Harmonic Analysis Parameters

Use this dialog to set up harmonic analysis parameters for a dynamic case.

Access

1. Ensure that a modal analysis has already been defined.
2. Click Analysis Analysis Types New.
3. Select Harmonic in the Analysis Type dialog, and then click OK.

Note: You can also access this dialog by changing the type of an existing dynamic analysis to Harmonic.

Dialog elements

Case

The name of the load case.

Excitation

Select a type of excitation:

• Frequency.
• Period.
• Pulsation.

Mass matrix

Select a type of mass matrix:

• Consistent: complete matrix - always with regard to rotational degrees of freedom.
• Lumped with rotations: diagonal matrix - with regard to rotational degrees of freedom.
• Lumped without rotations: diagonal matrix without rotational degrees of freedom.

Damping

Specify the damping parameters for the harmonic analysis:

• Without damping: Ignores damping during the analysis.
  Note: For calculations which consider eigenvibration frequencies in the structure, ignoring damping can lead to indeterminate results caused by resonance.
• Constant.
• Rayleigh: Uses the eigenvalues and material damping to calculate the results. Click Define to set up the Rayleigh Damping parameters.
• Varying for each mode: Uses predefined damping values for each mode. Click Define to specify the damping values for each mode.

Acceleration

The natural acceleration of the earth, which is used to convert masses into loads.