CN102278947A - Packaged FBG (Fiber Bragg Grating) sensor for strain and crack test of bituminous concrete road surface - Google Patents

Abstract

A packaged FBG sensor for strain and crack testing of asphalt concrete pavement, the sensor includes three spring fiber gratings, three pure fiber gratings, prefabricated asphalt concrete package structure, six through slots, temperature sensing slots, temperature sensors, armored fiber optic cable. Three spring optical fiber gratings and three pure optical fiber gratings were embedded in the upper and lower two-layer through grooves respectively, and then one end of the spring optical fiber gratings and pure optical fiber gratings was consolidated with the asphalt concrete package structure where they were located, and then the spring optical fiber gratings and pure optical fiber The grating is prestressed, and the other end of the six groups of fiber gratings is consolidated, and then the temperature sensor is embedded in the temperature sensing area, and finally the six groups of fiber gratings and the temperature sensor are connected with the armored optical cable. The sensor is simple in process, convenient in layout, high in accuracy and large in measuring range, and can monitor the principal stress direction and magnitude of asphalt concrete pavement.

Description

Packaged FBG sensor for strain and crack testing of asphalt concrete pavement

technical field

The invention relates to a packaged FBG sensor used for strain and crack testing of asphalt concrete pavement, specifically through the strain sensing technology based on fiber grating (FBG), using pure fiber grating and grating optical fiber consolidated with micro springs Two sets of strain rosettes realize the monitoring of the principal stress direction and magnitude of the asphalt concrete pavement. The sensor uses asphalt concrete to encapsulate the grating optical fibers with different functions inside to realize the protection of the optical fiber grating.

Background technique

It has only been a short ten years since the appearance of fiber gratings, but due to a series of advantages such as precision and durability of fiber gratings, it has rapidly developed into the focus of human science. The application of optical fiber in the field of communication has affected the daily life of tens of millions of people, and fiber gratings have gradually shown their importance in the field of monitoring and have been widely used.

Embedded fiber grating sensor is a new type of strain sensor based on fiber grating technology, which is widely used in the field of engineering monitoring and gradually replaces traditional strain gauges. However, most fiber grating sensors are used to monitor the stress state of concrete structures such as large bridges, dams, highways, tunnels, and high-rise buildings, but rarely involved in the monitoring of asphalt concrete pavements. At the same time, the only fiber grating sensors used to measure the internal strain of asphalt concrete also have the following two problems:

(1) Errors caused by packaging materials: Since bare fiber gratings are too thin, they are easily damaged during road construction when embedded in asphalt concrete pavement. Therefore, fiber gratings must be packaged to protect them from external damage. Existing sensors mostly use non-asphalt concrete materials such as composite materials, steel pipes, and steel sheets as packaging materials. Since the elastic modulus of such materials is inconsistent with the elastic modulus of asphalt concrete in the environment to be measured, the sensor will make the surrounding area The stress field and strain field are redistributed, resulting in a large difference between the measured strain result and the true value.

(2) Limitation of the measurement strain range: Due to the limitation of the stretching length of the FBG itself, the existing FBG strain sensor can only monitor the small strain in the asphalt concrete structure. However, for asphalt concrete structures subject to large external loads such as pavements, large strains and even cracks are often generated inside, and existing sensors will not be able to meet the monitoring requirements.

(3) Limitation of monitoring strain type: the existing FBG sensor can only monitor the strain in a certain direction in the concrete, and cannot measure the magnitude and direction of the principal strain in the concrete plane.

Contents of the invention

The invention provides an optical fiber grating sensor capable of accurately monitoring the strain and cracks of asphalt concrete pavement. The sensor is packaged with asphalt concrete, which is the material of the monitored asphalt concrete pavement. Using the same material, it overcomes the influence of different elastic moduli of different materials on the monitoring results: the optical fiber grating in the sensor is arranged in a triangular strain rosette, and through the triangular In the strain rosette, the measurement of each strain can accurately monitor the direction and magnitude of the principal stress of the concrete plane. The gratings in the sensor all work at a large gauge distance, and the effective working range is increased, so it can reflect the material strain more realistically and objectively, and overcome the relatively large impact that accidental factors may have on the monitoring; the spring grating strain flower is buried inside the sensor, realizing Effective monitoring of large strains, large cracks and even large cracks; the combined application of pure grating rosettes, spring grating rosettes, and temperature sensing gratings in the sensor not only realizes high and low precision complementary work, but also realizes effective monitoring of large and small strains. The temperature compensation is adopted to solve the influence of temperature on the measurement results during measurement.

Technical scheme of the present invention is as follows:

The packaged FBG sensor for strain and crack testing of asphalt concrete pavement includes three spring fiber gratings, three pure fiber gratings, a prefabricated asphalt concrete package structure, six through slots, a temperature sensing slot, a temperature sensor and an armored optical cable. The prefabricated asphalt concrete mold has six through-slots and one temperature-sensing slot. The six through-slots are divided into upper and lower layers, with three upper and lower layers each; three spring fiber gratings in tension are placed in the upper three The spring grating rosette is formed in the through groove; three pure optical fiber gratings are placed in the three through grooves of the lower layer to form a pure grating rosette; The two ends of the groove are consolidated; the temperature sensor is placed in the temperature sensing groove, and the spring fiber grating, pure fiber grating and temperature sensor are connected and led out with armored optical cables.

The invention has the beneficial effects of simple process, suitable for industrial production, and low cost; it can monitor the principal stress direction and size of the asphalt concrete plane for a long time; the packaging material adopted by the sensor is asphalt concrete, and the measurement accuracy is high.

Description of drawings

Figure 1 is a schematic diagram of the prefabricated asphalt concrete package structure.

Figure 2 is a schematic diagram of the structure of the packaged FBG sensor used for strain and crack testing of asphalt concrete pavement.

Fig. 3 is a sectional view A-A of the packaged FBG sensor of the present invention.

Fig. 4 is a B-B sectional view of the packaged FBG sensor of the present invention.

In the figure: 1 spring fiber grating; 2 pure fiber grating; 3 temperature sensor; 4 armored optical cable; 5 prefabricated asphalt concrete encapsulation structure;

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with technical solutions and accompanying drawings.

Fiber Bragg grating strain sensor structure, the structure is shown in Figure 1, Figure 2, Figure 3 and Figure 4, the strain sensor includes three spring fiber Bragg gratings 1, three pure fiber Bragg gratings 2, prefabricated asphalt concrete packaging structure 5, two through Groove 6, temperature sensing groove 7, temperature sensor 3 and armored optical cable 4. First, respectively embed three spring fiber gratings and three pure fiber gratings in the upper and lower two-layer through grooves, and then use glue to consolidate one end of the spring fiber gratings and pure fiber gratings with the asphalt concrete package structure, and finally fix the spring fiber gratings, The pure fiber grating is prestressed, and then the other end of the six groups of fiber gratings is consolidated, and then the temperature sensor is embedded in the temperature sensing area, and finally the six groups of fiber gratings and the temperature sensor are connected with the armored optical cable.

Claims (1)

1. packaging FBG sensor that is used for the test of bituminous concrete pavement strain, crackle, it is characterized in that this application bituminous concrete packaging FBG strain transducer comprises spring fiber grating (1), three pure fiber gratings (2), three prefabricated pitch bituminous concrete encapsulating structures (5), six through slots (6), temperature-sensitive groove (7), temperature sensor (3), armouring optical cable (4); Prefabricated bituminous concrete encapsulating structure has six through slots and a temperature-sensitive groove, and six through slots are divided into upper and lower two layers, each three of the upper and lower; Three spring fiber gratings that are in tensile state place three through slots on upper strata, form the spring grating strain floriation; Three pure fiber gratings place three through slots of lower floor, form pure grating strain floriation; Residing through slot two ends are fixed respectively with separately for the two ends of spring fiber grating, the two ends of pure fiber grating; Temperature sensor places the temperature-sensitive groove, and spring fiber grating, pure fiber grating and temperature sensor connect with the armouring optical cable draws.

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