Absorbent Boundaries

[partla]

I use this method for a geotechnical model as absorbent boundaries. But in the boundaries I get large strains. What's the problem? I'll be happy hearing from you.

set DampP [expr $ro*$vs]
set DampN [expr $ro*$vp]
uniaxialMaterial Elastic 1 0 $DampP
uniaxialMaterial Elastic 2 0 $DampN
node 1 16.0 0.0
node 2 16.0 0.0
fix 2 1 1
element zeroLength 1 1 2 -mat 1 2 -dir 1 2

[fmk]

the command you are using is correct. the strains must be non-zero otherwise the strain rate would be 0 and the dashpots would not contribute anything. As for the material parameters you are using, you may be missing an area term.

[partla]

thanks for your reply. The model of my project is 2D and size of quad elements (soil elements) are about 1 meter. Because of that the area term is missed. The strain rate is about 0.05 in the boundaries. Is it so large or logical?