On the effects of floor flexibility on floor response spectra

Methods of computing floor response spectra in nuclear power plant structures have been receiving increased attention in recent years. Although it has been recognized for some time that the more popular in-cascade approach generally results in conservative response, it was not until older plants were being reviewed that the significance of the issue was emphasized. As a result, several methods have been recently proposed to evaluate more realistic floor response spectra. This paper reviews the concept embodied in these methods and develops a methodology to validate them for a wide range of secondary system characteristics. (orig./HP)