The safe post-earthquake functionality of critical facilities like healthcare structures is one of the primary concerns because of their importance in emergency response management. The integrity of structural and non-structural components (NSCs), utilities, and medical equipment is pivotal in maintaining the serviceability of healthcare facilities. Minor structural damages can compromise the integrity of NSCs and equipment, potentially resulting in failures that disrupt functionality and lead to public issues such as delays in medical care or interruptions in essential services. Moreover, installation and maintenance costs for healthcare equipment are substantial (1.5 to 1.9 times the construction cost), underscoring the need for comprehensive seismic design practices. Despite guidelines (NDMA, 2016) recommending base isolation in high-risk seismic zones, its implementation remains limited. This limitation exposes healthcare infrastructure to vulnerability, particularly noteworthy as over 75% of hospitals in India are located in medium to very high-risk seismic zones.
Therefore, this research aims to assess the robustness of the isolation design procedure (IS 1893 Part-6, 2022) and the effectiveness of base isolation technology in critical healthcare facilities. The study utilizes three specific types of isolators: Lead Rubber Bearing (or New Zealand-Bearing, NZ-B), Single Friction Pendulum Bearing (SFPB), and Triple Friction Pendulum Bearing (TFPB). A comprehensive parametric investigation includes effective isolation periods (2 s, 2.5 s, and 3 s) and effective isolation damping levels (10%, 20%, and 30%). The building models are designed to incorporate structural plan irregularities, focusing on re-entrant corners and torsional irregularities prevalent in typical hospital architectural plans. The modeling and analysis employ the ETABS and OpenSees platforms, with nonlinear time history analysis performed on three-component ensembles of 60 seismic records (30 Near-field and 30 Far-field). The research aims to verify the isolation design procedure and enhance the overall response estimation of isolated structures by considering axial force variations during seismic events, addressing a limitation in current isolation design guidelines that assume constant axial bearing force. The study also explores the Floor Response Spectrum (FRS) for base-isolated structures, a crucial tool for assessing the seismic performance of NSCs and their design. The expected outcome is to improve post-earthquake functionality and seismic design practices for health facility structures, ensuring safety and protecting vibration-sensitive medical equipment.