Long-gauge ultra-weak FBG strain sensor insensitive to structural defects: numerical simulation and experimental...

Area of Science:

• Structural Engineering
• Materials Science
• Fiber Optic Sensing

Background:

• Strain monitoring of concrete structures is crucial for safety and maintenance.
• Surface defects and material inhomogeneity pose significant challenges for traditional strain sensors.
• Accurate strain measurement is vital for assessing the structural integrity of concrete infrastructure.

Purpose of the Study:

• To propose a novel strain sensor array for concrete structures with improved performance in the presence of defects.
• To develop a long-gauge sensor based on ultra-weak fiber Bragg gratings (UWFBGs) that mitigates strain mutation phenomena.
• To evaluate the sensor's effectiveness in accurately reflecting strain field distribution and overall deformation.

Main Methods:

• Utilizing a long-gauge structure combined with an ultra-weak fiber Bragg grating (UWFBG) array.
• Converting continuous structural strain into average strain across UWFBGs to suppress defect-induced mutations.
• Conducting simulations to analyze the sensor's performance and defect interference reduction.
• Performing experimental tests to compare the proposed sensor with traditional point-type fiber Bragg grating (FBG) sensors.

Main Results:

• Simulations demonstrated that the long-gauge sensor effectively reduces interference from structural defects.
• Sensor sensitivity to defects decreased with increasing gauge length.
• Experimental tests confirmed the sensor's ability to accurately map surface strain fields and overall deformation in concrete structures.
• The proposed sensor showed superior performance compared to traditional point-type FBG sensors in challenging conditions.

Conclusions:

• The proposed long-gauge UWFBG sensor array offers a robust solution for strain monitoring in concrete structures with surface defects and material inhomogeneity.
• This technology provides a low-requirement, long-distance strain sensing capability, enhancing structural health monitoring.
• The sensor accurately captures global deformation while effectively filtering out localized strain anomalies caused by defects.