Strategies of Identification of a Base-Isolated Hospital Building by Coupled Quasi-Static and Snap-Back Tests

In this paper, the description of a series of quasi-static pushing tests and dynamic snap-back tests is proposed, involving the base-isolated emergency building of the Palermo university hospital. The base isolation system is characterized by a set of double-curved friction pendulum isolators placed on the top of the columns of the underground level, characteristics that cannot be found in the experimental studies available in the literature. The aim of the work was to investigate the static and dynamic properties of the building in question and comparing the in-situ results with the characteristics assigned during the design process and to assess the level of agreement. Static lateral pushing tests were aimed at identifying the main mechanical properties of the whole isolation level (e.g. friction forces and stiffness). Moreover, dynamic snap-back tests were carried out for different levels of displacement to characterize the dynamics of the building and the re-centering capacity of the isolation system. The design of the field testing, comprising the thrust mechanical device and the reaction RC wall, is described along the paper followed by the description of the in-situ testing and its main results. Then, the role of the in situ tests in proving the structural reliability and how to choose/use them in the case of friction pendulum base-isolated structures are discussed.