CN105572329A - Concrete crack scale distance adaptive monitoring method - Google Patents

Abstract

The invention discloses a method for self-adaptive monitoring of concrete crack gauge length based on a distributed strain sensing array. The equipment measures the strain data under constant load conditions, and applies the gauge length adaptive algorithm to analyze and process it. The current minimum gauge length obtained is used as the damage area, and the measured strain represents the crack damage degree. The present invention is different from the strain monitoring with a fixed gauge length. The measurement gauge length of the focused strain monitoring can be customized according to the centimeter to meter level. While performing damage diagnosis, the strain data itself can be used to judge whether the crack damage has evolved across the gauge length. , to adapt the current minimum gauge length to the changed damage hotspot area. The invention utilizes stable and high-precision static strain data, does not need known loads and numerical models, and is suitable for on-line real-time monitoring.

Description

Adaptive monitoring method for gauge length of concrete cracks

technical field

The invention belongs to the technical field of structural health monitoring and modern detection, and in particular relates to a method for self-adaptive monitoring of concrete crack gauge length based on a distributed strain sensing array.

Background technique

During the construction and service period, the concrete structure is subject to the physical and chemical effects of load, environment and material itself, and it is very easy to crack. While suppressing harmful cracks, it is necessary to use damage detection technology to monitor and diagnose concrete cracks.

Traditional crack detection mainly includes visual inspection, crack width gauge, ultrasonic wave, acoustic emission, photography, and Carlson type or string type crack gauge. It is difficult to cover the random crack information of concrete structure on the scale. Due to the advantages of real-time monitoring, large coverage, continuous space, and high precision, distributed sensing technology has gradually been applied to concrete crack monitoring. Hale et al. first proposed to use optical fiber as a structural crack sensor; researchers at the University of Toronto in Canada proposed a damage location system based on the principle of optical fiber fracture. When the output power of an optical fiber in a certain area of the structure is zero, the damage location can be judged; LeMaou et al. Using embedded multimode fiber optics to monitor concrete cracks, this technology has been successfully applied to tunnel linings and detected the occurrence of cracks. Leung monitors the crack growth based on the light intensity loss caused by the microbending of the optical fiber. As long as the crack direction is oblique to the optical fiber, the sensing probe can sense the existence of cracks in the concrete structure. In recent years, researchers have used Rayleigh, Brillouin and Raman scattering characteristics to analyze the reflected (or transmitted) signal by inputting a pulse signal in the optical cable, and characterize the crack damage through the strain data obtained by demodulation. However, due to crack damage, the test strain reaches more than 10%, which is far beyond the deformation capacity of the glass optical fiber, and it is prone to shear brittle fracture. 20,000 microstrain. In addition, some people have preliminarily realized the real-time monitoring of structural cracks with the help of electrical time domain reflection technology of high-ductility coaxial cables (a distributed crack sensor based on coaxial cables, application number: 201110027121.1), but this method is sensitive to cracks. Performance, distributed testing and reuse capabilities need to be verified. In addition, the existing distributed strain sensors use a preset measuring gauge length, and the large gauge-length sensing probe is not sensitive to the early stage of crack damage, which is likely to cause missed judgment of damage; due to the nonlinearity and randomness of crack damage evolution, fixed The average strain of the gauge length is used to describe the crack, and it is easy to cause damage misjudgment.

In view of the above shortcomings, it is considered that the distributed strain monitoring information can cover the structural damage area in a large range while focusing on the local stress/strain concentration of the structure. The invention provides a concrete crack monitoring method based on an adaptive algorithm of multi-level measuring gauge length, so that the concrete crack damage can automatically adjust a suitable measuring gauge length while evolving across the gauge length, and through its strain data to characterize crack damage.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for self-adaptive monitoring of concrete crack gauges based on a distributed strain sensing array. , judge whether the crack damage has cross-gauge evolution by the strain data itself. When the crack damage evolution exceeds the coverage area of the minimum gauge length, the current minimum gauge length should be further selected and re-determined to adapt to the changing damage hot spot area, so as to describe the crack damage more accurately and robustly.

To achieve the above object, the technical solution of the present invention is:

A method for self-adaptive monitoring of concrete crack gauge length based on a distributed strain sensing array, which mainly includes the following steps:

The first step is to adopt the method of internal pre-embedding or surface fixing, and arrange optical fiber distributed strain sensing probes and coaxial cable distributed strain sensing probes in parallel on the concrete substrate. Multi-level (m-level) strain sensor array for measuring gauge length;

The second step is to arrange and combine all the current 1 to m measurement gauge lengths to construct all possible n gauge length sequences ${\left\{{\tilde{L}}_i\right\}}_j,\left(\begin{array}{cc}i=0,...,m-1& j=1,...,\mathrm{no}\end{array}\right),$ The static strain data of the concrete matrix under constant load is measured by using the above-mentioned strain sensing probe and corresponding demodulation equipment The static strain data described Test each gauge sequence for multiple times the average value obtained;

The third step is to obtain static strain data by whether to test Judging whether the strain sensing probe corresponding to the measuring gauge length is damaged: if the static strain data is not measured If the strain sensing probe is damaged, repeat the second step; if the measured static strain data If the strain sensing probe is not damaged, proceed to the next step.

The fourth step, for each gauge sequence Take the gauge length L _i of the measuring gauge length as the horizontal axis, and take the deformation ΔL _i corresponding to the measuring gauge length as the vertical axis, establish a plane Cartesian coordinate system, and draw a polyline L _i -ΔL _i .

Step five, with each gauge sequence Based on the measured polyline L _i -ΔL i in the healthy state of the concrete matrix, judge whether the crack damage occurs according to whether the polyline L _i -ΔL _i of each gauge sequence moves up _. If L _i -ΔL _i does not occur Move up and repeat the fourth step; if L _i -ΔL _i moves up, the concrete matrix measured by the gauge length sequence corresponding to the polyline will be damaged, and the crack damage area will be determined according to the minimum gauge length in the gauge length sequence where the damage occurs and its quantity, proceed to the next step.

In the sixth step, in the polyline L _i -ΔL _i that moves upward, if there is a significant difference in the upward movement corresponding to the measurement gauge length of different levels, the crack damage of the concrete matrix measured by the gauge length sequence occurs across the gauge length evolution;

6.1 Among the polylines L _i -ΔL _i , the upward movement corresponding to all gauge lengths after a certain level of measuring gauge length (gauge length is greater than or equal to the gauge length of this level) is greater than that of all gauge lengths before this level of gauge length (gauge length If the distance length is less than the gauge length), select the measurement gauge length of this level as the current minimum gauge length of the corresponding gauge length sequence of the polyline L _i -ΔL _i ;

6.2 In the fifth step, in each damaged area of all damaged gauge length sequences, repeat step 6.1 to obtain multiple current minimum gauge lengths, and select the current minimum gauge length with the minimum gauge length as the current minimum gauge length of the damaged area ;

6.3 If the current minimum gauge length of each damaged area has been determined, exclude all gauge lengths in the gauge sequence whose gauge length is less than the current minimum gauge length, and repeat steps 2 to 5;

In the seventh step, in the polyline L _i -ΔL _i that has moved upward, if there is no significant difference in the upward movement corresponding to the measurement gauge length of different levels, the current minimum gauge length in each damaged gauge length sequence as the damaged area, Strain data measured on It is used to characterize the degree of crack damage and output diagnostic results.

The invention is based on the parallel arrangement of distributed strain sensing probes, and obtains strain data under constant load conditions through a strain sensing array inside or on the surface of the concrete matrix. The present invention focuses on the sensitivity of strain monitoring to local crack damage in the structure, the distributed coverage capability, and the self-advantages that the measurement gauge length can be customized from centimeters to meters. The gauge-length self-adaptive monitoring method is capable of self-adjusting a suitable measuring gauge-length to adapt to changed damage hotspot areas, wherein the gauge-length self-adaptive algorithm is the core content of the present invention.

The effects and benefits of the present invention are: 1) For different levels of measuring gauge lengths in the strain sensing array, using the gauge length adaptive monitoring method can avoid: crack damage causes local stress/strain concentration of the concrete structure, resulting in small gauge length sensing The probe was damaged beyond its own deformation capacity and could not continue testing; the large gauge sensing probe was not sensitive to early damage, resulting in missed judgment of damage; the use of fixed gauge strain data to characterize crack damage resulted in misjudgment of damage. 2) By using only the static strain data under constant load, stable testing and high accuracy can be achieved without considering specific load values. 3) The gauge length self-adaptive algorithm of the present invention does not require a numerical model of the structure, and the calculation process is all algebraic operations, which greatly reduces the amount of calculation and is suitable for real-time monitoring. It can provide technical support for the rapid warning of concrete structures and the study of damage and collapse mechanisms. It provides a reference for structural health diagnosis of other damage characteristics.

Description of drawings

Fig. 1 is a schematic diagram of strain sensing array concrete crack damage monitoring of the present invention;

Fig. 2 is a block diagram of gauge length adaptive algorithm of the present invention;

Fig. 3 is a schematic diagram of a certain gauge sequence of the multi-level measuring gauge (m=4) in the embodiment;

Fig. 4 is the polyline L _i -ΔL _i corresponding to a certain gauge length sequence in the embodiment;

Figure 1 is a strain sensing array composed of multi-level measuring gauge lengths.

detailed description

Describe the specific embodiment of the present invention in detail below in conjunction with accompanying drawing:

The present invention is based on the parallel arrangement of distributed strain sensing probes, as shown in Figure 1, through the strain sensing array 1 inside or on the surface of the concrete matrix and the strain demodulation equipment to measure the strain data under constant load conditions. Apply the gauge adaptive algorithm to analyze and process the deformation corresponding to the measurement gauge lengths of each gauge sequence at each level, as shown in Figure 2, and finally obtain the current minimum gauge length as the damage area, and the measured strain data is Indicates the degree of crack damage.

Customize the measurement gauge length according to Figure 3, and take the average value of the static strain data obtained from multiple tests $\left\{\begin{array}{cccc}\stackrel{-}{{\mathrm{\ϵ}}_0}& \stackrel{-}{{\mathrm{\ϵ}}_1}& \stackrel{-}{{\mathrm{\ϵ}}_2}& \stackrel{-}{{\mathrm{\ϵ}}_3}\end{array}\right\},$ Calculate the measurement gauge length deformation at all levels {ΔL ₀ ΔL ₁ ΔL ₂ ΔL ₃ }. Further, according to the gauge-length adaptive algorithm:

S1) Undamaged (healthy) state:

The sensing probe is not damaged, and a polyline L _i -ΔL _i is drawn, as shown by the solid line in Fig. 4 . According to the solution principle of the static force problem, under the condition of constant load, the deformation of the measuring gauge length at all levels does not change.

S2) Occurrence of damage (represented by subscript α):

The sensor probe is not damaged, make a polyline It is shown by the long dotted line in Fig. 4. The multi-segment line moves up, and the upward movement of the measuring gauge length at each level is equal. Crack damage occurred in the concrete matrix, but no cross-gauge evolution occurred.

Due to the decrease in the local stiffness of the concrete structure in the minimum gauge length measurement area after damage, the strain in the damage area increases within a certain time span, that is, can also be written as In the formula is the strain after damage, δ _α is the relative strain increment, then

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; )</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; \&rsqb;</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

According to the principle of strain equivalent and no damage occurs in the AB section of the measuring gauge length, it is obtained

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Empathy

${\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

From the formulas (1)-(4), the phenomenon shown by the long dotted line in Fig. 4 can be intuitively obtained. In the current state, the crack damage area is and Indicates the degree of crack damage.

S3) Cross-gauge evolution (represented by subscript β):

The sensor probe is not damaged, make a polyline It is shown by the dashed line in Figure 4. The multi-segment line moves up, and the upward movement of the measurement gauge lengths of each level is different, and the measurement gauge length The shifting amount of the multi-segment line is the same as that of the above example, and the shifting amount of other gauge lengths is the same and increased compared with the previous example. The crack damage of the concrete matrix has evolved across the gauge length.

According to the example derivation of S2), it can be obtained in the same way

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

In the formula, δ _β is the relative strain increment of measuring gauge length AB section.

Select gauge length It is the current minimum gauge length, exclude the gauge length Redefine the gauge sequence $\left\{\begin{array}{ccc}\widetilde{L_1}& \widetilde{L_2}& \widetilde{L_3}\end{array}\right\}.$ At this time, the subscript αβ represents the damage state corresponding to the current minimum gauge length

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; )</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&rsqb;</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

In the formula is the strain after damage, and δ _αβ is the relative strain increment of the current minimum gauge length.

From the formulas (5)-(8), it can be intuitively obtained the phenomenon shown by the short dashed line in Fig. 4; according to the formulas (9)-(11), the crack damage area in the current state is and Indicates the degree of crack damage. The above derivation process proves the feasibility of the gauge length adaptive algorithm proposed by the present invention.

The above examples are only used to illustrate the technical solutions of the present invention and preferred implementation modes with certain generality. Improvements should be regarded as the coverage and protection scope of the present invention.

Claims (2)

1. A concrete crack gauge length self-adaptive monitoring method, is characterized in that, comprises the following steps: In the first step, the distributed strain sensing probes of optical fiber and coaxial cable are arranged in parallel on the concrete substrate, and different measuring gauge lengths are set to form a strain sensing array with m-level measuring gauge length; The second step is to construct n gauge length sequences for all the current 1 to m level measuring gauge length permutations and combinations The static strain data of the concrete matrix under constant load is measured by using the above-mentioned strain sensing probe and corresponding demodulation equipment The static strain data described Test each gauge sequence for multiple times the average value obtained; The third step is whether the static strain data is measured Judging whether the strain sensing probe corresponding to the measuring gauge length is damaged, if the static strain data is not measured If the strain sensing probe is damaged, repeat the second step; if the measured static strain data If the strain sensing probe is not damaged, proceed to the next step; The fourth step, for each gauge sequence Take the gauge length L _i of the measuring gauge length as the horizontal axis, and take the deformation amount ΔL _i corresponding to the measuring gauge length as the vertical axis, establish a plane Cartesian coordinate system, and make a polyline L _i -ΔL _i ; Step five, with each gauge sequence Based on the measured polyline L _i -ΔL i in the healthy state of the concrete matrix, judge whether crack damage occurs according to whether the polyline L _i -ΔL _i of each gauge sequence moves up _. If L _i -ΔL _i does not occur Move up, repeat the fourth step; if L _i -ΔL _i moves up, the concrete matrix measured by the gauge length sequence corresponding to the polyline will be damaged, and the crack damage area will be determined by the minimum gauge length in the gauge length sequence where damage occurs and quantity, proceed to the next step; In the sixth step, in the polyline L _i -ΔL _i that moves upward, if the upward movement corresponding to different levels of measurement gauge length is different, the crack damage of the concrete matrix measured by the gauge sequence will evolve across the gauge length; 6.1 Among the polylines L _i -ΔL _i , the upward movement corresponding to all gauge lengths after a certain level of measuring gauge length is greater than the upward movement corresponding to all gauge lengths before this level of measuring gauge length, and the measuring gauge length of this level is selected as The current minimum gauge length of the corresponding gauge length sequence of the polyline L _i -ΔL _i ; 6.2 In the fifth step, in each damaged area of all damaged gauge length sequences, repeat step 6.1 to obtain multiple current minimum gauge lengths, and select the current minimum gauge length with the minimum gauge length as the current minimum gauge length of the damaged area ; 6.3 If the current minimum gauge length of each damaged area is determined, exclude all gauge lengths in the gauge sequence whose gauge length is less than the current minimum gauge length, and repeat steps 2 to 5; In the seventh step, in the polyline L _i -ΔL _i that moves upward, the upward movement corresponding to the measurement gauge length of different levels is the same, then the current minimum gauge length in each damaged gauge length sequence as the damaged area, Strain data measured on It is used to characterize the degree of crack damage and output diagnostic results. 2. A method for self-adaptive monitoring of concrete crack gauge length according to claim 1, characterized in that in the first step, the strain sensing probe is pre-embedded or surface-fixed on the concrete substrate.