3D nonlinear seismic analysis and design of base-isolated buildings under near field ground motions

The structural performance of base-isolated buildings during past earthquakes confirmed the suitability of Lead Rubber Bearing (LRB) isolators. To assess the effectiveness of such isolators, 3D base-fixed and associated base-isolated models of a multi-story building are performed for three components recorded at each of the three stations with the closest distances to the seismic fault of approximately 5.54, 11.39, and 17.82 km during the 6.7 Mw Northridge earthquake in 1994. In this study, we discuss important issues regarding the analysis and design of base-isolated buildings under near-field ground motions at both the Design Basis Earthquake (DBE) and Maximum Capable Earthquake (MCE) levels. The results demonstrate that although the shear strain and stability conditions are fulfilled, it is crucial to satisfy the rollout condition requirements because of the large isolator displacement at MCE level while utilising supplemental viscous dampers to improve the desired efficiency of isolation.