• 한국기계가공학회지
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• 제16권4호
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• pp.89-96
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• 2017

A cable tray is a structure made of metal or a non-combustible material that supports cables in the electrical wiring of buildings. Cable trays should be developed to meet the various requirements of the construction site. In this study, a design system was developed to calculate the maximum support load and the maximum deflection according to the cross-sectional shape of the cable tray. The cross-sections of cable trays were modeled by combining linear and arc elements, and cross-sectional characteristics such as the 2nd moment of area were calculated. The distributed load and the concentrated load were applied to the cable tray using the Euler beam theory, and then the deflection profiles and maximum stress were calculated. To verify the developed system, deflection distributions and maximum stresses for two types of cable trays were calculated and compared. The maximum deflection and maximum stress errors calculated from the developed system were found to be less than 4% compared with numerical analysis results.

• Structural Engineering and Mechanics
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• 제4권1호
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• pp.25-35
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• 1996

This paper describes a continuum variational formulation for design optimization of nonlinear structures in the elastic-plastic domain, where unloading and reloading of the structures are allowed to occur. The Total Lagrangian procedure is used for the description of the structural deformation. The direct differentiation approach is used to derive the sensitivities of the various structural response measures with respect to the design parameters. Since the material goes into the inelastic range and unloading and reloading of the structure are allowed to occur, the structural response is path dependent and an additional step is needed to integrate the constitutive equations. It can be shown, consequently, that design sensitivity analysis is also path-dependent. The theory has been discretized by the finite element technique and implemented in a structural analysis code. Mathematical programming approach is used for the optimization process. Numerical applications on trusses are performed, where cross-sectional areas and nodal point coordinates are treated as design variables. Optimal designs have been obtained and compared by using two different strategies: a two level strategy where the levels are defined accordingly the type of design variables, cross sectional areas or node coordinates, and optimizing simultaneously with respect to both types of design variables.

• 한국전산구조공학회논문집
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• 제17권2호
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• pp.215-222
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• 2004

재분배기법을 이용한 변위조절설계법이 고층건물의 실용적인 변위제어 기법으로 제안되고 있다. 현재까지 대부분의 재분배기법을 이용한 변위조절설계법은 일률적으로 단면적을 설계변수로 사용하고 있으나, 부재 특성에 따라 지배적인 부재력이 다르므로 부재적 특성을 고려하여 설계변수를 선택할 필요가 있다. 그러므로 본 연구에서는 부재별로 부재력 특성을 고려한 설계변수를 사용한 변위조절설계법을 제안하고 이를 20층 강접골조-전단벽 구조물의 변위조절설계에 적용하여 기존의 단면적을 설계변수로 사용한 변위조절설계법과 비교 평가하였다. 적용 결과, 부재 특성을 고려한 변위조설설계법이 부재별로 지배적인 부재력에 해당하는 부재 단면성능을 설계변수로하여 부재별 변위기여도를 직접 조절하므로 물량 및 변위 예측의 정확도 측면에서 비슷하거나 더 우수함을 알 수 있었다.

• 한국실천공학교육학회논문지
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• 제4권2호
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• pp.84-90
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• 2012

화학분석 설계의 한 사례로서 디지털 기록매체 중 하나인 CD-R (Compact Disc Recordable) 기록층의 단면구조와 기록층의 주요성분인 염료의 구성성분 및 화학구조를 분석하기 위해 분석계획을 수립하고 분석을 수행하는 전 과정을 기술하였다. 미지시료의 화학분석은 많은 경험과 지식을 요하는 복잡한 과정이기 때문에 학생들이 화학분석을 위한 설계 절차를 수립하고 분석방법의 선택이나 자료해석 등에 어려움을 겪고 있어 이해를 돕기 위한 사례로서 CD-R 개발단계에서 실제로 수행했던 한 제품분석의 전 과정을 제시하였다. 본 연구에서는 SEM을 사용하여 CD-R의 substrate (기판) 및 기록층 (Dye 층)의 단면적 구조를 확인하였다, 기록층인 염료는 적절한 용매를 이용하여 용해 수집한 후 TLC (얇은 막 크로마토그래피)를 이용해 성분별로 분리하였다. 분리된 각 성분을 UV-Vis 흡수분광법으로 흡광도를 측정하여 정량하였고, GC-MS와 NMR을 이용해 각 성분의 화학구조를 분석하고 질량분석법을 통해 최종적으로 질량을 확인하였다.

• 한국생산제조학회지
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• 제21권3호
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• pp.421-424
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• 2012

Carbon Fiber reinforced composite material can be designed for the optimized performances of structural member that have achieve appropriate mechanical properties with cross-sectional shape, fiber direction, stacking sequence and thickness. So there are needed extensive databases each optimal design of CFRP structural member by impact through the preparation of different shape, interface number, thickness and stacking angle. When pressure is applied to structural member, compression, bending and torsion is shown on the corresponding member. For the effective utilization of fiber reinforced composite material as main structural member, optimized design technology should be established to maximize mechanical properties for compression, bending and torsion. In this paper, CFRP prepreg sheet with different stacking angle is manufactured in CFRP and hybrid(Al+CFRP) with circular cross-section. Strength and stiffness is gotten respectively by flexure test. CFRP structure and hybrid structure can be compared with each other. The best design guideline can be analyzed by use of this study result.

• 한국건설순환자원학회논문집
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• 제8권4호
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• pp.545-552
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• 2020

본 연구에서는 터널 지보재로서의 역학적 성능을 충분히 발휘하면서 시공성 및 안정성을 보다 향상시키기 위한 목적으로 개발된 숏크리트용 섬유 그물망 일체형 터널 지보시스템의 지보 성능을 4점 굽힘 시험, 2차원 유한요소해석 및 단면 해석을 통해 평가하였다. 4점 굽힘 시험을 통한 휨 성능 평가 결과, 섬유 그물망 보강 숏크리트의 경우, 강섬유 보강 숏크리트와는 달리 섬유 그물망의 인장 성능이 발휘되면서 균열 이후에도 하중이 지속적으로 증가하는 결과가 나타났다. 또한, 지반 조건에 대한 터널 단면 구조 해석, 섬유 그물망 및 강섬유 보강 숏크리트의 단면 해석 결과, 섬유 그물망 보강 숏크리트의 타설 두께를 기존에 비해 감소시켜도 충분한 지보 성능이 발휘될 수 있는 것으로 나타났다. 추가적으로, 이와 같은 결과를 종합하여, 암반등급 3등급 지반 중 보다 높은 안정성을 요구하는 시공 구간에 효율적으로 적용될 수 있는 숏크리트용 섬유 그물망 일체형 터널 지보시스템의 지보패턴이 제안되었다.

• Wind and Structures
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• 제16권5호
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• pp.457-476
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• 2013

This paper presents theoretical background for a semi-empirical, mathematical model of critical vortex excitation of slender structures of compact cross-sections. The model can be applied to slender tower-like structures (chimneys, towers), and to slender elements of structures (masts, pylons, cables). Many empirical formulas describing across-wind load at vortex excitation depending on several flow parameters, Reynolds number range, structure geometry and lock-in phenomenon can be found in literature. The aim of this paper is to demonstrate mathematical background of the vortex excitation model for a theoretical case of the structure section. Extrapolation of the mathematical model for the application to real structures is also presented. Considerations are devoted to various cases of wind flow (steady and unsteady), ranges of Reynolds number and lateral vibrations of structures or their absence. Numerical implementation of the model with application to real structures is also proposed.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.408-413
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• 2004

Numerical and experimental investigation were car-ried out to clarify the flow structure of underexpanded jet from a square nozzle. The square nozzle rep-resents one of the clustered combustors of a linear aerospike engine. From the numerical results, the three-dimensional shock wave of the underexpanded square jet was found to be composed of two shocks. One is the intercepting shock which corresponds to the shock observed in two-dimensional planar jet. The other is the recompression shock divided into two types. The expansion fans coming from the nozzle edges interact with each other at the comers of the nozzle exit, and overexpanded regions are generated. Therefore one of the two recompression shocks is formed at the comers of the nozzle exit behind the overexpanded regions. As the jet goes downstream, the overexpanded regions grow larger to coalesce at the symmetry planes. Then, the other type of the recompression shock is generated. The three-dimensional shock structure formed by the intercepting shock and the recompression shocks dominates the expansion of the jet boundary. The shock detection algorithm us-ing CFD results was developed to reveal the relation between the shock waves and the jet boundary, and it was found that the cross-sectional jet shape becomes cross-shape. The key features observed in the numerical investigation were verified by the experimental results. The shock structure at the diagonal plane was in good agreement with the experimental schlieren images. Moreover, the cross-sections visualized by the Mie scattering method confirmed that the cross-section of the jet becomes cross-shape.

• 대한조선학회논문집
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• 제60권6호
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• pp.460-472
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• 2023

This study was conducted based on the case of an accident (excessive deformation) that occurred during the hydraulic test of a shipboard tank manufactured in accordance with the design regulations. Over-pressure phenomenon was noted as the main cause of accidents in the process of testing tanks without physical damage, which can be found in external factors such as cross-sectional difference between inlet pipe and air pipe and higher water filling rate than the recommended one. The main goal of this paper is to establish a safe water filling rate according to the range of sectional area ratio(SAR) reduced below the regulations for each test situation. The simulation was conducted in accordance with the hydraulic test procedure specified in the Ship Safety Act, and the main situation was divided into two types: filling the tank with water and increasing the water head to the test pressure. The structural safety evaluation of the pressure generated inside the tank and the effect on the structure during the test was reviewed according to the SAR range. Based on the results, guidelines for the optimal filling rate applicable according to SAR during the hydraulic test were presented for the shipboard tanks used in this study.

• 한국해양공학회지
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• 제17권4호
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• pp.66-72
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• 2003

This paper proposes an optimum, problematic design for structural and control systems, taking a 3-D truss structure as an example. The structure is subjected to initial static loads and time-varying disturbances. The structure is controlled by a state feedback H$_{\infty}$ controller which suppress the effects of disturbances. The design variables are the cross sectional areas of truss members. The structural objective function is the structural weight. For the control objective, we consider two types of performance indices, The first function represents the effect of the initial loads. The second function is the norm of the feedback gain, These objective functions are in conflict with each other but are transformed into one control objective by the weighting method. The structural objectives is treated as the constraint, By introducing the second control objective which considers the magnitude of the feedback gain, we can create a design to model errors.