ssi-boundary conditions

[kgkoktsi]

Dear all,

I'm trying to simulate a soil-structure iteration system (ssi) but I have some questions concerning the boundary conditions of that problem.
I simulated the soil system as it is proposed in the site of opensees with the use of the quadrilateral elements and the dashpots.
"http://opensees.berkeley.edu/wiki/index ... nalysis%29"

Does anybody know if I should use other boundary conditions for the gravity analysis (i.e. to fix both the x and y directions of the base soil nodes with no use of dashpot) and other boundary conditions for the dynamic analysis (i.e. to fix only the y direction of the base nodes with the use of dashpot and the necessairy equal DOF for dashpot and base soil nodes) ?

Thanks in advance!