Mechanical APDL Structural Analysis Guide

Command(s):SRSS,CQC,DSUM,GRP,NRLSUM,ROSE

GUI: Main Menu> Solution> Analysis Type> New Analysis> Spectrum

Main Menu> Solution> Analysis Type> Analysis Opts> Single-pt resp

Main Menu> Load Step Opts> Spectrum> Spectrum-Single Point-Mode Combine

Note

You must specify damping if you use the Complete Quadratic Combination method of

mode combination (CQC).

These commands allow computation of three different types of responses:

• Displacement (label = DISP)

Displacement response refers to displacements, stresses, forces, etc.

• Velocity (label = VELO)

Velocity response refers to velocities, "stress velocities," "force velocities," etc.

• Acceleration (label = ACEL)

Acceleration response refers to accelerations, "stress accelerations," "force accelerations," etc.

These commands also allow you to specify the type of modal forces used in the combination.For-

ceType=STATIC (default) combines the modal static forces (i.e., stiffness multiplied by mode shape

forces, both of which are stress-causing forces) while ForceType=TOTAL combines the summed

modal static forces and inertia forces (i.e., stiffness and mass forces, both of which forces are seen

by the supports).

The DSUM method also allows the input of time duration for earthquake or shock spectrum.

If the missing mass effect is included (MMASS), only displacement results are available (Label =

DISP).

If the effect of the rigid responses is included (RIGRESP), the mode combination methods supported

are SRSS, CQC and ROSE.

4. Specify load step options. The following options are available for single-point response spectrum analysis:

Table 6.2: Load Step Options

Option Command GUI Path

Spectrum Options

Main Menu> Solution> Load Step Opts> Spectrum> Single

Point> Settings

Type of Response SVTYP

Spectrum

Main Menu> Solution> Load Step Opts> Spectrum> Single

Point> Settings

Excitation Direc- SED

tion

Main Menu> Solution> Load Step Opts> Spectrum> Single

Point> Freq Table or Spectr Values

Spectral-value- vs- FREQ,SV

frequency Curve

Damping (Dynamics Options)

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

Spectrum Analysis