CN112630270A - Method for detecting state of reinforcing steel bar in concrete structure - Google Patents
Method for detecting state of reinforcing steel bar in concrete structure Download PDFInfo
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- CN112630270A CN112630270A CN202011584264.8A CN202011584264A CN112630270A CN 112630270 A CN112630270 A CN 112630270A CN 202011584264 A CN202011584264 A CN 202011584264A CN 112630270 A CN112630270 A CN 112630270A
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Abstract
The invention provides a method for detecting the state of a reinforcing steel bar in a concrete structure, which relates to the field of nondestructive testing of concrete, and establishes the representation mapping between the capacitance value data and the capacitance peak obtained by scanning a reinforced concrete member and the state of the reinforcing steel bar; scanning and detecting concrete members with different specifications; establishing a corresponding relation between the detection position and the scanning detection capacitance value, and acquiring the position of a steel bar, the size of the steel bar and the thickness of a steel bar protective layer of the concrete member by combining representation mapping; the steel bars in the concrete are subjected to targeted detection, and the representation mapping and the corresponding relation are utilized, so that the accurate results including the steel bar positions, the steel bar sizes and the thickness of the steel bar protective layer can be conveniently obtained, and the work efficiency of acceptance of constructional engineering and detection, reinforcement and identification of the existing reinforced concrete structure is improved.
Description
Technical Field
The invention relates to the field of nondestructive testing of concrete, in particular to a method for detecting the state of a reinforcing steel bar in a concrete structure.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The state of the reinforcing bars in a reinforced concrete structure has a profound effect on the state of the entire building/structure. To ensure safe use of the building, acceptance of completion after construction, and later reinforcement, the steel reinforcement in the structure needs to be inspected. According to the unified standards for construction quality acceptance of constructional engineering GB50300-2013, the state of the steel bar in the reinforced concrete structure mainly comprises the position of the steel bar, the size of the steel bar, the thickness of a protective layer of the steel bar and the like, and whether the position, the size, the thickness and the like are the same as the design or not is judged. The steel bar is used as a main stressed component in a building/structure, if the diameter of the steel bar does not reach the designed size, the bearing capacity of the reinforced concrete structure is reduced, the service life of the reinforced concrete structure is influenced, and danger is caused. The thickness of a protective layer of the steel bar plays an important role in protecting the steel bar in the concrete structure, and requirements are provided for the minimum thickness of the protective layer of the reinforced concrete structure under different using environment conditions in the concrete structure design specification GB 50010-2010 and the concrete structure durability design specification GB/T50476-2019 so as to ensure the durability and the safety of the building/structure; the more severe the environment in which the building/structure is located, the greater the minimum protective layer thickness is required. Therefore, the detection of the state of the steel bars in the concrete structure is an important ring for ensuring the safe service of the building/structure.
In the prior art, there are many methods for detecting the reinforcing steel bar in the civil engineering/structural structure, including acoustic emission, electromagnetic induction, microwave detection, infrared scanning and tomography. The acoustic emission technology is that a special detecting instrument is used for collecting acoustic emission signals, acoustic emission parameters corresponding to characteristics are obtained through signal processing, and the position and the state of a component are judged through analyzing the acoustic emission parameters; but the method is mostly used for detecting the damage of the concrete. The electromagnetic induction method is the most widely applied detection method in steel bar detection at present, the technology is relatively mature, and the state of the steel bar can be relatively accurately positioned, but the method is easily interfered by other factors such as material components and environment, and an assumed steel bar diameter is often required to be input when the thickness of the protective layer is determined by the method. The infrared scanning technology is to use an infrared scanner to scan and shoot a building structure, and judge the state of the reinforcing steel bar in the concrete by analyzing the image. Tomography is also commonly used to evaluate concrete, but its application in practical engineering is limited due to expensive equipment and cumbersome operation and data processing.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for detecting the state of a steel bar in a concrete structure, which is characterized in that the steel bar in the concrete is subjected to targeted detection, and the representation mapping and the corresponding relation are utilized to conveniently obtain the result which comprises the position of the steel bar, the size of the steel bar and the thickness of a protective layer of the steel bar, so that the work efficiency of acceptance of construction engineering and detection, reinforcement and identification of the existing reinforced concrete structure is improved.
In order to realize the purpose, the following technical scheme is adopted:
a method for detecting the state of a reinforcing steel bar in a concrete structure comprises the following steps:
establishing representation mapping between the capacitance value data and the capacitance peak obtained by scanning the reinforced concrete member and the state of the steel bar according to the capacitance value data and the area of the capacitance peak;
scanning and detecting reinforced concrete members with different specifications;
and establishing a corresponding relation between the detection position and the scanning detection capacitance value, and combining representation mapping to obtain the steel bar position, the steel bar size and the steel bar protective layer thickness of the reinforced concrete member.
And further, calibrating the capacitance value data, the area of the capacitance peak and the representation mapping of the steel bar state.
Further, the calibration process comprises the calibration of a capacitance peak value and the diameter of the steel bar, the calibration of the capacitance peak value and the thickness of the steel bar protective layer, the calibration of the area of the capacitance peak and the diameter of the steel bar, the calibration of the area of the capacitance peak and the thickness of the steel bar protective layer, the calibration of the area of the capacitance peak and the diameter of the steel bar, and the calibration of the area of the capacitance peak and the thickness of the steel bar protective layer.
Furthermore, the diameter of the steel bar and the thickness change of the protective layer are controlled, and the representation mapping of the steel bar, capacitance value data and the area of a capacitance peak is established.
Further, the scanning detection process comprises the following steps: and (3) detecting the reinforced concrete structure by adopting a capacitive reinforcing steel bar detection device.
And further, placing an electrode plate of the capacitive steel bar detection device on one side of the concrete, inputting engineering information, and scanning the electrode plate from one side of the concrete to the other side at a constant speed to obtain capacitance values at different positions.
And further, respectively scanning and detecting concrete members with different steel bar diameters and different protective layer thicknesses by using the capacitive steel bar detection device.
Further, a two-dimensional coordinate system is established along the detection direction, the X axis is the position of the polar plate, the diameter of the steel bar or the thickness of the protective layer of the steel bar, and the Y axis is the capacitance value detected by the capacitance type steel bar detection device;
the moving direction of the capacitive steel bar detection device is the detection direction.
Further, a two-dimensional coordinate system is established along the detection direction, the X axis is the diameter of the steel bar or the thickness of the protective layer, and the Y axis is the area of a capacitance peak obtained by the capacitance type steel bar detection device through data processing.
Further, a three-dimensional coordinate system is established, the X axis is a capacitance peak value detected by the capacitance type steel bar detection device, the Y axis is the area of the capacitance peak value obtained by the capacitance type steel bar detection device through data processing, and the Z axis is the diameter of the adopted steel bar or the thickness of the protective layer of the steel bar.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) the steel bars in the concrete are subjected to targeted detection, and the representation mapping and the corresponding relation are utilized, so that the accurate results including the steel bar positions, the steel bar sizes and the thickness of the steel bar protective layer can be conveniently obtained, and the work efficiency of acceptance of constructional engineering and detection, reinforcement and identification of the existing reinforced concrete structure is improved.
(2) By establishing a characterization relation among a capacitance peak value, a capacitance peak area and a steel bar state, a basis is provided for rapidly determining the state of the steel bar in the concrete after the concrete is scanned, compared with the traditional calculation of the steel bar state according to a capacitance value, the influence of a non-steel bar coverage area on the capacitance value can be directly eliminated by adopting the capacitance peak value, only the parameter of the capacitance peak value part is considered, and the overall calculation difficulty is reduced; the area of the capacitor peak can represent the state of the steel bar and the change of the state of the steel bar more visually, so that the rapid and visual comparison of different areas of the reinforced concrete structure is realized.
(3) The problem that under the condition that the diameter of the steel bar and the thickness of the steel bar protection layer are unknown, the state of the steel bar in the concrete is accurately measured is solved for the first time, and the diameter of the steel bar and the thickness of the steel bar protection layer can be obtained according to the measured areas of the capacitance peak value and the measured peak.
(4) The detection and data correction are carried out through the capacitive sensor, the result is more accurate, efficient and convenient, the influence of material difference is avoided in the detection process of the capacitive sensor, and the error under the complex construction environment is effectively avoided.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
Fig. 1 is a schematic diagram of the front structure of an anode plate in embodiments 1 and 2 of the present invention;
fig. 2 is a schematic view of detecting the position of a reinforcing bar in embodiments 1 and 2 of the present invention;
FIG. 3 is a schematic diagram of data analysis for detecting the diameter of the steel bar and the capacitance peak value according to embodiments 1 and 2 of the present invention;
fig. 4 is a schematic diagram of data analysis for detecting the thickness of the steel bar protection layer and the capacitance peak in embodiments 1 and 2 of the present invention;
fig. 5 is a schematic diagram of data analysis for detecting the diameter of the steel bar and the area of the capacitance peak in embodiments 1 and 2 of the present invention;
fig. 6 is a schematic diagram of data analysis for detecting the thickness of the steel bar protection layer and the area of the capacitance peak in embodiments 1 and 2 of the present invention;
fig. 7 is a schematic diagram of data analysis of the diameter of the steel bar and the areas of the capacitance peak value and the capacitance peak value detected in embodiments 1 and 2 of the present invention;
fig. 8 is a schematic diagram of data analysis of thickness of the protective layer of the steel bar, the capacitance peak value and the area of the capacitance peak in embodiments 1 and 2 of the present invention.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an", and/or "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof;
for convenience of description, the words "up", "down", "left" and "right" in the present invention, if any, merely indicate correspondence with the directions of up, down, left and right of the drawings themselves, and do not limit the structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the invention.
As introduced in the background art, in the prior art, under the condition that the diameter of the steel bar and the thickness of the steel bar protective layer are unknown, the state of the steel bar in the concrete is difficult to be accurately measured; aiming at the problems, the invention provides a method for detecting the state of a reinforcing steel bar in a concrete structure.
Example 1
In a typical embodiment of the present invention, as shown in fig. 1 to 8, a method for detecting a state of a reinforcement bar in a concrete structure is provided.
The method comprises the following steps:
establishing representation mapping between the capacitance value data and the capacitance peak obtained by scanning the concrete and the state of the reinforcing steel bar according to the capacitance value data and the area of the capacitance peak;
scanning and detecting reinforced concrete members with different specifications;
and establishing a corresponding relation between the detection position and the scanning detection capacitance value, and combining representation mapping to obtain the steel bar position, the steel bar size and the steel bar protective layer thickness of the concrete member.
The steel bars in the concrete are subjected to targeted detection, and the representation mapping and the corresponding relation are utilized, so that the accurate results including the steel bar positions, the steel bar sizes and the thickness of the steel bar protective layer can be conveniently obtained, and the work efficiency of acceptance of constructional engineering and detection, reinforcement and identification of the existing reinforced concrete structure is improved.
The state of the reinforcing steel bar is judged according to the position of the capacitance peak value, the numerical value of the capacitance peak value, the area of the capacitance peak value and other data, and the utilized calculation formula is as follows:
wherein C is the capacitance between two polar plates of the capacitance sensor, and takes Farad (F) as a unit; q is the charge between the two plates, in coulombs (C); u is the voltage between the plates in volts (V).
The variation trend of the capacitance between the electrode plates represents the difference of the position of the steel bar, the size of the steel bar and the thickness of the protective layer of the steel bar in the concrete.
The calibration refers to establishing a characterization mapping between the capacitance value data and the state of the steel bar according to the area of the capacitance peak, wherein the establishment process of the characterization mapping is a calibration process, and specifically, the calibration process comprises the calibration of the capacitance peak and the diameter of the steel bar, the calibration of the capacitance peak and the thickness of the protective layer of the steel bar, the calibration of the area of the capacitance peak and the diameter of the steel bar, and the calibration of the area of the capacitance peak and the thickness of the protective layer of the steel bar.
By establishing a characterization relation among a capacitance peak value, a capacitance peak area and a steel bar state, a basis is provided for rapidly determining the state of the steel bar in the concrete after the concrete is scanned, compared with the traditional calculation of the steel bar state according to a capacitance value, the influence of a non-steel bar coverage area on the capacitance value can be directly eliminated by adopting the capacitance peak value, only the parameter of the capacitance peak value part is considered, and the overall calculation difficulty is reduced;
it should be noted that the areas of the capacitance peaks can be used for representing the states of the steel bars and the changes of the states of the steel bars more intuitively, so that the rapid and intuitive comparison of different areas of the concrete structure is realized.
In the process of scanning and detecting the concrete member, an electrode plate is adopted as a detection unit, and the method specifically comprises the following steps:
detecting the reinforced concrete structure by using a plate electrode of the capacitive steel bar detection device;
engineering information is input into the capacitance type steel bar detection device, the electrode plate is placed on one side of the concrete, and the electrode plate is scanned at a constant speed from one side of the concrete to the other side of the concrete to obtain capacitance values at different positions.
And after the capacitance value is obtained by scanning, processing and analyzing the data of the capacitance value, and establishing a corresponding relation between the detection position and the scanning detection capacitance value.
The method comprises the following specific steps:
the electrode plate moving direction of the capacitive steel bar detection device is used as the detection direction;
establishing a two-dimensional coordinate system along the detection direction, wherein the X axis is the position of the polar plate, the diameter of the reinforcing steel bar or the thickness of the protective layer of the reinforcing steel bar, and the Y axis is the capacitance value obtained by the capacitive reinforcing steel bar detection device;
and (3) detecting the position of the steel bar: the position corresponding to the capacitance peak value is the position of the steel bar.
The relation between the diameter of the detected steel bar and the peak value of the capacitance is as follows: c ═ aB + b (1)
Wherein C is the capacitance value of the position of the steel bar, B is the diameter of the steel bar, and a and B are values obtained after fitting. As shown in fig. 3, when the thickness of the steel bar protective layer is determined, the capacitance value at the steel bar position and the steel bar diameter conform to a linear function relationship, and the steel bar diameter can be calculated according to the capacitance value at the steel bar position by formula (1).
The relation formula for detecting the thickness of the steel bar protection layer and the capacitance peak value is as follows: c ═ C × dD+e (2)
Wherein C is the capacitance value at the position of the steel bar, D is the thickness of the steel bar protective layer, and C, D, and e are the values obtained after fitting, as shown in fig. 4, it is shown that under the condition that the diameter of the steel bar is determined, the capacitance value at the position of the steel bar and the diameter of the steel bar conform to an exponential function relationship, and the thickness of the steel bar protective layer can be calculated according to the capacitance value at the position of the steel bar through a formula (2).
Establishing a two-dimensional coordinate system along the detection direction, wherein the X axis is the diameter of the steel bar or the thickness of the protective layer, and the Y axis is the area of a capacitance peak obtained by the capacitance type steel bar detection device;
the relation between the diameter of the detected steel bar and the area of the peak is as follows: a ═ fB + g (3)
Wherein, a is the area of the capacitance peak calculated after the detection of the capacitive steel bar detection device, B is the diameter of the steel bar, f and g are the values obtained after fitting, as shown in fig. 5, it is shown that under the condition that the thickness of the steel bar protection layer is determined, the area of the capacitance peak and the diameter of the steel bar accord with a linear relationship, and the diameter of the steel bar can be calculated according to the area of the capacitance peak through a formula (3).
Detecting the relation between the thickness of the steel bar protection layer and the area of the peak as follows: a ═ h × iD+j (4)
Wherein, a is the area of the capacitance peak calculated after the detection of the capacitive steel bar detection device, D is the thickness of the steel bar protection layer, and h, i, and j are the values obtained after fitting, as shown in fig. 6, it indicates that the thickness of the steel bar protection layer and the value in accordance with the exponential relationship under the condition that the diameter of the steel bar is determined, and the thickness of the steel bar protection layer can be calculated according to the area of the capacitance peak by formula (4).
Establishing a three-dimensional coordinate system, wherein the X axis is a capacitance peak value detected by the capacitance type steel bar detection device, the Y axis is the area of the capacitance peak calculated after the detection of the capacitance type steel bar detection device, the Z axis is the diameter of the adopted steel bar or the thickness of a protective layer of the steel bar, a1-a12、b1-b12The values obtained after fitting;
the relational expression of the diameter of the steel bar and the areas of the peak value and the peak value of the capacitance is as follows:
z＝a1+a2*(a3/((1+((x-a4)/a5)2)*(1+((y-a6)/a7)2))+(1-a8)*exp(-0.5*((x-a9)/a10)2-0.5*((y-a11)/a12)2)) (5)
the relational expression of the thickness of the steel bar protective layer and the areas of the capacitance peak value and the capacitance peak value is as follows,
z＝b1+b2*exp(-0.5*pow((log(x/b3)/b4),2))+b5*exp(-0.5*pow((log(y/b6)/b7),2))+b8*exp(-0.5*(pow((log(x/b9)/b10),2)+pow((log(y/b11)/b12),2))) (6)
the method solves the problems that under the condition that the diameter of the steel bar and the thickness of the steel bar protective layer are unknown, the state of the steel bar in the concrete is subjected to accurate nondestructive testing, and the diameter of the steel bar and the thickness of the steel bar protective layer can be obtained according to the measured areas of the capacitance peak value and the capacitance peak value.
By the method, the test data of the capacitive steel bar detection equipment are processed and corrected, the result is more accurate, the test is more efficient and convenient, the detection process is not influenced by the difference of materials, and errors in a complex construction environment are effectively avoided.
Example 2
In another exemplary embodiment of the present invention, a method for detecting a state of a reinforcement bar in a concrete structure is provided in conjunction with fig. 1-8.
Fig. 1 shows an electrode plate of the capacitive reinforcement bar detection device in this embodiment;
the electrode plate in the embodiment is composed of a copper electrode and polymethyl methacrylate; the copper electrodes are used for generating excitation voltage and induction voltage, the distance between the copper electrodes is 1cm, the two copper electrodes are placed at the same horizontal height and the same horizontal plane, the size of the copper electrodes is 7.5cm multiplied by 4.5cm multiplied by 0.1cm, and the size of the electrode plates is 10.2cm multiplied by 7.7cm multiplied by 0.3 cm.
It can be understood that electrode plates made of other materials and having other specifications can be adopted, and after the electrode plates are changed, the distance between the electrodes can be adaptively adjusted to meet the detection requirement.
The detection principle is to judge the state of the reinforcing steel bar according to the fluctuation condition of the capacitance value, the size of the capacitance value and the area of a capacitance peak.
The capacitance value of the parallel capacitance type steel bar detection device can be calculated by the following formula:
wherein C is the capacitance between two polar plates of the capacitance type steel bar detection device, and takes Farad (F) as a unit;
q is the charge between the two plates, in coulombs (C);
u is the voltage between the plates in volts (V).
Since the distance between the electrode plates and the effective area of the electrode plates are kept constant, the detection substance between the copper electrodes changes, that is, the charge amount (Q) between the copper electrode plates changes, while the voltage between the electrode plates is kept constant, so that the capacitance (C) between the electrode plates changes.
The difference of reinforcing bar position, size and protective layer thickness in the concrete between the plate electrode all can lead to the electric charge (Q) between the plate electrode to change, detects the state of reinforcing bar in the concrete through this principle.
The detection method is that a capacitance type steel bar detection device based on the electrostatic field capacitance principle detects the state of the steel bar in the concrete, and comprises the following implementation steps:
1) calibration
And the calibration refers to establishing a representation mapping between the capacitance value data and the state of the steel bar according to the capacitance value data. The calibration comprises the calibration of a capacitance peak value and the diameter of the steel bar, the calibration of the capacitance peak value and the thickness of the steel bar protective layer, the calibration of the area of the capacitance peak and the diameter of the steel bar, the calibration of the area of the capacitance peak and the thickness of the steel bar protective layer, the calibration of the area of the capacitance peak and the diameter of the steel bar, and the calibration of the area of the capacitance peak and the area of the reinforcement peak. In particular, the amount of the solvent to be used,
1.1 calibration of capacitance peak value and diameter of steel bar
1.1.1, putting steel bars with different diameters into concrete with the same thickness of a protective layer;
1.1.2, setting parameters of concrete, setting the dielectric constant of the concrete to be 6, and setting other parameters to be initial parameters of equipment;
1.1.3 scanning the electrode plate along one side of the concrete to the other side at a constant speed by using a capacitance type steel bar detection device, measuring capacitance peak values corresponding to different steel bar diameters, and establishing a one-to-one correspondence relationship between the capacitance peak values and the steel bar diameters;
1.1.4 substituting the obtained capacitance value into a formula (1) to detect the diameter of the steel bar; the formula (1) for representing the relation between the capacitance peak value and the diameter of the steel bar is that C is aB + b;
1.2 calibration of capacitance peak value and thickness of steel bar protective layer
1.2.1 placing the steel bars with the same diameter into concrete with different protective layer thicknesses;
1.2.2, setting parameters of concrete, setting the dielectric constant of the concrete to be 6, and setting other parameters to be initial parameters of equipment;
1.2.3 scanning the polar plate of the capacitance type steel bar detection device along one side of a steel bar in concrete at a constant speed to the other side, measuring capacitance peak values corresponding to different thicknesses of the steel bar protective layers, and establishing a one-to-one correspondence relationship between the capacitance peak values and the thicknesses of the steel bar protective layers;
1.2.4 substituting the capacitance value obtained by detection into a formula (2) to detect the thickness of the steel bar protective layer; the formula (2) representing the relationship between the capacitance and the thickness of the steel bar protective layer is that C ═ C ═ dD+e；
1.3 calibration of area of capacitance peak and diameter of reinforcing steel bar
1.3.1 placing the reinforcing steel bars with different diameters into the concrete with the same thickness of the protective layer;
1.3.2, setting parameters of concrete, setting the dielectric constant of the concrete to be 6, and setting other parameters to be initial parameters of equipment;
1.3.3 scanning the electrode plate along one side of the concrete to the other side at a constant speed by using a capacitive steel bar detection device, detecting and processing the areas of capacitance peaks corresponding to different steel bar diameters, wherein the adopted baseline is 5.8pF, and establishing a one-to-one correspondence relationship between the areas of the capacitance peaks and the steel bar diameters;
1.3.4, substituting the area of a capacitance peak obtained after detection and data processing into a formula (3) to detect the diameter of the steel bar; the formula (3) representing the relation between the area of the capacitance peak and the diameter of the reinforcing steel bar is that A is fB + g;
1.4 calibration of area of capacitance peak and thickness of steel bar protective layer
1.4.1 placing the steel bars with the same diameter into concrete with different protective layer thicknesses;
1.4.2, setting parameters of concrete, setting the dielectric constant of the concrete to be 6, and setting other parameters to be initial parameters of equipment;
1.4.3 scanning the polar plate of the capacitance type steel bar detection device along one side of a steel bar in concrete at a constant speed to the other side, detecting and processing the areas of capacitance peaks corresponding to different thicknesses of steel bar protective layers, wherein the adopted base line is 5.8pF, and establishing the one-to-one correspondence relationship between the areas of the capacitance peaks and the thicknesses of the steel bar protective layers;
1.4.4, substituting the area of a capacitance peak obtained after detection and data processing into a formula (4), and detecting the thickness of the steel bar protective layer; the formula (4) for representing the relation between the area of the capacitance peak and the thickness of the steel bar protective layer is that A ═ h × iD+j。
1.5 calibration of capacitance peak value, area of peak and diameter of reinforcing steel bar
1.5.1 placing the reinforcing steel bars with different diameters into the concrete with the same thickness of the protective layer;
1.5.2 setting parameters of the concrete, setting the dielectric constant of the concrete to be 6, and setting other parameters to be initial parameters of equipment;
1.5.3 scanning the electrode plate along one side of the concrete to the other side at a constant speed by using a capacitive steel bar detection device, measuring capacitance peak values corresponding to different steel bar diameters and areas of peaks obtained after data processing, and establishing a one-to-one correspondence relationship among the capacitance peak values, the areas of the peaks and the steel bar diameters;
1.5.4, the capacitance peak value obtained by detection and the peak area after data processing are carried into a formula (5) to detect the diameter of the steel bar; the equation (5) for representing the relation between the peak value of the capacitance and the area of the peak and the diameter of the reinforcing steel bar is that z is a1+a2*(a3/((1+((x-a4)/a5)2)*(1+((y-a6)/a7)2))+(1-a8)*exp(-0.5*((x-a9)/a10)2-0.5*((y-a11)/a12)2))；
1.6 calibration of capacitance peak value, area of peak and thickness of reinforcing steel bar protective layer
1.6.1 placing the steel bars with the same diameter into concrete with different thicknesses of the protective layer;
1.6.2 setting parameters of the concrete, setting the dielectric constant of the concrete to be 6, and setting other parameters to be initial parameters of equipment;
1.6.3 scanning the electrode plate along one side of the concrete to the other side at a constant speed by using a capacitance steel bar detection device, measuring capacitance peak values corresponding to different steel bar protective layer thicknesses and areas of peaks obtained after data processing, and establishing a one-to-one correspondence relationship among the capacitance peak values, the areas of the peaks and the thicknesses of the steel bar protective layers;
1.6.4, the capacitance peak value obtained by detection and the peak area obtained after data processing are carried into a formula (6) to detect the diameter of the steel bar; the formula (6) representing the relation between the capacitance peak value, the area of the peak and the thickness of the steel bar protective layer is as follows,
z＝b1+b2*exp(-0.5*pow((log(x/b3)/b4),2))+b5*exp(-0.5*pow((log(y/b6)/b7),2))+b8*exp(-0.5*(pow((log(x/b9)/b10),2)+pow((log(y/b11)/b12),2)))。
2) finite element calculation to obtain data
2.1 respectively scanning the capacitive steel bar detection device and reinforced concrete members with different steel bar diameters and different protective layer thicknesses;
2.2 detecting the reinforced concrete structure
Placing an electrode plate of the capacitance type steel bar detection device on one side of concrete, inputting necessary engineering information and equipment parameters, scanning the electrode plate along one side of the concrete to the other side at a constant speed to obtain capacitance values of different positions, wherein the capacitance between the electrode plates can be expressed as:
wherein C is the capacitance between two polar plates of the capacitance sensor, and takes Farad (F) as a unit;
q is the charge between the two plates, in coulombs (C);
u is the voltage between the plates in volts (V).
3) Data processing and analysis
3.1 taking the moving direction of the electrode plate as a detection direction;
3.2, establishing a two-dimensional coordinate system, wherein the X axis is the position of the electrode plate, and the Y axis is the capacitance value actually measured by the capacitance type steel bar detection device.
And calculating the position of the steel bar in the concrete, the size of the steel bar and the thickness of the steel bar protection layer by using the data.
Detecting the position of a reinforcing bar
The position of the steel bar in the concrete can be judged according to the position condition of the peak value of the capacitance;
placing an electrode plate of the capacitive steel bar detection device on the surface of the reinforced concrete, scanning the electrode plate along one side of the surface of the reinforced concrete to the other side at a constant speed, and measuring the capacitance value of each position of the reinforced concrete member by taking 2mm as a step length;
the capacitance value at each position after correction is obtained is plotted, which shows that the capacitance sensor can detect the position relationship of the reinforcing steel bars as shown in fig. 2.
Detecting the diameter of a reinforcing bar
Placing an electrode plate of the capacitive steel bar detection device on the surface of reinforced concrete, scanning the electrode plate along one side of the surface of the reinforced concrete member with the same steel bar protective layer thickness and different steel bar diameters at a constant speed to the other side, counting the capacitance peak value measured each time, and comparing the capacitance values of the same steel bar protective layer thickness under different steel bar diameters;
the relation between the diameter of the steel bar and the capacitance value is as follows: c is the capacitance value detected by the capacitive rebar detection device, B is the diameter of the rebar, and a and B are the fitted values, which shows the relationship between the diameters of the rebar detected by the capacitive sensing device as shown in fig. 3.
Placing an electrode plate of the capacitive steel bar detection device on the surface of reinforced concrete, scanning the electrode plate along one side of the surface of a reinforced concrete member with the same steel bar protective layer thickness and different steel bar diameters at a constant speed to the other side, counting the area of a capacitance peak value after each measurement and processing, and comparing the area relations of the capacitance peak values of the same steel bar protective layer thickness under different steel bar diameters;
the relational expression of the diameter of the steel bar and the area of the capacitance peak is as follows: and a is fB + g, where a is the area of the capacitance peak obtained after detection and processing by the capacitive rebar detection device, B is the diameter of the rebar, and f and g are values obtained after fitting, which shows that the capacitance sensor can detect the diameter relationship of the rebar as shown in fig. 5.
Detecting protective layer thickness of steel bar
Placing an electrode plate of the capacitive reinforcing steel bar detection device on the surface of reinforced concrete, scanning the electrode plate along one side of the surface of the reinforced concrete member with the same reinforcing steel bar diameter and different reinforcing steel bar protective layer thicknesses at a constant speed to the other side, counting the capacitance peak value detected by the capacitive reinforcing steel bar detection device each time, and comparing the capacitance peak values of the same reinforcing steel bar diameter under different reinforcing steel bar protective layer thicknesses;
the relational expression between the thickness of the steel bar protective layer and the area of the capacitance peak is as follows: c ═ C × dD+ e, where C is a capacitance peak value detected by the capacitive steel bar detection device, D is a steel bar protective layer thickness, and C, D, and e are values obtained after fitting, which shows a relationship that the capacitance sensor can detect the steel bar protective layer thickness as shown in fig. 4.
Placing an electrode plate of the capacitive steel bar detection device on the surface of reinforced concrete, scanning the electrode plate along one side of the surface of the reinforced concrete member with the same steel bar diameter and different steel bar protective layer thicknesses at a constant speed to the other side, counting the area of a capacitance peak after each time of detection and processing by the capacitive steel bar detection device, and comparing the relation of the areas of the capacitance peaks of the same steel bar diameter under different steel bar protective layer thicknesses;
the relational expression between the thickness of the steel bar protective layer and the area of the capacitance peak is as follows: a ═ h × iD+ j, where a is the area of the capacitance peak obtained after detection and processing by the capacitive rebar detection device, D is the thickness of the rebar protection layer, and h, i, j are the values obtained after fitting, as shown in fig. 6, it indicates that the capacitance sensing can detect the relationship of the thickness of the rebar protection layer.
The capacitance value data, the capacitance peak value and the area of the capacitance peak value detected by the capacitance type steel bar detection device are utilized, so that the quantitative judgment is small in error, the field detection is convenient, and the application of the capacitance value data, the capacitance peak value and the area of the capacitance peak value in practical engineering is realized.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for detecting the state of a reinforcing steel bar in a concrete structure is characterized by comprising the following steps:
establishing representation mapping between the capacitance value data and the capacitance peak obtained by scanning the reinforced concrete member and the state of the steel bar according to the capacitance value data and the area of the capacitance peak;
scanning and detecting concrete members with different specifications;
and establishing a corresponding relation between the detection position and the scanning detection capacitance value, and combining representation mapping to obtain the steel bar position, the steel bar size and the steel bar protective layer thickness of the concrete member.
2. The method of claim 1, wherein the calibration capacitance value data, the area of the capacitance peak and the characterization of the state of the steel bar are mapped.
3. The method of claim 2, wherein the calibration process comprises calibrating the capacitance peak value and the steel bar diameter, calibrating the capacitance peak value and the steel bar protection layer thickness, calibrating the capacitance peak area and the steel bar diameter, calibrating the capacitance peak area and the steel bar protection layer thickness, calibrating the capacitance peak value and the capacitance peak area and the steel bar diameter, and calibrating the capacitance peak value and the capacitance peak area and the steel bar protection layer thickness.
4. The method of claim 3, wherein the diameter of the steel bar and the thickness of the protective layer are controlled to create a mapping of the diameter of the steel bar and the thickness of the protective layer to the capacitance value data and the area of the capacitance peak.
5. The method for detecting the state of reinforcing bars in a concrete structure according to claim 1, wherein said scanning detection process comprises the steps of: and setting parameters of the capacitive steel bar detection device and detecting the reinforced concrete members in different states.
6. The method according to claim 5, wherein an electrode plate of the capacitive reinforcement sensing device is placed on one side of the reinforced concrete member, engineering information is inputted into the capacitive reinforcement sensing device, and the electrode plate is scanned at a constant speed along one side of the reinforced concrete member to the other side thereof, thereby obtaining capacitance values at different positions.
7. The method of claim 5, wherein the capacitive reinforcement sensing device is used to scan and sense concrete members with different reinforcement diameters and different protective layer thicknesses.
8. The method according to claim 1, wherein a two-dimensional coordinate system is established along the detection direction, the X-axis is the position of the plate, the diameter of the reinforcing steel bar or the thickness of the protective layer of the reinforcing steel bar, and the Y-axis is the capacitance detected by the capacitive reinforcing steel bar detector;
the moving direction of the capacitive steel bar detection device in the scanning detection process is the detection direction.
9. The method of claim 8, wherein a two-dimensional coordinate system is established along the detection direction, the X-axis is a diameter of the reinforcing bar or a thickness of the protective layer, and the Y-axis is an area of a capacitance peak obtained by the capacitive reinforcing bar detecting device through data processing.
10. The method of claim 8, wherein a three-dimensional coordinate system is established, the X-axis is a capacitance peak value detected by the capacitance steel bar detecting device, the Y-axis is an area of the capacitance peak value obtained by the capacitance steel bar detecting device through data processing, and the Z-axis is a diameter of the steel bar or a thickness of the protective layer of the steel bar.
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| CN113566692A (en) * | 2021-07-23 | 2021-10-29 | 国网天津市电力公司电力科学研究院 | Nondestructive testing method for quality of cable cement protection cover plate |
| WO2022143281A1 (en) * | 2020-12-28 | 2022-07-07 | 青岛理工大学 | Method for inspecting state of steel bar in concrete structure |
| CN114777642A (en) * | 2022-03-16 | 2022-07-22 | 交通运输部公路科学研究所 | In-service concrete pavement slab passes three-dimensional space position detecting system of lotus component |
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