Intelligent bolt based on piezoelectric impedance and concrete structure health monitoring method

Abstract

The invention relates to the field of concrete structure health monitoring, in particular to an intelligent bolt based on piezoelectric impedance and a concrete structure health monitoring method, the structure comprises a bolt and an impedance sensing unit, the bolt comprises a screw rod and a nut, the nut is arranged at the top of the screw rod, and the impedance sensing unit is arranged at the top of the screw rod. The nut is fixedly connected with the screw rod, the screw rod is arranged in concrete, and the nut is provided with a groove; the impedance sensing unit is arranged in the groove, the impedance sensing unit is used for sending and receiving impedance signals, the impedance sensing unit is arranged in the nut, signal sending and signal receiving are achieved through a single bolt, and concrete structure health monitoring can be completed through the single bolt; other detachable intelligent sensing components are not needed, and weakening of the strength of the concrete structure is avoided.

Description

Technical Field

[0001] The present invention relates to the field of health monitoring of concrete structures, and more particularly, to an intelligent bolt based on piezoresistive impedance and a method for health monitoring of concrete structures. Background Art

[0002] In the prior art, multiple sensors are usually used in combination to monitor concrete structures. However, this method will weaken the strength of the concrete structure, and due to the insufficient tightness of the combination of other components and the structure, there are gaps at the interface, so the monitoring accuracy is not high. At the same time, existing intelligent bolts are usually used to detect the working performance of the bolts themselves. Summary of the Invention

[0003] The purpose of the present invention is to provide an intelligent bolt based on piezoresistive impedance and a method for health monitoring of concrete structures to improve the above problems. To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0004] On the one hand, the present application provides an intelligent bolt based on piezoresistive impedance, including: a bolt and an impedance sensing unit. The bolt includes a screw rod and a nut. The nut is arranged at the top of the screw rod, and the nut is fixedly connected to the screw rod. The screw rod is arranged inside the concrete, and the nut is provided with a groove; the impedance sensing unit is arranged inside the groove, and the impedance sensing unit is used for sending and receiving impedance signals.

[0005] On the other hand, the present application provides a method for health monitoring of a concrete structure based on piezoresistive impedance, and the method includes:

[0006] Obtaining first information and second information, where the first information includes impedance signals collected in a first mode, and the second information includes impedance signals collected in a second mode;

[0007] Determining a conductance offset index according to the first information;

[0008] Determining a conductance attenuation index according to the second information;

[0009] Monitoring the health of the concrete structure according to the conductance offset index and the conductance attenuation index.

[0010] The beneficial effects of the present invention are:

[0011] By arranging the impedance sensing unit inside the nut, the present invention enables a single bolt to both send and receive signals, realizing the health monitoring of the concrete structure through a single bolt, without the need to use other detachable intelligent sensing components, and avoiding weakening the strength of the concrete structure.

[0012] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the embodiments of the present invention. The objectives and other advantages of the present invention may be realized and attained by the structure particularly pointed out in the written description, claims, as well as the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0014] Figure 1 Schematic diagram of the piezoresistive impedance-based smart bolt described in the embodiments of the present invention.

[0015] Figure 2 Exploded view of the structure of the piezoresistive impedance-based smart bolt described in the embodiments of the present invention.

[0016] Figure 3 Schematic connection diagram of the impedance analyzer.

[0017] Reference numerals in the figures: 1, screw rod; 2, impedance sensing unit; 201, piezoelectric ceramic; 202, protective layer; 203, wire; 204, circuit board; 205, guide rail; 206, PVC board. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0019] It should be noted that: similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0020] Example 1

[0021] As Figure 1 shown, this embodiment provides an intelligent bolt 1 based on piezoresistive impedance, including: a bolt 1 and an impedance sensing unit 2. The bolt 1 includes a screw rod and a nut. The nut is arranged at the top of the screw rod, and the nut is fixedly connected to the screw rod. The screw rod is arranged inside the concrete, and the nut is provided with a groove. The impedance sensing unit 2 is arranged inside the groove. The impedance sensing unit 2 is used to send and receive impedance signals. The prior art monitoring method depends on the arrangement of multiple sensors, so only the middle area where the sensors are arranged can be monitored. In the present invention, since the impedance sensing unit 2 is inside the nut, a single bolt 1 can both send and receive signals, without the need to use other detachable intelligent sensing components, avoiding more loss of the effective cross-sectional area of the concrete caused by opening multiple bolt holes in the concrete structure, resulting in the concrete being more likely to crack and other damages starting from these weakened parts when stressed, thereby reducing the overall bearing capacity of the concrete structure.

[0022] As Figure 2 shown, in a specific embodiment of the present disclosure, the impedance sensing unit 2 includes a piezoelectric ceramic 201, a circuit board 204, and a PVC board 206. The circuit board 204 is arranged between the piezoelectric ceramic 201 and the PVC board 206. The bottom of the circuit board 204 is in contact with the top of the piezoelectric ceramic 201, and the top of the circuit board 204 is in contact with the bottom of the PVC board 206. The piezoelectric ceramic 201 is electrically connected to the circuit board 204. Two guide rails 205 are arranged on the circuit board 204. The piezoelectric ceramic 201 is connected to the base of the guide rail 205 through a wire 203. Two through holes are arranged on the PVC board 206, and the through holes correspond to the guide rails 205 one by one. As Figure 3 shown, an impedance analyzer is connected to the two guide rails 205. For impedance monitoring in different modes, by monitoring impedance signals in different modes, more damage characteristics can be captured from multiple angles, thereby improving the monitoring accuracy.

[0023] In a specific embodiment of the present disclosure, the piezoelectric ceramic 201 is cylindrical, and a protective layer 202 is arranged on the side wall of the piezoelectric ceramic 201. The protective layer 202 can protect the impedance sensing unit 2 and extend its service life.

[0024] Example 2

[0025] This embodiment provides a method for health monitoring of a concrete structure based on piezoresistive impedance. The method includes step S1, step S2, step S3, and step S4, which specifically include:

[0026] Step S1: Obtain the first information and the second information. The first information includes the impedance signal collected in the first mode, and the second information includes the impedance signal collected in the second mode;

[0027] In this step, the first mode is the vibration extending along the radial direction of the piezoelectric ceramic 201, and the second mode is the vibration extending along the height direction of the piezoelectric ceramic 201. More damage characteristics can be captured from multiple angles, and the combination of the two can comprehensively monitor the health status of the interior of the concrete structure.

[0028] Step S2: Determine the conductance offset index according to the first information;

[0029] In step S2, there are also steps S21, S22, and S23, which specifically include:

[0030] Step S21: Determine the main peak frequency corresponding to the impedance signal collected by the bolt according to the first information;

[0031] Step S22: Obtain the main peak frequency corresponding to the impedance signal in the first mode collected by the bolt under the condition of no damage;

[0032] Step S23: Calculate according to the main peak frequency corresponding to the impedance signal collected by the bolt and the main peak frequency corresponding to the impedance signal collected by the bolt under the condition of no damage to obtain the conductance offset index.

[0033] In this embodiment, the specific calculation process of the conductance offset index is as follows:

[0034]

[0035] In the above formula, k i,j represents the main peak frequency of the j-th sampling point during the monitoring of the i-th bolt, represents the main peak frequency of the j-th sampling point during the monitoring of the i-th bolt under the condition of no damage, m represents the number of sampling points, n represents the number of scanning frequencies in the impedance signal spectrum, and V represents the conductance offset index. The larger V is, the greater the mechanical property change occurring inside the main structure.

[0036] Step S3: Determine the conductance attenuation index according to the second information;

[0037] In step S3, there are also steps S31, S32, and S33, which specifically include:

[0038] Step S31: Determine the value of the real part signal corresponding to the impedance signal according to the second information;

[0039] Step S32: Obtain the value of the real part signal corresponding to the impedance signal in the second mode collected by the bolt under the condition of no damage;

[0040] Step S33: Calculate based on the value of the real part signal corresponding to the impedance signal and the value of the real part signal corresponding to the impedance signal in the second mode collected by the bolt under the non-destructive condition to obtain the conductance attenuation index.

[0041] In this embodiment, the specific calculation formula for the conductance attenuation index is:

[0042]

[0043] In the above formula, m represents the number of sampling points, n represents the number of scanning frequencies in the impedance signal spectrum, Re(Y i,j ) represents the real part signal corresponding to the impedance signal at the j-th sampling point during the monitoring of the i-th bolt, represents the real part signal corresponding to the impedance signal at the j-th sampling point during the monitoring of the i-th bolt under the non-destructive condition, I represents the conductance attenuation index. It should be noted that the impedance signal is composed of a real part signal and an imaginary part signal. The conversion process of the impedance signal is specifically as follows:

[0044]

[0045] In the above formula, Y(ω) represents the impedance signal, G(ω) and B(ω) respectively represent the real part and the imaginary part of the impedance signal, ω represents the angular frequency, l, b, and h respectively represent the length, width, and thickness of the piezoelectric ceramic 201, Z a (ω) and Z s (ω) respectively represent the mechanical impedances of the piezoelectric ceramic 201 and the concrete structure, ε represents the complex dielectric constant (zero electric field) of the piezoelectric ceramic 201, Y represents the Young's modulus under the zero stress state, d represents the piezoelectric strain coefficient under the zero stress state. Through the above formula, the impedance signal can be determined, and taking its real part signal can be used for subsequent calculations.

[0046] Step S4: Monitor the health of the concrete structure based on the conductance offset index and the conductance attenuation index.

[0047] In the step S4, it also includes step S41, step S42, and step S43, which specifically include:

[0048] Step S41: Process the second information using the inverse fast Fourier transform to obtain the time-domain signal corresponding to the impedance signal collected in the second mode;

[0049] In this step, since frequency-domain analysis ignores the time distribution characteristics of the signal and is difficult to reflect the transient characteristics of non-stationary signals, for non-stationary signals or short-time signals, only frequency-domain analysis is not accurate. Therefore, it is necessary to convert it into a time-domain signal to supplement the frequency-domain signal, and jointly calibrate and quantify the minor damages and damages in the thickness direction of the concrete structure, so as to improve the accuracy of the health monitoring of the concrete structure.

[0050] Step S42, determining an impedance attenuation index according to a time domain signal corresponding to the impedance signal collected in the second mode;

[0051] The step S42 also includes step S421 and step S422, which specifically include:

[0052] Step S421, determining the conductance received by each bolt according to the time domain signal;

[0053] Step S422: Calculate the impedance attenuation index according to the conductance received by each of the bolts.

[0054] In this embodiment, the specific calculation formula of the impedance attenuation index is:

[0055]

[0056] In the above formula, E i Indicates the conductivity received when monitoring bolt No. i, It indicates the conductivity received when bolt No. i is in an intact state.

[0057] Step S43: monitoring the health of the concrete structure according to the impedance attenuation index, the conductivity deviation index and the conductivity attenuation index.

[0058] By taking the damage assessment under the first mode and the second mode as the evaluation subject, and then correcting it through the time domain index corresponding to the second mode, the concrete structure in the monitoring area can be comprehensively and accurately monitored and the damage status can be evaluated. Combined with the array distribution, the monitoring effect of large concrete structures can be achieved. It should be noted that this embodiment uses a neural network for damage assessment, and the specific steps are as follows: First, a large number of 500mm*500mm*100mm concrete slabs are cast, and the monitoring method of the present invention is used to monitor and add the data set. Subsequently, random damage is caused to the concrete slabs by means of freezing and thawing, knocking, bending, compression, etc., and then the three indicators obtained are input into the data set. Finally, the damage status of these concrete slabs is evaluated by traditional destructive test indicators such as mass loss, flexural strength, compressive strength and elastic modulus. The three damage indicators and the damage conditions measured by traditional technology are input into the densely connected convolutional neural network for training and verification. After completing the training and verification, the concrete damage monitoring method can be applied to the damage monitoring and evaluation of concrete structures. With regular manual inspections, the data set can be continuously expanded, and the accuracy of monitoring can be continuously improved and improved.

[0059] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0060] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0062] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or replacements, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An intelligent bolt based on piezoresistive impedance, characterized in that, Comprising: A bolt, the bolt includes a screw rod (1) and a nut, the nut is arranged at the top of the screw rod (1), the nut is fixedly connected to the screw rod (1), the screw rod (1) is arranged inside the concrete, and the nut is provided with a groove; An impedance sensing unit (2), the impedance sensing unit (2) is arranged inside the groove, and the impedance sensing unit (2) is used for sending and receiving impedance signals.

2. The piezoresistive impedance-based smart bolt according to claim 1, characterized in that: The impedance sensing unit (2) includes a piezoelectric ceramic (201), a circuit board (204) and a PVC board (206), the circuit board (204) is arranged between the piezoelectric ceramic (201) and the PVC board (206), the bottom of the circuit board (204) is in contact with the top of the piezoelectric ceramic (201), the top of the circuit board (204) is in contact with the bottom of the PVC board (206), and the piezoelectric ceramic (201) is electrically connected to the circuit board (204).

3. The piezoresistive impedance-based smart bolt according to claim 2, characterized in that: The piezoelectric ceramic (201) is cylindrical, and a protective layer (202) is arranged on the side wall of the piezoelectric ceramic (201).

4. The piezoresistive impedance-based intelligent bolt according to claim 2, wherein: Two guide rails (205) are arranged on the circuit board (204), and the piezoelectric ceramic (201) is connected to the base of the guide rail (205) through a wire (203).

5. The piezoresistive impedance-based intelligent bolt according to claim 4, wherein: Two through holes are arranged on the PVC board (206), and the through holes correspond to the guide rails (205) one by one.

6. A method for health monitoring of concrete structures based on piezoresistive impedance, characterized in that, Comprising: Obtaining first information and second information, the first information includes impedance signals collected in a first mode, and the second information includes impedance signals collected in a second mode; Determining a conductance offset index according to the first information; Determining a conductance attenuation index according to the second information; Monitoring the health of the concrete structure according to the conductance offset index and the conductance attenuation index.

7. The method for health monitoring of concrete structures based on piezoresistive impedance according to claim 6, characterized in that, Determining a conductance offset index according to the first information, including: Determining the main peak frequency corresponding to the impedance signal collected by the bolt according to the first information; Obtaining the main peak frequency corresponding to the impedance signal in the first mode collected by the bolt under non-destructive conditions; Calculating according to the main peak frequency corresponding to the impedance signal collected by the bolt and the main peak frequency corresponding to the impedance signal collected by the bolt under non-destructive conditions to obtain a conductance offset index.

8. The piezoresistive impedance-based concrete structure health monitoring method according to claim 6, wherein Determining a conductance attenuation index according to the second information, including: Determining the value of the real part signal corresponding to the impedance signal according to the second information; Obtaining the value of the real part signal corresponding to the impedance signal in the second mode collected by the bolt under non-destructive conditions; Calculating according to the value of the real part signal corresponding to the impedance signal and the value of the real part signal corresponding to the impedance signal in the second mode collected by the bolt under non-destructive conditions to obtain a conductance attenuation index.

9. The method for health monitoring of concrete structures based on piezoresistive impedance according to claim 6, wherein Monitoring the health of the concrete structure according to the conductance offset index and the conductance attenuation index, including: Processing the second information by using an inverse fast Fourier transform to obtain a time domain signal corresponding to the impedance signal collected in the second mode; Determining an impedance attenuation index according to the time domain signal corresponding to the impedance signal collected in the second mode; Monitoring the health of the concrete structure according to the impedance attenuation index, the conductance offset index and the conductance attenuation index.

10. The method for health monitoring of concrete structures based on piezoresistive impedance according to claim 9, characterized in that, Determining an impedance attenuation index based on the time-domain signal corresponding to the impedance signal collected in the second mode, includes: Determining the conductance received by each bolt according to the time-domain signal; Calculating the impedance attenuation index according to the conductance received by each bolt.

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