• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.1
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• pp.16-22
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• 2003

While passing through the AC/DC section insulators installed at electric railroad catenary, some electric trains undergo mis-operation of main circuit breaker after AC/DC change-over operation. This paper provides insulation resistance measurements of AC/DC section insulators, which confirm the insulation levels of section insulators are below the standard of insulators. The insulation deterioration and pantograph arrangement on the electric train can produce voltage impression on section insulator which induces mis-operation of main circuit breaker To mitigate the insulation deterioration of the section insulator installed at underground railroads, the section insulators have been cleaned periodically, but section insulator structure should be modified to make the section insulator performance perfect. Based on the above analysis, effective modification method of AC/DC section insulator is provided.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.152-159
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• 2018

A numerical simulation was conducted to establish the analysis methods of the unsteady conjugated heat transfer with a hot gas valve. Two methods are proposed to reduce the computational cost and analysis time of the unsteady conjugate heat transfer; namely, the multi-section analysis method and the one-way analysis method. The multi-section analysis method exhibits relatively high reliability. In the one-way analysis method, the unsteady conjugate heat transfer from the fluid domain to the solid domain was simulated from the analysis results of the steady-state flowfield. The incipient accuracy of the analysis results obtained by the one-way analysis method was slightly lower than that of the results obtained by the multi-section analysis method. However, the discrepancy became smaller with time, as the analysis progressed.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.155-160
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• 2002

This study is performed to analyze of reinforced concrete beams under fire and to calculate remaining strength. The analysis is based on the assumption that plane section remains plane after bending due to load and non-linear temperature increases. Finite difference method is used to find temperature field in a section. The residual strength is attained considering the effect of temperature rise on the mechanical properties of concrete, self-equilibrium stress and reduced section. Further research in much needed on the material models of concrete since it governs temperature distribution and theoretical results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.4
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• pp.177-185
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• 1998

This paper deals with the flexural behaviors of R.C beams strengthened by carbon fiber sheets. The behaviors of strengthened beams which were preloaded up to 50%, 60% and 70% of the ultimate load of unstrengthened beam are compared with that of a beam which was not preloaded. The structural behaviors of strengthened beams are compared with analytical method in terms of load-strain of concrete, load-strain of steel bar, load-strain of CFS and falilure load. Four cases of analytical method are investigated according to cracked section or partially cracked section and including strain hardening effect of steel bar or not. Comparing the results of test and analysis, both are similar in terms of load-strain of concrete, and falilure load, the results of analytical method underestimate the failure load. But each results of load-strain of steel bar, load-strain of CFS near at failure is some different, thus near at failure the composite action between CFS and upper concrete is assumed to be disturbed. Consequently, the analytical method was proved to be efficient and accurate in estimating the flexural response of CFS strengthened RC beams.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.4 s.34
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• pp.19-25
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• 2005

This study suggests a method for securing road safety by extracting the expected surface freezing section in planning a route using GIS. When planning a road construction in a mountainous area it is possible to confront surface freezing especially in the wintertime. In addition, it is required assessment data of surface freezing rates in the case of turnkey inspections of newly constructed or expanded roads. Consequently, an analysis method that can quantitatively estimate the surface freezing section and sunshine influence on each section of a road is needed. We can extract the expected surface freezing section which amounted to around 29km of the Donghae highway, with such techniques as three-dimensional modeling, sunshine simulation geographical database construction and spatial analysis using the overlay function of the GIS spatial analysis. This study can be used as a method to assess advance safety which has a direct influence on planning the blueprint that should be approved by a policy maker after efficiently understanding the expected surface freezing section in accordance with hill shade.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.462-467
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• 1998

A rational method for prediction of long-term deflections of reinforced concrete beams under sustained loads was proposed. Strain and stress distributions of uncracked and fully cracked sections after creep and shrinkage were determined from the requirements of strain compatibility and force equilibrium of a section, and then long-term deflections were calculated from the section analysis results. In fully cracked section analysis, noncoincidence of the neutral axis of strain and the neutral axis of stress after creep and shrinkage was taken into account. The accuracy of the proposed method was verified by comparison with several experimental measurements of beam deflections. The proposed approximate procedure gave the better predictions than the existing approximate methods. At the same time, the proposed method also retained simplicity of the calculation, since maximum long-term deflection could be obtained without tedious integration of the curvatures.

• Steel and Composite Structures
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• v.13 no.2
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• pp.171-185
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• 2012

The calculation of fire resistance for a composite structural element comprises the calculation of the temperature within its cross-section and of the load bearing capacity, considering the evolution of the steel and concrete mechanical properties, function of the temperature. The paper proposes a method to calculate the bending capacity under ISO fire, for Slim Floor systems using asymmetric steel beams, with a wider lower flange or a narrow upper flange welded onto a half hot-rolled profile. The temperatures in the cross-section are evaluated by means of empirical formulas determined through a parametrical analysis, performed with the special purpose non-linear finite element program SAFIR. Considering these formulas, the bending capacity may be calculated, using an analytical approach to determine the plastic bending moment, for different fire resistance demands. The results obtained with this simplified method are validated through numerical analysis.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.23-29
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• 2013

PURPOSES: This paper aims to give a guideline and the way to apply the advanced composite materials theory to the road structures with different cross sections to the practicing engineers. METHODS: To simple but exact method of calculating natural frequencies corresponding to the modes of vibration of road structures with different cross sections and arbitrary boundary conditions. The effect of the $D_{22}$ stiffness on the natural frequency is rigorously investigated. RESULTS: Simple method of vibration analysis for calculating the natural frequency of the different cross sections is presented. CONCLUSIONS: Simple method of vibration analysis for calculating the natural frequency of the different cross sections is presented. This method is a simple but exact method of calculating natural frequencies of the road structures with different cross sections. This method is extended to be applied to two dimensional problems including composite laminated road structures.

• Journal of KSNVE
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• v.9 no.5
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• pp.914-921
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• 1999

There are many theoretical investigations to analyze higher order mode of reactive type single expansion chambers with offset inlet/outlet locations. But the conventional method has the restriction that the ratio between the area of inlet(or outlet) pipe and that of chamber must be natural number. In the paper, a new method was suggested to apply the Kim's method to silencer with circular cross-section. Not only the offset location but also the magnitude of cross-section area of inlet/outlet pipe can be considered by the suggested method. The predictions by this new method also compared with those by the finite element method and Munjal's method in order to verify the accuracy of the suggested method presented here.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.4
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• pp.310-323
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• 2013

In this paper, the aeroelastic static response of flexible wings with arbitrary cross-section geometry via a coupled CUF-XFLR5 approach is presented. Refined structural one-dimensional (1D) models, with a variable order of expansion for the displacement field, are developed on the basis of the Carrera Unified Formulation (CUF), taking into account cross-sectional deformability. A three-dimensional (3D) Panel Method is employed for the aerodynamic analysis, providing more accuracy with respect to the Vortex Lattice Method (VLM). A straight wing with an airfoil cross-section is modeled as a clamped beam, by means of the finite element method (FEM). Numerical results present the variation of wing aerodynamic parameters, and the equilibrium aeroelastic response is evaluated in terms of displacements and in-plane cross-section deformation. Aeroelastic coupled analyses are based on an iterative procedure, as well as a linear coupling approach for different free stream velocities. A convergent trend of displacements and aerodynamic coefficients is achieved as the structural model accuracy increases. Comparisons with 3D finite element solutions prove that an accurate description of the in-plane cross-section deformation is provided by the proposed 1D CUF model, through a significant reduction in computational cost.