Novel devices and strategies in earthquake protection of structures

The base isolation technique is one of the most widespread solutions for the mitigation of damage induced by seismic action on structures. The basic idea of this system is to disconnect the superstructure response from the ground motion by inserting appropriate mechanical devices placed between the foundation and the structure. Since generally the most significant component of the seismic action is the wave one, the isolation effect is achieved using devices generally characterized by a low horizontal rigidity combined with a high vertical rigidity, dictated by the need to withstand excessive static deformation for project loads. There are various horizontal isolation devices currently widespread on the market but nevertheless present unresolved problems. Moreover, it is widely documented in the scientific literature, as well as confirmed by recent seismic events (L'Aquila 2009 and Norcia of 2016) that if the structure is near the epicentre of the earthquake (near fault seismic event), the vertical component seismic waves is significant and may be the main cause of damage to structures. It is therefore necessary to reduce the vulnerability of the structures with respect to the vertical component of the seismic action. The insertion of the base isolation system has the effect that the displacement request induced by the earthquake is mainly absorbed by the isolation system itself, which should therefore be designed to withstand significant displacements. The aim of this PhD thesis was the proposal of new devices and strategies able to overcome the problems of existing isolation devices that are currently more widespread and also fill the technological vacuum currently present in the field of vertical isolation. In particular, a horizontal isolation device, called HFRI, has been proposed which exploits techniques and materials used in the most common devices on the market (elastomer, steel and friction dissipation), overcoming the problems related to them, and a vertical isolation device, called VID, that thanks to a particular geometry, use materials and techniques typical of horizontal isolators. Both devices are the subject of Italian patent applications. To overcome the problems related to displacement requests, an innovative passive vibration control system has been proposed based on the use of a mechanical device called inerter. Finally, a reinforcement for the interface material (PTFE) of the two studied devices was studied, by means of a glass fiber in order to increase the compressive strength.