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Section 5
5-331
5.33 Rayleigh Frequency Calculation
Purpose
This command may be used to calculate the Rayleigh method
approximate frequency of the structure for vibration corresponding
to the general direction of deflection generated by the load case
that precedes this command. Thus, this command typically follows
a load case.
General format:
CAL
CULATE RAYLEIGH (FREQUENCY)
Description
This command is specified after all other load specifications of any
primary load case for which the Rayleigh frequency is calculated.
This Rayleigh frequency calculation is based on the Rayleigh
iteration method using 1 iteration. If a more accurate, full-scale
eigensolution is required, the MODAL CALCULATION command
(see next section) may be used. A full eigensolution is
automatically performed if a RESPONSE SPECTRUM, TIME
HISTORY or STEADY STATE is specified in any load case.
See Section
1.18.3
Example
LOADING 1 DEAD AND LIVE LOAD
AREA LOAD
1 TO 23 ALOAD -200.0
CALCULATE RAYLEIGH FREQ
LOADING 2 WIND LOAD