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Seki, Hajime*; Fujita, Satoshi*; Minagawa, Keisuke*; Kitamura, Seiji; Watakabe, Tomoyoshi
Dynamics and Design Conference 2013 (D&D 2013) Koen Rombunshu (USB Flash Drive), 8 Pages, 2013/08
When we study the behavior of the pipes during an earthquake, the most important damage doesn't come from the maximal load by itself, but from the accumulation of the fatigue damage caused by the repetition of the cyclic load. Therefore, from the point of view of seismic design evaluation methods, techniques that can quantitatively assess the probability of fatigue failure of mechanical structures are needed. The relationship between failure and energy is evaluated, and examined by focusing on the Energy Balance Method said to be effective as an earthquake response analysis technique in the present. This study carries out failure experiments using 2-mass system model based on Energy Balance Method. Furthermore, we focus on the strain from the vicinity of broken point as local response.
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Nihon Kikai Gakkai Rombunshu, C, 79(804), p.2684 - 2693, 2013/08
Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Proceedings of 15th World Conference on Earthquake Engineering (WCEE-15) (USB Flash Drive), 9 Pages, 2012/09
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Transactions of the 21st International Conference on Structural Mechanics in Reactor Technology (SMiRT-21) (CD-ROM), 8 Pages, 2011/11
We carried out fundamental seismic response analysis that considers both horizontal and vertical nonlinearity of rubber bearing. In this study, the horizontal nonlinearity was considered independently from vertical response in order to construct accurate nonlinear analytical model of rubber bearing. That is to say, the coupling effect was not considered. Both horizontal and vertical nonlinear characteristics of rubber bearing were explained by multi-linear model. Analytical model of building for horizontal direction consists of 3 mass points that is the isolation layer, lower and upper layer of the building. It for vertical direction consists of 4 mass points, that is ground layer, the isolation layer, lower and upper layer of the building. At first, nonlinear seismic response analysis was executed in order to confirm nonlinear characteristics of analytical model of rubber bearing. Influence of nonlinearity of rubber bearing upon response of building was also investigated by the analysis. After that, sensitivity analysis was executed. Parameters of rubber bearing, oil damper and building were fluctuated, and influence of variation of these parameters upon response of building was investigated.
Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Dynamics and Design Conference 2011 (D&D 2011) Koen Rombunshu (CD-ROM), 7 Pages, 2011/09
The response to the input more than assumption is requested in the seismic response analysis used for the Probabilistic Safety Assessment. Rubber bearings used as the isolation system cause nonlinearity in the restoring force when the input more than assumption is received. However, the seismic response analysis method for considering nonlinear of the rubber bearing has not been established. Therefore, this study aims at the development of the seismic response analysis method of an isolated nuclear power plant based on the probabilistic safety assessment. In this paper, isolated building model that the nonlinearity of the rubber bearing is considered is made, the seismic response analysis is done, and the influence that it gives respond was verified. As a result, in horizontal direction, it was confirmed that the increasing tendency of the response acceleration was remarkable because of the increase of the earthquake size. In vertical direction, it was confirmed that the increasing tendency of the response displacement was remarkable.
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
Dynamics and Design Conference 2011 (D&D 2011) Koen Rombunshu (CD-ROM), 10 Pages, 2011/09
It is necessary to consider the change in the response by the difference of the physical properties value and the material characterizations of an isolation layer and a building in Probabilistic Safety Assessment. Then, in this paper, the sensitivity analysis of the parameter of the isolated building model that the nonlinearity of rubber bearing is considered used for the seismic response analysis done by the first report is done. The response when an arbitrary parameter is set to the upper limit or the lower limit by the logarithm standard deviation is compared with the response when all parameters are set to the median, and the error ratio is examined as sensitivity. As a result, in the earthquake size in which the nonlinearity is caused, the difference of the parameter of the building, the isolation layer such as the displacement that hardening begins and the load that softening begins of the rubber bearing shows high sensitivity, and it has a bad influence for the building response. Therefore, it was confirmed that the parameter that showed high sensitivity had to examine the difference in detail.
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
Proceedings of 2009 ASME Pressure Vessels and Piping Division Conference (PVP 2009) (CD-ROM), 7 Pages, 2009/07
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
Proceedings of 2008 ASME Pressure Vessels and Piping Division Conference (PVP 2008) (CD-ROM), 6 Pages, 2008/08
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
Transactions of the 19th International Conference on Structural Mechanics in Reactor Technology (SMiRT-19) (CD-ROM), 7 Pages, 2007/08
Although mechanical structures have sufficient seismic safety margin, comprehending the ultimate strength is very important in order to improve the seismic safety reliability in unexpected severe earthquake. The energy balance is adequate to investigate the influence of cumulative load because it includes cumulative information. The vibration experiments using simple single-degree-of-freedom experimental model are carried out in order to confirm a calculation technique of energy and to investigate behavior of energy in elasto-plastic region. The vibration failure experiments that lead experimental model to fatigue failure are carried out in order to investigate the relationship between input energy and fatigue failure.
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
Proceedings of 2007 ASME Pressure Vessels and Piping Division Conference/8th International Conference on Creep and Fatigue at Elevated Temperatures (PVP 2007/CREEP-8) (CD-ROM), 6 Pages, 2007/07
This paper describes the dynamic strength evaluation of piping installed in nuclear power plants from a viewpoint of energy balance. In this study, ultimate strength of a simple single degree of freedom model is investigated from a viewpoint of energy balance equation that is one of valid methods for structural calculation. The investigation is implemented by forced vibration experiment. In the experiment, colored random wave having predominant frequency similar to natural frequency of the experimental model is input. Stainless steel and carbon steel are selected as material of experimental model. As a result of the experiment, it is confirmed that input energy for fracture increase with an increase of time for fracture. In other words, more input energy for fracture is needed in case of small input level. Additionally it is confirmed that input energy for fracture depend on the material.
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
no journal, ,
In this research, The strength evaluation technique for paying attention into energy is examined for the equipments and the piping in the nuclear power plant during the earthquakes. In this report, the shaking table tests for the one mass model were conducted, and the behavior of energy was examined.
Kitamura, Seiji; Okamura, Shigeki; Minagawa, Keisuke*; Fujita, Satoshi*
no journal, ,
The dynamic strength evaluation method that pays attention into energy is examined so that the equipment and piping in the nuclear power plant may clarify the condition to plasticity/destruction. It reports on the result of applying the idea of the energy evaluation to the dynamic excitation examination result of the Elbo element.
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
no journal, ,
It proposes a dynamic strength evaluation method of the piping systems, and the effectiveness of this method is examined. In this report, the behavior of the energy at the vibration fatigue failure by the one mass model was examined.
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
no journal, ,
Mechanical structures installed in nuclear power plants such as piping are usually designed staically in elastic region. Although these mechanical structures have sufficient seismic safety margin, comprehending the ultimate strength is very important in order to improve of the seismic safety reliability in unexpected severe earthquake. The ultimate strength of piping is investigated from the viewpoint of energy balance method in this research. Vibration fracture experiments that lead one mass model to fatigue fracture are carried out in order to investigate the relationship between input energy and fracture.
Minagawa, Keisuke*; Fujita, Satoshi*; Kitamura, Seiji; Okamura, Shigeki
no journal, ,
In this research, it has aimed to develop the dynamic strength evaluation of the piping system by using the energy balance equation. The relation between the fatigue failure and energy by the vibration has been investigated by having used one mass model up to now. The vibration experiment by the straight piping model was executed and it reports on the result of the arrangement by energy.
Yamanaka, Takahiro*; Fujita, Satoshi*; Minagawa, Keisuke*; Kanaeda, Shingo*; Kitamura, Seiji; Watakabe, Tomoyoshi
no journal, ,
no abstracts in English
Minagawa, Keisuke*; Fujita, Satoshi*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
no journal, ,
In order to reduce the seismic load that is inputted into the reactor building and its internal components, adoption of an advanced seismic isolation system in the sodium-cooled fast reactor (SFR) is considered. Laminated rubber bearings have linear stiffness in the normal operation range. But as deformation increases, the bearings show non-linearity that causes hardening in the horizontal direction, and softening in the vertical. In this study, a simulation analysis was made to investigate an effect of the non-linearity on the building and internal components. In this analysis, the building was simulated with a mass-model and mechanical property of the bearings was simulated with multi-linear model. As a result, it was confirmed that (1) as the seismic load increases, the bearings indicate the hardening and it affects seismic response of the building, and that (2) a sensitivity of the seismic response to the parameters related to the bearings becomes high due to the hardening.
Oguro, Masato*; Fujita, Satoshi*; Minagawa, Keisuke*; Yamaguchi, Akira*; Takata, Takashi*; Kurisaka, Kenichi
no journal, ,
The concept of "Residual Risk" was introduced in "Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities" that had been revised in 2006. As for the assessment of "Residual risk", it is necessary to consider the response to unexpected input wave. The other side, the application of an isolation system is examined as a technique to decrease the input to the nuclear power plant. Rubber bearings used as the isolation system cause nonlinearity in the restoring force when unexpected earthquake and has a bad influence for the response. Therefore, in this study, isolated building model considering nonlinearity of the rubber bearing was used, the effect of the isolation system is examined from the response of the building. In this paper, the observed wave of "The 2011 off the Pacific coast of Tohoku Earthquake" was used and seismic response analysis was carried out. As a result, it was confirmed to be able to decrease the response acceleration to 1/10 by the isolation system and the nonlinearity of the rubber bearing was generated by 5.2 times this earthquake wave.
Nishino, Hiroyuki; Fujita, Satoshi*; Minagawa, Keisuke*; Takata, Takashi*; Yamaguchi, Akira*; Kurisaka, Kenichi
no journal, ,
no abstracts in English
Seki, Hajime*; Fujita, Satoshi*; Omi, Toshio*; Minagawa, Keisuke*; Kitamura, Seiji; Watakabe, Tomoyoshi
no journal, ,
no abstracts in English
