Seismic performance of attached equipment in a base isolated building

Document Type

Conference Proceeding

Publication Date


Publication Title

NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering


Base isolation is an increasingly common approach to reducing the damaging effects of earthquakes on a structure and its contents. As application of base isolation becomes more commonplace, new devices and technologies continue to be introduced aiming to improve the economics and effectiveness of the system. Although it is widely accepted that base isolation is effective in protecting the structure, the influence of the isolation system on the contents of the structure is less clear. In this paper, the seismic performance of attached light equipment in a base isolated structure is assessed using floor response spectra. Two types of isolation systems are considered: Triple Friction Pendulum (TFP) and Stable Unbonded Fiber Reinforced Elastomeric Isolator (SU-FREI). The hysteretic responses of TFP and SU-FREI systems share similar basic characteristics, notably both systems exhibit a softening and stiffening response. This adaptive behavior is often considered advantageous: the softening increases the shift in the fundamental period of the structure, reducing the base shear, interstorey drifts and floor accelerations; whereas the stiffening limits the displacement of the structure in events meeting or exceeding the maximum considered earthquake. The systems are compared in terms of the peak isolator displacement, interstorey drifts and peak floor acceleration. It is shown that the floor spectral acceleration of a base isolated structure with a TFP system is larger than a SU-FREI system in the frequency range of typical equipment.