Floor acceleration spectra, which are important for seismic design and assessment of accelerationsensitive
equipment, were studied in the dissertation. A relatively simple practice-oriented method for
the determination of floor acceleration spectra directly from the ground motion spectra was developed.
Elastic and inelastic structural behaviour was taken into account. Extensive parametric studies were
performed on single- (SDOF) and multi-degree-of-freedom (MDOF) structures and a large number of
floor acceleration (response) spectra were calculated by using the response-history analysis (RHA). In
the case of SDOF structures two different sets of ground records were used, whereas in the case of
MDOF structures only one of these sets was considered. The influences of the type, natural period,
hysteretic behaviour, and ductility of the primary structure, as well as the influence of the equipment
damping, were studied. Additionally, in the case of SDOF structures, the influence of input ground
motion characteristics was also investigated. The obtained results confirmed the fact that inelastic
behaviour of the primary structure can significantly reduce floor acceleration spectra, especially their
peak values. The method for direct determination of floor response spectra was firstly developed for
SDOF structures and it was validated by comparing its results with the floor response spectra obtained
from the RHA. A good agreement between the results obtained for both elastic and inelastic structural
behaviour was observed. The method was extended to MDOF structures and it was coupled with the
nonlinear pushover-based N2 method. In the case of elastic structures the method provides floor
response spectra which are in very good agreement with the results obtained from the RHA. In the
case of inelastic structures, in general, a satisfactory accuracy can be achieved.
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