Concrete filled steel tube void detection method based on frequency dynamic response characteristics of impact elastic waves

Abstract

According to the concrete-filled steel tube void detection method based on the impact elastic wave frequency dynamic response characteristic, the impact elastic wave frequency dynamic response characteristic is creatively used for concrete-filled steel tube void detection, the tedious calibration process in a traditional method is overcome, detection can be rapidly and accurately carried out, the detection result is stable, and the detection accuracy is high. And intuitively and clearly displaying through a contour map.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for voids in steel-concrete composite pipes, specifically to a method for detecting voids in steel-concrete composite pipes based on the frequency dynamic response characteristics of impact elastic waves. Background Technology

[0002] Concrete-tube steel (CTB) has a wide range of applications in civil engineering. It is increasingly being chosen for bridge construction and other large-scale infrastructure projects, with arch bridges built using CTB found all over the world. The widespread use of CTB in bridge construction is inseparable from its superior mechanical properties and structural characteristics. CTB possesses good plasticity, high ductility, and high strength. However, numerous engineering examples have shown that, because the concrete is sealed inside the steel tube, and due to the inherent properties of the concrete and on-site construction techniques, voids often occur within CTBs. This means that a large amount of air exists between the concrete surface and the inner surface of the steel tube, making these void defects difficult to detect during inspection.

[0003] In the field of non-destructive testing, the impact-echo method is commonly used to detect voids in concrete-filled steel tubes. This method is widely applied in engineering projects. However, the results are unstable, and it cannot accurately reflect the internal quality of the concrete-filled steel tubes under complex environments. This leads to reduced structural safety and can easily cause significant personal injury and property damage. Therefore, how to accurately detect voids in concrete-filled steel tubes is a technical problem that urgently needs to be solved by professionals in this field. Summary of the Invention

[0004] This invention aims to quickly and accurately locate void areas in steel-concrete composite tubes, providing a method for detecting void defects in steel-concrete composite tubes.

[0005] The present invention provides a method for detecting voids in steel-concrete composite structures based on the frequency response characteristics of impact elastic waves, comprising the following steps:

[0006] S1. Place the sensor in the area to be measured, that is, place the sensor on the surface of the steel pipe concrete structure;

[0007] S2. By striking the structural surface around the sensor with a vibrating hammer, the sensor collects vibration signals from the steel-concrete composite surface.

[0008] S3. The signal acquired by the sensor is processed by fast Fourier transform spectrum analysis, and frequency response analysis is performed to extract the measurement index A.

[0009] S4. Assign the measurement indices A1, A2, A3, ..., A... to the survey area. n Fill in the corresponding locations in the survey area to create contour maps.

[0010] In the above scheme, the impact elastic wave exhibits frequency response characteristics. That is, after acquiring waveform data and performing fast Fourier transform spectral analysis to obtain the frequency domain data of the waveform, the vibration energy in the vacuolated region is higher than that in the dense region within a certain frequency range. This characteristic can be used to detect the quality of steel-concrete composite tubes. By analyzing the acquired data, the energy level can be determined to reflect the quality of the steel-concrete composite tube. This scheme uses a single-channel accelerometer and a D17 model impact hammer to acquire appropriate data under different conditions. After processing the data through fast Fourier transform spectral analysis, the frequency response characteristics are used to analyze the data, derive the measurement index, and generate contour maps to reflect the internal quality of the steel-concrete composite tube.

[0011] In one optional embodiment, the data processed using frequency response characteristics is used to extract the measurement index, including:

[0012] Step S31. Several data points (at least 9 data points) are collected and subjected to Fast Fourier Transform spectral analysis to obtain several frequency domain data points S1 ((x 11 y 11 (x) 12 y 12 (x) 13 y 13 ), ..., (x 1i y 1i S2((x)) 21 y 21 (x) 22 y 22 (x) 23 y 23 ), ..., (x 2i y 2i S3((x)) 31 y 31 (x) 32 y 32 (x) 33 y 33 ), ..., (x 3i y 3i ), ..., S n ((x) n1 y n1 (x) n2 y n2 (x) n3 y n3 ), ..., (x ni y ni ), where (x) ni y ni () represents the data collected in the nth time, the i-th coordinate point, x represents the frequency, and y represents the amplitude;

[0013] Step S32. Process the obtained frequency domain data S1, S2, S3, ..., S n Calculate the centroid frequencies f1, f2, f3, ..., f n ;

[0014] Step S33. Based on the calculated centroid frequencies f1, f2, f3, ..., f n Find f min ={f1, f2, f3, ..., f n} min and f max ={f1, f2, f3, ..., f n} max ;

[0015] Step S34. In [f min f max Search within the frequency range for values ​​at S1, S2, S3, ..., S n The maximum values ​​are Y1, Y2, Y3, ..., Y n ;

[0016] Step S35. Based on the obtained Y1, Y2, Y3, ..., Y n The measured indices are calculated respectively, and their corresponding values ​​are A1, A2, A3, ..., A n .

[0017] In one alternative embodiment, calculating the centroid frequency f includes:

[0018]

[0019] In the above formula, N is the number of data collection points.

[0020] In an optional embodiment, the determination index A is calculated. n include:

[0021]

[0022] In the above formula, j = 1, 2, 3, ..., n;

[0023] In one alternative embodiment, a measurement index A is calculated by weighting the results, and the measurement index ranges from 0 to 1.

[0024] Compared with the prior art, the present invention has the following advantages and intuitive effects:

[0025] 1. Innovatively utilizes the frequency response characteristics of impact elastic waves for the detection of voids in steel-concrete composite pipes, simplifying the cumbersome calibration process in traditional methods;

[0026] 2. This invention can quickly and accurately detect voids in steel pipe concrete;

[0027] 3. The results of this invention are presented through images, and the results are stable, intuitive and clear. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Those skilled in the art can also obtain other related drawings based on the following drawings. In the drawings:

[0029] Figure 1 This is a schematic diagram of the detection of voids in steel-concrete composite pipes provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of contour line results provided in an embodiment of the present invention;

[0031] Figure 3 A schematic flowchart of a method for detecting voids in steel-concrete composite structures based on the frequency response characteristics of impact elastic waves, provided for an embodiment of the present invention;

[0032] Figure 4 The model of the excitation hammer provided in the embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are limited to this invention and are not intended to limit this invention.

[0034] Example

[0035] Figure 3 This invention provides a flowchart illustrating a method for detecting voids in steel-concrete composite structures based on the frequency response characteristics of impact elastic waves, as shown in the following embodiment. Figure 3 As shown, a method for detecting voids in steel-concrete composite structures based on the frequency response characteristics of impact elastic waves includes the following steps:

[0036] Step S1. Place the sensor in the area to be measured, that is, place the sensor on the surface of the steel pipe concrete structure;

[0037] It should be noted that impact elastic waves exhibit frequency response characteristics. This means that after acquiring waveform data and performing fast Fourier transform spectral analysis to obtain the frequency domain data of the waveform, the vibration energy in the vacuolated region is higher than that in the dense region within a certain frequency range. This characteristic can be used to detect the quality of steel-concrete composite structures. By analyzing the acquired data, the energy level can be determined, reflecting the quality of the steel-concrete composite structure. The sensor used in this step is a single-channel sensor, and data is acquired through a single channel as follows: Figure 1As shown.

[0038] Furthermore, a vibratory hammer with a diameter of 17mm is selected, such as... Figure 4 As shown.

[0039] Step S2. The structural surface is struck around the sensor by a vibrating hammer, and the sensor collects the vibration signal of the steel pipe concrete surface.

[0040] It should be noted that the distance between the striking point and the sensor can be any value between 0.02m and 0.03m. In this embodiment, the striking point is 0.02m away from the sensor.

[0041] Step S3. The signal acquired by the sensor is processed by fast Fourier transform spectrum analysis, and the frequency response characteristics are analyzed to extract the measurement index A.

[0042] It should be noted that the acquired signal first needs to be processed by low-pass filtering.

[0043] In one optional embodiment, the quality judgment index is extracted from the data processed by frequency response characteristic analysis, including:

[0044] Step S31. Several data points (at least 9 data points) are collected and subjected to Fast Fourier Transform spectral analysis to obtain several frequency domain data points S1 ((x 11 y 11 (x) 12 y 12 (x) 13 y 13 ), ......, (x 1i y 1i S2((x)) 21 y 21 (x) 22 y 22 (x) 23 y 23 ), ......, (x 2i y 2i S3((x)) 31 y 31 (x) 32 y 32 (x) 33 y 33 ), ......, (x 3i y 3i ), ..., S n ((x) n1 y n1 (x) n2 y n2 (x) n3 yn3 ), ......, (x ni y ni ), where (x) ni y ni () represents the data collected in the nth time, the i-th coordinate point, x represents the frequency, and y represents the amplitude;

[0045] Step S32. Process the obtained frequency domain data S1, S2, S3, ..., S n Calculate the centroid frequencies f1, f2, f3, ..., f n；

[0046] In one alternative embodiment, calculating the centroid frequency f includes:

[0047]

[0048] In the above formula, N is the number of data collection points.

[0049] Step S33. Based on the calculated centroid frequencies f1, f2, f3, ..., f n Find f min ={f1, f2, f3, ..., f n} min and f max ={f1, f2, f3, ..., f n} max ;

[0050] Step S34. In [f min f max Search within the frequency range for values ​​at S1, S2, S3, ..., S n The maximum values ​​are Y1, Y2, Y3, ..., Y n ;

[0051] Step S35. Based on the obtained Y1, Y2, Y3, ..., Y n The measured indices were calculated respectively, and their corresponding values ​​are A1, A2, A3, ..., A n ;

[0052] In an optional embodiment, the determination index A is calculated. n include:

[0053]

[0054] In the formula, j = 1, 2, 3, ..., n.

[0055] In one alternative embodiment, a measurement index A is calculated by weighting the results, and the measurement index ranges from 0 to 1.

[0056] It should be noted that the measured index is plotted as contour lines, such as... Figure 2 As shown, the colors are used to distinguish the magnitude of the measured index. Testing is performed using a single-channel sensor, the measured index is extracted, and contour lines are filled into a map according to the grid of the test area.

[0057] Compared with the prior art, the present invention has the following advantages and intuitive effects:

[0058] 1. Innovatively utilizes the frequency dynamic characteristics of impact elastic waves for the detection of voids in steel-concrete composite pipes, simplifying the cumbersome calibration process in traditional methods;

[0059] 2. This invention can quickly and accurately detect voids in steel pipe concrete;

[0060] 3. The results of this invention are presented through images, making the results intuitive and clear.

[0061] To illustrate the effectiveness of this invention, this embodiment uses a steel-concrete composite model of a construction project (the steel pipe has an outer diameter of 650mm, a wall thickness of 4mm, and is filled with self-compacting concrete). A void defect is set in the middle of the test area. After being struck by the vibration device, data is collected by a single-channel sensor. After frequency response characteristic analysis, the results are as follows: Figure 2 According to the contour map results, the analysis and testing results of the steel-concrete composite void detection method based on the frequency response characteristics of impact elastic waves used in this invention coincide with the actual defect location.

Claims

1. A method for detecting voids in steel pipes based on the frequency response characteristics of impact elastic waves, characterized in that, The method includes the following steps: S1. Place the sensor in the area to be measured, that is, place the sensor on the surface of the steel pipe concrete structure; S2. By striking the structural surface around the sensor with a vibrating hammer, the sensor collects vibration signals from the steel-concrete composite surface. S3. The signal acquired by the sensor is processed by fast Fourier transform spectrum analysis, and the frequency response analysis is performed to extract the measurement index A. S4. Assign the measurement indices A1, A2, A3, ..., A... to the survey area. n Fill in the corresponding locations in the survey area to create contour maps.

2. The method for detecting voids in steel pipes based on the frequency response characteristics of impact elastic waves as described in claim 1, characterized in that, The measured indices are extracted from the data processed using frequency response characteristics analysis, including: Step S31. Several data points (at least 9 data points) are collected and subjected to Fast Fourier Transform spectral analysis to obtain several frequency domain data points S1 ((x 11 y 11 (x) 12 y 12 (x) 13 y 13 ), ..., (x 1i y 1i S2((x)) 21 y 21 (x) 22 y 22 (x) 23 y 23 ), ..., (x 2i y 2i S3((x)) 31 y 31 (x) 32 y 32 (x) 33 y 33 ), ..., (x 3i y 3i ), ..., S n ((x) n1 y n1 (x) n2 y n2 (x) n3 y n3 ), ..., (x ni y ni ), where (x) ni y ni () represents the data collected in the nth time, the i-th coordinate point, x represents the frequency, and y represents the amplitude; Step S32. Process the obtained frequency domain data S1, S2, S3, ..., S n Calculate the centroid frequencies f1, f2, f3, ..., f n ; Step S33. Based on the calculated centroid frequencies f1, f2, f3, ..., f n Find f min ={f1, f2, f3, ..., f n } min and f max ={f1, f2, f3, ..., f n } max ; Step S34. In [f min f max Search within the frequency range for values ​​at S1, S2, S3, ..., S n The maximum values ​​are Y1, Y2, Y3, ..., Y n ; Step S35. Based on the obtained Y1, Y2, Y3, ..., Y n The measured indices are calculated respectively, and their corresponding values ​​are A1, A2, A3, ..., A n .

3. The method for detecting voids in steel pipes based on the frequency response characteristics of impact elastic waves as described in claim 2, characterized in that, In one alternative embodiment, calculating the centroid frequency f includes: In the above formula, N is the number of data collection points.

4. The method for detecting voids in steel pipes based on the frequency response characteristics of impact elastic waves as described in claim 2, characterized in that, In an optional embodiment, the determination index A is calculated. n include: In the above formula, j = 1, 2, 3, ..., n.

5. The method for detecting voids in steel pipes based on the frequency response characteristics of impact elastic waves as described in claim 4, characterized in that, In one alternative embodiment, a measurement index A is calculated by weighting the results, and the measurement index ranges from 0 to 1.

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