Seismosoft | Earthquake Engineering Solutions

Hello, i use two different programs (Seismostruct and Opensees) to model a linear oscillator with fixed base, i lunch a time history and the two programs give me the same results, but if i consider a non-fixed base (Soil-structure interaction problem) for my oscillator, composed by a dashpot and a spring (using the same parameter in both programs) results are not equal: the phase of displacement is the same, the only difference is in the peak of displacement.
Now, i tried to model the soil-foundation problem only with springs, and the results are equal in every way. The problem seems to be the dashpot, but the strange things is that only the peak is different, phase and period of the motion are the same.Any ideas?

Dear Bassking,

By your description, something strange is happening indeed. If the same stiffness and different damping was being assumed in both cases, there should also be a phase difference between them... Unfortunately, I would need more information on your models in order to give you a better answer. You can also try the modelling option I suggested you in your other query.

Best regards,
Antonio