Seismic floor spectra and structure-equipment interaction effects

In seismic analysis and qualification of equipment, interaction free floor response spectra are commonly used. In the development of these spectra, the supporting primary structure and the equipment are considered decoupled. In some cases, however, the dynamic interaction has been observed to play an important role and must be considered to obtain an accurate estimate of the equipment response. Herein, a new approach based on the method of mode synthesis is developed to incorporate the equipment-structure interaction effect in the direct generation of floor response spectra. The nonclassicality of the damping matrix of the coupled system is included. Numerical results obtained by this approach compare very well with the results obtained by time history analysis. (orig.)