• Title/Summary/Keyword: 뒤틀림 응력

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Design of Longitudinal prestress of precast decks in twin-girder continuous composite bridges (강박스거더 교량의 프레임 형식 중간다이아프램의 설계)

  • Yoon, Dong Yong;An, Sung Hyun;Lee, Sung Chul
    • Journal of Korean Society of Steel Construction
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    • v.18 no.5
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    • pp.515-524
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    • 2006
  • Cross-sectional distortions take place when steel box girders a re subjected to torsional moment, as a consequence of which distortional warping stresses are necessarily developed. Additional normal stresses due to the distortion are should be included at the design stage. The relative magnitude with respect to the maximum bending stress are kept less than the specific values, i.e., at 5~10%, by properly spaced intermediate diaphragms that could prevent the distortional deformation of the box girder. However, current design equations for the stiffness of intermediate diaphragms were derived based on BEF. In this study, the area required by the intermediate diaphragm members are investigated through three-dimensional finite element analyses. The results of the analyses indicate that the current equations give to conservative values for the intermediate diaphragm of box girder bridges. Finally, an improved equation for the area of the intermediate diaphragm is derived from a regression analysis from the finite element analysis results.

Distortion of Tempered Thin Plate Glasses (열처리된 얇은 판유리의 뒤틀림)

  • 이성근;정관수;강태진;윤재륜
    • Proceedings of the Korean Fiber Society Conference
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    • 2003.04a
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    • pp.231-234
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    • 2003
  • 폭과 길이에 비해 상대적으로 두께가 아주 얇은 판유리 생산에 있어서 여러 가지 형태 불안정성이 문제가 되는데, 본 논문에서는 이러한 형태 불안정성 중 완성된 판유리를 용도에 따라 절단했을 때 판 유리가 뒤틀리는 현상을 다루었다. 이러한 뒤틀림 현상을 해결하기 위한 노력의 일환으로 뒤틀림의 원인이 냉각 후 판유리에 남아있는 잔류 응력이라 생각하고, 판유리 제조 공정 중 여러 가지 온도 분포와 다양한 경계 조건을 사용했을 때 잔류응력 분포 변화를 해석하고 그에 따른 뒤틀림 거동을 해석하였다. (중략)

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Stress Behavior of Substrate by Thin Film Pattern (박막 패턴에 의한 기판의 응력 거동)

  • Nam, Myung Woo;Hong, Soon Kwan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.1
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    • pp.8-13
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    • 2020
  • Stress is the main cause of warpage failure of very thin substrates with thickness of several hundred ㎛, such as IC packages. Stress usually results from differences in crystal structures and corresponding thermal expansion coefficients when depositing different substances on a substrate. In this study, the behaviors of stress occurring in substrates were numerically analyzed by the thin-film pattern of the rectangles stacked on the substrates. First, the substrate displacement was obtained and the substrate strain and stress were obtained using it. When the tensile force is concentrated at the edge of the thin film pattern, normal and shear stresses are generated around the edge of the thin film pattern. Normal stress occurs near the edges of the thin film pattern and the vertexes. Shear stress also occurs around the edge of the thin film pattern, but unlike normal stress, it does not appear near the vertexes. It was also confirmed that the magnitude and direction of shear stress are changed around the edge. When edge forces of thin-film pattern are equal, the normal stress was about 10 times larger than the shear stress. This indicates that normal stress is the biggest cause of warpage failure.

Spacing of Intermediate Diaphragms Horizontally Curved Steel Box Girder Bridges considering Bending-distortional Warping Normal Stress Ratio (곡선 강박스 거더의 휨-뒤틀림 응력비에 따른 중간 다이아프램 간격)

  • Lee, Jeong-Hwa;Lee, Kee-Sei;Lim, Jeong-Hyun;Choi, Jun-Ho;Kang, Young-Jong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.9
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    • pp.6325-6332
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    • 2015
  • Although distortions of horizontally curved box girder are more susceptible than which of the straight girder due to curvature effect, current domestic design standards does not present spacing of intermediate diaphragms for the curved box girder. In this study, parametric studies for straight and curved box girder considering distortional warping normal stresses based on linear finite element analysis were carried out. Single span curved girders were chosen for analysis based on current domestic bridge data with 1-6 of solid intermediate diaphragms, 0-30 degree of subtended angle, 30m and 60m of span length and 2-3m of flange width and web height. The adequate spacing of diaphragms for the box girder were suggested considering subtended angles and bending and distortional warping normal stress ratios with 5%, 10%, 15% and 20%. The analysis results were also compared to a current design standard and suggested spacing of diaphragm were evaluated.

Inelastic Buckling Behavior of I-Beam Under Uniform Bending (균일한 수직하중을 받는 I형강의 비탄성 좌굴거동에 의한 설계)

  • Lee, Dong Sik;Oh, Soon Taek
    • Journal of Korean Society of Steel Construction
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    • v.16 no.1 s.68
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    • pp.61-72
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    • 2004
  • This study investigated the inelastic lateral-torsional buckling of simply supported beams under a central concentrated load and a uniformly distributed load. A line-type finite element, method was incorporated with the "so-called" simplified and polynomial patterns of residual stresses. The effect of the load height was also considered in this study. The polynomial residual stresses assumed in this study was a quartic distribution in the flange and a parabolic distribution in the web. The inelastic lateral-torsional buckling of beam was analyzed with four different I-sections manufactured in Korea. Results obtained in this study were compared with KSDM(design method in the 1995 Korean Steel Designers' Manual). The design method in KSDM was found to be generally conservative with and without a sub-beam attached to the main beam, which acted as an intermediate restraint.

A Behavioral Analysis of Curved Steel Box Bridge Associated with Diaphragm's Shape and Spacing (다이아프램 형상 및 간격에 따른 곡선 강박스거더의 거동해석)

  • Kim, Yun-Tae;Kim, Sang-Chel
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.1
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    • pp.205-215
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    • 2006
  • In this study 3-D shell FEM model was applied to analyze the behavior of curved steel box girders stiffened by diaphragms. The reliability of the analytical method has been proved by comparing with the existing results. It was also found from this analysis that main factors affecting a distortional stress are length of a girder, curvature of the girder, and spacing of diaphragms. A modelled bridge with 30m of span length and 40m of radius was analyzed to find an optimum spacing of diaphragm, and as a result of applying different spacings, 5m was found to be most appropriate to control the stress ratio regulated by specifications. In the effect of diaphragm shape, the rhamen-typed diaphragm is found to be more effective than the fully filled-up one in the range of opening ratio of 0.4 to 0.6. But, the fully filled-up diaphragm had more efficiency in terms of reducing the distortional stress than X-truss typed diaphragm.

Analysis of Thermal Deformation of Carbon-fiber Reinforced Polymer Matrix Composite Considering Viscoelasticity (점탄성을 고려한 탄소 섬유강화 복합재의 열 변형 유한요소 해석)

  • Jung, Sung-Rok;Kim, Wie-Dae;Kim, Jae-Hak
    • Composites Research
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    • v.27 no.4
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    • pp.174-181
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    • 2014
  • This study describes viscoelasticity analysis of carbon-fiber reinforced polymer matrix composite material. One of the most important problem during high temperature molding process is residual stress. Residual stress can cause warpage and cracks which can lead to serious defects of the final product. For the difference in thermal expansion coefficient and change of resin property during curing, it is difficult to predict the final deformed shape of carbon-fiber reinforced polymer matrix composite. The consideration of chemical shrinkage can reduce the prediction errors. For this reason, this study includes the viscoelasticity and chemical shrinkage effects in FE analysis by creating subroutines in ABAQUS. Analysis results are compared with other researches to verify the validity of the subroutine developed, and several stacking sequences are introduced to compare tested results.

Stress Analysis of Cold-Formed Steel Beams Considering Local Buckling Effects (국부좌굴을 고려한 냉간성형 ㄷ 형강보의 응력해석)

  • Jeon, Jae Man;Hyun, Ja Young;Lee, Jae Hong
    • Journal of Korean Society of Steel Construction
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    • v.16 no.1 s.68
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    • pp.51-60
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    • 2004
  • The stress analysis of cold-formed channel section steel beams under transverse load was conducted. The local buckling effect was included in the analysis using effective area concept. The proposed analytical model is capable of predicting accurate normal stress in the beam due to various behaviors including biaxial bending and warping. It was found to be appropriate for predicting stresses as well as deflection in the beam. A finite element model was developed to solve the analytical model.

Numerical Analysis and Experimental Measurement of Hygroscopic Warping Effects for Cellulose Fibres (셀룰로스 복합소재에서의 수분에 의한 뒤틀림 변형효과를 위한 수치해석적 실험적 연구)

  • Kim, Byeong-Sam;Kim, Ki-Jun
    • Journal of the Korean Society of Safety
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    • v.19 no.1
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    • pp.117-123
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    • 2004
  • The prediction to the hydroscopic moisture warping behaviors is analyzed for cellulose-based laminates using a numerical method base on a modified classical laminate(MCL) theory for hygroscopic moisture deformations with cycling testing data. The experimental measurement of the interferometric hygroscopic warping effects, moisture generator, and curvature of cellulose reinforced epoxy laminates is studied under cyclic environmental conditions using a Moire interferometer coupled. Accurate determination of curvatures provides a description of dimensional stability evolution; the tools for validation of computational internal stress and for the warpage prediction in model safety.

A Study on the Distortional Analysis of Curved Steel Box Girders and Determination of Diaphragm Spacing (곡선 강상자형 거더의 뒤틀림 해석 및 격벽간격산정)

  • Koo, Min Se;Yoon, Wo Hyun;Lee, Ho Kyoung;Kim, Dae Hong
    • Journal of Korean Society of Steel Construction
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    • v.15 no.2
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    • pp.125-135
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    • 2003
  • A 3-dimensional model of curved steel box girder bridges without diaphragm was presented. This model yielded results that were consistent with those of the parameter analysis using the BEF and Ritz methods. Se veralmodels with diaphragms were analyzed to estimate the appropriate diaphragm spacing. In case of 50m span, models A-10, A-20, A-30, B-10, B-20, and B-30 were found to have 5(8.3m), 7(6.25m), 8(5.5m), 4(10m), 6(7.1m), and 7(6.25m) diaphragms, respectively. In addition, a formula that presents the ratio of distortional stress to bending stresswas created from the results of the 3-dimensional FEM model analysis.