PSI - Issue 44

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

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3

parallel to the floor slab direction, while all the others are deep; square and rectangular cross-sections are considered for the interior and exterior columns, respectively. Cylindrical compressive strength of 25 MPa, for the concrete, and yield strength of 450 MPa, for the steel reinforcement, are assumed for RC frame members. Fundamental vibration periods of the original (fixed-base) structure are equal to T FB,1X =0.677s and T FB,1Y =0.574s, while further details on the test structure are reported in a previous paper (Mazza (2021)).

(a)

(b)

(c) (d) Fig. 1. Test structures (unit in m): (a, b) horizontal base-isolation ( BI.H); (c, d) horizontal and vertical base-isolation ( BI.HV).

Property modification ( l ) and combination ( y ) factors are also evaluated in order to define upper (UBDP) and lower (LBDP) bound design properties of HDRBs, in line with European codes (EC8 (2005); UNI EN 15129 (2009)). A mixed design is also carried out considering lower bound strength and upper bound stiffness. Specifically, starting from the nominal design property (NDP), ageing (i.e. l max,f1 =1.2 and y f1 =0.7), temperature (i.e. l max,f2 =1.2 and l max,f2 =1.4 for strength and stiffness properties at the design temperature T= - 10°C, respectively, and y f2 =0.7) and production variability (i.e. l min,f1 =0.8) factors are selected in order to evaluate

(

)

UBDP NDP =

,

max,fi = + l - ×y 1 1

(1)

× l × l

l

U,f1 U,f 2

U,fi

fi

(2)

min,f1 LBDP NDP = × l