Observed behavior of buildings seismically isolated with CSSs under a low energy earthquake

The observed behavior of four buildings, seismically isolated by means of curved surface sliders (CSS), under a moderate seismic event is analyzed in the framework of their structural health monitoring. The results showed that the CSS isolation systems were not activated for most of the buildings, even though the acceleration peaks in the superstructures were significant. The reason for this behavior is related to an inaccurate evaluation of the friction coefficients under the vertical loads acting on the devices in seismic conditions. Actually, vertical loads influence the friction and so the onset of motion. The importance of a continuous monitoring of the actual seismic behavior is also evident to analyze the structural health status of the devices and to plan maintenance interventions when needed.