• 마이크로전자및패키징학회지
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• 제16권3호
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• pp.67-73
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• 2009

Cu pillar 범프를 사용한 플립칩 접속부는 솔더범프 접속부에 비해 칩과 기판사이의 거리를 감소시키지 않으면서 미세피치 접속이 가능하기 때문에, 특히 기생 캐패시턴스를 억제하기 위해 칩과 기판사이의 큰 거리가 요구되는 RF 패키지에서 유용한 칩 접속공정이다. 본 논문에서는 칩에는 Cu pillar 범프, 기판에는 Sn 범프를 전기도금하고 이들을 플립칩 본딩하여 Cu pillar 범프 접속부를 형성 한 후, Sn 전기도금 범프의 높이에 따른 Cu pillar 범프 접속부의 접속저항과 칩 전단하중을 측정하였다. 전기도금한 Sn 범프의 높이를 5 ${\mu}m$에서 30 ${\mu}m$로 증가시킴에 따라 Cu pillar 범프 접속부의 접속저항이 31.7 $m{\Omega}$에서 13.8 $m{\Omega}$로 향상되었으며, 칩 전단하중이 3.8N에서 6.8N으로 증가하였다. 반면에 접속부의 종횡비는 1.3에서 0.9로 저하하였으며, 접속부의 종횡비, 접속저항 및 칩 전단하중의 변화거동으로부터 Sn 전기도금 범프의 최적 높이는 20 ${\mu}m$로 판단되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.483-488
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• 2001

The RC beams subjected to bending and shear are an important substructure. After flexural cracking, the internal stress state in the beam could not be explained by the classical beam theory. In this study the internal force state factor is introduced to explain the stress state change in the RC beams. The internal force state factor of uniform load was expanded by superposition method using infernal force state factor of point load. As the load types change, the operator that would be calculated the internal force state factor was proposed.

• Advances in materials Research
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• 제8권3호
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• pp.197-217
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• 2019

In this study, the interfacial stresses in RC beams strengthened by externally bonded prestressed GFRP laminate are evaluated using an analytical approach, based on the equilibrium equations and boundary conditions. A comparison of the interfacial stresses obtained from the present analytical model and other existing models is undertaken. Otherwise, a parametric study is conducted to investigate the effects of geometrical and material properties on the variation of interfacial stresses in damaged RC beams strengthened by externally bonded prestressed GFRP laminate. The results obtained indicate that the damage degree has little effect on the maximum shear stress, with a variation less than 5% between the damaged and undamaged RC beams. However, the results also reveal that the prestressing level has a significant effect on the interfacial stresses; hence the damaged RC beam strengthened with an initial prestressing force of 100 kN gives 110% higher maximum shear stress than the damaged RC beam strengthened with an initial prestressing force of 50 kN. The values of shear stress obtained by the analytical approach are approximately equal to 44% of those obtained from the numerical solution, while the interfacial normal stresses predicted by the numerical study are approximately 26% higher than those calculated by the analytical solution.

• 한국공간구조학회논문집
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• 제5권1호
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• pp.99-105
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• 2005

The pushover analysis is becoming a popular tool for seismic design of building structures. In this paper the state-of-art on static nonlinear analysis of building structures is presented with the emphasis on the effects of analysis parameters; i. e., lateral load patterns, modeling of members, and analysis computer programs. The analysed results may have variation even if a same structure is analysed. This paper is to investigate how large the variation is and what the main causes of the variation are. The difference of analysed results, the resultant variation of lateral story shear force and flexural strength of structural members are discussed. The pushover analysis procedure are routinely used in the seismic design of building structures, but some problems must yet be clarified, such as the effects to evaluate the parameters of analysis on the basis of a lateral load patterns and modeling of members.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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• pp.103-110
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• 2004

The pushover analysis is becoming a popular tool for seismic design of building structures. In this paper the state-of-art on static nonlinear analysis of building structures is presented with the emphasis on the effects of analysis parameters; i. e., lateral load patterns, modeling of members, and analysis computer programs. The analysed results may have variation even if a same structure is analysed. This paper is to investigate how large the variation is and what the main causes of the variation are. The difference of analysed results, the resultant variation of lateral story shear force and flexural strength of structural members are discussed. The pushover analysis procedure are routinely used in the seismic design of building structures, but some problems must yet be clarified, such as the effects to evaluate the parameters of analysis on the basis of a lateral load patterns and modeling of members.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.247-268
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• 2006

The parts of pile, above the soil and embedded in the soil are called the first region and second region, respectively. The forth order differential equations of both region for critical buckling load of partially embedded pile with shear deformation are obtained using the small-displacement theory and Winkler hypothesis. It is assumed that the behavior of material of the pile is linear-elastic and that axial force along the pile length and modulus of subgrade reaction for the second region to be constant. Shear effect is included in the differential equations by considering shear deformation in the second derivative of the elastic curve function. Critical buckling loads of the pile are calculated for by differential transform method (DTM) and analytical method, results are given in tables and variation of critical buckling loads corresponding to relative stiffness of the pile are presented in graphs.

• Earthquakes and Structures
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• 제11권4호
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• pp.723-740
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• 2016

Reinforced concrete corbels are generally used to transfer loads within a structural system, such as buildings, bridges, and facilities in general. They commonly present low aspect ratio, requiring an accurate model for shear strength prediction in order to promote flexural behavior. The model described here, originally developed for walls, was adapted for corbels. The model is based on a reinforced concrete panel, described by constitutive laws for concrete and steel and applied in a fixed direction. Equilibrium in the orthogonal direction to the shearing force allows for the estimation of the shear stress versus strain response. The original model yielded conservative results with important scatter, thus various modifications were implemented in order to improve strength predictions: 1) recalibration of the strut (crack) direction, capturing the absence of transverse reinforcement and axial load in most corbels, 2) inclusion of main (boundary) reinforcement in the equilibrium equation, capturing its participation in the mechanism, and 3) decrease in aspect ratio by considering the width of the loading plate in the formulation. To analyze the behavior of the theoretical model, a database of 109 specimens available in the literature was collected. The model yielded an average model-to-test shear strength ratio of 0.98 and a coefficient of variation of 0.16, showing also that most test variables are well captured with the model, and providing better results than the original model. The model strength prediction is compared with other models in the literature, resulting in one of the most accurate estimates.

• Wind and Structures
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• 제30권3호
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• pp.245-260
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• 2020

Wind load and responses are the major factors which govern the design norms of tall buildings. Corner modification is one of the most commonly used minor shape modification measure which significantly reduces the wind load and responses. This study presents a comparison of wind load and pressure distribution on different corner modified (chamfered and rounded) Y plan shaped buildings. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and Shear Stress Transport (SST), are used in the simulation of the building and the data are compared with the previous experimental results in a similar flow condition. The variation of the flow patterns, distribution of pressure over the surfaces, force and moment coefficients are evaluated and the results are represented graphically to understand the extent of nonconformities due to corner modifications. Rounded corner shape is proving out to be more efficient in comparing to chamfered corner for wind load reduction. The maximum reduction in the maximum force and moment coefficient is about 21.1% and 19.2% for 50% rounded corner cut.

• 한국공작기계학회논문집
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• 제11권3호
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• pp.8-13
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• 2002

In order to obtain the basic informations for the development of high strength and high weldability aluminum alloy sheets, the experimental study was carried out to evaluate resistance spot welding characteristics and welding parameters (welding current, welding time, electrode force) far the aluminum alloy sheets. The mechanical properties of spot weld of aluminum alloy were evaluated by tensile shear test and by peel test at room temperature and also the welding possible zone was established through variation of current electrode force and welding time.

• 한국지반공학회논문집
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• 제34권6호
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• pp.61-73
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• 2018

쏘일네일 보강지반에 전단변형이 발생하면 쏘일네일 주변지반에는 수동토압이 유발되고, 전단변형의 증가는 주변지반의 토압 변화와 쏘일네일의 변형 및 부재력 변화를 야기한다. 본 연구에서는 대형 직접전단시험기를 이용하여 쏘일네일의 수직방향으로 전단변형을 유발하면서 쏘일네일의 전단거동을 실험적으로 분석하였으며, 수치해석을 통해 검증하였다. 전단면에서 이격된 쏘일네일의 정착부 길이(6D, 8D, 10D, 12D) 변화를 변수로 전단시험을 실시하였다. 연구결과, 전단변형의 지속적인 증가는 그라우트의 손상을 유발함을 확인하였으며, 정착부 길이변화에 따른 영향을 확인하였다. 모형시험과 수치해석을 통해 분석된 쏘일네일의 전이길이는 0.2~0.22m로 기존 연구에서 제시한 0.1m보다 크게 증가하였으며, 전단영역은 전단면에서 0.6m까지의 범위로 확인되었다.