Distributed crack monitoring network and application thereof

Abstract

The invention discloses a distributed crack monitoring network and an application thereof, a glass fiber geogrid which has good synergy with concrete and can transmit strain to the greatest extent is used as a flexible substrate, and a plurality of fiber grating sensors of which the scale length is determined to be 100mm through experimental optimization are consolidated on the flexible substrate in a distributed manner, so that an integrated sensing network is formed. The monitoring net can be directly adhered to the surface of a concrete test piece, and strain is sensed through a sensing network so as to monitor generation and expansion of cracks in real time. According to the invention, the glass fiber geogrid is selected and combined with the optimal sensor scale distance of 100mm, so that high-efficiency strain transmission is ensured, the monitoring sensitivity and precision of the microcrack are remarkably improved, and distributed and long-term monitoring of a large-range area is realized. The design and manufacture are simple and convenient, the cost is low, the layout is flexible, and an economical, efficient and reliable solution is provided for structural health monitoring.

Description

Technical Field

[0001] This invention belongs to the field of engineering structure technology and relates to a novel gauge length optimized FBG-geogrid composite crack monitoring network. Background Technology

[0002] Airport pavements are prone to cracking under the combined effects of long-term, high-frequency, and high-intensity aircraft loads and environmental factors, directly impacting operational safety and structural durability. Current crack monitoring of cement concrete pavements mainly relies on manual inspections or traditional point sensors. The former is inefficient and limited by operational time windows, while the latter struggles to achieve distributed, real-time monitoring over large areas. While fiber optic grating (FBG) sensing technologies offer advantages such as resistance to electromagnetic interference and the ability to achieve long-distance distributed measurements, their application to pavements still faces challenges including low sensor deployment efficiency, insufficient ability to coordinate with pavement deformation, and difficulty in guaranteeing long-term stability, resulting in high monitoring costs and limited accuracy. Therefore, developing a distributed crack monitoring technology that can be efficiently deployed, coordinates with pavement deformation, and combines good monitoring performance with cost-effectiveness is crucial for achieving real-time perception and intelligent operation and maintenance of airport pavement structural conditions. Summary of the Invention

[0003] To address the challenge of monitoring cracks in airport pavements, this invention proposes a gauge-optimized FBG-geogrid composite crack monitoring network to achieve efficient monitoring of airport pavement cracks.

[0004] The technical solution adopted in this invention is: a distributed crack monitoring network, wherein the monitoring network includes a flexible substrate, and the flexible substrate is a geogrid structure; It also includes multiple fiber Bragg grating (FBG) sensors, which are fixed on the geogrid. The length of the grating of each FBG sensor is the gauge length, and the lengths are equal.

[0005] Furthermore, the gauge length ranges from 30mm to 150mm.

[0006] Furthermore, the two ends of the fiber Bragg grating sensor are fixedly connected to the geogrid, and the middle part of the fiber Bragg grating sensor is suspended and in a taut state.

[0007] Furthermore, the distributed crack monitoring network is adhered to the clean surface of the test piece, and the strain change of the test piece is monitored by the fiber optic grating sensor to obtain the detection result of whether there are cracks on the surface of the test piece.

[0008] In a preferred embodiment of this application, the gauge length is 100 mm.

[0009] Compared with the prior art, the advantages of the present invention are as follows: 1. Compared with traditional point sensors, this invention pre-integrates multiple sensors onto a geogrid to form a "plug-and-play" sensor network, which greatly simplifies the on-site installation process, reduces the sensing cost per unit area and time cost, and is suitable for monitoring scenarios with large-scale and densely distributed points.

[0010] 2. The core innovation of this invention lies in the experimental determination that the optimal gauge length for the FBG sensor to monitor concrete cracks is 100 mm. This gauge length can both capture the early initiation of micro-cracks and effectively track their subsequent expansion, avoiding the problems of insufficient measurement range of traditional short-gauge sensors or decreased sensitivity of long-gauge sensors, thus obtaining more accurate and reliable quantitative monitoring data.

[0011] 3. The entire crack monitoring network exhibits excellent corrosion resistance and aging resistance, and the FBG sensor itself is resistant to electromagnetic interference. The full-coverage fixation with epoxy resin effectively protects the sensor and interface, enabling the monitoring system to operate stably for a long time in harsh engineering environments such as humidity and salt spray, overcoming the shortcomings of traditional electrical sensors that are susceptible to environmental influences and have poor long-term stability.

[0012] 4. The monitoring network is a flexible, thin sheet structure that can be directly pasted onto the surface of the specimen without drilling or pre-embedding. It is a non-destructive installation and is especially suitable for health monitoring and assessment of existing structures, with a wide range of applications. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the FBG-geogrid composite crack monitoring network with gauge length optimized according to this application: In the figure, 1-concrete specimen, 2-fiberglass geogrid, 3-FBG sensor, 4-grating, 5-sensor attachment point. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1:

[0017] This embodiment is a distributed crack monitoring network, the monitoring network includes a flexible substrate, the flexible substrate being a geogrid structure; It also includes multiple fiber Bragg grating (FBG) sensors, which are fixed on the geogrid. The length of the grating of each FBG sensor is the gauge length, and the lengths are equal.

[0018] Furthermore, the gauge length ranges from 30mm to 150mm. Furthermore, both ends of the fiber Bragg grating sensor are fixedly connected to the geogrid, while the middle of the fiber Bragg grating sensor is suspended and taut.

[0019] Furthermore, the distributed crack monitoring network is adhered to the clean surface of the test piece, and the strain change of the test piece is monitored by the fiber optic grating sensor to obtain the detection result of whether there are cracks on the surface of the test piece.

[0020] Based on the above-mentioned solutions, this embodiment, as a preferred embodiment of this application, has a gauge length of 100 mm. This gauge length can both capture the initiation of micro-cracks at an early stage and effectively track the subsequent expansion of cracks, avoiding the problems of insufficient range of traditional short gauge length sensors or decreased sensitivity of long gauge length sensors, thereby obtaining more accurate and reliable quantitative monitoring data.

[0021] Example 2:

[0022] 1. Integration of the monitoring network substrate and sensing units: Fiberglass geogrid was used as a flexible, high-tensile-strength distributed sensing substrate. Fiber Bragg grating sensors were employed as sensing units, with their gauge length optimized experimentally to be 100 mm. The sensors were arranged in a distributed array on the geogrid. Each sensor was installed and fixed only at its two ends (i.e., the two endpoints) to the geogrid. Initial positioning was achieved using 502 glue, followed by permanent, high-strength fixation with epoxy resin. During the bonding process, it was crucial to ensure that the sensor fiber was axially taut and straight between the two points to avoid any impact on measurement accuracy due to slack.

[0023] 2. Installation of the monitoring network on the specimen surface: First, clean the surface of the area to be monitored on the concrete specimen. Then, lay the geogrid monitoring network integrating the FBG sensor in this area. Use the same two-step bonding method as for sensor fixing: first, use 502 glue to initially bond and position the geogrid onto the specimen surface; then, use epoxy resin adhesive to perform a large-area, full-coverage final fixation of the entire geogrid substrate and the specimen contact surface. This step ensures a high degree of coordination between the deformation of the substrate and the specimen surface.

[0024] 3. Curing and Formation: After the epoxy resin has fully cured, the geogrid, FBG sensor, and concrete specimen surface bond together to form a complete and co-deformable mechanical whole. At this point, a reliable strain transfer path is formed among the FBG sensor, the matrix, and the specimen.

[0025] 4. Monitoring and Data Processing: The optical fibers leading from all FBG sensors in the monitoring network are connected to the fiber optic demodulator. When the specimen deforms or cracks under external loads, the strain is effectively transferred to the 100mm gauge length of each FBG sensor through the geogrid matrix, causing Bragg wavelength drift. Wavelength data is acquired in real time by the demodulator, allowing for the calculation of strain at each measuring point. By analyzing anomalies in the distributed strain field (such as strain abrupt peaks or discontinuities), the initiation location of cracks can be accurately identified, the crack opening width quantified, and their propagation trend monitored in real time.

[0026] First, the FBG sensors with a gauge length of 100mm are initially fixed to the predetermined positions on the fiberglass geogrid using 502 glue, ensuring the sensor fibers are taut. Then, the ends are reinforced with epoxy resin to create an integrated monitoring network. Next, the specimen surface is cleaned, and the monitoring network is initially positioned and adhered to the test area using 502 glue. Finally, the entire geogrid is completely covered and fixed with epoxy resin. After the epoxy resin cures, the monitoring network and specimen are integrated into a single unit. Finally, the optical fiber is connected to a demodulator. By real-time acquisition and analysis of the strain field formed by the wavelength changes of each FBG sensor, the location of cracks can be identified and their development monitored.

[0027] As shown in the figure, there are three FBG sensors (AB—FBG1, BC—FBG2, CD—FBG3). FBG installation: First, use 502 glue to fix one end of FBG1 to point A on the geogrid, keeping it taut, then use 502 glue to fix the other end of FBG1 to point B. Repeat the above steps for the second sensor, FBG2: first fix one end of FBG2 to point B, keeping it taut, then use 502 glue to fix the other end of FBG2 to point C. Repeat the same steps for the third sensor, FBG3. The three sensors are connected end-to-end to ensure that cracks throughout the entire monitoring area can be detected. Finally, at points A, B, C, and D, and at the ends of the FBGs fixed with 502 glue, epoxy resin is used for encapsulation to prevent breakage at the ends during monitoring. This implementation method, through gauge length optimization, a reliable bonding process, and the combination of a flexible substrate, achieves stable, distributed crack monitoring.

[0028] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, for the device embodiments, the above descriptions are merely preferred embodiments of the present invention. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple, and relevant parts can be referred to the descriptions of the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, without departing from the principle of the present invention, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A distributed crack monitoring network, characterized in that, The detection net includes a flexible substrate, which is a geogrid structure; It also includes multiple fiber Bragg grating (FBG) sensors, which are fixed on the geogrid. The length of the grating of each FBG sensor is the gauge length, and the lengths are equal.

2. The distributed crack monitoring network according to claim 1, characterized in that, The gauge length ranges from 30mm to 150mm.

3. The distributed crack monitoring network according to claim 1, characterized in that, The two ends of the fiber Bragg grating sensor are fixedly connected to the geogrid, and the middle part of the fiber Bragg grating sensor is suspended and in a taut state.

4. The distributed crack monitoring network according to claim 2 or 3, characterized in that, The gauge length is 100 mm.

5. The application of the distributed crack monitoring network according to any one of claims 1 to 4, characterized in that, The distributed crack monitoring network is attached to the clean surface of the test piece, and the strain change of the test piece is monitored by the fiber optic grating sensor to obtain the detection result of whether there are cracks on the surface of the test piece.

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