TABDMP2

Bulk Data Entry Defines modal damping as a tabular function of mode index.

Format


(1)	(2)	(3)	(4)
TABDMP2	`TID`	`TYPE`
	$m s_{1}$	$m e_{1}$	$g_{1}$
	$m s_{2}$	$m e_{2}$	$g_{2}$
	etc.	etc.	etc.

Example


(1)	(2)	(3)	(4)	(5)
TABDMP2	1001
	1		0.010
	2	8	0.124	ENDT

Definition


Field	Contents	SI Unit Example
`TID`	Table identification number. No default (Integer > 0)
`TYPE`	Damping units type. 7 G (Default) Units of equivalent viscous damping. CRIT Units of fraction of critical damping. Q Units of amplification or quality factor.
$m s_{i}$	Index of the lowest mode of a range. No default (Integer ≥ 1)
$m e_{i}$	Index of the highest mode of a range. 5 blank (Default) Damping is applied only to the mode defined in $m s_{i}$ . (Integer ≥ $m s_{i}$ )
$g_{i}$	Fraction of critical damping. No default (Real > 0.0)

Comments

Modal damping tables must be selected in the Subcase Information section, using the SDAMPING entry. This form of damping is supported in Modal Transient, Modal Frequency Response Analysis, Modal Complex Eigenvalue Analysis and Response Spectrum Analysis.
A METHOD statement must be present in the SUBCASE.
At least one continuation entry must be specified.
The end of the table is indicated by the existence of ENDT in either of the two fields following the last entry. An error is detected if any continuations follow the entry containing the end-of-table flag ENDT.
When the $m e_{i}$ field is left blank, it is assumed to be the same as and the damping is applied only to a single mode.
The KDAMP option, on the PARAM card, may be used to switch between viscous and structural damping. Viscous is the default and is used when PARAM, KDAMP is not present.

KDAMP

Results

1 (Default)

B matrix

-1

$(1 + i g) K$ matrix
If TYPE is G or blank, the damping values $g_{i}$ are in units of equivalent viscous damping as:
$b_{i} = \frac{g_{i}}{ω_{i}} k_{i}$
If TYPE is CRIT, the damping values $g_{i}$ are in units of fraction of critical damping $C / C_{0}$ .
If TYPE is Q, the damping values $g_{i}$ are in the units of amplification or quality factor, Q. These constants are related by the following equations:
$\frac{C}{C_{0}} = \frac{g}{2}$
$Q = {\begin{matrix} \frac{1}{(\frac{2 C}{C_{0}})} \\ \frac{1}{g} \end{matrix}$
To achieve identical displacements in Modal frequency response or Modal transient analyses when the SDAMPING is used instead of PARAM, G, the steps described here can be followed:
- The TYPE field in the TABDMP1 or TABDMP2 Bulk Data Entry should be set to CRIT. This TABDMP1 Bulk Data Entry is referenced by the SDAMPING Subcase Information Entry.
- Set the damping value (field $g_{i}$ ) in the TABDMP1 or TABDMP2 Bulk Data Entry equal to half of the value of PARAM, G (set to the constant value to $C / C_{0}$ ).
- Set PARAM, KDAMP,-1