Numerical Assessment of Bidirectional Roller Bearing Isolators under Near-Fault Earthquakes

Base isolation with roller bearing systems has been widely studied in recent years due to its successful performance in the seismic protection of buildings and bridges. This paper numerically evaluates the effectiveness of a bi-directional roller bearing (RB) seismic isolation system composed of sloped bearing plates and multiple rollers arranged in both orthogonal-in-plane directions. Previous experimental results obtained with unidirectional and bidirectional RBs were used to validate the 3D numerical model of an isolated building with RBs. The model was used to obtain the nonlinear response of a four-story multi-column building when subjected to pairs of scaled near-fault earthquake records. The effects of the bearing plate inclination angle (ranging from 1.0 to 4.0 degrees), the sliding friction force, and supplementary dissipation mechanisms (0.0-0.5 N/kg, i.e. friction force normalized with the structure mass) were evaluated. The results show that the proposed bidirectional RB system is suitable for reducing the seismic response of stiff and flexible multi-column structures. In particular, the RB system reduces the acceleration responses by 5-85% in flexible structures and by 86-96% in stiff ones. Furthermore, bearing plates with an inclination angle greater than or equal to 3.0 degrees have significant benefits in terms of self-centering capacity.