Abstract | In seismic risk assessment, one is often in need of employing fragility curves that are readily available in literature, rather than developing one’s own. Unfortunately, such fragilities are essentially summaries of the detailed intensity measure (IM) versus engineering demand parameter (EDP) information. When, as usual, the original data is not available, finding a way to disaggregate the fragilities back into the individual IM-EDP record responses can be useful. For example, it would allow converting them to arbitrary IMs. The authors have previously presented an idea of using equivalent single-degree-of-freedom (ESDOF) models to achieve this, showing acceptable results for global EDPs, such as roof drift. These global response parameters are typically governed by the fundamental eigenmode of the structure, and are thus easier to capture by the proposed ESDOF models. To further build upon this concept, different multiple-degree of freedom (MDOF) structure examples are examined, validating the results of fragility disaggregation and IM conversion for limit-states based on more localized measures of response, such as interstorey drifts or peak floor accelerations. The accuracy of the method is therefore further challenged, going after local EDPs via a proxy that discards the effect of higher modes. The target is to specify the limits of the proposed methodology and quantify the potential error
introduced by the method’s assumptions, evaluating its usefulness for such cases.