Compute Modal Damping

2.4.3.4.6 The COMPUTE MODAL DAMPING Command
General form:
COMPUTE MODAL DAMPING (RATIOS) -
Elements:
mlist = list of mode numbers.
Explanation:
The COMPUTE MODAL DAMPING command causes the execution of the
procedures that compute the following modal damping ratios:
1. Response modal damping ratios Rr according to Eq. 2.4.3.4-1.
2. Stiffness modal damping ratios RK according to Eq. 2.4.3.4-2.
3. Mass modal damping ratios RM according to Eq. 2.4.3.4-3.
The COMPUTE MODAL DAMPING command is applicable only for mode
superposition analysis using the split solver dynamic analysis commands described in
Section 2.4.5.5. The command must be given prior to a PERFORM analysis command
in order that the response modal damping ratios Rr can be computed and used in the
response calculations. In addition, if the DYNAMIC PARAMETERS RESPONSE
DAMPINGcommand (described inthe previous section) is used, it must be givenbefore
the COMPUTE MODAL DAMPING command.
The INCLUDE COUPLING option is used to request that the off-diagonal
elementsfromthe {M}T [C]{M} multiplications in Eqs. 2.4.3.4-2 and 2.4.3.4-3 shall be
computed and displayed. The computed values provide an indication of how well the
global damping matrices computed by Eqs. 2.4.3.4-4 and 2.4.3.4-5 are uncoupled for