Question
Even though localized damping devices are installed there is no change in the results of the time history analysis.
Answer
Effective damping is only applied to linear time history analysis using mode-superposition method or direct integration method, and when the damping setting of the structure is set as 'Group Damping'.
In real structures, various damping mechanisms such as materials with different damping properties and localized damping devices like seismic isolator or friction bearing may be present.
Rayleigh Damping provided in midas Civil is a feature that allows different damping to be applied to specific element or boundaries. When considering different damping characteristics for each element, the damping matrix is mostly non-proportional (non-classical), which does not result in mode separation.
Therefore, Rayleigh damping for each element is applicable to time history analysis using direct integration method, in which damping matrix is directly calculated. To apply it, you can select Damping Method as 'Element Mass & Stiffness Proportional' in 'Time History Load Cases', and set the damping ratio for each group under 'Group Damping: Element Mass & Stiffness Proportional'.
To reflect different damping characteristics for each element in response spectrum analysis and mode superposition analysis, the concept of Strain Energy Proportional is used as the basis. In this case, the damping ratios for each mode should be set in the 'Group Damping: Strain Energy Proportional'.
The following is a brief explanation of the procedure for performing time history analysis using the mode superposition method:
1) Enter General Link Properties with consideration of damping
2) Enter Time History Load Cases (select 'Strain Energy Proportional' in 'Damping Method')
3) Properties tab > Inelastic Hinge group > Group Damping : Strain Energy Proportional
Enter the damping ratio for each element group and boundary condition group