Dong-Ju Min

Seoul National University

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Research Field

A Simulation Study on the Optimum Array of Seismic Method to Investigate Fracture Zone

Journal of the Korean earth science society (1997)

Baek-Su Seo Gwon-Ik Son Dong-Ju Min

Fractures in rocks are closely related to the physical properties such as hydraulic conductivity, mechanical stiffness and attenuation and/or delay of seismic waves. Detection of orientation and thickness of fracture zones has been a major topic of interest, particularly, for the investigation of oil and geothermal resources. In this study, optimum arrays in the seismic method are investigated by conducting a computer simulation through theoretical fracture models. Finite element method is used to calculate the traveltime, and geotomographycal inversion is conducted using ART, SIRT and LSQR method.

Geothermal exploration

Microseism

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Nonlinear analysis methods based on the unstrained element length for determining initial shaping of suspension bridges under dead loads

Computers & Structures (2013)

Myung-Rag Jung Dong-Ju Min Moon‐Young Kim

Catenary

Suspension

Structural load

10.1016/j.compstruc.2013.06.014

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Citations (51)

Structural Damping Effects on Dynamic Instability of Subtangentially Loaded and Shear Deformable Beck’s Columns

Mathematical Problems in Engineering (2016)

Dong-Ju Min Jaegyun Park Sang-Ho Yeon Moon‐Young Kim

A frequency equation of externally and internally damped and shear-flexible cantilever columns subjected to a subtangentially follower force is analytically derived in a dimensionless form with relation to the linear instability theory of Beck’s columns. Some parametric studies are then performed with variation of two damping coefficients under the assumption of Rayleigh damping. Based on the analysis results, it is demonstrated that three damping cases in association with flutter loads of Beck’s columns can be selected including one case representative of structural damping. Finally, stability maps of shear-flexible and damped Beck’s columns are constructed for the three damping cases and discussed in the practical range of damping coefficients and shear parameters. In addition, flutter loads and time history analysis results are presented using dimensionless FE analysis and compared with exact solutions.

Dimensionless quantity

Flutter

Damping ratio

10.1155/2016/3568970

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Citations (1)

Lagrangian Formulation of a Geometrically Exact Nonlinear Frame-Cable Element

Journal of the Computational Structural Engineering Institute of Korea (2012)

Myung-Rag Jung Dong-Ju Min Moon‐Young Kim

기하학적 비선형성을 고려한 두 개의 비선형 프레임요소의 co-rotational 정식화 과정을 제시한다. 운동학적으로 엄밀한 첫 번째 프레임요소는 변형된 상태의 총 변형성분으로부터 부재력을 산정하며, 정확한 접선강성행렬을 적용한다. 아울러 total Lagrangian 및 updated Lagrangian 정식화에 따른 첫 번째 요소의 엄밀한 접선강성행렬이 동일하다는 것을 보인다. 이에 반하여 두 번째 프레임요소는 절점과 절점사이의 변형을 무시하고 직선으로 가정하여 근사적인 접선강성행렬을 산정하고, 반복계산 시 증분변위로 부터 증분부재력을 구하여 총부재력을 산정한다. 두 개의 수치예제를 통해 첫 번째 프레임 요소가 기하비선형 거동을 추적하는데 있어서 더 정확하고 성능이 우수하다는 것을 입증한다. 특히 케이블부재의 비선형해석 예제를 통하여 첫 번째 프레임 요소가 휨강성을 고려한 케이블요소로 사용할 수 있음을 보인다. Two nonlinear frame elements taking into account geometric nonlinearity is presented and compared based on the Lagrangian co-rotational formulation. The first frame element is believed to be geometrically-exact because not only tangent stiffness matrices is exactly evaluated including stiffness matrices due to initial deformation but also total member forces are directly determined from total deformations in the deformed state. Particularly two exact tangent stiffness matrices based on total Lagrangian and updated Lagrangian formulation, respectively, are verified to be identical. In the second frame element, the deformed curved shape is regarded as the polygon and current flexural deformations in iteration process are neglected in evaluating tangent stiffness matrices and total member forces. Two numerical examples are given to demonstrate the accuracy and the good performance of the first frame element compared with the second element. Furthermore it is shown that the first frame element can be used in tracing nonlinear behaviors of cable members.

Tangent stiffness matrix

10.7734/coseik.2012.25.3.195

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타이드 아치교와 KTX열차의 동적상호작용을 고려한 공진현상 분석

한국지진공학회 논문집 (2016)

장정환 Dong-Ju Min Kim Moon Young

Resonance occurrence conditions are explored by performing dynamic interaction analysis of arch bridge and KTX trains. The target bridge is a 3D tied-arch bridge having span length of 120m. KTX trains consist of two power carriages, two power and passenger carriages and sixteen passenger carriages. When KTX trains run on the target bridge with the uniform speed of 100 to 500km/h, the dynamic responses of the bridge induced by moving trains are obtained from railway arch bridge-train interaction analysis. Two resonance conditions are presented and whether the resonance phenomena occur or not at the suspicious resonance velocities is rigorously investigated through bridge deflections and accelerations and their FFT analysis.

Bridge (graph theory)

Arch bridge

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Investigation of Resonance Occurrence Conditions by Dynamic Interaction Analysis between Arch bridge and KTX Trains

Journal of the Earthquake Engineering Society of Korea (2016)

Jung-Hwan Jang Dong-Ju Min Moon‐Young Kim

Bridge (graph theory)

Arch bridge

10.5000/eesk.2016.20.2.103

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Dynamic Interaction Analysis of Train and Bridge According to Modeling Methods of Maglev Trains

Journal of the Computational Structural Engineering Institute of Korea (2011)

Myung-Rag Jung Dong-Ju Min Jun‐Seok Lee Soon-Duck Kwon Moon‐Young Kim

The purpose of this study is to examine the impact that change in speed and modeling methods has on maglevs' runnability. The study constructed equations of motion on 4-DOF, 6DOF, and 10-DOF vehicles respectively and carried out numerical analysis, applying 4th Runge Kutta method, in order to run six different model maglev as changing the vehicles speed on the same bridge that had 2000 to 1 deflection. The analysis revealed that maglev's runnability improved as speed was lower and the specific model had higher number of bogey and EMS.

Maglev

Runge–Kutta methods

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Citations (1)

Magnetic moments and internal structure of hyperons

Dong-Ju Min Yongseok Oh

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Post-divergence and post-flutter analysis of sub-tangentially loaded and damped Beck column using a nonlinear FE procedure

International Journal of Non-Linear Mechanics (2016)