• Title, Summary, Keyword: Effective stress

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Effective Notch Stress Method for Fatigue Evaluation of Welded Joints in a Steel Bridge Deck

  • Sim, Hyoung-Bo
    • International Journal of Railway
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    • v.5 no.2
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    • pp.89-92
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    • 2012
  • Effective notch stress, as an approach to evaluate the local stress at a notch (weld toe or root), is defined as the total stress assuming linear-elastic material behavior. This method can be effectively used to evaluate the fatigue performance of welded joints. In this study, finite element analysis results using the effective notch stress method were correlated with fatigue test results of rib-to-deck welded joints in a steel orthotropic bridge deck. Effective notch stress approach provided a good correlation with the crack pattern observed in the full-scale fatigue test. A higher effective notch stress at the critical weld toe than at the weld root was consistent with the dominant crack pattern observed at the weld toe during testing. The effective notch stress at the toe on the deck plate was about 80% higher than that on the rib; no cracks at the weld toe on the rib in the testing were observed. Maximum effective notch stress at the weld root occurred on the upper side of the root notch, which indicates that cracks are more likely to propagate into the deck plate, not into the weld metal. This is also consistent with the observed crack pattern in which the crack from the root propagated upward into the deck plate. No such crack pattern, propagating into the weld metal, was observed in the testing.

Design of the Prestressed Cold Extrusion Die with Two Stress Rings (이중 보강링으로 예압된 냉간압출 금형 설계)

  • Heo, Gwan-Do;Yeo, Hong-Tae;Ye, Sang-Don
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.10
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    • pp.77-82
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    • 2000
  • The design of the prestressed cold extrusion die with two stress rings has been performed in this study. The cold extrusion has been simulated by the rigid-plastic FEM. The stress analysis of die has been performed for both after shrink fitting and during extrusion by using the elastic FEM and the Lame's equation. According to the variation of interferences and diameter ratios, the maximum effective stress has been evaluated. As results, interferences and diameters were determined by the minimization of the maximum effective stress of die insert. The comparison of the maximum effective stress between the proposed design and the conventional design has been discussed. It was found that the maximum effective stress in the die insert is considerably affected by the stiffness of the first stress ring.

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Relationships between child′s Emotional Intelligence and Stress (아동의 정서지능과 스트레스와의 관계)

  • 정현희
    • Journal of the Korean Home Economics Association
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    • v.40 no.7
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    • pp.25-40
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    • 2002
  • The purpose of this study was to examine the relationships between child's emotional intelligence and stress according to child's sex. The subjects for this study were 380 children of 5-6th grade selected from elementary schools in Busan. Kwak's questionnaires(1994) on child's emotional intelligence and Han, Mi-Hyun's questionnaires(1996) on child's stress were used. Statistical techniques such as Manoya, Pearson's correlation, canonical were used. The results were as follows : (1) According to sex, there were significant differences in child's emotional intelligence and stress. The girls showed higher emotional expression, emotional empathy, emotional control, and the friend-related stress than boys. The boys showed higher parent-related stress than girls. (2) There were significant negative correlations between child's emotional intelligence and stress. The children who got higher emotion intelligence perceived lower stress. (3) Among five dimensions of emotional intelligence for boy, the effective variable was emotional utilization. And among six dimensions of stress, the effective variables were home-environment stress and school-related stress. Among fine dimensions of emotional intelligence for girl, the effective variables were emotional expression and emotional recognition. And among six dimensions of stress, the effective variables were friend-related stress and parent-related stress.

Characterization of Non-linear Consolidation of Dredged Soil from Incheon Area (인천 지역 준설토의 비선형 압밀특성 연구)

  • Oak, Young-Suk;An, Yong-Hoon;Lee, Chul-Ho;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1693-1706
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    • 2008
  • It is of importance to determine the zero effective stress void ratio($e_{00}$), which is the void ratio at effective stress equal to zero, and the relationships of void ratio-effective stress and of void ratio-hydraulic conductivity for characterizing non-liner finite strain consolidation behavior for ultra-soft dredged materials. The zero effective stress void ratio means a transitional status from sedimentation to self-weight consolidation of very soft soil deposits, and acts as a starting point for self-weight consolidation in the non-linear finite strain numerical analysis such as PSDDF. In this paper, a new method for determining the zero effective stress void ratio has been introduced with the aid of measuring electrical resistivity of the specimen. A correlation between the zero effective stress void ratio and the initial slurry void ratio has been proposed, which can be used in PSDDF analysis as an input parameter. Combining all of the accessible experimental data, the consolidation characteristics of a dredged soil from the Incheon area has been studied in detail.

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Seismic Risk Analysis of Quay wall Considering Effective Stress (유효응력효과를 고려한 안벽의 지진위험도 평가)

  • Kim, So Yeon;Kim, Dong Hyawn
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.29 no.1
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    • pp.1-11
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    • 2017
  • Seismic risk analysis was performed based on the total stress and effective stress of caisson type quay wall and pier type quay wall. In order to consider the effective stress effect, the pore pressure of the ground was distributed, using Byrne(1991) simple formula to estimate parameter and applied to the finn model. Through the results of seismic risk analysis according to the total stress and effective stress analysis method, the necessity of effective stress analysis in the seismic design of the quay wall installed on the soft ground was confirmed.

An Effective Stress Analysis of Unsaturated Slope Failures by Rainfall Infiltration (강우 침투로 인한 불포화 사면 붕괴의 유효응력 해석)

  • Lee, Young-Huy;Oh, Se-Boong;Jin, In-Chul;Kim, Jun-Woo;Park, Yeong-Mog
    • Journal of the Korean Geotechnical Society
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    • v.29 no.12
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    • pp.77-85
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    • 2013
  • Unsaturated slopes experience infiltration during rainfall and become unstable when saturated. On the viewpoint of unsaturated effective stress, as matric suction decreases, both effective stress and shear strength decrease, which declines slope stability consequently. This study is focused on describing effective stress based on suction stress. The actual slope failures are simulated to calculate factors of safety in the field of finite element stress. In the residual soils of Hadong and Pohang, unsaturated properties are evaluated by laboratory tests. For unsaturated slopes, analyses of infiltration, stress and stability were performed to simulate actual failures. Based on unsaturated effective stress principle, the stability of actual slopes could be evaluated successfully. It is verified for the effective stress concept to be applicable to the engineering practice on slope design which considers infiltration by rainfall.

Analysis of an Actual Slope Failure in the Residual Soil by Suction Stress Based Effective Stress (흡수응력에 기반한 유효응력에 의한 실제 잔류토 사면 붕괴의 해석)

  • Oh, Seboong;Lu, Ning;Park, Young Mog;Lee, Junsuk
    • Journal of The Korean Society of Civil Engineers
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    • v.32 no.3C
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    • pp.113-120
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    • 2012
  • An actual slope failure was analyzed in residual soils at Jinju. Due to rainfall infiltration, the safety factor decreases in the unsaturated layers, since the effective stress and shear strength decrease. In this study, the effective stress is based on suction stress using soil water retention curve. Unsaturated properties were evaluated on soil water retention curve, hydraulic conductivity and shear strength with samples from the site. After infiltration analysis of unsaturated flow under the actual rainfall, the distribution of pore water pressure could be calculated in the slope layers. In the stress field of finite elements, an elastic analysis calculated total stress distribution in the layers and also shear stresses on the slip surface using elastic model. On the slip surface, suction stress and effective stress evaluated the shear strength. As a result, the factor of safety was calculated due to rainfall, which could simulate the actual slope failure. In particular, it was found that the suction stress increases and both the effective stress and the shear strength decrease simultaneously on the slip surface.

A Study on the Effective Stress of RC Beams in Applying the Adhesion Reinforced and the External Post-Tensioning Method (RC보의 부착보강공법과 외부강선보강공법의 유효응력에 관한 연구)

  • Park, Yong-Gul;Choi, Jung-Youl;Choi, Jun-Hyeok
    • Journal of the Korean Society for Railway
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    • v.10 no.2
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    • pp.186-194
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    • 2007
  • This study was performed to compare the load-carrying capacities of the reinforced concrete structure between the carbon fiber adhesion reinforcement method and the external post-tensioning method and further estimate the effective stress of the reinforced material by analyzing the experimental reinforcing effect of each method and the behavior resulting from each method. As a result, it was found out that the effective stress of the carbon fiber reinforcement according to the carbon fiber adhesion reinforcement method had an unexpected value, and also, bearing of the stress was found to be far from sharing thereof. That is to say, while the carbon fiber was bearing the whole stress to some limits, it got to be momentarily ruptured as soon as it went beyond such limits. On the other hand, the external post-tensioning method has the advantage of inducing an initial effective stress by introducing a strain, and thus, it was found that behavior or bearing of the stress was also found to be a solid behavior of the steel wire. This method was also found to be more efficient and excellent than the carbon fiber adhesion reinforcement method in the reinforcing effect or securing the effective stress. Accordingly, we were to discuss the effective stress as comparatively examined, focusing on deriving of the more enhanced reinforcing effect on the basis of the experiment to which the field characteristic is added.

Energy-based evaluation of liquefaction potential of uniform sands

  • Sonmezer, Yetis Bulent
    • Geomechanics and Engineering
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    • v.17 no.2
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    • pp.145-156
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    • 2019
  • Since behaviors of loose, dense, silty sands vary under seismic loading, understanding the liquefaction mechanism of sandy soils continues to be an important challenges of geotechnical earthquake engineering. In this study, 36 deformation controlled cyclic simple shear tests were performed and the liquefaction potential of the sands was investigated using three different relative densities (40, 55, 70%), four different effective stresses (25, 50, 100, 150 kPa) and three different shear strain amplitudes (2, 3.5, 5%) by using energy based approach. Experiments revealed the relationship between per unit volume dissipated energy with effective stress, relative density and shear strain. The dissipate energy per unit volume was much less affected by shear strain than effective stress and relative density. In other words, the dissipated energy is strongly dependent on relative density and effective stress. These results show that the dissipated energy per unit volume is very useful and may contain the non-uniform loading conditions of the earthquake spectrum. When multiple regression analysis is performed on experiment results, a relationship is proposed that gives liquefaction energy of sandy soils depending on relative density and effective stress parameters.

A study on the fatigue crack growth behavior of aluminum alloy weldments in welding residual stress fields (용접잔류응력장 중에서의 Aluminum-Alloy용접재료의 피로균열성장거동 연구)

  • 최용식;정영석
    • Journal of Welding and Joining
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    • v.7 no.1
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    • pp.28-35
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    • 1989
  • The fatigue crack growth behavior in GTA butt welded joints of Al-Alloy 5052-H38 was examined using Single Edge Notched(SEN) specimens. It is well known that welding residual stress has marked influence on fatigue crack growth rate in welded structure. In the general area of fatigue crack growth in the presence of residual stress, it is noted that the correction of stress intensity factor (K) to account for residual stress is important for the determination of both stress intensity factor range(.DELTA.K) and stress ratio(R) during a loading cycle. The crack growth rate(da/dN) in welded joints were correlated with the effective stress intensity factor range(.DELTA.Keff) which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the welded joints were examined by using superposition of redistributed residual stress and discussed in comparison with the results of the initial welding residual stress superposition.

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