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Ichihara, Yoshitaka*; Nakamura, Naohiro*; Moritani, Hiroshi*; Horiguchi, Tomohiro*; Choi, B.
Nihon Genshiryoku Gakkai Wabun Rombunshi, 21(1), p.1 - 14, 2022/03
In this study, we aim to approximately evaluate the effect of nonlinearity of reinforced concrete structures through seismic response analysis using the equivalent linear analysis method. A simulation analysis was performed for the ultimate response test of the shear wall of the reactor building used in an international competition by OECD/NEA in 1996. The equivalent stiffness and damping of the shear wall were obtained from the trilinear skeleton curves proposed by the Japan Electric Association and the hysteresis curves proposed by Cheng et al. The dominant frequency, maximum acceleration response, maximum displacement response, inertia force-displacement relationship, and acceleration response spectra of the top slab could be simulated well up to a shear strain of approximately 
=2.0
10
. The equivalent linear analysis used herein underestimates the maximum displacement response at the time of ultimate fracture of approximately =4.010. Moreover, the maximum shear strain of the shear wall could not capture the locally occurring shear strain compared with that of the nonlinear analysis. Therefore, when employing this method to evaluate the maximum shear strain and test results, including those during the sudden increase in displacement immediately before the fracture, sufficient attention must be paid to its applicability.
Guglielmi, Y.*; Aoki, Kazuhiro; Cook, P.*; Soom, F.*; Cappa, F.*; Tanaka, Yukumo
Tectonophysics, 819, p.229084_1 - 229084_22, 2021/11
Times Cited Count：1 Percentile：10.41(Geochemistry & Geophysics)The reactivation mechanisms of coseismic surface ruptures associated with the 2011 Mw 6.7 Fukushima-ken Hamadori earthquake in Japan are investigated using in-situ controlled hydraulic injections in subsurface boreholes. Two fault segments were selected for reactivation studies, one across a coseismic rupture, the Shionohira site, and one across a non-coseismically ruptured segment, the Minakami-kita site. A series of water injections in sealed sections of boreholes set across the fault progressively bring the fault to rupture by a step-by-step decrease of the effective normal stress clamping the fault. While the fault is rupturing during these hydraulic stimulations, borehole displacements, fluid pressure and injection flowrate are continuously monitored. Then, the tests were analyzed using fully coupled hydromechanical modeling. The model was calibrated on field data, and a parametric study was conducted to examine the modes of fault reactivation. Coseismic surface rupture of the Shionohira fault showed a pure dilatant slip response to hydraulic tests, while the tectonically un-activated Itozawa fault (South) indicated a complex hybrid response to tests related to both a higher frictional and cohesive strengths of the fault. The analysis of the induced Shionohira slip event showed that it is reasonably modeled as a Coulomb rupture with an eventual dependency of friction on slip velocity, in good accordance with laboratory-derived rate-and-state friction data on the Shinohira gouge samples. In contrast, the Itozawa fault reactivation mechanism appears dominated by tensile failure with limited Coulomb shear failure. Thus, the applied protocol proves to be able to isolate significant differences in fault physical properties and rupture mechanisms between two segments of the same fault system, opening perspectives to better assess near-surface rupture effects, and therefore the safety of structures subject to large earthquakes.
Takeda, Nobukazu; Nakahira, Masataka
JAERI-Tech 2004-073, 59 Pages, 2005/01
JAERI-Tech-2004-073.pdf:11.36MB
The ITER toamak is composed of major components such as superconducting magnet and vacuum vessel whose operation temperatures are changed from room temperature to 4 K and room temperature to 200
C, respectively. The gravity support of the tokamak is flexible in order to accept the thermal deformation caused by temperature change. This structural feature causes the complex behaviors of the tokamak during seismic events. Therefore, the mechanical characteristics of the flexible support have to be investigated in detail. The present report describes the global plan of the series of vibration tests to estimate the seismic performance of the ITER tokamak. Although it is ideal that the vibration tests are carried out using a full-scale model, scale models are planned due to the limitation of the test facilities. The test results can be estimated by a scaling law. When the scaling law cannot be applied to some performances, the test is performed using a full-scale model. In addition, the other tests such as vacuum vessel and small-scaled models of the support structure are also planned.
Takeda, Nobukazu; Kakudate, Satoshi; Nakahira, Masataka
JAERI-Tech 2004-072, 43 Pages, 2005/01
JAERI-Tech-2004-072.pdf:6.06MB
The vibration experiments of the support structures with flexible plates for the ITER major components such as the vacuum vessel (VV) and the toroidal field (TF) coil were performed aiming to obtain its basic mechanical characteristics. Based on the experimental results, numerical analysis regarding the actual support structure was performed and a simplified model of the support structure was proposed. A support structure was modeled by only two spring elements. The stiffness calculated by the spring model agrees well with that of shell model, simulating actual structures based on the experimental results. It is therefore found that the spring model with the only two values of stiffness enables to simplify the complicated support structure with flexible plates. Using the spring model, the dynamic analysis of the VV and TF coil were performed to estimate the integrity under the design earthquake. As a result, the maximum relative displacement of 8.6 mm between VV and TF coil is much less than designed clearance, 100 mm, so that the integrity of the components is ensured.
Takeda, Nobukazu; Nakahira, Masataka; Kakudate, Satoshi; Takahashi, Hiroyuki*; Shibanuma, Kiyoshi; Yabana, Shuichi*; Matsuda, Akihiro*
Proceedings of 9th World Seminar on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures (CD-ROM), p.299 - 306, 2005/00
For the ITER, a fusion experimental reactor, it is planned to use rubber bearings in order to enhance the reliability of integrity with a sufficient margin even for the earthquakes beyond the design basis earthquake. In application for nuclear plants, the vertical compression of the isolator is 2
5 MPa and there is no experience for such a high compression as 10 MPa to be used for the ITER. Therefore, there is not enough design data of the rubber bearings with high compression, and thus a detailed estimation of performance is necessary. As a result of the endurance test after aging, it was validated that the bearing can be applied safely until 400th cycle even after 40 years of aging. On the other hand, the residual deformation was found at the 246th cycle. This means that the residual deformation can be observed enough earlier than the change of the macroscopic mechanical parameter such as stiffness. Therefore, it is possible to prevent break of the bearing during operation by sensing a sign of break with a periodical visual inspection.
Onozuka, Masanori*; Takeda, Nobukazu; Nakahira, Masataka; Shimizu, Katsusuke*; Nakamura, Tomomichi*
Fusion Engineering and Design, 69(1-4), p.757 - 762, 2003/09
Times Cited Count：2 Percentile：18.9(Nuclear Science & Technology)The dynamic behavior of the ITER tokamak assembly has been investigated. Three experimental models have been considered to validate the numerical analysis methods for the dynamic events, mainly seismic events. A 1/8-scaled tokamak model, which is based on the 1998 ITER design, is under construction. Non-linear vibration characteristics, such as damping, can only be identified by a full-scale model. Therefore, a full-scale gravity support structure for the coil system has been designed and will be tested. In addition, for the sub-scaled tokamak model, the VV is assumed to be a rigid structure. This assumption is to be verified using a 1/20-scaled model. The above experimental models and their testing conditions have analytically and numerically evaluated. For example, both the static and dynamic spring constants obtained by static analysis and eigen-value analysis, respectively, were evaluated to be in good agreement.
Takahashi, Hiroyuki*; Nakahira, Masataka; Yabana, Shuichi*; Matsuda, Akihiro*; Otori, Yasuki*
JAERI-Tech 2001-064, 111 Pages, 2001/11
JAERI-Tech-2001-064.pdf:8.96MB
no abstracts in English
Tsutsumi, Hideaki*; Yamada, Hiroyuki; Teragaki, Toshio*; Ebisawa, Katsumi; Shibata, Katsuyuki
Seismic Engineering 2000 (PVP-Vol.402-1), p.141 - 146, 2000/00
no abstracts in English
Nakahira, Masataka; Takeda, Nobukazu; Takahashi, Hiroyuki*; Yagenchi, Akira*; Akutsu, Yoichi; Tada, Eisuke; Yabana, Shuichi*
Proceedings of 7th International Conference on Nuclear Engineering (ICONE-7) (CD-ROM), 10 Pages, 1999/00
no abstracts in English
Iyoku, Tatsuo; Futakawa, Masatoshi; Ishihara, Masahiro
Nucl. Eng. Des., 148, p.71 - 81, 1994/00
Times Cited Count：7 Percentile：56.56(Nuclear Science & Technology)no abstracts in English
Iyoku, Tatsuo; Inagaki, Yoshiyuki; Shiozawa, Shusaku; Futakawa, Masatoshi; *
Nuclear Technology, 99, p.169 - 176, 1992/08
Times Cited Count：8 Percentile：61.46(Nuclear Science & Technology)no abstracts in English
Iyoku, Tatsuo; Inagaki, Yoshiyuki; Shiozawa, Shusaku; *
Nuclear Technology, 99, p.158 - 168, 1992/08
Times Cited Count：2 Percentile：27.46(Nuclear Science & Technology)no abstracts in English
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JAERI-M 88-085, 223 Pages, 1988/05
no abstracts in English
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Bull.JSME, 29(246), p.2986 - 2994, 1985/00
no abstracts in English
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Nihon Genshiryoku Gakkai-Shi, 27(2), p.145 - 158, 1985/00
Times Cited Count：2 Percentile：37.48(Nuclear Science & Technology)no abstracts in English
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Nihon Kikai Gakkai Rombunshu, C, 51(464), p.746 - 755, 1985/00
no abstracts in English
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JAERI 1282, 68 Pages, 1983/02
no abstracts in English
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Nucl.Eng.Des., 71, p.195 - 215, 1982/00
Times Cited Count：8 Percentile：65.66(Nuclear Science & Technology)no abstracts in English
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JAERI-M 9265, 90 Pages, 1981/01
no abstracts in English
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Journal of Nuclear Science and Technology, 18(7), p.514 - 524, 1981/00
Times Cited Count：3 Percentile：45.64(Nuclear Science & Technology)no abstracts in English
