COMPDYN 2017 6 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.) Rhodes Island, Greece, 15–17 June, 2017 NUMERICAL ASSESSMENTOF CONCAVE SLIDING ISOLATOR’S MECHANICAL BEHAVIOR UNDER BI-DIRECTIONAL MOTION Dario De Domenico 1 , Giuseppe Ricciardi 1 , and Gianmario Benzoni 2 1 Department of Engineering, University of Messina Contrada Di Dio, 98166 Sant’Agata, Messina, Italy e-mail: dario.dedomenico@unirc.it, gricciardi@unime.it 2 Department of Structural Engineering, University of California San Diego, La Jolla, California, 92093-0085, USA e-mail: gbenzoni@ucsd.edu Keywords: Friction pendulum system (FPS), seismic isolation, multi-directional excitation, friction coefficient degradation, finite element model, coupled thermo-mechanical analysis. Abstract. In this contribution, some aspects of the mechanical behavior of friction pendulum (FP) isolators are investigated from a numerical point of view. Attention is focused on the dis- tinctive features observed in FP bearings when subjected to multi-directional excitations like those occurring in a real earthquake scenario. Due to the peculiarities related to the kinematics of the device and the curvature of the sliding surface, neglecting the bi-directional interaction and considering a uni-directional idealization would lead to underestimate the displacements expected during seismic events and to overestimate the dissipative capacity of the isolator ac- cordingly. Furthermore, the resultant horizontal force of the FP bearing may differ markedly from what expected (and predicted by most numerical models) in the uni-directional case. This deviation is mainly ascribed to the geometrical features of the device itself. Additionally, the force-displacement behaviour of the FP bearing depends upon the coefficient of sliding fric- tion, which is not constant as postulated by the simplified Coulomb model but varies during the course of an earthquake with sliding velocity, vertical load and, above all, repetition of cycles and consequent heating phenomena arising at the sliding interface. Among these ef- fects, frictional heating has been recognized as the most important factor that affects the FP maximum displacement because it may induce significant friction degradation, consequently it should be properly considered in a truthful model of the FP bearing via a sophisticated coupled thermo-mechanical analysis. The aim of this paper is to scrutinize the above physical phenomena by means of a 3D finite element model. The developed model allows us to closely analyze the kinematics of the device, to assess the contact force distribution between the sliding surfaces and to examine certain nonlinear phenomena that become manifest especially during bi-directional excitations. 4288 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 4288-4305 © 2017 The Authors. Published by Eccomas Proceedia. Peer-review under responsibility of the organizing committee of COMPDYN 2017. doi: 10.7712/120117.5724.16749