Torsional constants of both rectangular cross section and circular cross section are induced by exact solution, and was easy to calculate since of simple shape. However, it is very difficult to calculate the torsional constant of both an arbitrary cross-section and a composite cross-section. In this study, a finite element formulation was proposed as a method to calculate the torsional constant of both an arbitrary cross-section and a composite cross-section. From the numerical study, numerical results was compared with exact solution.

In a PEMFC gas channel with a trapezoidal cross-section, the effect of air and water inlet velocities on water removal characteristics is numerically studied via the volume of fluid(VOF) method. When the channel wall contact angle is 60 degrees, the air inlet velocities higher than 2.5 m/s are advantageous to obtain lower GDL surface water coverage ratio(WCR). The WCR increases as the wall contact angle increases to 90 or 120 degrees due to the relatively lower surface tension force. In overall, WCR decreases as the air inlet velocity increases and WCR increases as the water inlet velocity increases.

In this paper, a local deformation effect in thin-walled box beams is investigated via a finite element modal analysis. The analysis is carried out for single-cell and multi-cell box beam configurations. The single-cell box beam with and without a neck, which mimics a simple wind-turbine blade, is analyzed first. The results obtained by shell elements are compared to those of one-dimensional(1D) beam elements. It is observed that the wall thickness plays a crucial role in the natural frequencies of the beam. The 1D beam analysis deviates from the shell analysis when the wall thickness is either thin or thick. The shell modes(local deformations) are dominant as it becomes thin, whereas the shear deformation effects are significant as it does thick. The analysis is extended to the single-cell box beam with a neck, in which the shell modes are confined to near the neck. Finally the multi-cell box beam with a taper, which is quite similar to real wind-turbine blade configuration, is considered to investigate the local deformation effect. The results reveal that the 1D beam analysis cannot match with the shell analysis due to the local deformation, especially for the lagwise frequencies. There are approximately 5∼7% errors even if the number of segments is increased.

PURPOSES :This study proposes standards for rural access road pavement section and thickness design considering existing access road construction conditions; the study also proposes a complementary policy that can be used for design convenience.METHODS:Various literature review and case studies had been performed in terms of rural access road section and thickness design, both domestically and internationally, and this was followed by domestic rural access road field surveys. KPRP and KENLAYER were used to analyze the commonalities and predict the remaining life. Data on real cost is used to select an appropriate construction method through economic analysis.RESULTS:The economic efficiency of concrete pavement (15×15) was the highest in terms of economic efficiency of performance life and traffic volume. In the case of asphalt pavement, it is considered that the most economical method is to implement micro-surfacing method four times as a preventive maintenance method (once every 10 years and 4.5 years for asphalt concrete pavement and MS construction method, respectively). Repairable asphalt pavement is advantageous for areas where heavy vehicles are expected to pass. In the case of other general areas, it is considered economical to place concrete (15×15) pavement. However, as analytical results on its performance life are unavailable, it is to be considered for study in the future.CONCLUSIONS :This study proposed interim design guidelines based on various domestic and international design guidelines and case studies. However, in order to develop the final design criteria applicable to the field, it is necessary to (a) estimate the bearing capacity of the lower level of the pavement at various sites, (b) estimate the daily traffic volume, (c) implement advanced low-cost pavement technologies, and (d) propose maintenance standards and techniques for long-term performance.

The water removal characteristics in a PEMFC trapezoidal gas channel are investigated with the volume of fluid (VOF) method. For the case of wall contact angle of 60 degree, liquid water attaches on the top wall and moves toward the exit. In contrast, liquid water moves along the channel side corner or GDL surface irregularly for the higher wall contact angles. The hydrophillic wall contact angle of 60 degrees provides more favorable diffusion of reactants to cathode reaction sites as the GDL surface water coverage ratio approaches zero even if the water flow rate increases.

Due to a lack of the hoop action of lateral reinforcements the effective confining force in rectangular sections reduces compared to circular ones. Therefore, the stress-strain model obtained from the experimental data with circular sections overestimates the lateral confinement effect in rectangular sections, which evaluates seismic safety margin of overall structural system excessively. In this study experiments with laterally-confined square sections have been performed and the characteristic values composing stress-strain model have been analyzed. With introduction of section coefficients, in addition, the new unified stress-strain model applicable to square sections as well as circular ones has been proposed.

In order to avoid collapse of bridges in earthquakes bridge piers are generally designed to attain sufficient ductility. This full-ductility design method has merits for securing the seismic safety readily against strong earthquakes but, it has weakness of high cost design because of excessive safety margin. Recently, in many countries with high seismic technologies, the seismic design concept tends to shift from the collapse prevention design to the performance-based one which requires different performance (damage) levels according to the structural importance. In order to establish this performance-based design method the displacement ductility of confined concrete members should be evaluated quantitatively. And the stress-strain model of confined concrete is indispensible in evaluating displacement ductility. In this study, 6 test groups with different lateral reinforcement ratios were prepared. 10 same specimens with circular section for each group were tested to obtain more reliable test results. The characteristic values necessary for composing the stress-strain model were obtained from experiments. Based on these characteristic values the new stress-strain model modifying the Hoshikuma's one has been proposed.

본 연구에서는 케이블교량에 사용되는 보강거더의 형식 중에서 2에지거더를 대상으로 거더형상의 변화에 따른 정/동적 풍응 답특성을 풍동실험을 통하여 고찰하였다. 하부거더의 단면형상은 I형, 사다리꼴 2종류, 5각형 2종류 및 원형(I)으로 총 6종류를 채택하 였고 변장비는 1:5로 하였다. 본 연구에서 얻어진 결과로서, 정적설계에 사용되는 항력계수의 경우 원형단면과 5각형단면이 다른 단면에 비하여 유리한 것으로 나타났다. 대상단면의 동적안정성은 모두 비틀림 플러터가 지배적이고 플러터 한계풍속은 영각증가에 따라 급격히 감소하는 경향을 나타냈으며, I형 단면과 비교할 때 5각형단면과 원형단면의 한계풍속은 증가하는 것으로 확인되었다. 와류진 동의 최대진폭은 전반적으로 (+)영각범위에서는 영각증가와 함께 증가하였으나 (-)영각범위에서는 증감폭이 두드려지지 않는 경향을 보였으며 단면형상변화에 대해서는 사다리꼴 > 5각형 > 원형의 순으로 진폭이 감소하였다. 소정의 평균풍속에 대한 정적변위를 조사 하였으며 연직변위의 경우 모든 단면에서 영각증가에 따라 증가하였고 비틀림변위는 (-)영각범위에서는 큰 변화가 없으나 (+)영각범위 에서는 영각증가와 함께 정적변위가 감소하였고 5각형단면인 P2가 가장 작은 값을 보였다. 본 연구에서 수행된 정/동적 응답실험결과 를 비교분석한 결과, 5각형단면인 P2단면과 원형단면의 내풍성이 우수한 것으로 나타났다.

Theories of advanced composite structures are too difficult for such field engineers and some simple methods are necessary. In this paper, Simple method of vibration analysis is presented. This method presented in this paper is studied self-weight and other loads. The result of the 2~3 times iteration is good enough for field engineering purposes. In the case of cantilevered composite materials beams with different cross section, increase of mass near the support does not significantly affect the vibration characteristics. As a calculations of the simple method of vibration analysis for cantilevered composite materials beams with different cross section, it is noted that the result of the second cycle at the point of free end (actually 5L/6 span) is only 2.2% away from the ‘exact’ solution.

In this study, factors analysis is performed for reducing friction in elevation motion of a large television stand over 50-inch. The first is a pipe type cross-section control for accurate position control of the piston rod. Here it was compared with the pipe type and labyrinth type orifice cross-section. The second study is for specification decision and volume compensation experiment as an apparatus for compensating of the volume of the cylinder is compressed as the volume of piston rod. Consequently, in the orifice cross section study between pipe type and labyrinth type through CAE and experimental consideration, cross section of labyrinth type orifice is preferred for reducing of friction. The result of total consideration in stability problem and performance of volume compensation for specification decision and volume compensation experiment is determined the final speculation of hollow rod φ8×φ4 and riveting system.

In this study, factors analysis is performed for reducing friction in elevation motion of a large television stand over 50-inch. The first is a pipe type cross-section control for accurate position control of the piston rod. Here, it was compared with the pipe type and labyrinth type orifice cross-section. The second study attempted to reduce the frictional force the gas seal lip technology. As the result of the first study, in the orifice cross section study between pipe type and labyrinth type through CAE and experimental consideration, cross section of labyrinth type orifice is preferred for reducing of friction. As the result of the second study, in the gas seal lip technology, the outer-inner diameter of φ20×φ8 in the test result of hollow rod is revealed more proper if the weight of 50 inch television assumed as 30kgf.

본 논문에서는 Co-Rotational plane beam transient analysis EDISON program(CR-보)를 이용한 에어포일 단면형상 변화 에 따른 진동특성 연구를 수행하였다. Co-Rotational 평면 보 해석은 대 회전과 작은 변형률을 갖는 보 해석에 적합하다. 항 공기의 날개를 외팔보로 가정하여, VABS를 통한 단면해석과 Fourier 변환을 통해 각 단면형상 변화에 따른 에어포일의 고 유진동수를 비교하였다. VABS를 사용하여 단면의 형상과 재료의 적층 정보를 고려한 단면에서의 유한요소 해석을 수행하 였다. 에어포일의 재질, spar 유무, 단일 등방성 재료·복합재료, 에어포일 최대두께의 변화에 따라 에어포일의 끝단 진폭과 고유진동수가 변화함을 확인할 수 있었다. 이를 바탕으로 에어포일 고유진동수 변화는 2차 관성모멘트/단면적, 밀도, 영률의 변화에 상당한 영향을 받음을 알 수 있었다.

The present study analyzes the flexure behavior of the circular CFT member through experiment and numerical analysis. Through comparison between experimental and numerical results, whether or not the member was a full composite have little effect on the behavior. There circular CFT’s flexure behavior when considering pure moment is almost similar regardless of the interface characteristics between the steel and concrete. This is because there is no difference in the neutral axis of the full-composite and non-composite circular CFT member.

해외에서 운용 중인 복층터널 중간슬래브의 경우 핵심 설계･시공 기술은 공개되지 않고 있다. 국내의 경우 도심지 교통정체 및 지상공간의 부족문제 등으로 복층터널의 수요가 증가할 것으로 예상되므로 복층 터널 중간슬래브 설계에 대한 국내 기술을 보유함으로써 복층터널 기술 보유국으로부터의 국내 건설시장 잠식을 방지하고 기술선점 및 세계 일류 원천기술 확보가 시급한 분야라고 할 수 있다. 복층터널의 중간슬래브는 터널 라이닝에 브래킷을 설치하여 그 위에 지지되는 구조이므로 하부층에 전 면 지지되는 콘크리트 도로 포장 슬래브와 교각과 거더에 지지되는 교량 슬래브와는 다른 구조적 형식을 가진다. 따라서 슬래브가 자중에 의해 과다한 응력이 발생하게 되는데 슬래브의 두께를 늘리게 되면 중간 슬래브에 발생하는 응력을 어느 정도 감소시킬 수 있다. 하지만 중간슬래브의 응력에 지배적인 영향이 미 치는 인자는 슬래브의 자중이기 때문에 슬래브의 두께를 늘 리는 것으로 응력을 감소시키는 데에는 한계가 있다. 실제 중간 슬래브의 설계를 위해서는 프리스트레싱과 같은 방법을 통해 응력을 감소시키는 방안이 필요하다. 본 연구에서는 중간슬래브 최적 단면 설계 방안을 도출 해 내기 위하여 프리스트레싱을 통한 복층터널 중간 슬래브의 단면 감소 방안에 대하여 검토하였다. 우선 그림 1과 같이 강선 배치 간격에 따른 주인장 응력을 검토 하였으며, 그림 에서 볼 수 있듯이 강선배치 간격이 1m인 경우 강선이 없는 중간슬래브에 비해 최대 인장응력이 약 16% 감소하였으며, 간격이 0.5m인 경우 강선이 없는 중간 슬래브에 비해 최대 인장응력이 약 31% 감소하는 것을 알 수 있다. 프리스트레싱에 따른 중간슬래브의 슬래브 두께 감소 효과 를 분석하였다. 그림 2에서 볼 수 있듯이 프리 스트레싱이 가 해지지 않은 두께 40cm의 슬래브에서 발생 하는 응력과 프리 스트레싱이 가해진 두께 30cm의 중간 슬래브에서 발생하는 응력이 유사하게 나타난다. 이와 같이 프리 스트레싱을 통해 서 중간슬래브의 두께 조절이 가능 하다는 것을 알 수 있다. 하지만 슬래브의 두께가 과도하게 얇아질 경우에는 차량하중 에 의한 처짐량을 제어할 수 없기 때문에 적정한 두께를 유지 하면서 프리스트레싱을 적용해야 할 것으로 판단된다.

본 연구에서는 섬유 그리드 보강재로 인한 아스팔트 포장의 단면 감소 효과를 정량적으로 분석하기 위 해, 포장 두께를 축소하지 않은 일반 아스팔트 포장 구간(그림 1 왼쪽)과 기층 두께를 5cm 축소하고 섬유 그리드를 시공하지 않은 구간(그림 1 가운데) 및 기층 두께를 5cm 축소하고 표층 하부에 섬유 그리드를 보강하여 시공한 구간(그림 1, 오른쪽)의 거동을 FWD를 이용하여 비교･분석하였다. FWD(Falling Weight Deflectometer) 하중은 4.1톤 2회, 8.0톤 2회 및 10.0톤 2회를 재하하였다. 일 반 아스팔트 포장구간과, 기층 두께를 5cm 축소한 구간, 기층 두께를 5cm 축소하고 섬유 그리드를 보강 한 구간의 처침량 데이터를 수집하였고, 동시에 시험구간 포장체 내부에 설치되어있는 계측기를 이용하여 변형률을 수집하였다. FWD 실험 결과, 기층두께 5cm 축소 + 섬유 그리드 보강 구간이 기층두께 5cm 축소 구간에 비해 처짐량 이 약 14% 작게 나타나 섬유 그리드의 구조적 보강 효과를 확인할 수 있었다. 또한 섬유 그리드 보강구간이 일반 아스팔트 포장구간에 비해서 처짐값은 37% 크지만 표층 하단부에서의 변형률은 유사하게 나타났으며 이를 이용한 구조해석 결과, 약 3cm의 섬유 그리드로 인한 포장 층의 두께 감소 효과를 확인할 수 있었다.

PURPOSES: This study aims to develop a repair material that can enhance pavement performance, inducing rapid traffic opening through early strength development and fast setting time by utilizing MgO-based patching materials for repairing road pavements. METHODS : To consider the applicability of MgO-based patching materials for repairing domestic road pavements, first, strength development and setting time of the materials were evaluated, based on MgO to KH2PO4 ratio, water to binder ratio, and addition ratio of retarder (Borax), by which the optimal mixture ratio of the developed material was obtained. To validate the performance of the developed material as a repair material, the strength(compressive strength and bonding strength) and durability (freezing, thawing, and chloride ion penetration resistance) was checked through testing, and its applicability was evaluated. RESULTS : The results showed that when an MgO-based patching material was used, the condensation time was reduced by 80%, and the compressive strength was enhanced by approximately 300%, as compared to existing cement-based repair materials. In addition, it was observed that the strength (compressive strength and bonding strength) and durability (freezing and thawing, and chloride ion penetration resistance) showed an excellent performance that satisfied the regulations. CONCLUSIONS : The results imply that an emergent repair/restoration could be covered by a rapid-hardening cement to meet the traffic limitation (i.e. the traffic restriction is only several hours for repair treatment). Furthermore, MgO-based patching materials can improve bonding strength and durability compared to existing repair materials.

Menopausal status and hormonal changes are important factors related to the prevalence of metabolic syndrome in women. Nutrient intake is also a risk factor for metabolic syndrome. Although, postmenopausal status and hormonal changes result in a 60% increased risk for metabolic syndrome, there has been no method to elucidate the effects of nutrient intake on metabolic syndrome following menopause. This study was conducted to evaluate the effects of nutrient intake by menopausal women on the prevalence of metabolic syndrome. All data were obtained from the Korean National Health and Nutrition Examination Survey 2007–2009. Menopausal women showed a 1.8-fold increase in the prevalence of metabolic syndrome. Metabolic syndrome group showed significantly lower values in calcium, iron, vitamin A, carotin, retinol and riboflavin intake than those of normal group in premenopausal women. In postmenopausal women, there are significant differences in crude fiber, calcium, iron, potassium, riboflavin and niacin. Indeed, different patterns of nutrient intake were observed by menopausal status and metabolic syndrome. As menopause cannot be controlled, a diet with adequate nutrient intake may be useful to control the rapid increase in the prevalence of metabolic syndrome due to menopause.

The volume of fluid (VOF) method is applied to study the effects of the gas channel cross-section shape on the removal characteristics of a water slug in a trapezoidal PEMFC gas channel. Two different open angles 50 and 60 degrees are selected to investigate the effect of cross-section shape on the behavior of a liquid water slug. In comparison to the 50 degrees case, the water slug is removed slightly faster for the 60 degrees case.

본 연구에서는 산화된 피복관으로부터 염소화 공정을 통해 Zr을 선택적으로 회수하기 위한 연구의 일환으로, 단면이 개방 된 ZIRLO 피복관의 염소화 반응 속도식을 열중량분석기를 이용하여 분석하였다. 실험을 통해 산화된 ZIRLO 피복관은 400 도 염소화 조건에서 염소 기체와 반응하지 않는 것으로 확인되었다. 하지만 피복관 한쪽 혹은 양쪽 끝의 새로운 단면이 개방 될 경우 ZIRLO의 염소화 반응이 가능함을 확인하였고 반응을 완료하기까지 8 시간이 소요되었다. 이는 반응 완료까지 7 시 간이 소요된 산화되지 않은 피복관에 비하여 반응시간이 14% 증가한 것이다. Sharp-Hancock 식을 이용하여 단면이 개방된 ZIRLO 피복관과 염소 기체의 반응을 모사하기 위한 구조함수를 도출하였으며, 부피축소 모델이 본 연구 조건에서 가장 적 합한 구조 함수로 확인되었다. 또한, 본 연구를 통해 ZIRLO 피복관의 표면이 산화되어 있는 조건에서도 단면노출을 통해 염 소화 공정에 적용이 가능함을 확인하였다.