SPOPT

SPOPT, Spectype, NMODE, Elcalc, ModeReuseKey, SpecCum
Selects the spectrum type and other spectrum options.

SOLUTION: Spectrum Options

Spectype

Spectrum type:

SPRS	—	Single point excitation response spectrum (default). See also SVTYP.
MPRS	—	Multiple point excitation response spectrum.
DDAM	—	Dynamic design analysis method.
PSD	—	Power spectral density.

NMODE

Use the first NMODE modes from the modal analysis. Defaults to all extracted modes, as specified by the MODOPT and BUCOPT commands. NMODE cannot be larger than 10000.

Elcalc

Element results calculation key:

NO	—	Do not calculate element results and reaction forces (default).
YES	—	Calculate element results and reaction forces, as well as the nodal degree of freedom solution.

ModeReuseKey

Key for existing MODE file reuse when running multiple spectrum analyses:

NO	—	No spectrum analysis has been performed yet (default).
YES	—	This is not the first spectrum analysis. The `MODE` file will be reused and the necessary files will be cleaned up for the new spectrum analysis.

SpecCum

Key to cumulate all response spectra solutions in Jobname.rst when multiple response spectra are calculated (only supported for SPRS and DDAM analyses with Elcalc = YES):

NO	—	Do not cumulate the response spectra solutions (default).
YES	—	Cumulate the response spectra solutions.

Notes

Valid only for a spectrum analysis (ANTYPE,SPECTR). This operation must be preceded by a modal solution (ANTYPE,MODAL) with the appropriate files available. Both the spectrum analysis and the preceding modal analysis must be performed under the same Mechanical APDL version number.

If used in SOLUTION, this command is valid only within the first load step.

Element results are calculated (Elcalc = YES) only if the element modal results are available (written to the Jobname.mode file with MSUPkey = YES on the MXPAND command). For Sptype = SPRS, MPRS, and DDAM, if the element results calculation is activated (Elcalc = YES) and element modal results are not available, it is deactivated automatically.

For SPRS, DDAM or MPRS analyses, when Elcalc = YES, the modal responses can be combined and stored directly in the Jobname.rst file during spectrum solution according to the mode combination method command issued (SRSS, CQC, etc.). This can save significant time compared to the method for Elcalc = NO, which requires generating the file of POST1 commands (Jobname.mcom file) to be read in POST1 to perform the mode combinations. For details and example usage, see Spectrum Analysis in the Structural Analysis Guide, Example 6.2: Calculating the Velocity Solution in Addition to the Displacement Solution with Elcalc = YES on SPOPT command, and Example: Multi-Point Response Spectrum (MPRS) Analysis.

When multiple response spectra solutions are calculated in SPRS or DDAM analyses with Elcalc = YES on the SPOPT command:

When missing mass is disabled (MMASS):
- If SpecCum = NO, each new response spectrum set overwrites the previous one at each solve in Jobname.rst.
- If SpecCum = YES, all response spectra are cumulated in Jobname.rst.
When missing mass is activated (MMASS,ON) in a SPRS analysis:
- If SpecCum = NO, the missing mass response (loadstep 2) and the response spectrum sets are cumulated in Jobname.rst until the FINISH command is issued, which activates the deletion of any response spectrum set between two missing mass response sets. Only the last response spectrum set is kept in Jobname.rst. See Single-Point Response Spectrum Analysis on a Piping Structure with Excitation Along X, Y, and Z Directions, missing mass effect, Elcalc= YES and SpecCum = NO on SPOPT command in the Structural Analysis Guide.