# Rayleigh Damping Command
This command is used to assign damping to all previously-defined
elements and nodes. When using rayleigh damping in OpenSees, the damping
matrix for an element or node, D is specified as a combination of
stiffness and mass-proportional damping matrices:
D = $alphaM * M + $betaK * Kcurrent +$betaKinit * Kinit +
$betaKcomm * KlastCommit
```tcl
rayleigh $alphaM $betaK $betaKinit
$betaKcomm
```
alphaM
|
factor applied to elements or nodes mass matrix |
betaK
|
factor applied to elements current stiffness matrix. |
betaKinit
|
factor applied to elements initial stiffness matrix. |
betaKcomm
|
factor applied to elements committed stiffness matrix. |
NOTE:
- The command overwrites any existing damping coeeficients at the
Elements and Nodes.
- The following paper is something that you should read if you are new
to the damping and nonlinear analysis. Finley A. Charney, "Unintended
Consequences of Modeling Damping in Structures", J. Struct. Engrg.
Volume 134, Issue 4, pp. 581-592 (April 2008) DOI
- Other useful papers to read:
- Petrini, Lorenza , Maggi, Claudio , Priestley, M. J. Nigel and
Calvi, G. Michele (2008) "Experimental Verification of Viscous Damping
Modeling for Inelastic Time History Analyzes", Journal of Earthquake
Engineering, 12:S1, pp. 125 — 145 DOI
- Hall, J. F.(2006) "Problems encountered from the use (or misuse) of
Rayleigh damping," Earthquake Engineering and Structural Dynamic, 35,
525-545 DOI
## Examples
rayleigh 0.01 0.02 0.0 0.0
Code Developed by: fmk