GFRP 보강근으로 겹침이음된 휨 부재의 거동에 관한 실험적 연구

최윤철,최현기,최창식,Choi, Yun-Cheul,Choi, Hyun-Ki,Choi, Chang-Sik 대한건축학회 2011 대한건축학회논문집 Vol.27 No.4

The use of glass-fiber-reinforced polymer (GFRP) bars in reinforced concrete (RC) structures has emerged as an alternative to traditional RC due to the corrosion of steel in aggressive environments. Although the number of analytical and experimental studies on RC beams with GFRP reinforcement has increased in recent decades, it is still lower than the number of such studies related to steel RC structures. This paper presents the experimental moment deflection relations of reinforced beam with spliced GFRP bars. Test variables were lab-spliced length of GFRP rebars. The development length was calculated according to the ACI 440 for GFRP rebars in concrete. A total of 6 concrete beams reinforced with steel and GFRP rebar tested. Three concrete beam reinforced with spliced GFRP rebars and 1 reference beams reinforced with non-spliced GFRP rebars were tested. All the specimens had a span of 4000mm, provided with 12.7mm nominal diameter steel and GFRP rebars. All test specimens were tested under 2-point loads so that the spliced region be subject to constant moment. The test results indicated that the modification factor of 1.6 and 1.75 is relatively sufficient for the bond development length of GFRP rebars archiving adequate tension lap splice length.

U자형 와이드 합성보의 거동특성

최윤철,이상섭,최현기,박금성,Choi, Yun-Cheul,Lee, Sang-Sup,Choi, Hyun-Ki,Park, Keum-Sung 한국구조물진단유지관리공학회 2017 한국구조물진단유지관리공학회 논문집 Vol.21 No.5

도심지 주차문제 해결에 있어 공작물 주차장이 주목을 받고 있다. 그러나 공작물 주차장은 전체 높이 8 m 이하로 건설되도록 규정되어 있다. 이에 본 연구에서는 층고 절감 및 장스팬화가 가능한 와이드 합성보를 대상으로 휨 및 전단성능을 평가하였다. 실험결과 보강철근(트러스 철근)은 휨강도에 영향을 미치지 않았다. 그러나, 보강철근이 없는 실험체의 경우 항복강도의 70%에서 슬립이 발생하여 기계적 부착능력이 저하되었다. 전단부착 실험결과 전단연결재가 없는 모든 실험체는 기계적 부착만으로 충분한 전단부착 성능을 가지지 못하므로, Flat Bar를 최소 2개 이상 설치하여야 한다. A parking structure has been on the spotlight to solve the parking problem in downtown area. However, the overall height of parking structure is stipulated less than 8m. Therefore, in this research, the flexural and shear capacity of 'wide composite beam' which can reduce story height and have long span, is evaluated. Based on test result, the rebar in truss did not affect its flexural strength. However, in the case of the specimen without the rebar, the mechanical bond strength decreased due to slip occurrence at 70% of the flexural yield strength. Based on the test of shear-bond behavior, all specimen without shear connector should be reinforced with 2 or more flat bar, because it did not have enough shear bond strength resisted by the mechanical bond mechanism.

고전압 IGBT SPICE 시뮬레이션을 위한 모델 연구

최윤철,고웅준,권기원,전정훈,Choi, Yoon-Chul,Ko, Woong-Joon,Kwon, Kee-Won,Chun, Jung-Hoon 대한전자공학회 2012 전자공학회논문지 Vol.50 No.8

본 논문에서는 SPICE 시뮬레이션을 위한 고전압 insulated gate bipolar transistor(IGBT)의 개선된 모델을 제안하였다. IGBT를 부속 소자인 MOSFET과 BJT의 조합으로 구성하고, 각 소자의 각종 파라미터 값을 조절하여 기본적인 전류-전압 특성과 온도변화에 따른 출력특성의 변화 등을 재현하였다. 그리고 비선형적인 리버스 트랜스퍼 커패시턴스 등의 기생 커패시턴스의 전압에 따른 변화를 높은 정확도로 재현하기 위해, 복수의 접합 다이오드, 이상적인 전압 및 전류 증폭기, 전압제어 저항, 저항과 커패시터 수동소자 등을 추가하였다. 본 회로모델을 1200V급의 트렌치 게이트 IGBT의 모델링에 이용하였으며, 실측자료와 비교하여 통해 모델의 정확도를 검증하였다. In this paper, we proposed a SPICE model of high-voltage insulated gate bipolar transistor(IGBT). The proposed model consists of two sub-devices, a MOSFET and a BJT. Basic I-V characteristics and their temperature dependency were realized by adjusting various parameters of the MOSFET and the BJT. To model nonlinear parasitic capacitances such as a reverse-transfer capacitance, multiple junction diodes, ideal voltage and current amplifiers, a voltage-controlled resistor, and passive devices were added in the model. The accuracy of the proposed model was verified by comparing the simulation results with the experimental results of a 1200V trench gate IGBT.

장스팬 및 층고저감형 와이드 복합보의 휨성능에 관한 연구

최윤철,박금성,이상섭,최현기,Choi, Yun-Cheul,Park, Keum-Sung,Lee, Sang-Sup,Choi, Hyun-Ki 한국구조물진단유지관리공학회 2017 한국구조물진단유지관리공학회 논문집 Vol.21 No.6

최근 국내 자동차 보유대수의 급격한 증가로 도심지 주차문제가 복잡해지고 있다. 도심지 주차문제 해결에 있어 공작물 주차장이 주목을 받고 있다. 그러나 공작물 주차장은 전체 높이 8 m 이하로 건설되도록 규정되어 있다. 이에 본 연구에서는 층고절감 및 장스팬화가 가능한 와이드 합성보를 개발하여 휨성능을 평가하였다. 휨 성능 실험 결과, 강재보의 두께가 3 mm 증가($6mm{\rightarrow}9mm$)함에 따라 휨강도는 약 20%가 증가하였다. 보 보강철근(트러스철근)의 형태(삼각형, 사각형)은 휨강도에 영향을 미치지 않았다. 보 보강철근(트러스철근)이 없는 경우는 있는 경우보다 약 10%가량 휨강도가 저하되었다. 또한 하중이 증가할수록 중립축은 상부로 이동하지만 일정하중을 넘어가면 중립축이 다시 하부로 이동하는 결과를 나타내었다. Recently, the parking in downtown area has caused severe problem due to the dramatic increase of possessing automobile in the country. A parking structure has been on the spotlight to solve the parking problem in downtown area. However, the overall height of parking structure is stipulated less than 8 m. Therefore, in this research, 'wide composite beam', which is possible for reducing story height and having long span, is developed and the flexural capacity of the wide composite beam is evaluated. Based on the result of the flexural test, the flexural strength of wide composite beam increased by 20% as the thickness of steel beam increased by 3 mm ($6mm{\rightarrow}9mm$) The shapes of rebar (whether it is triangle or rectangular shape) in the wide composite beam did not affect its flexural strength. The flexural strength of wide composite beam without rebar decreased by 10% compared to that of wide composite beam with rebar. In addition, the neutral axis moved upward as a load increased, but the neutral axis moved downward, when the load exceeded a certain level of load.

이음된 GFRP바를 사용한 콘크리트 보에서의 피복 두께의 영향에 대한 실험적 연구

최윤철 ( Choi Yoon Cheol ),최현기 ( Choi Hyun Ki ),최창식 ( Choi Chang Sik ) 한국구조물진단유지관리공학회 2009 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.13 No.2

In order to prevent the corrosion of conventional steel reinforcements in harsh enviornment, engineers may change the cover thickness of concrete structure. Cover thickness of reinforced concrete structure is very important factor for safety and serviceability of total structure. In the case of GFRP reinforced concrete structure it has very important role in strength development. However, there are no specification about lap splice length which was related to the cover thickness. This paper presents the experimental moment-deflection relations of GFRP reinforced beam which are spliced in the middle area of beam. One test specimen has no spliced area and other 4 test specimens have the same splice length and different cover thickness. Failure mode of these specimens were sensitively vary according to the cover thickness and maximum strength and deflection also show different values because of the change of the effective depth of beam and spalling of concrete cover in tension face.

GFRP 보강근으로 겹침이음된 휨 부재의 거동에 관한 실험적 연구

최윤철(Choi Yun-Cheul),최현기(Choi Hyun-Ki),최창식(Choi Chang-Sik) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.4

The use of glass-fiber-reinforced polymer (GFRP) bars in reinforced concrete (RC) structures has emerged as an alternative to traditional RC due to the corrosion of steel in aggressive environments. Although the number of analytical and experimental studies on RC beams with GFRP reinforcement has increased in recent decades, it is still lower than the number of such studies related to steel RC structures. This paper presents the experimental moment deflection relations of reinforced beam with spliced GFRP bars. Test variables were lab-spliced length of GFRP rebars. The development length was calculated according to the ACI 440 for GFRP rebars in concrete. A total of 6 concrete beams reinforced with steel and GFRP rebar tested. Three concrete beam reinforced with spliced GFRP rebars and 1 reference beams reinforced with non-spliced GFRP rebars were tested. All the specimens had a span of 4000mm, provided with 12.7mm nominal diameter steel and GFRP rebars. All test specimens were tested under 2-point loads so that the spliced region be subject to constant moment. The test results indicated that the modification factor of 1.6 and 1.75 is relatively sufficient for the bond development length of GFRP rebars archiving adequate tension lap splice length

이음된 GFRP바를 사용한 콘크리트 보의 보강근비 효과

최윤철(Choi, Yoon Cheol),최현기(Choi, Hyun Ki),최창식(Choi, Chang Sik) 한국구조물진단유지관리학회 2009 한국구조물진단학회 학술발표회논문집 Vol.2009 No.2

In order to prevent the corrosion of conventional steel reinforcements in harsh enviornment, Glass fiber reinforced polymer(GFRP) are used. Because of its original characteristic according to the corrosion, many standards already publicated and many researchers widely study this reinforcement. However, there are no exact solution for lap splice length for GFRP. This paper presents the experimental moment deflection relations of GFRP reinforced beam which are spliced. Test variables were reinforcement ratio of GFRP. All test specimens were tested under 4-point loads so that the spliced region be subject to constant moment. Three test specimens failed at spliced point and one test specimen, control specimen which used one GFRP bar, was failed in GFRP fracture. This failure mode influenced to concrete stress distribution that cannot show ultimate strain.

이음된 GFRP바를 사용한 콘크리트 보에서의 피복 두께의 영향에 대한 실험적 연구

최윤철(Choi, Yoon Cheol),최현기(Choi, Hyun Ki),최창식(Choi, Chang Sik) 한국구조물진단유지관리학회 2009 한국구조물진단학회 학술발표회논문집 Vol.2009 No.2

In order to prevent the corrosion of conventional steel reinforcements in harsh enviornment, engineers may change the cover thickness of concrete structure. Cover thickness of reinforced concrete structure is very important factor for safety and serviceability of total structure. In the case of GFRP reinforced concrete structure it has very important role in strength development. However, there are no specification about lap splice length which was related to the cover thickness. This paper presents the experimental moment-deflection relations of GFRP reinforced beam which are spliced in the middle area of beam. One test specimen has no spliced area and other 4 test specimens have the same splice length and different cover thickness. Failure mode of these specimens were sensitively vary according to the cover thickness and maximum strength and deflection also show different values because of the change of the effective depth of beam and spalling of concrete cover in tension face.

강봉 및 강판을 이용한 개구부를 갖는 전단벽의 보강효과에 관한 실험 연구

최윤철(Youn-Cheul Choi),배백일(Baek-Il Bae),최창식(Chang-Sik Choi),최현기(Hyun-Ki Choi) 한국콘크리트학회 2009 콘크리트학회논문집 Vol.21 No.2

개구부 형태 및 연결슬래브에 따른 전단벽의 거동특성

최윤철(Choi Yun-Cheul),황규장(Hwang Kyu-Jang),이문성(Lee Moon-Sung),최현기(Choi Hyun-Ki),최창식(Choi Chang-Sik) 대한건축학회 2008 大韓建築學會論文集 : 構造系 Vol.24 No.10

Many engineers find the way of improving the old building’s structural behavior in the remodeling project which is performed using artificial openings for merging two houses. This test was performed to verify the characteristics of coupling beams according to shape of the openings. One of the test specimens had rectangular shape openings, another one had circular shape openings, and the other one had coupling members only as slabs. Three specimens with openings had 23% ratio of opening area to total wall area. A solid type specimen which had no opening area showed shear failure. In the case of CW-RBS which had rectangular shape openings, cracks were developed in coupling beam significantly. CW-CS which had circular opening failed in shear showing development of diagonal cracks at the wall toes and wall mid-height. It was believed that degradation of wall strength was under the control regardless of the openings and coupling beam-wall connection area.