• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.1-9
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• 2009

This paper investigates inelastic lateral-torsional buckling of stepped beams subjected to uniformly distributed load and end moments. A three-dimensional finite-element program ABAQUS (2007) and a regression program MINITAB(2006) were used to analytically develop new design equation for singly and doubly stepped beams with simple boundary condition. The flanges of the smaller cross-section in the stepped beams were fixed at 30.48 by 2.54 cm, whereas the width and thickness of the flanges of the larger cross-section varied. The web thickness and height of the beams were kept at 1.65 cm and 88.9 cm, respectively. The ratios of the flange thickness, flange width, and stepped length of beam are considered with analytical parameters. Two groups of 27 cases and 36 cases, respectively, were analyzed for doubly and singly stepped beams in the inelastic buckling range. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. The distributions of residual stress of the cross-section is same as shown in Pi and Trahair (1995) and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The comparisons between results from proposed equations and the results from finite element analyses were presented in this paper. The maximum differences of two results are of 13% for the doubly stepped beam and 10% for the singly stepped beam. The proposed equations definitely improve current design methods for the inelastic lateral-torsional buckling problem and increase efficiency in building and bridge design.

• Journal of KSNVE
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• v.5 no.3
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• pp.292-302
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• 1995

압전재료를 이용한 능동진동제어에 관한 연구동향과 연구결과를 살펴보았다. 능동 진동제어에 사용되고 있는 감지기/작동기들 중 압전세라믹은 몇 가지 장점을 지니고 있어 그 적용에 관한 연구가 활발하게 진행되고 있는 것이 현실이며 실제 구조 물로의 적용이 이루어지고 있다. 압전세라믹을 이용한 진동제어는 박판으로 이루어진 국부구조물의 진동제어에 적합하며 그래서 자동차의 진동소음제어, 위성체 태양판의 진동제어에 사용할 수 있고 또한 겹쳐놓은 형태의 압전세라믹은 트러스 구조물의 능동 멤버로 활용할 수 있다. 이렇게 겹쳐놓은 압전세라믹 구조는 진동 고립(vibration isolation)을 원하는 장비의 지지대로 사용할 수 있어 그 응용분야가 넓다. 최근까지 도 압전세라믹을 이용한 진동제어는 주로 외팔보, 또는 평판과 같은 단순한 기하학적 형상을 가진 구조물에 국한되어 연구가 진행되어 왔고 제어기법 또한 그동안 전기 제어분야에서 개발되어 온 기법들을 적용하는 현상을 보였는데 구조물의 자유도가 무한대임을 고려할때 앞으로 구조물에 합당한 제어기법의 개발이 요망된다고 하겠다. 이 논문에서 선보인 PPF와 SRF 제어 기법은 필자가 간단히 회로를 구성하여 실험을 수행하였는데 압전재료의 진동제어 기법으로 단순하면서도 효율적인 제어기법이라고 말할 수 있다. 압전재료를 이용한 진동제어에 관한 국내의 연구활동이 미미한 상태 이으로 이분야에 대한 연구자들의 관심을 모을 필요가 있다. 압전세라믹 감지기와 작동기의 설치는 그동안 압전세라믹 판을 직접 구조물에 접착시킨 형태로 진행되었 는데 새로운 형태의 압전세라믹 작동기의 개발이 시급하다. 이는 높은 전압을 필요로 하는 진동제어는 필수적으로 커다란 부대시설을 요구하게 됨으로 전압을 높이지 않고 도 진동제어를 효율적으로 할 수 있는 압전세라믹의 제조가 필요하다고 하겠다. 필자 는 이런 목적으로 다층 압전세라믹(multilayer piezoceramic plate)을 제작한 적이 있었는데 실험결과는 신통치 않았다. 또한 압전세라믹을 길고 얇은 조각으로 잘라 사용하는 방법로 있었으나 세라믹의 절단시 다이아몬드 컷터를 사용해야 되어 제작이 곤란했다. 또한 압전세라믹이 부서지기 쉬운점을 개선한다면 진동제어에 있어 아주 효과적인 감지기/작동기가 될 수 있을 것이다.

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.75-82
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• 2000

Recently, many studies on connections in steel structures have been performed. In practice, designers assume that the connection is a rigid- or pinned-one, however, actually the connection behaves as partially restrained one, neither fully restrained nor unrestrained. This paper concentrates on the behavior of double angle connections in the field of semi-rigid connections. The behavior of double angle connection. induced by abrupt axial tension load or by collapsed brace in medium or low rise building, is analyzed by 3D nonlinear finite element method using ABAQUS(ver 5.8). From the analytic results. a simplified model of double angle and a rotational stiffness at the corner of the angle are derived, which are fundamentally used for understanding the behavior of the double angle connection.

• Journal of Veterinary Clinics
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• v.29 no.4
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• pp.339-343
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• 2012

Three dogs were presented with diaphyseal fracture of the tibia following separate motor vehicle accidents. On physical and orthopedic examinations, the dogs were noted to have soft-tissue swelling and a closed fracture in these tibia sites. Radiographs revealed a simple, short oblique fracture (case 1), a comminuted, spiral fracture (case 2), and a simple, spiral fracture (case 3) in tibia. Minimally invasive percutaneous plate osteosynthesis (MIPO) using a veterinary cuttable plate or locking plate was applied for the treatment of these fractures. The surgery was successful, and the fractures healed without any complications by 7 weeks (case 1), 10 weeks (case 2) and 8 weeks (case 3) after surgery. Our patients showed fast bone healing times and early weight-bearing during the treatment of their tibia fractures. Therefore, MIPO was a useful procedure for diaphyseal fracture of the tibia in veterinary orthopedics.

• Journal of Korean Society of Steel Construction
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• v.13 no.1
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• pp.101-113
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• 2001

The main purpose of this paper is to present deflections of laminated composite plates on the two-parameter foundations. that is an elastic foundation with shear layer. This paper focuses on the deformation behaviour of anisotropic structures on elastic foundations. The third-order shear deformation theory is applied by using the double-fourier series. To validate the derived equations the obtained displacements for simply supported isotropic and orthotropic plates on elastic foundations are compared with those of Timoshenko and LUSAS program. The results show an excellent agreement for the isotropic and LUSAS program. The results show an excellent agreement for the isotropic and orthotropic plates on the elastic foundations. Numerical results for displacements are presented to show the effects of side-to-thickness ratio aspect ratio, material anisotropy and shear modulus of foundations.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.140-148
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• 1992

The free vibration problem of symmetrically laminated composite rectangular plates is formulated based on anisotropic thick plate theory including the effects of shear deformation and rotary inertia. Considering the difficulty of obtaining closed-form solutions, Rayleigh-Ritz analysis using polynomials having the property of Timoshenko beam functions as trial functions is adopted. The boundary conditions elastically restrained against rotation are accomodated as well as classical boundary conditions. From the results of numerical studies, the validity of the present method is verified. And it is also found that the adoption of thick plate theory for the vibration analysis of laminated composite plates is essential because of the relatively large shear deformation effect, and that the convergence of the Rayleigh quotient to the stationary value is less rapid in anisotropic composite plates than that in the orthotropic ones due to more complicated mode shapes of the former.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.83-90
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• 2010

Composite materials can be used economically and efficiently in civil engineering applications when standards and procedure for analysis, design, construction and quality control are to be established. Bridge systems, including the girders and cross-beams, and concrete decks behave as the specially orthotropic plates. For such systems with sections, boundary conditions other than Navier solution types, it is very difficult to obtain its analytical solution. To design the bridge made by the composite materials, cross-section was used as the form-core shape for economical reason and finite difference method was used for output of the stress value. The Tsai-Wu failure criterion for stress space is used. In this paper, the rate of tensile strength reduction due to increased size was considered. And also numerical study is made for these cases.

• Information Systems Review
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• v.19 no.1
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• pp.101-121
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• 2017

This study explored the emotional and social implications of social media "like" behavior and examined the difference in this behavior across gender. Most studies on social media have analyzed the "like" behavior quantitatively and determined the number of "likes" produced and exchanged. The current study presented a different view by applying a social perspective and analyzing the user intrinsic motives embedded in the "like" behavior. Specifically, we identified empathy and social support as the "like" motivations and used relationship building and information sharing as the mediators. Furthermore, we hypothesized that empathy and social support exhibit different effects on the use of social media across gender: the female group shows strong empathy, and the male group shows strong social support. Validation was performed through a survey of 285 social media users. The results confirmed that empathy and social support have significant effects on the use of social media. However, gender difference in the use of social media was not evident and was only partially evident in the effects of empathy and social support.

• JOURNAL OF ELECTRICAL WORLD
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• s.268
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• pp.25-29
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• 1999

우리 국민에게 2000년은 야누스의 두 얼굴로 다가오고 있다. 새로운 천년에 대한 희망의 얼굴과, 세기말 대재양론에 Y2K문제까지 가세하여 불안함을 감추지 못하는 절망의 얼굴이다. 일부 종교단체나 예언가들은 Y2K문제로 인해 지구의 종말이 온다고 믿고서 피난처를 만들고 있으며 인터넷망 등을 이용, 지지세력의 확장을 꾀하고 있다. 그러나 우리는 이에 편승하여 인류의 미래를 이들에게 맡길 것이 아니라, Y2K문제의 실상을 정확히 이해하고 지혜로운 대처를 위해 모든 역량을 결집해야 할 것이다. Y2K문제는 개인용 컴퓨터에서부터 금융, 통신, 전력, 행정전산망 등 국가산업 전반에 영향을 미칠 뿐 아니라 모든 국민의 생활과 직결되는 문제이기 때문이다. 특히 안전성이 생명인 원자력 발전소에서의 Y2K문제는 모든 국민과 언론의 집중적인 관심의 대상이 되고 있다. 이 같은 관심과 우려의 표명은 원전의 특성을 고려할 때 당연한 현상이지만, 2000년이 되면 원전이 불시에 정지되고 큰 사고가 발생할 것이라는 일부의 시각은 국민의 불안만 가중시킬 뿐이다. 결론부터 말하자면 이러한 우려는 기우에 불과하다. 예를 들면 은행 전산망에서 이자를 계산할 때는 날짜가 필수적이다. 그러나 일반 산업 자동화 설비와 마찬가지로 24시간 연속 가동되는 원자력발전소를 운전 할 때는 미리 일정한 값으로 입력된 각종 운전자료, 즉 온도, 압력, 유량 등과 매순간 생성되는 운전자료들을 단순 비교하기 때문에 날짜가 필요치 않다. 이는 마치 실내 난방온도를 일정 값으로 미리 정해놓으면, 그때 그때의 실내온도와 미리 정해진 온도를 비교하여 난방기가 자동으로 작동되는 방식과 같다. 따라서 운전과 직접 관련되는 설비는 Y2K와 관련이 없고, 운전 편의를 위한 데이터취득설비 일부와 방사능 계측 등의 측정장비에 Y2K영향이 있다. 한전에서는 이들 문제의 적시 해결을 위해 충분한 예산과 인력을 확보하여 문제를 해결하는 과정에 있으며 3월 현재 약 70$\%$의 공정을 보이고 있다.

• Journal of Korean Association for Spatial Structures
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• v.4 no.1 s.11
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• pp.77-86
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• 2004

It is the buckling of the compression portions of the deckplate that govern its behaviour under wet concrete construction loading. The size and position of intermediate stiffeners in the compression flanges of thin-plate steel decks exert a strong influence on the dominant buckling mode of the flange. Test sections composed of high-strength steel were brake pressed with a variety of Flat-hat intermediate stiffeners in the compression flange forming a progression from small to large stiffeners. The ABAQUS program to determine the effectiveness of intermediate stiffeners in controlling buckling modes is undertaken. A series of specimens are loaded with simple beam. Various buckling wave forms prior to ultimate failure through a plastic collapse mechanism. The experimentally determined buckling stresses are found to be comparable with studies performed using the ABAQUS program analysis and using each country code.