Protecting vibration-sensitive contents: an investigation of floor accelerations in seismically isolated buildings

For the public welfare and safety, buildings such as hospitals, industrial facilities, and technology centers need to remain functional at all times; even during and after major earthquakes. The values of these buildings themselves may be insignificant when compared to the cost of loss of operations and business continuity. Seismic isolation aims to protect both the integrity and the contents of a structure. Since the tolerable acceleration levels are relatively low for continued services of vibration-sensitive high-tech contents, a better understanding of acceleration response behaviors of seismically isolated buildings is necessary. In an effort to shed light to this issue, following are investigated via bi-directional time history analyses of seismically isolated benchmark buildings subject to historical earthquakes: (i) the distribution of peak floor accelerations of seismically isolated buildings subject to seismic excitations in order to find out which floors are likely to sustain the largest accelerations; (ii) the influence of equivalent linear modeling of isolation systems on the floor accelerations in order to find out the range of possible errors introduced by this type of modeling; (iii) the role of superstructure damping in reducing floor accelerations of seismically isolated buildings with flexible superstructures in order to find out whether increasing the superstructure damping helps reducing floor accelerations notably. Influences of isolation system characteristics and superstructure flexibility are both taken into account.