• Nuclear Engineering and Technology
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• v.44 no.5
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• pp.437-452
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• 2012

The Tohoku earthquake (Mw9.0) occurred on March 11, 2011 and caused a large tsunami. The Fukushima Dai-ichi NPP (F1-NPP) were overwhelmed by the tsunami and core damage occurred. This paper describes the overview of F1-NPP accident and the usability of tsunami PRA at Tohoku earthquake. The paper makes reference to the following current issues: influence on seismic hazard of gigantic aftershocks and triggered earthquakes, concepts for evaluating core damage frequency considering common cause failure with correlation coefficient against seismic event at multi units and sites, and concepts of "seismic-tsunami PSA" considering a combination of seismic motion and tsunami effects.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.3 s.18
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• pp.11-21
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• 2005

This study is performed to understand complex behavior and to investigate the rational analysis methods for seismic design of the curved bridges. To analyze the curved bridges for the seismic loadings, it is used that the finite element analysis program has the 7-dof curved beam and straight beam element. The free vibration characteristics of the curved bridges are compared with the straight bridges that have span length same as the average arc length of inside and outside girder of those. For the same case, the dynamic behavior is compared under seismic loadings. It is found that regular bridges classified by AASHTO are analyzed as if those were straight. To investigate the dynamic behavior of general curved bridges under seismic loading, the seismic loading directions and the subtended angle of curved bridges are varied.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.591-592
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• 2005

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.607-617
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• 2019

Global warming and climate change are increasing the intensity of typhoons and hurricanes and thus increasing the risk effects of typhoon and hurricane hazards on nuclear power plants (NPPs). To reflect these changes, a new NPP should be designed to endure design-basis hurricane wind speeds corresponding to an exceedance frequency of $10^{-7}/yr$. However, the short typhoon and hurricane observation records and uncertainties included in the inputs for an estimation cause significant uncertainty in the estimated wind speeds for return periods of longer than 100,000 years. A logic-tree framework is introduced to handle the epistemic uncertainty when estimating wind speeds. Three key parameters of a typhoon wind field model, i.e., the central pressure difference, pressure profile parameter, and radius to maximum wind, are used for constructing logic tree branches. The wind speeds of the simulated typhoons and the probable maximum wind speeds are estimated using Monte Carlo simulations, and wind hazard curves are derived as a function of the annual exceedance probability or return period. A logic tree decreases the epistemic uncertainty included in the wind intensity models and provides reasonably acceptable wind speeds.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.5
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• pp.419-425
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• 2009

Although earthquake damage was negligible in Korea during the last a few decades, its historic records suggest that the peninsula have experienced severe earthquake damages throughout the history. The potential for disastrous earthquakes, therefore, should always be considered. Harbors handle 99.6% of imported and exported cargo in Korea. Thus, it is necessary to secure the safety of harbors against seismic events and to establish a support system of emergency measures. Although instrumental seismic data are favored for seismic hazard estimation, their history in the peninsula is limited only to the past 30 years, which does not represent the long-term seismic characteristics of the peninsula. We use historic earthquakes with magnitude greater than 5 to observe long-term regional seismic hazards. Results of historic earthquake records indicate relatively high seismic hazard at harbors in Pohang, Ulsan and Incheon. Analysis of instrumental earthquake records reveal relatively high seismic hazard for harbors located along the East coast including Okgye, Mukho, Donghae, Samcheok, Pohang, and Ulsan.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.48-54
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• 2010

The analysis of the seismic risk of an offshore structure with a control device is presented. First, a probability density function was developed to represent seismic hazard, and seismic fragility under artificial earthquake conditions was determined. Fragility curves for an offshore structure with both passive and active control devices were determined. Displacement criteria were set to evaluate the performance of the structure. Based on numerical analysis, the seismic risk to the structure was considerably reduced when the structure had a seismic control device. The seismic risk to the actively controlled structure was decreased by 80% compared to the uncontrolled case. Reasonable performance evaluations of offshore structure with control devices can be conducted through risk analysis.

• Earthquakes and Structures
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• v.5 no.5
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• pp.607-624
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• 2013

In this study the seismic risk assessments of six- and twelve-story staggered wall system structures with three different structural variations were performed. The performances of staggered wall structures with added columns along the central corridor and the structures with their first story walls replaced by beams and columns were compared with those of the regular staggered wall structures. To this end incremental dynamic analyses were carried out using twenty two pairs of earthquake records to obtain the failure probabilities for various intensity of seismic load. The seismic risk for each damage state was computed based on the fragility analysis results and the probability of occurrence of earthquake ground motions. According to the analysis results, it was observed that the structures with added columns along the central corridor showed lowest probability of failure and seismic risk. The structures with their first story walls replaced by beams and columns showed lowest margin for safety.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.19-27
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• 2002

The four agencies in Korea - KMA, KIGAM, KEPRI, and KINS - have been operating their own seismic network for many years. In this study we have developed an integrated seismic system named KISS (Korea Integrated Seismic System), which is very similar to LISS (Live Internet Seismic Server) of Albuquerque Seismological Laboratory. Through KISS we could share all the earthquake data observed by those organizations in near real time. This research result will lead to provide the opportunity to use all seismic information of the earthquakes around Korean peninsula. And KISS will make us enable to do systematic researches, such as study on focal mechanisms of earthquakes around Korean peninsula, seismic design, earthquake prediction, etc. KISS will be used in developing an Early Earthquake Warning System like TriNet in Southern California, USA so as to minimize seismic hazard.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.33-36
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• 2008

In Korean Building Code 2005(KBC-2005), the Seismic Zone Factor is regulated by separating the seismic zone into two part. This seismic zone factor is not matched to regional seismic characteristics of our country because the factor is based on International Building Code 2000 (IBC-2000) of USA. This study inquiry for having a sufficient grasp of the seismic characteristics of south Korea region and appling for the seismic cope plan. We have collected and analyzed earthquake record happened in domestic region. There are two kinds of earthquake record. One is Historical earthquake data, another is Instrumental earthquake data. I used Instrumental earthquake record data which reliance is higher than historical earthquake data for proposing attenuation formulas by analyzing a correlation the epicenter and the distance.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.4
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• pp.25-31
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• 2007

For areas such as the Korean Peninsula, which have moderate seismic activity but no available records of strong ground motion, synthetic seismograms can be used to evaluate ground motion without waiting for a strong earthquake. Such seismograms represent the estimated ground motions expected from a set of possible earthquake scenarios. Local site effects are especially important in assessing the seismic hazard and possible ground motion scenarios for a specific fault. The earthquake source and rupture dynamics can be described as a two-step process of rupture initiation and front propagation controlled by a frictional sliding mechanism. The seismic wavefield propagates through heterogeneous geological media and finally undergoes near-surface modulations such as amplification or deamplification. This is a complex system in which various scales of physical phenomena are integrated. A unified approach incorporates multi-scale problems of dynamic rupture, radiated wave propagation, and site effects into an all-in-one model using a three-dimensional, fourth-order, staggered-grid, finite-difference method. The method explains strong ground motions as products of complex systems that can be modified according to a variety of fine-scale rupture scenarios and friction models. A series of such deterministic earthquake scenarios can shed light on the kind of damage that would result and where it would be located.