GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 2.2 346 Among the possible combinations for the mechanical parameters described above, the attention of this paper is focused on some limit configurations of the examined system: • BLD: un-retrofitted building, with K 2 the stiffness, R 2 the resistance and μ 2 =2 the ductility ( K 3 →∞); • EXO-1: rigid foundation ( K 3 →∞), with an exoskeleton less rigid ( K 1 = 0.5 K 2 ), but much more resistant ( R 1 = 1.5 R 2 ) and ductile ( μ 1 = 7 μ 2 ) than the RC building; • EXO-2: rigid foundation ( K 3 →∞), with an exoskeleton much more rigid ( K 1 = 10 K 2 ), but less resistant ( R 1 = 0.75 R 2 ) than the RC building ( μ 1 = 7 μ 2 ); • EXO-3: hybrid RC-steel system with an additional coupled sliding system ( K 3 = 0), where the steel exoskeleton has a given stiffness K 1 , high resistance ( R 1 = 1.2 R 2 ) , and ductility μ 1 (to define based on the input seismic design loads, independently from the RC building mechanical characteristics). Fig. 1 - (a) Reference model for the parametric analysis, showing the RC building, the steel exoskeleton and the base sliding device; (b) shear-displacement response of BLD system, (c) EXO-1 system, (d) EXO-2 system and (e) EXO-3 system. P1 and P2 denote yielding and collapse respectively of the RC frame, while P3 is the post-failure stage. P0 represents the yielding point of the steel exoskeleton. In (e) P1 denotes the yielding configuration for the exoskeleton / hybrid system, while P2 is the post-yielding stage.