Development of Long-Period Fiber Grating Sensors for Concrete Structural Monitoring (05-1982)
Jian-Neng Wang, National Yunlin University of Science and Technology
Hsiang-Ping Chang, National Yunlin University of Science and Technology, China
Tien-Min Lin, National Chung Cheng University, Taiwan
Yi-Chong Lin, National Yunlin University of Science and Technology, China
Ken-ming Guo, National Chung Cheng University, Taiwan

We report the development of a long-period fiber grating (LPG) fabrication system based on CO2 laser irradiation method. The system has been used to produce low loss and strong LPGs that are demonstrated as versatile sensors for temperature, strain and index of refraction measurements. We have used the system to develop a prototype sensor based on thermal properties of LPG. The LPG sensor is still in development stage and the prototype sensor was preliminarily implemented on the concrete cylinder specimen to measure the surface temperature. The reliability and long-term stability tests for this sensor were performed by mounting it on the surface of a concrete specimen, and several temperature cycles with a designed working temperature range up to 110oC were applied for at least 48 hours. Small rms temperature variations (about 1oC) was obtained and the maximum variations of temperature was 8%. The temperature characterization could be potentially used to monitor or detect chemical changes, corrosion condition inside concrete structures and deterioration in reinforced or pre-stressed concrete structures, though some improvements needed to be made in the future. This type of compact and inexpensive LPG sensor could be a high potential to contribute an economical and safe monitoring transportation infrastructure, especially for concrete structures.