Fiber Grating Sensor Packaging for Bridge Cable Monitoring
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Solution Overview
Problem
Existing fiber grating sensors integrated into bridge cables face challenges such as fragility, packaging issues, unreliable embedding technology, and signal distortion when monitoring stress and temperature parameters, which affect their survival rates and reliability in harsh environments.
Innovation Solution
A fiber grating sensor is integrated into the connecting cylinder of the cable, using a package structure with steel pipes and heat shrinkable sleeves to protect the sensor, and a demodulator is used to measure the central wavelength changes, allowing real-time monitoring of stress distribution and overall stress without signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fiber grating is directly laid in the cable without special treatment, then the cable structure remains simple, but the fiber grating is easily broken due to its fragility
Solution Approach 1:
A protective steel pipe is introduced as an intermediary between the fiber grating and the cable environment. The steel pipe encapsulates the fragile fiber grating, providing mechanical protection while allowing the fiber to sense strain through the pipe wall, thus resolving the contradiction between structural simplicity and sensor reliability
Solution Approach 2:
The sensor package combines multiple materials with complementary properties: the steel pipe provides mechanical strength and protection, while the fiber grating provides sensing capability. This composite structure allows the system to simultaneously achieve durability in harsh environments and functional sensitivity
2Reliability
If fiber grating sensor is packaged with protection steel pipe, then the fiber grating survival rate improves, but the cable structure becomes more complex
Solution Approach 1:
The fiber grating is nested within the protective steel pipe, which itself is embedded within the cable structure. This nested arrangement provides multiple levels of protection while maintaining a compact overall structure, balancing reliability enhancement with structural complexity
3Extent of automation
If fiber grating is embedded in the cable, then real-time monitoring of stress and temperature is enabled, but signal distortion may occur
Solution Approach 1:
The protective steel pipe acts as an intermediary that transmits mechanical strain from the cable to the fiber grating sensor. This intermediate structure ensures that the fiber experiences accurate strain measurements without direct contact with the cable, preventing signal distortion while enabling real-time monitoring
Solution Approach 2:
The system monitors changes in the fiber grating's physical parameters (strain, temperature) and converts them into optical signal changes (wavelength shift). This parameter transformation enables accurate measurement while isolating the sensor from direct cable contact, preventing signal distortion
4Extent of automation
If fiber grating sensor is integrated into cable, then automatic sensing capability is achieved, but embedding technology reliability is compromised
Solution Approach 1:
The fiber grating is pre-protected with the steel pipe and pre-assembled into a complete sensor package before being embedded in the cable. This preliminary preparation ensures that the fragile sensor is already protected and ready for installation, significantly improving the reliability of the embedding process and long-term operation
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
This solution enhances the reliability and survival rates of fiber grating sensors, enabling real-time monitoring of bridge cable stress and temperature, thereby improving bridge safety and structural health monitoring.
Implementation Method 1
A fiber grating is a sensitive element with excellent performance, and senses external slight strain change through movement of Bragg reflection wavelength
Data Source
AI summary
A bridge intelligent cable system with a built-in fiber grating sensor is provided, which is applied in a cable bearing structure such as a cable-stayed bridge, a suspension bridge, and an arch bridge. The system includes an anchor cup (1), a wire dividing plate (5), a connecting cylinder (4), a fiber grating sensor, and a cable body (11), in which the fiber grating sensor includes a fiber grating strain sensor (9) and a fiber grating temperature sensor (10), tail fibers of the fiber grating strain sensor (9) and the fiber grating temperature sensor (10) are led out, the packaged fiber grating strain sensor (9) is fixedly connected to an outer-layer steel wire (3) of the connecting cylinder (4), the packaged fiber grating temperature sensor (10) is suspended on the steel wire (3) of the connecting cylinder (4), holes (5-1) are punched in the wire dividing plate (5), and a preserved steel pipe (7) is buried in advance in the connecting cylinder (4) and the anchor cup (1). The system improves survival rates of the fiber grating sensor and the fibers in cable manufacturing and application processes, ensures reliability of the embedding technology of the fiber grating sensor, and effectively leads a fiber grating signal out of the cable body without distortion.