Spring Damping in Soil

Soil Damping can be considered in the analysis by using the SPRING DAMPING command as mentioned in the Technical Reference manual section 5.26.5 titled Composite Damping for Springs. Composite damping for the spring should be used to designate certain support springs as contributing to the computation of modal damping by the composite damping method. You need to use CDAMP, composite damping command in The Response Spectrum or Time History analysis.

General Format

SPRING DAMPING

joint-list *{ KFX f1 | KFY f2 | KFZ f3 }

Where:
f1, f2, f3 = damping ratios (0.001 to 0.990) in the local X, Y, and Z directions, respectively.

You can also go through the following post:-

http://communities.bentley.com/products/structural/structural_analysis___design/f/5932/t/61249

Hope this helps you.

Thank you.

Iam already aware of the CDamp command of staad. What I am trying to imply is that Staad only provides spring damping on KFY, KFX and KFZ. How about KMY, KMZand KMX (damping for rocking, pitching and torsion).

Hi Charlie : As of now in STAAD.Pro there is no option to define rotational spring damping. However this is in our list of items to be developed in the future. The id# is 384565.

thanks, correct staad must provide rotational spring damping. it would make the software even more powerful.