• 지질공학
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• 제24권3호
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• pp.323-332
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• 2014

The Nobi fault zone, which generated the 1891 Nobi Earthquake (M8.0), includes five or six faults distributed in and around Gifu and Aichi prefectures, Japan. Because large cities are located near the fault zone (e.g., Gifu and Nagoya), and because the zone will likely be reactivated in the future, relatively thorough surveys have been conducted on the 1891 Nobi earthquake event, examining the fault geometry, house collapse rate, and the magnitude and distribution of earthquake intensity and fault displacement. In this study, we calculated the earthquake slip along faults in the Nobi fault zone by applying a 3D numerical analysis. The analysis shows that a zone with slip displacements of up to 100 mm included all areas with house collapse rates of 100%. In addition, the maximum vertical displacement was approximately ${\pm}1700mm$, which is in agreement with the ${\pm}1400mm$ or greater vertical displacements obtained in previous studies. The analysis yielded a fault zone with slip displacements of > 30 mm that is coincident with areas in which house collapse rates were 60% of more. The analysis shows that the regional slip sense was coincident with areas of uplift and subsidence caused by the Nobi earthquake.

• Computers and Concrete
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• 제21권6호
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• pp.717-726
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• 2018

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that $SiO_2$ nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as $SiO_2$ nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of $SiO_2$ nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3361-3379
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• 2022

A nuclear power plant (NPP) piping is designed against low-frequency earthquakes. However, earthquakes that can occur at NPP sites in the eastern part of the United States, northern Europe, and Korea are high-frequency earthquakes. Therefore, this study conducts bi-directional shaking table tests on actual-scale NPP piping and studies the response characteristics of low- and high-frequency earthquake motions. Such response characteristics are analyzed by comparing several responses that occur in the piping. Also, based on the test results, a piping numerical analysis model is developed and validated. The piping seismic performance under high-frequency earthquakes is derived. Consequently, the high-frequency excitation caused a large amplification in the measured peak acceleration responses compared to the low-frequency excitation. Conversely, concerning relative displacements, strains, and normal stresses, low-frequency excitation responses were larger than high-frequency excitation responses. Main peak relative displacements and peak normal stresses were 60%-69% and 24%-49% smaller in the high-frequency earthquake response than the low-frequency earthquake response. This phenomenon was noticeable when the earthquake motion intensity was large. The piping numerical model simulated the main natural frequencies and relative displacement responses well. Finally, for the stress limit state, the seismic performance for high-frequency earthquakes was about 2.7 times greater than for low-frequency earthquakes.

• 대한토목학회논문집
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• 제39권6호
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• pp.821-831
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• 2019

9.12지진(2016.9.12., M_L=5.8)과 포항지진(2017.11.15., M_L=5.4)은 사회·경제적 피해를 야기시켰고, 이로 인해 지진에 대한 국민의 관심이 과거보다 크게 높아졌다. 지진 빈도가 높은 미국, 일본, 칠레 등 불의 고리 인근의 국가에서는 이미 지진재난에 대비·대응을 위하여 지진재해도(PSHA), 지반운동예측모델(GMPE) 등을 기반으로 인프라 시설을 관리하고 있다. 국내도 앞서 설명된 PSHA, GMPE가 개별 연구자들을 통해 독자적으로 개발되고 있지만, 모델 개발시 생성한 기초 데이터 산출 방법, 최종 결과물의 주요 요소 등이 제한적으로 공개되었다. 이는 해마다 발생하는 지진의 추가를 통한 모델 개선이 아닌 과거 지진에 대해 매번 새롭게 자료 구축을 해야 한다는 문제점을 내포하고 있다. 따라서, 본 연구에서는 GMPE 개발의 기초자료인 플랫파일 생성 방법과 지진 관측자료의 지진파형의 계기보정 방법, 계기진도 생성 방법 등을 기술하였다.

• 한국지진공학회논문집
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• 제7권6호
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• pp.35-47
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• 2003

다수의 지점 위에 놓인 교량의 경우, 지진으로 인한 지반운동은 교량길이에 따른 거리에 걸쳐 지점마다 현저하게 다를 수 있다. 본 연구는 이러한 공간적 특성을 고려하기 위하여 지점마다 다른 진폭과 위상 그리고 주파수 성분을 갖도록 지반운동 시간이력곡선을 생성하였고, Monte Carlo 해석기법을 사용하여 생성된 지반운동 하에서 교량의 비선형 동적거동을 고찰하였으며 두개의 실제 교량에 대한 취약도 해석을 수행하였다. 공간적 특성이 지진반응에 미치는 영향을 고려하여 교량교각의 연성도에 대한 취약도 곡선을 개발하였고, 동일지진 하에서의 취약도 곡선과 비교 검토하였다. 본 연구는 동일 지반운동을 사용하여 교량해석을 수행하는 경우 교각의 요구 연성계수가 상이 지반운동을 사용하는 경우보다 저평가 될 수 있다는 것을 입증하였다. 지진취약도 곡선은 지반운동의 강도를 표시하는 PGA, PGV, SA, SV와 SI의 함수로 나타내어졌다. 본 연구는 최초로 공간적 특성을 반영한 지반운동 하에서의 지진취약도 곡선을 개발하였으며, 다경간 교량의 내진설계시 시방서에 그 영향을 고려하기 위한 설계지침의 근거를 제공할 것이다.

• Earthquakes and Structures
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• 제22권1호
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• pp.1-13
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• 2022

When a building suffers damages under moderate to severe loading condition, its physical properties such as damping and stiffness parameters will change. There are different practical methods besides various numerical procedures that have successfully detected a range of these changes. Almost all the previous proposed methods used to work with translational components of mode shapes, probably because extracting these components is more common in vibrational tests. This study set out to investigate the influence of using both rotational and translational components of mode shapes, in detecting damages in 3-D steel structures elements. Three different sets of measured components of mode shapes are examined: translational, rotational, and also rotational/translational components in all joints. In order to validate our assumptions two different steel frames with three damage scenarios are considered. An iterative model updating program is developed in the MATLAB software that uses the OpenSees as its finite element analysis engine. Extensive analysis shows that employing rotational components results in more precise prediction of damage location and its intensity. Since measuring rotational components of mode shapes still is not very convenient, modal dynamic expansion technique is applied to generate rotational components from measured translational ones. The findings indicated that the developed model updating program is really efficient in damage detection even with generated data and considering noise effects. Moreover, methods which use rotational components of mode shapes can predict damage's location and its intensity more precisely than the ones which only work with translational data.

• Earthquakes and Structures
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• 제14권1호
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• pp.55-71
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• 2018

This paper investigates the role of the masonry infills on the correlation between widely used earthquake Intensity Measures (IMs) and the damage state of 3D R/C buildings taking into account the orientation of the seismic input. For the purposes of the investigation an extensive parametric study is conducted using 60 R/C buildings with different heights, structural systems and masonry infills' distributions. The results reveal that the correlation between the IMs and the seismic damage can be strongly affected by the masonry infills' distribution, depending on the special characteristics of the structural system, the number of stories and the incident angle.

• 한국지진공학회논문집
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• 제22권3호
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• pp.175-184
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• 2018

In this paper, comparative analysis of the 9.12 Gyeongju and 11.15 Pohang earthquakes was conducted in order to provide probable explanations and reasons for the damage observed in the 11.15 Pohang earthquake from both earthquake and structural engineering perspectives. The damage potentials like Arias intensity, effective peak ground acceleration, etc observed in the 11.15 Pohang earthquake were generally weaker than those of the 9.12 Gyeongju earthquake. However, in contrast to the high-frequency dominant nature of the 9.12 Gyeongju earthquake records, the spectral power of PHA2 record observed in the soft soil site was highly concentrated around 2Hz. The base shear around 2 Hz frequency was as high as 40% building weight. This frequency band is very close to the fundamental frequency of the piloti-type buildings severely damaged in the northern part of Pohang. Unfortunately, in addition to inherent vertical irregularity, most of the damaged piloti-type buildings had plan irregularity as well and were non-seismic. All these contributed to the fatal damage. Inelastic dynamic analysis indicated that PHA2 record demands system ductility capacity of 3.5 for a structure with a fundamental period of 0.5 sec and yield base shear strength of 10% building weight. The system ductility level of 3.5 seems very difficult to be achievable in non-seismic brittle piloti-type buildings. The soil profile of the PHA2 site was inversely estimated based on deconvolution technique and trial-error procedure with utilizing available records measured at several rock sites during the 11.15 Pohang earthquake. The soil profile estimated was very typical of soil class D, implying significant soil amplification in the 11.15 Pohang earthquake. The 11.15 Pohang earthquake gave us the expensive lesson that near-collapse damage to irregular and brittle buildings is highly possible when soil is soft and epicenter is close, although the earthquake magnitude is just minor to moderate (M 5+).

• Earthquakes and Structures
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• 제21권6호
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• pp.601-612
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• 2021

The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

• 한국지진공학회논문집
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• 제9권3호
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• pp.1-8
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• 2005

본 연구는 지진으로 인하여 발생한 건물의 피해액을 보다 객관적으로 예측 평가할 수 있는 ACM(Advanced Component Method) 개발 방법에 관한 것이다. ACM은 지금까지의 재래식 손실 평가방법에 사용된 구조 기술자들의 주관적인 관점과 전문가적 견해에서 탈피하여, 지진의 크기에 따른 구조형식이 각기 다른 건물들의 내진 성글 평가 기술에 바탕을 둔 지진 손실 평가 방법이다. 그 과정을 살펴보면 먼저 선별된 전형적인 건축 구조물에 대하여 비선형 정적 내진 해석인 pushover 해석을 실행하여 그들의 건물 능력도와 각 부재의 비선형 응답을 계산한다. 지진하중은 ADRS(Acceleration-Displacement Response Spectrum)의 응답 가속도와 응답 변위의 형태로 표현하여 이를 건물 능력도와 함께 능력 스펙트럼법(Capacity Spectrum Method) 기법을 이용하여 건물의 내진 성능점을 찾는다. 또한 전체 건물을 주요 구조체인 기둥, 보, 슬래브 등과 비구조체인 비내력 벽판, 외벽 장식용 요소 등을 각각 분리하여 건물 각 부재들의 지진 응답 변위에 따른 피해율을 산출한다. 이들 각 부재들의 피해는 그 부재들의 특성에 따른 적절한 보수보강기법과 그에 따른 비용산정 모델을 이용하여 각 부재의 금전적인 피해액으로 전환한다. 마지막으로 Monte Carlo기법을 이용하여 지금까지 얻은 건물의 응답과 각 부재들의 지진에 따른 피해율, 그리고 그 부재들의 비용산정 모델을 종합하여 전체 건물의 최종의 피해율을 얻는다. 특히, 현존하는 건물에 사용된 재료와 설계 가정 하중의 가변성에 따른 건물 거동에 대한 불확실성 등을 고려하기 위하여 Latin Hypercube 추출 기법을 사용하며, 마지막으로 본 연구의 사례평가를 위하여 과거 일어났던 지진 피해정보와 손실 자료들을 바탕으로 ACM방법과 재래식 방법을 이용한 건물 손실 평가 방법을 비교 분석하였다.