Bolt based on piezoelectric active sensing and concrete damage monitoring method thereof

Abstract

The invention relates to the field of concrete structure health monitoring, in particular to bolts based on piezoelectric active sensing and a concrete damage monitoring method thereof.The structure comprises a bolt unit and a sensing unit, the bolt unit comprises nine bolts, the bolts are arranged on concrete in an array mode, each bolt comprises a threaded rod and a nut, and the threaded rod is connected with the sensing unit. The screw cap is arranged at the top of the screw rod, and the screw cap is fixedly connected with the screw rod; the sensing unit is arranged in the nut, the sensing unit is used for monitoring damage to the concrete structure, the sensor unit is arranged in the nut, the sensor unit can be protected and is convenient to replace, in addition, the torque of the bolts is controlled through the torque wrench, all the bolts are tightened to the same degree, and the reliability of the bolts is improved. Stress waves can enter and exit the bolts without damage, and accuracy of monitoring results is ensured.

Description

Technical Field

[0001] The present invention relates to the field of concrete structure health monitoring, and in particular to a bolt and concrete damage monitoring method based on piezoelectric active sensing. Background Art

[0002] Since concrete has poor tensile strength, is brittle and prone to cracking, under the influence of external environments such as freeze-thaw, corrosion, and complex dynamic and static loads, the potential risk of cracks in concrete structures gradually increases with the extension of service time. Therefore, the implementation of intelligent damage monitoring has become the key to ensuring the safe operation of concrete structures. At present, the health monitoring of concrete structures is mainly carried out by sticking or burying piezoelectric ceramic sheets on the surface. However, the sensors stuck on the surface are easily damaged, which not only makes it difficult to repair and replace, but also makes it difficult to ensure the accuracy of monitoring. Summary of the invention

[0003] The purpose of the present invention is to provide a bolt and concrete damage monitoring method based on piezoelectric active sensing to improve the above problems. In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: 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, the bolts are arranged in an array on concrete, the bolts include 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 the sensing unit is used to monitor damage to the concrete structure.

[0004] On the other hand, the present application provides a concrete damage monitoring method based on piezoelectric active sensing, the method comprising: Acquiring first information, wherein the first information includes a stress wave signal collected by the bolt; 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; The damage of the concrete is determined according to the third information.

[0005] The beneficial effects of the present invention are: The present invention arranges a sensing unit in the nut and then controls the torque of the bolt through a torque wrench, so that each bolt is tightened to the same degree. While reinforcing the concrete, stress waves can enter and exit the bolt without damage, thereby ensuring the accuracy of the monitoring result.

[0006] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by implementing the embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0008] Figure 1 Schematic diagram of the bolt structure based on piezoelectric active sensing described in an embodiment of the present invention.

[0009] Figure 2 This is the structural explosion diagram of the bolt based on piezoelectric active sensing.

[0010] Figure 3 This is the arrangement diagram of the bolt unit.

[0011] Markings in the figure: 1, bolt; 2, sensor unit; 201, piezoelectric ceramic; 202, protective layer; 203, wire; 204, first joint; 205, circuit board; 206, PVC board; 207, second joint. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally 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 invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0013] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0014] Embodiment 1: like Figure 1 As shown, this embodiment provides a bolt based on piezoelectric active sensing, including: a bolt unit and a sensor unit 2, the bolt unit includes nine bolts 1, the bolts 1 are arranged on the concrete in an array, the bolts 1 include 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; the sensor unit 2 is arranged inside the nut, and the sensor unit 2 is used to monitor the damage of the concrete structure. The specific arrangement of the bolt unit is as follows Figure 3 As shown, the central bolt 1 is an exciter, and the remaining eight bolts 1 are receivers. Large-scale concrete crack monitoring can be achieved through the array-arranged bolt units.

[0015] In a specific embodiment of the present disclosure, the nut is provided with a groove, the sensor unit 2 is provided inside the groove, and a protective layer 202 is provided between the bottom of the sensor unit 2 and the groove. The sensor unit 2 is provided in the groove to protect the sensor unit 2. The protective layer 202 can extend the service life of the sensor unit 2. The material of the protective layer 202 includes but is not limited to epoxy resin.

[0016] like Figure 2 As shown in 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 arranged on the top of the circuit board 205, the second connector 207 is arranged on the top of the PVC board 206, the first connector 204 is a 2-pin PWM connector, the 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, the middle of the PVC board 206 is hollow, the bottom of the second connector 207 is arranged on the circuit board 205, the second connector 207 is electrically connected to the circuit board 205, the piezoelectric ceramic 201 has positive and negative piezoelectric effects, can convert electrical signals and vibrations to each other, thereby realizing the emission and reception of stress waves, and can keenly perceive the slight attenuation of stress waves. When stress waves pass through cracks, diffraction and reflection phenomena will occur, causing the wave signal to attenuate. Therefore, by using the bolts 1 on the two concrete structures as actuators and receivers respectively, the damage of the area between the two can be monitored through the attenuation of stress waves.

[0017] Embodiment 2: This embodiment provides a concrete damage monitoring method based on piezoelectric active sensing, the method comprising steps S1, S2, S3, S4 and S5, which specifically include: Step S1, obtaining first information, wherein the first information includes a stress wave signal collected by bolt 1; 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 surrounding bolt 1 to receive stress waves passing through the concrete structure.

[0018] Step S2, decomposing the first information to obtain signal set information; In this step, the received stress wave is decomposed into two n signal set and obtain signal set information.

[0019] Step S3, calculating the energy of the signal set according to the signal set information to obtain second information; In this step, calculating the energy of the signal set is a technical solution well known to those skilled in the art, and thus will not be described in detail here.

[0020] Step S4, calculating third information according to the second information, wherein the third information includes a signal fluctuation index; The step S4 also includes step S41, step S42 and step S43, which specifically include: Step S41, obtaining the energy of the initial state and the number of signal sets; Step S42: determining the energy corresponding to each signal set according to the second information; Step S43: Calculate according to the energy of the initial state, the energy corresponding to each of the signal sets, and the number of the signal sets to obtain third information.

[0021] In this step, the specific calculation process of the signal fluctuation 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 the stress wave, and the larger the damage fluctuation index is, the more severely the wave signal is affected by the internal damage of the concrete.

[0022] It should be noted that the concrete damage index can also characterize the damage state of concrete. The specific calculation process of the concrete damage index is: ; In the above formula, It 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 lot of cracks in the concrete and the structure is damaged.

[0023] Step S5: Determine the damage of the concrete according to the third information.

[0024] The step S5 also includes step S51, step S52 and step S53, which specifically include: Step S51, obtaining the stress wave peak in the initial state; Step S52, calculating according to the stress wave peak in the initial state and the stress wave peak collected during bolt monitoring to obtain peak attenuation information; Step S53: determining concrete damage according to the peak attenuation information and the third information.

[0025] In this embodiment, the specific calculation process of the peak attenuation information is: ; In the above formula, N represents the peak attenuation information, W represents the stress wave peak collected during bolt monitoring, The stress wave peak represents the initial state.

[0026] The step S53 also includes step S531, step S532 and step S533, which specifically include: Step S531, obtaining the time required for the peak of the stress wave to pass through the concrete at the initial moment; Step S532, calculating the peak velocity attenuation information 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 bolt 1 to pass through the concrete; In this step, the specific calculation process of the peak velocity attenuation information is: ; In the above formula, P represents the peak velocity attenuation information, t represents the time required for the peak of the stress wave collected during bolt 1 monitoring to pass through the concrete, Indicates the time required for the peak of the stress wave to pass through the concrete at the initial moment.

[0027] Step S533: determine concrete damage according to the wave peak attenuation information, the peak velocity attenuation information and the third information.

[0028] In this embodiment, the structure of the swept-frequency stress wave emitted by the piezoelectric sensor is very complex, so it is necessary to process and analyze the wave signal from different characteristics. Among them, the signal fluctuation index and the concrete damage index are overall indicators, and the overall change characteristics of the wave signal are analyzed. The two analyze the waveform and energy characteristics of the stress wave respectively, which can pay attention to the changes of the wave signal as comprehensively as possible. Although the overall index is comprehensive enough, it is still insufficient for 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 peak segment with the most sensitive stress wave changes to correct the monitoring results and improve the monitoring accuracy. Peak attenuation and peak velocity attenuation are local indicators for analyzing the peak segment. When the stress wave passes through the damaged area, the peak and peak velocity will change sharply due to diffraction and reflection phenomena. Therefore, on the basis of evaluating the concrete structure by using two overall indicators as the main body, giving a certain weight to the two local indicators based on the peak and peak velocity as a correction can further improve the accuracy of monitoring.

[0029] The step S533 also includes step S5331, step S5332, step S5333, step S5334, step S5335, step S5336 and step S5337, which specifically include: Step S5331, applying a random damage state to the concrete using three-point bending loading; Step S5332, determining 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; Step S5333: Perform a bending test on the concrete to determine the bending strength and elastic modulus corresponding to the concrete to construct a second sample set; Step S5334: training a neural network according to the first sample set and the second sample set to obtain a concrete damage assessment model; Step S5335, obtaining fourth information, wherein the fourth information includes stress waves collected during real-time monitoring of the bolts; Step S5336: Process the fourth information to obtain fifth information, where the fifth information includes peak attenuation information, peak velocity attenuation information, and signal fluctuation index corresponding to the fourth information; Step S5337: Send the fifth information to the concrete damage assessment model to assess the damage of the concrete structure.

[0030] In this embodiment, a large number of 400mm*100mm*100mm concrete specimens are cast using concrete of the same type and number as the structure, and the damage monitoring method of the present invention is used to monitor and obtain four stress wave damage assessment indices based on signal fluctuation index, concrete damage index, peak attenuation and peak velocity attenuation. Random damage states are applied to these specimens by means of three-point bending loading, freeze-thaw loading, triaxial compression, etc., and then these specimens are monitored and the signals are processed to obtain four indicators. Thereafter, the mass damage, flexural strength and elastic modulus of these specimens are tested by means of traditional destructive testing. The monitoring and test results of these specimens are trained and verified using the 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 concrete structures can be classified and evaluated through the concrete damage assessment model.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0034] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A bolt based on piezoelectric active sensing, characterized in that: include: A bolt unit, the bolt unit comprising nine bolts (1), the bolts (1) being arranged in an array on concrete, the bolts (1) comprising a screw rod and a nut, the nut being arranged on the top of the screw rod, and the nut being fixedly connected to the screw rod; A sensor unit (2), wherein the sensor unit (2) is arranged inside the nut, and the sensor unit (2) is used to monitor damage to the concrete structure.

2. The bolt 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.

3. The bolt based on piezoelectric active sensing according to claim 1, 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).

4. The bolt based on piezoelectric active sensing according to claim 3 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).

5. The bolt based on piezoelectric active sensing according to claim 3 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).

6. A concrete damage monitoring method based on piezoelectric active sensing, characterized in that: include: 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; The damage of the concrete is determined according to the third information.

7. The concrete damage monitoring method based on piezoelectric active sensing according to claim 6 is characterized in that: Calculating third information according to the second information includes: Get the energy of the initial state and the number of signal sets; determining the energy corresponding to each signal set according to the second information; The third information is obtained by performing calculation according to the energy of the initial state, the energy corresponding to each of the signal sets and the number of the signal sets.

8. The concrete damage monitoring method based on piezoelectric active sensing according to claim 6 is characterized in that: Determining concrete damage according to the third information includes: Obtain the stress wave peak of the initial state; Calculating 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; The damage of the concrete is determined according to the peak attenuation information and the third information.

9. The concrete damage monitoring method based on piezoelectric active sensing according to claim 8 is characterized in that: Determining concrete damage 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 bolt (1) monitoring 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.

10. The concrete damage monitoring method based on piezoelectric active sensing according to claim 9 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.

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