Sensitivity Study of Coupling Effect of Upper Substructure on Main Structure in Floor Response Spectrum Analysis of Nuclear Power Plant Building

Floor response spectrum analysis serves as an important basis for seismic design of main structure, equipment & system of safety-related buildings in nuclear power plants. Taking the main concrete structure and the upper steel substructure of one combined pumping house of a HPR 1000 nuclear power plant as an example, the three-dimensional finite element models with and without considering main-sub-structure coupling effect are established by using ANSYS finite element analysis software. The sensitivity study about whether considering coupling effect or not for floor response spectrum calculations of main concrete pumping structure under SL-2 ultimate safety seismic ground motion has been analyzed by comparative calculation. The calculation results show that when the mass ratio and stiffness ratio between the upper substructure and the main structure are small, the discrepancies of calculated floor response acceleration values and the primary frequency of the main concrete structure are minimal. Therefore, the main-sub-structure coupling effect can be neglected when calculating and analyzing the floor response spectrum of the main structure of combined pumping house. The analysis results can deepen the understanding of the floor response spectrum calculation analysis of the combined pumping houses and other nuclear island buildings in nuclear power plants, and meanwhile can also provide reference for correlational seismic design and research.