Derivation of seismic fragility curves of a gravity-load designed RC school building through NLTHA

School buildings are considered relevant structures and their safety towards seismic actions shall be verified in consideration of the significant consequences of their collapse. With reference to Italy, most reinforced concrete (r.c.) schools were built after the second world war and in the later years of the economic boom, before a widely applied seismic regulation. In fact, seismic classification of Italy was a long process developing throughout the XX century, with significant areas which were not considered seismic until the early 2000s. The paper presents the evaluation of the seismic behavior of a representative 2-story Italian r.c. school building designed for gravitational loads only, and the derivation of a fragility curve set describing the seismic behavior of the macro-class of buildings. A series of NonLinear Time History Analyses (NLTHA), with sets of natural ground motion records of increasing intensity, were implemented on two fiber models, developed in Midas GEN, representing the bare frame (BF) and the infilled frame (IF) configurations, respectively. Inter-story drift ratio (IDR) was chosen as demand parameter to identify the Damage State (DS) exceeded by each analysis and explicitly calculated for the analyzed structure. Fragility curve sets, describing five increasing DSs, were derived, for both the BF and the IF configurations, through the statistical processing of NLTHA results. A comparison of the calculated fragilities, between BF and IF models, is finally provided.