• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.253-256
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• 2011

본 논문에서는 표면효과와 비선형 탄성효과를 고려한 FCC 나노박막의 순차적 멀티스케일 해석 모델을 제시한다. 표면에서의 구성방정식은 표면응력과 표면탄성계수를 이용하여 선형으로 표시되며, 표면효과를 나타내기 위한 표면물성들은 EAM 포텐셜을 이용한 원자적 계산 방법으로 계산된다. 두께가 얇은 나노박막은 표면응력으로 인하여 면내 방향으로 수축 또는 인장의 변형이 발생하게 된다. 나노박막의 평형상태에서의 변형율은 두께가 얇은 박막의 경우 재료가 선형 탄성 영역을 벗어나는 값을 가지는 경우가 많으므로 나노박막의 해석시 벌크 영역의 비선형 탄성 효과를 고려해야 한다. 이러한 비선형 탄성 효과를 고려하기 위해 본 연구에서는 FCC 구조를 가지는 금속의 비선형 탄성 모델을 제시하고, EAM 포텐셜로 계산된 응력과 탄성 계수를 이용하여 매칭 기법을 통하여 비선형 탄성 모델의 계수들을 결정한다. 또한 Cauchy-Born Rule 모델과 분자동역학 전산모사를 통하여 본 연구에서 제안된 비선형 탄성 모델에 대한 검증을 수행한다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.10-13
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• 2010

세그먼트 자중 등에 의한 휨모멘트와 케이블 수직압축력에 의한 합성응력이 발생되고 바닥판 경간비가 변하는 사장교의 시공단계에서는 전단지연의 영향범위가 다를 수 있다. 이 연구에서는 1면 케이블 콘크리트 박스 사장교를 대상으로 시공단계시 보강형에 고려되어야 할 합성응력에 의한 유효플랜지폭을 분석하였다. 그 결과 바닥판 경간비가 0.38 이하의 범위에서 보강형의 전폭을 유효플랜지폭으로 적용할 수 있는 것으로 해석되었다. 따라서 시공단계시 변화되는 바닥판 경간비의 크기에 관계없이 전폭을 유효플랜지폭으로 반영하는 실무관행은 안전측 설계가 되지 못할 수 가 있다. 바닥판 경간비가 작아짐에 따라서는 전폭과 캔틸레버 구조계로 유효플랜지폭을 결정하는 것이 타당하다. 이 연구에서는 수직력에 대한 도로교설계기준의 유효플랜지폭 규정에 대한 평가도 수행하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.159-167
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• 1995

본 연구는 유도탄 비행시험시에 연소관의 스커트와 날개 장착용 브라켓에 작용하는 공력하중과 연소관에 내압이 동시에 작용하는 추진기관에 대하여 구조 해석하였다. 추진기관의 스커트부 및 브라켓부의 공력하중은 3차원적으로 작용하기 때문에 대칭성을 이용한 $180^{\circ}C$3차원 구조 해석을 수행하여 비행시험, 수압시험, 지상시험 모드에 대하여 응력 수준을 비교하였다. 해석 결과 3가지 모드의 최대 등가응력은 거의 같으며, 비행시험시 공력하중이 앞마개부에 미치는 영향은 최대 등 가응력의 6%이내로 상당히 작았다. 수압시험 모드와 지상시험 모드의 실험치와 해석치를 비교한 결과 정확한 해석을 위해서는 점화기를 모델링과 점화기와 연소관, 브라켓과 연소관에 접촉요소의 적용, 3차원 비선형 해석등 보다 상세한 해석이 필요함을 알 수 있었다.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.311-321
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• 2007

Failure of underground structures in hard rocks is a function of the in-situ stress, the intact rock strength and the distribution of fractures in the rock mass. At highly stressed regime, brittle failure is often observed due to excavation-induced stress. The characteristics of brittle failure are classified as failure grade, failure initiation stress, extent of failure and depth of failure. For safety construction of underground structures, these characteristics of brittle failure with stress conditions should be understood. In this study we evaluated the relationship between the extent and depth of failure with stress conditions for failure happened model specimens through true triaxial model experiments. The extent and depth of failure were determined using visual observation and computed tomography (CT). The results indicate that the depth of failure was affected by differential stress perpendicular to the axis of tunnel. However the extent of failure was irrelevant to the stress conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.68-77
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• 2014

In this study, polysulfide epoxy polymer concrete was chosen as an ultra thin bridge deck overlay, and the effect of polymer concrete pavement on the fatigue stress range of the orthotropic steel deck was analyzed through the comparative analysis with epoxy asphalt pavement and SFRC pavement. Abaqus was used to estimate the fatigue stress range, and signed von-mises stress was used to estimate fatigue stress range according to pavement materials and thickness, considering there were multi axis stresses which have longitudinal and lateral direction on the welded parts of the steel deck.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.423-431
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• 2004

For the fracture mechanics analysis of cracks in welds of dissimilar steels, residual stress analysis and fracture analysis must be performed simultaneously. The standard definition of the J -integral leads to a path dependent value in the presence of a residual stress field. And unlike cracks in homogeneous materials, a bimaterial interface crack always induces both opening and shearing modes of stress in the vicinity of the crack tip. Therefore, it is necessary to develope a path independent J-integral definition for a crack in a residual stress field generated by welding of dissimilar steels. This paper addresses the modification of the Rice-J-integral to produce a path independent J -integral when residual stresses due to welding of dissimilar steels and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this class of problems is used. And a program which can evaluate the J -integral for a crack in a weld of dissimialr steels is developed using proposed J integral definition.

• 전기의세계
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• v.34 no.4
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• pp.205-212
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• 1985

기계적응력하에서의 고분자재료의 절연강도특성은 시료의 종류, 시료의 기계적 특성 및 기계적응력의 조건등의 주변조건에 따라 크게 변화하지만, 고분자내부구조의 변화에 기인한 절연파환계조의 변화를 고찰함으로써 어느정도 이방면의 해석이 가능할 것으로 생각된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.415-425
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• 2017

Stresses occur in the spent nuclear fuel disposal canister due to the impulsive forces incurred in the accidental drop and impact event from the transportation vehicle onto the ground during deposition in the repository. In this paper, the comparative study of finite element analysis for stresses occurring in various models of the spent nuclear fuel disposal canister due to these impulsive forces is presented as one of design processes for the structural integrity of the canister. The main content of the study is about the design of the structurally safe canister through this comparative study. The impulsive forces applied to the canister subjected to the accidental drop and impact event from the transportation vehicle onto the ground in the repository are obtained using the commercial rigid body dynamic analysis computer code, RecurDyn. Stresses and deformations occurring due to these impulsive forces are obtained using the commercial finite element analysis computer code, NISA. The study for the structurally safe canister is carried out thru comparing and reviewing these values. The study results show that stresses become larger as the wall encompassing the spent nuclear fuel bundles inside the canister becomes thicker or as the diameter of the canister becomes larger. However, the impulsive force applied to the canister also becomes larger as the canister diameter becomes larger. Nonetheless, the deformation value per unit impulsive force decreases as the canister diameter increases. Therefore, conclusively the canister is structurally safe as the diameter increases.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.205-212
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• 2021

Offshore jacket structures generally comprise steel members, and the safety standard for jacket structures typically focuses on the steel components. However, large amounts of concrete grouting is filled in the legs of the Gageocho jacket structure to aid in the recovery from typhoon damage. This paper proposes a safe and lightweight design for the Gageocho ocean research station comprising steel members instead of large amounts of concrete reinforcement in the legs. Based on the actual design, the structural members are grouped according to their functional roles, and the inner diameter of the cross-section in each design group is defined as a design variable. Structural optimization is carried out using a genetic algorithm to minimize the total weight of the structure. To satisfy the conservative safety standards in the offshore field, both the maximum stress and the unity check criteria are considered as design constraints during optimization. For enhanced safety confidence, extreme environmental conditions are assumed. The maximum marine attachment thickness and the section erosion in the splash zone are applied. Additionally, the design load is defined as the force induced by extreme waves, winds, and currents aligned in the same direction. All the loading directions surrounding the structure are considered to design the structure in a balanced and safe manner. As a result, compared with the current structure, the proposed structure features a 45% lighter design, satisfying the strict offshore safety criteria.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.542-549
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• 2022

Purpose: Pipes are widely used as applied devices in many industrial fields such as machinery, electronics, electricity, and plants, and are also widely used in safety-related fields such as firefighting and chemistry. With the diversification of products, the importance of technology in the piping field is also increasing. In particular, when changing the existing copper pipe to stainless steel, it is necessary to evaluate safety and flow characteristics through structural analysis or flow analysis. Method: This study investigated the structural stability of the 6.35 and 15.88 socket models, which are integrated insert type connectors developed by a company, using FEM. For structural analysis, HyperMesh as pre-processor, HYPER VIEW as post-processor, and LS-DYNA as solver were used. Result: In the case of 6.35 socket, the maximum stresses at hook, holder and hinge were 95.02MPa, 19.59MPa and 44.01MPa, respectively, and in case of 15.88 socket, it was 127.7 MPa, 40.09MPa and 45.23MPa, respectively. Conclusion: Comparing the stress distribution of the two socket models, the stress in the 15.88 socket, which has a relatively large outer diameter, appears to be large overall, but it is significantly lower than the yield stress of each material, indicating that there is no problem in structural safety in both models.