Seismic fragility curves for the Italian RC residential buildings based on non‑linear dynamic analyses

In the present paper, Fragility Curves (FCs) of Reinforced Concrete (RC) building types with moment-resisting frame structure representative of the existing Italian building stock have been derived through an analytical approach. The proposed methodology is based on Non-Linear Dynamic Analyses encompassing all the steps required to bring about reliable as well realistic fragility results. First, prototype building types have been selected by considering the main attributes affecting the seismic vulnerability of existing RC buildings, that is: age of construction (i.e. ‘50 s, ‘70 s and ‘90 s), number of storeys (i.e. 2, 4 and 6 storeys), arrangement in elevation of infills (i.e. Bare-, Infilled-, Pilotis-frame) and design level (i.e. seismic or gravity loads). A simulated design has been used for detailing the building types at hand, whose non-linear dynamic response has been computed by using a large set of signals. The signals have been purposely selected in order to approach the elastic design spectra provided in the Italian seismic code for different return periods, being able to take into account also record-to-record variability and soil-amplification effects. A specific relationship between the considered engineering demand parameter (i.e. interstorey drift ratio) and all damage levels proposed in the EMS-98 scale have been defined on the basis of empirical data and expert judgement. A set of FCs in terms of peak ground acceleration are finally derived and compared to point out the role of the considered vulnerability attributes.