Vibration tests for failure mode analysis of piping system toward Natech risk assessment

Takito, Kiyotaka; Furuya, Osamu*; Nakamura, Izumi*; Okuda, Yukihiko

Proceedings of the ASME 2025 Pressure Vessels & Piping Conference (PVP2025) (Internet), 10 Pages, 2025/07

Natech stands for Natural Hazard Triggered Technological Accidents. The assessment of Natech and the implementation of appropriate measures have been highlighted by the accidents at the Fukushima Daiichi Nuclear Power Plant (NPP), and the gas tank fire caused by the earthquake in Japan. However, the data related to the structural failure with the system function is not sufficient to carry out the assessment of Natech in industrial plants, not only at NPPs. Therefore, the authors have investigated piping failure modes under seismic input to refer to the relationship between piping failure modes and assurance of piping function. Moreover, the authors have already performed the elbow and tee loading tests, the shaking table tests on a simple piping system to observe the referred failure modes of small-bore carbon steel piping. As a result, the authors have shown two of the referred modes are an elbow collapse and the axial crack growth of an elbow. In addition, it observed bifurcating into collapse mode and low cycle fatigue mode due to the relation between the dead load and input acceleration level. Consequently, to observe the failure modes under more realistic configurations, the authors fabricated a three-dimensional pipe specimen with multiple elbows and performed vibration tests using the vibration table in this study. The test specimen was designed to observe an elbow collapse or the axial crack growth on an elbow and under shaking table test. From the above, this paper reports the overview of this study and the results of the vibration tests. Especially, it shows the observed two different failure modes, axial plus circumferential crack and not just an elbow collapse but the overall fall including deformation of multiple elements under the shaking table tests.

Effects on a bending pipe behaviour via simple pre-loading for considering functional limitations of piping in industrial facilities

Sugiura, Ayumu*; Takito, Kiyotaka; Furuya, Osamu*; Nakamura, Izumi*; Okuda, Yukihiko

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 8 Pages, 2024/11

https://doi.org/10.1115/ICONE31-133764

Investigating the influence of analysis parameters in three-dimensional elasto-plastic finite element analysis of a gate-type piping support structure

Takito, Kiyotaka; Okuda, Yukihiko; Nishida, Akemi; Li, Y.

Proceedings of the ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 9 Pages, 2024/07

In probabilistic risk assessment against earthquakes (seismic PRA), one of the important issues is the development of a realistic response analysis method for evaluating the fragility of equipment and piping systems subject to input ground motions exceeding design assumption. Particularly, piping systems have complex plant-specific three-dimensional geometries. The arrangement and rigidity of piping support structures have significant impact on the response characteristics of the entire piping system. Therefore, it is necessary to develop a seismic response analysis method for piping systems, including piping support structures. To this end, the authors have been working on the development of elasto-plastic analysis method for piping support structures in order to establish a realistic response analysis method for piping systems including piping support structures. In this study, parametric studies on important analytical parameters were conducted to understand the influence of the analytical parameters on the deformation in the elasto-plastic analysis of piping support structures. At first, a three-dimensional finite element analysis model was created for cyclic loading tests of a gate type piping support structure assuming large deformations. Using the model, parametric studies were conducted for analysis parameters such as yield stress, secondary stiffness and element size. As the result, the influences of the analysis parameters on the analysis results were quantitatively clarified, which provided insight into the methodology for setting appropriate analysis parameters on elasto-plastic analysis for piping support structures.

Investigation on damage evaluation index with ductility factor based on simulation analysis for loading test of piping support structure

Okuda, Yukihiko; Takito, Kiyotaka; Nishida, Akemi; Li, Y.

Mechanical Engineering Journal (Internet), 11(2), p.23-00405_1 - 23-00405_12, 2024/04

https://doi.org/10.1299/mej.23-00405

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.

Study on response correlation during earthquakes using a three-dimensional detailed model and a Sway-Rocking model for nuclear building

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

Development of seismic response analysis method of piping system; Proposal of the nonlinear spring model for piping support structures

Takito, Kiyotaka; Okuda, Yukihiko; Nishida, Akemi; Li, Y.

Proceedings of the 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.

Comparative study on equipment damage correlation during earthquakes using a three-dimensional detailed and a sway-rocking analysis models for nuclear reactor building

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

Time-history volume estimating method for a deforming piping element under loading test

Takito, Kiyotaka; Takeda, Keita*; Furuya, Osamu*

no journal, , 

no abstracts in English

Development of PRA methodology considering multi-hazards, 8; Proposal of a basic concept for a combined-event PRA method

Takada, Tsuyoshi; Choi, B.; Kubo, Kotaro; Takito, Kiyotaka; Tsutsumi, Hideaki; Nishida, Akemi; Muramatsu, Ken

no journal, , 

no abstracts in English

Evaluation of energy dissipation in pipe supports through parametric analysis

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.