Seismic design of equipment in industrial buildings is mostly conducted using the floor response spectra, which are often based on the assumption that the behaviour of the structure and the equipment is linear elastic. Essential reductions in peak values of floor response spectra can be obtained if inelastic behaviour of the structure is taken into account. This paper presents the most important results of an extensive parametric study of floor response spectra, taking into account the inelastic behaviour of the structure and the linear elastic behaviour of the equipment. The structure and the equipment were modelled as single-degree-of-freedom (SDOF) systems. Response-history analyses were performed for a set of recorded ground acceleration time-histories and for different properties of the structure. The influences of input ground motion, ductility, hysteretic behaviour and natural period of the structure, as well as damping of the equipment have been studied. Based on the results obtained and the conclusions made, a simple practice-oriented method for direct generation of floor response spectra from the design spectrum is proposed. The method is intended for a quick estimation of approximate floor response spectra.
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