On the utility of story loss functions for regional seismic vulnerability modeling and risk assessment

Vulnerability functions relate loss to seismic intensity and can be developed via several approaches. They are a fundamental part of seismic risk assessment on a regional level and support decision-making and intervention strategies aimed at reducing risk. This article discusses a prominent analytical approach to developing seismic vulnerability models for buildings based on equivalent single-degree-of-freedom (SDOF) modeling, fragility function, and damage-to-loss model integration. The fundamental assumptions are scrutinized, and their principal drawbacks are highlighted. An alternative approach also based on an equivalent SDOF modeling approach is discussed but instead capitalizes on story loss functions (SLFs) as a means to more accurately compute economic losses and their sources. The main benefit is that the contribution of floor acceleration-based losses can be directly considered, and the disaggregation of losses is fully represented. A case study comparison is presented to highlight the similarities and key benefits. It is seen that the SLF-based approach can provide a much more comprehensive means to compute and communicate loss contributions among different element groups (i.e., structural, non-structural, and contents) and individual stories along the building height. Existing models can simply be adjusted to this approach and provide a more holistic view of risk. The benefits and potential applications in the (re)insurance sector are also discussed.