• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.156-164
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• 1999

The body structure of a bus is generally assembled by using various spot welded box sectional members. The shape of window pillar joint is ordinarily built up by T-type member. It has been shown that T-type member has problems like high stress concentrations, low fatigue strength and low structural rigidity. In this study, to solve these problems a new approach to optimize the design of the bus window pillar joint was tried by FEM analysis and experiments. To describe the shape of the gusset connecting the vertical and horizontal members of the T-type window pillar joint B-spline curve was adopted and this curve was optimized . It was found that the new model developed could effectively improve fatigue durability an structural rigidity.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.463-475
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• 2022

In the mine exploitation stage; one of the critical issues is the stability assessment of post-pillars. The instability of post-pillars leads to serious safety hazards in mining operations. The focus of this study is to assess the stability of post-pillars in the 130# stope in the central ore body at Trepça hard rock mine by employing both conventional (i.e., critical span curve) and numerical methods (i.e., FLAC3D). Moreover, a new numerical based index (i.e., Pillar Yield Ratio-PYR) was proposed. The aim of PYR index is to determine a border line between stable, potentially unstable, and failure state of post-pillars at a specific mine site. The critical value of pillar width to height ratio is 2.5 for deep production stopes (e.g., > 800 m). Results showed that pillar size, mining height and mining depth significantly have affected the post-pillar stability. The reliability of numerical based index (i.e., PYR) is verified based on empirical underground pillar stability graph developed by Lunder, 1994. The proposed pillar yield ratio index and pillar stability graph can be used as a design tool in new mining areas at Trepça hard rock mine and for other situations with similar geotechnical conditions.

• Tunnel and Underground Space
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• v.24 no.5
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• pp.344-353
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• 2014

In this study, the behavior of rock pillar in the diverging area of road tunnel was assessed by using a three dimensional numerical analysis. Based on parameters affecting the behavior of rock pillar, different safety factors according to pillar width, depth and rock conditions were evaluated. It turned out that as the pillar width increases, the change curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. By the assessment of the minimum safety factor, a safety factor chart on the behavior of rock pillar in the diverging area of road tunnel was suggested.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.81-88
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• 2015

This study assessed the behavior of rock pillar in tunnel diverging area by using a three dimensional numerical analysis. Based on parameters affecting the behavior of rock pillar, this study evaluated different safety factors according to pillar width, depth and rock conditions. It turned out that as the rock pillar width increases, the change curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. By the assessment of the minimum safety factor, a safety factor chart on the behavior of rock pillar in tunnel diverging area was suggested.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.17-23
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• 2016

This study assessed the behavior of rock pillar in tunnel asymmetric diverging area by using a three dimensional numerical analysis. The stability of pillar is very important for the ensure the stability of the tunnel asymmetric diverging area. Based on parameters affecting the behavior of rock pillar, this study evaluated different safety factors according to pillar width, depth and rock conditions. It turned out that as the rock pillar width increases, the change curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. By the assessment of the minimum safety factor, a safety factor chart on the behavior of rock pillar in tunnel asymmetric diverging area was suggested.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.3
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• pp.20-27
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• 2003

Compensation of probe radius is required for accurate measurement in metal working industry. Compensation involves correctly measuring data on the surface in the amount of radius of the touch probe with a Coordinate Measuring Machine (CMM). Mechanical parts with free-formed curves and surfaces are complex enough so that accurate measurement and compensation are indispensable. This paper presents necessary algorithms involved in the compensation of the probe radius for free-formed curves and surfaces. Application of pillar curve is the focus for the compensation.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.60-68
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• 2012

Focusing on the load tunnel, this study assessed the behavior of rock pillars with less than 0.5D of the minimized distance between the two horizontal tunnels by using a three dimensional numerical analysis. Based on a parameter affecting the behavior of rock pillars, this study evaluated different safety factors according to pillar width, depth and rock conditions. It turned out that as the pillar width increases, the current curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. Judging from the minimum safety factor, the study suggested a design chart, working on the minimized distance between the two horizontal tunnels.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.106-113
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• 2004

Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. In this study, the dynamic response of vehicle structure to external forces is classified an inverse problem involving strains from the experiment and the analysis. The practical dynamic forces are determined by the combination of the analytical and experimental method with analyzed strain by quasi-static finite element analysis under unit force and with measured strain by a strain gage under driving load, respectively. In a stressed body, inter-molecular chemical bonds are failed beyond the certain magnitude. The failure of molecular structure in material is considered as a time process of which rate is determined by mechanical stress. That is, the failure of inter-molecular chemical bonds is the fatigue lift of material. This kinetic concept is expressed as lethargy coefficient. And S-N curve is obtained with the lethargy coefficient from quasi-static tensile test. Equivalent practical dynamic force is obtained from the identification of practical dynamic force for one loading point. Using the practical dynamic force and S-N curve, fatigue life of a window pillar is analyzed with FEM under the identified force by the procedure of above mentioned.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.243-251
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• 2008

Recently, the mining methods are changing from surface mining to underground mining because of the increment of the environmental issues and legal regulations. Therefore, the stability of underground openings is a major concern for the safety and productivity of mining operations. In this paper, a survey of structural geology and discontinuities were carried out at a limestone mine. The relevant mechanical properties of rocks were determined by the laboratory tests and rock mass classifications (RMR and Q-system) for the mine design and input data for the stability analysis. The dimensions of unsupported span for underground openings and pillar were decided based on the RMR values of rock mass classifications. The stability analysis for the suggested mine design was examined through the empirical methods (stability graph method and critical span curve) and 3-D numerical analysis (Visual-FEA).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3894-3906
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• 2014

The aim of this study was to classify the central Buddhist temple among the state-designated cultural assets, which were measured precisely, into the gable roof buildings and the gambrel roof buildings to analyze the Ang-Goak, Inside waist, ridge ratio, and roof inclination represented on the roof, and prepare basic objective material for the restoration and repair of cultural assets. As a result, as for the relationship between the roof curve and the inclination of the gable roof building and gambrel roof building, the following conclusions could be drawn. First, the Ang-Goak and Inside waist of the gable roof building had a close correlation with the building size, and the internal high pillar existence. In addition, the Ang-Goak and Inside waist were shown in the 7-ryangga structure, which is greater in size than in the 5-ryangga structure. This was found to be related to the building size. Second, the Ang-Goak and Inside waist of the gable roof building has a correlation with each other, and it was found that Inside waist also was large in the building with a larger Ang-Goak. The roof inclination rarely had a connection with variable factors (plane factor, elevation factor, and cross section factor). The sizes of Ang-Goak, Inside waist, and ridge ratio were similar in the outside 1 chulmok and outside 2 chulmok of gongpo but those sizes were relatively larger in outside 3 chulmok. Third, the Ang-Goak and Inside waist of the gambrel roof building moved independently for each building without a correlation with each other, unlike the case of the gable roof building. The front and the side showed a correlation with each other, and in the building with the large curve of the front side, the curve was also large in the sides. Fourth, in the case of the building with a high pillar inside the gambrel roof building, the Ang-Goak and Inside waist were larger. On the other hand, they were smaller in the case of a building without a high pillar. This was found to have a close relationship with the building size. In addition, the ridge ratio has a close connection with the building size and building height. Therefore, the ridge ratio is larger in a high building or large sized building. The roof inclination rarely has a correlation with variable factors, as in the case of the gable roof building.