Evidence-based seismic performance assessment of non-structural components in fixed-base and base-isolated hospital buildings using monitoring data

Abstract

Hospitals are critical facilities that must remain operational during and after earthquakes. However, the seismic vulnerability of non-structural hospital components (NSCs), which often determines post-earthquake functionality, is usually estimated using analytical or code-based demand models rather than quantified using observed earthquake data. This study presents a quantifiable, evidence-based assessment of the real earthquake performance of fixed-base and base-isolated hospital buildings using monitoring data. A representative set of hospital buildings in California was examined, including both isolated and non-isolated configurations with different isolation systems and site conditions. Multi-site strong-motion records were analyzed to evaluate ground- and floor-level accelerations, displacements, inter-story drift ratios (IDRs), fundamental periods and response spectral characteristics over a range of seismic intensities. The measured demands were then directly compared with the established acceleration- and drift-based NSC damage thresholds, as well as the roof-level design response spectra. The results show that fixed-base hospitals often exceed critical NSC thresholds due to significant roof acceleration amplification, high IDRs and substantial high-frequency transmission. In contrast, base-isolated hospitals consistently maintain floor accelerations and IDRs below critical NSC limits, demonstrating effective low-pass filtering and reduced exceedance potential.