Economic losses and collapse probability are critical measures for evaluating the earthquake risk of existing buildings. In this context, this study sheds light on several problems and limitations in current practice of hazard-consistent ground-motion selection and fragility analysis, focusing on the impact that (commonly assumed) approximations in disaggregation outputs have on the aforementioned risk metrics, as opposed to an exact solution. These issues are investigated for several building classes, seismicity models and ground motion prediction equations (GMPE), for a site in the city of Lisbon (Portugal). It is observed that only an exact (i.e., rupture-by-rupture) disaggregation can lead to satisfactory results in terms of accuracy, when limit state criteria are not structure-specific. On the other hand, an approximate method is proposed, which still leads to statistically valid results regardless of the chosen structural class, seismicity model or GMPE.

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