Fiber Bragg Grating-Based Long-Gauge fiber Optic Sensor for Monitoring of a 60 m Full-Scale Prestressed Concrete Girder During Lifting and Loading

Significance Statement

The use of fiber optical sensors which incorporates the fiber Bragg grating technique has multifarious features, aiding an encompassing and ample knowledge on the behaviors of structures as discontinuous features which are likely to occur play a minor role on their sensing abilities.

Researchers let by Professor Yun Mook Lim from Yonsei University in Republic of Korea developed fiber Bragg grating based long-gauge fiber optic sensors to examine the behavior of a prestressed concrete girder, during transportation and lifting in order to find a comprehensive measurement on the construction process of a prestressed concrete girder. The research is now published in the journal, Sensors and Actuators A: Physical.

The authors fabricated a full-scale prestressed concrete girder spanning at 60m coupled with a girder depth of 2.3m. Four fibers Bragg grating-based long-gauge fiber optical sensors were installed and protected on the prestressed concrete girder with the addition of conventional sensors in order to compare their capabilities.

The four fiber Bragg grating-based long-gauge fiber optical sensors, with three placed at the bottom and one placed at the mid top of the prestressed concrete girder were able to measure different strain values at events involved in the lifting and transportation of the girder. This result confirms that there exists certain induction of defective stresses during the construction process of lifting and transportation of the prestressed concrete girder.

A four point load bending test was conducted in order to ascertain the applicability of the long-gauge fiber optical sensors. The results compared with the conventional sensors; concrete and steel strain gauges showed that despite similar results achieved in both sensors, a point of cracking load led to unobtainable measurements for the conventional sensors but the long-gauge fiber optical sensors still provided stable measurements.

Results observed from the comparison of deflection estimations between the regression method used in analyzing the data gotten from fiber Bragg grating-based long-gauge fiber optical sensors and an installed linear variable differential transformer indicated that the former especially at small load capacity has the ability of providing deflection results.

The authors’ use of the fiber Bragg grating-based long-gauge fiber optical sensors when compared with the conventional sensors provided a better sensing technique for monitoring prestressed concrete bridges during construction process.

Reference

Kim, T.M., Kim, D.H., Kim, M.K., Lim, Y.M. Fiber Bragg Grating-Based Long-Gauge fiber Optic Sensor for Monitoring of a 60 m Full-Scale Prestressed Concrete Girder During Lifting and Loading, Sensors and Actuators A 252 (2016) 134–145.

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