• 대한기계학회논문집A
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• 제38권4호
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• pp.451-457
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• 2014

최근에는 법공학 분야에 구조해석 및 구조-유동 연성해석을 이용한 다양한 시뮬레이션 기법을 활용하여 안전사고 및 재난사고에 대한 법적 책임문제를 해명하고, 보다 정확한 원인분석을 통해 원인을 규명하고 있는 추세이다. 본 연구에서 다룬 플레이트 거더교 사고는 교각과 교대 사이의 기존 교각에 대하여 확장 교각을 신설하던 중 방호벽 콘크리트 타설이 완료되는 시점에 전도 추락되어 발생되었다. 본 사고는 설계와 다른 시공 작업과 설계 시 고려되지 않은 추가 하중 등으로 인해 확장 교량에 부반력이 발생하여 구조적 불안정을 가져와 붕괴된 사고로 MIDAS 구조 해석을 통해 설계와 실제 시공 시 작업 하중에 대한 구조적 안정성을 비교 평가하여 정확한 공학적 사고의 원인을 규명하고자 한다.

• 한국전산구조공학회논문집
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• 제27권2호
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• pp.71-78
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• 2014

회전익 항공기 중 군에서 운용하는 기동헬기는 전장상황에서 운용되기 때문에 연료셀 피탄 상황에 직면할 가능성이 높다. 연료셀 피탄에 따른 내부압력 증가로 내부폭발이나 화재가 발생할 수 있으며, 이는 승무원의 생존 가능성에 치명적인 영향을 주게 된다. 따라서, 승무원의 생존성을 극대화하기 위해서는 연료셀이 직면 가능한 극한 상황을 예측하여 설계에 반영해야 한다. 항공기 연료셀 설계시 고려해야 하는 데이타는 피탄에 의한 연료셀 내부압력, 수압램 영향에 의한 연료셀 자체 및 금속피팅부 응력, 탄환의 운동에너지 등이 포함될 수 있다. 이러한 설계 데이터 확보를 위해서는 실물 시험을 수행하는 것이 가장 바람직하지만, 시간과 비용의 부담과 더불어 시험실패와 같은 시행착오 위험성으로 많은 제약이 따른다. 따라서, 사전에 다양한 설계 데이터 예측과 시행착오의 최소화를 위해서는 피탄 상황에 대한 수치해석이 필요하다. 본 연구에서는 입자법을 사용하여 연료셀 피탄 조건에 대한 유체-구조 연성 수치해석을 수행하였다. 수치해석은 전용 충돌해석 프로그램인 LS-DYNA를 사용하였고, 결과로 얻어진 탄의 거동과 에너지, 연료셀 내부압력과 등가응력의 평가를 통해 연료셀 설계와 관련한 데이터 확보 가능성을 타진하였다.

• Structural Engineering and Mechanics
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• 제66권4호
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• pp.505-513
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• 2018

Steam flooding is widely used in heavy oil reservoir with coupling effects among the formation temperature change, fluid flow and solid deformation. The effective stress, porosity and permeability in this process can be affected by the multi-physical coupling of thermal, hydraulic and mechanical processes (THM), resulting in a complex interaction of geomechanical effects and multiphase flow in the porous media. Quantification of the state of deformation and stress in the reservoir is therefore essential for the correct prediction of reservoir efficiency and productivity. This paper presents a coupled fluid flow, thermal and geomechanical model employing a program (MATLAB interface code), which was developed to couple conventional reservoir (ECLIPSE) and geomechanical (ABAQUS) simulators for coupled THM processes in multiphase reservoir modeling. In each simulation cycle, time dependent reservoir pressure and temperature fields obtained from three dimensional compositional reservoir models were transferred into finite element reservoir geomechanical models in ABAQUS as multi-phase flow in deforming reservoirs cannot be performed within ABAQUS and new porosity and permeability are obtained using volumetric strains for the next analysis step. Finally, the proposed approach is illustrated on a complex coupled problem related to steam flooding in an oil reservoir. The reservoir coupled study showed that permeability and porosity increase during the injection scenario and increasing rate around injection wells exceed those of other similar comparable cases. Also, during injection, the uplift occurred very fast just above the injection wells resulting in plastic deformation.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.747-760
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• 2018

In the present study, a methodology for developing fragilities of arch concrete dams to assess their performance against seismic hazards is introduced. Firstly, the probability risk and fragility curves are presented, followed by implementation and representation of the way this method is used. Amirkabir arch concrete dam was subjected to non-linear dynamic analyses. A modified three dimensional rotating smeared crack model was used to take the nonlinear behavior of mass concrete into account. The proposed model considers major characteristics of mass concrete. These characteristics are pre-softening behavior, softening initiation criteria, fracture energy conservation, suitable damping mechanism and strain rate effect. In the present analysis, complete fluid-structure interaction is included to account for appropriate fluid compressibility and absorptive reservoir boundary conditions. In this study, the Amirkabir arch concrete dam is subjected to a set of 8 three-component earthquakes each scaled to 10 increasing intensity levels. Using proposed nonlinear smeared crack model, nonlinear analysis is performed where the structure is subjected to a large set of scaled and un-scaled ground motions and the maximum responses are extracted for each one and plotted. Based on the results, fragility curves were plotted according to various and possible damages indexes. Discrete damage probabilities were calculated using statistical methods for each considered performance level and incremental nonlinear analysis. Then, fragility curves were constructed based on the lognormal distribution assumption. Two damage indexes were introduced and compared to one another. The results indicate that the dam has a proper stability under earthquake conditions at MCE level. Moreover, displacement damages index is more conservative and impractical in the fragility analysis than tensional damage index.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.1-15
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• 2018

In ocean industry, free surface type ART (Anti Roll tank) system has been widely used to suppress the roll motion of floating structures. In those, various obstacles have been devised to obtain the sufficient damping and to enhance the controllability of freely rushing water inside the tank. Most of previous researches have paid on the development of simple mathematical formula for coupled ship-ARTs analysis although other numerical and experimental approaches exist. Little attention has been focused on the use of 3D panel method for preliminary design of free surface type ART despite its advantages in computational time and general capacity for hydrodynamic damping estimation. This study aims at developing a potential theory based hydrodynamic code for the analysis of floating structure with baffled ARTs. The sloshing in baffled tanks is modeled through the linear potential theory with FE discretization and it coupled with hydrodynamic equations of floating structures discretized by BEM and FEM, resulting in direct coupled FE-BE formulation. The general capacity of proposed formulation is emphasized through the coupled hydrodynamic analysis of floating structure and sloshing inside baffled ARTs. In addition, the numerical methods for natural sloshing frequency tuning and estimation of hydrodynamic damping ratio of liquid sloshing in baffled tanks undergoing wave exiting loads are developed through the proposed formulation. In numerical examples, effects of natural frequency tuning and baffle ratios on the maximum and significant roll motions are investigated.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.22-30
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• 2005

Sloshing loads, produced by the violent liquid free-surface motions inside the cargo tank have become an important design parameter in ship building industry since there have been demands for the increased sizes of the cargo containment system of LNG carriers. In this study, sloshing impact pressure acting on the shell of the spherical cargo tank of an LNG carrier as well as dynamic pressure and flow behavior around the pump tower located at the center of the tank have been calculated. Comparative numerical sloshing simulations for a spherical LNG tank using 2-D LR.FLUIDS which is based on the finite difference method and 3-D MSC.DYTRAN which is capable of calculating nonlinear fluid-structure interaction have been carried out. A method of calculating sloshing-induced dynamic loads and the subsequent structural strength analysis for pump tower of a spherical LNG carrier using MSC. DYTRAN and MSC.NASTRAN have been presented.

• 대한조선학회논문집
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• 제44권4호
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• pp.360-369
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• 2007

When a large ship is advancing in waves, ship undergoes the hydroelastic response, and this have influence on structural stability and the fatigue destruction etc. of ship. The main objective of this research is to develop an accurate and convenient method on the hydroelastic response analysis of ships on the real sea states. We analyzed hydroelastic responses, which is formulated by finite element method. The numerical approach for the hydroelastic responses is based on the combination of the three dimensional source distribution method, the dynamic response analysis and the spectral analysis method. The calculated results show good agreement with the experimental and calculated ones by Watanabe.

• 대한조선학회논문집
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• 제48권6호
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• pp.552-559
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• 2011

An interest in Arbitrary Lagrangian Eulerian (ALE) finite element methods has been increased due to more accurate responses in Fluid-Structure Interaction(FSI) problems. The multi-material ALE approach was applied to the prediction of the acceleration response of free-fall lifeboat, and its responses were compared to those of the single-material ALE one. It could be found that even though there was no big difference in the simulation responses of two methods, the single-material and multi-material ALE ones, the latter multi-material ALE method showed a little bit more close response to those of experimental results compared to the former single-material ALE one, especially in the x- and z-direction acceleration responses. Through this study, it could be found that several parameters in the ALE algorithms have to be examined more carefully for a good structural safety assessment of FSI problems.

• 한국군사과학기술학회지
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• 제19권3호
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• pp.302-310
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• 2016

An underground ammunition facility requires less quantity distances than the aboveground counterpart. However, chamber blast doors which resist the high blast-pressures are necessary for prevention of the consecutive explosions when an accident explosion occurs at any chamber. This paper aims to propose an procedure for calculation of the design loads for the chamber blast doors. Modeling considerations are drawn through analyzing the influences of the geometrical shapes and mechanical properties of rocks on the propagation of pressure wave along with the tunnels. Additionally, the design loads for the chamber blast doors in a newly-built underground ammunition facility are calculated based on the proposed procedure.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.235-237
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• 2008

A unified hydrocode, ExLO, in which Largrangian, ALE and Eulerian solvers are incorporated into a single framework, has recently been developed in Korea. It is based on the three dimensional explicit finite element method and written in C++. ExLO is mainly designed for the calculation of structural responses to highly transient loading conditions, such as high-speed impacts, high-speed machining, high speed forming and explosions. In this paper the numerical schemes are described. Some improvements of the material interface and advection scheme are included. Details and issues of the momentum advection scheme are provided. In this paper the modeling capability of ExLO has been described for two extreme loading events; high-speed impacts and explosions. Numerical predictions are in good agreement with the existing experimental data. Specific applications of the code are discussed in a separate paper in this journal. Eventually ExLO will be providing an optimum simulation environment to engineering problems including the fluid-structure interaction problems, since it allows regions of a problem to be modeled with Lagrangian, ALE or Eulerian schemes in a single framework.