A Method for Direct Determination of Inelastic Floor Response Spectra

Floor response spectra, which are usually based on the assumption that the behaviour of the primary (building) and the secondary systems (equipment) is linear, are used for the seismic design of equipment in industrial buildings. In general, essential reductions in peak values of floor response spectra can be obtained if inelastic behaviour of the primary system is taken into account. The paper presents the most important results of an extensive parametric study of floor response spectra, taking into account the inelastic behaviour of the primary system and the linear behaviour of the secondary system. Both systems were modeled as single-degree-offreedom systems. The influences of input ground motion, ductility, hysteretic behaviour and natural period of the primary system, as well as damping of the secondary system have been studied. A simple approximate method for direct determination of floor response spectra from the design spectrum is proposed.