A method for testing the natural frequency of bridge dynamic deflection based on millimeter wave radar

Abstract

An embodiment of the present invention discloses a method for testing the natural frequency of bridge dynamic deflection based on millimeter-wave radar. The method comprises: determining a target vibration order corresponding to a target bridge to be analyzed; determining a target excitation method for dynamic load testing the target bridge; performing a dynamic load test on the target bridge based on the target excitation method and in combination with millimeter-wave radar to obtain a target dynamic deflection time-history curve; bandpass filtering the target dynamic deflection time-history curve to obtain a target vibration time-history curve containing only a single waveform; using the target vibration time-history curve as a target reference curve for extracting the natural frequency of the target bridge; obtaining waveforms of several cycles from the target reference curve, and obtaining the target natural frequency of the target bridge within the target vibration order range based on the waveforms of the several cycles. The present invention can use millimeter-wave radar to test the dynamic deflection of a bridge and extract the natural frequency of the bridge in combination with theoretical structural analysis of the bridge.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge dynamic performance testing, and in particular to a method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar. Background Art

[0002] At present, the main parameters for evaluating the dynamic performance of highway bridges in my country include mode shape, damping ratio, and natural frequency. However, the evaluation standards for mode shape and damping ratio parameters in the current specifications are unclear, and the dynamic stiffness of the bridge reflected by the natural frequency is a key parameter for evaluating the dynamic performance of the bridge. Pedestrian bridges have clear requirements for the natural frequency of bridges, so the natural frequency of pedestrian bridges is also a key parameter that requires testing. Traditional tests of the natural frequency of bridge structures are often carried out using pulse tests, that is, dynamic tests are performed using acceleration and velocity sensors, and the natural frequency of the bridge is tested through modal analysis. In the existing technology, the method of using millimeter-wave radar to test the dynamic deflection of bridges has the characteristics of non-contact, all-weather, multi-target, and high precision. Its time history curve can be used to extract the natural frequency in bridge dynamic testing. However, there is currently no complete method for extracting the natural frequency of bridge dynamic deflection combined with theoretical analysis of bridge structure. Summary of the Invention

[0003] Based on this, it is necessary to propose a method for testing the natural frequency of bridge dynamic deflection based on millimeter-wave radar to address the above problems, so as to solve the following problems of the existing technology: the traditional test of the natural frequency of bridge structure needs to be carried out by pulse test, that is, dynamic test is carried out using acceleration and velocity sensors, and the natural frequency of the bridge is tested through modal analysis. However, there is currently no complete method for extracting the natural frequency of bridge dynamic deflection by combining theoretical analysis of bridge structure.

[0004] The technical solution of the embodiment of the present invention is:

[0005] A method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar comprises the following steps:

[0006] Step one, determining the target vibration order corresponding to the target bridge to be analyzed; step two, determining the target excitation method for dynamic load testing of the target bridge according to the structural type corresponding to the target bridge and the target vibration order; step three, performing a dynamic load test on the target bridge according to the target excitation method and in combination with millimeter-wave radar, and obtaining a target dynamic deflection time-history curve corresponding to the target bridge; step four, based on the target vibration order, using a band-pass filter to band-pass filter the target dynamic deflection time-history curve to obtain a target vibration time-history curve containing only a single waveform; step five, if the single waveform of the target vibration time-history curve is the vibration waveform corresponding to the target vibration order, then using the target vibration time-history curve as the target reference curve for extracting the natural frequency of the target bridge at the target vibration order; step six, obtaining waveforms of several cycles in the target reference curve, and obtaining the target natural frequency of the target bridge in the target vibration order range according to the waveforms of the several cycles.

[0007] Preferably, in step five, if the single waveform of the target vibration time-history curve is different from the waveform corresponding to the target vibration order, the excitation mode of the target bridge is re-determined according to the method of step two, and the dynamic working condition test of the target bridge is re-performed in combination with the millimeter-wave radar according to the method of step three to obtain another target dynamic deflection time-history curve corresponding to the target bridge.

[0008] Preferably, determining the target vibration order corresponding to the target bridge to be analyzed includes: obtaining the target structural type and construction mode corresponding to the target bridge, and determining the target vibration order corresponding to the target bridge to be analyzed based on the current national highway bridge specifications.

[0009] Preferably, determining the target excitation method for performing a dynamic load test on the target bridge based on the structural type corresponding to the target bridge and the target vibration order includes: determining several excitation methods suitable for the target bridge based on the structural type corresponding to the target bridge; selecting at least one excitation method that can excite the target vibration order from the several excitation methods suitable for the target bridge, and using it as the target excitation method for performing a dynamic load test on the target bridge; wherein different excitation methods excite different vibration orders for bridges of different structural types.

[0010] Preferably, the target bridge is subjected to a dynamic load test according to the target excitation mode and in combination with a millimeter-wave radar to obtain a target dynamic deflection time-history curve corresponding to the target bridge, including: arranging corner reflectors on the test section of the target bridge according to the on-site conditions of the target bridge, or using a wireless distributed millimeter-wave radar test system on the target bridge; and the dynamic deflection corresponding to the target bridge is subjected to a dynamic load test by a millimeter-wave radar according to the target excitation mode to obtain the target dynamic deflection time-history curve corresponding to the target bridge.

[0011] Preferably, the sampling frequency of the millimeter wave radar is not less than 10 times the analysis frequency corresponding to the target vibration order.

[0012] Preferably, based on the target vibration order, the target dynamic deflection time history curve is band-pass filtered using a band-pass filter to obtain a target vibration time history curve containing only a single waveform, including: obtaining the target natural frequency corresponding to the target bridge at the target vibration order; according to the target natural frequency, setting the analysis frequency bandwidth of the band-pass filter to the target analysis frequency bandwidth, wherein the target analysis frequency bandwidth includes the target natural frequency; using the band-pass filter with the analysis frequency bandwidth set to the target analysis frequency bandwidth to band-pass filter the target dynamic deflection time history curve to obtain the target vibration time history curve containing only a single waveform.

[0013] Preferably, obtaining waveforms of several cycles in the target reference curve includes: selecting several complete waveforms through key feature points in the target reference curve, the key feature points including zero points, peak points and trough points; and obtaining waveforms of several cycles in the target reference curve based on the several complete waveforms.

[0014] Preferably, obtaining the target natural frequency of the target bridge within the target vibration order range based on the waveforms of the several cycles includes: calculating the target time difference between the starting point and the end point corresponding to the waveforms of the several cycles, and dividing the target time difference by the number of cycles corresponding to the several cycles to obtain the target vibration period of the target bridge within the target vibration order range; and obtaining the target natural frequency of the target bridge within the target vibration order range based on the target vibration period.

[0015] Preferably, obtaining the target natural frequency of the target bridge within the target vibration order range based on the target vibration period includes: obtaining the target natural frequency of the target bridge within the target vibration order range by taking the inverse of the target vibration period.

[0016] The embodiments of the present invention have the following beneficial effects:

[0017] The present invention first determines the target vibration order corresponding to the target bridge to be analyzed. Then, based on the structural type and target vibration order corresponding to the target bridge, a target excitation method is determined for dynamic load testing of the target bridge. Next, the target excitation method is combined with millimeter-wave radar to perform dynamic load testing on the target bridge, obtaining a target dynamic deflection time-history curve corresponding to the target bridge. Next, based on the target vibration order, the target dynamic deflection time-history curve is bandpass filtered using a bandpass filter to obtain a target vibration time-history curve containing only a single waveform. If the single waveform of the target vibration time-history curve is the vibration waveform corresponding to the target vibration order, the target vibration time-history curve is used as a target reference curve for extracting the natural frequency of the target bridge at the target vibration order. Finally, waveforms of several cycles are obtained from the target reference curve, and the target natural frequency of the target bridge within the target vibration order range is obtained based on the waveforms of the several cycles. The present invention can use millimeter-wave radar to test bridge dynamic deflection and extract the natural frequency of the bridge dynamic deflection in combination with theoretical analysis of the bridge structure. This method has the advantages of being non-contact, all-weather, multi-target, and highly accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] in:

[0020] Figure 1 This is a flowchart of an implementation method for testing the natural frequency of dynamic deflection of a bridge based on millimeter-wave radar in one embodiment;

[0021] Figure 2 Schematic diagram of a dynamic deflection test curve based on millimeter wave radar in one embodiment;

[0022] Figure 3 A schematic diagram of determining the starting point of residual vibration in a sports car test in one embodiment;

[0023] Figure 4 This is a single vibration waveform diagram extracted based on dynamic deflection of millimeter-wave radar in one embodiment. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0025] See also Figure 1-4 , combined with Figure 1-4 It can be seen that a method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar in an embodiment of the present invention includes the following steps:

[0026] Step 1: Determine the target vibration order corresponding to the target bridge to be analyzed.

[0027] Among them, this step needs to be based on the results of the modal analysis of the target bridge structure and the requirements of the specific structural type of the target bridge on the natural frequency to determine the vibration order that needs to be analyzed for the target bridge.

[0028] Different bridge structures require different vibration orders to be analyzed. The current specifications for highway bridges require that the vibration order analysis be tested at the first order for simply supported beam bridges, the third order for non-simply supported beam and arch bridges, and the ninth order for long-span bridge structures such as cable-stayed and suspension bridges.

[0029] Step 2: Determine a target excitation method for performing a dynamic load test on the target bridge according to the structural type corresponding to the target bridge and the target vibration order.

[0030] Different excitation methods will induce different vibration orders for different bridge structures. Different bridge structures require analysis of different natural vibration frequencies, so the appropriate test method (excitation method) must be selected based on the bridge structure. The target excitation method used in this step for dynamic load testing of the target bridge should theoretically produce the target vibration order.

[0031] Step three: Perform a dynamic load test on the target bridge according to the target excitation method and in combination with the millimeter wave radar to obtain a target dynamic deflection time history curve corresponding to the target bridge.

[0032] Among them, this step uses millimeter-wave radar to test the deflection time history, and it is advisable to use a sports car test for excitation to obtain the dynamic deflection time history curve corresponding to the residual vibration of the bridge after the vehicle passes the bridge, and then analyze the natural vibration frequency based on the dynamic deflection time history curve.

[0033] Step 4: Based on the target vibration order, the target dynamic deflection time history curve is subjected to band-pass filtering using a band-pass filter to obtain a target vibration time history curve containing only a single waveform;

[0034] In this step, the target dynamic deflection time-history curve often contains multiple waveforms, requiring a bandpass filter. The key is to set the upper and lower cutoff frequencies of the bandpass filter, that is, to set the analysis frequency bandwidth of the bandpass filter. In this step, the upper and lower cutoff frequencies of the bandpass filter need to be determined based on the structural type of the target bridge and the results of modal theory calculations.

[0035] Step 5: If the single waveform of the target vibration time-history curve is the vibration waveform corresponding to the target vibration order, the target vibration time-history curve is used as a target reference curve for extracting the natural frequency of the target bridge at the target vibration order.

[0036] Among them, in this step, the target vibration time-history curve obtained may not be a single waveform, which requires further adjusting the upper and lower cutoff frequencies of the bandpass filter, and further using the bandpass filter to bandpass filter the target dynamic deflection time-history curve until a target vibration time-history curve containing only a single waveform is obtained.

[0037] Step six: obtaining waveforms of several cycles from the target reference curve, and obtaining the target natural frequency of the target bridge within the target vibration order range based on the waveforms of several cycles.

[0038] In this embodiment, optionally, in step five, if the single waveform of the target vibration time-history curve is different from the waveform corresponding to the target vibration order, the excitation mode of the target bridge is re-determined according to the method of step two, and the dynamic working condition test of the target bridge is re-performed in combination with the millimeter-wave radar according to the method of step three to obtain another target dynamic deflection time-history curve corresponding to the target bridge.

[0039] In this embodiment, optionally, determining a target vibration order corresponding to a target bridge to be analyzed includes:

[0040] Obtain the target structural type and construction mode corresponding to the target bridge, and determine the target vibration order corresponding to the target bridge to be analyzed based on the current national highway bridge specifications. Different bridges have different structural types and construction modes, and therefore require different vibration orders to be analyzed.

[0041] In this embodiment, optionally, determining a target excitation mode for performing a dynamic load test on the target bridge according to the structural type corresponding to the target bridge and the target vibration order includes:

[0042] First, based on the structural type of the target bridge, several excitation methods suitable for the target bridge are determined. Different bridge structures require different excitation methods, and the excitation method must be selected based on the vibration order to be analyzed.

[0043] Second, at least one excitation method that can excite the target vibration order is selected from several excitation methods suitable for the target bridge, and is used as the target excitation method for dynamic load testing of the target bridge; wherein different excitation methods excite different vibration orders for bridges of different structural types.

[0044] In this embodiment, optionally, performing a dynamic load test on the target bridge according to the target excitation mode in combination with a millimeter-wave radar to obtain a target dynamic deflection time-history curve corresponding to the target bridge includes:

[0045] First, according to the on-site conditions of the target bridge, corner reflectors are arranged on the test section of the target bridge, or a wireless distributed millimeter wave radar test system is used on the target bridge.

[0046] Among them, in this step, the testing methods of the above two millimeter-wave radars can be selected according to the on-site conditions of the bridge. If there is water under the bridge or it is inconvenient to deploy equipment below the corresponding test point under the bridge, a measurement point deployment method of deploying corner reflectors on the test section of the target bridge can be adopted; if it is easy to deploy detection equipment under the bridge, a wireless distributed millimeter-wave radar test system can be used on the target bridge for testing.

[0047] Second, according to the target excitation method, a dynamic load test is performed on the dynamic deflection corresponding to the target bridge through a millimeter wave radar to obtain the target dynamic deflection time history curve corresponding to the target bridge.

[0048] This step requires developing a bridge natural frequency test plan (excitation method). This test plan serves as a guide for dynamic load testing of bridges. Different excitation methods will induce different vibration orders for different bridge structures. Field testing of bridge dynamic performance based on this test plan should consider different vehicle speed conditions and the placement of millimeter-wave radar deflection measurement points.

[0049] Bridge dynamic performance testing should collect a complete dynamic deflection time history curve of the bridge vibration for each sports car test condition. Before the sports car test, the millimeter-wave radar equipment should be debugged and the dynamic deflection test of the target bridge should be started under closed traffic conditions. Data collection should not be stopped until the vehicle leaves the bridge and the residual vibration signal gradually decays to near zero, that is, it reaches a stable state. Data collected for each test condition should be collected according to the above requirements to ensure that the collected data includes the curve segments that require analysis. Because the frequencies included in the bridge dynamic deflection time history curve are directly related to vehicle speed, smoothness, and bridge structure, obtaining the natural frequencies corresponding to the vibration orders to be analyzed according to the predetermined test conditions requires additional sports car test conditions, such as changing the driving speed or increasing the vehicle weight.

[0050] In this embodiment, millimeter-wave radar is used to test the dynamic deflection of a bridge using the residual vibrations from the bridge race car test. Because the frequencies included in the bridge dynamic deflection time history curve are directly related to factors such as the test speed and bridge deck roughness, the bridge natural frequency testing plan should include different speeds for different operating conditions, such as 10 km / h, 20 km / h, and 30 km / h. Dynamic deflection time history curves should be collected based on the different test conditions.

[0051] Furthermore, when using millimeter-wave radar to measure bridge dynamic deflection during bridge dynamic characteristic tests, the instrument should be adjusted before testing to ensure proper operation. Because the electromagnetic waves emitted by millimeter-wave radar are distributed in a fan-shaped pattern within its beam angle, the measurement point location should be determined using the distance-assisted laser rangefinder before testing.

[0052] In this embodiment, for the bridge dynamic characteristics test, the complete dynamic deflection vibration time history curve of each working condition should be collected to facilitate the selection of a reasonable time history curve segment for the bridge natural frequency analysis. In this example, the millimeter wave radar deflection time history curve is as follows: Figure 2 shown.

[0053] In this embodiment, the natural frequency analysis is performed using the time history curve of the bridge dynamic deflection in the sports car test. A reasonable residual vibration signal should be selected on the vibration time history curve, and the starting position of the residual vibration signal should be determined first. When using the driving (such as sports car test) excitation method, it is usually necessary to determine the exact moment when the vehicle leaves the bridge to avoid treating the forced vibration as free vibration, which will lead to misjudgment of the natural frequency. The starting point of the residual vibration is generally determined based on the starting position of the static component in the measured signal of the vibration signal (acceleration, dynamic strain, dynamic deflection, etc.) collected at the same time (such as Figure 3 As shown in Figure 2), the forced vibration response is discarded using the data truncation function in the data analysis software. The length of the truncated data block usually needs to meet the frequency resolution requirements.

[0054] In this embodiment, optionally, the sampling frequency of the millimeter wave radar is not less than 10 times the analysis frequency corresponding to the target vibration order.

[0055] In this embodiment, optionally, based on the target vibration order, the target dynamic deflection time history curve is subjected to bandpass filtering using a bandpass filter to obtain a target vibration time history curve containing only a single waveform, including:

[0056] First, the target natural frequency corresponding to the target bridge at the target vibration order is obtained.

[0057] Second, according to the target natural frequency, the analysis frequency bandwidth of the bandpass filter is set to the target analysis frequency bandwidth, wherein the target analysis frequency bandwidth includes the target natural frequency.

[0058] Third, the target dynamic deflection time history curve is subjected to band-pass filtering using the band-pass filter whose analysis frequency bandwidth is set to the target analysis frequency bandwidth, so as to obtain the target vibration time history curve containing only a single waveform.

[0059] For example, for a simply supported beam bridge, the vibration order that needs to be tested and analyzed is the first order, and the analysis frequency bandwidth of the bandpass filter needs to be determined based on the natural frequency corresponding to the first order vibration mode of the bridge structure according to structural theory. For example, a millimeter-wave radar is used to test the dynamic deflection of a simply supported beam under vehicle excitation, and the first-order vertical vibration frequency obtained by theoretical calculation and analysis of the bridge structure is 4.888Hz. Since the measured natural frequency of the bridge structure is normally greater than the theoretically calculated frequency of the bridge structure, the analysis frequency bandwidth of the bandpass filter can be preliminarily selected to analyze the vibration signal as 4.5 Hz-6Hz. When the selected analysis frequency bandwidth is inappropriate, that is, the waveform obtained may contain signals with more than one natural frequency, the analysis frequency bandwidth of the bandpass filter needs to be adjusted until a satisfactory result (a signal containing only one natural frequency) is obtained before the natural frequency is calculated. Among them, the deflection data of one millimeter-wave radar measuring point of the simply supported beam bridge is filtered by a bandpass filter to obtain a waveform of the first-order vibration, as shown in the figure below. Figure 4 shown.

[0060] In this embodiment, optionally, obtaining waveforms of several cycles in the target reference curve includes:

[0061] First, a number of complete waveforms are selected based on key characteristic points in the target reference curve, wherein the key characteristic points include zero points, peak points, and trough points;

[0062] Second, based on the several complete waveforms, waveforms of several cycles in the target reference curve are obtained.

[0063] In this embodiment, optionally, obtaining the target natural frequency of the target bridge within the target vibration order range based on the waveforms of the multiple cycles includes:

[0064] First, calculating a target time difference between the start and end points of the waveforms of the plurality of cycles, and dividing the target time difference by the number of cycles corresponding to the plurality of cycles to obtain a target vibration period of the target bridge within the target vibration order range;

[0065] Second, according to the target vibration period, the target natural frequency of the target bridge in the target vibration order range is obtained.

[0066] In this embodiment, optionally, obtaining the target natural frequency of the target bridge within the target vibration order range according to the target vibration period includes:

[0067] The target vibration period is inversely calculated to obtain the target natural frequency of the target bridge within the target vibration order range.

[0068] The present invention first determines the target vibration order corresponding to the target bridge to be analyzed. Then, based on the structural type and target vibration order corresponding to the target bridge, a target excitation method is determined for dynamic load testing of the target bridge. Next, the target excitation method is combined with millimeter-wave radar to perform dynamic load testing on the target bridge, obtaining a target dynamic deflection time-history curve corresponding to the target bridge. Next, based on the target vibration order, the target dynamic deflection time-history curve is bandpass filtered using a bandpass filter to obtain a target vibration time-history curve containing only a single waveform. If the single waveform of the target vibration time-history curve is the vibration waveform corresponding to the target vibration order, the target vibration time-history curve is used as a target reference curve for extracting the natural frequency of the target bridge at the target vibration order. Finally, waveforms of several cycles are obtained from the target reference curve, and the target natural frequency of the target bridge within the target vibration order range is obtained based on the waveforms of the several cycles. The present invention can use millimeter-wave radar to test bridge dynamic deflection and extract the natural frequency of the bridge dynamic deflection in combination with theoretical analysis of the bridge structure. This method has the advantages of non-contact, all-weather, multi-target, and high precision.

[0069] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for testing the natural frequency of bridge dynamic deflection based on millimeter wave radar, characterized in that: The following steps are involved: Step 1: determine the target vibration order corresponding to the target bridge to be analyzed; Step 2: determining a target excitation mode for performing a dynamic load test on the target bridge according to the structural type corresponding to the target bridge and the target vibration order; Step 3: Performing a dynamic load test on the target bridge according to the target excitation mode and in combination with a millimeter-wave radar to obtain a target dynamic deflection time history curve corresponding to the target bridge; Step 4: Based on the target vibration order, the target dynamic deflection time history curve is subjected to band-pass filtering using a band-pass filter to obtain a target vibration time history curve containing only a single waveform; Step 5: If the single waveform of the target vibration time-history curve is the vibration waveform corresponding to the target vibration order, the target vibration time-history curve is used as a target reference curve for extracting the natural frequency of the target bridge at the target vibration order; Step six: obtaining waveforms of several cycles from the target reference curve, and obtaining the target natural frequency of the target bridge within the target vibration order range based on the waveforms of several cycles.

2. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 1 is characterized in that: In step five, if the single waveform of the target vibration time-history curve is different from the waveform corresponding to the target vibration order, the excitation mode of the target bridge is re-determined according to the method of step two, and the dynamic working condition test of the target bridge is re-performed in combination with the millimeter-wave radar according to the method of step three to obtain another target dynamic deflection time-history curve corresponding to the target bridge.

3. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 1 is characterized in that: Determining a target excitation mode for performing a dynamic load test on the target bridge according to the structural type corresponding to the target bridge and the target vibration order includes: Determining several incentive methods suitable for the target bridge according to the structural type corresponding to the target bridge; At least one excitation method that can excite the target vibration order is selected from several excitation methods suitable for the target bridge, and is used as the target excitation method for dynamic load testing of the target bridge; wherein different excitation methods excite different vibration orders for bridges of different structural types.

4. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 1 is characterized in that: The method of performing a dynamic load test on the target bridge according to the target excitation mode and in combination with the millimeter wave radar to obtain a target dynamic deflection time history curve corresponding to the target bridge includes: According to the on-site conditions of the target bridge, corner reflectors are arranged on the test section of the target bridge, or a wireless distributed millimeter wave radar test system is used on the target bridge; According to the target excitation method, a dynamic load test is performed on the dynamic deflection corresponding to the target bridge through a millimeter wave radar to obtain the target dynamic deflection time history curve corresponding to the target bridge.

5. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 4 is characterized in that: The sampling frequency of the millimeter-wave radar is not less than 10 times the analysis frequency corresponding to the target vibration order.

6. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 1 is characterized in that: Based on the target vibration order, the target dynamic deflection time history curve is subjected to bandpass filtering using a bandpass filter to obtain a target vibration time history curve containing only a single waveform, including: Obtaining a target natural frequency corresponding to the target bridge at the target vibration order; According to the target natural frequency, setting the analysis frequency bandwidth of the bandpass filter to the target analysis frequency bandwidth, wherein the target analysis frequency bandwidth includes the target natural frequency; The target dynamic deflection time history curve is subjected to bandpass filtering using the bandpass filter whose analysis frequency bandwidth is set to the target analysis frequency bandwidth to obtain the target vibration time history curve containing only a single waveform.

7. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 1 is characterized in that: The step of obtaining waveforms of several cycles from the target reference curve comprises: Selecting a number of complete waveforms through key characteristic points in the target reference curve, wherein the key characteristic points include zero points, peak points, and trough points; According to the several complete waveforms, waveforms of several cycles in the target reference curve are obtained.

8. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 1 is characterized in that: Obtaining the target natural frequency of the target bridge within the target vibration order range based on the waveforms of the plurality of cycles includes: Calculating a target time difference between a start point and an end point corresponding to the waveforms of the plurality of cycles, and dividing the target time difference by the number of cycles corresponding to the plurality of cycles to obtain a target vibration period of the target bridge within the target vibration order range; The target natural frequency of the target bridge within the target vibration order range is obtained according to the target vibration period.

9. The method for testing the natural frequency of dynamic deflection of a bridge based on millimeter wave radar according to claim 8, characterized in that: Obtaining the target natural frequency of the target bridge within the target vibration order range according to the target vibration period includes: The target vibration period is inversely calculated to obtain the target natural frequency of the target bridge within the target vibration order range.

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