Differences Between two uniaxialMaterials

[rmandok]

Hi dear Vesna and dear all.
Is ViscousDamper uniaxialMaterial different from defining Viscous uniaxialMaterial and stiffness material in series (Maxwell model)?
If there is difference, what are they? (I believe there is, because the results are not the same)
Which is preferred to use?
Consider this post:
http://opensees.berkeley.edu/community/ ... 421#p97421

and the response of code developer, below:

Dr. Dimitrios Lingos response:
"Dear Arman,

I hope you are doing well.
I checked your file and the problem is not the ViscousDamper material but the fact that you are using force based beam-column elements. These are the ones that are not converging. I switched to displacement-based beam-column elements and both options work fine.

I can run the analysis with no problems.

Best Regards,

Dimitrios Lignos"

[vesna]

ViscousDamper is a new material that I did not get a chance to test. You can either look at the source code for these two materials or you can contact Professor Lignos again.