• Fire Science and Engineering
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• v.24 no.6
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• pp.69-75
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• 2010

A concrete filled square steel tube (CFT) is composed of the external steel material, which its strength is reduced in fire due to sudden temperature increase, and the internal concrete with high thermal capacity that can ensure the fire resistance performance of the structure. Therefore, research about the influence factors of the structural performance of CFT column is required in order to apply CFT column to a fire resisting structure, and additional research about influence for each condition is also necessary. Among the influence factors, the boundary condition between column and beam is important structurally, and it is one of the major factors that determine overall fire resisting performance. This study performed a fire experiment under loading in order to analyse the influences of CFT column to the boundary condition. As the results of the experiment, fire resistance time of 106 minutes was ensured for the clamped-end condition but 89 minutes for the hinge-end condition in case of the 360 cross section. And, fire resistance time of 113 minutes was ensured for the clamped-end condition but 78 minutes for the hinge-end condition in case of the 280 cross section.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.132-142
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• 2019

Purpose: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. Materials and Methods: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. Results: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. Conclusion: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.47-60
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• 2023

At present, in South Korea, there is a growing concern regarding solar power facilities installed on slopes because they are prone to damage caused by natural disasters, such as heavy rainfall and typhoons. Each year, these solar power facilities experience soil erosion due to heavy rainfall and foundation damage or detachment caused by strong wind loads. Despite these challenges, the interaction between the ground and structures is not adequately considered. Current analyses primarily focus on the structural stability under external loads; the overall facility site's stability-excluding the solar structures-in relation to its surrounding slopes is neglected. Therefore, in this study, we use finite-difference method analysis to simulate the behavior of the foundation and piles to assess changes in lateral displacement and bending stress in piles, as well as the safety factor of sloped terrains, in response to various influencing factors, such as pile diameter, spacing between piles, pile-embedding depth, wind loads, and dry and wet conditions. The analysis results indicate that pile spacing and wind loads significantly influence lateral displacement and bending stress in piles, whereas pile-embedding depth strongly influences the safety factor of sloped terrains. Moreover, we found that under certain conditions, the design criteria in domestic standards may not be met.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.10-18
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• 2014

Mechanically fastening FRP (MF-FRP) strips using nails and anchors, has been shown to provide a more ductile behavior to the strengthened structural element than using bonded FRP. To further advance the state of the knowledge on this strengthening method, the current study examined environmental effects for six months on MF-FRP beams. Reinforced concrete beams strengthened with mechanically fastened FRP strips and subjected to sustained loads for six months were exposed to outdoor weather and constant high temperatures ($40^{\circ}C$). For comparison, the behavior of RC beam with and without sustained loads was evaluated. Results from flexural tests did not show any significant degradation or change of failure mode as a result of sustained load and of environmental effects such as high temperatures and outdoor weather over a period of six months. Failure of the beams was governed by FRP delamination followed by concrete crushing as not much load applied to the nail and anchors because of slip effects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.777-783
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• 2021

Aircraft are affected by various vibrations during maneuvering. These vibrations may have a fatal effect on the survival of aircraft in some cases, so the safety of components applied to the aircraft should be proven against various vibrations through random vibration analysis. In this study, the structural robustness of an external fuel tank and pylon for military aircraft was evaluated under random vibration conditions using commercial software, MSC Random. In the random vibration analysis, a frequency response analysis was performed by imposing a unit load on the boundary condition point, and then excitation was performed with a PSD profile. In this process, the required mode data was extracted through a modal analysis method. In addition, the random vibration profile specified in the US Defense Environment Standard was applied as random vibration conditions, and the PSD profile given in units of G's was converted into units of gravitational acceleration. As a result of the numerical analysis, we evaluated the structural robustness of the external fuel tank and pylon by identifying the safety margins of beam elements, shell elements, and solid elements in a numerical model for random vibration in the x, y, and z directions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.570-573
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• 2011

본 논문에서는 배관의 국부변형을 고려하여 각 배관의 특성으로 인하여 발생하게 되는 최대 응력 발생지점에 대한 평가 및 설계기법을 제안한다. 다중관은 일반적으로 배관의 매설 조건이 불안정한 곳이나 배관의 내부 유체의 유출 모니터링 및 난방관 등의 보온을 목적으로 사용되나, 다중관의 거동에 대한 거동 및 설계에 대한 연구는 미비한 실정이다. 본 연구에서 제안한 기법은 탄성범위에서 거동하는 연성관을 대상으로 하며 외관의 형상 및 외부 하중에 의하여 예상되는 국부 변형을 설계 인자로 고려하는 방법이다. 일반적인 원형관의 경우 관의 하단부에서 가장 큰 국부 변형 반경을 나타나며, 국내외에서 사용하고 있는 정사각 콘크리트 보호공의 경우 관의 상측, 하측부($45+90n^{\circ}$)에서 가장 큰 반경을 관찰할 수 있다. 이는 내압이 작용하는 구조물에 대하여 낮은 압력에도 항복에 이르는 환경을 제공하기 때문에 설계 시 반영되어야 할 중요한 요소이다.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.779-788
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• 2013

The load requirements should be known to design mechanical structure. This paper proposes a generation method of load requirements using U.S. military specification to design the external mounting structure of the helicopters of which the flight environments such as aerodynamic forces and inertia forces are unknown. In this study, the load requirements which were applied at the design of the pod structure for helicopter captive flight test could be computed by using this method. The validation of proposed method was confirmed from the test flight using developed pod system.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.91-91
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• 2017

최근 국민 삶의 질 향상, 건강한 먹거리 인식 및 국내 여건 변화 등으로 벼농사에 비해 상대적으로 소득 수준이 높은 밭작물 생산에 대한 수요가 증가하고 있으나, 관련 농업기계 개발이 미흡하여 밭농업 기계화가 절실한 실정이다. 밭작물의 경우 기계화율이 2015년 56.3%이며, 특히 파종, 이식작업이 5%, 수확작업이 13.3% 수준으로 열악한 실정임. 경운정지 기계화율은 99%를 넘으며, 방제 작업도 기계화율이 85~99% 수준으로 다른 작업에 비해 높은 실정으로, 파종, 이식, 수확작업의 기계화는 밭농업 일관기계를 위하여 반드시 필요하다. 감자는 주요 밭작물 중 하나로, 최근 가공용 소비로 수입량이 증가하여 국내에서 자주식 굴취/선별/수집형 수확기(2011, 농촌진흥청)가 개발되었으나, 가격이 높고 표피손상 등 개선이 필요하여 트랙터 부착형 수집형 감자수확기가 개발 중에 있다. 따라서 본 연구에서는 수집형 감자 수확기 시작기 구조해석을 하려고 한다. 우선 시작기의 도면을 CATIA를 활용하여 3D로 작성한 뒤, MIDAS NFX 시뮬레이션 및 구조해석 프로그램으로 구조해석을 진행하였다. 수행한 해석으로는 선형정적해석으로서 외부하중에 대해 구조물의 변형을 검토하는 해석이다. 재질은 SM45C로 선정하였고, 접촉조건과 구속조건을 설정한 뒤 감자수확기 굴취부에 집중하중을 200 ~ 1000 N 까지 200N 간격으로 선형정적해석을 진행하여 Von-Mises 응력, 허용응력, 극한응력, 안전율을 해석하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.107-115
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• 2002

A parametric study has been conducted to evaluate the effects of finite element modeling methods on the internal loads, sizing and the weight of the multi-spar aircraft wing structures. The wing is idealized into total 18finite element models and subjected to 4typical external load conditions. An automatic sizing algorithm based on MSC/NASTRAN and MSC/PATRAN is developed. The results show that the critical part affection the internal loads and weight of the structure is wing skin. Effect of modeling of the spar and rib on the structural behavior is not manifest. On the contrast to the general expectation, the models using the bending-resistant elements show the heavier weight than ones by the elements without bending stiffness. From this results, designers of multi-spar wing are recommended to construct the finite element model considering the bending stiffness, or to check the characteristics of the structure before modeling.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.539-549
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• 2017

In this paper, experimental studies on the shroud separation were performed to investigate characteristics of the shroud separation at mach 3. Shroud separation tests were carried out in the vertical free-jet wind tunnel that is capable of testing separable structures. A shroud model was miniaturized to meet test objectives and test section dimensions of the wind tunnel. Pneumatic Locking and separation mechanisms were designed considering external force due to free stream. High speed cameras were used to record the shroud motion and unsteady shock patterns over the deploying shrouds during the shroud separation process. Also, unsteady pressures on the nose surface were measured by using the pressure sensors. Through the tests, the measurement data necessary for researches on the shroud separation technology were obtained. Shroud separation behaviors and characteristics of unsteady pressure on the nose surface for each external flow conditions were analyzed.