• 한국지구과학회지
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• 제34권6호
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• pp.492-506
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• 2013

최근 백두산의 재분화 문제가 하나의 중요한 지구과학적 문제로 부상하고 있다. 백두산과 같이 대규모 칼데라 호수를 갖고 있는 화산의 폭발은 단순히 화산분출뿐만 아니라 칼테라 호수에 저장된 물의 유출로 인해 큰 재해를 유발할 수 있어 연구가 필요하다. 대형 화산성 홍수는 모든 종류의 인공 구조물을 파괴할 수 있는 에너지를 가지고 있고, 유속이 100 km $hr^{-1}$에 달하며, 도달거리가 수 백 km까지 이르기 때문에 치명적인 피해를 가져올 수 있다. 연구의 최종목표는 백두산의 지질과 지반 조건에서 분화 시 예상되는 화산성 홍수의 피해를 예측하는 것이다. 하나의 사전 연구로서 백두산 화산이 분출되면서 천지에 저장된 물이 방류될 경우를 가정한 유량곡선 시나리오에 근거하여 수치해석을 실시하였다. 각각의 시나리오 별(림 붕괴, 단순융기, 림 붕괴와 융기의 조합, 강우형성 등)로 시간의 함수로서 유량변화를 이끌어내기 위해 선행 연구를 바탕으로 백두산 천지 유출 모형을 전개하였다. 천지에서 마그마 융기와 림 붕괴가 동시에 발생하면 최고 유량이 25,000 $m^3s^{-1}$에 이르러 백두산 천지의 화산홍수가 주변 지역에 심각한 자연재해를 가져올 수 있는 것으로 보인다. 이 연구에서는 저수지의 물이 방류되는 순간유량곡선에 치중하였으며 천지 유량 방출 후 하류 하천 하도 추적은 다루지 않았다.

• Structural Engineering and Mechanics
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• 제73권3호
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• pp.303-317
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• 2020

In this study an innovative rocking zipper braced frame (RZBF) is proposed to overcome the deficiencies of common concentrically braced frames. RZBF is an improved rocking concentrically braced frame which is based on combination of rocking behavior and zipper columns. The base rocking joints and post-tensioned bars provide rocking response and restoring force, respectively. Also, zipper columns distribute the unbalance force over the frame height and reduce the damage concentration. To evaluate seismic performance of RZBF, a comparison study is carried out considering concentrically braced frame, zipper braced frame, rocking concentrically braced frame and RZBF. Thereby, a suite of non-linear time history analyses had been performed on four different types of archetypes with four, six, eight, ten and twelve stories. Frames were designed and non-linear time history analyses were conducted in OpenSees. To compare the seismic behavior of the archetypes, roof drifts, residual roof drifts, story drifts, the forces of first and top story braces, PT bars forces, column uplift and base shears were taken in to consideration. Results illustrate that using RZBF, can reduce the damage due to reduced residual drifts. Zipper columns enhance the seismic performance of rocking systems. As the number of stories increase in the RZBF systems, larger top story braces were needed. So the RZBF system is applicable on low and midrise buildings.

• Geomechanics and Engineering
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• 제14권4호
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• pp.377-386
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• 2018

This paper focuses on the development of a new non-linear macro-element for the modelling of soil-foundation interaction. Material and geometrical nonlinearities (soil yielding and foundation uplift respectively) are taken into account in the present macro-element to examine the response of shallow foundations under monotonic and cyclic loads. Several applications of soil-foundation systems are studied. The results obtained from these applications are in very favourable agreement with those obtained through other numerical models in the literature.

• Geomechanics and Engineering
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• 제17권2호
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• pp.165-173
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• 2019

Plate anchors are generally used for structures like transmission towers, mooring systems etc. where the uplift and lateral forces are expected to be predominant. The capacity of anchor plate can be increased by the use of geosynthetics without altering the size of plates. Numerical simulations have been carried out on three different sizes of square anchor plates. A single layer geosynthetic has been used as reinforcement in the analysis and placed at three different positions from the plate. The effects of various parameters like embedment ratio, position of reinforcement, width of reinforcement, frequency and loading amplitude on the pull out capacity have been presented in this study. The load-displacement behaviour of anchors for various embedment ratios with and without reinforcement has been also observed. The pull out load, corresponding to a displacement equal to each of the considered maximum amplitudes of a given frequency, has been expressed in terms of a dimensionless breakout factor. The pull out load for all anchors has been found to increase by more than 100% with embedment ratio varying from 1 to 6. Finally a semi empirical formulation for breakout factor for square anchors in reinforced soil has also been proposed by carrying out regression analysis on the data obtained from numerical simulations.

• Structural Engineering and Mechanics
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• 제83권5호
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• pp.627-644
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• 2022

In past major earthquakes (1994 Northridge, 1995 Kobe, Chi-Chi 1999, Kocaeli 1999), significant damages occurred in the liquid storage tanks. The basic failure patterns were observed to be the buckling of the tank wall and uplift of the anchorage system. The damages in the industrial facilities and nuclear power plants have caused the spread of toxic substances to the environment and significant fires. Seismic isolation can be used in liquid storage tanks to decouple the structure and decrease the structural demand in the superstructure in case of ground shaking. Previous studies on the use of seismic isolation systems on liquid storage tanks show that an isolation system reduces the impulsive response but might slightly increase the convective one. There is still a lack of understanding of the seismic response of seismically isolated liquid storage tanks considering the fluid-structure interaction. In this study, one broad tank, one medium tank, and one slender tank are selected and designed. Two- and three-dimensional elastomeric bearings are used as seismic isolation systems. The seismic performance of the tanks is then investigated through nonlinear dynamic time-history analyses. The effectiveness of each seismic isolation system on tanks' performance was investigated. Isolator tension forces, modal analysis results, hydrodynamic stresses, strains, sloshing heights and base shear forces of the tanks are compared. The results show that the total base shear is lower in 3D-isolators compared to 2D-isolators. Even though the tank wall stresses, and strains are slightly higher in 3D-isolators, they are more efficient to prevent the tension problem.

• 대한토목학회논문집
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• 제33권1호
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• pp.101-113
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• 2013

반복적인 하중을 받는 볼트 연결부의 비선형적인 거동을 예측할 수 있는 역학적 고등해석 모델을 개발하는 데 주된 초점을 두어 본 연구를 수행하였다. 또한 대표적인 접합부 형태인 T-stub 접합부의 연결 컴포넌트에 대한 실제의 하중 재하 실험값을 활용한 해석으로 얻어진 거동에 대한 예측의 정확성 및 모형화의 타당성을 입증하였다. 연결부를 이루고 있는 구성요소들의 거동은 볼트의 인장변형, T-stub 플랜지의 휨변형, T-stub 몸체의 신장, 전단볼트의 지압 및 미끄러짐을 포함하며 접합부내에서 개별적인 힘-변위 메커니즘으로부터 정의된 다중 선형의 강성모델에 의하여 재현된다. 이러한 구성요소들은 그들의 거동특성을 지닌 비선형 스프링으로 모형화되어 역학적 해석 모델에 설치되어 연결부 전체의 거동을 수치해석적인 방법으로 예측하도록 한다. 해석 모델에 의한 예측값은 강성, 강도 및 변형 측면에서 실험값과 비교하여 정확성을 평가하였으며 이를 근거로 본 연구에서 제안된 역학적 해석 모델이 볼트 연결부의 거동과 성능을 만족하며 예측 가능하다는 결론을 내렸다.

• Smart Structures and Systems
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• 제26권3호
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• pp.277-290
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• 2020

Disasters, including earthquakes and landslides, have enormous economic and social losses besides their impact on environmental disruption. Iran, and particularly its Western part, is known as an earthquake susceptible area due to numerous strong ground motions. Studying ecological changes due to climate change can improve the public and expert sector's awareness and response to future disastrous events. Synthetic Aperture Radar (SAR) data and Interferometric Synthetic Aperture Radar (InSAR) technologies are appropriate tools for modeling and surface deformation modeling. This paper proposes an efficient approach to detect ground deformation changes using Sentinel-1A. The focal point of this research is to map the ground surface deformation modeling is presented using InSAR technology over Sarpol-e Zahab on 25^th November 2018 as a study case. For surface deformation modeling and detection of the ground movement due to earthquake SARPROZ in MATLAB programming language is used and discussed. Results show that there is a general ground movement due to the Sarpol-e Zahab earthquake between -7 millimeter to +18 millimeter in the study area. This research verified previous researches on the advanced image analysis techniques employed for mapping ground movement, where InSAR provides a reliable tool for assisting engineers and the decision-maker in choosing proper policies in a time of disasters. Based on the result, 574 out of 682 damaged buildings and infrastructures due to the 2017 Sarpol-e Zahab earthquake have moved from -2 to +17 mm due to the 2018 earthquake with a magnitude of 6.3 Richter. Results show that mountainous areas have suffered land subsidence, where urban areas had land uplift.

• 한국지구과학회지
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• 제33권6호
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• pp.519-533
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• 2012

본 연구는 호주 남동부 Victoria 남부 해안을 따라 발달하고 있는 Otway 산맥 일대에서 지난 5 Ma 동안의 신기지체구조 운동의 성격을 해안 산악 지역을 따라 분포하고 있는 해안단구의 발달상을 통해 밝히고 있다. OSL 연대 측정으로부터 얻은 저위 해안단구면의 융기율은 판 내부 구조운동의 영향이 현생 지형 발달에 미치는 결과를 명확히 보여주고 있다. 또한 본 연구는 제4기 해안단구와 플라이오세 고해수준 기록 간의 층서적 관계를 통해 후기 신제3기 이후에 나타나는 지구조 운동의 변화적 속성을 밝히고 있다. 이와 같은 후기 신제3기 이후 가속화된 지구조 운동 반응은 호주-태평양판의 이동성의 변화와 이에 따른 경계 응력의 증가가 대륙 내부 응력 수준에도 영향을 미친 결과로 이해된다.

• 지질공학
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• 제31권3호
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• pp.269-281
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• 2021

Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

• 문화기술의 융합
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• 제8권3호
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• pp.265-270
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• 2022

본 연구는 콘크리트 궤도용 탄성레일체결장치(System 300-1)의 손상취약부에 관한 실험 및 해석적 연구이다. 콘크리트 궤도에서 탄성레일체결장치는 열차주행 시 레일과 침목을 결속하는 핵심 궤도구성품이다. 레일체결장치 구성품 중 방진패드와 텐션 클램프(Tension Clamp)는 압축력과 부상력에 대응하며 상시 변형이 발생되는 피로부재이다. 본 연구에서는 동일구간의 운행선에서 6년, 11년, 16년 동안 사용된 탄성레일체결장치를 채취하여 사용년수에 따른 텐션 클램프의 잔류변형 특성을 분석하였다. 또한 수치해석을 바탕으로 주요 구성품별 거동메커니즘을 분석하고 손상취약부를 도출하였다. 본 연구에서 수행한 수치해석을 통해 체결력 도입부터 외력 작용에 따른 텐션 클램프 각부의 응력(변형율)을 분석하여 텐션 클램프의 손상취약부를 도출하였다.