Department of Civil Systems Engineering, Ajou University, 206, Worldcup-ro, Yeongtong-gu, Suwon-si 16499, Gyeonggi-do, Korea.
Department of Structural Engineering Research, Korea Institute of Civil Engineering and Building Technology, 283, Goyang-daero, Ilsanseo-gu, Goyang-si 10223, Gyeonggi-do, Korea.
Sensors (Basel). 2022 Apr 25;22(9):3282. doi: 10.3390/s22093282.
Compared to other types of sensors, fiber optic sensors have improved accuracy and durability. Recently, the Smart Strand was developed to maximize the advantages of fiber optic sensors for measuring the cable forces in prestressed concrete structures or cable-supported bridges. The Smart Strand has fiber Bragg gratings (FBGs) embedded in a core wire of the seven-wire strand. Similar to other sensors, the strain measured at an FBG is affected by temperature; therefore, the temperature effect that is not related to the mechanical strain should be compensated for or corrected in the long-term measurement subjected to temperature variation. However, a temperature compensation procedure for the FBG has yet to be established, and relevant studies have used different formulas for the compensation. Moreover, when the FBG sensors are packaged with a certain material-such as fiber reinforced polymer-for protection, it is important to consider the interaction between the FBG, packaging material, and host material during thermal behavior. Therefore, this study proposed a reasonable procedure for temperature compensation for the FBG sensors embedded in packaging material and host material. In particular, the thermal sensitivity of the Smart Strand was intensively investigated. The proposed theoretical formulas were validated through comparison with data obtained from various specimens in a temperature-controlled chamber. Finally, the procedure was applied to correct the data measured using the Smart Strands in a 20-m-long full-scale specimen for about a year, thus resulting in a realistic trend of the long-term prestressing force.
与其他类型的传感器相比，光纤传感器具有更高的精度和耐用性。最近，开发出了 Smart Strand，旨在最大限度地发挥光纤传感器在测量预应力混凝土结构或斜拉桥中电缆力的优势。Smart Strand 在七股钢绞线的芯线中嵌入了光纤布拉格光栅（FBG）。与其他传感器类似，FBG 测量的应变受温度影响；因此，在长期测量中，应补偿或修正与机械应变无关的温度效应。然而，尚未为 FBG 建立温度补偿程序，相关研究使用了不同的补偿公式。此外，当 FBG 传感器用某种材料（如纤维增强聚合物）进行封装以进行保护时，重要的是要考虑 FBG、封装材料和主体材料在热行为中的相互作用。因此，本研究提出了一种合理的封装材料和主体材料中 FBG 传感器温度补偿程序。特别地，深入研究了 Smart Strand 的热灵敏度。通过与在控温室内的各种试件获得的数据进行比较，验证了所提出的理论公式。最后，该程序应用于修正使用 Smart Strand 在一个 20 米长的全尺寸试件中测量的约一年的数据，从而得出预应力的真实长期趋势。
