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Takito, Kiyotaka; Okuda, Yukihiko; Nakamura, Izumi*; Furuya, Osamu*
Transactions of the 27th International Conference on Structural Mechanics in Reactor Technology (SMiRT 27) (Internet), 10 Pages, 2024/03
no abstracts in English
Choi, B.; Nishida, Akemi; Takito, Kiyotaka; Tsutsumi, Hideaki*; Takada, Tsuyoshi
Transactions of the 27th International Conference on Structural Mechanics in Reactor Technology (SMiRT 27) (Internet), 10 Pages, 2024/03
no abstracts in English
Okuda, Yukihiko; Takito, Kiyotaka; Nishida, Akemi; Li, Y.
Mechanical Engineering Journal (Internet), 12 Pages, 2024/00
After the Great East Japan earthquake and the accident at the TEPCO's Fukushima Daiichi Nuclear Power Stations in March 2011, the regulation for nuclear power plants (NPPs) has been enhanced to take countermeasures against beyond-design-basis events. To improve the seismic safety of nuclear facilities against earthquakes that exceed the design input ground motion, the importance of seismic probabilistic risk assessment (PRA) has drawn much attention. It is essential to evaluate the realistic seismic response of the equipment and piping in NPPs for fragility assessment in seismic PRA. In particular, since piping systems have plant-specific complex route geometries, it is known that the arrangement and stiffness of piping support structures have a significant impact on seismic response characteristics of the entire piping system. To construct a realistic seismic response analysis method for excessive input ground motion exceeding the elastic response, it is desired to develop an elastic-plastic response analysis method that can estimate the realistic response of piping systems including pipe support structures. In this study, the applicability of the method is confirmed by the simulation analysis of the elasto-plastic response for the piping support structure loading test previously reported. Moreover, based on the good correlation between the ductility factor and the damage status obtained from the test results and simulation analysis results, it is shown that the ductility factor is effective as a damage evaluation index for piping support structures.
Nakamura, Izumi*; Otani, Akihito*; Okuda, Yukihiko; Watakabe, Tomoyoshi; Takito, Kiyotaka; Okuda, Takahiro; Shimazu, Ryuya*; Sakai, Michiya*; Shibutani, Tadahiro*; Shiratori, Masaki*
Dai-10-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR2023) Koen Rombunshu (Internet), p.143 - 149, 2023/10
In 2019, the JSME Code Case for seismic design of nuclear power plant piping systems was published. The Code Case provides the strain-based fatigue criteria and detailed inelastic response analysis procedure as an alternative design rule to the current seismic design, which is based on the stress evaluation by elastic response analysis. In 2022, it was approved to revise the Code Case with improving the cycle counting method for fatigue evaluation to the Rain flow method. In addition, the discussion to incorporate the elastic-plastic behavior of support structures is now in progress for the next revision of the Code Case. This paper discusses the contents and background of the 2022 revision, the progress of the next revision, and future tasks.
Takito, Kiyotaka; Okuda, Yukihiko; Nishida, Akemi; Li, Y.
Proceedings of ASME 2023 Pressure Vessels and Piping Conference (PVP 2023) (Internet), 10 Pages, 2023/07
In probabilistic risk assessment against earthquakes (seismic PRA) for nuclear power plants, the development of a realistic response analysis method for the fragility assessment of piping systems considering input seismic motions exceeding design assumptions is one of the important issues. Usually, piping systems exhibit complex three-dimensional shapes. The arrangement and stiffness of the piping support structures significantly affect the response characteristics of the entire piping system. Therefore, it is necessary to develop a realistic response analysis method of piping systems including piping support structures. In this study, a method for modeling the elasto-plastic hysteresis characteristics of piping support structures is developed to establish a seismic response analysis method of piping systems including piping support structures. First, we formulate an elatsto-plastic spring model that can express the elasto-plastic hysteresis characteristics of a piping support structure. Subsequently, we perform a simulation analysis for the loading test of a piping support structure using this model. As the analysis results and test results were in good agreement, we confirmed the effectiveness of the formulation of the model. The main contents, such as the formulation of the elasto-plastic spring model, the simulation analysis of the loading test, and the comparison between the analysis results and the test results, and the results of this study are reported in this paper.
Okuda, Yukihiko; Takito, Kiyotaka; Nishida, Akemi; Li, Y.
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05
After the Great East Japan earthquake and the accident at the TEPCO's Fukushima Daiichi Nuclear Power Stations in March 2011, the regulation for nuclear power plants (NPPs) has been enhanced to take countermeasures against beyond-design-basis events. To improve the seismic safety of nuclear facilities against earthquakes that exceed the design input ground motion, the importance of seismic probabilistic risk assessment (PRA) has drawn much attention. It is essential to evaluate the realistic seismic response of the equipment and piping in NPPs for fragility assessment in seismic PRA. In particular, since piping systems have plant-specific complex route geometries, it is known that the arrangement and stiffness of piping support structures have a significant impact on seismic response characteristics of the entire piping system. In contrast, the current seismic design procedure adopts an evaluation method assuming an elastic response. To construct a realistic seismic response analysis method for excessive input ground motion exceeding the elastic response, it is desired to develop an elastic-plastic response analysis method that can estimate the realistic response of piping systems including pipe support structures. In this study, the applicability of the method is confirmed by the simulation analysis of the elasto-plastic response for the piping support structure loading test previously reported. Moreover, based on the good correlation between the ductility factor and the damage status obtained from the test results and simulation analysis results, it is shown that the ductility factor is effective as a damage evaluation index for piping support structures.
Choi, B.; Nishida, Akemi; Takito, Kiyotaka; Tsutsumi, Hideaki*; Takada, Tsuyoshi
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 8 Pages, 2023/05
no abstracts in English
Takito, Kiyotaka; Okuda, Yukihiko; Nishida, Akemi; Li, Y.
no journal, ,
Elasto-plastic response analysis of pipe systems including the pipe supports is necessary to evaluate the seismic fragility for input seismic motions exceeding the design assumptions. However, the elasto-plastic response analysis method for pipe supports has not been developed yet. In this study, we aim to develop the elasto-plastic response analysis method for pipe supports by focusing on the non-linearity of the load-displacement characteristics. We also conduct parametric analyses on the material properties, etc., for existing loading tests. This paper reports the quantitative computing for energy dissipation with the load-displacement characteristic curves obtained via the analyses, and the comparison between the analytic results and experimental results.
Nakamura, Izumi*; Otani, Akihito*; Morishita, Masaki; Okuda, Yukihiko; Watakabe, Tomoyoshi; Shibutani, Tadahiro*; Takito, Kiyotaka; Okuda, Takahiro; Shiratori, Masaki*
no journal, ,
no abstracts in English
Takada, Tsuyoshi; Nishida, Akemi; Choi, B.; Takito, Kiyotaka; Tsutsumi, Hideaki*; Muramatsu, Ken; Kubo, Kotaro*
no journal, ,
no abstracts in English
Choi, B.; Takito, Kiyotaka; Nishida, Akemi; Takada, Tsuyoshi
no journal, ,
no abstracts in English
Kubo, Kotaro*; Takito, Kiyotaka; Choi, B.; Nishida, Akemi; Muramatsu, Ken; Takada, Tsuyoshi
no journal, ,
no abstracts in English
Takito, Kiyotaka; Nakamura, Izumi*; Okuda, Yukihiko; Sakai, Michiya*; Shimazu, Ryuya*; Otani, Akihito*; Watakabe, Tomoyoshi; Okuda, Takahiro; Shibutani, Tadahiro*; Shiratori, Masaki*
no journal, ,
The Piping systems in the nuclear power plants are known to exhibit significant elastic plastic behavior before failure caused by the response displacement under serve seismic load. Current Code Case considers the elastic-plastic behavior of piping system itself, but assumes the elastic behavior for the support structure. Thus, it is desirable to incorporate the inelastic behavior of piping support structure as the future upgrading of the Code Case. In order to develop an evaluation method for inelastic behavior of support structures, the authors as the JSME task group carried out benchmark analyses of piping support structures. Then, the purpose of the benchmark analysis is in order to evaluate the influence of the analysis parameters in the elastic plastic analysis of piping support structures and to obtain knowledge on the variability of the analysis results. This paper reports on the outline and progress of the benchmark analyses.
Nakamura, Izumi*; Takito, Kiyotaka; Okuda, Yukihiko; Furuya, Osamu*
no journal, ,
no abstracts in English
