HYBRID TESTING OF SEISMIC ISOLATED STRUCTURES: FACING TIME AND GEOMETRY SCALING ISSUES

Hybrid Testing is becoming very popular within the most advanced testing techniques; the use of sub-st r cturing further enhance the appeal of such testing method, allowing cost effective full scale tests. Full scal e specimens, in fact, generally require large testing installati ons, high force and displacement capacity. On the other hand, full or large scale specimens ar e often necessary in civil engineering field, to av id distortions due to the concrete mix, rebars availability and me chanical characteristics, elements realistic damage and failure mechanisms. In some cases, scaling induces distorti ons hat cannot be effectively compensated; this is typically the case of some isolation devices, such as CurvedSurface Slider (CSS) bearings. Experimental data of seismic isolated structures is still very limited, mainly because of the above me ntioned test requirements. In addition, since base isolation is w dely recognized as one of the most effective seis mic protection strategy (Dolce and Cardone 1999), new d vices are continuously proposed by the manufacture rs, therefore needing accurate experimental validation. The above reasons underline the importance of reli abl experimental testing of isolated structures. Standa rd characterization tests give important informatio n on the device response, while the structural context is al most neglected. In this contribution, the topic of reliable and cos t effective experimental testing of seismic isolate d structures is addressed. The attention is mainly focused on the s caling possibilities considering both time scale an d geometry. The proposed approach is supported by the experimen tal vidences of the dynamic hybrid testing campaig ns carried out at EUCENTRE (European Centre for Traini ng and Research in Earthquake Engineering) of Pavia , Italy, in the last 5 years. The aspects related to the reliability of the numerical sub-structure and the improvement possibilities are discussed as well. Future perspec tive of experimental testing of structures equipped with the most advanced nowadays available seismic devices ar e illustrated