ORIGINAL RESEARCH PAPER
Torsional response of ﬁre-damaged base-isolated
buildings with elastomeric bearings subjected to
Received: 28 October 2016 / Accepted: 5 February 2017 / Published online: 14 February 2017
Ó Springer Science+Business Media Dordrecht 2017
Abstract Information is lacking on the nonlinear dynamic response of r.c. base-isolated
buildings where asymmetries are due to ﬁre-induced lateral stiffness eccentricities in the
frame members of the superstructure or in the base-isolation system. To study the seismic
response following ﬁre, a numerical investigation is carried out on four-, six- and eight-
storey r.c. base-isolated structures composed of a basement and three, ﬁve and seven
storeys above ground level, respectively. The base-isolation system is constituted of High-
Damping-Laminated-Rubber Bearings, inserted on the top of the columns of the basement.
Different values of the isolation ratio, deﬁned as the ratio between the fundamental
vibration period of the base-isolated and ﬁxed-base structures above the isolation system,
and plan-aspect ratio, deﬁned as the ratio between the plan dimensions of the building, are
considered. Fire scenarios correspond to the ﬁre compartment conﬁned to the whole (i.e.
symmetric case) and half (i.e. asymmetric case) area of the base-isolation level (i.e.
basement, F0) and superstructure (i.e. ﬁrst level, F1) at 30 and 60 min of ﬁre resistance,
respectively. A thermal–mechanical mapping analysis is carried out, with reduced
mechanical properties of r.c. cross-sections, in line with the 500 °C isotherm method
proposed by Eurocode 2, and HDLRBs, in accordance with a proposed 200 °C isotherm
method. Finally, the nonlinear dynamic analysis is carried out with reference to near-fault
earthquakes selected and scaled on the design hypotheses adopted for the test structures.
Keywords Base-isolated structures Á Torsional effects Á Fire-damage of r.c. beams and
columns Á Fire-damage of HDLRBs Á Near-fault earthquakes
& Fabio Mazza
Dipartimento di Ingegneria Civile, Universita
della Calabria, 87036 Rende, CS, Italy
Bull Earthquake Eng (2017) 15:3673–3694