Earthquake motion filtering effect by pile foundations considering nonlinearity of soil and piles

In recent years, Japan has experienced an increasing number of short-period-dominated, high-acceleration earthquake motions. These strong motions, however, have caused only a limited damage to structures founded on piles. Among the possible reasons for the limited damage is the earthquake motion filtering effect of pile foundations. This filtering effect has been amply examined in numerous studies, most of which are based on an assumption that both the soil and piles behave linearly. This linearity-based approach, however, cannot be fully applied to strong earthquake motions as they essentially involve nonlinearity of both the soil and piles. With such considerations, the current work assesses the impact of nonlinear behavior of soil and piles on the filtering effect of pile foundations. As a first step, the filtering effect produced by a lumped mass model is examined for validation against the closed-form solutions. Secondly, dynamic analysis is conducted considering nonlinear behavior of soil and piles on the filtering effect. Finally, the impact of the filtering effect on the response of structures is examined using short-period-dominated earthquake motions.