Abstract
A long-gauge fiber Bragg grating (FBG) strain sensor with enhanced strain sensitivity is proposed, which is encapsulated with two T-shaped metal blocks. Its fabrication method is described briefly, and the strain sensitivity can be flexibly adjusted through changing its packaging method. A series of experiments are carried out to study the packaging and its sensing properties. The experimental results show that the strain and temperature sensitivity coefficient of the sensor are three times larger than the common FBG sensors. The linearity coefficients of the FBG sensor are larger than 0.999, and the relative error of the repeatability of all sensor samples is less than 1%. Through the stability test on the actual bridge, it is revealed that the long-term stability of the sensor is excellent, and the maximum error is less than 1.5%. In addition, the proposed FBG strain sensors are used to conduct a shear strengthening experiment on a reinforced concrete (RC) beam to verify its working performance. The experimental results show that the strain change and crack propagation of the RC beam are well monitored by the sensors during the loading process.
Highlights
The health monitoring technology of bridge structures has attracted widespread attention in the transport sector
The results indicate that the proposed fiber Bragg grating (FBG) sensor has good long-term measurement stability
The correlation linearity of the FBG sensor is higher than 0.999, and the relative error of different samples is less than 3%, which indicates good accuracy and stability
Summary
The health monitoring technology of bridge structures has attracted widespread attention in the transport sector. The research and development of sensing technology is essential to achieve the consequent structural health monitoring (SHM). The resistance strain gauge is characterized by high measurement accuracy, a wide measuring range and a simple structure. It has a distinct non-linearity when faced with a large strain and weak signal. These shortcomings severely limit its application, especially in long-distance monitoring and harsh environments. FBG sensing technology has developed rapidly in recent years. It is characterized by high measurement precision, immunity to electromagnetic interference, stability of long-term sensing and so on. The FBG sensing technology favors the long-term SHM [7,8,9]
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