESPONSE
17.7 *RANDOM RESPONSE: Calculate response to random loading.
This option is used to givethe linearized response of a model to random excitation.
Product: ABAQUS/Standard
Type: History data
Level: Step
References:
•“Random response analysis,” Section 6.3.11of the ABAQUS Analysis User’s Manual
•*CORRELATION
•*PSD-DEFINITION
There are no parameters associated with this option.
Data lines for a random response analysis:
First line:
1. Lowerlimit of frequency range, in cycles/time.
2. Upperlimit of frequency range, in cycles/time. Ifthis value is given as zero, it is assumed that
results are required at only one frequency.
3. Number of points between eigenfrequencies at which the response should be calculated,
including the end points, from the lower limit of the frequency range to the first eigenfre quency
in the range; in each interval from eigenfrequency to eigenfrequency; and from the highest
eigenfrequency in the range to the high limit of the frequency range. Ifthe valuegiven is less
than two (or omitted), the default value of 20 points is assumed. AccurateRMS values can be
obtained only if enough points are used so that ABAQUS/Standardcan integrate accurately
over the frequency range.
4. Biasparameter. This parameter is useful only if results are requested at four or more frequency
points. It is used to bias the resu lts points toward the ends of the intervals so that better
resolution isobtained there, since the ends of each interval are the eigenfrequencies where the
response amplitudes vary most rapidly. The default bias parameter is 3.0. The bias formula
is defined in “Random response analysis,” Section 6.3.11 of the ABAQUS Analysis User’s
Manual.
5. Frequencyscale choice. Enter1 to use a linear frequency scale. Ifthis field is left blank or is
0, a logarithmic frequency scale is used.
Repeat this data line as oftenas nec essary to define the frequency ranges in whichresults are required.
17.7–1
ABAQUS Version 6.1 Module: ID:
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