ON THE BEHAVIOUR OF BUILDINGS WITH CURVED SURFACE SLIDERS: CONSIDERATIONS AND PRELIMINARY ANALYSES

As well-known seismic isolation is based on the terrific reduction of the seismic actions, which affect the structure, instead of relying on its strength. This result is obtained by increasing the fundamental period of vibration of the building, so that it becomes less vulnerable to earthquakes. In fact, thanks to the filtering due to the seismic isolation system the superstructure is loaded by low effects that can be supported in the elastic range. All the structures protected by seismic isolation exhibited an excellent behaviour with no or very low damage, even under severe earthquakes, demonstrating that seismic isolation is a reliable technology, ready for a large application. As a matter of fact, the number of applications of seismic isolation is increasing all over in the world. Approximately 20,000 structures in the world are protected by new anti-seismic techniques, such as seismic isolation and energy dissipation systems. In this paper the attention is focused on application of curved surface sliders. These have a cost lower than that of the elastomeric isolators and present quite interesting characteristics, such as the automatic coincidence between the gravity mass center and the isolation stiffness center. In practice this characteristic could be not effective due to differences in sliding friction values. Furthermore the uplift of the structure could cause the loss of contact in some devices. These aspects are analyzed and discussed in this paper.