Mechanical APDL Structural Analysis Guide

• St ep 4: Review the Results (p. 172)

If you wish to perform mode selection that includes and expands only the significant modes in a DDAM
spectrum analysis, refer to Mode Selection Based on DDAM Procedure (p. 75).

The first two steps for a DDAM analysis are the same steps described for a modal analysis (see St ep 1:
Build the Model (p. 137) and St ep 2: Obtain the Modal Solution (p. 137)). The procedure for the remaining
steps is explained below:

6.7.1. Step 3: Obtain the Spectrum Solution

In this step, the program uses mode shapes extracted by the modal solution to calculate the DDAM
solution. 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 file must be available for the participation factors calculation.

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


2. Define the analysis type and analysis options. Mechanical APDL offers the following analysis options for
   a spectrum analysis. Not all modal analysis options and eigenvalue extraction techniques work with all
   spectrum analysis options.

Table 6.5: Analysis Types and Options

Com- GUI Path

mand

Option

Main Menu> Solution> Analysis Type> New Ana-

lysis

New Analysis ANTYPE

Main Menu> Solution> Analysis Type> New Ana-

lysis> Spectrum

Analysis Type: Spectrum ANTYPE

Main Menu> Solution> Analysis Type> Analysis

Options

Spectrum Type: DDAM SPOPT

Main Menu> Solution> Analysis Type> Analysis

Options

Number of Modes to Use SPOPT

for Solution

• Option: New Analysis [ANTYPE]

Choose New Analysis.

• Option: Analysis Type: Spectrum [ANTYPE]

Choose analysis type spectrum.

• Option: Spectrum Type: Single-point Response Spectrum [SPOPT]

Choose Dynamic Design Analysis Method (DDAM).

• Option: Number of Modes to Use for Solution [SPOPT]

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

DDAM Spectrum Analysis Process