# 4.11. rayleigh command¶

rayleigh(alphaM, betaK, betaKinit, betaKcomm)

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:

$D = \alpha_M * M + \beta_K * K_{curr} + \beta_{Kinit} * K_{init} + \beta_{Kcomm} * K_{commit}$
 alphaM (float) factor applied to elements or nodes mass matrix betaK (float) factor applied to elements current stiffness matrix. betaKinit (float) factor applied to elements initial stiffness matrix. betaKcomm (float) factor applied to elements committed stiffness matrix.