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.
After a large earthquake, aftershocks occur subsequently in a wide region, as were seen in the 2011 Tohoku earthquake. Those aftershocks cause secondary damage or delay of restoration activity. In addition, it is reported that there were the region where intensity of shaking due to aftershocks were bigger than that due to a main shock in some past earthquakes. Therefore, it is necessary to take account of the seismic risk due to aftershocks, too. In this study, using aftershocks data obtained in the events of the 2011 Tohoku earthquake and of other historical large earthquakes, the spatial and temporal distribution of aftershock occurrence is investigated and modeled based on the Gutenberg-Richter law and the Modified Omori�s law. Then, a probabilistic aftershock occurrence model to predict the aftershocks of future large earthquakes is proposed, which is expected to be useful for development of restoration activity plan after future large earthquakes.
In this study, the seismic response analysis model of a human body based on cart-type double inverted pendulum was developed based on the shaking table tests with a human subject. The behavior of two types of model, the model without torque control of hip and the model with that, were compared with respect to response of human subject. The results from the model with torque control of hip agreed well with the human subject's behavior. Finally, the validity of the model was confirmed by the analysis with other input motions.
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