Hybrid-range FBG (fiber bragg grating) strain and crack sensor for concrete material package

Abstract

The invention discloses a hybrid-range FBG (fiber bragg grating) strain and crack sensor for a concrete material package. The sensor comprises a pre-cast concrete material package structure, a spring FBG firmly combined with a micro spring, a pure FBG, a temperature sensor, two penetration grooves, a temperature sensing area and an armored optical cable. Firstly, the pure FBG and the spring FBG firmly combined with the micro spring are embedded in the two penetration grooves, then, one segment of two groups of the FBG is firmly combined with a die through a high-performance adhesive, a tension pre-stress is applied on the two groups of the FBG, and then, the other end of each one of the two groups of the FBG is firmly combined, the temperature sensor is embedded in the package structure, and finally, the armored optical cable is used for connecting the two groups of the led out FBG and the temperature sensor. The hybrid-range FBG strain and crack sensor is suitable for structural health monitoring in various concrete structures of civil engineering, is simple in technology, convenient to arrange, high in accuracy and wide in range, and can monitor internal strain and cracks in overall process of destroying the concrete structure by pulling and pressing.

Description

technical field [0001] The present invention relates to a kind of sensor that uses optical fiber grating to monitor the strain in the concrete, specifically is to use the optical fiber grating (FBG) based strain sensing technology, respectively through pre-tensioned optical fiber grating and the spring grating consolidated with the micro spring The optical fiber realizes the measurement of small strain, large strain and even crack inside the concrete. The sensor uses concrete to encapsulate the grating fiber to protect the fiber grating, and more importantly, eliminate the measurement error caused by the mismatch of the elastic modulus of the package structure. Background technique [0002] Fiber Bragg Grating (FBG) is a brand-new sensing technology that has opened up a new path along with the development of optical fiber and optical fiber communication technology. In the past 10 years, it has become the fastest growing technology in the field of sensors and is considered to...

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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 concrete construction when embedded in concrete structures. Therefore, fiber gratings must be packaged to protect them from external damage

However, the existing sensors mostly use non-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 concrete in the environment to be measured, such sensors will make nearby The stress field and strain field of the region 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 concrete structure

However, for concrete structures subject to large external loads such as pavements, large strains and even cracks are often generated inside, and the existing sensors will not be able to meet the monitoring requirements.

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