Comparative Experiment and Analysis of a Base-Isolated Structure with Small Aspect Ratio on Multi-Layered Soft Soil Foundation and Rigid Foundation

Abstract

Through conducting a comparative experimental study of small-aspect-ratio isolated structure models on multi-layered soft soil foundations and rigid foundations, this paper investigates the influence of soil–structure interaction (SSI) effects on the seismic response of small-aspect-ratio isolated structures on multi-layered soft soil foundations. An energy balance equation for isolated structure systems considering SSI effects is proposed, and the impact of SSI effects on the energy dissipation response of small-aspect-ratio isolated structures on multi-layered soft soil foundations is analyzed in depth. The analysis results reveal that SSI effects on multi-layered soft soil foundations reduce the first-order natural frequency of the isolated structure system and significantly increase the damping ratio of the system. Furthermore, the rotational effect of the isolated structure foundation is significant on multi-layered soft soil foundations, and the isolation layer has a certain amplification effect on the rotational effect of the foundation. The study shows that SSI effects on multi-layered soft soil foundations may either increase or decrease the seismic response of isolated structures. Moreover, due to the influence of SSI effects, the ratios of kinetic energy, damping energy dissipation, and hysteresis deformation energy dissipation of the isolated structure on multi-layered soft soil foundations are significantly different from those on rigid foundations. The research concludes that the influence of SSI effects is more significant during large earthquakes, where the ratios of kinetic energy and damping energy dissipation of the isolated structure increase, the hysteresis deformation energy dissipation ratio of the isolation layer decreases, and the magnitude of the decrease is related to the characteristics of the input seismic motion. This research has significant implications for improving the seismic design theory of small-aspect-ratio isolated structures on multi-layered soft soil foundations.