Seismic Resilience of Hospital Buildings with Soft Stories: A Probabilistic Vulnerability Analysis

Hospital structures featuring soft stories—marked by substantially reduced lateral stiffness at ground level—exhibit heightened vulnerability to seismic forces, critically compromising post-disaster functionality. Seismic resilience, defined as a system’s capacity to absorb earthquake impacts, sustain essential operations during events, and rapidly restore normalcy, forms the core focus of this study. The research employs probabilistic vulnerability analysis to evaluate resilience in such buildings, developing fragility curves across four seismic hazard levels. Through incremental dynamic analysis, collapse vulnerability was assessed for Olive View Hospital’s Wing D—a soft-story structure modeled with nonlinear material behavior. Three configurations were examined: the original wing design, a frame model, and a shear wall model. The investigation uniquely prioritizes nonstructural components (NSCs) (drift- and acceleration-sensitive elements), historically neglected in seismic studies, while analyzing how abrupt stiffness discontinuities at the second story amplify interstory drift ratios. Beyond conventional structural assessments, this work introduces a novel resilience index quantifying hospital functionality loss through: (1) nonstructural component damage quantification; (2) downtime estimation; (3) functional recovery curve modeling; and (4) probabilistic serviceability metrics. Key findings reveal that nonstructural component losses consistently exceeded structural damage across low-to-high seismic intensities. The framework demonstrates that post-earthquake operational capacity depends critically on mitigating nonstructural failures, providing a paradigm shift in hospital seismic resilience evaluation. This methodology offers healthcare administrators and engineers actionable metrics to prioritize retrofitting strategies that safeguard life-sustaining functions during seismic events.