A fundamental issue that arises in the framework of probabilistic seismic risk analysis is the choice of ground motion intensity measures (IMs). A new structure-specific IM, namely, relative average spectral acceleration (ASAR), is being proposed herein, and a comparison with current IMs is performed based on (1) a large data set of recorded earthquake signals; (2) numerical analyses conducted with state-of-the-art finite element (FE) models, representing actual load-bearing walls and frame structures, and validated against experimental test; and (3) systematic statistical analyses of the results. According to a comparative study of the case of nonlinear structural behavior, the ASAR proves to be the most efficient IM with respect to demand parameters, such as maximum interstory drift, frequency drop and maximum ductility demand. Beyond the sufficiency and simplicity of its formulation, which allow for the use of existing ground motion prediction models, the ASAR offers a promising IM for performance-based seismic design and/or assessment.

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