Some Considerations on the “Elastically Dynamic Design Earthquake” and Static Seismic Design Coefficient Considered in the Nuclear Power Plant Seismic Design in Japan

Regarding the two different seismic design requirements with the same design limit to keep elastic behavior under seismic loadings due to, (first) “Elastic Design Earthquake Ground Motion” whose acceleration response spectra are assumed to be one-half of those by ” Standard Earthquake Ground Motion”, and (second) static seismic force based on “Static Seismic Coefficient” adopted in the seismic design of Nuclear Power Plants in Japan, elastoplastic response analysis by the one-DOF bilinear model and comparative evaluation was carried out using the observed seismic motion 48 waveforms of the Japan Meteorological Agency seismic intensity 7 and 6-Upper. Response ductility factor was proposed as damage assessment index to evaluate the reliability of seismic capacity against ductile failure modes of mechanical components due to seismic inertia force. As a result, it was clarified that by setting the static seismic intensity to about 0.6 to 1.2, the static design based on the static seismic coefficient may be able to substitute the dynamic design based on the seismic motion for elastic design.