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The main activities and the relevant results of an experimental program aimed at evaluating the dynamic characteristics of a large seismically isolated building are described. The building is situated in Potenza (Italy) and is the largest of five seismically isolated blocks of the University of Basilicata. Cyclic shear tests on scaled isolators and some small amplitude free vibration tests were preliminarily carried out. The latter ones were aimed at getting a preliminary linear characterisation of the structure. Finally, many in situ release tests on the isolated structure were carried out, using a mechanical device purposely designed to statically move the building and then suddenly release it, thus making it vibrate freely. The variations of the dynamic characteristics of the system while the oscillation amplitude decreases have been evaluated by using the "Short Time Fourier Transform (STFT)". The results were elaborated in terms of stiffness and equivalent damping and compared to the results of the laboratory tests on scaled isolators, finding an excellent agreement.
Earthquake response of the elevated liquid storage tanks isolated by the elastomeric bearings is investigated under real earthquake ground motion. The tanks are isolated by implanting the isolation bearings at base of the tower structure. The isolation bearings considered are laminated rubber bearings with and without lead core. The force-deformation behaviour of the bearing without lead core is considered as linear while with lead core is represented by non-linear behaviour. The continuous tank liquid is modelled as lumped mass, which is referred as sloshing mass, impulsive mass and rigid mass. The corresponding properties such as stiffness and damping are evaluated using single-degree-of-freedom concept. For detailed investigation two types of the tanks are considered, namely slender and broad tanks. Furthermore, the response of isolated tanks is compared with corresponding non-isolated tanks, in order to measure the effectiveness of the isolation systems. In addition, the comparative study of performance of the two types of isolation systems revealed that non-linear elastomeric bearings are more effective in reducing the response of the elevated tank.