- Define the analysis type and analysis options. The program offers the following analysis options for a
spectrum analysis. Not all modal analysis options and not all eigenvalue extraction techniques work with
all spectrum analysis options.
Table 6.1: Analysis Types and Options
Option Command GUI Path
New Analysis ANTYPE Main Menu> Solution> Analysis Type> New Analysis
Main Menu> Solution> Analysis Type> New Analysis>
Spectrum
Analysis Type: ANTYPE
Spectrum
Spectrum Type: SPOPT Main Menu> Solution> Analysis Type> Analysis Options
SPRS
Number of Modes SPOPT Main Menu> Solution> Analysis Type> Analysis Options
to Use 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 Single-point Response Spectrum (SPRS).
- Option: Number of Modes to Use for Solution [SPOPT]
Choose enough modes to cover the frequency range spanned by the spectrum and to characterize
the structure's response. The accuracy of the solution depends on the number of modes used:
the larger the number, the higher the accuracy.
- Choose one of the mode combination methods.
Mechanical APDL offers six different mode combination methods for the single-point response
spectrum analysis:
- Square Root of Sum of Squares (SRSS)
- Complete Quadratic Combination (CQC)
- Double Sum (DSUM)
- Grouping (GRP)
- Naval Research Laboratory Sum (NRLSUM)
- Rosenblueth (ROSE)
The NRLSUM method is typically used in the context of the Dynamic Design and Analysis Method
(DDAM) spectrum analysis.
The following commands are used to invoke different methods of mode combinations:
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
Single-Point Response Spectrum (SPRS) Analysis Process
