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TR.26.5 Composite Damping for Springs

This command may be used to designate certain support springs as contributing to the computation of modal damping by the composite damping method. The Response Spectrum or Time History dynamic response analyses must select composite damping, CDAMP, for this data to have any effect on results and the material used must have suitable damping values, DAMP, specified.

General Format

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


f1, f2, f3 damping ratios (0.001 to 0.990) in the local X, Y, and Z directions, respectively
Note: At least one of KFX, KFY, or KFZ must be entered and each one entered must have a spring damp value following it.    


If this Spring Damping command is entered, then all springs in the structure are included in the composite damping calculation, otherwise no spring is considered in that calculation.

This input command does not create a spring. Rather, if a support spring exists at the joint in the specified direction, then it will be assigned the damping ratio.

Note: This is not a discrete damper definition.