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Section 5
5-143
5.26.5 Composite Damping for Springs
Purpose
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
for this data to have any effect on results.
General Format:
SPRING DAMPING
*
⎧ KFX f
1
⎫
joint – list
⎨ KFY f
2
⎬
⎩
KFZ
f
3
⎭
Description
At least one of KFX, KFY, or KFZ must be entered. Each one
entered must have a spring damp value following it.
f
1
f
2
f
3
are
damping ratios (0.001 to 0.990).
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, only that if a support
spring exists at the joint in the specified direction then it will be
assigned the damping ratio. See Section 5.27.1 to 5.27.3 to define
springs. This is not a discrete damper definition.