A crack discrimination method for steel-concrete composite beams based on bending wave structural acoustic intensity concentration test

Abstract

The application discloses a steel-concrete composite beam crack discrimination method based on bending wave structural sound intensity aggregation degree testing, which comprises the following steps: dividing a to-be-tested plate into a series of scanning areas, setting a scanning path, and calculating the bending wave structural sound intensity aggregation degree; traversing the plate according to a scanning algorithm and calculating the bending wave structural sound intensity aggregation degrees of all areas; calculating the bending wave structural sound intensity aggregation degrees of all areas of the steel-concrete composite beam plate in a service period; comparing the bending wave structural sound intensity aggregation degree spectrum peak values, and if the difference between the bending wave structural sound intensity aggregation degree spectrum peak values of a scanning area of the two exceeds a preset threshold value, it is determined that the scanning area of the steel-concrete composite beam plate in the service period has cracks. The application combines the characteristics that the bending wave signal is easy to test, adopts the bending wave structural sound intensity testing technology and the structural sound intensity aggregation degree scanning algorithm, and can realize efficient discrimination and positioning of the steel-concrete composite beam cracks, and has great theoretical significance and engineering value for damage identification of the bridge.

Description

Technical Field

[0001] The invention relates to a steel-concrete composite beam crack identification method based on bending wave structural sound intensity concentration test, and belongs to the technical field of bridge damage identification. Background Art

[0002] Steel-concrete composite beam bridges suffer from serious plate cracking due to fatigue loads, cyclical temperatures, and environmental corrosion. Common types of cracks experienced by such bridges during service include: plate cracking at coupling boundaries due to fatigue loads, top plate cracking due to negative bending moments, and plate splitting due to slippage of shear connectors. The causes of the above damage are complex, and some cracks are typical hidden damage that cannot be effectively identified by existing methods such as manual visual inspection and machine vision. For complex and large steel-concrete composite beam structures, existing non-destructive testing methods such as acoustic emission, ultrasound, radiography, and eddy current testing have the disadvantages of low efficiency and inaccurate detection. In addition, since structural cracks are relatively small, their impact on the overall stiffness of the structure is relatively small. Conventional identification methods such as vibration fundamental frequency and mode are more effective in identifying overall damage, but their sensitivity to this type of local damage is low, and it is difficult to locate the damage when the number of sensors is limited.

[0003] When the vibration power flow passes through a structural crack, a bypass phenomenon will occur, and obvious vibration energy accumulation will appear at the tip of the crack. This point can be used to identify damage to the plate. Since the bridge bears vertical excitation loads, the vibration energy in its top and bottom plates is mainly carried by bending waves. Bending waves are out-of-plane vibration waves and are easy to test using sensors or high-speed cameras. However, most current research is theoretical, and its calculation method is not suitable for actual measurement operations, and there is no unified judgment index. For example, patents CN202410109372.1 and CN202210364847.2 only use finite element numerical methods to calculate structural sound intensity, and do not provide a calculation method for structural sound intensity from a measurement perspective, nor do they provide discrimination indicators and damage location methods. Summary of the Invention

[0004] In order to overcome the defects existing in the prior art, the present invention aims to provide a method for identifying cracks in steel-concrete composite beams based on bending wave structural sound intensity concentration testing. This method combines the characteristics of bending wave signals that are relatively easy to test, adopts bending wave structural sound intensity testing technology and structural sound intensity concentration scanning algorithm, and can realize the efficient identification and location of cracks in steel-concrete composite beams. It has important theoretical significance and engineering value for damage identification of such bridges.

[0005] The present invention provides a technical solution to solve the above technical problems: a method for identifying cracks in steel-concrete composite beams based on bending wave structural sound intensity concentration testing, comprising the following steps:

[0006] S1. Delimit the panel to be tested into a series of scanning areas and set the scanning path, and calculate the bending wave structural sound intensity concentration of the initial steel-concrete composite beam scanning area;

[0007] The scanning area size is length × width = a × b, where a and b are integer multiples of the measurement point spacing, and the area of ​​a × b is no more than 1 / 4 of the total area of ​​the panel.

[0008] S2. Traverse the plate according to the scanning algorithm, calculate the bending wave structure sound intensity concentration of all regions of the initial steel-concrete composite beam plate, and draw a bending wave structure sound intensity concentration spectrum of the initial steel-concrete composite beam plate;

[0009] S3, calculating the bending wave structural sound intensity concentration of the scanning area of ​​the service-period steel-concrete composite beam according to the scanning area and scanning path in step S1;

[0010] S4. Traverse the plate according to the scanning algorithm, calculate the bending wave structure sound intensity concentration of all regions of the steel-concrete composite beam plate during service, and draw a bending wave structure sound intensity concentration spectrum of the steel-concrete composite beam plate during service;

[0011] S5. Compare the peak values ​​of the flexural wave structure sound intensity concentration spectrum of all regions of the initial steel-concrete composite beam plate with the peak values ​​of the flexural wave structure sound intensity concentration spectrum of all regions of the service-period steel-concrete composite beam plate. If the difference in the peak values ​​of the flexural wave structure sound intensity concentration spectrum of a certain scanning area between the two exceeds a preset threshold, it is determined that cracks exist in the scanning area of ​​the service-period steel-concrete composite beam plate.

[0012] A further technical solution is that the scanning area includes several target points.

[0013] A further technical solution is to set four measuring points at the same interval d / 2 at 0°, 90°, 180° and 270°; the upper limit of the ratio of the measuring point interval d to the plate bending wavelength λ is 0.2.

[0014] The calculation formula for the plate bending wavelength λ is as follows:

[0015]

[0016] Where: h is the thickness of the plate to be tested, C1 is the longitudinal wave velocity of the plate material to be tested, and f is the frequency.

[0017] A further technical solution is that the calculation process of the sound intensity concentration of the bending wave structure includes:

[0018] Step 1: Determine the density of measuring points and obtain vibration data of four measuring points, where the vibration data is vibration acceleration or vibration displacement;

[0019] Step 2: Calculate the magnitude and amplitude of the bending wave structure sound intensity vector based on the vibration data of the four measuring points;

[0020] Step 3: Construct a frequency domain three-dimensional vector cloud and streamlines based on the bending wave structure sound intensity amplitude;

[0021] Step 4: Calculate the bending wave structure sound intensity concentration in the scanning area based on the bending wave structure sound intensity amplitude.

[0022] A further technical solution is that in step 1, an acceleration sensor is placed at each measuring point to obtain vibration data, wherein the mass m of the acceleration sensor is A <1% of the structural mass m.

[0023] A further technical solution is that the specific process of step 2 includes:

[0024] Step 21: Convert the vibration data into acceleration and perform Fourier transform to obtain the real part and imaginary part;

[0025] Step 22: Differentiate the vibration acceleration data in the frequency domain;

[0026] Step 23: Calculate the magnitude and amplitude of the bending wave structural sound intensity vector at each grid point based on the measured vibration acceleration data.

[0027] The bending wave structure-borne sound intensity amplitude I at the i-th grid point is i The structural sound intensity components I of the bending wave in the x and y directions xi , I yi Obtained by vector addition.

[0028] A further technical solution is that the calculation formula in step 23 is:

[0029]

[0030] Where: m is the mass per unit area of ​​the plate; d is the distance between the measuring points; D x and D y are the bending stiffness of the plate in the x and y directions respectively; G 12 , G 34 The cross spectrum of the acceleration signal in the x and y directions for each grid point.

[0031] A further technical solution is that the specific process of step 3 includes:

[0032] Step 31: performing normalization processing based on the bending wave structure-borne sound intensity amplitude obtained in step S2;

[0033] Normalized bending wave structure-borne sound intensity I i ' is expressed as:

[0034]

[0035] Where: I max represents the maximum bending wave structure-borne sound intensity amplitude among all grid points;

[0036] Step 32: Determine the spatial coordinates of the grid points based on the density of the measuring points, and draw a three-dimensional cloud map based on the normalized bending wave structure sound intensity;

[0037] Step 33: Using the grid point coordinates as the starting point and the normalized bending wave structure-borne sound intensity as the vector length, draw a three-dimensional vector diagram and a streamline diagram of the bending wave structure-borne sound intensity;

[0038] Step 34: superimpose the three-dimensional cloud map, vector map, and streamline map to obtain a three-dimensional vector cloud map and streamline map of bending wave structure sound intensity.

[0039] A further technical solution is that the calculation formula in step 4 is:

[0040]

[0041] Where: Max.I j is the maximum bending wave structure-borne sound intensity amplitude in the jth scanning area, Ave.I plate A is the average bending wave structure-borne sound intensity amplitude of all grid points of the panel to be tested; j is the concentration of the bending wave structure sound intensity in the j-th scanning area.

[0042] A further technical solution is that the specific process of the scanning algorithm traversing the plate includes:

[0043] A. Determine the appropriate step size k and translate the scanning area;

[0044] Wherein, the step length k is an integer multiple of the measurement point spacing d, and k < 5d;

[0045] B. According to the scanning path, the scanning area is translated by a distance k, and the bending wave structure sound intensity concentration A of the scanning area is calculated. j+1 ;

[0046] C. Repeat step B until the entire panel to be tested is traversed and the bending wave structure sound intensity concentration of each scanning area is obtained.

[0047] The present invention has the following beneficial effects: the present invention draws a spectrum diagram of the sound intensity concentration of the bending wave structure in each area. By comparing its single-frequency pulse peak value, the cracks in the steel-concrete composite beam can be identified, which has great theoretical significance and engineering value for the vibration wave transmission analysis and crack identification of thin-walled bridge damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1This is a schematic diagram of the steel-concrete composite beam structure according to an embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram of acceleration measurement points according to an embodiment of the present invention;

[0050] Figure 3 Schematic diagram of the scanning algorithm for the acoustic intensity concentration of bending wave structures according to an embodiment of the present invention;

[0051] Figure 4 This is a vector cloud diagram of the sound intensity of bending waves in a concrete slab according to an embodiment of the present invention;

[0052] Figure 5 This is a spectrum diagram of the acoustic intensity concentration of the bending wave structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] Before describing the specific embodiments of the present invention, some key terms need to be explained to make the present invention more clear and complete:

[0055] Steel-concrete composite box girder: A box structure composed of an upper concrete slab 01 and a lower steel beam 02 that jointly bears the upper load of the bridge. Its plates can all be regarded as thin-walled plates.

[0056] Lower steel beam 02: A steel trough structure composed of flange plate 021, web plate 022, diaphragm 023 and bottom plate 024.

[0057] Structural sound intensity: mathematically defined as the product of stress and velocity response at any point, it represents the magnitude of the power flow through the unit cross-section of the structure. It is composed of longitudinal wave, shear wave, bending wave, and torsional wave components.

[0058] Bending wave structure-borne sound intensity: a component of the structure-borne sound intensity that dominates the top and bottom plates of steel-concrete composite beams.

[0059] Measuring point 03: The test point of vibration acceleration, used to differentially calculate the original data of bending wave structural sound intensity. There are 4 target points 04, namely 031, 032, 033, and 034.

[0060] Target point 04: The point where the bending wave structure-borne acoustic intensity is to be obtained.

[0061] Scanning area 05: An area in which the plate is further divided according to the estimated crack size, including several target points 04, and is the minimum area for determining whether there are cracks.

[0062] Maximum bending wave structure-borne sound intensity point 06: The target point with the maximum bending wave structure-borne sound intensity amplitude within the scanning area.

[0063] Scanning path 07: Ensures that the scanning area 05 can traverse the translation route of the entire panel.

[0064] In this embodiment, Figure 2 As shown in the figure, the flexural wave structure-borne acoustic intensity of the top plate of a steel-concrete composite box girder was measured using differential acceleration sensors, achieving three-dimensional visualization of the flexural wave energy transfer. A scanning algorithm was used to compare the structural acoustic intensity concentration in damaged and undamaged states. Specifically, a single-box, single-chamber steel-concrete composite box girder model was investigated. The model consists of an upper concrete slab and a lower steel beam, with total dimensions of 3180 (length) × 1150 (width) × 680 (height) mm. The concrete slab is 60 mm thick, and the steel beams are 6 to 10 mm thick. A sinusoidal excitation was applied at the center of the top plate using a vibrator.

[0065] The present invention provides a method for identifying cracks in steel-concrete composite beams based on a bending wave structural sound intensity concentration test, which specifically includes the following steps:

[0066] S1. Delimit the panel to be tested into a series of scanning areas and set the scanning path, and calculate the bending wave structural sound intensity concentration of the initial steel-concrete composite beam scanning area;

[0067] In this embodiment, assuming that the estimated crack length is 0.4 mm, a scanning area 05 size of 0.6 × 0.4 m is selected, with the horizontal and vertical dimensions being 6 times and 4 times the test grid size, respectively. The area of ​​the scanning area 05 is much smaller than 1 / 4 of the total area of ​​the panel.

[0068] The scanning area 05 includes 10 target points 04, and the target points 04 are provided with 4 measuring points at the same interval d / 2 at 0°, 90°, 180°, and 270°;

[0069] In this embodiment, the frequency range is 20 to 2000 Hz, and the bending wavelength of the concrete slab at 2000 Hz is determined to be λ = 0.46 mm. The calculation formula is as follows:

[0070]

[0071] Where: h is the thickness of the plate to be tested, C1 is the longitudinal wave velocity of the plate material to be tested, and f is the frequency;

[0072] Therefore, the target point spacing is determined to be 0.1 m, and the spacing is 0.1 m. At this time, the ratio of the test grid to the bending wavelength of the plate is 0.19 < 0.2, and the measurement point spacing d = 0.2 m.

[0073] The specific calculation process of the acoustic intensity concentration of the bending wave structure is as follows:

[0074] Step 1: Determine the density of measuring points and place an acceleration sensor at each measuring point to obtain vibration data. Obtain vibration data of four measuring points;

[0075] like Figure 3 As shown, the mass of the acceleration sensor is m A About 50g, much less than 1% of the structure's mass;

[0076] Step 2: Calculate the magnitude and amplitude of the bending wave structure sound intensity vector based on the vibration data of the four measuring points;

[0077] Step 21: Convert the vibration data into acceleration and perform Fourier transform to obtain the real part and imaginary part;

[0078] Step 22: Circularly select the measurement point 03 corresponding to each target point 04, perform differential on the acceleration signal, and calculate the cross-spectrum G of the acceleration signal of each target point 04 in the x and y directions. 12 , G 34 ;

[0079] The cross spectrum G of the acceleration signal in the x and y directions of each grid point 12 , G 34 Expressed as:

[0080]

[0081] Where: is the complex conjugate of the acceleration of the measuring points 031 and 033 at the frequency ω, A2(ω) and A4(ω) are the complex acceleration of the measuring points 032 and 034 at the frequency ω, G 12 The positive direction is 032 pointing to 031, G 34 The positive direction is 034 pointing to 033;

[0082] Step 23, calculating the magnitude and amplitude of the bending wave structure sound intensity vector at each target point 04;

[0083] The bending wave structure-borne sound intensity amplitude I at the i-th grid point is i The structural sound intensity components I of the bending wave in the x and y directions xi , I yi Obtained by vector addition;

[0084]

[0085] Where: m is the mass per unit area of ​​the plate; d is the distance between the measuring points; D x and D y are the bending stiffness of the plate in the x and y directions respectively; G 12 , G34 The cross spectrum of the acceleration signal in the x and y directions for each grid point;

[0086] Step 3: Construct a frequency domain three-dimensional vector cloud and streamlines based on the bending wave structure sound intensity amplitude;

[0087] Step 31: Based on the result obtained in step S2, normalization processing is performed to normalize the amplitude of the global maximum structure-borne sound intensity vector to 1;

[0088] Normalized bending wave structure-borne sound intensity I i ' is expressed as:

[0089]

[0090] Where: I max represents the maximum bending wave structure-borne sound intensity amplitude among all grid points;

[0091] Step 32: Visualize the structural sound intensity of the steel-concrete composite beam by using Tecplot software to draw a three-dimensional cloud map based on the geometric position of the target point 04 and its corresponding bending wave structural sound intensity vector;

[0092] Step 33, take the coordinates of target point 04 as the starting point of the vector and calculate I x and I y As the vector length, draw the three-dimensional vector diagram of the bending wave structure sound intensity;

[0093] Step 34: superimpose the three-dimensional cloud map, vector map, and streamline map to obtain a three-dimensional vector cloud map and streamline map of bending wave structure-induced sound intensity.

[0094] Step 4: Calculate the bending wave structure sound intensity concentration in the scanning area based on the bending wave structure sound intensity amplitude;

[0095] Calculate the maximum bending wave structure-borne acoustic intensity amplitude within the first scanning area 05 as Max.I1, where Max.I1 is obtained by comparing the bending wave structure-borne acoustic intensity of all target points 04 within the scanning area 05;

[0096] The bending wave structure acoustic intensity concentration A1 of the scanning area 05 (j=1) is calculated as follows:

[0097]

[0098] Where: Max.I1 represents the maximum bending wave structure-borne sound intensity amplitude in the first scanning area, Ave.I plate Indicates the average bending wave structure-borne sound intensity amplitude of all grid points of the panel to be tested;

[0099] S2. Traverse the plate according to the scanning algorithm, calculate the bending wave structure sound intensity concentration of all regions of the initial steel-concrete composite beam plate, and draw a bending wave structure sound intensity concentration spectrum of the initial steel-concrete composite beam plate;

[0100] The specific process of the scanning algorithm traversing the plate is as follows:

[0101] A. In this embodiment, the step size k is determined to be 0.1 m, which is 1 times the grid size;

[0102] B. Figure 3 As shown, the scanning area 05 is translated by 0.1 m along the scanning path 07, and the bending wave structure sound intensity concentration A2 of the scanning area 05 is recalculated;

[0103] C. After completing the previous step, continue translating scanning area 05 by 0.1 m along scanning path 07 and calculate the bending wave structure-acoustic intensity concentration A3 of scanning area 05. Repeat this process until the entire panel is traversed to obtain the bending wave structure-acoustic intensity concentration A3 of each scanning area 05.

[0104] S3. Calculate the bending wave structural acoustic intensity concentration of the service-period steel-concrete composite beam in the scanning area according to the scanning area and scanning path in step S1 (using the same calculation steps as step S1);

[0105] S4. Traverse the plate according to the scanning algorithm (using the same traversal steps as step S2), calculate the bending wave structure sound intensity concentration of all regions of the steel-concrete composite beam plate during service, and draw a bending wave structure sound intensity concentration spectrum of the steel-concrete composite beam plate during service;

[0106] S5. Compare the peak values ​​of the flexural wave structure sound intensity concentration spectrum of all regions of the initial steel-concrete composite beam plate with the peak values ​​of the flexural wave structure sound intensity concentration spectrum of all regions of the service-period steel-concrete composite beam plate. If the difference in the peak values ​​of the flexural wave structure sound intensity concentration spectrum of a certain scanning area between the two exceeds a preset threshold (the difference between the two is 20 dB), it is determined that cracks exist in the scanning area of ​​the service-period steel-concrete composite beam plate.

[0107] According to the concentration of structural sound intensity in each scanning area, a spectrum curve of the bending wave structural sound intensity concentration in the crack area is drawn. The black solid line and dotted line in the figure represent the concentration of bending wave structural sound intensity before and after damage, respectively. Figure 5 The frequency spectrum graphs of three scanning areas with cracks are given;

[0108] Obtain the single frequency peak of the bending wave structure sound intensity concentration spectrum in each scanning area, by Figure 5It can be seen that the flexural wave structural sound intensity concentration of scanning area 05, where the three cracks 081, 082, and 083 exist, shows a clear peak at 190 Hz. Its amplitude is generally more than 20 dB higher than that of other frequencies. It is highly suspected that cracks are present in this area. The coordinates of the three scanning areas are recorded to complete the crack identification of the steel-concrete composite beam based on the flexural wave structural sound intensity concentration test.

[0109] In this embodiment, combined with Figure 4 and Figure 5 By using flexural wave measurement and scanning algorithm, the flexural wave structural sound intensity vector cloud map and spectrum curve were obtained, revealing the flexural wave transmission characteristics of the steel-concrete composite beam concrete slab with cracks; generally, the flexural wave structural sound intensity will be significantly concentrated in the crack area, which appears as a significant single-frequency peak on the spectrum curve, and this point can be used to accurately identify the crack area.

[0110] In this embodiment, the bending wave structure sound intensity test method adopted is an acceleration sensor, and the method of obtaining the original data for bending wave structure sound intensity calculation using a laser vibrometer, a high-speed camera, etc. should also be included in the protection scope of the present invention.

[0111] The above description does not limit the present invention in any form. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can use the technical content disclosed above to make some changes or modifications to equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A method for identifying cracks in steel-concrete composite beams based on bending wave structural acoustic intensity concentration test, characterized in that: The following steps are involved: S1. Delimit the panel to be tested into a series of scanning areas and set the scanning path, and calculate the bending wave structural sound intensity concentration of the initial steel-concrete composite beam scanning area; The scanning area includes a plurality of target points; the target points are set with four measuring points at the same intervals of 0°, 90°, 180° and 270°; The calculation process of the bending wave structure sound intensity concentration includes: Step 1: Determine the density of measuring points and obtain vibration data of four measuring points; Step 2: Calculate the magnitude and amplitude of the bending wave structure sound intensity vector based on the vibration data of the four measuring points; Step 3: Construct a frequency domain three-dimensional vector cloud and streamlines based on the bending wave structure sound intensity amplitude; Step 4: Calculate the bending wave structure sound intensity concentration in the scanning area based on the bending wave structure sound intensity amplitude; Where: Max. I j For the j The maximum bending wave structure-borne sound intensity amplitude in the scanning area, Ave. I plate is the average bending wave structure-borne sound intensity amplitude of all grid points of the panel to be tested; A j For the j The concentration of bending wave structure sound intensity in each scanning area; S2. Traverse the plate according to the scanning algorithm, calculate the bending wave structure sound intensity concentration of all regions of the initial steel-concrete composite beam plate, and draw a bending wave structure sound intensity concentration spectrum of the initial steel-concrete composite beam plate; S3, calculating the bending wave structural sound intensity concentration of the scanning area of ​​the service-period steel-concrete composite beam according to the scanning area and scanning path in step S1; S4. Traverse the plate according to the scanning algorithm, calculate the bending wave structure sound intensity concentration of all regions of the steel-concrete composite beam plate during service, and draw a bending wave structure sound intensity concentration spectrum of the steel-concrete composite beam plate during service; S5. Compare the peak values ​​of the flexural wave structure sound intensity concentration spectrum of all regions of the initial steel-concrete composite beam plate with the peak values ​​of the flexural wave structure sound intensity concentration spectrum of all regions of the service-period steel-concrete composite beam plate. If the difference in the peak values ​​of the flexural wave structure sound intensity concentration spectrum of a certain scanning area between the two exceeds a preset threshold, it is determined that cracks exist in the scanning area of ​​the service-period steel-concrete composite beam plate.

2. The method for identifying cracks in steel-concrete composite beams based on bending wave structural acoustic intensity concentration test according to claim 1 is characterized in that: In step 1, an acceleration sensor is placed at each measuring point to obtain vibration data.

3. The method for identifying cracks in steel-concrete composite beams based on bending wave structural acoustic intensity concentration test according to claim 1 is characterized in that: The specific process of step 2 includes: Step 21: Convert the vibration data into acceleration and perform Fourier transform to obtain the real part and imaginary part; Step 22: Differentiate the vibration acceleration data in the frequency domain; Step 23: Calculate the size and amplitude of the bending wave structural sound intensity vector at each grid point based on the measured vibration acceleration data.

4. The method for identifying cracks in steel-concrete composite beams based on bending wave structural acoustic intensity concentration test according to claim 3 is characterized in that: The calculation formula of step 23 is: Where: m is the mass per unit area of ​​the plate; d is the distance between the measuring points; D x and D y The panels are x 、 y Bending stiffness in the direction; G 12 、 G 34 For each grid point x and y Cross spectrum of acceleration signals in different directions.

5. The method for identifying cracks in steel-concrete composite beams based on bending wave structural acoustic intensity concentration test according to claim 1 is characterized in that: The specific process of step 3 includes: Step 31: performing normalization processing based on the bending wave structure-borne sound intensity amplitude obtained in step S2; Step 32: Determine the spatial coordinates of the grid points based on the density of the measuring points, and draw a three-dimensional cloud map based on the normalized bending wave structure sound intensity; Step 33: Using the grid point coordinates as the starting point and the normalized bending wave structure-borne sound intensity as the vector length, draw a three-dimensional vector diagram and a streamline diagram of the bending wave structure-borne sound intensity; Step 34: superimpose the three-dimensional cloud map, vector map, and streamline map to obtain a three-dimensional vector cloud map and streamline map of bending wave structure sound intensity.

6. The method for identifying cracks in steel-concrete composite beams based on bending wave structural acoustic intensity concentration test according to claim 1, characterized in that: The specific process of the scanning algorithm traversing the plate includes: A. Determine the appropriate step length k , translate the scanning area; B. According to the scanning path, move the scanning area horizontally k , calculate the bending wave structure intensity concentration of the scanning area A j+1 ; Repeat step B until the entire panel to be tested is traversed to obtain the bending wave structure sound intensity concentration in each scanning area.

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