Seismic Isolation of Sensitive Equipment

Abstract eng:
Seismic isolation has been used effectively over the past three decades to protect contents of structures and maintain the functionality of buildings. In recent years, there has been a growing interest in isolating only specific floors within buildings or select equipment. Isolating equipment poses unique challenges due to the relatively light mass supported by the isolators and the consequent need for isolator stiffness that is two to three orders of magnitude lower than conventional isolation. Moreover, space constraints inside the buildings and around the equipment require innovative solutions to accommodate the required isolation hardware. This paper discusses seismic isolation of equipment using a patented multi-directional spring. This innovative spring provides damping and self-centering capability while occupying much smaller space than conventional method of using orthogonal springs and dampers. This system was extensively tested on shake tables at the University of Nevada, Reno, SUNY University at Buffalo and the University of California, Berkeley. Over 300 seismic tests demonstrated the effectiveness of the system, which lowered accelerations transmitted by a factor of three or more. The system has been used in the US, Canada, Costa Rica, Venezuela and Ecuador. Size of applications ranges from a fully isolated floor of 1500 sq. m. to a single platform of 0.5 sq. m. In multiple modular format, the system was used to protect the super computers at the Lawrence Berkeley Labs where an entire 1500 sq. m. floor was isolated. In this case, the isolated floor was a physical substitute to the raised access floor (1220 mm tall). Moreover, the system provide a displacement capacity of 460 mm, while accommodating cables, cooling & sprinkler lines underneath. At the other end of the spectrum, individual platforms have been isolated to protect sensitive equipment in the Public Safety Building in Salt Lake City. These platforms provided a lateral displacement capacity of 610 mm, while measuring merely 180 mm in height. In a unique application for a control building on top of a dam in Canada, three-dimensional isolation was designed to protect critical control equipment from large accelerations generated from amplification through the extremely rigid dam structure. Other applications, such as isolation of statues located in a park and containerized data centers, show the wide potential of this system’s ability to be used in outdoor conditions exposed to elements.

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