A bolt based on piezoelectric active sensing and its method for monitoring concrete damage

Abstract

The present invention relates to the field of health monitoring of concrete structures, and relates to a bolt based on piezoelectric active sensing and a method for monitoring concrete damage. The structure includes a bolt unit and a sensing unit. The bolt unit includes nine bolts, which are arranged in an array on the concrete. 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 sensing unit is arranged inside the nut and is used for monitoring the damage of the concrete structure. In the present invention, setting the sensor unit inside the nut can not only protect the sensor unit but also facilitate replacement. In addition, by controlling the torque of the bolt with a torque wrench, the bolts are tightened to the same degree, and stress waves can enter and exit the bolt without loss, ensuring the accuracy of the monitoring results.

Description

Technical Field

[0001] The present invention relates to the field of health monitoring of concrete structures, and more particularly, to a bolt based on piezoelectric active sensing and a method for monitoring concrete damage thereof. Background Art

[0002] Due to the poor tensile capacity, high brittleness and easy cracking of concrete, under the influence of external environments such as freeze-thaw cycles, corrosion, and complex dynamic and static loads, with the extension of the service time, the potential risk of damage to concrete structures gradually increases. Therefore, implementing intelligent damage monitoring has become the key to ensuring the safe operation of concrete structures. Currently, the health monitoring of concrete structures is mainly carried out by pasting or embedding piezoelectric ceramic chips on the surface. However, the sensors pasted on the surface are easily damaged, which is not only difficult to repair and replace, but also difficult to ensure the accuracy of monitoring. Summary of the Invention

[0003] The purpose of the present invention is to provide a bolt based on piezoelectric active sensing and a method for monitoring concrete damage thereof 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 a bolt based on piezoelectric active sensing, including: a bolt unit and a sensing unit. The bolt unit includes nine bolts, which are arranged in an array on the concrete. 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 sensing unit is arranged inside the nut and is used for monitoring the damage of the concrete structure.

[0005] On the other hand, the present application provides a method for monitoring concrete damage based on piezoelectric active sensing, and the method includes:

[0006] Obtaining first information, where the first information includes stress wave signals collected by bolts;

[0007] Decomposing the first information to obtain signal set information;

[0008] Calculating the energy of the signal set according to the signal set information to obtain second information;

[0009] Calculating third information according to the second information, where the third information includes a signal fluctuation index;

[0010] Determining the damage of the concrete according to the third information.

[0011] The beneficial effects of the present invention are:

[0012] In the present invention, a sensing unit is arranged inside the nut, and then the torque of the bolt is controlled by a torque wrench, so that each bolt is tightened to the same degree. While strengthening the concrete, stress waves can enter and exit the bolt without damage, ensuring the accuracy of the monitoring results.

[0013] Other features and advantages of the present invention will be described in the subsequent specification, and in part, will become apparent from the specification or be understood by implementing the embodiments of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the written specification, claims, and drawings. Brief Description of the Drawings

[0014] 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 therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0015] Figure 1 It is a schematic structural diagram of a bolt based on piezoelectric active sensing described in the embodiments of the present invention.

[0016] Figure 2 It is an exploded view of the structure of a bolt based on piezoelectric active sensing.

[0017] Figure 3 It is a layout diagram of bolt units.

[0018] Reference numerals in the figures: 1, bolt; 2, sensing unit; 201, piezoelectric ceramic; 202, protective layer; 203, wire; 204, first connector; 205, circuit board; 206, PVC board; 207, second connector. Detailed Embodiments

[0019] 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 shown 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0020] 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, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0021] Embodiment 1:

[0022] As Figure 1 shown, this embodiment provides a bolt based on piezoelectric active sensing, including: a bolt unit and a sensing unit 2. The bolt unit includes nine bolts 1, and the bolts 1 are arranged in an array on the concrete. The bolt 1 includes a screw rod and a nut, and the nut is arranged at the top of the screw rod, and the nut is fixedly connected to the screw rod; the sensing unit 2 is arranged inside the nut, and the sensing unit 2 is used to monitor the damage of the concrete structure. The specific arrangement of the bolt unit is as Figure 3 shown. The central bolt 1 is an actuator, and the remaining 8 bolts 1 are receivers. The bolt unit arranged in an array can realize large-range monitoring of concrete cracking damage.

[0023] In a specific embodiment of the present disclosure, the nut is provided with a groove, the sensing unit 2 is arranged inside the groove, and a protective layer 202 is arranged between the bottom of the sensing unit 2 and the groove. Arranging the sensing unit 2 in the groove can protect the sensing unit 2, and arranging the protective layer 202 can extend the service life of the sensing unit 2. The material of the protective layer 202 includes but is not limited to epoxy resin.

[0024] As Figure 2In a specific embodiment of the present disclosure, the sensing unit 2 includes a piezoelectric ceramic 201, a first connector 204, a circuit board 205, a PVC board 206, and a second connector 207. The piezoelectric ceramic 201 is connected to the circuit board 205 through the first connector 204. The PVC board 206 is disposed on the top of the circuit board 205, and the second connector 207 is disposed on the top of the PVC board 206. The first connector 204 is a 2-pin PWM connector. Two ends of the first connector 204 are respectively disposed on the top of the piezoelectric ceramic 201 and the bottom of the circuit board 205. The middle of the PVC board 206 is hollow. The bottom of the second connector 207 is disposed on the circuit board 205, and the second connector 207 is electrically connected to the circuit board 205. The piezoelectric ceramic 201 has positive and negative piezoelectric effects, and can convert electrical signals and vibrations into each other, so as to realize the emission and reception of stress waves, and can sensitively sense the slight attenuation of stress waves. When the stress wave passes through the crack, diffraction and reflection phenomena will occur, resulting in attenuation of the wave signal. Therefore, by using the two bolts 1 on the two concrete structures as an actuator and a receiver respectively, the damage condition of the area between the two can be monitored through the attenuation of the stress wave.

[0025] Example 2:

[0026] This embodiment provides a method for monitoring concrete damage based on piezoelectric active sensing. The method includes step S1, step S2, step S3, step S4, and step S5, which specifically include:

[0027] Step S1: Obtain first information, where the first information includes stress wave signals collected by the bolts 1.

[0028] In this step, one signal acquisition device is connected to the central bolt 1 to emit stress waves, and the other is connected to any one of the surrounding bolts 1 to receive the stress waves passing through the concrete structure.

[0029] Step S2: Decompose the first information to obtain signal set information.

[0030] In this step, the received stress wave is decomposed into 2 n signal sets by using n-level wavelet packet to obtain signal set information.

[0031] Step S3: Calculate the energy of the signal set according to the signal set information to obtain second information.

[0032] In this step, calculating the energy of the signal set is a well-known technical solution to those skilled in the art, so it will not be elaborated here.

[0033] Step S4: Calculate third information according to the second information, where the third information includes a signal fluctuation index.

[0034] In step S4, steps S41, S42 and S43 are further included, which specifically include:

[0035] Step S41: Obtain the energy and the number of signal sets in the initial state;

[0036] Step S42: Determine the energy corresponding to each signal set according to the second information;

[0037] Step S43: Calculate according to the energy in the initial state, the energy corresponding to each signal set and the number of signal sets to obtain the third information.

[0038] In this step, the specific calculation process of the signal fluctuation index is as follows:

[0039] ;

[0040] In the above formula, C represents the signal fluctuation index, E j represents the energy of the signal set, E 0，j represents the energy in the initial state, n represents the number of levels of the wavelet packet used to decompose the stress wave. When the damage fluctuation index is larger, it indicates that the wave signal is more severely affected by the internal damage of the concrete.

[0041] It should be noted that the concrete damage index can also characterize the damage state of the concrete. The specific calculation process of the concrete damage index is as follows:

[0042] ;

[0043] In the above formula, represents the concrete damage index. When the index is close to 0, the concrete structure is not damaged. When the index is close to 1, it indicates that there are a large number of cracks in the concrete and the structure is damaged.

[0044] Step S5: Determine the damage of the concrete according to the third information.

[0045] In step S5, steps S51, S52 and S53 are further included, which specifically include:

[0046] Step S51: Obtain the stress wave peak in the initial state;

[0047] Step S52: Calculate according to the stress wave peak in the initial state and the stress wave peak collected during the bolt monitoring to obtain the wave peak attenuation information;

[0048] Step S53: Determine the damage of the concrete according to the wave peak attenuation information and the third information.

[0049] In this embodiment, the specific calculation process of the wave peak attenuation information is as follows:

[0050] ;

[0051] In the above formula, N represents the wave crest attenuation information, W represents the stress wave crest collected during bolt monitoring, represents the stress wave crest in the initial state.

[0052] In the step S53, there are also included step S531, step S532 and step S533, which specifically include:

[0053] Step S531: Obtain the time required for the stress wave crest at the initial moment to pass through the concrete;

[0054] Step S532: Calculate based on the time required for the stress wave crest at the initial moment to pass through the concrete and the time required for the stress wave crest collected during bolt 1 monitoring to pass through the concrete, and obtain the peak velocity attenuation information;

[0055] In this step, the specific calculation process of the peak velocity attenuation information is as follows:

[0056] ;

[0057] In the above formula, P represents the peak velocity attenuation information, t represents the time required for the stress wave crest collected during bolt 1 monitoring to pass through the concrete, represents the time required for the stress wave crest at the initial moment to pass through the concrete.

[0058] Step S533: Determine the damage of the concrete based on the wave crest attenuation information, the peak velocity attenuation information and the third information.

[0059] In this embodiment, the structure of the swept-frequency stress wave emitted by the piezoelectric sensor is very complex. Therefore, it is necessary to process and analyze the wave signal from different features. Among them, the signal fluctuation index and the concrete damage index are overall indicators, which analyze the overall change characteristics of the wave signal. The two respectively analyze from the waveform and energy characteristics of the stress wave to pay attention to the changes of the wave signal as comprehensively as possible. Although the overall indicators are comprehensive enough, there are still deficiencies in the accuracy of the association between specific damage and signal changes, especially the development of minor damage. Therefore, it is necessary to process and analyze the wave crest section where the stress wave changes most acutely to correct the monitoring results and improve the monitoring accuracy. The wave crest attenuation and the peak velocity attenuation are local indicators for analyzing the wave crest section. When the stress wave passes through the damaged area, due to diffraction and reflection phenomena, the wave crest and the peak velocity will change acutely. Therefore, on the basis of evaluating the concrete structure with two overall indicators as the main body, assigning certain weights to the two local indicators based on the wave crest and the peak velocity as corrections can further improve the monitoring accuracy.

[0060] In step S533, there are also steps S5331, S5332, S5333, S5334, S5335, S5336, and S5337, which specifically include:

[0061] Step S5331: Apply a random damage state to the concrete by three-point bending loading;

[0062] Step S5332: Determine the corresponding wave peak attenuation information, peak velocity attenuation information, and third information of the concrete according to the damage state, and construct a first sample set;

[0063] Step S5333: Conduct a bending test on the concrete to determine the corresponding flexural strength and elastic modulus of the concrete, and construct a second sample set;

[0064] Step S5334: Train a neural network according to the first sample set and the second sample set to obtain a concrete damage assessment model;

[0065] Step S5335: Obtain fourth information, where the fourth information includes stress waves collected during real-time monitoring of bolts;

[0066] Step S5336: Process the fourth information to obtain fifth information, where the fifth information includes the corresponding wave peak attenuation information, peak velocity attenuation information, and signal fluctuation index of the fourth information;

[0067] Step S5337: Send the fifth information to the concrete damage assessment model to evaluate the damage of the concrete structure.

[0068] In this embodiment, a large number of 400mm * 100mm * 100mm concrete specimens are cast with the same type and grade of concrete as the structure. The damage monitoring method of the present invention is used for monitoring, and four stress wave damage assessment indexes based on the signal fluctuation index, concrete damage index, wave peak attenuation, and peak velocity attenuation are obtained. By means of three-point bending loading, freeze-thaw loading, triaxial compression, etc., a random damage state is applied to these specimens. Subsequently, these specimens are monitored, and signals are processed to obtain four indexes. Then, the quality damage, flexural strength, and elastic modulus of these specimens are tested by traditional destructive testing methods. The monitoring and test results of these specimens are trained and verified by a CNN model to obtain a concrete damage assessment model, which can be applied to the damage monitoring of actual structures, and the damage state of the concrete structure can be classified and evaluated through the concrete damage assessment model.

[0069] 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 product of the present invention is customarily placed. 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 on the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0070] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "installed", "connected", "connected to" 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.

[0071] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. 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.

[0072] 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. A concrete damage monitoring method based on piezoelectric active sensing, using a bolt based on piezoelectric active sensing, characterized in that: The bolt based on piezoelectric active sensing comprises: a bolt unit, the bolt unit comprises nine bolts (1), the bolts (1) are arranged on concrete in an array, the bolts (1) comprise a screw rod and a nut, the nut is arranged on the top of the screw rod, and the nut is fixedly connected to the screw rod; A sensor unit (2), the sensor unit (2) being arranged inside the nut, and the sensor unit (2) being used to monitor damage to the concrete structure; The concrete damage monitoring method based on piezoelectric active sensing comprises the following steps: Acquiring first information, the first information comprising a stress wave signal collected by the bolt (1); Decomposing the first information to obtain signal set information; Calculate the energy of the signal set according to the signal set information to obtain second information; Calculate third information according to the second information, wherein the third information includes a signal fluctuation index; determining damage of concrete according to the third information; The specific calculation process of the signal volatility index is: In the above formula, C represents the signal fluctuation index, E j represents the energy of the signal set, E 0，j It represents the energy of the initial state, n represents the series of wavelet packets used to decompose stress waves, and the larger the damage fluctuation index is, the more severely the wave signal is affected by the internal damage of concrete; Wherein, determining the damage of concrete according to the third information includes: Obtain the stress wave peak of the initial state; Calculation is performed based on the stress wave peak in the initial state and the stress wave peak collected during the monitoring of the bolt (1) to obtain peak attenuation information; determining concrete damage according to the peak attenuation information and the third information; Wherein, determining the damage of concrete according to the peak attenuation information and the third information includes: Obtain the time required for the peak of the stress wave to pass through the concrete at the initial moment; The peak velocity attenuation information is calculated based on the time required for the stress wave peak to pass through the concrete at the initial moment and the time required for the stress wave peak collected during the monitoring of the bolt (1) to pass through the concrete; The damage of concrete is determined according to the peak attenuation information, the peak velocity attenuation information and the third information.

2. The concrete damage monitoring method based on piezoelectric active sensing according to claim 1 is characterized in that: Determining concrete damage according to the wave crest attenuation information, the peak velocity attenuation information and the third information includes: A random damage state is imposed on concrete using three-point bending loading; Determine the peak attenuation information, the peak velocity attenuation information and the third information corresponding to the concrete according to the damage state to construct a first sample set; Performing a bending test on the concrete to determine the bending strength and elastic modulus corresponding to the concrete to construct a second sample set; Training a neural network according to the first sample set and the second sample set to obtain a concrete damage assessment model; Acquiring fourth information, wherein the fourth information includes stress waves collected during real-time monitoring of the bolt; Processing the fourth information to obtain fifth information, wherein the fifth information includes peak attenuation information, peak velocity attenuation information, and a signal fluctuation index corresponding to the fourth information; The fifth information is sent to the concrete damage assessment model to assess the damage of the concrete structure.

3. The concrete damage monitoring method based on piezoelectric active sensing according to claim 1 is characterized in that: The nut is provided with a groove, the sensor unit (2) is arranged inside the groove, and a protective layer (202) is provided between the bottom of the sensor unit (2) and the groove.

4. The concrete damage monitoring method based on piezoelectric active sensing according to claim 1 is characterized in that: The sensing unit (2) comprises a piezoelectric ceramic (201), a first joint (204), a circuit board (205), a PVC board (206) and a second joint (207); the piezoelectric ceramic (201) is connected to the circuit board (205) via the first joint (204); the PVC board (206) is arranged on top of the circuit board (205); and the second joint (207) is arranged on top of the PVC board (206).

5. The concrete damage monitoring method based on piezoelectric active sensing according to claim 4 is characterized in that: The first connector (204) is a 2-pin PWM connector, and two ends of the first connector (204) are respectively arranged on the top of the piezoelectric ceramic (201) and the bottom of the circuit board (205).

6. The concrete damage monitoring method based on piezoelectric active sensing according to claim 4 is characterized in that: The middle of the PVC board (206) is hollow, the bottom of the second connector (207) is arranged on the circuit board (205), and the second connector (207) is electrically connected to the circuit board (205).

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