Seismic Evaluation of Equipment for Seismic Demand Based on Uniform Hazard Spectra (UHS) - Implications and Impact

Abstract

Per the recent changes in the CSA standard N289.1, a re-assessment of the seismic capacity of an existing nuclear power plant may be required whenever new seismological and geological data indicate that the site seismic hazard has changed since the original design. The seismic uniform hazard spectra (UHS) are considered in addition to the original Design Ground Response Spectra (DGRS) expressed in terms of standard spectrum. UHS usually show higher accelerations and rich energy content at the medium to high frequencies. The concept of the UHS is illustrated. Comparisons of UHS and DGRS are presented to show the fundamental differences between UHS and DGRS. This paper shows the engineering challenge due to UHS. A practical approach is proposed to address this challenge in this paper.