3D Numerical Characterization Efficiency Assessment of RNC Isolator Experimental Prototypes

This paper numerically investigates the 3D behavior of a recently proposed seismic isolation system, referred to as roll-in-cage (RNC) isolator, when implanted into a bridge structure. The RNC isolator provides in a single unit all the necessary functions of rigid support, horizontal flexibility and energy dissipation characteristics in addition to and integrated by buffer mechanism. The goal of this study is twofold: first, to examine the main integrated mechanisms of the RNC isolator through sophisticated 3D finite element (FE) simulation models using a multipurpose FE code. The main result of this step is to attempt modeling force-displacement relationship using the Bouc-Wen model of smooth hysteresis. The second goal of this study is the numerical assessment of the device efficiency through its implementation into a bridge model considering several ground motions as external excitations. Based on these extensive studies, it was found that the RNC isolator is a robust isotropic horizontal isolation device for bridge structures. The force-displacement relationship is satisfactorily predicted by the unidirectional Bouc-Wen model of smooth hysteresis. The buffer mechanism can limit the bearing displacement under severe earthquakes stronger than the design earthquake. The no-uplift mechanism prevents the generation of vertical acceleration components out from the horizontal earthquake components.