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대형 구조물의 변형률 측정을 위한 광섬유 TR-EFPI 센서의 개량
권일범 ( Kwon¸ Il-bum ),최만용 ( Choi¸ Man-yong ),김치엽 ( Kim¸ Chi-yeop ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.4 No.2
The sensor for continuous in-situ monitoring is better to be embedded in large structures. Fiber optic sensors can be embedded in the structures to get the health information in the structures. Fiber optic EFPI(extrinsic Fabry-Perot interferometric) sensors had been shown in many publications which concerned about the structural strain measurement. However, the gage lengths of the sensors in these papers were limited at about 1 cm because it is very difficult to make the long gage length fiber optic EFPI sensor. If the gage length of the fiber optic EFPI sensor could be made as long as about 90 mm, then the sensitivity is to be more higher than the short gage length fiber sensor at about 9 times. In this study, the fiber optic TR-EFPI (total reflected - extrinsic Fabry-Perot interferometric) sensor was developed and was improved to be get the long gage length about 90 mm. The loading-unloading test was performed to confirm the performance of the improved fiber optic TR-EFPI sensor. In this experiment, the strain which was determined by the fiber optic signal had some errors. It was considered that this errors caused by the sliding mismatch in the sensor probe.
권일범 ( Kwon Il-bum ),박휘립 ( Park Philip ),허용학 ( Huh Yong-hak ),김동진 ( Kim Dong-jin ),이동춘 ( Lee Dong-chun ),홍성혁 ( Hong Sung-hyuk ),문한규 ( Moon Hahngue ) 한국구조물진단유지관리공학회 1999 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.3 No.1
Fiber optic sensors can be embedded in the structures to get the health information in the structures. The fiber sensor was constructed with 3x3 fiber couplers to sense the multi-point strains and failure instants. The 2 RC(reinforced concrete) beams were made to one of A type, one of B type beams. These beams were reinforced by the steel bars, and were experimented under the flexural loading. The behavior of the beams was simultaneously measured by the fiber optic sensors, electrical strain gages, and LVDT. The states of the beams were interpreted by these all signals. By these experiments, There were verified that the fiber optic sensors could measure the structural strains and failure instants of the RC beams. The fiber sensors were well operated until the failure of the beams. It was shown that the strains of the reinforcing steel bar can be used to monitor the health of the beams through the flexural test of RC beams. On the other words, the results were arrived that the two strains in the reinforcing bar measured at the same point can give the information of the structural health status. Also, the failure instants of beams were well detected from the fiber optic filtered signals.
구조물의 변형률 측정을 위한 광섬유 TR-EFPI 센서의 개발
권일범(Il Bum Kwon),최만용(Man Yong Choi),문한규(Han Gue Moon),김민수(Min Soo Kim) 한국센서학회 2000 센서학회지 Vol.9 No.2
Fiber optic TR-EFPI(total reflected extrtinsic Fabry-Perot interferometric) sensor was developed to measure the strain of structures, such as building, bridge, aircraft, etc. It has been difficult to distinguish the increase and decrease of the strain from the conventional fiber optic EFPI sensor because their signals only have a sinusoidal wave pattern related to the change of strain. Also, the absolute strain could not be measured by the simple fiber optic EFPI sensor. In this study, in order to measure the magnitude of strain with the direction of strain, the fiber optic sensor was simply constructed with the total reflected EFPI sensor probe. This probe was manufactured with a single mode fiber and a mirror coated fiber in a silica glass capillary tube. The output signal of this fiber optic TR-EFPI sensor can give the information about the magnitude and the direction of strain. The loading-unloading test was performed by the universal testing machine with alluminum beam specimen to compare the strain from fiber optic TR-EFPI sensor with the value from electrical strain gauge. In the result of this experiment, the strain from fiber optic TR-EFPI sensor had a good agreement with the values from the electrical strain gauge.
권일범 ( Kwon Ii-bum ),김치엽 ( Kim Chi-yeop ),최만용 ( Choi Man-yong ),임종묵 ( Lim Jong-mook ),김인걸 ( Kim In-gul ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.4 No.1
PVDF film sensor was applied to measure the stress concentration for monitoring the structur The strain calibration of this film sensor was performed by aluminum beam test. The PVDF se the electrical strain gage were bonded on the beam. When the beam was loaded, the output of strain gage was compared with the output of the PVDF sensor. The waveform of PVDF sensor outpu shown as the same form of the output of electrical strain gage. The gain was determined comparing these two signals to determine the exact value of the strain. The tensile test of specimens was conducted to develop the measurement technique of stress concentration. The outp ratio between the PVDF sensor near the notch and the PVDF sensor far from the notch could g information about the load bearing capacity of steel specimen.
압전필름센서에 의한 충격하중을 받는 보의 응력파의 측정
권일범 ( Kwon Ii-bun ),최만용 ( Choi Man-yong ),김진기 ( Kin Jin-ki ),정현조 ( Jeong Hyun-jo ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.4 No.1
충격하중을 받는 구조물의 응력파를 측정함에 의하여 구조물의 손상을 감시할 수 있다. 이러한 충격하중에 따른 응력파를 측정하기 위한 압전 센서의 적용 가능성을 점검하기 위하여 강재 보에서 충격하중으로 인하여 전파되는 응력파를 PVDF 필름 센서와 재래식 초음파 및 음향방출 (AE) 센서를 사용하여 수신하였다. 실험에서 수신한 시간 영역의 신호 해석을 위하여 분산성 파의 시간-주파수 분석이 가능한 wavelet 변환(WT)을 적용하였다. 보에서 충격하중을 모사하기 위하여 연필심을 파단시켰으며, PVDF 필름, 초음파 및 AE 센서의 출력 전압은 변형률 게이지로 측정한 변형률에 비례하였다. 보에서 굽힘파의 속도는 전단 변형과 회전관성을 고려한 Timoshenko 보 이론과 잘 일치하였다.
광섬유 마이켈슨 센서에 의한 축소모형 강트러스 교량의 변형률 측정
권일범 ( Kwon Il-bum ),최만용 ( Choi Man-yong ),문한규 ( Moon Hahngue ) 한국구조물진단유지관리공학회 1998 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.2 No.1
The strains of a steel truss bridge, which was scaled down to 1/15 of the real bridge for the laboratory experiments, were measured to monitor the health status of the bridge by quadrature phase-shifted 3x3 fiber optic Michelson sensors. The fiber optic sensors and electrical strain gages were bonded on the surface of some frames to sense the strain pattern induced by the abnormal structural behavior. The fiber optic signals were immediately processed by personal computer for the strain determination. In order to confirm the strain sensitivity of the fiber optic sensors, these fiber optic strains were compared with the strains of the strain gages. The static behavior of the bridge was analyzed by finite element analysis with SaP2000. These unite element analysis results were compared with the structural strain pattern obtained by the electrical strain gages and were arranged with the database for the determination of the bridge health condition. It was shown that the breakage of some frames could be detected from the changes in strain pattern.