Long Gauge Fiber Bragg Grating Sensor Anchoring
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Solution Overview
Problem
Conventional sensors used in structural health monitoring for large-scale civil and transportation engineering structures have poor durability and stability, making them unsuitable for long-term real-time monitoring, and face issues with slippage and stress concentration in anchoring segments, limiting their effectiveness in harsh environments.
Innovation Solution
The development of long gauge fiber Bragg grating (LG-FBG) sensors with a manufacturing method that includes anchoring segments with variable elastic modulus resin, basalt fiber reinforcement, and pre-tensioning to enhance durability and prevent slippage, allowing for distributed area sensing and improved measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional strain foils are deployed for local sensing, then sensing capability at specific points is achieved, but durability and stability in harsh environments deteriorate
Solution Approach 1:
The patent replaces conventional electrical strain foils with optical fiber Bragg grating sensors. The optical fiber sensor uses light wavelength shifts to measure strain, eliminating the electrical components and mechanical structures of conventional strain foils that are susceptible to environmental degradation. This substitution provides both the sensing capability and the durability required for harsh environments.
Solution Approach 2:
The patent employs composite material structures including fiber-reinforced polymer (FRP) coatings and multi-layer protective coatings on the optical fiber. These composite structures provide mechanical protection, environmental resistance, and enhanced durability while maintaining the sensing functionality of the optical fiber core.
2Area of stationary object
If accelerometers are deployed for global sensing, then coverage area is increased, but measurement precision and relation to actual damage deteriorate
Solution Approach 1:
The patent segments the global sensing area into multiple distributed optical fiber sensor sections along the structure. Each section contains multiple Bragg grating sensors at different positions, creating a distributed sensing network that provides both wide coverage and localized measurement precision simultaneously.
Solution Approach 2:
The patent transitions from point-based accelerometer measurements to continuous distributed sensing along the optical fiber length. This adds a spatial dimension to the sensing capability, allowing precise localization of damage while maintaining global coverage through the extended fiber optic network.
3Measurement precision
If fiber Bragg grating sensors are packaged by fiber-reinforced polymer composites to achieve long gauge length, then distributed sensing capability is improved, but slippage between anchoring ends deteriorates
Solution Approach 1:
The patent applies preliminary anchoring treatments to the optical fiber ends before packaging, including specialized coating removal and surface preparation. This preliminary action ensures optimal bonding conditions that prevent slippage during subsequent packaging and long-term operation, maintaining both distributed sensing capability and anchoring stability.
Solution Approach 2:
The patent modifies the elastic modulus distribution in the anchoring segments through variable stiffness packaging materials. By changing the mechanical parameters of the packaging structure in different regions, the patent optimizes stress distribution and prevents slippage while maintaining the long gauge length and distributed sensing capabilities.
4Measurement precision
If strain foils are deployed at damage locations for local monitoring, then measurement precision is improved, but device durability deteriorates due to easy damage
Solution Approach 1:
The patent replaces fragile conventional strain foils with robust optical fiber sensors at damage-prone locations. The optical fiber's inherent flexibility and resistance to environmental damage provide both the precision needed for damage monitoring and the durability required to survive in harsh, damage-prone environments.
Solution Approach 2:
The patent uses composite protective packaging including FRP coatings and specialized protective layers on the optical fiber sensors deployed at damage locations. These composite structures provide enhanced mechanical protection while maintaining the sensor's measurement precision capabilities.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The LG-FBG sensors provide high durability and long-term stability, enabling effective monitoring of large-scale structures with improved accuracy and resistance to environmental factors like temperature and humidity, suitable for dynamic and static sensing across extensive areas.
Implementation Method 1
fiber Bragg grating sensor
Data Source
AI summary
A high-durability and long-scale-distance fiber grating sensor and a manufacturing method therefor, which relate to the technical field of fiber grating sensors. A fiber grating is disposed on the middle segment of a commercial optical fiber. A bushing, a woven fiber jacket layer, and a packaging structure are disposed on the periphery of the commercial optical fiber. The commercial optical fiber and the bushing therebetween are fixed by using fixing points in the bushing. Anchoring segments are disposed between the fixing points in the bushing and the woven fiber jacket layer. Two ends of the commercial optical fiber are sequentially connected to optical fibers on the anchoring segments and connecting optical fibers. Tail ends of the connecting optical fibers are connected to a transmission cable by using connecting flanges. By using the apparatus and the manufacturing method, the applicability and the durability of application of the fiber grating sensor in the civil traffic engineering field are improved, thereby providing a stable and reliable apparatus for long-time detection and sound monitoring of large engineering structures in the civil traffic engineering field.