The Effect of Varied Eccentricities of the Friction Pendulum Bearings on the Nonlinear Response of the Base-Isolated Asymmetric Buildings

After a strong earthquake, archetypes of earthquake-resistant structural systems suffer damages that cause irreparable human, financial, social and economic effects. Friction pendulum base isolation technique is a system to reduce seismic vulnerability using subsystem isolation. The base isolation layouts are less studied. A proper layout of friction pendulum bearing system (FPS) in base-isolated asymmetric buildings has been derived and confirmed using 12 bi-directional ground motions to estimate mean maximum response values for various eccentricities. The FPS bearings were divided into two models: conventional, where all bearings have the same curvature radius, and non-conventional, where some bearings have a different curvature radius or stiffness. The center of the radius of curvature for the non-conventional models was aligned with six different points, including the roof's geometric center, the center of cumulative mass in the base, and the center of rigidity in the first story. Additionally, the center of stiffness of FPS bearings coincided with the centers of the cumulative mass at base level and the rigidity of the superstructure in the first story. The results of the non-linear time history analysis show that, for a low superstructure eccentricity of %5, responses did not differ significantly among the nine configurations tested. At higher eccentricities, there was a significant difference between the responses of the different models. It is recommended that the stiffness center of all FPS coincide with the superstructure’s cumulative mass center for proper responses. This layout can be effective in improving the seismic performance of FPS-base-isolated asymmetric buildings. Graphical Abstract