• 복합신소재구조학회 논문집
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• 제3권3호
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• pp.9-21
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• 2012

Concrete filled steel tube (CFT) columns have been widely used in moment resisting frame structures both in seismic zones. This paper discusses the design of such members based on the advanced methods introduced in the 2005 AISC Specification and the 2005 Seismic Provisions. This study focuses particularly on design following both linear and nonlinear methods utilizing equivalent static and dynamic loads for low-rise moment frames. The paper begins with an examination of the significance of pseudo-elastic design interaction equations and the plastic ductility demand ratios due to combined axial compressive force and bending moment in CFT members. Based on advanced computational simulations for a series of five-story composite moment frames, this paper then investigates both building performance and new techniques to evaluate building damage during a strong earthquake. It is shown that 2D equivalent static analyses can provide good design approximations to the force distributions in moment frames subjected to large inelastic lateral loads. Dynamic analyses utilizing strong ground motions generally produce higher strength ratios than those from equivalent static analyses, but on more localized basis. In addition, ductility ratios obtained from the nonlinear dynamic analysis are sufficient to detect which CFT columns undergo significant deformations.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.127-133
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• 2005

Rotary swaging is one of the incremental forming process which is a chipless process using the reduction of cross-sections of bars, tubes and wires. The TDS(Tube Drive Shaft) of monobloc used in automotive has been developed by the rotary swaging process. The mechanical characteristics of swaged parts such as the hardness, thickness and roughness are also estimated to conduct experimental analyses of rotary swaging process with the materials of 34Mn5 Furthermore the change in the vibration mode of TDS due to design parameters, which are the tube length, diameter and thickness, has been investigated and analysed. The weight of the TDS product is smaller by about $12.8\%$ than that of SDS with the same performance. It could be evidently found that the TDS is designed to be much lighter than SDS (Solid Drive Shaft). This advantage might give some possibility to improve the NVH (Noise-Vibration-Harshness) characteristics. A maximum torque and a total number of torsional repetitions for the TDS is checked and measured to know the torsional intensity and fatigue strength through the static torsion test and torsional durability test, respectively. A total number of the torsional repetitions up to the fracture for the TDS is greater than 250,000 times.

• 한국철도학회논문집
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• 제12권4호
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• pp.590-596
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• 2009

본 연구에서는 탄소, 유리, 케블라 및 탄소-케블라 하이브리드 섬유로 제작된 원형튜브를 이용하여 각 소재별 에너지 흡수특성과 파손메커니즘을 규명하였다. 이를 위해 각 튜브에 대한 10mm/min의 준정적 압축시험을 수행하였다. 시험결과 탄소섬유 튜브가 가장 에너지 흡수특성이 우수했으며 탄소-케블라 하이브리드 섬유 튜브가 가장 낮은 에너지 흡수율을 보였다. 또한, 각 소재별 에너지 흡수메커니즘을 분석한 결과 탄소 및 유리섬유튜브는 취성파괴 모드로 압축되었다. 또한, 케블라 섬유 튜브는 국부좌굴에 의한 접힘모드가 지배적이고, 탄소와 케블라 하이브리드 섬유 튜브의 경우 단층굽힘과 국부좌굴모드가 혼합되어 나타났다.

• 대한기계학회논문집A
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• 제37권12호
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• pp.1541-1546
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• 2013

공압피팅은 공압이 사용되는 시스템 및 기계에서 작동유체를 공급하기 위한 유연호스의 접속 및 탈착을 원활히 할 수 있게 하는 공압 시스템의 핵심 요소이다. 공압피팅의 구성요소인 원형 판스프링의 응력분포를 유한요소해석을 통하여 살펴본 결과 원형 판스프링은 공압피팅에 유연호스가 장착 될 때 국부적인 소성변형이 일어나는 것으로 나타났다. 원형 판스프링의 응력집중을 분산시키기 위해 다구찌 실험계획법을 이용하여 최적설계를 수행하였다. 원형 판스프링의 반경, 외측폭, 굽힘각을 주요 설계변수로 설정하였으며 다구찌 실험계획법을 통해 원형 판스프링에 작용하는 최대응력에 폭이 81.3%, 굽힘각이 10.9%, 반경이 1.5%의 기여율을 가짐을 확인하였으며, 최적설계시 초기 형상의 원형 판스프링에 비해 약 4% 정도 응력분산의 효과가 있음을 알 수 있었다.

• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.33-42
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• 2004

SN 강재를 건축구조용으로 사용하기 위해서는 설계기준강도가 제정되어야 한다. 선행 연구로써, SN400B/490B 후판재로 재판한 SN400B/490B 원형강관과 SPAP235/325 및 SPAR295 각형강관의 물성을 평가하였다. SN400B/490B 후판재와 비교했을 때 STKN400B/490B 원형강관의 항복인장 및 인장강도는 상승하였지만, 제조 프로세스에 무관하게 STKN400B/490B 원형강관의 규격을 만족 하였다. 그러나 SPAP235/325 각형강관 모서리부에서의 항복인장 및 인장강도는 규격을 벗어났다. 이것은 SPAP235/325 각형강관 규격에서 정하고 있는 값이 모서리부에서의 값이 아니라 변에서의 값이기 때문이다. STKN490B 원형강관에 발생한 최대 인장잔류응력은 모재 항복강도 수준이며, 최대 압축잔류응력은 모재 항복강도의 40% 수준이었다. 또한 SPAP325 각형강관에 발생한 최대 인장잔류응력과 최대 압축잔류응력은 모두 모재 항복강도의 80% 수준이었다. 중심압축실험을 한 결과 STKN490B 원형강관의 좌굴강도는 제조 프로세스에 관계없이 별 차이를 보이지 않았다. 그러나 각형강관의 경우는 SPAP325 각형강관이 SN490B로 built-up한 각형강관보다 좌굴강도가 높게 나타났다.

• 한국전산구조공학회논문집
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• 제12권3호
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• pp.363-370
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• 1999

본 연구에서는 철근콘크리트기둥과 철골보로 이루어진 혼합구조 접합부의 해석에 대한 유한 유소법을 이용한 해석 모델 방법을 제시하였다. 혼합구조 접합부에서 콘크리트와 강판이 접하는 접촉면은 두 접촉면 사이를 부착과 마찰의 개념으로 표현할 수 있는 주-종속 접촉 알고리즘(master-slave contact algorithm)을 이용하여 모델링하였다. 그리고, 휨응력의 지배를 받는 강관에는 비적합 모드 요소를 사용하였다. 본 연구에서의 혼합구조 특징은 보에서 기둥으로 힘의 전달을 원활히 하기 위하여 다이아프램이 사용되었고, 이러한 혼합구조 접합부 모델링 방법에 대한 타당성을 알아보기 위하여 3차원 비선형 해석을 행하여 실험결과와 비교한 결과 잘 일치하는 결과를 얻었다.

• 한국소음진동공학회논문집
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• 제25권12호
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• pp.881-887
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• 2015

The stiffness and natural frequencies for blades, flexbeam, and torque tube of bearingless rotor system are measured to determine the material input properties such as mass distributions and stiffness distribution for the rotor dynamics and load analysis. The flap stiffness, lag stiffness, and torsional stiffness are calculated by measuring section strain or twist angle, gages position, and applied loads through bending and twist tests. The modal tests are undertaken to find out the natural frequencies for flap, lag, torsion modes in non-rotating conditions. The stiffness values and mass properties are tuned and updated to match prediction frequencies to the measured frequencies. The rotorcraft comprehensive code(CAMRAD II) is used to analyze the natural frequencies of the specimens. The analysis results with the updated material properties agree well with the measured frequencies. The updated properties will be used to analyze the rotor stability, dynamic characteristics and loads for the rotor rotation test in a whirl tower.

• Advances in Computational Design
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• 제1권4호
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• pp.297-313
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• 2016

The flexural strength of circular concrete-filled tubes (CCFT) can be estimated by several codes such as ACI, AISC, and Eurocode 4. In AISC and Eurocode, two methods are recommended, which are the strain compatibility method (SCM) and the plastic stress distribution method (PSDM). The SCM of AISC is almost the same as the SCM of the ACI method, while the SCM of Eurocode is similar to the ACI method. Only the assumption of the compressive stress of concrete is different. The PSDM of Eurocode approach is also similar to the PSDM of AISC, but they have different definitions of material strength. The PSDM of AISC is relatively easier to use, because AISC provides closed-form equations for calculating the flexural strength. However, due to the complexity of calculation of circular shapes, it is quite difficult to determine the flexural strength of CCFT following other methods. Furthermore, all these methods give different estimations. In this study, an effort is made to review and compare the codes to identify their differences. The study also develops a computing program for the flexural strength of circular concrete filled tubes under pure bending that is in accordance with the codes. Finally, the developed computing algorithm, which is programmed in MATLAB, is used to generate design aid graphs for various steel grades and a variety of strengths of steel and concrete. These design aid graphs for CCFT beams can be used as a preliminary design tool.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.318-321
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• 2002

As a part of the next generation PET project, we have developed a depth of interaction detector which is consist of three-dimensional arrays of GSO crystal elements sized 2.9mm ${\times}$ 2.9mm ${\times}$ 7.5mm. The basic structure of a detector block is 4-stages in depth, one stage is composed of 2 by 2 array of the crystal elements. The blocks are optically coupled to a position sensitive photomultiplier tube. Each crystal element can be in different conditions; rough or chemical etching for the crystal surface. The effect of the difference of crystal surface condition on the detector performance was analyzed in one-dimensional crystal array as a basic study for the three-dimensional detector by a simple model which is considered only probabilities of transmission, reflect and absorption of photons are in a crystal. As the next step, we investigated the effect of different crystal surface condition in a "U shaped detector" which is an array of stacked crystals bending at the center.

• Steel and Composite Structures
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• 제29권2호
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• pp.187-200
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• 2018

This paper handles the repairing of deficient square Concrete-Filled Steel-Tube (CFST) beams subject to bending through an experimental and numerical program. Eight square-CFST beams were tested. A 5-mm artificial notch was induced at mid-span of seven beams, four of them were repaired by using CFRP sheets and two were repaired by using GFRP sheets. The beam deflection, strain and ultimate moments were recorded. It was found that providing different cut-off points for the different layers of FRP sheets prohibited failure at termination points due to stress concentrations. Using different lengths of FRP sheets around the notch retarded crack propagation and prevented FRP rupture at the crack position. Finite element analysis was then conducted and the proposed FE model was verified against the recorded experimental data. The influence of various parameters as FRP sheet length, tensile modulus and the number of layers were studied. The moment capacity of damaged square-CFST beams was improved up to 77.6% when repaired by using four layers of CFRP, however, this caused a dramatic decrease in beam deflection. U-wrapping of notched-CFST beam with 0.75 of its length provided a comparable behaviour as wrapping the full length of the beam.