구조물 모니터링을 위한 BOCDA 및 내적 기법 기반 데이터 내 온도의 영향 제거 기법
Temperature Effect Compensation Method Based on BOCDA and Inner Product
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초록
구조물의 건전성 평가에서는 다양한 센서를 활용하여 물리량을 계측하고 상태를 평가한다. 이 중 변형률 계측은 시설물의 전역, 국부적인 상태 평가가 가능하나, 통상 활용되는 전기저항식 변형률 게이지는 점 계측을 수행하므로 전역적인 시설물의 상태 평가에 어려움이 있다. 이를 극복하기 위해 분포형 광섬유 센서를 활용한 계측이 연구되고 있다. 그러나, 시설물의 상태 평가에 있어서 하중뿐만 아니라 온도, 습도등과 같은 환경적 요소에 의한 영향도 받기 때문에 정확한 상태 평가를 수행하기 위해서는 온도의 영향을 보정할 필요가 있다. 따라서, 본 연구에서는 이러한 온도의 영향을 보정하기 위해, 분포형 광섬유 센서인 BOCDA 센서 기반으로 취득된 변형률 데이터를 대상으로 내적 기법을 적용하여 온도의 영향을 제거하는 기법을 제안하였다. 제안 방법은 온도에 의한 변형률과 하중(손상)에 의한 변형률은 독립적이라는 이론을 토대로, 변형률 데이터가 계측된 온도와 비슷한 온도 대의 변형률을 기저 벡터(Basis Vector)를 활용하여 내적 기법을 통해 계산하여 온도의 영향을 제거한다. 제안한 기법을 검증하기 위해 알루미늄 시편과 온도 챔버를 활용하여 실내 실험을 진행한 결과, 계측 환경에 따라 보정값을 동적으로 업데이트하는 방식에서는 대입한 하중과 유사한 값과 위치를 파악할 수 있었다.
Abstract
In structural health monitoring, various sensors are used to measure physical quantities and assess the condition of structures. Among these, strain measurement enables both global and local assessment. However, conventional electrical resistance strain gauges perform point measurements, which makes it challenging to evaluate the global condition of a structure. To overcome this limitation, distributed fiber optic sensors have been investigated. However, structural conditions are influenced not only by loads but also by environmental factors such as temperature and humidity. Therefore, to achieve accurate condition assessment, it is necessary to compensate for the effects of temperature. In this study, a method to compensate for temperature effects is proposed using strain data obtained from a BOCDA-based distributed fiber optic sensor. The proposed method is based on the theory that strain caused by temperature and strain caused by load (or damage) are independent. The method eliminates the temperature effect by calculating strain data at a temperature similar to the measured temperature using a basis vector and applying an inner product technique. To validate the proposed method, indoor experiments were conducted using an aluminum specimen and a temperature chamber. The results demonstrated that dynamically updating the compensation values based on the measurement environment allowed for the accurate identification of values and locations similar to the applied load.
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