Seismic fragility analysis of nuclear power plant structure under far-field ground motions

This manuscript presents a fragility assessment to evaluate the effects of far-field earthquakes on the damage of the AP1000 nuclear island building (NIB), by using Incremental Dynamic Analysis (IDA) and Multiple Stripes Analysis (MSA) methods. Five categories of performance levels (PL), four limit states (LS) and the relative intensity measure ( IM ) having a high relation with the ground motion are defined to calculate the fragility of the AP1000 NIB under 15 earthquake sequences. A comparison of the results shows that the probabilities of minor damage, severe damage, and collapse damage for concrete are much higher than the reinforcement bar, which indicates that the fragility of concrete dominates the damage probability of the NIB. The fragility curves of the auxiliary building (AB) and shield building (SB) obtained by IDA and MSA are consistent with each other, but the distinction is mainly on the peak values or increasing ratio. Additionally, the probabilities of minor damage, moderate damage, severe damage and collapse damage of AB are less than the cases of SB. Lastly, the results also indicate that fragility curves are efficiently assessed and essential for risk assessments of the NIB.