A method for locating broken wires of a stay cable

Abstract

The present invention relates to a method for locating a broken wire of a cable, comprising the following steps: S1, connecting one end of a plurality of cables in series through a waveguide rod; S2, arranging acoustic emission sensors at both ends of the waveguide rod, the acoustic emission sensors being used to obtain acoustic emission signals when broken wires occur in different cables; S3, filtering the acoustic emission signals by calculating their cross-correlation, filtering out noise interference, and filtering out the acoustic emission signals of the best frequency band; S4, using the cross-correlation function to perform time delay calculation based on the screened acoustic emission signals to obtain the time difference between the signals arriving at the two acoustic emission sensors; S5, using the waveguide rod waveguide range positioning method to calculate the position where the signal is emitted on the waveguide rod based on the time difference in signal arrival, thereby determining the broken wire cable in the plurality of cables connected in series. The present invention adopts the waveguide rod waveguide technology to directly monitor the damage conditions of different cables, and can relatively simply and accurately determine the cable where the broken wire occurs.

Description

Technical Field

[0001] The invention relates to the technical field of cable-stayed bridge detection, in particular to a method for locating broken wires of a cable-stayed bridge. Background Art

[0002] Cable-stayed bridges have been widely used in modern large-span bridge construction due to their beautiful appearance, large span capacity, and good wind resistance and stability, bringing great convenience to people's lives. However, due to natural erosion and frequent load-bearing, many bridge diseases have occurred in various components of cable-stayed bridges, among which the damage to the cable-stayed cables is the most fatal. At present, bridge collapses caused by cable-stayed cable damage occur from time to time, and it is unbearable to deploy high-cost health monitoring equipment on large-scale cable-stayed bridges. Common non-destructive testing methods such as ultrasonic testing, magnetic particle testing, infrared testing and other active testing methods cannot achieve long-term monitoring, and the testing cycle is long and is greatly restricted by the test object. Therefore, there is an urgent need for a low-cost, convenient and accurate cable-stayed cable wire positioning method that is suitable for complex on-site environments. Summary of the invention

[0003] To this end, the technical problem to be solved by the present invention is to overcome the problem that the existing technology cannot accurately detect broken wires of inclined cables due to the complex use environment and the current technology is expensive to use for monitoring broken wires of inclined cables. The present invention proposes a method for locating broken wires of inclined cables, which uses waveguide rod waveguide technology to directly monitor the damage conditions of different inclined cables, and can relatively easily and accurately determine the inclined cables where broken wires have occurred.

[0004] In order to solve the above technical problems, the present invention provides a method for locating a broken wire of a stay cable, comprising the following steps:

[0005] S1, connect one end of multiple inclined cables in series through waveguide rods;

[0006] S2. Acoustic emission sensors are arranged at both ends of the waveguide rod, and the acoustic emission sensors are used to obtain acoustic emission signals when wire breakage occurs in different inclined cables;

[0007] S3, filtering the frequency band nodes of the acoustic emission signal by calculating its cross-correlation, filtering out noise interference, and screening out the acoustic emission signal of the best frequency band;

[0008] S4, using the cross-correlation function to perform time delay calculation based on the selected acoustic emission signals to obtain the time difference between the signals reaching the two acoustic emission sensors;

[0009] S5. According to the time difference of signal arrival, the position where the signal is emitted on the waveguide rod is calculated by using the waveguide rod waveguide range positioning method, so as to determine the broken wire inclined cable among multiple series-connected inclined cables.

[0010] In one embodiment of the present invention, in step S1, a plurality of the stay cables are connected by using a metal sleeve, and the waveguide rod is fixed in the metal sleeve.

[0011] In one embodiment of the present invention, in step S2, two acoustic emission sensors are symmetrically arranged at two ends of the waveguide rod, and the positions of the two acoustic emission sensors at the two ends of the waveguide rod are the same.

[0012] In one embodiment of the present invention, in step S2, a coupling agent is applied between the two acoustic emission sensors and the waveguide rod.

[0013] In one embodiment of the present invention, in step S3, the following steps are also included:

[0014] S301, first perform Fourier transform on the acoustic emission signal to determine the main frequency distribution range;

[0015] S302, performing wavelet packet transform on the acoustic emission signal to decompose it into multiple small frequency band signals;

[0016] S303, selecting a frequency band signal that is determined to be within the main frequency range after Fourier transform from a plurality of small frequency band signals to calculate a cross-correlation function;

[0017] S304, determining the result of the calculation of the cross-correlation function. If the result is 0, it is determined that the signal in the frequency band is greatly affected by noise. If the result is not 0, it is determined that the signal in the frequency band is less affected by noise.

[0018] In one embodiment of the present invention, step S305 is further included: when the cross-correlation function calculation results of multiple small frequency band signals are not 0, the standard deviation of the arrival time difference of signals corresponding to different frequency bands is calculated, and the frequency band with a larger standard deviation is excluded. The remaining frequency band signals are reconstructed to obtain a reconstructed signal that can represent the effective information in the original signal.

[0019] In one embodiment of the present invention, in step S302, Dociby wavelet with symmetry and regularity is selected to perform wavelet packet transform decomposition.

[0020] In one embodiment of the present invention, in both step S303 and step S4, a cross-correlation function is used to perform cross-correlation calculation on the acoustic emission signals, and the cross-correlation function can not only determine the correlation between the two acoustic emission signals, but also calculate the arrival time difference of the acoustic emission signals detected by the two acoustic emission sensors.

[0021] In one embodiment of the present invention, step S3 and step S4 are completed based on software analysis.

[0022] In one embodiment of the present invention, in step S5, the theoretical value X of the demarcation point is calculated using the waveguide rod waveguide range positioning method. n1n2 , X n1n2 It can be expressed as:

[0023] X n1n2 =(L-(T s1 -T s2 )∙v) / 2;

[0024] Where: L is the length of the waveguide rod, T s1 -T s2 That is, it is the time difference between the two acoustic emission sensors receiving the acoustic emission signal, and v is the transmission speed of the acoustic emission signal in the waveguide rod.

[0025] The above technical solution of the present invention has the following advantages compared with the prior art:

[0026] The method for locating the broken wire of the inclined cable of the present invention utilizes waveguide rods to guide waves, directly monitors the damage conditions of different inclined cables, transmits the sound wave signal emitted from the broken wire position to two different acoustic emission sensors through the waveguide rods, determines the time difference of the two sound waves arriving by detecting the correlation of the two sound wave signals, and calculates the position where the sound wave signal is transmitted in the waveguide rod by using the waveguide rod guided wave range positioning method, thereby being able to determine the position of the transverse broken wire;

[0027] Moreover, when the acoustic wave signal is transmitted, there is a lot of noise interference due to the noisy environment on site. In order to filter out this interference, the present invention performs frequency band node screening and correlation calculation on the acoustic emission signal, thereby achieving the effect of filtering out the noise, and can relatively easily and accurately determine the inclined cable where the wire is broken. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 It is a flow chart of the steps of the method for locating the broken wire of the inclined cable of the present invention;

[0030] Figure 2 is a flow chart of step 3 of the present invention;

[0031] Figure 3 It is a structural schematic diagram simulating the broken wire of the inclined cable;

[0032] Figure 4 is a flow chart for verifying the method for locating a broken wire of a stay cable of the present invention;

[0033] Figure 5The error comparison is between the positioning method of the broken wire of the inclined cable using the present invention and the positioning method using the amplitude threshold method in the prior art. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0035] Reference Figure 1 As shown, the present invention discloses a method for locating a broken wire of a stay cable, comprising the following steps:

[0036] S1. Connect one end of multiple cable-stayed cables in series through waveguide rods. When laying out the cables, select a waveguide rod of appropriate length according to the length of the bridge. When a single waveguide rod is not long enough, multiple waveguide rods can be used for splicing. The length of each cable-stayed bridge is different, and the number of cables used is also different. It is necessary to ensure that each cable-stayed cable can be connected to the waveguide rod to ensure that the sound wave can be transmitted from the position where the cable is broken to the waveguide rod.

[0037] Specifically, since the inclined cables are arranged on the bridge, long-term use can easily cause damage to the waveguide rod. Therefore, during the actual layout, a metal sleeve is provided outside the waveguide rod. The metal sleeve is used to connect multiple inclined cables, and the waveguide rod is fixed in the metal sleeve. The metal sleeve can protect the waveguide rod and reduce the impact damage to the waveguide rod caused by the environment.

[0038] S2. Acoustic emission sensors are arranged at both ends of the waveguide rod, and the acoustic emission sensors are used to obtain acoustic emission signals when wire breakage occurs in different inclined cables; when wire breakage occurs, the acoustic emission signal is transmitted to the waveguide rod through the inclined cable, and is transmitted to both ends of the waveguide rod respectively. The acoustic emission sensors arranged at both ends of the waveguide rod can detect two acoustic emission signals;

[0039] Specifically, when actually deploying the acoustic emission sensors, it is necessary to symmetrically set the two acoustic emission sensors at the two ends of the waveguide rod, and ensure that the positions of the two acoustic emission sensors at the two ends of the waveguide rod are the same. This can ensure the consistency of the acoustic emission signals received at both ends as much as possible and reduce the noise impact caused by the different positions of the acoustic emission sensors.

[0040] It should be noted that in order to ensure that the acoustic emission sensor can accurately and effectively detect the sound wave signal, a coupling agent is coated between the two acoustic emission sensors and the waveguide rod. The coupling agent for sound wave conduction plays a vital role in sound detection. The main function of the coupling agent is to fill the air gap between the acoustic emission sensor and the waveguide rod. Because the propagation efficiency of sound waves in the air is extremely low, by using a coupling agent, it can be ensured that the sound wave energy is effectively transmitted from the probe to the inside of the workpiece, thereby improving the accuracy and efficiency of detection.

[0041] S3, the acoustic emission signal is subjected to frequency band node screening and cross-correlation function calculation, noise interference is filtered out, and the acoustic emission signal of the best frequency band is screened out; when the acoustic wave signal is transmitted, there is a lot of noise interference due to the noisy environment on site. In this step, in order to filter out this interference, the acoustic emission signal is subjected to frequency band node screening and correlation calculation, thereby achieving the effect of filtering out noise;

[0042] Specifically, in this embodiment, refer to Figure 2 As shown, the implementation of frequency band node screening and correlation calculation includes the following steps:

[0043] S301, first perform Fourier transform on the acoustic emission signal to determine the main frequency range.

[0044] S302, performing wavelet packet transform on the acoustic emission signal within the main frequency range to decompose it into multiple small frequency band signals;

[0045] Specifically, in this embodiment, the Docibin wavelet with symmetry and regularity is selected for wavelet packet transform decomposition, and the transformation process is:

[0046] Assume that the parent wavelet in wavelet transform for , mother wavelet for ,

[0047] The above recursive relationship can be expressed as follows:

[0048] ;

[0049] ;

[0050] Right now:

[0051] ;

[0052] S303, selecting a frequency band signal that is determined to be within the main frequency range after Fourier transform from a plurality of small frequency band signals to calculate a cross-correlation function, the calculation formula of the cross-correlation function is:

[0053] ;

[0054] Wherein: x, y represent the acoustic emission signals received by the two acoustic emission sensors respectively. By judging the correlation between the two acoustic emission sensors, it can be determined whether it is a noise signal; N is the sample length of the two signals; n0 represents the first sampling point, and n is a single sampling point.

[0055] S304, determining the result of the calculation of the cross-correlation function, if the result is 0, determining that the small frequency band signal is a noise signal, if the result is not 0, determining that the small frequency band signal is the best frequency band signal emitted by the broken wire.

[0056] Specifically, during actual detection, there may be multiple small frequency band signals that meet the screening conditions of the above-mentioned steps S303 and S304, thereby obtaining multiple optimal frequency band signals. Therefore, step S305 is also included. When the calculation results of the cross-correlation functions of multiple small frequency band signals are not 0, these small frequency band signals are reconstructed, and the reconstructed signals are used as the best frequency band signals to be screened out.

[0057] S4, performing cross-correlation calculation based on the screened acoustic emission signals to obtain the time difference between the signals reaching the two acoustic emission sensors;

[0058] Specifically, in step S303 and step S4, the same cross-correlation function is used to perform cross-correlation calculation on the acoustic emission signals, and the cross-correlation function can not only determine the correlation between the two acoustic emission signals, but also detect the time when the two acoustic emission sensors detect the acoustic emission signals.

[0059] It should be noted that the steps S3 and S4 are completed based on MATLAB simulation.

[0060] S5. According to the time difference of signal arrival, the position of the signal emitted on the waveguide rod is calculated by using the waveguide rod waveguide range positioning method, so as to determine the broken wire of the multiple series-connected inclined cables;

[0061] Specifically, the theoretical value X of the demarcation point is calculated using the waveguide rod wave range positioning method. n1n2 , X n1n2 It can be expressed as:

[0062] X n1n2 =(L-(T n1 -T n2 )∙v) / 2;

[0063] Where: L is the length of the waveguide rod, T n1 -T n2 That is, it is the time difference between the two acoustic emission sensors receiving the acoustic emission signal, and v is the transmission speed of the acoustic emission signal in the waveguide rod.

[0064] The method for locating broken wires of a stay cable of the present invention is adopted, and waveguide rods are used to guide waves to directly monitor the damage conditions of different stay cables. The sound wave signal emitted from the broken wire position is transmitted to two different acoustic emission sensors through the waveguide rods. The time difference between the arrival of the two sound waves is determined by detecting the correlation of the two sound wave signals. The position where the sound wave signal is transmitted in the waveguide rod is calculated by the waveguide rod guided wave range positioning method, so that the position of the transverse broken wire can be determined. The acoustic emission signal is subjected to frequency band node screening and correlation calculation, so as to achieve the effect of filtering out noise, and the stay cable with broken wires can be determined relatively simply and accurately.

[0065] Reference Figure 3 and Figure 4 As shown, in order to verify the above method, the present invention also carried out a simulation test, and built a cable model in the laboratory, using three cables C1, C2, and C3, connecting one end of the three cables through a waveguide rod, and setting acoustic emission sensors at both ends of the waveguide rod, and knocking on the cable to simulate wire breakage, referring to Figure 3 As shown, ten knocks are first performed on the inclined cable C1 to generate ten groups of acoustic wave signals caused by the knocks. Both acoustic emission sensors can detect the acoustic wave signals as acoustic emission signals. According to step S3, the acoustic emission signals are first subjected to Fourier transform to determine the main frequency range, and then the acoustic emission signals within the main frequency range are subjected to wavelet packet transform to decompose into multiple small frequency band signals. Among multiple small-band signals, the frequency band signal that meets the requirements of Fourier transform and is determined to be within the main frequency range is selected for calculation of the cross-correlation function, and finally the correlation is judged to select the best frequency band signal caused by broken wire; when conducting simulation tests, in order to verify the universality of the best frequency band signal, ten knocks are performed on the inclined cables C2 and C3 to generate twenty groups of sound wave signals caused by knocking, which are decomposed into multiple small-band signals by wavelet packet transform, and the cross-correlation function of the best frequency band signal obtained is calculated with multiple small-band signals, and finally the best frequency band signal that satisfies the three inclined cables C1, C2, and C3 is obtained. If the cross-correlation function calculation results of multiple small-band signals are not 0, these small-band signals are reconstructed, and the reconstructed signals are used to screen out the best frequency band signals.

[0066] After determining the best frequency band signal, the acoustic wave signals detected by the two acoustic emission sensors in this frequency band are selected, and the time difference of the signal reaching the two acoustic emission sensors is obtained by cross-correlation calculation. According to the time difference of signal arrival, the position of the signal on the waveguide rod is calculated by the waveguide rod guided wave range positioning method:

[0067] ;

[0068] ;

[0069] ;

[0070] According to the distance between the position and the two inclined cables, determine which of the three inclined cables C1, C2, and C3 has a broken wire;

[0071] Furthermore, when the present embodiment is used for verification, since multiple sets of data are used for verification, the theoretical value X of the demarcation point can also be calculated based on the position of the signal emitted on the waveguide rod monitored by the multiple sets of data. n1n2 , X n1n2 It can be expressed as:

[0072] X n1n2 =(L-(T s1 -T s2 )∙v) / 2;

[0073] Where: L is the length of the waveguide rod, T s1 -T s2 That is, it is the time difference between the two acoustic emission sensors receiving the acoustic emission signal, and v is the transmission speed of the acoustic emission signal in the waveguide rod.

[0074] Reference Figure 5 As shown, in order to further illustrate the accuracy of the positioning method of the present invention, the positioning method of the present invention is also compared with the offset between the measured value and the theoretical value calculated by the amplitude threshold method in the prior art. The experimental results show that the positioning method of the present invention is more accurate than the amplitude threshold method in the prior art, thereby judging the position of the broken wire more accurately.

[0075] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for locating a broken wire of a stay cable, characterized in that: The following steps are involved: S1, connect one end of multiple inclined cables in series through waveguide rods; S2. Acoustic emission sensors are arranged at both ends of the waveguide rod, and the acoustic emission sensors are used to obtain acoustic emission signals when wire breakage occurs in different inclined cables; S3. Filter the frequency band nodes of the acoustic emission signal by calculating its cross-correlation, filter out noise interference, and select the acoustic emission signal of the best frequency band, including: S301, first perform Fourier transform on the acoustic emission signal to determine the main frequency distribution range; S302, decomposing the acoustic emission signal into multiple small frequency band signals by performing wavelet packet transform, and selecting Docibin wavelet with symmetry and regularity for wavelet packet transform decomposition; S303, selecting a frequency band signal that is determined to be within the main frequency range after Fourier transform from a plurality of small frequency band signals to calculate a cross-correlation function, the calculation formula of the cross-correlation function is: ； Where: x, y represent the acoustic emission signals received by the two acoustic emission sensors respectively. By judging the correlation between the two acoustic emission sensors, it can be determined whether it is a noise signal; N is the sample length of the two signals; n0 represents the first sampling point, and n is a single sampling point; S304, determining the result of the calculation of the cross-correlation function. If the result of the cross-correlation function is 0, it is determined that the signal in the frequency band is greatly affected by the noise signal. If the result is not 0, it is determined that the signal in the frequency band is less affected by the noise signal. S305, when the calculation results of the cross-correlation function of multiple small frequency band signals are not 0, calculate the standard deviation of the arrival time difference of the signals corresponding to different frequency bands, exclude the frequency bands with larger standard deviations, reconstruct the remaining frequency band signals, and obtain a reconstructed signal that can represent the effective information in the original signal; S4, using the cross-correlation function to perform time delay calculation based on the selected acoustic emission signals to obtain the time difference between the signals reaching the two acoustic emission sensors; S5. According to the time difference of signal arrival, the position of the signal emitted on the waveguide rod is calculated by using the waveguide rod waveguide range positioning method, so as to determine the broken wire cable among multiple series-connected cables, including: The theoretical value X of the demarcation point is calculated by using the waveguide rod wave range positioning method n1n2 , X n1n2 It can be expressed as: X n1n2 =(L-(T s1 -T s2 )∙v) / 2; Where: L is the length of the waveguide rod, T s1 -T s2 That is, it is the time difference between the two acoustic emission sensors receiving the acoustic emission signal, and v is the transmission speed of the acoustic emission signal in the waveguide rod.

2. The method for locating a broken wire of a stay cable according to claim 1, characterized in that: In step S1, a plurality of the inclined cables are connected by using a metal sleeve, and the waveguide rod is fixed in the metal sleeve.

3. The method for locating a broken wire of a stay cable according to claim 1, characterized in that: In step S2, two acoustic emission sensors are symmetrically arranged at two ends of the waveguide rod, and the positions of the two acoustic emission sensors at the two ends of the waveguide rod are the same.

4. The method for locating a broken wire of a stay cable according to claim 1, characterized in that: In step S2, a coupling agent is applied between the two acoustic emission sensors and the waveguide rod.

5. The method for locating a broken wire of a stay cable according to claim 1, characterized in that: In both step S303 and step S4, the cross-correlation function is used to perform cross-correlation calculation on the acoustic emission signals. The cross-correlation function can not only determine the correlation between the two acoustic emission signals, but also calculate the arrival time difference of the acoustic emission signals detected by the two acoustic emission sensors.

6. The method for locating a broken wire of a stay cable according to claim 1, characterized in that: The steps S3 and S4 are completed based on software analysis.

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