원전격납구조물의 지진취약도 분석을 통한 강진지속시간의 영향평가

In this study effect of the strong motion duration on the seismic fragility of NPP structures is investigated to verify applicability of the associated design guideline newly suggested in ASCE Standard 4-98. First of all, 30 artificial accelerograms for each of 20 specified PGA values with interval of 0.2g in the range from 0.2g to 4.0g are generated in accordance with the strong motion duration criterion and the envelop function in ASCE Standard 4-98. Using these synthetically generated 600 earthquake time histories for each of four cases whose strong motion duration varies from 7 to 15 seconds, intensive nonlinear time history analyses for the Ulchin NPP Unit 3&4 structure are then carried out to identify its structural damage status predefined in terms of the maximum member force and displacement. A seismic fragility analysis is finally conducted to evaluate effect of the strong motion duration on the seismic risk of a NPP structure. Some observations are made from the results of the fragility analysis.