I am modeling the OWT for earthquake loading considering the soil monopile and tower structure using the Dynamic Explicit scheme. I have used the infinite element at the boundary in direction of earthquake loading and base is made rigid and the earthquake acceleration is being applied through the Reference Point (RF) used for rigid body at the base. the Tower and monopile is tied together with the help of coupling constraint. I have also used the Rayleigh damping of 5% for all tower monopile and soil. while job is completed when i am seeing the odb output the monopile as well as the tower are distorted in shape, even the expected displacement at the tower top is much lesser as compared to the displacement mentioned in the literatures. Anyone please help me for the same. 
Edu SIMULIA BIOVIA