• 한국지진공학회논문집
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• 제7권4호
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• pp.39-49
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• 2003

본 연구는 철근콘크리트 교각에 대한 새로운 내진설계법을 개발하기 위한 연구의 일환으로서, 축력과 함께 반복 횡하중을 받는 철근콘크리트 교각의 모멘트-곡률 포락곡선 및 하중-변위 포락곡선을 얻기 위한 비선형 해석방법을 제시한다. 철근콘크리트 교각의 내진성능에 영향을 미치는 주요변수들에 대한 기존의 해석모델을 적용하였으며, 국내ㆍ외에서 수행된 나선철근 및 원형띠철근 기둥의 준정적 실험결과와의 비교 분석을 통하여 실험결과와 유사한 해석결과를 제공할 수 있도록 기존의 해석모델을 일부 수정 제안하였다. 해석에는 횡방향 구속효과를 고려한 콘크리트 모델, 반복하중을 받는 철근의 포락선 모델, 축방향철근의 부착슬립 모델, 전단변형 모델 등을 적용하였다. 제안된 해석방법은 실험결과를 비교적 잘 예측할 수 있는 것으로 평가되며, 특히 변형능력 및 연성도에 대하여는 실험결과에 비하여 안전측의 결과를 제공한다.

• 한국해양공학회지
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• 제22권2호
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• pp.85-90
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• 2008

Ships in bad weather conditions are likely to be subjected to accidental loads, such as high bending moment, collision, and grounding. Once she has damage to her hull, her ultimate strength will be reduced. This paper discusses an investigation of the effect of collision damage on the ultimate strength of a ship structure by performing a series of collapse tests. For the experiment, five box-girder models with stiffeners were prepared with a cross section of $720mm\;{\times}\;720mm$ and a length of 900mm. Of the five, one had no damage and four had an ellipse shaped damage area that represented the shape of the bulbous bow of a colliding ship. The amount of damage size was different between models. Among the damaged models, the damage in three of them was made by cutting the plate and stiffener, and in one by pressing to represent collision damage. Experiments were carried out under a pure bending load and the applied load and displacements were recorded. The ultimate strength was reduced as the damage size increased, as expected. The one with the largest amount of damage had damage to 30% of the depth, and its ultimate strength was reduced by 19% compared to the undamaged one. The pressed one has higher ultimate strength than those that were cut. This might be due to the fact that the plate around the pressed damage area contributes to the ultimate strength, whereas the cut one has no plate to contribute.

• 한국해양공학회지
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• 제33권1호
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• pp.33-41
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• 2019

Estimating fatigue damage is a very important issue in the design of ships. The springing and whipping response, which is the hydro-elastic response of the ship, can increase the fatigue damage of the ship. So, these phenomena should be considered in the design stage. However, the current studies on the the application of springing and whipping responses at the design stage are not sufficient. So, in this study, a prediction method was developed using fluid-structural interaction analysis to assess of the fatigue damage induced by springing and whipping. The stress transfer function (Stress RAO) was obtained by using the 3D FE model in the frequency domain, and the fatigue damage, including linear springing, was estimated by using the wide band damage model. We also used the 1D beam model to develop a method to estimate the fatigue damage, including nonlinear springing and whipping by the vertical bending moment in the short-term sea state. This method can be applied to structural members where fatigue strength is weak to vertical bending moments, such as longitudinal stiffeners. The methodology we developed was applied to 325K VLOC, and we analyzed the effect of the springing and whipping phenomena on the existing design.

• Geomechanics and Engineering
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• 제31권3호
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• pp.237-248
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• 2022

Nowadays, more and more subway tunnels were planed and constructed underneath the ground of urban cities to relieve the congested traffic. Potential damage may occur in existing tunnel if the new tunnel is constructed too close. So far, previous studies mainly focused on the tunnel-tunnel interactions with circular shape. The difference between circular and horseshoe shaped tunnel in terms of deformation mechanism is not fully investigated. In this study, three-dimensional numerical parametric studies were carried out to explore the effect of different tunnel shapes on the complicated tunnel-tunnel interaction problem. Parameters considered include volume loss, tunnel stiffness and relative density. It is found that the value of volume loss play the most important role in the multi-tunnel interactions. For a typical condition in this study, the maximum invert settlement and gradient along longitudinal direction of horseshoe shaped tunnel was 50% and 96% larger than those in circular case, respectively. This is because of the larger vertical soil displacement underneath existing tunnel. Due to the discontinuous hoop axial stress in horseshoe shaped tunnel, significant shear stress was mobilized around the axillary angles. This resulted in substantial bending moment at the bottom plate and side walls of horseshoe shaped tunnel. Consequently, vertical elongation and horizontal compression in circular existing tunnel were 45% and 33% smaller than those in horseshoe case (at monitored section X/D = 0), which in latter case was mainly attributed to the bending induced deflection. The radial deformation stiffness of circular tunnel is more sensitive to the Young's modulus compared with horseshoe shaped tunnel. This is because of that circular tunnel resisted the radial deformation mainly by its hoop axial stress while horseshoe shaped tunnel do so mainly by its flexural rigidity. In addition, the reduction of soil stiffness beneath the circular tunnel was larger than that in horseshoe shaped tunnel at each level of relative density, indicating that large portion of tunneling effect were undertaken by the ground itself in circular tunnel case.

• 한국전문물리치료학회지
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• 제13권3호
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• pp.75-83
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• 2006

The purpose of this study was to examine the isokinetic moment of quadriceps and hamstring strength ratio among women of different ages. The study population consisted of 1,184 women referred to the Health Promotion Center at the S district. All subjects were aged 20 to 69 years old and divided into 5 groups; 20s (n=248), 30s (n=255), 40s (n=248), 50s (n=228), and 60s (n=205). The strength of the knee extensor and flexor, quadriceps, and hamstring of all the participants were assessed at 60 degrees/second with an isokinetic machine. We calculated the peak torque, peak torque %BW (%Body Weight), deficit of peak torque and hamstring/quadriceps ratio of the knee. The data were analyzed by one way ANOVA to investigate statistical differences in strength variation between different age groups and were computed by ${\Delta}%$ difference from women in their 20's. The results were obtained as follows: 1. Peak torque of the knee extensor, quadriceps, were significantly reduced in women older than 30, but peak torque of the knee flexor, hamstring, were significantly reduced in women older than 50 compared to women in their 20's. (p<.05). 2. Peak torque %BW of the knee extensor, quadriceps, were significantly reduced in women older than 20, but peak torque %BW of knee flexor, hamstring, were significantly reduced in women older than 40 compared to women in their 30's (p<.05). 3. Compared to the women in their 20's, there was no significant difference among any of the age groups in the deficit of peak torque of the knee extensor and flexor, but the deficit of peak torque of knee extensor among women between 30 and 50showed significant difference within the normal range of deficit. 4. Compared to the women in their 20's, there was no significant difference among any of the age groups in the hamstring/quadriceps ratio These results showed that peak torque, peak torque %BW, deficit of peak torque, and hamstring/quadriceps ratio of the knee were reduced in each age group, but especially among the women over 50. Further longitudinal study may be needed to see if volume of muscle mass and intervention of exercise affect knee strength in spite of aging.

• 콘크리트학회논문집
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• 제14권5호
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• pp.645-652
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• 2002

본 논문은 탄소 FRP 판을 이용한 철근 콘크리트 보의 휨 보강효과와 거동에 대한 연구이다. 본 연구에서의 실험인자로는 휨보강 탄소 FRP 판의 부착길이와 탄소 FRP 쉬트의 복부정착 길이이다. 시험보는 탄소 FRP 판으로 인장면에 부착하여 휨 보강하고 FRP 판을 탄소 FRP 쉬트로 복부에 정착하였다. 일반적으로 복부정착이 없는 휨 보강된 보들의 파괴형태는 횡방향 주철 근을 따라 발생한 콘크리트 덮개 박리파괴를 나타내었다. 반면, 탄소 FRP 쉬트로 복부 정착된 휨 보강 보들은 CFRP 파단파괴 후 콘크리트 경계면 전단 박리파괴를 나타내었다. 보강된 보들의 극한하중과 극한처짐은 FRP 판의 휨 부착길이의 증가에 따라 증가하였다. 또한, 휨 보강된 보들은 FRP 쉬트의 복부정착 길이의 증가에 따라 극한하중과 극한처짐 값이 증가하였다. 특히, 복부 정착한 보들은 최대 극한하중에 도달한 후에도 상당한 극한하중 지지능력을 상당한 극한 처짐 시까지 유지하였다. 시험보의 길이에 걸친 FRP 판의 변형률 분포는 휨 모멘트도의 모양과 거의 유사하여 전단지간에서 일정한 전단응력 분포를 가정할 수 있었다. 전지간을 휨 보강한 보에 있어서는 콘크리트와 FRP 쉬트에 의한 경계면에서의 극한전단 저항강도는 복부정착 길이가 늘어남에 따라 증가하였다. 전단 저항강도 중에서 본 실험에서 사용한 복부 정착 FRP 쉬트도 일부의 전단 저항강도를 부담하였다.

• 한국터널지하공간학회 논문집
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• 제16권1호
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• pp.105-115
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• 2014

터널내의 연기거동 및 대피안전성을 평가하기 위하여 수치해석을 수행하였다. 본 연구의 목적은 최근 더욱 길어지고 있는 장대터널의 화재로 인한 연기 및 온도 분포와 안전성을 평가할 수 있는 수치적 방법을 구현하는데 있다. 계산에 사용되는 컴퓨터자원을 최소화하기 위하여 모델로 선정한 터널의 전체길이인 3 km을 사용하는 대신 여러 개의 대피터널이 포함되는 1.5 km만을 해석영역으로 사용하였다. 터널내의 연기거동에 의한 대피자의 안전성을 평가하기 위하여 연기의 밀도에 의한 기시도와 바닥으로부터의 높이를 고려한 SE (smoke environment)값을 사용하였다. 공기 중에 포함된 연기의 밀도는 3차원 전산유체역학을 통하여 구하였다. 이러한 연기 거동에 영향을 미치는 온도분포를 정확하게 모사하기 위하여 터널 벽면을 단열 혹은 일정한 열유속(heat flux) 가정을 사용하는 대신 1차원 열전도(heat conduction)방정식을 이용하여 터널벽면의 온도를 계산하였다. 대피터널간의 거리가 가까울수록 대피자의 안전성은 높아지겠지만 상대적으로 건설비용이 증가하게 된다. 본 연구에서 대피터널의 길이는 250 m로 하였으며 화재 시 제연팬의 운전 조건을 3가지 (팬이 가동되지 않는 조건, 임계풍속이하조건, 임계풍속이상조건)로 나누어 연기의 거동과 온도분포를 고찰하였다. 그리고 화재가 발생한 시간부터 플래쉬오버가 발생한 시간까지의 연기의 거동과 대피자의 상황을 SE를 이용하여 고찰하였다.

• 모자간호학회지
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• 제2권1호
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• pp.5-20
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• 1992

This study was undertaken to identify the levels and affecting factors of the maternal role attainment(MRA) in the primipara during the postpartum period. The healthy ninety primiparous from the one university hospital and two local clinics in KwangJu city were selected and two Semantic Differential Scales (SD-Myself as Mothers, SD-My Baby) and the Pharis Self Confidence Scale were used in this study. Questionnaires were distributed at the 3rd days and the 4-6 weeks of the primiparous not showing any complication after normal delivery. The data collected were analysed statistically using t-test, Pearson's Product Moment Correlation Coefficient and ANOVA. The results obtained were summarized as follows; 1) On the 3rd day after the delivery, the scores of SD-myself as mother, SD-baby and Pharis Self Confidence were 70.6 points, 73.6 points and 78.6 points, respectively, showing the low level of MRA. 2) On the 4-6 weeks after delivery, the score of SD-myself as mother, SD-baby and Pharis Self Confidence were 72.8 points, 77.9 points, and 86.9 points, respectively, indicating the moderate level of MRA. 3) The mean scores of the SD scale and the Pharis Self Confidence during the postpartum periods were higher than those of the 3rd days, showing the SD-myself as mother (t=-2.09, P<.05), SD-baby(t=-4.12, P<.001), Pharis Self Confidence(t=-6.59, P<.001), respectively. 4) Positive correlations (r=.24$\sim$.69) were shown in the concepts related to the MRA and the cognitive-motor skill components and cognitive-affective skill components of the MRA became harmonious over time. 5) The relationships between the score of the MRA and the demographic and obstetric variables were as follows ; a) the score of the MRA in the twenties was higher than those of the thirties. b) the group with higher educational background showed higher MRA socres than the group with lower one. c) those who wanted pregnancy sustenance had higher MRA scores than those who did not. d) the group that did think of festus-feature represented higher MRA scores than those who did not. e) the group of mothers who have the daughters showed higher MRA scores than those who have boys. It can be concluded from the results that the MRA in the primiparous increased gradually, and that the cognitive-motor skills and cognitive-affective skills became harmonious over time. The level of the MRA was affected partly by the mothers general, obstetrical variables. Following suggestion were made oil the basis of the present study ; a) The longitudinal study on the MRA is needed. b) Multivariate analyses should be done for the identification of the factors influcening on the MRA. c) Education program for primiparous mother should be designed and developed to improve the MRA.

• 대한정형외과스포츠의학회지
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• 제2권2호
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• pp.77-81
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• 2003

목적: 슬관절 주위 골격의 기초과학을 생체역학을 중심으로 설명하고 빈도가 높은 스포츠 손상들에 대해 기술하고자 한다. 해부 밀 운동학: 슬관절은 순수한 경첩 관절이 아니며 적합하지 않으므로 여섯 방향의 운동이 가능하다. 경골대퇴간 운동역학: 슬관절의 굴곡-신전 축은 시상면에 수직이 아닐 뿐 아니라, 관상면상 관절선과 평행하지 않으므로, 경골대퇴관절은 굴곡 시 내반과 내회전이 동반되고 신전 시에는 외반과 외회전이 동반된다. 슬개대퇴 관절: 슬개대퇴 관절 압박력은 슬관절의 굴곡 각도와 사두고근력에 비례한다 슬개골은 신전기전의 moment arm을 증가시켜 신전기전의 효율을 증대시키고 지렛대 역할을 한다. 슬개골 골절: 비전위성 골절이면서 하지 직거상 운동이 보존된 경우에 비수술적 치료의 적응증이 되며 수술적 치료 시 고정 방법의 선택은 골절 양상에 따라 결정되겠으나 어느 술식을 선택하여도 신전지대의 봉합은 필수적이며 중요하다 슬개골 불안정성: 선행 해부학적 이상을 조사해야 하며 급성 탈구에서도 골연골 골절편이 있거나 재발의 위험이 높은 운동선수에서 인대 봉합을 고려할 수 있다. 비수술적 치료 및 재활에도 불수하고 계속되는 재발성 아탈구나 탈구는 수술이 필요하다 학령기 스포츠 손상: Idiopathic Adolescent Anterior Knee Pain, Osgood-Schlatter Disease, Sinding-Larsen-Johansson Disease 등이 흔하다

• 한국항공우주학회지
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• 제30권6호
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• pp.69-77
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• 2002

수직 돌풍이 작용하는 비행선의 비선형 방정식을 이용하여 종방향 운동에 대한 동적 반응을 살피고 제어기를 설계하였다. 비행선의 부가 질량과 부가 관성 모멘트는 동적 반응 및 정착시간을 지연시키므로 일반적인 항공기에 비해 매우 느리다. 본 논문에서는 사용된 비행선은 고도 500m에서 1,000m 상공을 순항하며 임무를 수행하기 위한 것으로, 그 고도에서 대기 조건은 바람이나 돌풍에 의해 영향을 받아 매우 불안정하다. 따라서 가상 질량 효과가 두드러지는 수직 평면에 작용하는 수직 돌풍이 비행선에 미치는 영향을 살펴보고, PID-제어기를 사용하여 제어기를 설계하였다. 돌풍이 작용하면 비행선은 평형 상태로 회복하지만, 회복 시간이 매우 오래 걸릴 뿐 아니라 속도에 있어 손실이 발생한다. 따라서 본 논문의 목적은 회복 시간은 빠르게 하는 것과 순항 속도로 되돌아가는 것이다. 제어기에 사용된 피라미터들은 안정 모드 해석으로부터 결정되었으며, 이때 제어 압력은 추력 및 엘리베이터 각이다.