The Cu2ZnSn(SxSe1-x)4 (CZTSSe) absorbers are promising thin film solar cells (TFSCs) materials, to replace existing Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic technology. However, the best reported efficiency for a CZTSSe device, of 13.6 %, is still too low for commercial use. Recently, partially replacing the Zn2+ element with a Cd2+element has attracting attention as one of the promising strategies for improving the photovoltaic characteristics of the CZTSSe TFSCs. Cd2+ elements are known to improve the grain size of the CZTSSe absorber thin films and improve optoelectronic properties by suppressing potential defects, causing short-circuit current (Jsc) loss. In this study, the structural, compositional, and morphological characteristics of CZTSSe and CZCTSSe thin films were investigated using X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), and Field-emission scanning electron microscopy (FE-SEM), respectively. The FE-SEM images revealed that the grain size improved with increasing Cd2+ alloying in the CZTSSe thin films. Moreover, there was a slight decrease in small grain distribution as well as voids near the CZTSSe/Mo interface after Cd2+ alloying. The solar cells prepared using the most promising CZTSSe absorber thin films with Cd2+ alloying (8 min. 30 sec.) exhibited a power conversion efficiency (PCE) of 9.33 %, Jsc of 34.0 mA/cm2, and fill factor (FF) of 62.7 %, respectively.

최근 경주, 포항에 연이은 지진 발생으로 인하여 내진설계에 관심이 높아지고 있다. 다가구주택 필로티기둥은 수직 비정형 시스템으로 상,하부층의 강성 차이로 인하여 지진 발생 시 막대한 피해가 예상되기 때문에 다가구주택 필로티기둥의 내 진보강이 필요하다. 그러나 민간 소유인 다가구주택의 경우 막대한 비용과 시간으로 인하여 보강이 어려운 실정이다. 이에 따 라, 복합섬유패널로 에폭시 접착제 미사용으로 건식시공이 가능한 전단보강공법을 제안하고자 한다. 본 연구에서는 복합섬유패 널 보강 유무에 따른 내진보강공법의 전단내력을 실험을 통하여 검증하였고, 에폭시를 사용하지 않아 일체화 거동을 하지는 않 지만 복합섬유패널의 영향으로 전단내력은 1.46∼1.49배 증가하는 것으로 평가되었다. 따라서 다가구주택 필로티기둥의 내진보 강효과가 있을 것으로 판단된다.

The collapse of reinforced concrete (RC) frame buildings is mainly caused by the failure of columns. To prevent brittle failure of RC column, numerous studies have been conducted on the seismic performance of strengthened RC columns. Concrete jacketing method, which is one of the retrofitting method of RC members, can enhance strength and stiffness of original RC column with enlarged section and provide uniformly distributed lateral load capacity throughout the structure. The experimental studies have been conducted by many researchers to analyze seismic performance of seismic strengthened RC column. However, structures which have plan and vertical irregularities shows torsional behavior, and therefore it causes large deformation on RC column when subjected to seismic load. Thus, test results from concentric cyclic loading can be overestimated comparing to eccentric cyclic test results, In this paper, two kinds of eccentric loading pattern was suggested to analyze structural performance of RC columns, which are strengthened by concrete jacketing method with new details in jacketed section. Based on the results, it is concluded that specimens strengthened with new concrete jacketing method increased 830% of maximum load, 150% of maximum displacement and changed the failure modes of non-strengthened RC columns.

해저 파이프라인 예비커미셔닝(Pre-commissioning) 단계는 입수(Flooding), 배수(Venting), 하이드로테스팅(Hydrotesting), 탈수 (Dewatering), 건조(Drying), 질소충진(N2 Purging)의 공정과정으로 구성된다. 이 중 건조와 질소충진 과정은 운용 중 파이프라인 내부에 하이 드레이트(Hydrate)의 발생과 가스 폭발의 위험을 방지하기 위해 상대습도를 이슬점 아래로 감소 및 유지되도록 규정되어 있다. 본 연구의 목적은 해저 파이프라인 예비커미셔닝 중, 공기건조(Air Drying)와 질소충진 공정과정에 대한 해석법을 개발하고 현장계측 결과와의 상호 비교를 통해 해석법의 활용가능성을 평가하는 데 있다. 해저 파이프라인 내부 상대습도 평가를 위한 방법으로 전산열유체(CFD)를 활용한 해석기법을 도입·적용하였고 해양공사 해저 파이프라인 공기건조와 질소충진 공정과정에 대한 현장계측 결과와 잘 일치함을 확인하였다. 개발된 공기건조와 질소충진 해석법 및 평가방법을 향후 해저 파이프라인 예비커미셔닝 작업의 사전 엔지니어링 도구로 활용할 경우, 작 업생산성 향상에 크게 기여할 것으로 사료된다.

In the case of columns in buildings with soft story, the concentration of stress due to the difference in stiffness can damage the columns. The irregularity of buildings including soft story requires retrofit because combined load of compression, bending, shear, and torsion acts on the structure. Concrete jacketing is advantageous in securing the strength and stiffness of existing members. However, the brittleness of concrete make it difficult to secure ductility to resist the large deformation, and the complicated construction process for integrity between the existing member and extended section reduces the constructability. In this study, two types of Steel Grid Reinforcement (SGR), which are Steel Wire Mesh (SWM) for integrity and Steel Fiber Non-Shrinkage Mortar (SFNM) for crack resistance are proposed. One reinforced concrete (RC) column with non-seismic details and two columns retrofitted with each different types of proposed method were manufactured. Seismic performance was analyzed for cyclic loading test in which a combined load of compression, bending, shear, and torsion was applied. As a result of the experiment, specimens retrofitted with proposed concrete jacketing method showed 862% of maximum load, 188% of maximum displacement and 1,324% of stiffness compared to non-retrofitted specimen.

PURPOSES : The actual service life of repair methods applied to cement concrete pavement is analyzed based on de-icing agent usage. METHODS : Highway PMS data pertaining to de-icing agent usage are classified into three grades: low (1~5 ton/lane/year), medium (5~8 ton/lane/year), and high (greater than 8 ton/lane/year). The repair methods considered include diamond grinding, patching, joint repair, partial depth repair, and asphalt overlay on five major highways. The service life of each repair method is analyzed based on the usage level of the de-icing agent. RESULTS : The service lives of the applied repair methods are much shorter than expected. It is confirmed that the service life afforded by diamond grinding, patching, and joint repair methods are not significantly affected by the use of de-icing agents, whereas that afforded by asphalt overlay and partial depth repair methods is affected significantly. The service life afforded by the asphalt overlay and partial depth repair methods decreases at high usage levels of the de-icing agent (greater than 8 ton/lane/year). CONCLUSIONS : Among the repair methods considered, the service life afforded by partial depth repair and asphalt overlay is affected significantly by the amount of de-icing agent used. Additionally, the differences between the expected and actual analyzed service lives should be considered in the next-generation maintenance strategy for cement concrete pavements.

본 논문은 FRCM 공법으로 보강된 철근콘크리트 보의 휨 성능을 예측하기 위한 해석적 연구결과를 제시한다. FRCM 공법으로 보강된 철근콘크리트 보의 휨 성능 예측을 위해 상용구조해석 프로그램인 LS-DYNA를 이용하여 유한요소해석이 수행되었다. 유한요소해석시 콘크리트와 모르타르는 Solid 요소로 모델링 되었으며, 철근과 FRP 그리드는 각각 Beam 요소 및 Shell 요소로 모델링되었다. 또한, 콘크리트와 철근은 완전부착하는 것으로 가정되었으며, 콘크리트와 모르타르 경계면의 부착파괴를 모사하기 위하여 Contact_Tiebreak_Surface_to_Surface 요소가 사용되었다. 이후, 국내⋅외 여러 연구자들에 의해 수행된 실험의 재현해석을 통해 제안된 유한요소해석 모델의 신뢰성이 검증되었다. 실험결과와 해석결과의 파괴양상을 분석하였을 때, 본 연구에서 제안된 유한요소해석 모델은 실험체의 부착파괴를 적절히 모사할 수 있는 것으로 나타났다. 또한, 해석을 통해 예측된 극한 강도에 대한 실험결과의 비는 평균 1.04, 표준편차 0.064로 제안된 해석모델은 FRCM 공법으로 보강된 철근콘크리트 보의 휨 성능을 비교적 잘 예측할 수 있는 것으로 나타났다.