Seismic performance of a structure with double concave frıctıon pendulum ısolation system.

An extensive experimental seismic testing programme, named project JETBIS (Joint Experimental Testing of Base Isolation Systems), has been developed within the RELUIS (2010-2013) project - Task 2.3.2, involving partners from different Italian universities. This paper describes the tests performed on seismic devices based on Double Concave Friction Pendulum (DCFP). In order to assess the fidelity of the considered non-linear model under uni-directional motion, controlled-displacement and seismic-input experiments were conducted using shaking table at University of Basilicata and at University of Naples “Federico II”, respectively. The DCFP isolator contains two separate concave sliding surfaces and exhibits different hysteretic properties at different stages of displacement. The numerical model of DCFP used is general so that no condition regarding bearing properties, which effect the sequence of sliding stages, are required for the validity of the model. The experimental model for seismic tests was a 1/3 scaled steel framed structure with one storey and one bay in both directions. Four DCFP bearings with equal properties of the concave sliding surfaces were mounted under each column. The main objective of this work is to evaluate the effectiveness of nonlinear modelling considering two different finite element programme SAP2000 and CDS-Opensees to investigate on influence of the sliding velocity and of the vertical load on the behavior of DCFP devices under different condition of the sliding surfaces (with and without lubrication). A further goal was to verify the reliability of the numerical models also when large residual displacements due to previous earthquakes are present in the isolation system. In this paper the experimental outcomes of various testing model configurations are compared with the results of non linear dynamic analyses obtain by both numerical simulations.