• Journal of the Korean Professional Engineers Association
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• v.44 no.5
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• pp.36-41
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• 2011

Design of blast resistant structures (protective structures) require the adequate design and construction practices as well as the knowledge of characteristics of the blast loads, behavior of structures and their components under these loads. This paper focuses on how to design and evaluate the structures for blast resistance, and provides principles and discussion on analysis and design capability in protective technology and recommendations.

• Journal of KSNVE
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• v.4 no.4
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• pp.451-457
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• 1994

A numerical method is presented to obtain natural frequencies and mode shapes of uniform elastic beams with static deflections due to dead loads. The differential equation governing the free vibration of beam taken into account the static deflection due to deal loads is derived and solved numerically. The hinged-hinged, clamped-clamped and clamped-hinged end constraints are applied in the numerical examples. As the numerical results, the lowest three nondimensional frequency parameters are reported as functions of nondimensional system parameters; the load parameters, and the slenderness rations. And some typical mode shapes of free vibrations are also presented in figures.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.3
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• pp.81-87
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• 2015

Load master is authorized to be controlled all of loading stuffs for safety of flight such as passenger, baggage, cargo and e.t.c. There are many things are missed even though the weight and balance is the most important process. This study analyzes how the differences of C.G. by among ten load masters of each careers. This study is tested how load-master takes load-control by the respective result based on differences of each practical experiences, gender and a number of certification. In result, all of load masters set C.G. on the stability region. But the practical experience of load master is relative to set better C.G. for economical effectiveness of weight and balance control work.

• Journal of Korea Foundry Society
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• v.43 no.3
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• pp.107-136
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• 2023

Natural silica sand was commonly used for sand casting of cast steel products, and chromites sand was used to suppress seizure defects due to the lack of thermal properties of silica sand. However there are disadvantages such as deterioration by repeated use, system sand mixing problem, difficulty separating and removing, increased during mold according to high density and to being waste containing chrome. Recently, industrial waste reduction and atmospheric environment improvement have been highlighted as important tasks in the casting industry. In order to solve the problems that occur when using foundry Sand and to improve the environment of casting factories, various artificial sands that can be applied instead of natural silica sand have been developed and introduced. Artificial sands can be classified into artificial sand manufactured by the electric arc atomization or gas flame atomization, artificial sand manufactured by the spray drying & sintering process, artificial sand manufactured by the sintering & crushing process and exhibit different physical properties depending on the type of raw-minerals and manufacturing method. In this study, comparative evaluation tests were conducted on the physical properties of various foundry sands, mold strength, physical durability, thermal durability, and casting test pieces. When comprehensively considering the actual amount of molding sand used according to density, the mold strength according to the shape of sand, the physical and thermal durability of foundry sand, and the heat resistance characteristics of foundry sand, 'Molten artificial sand A1' or 'Molten artificial sand B' is judged to be the most suitable spherical artificial sand for casting of heavy steel castings.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.65-65
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• 2012

The air texturing공정은 노즐에서 전달되는 초음속 에어기류에 의해 overfeed를 수반하여 yarn속 fiber가 뒤얽혀 loop와 crimp를 발달시키는데, 고강력 고탄성율 고내열성 내절단성 등의 특성을 가지는 아라미드섬유를 에어 가공사로 가공 할 경우 가공 전 필라멘트 상태일 때 보다 표면에 생기는 loop로 인하여 촉감이 좋아지고 또한 타 소재와 접착 시 접착제 담지 성능이 향상 되어 접착력이 상승되고, 이를 통해 보강재로서의 기능이 강화되는 반면 역학물성이 기존의 아라미드 보다 저하되는 약점을 가지고 있어 최근 ATY 공정조건이 ATY 사의 구조와 물성변화에 미치는 영향에 대한 많은 연구결과가 발표되고 있다. 본 연구에서는 Aiki air jet texturing machine에서 $Heracron^{(R)}$ para-aramid(840, 1000d, 1500d)를 사용하여 ATY nozzle의 직경을 0.6, 0.75, 1, 1.2mm로 변화를 주어 12개의 para-aramid ATY 시료를 제조하여 이들의 섬도, 강신도, 초기탄성률, 열수축률 그리고 형태불안정성(instability)등의 물성변화를 분석하여 다음과 같은 결과를 얻었다. 노즐의 직경이 증가함에 따라 사 내의 filament간의 움직임이 자유로워 교락이 증가하고 루프가 형성되어 단위길이 당 mass가 커지므로 섬도가 미세하게 증가하는 것을 볼 수 있다. 또한 직경이 증가할수록 절단강도와 초기탄성률은 감소하고 절단신도가 증가하는 경향을 볼 수 있는데 이는 축 방향으로의 배열이 적어져 하중을 분담하는 portion이 감소하고 사의 loop형성이 많아짐으로서 상대적으로 인장력에 대응하는 fiber의 수가 적어지기 때문으로 사료된다. 이는 현미경 관찰로 확인할 수 있는데 직경이 증가함에 따라 사의 loop의 엉킴이 증가하고 filament가 조밀한 것을 확인할 수 있다. 직경 변화에 따른 건 습열 수축률은 1% 미만의 매우 낮은 값으로 영향을 받지 않는 것을 확인 할 수 있는데 para-aramid의 열적특성의 안정성에 기인하는 것으로 사료되며 ATY의 불안정성은 노즐 직경 증가에 따른 어떤 경향성을 찾아볼 수 없었지만 840d, 1000d, 1500d로 섬도가 증가함에 따라 사의 불안정성이 증가하였다.

• Journal of the Korean Geosynthetics Society
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• v.4 no.2
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• pp.39-45
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• 2005

New concept called the pullout resistance angle has been used to express the friction, cohesion and passive resistance by pullout test at geosynthetics reinforced soil. And also in order to calculate the pullout area, the distribution area method has been used, which is a method of using the curve of tensile force exerted in geogrid. The distribution area ratio showed nearly the same result in the two kind of soils, the granite soil and the standard soil. The pullout resistance angle showed the greater value than friction angle of soil in case of low confining stress of $0.2kg/cm^2$, while it showed the smaller angle than friction of soil in case of high confining stress of $0.8kg/cm^2$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.158-166
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• 2008

Member force, strain and stress distribution of a section are obtained for prestressed steel and concrete(PSSC) composite bridge subjected to dead and live load in order to interpret the effect of prestressing and deformation of tendon. The stress and strain distribution and moment capacity are obtained for both noncomposite and composite section and for allowable stress limit state, yield limit state and strength limit state. Reliability analysis is conducted after assuming limit states for deflection, stress and flexural strength. Comparing that the reliability index for stress is near 0 for example section which is designed to satisfy the allowable stress exactly, the reliability indexes for deflection and flexural strength are high. Reliability of PSSC girder which is designed based on allowable stress of bridge design code is high for deflection and flexural strength.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.79-86
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• 1990

A method to determine directly $J_{IC}$ from load-displacement curve without measuring crack growth amount is studied. A method to use key curve in determination of $J_{IC}$ is also considered. The values of $J_{IC}$ obtained from the above methods are compared with that obtained from the ASTM standard test method (E813). By performing experiments using both compact-tension specimen and three-point-bending specimen of a structural alloy steel SCM4, it is shown that the methods proposed here may be used in determination of $J_{IC}$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.11-20
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• 1988

A general finite element method is developed to analyze reinforced concrete plates under dead loads and monotonically increasing live loads. This method can be used to trace the load-deformation response and crack propagation through elastic, inelastic and ultimate ranges. The internal concrete and steel stresses can also be determined for any stage of the response history. A layered 8 node isoparametric element taking account of coupling effect between the membrane and the bending action is developed. An incremental tangent stiffness method is used to obtain a numerical solution. Validity of the method is studied by comparing the numerical solutions with other results.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.661-670
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• 2000

To investigate the characteristics of the dynamic response of long-span cable-stayed bridges due to various dynamic loadings likes moving traffic loads, two different 3-D cable-stayed bridge models are considered in this study. Two models are exactly the same in structural configurations but different in finite element discretization. Modal analysis is conducted using the deformed dead-load tangent stiffness matrix. A new concept was presented by using divided a cable into several elements in order to study the effect of the cable vibration (both in-plane and swinging) on the overall bridge dynamics. Futhermore case of asymmetric traffic loading clustered in one direction are also considered to study the torsional response of the bridge. The result of this study demonstrates the importance of cable vibration on the overall bridge dynamics.