Investigation of Isolation Systems with Geometrically Nonlinear Damping for Seismic Protection of Sensitive Equipment

Investigation of Isolation Systems with Geometrically Nonlinear Damping for Seismic Protection of Sensitive Equipment

Earthquakes pose risks to sensitive equipment in a structure and may sometimes result in significant economic losses. A widely utilized technique to mitigate seismic responses involves the installation of an isolation system underneath such equipment; however, excessive displacements along isolation layers may occur during severe earthquakes. It is recommended that viscous dampers be included with the isolation layer. However, this combination is only designed for earthquakes of a certain magnitude and may not be effective for small or moderate earthquake events. In this study, an isolation system with geometrically nonlinear damping is developed to mitigate the seismic responses of important equipment. For example, this system provides a better reduction in acceleration responses during small to moderate earthquakes, while excessive displacement responses can be effectively reduced during severe earthquakes. To understand the dynamic behavior of this system, a series of investigations is carried out. Considering the dynamic characteristics, the control force surface is first generated in terms of displacement and velocity to determine the contributions of the geometric nonlinearity. Moreover, this isolation system is investigated under harmonic excitation to understand its generalized frequency-domain performance. The control effectiveness of the proposed isolation system is also evaluated under non-periodic excitations, such as earthquakes, and the results are compared with those of conventional isolation systems. The results show that seismic isolation with a geometrically nonlinear viscous damper can be effective and adaptive at all levels of earthquakes.