Strain measurement of steel structure using a novel FBG sensor packaged by titanium alloy slice

In recent years, Fiber Bragg grating (FBG) sensors become a focus in civil structure health monitoring because they have many advantages and show superior potential for health monitoring to ensure their structural integrity, durability and reliability. In this paper, fiber Bragg grating (FBG) sensors are used to monitoring the strain of steel structure. A designed novel titanium alloy slice is introduced to package the used FBG. A shallow rectangular groove is notched on the titanium alloy slice. Coated with a thin layer of epoxy, the FBG is fixed and protected on the groove. In order to eliminate to the temperature vibration effect on the wavelength shift of FBG sensors, a FBG temperature sensor is used for compensation. The traditional resistance strain gauges are also used to measure the strain for the comparison with the FBG sensors to validate the effectiveness. The strain of the flat steel at the elastic and yield stage of the steel are measured by monitoring the shift of center wavelength of FBG sensors and the change of the resistance strain gauges. The experimental results show that FBG sensors packaged by titanium alloy slice possess good stain sensing property and the strain sensitivity coefficients are 1.25pm/με. The shifts of center wavelengths of FBG are in good linear relationship with the tensile force and the strain measured by the resistance strain gauge. The linear correlation coefficients both reach 0.999.