• 제목/요약/키워드: external bars

검색결과 80건 처리시간 0.021초

콘크리트 교량의 보강을 위한 온도 프리스트레싱 공법의 실험적 연구 (An Experimental Study on Thermal Prestressing Method for Strengthening Concrete Bridge)

  • 안진희;김준환;최규태;김상효
    • 콘크리트학회논문집
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    • 제19권4호
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    • pp.483-490
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    • 2007
  • 현재 콘크리트 교량의 보강 공법으로 주로 사용되는 외부 강봉을 이용한 후 인장 공법은 적용 범위가 넓고 교량의 극한 및 항복에 대한 강성을 증가시켜 휨보강 효과가 뛰어나지만, 모재 접합부의 응력집중, 비효율적인 하중 분배, 고정앵커부 설치, 유지관리의 어려움 등의 단점이 있다. 본 연구는 기존의 외부 강봉을 이용한 후 인장 공법이 가지는 단점을 보완하고 강판 접합 공법의 장점을 접목한 새로운 개념의 보강 공법으로 온도 프리스트레싱 보강 공법을 제안하고자 한다. 온도 프리스트레싱 보강 공법은 프리스트레싱 보강 강판을 다단계로 가열하여 가열 단계별로 콘크리트 교량의 하부에 접합한 뒤, 열원을 제거하여 발생하는 다단계 수축력을 보강에 필요한 프리스트레싱력으로 이용하는 보강 공법이다. 본 연구에서 제안된 온도 프리스트레싱 보강 공법의 적용을 위한 기초적인 연구로 프리스트레싱 보강 강판을 콘크리트 교량에 설치하기 위한 고정장치의 마찰저항 강도 실험과 온도 프리스트레싱에 의하여 콘크리트 교량에 도입되는 프리스트레싱 효과의 확인을 위한 응력 도입 실험을 실시하여 제안된 공법을 검증하였다.

한국, 중국, 미국 소비자들의 에너지 바에 대한 인식 및 소비 행동 비교 연구 (A Comparative Study on the Perception and Consumption Behaviors of Korean, Chinese, and US Consumers for Energy bars)

  • 오지은;윤혜려
    • 한국식생활문화학회지
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    • 제35권4호
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    • pp.333-341
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    • 2020
  • This study evaluated the perception, consumption behavior, and optional attributes of Korean, Chinese, and U.S. consumers of energy bar products. Data were compared and analyzed by surveying 300 consumers in each country. Significant differences were observed in preference for energy bars according to their nationality, in the order China, the U.S., and Korea. Perception of taste, types and dietary suitability of the products ranked lower for Korean consumers, as compared to consumers of the United States and China. The order dietary fiber, protein, and calcium were the sought-after nutritional requirements of the products. The demand for protein was significantly higher in the U.S. Calcium demand was low in the United States and China, but was very high in Korea, which could be attributed to the low calcium intake of Koreans. Other optional attributes which were closely associated with the purchase and re-purchase decision, included price, taste and delivery period. All three factors were recognized as important options in Korea, whereas awareness of packaging/appearance and brand was not. The taste, nutrients and price in the U.S. ranked high as important optional attributes, while the packaging, external and expiration dates were recognized as low. Unlike Korea and the U.S., important optional attributes for Chinese consumers were determined in the order expiration date, taste, and nutrients, and showed low perception for packaging, appearance, weight, counts, and prices. Evaluating the preference for the main and secondary ingredients, Koreans preferred nuts over grains, Americans preferred dried fruits over nuts, and Chinese preferred nuts and grains; both Korean and American consumers had low preference for dried vegetables. The preference for chocolate was low in Korea and China, whereas preference for jelly was high in China as compared to Korea and the U.S. The intention of purchasing energy bars was significantly lower in Korea than in the U.S. and China. A variety of nutritious functional bars have recently been distributed and sold in Korea, but they are mostly produced in the U.S., which is the largest producer and consumer worldwide. Taken together, results of this study indicate that the demand for nutritional enhancement and preferred materials vary according to the nationality. Hence, it is necessary to develop products that reflect these criteria. Further research is required to analyze the relationship between preference and consumption behavior for each material product developed in the future.

Accuracy of image registration for radiation treatment planning using a brain phantom

  • Jin, Ho-Sang;Suh, Tae-Suk;Song, Ju-Young;Juh, Ra-Hyeong;Kwark, Chul-Eun;Lee, Hyoung-Koo;Choe, Bo-Young
    • 대한자기공명의과학회:학술대회논문집
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    • 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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    • pp.106-106
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    • 2002
  • Purpose: The purposes of our study are (1) to develop a brain phantom which can be used for multimodal image registration, (2) to evaluate the accuracy of image registration with the home-made phantom. Method: A brain phantom which could be used for image registration technique of CT-MR and CT-SPECT images using chamfer matching was developed. The brain phantom was specially designed to obtain imaging dataset of CT, MR, and SPECT. The phantom had an external frame with 4 N-shaped pipes filled with acryl rods for CT, MR imaging and Pb rods for SPECT imaging. 8 acrylic pipes were inserted into the empty space of the brain phantom to be imaged for geometric evaluation of the matching. Accuracy of image fusion was assessed by the comparison between the center points of the section of N-shaped bars in the external frame and the inserted pipes of the phantom. Technique with partially transparent, mixed images using color on gray was used for visual assessment of the image registration process.

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Strengthening of T-beams using external steel clamps and anchored steel plates

  • Yunus Dere;Yasin Onuralp Ozkilic;Ali Serdar Ecemis;Hasan Husnu Korkmaz
    • Steel and Composite Structures
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    • 제48권4호
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    • pp.405-417
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    • 2023
  • In order to strengthen the reinforced concrete T-beams having insufficient shear strength, several strengthening techniques are available in the literature. In this study, three different strengthening strategies were numerically studied. First one is affixing steel plates to the beam surfaces. Second one includes tightening external steel bars vertically similar to beam stirrups. The last one is simultaneous application of these two strengthening procedures which is particularly proposed in this work. Available experimental test series in the literature were handled in the study. Finite element (FE) models of reinforced concrete beam specimens having sufficient (Beam-1) and low shear capacity (Beam-2) were created within ABAQUS environment. Strengthened beams with different techniques were also modelled to reflect improved shear capacity. FE simulations made it possible to investigate parameters that were not examined during the previous experimental studies. The results of the analyses were then compared and found consistent with the experimentally obtained data. Experimental and FEM analysis results are in agreement between 1% (closest) and 6%. (maximum). Beam-2 was stregthened with 5 new porposed methods. The rate of increase in shear strength varies between 33% and 64%. It was found that, the strengthening techniques were fairly useful in improving the shear capacity of the considered girder. The model with the proposed strengthening alternative has accomplished a higher load carrying capacity, ductility and stiffness than all of the other models.

원전 구조물의 고강도 철근 적용 기술개발 : 벽체의 성능평가 실험 (Development of Application Technology of High-Strength Reinforcing Bars for Nuclear Power Plant Structure : Performance Evaluation Test of the Wall)

  • 김석철;임상준;이병수;방창준
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2012년도 추계 학술논문 발표대회
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    • pp.201-202
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    • 2012
  • Recently, High-Strength steel reinforcement has been studied throughout the internal and external. One of the advantages using High-Strength steel reinforcement in construction is the economic effect due to the decreasing of its quantity. Also, another good effect is the increases of workability by reason of reducing the congestion. But, realistically it is not used in nuclear power plant construction site because of the restriction of design standard. The purpose of this report secures the reliability and changes the code through the performance evaluation test of the wall using the high-strength steel reinforcement in nuclear power plant.

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섬유복합재봉(FRP ROD)과 고강도 모르터를 이용한 철근 콘크리트 구조물의 휨 보강공법(MFRI) 공법 (Reinforcing System(MFRI) for Concrete Structure using FRP ROD & High-performance Mortar)

  • 배기선;박상훈;이상욱
    • Composites Research
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    • 제18권4호
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    • pp.59-65
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    • 2005
  • This report is on the Reinforcing System(MFRI) for Concrete Structure using FRP ROD & High-Performance Mortar. The main characteristic of this system is as follow. First, the fiber rods in this system have seven times greater tensile strength than general reinforcing steel bars(re-bar) and the weight is a fifth lighter. Camels coated on the fiber rods' surfaces to improve adhesive strength and pull-out strength. Second, high strength shotcrete mortar is has very good workability and low rebound rate. After installing the Fiber Rods, Shotcrete mortar Is applied or sprayed to finish reinforcement. Finally, MFRI system has excellent fire-resisting performance and sogood tolerance against external environment by inserting fiber rods and reinforcing materials into mortar which has high compressive strength. It is applied to bridge slab, utility box and tunnel of civil engineering works, and beam and slab of building structures.

Experimental study on reinforced concrete filled circular steel tubular columns

  • Hua, Wei;Wang, Hai-Jun;Hasegawa, Akira
    • Steel and Composite Structures
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    • 제17권4호
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    • pp.517-533
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    • 2014
  • Experimental results of 39 specimens including concrete columns, RC columns, hollow steel tube columns, concrete filled steel tubular (CFT) columns, and reinforced concrete filled steel tubular (RCFT) columns are presented. Based on the experimental results, the load-carrying capacity, confined effect, ductility, and failure mode of test columns are investigated. The effects of the main factors such as width-thickness ratio (the ratio of external diameter and wall thickness for steel tubes), concrete strength, steel tube with or without rib, and arrangement of reinforcing bars on the mechanical characteristics of columns are discussed as well. The differences between CFT and RCFT are compared. As a result, it is thought that strength, rigidity and ductility of RCFT are improved; especially strength and ductility are improved after the peak of load-displacement curve.

Plastification procedure of laterally-loaded steel bars under a rising temperature

  • Huang, Zhan-Fei;Tan, Kang-Hai;England, George L.
    • Structural Engineering and Mechanics
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    • 제35권6호
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    • pp.699-715
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    • 2010
  • This paper investigates the structural responses of axially restrained steel beams under fire conditions by a nonlinear finite element method. The axial restraint is represented by a linear elastic spring. Different parameters which include beam slenderness ratio, external load level and axial restraint ratio are investigated. The process of forming a mid-span plastic hinge at the mid-span under a rising temperature is studied. In line with forming a fully plastic hinge at mid-span, the response of a restrained beam under rising temperature can be divided into three stages, viz. no plastic hinge, hinge forming and rotating, and catenary action stage. During catenary action stage, the axial restraint pulls the heated beam and prevents it from failing. This study introduces definitions of beam limiting temperature $T_{lim}$, catenary temperature $T_{ctn}$ and warning time $t_{wn}$. Influences of slenderness ratio, load level and axial restraint ratio on $T_{lim}$, $T_{ctn}$ and $t_{wn}$ are examined.

有限要素法에 의한 舶用機關軸系裝置의 最適配置에 關한 硏究 (Optimum Alignment of Marine Engine Shaftings by the Finite Element Method)

  • 전효중;박진길;최재성
    • Journal of Advanced Marine Engineering and Technology
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    • 제2권1호
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    • pp.3-14
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    • 1978
  • The authors have developed a calculating method of propeller shaft alignment by the finite element method. The propeller shaft is divided into finite elements which can be treated as uniform section bars. For each element, the nodal point equation is derived from the stiffness matrix, the external force vector and the section force vector. Then the overall nodal point equation is derived from the element nodal point equation. The deflection, offset, bending moment and shearing force of each nodal point are calculated from the overall nodal point equation by the digital computer. Reactions and deflections of supporting points of straight shaft are calculated and also the reaction influence number is derived. With the reaction influence number the optimum alignment condition that satisfies all conditions is calculated by the simplex method of linear programming. All results of calculation are compared with those of Det norske Veritas, which has developed a computor program based on the three-moment theorem of the strength of materials. The authors finite element method has shown good results and will be used effectively to design the propeller shaft alignment.

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용사 코팅된 그레이트바의 고온 내마모 특성 평가 (Evaluation of High Temperature Abrasion Resistance of Spray-Coated Grate Bar)

  • 조희근;안진효
    • 한국기계가공학회지
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    • 제16권5호
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    • pp.55-62
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    • 2017
  • The grate bar, a component used in steel mills, is used in harsh environments where external disturbances such as high temperature, abrasion, corrosion, and impacts are present. Therefore, in this study, spray-coating was performed on the most severely affected surface to extend the lifetime of the grate bar. The thermal and mechanical properties of the sprayed coated bars were investigated based on the performances under abrasion, thermal shock, tension, and sand blasting, and the microstructures by microscope. By analyzing the thermal and mechanical properties of the uncoated original grate bar and coated grate bar and comparing them with one another, the physical performance improvement of the coated grate bar can be verified.