GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 2.2 249 in particular, the study resulted in up to 25 m 2 of covered surface and around 2350 kg for the facade components (of which around 310 kg of glass). The experimental analysis and interpretation of OMA results with the support of a validated structural FE numerical model (ABAQUS/Standard) also confirmed that monolithic glass panels have 5 mm of total thickness only (Fig. 2(f)), which is not in line with current requests as in CNR-DT 210/2013. This finding was confirmed by fundamental vibration frequencies of the system as in Fig. 2(f), with f 1 ≈ 6.5 Hz for the envelope as a whole. In terms of seismic analysis, according to CNR-DT 210/2013 recommendations, the primary construction falls in fact in a Class of use III (i.e., relevant buildings with possible overcrowding), with V N ≥ 50 years. Most importantly, the design tensile strength of glass under seismic action should be calculated as: (1) with f g;k = 45 MPa; k mod depending on the loading time (1 for instantaneous loads, 0.78 for transient seismic loads); R M = 1 for second-class annealed glass; g M = 2.5 for annealed glass. When the resistance check is carried out at a distance d from glass edges which is at least equal (or higher) than 5 s = 25 mm (with s = 5 mm the thickness of glass), it is assumed that k ed = 1 and l gl = 1. Further, k sf = 1 for float glass. Finally, l gA is comprised between 0.75 and 1, to account for the area of glass under maximum stress and the statistically higher probability of the presence of defects in glass. Worth to note that for d < 5 s , Eq. (1) suggests that k ed → 0.7 (for annealed glass); λ GA → 0.75; λ gl < 1 (depending on size of glass and load pattern), thus reducing even down to ≈-50% the reference strength value for seismic verification. Overall, the reference value for the resistance check to take into account for the present study should be assumed equal to ≈14 MPa ( d > 5 s ) and ≈10 MPa ( d < 5 s ). Further, the limit out-of-plane deflection for SLD (monolithic glass with linear supports at the edges) was derived equal to u lim,out = L /60≈ 40 mm (with L = 2.58 m the minimum size of central glass panel). Fig. 2 - Examined glass envelope: (a)-(b) context view in the CID museum; (c) front view, with dimensions in cm; (d) detail of frame-to-glass connection (dimensions in mm); (e) in-field OMA investigation (Spring 2022); (f) Finite Element numerical model (ABAQUS).