PSI - Issue 78

Enrico Bernardi et al. / Procedia Structural Integrity 78 (2026) 599–606

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isolation drift ( D IS ), OPT1 proves effective in reducing this parameter by approximately 45% to 50% across the considered values of μ . Regarding the superstructure acceleration ( A IS ), OPT2 achieves a reduction ranging from 35% (for μ = 0.25) to 15% (for μ = 0.75), which corresponds to a decrease in the dimensionless stiffness parameter ν and an increase in the damping ratio ζ IS . Furthermore, the A IS parameter is the most sensitive to changes in the mass ratio. Specifically, increasing the mass ratio (i.e., decreasing stiffness and increasing damping) results in a greater reduction in the superstructure acceleration.

a)

b) Fig. 6. Profiles of maximum inter - story drifts for OPT1 ( a ) and OPT 2 ( b ), for the values of μ and β performed.

Fig. 7. Maximum values of the substructure inter - story drift ( θ L ), IIS deflection ( D IS ) and IIS acceleration ( A IS )obtained for β =0 and 0.5.

5. Conclusions This paper presents a model for designing the optimal isolation system in IIS, based on a multi-objective optimization approach. The study introduces the proposed model and evaluates its reliability through time history analyses conducted on a simplified model representative of six-story RC structure.