• Title/Summary/Keyword: Steel Jacket

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Shear behaviour of RC T-beams strengthened with U-wrapped GFRP sheet

  • Panda, K.C.;Bhattacharyya, S.K.;Barai, S.V.
    • Steel and Composite Structures
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    • 제12권2호
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    • pp.149-166
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    • 2012
  • This paper presents an experimental investigation on the performance of 2.5 m long reinforced concrete (RC) T-beams strengthened in shear using epoxy bonded glass fibre fabric. Eighteen (18) full scale, simply supported RC T-beams are tested. Nine beams are used as control beam specimens with three different stirrups spacing without glass fibre reinforced polymer (GFRP) sheet and rest nine beams are strengthened in shear with one, two, and three layers of GFRP sheet in the form of U-jacket around the web of T-beams for each type of stirrup spacing. The objective of this study is to evaluate the effectiveness, the cracking pattern and modes of failure of the GFRP strengthened RC T-beams. The test result indicates that for RC T-beams strengthened in shear with U-jacketed GFRP sheets, increase the load carrying capacity by 10-46%.

Comparative study on the structural behavior of a transition piece for offshore wind turbine with jacket support

  • Ma, Chuan;Zi, Goangseup
    • Steel and Composite Structures
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    • 제43권3호
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    • pp.363-373
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    • 2022
  • As a key reinforcement connection between a tower and a substructure in offshore wind turbine system, the transition piece is inevitably subjected to cyclic dynamic environmental loads such as wind, current and wave. Therefore, well designed transition piece with high strength and good fatigue resistance is of great significance to the structural safety and reliability of offshore wind power systems. In this study, the structural behavior of the transition piece was studied by an extensive sets of finite element analyses. Three widely used types of transition piece were considered. The characteristics of stress development, fatigue life and weight depending on the type of the transition piece were investigated in the ultimate limit state (ULS) and the fatigue limit state (FLS) of a 5-MW offshore wind turbine to be placed in Korea. An optimal form of the transition piece was proposed based on this parametric study.

법랑질형성부전증에 대한 증례보고 (CASE REPORT OF AMELOGENESIS IMPERFECTA)

  • 백병주;김상훈;이승익;김재곤
    • 대한소아치과학회지
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    • 제27권4호
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    • pp.499-504
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    • 2000
  • 법랑질형성부전증은 주로 법랑기의 기능불량으로 야기된 법랑질의 형태이상을 말하며, 치아의 중배엽은 정상이기 때문에 완전한 외배엽성 이상이다. 법랑질형성부전증은 유치와 영구치 모두에서 발생할 수 있으며, 발생빈도는 1:14,000 혹은 1:16,000정도이다. 법랑질형성부전증은 다양한 임상증상을 나타낼 수 있으며, 임상적으로 형성부전증(hypoplastic), 석회화부전증(hypocalcified). 성숙부전증(hypomatruation)등으로 나눌 수 있다 대부분 법랑질 형성부전증 환자들은 심미성, 치아의 냉온에 대한 과민반응, 교합면의 마모 등의 문제를 가지고 있다. 형성부정증에서는 비교적 위의 문제가 경미하나, 석회화부전증에 있어서는 더욱 심각하다. 치료방법으로는 먼저 유전적 상담이 선행돼야하며, 전치부 심미성의 해결을 위한 composite resin veneer나 jacket crown을 이용하고, 구치부에 있어서는 S-S crown을 이용한 방법이 있을 수 있다. 본 증례는 전북대학교 치과병원에 내원한 3명의 법랑질형성부전증 환아의 임상검사 및 치료과정에 대하여 보고하는 바이다.

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Compressive behavior of galvanized steel wire mesh (GSWM) strengthened RC short column of varying shapes

  • Marthong, Comingstarful
    • Structural Monitoring and Maintenance
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    • 제7권3호
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    • pp.215-231
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    • 2020
  • In a reinforced concrete building different shapes of column are adopted depending on the structural orientation and the architectural aspect. When there is an increase in loading due to changes in usage or revision in the design codes these columns need to be strengthened for enhanced performance during their service life. Strengthening materials such as carbon fiber and glass fiber polymer has been successfully used however, due to high cost application other alternative materials need to be explore. Galvanized steel wire mesh (GSWM) is one of the suitable materials locally available. High tensile strength, low weight, corrosion resistance, easy installation, minimum change in dimensions of the sections and cost effectives are the advantages of GSWM. Therefore, in this paper, four different shapes of column such as circular, square, rectangular and L were wrapped with different layers GSWM and jacketed with mortar. All the specimens were tested under axial compression. The objective of the study is to investigate the effectiveness of GSWM as a confining material for strengthening of column having varying shape. Test results shows that the axial strength enhanced with wrapping of GSWM jacket and a circular column presented the highest load carrying capacity and ductility as compared to the others. From the study of 22 column specimens, it is found that axial load is increased upto 20% and 19% when circular and square column are strengthened with one wrap of GSWM respectively, while a rectangular and L column required a wraps of two and three layers respectively in order to achieved the same load capacity as that of a circular column. Based on the present study, it is concluded that GSWM can be effectively used for strengthening of different shapes of concrete columns economically.

횡방향 구속응력에 의한 자켓팅-콘크리트 공시편 거동 (Behavior of concrete cylinders confined by jacketing with lateral confining stress)

  • 조성철;최은수;정영수;조백순;최지호
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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    • pp.157-160
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    • 2008
  • 국내에는 내진설계가 적용되어지지 않고 설계 시공된 교량과 교각이 상당수 존재하며 지진 발생 시 취약한 소성흰지구간에서 충분한 횡구속 없이 주철근 겹침 이음을 가지고 있는 교각들이 다수 존재하고 있는 실정이다. 내진 성능향상을 위한 국내 많은 보강방법들이 연구되고 있는 추세이며 보다 효과적인 콘크리트 보강기법을 개발하기 위하여 횡방향 구속응력을 도입한 자켓팅 보강공법을 제시하였다. 자켓팅-콘크리트 공시편 압축 실험에서 강도 및 연성도에 영향을 주는 주요 요인 콘크리트은 압축강도, 보강량 및 보강재의 강도 등이다. 본 연구에서는 실시된 실험결과를 바탕으로 콘크리트 비선형 재료를 사용한 해석적 연구를 추가로 실시하여 실험에서 나타난 결과 값과 비교하고 실험 변수와 보강효과에 영향을 미치는 추가적인 변수를 추정하였다. 또한 선행 연구에서 제시된 횡방향구속응력을 사용한 자켓팅 보강공법의 적용성을 높이기 위한 방법들은 어떤 것들이 있는지에 대하여 서술 하였다.

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해상기상탑 설계에 관한 연구 (A Study on Design of Offshore Meteorological Tower)

  • 문채주;장영학;박태식;정문선;주효준;권오순;곽대진;정권성
    • 한국태양에너지학회 논문집
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    • 제34권2호
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    • pp.60-65
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    • 2014
  • A meteorological(met) tower is the first structure installed during the planning stages of offshore wind farm. The purpose of this paper is to design the met tower with tripod bucket type support structure and to install the sensors. The support structure consist of a central steel shaft connected to three cylindrical steel suction buckets which is more cheaper than monopile or jacket type. And the remote wind condition sensors and marine monitoring equipment, including adcp, pressure type tide gauge, wave height sensors, and scour sensors, remote power supply are installed. The manufactured met tower constructed on sea area which is in front of Gasa island. All of functions of met tower showed normal operation conditions and the wind data got by remote data collection system successfully.

선천성(先天性) 치아(齒牙) 결손증(缺損症) 1례(一例) 증례보고(症例報告) (OLIGODONTIA Report of case.)

  • 이종갑;최선옥;손흥규;허만욱
    • 대한소아치과학회지
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    • 제7권1호
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    • pp.41-45
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    • 1980
  • The term "Oligodontia" or "Hypodontia" have been used to describe variable degrees of reduction in number of teeth. Oligodontia may occur alone or as a result of some syndrome. Although the teeth are derived in part from ectoderm, the current opinion of reason of oligodontia should be reserved for those disorders in which there is abnormal development of one or more ectodermal tissues. 7 year 5 months old female was refered to the department of pedodontics, college of dentistry Yonsei university for evaluation and replacement of absent teeth. She had no special inf.ectious disease in her childhood, and her parents were healthy. She had no special syndrome of ectodermal disorders except the saddle nose, yellow and fine hair, and notched upper anterior central incisor. Panex radiogram was showing 6 anterior primary teeth, 2 permanent first molars and 2 unerupted first bicuspid in mandible. Another permanent teeth were absent. and normal number of primary and permanent teeth in maxilla. Lateral cephalogram showed no special abnormality in growth pattern. We had evaluated lower anterior decayed teeth with jacket resin and chrome steel crown and removable partial denture at missing area. We had got good results for rehabilitation of function and aesthetic.

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Interface treatment in shotcrete jacketing of reinforced concrete columns to improve seismic performance

  • Vandoros, Konstantinos G.;Dritsos, Stephanos E.
    • Structural Engineering and Mechanics
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    • 제23권1호
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    • pp.43-61
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    • 2006
  • An investigation of the effectiveness of the interface treatment when column concrete jacketing is performed is presented. Alternative methods of interface connection were used in order to investigate the performance of strengthened concrete columns. These connecting techniques involved roughening the surface of the original column, embedding steel dowels into the original column and a combination of these two techniques. The experimental program included three strengthened specimens, one original specimen (unstrengthened) and one as-built specimen (monolithic). The specimens represented half height full-scale old Greek Code (1950's) designed ground floor columns of a typical concrete frame building. The jackets of the strengthened specimens were constructed with shotcrete. All specimens were subjected to displacement controlled earthquake simulation loading. The seismic performance of the strengthened specimens is compared to both the original and the monolithic specimens. The comparison was performed in terms of strength, stiffness and hysteretic response. The results demonstrate the effectiveness of the strengthening methods and indicate that the proper construction of a jacket can improve the behaviour of the specimens up to a level comparable to monolithic behaviour. It was found that different methods of interface treatment could influence the failure mechanism and the crack patterns of the specimens. It was also found that the specimen that combined roughening with dowel placement performed the best and all strengthened columns were better at dissipating energy than the monolithic specimen.

Effects of Wet Feeding of Diets with or without Food Waste on Growth Performance and Carcass Characteristics in Finishing Pigs

  • Moon, J.S.;Kwon, I.K.;Chae, B.J.
    • Asian-Australasian Journal of Animal Sciences
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    • 제17권4호
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    • pp.504-510
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    • 2004
  • Two experiments were conducted. In expt. 1, a total of fifty-four pigs (L$\times$Y$\times$D, 56.14$\pm$1.7 kg) were used for a feeding trial to determine the effect of wet feeding of a commercial-type diet without food waste (FW). Treatments were dry (Control), wet (WF) and wet+dry feeding (WDF). For wet feeding, the diet was mixed with water at a ratio of 1:2.5 (feed:water). A wet feed was given during the whole experimental period for the WF group, but the dry feed was given during the finisher period for the WDF group. In expt. 2, a total of fifty-four pigs(L$\times$Y$\times$D, 55.7$\pm$1.8 kg) were used for a feeding trial to determine the effect of wet feeding of FW. Treatments were a commercial-type dry (Control), wet fermented food waste (WFFW) and WFFW+dry feeding (WFFW+DF). For wet feeding of fermented food waste, however, some ingredients (concentrate) were added to make nutrient contents comparable to the control diet. The FW collected was ground ($\leq$5 mm), heated with a steam jacket (140$\pm$3$^{\circ}C$) and fermented with probiotics for one day in a steel container at 30-40$^{\circ}C$. For the WFFW group, the wet feed was given during the whole experimental period, but a dry feed was given during finisher period for the WFFW+DF group. In expt. 1, during the grower period, pigs fed wet feed showed higher average daily gain (ADG) and feed conversion ratio (FCR) than those fed only dry feed (p<0.05). During the finisher period, pigs in the WDF group showed better ADG and FCR than the control group. During the entire experimental period, pigs in the WDF group grew faster (p<0.05) than those in the control group, and the same trend was found in FCR. Also, dressing percentage, backfat thickness, lean %, and pork color were not affected by the wet feeding of diets in this study. In expt. 2, during the grower period, pigs fed diets containing FW showed lower (p<0.05) ADG than those fed the control diet. But FCR was better (p<0.05) in pigs fed FW than in the control group. During the finisher period, pigs in the WFFW+DF group grew faster (p<0.05) than those in the control and WFFW groups. During the entire experimental period, pigs fed the control diet showed better ADG (p<0.05) than those fed FW, but feed intake and FCR were vice versa. Dressing percentage was lower (p<0.05) in the WFFW than in the control group, but backfat was thinner in the WFFW group than in the control group. In summary, it can be concluded that wet feeding of formula feed can improve daily gain, however, feeding fermented wet food waste may reduce daily gain of finishing pigs, even though it was fermented and the nutrient was fortified with concentrates. In addition, dry feeding of a formula feed during the finishing period can improve daily gain in pigs fed a wet feed with or without food waste during the grower period.