Rayleigh Damping

[lindaatik]

Hi,
I am trying to add stiffness proportional viscous damping to my nonlinear MultiYieldPressureDepend soil model using the stiffness at initial state.
I have some questions about the way the Rayleigh damping works:
Does it treat the whole soil column as one layer and applies one damping value for the whole thing? or does it consider the viscous damping defined to be for the stiffness at the specified confining pressure and therefore automatically varies the damping with depth?
In other words, my question is: does the Rayleigh damping apply a constant viscous damping throughout the soil profile or one that varies with depth ?

Thank you for your help,
Linda.

[silvia]

you should contact the material/element authors for specifics.
however, i do believe that the rayleigh damping looks at the system mass and stiffness matrices and goes from them directly, without thinking about what each term means. you just have to decide which stiffness to use, and whether you want to use mass, stiffness, or both-proportional damping.