An improved lump mass stick model of a nuclear power plant based on the Kriging surrogate model

This paper focuses on an improved lump mass stick model of the AP1000 nuclear power plant (NPP). The conventional method is used to calculate the parameters of the lump mass stick (LMS) model of the AP1000 NPP, which has great differences between the LMS model and the finite element (FEM) model in terms of frequency and vibration mode. Therefore, with optimizing the mass condensation size of a shear wall without a floor as a goal, the improved lump mass stick (I-LMS) model based on the Kriging surrogate model is established. The results illustrate that: (i) compared with the LMS model, the relative error of the I-LMS model and the FEM model, the maximum error of the frequency is reduced from 23.04% to 6.57% with nine order frequencies; (ii) the frequencies of the Kriging surrogate model and the I-LMS model are very close, with the largest error being only 1.45%, indicating that the Kriging surrogate model has obtained better correction accuracy; (iii) the modal assurance criterion (MAC) value of the I-LMS model for the same vibration mode is increased from 0.75 to 0.95 to 0.88–0.96, and the MAC values of different vibration modes are closer to 0; and (iv) comparison of the structural dynamic response under basic design earthquake to the FEM model shows that the I-LMS model has good calculation accuracy and obvious advantages in calculation efficiency.