• 한국강구조학회 논문집
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• 제17권4호통권77호
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• pp.491-498
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• 2005

본 연구는 온도상승에 따른 압축을 받는 I-형강 보의 플랜지와 웨브의 국부좌굴응력해석을 위한 컴퓨터프로그램과 항복파괴전에 I-형강 보의 플랜지와 웨브에 국부좌굴이 일어나지 않을 최적 폭-두께비를 구할 수 있는 최적알고리즘의 개발이다. 본 연구에서 사용한 고온에 있어서 강재의 응력-변형도 관계식은 EC3(Eurocode3) Part1.2(2000b)를 근거하였다. 본 연구에서 국부좌굴응력과 최적 폭-두께비는 항복응력, 플랜지와 웨브의 국부좌굴계수와 폭-두께비 영향을 고려하여 해석하였다. 그리고 본 연구의 컴퓨터 프로그램을 적용한 설계 예를 들었다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권1호
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• pp.54-62
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• 2019

본 논문에서는 압축파괴에너지를 이용하여 고강도 구속콘크리트에 대한 응력-변형률 모델을 제안하였다. 참고문헌[5]에서 저자가 실시한 압축실험에는 변형률 게이지를 부착한 아크릴 막대를 실험체의 중앙부에 매립하여 압축부재의 국부 변형률 측정을 시도하였다. 이 아크릴 막대를 이용한 국부 변형률 측정은 매우 효과적인 것으로 나타났다. 압축파괴영역길이는 아크릴 막대로부터 측정된 국부 변형률 분포에 기초하여 정의되었다. 구체적으로, 구속콘크리트의 국소파괴영역길이는 압축강도 발현시의 변형률 ${\varepsilon}_{cc}$의 2배 이상 변형률이 증가하는 영역으로 정의하였다. 또한, 동일한 횡구속압을 받는 압축부재에 흡수된 에너지양은 부재의 형상이나 크기에 관계없이 일정하다는 가정에서 압축 파괴에너지를 도입한 구속콘크리트의 응력-변형률 관계를 제안하였다. 본 연구에서 제안된 모델은 본 연구의 실험결과뿐만 아니라 타 연구자들의 실험결과를 대체적으로 잘 예측하는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제11권2호
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• pp.221-236
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• 2001

A local point interpolation method (LPIM) is presented for the stress analysis of two-dimensional solids. A local weak form is developed using the weighted residual method locally in two-dimensional solids. The polynomial interpolation, which is based only on a group of arbitrarily distributed nodes, is used to obtain shape functions. The LPIM equations are derived, based on the local weak form and point interpolation. Since the shape functions possess the Kronecker delta function property, the essential boundary condition can be implemented with ease as in the conventional finite element method (FEM). The presented LPIM method is a truly meshless method, as it does not need any element or mesh for both field interpolation and background integration. The implementation procedure is as simple as strong form formulation methods. The LPIM has been coded in FORTRAN. The validity and efficiency of the present LPIM formulation are demonstrated through example problems. It is found that the present LPIM is very easy to implement, and very robust for obtaining displacements and stresses of desired accuracy in solids.

• 대한치과마취과학회지
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• 제8권1호
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• pp.1-9
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• 2008

Common dental procedures (local anesthesia and dental treatment) are potentially stress-inducing in many patients, especially medically compromised patients. The body response to dental stress involves the cardiovascular system (an increase in cardiovascular workload), the respiratory organ and the endocrine system (change in metabolism). To minimize the stress to the medical risk patient, the stress reduction protocol was established. The obtained contents were as follows: (1) Recognize the patient's degree of medical risk (2) Complete medical consultation before dental therapy (3) Schedule the patient's appointment in the morning (4) Monitor and record preoperative, perioperative and postoperative vital signs (5) Use psychosedation during therapy (6) Use adequate pain control during therapy (7) Short length of appointment: do not exceed the patient's limits of tolerance (8) Follow up with postoperative pain/anxiety control (9) Telephone the higher medical risk patient later on the same day that treatment was given. This protocol is predicated on the belief that the prevention of or reduction of stress ought to begin before the start of an appointment, continue throughout treatment, and, if indicated, into the postoperative period. The authors used the stress reduction protocol in the care of local anesthesia infected teeth in medically compromised patients. The final prognosis was comfortable without any complications.

• 대한조선학회논문집
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• 제47권4호
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• pp.573-579
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• 2010

The notch effects on the fatigue strength of welded joints are both stress concentration and fatigue strength reduction. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. In this paper, well-known notch stress approaches - critical distance method, area method and fictitious rounding method are presented for the fatigue strength of cruciform joints. The estimated results of the present methods are applied to the experiments performed in this study and reported in the references. The results of the application show that the fatigue-life scatterness of the experimental data expressed in the nominal stress is significantly reduced by introducing the effective fatigue stress of the present study.

• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.51-60
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• 2004

본 논문에서는 냉간성형 ㄷ 형강보에 대해 국부좌굴을 고려한 휨해석을 하였다. 유한요소법을 이용하여 주어진 하중 상태에서의 응력을 구한후 국부좌굴 효과를 고려하기 위해규준에서 주어진 유효폭 개념을 이용하여 유효 단면적을 결정하였으며, 결정된 유효 단면적으로부터 응력을 계산 하였다. x축에 대한 휨응력 뿐 아니라 y축에 대한 휨응력과 뒤틀림 응력값을 고려하였으며, 이를 하중이 전단중심에 작용하는 경우와 도심에 작용하는 두가지의 경우에 대하여 연구를 수행하였다. 연구 결과는 하중-처짐 곡선으로 나타내었다.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.279-287
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• 2019

This paper intends to introduce a near-tip grid refinement and to explore its usefulness in the crack analysis by the natural element method (NEM). As a sort of local h-refinement in FEM, a NEM grid is locally refined around the crack tip showing the high stress singularity. This local grid refinement is completed in two steps in which grid points are added and Delaunay triangles sharing the crack tip node are divided. A plane-state plate with symmetric edge cracks is simulated to validate the proposed local grid refinement and to examine its usefulness in the crack analysis. The crack analysis is also simulated using a uniform NEM grid for the sake of comparison. The near-tip stress distributions and SIFs that are obtained using a near-tip refined NEM grid are compared with the exact values and those obtained using uniform NEM grid. The convergence rates of global relative error to the total number of grid points between the refined and non-refined NEM grids are also compared.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1782-1798
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• 2004

A numerical study of a natural convection in a rectangular cavity with the low-Reynolds-number differential stress and flux model is presented. The primary emphasis of the study is placed on the investigation of the accuracy and numerical stability of the low-Reynolds-number differential stress and flux model for a natural convection problem. The turbulence model considered in the study is that developed by Peeters and Henkes (1992) and further refined by Dol and Hanjalic (2001), and this model is applied to the prediction of a natural convection in a rectangular cavity together with the two-layer model, the shear stress transport model and the time-scale bound ν$^2$- f model, all with an algebraic heat flux model. The computed results are compared with the experimental data commonly used for the validation of the turbulence models. It is shown that the low-Reynolds-number differential stress and flux model predicts well the mean velocity and temperature, the vertical velocity fluctuation, the Reynolds shear stress, the horizontal turbulent heat flux, the local Nusselt number and the wall shear stress, but slightly under-predicts the vertical turbulent heat flux. The performance of the ν$^2$- f model is comparable to that of the low-Reynolds-number differential stress and flux model except for the over-prediction of the horizontal turbulent heat flux. The two-layer model predicts poorly the mean vertical velocity component and under-predicts the wall shear stress and the local Nusselt number. The shear stress transport model predicts well the mean velocity, but the general performance of the shear stress transport model is nearly the same as that of the two-layer model, under-predicting the local Nusselt number and the turbulent quantities.

• 대한기계학회논문집A
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• 제30권9호
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• pp.1086-1093
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• 2006

A local failure criterion for the API X65 steel is applied to predict ductile failure of full-scale API X65 pipes with simulated corrosion and gouge defects under internal pressure. The local failure criterion is the stress-modified fracture strain for the API X65 steel as a function of the stress triaxiality (defined by the ratio of the hydrostatic stress to the effective stress). Based on detailed FE analyses with the proposed local failure criteria, burst pressures of defective pipes are estimated and compared with experimental data. The predicted burst pressures are in good agreement with experimental data. Noting that an assessment equation against the gouge defect is not yet available, parametric study is performed, from which a simple equation is proposed to predict burst pressure fur API X65 pipes with gouge defects.

• 한국치위생학회지
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• 제12권3호
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• pp.471-483
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• 2012

Objectives : This study looked at the relationship between occupational stress and the Oral Health Impact Profile (OHIP), to evaluate the effect of occupational stress-related factors. Methods : Data was obtained from a cross-sectional survey of 260 local officials in Gangwondo. The research comprised three questions relating to subjective oral symptoms, an occupational stress measurement tool and an oral health impact factor which was composed of questions. The data was analysed using t-test, one-way ANOVA, Pearson correlation and path analysis in Amos. Results : Occupational stress had a positive correlation to drinking frequency, Oral symptoms had a negative correlation. And drinking frequency, smoking amount and occupational stress had a positive correlation to oral symptoms. It denoted that drinking frequency, occupational stress and oral symptoms had a negative correlation to OHIP. The path model had an excellent goodness of fit (p=0.07, namely p>0.05). Five 'goodness-of-fit indices' of the model were all above 0.9: GFI=0.987, AGFI=0.952, NFI=0.902, IFI=0.939, CFI=0.934), and its RMSEA was 0.045. Occupational stress and oral symptoms had a firsthand impact on OHIP. In addition, it affected OHIP through the parameters of oral symptoms. Occupational stress exercised a firsthand influence on drinking frequency, drinking frequency exercised a firsthand influence on smoking amount. Smoking amount had a firsthand impact on oral symptoms. Conclusions: Oral health education programs for the development of an improved oral hygiene environment through reduction in drinking and smoking also need to focus on relieving stress by improving workplace culture. In addition, due to good communication is required to reduce occupational stress caused by interpersonal conflict.