Effect of slab stiffness on floor response spectrum and fragility of equipment in nuclear power plant building

The floor response spectrum (FRS) is used to evaluate the seismic demand of equipment installed in nuclear power plants. In the conventional design practice of NPP structure, the FRS is simplified using the lumped-mass stick model (LMSM), assuming the floor slab as a rigid diaphragm. In the present study, to study the variation of seismic response in a floor, the FRSs at different locations were generated by 3-D finite element model, and the response was compared to that of the rigid diaphragm model. The result showed that the FRS significantly varied due to the large opening in a floor, which was not captured by the rigid diaphragm model. Based on the result, seismic fragility analysis was performed for the anchorage of a heat exchanger, to investigate the effect of location-dependent FRS disparity on the high confidence low probability of failure (HCLPF).

Automated summary

This study analyzed the floor response spectrum of equipment in nuclear power plants using a 3-D finite element model. It was found that the presence of large openings in the floor significantly affected the floor response. Additionally, a seismic fragility analysis showed that the location-dependent disparity in the floor response spectrum had an impact on the high confidence low probability of failure.