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검색결과 17건 처리시간 0.022초

Experimental investigation on optimal shear strengthening of RC beams using NSM GFRP bars

  • Ramezanpour, M.;Morshed, R.;Eslami, A.
    • Structural Engineering and Mechanics
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    • 제67권1호
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    • pp.45-52
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    • 2018
  • Several techniques have been developed for shear strengthening of reinforced concrete (RC) members by using fiber reinforced polymer (FRP) composites. However, debonding of FRP retrofits from concrete substrate still deemed as a challenging concern in their application which needs to be scrutinized in details. As a result, this paper reports on the results of an experimental investigation on shear strengthening of RC beams using near surface mounted (NSM) FRP reinforcing bars. The main objective of the experimentation was increasing the efficiency of shear retrofits by precluding/postponing the premature debonding failure. The experimental program was comprised of six shear deficient RC beams. The test parameters include the FRP rebar spacing, inclination angle, and groove shape. Also, an innovative modification was introduced to the conventional NSM technique and its efficiency was evaluated by experimental observation and measurement. The results testified the efficiency of glass FRP (GFRP) rebars in increasing the shear strength of the test specimens retrofitted using conventional NSM technique. However, debonding of FRP bars impeded exploiting all retrofitting advantages and induced a premature shear failure. On the contrary, application of the proposed modified NSM (MNSM) technique was not only capable of preventing the premature debonding of FRP bars, but also could replace the failure mode of specimen from the brittle shear to a ductile flexural failure which is more desirable.

연속지진에 대한 지진 취약 철근콘크리트 건축물의 FRP 재킷 보수 전략 연구 (Repair Scheme of FRP Column Jacketing System for Seismically-vulnerable RC Buildings under Successive Earthquakes)

  • 김수빈;김혜원;박재은;신지욱
    • 한국공간구조학회논문집
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    • 제23권2호
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    • pp.79-90
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    • 2023
  • Existing reinforced concrete (RC) frame buildings have seismic vulnerabilities because of seismically deficient details. In particular, since cumulative damage caused by successive earthquakes causes serious damage, repair/retrofit rehabilitation studies for successive earthquakes are needed. This study investigates the repair effect of fiber-reinforced polymer jacketing system for the seismically-vulnerable building structures under successive earthquakes. The repair modeling method developed and validated from the previous study was implemented to the building models. Additionally, the main parameters of the FRP jacketing system were selected as the number of FRP layers associated with the confinement effects and the installation location. To define the repair effects of the FRP jacketing system with the main parameters, this study conducted nonlinear time-history analyses for the building structural models with the various repairing scenarios. Based on this investigation, the repair effects of the damaged building structures were significantly affected by the damage levels induced from the mainshocks regardless of the retrofit scenarios.

유한요소해석을 활용한 지진하중에 대한 철근콘크리트 건축물의 부착성능 효과 연구 (Bond-slip Effect of Reinforced Concrete Building Structure under Seismic Load using Finite Element Analysis)

  • 김예은;김혜원;신지욱
    • 한국공간구조학회논문집
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    • 제22권4호
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    • pp.99-107
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    • 2022
  • Existing reinforced concrete building structures constructed before 1988 have seismically-deficient reinforcing details, which can lead to the premature failure of the columns and beam-column joints. The premature failure was resulted from the inadequate bonding performance between the reinforcing bars and surrounding concrete on the main structural elements. This paper aims to quantify the bond-slip effect on the dynamic responses of reinforced concrete frame models using finite element analyses. The bond-slip behavior was modeled using an one-dimensional slide line model in LS-DYNA. The bond-slip models were varied with the bonding conditions and failure modes, and implemented to the well-validated finite element models. The dynamic responses of the frame models with the several bonding conditions were compared to the validated models reproducing the actual behavior. It verifies that the bond-slip effects significantly affected the dynamic responses of the reinforced concrete building structures.

지역주민과 건강행태와 국민건강증진법에 대한 인식과 태도 (Health Behavior and Attitude of Residents toward the National Health Promotion Law in Kyungsan City)

  • 이관희;박재용;한창현;윤석옥
    • 보건교육건강증진학회지
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    • 제16권2호
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    • pp.19-40
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    • 1999
  • In order to ascertain the attitudes of residents to their health and the National Health Promotion Law, surveyors interviewed 1,220 subjects, 1% of men and women in Kyungsan city, who were twenty-year-old or more. The major findings are as follows: Men and women were 48.2% and 51.8%, respectively. The recognition rate of enacting and enforcing this law is 59.2% of men and 51.3% of women. With regard to the behavioral attitude to the health in the distinction of sex and age, current smokers are 31.2% of the interviewees, 61.6% of the men and 3.3% of the women. Current drinkers are 35.1%, 59.5% of the men and 12.3% of the women, but on the other hand there is little significance in the distinction of age. The acknowledgement proportion of enacting and enforcing this law is 59.2% of male and 51.3% of female. In terms of the recognition rate of the contents according to the general characteristics of interviewees, it appears that the indication of a warning expression on a packing paper of cigarette case and a liquor bottle is 92.4% and also the designation of a smoking free area in public facilities is 94.8%. Prohibition of cigarette-sale to the teenagers who are under 19, is 96.0%. Considering these facts, the recognition rate is high. On the contrary, 48.8% is accounted for encouraging a medical check-up before marriage which is in a low position. As a result of multiple behavior as a independent educational level, marital significant variables. In case of having undergone a periodic medical examination the recognition rate was high whereas frequent exercise led to the low recognition rate. Concerning the details of the undertaking in accordance with each factor of general characteristics, the greater part of them have been appraised successfully whether it is recognized or not. On the other side, no effect got answered about the result of the undertaking subjects to general and peculiar behavior attitude towards health was in effect or not. A great majority approved of more reinforcement of legal regulation about smoking and drinking regardless of whether they perceived the details of the law of promotion of National Health Promotion Law or not. Additionally there was significant difference in reinforcing legal regulation of smoking and drinking in compliance with the attitude of the substance of this law. With regard to education, public relations and evaluation about national health through public health centers by our government, the younger and the higher in education they are, the more deficient they feel. First of all, those who were aware of the enforcement of this law as well as plenty of scarcity answered that better service of disease prevention had to be expanded than ever. In consideration of the above-stated results, the education to public health and the business of public relations should be reinforced and a practical campaign for health life should also spread out for the purpose of encouraging to practise healthy life-style.

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일제하 근로자의 건강상태에 관한 문헌고찰 (A Literature Review on the Health Status of Korean Workers under the Japanese Colonialism)

  • 김창엽;문옥륜
    • Journal of Preventive Medicine and Public Health
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    • 제24권1호
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    • pp.45-56
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    • 1991
  • The history of occupational health in Korea s covered the era of the Republic of Korea after the Liberation from the Japanese colonialism. But the number of Korean workers exceeded about 2 millions at the times of liberation in 1945, so that it is expected that many occupational health problems inflicted Korean workers under the Japanese colonialism. The authors reviewed medical literatures, administrative documents, and other available data which were published under the colonial state, and collected things which had reference to the health status of Korean workers. The results were as follows : 1. Nutritional status of Korean workers was supposed to be inferior to that of general population, some students, and poor inhabitants in a remote mountain villages. 2. It was supposed that the constitution of Korean workers was near lower limit of average build of contemporary Koreans. 3. The accidents rate in mines was significantly high but decreasing year after year, and the most important cause of accidents was the fall of roof in the mine. The medical facilities and equipments for miners were supposed to be not sufficient in the mines and workshops. 4. Some occupational disease including silicosis, noise-induced hearing impairment, and decompression disease were known. But, overall incidence or prevalence of these diseases could not be identified. 5. On the whole, the fatalities of acute infectious diseases of Korean workers were higher than those of Japanese inhabitants in Korea and Korean inhabitants. The prevalence of pulmonary tuberculosis of Korean workers was increasing with every passing year. 6. The medical personnels and facilities were so deficient that most Korean workers were out of adequate medical use. We discussed only a part of the health status of Korean workers under the Japanese colonialism, so it would be necessary to have a better grasp of details of occupational health policy and health status in the era of afflicting.

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동병하치 확산을 위한 전략적 방향과 이행방안 (Strategic Direction and Road Map of Expanding Prevention of Winter Disease in the Summer)

  • 송호섭
    • Journal of Acupuncture Research
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    • 제27권3호
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    • pp.147-157
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    • 2010
  • Objectives : The purpose of this study was to propose appropriate strategic directions and road maps for successful achievement of programs preventing winter disease in the summer. Methods : Details on programs preventing winter disease in the summer such as clear concept, theoretical basis, current status, intervention or available prescriptions and indication/contraindication/caution were prepared through the related journal review, upon which an observational study was devised and done for simulation to find out even a trivial problem and to guarantee the safety beforehand. The experimental group was divided into 5 groups by the size of pill and the way ginger is treated; 1cm pill with ginger group, 3cm pill group without ginger, 3cm pill group dipped into ginger, 3cm pill group applying ginger to acupoints and 3cm pill group with ginger Results 1. program preventing winter disease in the summer was defined as representative winter diseases such as common cold, influenza, chronic asthma, chronic bronchitis, allergic rhinitis, emphysema, chronic gastritis and rheumatoid arthritis, and preventive care in the summer, reinforcing deficient yang qi of five viscera by using exuberant yang qi from summer heat. 2. It was based upon historically established theories which is 'nourishing yang qi in the spring and summer', 'long summer, namely rainy spell in the summer overwhelms the winter, because of earth winning water according to the five phases theory' and 'To replenish yang qi is major principle to treat winter diseases, which can be most appropriately and timely applied to the patient with deficient yang qi of five viscera inherently, especially in the three dog days of the summer, because of exuberant exterior yang qi and deficient interior yang qi in the five viscera'. 3. In the adjacent China and Taiwan, acupoint applying method in the three dog days named 'San Fu Tie' have been stirring a boom throughout the nation, in which Xiaochuan Gao was used as a basic prescription and it mainly was applied at bilateral $BL_{13}$, $_{15}$ and $_{17}$ for about 4 hours. As far as domestic current status, the necessity of adopting the above method prior to Herbal formula was also recognised, because not a few koreans have apprehension for the safety of it including medicinal herbs and are reluctant to take it any more due to negative advertisement of narrow minded doctors' association. 4. Indication of acupoint applying method in the three dog days included most of winter diseases such as common cold, influenza, chronic asthma, chronic bronchitis, allergic rhinitis, emphysema, chronic gastritis. contraindication was pregnant woman and the weak such as infants and the old. More attention was paid to grasp firmly the normal reaction following the treatment for preventing side effect and teasing blister. recommendation was also given to abstain from food inducing phlegm and dampness such as meat, shrimp and crab as well as cold drinks and foods 5. In the simulation observational study based upon the above findings following review the related articles, no blister was shown on the acupoints icluding bilateral $BL_{13}$, $_{15}$ and $_{17}$ in every experimental group during 24hr observation following the acupoint applying treatment with pills made by modified and devised prescription. At 4 hr, the effectiveness of it reached a peak showing redness and mild tenderness and there is little difference between groups 3cm pills groups regardless of the way ginger was treated. abdominal distention and growling was found in all the volunteers during the treatment at CV 8. Strategic directions and road maps : Through successful fulfillment of the program preventing winter disease in the summer, Korean traditional medicine should be integrated into mainstream national health care services. Cultural access was thought to be as important as Scientific EBM approach. First of all, To evoke potential cultural homogeneity from campaigns and press advertisement was needed for promoting public awareness about preventing winter disease in the summer by enhancing immunity via acupoint applying treatment in the three dog days, and then indigenous name as Sambokcheop, protocol, Clinical Research Form for data collection of it should be developed and prepared. Once the first step was taken this summer, through a thorough data collection and scrutinized scientific evaluation, drawbacks should be compensted for and the efficacy and safety should be substantiated.

생존으로서의 곡선(曲線)에 관한 연구 -물리적 구조법칙을 중심으로- (A Study of the Curved Line as a Survival -Especially Centered on the Physical Structure-)

  • 박규현;신기봉;박영민
    • 디자인학연구
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    • 제15권1호
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    • pp.181-190
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    • 2002
  • 모든 사물의 형태는 사물이 가진 내부에너지와 외부스트레스간의 균형관계라는 기존의 정의에서 출발된다. 이것을 생물체간의 균형관계로 볼 때 내부에너지는 생물체가 스스로의 존재유지를 위해 필요한 에너지의 발생일 것이며 외부스트레스는 주변환경에서 가해오는 압박이라고 할 수 있을 것이다. 즉 생존에 필요한 내부에너지의 유지와 여기에 가해지는 외부스트레스가 균형을 유지하는 점에서 우리는 사물의 형상이 존재하게됨을 알 수 있다. 그런데 여기서 아울러 발견되는 것은 이러한 형상들은 주로 비직선(非直線)인 곡선(曲線)과 곡면(曲面)으로 이루어져 있음이란 사실이다. 다시 말해 직선과 직면으로 이루어진 형상이란 존재하는 사물의 세계에서 발견하기란 거의 불가능하다. 대체로 우리는 그동안 곡선과 곡면을 주로 시각적 아름다음<美>의 대상으로만 여겨왔다. 본고에서는 곡선과 곡면에는 아주 먼 원인류(原人類)부터 우리의 생존을 지켜주는 중요한 기능(機能/function)들이 함께 하고있음을 제시하고, 다시 그러한 기능을 물리적 역학구조의 시각에서 좁혀 보다 세밀히 관찰해 봄으로서 특히 곡선형태를 다루는 디자인의 근원에서 무엇이 중요한 것인가를 살펴보았다. 물론 여기에는 수학이나 화차 또는 생물학 등의 관점에 따라 자연현상을 여러 갈래로 분석하여 이들을 종합하는 것이 더욱 타당할것이나 다만 본고에서는 연구능력의 한계로 물체의 외부형상을 다루는 디자인에 적응될 수 있는 물리적 구조에만 주된 관심을 두기로 하였다. 결과적으로 자연에서 발생한 곡선·곡면의 물리적 구조현상을 디자인에 더욱 충실할 때 시각적으로도 더욱 아름답다는 사실을 재차 확인할 수 있었음이 본고의 작은 결실이라 할 수 있다.

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