Packaged FBG Sensors for Strain and Crack Tests on Asphalt Concrete Pavements

Abstract

The invention discloses a packaged FBG (Fiber Bragg Grating) sensor for strain and crack test of bituminous concrete road surface. The sensor comprises three spring FBGs, three pure FBGs, a prefabricated bituminous concrete packaging structure, six through grooves, a temperature sensing groove, a temperature sensor and an armored cable, wherein the three spring FBGs and the three pure FBGs are respectively embedded into the upper and lower layers of through grooves; then, one ends of the spring FBGs and one ends of the pure FBGs are fixedly connected with the bituminous concrete packaging structure by glue; the spring FBGs and the pure FBGs are applied with prestress, and then the other ends of the six groups of FBGs are fixedly connected; the temperature sensor is embedded into the temperature sensing region; and finally, the armored cable is connected with the six groups of educed FBGs and the temperature sensor. The sensor disclosed by the invention has the advantages of simple process, convenience for laying, high precision and large measuring range, can realize the monitoring of main stress direction and size of the bituminous concrete road surface, is suitable for inside change of the bituminous concrete rod surface in health monitoring of civil engineering structures and is also suitable for industrialization.

Description

technical field [0001] 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 [0002] 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...

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Problems solved by technology

[0004] (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

[0005] (2) Limitation of the measuring strain range: Due to the limitation of the stretching length of the fiber grating itself, the existing fiber grating 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.

[0006] (3) Limitation of monitoring strain type: the existing fiber grating 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

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