Numerical investigation of AP1000 NIB under mainshock-aftershock earthquakes

This manuscript studies the seismic behavior of AP1000 nuclear power plant buildings (NPPB) under different mainshock and aftershock earthquakes. Three mainshock-aftershock seismic sequences, which satisfy RG 1.60 spectrum, are adopted in time history analysis. A 3D finite element model (FEM) is established to analyze the seismic response of AP1000 NPPB. Parametric analysis of maximum acceleration, peak displacement, acceleration response spectrum, and stress distribution are carried out to study the effects of mainshock-aftershock earthquakes. It is indicated that strong aftershock may aggravate the potential cumulative damage and take a significant influence on the seismic performance of the nuclear island building (NIB). Mainshock and aftershock also influence the floor acceleration response spectrum in horizontal directions significantly. Therefore, to assess the safety of AP1000 NIB, aftershock should be considered in the seismic design of strong mainshock with strong aftershock, especially for the isolated NPPB.