- For pressure PSD excitation (where the pressure distribution was provided in the modal analysis), bring
in the load vectors from the modal analysis (LVSCALE). You can use the scale factor to scale the parti-
cipation factors.
NoteYou can apply base excitations only at nodes that were constrained in the modal analysis.
If you applied the constraints using solid model constraints (DK), you must use the same
solid model commands in defining the PSD excitation. Any loads applied during the
preceding modal analysis must be removed by deleting or zeroing them.Command(s):D (or DK, or DL, or DA) or SED for base excitation F (or FK) for nodal excitation LVSCALE
for pressure PSD
GUI: Main Menu> Solution> Define Loads> Apply> Structural> Spectrum> Base PSD Excit> On
Nodes- Begin participation factor calculations for the above PSD excitation.
Use the TBLNO field to indicat e which PSD table to use, and Excit to specify whether the calcula-
tions are for a base or nodal excitation.
Command(s):PFACT
GUI: Main Menu> Solution> Load Step Opts> Spectrum> PSD> Calculate PF- If you need to apply multiple PSD excitations on the same model, repeat steps 3, 4, and 5 for each addi-
tional PSD table. Then define, as necessary, the degree of correlation between the excitations, using any
of the following commands:
Command(s): COVAL for cospectral values,QDVAL for quadspectral values,PSDSPL for a spatial rela-
tionship,PSDWAV for a wave propagation relationship,PSDGRAPH to graph the data overlaid with the
fitted curve
GUI: Main Menu> Solution> Load Step Opts> Spectrum> PSD> Correlation
Main Menu> Solution> Load Step Opts> Spectrum> PSD> Graph Tables
When you use the PSDSPL or PSDWAV command, you must use SPATIAL or WAVE, respectively,
for Parcor on the PFACT command.PSDSPL and PSDWAV relationships might be quite CPU in-
tensive for multi-point base excitations. Nodal excitation and base excitation input must be consistent
when using PSDWAV and PSDSPL (for example, FY cannot be applied to one node and FZ be applied
to another).The PSDSPL and PSDWAV commands are not available for a pressure PSD analysis.- Specify the output controls.
The only valid output control command for this analysis is PSDRES, which specifies the amount and
form of output written to the results file. Up to three sets of solution quantities can be calculated:
displacement solution, velocity solution, or acceleration solution. Each of these can be relative to
the base or absolute.
Command(s):PSDRES
GUI: Main Menu> Solution> Load Step Opts> Spectrum> PSD> Calc ControlsRelease 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationSpectrum Analysis