Significance of ground response effect in piles under earthquake loading

Several instances of damage at intermediate part of piles during the Hyogoken-Nambu earthquake have been clearly identified. Such damages are inherently difficult to detect, and even more difficult to repair, and it is imperative that such damages should be as unlikely as possible. Nonlinear soil structure interaction (SSI) analysis with 2-D FEM model, as well as a simpler analysis with 1-D lumped mass model, provide consistent results concerning the potential and significance of ground response effects responsible for higher moment and shear in the intermediate part of the piles. The ground response effect is not accounted for in the current design practice. The proposed simple approach to evaluate the ground response effect is found to give results compatible with the 2-D and 1-D SSI analysis, indicating that the approach may be development and refinement for application to design practice. Further research needs are identified and emphasized.