• Journal of Korean Association for Spatial Structures
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• v.14 no.3
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• pp.47-56
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• 2014

This paper investigates the characteristics of unstable behaviour and critical buckling load by joint rigidity of framed large spatial structures which are sensitive to initial conditions. To distinguish the stable from the unstable, a singular point on equilibrium path and a critical buckling level are computed by the eigenvalues and determinants of the tangential stiffness matrix. For the case study, a two-free node example and a folded plate typed long span example with 325 nodes are adopted, and these adopted examples' nonlinear analysis and unstable characteristics are analyzed. The numerical results in the case of the two-free node example indicate that as the influence of snap-through is bigger; that of bifurcation buckling is lower than that of the joint rigidity as the influence of snap-through is lower. Besides, when the rigidity decreases, the critical buckling load ratio increases. These results are similar to those of the folded-typed long span example. When the buckling load ratio is 0.6 or less, the rigidity greatly increases.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.251-257
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• 1998

Spherical space frame structure with triangular network pattern, which has the various characteristics for the mechanic property, a funtional property, an aesthetic property and so on, has often been used as one of the most efficient space structures. It is expected that this type will be used widely in large-span structural roofs. But because this structure is made of network by combination of line elements there me many nodes therefore, the structure behavior is very complicated and there can be an overall collapse of structure by buckling phenomenon if the external force reaches a limitation. This kind of buckling is due to geometric shape, network pattern, the number of layer and so on, of structure. Therefore spherical space frame with triangle network pattern have attracted many designers and researchers attention all over the world. The number of layer of space frame is divided in to the simgle, double, multi layer. That is important element which is considered deeply in the beginning of structural design. The buckling characteristics of single-layer model and double-layer model for the spherical space frame structure with triangular network pattern are evaluated and the buckling loads of these types are compared with investigation their structural efficiency in this study.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.2 s.146
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• pp.206-212
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• 2006

Structural reliability of electrical panels installed in naval vessels is of critical importance from structural performance viewpoint. The electrical panels may be exposed to vibration and fatigue loadings from internal and external sources as well as wave loadings which result into a crack and fracture due to the decrease of fatigue strength. It is also well known that welded joints including brackets within steel structures .such as vessels and bridges are vulnerable against such repeated loadings. This study introduces a preliminary result of the optimized shape of frame bracket consisting of electrical panels in navel vessels against fatigue loading and their fatigue life at brackets of electrical panels by means of hot spot stress and structural stress methods.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.119-128
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• 2016

In a performance-based design, the structural safety is estimated from pre-defined damage states and corresponding damage indices. Both damage states and damage indices are well defined for above-ground structures, but very limited studies have been performed on underground structures. In this study, we define the damage states and damage indices of a cut-and-cover box tunnel which is one of typical structures used in metro systems, under a seismic excitation from a series of inelastic frame analyses. Three damage states are defined in terms of the number of plastic hinges that develop within the structure. The damage index is defined as the ratio of the elastic moment to the yield moment. Through use of the proposed index, the inelastic behavior and failure mechanism of box tunnels can be simulated and predicted through elastic analysis. In addition, the damage indices are linked to free-field shear strains. Because the free-field shear strain can be easily calculated from a 1D site response analysis, the proposed method can be readily used in practice. Further studies are needed to determine the range of shear strains and associated uncertainties for various types of tunnels and site profiles. However, the inter-linked platform of damage state - damage index - shear wave velocity - shear strain provides a novel approach for estimating the inelastic response of tunnels, and can be widely used in practice for seismic designs.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.9-15
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• 2009

This research presents the structural performance and an improving technique for flexural capacity of road safety facilities based on the damage cases by wind pressure. Among road safety facilities, a support frame of soundproofing walls is considered as a prototype structure and its corresponding structural behaviors and section design are performed mainly by analytical and experimental studies. On the basis of analytical results, glass fiber reinforced polymer(GFRP) with an epoxy matrix which is high stiffness-to-weight ratio was used for applied one of strengthening techniques and their results shows that support frame strengthened by GFRP is the most effective compared to other cases proposed in this research for advancing its flexural improvement, Finally, optimum section design was performed analytically to evaluate wind-resistance capacity and its result would be very useful for developing a practical design guideline for Road safety facilities under strong wind.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.4
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• pp.435-447
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• 1999

It is main objective of this approach to present a method to analyse stochastic design sensitivity for problems of structural dynamics with randomness in design parameters. A combination of the adjoint variable approach and the second order perturbation method is used in the finite element approach. An alternative form of the constant functional that holds for all times is introduced to consider the time response of dynamic sensitivity. The terminal problem of the adjoint system is solved using equivalent homogeneous equations excited by initial velocities. The numerical procedures are shown to be much more efficient when based on the fold superposition method: the generalized co-ordinates are normalized and the correlated random variables are transformed to uncorrelated variables, whereas the secularities are eliminated by the fast Fourier transform of complex valued sequences. Numerical algorithms have been worked out and proved to be accurate and efficient : they can be readily adapted to fit into the existing finite element codes whose element derivative matrices can be explicitly generated. The numerical results of two cases -2 dimensional portal frame for the comparison with reference and 3-dimensional frame structure - for the deterministic sensitivity analysis are presented.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.273-284
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• 1995

카메라를 통하여 얻은 영상자료로부터 대상물의 특징을 추출하여 검사에 응용하는 자동검사기법의 수요가 늘고 있다. 본 연구에서는 그러한 자동검사의 실예로서 접속 케이블(wire hardness)의 색깔인식을 이용한 양/불량을 구별하는 시스템을 구축하였다. 색깔인식을 위한 도구로서 입력층, 1개의 은닉층 및 출력층으로 이루어진 2층 구조의 역전파신경망(back-propagation neural network)을 사용하였다. 입력자료로는, 화상에서 케이블의 위치를 파악하고 그 케이블에 속한 화소로부터 필요한 정보(Y, U, V)를 추출한 후, 보다 변별력이 좋은 (L, a, b) 좌표계로 변환하여 사용하였다. 본 검사시스템은 인식속도를 향상시키기 위하여 영상정보를 프레임 버퍼(frame buffer)에서 직접 사용하고 자료의 검사과정을 극소화 하였기 때문에 불량품의 실시간 검출이 가능하다. 불량품 검출의 성능을 평가하기 위하여 실제 표본을 가지고 시스템의 성능을 평가한 결과, 양/불량의 인식율이 100%를 나타내어 약간의 성능보완이 이루어지면 현장에서 바로 활용할 수 있을 것으로 판단된다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.117-120
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• 2017

IHO는 기존의 S-57 표준을 대체하고 수로정보 교환을 위한 공통 구조를 제공하기 위해 S-100 표준을 개발하고 S-100 표준화 체계 운영을 위한 S-100 표준 인프라를 개발 중이며, IHO 산하 실무그룹 및 프로젝트 그룹은 S-100 표준에 따라 S-10X 제품 표준개발을 수행하고 있다. S-100 표준에는 Portrayal process, Plug & Play, Interoperability 등의 신규 개념이 포함되어 있으므로, IHO는 이를 검증하기 위한 테스트 프레임워크 수립 하였다. 본 연구에서는 S-100 핵심 개념이 포함된 뷰어 기술을 현행 ECDIS 시스템에 적용하여 차세대 수로정보테스트 시스템을 개발한 결과를 소개하였다. 개발 결과물은 S-100 핵심 개념과 차세대 수로정보 시범 제작 결과를 검증하는데 사용하고, e-Navigation 사용자 시스템 개발로 활용될 수 있을 것으로 판단된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.631-641
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• 1988

Computational procedures associated with finite element nonlinear analysis of plane frame structures were examined and new solution schemes were suggested. Element stiffness matrix was derived from the principle of virtual displacements. Geometric and material nonlinearities were considered in the formulation. Solution method was based upon the constant displacement length method in conjunction with the Newton-Raphson method. New solution schemes were introduced in determining the initial load increment and the sign of load increments and predicting the length of displacement increment to improve user convenience, efficiency and stability. Numerical experiments were performed for several typical problems and suggested schemes were found efficient and convenient for analyzing nonlinear frame structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1341-1346
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• 2009

In this paper, the technique to reinforce the durability performance of structure using the sensitivity information for the frame structure is applied. The fatigue life calculation for the frame structure is performed from the quasi-static and transient analysis and the characteristics of two methods are compared for the fatigue analysis. Then the reinforcement technique is applied. First, some design variables related to the locations of fatigue failure is selected. Then sensitivities of fatigue life at fracture points with respect to the variation of design variables are calculated and the vector composed of gaps between the target life and initial life cycles is calculated. If the number of fatigue fracture points is same as the number of design variables, the variations of the design variables are calculated from the linear algebraic equation. If not, the variations of the design variables are calculated from the optimization formulation with the constraints.