• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.65-65
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• 2012

인류의 역사는 태풍, 지진, 해일, 홍수 그리고 가뭄 등과 같은 자연재해와의 끊임없는 투쟁으로 점철되어왔다. 최근 들어 지구 온난화는 인류의 생존에 커다란 위협으로 대두되었다. 우주시대에 접어들면서 인간의 활동은 지구 대기권 밖으로까지 확대되면서 인간의 사회 경제적인 활동이 인공위성을 위시하여 매우 정밀한 기기에 의존하게 되었다. 그러나 인공위성과 더불어 현대사회를 지탱하는 전력, 통신, 운송 등과 같은 사회기반시설들은 태양활동에 매우 취약하다는 점이 확인되었다. 태양에서 플레어나 CME가 발생하면 X-선 복사와 더불어 고에너지 하전입자가 방출되면서 지구주변 우주환경에 급격한 변화가 일어난다. 이 기간 동안 인공위성, 전력, 통신, 항법 등이 영향을 받아 다양한 사회 경제적인 손실이 유발된다. 따라서 태양활동으로 인한 이들 시설의 붕괴 내지는 기능 저하는 현대사회의 근간을 훼손하는 이제까지 경험하지 못했던 새로운 형태의 자연재해가 될 것이다. 이 논문에서는 역사적으로 우주환경의 급격한 변화가 야기한 문제점들을 살펴보고 태양활동이 장래에 인류의 삶에 어떠한 영향을 미칠지를 전망하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.191-191
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• 2020

현재 전 세계적으로 태풍, 지진, 홍수 등의 재해 피해가 빈번히 일어나고 있고, 4차 산업의 발달로 인한 AI기술을 활용하여 자연재해 전반을 예측 할 수 있는 시스템이 도입될 정도로 과학적으로 발전 되어진 반면에, 재난으로 인한 인명 피해 수를 저감 시키는 방향을 도모 하는 데에는 어려움이 있고, 국민들의 재난피해의식도 심각 하지 않은 추세이다. 이와 같은 문제점을 파악하기 위해 한국 국민 남녀 489명을 대상으로 재난위험인식에 대한 설문을 작성하여 조사를 진행하였다. 본 연구의 목적은 국민들의 재난 안전의 위험도에 대한 인식 수준이 어떠한지 분석하고, 영향 요인을 탐색 하는 데에 있고, 조사결과 안전취약계층은 스스로 대피 하는 데에 있어 큰 어려움이 있으며, 이중 여성은 남성에 비해 안전교육과 훈련의 접근성이 적음에 따라 위험도가 더 큰 것을 확인 할 수 있었다. 본 연구를 통해 재난 안전교육의 필요성을 가지고 재난 안전 시뮬레이션 프로그램이 구축되는 필요성이 있다고 사료되어지고, 미래에 자연재해 발생 시 문제점을 파악하고 인명피해 감소가 될 전망으로 기대가 된다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.357-358
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• 2022

지진, 호우, 태풍, 화재 등 긴급한 재난 알림 전달이 필요한 상황에서 청각장애인은 소리를 통한 알림을 인지할 수 없으며 문자를 통한 알림의 인지율도 비장애인에 비하여 상대적으로 낮은 편으로서 일반적인 수단의 재난알림을 신속하게 인지하기 어려운 경우가 많다. 이와 같은 청각장애인의 재난안전 긴급알림 인지의 취약성 문제를 해결하고자 픽토그램을 통한 재난안전 긴급 알림 시스템이 개발되었다. 본 연구에서는 재난문자 통보문의 문구를 기반으로 인공지능을 통하여 청각장애인이 인지하기 보다 용이한 일련의 픽토그램으로 자동으로 변환하는 기술을 개발하고자 하였다. 이를 위해 재난안전 관련 긴급 통보문과 관련되는 픽토그램 기반의 콘텐츠를 수집하고 문자 기반의 그림 출력에 적합한 인공신경망 구조와 훈련방법을 구성하여 인공신경망 기반으로 재난문자에 대응되는 픽토그램 기반의 청각장애인 재난안전 긴급알림이 생성될 수 있도록 하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.455-462
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• 2013

The effects of earthquakes can be devastating especially to existing structures that are not based on earthquake resistant design. This study proposes a steel grid shear wall that can provide a sufficient lateral resistance and can be used as a seismic retrofit method. The pushover analysis was performed on RC structure with and without the proposed steel grid shear wall. Obtain the performance point that the target structure for seismic loads applied to evaluate the response and performance levels. The capacity spectrum at performance point is nearly elastic range, so satisfied the performance objectives(LS level). And response modification factor(R factor) were calculated from the pushover analysis. The R factor approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. The R factor increases from 2.17 to 3.25 was higher than the design criteria. As a result, according to reinforcement by steel grid shear wall, strength, stiffness, and ductility of the low-rise RC structure has been appropriately improved.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.4
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• pp.19-26
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• 2012

For a seismic design or performance evaluation of a structure, an experimental investigation on a scale model of the structure or numerical analysis based on the finite element model is considered. Regarding the numerical analysis, a three-dimensional finite element analysis is performed if a high accuracy of the results is required, while a sensitivity or fragility analysis which uses huge seismic ground motions leads to the use of a lumped-mass stick model. The conventional modeling technique to build the lumped-mass stick model calculates the amount of the lumped mass by considering the geometric shape of the structure, like a tributary area. However, the eigenvalues of the conventional model obtained through such a calculation are normally not the same as those of the actual structure. In order to overcome such a deficiency, in this study, a new lumped mass stick model is proposed. The model is named the "frequency adaptive-lumped-mass stick model." It provides the same eigenvalues and similar dynamic responses as the actual structure. A non-prismatic column is considered as an example, and its natural frequencies as well as the dynamic performance of the new lumped model are compared to those of the full-finite element model. To investigate the damping effect on the new model, 1% to 5% of the critical damping ratio is applied to the model and the corresponding results are also compared to those of the finite element model.

• Journal of the Korean Geotechnical Society
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• v.34 no.8
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• pp.37-49
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• 2018

Since the observation of ground motions in South Korea, liquefaction manifestation was the first to be observed in Pohang earthquake in 2017 with $M_L$ 5.4. Because liquefaction causes ground settlement and lateral spread damaging in-ground or super structures, various researchers have been analyzing the Pohang liquefaction case history to better understand and predict liquefaction consequence and to prevent future disasters. In prior research at the 2018 EESK conference, a map of Liquefaction Potential Index (LPI), indicating the severity of liquefaction, in Pohang was created and compared with damage observations. The LPI correlated well with the observations, but the severity categorized by LPI range was significantly higher than the actual observations in most regions. The prior LPI map was created evaluating ground motions using the simplified approach. In this research, we perform the effective site response analyses with porewater pressure generation model for the detailed evaluation of liquefaction on the liquefied sites in Pohang. We found that the simplified approach for LPI evaluation can overestimate the severity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.426-433
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• 2019

After an earthquake, fire and gas explosions are more likely to cause more casualties in cities with many apartment buildings and large complex buildings. In order to prevent this, seismic design is necessary for the fire protection sprinkler system. However, most systems currently use stainless-steel pipes, although synthetic resin pipes are used in some special places. These materials are susceptible to vibration and earthquakes. This study evaluated the displacement absorption flexibility of polyethylene (PE) and aluminum (Al) multi-layered composite pipes to increase the seismic performance in a vibration environment and during earthquakes. The seismic performance was compared with that of a stainless-steel and PE pipes. The seismic characteristics can be measured by measuring the amount and extent of vibration transmitted by the sprinkler pipe. This method can be used to judge the seismic characteristics to attenuate the vibration during an earthquake. The seismic characteristics of the pipe were verified by comparing the logarithmic attenuation rate to the initial response displacement of the vibration generated by the transverse vibration measurement method.

• Land and Housing Review
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• v.13 no.1
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• pp.141-150
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• 2022

Responding to the increasing demand for research on seismic resistance of structures triggered by a large-scale earthquake in Korea, the Ministry of the Interior and Safety revised the typical application of the existing seismic design standards with the national seismic performance target enhanced. Therefore, in this paper, the dam body of the aged Test-Bed and the penstock with fluid were modeled by the three-dimensional finite element method by introducing several variables. The current seismic design standard law confirmed the safety of the dam structure and penstock against seismic waves. As a result of the 3D finite element analysis, the stress change due to the water impact of the penstock was minimal, and it was confirmed that the effect of the hydraulic pressure was more significant than the water impact in the earthquake situation. When the hydrostatic pressure is in the form of SPH, it was analyzed that the motion of the fluid and the location of stress caused by the earthquake can be effectively represented, and it will be easier to analyze the weak part. As a result of the analysis, which considers penstock's corrosion, the degree of stress dispersion gets smaller because the penstock is embedded in the body. The stress result is minimal, less than 1% of the yield stress of the steel. In addition, although there is a possibility of micro-tensile cracks occurring in the inlet of the dam, it has not been shown to have a significant effect on the stress increa.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.70-78
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• 2023

The ordinary concentrically braced frame has an advantage of having simple design procedure. For this reason, it has been widely used for the small-sized frame structures subject to moderate or lower magnitude earthquake, even though its seismic performance against the earthquake load is not much effective compared to that of other frame systems. To enhance seismic performance of the ordinary concentrically braced frame where the bracing has a weakness for compressive behavior under lateral earthquake, seismic retrofitting by viscous damper has been commonly introduced. However, the viscous damper, itself, generally does not have stiffness for restoring the structure to the original position. This may cause residual displacement to the structure. In this paper, a self-centering viscous damper system in which upper and lower beams having flexural rigidity play a role as a nonlinear-elastic spring, restoring the spring-damper system subject to external displacement history to its original location, is developed. The numerical analysis for a simplified frame structure shows how including the developed self-centering viscous damper system leads to an enhanced seismic performance of the frame structure through energy dissipation during earthquake excitation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.279-299
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• 2019

Recently occurred earthquake Gyeongju and Pohang served as a momentum to remind that Korean peninsular is not a safety zone from earthquake anymore. The importance of seismic design, therefore, have been realized and researches regarding design response spectrum have been actively carried out by many researchers and engineers. Current tunnel seismic design method is conducted to check safety of tunnel structure by dynamic numerical analysis with condition of completed lining installation, so, it is impossible to consider safety of tunnel behavior under construction. In this study, therefore, dynamic numerical analysis considering seismic wave propagations has been performed after back analysis using results from field monitoring of tunnel under construction in fractured zone and 1st reinforcement (shotcrete, rockbolt) behaviour are analyzed. Waves are classified by period characteristic (short and long). As a result, the difference depending on period characteristic is minor, and increasements of displacement are obtained at crown displacement due to seismic wave is 28~31%, 14~16% at left side of tunnel in the fractured zone, 13~27% at right side of tunnel in the bed rock, respectively. In case of shotcrete axial force is increased 113~115% at tunnel crown, 102% at left side, 106~110% at right side, respectively. Displacement and axial force of rockbolts which are selected by type of anchored grounds (only fractured zone, fractured zone and bed rock, only bedrock) are analyzed, as a result, rockbolt which is anchored to fractured zone and bed rock at the same time are weaker than any other case.