A dual-mode floor isolation system to achieve vibration isolation and absorption: Experiments and theory

During the event of an earthquake, motion-sensitive equipment inside a building can be protected from seismic disturbance using a floor isolation system (FIS). Its response is unimpeded when it displaces within the allowable clearance, but when this gap is exceeded impacts are induced between the FIS and the displacement limit. This induced nonlinearity may create a non-negligible dynamic coupling between the primary structure (PS) and the FIS, which can possibly be tuned to reduce the PS responses during strong earthquakes. Moreover, the dissipation during impact can be augmented with a shock absorber. This research aims to evaluate the performance of the FIS as a vibration isolator when subjected to low-intensity earthquakes (i.e., before impact occurs) and as a vibration absorber when subjected to high intensity earthquakes (i.e., after impact occurs). Such a FIS is termed dual-mode vibration isolator/absorber system whose quantities of interest concern peak FIS acceleration and peak PS interstory drift when evaluating the isolation performance and the absorption performance, respectively. A lab-scale experimental approach is used to study the FIS performance when attached to the second story of the PS that is subjected to four historic ground motions. Predictions from a mathematical model of the coupled, nonlinear PS-FIS system are compared to the experimental results. The experimental and numerical data shows promising results that suggest the dual performance of the FIS is achieved.

Automated summary

This research evaluates the performance of a floor isolation system (FIS) as a vibration isolator and absorber during earthquakes. The experimental and numerical data suggest that the FIS achieves dual performance.