An acoustic emission location method for orthotropic steel bridge deck damage with multi-objective optimization and efficiency improvement

Abstract

The present invention discloses a method for acoustic emission location of damage to orthotropic steel bridge decks with multi-objective optimization and efficiency improvement. It includes: 1. Collecting acoustic emission signals of the orthotropic steel bridge deck under working conditions through acoustic emission sensors at the four vertices of the rectangular area to be measured; 2. Deducing the formula for the shortest path of the acoustic emission signal propagating from potential damage sources at different positions to the acoustic emission sensors; 3. Using the Akaike information criterion to extract the arrival time of the initial arrival mode of the acoustic emission signal, obtaining the dispersion curve of the acoustic emission signal, respectively determining the characteristic frequencies and wave velocities of the initial arrival mode and the A0 mode, and determining the arrival time of the A0 mode of the acoustic emission signal; 4. Establishing a multi-objective optimization model for damage location of the orthotropic steel bridge deck with the determined multi-mode arrival time and wave velocity parameters; 5. Taking the first layer of the multi-objective optimization model as the important objective function, solving the multi-objective optimization model by the hierarchical sequence method to evaluate the location of the damage. The present invention can accurately identify the location of the damage.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering structure health monitoring and damage identification, and particularly relates to a method for acoustic emission localization of orthotropic steel bridge deck damage with multi-objective optimization and efficiency enhancement. Background Art

[0002] The orthotropic steel bridge deck is a complex thin-walled space structure welded by a deck plate, longitudinal U-ribs and diaphragms. This structure has the advantages of light self-weight, high load-bearing capacity, convenient construction, etc., and is the preferred deck structure for medium and large-span bridges. However, due to heavy vehicle loads, long-term environmental impacts, structural characteristics and manufacturing processes, etc., the fatigue crack problem of orthotropic steel bridge decks is prominent, resulting in a significant reduction in structural performance and driving comfort. Therefore, whether the fatigue cracks of orthotropic steel bridge decks can be accurately located is crucial for the operation and maintenance of the entire life cycle of the bridge. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for acoustic emission localization of orthotropic steel bridge deck damage with multi-objective optimization and efficiency enhancement, which overcomes the difficulty of multiple solutions existing in traditional acoustic emission localization methods, can achieve more accurate damage localization, and provides a scientific basis for the timely maintenance and repair of orthotropic steel bridge decks.

[0004] To solve the above technical problems, the specific technical solution of the present invention is as follows:

[0005] A method for acoustic emission localization of orthotropic steel bridge deck damage with multi-objective optimization and efficiency enhancement, comprising the following steps:

[0006] Step S1, collecting acoustic emission signals of the orthotropic steel bridge deck in the working state through acoustic emission sensors at four vertices of the rectangular area to be measured;

[0007] Step S2, deriving the shortest path formula for the acoustic emission signals to propagate from potential damage sources at different positions to the acoustic emission sensors according to the complex spatial thin-walled geometric structure of the orthotropic steel bridge deck;

[0008] Step S3, using the Akaike information criterion to extract the arrival time of the initial arrival mode of the acoustic emission signal, obtaining the dispersion curve of the acoustic emission signal through the lamb wave dispersion theory, respectively determining the characteristic frequencies and wave velocities of the initial arrival mode and the A0 mode, and using wavelet transform to determine the arrival time of the A0 mode of the acoustic emission signal;

[0009] Step S4, establishing a multi-objective optimization model for orthotropic steel bridge deck damage localization by using the shortest path derived in Step S2 and the multi-mode arrival time and wave velocity parameters determined in Step S3;

[0010] S5. Taking the first layer of the multi-objective optimization model as the important objective function, solve the multi-objective optimization model by the hierarchical sequence method to evaluate the location of the acoustic emission source, that is, the location of the damage.

[0011] Further, in step S2, the acoustic emission signal transmits energy in the most effective path in the plate-like structure, that is, the shortest path, which is called the geodesic distance; the orthotropic steel bridge deck is a thin-walled space structure composed of a deck plate and U-ribs welded together. The longitudinal direction of the orthotropic steel bridge deck is along the extension direction of the U-ribs, and the transverse direction is along the cross-section direction of the U-rib opening, with multiple acoustic emission signal propagation paths; the acoustic emission signal propagates through the deck plate and U-ribs; the geodesic distance is related to the path of the initial arrival component of the acoustic emission signal. Theoretically, the geodesic distance is the path of the initial arrival component of the acoustic emission signal; the length of the orthotropic steel bridge deck is l, the width is w, the width of the U-rib opening is w 1 , the bottom width is u 1 , the depth is h, the full length of the U-rib cross-section is u, and there are two dividing lines on the U-ribs defined by the following formula:

[0012]

[0013] Among them, w 2 is the distance from the weld on the deck plate to the acoustic emission sensor in the transverse direction, u 2 is the distance from the dividing line on the U-rib to the bottom of the U-rib in the transverse direction, u 3 is the distance from the dividing line on the U-rib to the weld in the transverse direction; based on the two dividing lines and the weld, the steel bridge deck is divided into four regions; the U-ribs are unfolded into a plane to obtain two sub-domains D 1 and D 2 for the two optimized searches of the orthotropic steel bridge deck. The sub-domain D 1 corresponds to the deck plate, and the sub-domain D 2 corresponds to the U-ribs. Taking the center of the deck plate as the coordinate origin to establish a coordinate system, the expressions of the two sub-domains are as follows:

[0014]

[0015] Among them, the coordinate system of the sub-domain D 1 is represented as x f and y f , and the coordinate system of the sub-domain D 2 is represented as x u and y u .

[0016] Further, in step S2, the formula for the shortest path from the damage source to the four acoustic emission sensors is deduced as:

[0017]

[0018]

[0019] Among them, d 1 , d 2 , d 3 , d 4 are respectively the geodesic paths for potential damage sources at different positions to reach four acoustic emission sensors; the shortest path from the source to the sensor calculated by formulas (3)-(6) is recognized as the actual propagation distance of the acoustic emission signal.

[0020] Furthermore, in step S4, the expression of the multi-objective optimization model is:

[0021]

[0022] Among them, E(x f , y f , x u , y u ) and E'(x f , y f , x u , y u ) are respectively the first-layer objective function and the second-layer objective function of the multi-objective optimization model; Δt ij is the arrival time of the initial arrival mode of the acoustic emission signal collected by the i-th sensor and the j-th sensor; d i and d j are respectively the geodesic distances from the damage source to the i-th sensor and the j-th sensor; v s is the wave speed of the initial arrival mode of the acoustic emission signal; in the second-layer objective function of the multi-objective optimization model, d i,M is the propagation distance of the acoustic emission signal calculated by formula (8):

[0023] d i,M =(t i,A -t i,S )×v S ×v A / (v S -v A ) (8)

[0024] In formula (9), t i,S and t i,A are respectively the arrival times of the initial arrival mode and the A0 mode of the acoustic emission signal, and v A is the wave speed of the A0 mode of the acoustic emission signal.

[0025] Furthermore, in step S5, the steps to solve the multi-objective optimization model using the hierarchical sequence method are:

[0026] Step S5.1, set E(x f , y f , xu , y u ) is an important objective function of the multi-objective optimization model, E'(x f , y f , x u , y u )

[0027] is the secondary important objective function;

[0028] Step S5.2. Use the genetic algorithm to optimize the function E(x f , y f , x u , y u )

[0029] separately in the four regions divided in Step S2 to find its optimal solution set Ω;

[0030] Step S5.3. If Ω is unique, output the damage location. If Ω is not unique, search on the basis of the optimal solution set Ω to find the coordinates that minimize the secondary important objective function E'(x f , y f , x u , y u ), and output the location of the acoustic emission source, that is, the location of the damage.

[0031] A multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks of the present invention has the following advantages:

[0032] (1) The present invention is a multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks, and derives the calculation formula for the shortest distance between the damage source and the sensor based on the complex spatial thin-walled geometric structure of the orthotropic steel bridge deck.

[0033] (2) The present invention is a multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks, and is used for the multi-objective optimization model for orthotropic steel bridge deck damage location, overcoming the problem that the traditional optimization-based location method cannot be applied to the acoustic emission location of spatial thin-walled structures.

[0034] (3) The present invention is a multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks. According to the accuracy difference of the arrival times of multiple modes of acoustic emission signals in the multi-objective model, the first layer of the multi-objective optimization model is used as the important objective function, and a more accurate damage source location is obtained by solving the multi-objective optimization model through the hierarchical sequence method. Description of the Drawings

[0035] Figure 1 is a flow chart of a multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks of the present invention;

[0036] Figure 2 It is a schematic diagram of the geometric structure of the ribbed surface of a typical orthotropic steel bridge deck;

[0037] Figure 3 It is a schematic diagram of the artificial lead-breaking experiment specimen of the steel bridge deck specimen in the embodiment of the present invention;

[0038] Figure 4 It is a schematic diagram of the distribution of test points in the embodiment of the present invention;

[0039] Figure 5 It is a schematic diagram of the setting of the artificial lead-breaking experiment of the steel bridge deck specimen of the present invention;

[0040] Figure 6 It is a schematic diagram of the arrival time extraction of typical acoustic emission signals and Akaike information criterion;

[0041] Figure 7 It is a schematic diagram of the theoretical dispersion curve of Lamb waves of Q345 steel plate with a thickness of 20 mm in the embodiment of the present invention;

[0042] Figure 8 It is a typical acoustic emission signal spectrogram;

[0043] Figure 9 It is a spectrogram of the first arrival mode in the embodiment of the present invention;

[0044] Figure 10 It is a schematic diagram of the arrival time determination of the A0 mode in the embodiment of the present invention;

[0045] Figure 11 It is the verification result of a multi-objective optimization and efficiency-enhancing acoustic emission localization method for orthotropic steel bridge deck damage of the present invention;

[0046] Figure 12 It is the verification result of the traditional optimization-based localization method. Detailed implementation manners

[0047] In order to better understand the purpose, structure and function of the present invention, the following further describes in detail a multi-objective optimization and efficiency-enhancing acoustic emission localization method for orthotropic steel bridge deck damage of the present invention with reference to the accompanying drawings.

[0048] Example 1:

[0049] The main content studied in this example is the artificial lead-breaking experiment of the steel bridge deck specimen to verify the effectiveness and practicability of a multi-objective optimization and efficiency-enhancing acoustic emission localization method for orthotropic steel bridge deck damage proposed in this patent. The flowchart of the present invention is as Figure 1 shown.

[0050] A multi-objective optimization and efficiency-enhancing acoustic emission localization method for orthotropic steel bridge deck damage of the present invention includes the following steps:

[0051] Step 1: The experimental equipment used is a multi-channel acoustic emission data acquisition system. The acoustic emission sensor is a WD model sensor with a frequency range of 100 - 1000 kHz. The acoustic emission sensor is installed on the high-strength bolt connection node using a magnetic fixture and a couplant, and then connected to the data acquisition board through a preamplifier for acoustic emission data acquisition. The amplification factor is set to 40 dB, the sampling rate is set to 5 MS / s, and a band-pass filter of 100 - 1000 kHz is set to filter out possible noise.

[0052] Step 2: Figure 2 is a schematic diagram of the geometric structure of the ribbed surface of a typical orthotropic steel bridge deck. Acoustic emission signals transfer energy in the most effective path in the plate structure, that is, the shortest path, called the geodesic distance; the orthotropic steel bridge deck is a thin-walled space structure composed of a deck plate and U-ribs welded together. The longitudinal direction of the orthotropic steel bridge deck is along the extension direction of the U-ribs, and the transverse direction is along the cross-section direction of the U-rib opening, with multiple acoustic emission signal propagation paths; these acoustic emission signals propagate not only through the deck plate but also through the U-ribs; the geodesic distance is related to the path of the initial arrival component of the acoustic emission signal. The orthotropic steel bridge deck has a length of l, a width of w, the width of the U-rib opening is w 1 , the bottom width is u 1 , the depth is h, the cross-section of the U-rib is u in length, and there are two dividing lines on the U-rib that satisfy the following formula:

[0053]

[0054] Among them, w 2 is the distance from the weld on the deck plate to the acoustic emission sensor in the transverse direction, u 2 is the distance from the dividing line on the U-rib to the bottom of the U-rib in the transverse direction, and is the distance from the dividing line to the weld in the transverse direction. Based on the above two dividing lines and the weld, the steel bridge deck is divided into four regions. Unfolding the U-rib into a plane, two sub-domains D 1 and D 2 for optimized search of the orthotropic steel bridge deck are obtained. Sub-domain D 1 corresponds to the deck plate, and sub-domain D 2 corresponds to the U-rib. Taking the center of the deck plate as the coordinate origin to establish a coordinate system, the expressions of the two sub-domains are as follows:

[0055]

[0056] Among them, the coordinate system of sub-domain D 1 is represented as x f and y f , and the coordinate system of sub-domain D 2 is represented as x u and y u。The formula for deriving the shortest path from the damage source to the four acoustic emission sensors is as follows:

[0057]

[0058] where d 1 、d 2 、d 3 、d 4 are the geodesic paths for potential damage sources at different positions to propagate to the four acoustic emission sensors respectively. The dimensions of the steel bridge deck specimen in this embodiment are as Figure 3 shown. The material of the steel plate is Q345 steel, with a yield strength of 345 MPa and an ultimate strength of 490 MPa. The length and width of the deck are both 1500 mm, and the thickness is 20 mm. The U-rib section is 300×200×245 mm (opening width×bottom width×depth), and the thickness is 8 mm. The width of the test area on the deck is 800 mm, and the length is 1200 mm. Twenty test points are selected to simulate the damage source using the lead-breaking experiment, Figure 4 which is a schematic diagram of the test point distribution. Figure 5 is a schematic diagram of the artificial lead-breaking experiment setup for the steel bridge deck specimen;

[0059] According to the geometric structure of the steel bridge deck, substituting into Equation (17), we get that u 1 、u 2 、u 3 are 200, 50, and 200 mm respectively, and w 1 、w 2 are 300 and 250 mm respectively. Substituting into Equations (18)-(22), we get the following formula:

[0060]

[0061]

[0062] The shortest path from the damage source to the sensor in the steel bridge deck of the embodiment can be calculated through Equations (24)-(27), which is recognized as the actual propagation distance of the acoustic emission signal.

[0063] Step 3: For the collected acoustic emission signals, use the Akaike information criterion to extract the arrival time of the first arrival mode, and the result examples are as Figure 6 shown. According to the material properties and thickness of the steel bridge deck, the schematic diagram of the Lamb wave theoretical dispersion curve of the 20-mm-thick Q345 steel plate is as Figure 7 shown. The typical acoustic emission signal spectrogram is obtained through fast Fourier transform as Figure 8 shown. From Figure 8It can be seen that there is almost no energy distribution in the acoustic emission signal below 100 kHz. For frequencies above 100 kHz, the group velocity of the S0 mode is less than 4600 m / s. Therefore, the obtained initial mode is no longer the S0 mode. The energy in the frequency domain is mainly distributed around 130 kHz and 200 kHz, corresponding to the A0 mode and the S1 mode. Select the waveform with 200 sampling points before and after the arrival time of the initial arrival mode, and obtain the frequency domain characteristics as shown in Figure 9 . It is found that the initial arrival mode is the S1 mode near 200 kHz. Then, the fastest wave velocity of the S1 mode in the dispersion curve is found to be 4933 m / s at 211 kHz. The arrival time of the A0 mode is extracted by wavelet transform and shown in 10, the schematic diagram for determining the arrival time of the A0 mode.

[0064] Step 4: Establish a multi-objective optimization model for damage location of orthotropic steel bridge decks by using the shortest path deduced in Step 2 and the multi-mode arrival time and wave velocity parameters determined in Step 3,

[0065]

[0066] where E(x f , y f , x u , y u ) and E'(x f , y f , x u , y u ) are the first-layer objective function and the second-layer objective function of the multi-objective optimization model respectively; Δt ij is the arrival time of the initial arrival mode of the acoustic emission signal collected by the i-th sensor and the j-th sensor; d i and d j are the geodesic distances from the damage source to the i-th sensor and the j-th sensor respectively; v s is the wave velocity of the initial arrival mode of the acoustic emission signal; in the second-layer objective function of the multi-objective optimization model, d i,M is the propagation distance of the acoustic emission signal calculated by Equation (29):

[0067] d i,M =(t i,A -t i,S )×v S ×v A / (v S -v A ) (29)

[0068] In Equation (29), t i,S and t i,A are the arrival times of the initial arrival mode and the A0 mode of the acoustic emission signal respectively, and v AIt is the wave velocity of the A0 mode of the acoustic emission signal. Substituting the parameters of the steel bridge deck in the embodiment, a multi-objective optimization model is obtained:

[0069]

[0070] Step 5: Solve the multi-objective optimization model by the hierarchical sequence method. First, search for the optimal solution set of the first-layer function of the multi-objective model in the four regions of the steel bridge deck. If the optimal solution is unique, the output is the damage location; if the optimal solution of the first-layer function is not unique, solve the second-layer function on this solution set, and then output the unique damage location. Finally, for a multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks proposed in this patent, the location errors at 20 test points are: average error 49 mm, standard deviation 56 mm. See details in Figure 11 The verification results of a multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks. To highlight that the multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks proposed in this patent has a high damage location accuracy, compare it with the traditional optimization-based acoustic emission location method. The errors of the traditional optimization-based acoustic emission location method are: average error 94 mm, standard deviation 84 mm. The results are shown in details in Figure 12 The verification results of the traditional optimization-based location method. It is found by comparison that the location accuracy of the multi-objective optimization and efficiency-enhancing acoustic emission damage location method for orthotropic steel bridge decks proposed in this patent is increased by 1.9 times.

[0071] It can be understood that the present invention is described by some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A multi-objective optimization and efficiency-enhanced orthotropic steel bridge deck damage acoustic emission positioning method, characterized in that: The steps include: Step S1, collecting acoustic emission signals of the orthotropic steel bridge deck in a working state through acoustic emission sensors at four vertices of the rectangular area to be measured; Step S2, according to the complex spatial thin-wall geometric structure of the orthotropic steel bridge deck, deriving the shortest path formula for the acoustic emission signal propagating from the potential damage sources at different positions to the acoustic emission sensor; Step S3, using the Akaike information criterion to extract the arrival time of the first arrival mode of the acoustic emission signal, obtaining the dispersion curve of the acoustic emission signal through the lamb wave dispersion theory, determining the characteristic frequency and wave velocity of the first arrival mode and the A0 mode respectively, and determining the arrival time of the A0 mode of the acoustic emission signal by wavelet transform; Step S4, establishing a multi-objective optimization model for orthotropic steel bridge deck damage location using the shortest path derived in step S2 and the multi-mode arrival time and wave velocity parameters determined in step S3; S5. Taking the first layer of the multi-objective optimization model as the important objective function, the multi-objective optimization model is solved by the hierarchical sequence method to evaluate the location of the acoustic emission source, that is, the location of the damage.

2. The multi-objective optimization and efficiency-enhanced orthotropic steel bridge deck damage acoustic emission positioning method according to claim 1 is characterized in that: In step S2, the acoustic emission signal transmits energy in the plate structure in the most effective path, that is, the shortest path, which is called the geodesic distance; the orthotropic steel bridge deck is a thin-walled space structure composed of a panel and a U-rib welded together, the longitudinal direction of the orthotropic steel bridge deck is along the extension direction of the U-rib, and the transverse direction is along the cross-sectional direction of the U-rib opening, and has multiple acoustic emission signal propagation paths; the acoustic emission signal propagates through the panel and the U-rib; the geodesic distance is related to the path of the initial arrival component of the acoustic emission signal; the orthotropic steel bridge deck is l long and w wide, the U-rib opening width is w1, the bottom width is u1, the depth is h, the U-rib cross-section length is u, and there are two dividing lines on the U-rib defined by the following formula: Among them, w2 is the distance from the weld on the panel to the acoustic emission sensor in the transverse direction, u2 is the distance from the dividing line on the U rib to the bottom of the U rib in the transverse direction, and u3 is the distance from the dividing line on the U rib to the weld in the transverse direction. Based on the two dividing lines and the weld, the steel bridge deck is divided into four areas. The U rib is unfolded into a plane to obtain two sub-domains D1 and D2 of the optimized search of the orthogonal anisotropic steel bridge deck. The sub-domain D1 corresponds to the panel, and the sub-domain D2 corresponds to the U rib. The coordinate system is established with the center of the panel as the coordinate origin. The expressions of the two sub-domains are as follows: The coordinate system of the subdomain D1 is represented by x f and f , the coordinate system of the subdomain D2 is represented by x u and u .

3. The multi-objective optimization and efficiency-enhanced orthotropic steel bridge deck damage acoustic emission positioning method according to claim 2 is characterized in that: In step S2, the formula for the shortest path from the damage source to the four acoustic emission sensors is derived as follows: Among them, d1, d2, d3, and d4 are the geodesic paths of the potential damage sources at different locations to reach the four acoustic emission sensors. The shortest path from the source to the sensor calculated by formulas (3)-(6) is considered to be the actual propagation distance of the acoustic emission signal.

4. The multi-objective optimization and efficiency-enhanced orthotropic steel bridge deck damage acoustic emission positioning method according to claim 3 is characterized in that: In step S4, the proposed multi-objective optimization model expression is: Among them, E(x f ,y f ,x u ,y u ) and E'(x f ,y f ,x u ,y u ) are the first-level objective function and the second-level objective function of the multi-objective optimization model respectively; Δt ij is the arrival time of the first arrival mode of the acoustic emission signal collected by the i-th sensor and the j-th sensor; d i and d j are the geodesic distances from the damage source to the i-th sensor and the j-th sensor respectively; v s is the wave velocity of the first arrival mode of the acoustic emission signal; in the second level objective function of the multi-objective optimization model, d i,M is the propagation distance of the acoustic emission signal calculated using formula (8): d i,M =(t i,A -t i,S )×v S ×v A / (v S -v A ) (8) In formula (9), t i,S and t i,A are the arrival times of the acoustic emission signal in the first arrival mode and A0 mode, respectively, and v A is the wave velocity of the A0 mode of the acoustic emission signal.

5. The multi-objective optimization and efficiency-enhanced orthotropic steel bridge deck damage acoustic emission positioning method according to claim 4 is characterized in that: In step S5, the steps of solving the multi-objective optimization model using the hierarchical sequence method are: Step S5.1, set E(x f ,y f ,x u ,y u ) is an important objective function of the multi-objective optimization model, E'(x f ,y f ,x u ,y u ) is the secondary important objective function; Step S5.2: Genetic algorithm is used to calculate the function E(x f ,y f ,x u ,y u ) to optimize and find its optimal solution set Ω; Step S5.3: If Ω is unique, then output the damage location. If Ω is not unique, then search for the next most important objective function E'(x f ,y f ,x u ,y u ) obtains the coordinates of the minimum value and outputs the location of the acoustic emission source, that is, the location of the damage.

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