PSI - Issue 44

Fabio Mazza et al. / Procedia Structural Integrity 44 (2023) 1172–1179 Fabio Mazza / Structural Integrity Procedia 00 (2022) 000–000

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5. Conclusions The combination of horizontal and vertical base-isolation investigated herein refers to a RC fixed-base hospital pavilion retrofitted by means of an in-series vertical combination of HDRBs and HDRLs, where the vertical stiffness of the HDRL is tuned without affecting the shear deformation of the HDRB. The most unfavourable design properties of the isolation systems are evaluated referring to nominal values and variability resulting from upper-bound, lower bound and mixed approaches. Thirty-six base-isolated test structures are considered, combining the four design approaches with nine values of stiffness ratio a Ke . Ten near-fault earthquakes with significant vertical component are scaled to the life-safety limit state and considered for nonlinear dynamic analyses. The following conclusions can be drawn briefly. Ductility demand and vertical acceleration at the mid-span section of beams are increasing along the height of horizontally base-isolated buildings, but a slight difference is observed when different design properties of the base isolation system are considered. The insertion of the vertical base-isolation can reduce structural and non-structural damage parameters, with the trend towards an almost constant vertical distribution when decreasing values of the stiffness ratio are assumed. Continuous wavelet transforms of the vertical floor acceleration time histories, at the mid span section of the beams at the top floor, indicate that the effectiveness of the vertical base-isolation is attained for an isolation ratio a T in the vertical direction at least equal to 1.7. Acknowledgements The present work is financed by Re.L.U.I.S. 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