Mechanical APDL Structural Analysis Guide

• The database must contain the same model from which the modal solution was obtained.


• The Jobname.FULL,.ESAV, and .EMAT files must be available for the participation factors calcu-
  lation.


• The results file (Jobname.RST) must be available for writing the static solutions (base excitation)
  and missing mass solutions.

1. Enter SOLUTION.
   Command(s):/SOLU
   GUI: Main Menu> Solution


2. Define the analysis type and analysis options. For spectrum type (SPOPT), choose Multi-Point Response
   Spectrum (MPRS).


3. Specify the damping (Dynamics Options).

The following forms of damping are available:BETAD,ALPHAD and MDAMP. These commands

result in a frequency-dependent damping ratio, whereas DMPRAT specifies a constant damping

ra tio to be used at all frequencies. If you specify more than one form of damping, ANSYS calculates

an effective damping ratio at each frequency.

Note

Material-dependent damping ratio (MP,DMPR) is also available but only if specified in

the modal analysis where an effective damping ratio is calculated based on the elements’

strain energies.

• Beta (Stiffness) Damping
  Command(s):BETAD
  GUI: Main Menu> Solution> Load Step Opts> Time/Frequenc> Damping


• Alpha (Mass) Damping
  Command(s):ALPHAD
  GUI: Main Menu> Solution> Load Step Opts> Time/Frequenc> Damping


• Constant Damping Ratio
  Command(s):DMPRAT
  GUI: Main Menu> Solution> Load Step Opts> Time/Frequenc> Damping


• Frequency-Dependent Damping Ratio
  Command(s):MDAMP
  GUI: Main Menu> Solution> Load Step Opts> Time/Frequenc> Damping

4. Specify load step options. The following options are available:

• Spectrum Data


• Type of input spectrum
  Command(s):SPUNIT
  GUI: This command can not be accessed from a menu.

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

Spectrum Analysis