How to assign structural damping to the soil domain

[sreedharrao144]

Sir,I am working on soil structure interaction problem.I could not give Rayleigh damping to the system.
rayleigh 0. 0. 0. [expr 2*0.02/pow([eigen 1],0.5)]; command is not working.If I give this command there is a runtime error.Then how to assign damping to the system.I performed linear time history analysis.It is a undamped case.I did not mention any damping in the code.But response I am not getting osilating pattern.Response keeps on increasing upto the end of ground motion.It seems there is no damping.How to assign damping to the soil system?

[fmk]

the rayleigh command is what is used to apply damping .. you can also use the region command if you want to have different factors on different parts of the domain .. did you spiy out what the values you use in the expression are to make sure they are not 0.0's .. if not 0.0's tell, the problem may lay in the elements you are using .. if so tell me the element types and materials you are using.

[jdong057]

thank you submit, that's a very goodness overview of the factors. It's invariably good