Seismic fragility analysis of nuclear power plants based on the substructure method

Abstract

This paper focuses on seismic fragility analysis of the AP1000 Nuclear Power Plant (NPP) with a substructure (SUB) model. To improve the efficiency of the analysis and calculation, this study treats the steel vessel containment (SVC) and equivalent equipment as a substructure and connects them with the residual structure to form an SUB model. The SUB model is verified to determine its rationality. Based on the verified model, 160 working conditions are calculated, and an incremental dynamic analysis (IDA) is performed. The AP1000 NPP is divided into 11 zones and 6 layers to investigate the seismic fragility analysis in detail. The results illustrate that (i) the calculation time of the SUB model is reduced by 1/4 compared to that of the full finite element model of the AP1000 NPP (FULL model) under the premise of ensuring calculation accuracy; (ii) the divided zones provide an accurate judgment basis for the failure mode and damage state directly; (iii) for the reinforced concrete shield building (RCSB), the damage gradually expands upon a sudden change in structural stiffness at the upper junction of the reinforced concrete auxiliary building (RCAB); (iv) seismic fragility analysis of the RCAB presents the form of gradual reduction of damage from the upper layer to the lower layer.