GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 2.2 314 3.1.1 Identification of IM and EDP In order to consider the specific structural response under seismic load in a proper manner, different variables representing seismic intensity are considered: peak ground acceleration (PGA) and pseudo-spectral acceleration Sa(T1) corresponding to the fundamental period T1 (0.65 s). Moreover, in order to construct fragility curves, it is necessary to establish damage thresholds related to the specific structural element. Highlighting that the seismic behaviour of the façade depends strictly on the seismic response of the load-bearing structure and, in particular, may be subject to high stresses resulting from the interstorey displacements of the structure background. It is possible to foresee, in fact, that the most difficult condition to consider in the case of seismic analysis of the facades is related to the in-plane deformations, which takes interstorey drift as its reference parameter. 4 Results and conclusions In the field of structural engineering, the existing regulations classify curtain wall as non- structural element. For this reason, the façade is required to be able to accommodate the relative seismic displacement (D p ) of the structure for a selected limited state. The most widely used investigation methods refer to the methods reported by the American Architectural Manufactures Association (2001), which, in accordance with the American code, Fig. 3 - Fragility curves with respect to (a) S a (T 1 ) and (b) PGA.