Concrete beam deformation measuring device based on ultra-weak fiber grating sensing

Abstract

The utility model discloses a concrete beam deformation measuring device based on ultra-weak fiber bragg grating sensing, which comprises a concrete beam to be measured, an ultra-weak fiber bragg grating strain sensing optical cable, an ultra-weak fiber bragg grating demodulator and an upper computer, a reinforcing bonding layer is arranged between the bottom of the to-be-tested concrete beam and the outer-layer carbon fiber cloth, the to-be-tested concrete beam is bonded and matched with the outer-layer carbon fiber cloth through the reinforcing bonding layer, and an ultra-weak fiber grating strain sensing optical cable is embedded in the middle of the reinforcing bonding layer; one end of the ultra-weak fiber bragg grating strain sensing optical cable penetrates through the reinforcing bonding layer and then is electrically connected with an ultra-weak fiber bragg grating demodulator through an optical fiber patch cord, and the ultra-weak fiber bragg grating demodulator is electrically connected with an upper computer through an electric wire; the device is reasonable in structure, easy to construct and good in use durability, and the deflection deformation of the concrete beam is monitored in real time under the condition that the concrete beam body is not damaged.

Description

Technical Field

[0001] The utility model relates to the technical field of deformation monitoring of concrete beams, in particular to a concrete beam deformation measuring device based on ultra-weak fiber Bragg grating sensing. Background Technique

[0002] A concrete beam refers to a reinforced concrete beam. At present, as a basic concrete building structure, the reinforced concrete beam has been widely used in engineering construction fields such as civil engineering and water conservancy projects. However, due to various factors such as years of aging, construction quality, and natural disasters, the reinforced concrete beam structure is prone to quality problems such as beam body deformation and cracks, which will directly affect the service life of the project. Especially if the problem of beam body deformation fails to be detected, engineering safety accidents may occur. Therefore, the real-time monitoring of the deformation of concrete beams has become an important option for engineering safety.

[0003] At present, for the deformation monitoring of concrete beams, traditional sensors such as embedded steel bar stress gauges and resistive strain gauges are mainly used. These sensors are easily affected by the monitoring environment, and their monitoring capabilities are limited in some relatively harsh engineering environments, and their monitoring life is short, and they cannot meet the requirements of long-term distributed monitoring of concrete beams. Content of the Utility Model

[0004] The utility model provides a concrete beam deformation measuring device based on ultra-weak fiber Bragg grating sensing, aiming to solve many problems of existing concrete beam deformation monitoring facilities in terms of multiplexing capacity, measurement accuracy, and durability.

[0005] To solve the above technical problems, the technical solution adopted by the utility model is:

[0006] A concrete beam deformation measuring device based on ultra-weak fiber Bragg grating sensing includes a concrete beam to be measured, an ultra-weak fiber Bragg grating strain sensing optical cable, an ultra-weak fiber Bragg grating demodulator, and a host computer. The bottom of the concrete beam to be measured is flat and provided with an outer carbon fiber cloth. There is a reinforcement adhesive layer between the bottom of the concrete beam to be measured and the outer carbon fiber cloth, and the concrete beam to be measured forms an adhesive fit with the outer carbon fiber cloth through the reinforcement adhesive layer. The ultra-weak fiber Bragg grating strain sensing optical cable is buried in the middle position of the reinforcement adhesive layer. One end of the ultra-weak fiber Bragg grating strain sensing optical cable penetrates through the reinforcement adhesive layer and is electrically connected to the ultra-weak fiber Bragg grating demodulator through an optical fiber jumper. The ultra-weak fiber Bragg grating demodulator is electrically connected to the host computer through an electric wire.

[0007] Preferably, the middle position in the longitudinal direction of the concrete beam to be measured coincides with the middle position of the reinforcement adhesive layer in the vertical direction, and the ultra-weak fiber Bragg grating strain sensing optical cable is parallel to the middle position in the longitudinal direction of the concrete beam to be measured.

[0008] More preferably, both the reinforcement adhesive layer and the outer carbon fiber cloth are flat.

[0009] Furthermore, the reinforcement bonding layer is made of a fiber resin matrix composite material, and the thickness of the reinforcement bonding layer is greater than the diameter of the ultra-weak fiber Bragg grating strain sensing optical cable.

[0010] Even further, the outer carbon fiber cloth is a unidirectional carbon fiber cloth with a thickness of 0.1 mm - 0.17 mm.

[0011] Specifically, the ultra-weak fiber Bragg grating strain sensing optical cable includes an ultra-weak fiber Bragg grating core, and an optical fiber cladding is concentrically and coaxially wrapped around the periphery of the ultra-weak fiber Bragg grating core, and an optical fiber coating is concentrically and coaxially wrapped around the periphery of the optical fiber cladding.

[0012] More specifically, ultra-weak fiber Bragg grating arrays are inscribed at equal intervals along the axial direction at the central position inside the ultra-weak fiber Bragg grating core.

[0013] Advantages of the present utility model:

[0014] The present utility model introduces ultra-weak fiber Bragg gratings into the deformation monitoring of concrete beams, and proposes a concrete beam deformation measuring device based on ultra-weak fiber Bragg grating sensing. Without damaging the concrete beam body, this device can monitor the deflection deformation of the concrete beam in real time, and has good application prospects. Description of the drawings

[0015] Figure 1 is the overall schematic diagram of the measuring device of the present utility model;

[0016] Figure 2 is the schematic diagram of the optical cable embedding of the measuring device of the present utility model;

[0017] Figure 3 is the schematic diagram of the optical cable structure of the measuring device of the present utility model;

[0018] In the figure: 1. Ultra-weak fiber Bragg grating strain sensing optical cable; 101. Ultra-weak fiber Bragg grating core; 1011. Ultra-weak fiber Bragg grating array; 102. Optical fiber cladding; 103. Optical fiber coating; 2. Reinforcement bonding layer; 3. Outer carbon fiber cloth; 4. Concrete beam to be measured; 5. Optical fiber jumper; 6. Ultra-weak fiber Bragg grating demodulator; 7. Host computer. Specific embodiments

[0019] As follows, the embodiments will be further described with reference to the drawings.

[0020] As Figures 1 to 3As shown in the figure, as a preferred Embodiment 1, a deformation measurement device for a concrete beam based on ultra-weak fiber Bragg grating sensing includes a concrete beam 4 to be measured, an ultra-weak fiber Bragg grating strain sensing optical cable 1, an ultra-weak fiber Bragg grating demodulator 6, and a host computer 7. The bottom of the concrete beam 4 to be measured is flat and provided with an outer carbon fiber cloth 3. There is a reinforcing adhesive layer 2 between the bottom of the concrete beam 4 to be measured and the outer carbon fiber cloth 3. And the concrete beam 4 to be measured forms an adhesive fit with the outer carbon fiber cloth 3 through the reinforcing adhesive layer 2. The ultra-weak fiber Bragg grating strain sensing optical cable 1 is buried in the middle position of the reinforcing adhesive layer 2. One end of the ultra-weak fiber Bragg grating strain sensing optical cable 1 penetrates through the reinforcing adhesive layer 2 and is electrically connected to the ultra-weak fiber Bragg grating demodulator 6 through an optical fiber jumper 5. The ultra-weak fiber Bragg grating demodulator 6 is electrically connected to the host computer 7 through an electric wire. The ultra-weak fiber Bragg grating demodulator 6 demodulates and analyzes the reflection pulse signal of the ultra-weak fiber Bragg grating strain sensing optical cable 1 to obtain the deformation information of the concrete beam 4 to be measured, and transmits it to the host computer 7. The host computer 7 receives the data from the ultra-weak fiber Bragg grating demodulator 6 and processes it.

[0021] Preferably, the host computer 7 can be a computer; the ultra-weak fiber Bragg grating strain sensing optical cable 1 can be a 900μm tight-buffered optical fiber; the ultra-weak fiber Bragg grating demodulator 6 can be an RS-HFBGA-04 decimeter-level ultra-weak fiber Bragg grating wavelength demodulation module, which is based on real-time wavelength demodulation at the bottom layer, has strong spatial resolution ability and high resolution, adopts the TDM+WDM multiplexing method, and the number of sensors that can be multiplexed on a single optical fiber exceeds 20,000; the system integration is high, and multi-channel expansion can be realized to achieve multi-measurement line integration.

[0022] The middle position in the longitudinal direction of the concrete beam 4 to be measured coincides with the middle position of the reinforcing adhesive layer 2 in the vertical direction, and the ultra-weak fiber Bragg grating strain sensing optical cable 1 is parallel to the middle position in the longitudinal direction of the concrete beam 4 to be measured. Ensure that the strain of the concrete beam can be transmitted to the internal ultra-weak fiber Bragg grating strain sensing optical cable 1, and the ultra-weak fiber Bragg grating strain sensing optical cable 1 is uniformly stressed.

[0023] Both the reinforcing adhesive layer 2 and the outer carbon fiber cloth 3 are flat.

[0024] The reinforcing adhesive layer 2 is made of a fiber resin-based composite material, and the thickness of the reinforcing adhesive layer 2 is greater than the diameter of the ultra-weak fiber Bragg grating strain sensing optical cable 1.

[0025] The outer carbon fiber cloth 3 is a unidirectional carbon fiber cloth with a thickness of 0.1mm - 0.17mm.

[0026] The ultra-weak fiber Bragg grating strain sensing optical cable 1 includes an ultra-weak fiber Bragg grating core 101, an optical fiber cladding 102 is coaxially wrapped around the periphery of the ultra-weak fiber Bragg grating core 101, and an optical fiber coating 103 is coaxially wrapped around the periphery of the optical fiber cladding 102.

[0027] An ultra-weak fiber grating array 1011 is inscribed at equal intervals along the axial direction at the central position within the core 101 of the ultra-weak fiber grating.

[0028] As a preferred Embodiment 2, the ultra-weak fiber grating array 1011 in the ultra-weak fiber grating strain sensing optical cable 1 reconstructs the linear deformation of the concrete beam through the relationship between the central wavelength drift value of the Bragg grating and the curvature.

[0029] The calculation formula for the central wavelength of the Bragg grating is:

[0030] ,

[0031] In the formula, λ B is the central wavelength of the Bragg grating, n eff is the effective refractive index of the core, and ∧ is the period of the ultra-weak fiber grating.

[0032] The principle of the formula is: The central wavelength of the Bragg grating of the ultra-weak fiber grating strain sensing optical cable 1 is affected by the effective refractive index of the core and the period of the ultra-weak fiber grating. Changes in external physical quantities such as the strain and temperature of the concrete beam, which cause changes in the fiber period and the effective refractive index of the core, will cause the central wavelength of the Bragg grating of the ultra-weak fiber grating strain sensing optical cable 1 to drift;

[0033] The calculation formula for the change amount of the central wavelength of the Bragg grating of the ultra-weak fiber grating strain sensing optical cable 1 is:

[0034] ,

[0035] In the formula, Δλ B is the change amount of the central wavelength of the Bragg grating of the ultra-weak fiber grating strain sensing optical cable, Δn eff is the change amount of the effective refractive index of the core caused by the elasto-optic effect or the thermo-optic effect, and Δ∧ is the change amount of the period of the ultra-weak fiber grating caused by the thermal expansion effect or the stress strain.

[0036] When the ultra-weak fiber grating strain sensing optical cable 1 is affected by external stress strain and temperature changes, the calculation formula for the change amount of its Bragg central wavelength is:

[0037] ,

[0038] When the external temperature is constant and the stress strain changes, , and at this time, the calculation formula for the change amount of the central wavelength of the Bragg grating of the ultra-weak fiber grating strain sensing optical cable is:

[0039] .

[0040] The calculation formula for the curvature at the grating is:

[0041] ,

[0042] Use the chamfering recurrence algorithm for curve reconstruction. For a curve, when the distance between two points on the curve is small enough, the arc segment between these two points can be approximately regarded as a small circular arc.

[0043] According to the definition of curvature, it can be known that integrating the curvature can obtain the deformation curve equation of the concrete beam:

[0044] 。

[0045] As a preferred embodiment 3, the concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing, wherein the measurement includes the following steps:

[0046] Step 1: Grind the surface of the concrete beam 4 to be measured smoothly, evenly coat a layer of fiber resin-based composite material on the surface of the concrete beam 4 to be measured as the reinforcement bonding layer 2. Subsequently, arrange the ultra-weak fiber Bragg grating strain sensing optical cable 1 with a predetermined length longitudinally and parallelly on the center line of the reinforcement bonding layer 2 along the concrete beam. After completing the arrangement of the ultra-weak fiber Bragg grating strain sensing optical cable 1, lay the outer carbon fiber cloth 3 on the reinforcement bonding layer 2 as the external protection layer. After the laying is completed, connect the ultra-weak fiber Bragg grating strain sensing optical cable 1 to the ultra-weak fiber Bragg grating demodulator 6 through the fiber jumper 5;

[0047] Step 2: After the reinforcement bonding layer 2 is cured, connect the ultra-weak fiber Bragg grating demodulator 6 to the host computer 7, check the circuit, and check whether the ultra-weak fiber Bragg grating array 1011 in the ultra-weak fiber Bragg grating strain sensing optical cable 1 is alive;

[0048] Step 3: Apply static load to the concrete beam. The ultra-weak fiber Bragg grating demodulator 6 collects and demodulates the fiber wavelength change data of the ultra-weak fiber Bragg grating strain sensing optical cable 1 under different loads, thereby analyzing the distribution of load and strain, and transmitting the data to the host computer 7 to display the static load bearing deformation of the concrete beam and analyze the results.

[0049] The working principle of the present utility model:

[0050] The present utility model demodulates and analyzes the reflection pulse signal of the ultra-weak fiber Bragg grating strain sensing optical cable 1 by the ultra-weak fiber Bragg grating demodulator 6 to obtain the deformation information of the concrete beam 4 to be measured, and transmits it to the host computer 7. The host computer 7 receives the data from the ultra-weak fiber Bragg grating demodulator 6 and processes it.

Claims

1. A concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing, comprising a concrete beam to be measured (4), an ultra-weak fiber Bragg grating strain sensing optical cable (1), an ultra-weak fiber Bragg grating demodulator (6) and a host computer (7), characterized in that: The bottom of the concrete beam to be tested (4) is flat and provided with an outer layer of carbon fiber cloth (3); a reinforcing adhesive layer (2) is provided between the bottom of the concrete beam to be tested (4) and the outer layer of carbon fiber cloth (3); the concrete beam to be tested (4) is bonded to the outer layer of carbon fiber cloth (3) through the reinforcing adhesive layer (2); an ultra-weak fiber Bragg grating strain sensing optical cable (1) is buried in the middle of the reinforcing adhesive layer (2); one end of the ultra-weak fiber Bragg grating strain sensing optical cable (1) passes through the reinforcing adhesive layer (2) and is electrically connected to an ultra-weak fiber Bragg grating demodulator (6) through an optical fiber jumper (5); and the ultra-weak fiber Bragg grating demodulator (6) is electrically connected to a host computer (7) through an electric wire.

2. The concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing according to claim 1 is characterized in that: The longitudinal middle position of the concrete beam (4) to be measured overlaps with the longitudinal middle position of the reinforcing adhesive layer (2) in the vertical direction, and the ultra-weak fiber grating strain sensing optical cable (1) is parallel to the longitudinal middle position of the concrete beam (4) to be measured.

3. The concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing according to claim 2 is characterized in that: The reinforcing adhesive layer (2) and the outer carbon fiber cloth (3) are both flat.

4. The concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing according to claim 3 is characterized in that: The reinforcing adhesive layer (2) is made of a fiber resin-based composite material, and the thickness of the reinforcing adhesive layer (2) is greater than the diameter of the ultra-weak fiber Bragg grating strain sensing optical cable (1).

5. The concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing according to claim 4 is characterized in that: The outer layer carbon fiber cloth (3) is unidirectional carbon fiber cloth with a thickness of 0.1 mm to 0.17 mm.

6. The concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing according to claim 5 is characterized in that: The ultra-weak fiber Bragg grating strain sensing optical cable (1) comprises an ultra-weak fiber Bragg grating core (101), the ultra-weak fiber Bragg grating core (101) is coaxially and concentrically wrapped with a fiber cladding (102) on the periphery, and the fiber cladding (102) is coaxially and concentrically wrapped with a fiber coating layer (103) on the periphery.

7. The concrete beam deformation measurement device based on ultra-weak fiber Bragg grating sensing according to claim 6 is characterized in that: Ultra-weak fiber grating arrays (1011) are inscribed at equal intervals along the axial direction at the center position of the ultra-weak fiber grating core (101).

Images