A Unit-level framework for Multi-storey seismic loss and risk assessment of buildings

Seismic loss assessment of residential buildings is commonly performed at the building or storey level, providing limited information on how risk varies between individual units within the same storey. This thesis develops a unit-level framework for seismic loss and risk assessment of multi-storey reinforced concrete residential buildings, with particular attention to torsional response and plan-position effects. The methodology extends existing storey-level loss functions to unit-level loss by distributing structural, drift-sensitive non-structural, and acceleration-sensitive non-structural losses using interpolated engineering demand parameters (EDP) at each unit centroid. This is based on the assumption that the floor is a rigid diaphragm, there is a linear variation of EDPs from stiff to flexible edge, and the unit’s response can be represented by the structural response at its centroid. The framework is applied to a six-storey reinforced concrete case-study building in Gemona del Friuli, Italy. Structural response parameters, including inter-storey drift ratio and peak floor acceleration, are obtained through three-dimensional nonlinear time-history analysis in MIDAS GEN NX using bidirectional ground-motion records selected in accordance with NTC 2018 limit states from REXELweb. The numerical model is validated against published dynamic properties of a comparable Italian reinforced concrete frame and then used to evaluate unit-level expected annual loss and expected loss ratio for unit risk rating classification. The proposed approach investigates how apartments located on different floors or at flexible-edge plan positions may experience different seismic risk levels due to torsional amplification and non-uniform demand distribution. By resolving seismic loss at the individual unit scale, the study supports more transparent retrofit prioritisation, improved insurance and risk communication, and a more detailed interpretation of building-level seismic risk classifications for owners and tenants.