• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.417-426
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• 2006

Various fatigue damages have been reported in orthotropic steel deck structures put upon girders. These damages are caused by complex behaviors of the deck, which is directly subjected to vehicle loads. To estimate the causes of fatigue cracks at the welded connected parts of the trough rib and the flor beam, and the trough rib and the deck plate, in orthotropic steel deck structures, FE analyses were first, performed in this study. Parameter studies were carried out to suggest effective structural details that consider fatigue, in which the main parameters are the thickness of the deck plate, the shape of the connection of the trough rib and the flor beam such as the slit form, and the welding length. This study suggests that the effective structural details improved the fatigue strength and discusses.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.277-288
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• 2014

In this study, the local displacement and moment characteristics of a plate stiffened with closed ribs are analyzed according to the dimensions of stiffened plates. The analyzed results of various stiffened plates under square distributed load show that the effect of the loading panel width to the local behavior is dominant but that of the next panel width is very small. And the local behavior of reference stiffened plates can be expressed by the angle between the plate and the rib, and that of other stiffened plates can be obtained by multiplying ratio functions of the loading panel width, plate thickness, rib thickness, rib height and next panel width and they give good results. Applying ratio functions to other loading sizes shows that the applicability of ratio functions except for the loading panel width is proved and the modified ratio functions of the loading panel width improve error ratios. Therefore, the local displacement and moments of a plate stiffened with closed ribs can easily achieve proper results regardless of the dimensions using ratio functions proposed in this study.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1138-1139
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• 2007

위상이 반대인 두 컨버터를 병렬로 사용하는 인터리브 DC/DC 컨버터는 고밀도, 고직접화가 가능하며 전류 잡음이 적다는 장점이 있지만 시비율이 50% 가 아닐 때에는 전류 리플이 존재하게 된다는 단점이 있다. 본 논문에서는 이런 단점을 보완하기 위해 50% 시비율로 동작하는 인터리브 DC/DC 컨버터와 인터리브 PFC를 결합하여 단점을 개선한 저잡음 인터리브 DC/DC 컨버터를 제안하였다. 인터리브 DC/DC 컨버터는 반대 위상의 50% 시비율로만 스위칭되어 이상적으로 전류 리플이 상쇄되게 된다. 인터리브 PFC는 인터리브 DC/DC 컨버터의 출력 전압을 피드백 받아 입력 전압을 변화시켜 항상 DC/DC 컨버터의 출력전압이 일정하도록 유지한다. 실험을 통하여 이를 입증하고 그 결과를 보인다.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.683-690
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• 2002

Static and fatigue tests were performed to evaluate fatigue strength in scallop at field bolted joints of longitudinal rib and deck plate in orthotropic steel decks. Numerical parametric studies using finite elemtn analysis were also conducted to show the influence of parameters such as length and radius of scallop, and thickness of deckplate on the stress concentration at the scallop. In the low stress level, fatigue tests yielded cracks at the scallop while in the high stress level, catastrophic failure of longitudinal rib occurred following the failure of handhole cover plate. Fatigue strength was compared with JSSC specification and the predicted S-N curves using Shigley and Juvinall methods, and a satisfactory result was obtatined.

• Journal of Korean Society of Steel Construction
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• v.24 no.6
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• pp.659-670
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• 2012

The purpose of this study is to formulate the local displacement and moments of a plate stiffened with open ribs according to the dimensions of stiffened plates. Analyzed results of various plates stiffened with rectangular and reverse T ribs show that the effect of the lower flange to the local behavior is very small, so the local behavior can be expressed by ratio functions of the rib space, web thickness, web height and plate thickness and the ratio functions of rectangular and reverse T ribs can be unioned. The application of ratio functions to other types of stiffened plates shows that the increment of the error ratio is so small compared with examples of this study that the applicability of this study is proved.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.45-53
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• 2013

In this study, steel-pier's structural behavior by design variables of ribs were analyzed in order to improve structural details of ribs supporting double base plates. A numerical analysis was conducted using commercial FE analysis program. Anchor bolts and reinforced bars were made of BEAM element, and coefficient of friction was applied to contact surfaces. After that, the analytical result was compared with experiment of previous study to verify analysis methods. Steel-pier's load-displacement relation was analyzed according to various rib's design variables (rib's central angle, height, thickness) by using proven analysis methods, and proper rib's design ranges were proposed.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.1
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• pp.29-34
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• 2012

Even though the longitudinally stiffened laminated composite plates with closed section ribs should be an effective system for axially compressed members, the existing researches on the applications of closed-section ribs, especially for the laminated composite plates, are not sufficient. This study is aimed to examine the influence of the sectional stiffness of U-shaped ribs on the buckling modes and strengths of laminated composite plates. Applying the orthotropic plates with eight layers of the layup $[(0^{\circ})_4]_s$ and $[(0^{\circ}/90^{\circ})_2]_s$, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. From the parametric studies, the minimum required ply thicknesses as well as the buckling strengths were presented for the analysis models. The buckling strengths were compared with the theoretical critical stress equation for simply supported plates based on the Classical laminated plate theory. This study will contribute to the future study for evaluating the minimum required stiffness and optimum design of U-rib stiffened plates.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.737-746
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• 2006

The elastic buckling strength of a Glass Fiber Reinforced Plastic (GFRP) pipe reinforced with ribs was evaluated. The height and thickness of a rib and the spacing between two adjacent ribs were considered as factors affecting the buckling strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting the buckling strength as the GFRP is orthotropic material. Buckling strengths of various GFRP pipe models with different shapes and stiffness ratios were evaluated by FE analyses and a formula to estimate the elastic buckling strength of a rib-reinforced pipe made of orthotropic material was suggested from the regression with the results from the FE analysis. Analytical results show that a rib-reinforced pipe has a buckling strength superior to a general flat pipe and the suggested formula estimates accurate buckling strength of the rib-reinforced pipe.

• Composites Research
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• v.19 no.2
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• pp.13-19
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• 2006

In this paper, parametric study was carried out to design sandwich structures for EDM machines controlling stacking sequence, stacking thickness of composites and rib configuration. Sandwich structures which are dealt with in this paper are composed of fibre reinforced composite for skin material and foam or resin concrete for core materials. The sandwich column has cruciform rib to enhance bending stiffness of the structure and the bed has several vertical ribs to resist the normal forces and vibration. The design parameters such as rib thickness and stacking sequence were controlled to enhance the system robustness. Finite element analysis was also carried out to verify the variation of static and dynamic stiffness of the structures according to the variation of the parameters. Vibration tests were performed to verify the natural frequencies and damping ratios of the manufactured composite structures. The appropriate shape and configuration conditions for micro-EDM machine structures are proposed.

• Journal of Korean Society of Steel Construction
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• v.26 no.5
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• pp.419-430
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• 2014

On going researches which are being made on the welded joints at the intersections of closed ribs such as U-ribs with floor-beams in ortho-tropic steel decks still have been used the shape of scallops with or with not diaphragm inside. Stress Relief Hole(SRH) being presented in this study was investigated in order to reduce the fatigue damage in the intersections of U-rib with floor-beam. Finally, it is verified that circular SRHs sufficiently relief the concentration stress at the intersections of U-rib with floor-beam and shows that SRH can be offer one of the methods that can prevent the fatigue damage in these structural details.