Nonlinear soil-structure interaction effects under strong ground motions should be considered in the seismic design of pile foundation. Inorder to investigate influence of nonlinear soil-structure interaction, the centrifugal shaking table tests considering the plastic behavior ofpile cap are conducted. This paper presents the damage evaluation method of pile cap based on the simulation analysis of the centrifugalshaking table tests, in which the effects of local nonlinearity of pile-soil system on the seismic behavior of pile structures are clarified. Themajor findings obtained from this study are summarized as follows; 1) The test results are precisely simulated by the 3-dimensional finiteelement analysis 2) the slip and separation behavior between the pile and the soil do not affects the seismic behavior of pile structures verymuch, so the test results are simulated by winklerian model analysis 3) the plasticity of pile cap emphasizes the influence of the grounddisplacement subjected to pile on ductility ratio at pile.
