• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.119-122
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• 2008

Recently, Geographical Information System (GIS) has been progressed in the fields of not only earth sciences and disaster problems, but also medical sciences, economical and social sciences. the southern region of Mid Niigata Region was attacked by intensive earthquake of M.6.8 on Richter Scale on October 23, 2004. The aim of this study was to improve efficiency of restoration operation for early victims relief. Significant issue is achieving the information processing required in restoration operation by spatial temporal information system.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1223-1234
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• 2009

The outlines of seismic PSA implementation standards and seismic hazard evaluation procedure were shown. An overview of the cause investigation of seismic motion amplification on the Niigata-ken Chuetsu-oki (NCO) earthquake was also shown. Then, the contents for improving the seismic hazard evaluation methodology based on the lessons learned from the NCO earthquake were described. (1) It is very important to recognize the effectiveness of a fault model on the detail seismic hazard evaluation for the near seismic source through the cause investigation of the NCO earthquake. (2) In order to perform and proceed with a seismic hazard evaluation, the Japan Nuclear Energy Safety Organization has proposed the framework of the open deliberation rule regarding the treatment of uncertainty which was made so as to be able to utilize a logic tree. (3) The b-value evaluation on the "Stress concentrating zone," which is a high seismic activity around the NCO hypocenter area, should be modified based on the Gutenberg-Richter equation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.430-433
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• 2006

Damage to earth structures for roads, railways and residential areas, as well as dams and river levees, during the 2004 Niigata-ken Chuetsu earthquake in Japan, and their rehabilitation works are overviewed. Several influential factors are pointed out, such as a) heavy rainfall preceding the earthquake, b) large aftershocks, c) geological conditions for subsoil including existence of liquefiable layers, d) compaction degrees for embankment, and e) drainage capacity from subsoil/embankments. It is also reported that, in the reconstruction works of damaged roads and railways, preferred use of geogrid-reinforced soil retaining walls was implemented.

• Geomechanics and Engineering
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• 제21권2호
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• pp.179-186
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• 2020

Investigating damage potential of the railway infrastructure requires either large amount of case histories or in-depth numerical analyses, or both for which large amounts of effort and time are necessary to accomplish thoroughly. Rather than performing comprehensive studies for each damage case, in this study we collect and analyze a case history of the high-speed railway system damaged by the 2004 M6.6 Niigata Chuetsu earthquake for the development of the seismic fragility curve. The development processes are: 1) slice the railway system as 200 m segments and assigned damage levels and intensity measures (IMs) to each segment; 2) calculate probability of damage for a given IM; 3) estimate fragility curves using the maximum likelihood estimation regression method. Among IMs considered for fragility curves, spectral acceleration at 3 second period has the most prediction power for the probability of damage occurrence. Also, viaduct-type structure provides less scattered probability data points resulting in the best-fitted fragility curve, but for the tunnel-type structure data are poorly scattered for which fragility curve fitted is not meaningful. For validation purpose fragility curves developed are applied to the 2016 M7.0 Kumamoto earthquake case history by which another high-speed railway system was damaged. The number of actual damaged segments by the 2016 event is 25, and the number of equivalent damaged segments predicted using fragility curve is 22.21. Both numbers are very similar indicating that the developed fragility curve fits well to the Kumamoto region. Comparing with railway fragility curves from HAZUS, we found that HAZUS fragility curves are more conservative.

• 농촌계획
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• 제19권3호
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• pp.89-106
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• 2013

In this study, the effectiveness of the method for the promotion council to make rehabilitation community development plan with rural villages to continue community development is investigated in Ota-district, which is affected by chuetu earthquake. Initially, Ota-district made the acting contents of the plan based on the village's request, which is considered resident life and problems in village. Next, Ota-district made the vision of plan based on the acting contents. This plan procedure has been effective to compliment the village community facilities and running on village event, in addition to setting the village's community to continue to manage community facilities and event. As a result, this way has helped good management of village event using the facilities and interchanging among residents. Also, the use of acting contents by request of the promotion council and village's community, while respecting both, has been effective in that the promotion council assists the village event after the rehabilitation community development plan is finished.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.9-16
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• 2016

2004년 일본의 니가타켄 츄에츠 지방의 나가오카, 오지야시에서 1,450개 이상의 지하구조물이 1.5m까지 부상하였다. 융기손상은 Lifeline 시스템의 일부인 하수 시스템의 흐름뿐만 아니라 교통흐름을 방해로 인해 심각한 문제를 야기 시킨다. 복구작업의 경우 손상된 하수 시스템의 오픈 컷 조사는 나가오카시 정부에 의해 수행되었다. 지진으로 인한 매설된 파이프 라인의 손상에 대한 중요한 데이터는 조사결과로부터 수집하였다. 본 연구는 지하 구조물의 부상량에 영향을 미치는 요인을 SPT 시추공 logs를 통해 손상된 지역의 위치와 파이프라인의 경사를 포함하는 데이터를 사용하여 조사하였다. 지하구조물의 부상과 영향을 받는 지역의 지질학적 특성 사이의 상관관계 분석을 통해 부상현상의 주요변수는 지하수의 깊이, 원지반에서의 점토층 두께, SPT N값인 것으로 밝혔다.

• 한국지반공학회논문집
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• 제35권11호
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• pp.111-119
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• 2019

지진에 대한 경각심이 높아지는 가운데 고속철도 시스템의 지진 취약성을 분석하는 것은 지진피해 사전대응분석을 위해 필수적이다. 고속철도를 이루는 구조물은 400km/s 정도까지 속도를 낼 수 있는 고속열차의 직진성을 유지하기 위해 주로 교량, 터널 등으로 구성되어 있다. 이러한 구조물의 지진에 대한 취약도는 각 구조물의 단면을 분석하여 해석적 또는 수치적 방법으로 구할 수도 있으나, 고속철도 전체 시스템을 이러한 방법으로 분석하기에는 그 대상이 넓어 많은 연구 노력이 필요하다. 본 연구에서는 이런 해석적 방법이 아닌 경험적 방법을 사용하여 고속철도 시스템 전체의 일반적인 지진 취약도 곡선을 개발하였다. 연구에 활용한 대상 지진 사례는 규모 6.6 2004년 니가타 지진으로, 이 지진은 진앙 인근 부근을 지나는 고속철도에 심각한 피해를 초래하였다. 본 연구에서는 고속철도에서의 계기진도 및 피해 사례를 수집하였고, 통계분석을 통해 각 피해 정도에 따른 피해 확률을 결정하였다. 그 후, 최대우도추정법을 사용하여 계기진도를 함수로 하는 초과피해 확률을 로그정규누적분포함수로 추정하였다. 이러한 취약도 곡선을 분석한 결과, 장주기 성분의 계기진도인 주기 3초의 응답스펙트럼(SA_T3.0)이 로그정규누적분포함수의 표준편차가 가장 작게 나타나고 오차의 표준편차 또한 작게 나타나 터널 및 교량 등 고속철도 시스템의 피해 확률을 추정하는데 가장 적합한 계기진도로 판단되었다. 이는 장주기 성분의 지진파가 터널 및 교량 등의 피해에 큰 연관성이 있기 때문으로 유추된다. 개발된 취약도 곡선으로부터 보통 이상(DL > 1)의 피해에 대해 SA_T3.0 = 0.1g일 때 2%의 피해확률을 예측하였으며, SA_T3.0 = 0.2g일 때 23.9%의 피해확률을 예측하였다.

• Earthquakes and Structures
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• 제10권5호
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• pp.1089-1109
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• 2016

Modified two-surface model (M2SM) is one of the steel elasto-plastic hysteretic constitutive models that consider both analysis accuracy and efficiency. However, when M2SM is used for complex strain history, sometimes the results are irrational due to the limitation of stress-strain path judgment. In this paper, the defect of M2SM was re-modified by improving the judgment of stress-strain paths. The accuracy and applicability of the improved method were verified on both material and structural level. Based on this improvement, the nonlinear time-history analysis was carried out for a deck-through steel arch bridge with a 200 m-long span under the ground motions of Chi-Chi earthquake and Niigata earthquake. In the analysis, we compared the results obtained by hysteretic constitutive models of improved two-surface model (I2SM) presented in this paper, M2SM and the bilinear kinematic hardening model (BKHM). Results show that, although the analysis precision of displacement response of different steel hysteretic models differs little from each other, the stress-strain responses of the structure are affected by steel hysteretic models apparently. The difference between the stress-strain responses obtained by I2SM and M2SM cannot be neglected. In significantly damaged areas, BKHM gives smaller stress result and obviously different strain response compared with I2SM and M2SM, and tends to overestimate the effect of hysteretic energy dissipation. Moreover, at some position with severe damage, BKHM may underestimate the size of seismic damaged areas. Different steel hysteretic models also have influences on structural damage evaluation results based on deformation behavior and low cycle fatigue, and may lead to completely different judgment of failure, especially in severely damaged areas.

• Geomechanics and Engineering
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• 제20권3호
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• pp.243-254
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• 2020

Due to the permanent damage to structures during earthquakes, soil liquefaction is an important issue in geotechnical earthquake engineering that needs to be investigated. Typical examples of soil liquefaction have been observed in many earthquakes, particularly in Alaska, Niigata (1964), San Fernando (1971), Loma Prieta (1989), Kobe (1995) and Izmit (1999) earthquakes. In this study, liquefaction behavior of uniform sands of different grain sizes was investigated by using the energy-based method. For this purpose, a total of 36 deformation-controlled tests were conducted on water-saturated samples in undrained conditions by using the cyclic simple shear test method and considering the relative density, effective stress and mean grain size parameters that affect the cumulative liquefaction energy. The results showed that as the mean grain size decreases, the liquefaction potential of the sand increases. In addition, with increasing effective stress and relative density, the resistance of sand against liquefaction decreases. Multiple regression analysis was performed on the test results and separate correlations were proposed for the samples with mean grain size of 0.11-0.26 mm and for the ones with 0.45-0.85 mm. The recommended relationships were compared to the ones existing in the literature and compatible results were obtained.

• 한국지반공학회논문집
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• 제28권10호
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• pp.5-16
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• 2012

지진에 의해 지반의 액상화가 발생하면 상대적으로 가벼운 지중 매설구조물은 부상하는 현상이 발생하며 이러한 피해는 과거 여러 지진에서 계속해서 보고되고 있다. Koseki et al.(1997a)에 의해 제안된 안전율은 액상화 지반에서 매설구조물의 부상 유무를 판단할 수 있으며 현재 내진설계에 이용되고 있지만 부상량의 "정량적인" 예측은 불가능하며 아직 확립되지 않았다. 지중 매설구조물의 부상량의 예측은 구조물의 성능성과 관련 있는 내진성능설계에 있어서 중요한 요소가 된다(ISO23469, 2005). 따라서 지중 매설구조물에 대한 내진성능평가를 위해 실용적인 부상량의 평가가 필요하다. 지중 매설구조물의 부상량을 예측하기 위한 방법으로 구조물에 작용하는 수직방향 힘의 평형을 바탕으로 간이법이 정식화 되었고(Tobita et al., 2012), 간이법의 신뢰성 확보를 위해 원심모형시험 결과 및 2004년 니가타켄츄에츠 지진시의 매설구조물 피해와 비교하였다. 본 연구에서 제안된 내진성능설계 흐름도는 뒷채움의 액상화 판정뿐만 아니라, 지중 매설구조물의 부상량 예측도 가능하다.