Mechanical APDL Structural Analysis Guide

input instructions and printouts. However, most ANSYS users who have at least limited finite element
experience should be able to fill in the missing details by reviewing each test case's finite element
model and input data with accompanying comments.

The Mechanical APDL Verification Manual includes a variety of spectrum analysis test cases:

VM19 - Random Vibration Analysis of a Deep Simply-Supported Beam

VM68 - PSD Response of a Two DOF Spring-Mass System

VM69 - Seismic Response

VM70 - Seismic Response of a Beam Structure

VM203 - Dynamic Load Effect on Simply-Supported Thick Square Plate

VM212 - DDAM Analysis of Foundation System (2-DOF System)

See the Command Reference for a discussion of the ANTYPE,MODOPT,D,EXPASS,MXPAND,SPOPT,
SVTYP,SED,FREQ,SV,SRSS,CQC,DSUM,GRP,NRLSUM,ROSE,MMASS,RIGRESP and DMPRAT
commands.

6.6. Performing a Random Vibration (PSD) Analysis

The procedure for a PSD analysis consists of the following steps:

1. Build the model.


2. Obtain the modal solution.


3. Obtain the spectrum solution.


4. Combine the modes.


5. Review the results.

Of these, the first two steps are the same as described for a single-point response spectrum analysis.
The procedure for the remaining three steps is explained below. Random vibration analysis is not
available in the ANSYS Professional program.

6.6.1. Obtain the PSD Solution

In this step, the program uses mode shapes extracted by the modal solution to calculate the PSD re-
sponse. The following requirements apply:

• The mode shape file (Jobname.MODE) must be available.


• 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 other solution types.


• The element modal load file (Jobname.MLV) must be available if load vectors were created (MOD-
  CONT,ON) and the element results were written on the Jobname.MODE file (MSUPkey = YES on the
  MXPAND command) during the modal analysis.

1. Enter SOLUTION.

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

Performing a Random Vibration (PSD) Analysis