• Proceedings of the KSME Conference
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• 2004.04a
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• pp.462-467
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• 2004

In order to determine the most suitable material system which can achieve the lightweight design and fulfill the design requirements of carbody structures of Korean Tilting Train eXpress (TTX), aluminum carbody, composite carbody, and hybrid carbody combined with aluminum and composite structures were considered in present study. The finite-element analysis was used to verity the design requirements of the TTX carbody structures with the material system being considered in the design stages. The stresses in the carbody structures and deflections of underframe against static load cases were checked as design criteria. The results show that the hybrid carbody structures are beneficial with regard to weight savings and structural integrity when compared to aluminum and composite carbody structures.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.133-139
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• 2000

Vibrational characteristics of the vehicle structure are mainly influenced by the shape of the pillar cross section. In this paper a vehicle structural optimization technique has been developed to investigate a lightweight vehicle structure subject to constraints on natural frequencies in a simple beam-and-shell model. In this technique, the optimization procedures involve two stages. In the first stage, the section procedures involve tow stages. In the first stage, the section properties of beam elements of the vehicle structure has been optimized to have minimum weight while satisfying the constraints of natural frequencies. And, in the second stage, the shape of the cross section of the elements of the structure has been determined.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.456-461
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• 2002

Nowadays, there are required more speed and accurate machining in order to improve the productivity through the reduction of cutting and non-cutting time. In this study, the high-speed HMC is specially designed to do remote control and high-speed mechanism with 30000rpm, 50000rpm, 40m/min, 100m/min and bridge type structure. Every structural deformation and vibration that is generated from all of factor is analyzed being based on the virtual manufacturing technologies: thermal characteristic analysis, machine-ability, tool wear measuring system, driving characteristic of linear motor and so on. As the application of these results had been consisted of three axes to move slight and rigid finally. Therefore, table errors that are resulted in change of work weight can be removed.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.113-118
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• 2005

Maglev vehicles, which are levitated and propelled by electromagnets, often run on elevated flexible guideways comprised of steel, aluminum and concrete. Therefore. an analysis of the dynamic interaction between the Maglev vehicle and the flexible guideway is needed in the design of the critical speed, ride, controler design and weight reduction of the vehicle. This study introduces a dynamic interaction simulation technique that applies structural dynamics. Because the proposed method uses FEM, it is useful to calculate the deformation of the elevated flexible guideway, the dynamic stress, and the motion of the vehicle. By applying the proposed method to an urban transit Maglev vehicle, UTM01, the dynamic response is simulated and validated. From the result of the study, we concluded, that the dynamic interaction between the maglev vehicle and the flexible guideway is possible.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1083-1088
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• 2005

As the industrial society develops rapidly, the weight reduction and high strength are demanded gradually. In case of the welded joint for the rolling stock which receives the repeat load, the structural failure can occur easily. However, if the shot peening technique is applied, the durability and the fatigue characteristics of the rolling stock will be improved because the hardness increases and the residual stress is induced. In this study, the fatigue characteristics of shot peened welled joints for the rolling stock was investigated. The crack initiation was examined and hardness was also evaluated. the results show that the fatigue characteristics of welded joints was improved.

• International Journal of High-Rise Buildings
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• v.2 no.2
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• pp.141-152
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• 2013

This paper presents a brief overview of the recently developed performance-control method of moment frame design subjected to monotonously increasing lateral loading. The final product of any elastic-plastic analysis is a nonlinear loaddisplacement diagram associated with a progressive failure mechanism, which may or may not be as desirable as expected. Analytically derived failure mechanisms may include such undesirable features as soft story failure, partial failure modes, overcollapse, etc. The problem is compounded if any kind of performance control, e.g., drift optimization, material savings or integrity assessment is also involved. However, there is no reason why the process can not be reversed by first selecting a desirable collapse mechanism, then working backwards to select members that would lead to the desired outcome. This article provides an overview of the newly developed Performance control methodology of design for lateral resisting frameworks with a view towards integrity control and prevention of premature failure due to propagation of plasticity and progressive P-delta effects.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.179-185
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• 2002

In this study, the structural design method for the modified long-endurance UAV is presented. Composite materials using room temperature curing method and wet lay up procedure is applied to all wing structures. The modified wing is composed of 3-piece component for improvement of ground handling. As the sandwich structure is efficient for light weight and high stiffness, all skin is used the sandwich consisting of glass/ epoxy fabric and balsa wood. The proof test is performed up to limit load corresponding to 4g load condition for the modified wing structure.

• Smart Structures and Systems
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• v.7 no.1
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• pp.27-40
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• 2011

Geopolymer concrete is finding a growing number of niche applications in the field of civil engineering due to its high compressive strength and strength gain rate, retainage of structural properties in elevated temperature environments, chemical stability in highly acidic conditions and environmental benefits. Combining the above mentioned characteristics with induced electrical conductivity, could enable geopolymer cement to serve as a smart and sustainable cementitious material suitable for health monitoring of civil structures. Carbon fibers were added to fresh geopolymer and OPC (ordinary Portland cement) mixes to enhance their electrical conductivities. AC-impedance spectroscopy analysis was performed on the specimens with fiber fraction ranging from 0.008 to 0.8 with respect to the weight of cementitious binder, to measure their electrical resistivity values and to determine the maximum beneficial fiber content required to attain electrical percolation. Experimental observations suggest that CFR-geopolymer cement exhibits superior performance to CFR-OPC in terms of conducting electrical current.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.1
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• pp.96-102
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• 2015

Composite materials are widely used as structural materials for manufacturing an aircraft, due to their : low weight, low thermal expansion coefficient, production efficiency, anisotropy, corrosion resistance and long fatigue life. The range of using composite materials has been extended from the fuselage and the wings to the entire aircraft structure. In this paper, by analyzing the problems which were generated while designing and fabricating aircraft structures using composite materials, the differences between metallic structures and composite structures are described. In addition, the methodological improvement directions on design and fabricating are described.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.93-95
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• 2013

Recently, with the increase in the construction of ultra-high buildings and long-span structures, there is great demand for high-strength concrete which can reduce the structural weight and thickness of member sections. While developing high-strength concrete to meet performance requirements, certain issues at the design stage must also be considered. The issues include diseconomy from a great amount of per-unit cement, spalling failure by fire at ultra-high building, autogenous shrinkage caused by increased hydration activity of binder from use of a superplasticizer. Therefore, the purpose of this study is examined the strain characteristics of Fiber-reinforced-high-strength concrete(FRHSC), which differ from those of general concrete owing to autogenous shrinkage. Based on the experimental data, we proposed an autogenous shrinkage prediction model.