Validation of Physics-Based Simulated Accelerograms for Seismic Fragility Analyses of Italian RC Existing Building Types

This article aims at exploring and validating the use of 3D physics-based simulated ground motions as seismic input for the derivation of seismic fragility curves based on nonlinear dynamic numerical analyses. Fragility curves are computed for a set of pre-code (i.e., designed only for vertical loads), reinforced concrete building types representative of the Italian existing building stock, with fundamental vibration period between about 0.1 and 1.0 s, using two alternative sets of input signals from either recorded or simulated datasets. This latter dataset, named BB-SPEEDset, consists of broadband earthquakes ground motions obtained from the 3D physics-based numerical simulation of seismic wave propagation of several earthquakes worldwide in realistic geologic contexts. The comparison between the fragility curves obtained from these two sets of ground motion time histories (records vs. simulations) highlights that, when ground motion intensity measures deemed efficient for the considered buildings, such as peak ground velocity, average spectral acceleration and Housner intensity, are adopted, simulations provide results in very good agreement with recordings, with differences on the dispersion values less than about 10% on average.