Uncertainty Quantification of Seismic Response of Reactor Building Considering Different Modeling Methods

2021 ◽  
Author(s):  
Choi Byunghyun ◽  
Akemi Nishida ◽  
Ken Muramatsu ◽  
Tatsuya Itoi ◽  
Tsuyoshi Takada
Keyword(s):  
Uncertainty Quantification ◽  
Seismic Response ◽  
Modeling Methods ◽  
Reactor Building

Epistemic Uncertainty Quantification of Floor Responses for a Nuclear Reactor Building

2018 ◽  
Author(s):  
Byunghyun Choi ◽  
Akemi Nishida ◽  
Yinsheng Li ◽  
Ken Muramatsu ◽  
Tsuyoshi Takada
Keyword(s):  
Uncertainty Quantification ◽  
Seismic Response ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Epistemic Uncertainty ◽  
Ground Motions ◽  
Response Analysis ◽  
Fukushima Accident ◽  
Modeling Methods ◽  
Reactor Building

After the 2011 Fukushima accident, engineers of nuclear power plants are looking beyond the basic design requirements and ensuring that countermeasures are built in to avert possible nuclear accidents. In seismic probabilistic risk assessment (SPRA), uncertainties can be classified in two ways as aleatory uncertainties or epistemic uncertainties. To improve the reliability of SPRA, the difference in seismic response due to difference of building modelings related to epistemic uncertainty was focused on. Two modeling methods were used for a seismic response analysis: a three-dimensional finite-element model and a conventional sway-rocking stick model. Simulated input ground motions related to aleatory uncertainty were generated for the input waves. Then, the seismic floor response results of the various input ground motions of the two modeling methods were quantified. For the uncertainty quantification related to the different building modelings, a statistical analysis of the floor response results of the nuclear reactor building were further performed. Finally, for the quantification of the uncertainty in the fragility analysis for SPRA, the way to use of these results were discussed.

Uncertainty Quantification of Seismic Response of Reactor Building Considering Different Modeling Methods

2020 ◽  
Author(s):  
Byunghyun Choi ◽  
Akemi Nishida ◽  
Ken Muramatsu ◽  
Tatsuya Itoi ◽  
Tsuyoshi Takada
Keyword(s):  
Uncertainty Quantification ◽  
Seismic Response ◽  
Ground Motion ◽  
Power Plants ◽  
Epistemic Uncertainty ◽  
Response Analysis ◽  
Lumped Mass ◽  
Fukushima Accident ◽  
Mass System ◽  
Modeling Methods

Abstract After the 2011 Fukushima accident, the seismic regulations for nuclear power plants (NPP) in Japan have been strengthened to include countermeasures far beyond design-basis accidents. The importance of seismic probabilistic risk assessments, therefore, have been the focus of deserved attention. Generally, an uncertainty quantification has been a very important undertaking to assess for fragility in NPP buildings. Therefore, this study focuses on the reduction in epistemic uncertainty by aiming to clarify the seismic-response effects on NPP buildings based on different modeling methods. As a first step in this study, the authors compared the seismic-response effects using two modeling methods of analysis. To evaluate the seismic response, an analysis was performed on two building model types; these being the three-dimensional (3D) finite-element model and the sway-rocking model with a conventional lumped mass system. To input a ground motion, the authors adopted 200 types of simulated seismic ground motions, generated by fault-rupture models, using stochastic seismic source characteristics. For the uncertainty quantification, we conducted a statistical analysis of the seismic responses acquired from the two modeling methods based on the building response each ground-motion input, and quantitatively evaluated the uncertainty response by considering the different modeling methods. We found a clear difference in the modeling methods near the floor and wall openings. We also imparted our knowledge on these 3D effects for the seismic-response analysis.

scholarly journals Influence of Vertical Equivalent Damping Ratio on Seismic Isolation Effectiveness of Nuclear Reactor Building

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4602
Author(s):  
Xiuyun Zhu ◽  
Jianbo Li ◽  
Gao Lin ◽  
Rong Pan
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Nuclear Reactor ◽  
Damping Ratio ◽  
Response Spectra ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Vertical Acceleration ◽  
Equivalent Damping ◽  
Reactor Building

This paper aimed at evaluating the influence of different vertical equivalent damping ratios of a 3-dimensional combined isolation bearing (3D-CIB) as regards seismic response and isolation effectiveness. A comparative study of the seismic response in terms of acceleration floor response spectra (FRS), peak acceleration, displacement response of the nuclear reactor building, and dynamic response of the 3D-CIB was carried out. The results showed that: (1) the horizontal FRS is slightly influenced by the vertical equivalent damping ratio of 3D-CIB, whereas the increase of the vertical equivalent damping ratio has a significant effect on reducing the vertical FRS; (2) the peak vertical acceleration increased with the decrease in the vertical equivalent damping ratios of 3D-CIB and the difference of peak accelerations calculated by the damping ratio of 20 and 25% is within 10%; (3) the increase of the vertical equivalent damping ratio is capable of reducing the horizontal displacement and the rocking effect of the superstructure, and effectively controlling the vertical displacement amplitude; and (4) the vertical equivalent damping ratio of 3D-CIB has a slight effect on its axial force. Consequently, it is demonstrated that the increase of the vertical equivalent damping ratio is advantageous for isolation effectiveness. From the view of displacement control, it is suggested that the 3D-CIB with the vertical an equivalent damping ratio of 15~20% is appropriate and acceptable.

scholarly journals Study on Vertical Motions by Rocking Responses of Reactor Buildings

2012 ◽  
Vol 7 (5) ◽  
pp. 609-618
Author(s):  
Rikiro Kikuchi ◽  
◽  
Katsuichirou Hijikata ◽  
Takayuki Koyanagi ◽  
Mitsugu Mashimo ◽  
...  
Keyword(s):  
Power Plant ◽  
Seismic Response ◽  
Nuclear Power ◽  
Lumped Mass ◽  
Mass Model ◽  
Vertical Stiffness ◽  
Plant Site ◽  
Reactor Building ◽  
Lumped Mass Model ◽  
Earthquake Observation

Earthquake observation records were observed in reactor buildings of Kashiwazaki-Kariwa Nuclear Power Plant Site during the Niigata-ken Chuetsu-oki earthquake in 2007 (NCO). Some studies on the seismic response and simulation analyses were performed to investigate dynamic characteristics of the structures. In particular, it was clarified that the vertical motions of the reactor building of Unit 6 were greater than those of adjacent reactor buildings of Unit 5 and Unit 7. This paper discusses the causes of this by earthquake observation records and simulation analyses of the reactor buildings. In general, seismic response of vertical motions is relatively well-simulated using lumped mass model with stick elements that have vertical stiffness and with the soil spring between the basemat and support ground. However, vertical motions are influenced by rocking motions with horizontal response in some cases. This paper focuses on relationships between the vertical responses and the vertical motions induced by the rocking motions with simulation analyses and observation records during both NCO earthquake and aftershock of NCO. The reasons why the vertical motions of the reactor building of Unit 6 were larger are discussed.

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