• 한국농공학회지
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• 제44권3호
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• pp.73-84
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• 2002

Nominal shear strength of concrete beam is the combined strength of concrete shear strength and steel shear strength in current design code. But Torsional moment strength of concrete is neglected in calculation of the nominal torsional moment strength of reinforced concrete beam in current revised code. Tensile stress of concrete strut between cracks is still in effect due to tension stiffening effect. But the tensile stresses of concrete after cracking are neglected in bending and torsion in design. The torsional behavior is similar to the shear behavior in mechanics. Therefore the torsional moment strength of concrete should be concluded to the nominal torsional moment strength of reinforced concrete beam. To verify the validity of the proposed model, the nominal torsional moment strengths according to CEB, two ACI codes(89, 99) and proposed model are compared to experimental torsional strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.878-883
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• 2003

To modify some problems of ACI shear provisions, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear function in deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, namely d, , ρ, f/sub c/' and aid, about 250 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim & Park's equation and Zsutty's equation. While proposed shear equation is simpler than other shear equations, it is shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practice shear design.

• 콘크리트학회논문집
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• 제11권3호
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• pp.3-12
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• 1999

This study presents a suggestion of regulation of skewed slab bridge. In order to find the characteristic behavior of skew bridge, many cases of skew bridges were analyzed with changed angle of skew. The comparison of design methods for cantilever part in pier was also made. It was found that : (1) The lower the skew angle was, the higher the maximum support reaction forces at the end point were. (2) The higher the ratio of L/B was, the higher the maximum support reaction force at the point was. (3) The effect of skew may be neglected for skew angles of $70^{\circ}$or more. (4) If elastic springs are applied to the boundary conditions to simulate the rubber pad bearings, the results will be more reasonable. (5) The shear deformation effect must be considered in the analysis of cantilever part of substructure. (6) Using strut and tie model to design cantilever part of pier, it will be more simple than finite element method with same accuracy and more accurate than using frame element.

• 한국세라믹학회지
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• 제49권4호
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• pp.363-368
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• 2012

Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with $Si_3N_4$ content, while the highest extent of nitridation was measured in $Si_3N_4$-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the $Si_3N_4$-free specimen. On the other hand, pores from the decomposed pore former were retained in the $Si_3N_4$-added specimen. Introduction of small $Si_3N_4$ particles ($d_{50}=0.3{\mu}m$) into a powder compact consisting of large silicon particles ($d_{50}=7{\mu}m$) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to $Si_3N_4$ size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body.

• 콘크리트학회논문집
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• 제27권5호
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• pp.489-499
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• 2015

내진 보강 공법의 보강효과 파악을 위해선 이에 대한 이론적 규명이 필요하다. 이에 본 연구는 단부에 기둥 부재를 증타한 단근 배근된 전단벽체를 대상으로 해 보강되는 기둥의 상세와 일체화 거동을 고려한 전단강도 모델을 제안했다. 이 모델은 증타된 기둥부재의 전단변형이 집중되는 길이를 가정해 이를 일체화된 벽체 내에 발생하는 스트럿 두께 산정에 이용했다. 뿐만 아니라 이 길이 내에 집중 발생하는 전단변형률을 유도, 이를 일체화 거동을 고려한 적합성 조건을 기존 전단벽체의 해석 알고리즘에 도입함으로써 증타 보강된 벽체의 해석 알고리즘을 새로이 제안했다. 또한 제안된 알고리즘을 통해 계산된 전단강도로 횡력 저항 메커니즘을 단일 스트럿 화 시켜줌으로써 보강부재의 초기강성을 제안하였다. 본 연구에서 제안한 방법의 타당성을 확인하기 위해 해석 결과 값을 본 연구에서 수행한 증타 보강된 벽체를 대상으로 한 실험뿐만 아니라 기존 RC 골조 내에 RC 전단벽체를 신설해 보강한 실험의 결과와 비교해 본 결과, 기둥부재의 상세를 고려하면서 동시에 기존 기준들에 비해 실험결과에 가깝게 예측할 수 있음을 확인했다.

• 콘크리트학회논문집
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• 제15권5호
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• pp.697-704
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• 2003

본 연구의 목적은 장방형 개구부를 갖는 철근콘크리트 깊은 보에서 개구부 폭, 깊이 및 위치변화와 부재의 전단거동의 관계를 파악하고, 최대내력을 예측하기 위한 모델을 제시하는데 있다. 주요 변수로는 콘크리트 강도, 전단경간비, 개구부 폭, 깊이 및 위치 등이다. 시험체는 모두 25개이며 2점 대칭가력하였다. 실험결과로부터 개구부를 갖는 깊은 보의 전단거동은 개구부 크기와 전단경간비에 의해 가장 큰 영향을 받았으며, 이들이 증가할수록 이들이 증가 할 수록 콘크리트 설계기준은 불안전측에 있었다. 따라서 개구부 상$.$하 스트럿 작용과 주철근의 타이작용을 고려하여 개구부 효과를 반영한 깊은 보의 전단내력을 적절히 평가할 수 있는 모델을 제시하였다.

• 한국강구조학회 논문집
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• 제12권4호통권47호
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• pp.351-362
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• 2000

이 논문은 반복하중을 받는 관통형 고력볼트를 사용한 엔드플레이트형식 콘크리트 충전 각형강관 기둥-H형강 보 접합부의 거동에 관한 연구이다. 주요변수는 엔드플레이트의 두께(16mm, 22mm, 25mm)와 기둥의 두께(9mm, 12mm)이다. 각 변수에 대해 실험결과와 비교 분석한다. 보-기둥 접합부의 에너지 흡수능력을 구하고, 접합부 패널의 전단내력을 분석한다. 접합부 패널의 전단 내력은 von Mises 항복조건에 의한 강재의 내력과 콘크리트 충전효과를 고려한 Strut 모델을 사용한 콘크리트의 내력을 단순누가해서 구한다.

• 한국재료학회지
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• 제28권2호
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• pp.108-112
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• 2018

The present study demonstrates the effect of raw powder on the pore structure of porous W-Ni prepared by freeze drying of camphene-based slurries and sintering process. The reduction behavior of $WO_3$ and $WO_3-NiO$ powders is analyzed by a temperature programmed reduction method in Ar-10% H2 atmosphere. After heat treatment in hydrogen atmosphere, $WO_3-NiO$ powder mixture is completely converted to metallic W without any reaction phases. Camphene slurries with oxide powders are frozen at $-30^{\circ}C$, and pores in the frozen specimens are generated by sublimation of the camphene during drying in air. The green bodies are hydrogen-reduced at $800^{\circ}C$ and sintered at $1000^{\circ}C$ for 1 h. The sintered samples show large and aligned parallel pores to the camphene growth direction, and small pores in the internal wall of large pores. The strut between large pores, prepared from pure $WO_3$ powder, consists of very fine particles with partially necking between the particles. In contrast, the strut densification is clearly observed in the Ni-added W sample due to the enhanced mass transport in activation sintering.

• 한국항공우주학회지
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• 제35권2호
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• pp.130-135
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• 2007

스마트무인기 파워효과 풍동시험은 2005~2006에 3달여간 항공우주연구원 중형아음속풍동에서 수행되었다. 풍동시험 모델은 정적시험 모델을 활용하였고, 틸트로터 형태의 추진장치를 시험부에 고정하여 파워효과를 모사하였다. 파워효과는 기본적으로 로터가 장착된 시험과 로터가 장착되지 않은 시험의 차로 구해지나, 이 때 두 시험간의 흐름각 차이 및 지지부 간섭량 변화 등을 적절히 보정하여야 한다.

• Earthquakes and Structures
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• 제19권5호
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• pp.315-329
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• 2020

Through bolt connections in Concrete Filled Steel Tubes (CFSTs) has been proved to be good in terms of seismic performance and constructability. Stiffened extended end plate connection with full through type bolt helps to avoid field weld altogether, and hence to improve the quality of joints. An experimental study was conducted on the hysteretic performance of square interior beam-column connections using flat extended end plates with through bolt. The study focuses on the effect of the bond between the tie rod and the core concrete on the cyclic performance of the joint. The study also quantifies how much the interior joint is getting strengthened due to the confinement effect induced by bi-directional bolting, which is widely used in 3D moment resisting frames. For a better understanding of the mechanism and for the prediction of shear capacity of the panel zone, a mathematical model was generated. The various parameters included in the model are the influence of axial load, amount of prestress induced by bolt tightening, anchorage, and the concrete strut action. The study investigates the strength, stiffness, ductility, and energy dissipation characteristics. The results indicate that the seismic resistance is at par with American Institute of Steel Construction (AISC) seismic recommendations. The bidirectional bolting and bond effect have got remarkable influence on the performance of joints.