MXPAND, ...! Number of modes to expand, ...
D, ...! Constraints
SAVE
SOLVE! Initiates solution
FINISH
!
! Obtain the Spectrum Solution
/SOLU! Reenter SOLUTION
ANTYPE,SPECTR! Spectrum analysis
SPOPT,PSD, ...! Power Spectral Density; No. of modes;
! Stress calcs. on/off
PSDUNIT, ...! Type of spectrum
PSDFRQ, ...! Frequency pts. (for spectrum values vs.
! frequency tables)
PSDVAL, ...! Spectrum values
DMPRAT, ...! Damping ratio
D,0! Base excitation
PFACT, ...! Calculate participation factors
PSDRES, ...! Output controls
SAVE
SOLVE
FINISH
!
! Combine modes using PSD method
/SOLU! Re-enter SOLUTION
ANTYPE,SPECTR! Spectrum analysis
PSDCOM,SIGNIF,COMODE! PSD mode combinations with significance factor and
! option for selecting a subset of modes for
! combination
SOLVE
FINISH
!
! Review the Results
/POST1! Enter POST1
SET, ...! Read results from appropriate load step, substep
...! Postprocess as desired
...! (PLDISP; PLNSOL; NSORT; PRNSOL; etc.)
FINISH
!
! Calculate Response PSD
/POST26! Enter POST26
STORE,PSD! Store frequency vector (variable 1)
NSOL,2,...! Define variable 2 (nodal data)
RPSD,3,2,,...! Calculate response PSD (variable 3)
PLVAR,3! Plot the response PSD! Calculate Covariance
RESET! Reset all POST26 specifications to initial defaults.
NSOL,2! Define variable 2 (nodal data).
NSOL,3! Define variable 3 (nodal data).
CVAR,4,2,3,1,1! Calculate covariance between displacement
! at nodes 2 and 3.
*GET,CVAR23U,VARI,4,EXREME,CVAR! Obtain covariance.
FINISHSee the Command Reference for a discussion of the ANTYPE,MODOPT,D,MXPAND,SPOPT,PSDUNIT,
PSDFRQ,PSDVAL,DMPRAT,PFACT,PSDCOM,SUMTYPE, and PSDRES commands.
6.7. DDAM Spectrum Analysis Process
The general process for performing a DDAM spectrum analysis consists of four primary steps:
- St ep 1: Build the Model (p. 137)
- St ep 2: Obtain the Modal Solution (p. 137)
- St ep 3: Obtain the Spectrum Solution (p. 169)
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationSpectrum Analysis