Estimating fragility curves of pre-70 RC frame buildings considering different performance limit states

In seismic risk assessment, fragility (or vulnerability) curves are commonly used to express the likelihood that constructions (e.g. buildings) will sustain different degrees of loss over a range of earthquake ground motion intensities. In the paper, fragility curves for typical older residential RC buildings, realized in Italy and other southern Europe countries from the 50s to the early 70s, are derived following a hybrid approach. Fragility curves are expressed in terms of spectral acceleration. Median values for each damage state (or performance limit state) are estimated based on the results of comprehensive loss assessment analysis and the definition of a suitable loss index. Dispersions are evaluated based on the results of accurate inelastic dynamic analyses carried out for a number of archetype buildings at increasing levels of seismic intensity. A detailed discussion on the parameters that influence most the fragility curves, such as the number of storeys of the building, is provided.