• Title, Summary, Keyword: 평균응력

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Numerical Analysis of Prestressed Concrete Pavements Subjected to Transverse Post Tensioning (횡방향 긴장에 의한 프리스트레스트 콘크리트 포장의 거동분석)

  • Kim, Seong-Min;Yoon, Dong-Joo;Kim, Dong-Ho
    • International Journal of Highway Engineering
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    • v.10 no.4
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    • pp.257-267
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    • 2008
  • This study was conducted to investigate the stress distribution in the prestressed concrete pavement (PSCP) when the transverse post tensioning was applied. By performing the structural analyses using a finite element model of PSCP, the effect of anchor spacing and the relationship between the longitudinal and transverse post tensioning were evaluated. The analysis results showed that as the anchor spacing became smaller, the stresses were more uniformly distributed and the ranges of the stress losses were reduced; however, the economy should be considered. As the anchor spacing became larger, the difference between the average transverse stress and the transverse stresses at various locations such as shoulder, wheel pass, and center of the slab, increased. The transverse post tensioning induced the additional tensile forces in the longitudinal tendons, but the magnitude was negligibly small, and the longitudinal and transverse post tensioning could be designed independently. The use of the transverse stress distribution for the design of the post tensioning was also discussed in this paper.

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Fatigue Behavior of PP-LFT used in FEM Carreir with Variation of Stress Ratio (FEM Carrier용 PP-LFT 소재의 응력비 변화에 따른 피로 거동)

  • Moon, Jong-Sin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.1
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    • pp.8-14
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    • 2015
  • Plastics have brought a significant progress in reducing the weight of automotive parts and improving gas emissions by replacing steel parts. The front end module (FEM) carrier, which was made from long glass fiber reinforced polypropylene (PP-LFT), is one of the most successful examples. On the other hand, more research on the fatigue behavior and vibration durability of automotive plastic parts will be needed to improve the long-term reliability. This paper analyzed the durability of the PP-LFT, which is fundamental to fatigue design and analysis of FEM carrier. Various fatigue tests were conducted at different stress ratios to evaluate the relationship between the fatigue life and stress amplitude or mean stress level. In the case of a fixed stress amplitude, the change in fatigue life with the stress ratio was 2~6% larger than the case of fixed maximum stress. Furthermore, this study observed the mechanism of initiation and propagation of the fatigue cracks in PP-LFT by scanning electron microscopy.

Effect of Specimen Geometry on Bending and Tensile Strength of Material Used in Dissimilar Joints (이종 접합재의 굽힘 및 인장강도에 미치는 시험편 형상의 효과)

  • Hur, Jang-Wook
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.3
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    • pp.341-346
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    • 2010
  • The effect of specimen geometry on the bending and tensile strengths of dissimilar joints ($\beta-Si_3N_4/S45C$) with copper interlayers was evaluated. The average bending strength of specimens with circular cross sections was higher than that of specimens with rectangular cross sections. The crack initiation stress ($\sigma_i$) was successfully determined by the acoustic emission (AE) method and was approximately 60~80% of the bending strength. The residual stresses near the interfaces on the ceramic side were measured by X-ray diffraction before conducting the bending test. The bending strength and the crack initiation stress decreased with an increase in the residual stresses. The effect of the bending strain component was evaluated by the tensile testing; the tensile strength decreased with an increase in the bending strain component and was approximately 80% of the bending strength.

Stress Index Development of Trunnion Pipe Support for Pressure and Moment Loads (압력과 모멘트 하중을 받는 원통형 배관 지지대의 응력계수 개발)

  • Kim, J. M.;Lee, D. H.
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.27-39
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    • 1996
  • A finite element analysis of a trunnion pipe anchor is presented. The structure is analyzed for the case of internal pressure and moment loadings. The stress results are categorized as average and linearly varying(through the thickness) stresses. The resulting stresses are interpreted per Section 111 of the ASME Boiler and Pressure Vessel Code from which the Primary(B$_1$) and Secondary(C$_1$) stress indices for pressure, the Primary(B$_2$) and Secondary(C$_2$) stress indices for moment are developed. Several analysis were peformed on various structural geometries in order to determine empirical relationships for the stress indices as a function of dimensionless ratios.

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불확정적 특성을 고려한 응력해석에 관한 일고찰

  • 정명채
    • Computational Structural Engineering
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    • v.6 no.4
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    • pp.10-13
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    • 1993
  • 본 고에서는 불확정적 Approach에 의한 구조물 거동파악의 일례를 소개한다. 이 예에서는 극치통계와 엔트로피 최대원리를 이용하여, 부동침하를 받은 쉘구조물의 응력을 추정하는 이론을 취급한다. 부동침하는 불확정적 특성을 비교적 많이 지니고 있으며, 특히 구조물을 지지하고 있는 지반의 경우는 그 물리적 정수와 침하특성이 확정론적으로는 취급이 곤란한 경우가 많다고 생각된다. 구체적으로 극치통계법에서는 부동침하를 기초 Ring의 원주방향으로의 Fourier 계수로 가정하여, 위상각과 침하의 2승평균치가 확정치로 주어졌을 때, 진폭 Spectrum을 불확정변수로 간주하여 추정하는 방법을 소개한다. 일단 진폭 Spectrum이 구해지면 응력은 간단히 구해지므로 여기서는 Spectrum에 관해서만 언급하기로 한다.

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Theoretical Investigation on the Stress-Strain Relationship for the Porous Shape Memory Alloy (기공을 갖는 형상기억합금의 응력 및 변형률 관계에 대한 이론적 고찰)

  • Lee Jae-Kon;Yum Young-Jin;Choi Sung-Bae
    • Composites Research
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    • v.17 no.6
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    • pp.8-13
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    • 2004
  • A new three-dimensional model fur stress-strain relation of a porous shape memory alloy has been proposed, where Eshelby's equivalent inclusion method with Mori-Tanaka's mean field theory is used. The predicted stress-strain relations by the present model are compared and show good agreements with the experimental results for the Ni-Ti shape memory alloy with porosity of 12%. Unlike linear stress-strain relations during phase transformations by other models from the literature, the present model shows nonlinear stress-strain relation in the vicinity of martensite finish region.

Sediment Transport Paths of the East China Sea (동지나해(東支那海)의 토사이동경로(土砂移動經路))

  • Choi, Byung Ho
    • Journal of The Korean Society of Civil Engineers
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    • v.3 no.4
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    • pp.83-93
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    • 1983
  • A non-linear numerical tidal model of the Yellow Sea and the East China Sea is used to derive the mean and maximum bed stress the mean and maximum transport potential on the continental shelf. It has provided a preliminary assessment of relation between sediment transport paths and the mean and maximum bed stress distribution determined from the numerical model.

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A Constitutive Model for Normally Consolidated Clays (정규압밀점토의 응력 -변형률 구성 방정식)

  • 이영휘
    • Geotechnical Engineering
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    • v.8 no.2
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    • pp.71-80
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    • 1992
  • A new constitutive model is proposed for normally consolidated clays. A main skeleton of the proposed model is based on the concepts of the incremental stress-strain theory by Roscoe and Poorooshasb. The equation of the undrained stress path is formulated by introducing the new pore pressure parameter(C), which is the slope of the linear line in the plot of the normalized pore pressure against the stress ratio. Once the stress increment along the constant stress ratio path (followed by untrained stress path) is know, the volumetric strains are calculated from the linear characteristics between void ratio and logarithm of the mean normal stress for any stress ratio. Then the incremental shear strains are successfully predicted by applying the flow rule derived in the modified theory by Roscoe and Burland.

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Consolidation Test Method Considering Sample Deformation Due to Stress Release by Sampling (시료채취에 의한 응력해방시 시료변형을 고려한 압밀시험)

  • Kim Jae-Young;Takada Naotoshi
    • Journal of the Korean Geotechnical Society
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    • v.20 no.7
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    • pp.99-105
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    • 2004
  • When a saturated clay is sampled from a borehole in an undisturbed manner, the exerted negative pore water pressure restricts the volume expansion. The vertical and horizontal stresses to which the clay was subjected in the ground are smaller and larger than this isotropically confining stress equivalent to the mean principal stress in the ground, respectively. Therefore the sample expands vertically and shrinks laterally under an undrained condition. In the ordinary consolidation test, the sample thus deformed is trimmed to fit the inside of the consolidometer ring. Thus, the specimen generates larger consolidation displacement due to confining larger horizontal stress when in-situ effective pressure is loaded. The specimen does not reproduce the in-situ consolidation behavior, In this paper, considering sample deformation, the test specimen is made to expand laterally to fit the inside of the ring in the undrained manner when the in-situ effective pressure is loaded. And applicability of this proposed test procedure was verified; results from the conventional consolidation test procedure are also discussed.

Influence of the Geometry of Guide Groove on Stress Corrosion Index of Rock in Double Torsion Test (이중 비틀림 시험에서 유도 홈의 형상이 암석의 응력부식지수에 미치는 영향)

  • 정해식;미원우삼;전석원
    • Tunnel and Underground Space
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    • v.14 no.5
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    • pp.363-372
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    • 2004
  • Double torsion (DT) tests were carried out to investigate the influence of the geometry of guide groove on stress corrosion index of Kumamoto andesite. The fracture toughness was measured in the constant displacement rate, which was set to 2.07 MN/m$^{3}$2/ in average regardless of crack velocity. Stress corrosion indices, n were evaluated using specimens with rectangular, circular and triangular grooves and were 37, 36 and 38 in average, respectively. The n values were constant regardless of the groove geometry, however the DT specimen with triangular groove geometry showed the largest standard deviation in the relationship between crack velocity and stress intensity factor. The DT test was found to be effective in using a rectangular-grooved specimen and the width of the groove must be greater than the average grain size of minerals.