KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
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Monitoring the Structural Behavior of Reinforced RC Slabs Using Optical Fiber-embedded CFRP Sheets

광섬유 매립 CFRP 시트를 활용한 RC 슬래브의 구조적 거동 모니터링 기술 개발

  • Kim, Jaehwan (Korea Institute of Civil Engineering and Building Technology) ;
  • Jung, Kyu-San (Korea Institute of Civil Engineering and Building Technology) ;
  • Kim, Byeong-Cheol (Korea Institute of Civil Engineering and Building Technology) ;
  • Kim, Kun-Soo (Korea Institute of Civil Engineering and Building Technology) ;
  • Park, Ki-Tae (Korea Institute of Civil Engineering and Building Technology)
  • 김재환 (한국건설기술연구원 구조연구본부) ;
  • 정규산 (한국건설기술연구원 구조연구본부) ;
  • 김병철 (한국건설기술연구원 구조연구본부) ;
  • 김건수 (한국건설기술연구원 구조연구본부) ;
  • 박기태 (한국건설기술연구원 구조연구본부)
  • Received : 2021.07.05
  • Accepted : 2022.01.25
  • Published : 2022.06.01
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Abstract

This study performed 4-point flexural tests of reinforced concrete to which was attached a distributed optical fiber sheet and carbon fiber reinforced polymer (CFRP) sheets in order to assess the effect of the CFRP sheets and the applicability of a BOTDR sensor simultaneously. To evaluate the reinforcing effect, various degrees of CFRP sheet attachment were manufactured, and to evaluate the sensing ability, strains obtained from a BOTDR sensor were compared with strains measured from electric resistance strain gauges that were attached to the concrete surface. From the results, the reinforcing effects were evidently different according to the attachment type of the CFRP sheets, and it was confirmed that the main influencing factor on the reinforcing effect was the type of attachment rather than the attachment area. The reinforced concrete structural behavior was visualized with strains measured from the BOTDR sensor as load increased, and it was identified that load was concentrated in the CFRP reinforced area. Strains from the BOTDR sensor were similar to those from the electric resistance strain gauge; thereby a BOTDR sensor can be effective in the analysis of structural behaviorsof massive infrastructure. Finally, the strain from a BOTDR sensor was high where CFRP sheet fall-off occurs, and it would therefore be efficient to track local damage locations of CFRP sheets by utilizing a BOTDR sensor.

본 연구에서는 분포형 광섬유 시트와 탄소섬유 시트를 콘크리트 표면에 부착하여 철근 콘크리트를 사용하는 구조물의 보강 효과 및 BOTDR 센서를 활용한 상태 평가를 4점 휨 실험을 통해 수행하였다. 부착 정도에 따른 보강 효과를 확인하기 위하여 탄소섬유 시트의 부착 형태를 다양하게 제작하였으며, BOTDR 센서의 활용성을 확인하기 위하여 실험체에 다수의 전기저항식 변형률 게이지를 부착하여 BOTDR 센서의 변형률과 비교하였다. 실험 결과를 살펴보면, 우선 CFRP시트 부착 정도에 따른 보강 효과에 분명한 차이가 나타나는데, 이는 부착 면적보다는 부착 형태에 더 영향을 받는 것으로 확인되었다. BOTDR 센서로부터 계측된 변형률로부터 하중 증가에 따른 철근 콘크리트 실험체의 구조적 거동을 시각화 할 수 있었으며, CFRP 보강 부위에서 하중이 집중되는 것을 알 수 있다. BOTDR 센서에서 계측된 변형률이 전기저항식 게이지로부터 계측된 변형률과 유사하게 계측되는 것을 알 수 있는데, 이를 통해 대형 토목 구조물의 전체적 거동을 분석하는데 BOTDR 센서가 효과적일 수 있음을 확인하였다. 다시 말해서, 국부적 변형률을 측정하는 전기식 변형률 게이지로 계측을 하면 계측 오차는 상당할 수 있는 반면에, 분포형으로 측정되는 BOTDR 센서는 이러한 문제를 줄일 수 있는 대안으로 판단된다. 마지막으로, CFRP 시트 탈락이 발생되는 부분에서 계측 BOTDR 센서 변형률이 높게 나타나는데 이를 활용하면 CFRP 시트의 국부적 손상 위치를 효율적으로 추적할 수 있을 것으로 판단된다.

Keywords

Acknowledgement

본 연구는 한국건설기술연구원 주요사업 "DNA 기반 노후 교량 구조물 스마트 유지관리 플랫폼및 활용기술개발" 과제(20210289-001)를 통해 수행되었음.

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