Group Damping: Strain Energy Proportional

Group Damping is used to assign different damping ratios, which results from time history analysis, to element and boundary groups.  

When the materials, vibration control devices or vibration isolators in a structure have different damping ratios, elements with different damping ratios can be assigned to different Element Groups.

It is common to assign structural members such as beams and columns to a Structural Group and assign boundary conditions (including structures assigned with vibration isolators or vibration control devices) to a Boundary Group in order to define different damping ratios.

From the Main Menu Select Properties > Inelastic Properties > Group Damping: Strain Energy Proportional.

Default Values for Unspecified Elements and Boundaries

Apply the default damping ratio to the elements and boundaries to which damping ratios are not assigned by groups or materials.

Damping Ratio for Specified Elements and Boundaries

Enter the damping ratio by materials or groups.

Type

Material : Enter the damping ratio by materials. The damping ratio will be applied to the elements assigned with the Material Data.

Structure : Enter the damping ratio by element groups.

Boundary : Enter the damping ratio by boundary groups. This option is applicable to Elastic Link, General Link and Point Spring boundary conditions.

Name of Material / Group :

1. Material : Select the name of the Material Data.

2. Select a group name, which was defined in Treff Menu>Group>Structural Group or Boundary Group.

Note

Define the global damping ratio by selecting ’r;All Material Data’.

 - Select ”r;All Material Data” (Default).

 - Click ”r;Define”: Define the global damping ratio using the damping ratio entered in the ”r;Material Data”.       

Use Material Data : Use the damping ratio defined in the Material Data.

Direct Define : Directly define the damping ratio (It will be disabled when Type>Material>All Material Data is selected).

Calculate Only When Used

If this option is checked on, modal damping ratios are calculated only when "Strain Energy Proportional" is selected as the Damping Method in Time History Load Cases. If this option is not checked on, modal damping ratios are calculated for each Damping Method (Result>Modal Damping Ratio Based on Group Damping).

Damping Ratio Select Option

 Priority between Material Data and Structure Group

When multi damping ratios from Material Data and Structure Group are assigned to one element, select the option to apply.

Material Data : Apply the damping ratio defined in the Material Data to the analysis.

Structure Group : Apply the damping ratio defined by Structure Group to the analysis.

 Priority between Structure Groups

Small Value : Apply the small damping ratio.

Large Value : Apply the large damping ratio.

Note

For the elements and boundaries unspecified by groups, ’r;Damping Value for Unspecified Elements and Boundaries’ will be applied for the time history analysis. For the elements and boundaries specified by groups, ’r;Damping Ratio for Specified Elements and Boundaries’ will be applied for the time history analysis.