Seismic Analyses of Viscously-Damped Structures With an Unbounded Foundation

The method of supplemental damping for dissipating seismic energy has been recognized as an effective and attractive way to reduce the seismic response of structures under seismic loadings. In recent years, an extensive number of structural control devices have been proposed to mitigate the vibration response of structures subjected to wind load and earthquake excitations. However, rare publications regarding the interactions between the soil and seismically damped structure have been unfolded. In order to ensure the safety of structures equipped with viscous fluid damper devices under seismic loadings, it is required to take into account the effects of radiation damping and the flexibility resulting from the unbounded soil media. In this study, two numerical methods, the consistent-infinitesimal finite element cell method and the quiet boundary method, have been proposed to simulate the radiation damping effects of far-field unbounded media. The numerical results show that the differences in seismic responses with or without unbounded media are significant. Therefore, it is illustrated that the radiation damping resulting form unbounded media should be taken into special consideration in seismic analyses.