COLLAPSE RISK OF ITALIAN BUILDINGS COMPUTED USING AVERAGE SPECTRAL ACCELERATION

Abstract eng:
Average Spectral Acceleration, AvgSA, has been proven to be a promising Intensity Measure (IM) for the prediction of both deformation-related Engineering Demand Parameters (EDPs), such as Maximum Interstory Drift Ratio (MIDR), and acceleration-related EDPs, e.g. Peak Floor Acceleration (PFA), along the height of the building in the entire range of post-elastic response. Replacing the typical spectral acceleration, Sa, with AvgSA in the framework of a Conditional Spectrum (CS) based record selection, guarantees hazard consistency (as a result of the CS method) and also higher efficiency in predicting multiple EDPs, which are required for probabilistic seismic demand analysis (PSDA) and loss estimation. The impact of using AvgSA for single building risk assessment will be evaluated for two buildings with different structural characteristics: a 2-story masonry building and a 6 story RC soft-story frame. We will consider three different variants of these structures designed for the Italian cities of Milano, Napoli and L’Aquila characterized different hazard levels. After convolution with the site-specific seismic hazard, we will compare and contrast different estimates of the nominal annual rates of collapse and of exceeding other less severe limit states. The different estimates will be obtained using the same approach, namely convolution of site specific seismic hazard with probabilistic structural response based on stripe analysis of hazard-consistent ground motion records selected based on the CS approach. However, in one case hazard and ground motion selection will be based on AvgSA and in the other cases hazard and ground motion selection will be based on two sets of different but plausible choices of period-specific Sa’s as intensity measure.

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