• Steel and Composite Structures
• /
• 제47권2호
• /
• pp.217-238
• /
• 2023

In this study, a parametric study was performed considering material properties of concrete, material properties of steel, the number of longitudinal reinforcement (reinforcement ratio), CFRP ply orientations, a number of layers as variables by using ABAQUS. Firstly, the parameters used in the Hashin failure criteria were verified using four coupon tests of CFRP. Secondly, the numerical models of the beams strengthened by CFRP were verified using five experimental data. Finally, eighty numerical models and eighty analytic calculations were developed to investigate the effects of the aforementioned variables. The results revealed that in the case of using fibrous polymer to prevent shear failure, the variables related to reinforced concrete significantly affected the behavior of specimens, whereas the variables related to CFRP composite have a slight effect on the behavior of the specimens. As a result of numerical analysis, while the increase in the longitudinal tensile and compression reinforcement, load bearing capacity increases between 23.6%-70.7% and 5.6%-12.2%, respectively. Increase in compressive strength (29 MPa to 35 MPa) leads to a slight increase in the load-carrying capacity of the specimens between 4.6% and 7.2%. However, the decrease in the compressive strength (29 MPa to 20 MPa) significantly affected (between 6.4% and 8.1% decrease observed) the behavior of the specimens. As the yield strength increases or decreases, the capacity of specimens increase approximately 27.1% or decrease 12.1%. The effects of CFRP ply orientation results have been obtained as a negligible well approximately 3.7% difference. An increasing number of CFRP layers leads to almost no effect (approximately 2.8%) on the behavior of the specimen. Finally, according to the numerical analysis, the ductility values obtained between 4.0 and 6.9 indicate that the beams have sufficient ductility capacity.

• 한국산학기술학회논문지
• /
• 제20권10호
• /
• pp.229-235
• /
• 2019

지구 환경문제와 자원 고갈에 따른 에너지 위기로 인해 화석 연료를 사용하지 않아 이산화탄소와 같은 온실가스 배출이 없는 청정 에너지원으로서 신재생 에너지는 중요성이 강조되고 있다. 부유식 태양광발전은 기존의 태양광 발전기술과 플로팅 기술을 융합한 신개념의 발전 방식이다. 종래의 육상이나, 건축물이 아닌 유휴수면에 설치하는 재생에너지원으로 구조체, 계류장치, 태양광 발전설비, 수중케이블 등으로 구성된다. 또한 단위모듈 형태로 설계되어 발전용량에 따라 단위모듈을 서로 연결하여 대규모 발전 시설을 조성할 수 있다. 태양광 발전기는 옥외에 설치되기 때문에 구조물에 대한 풍하중의 영향이 매우 크다. 본 연구에서는 부유식 태양광 발전 구조물에 큰 영향을 주는 풍하중을 전산유체역학을 통해 해석하였다. 유동 특성과 풍하중에 대한 풍향과 경사각의 영향을 분석하였다. 모듈의 개수와 바람의 방향에 따라 최대 하중을 받는 위치와 크기 그리고 태양광 패널과 부유체 주위의 유동 특성을 구하였다. 태양광 패널의 지면에 대한 경사각이 클수록 풍하중은 증가하였다.

• 한국건축시공학회지
• /
• 제22권2호
• /
• pp.161-169
• /
• 2022

정부[3]에서는 강관비계를 재래식 비계로 규정하고 일체형 작업발판인 시스템비계를 우선 설치하도록 제도화 하고 강관비계의 사용을 최대한 지양하고 있는 추세이다. 하지만 발전소, 플랜트 현장 등 장비의 진입이 안 되거나 본 구조물의 구조가 복잡한 곳, 그리고 지면에서 비계를 쌓아 올리지 못하는 곳에서는 강관비계를 설치하여 작업할 수 밖에 없다. 고소부위의 H-beam 구조물에 강관비계를 설치하여 작업자들이 안전하게 작업을 할 수 있도록 작업공간을 형성하기 위해서는 철골용 클램프의 성능은 매우 중요한 요소이다. 본 연구에서는 철골용 클램프의 설치 방향별 부재의 변형 및 인장하중에 대해 성능시험 및 구조해석 모델링을 통해 확인한 결과 설치 방향별 성능은 안전인증 기준인 인장하중 10,000N을 만족하는 것으로 확인 되었다. 다만 성능값은 만족하지만 부착부 누름 볼트의 변형발생이 확인되었고, 부착부 본체는 변형이 미미한 것으로 확인되었으므로 철골용 클램프는 하중이 전달되는 방향으로 설치하여 부착부 본체에 하중이 제대로 전달될 수 있도록 하는 것이 보다 안전한 방법이다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2142-2147
• /
• 2007

Experimental study was conducted to evaluate the performance of a miniature loop heat pipe (MLHP) with non-inverted meniscus type capillary structure. All parts of MLHP in this study were made of copper including the capillary structure and the distilled water was used as a working fluid of MLHP. The outer diameter of evaporator was 9 mm and its length was 119 mm. The effective pore size of the capillary structure was 30 micron and its porosity was 60%. The vapor transport line, the liquid transport line and the condenser were consisted of single 4.0 mm copper tube. The distance between the evaporator and the condenser region was 200 mm and the length of the loop was 969 mm. This MLHP was operated successfully at any orientation but the gravity highly influenced the thermal performance of the MLHP. The maximum thermal load was 130 watts at the bottom heat mode and the 20 watts at the top heat mode.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2004년도 학술대회지
• /
• pp.342-346
• /
• 2004

Recently there has been a great world-wide interest in developing and characterizing new nano-structured materials. These newly developed materials are often prepared in limited quantities and shapes unsuitable for the extensive mechanical testing. The development of depth sensing indentation methods have introduced the advantage of load and depth measurement during the indentation cycle. In the present work, ZnO thin films are prepared on the Glass, GaAs(100), Si(111), and Si(100) substrates at different temperatures by pulsed laser deposition(PLD) method. Because the potential energy in c-axis is law, the films always shaw c-axis orientation at the optimized conditions in spite of the different substrates. Thin films are investigated by X-ray diffractometer and Nano indentation equipment. From these measurements it is possible to get elastic modulus and hardness of ZnO thin films on all substrates.

• Interaction and multiscale mechanics
• /
• 제5권1호
• /
• pp.57-73
• /
• 2012

The paper presents the analysis of two groups of piles subjected to lateral loads incorporating the non-linear behaviour of soil. The finite element method is adopted for carrying out the parametric study of the pile groups. The pile is idealized as a one dimensional beam element, the pile cap as two dimensional plate elements and the soil as non-linear elastic springs using the p-y curves developed by Georgiadis et al. (1992). Two groups of piles, embedded in a cohesive soil, involving two and three piles in series and parallel arrangement thereof are considered. The response of the pile groups is found to be significantly affected by the parameters such as the spacing between the piles, the number of piles in a group and the orientation of the lateral load. The non-linear response of the system is, further, compared with the one by Chore et al. (2012) obtained by the analysis of a system to the present one, except that the soil is assumed to be linear elastic. From the comparison, it is observed that the non-linearity of soil is found to increase the top displacement of the pile group in the range of 66.4%-145.6%, while decreasing the fixed moments in the range of 2% to 20% and the positive moments in the range of 54% to 57%.

• KIEAE Journal
• /
• 제15권1호
• /
• pp.53-60
• /
• 2015

Increase in energy consumption in building is a big concern world over. In Nepal, energy crisis is a big issue but energy demand in buildings is barely even thought about. In the southern part of Nepal, where the weather is mostly hot during the year, cooling in buildings is very important. This is an initial study regarding building design strategies which focuses on cooling energy consumption in the building. It can be seen from the study that simple passive strategies can be applied in building design which can support in decreasing cooling load. Different passive cooling strategies like orientation, building size, thermal mass, window design and two direct cooling strategies have been investigated in this study. Direct cooling strategies like shading and natural cooling helps in passive cooling. Different desing strategies have different impact on the cooling energy requirement and the study shows that thermo physical property of building materials has the maximum effect on the energy consumption of the building. Each design strategy creates and average of 20% decrease in energy consumption, whereas the thermal conductivity can have as much as 10 times more effect on the energy consumption than other design strategies.

• Steel and Composite Structures
• /
• 제19권1호
• /
• pp.153-171
• /
• 2015

Twelve large-scale composite deck slabs were instrumented and tested in a cantilever diaphragm configuration to assess the effect of fibers and welded wire mesh (WWM) on the in-plane shear capacity of composite deck slabs. The slabs were constructed with reentrant decking profile and reinforced with different types and dosages of secondary reinforcements: Conventional welded wire mesh (A142 and A98); synthetic macro-fibers (dosages of $3kg/m^3$ and $5.3kg/m^3$); and hooked-end steel fibers with a dosage of $15kg/m^3$. The deck orientation relative to the main beam (strong and weak) was also considered in this study. Fibers and WWM were found efficient in distributing the applied load to the whole matrix, inducing multiple cracking, thereby enhancing the strength and ductility of composite deck slabs. The test results indicate that fibers increased the slab's ultimate in-plane shear capacity by up to 29% and 50% in the strong and weak directions, respectively. WWM increased the ultimate in-plane shear capacity by up to 19% in the strong direction and 9% in the weak direction. The results suggest that discrete fibers can provide comparable diaphragm behavior as that with the conventional WWM.

• 대한토목학회논문집
• /
• 제13권1호
• /
• pp.65-74
• /
• 1993

중립축에 대하여 대칭인 보강된 적층평판의 좌굴하중을 극대화 하는 최적설계를 시도하였다. 전체 평판의 무게가 일정한 가운데 적층평판을 이루는 각기 판의 두께와 보강재의 단면을 이루는 두께와 높이를 설계변수로 취하였다. 유한요소법을 이용하여 평판의 좌굴하중이 계산되었으며 최적설계는 IMSL program routine을 사용하였다. 최적설계시 나타나는 optimality condition이 고도의 비선형 연립방정식이 되므로 이경우 여러개의 국부 최적점이 발견되었다. 보강재와 평판의 각층에서의 보강섬유의 방향을 달리하며 각자의 효율성을 연구 조사하였으며 이중($0^{\circ}Beam/0^{\circ}/90^{\circ}$)s인 경우에 사장 우수한 설계를 할수 있는것으로 나타났다.

• 에너지공학
• /
• 제12권1호
• /
• pp.17-22
• /
• 2003

본 연구는 소형 CPL히트파이프의 제작 및 작동 특성에 대한 기초 지식을 얻기 위하여 수행되었다. CPL 히트파이프는 중력장 내에서 먼 거리까지 효과적으로 열을 이송할 수 있는 능력을 가지고 있다. 컴퓨터 칩에서 발생되는 열을 냉각하기 위하여 원판형 증발부로 구성된 소형 CPL을 설계 및 제작하여 그 작동 성능을 실험하였다. 두께 3mm, 직경 50mm의 원판형 청동 분발 소결 (equation omitted)를 사용하여 작동유체를 순환하기 위한 압력 구배를 얻을 수 있었으며 작동유체는 에탄올을 사용하였다. 실험은 응축부의 주위온도를 13$^{\circ}C$로 고정시킨 후 각각 다른 열부하에서의 CPL 작동 상태를 확인해 보았다.