Simplified soil-structure interaction analysis using efficient lumped-parameter models for soil

Efficient lumped-parameter models recently developed by the authors for generally representing the vibrations of foundations are applied in this study to perform simplified soil-structure interaction (SSI) analysis for seismic excitations. A number of important computational issues, especially the determination of an appropriate input motion modified from the foundation input motion, are discussed for effectively incorporating the lumped-parameter models with the structural parameters to represent the whole structure-foundation-soil system. It is found that the modification of the foundation input motion is dependent on the frequency and may increase to a significant level in the high frequency range. It is also demonstrated that the application of the lumped-parameter models can accurately represent the time responses of the actual SSI system. More specifically, since the adopted lumped-parameter models exhibit better accuracy in approximating the translational foundation vibrations than in the cases of rotational foundation vibrations, results from the numerical example indicate that relatively more significant error can be induced in conducting the simplified SSI analysis for the slender system.