Technical status evaluation method for rust layer stability of unpainted weathering steel plate girder bridge

Abstract

The present invention discloses a method for evaluating the stability of the rust layer of a non-painted weathering steel plate girder bridge, which belongs to the technical field of bridge engineering. Specifically, the method comprises the following steps: obtaining the overall rust layer appearance status information and the rust layer tape adhesion test sample through an in-situ test of the rust layer of the non-painted weathering steel plate girder bridge; determining the rust layer stability classification index, analyzing the proportion of the adhered rust particle products of the tape test sample to the test area ρ s and the maximum rust particle diameter R s Two quantitative grading indicators; grading the stability of rust layer at different measuring points, and dividing the rust layer stability at measuring points into grades 1 to 4 from best to poor; determining the evaluation grading indicator weights for the rust layer condition of the main beam structure, the condition of the bridge ancillary structure and the condition of the bridge site environment, and classifying and evaluating the three conditions; comprehensively evaluating the technical status of the rust layer stability of the entire bridge, and providing reference and basis for the structural design and rust layer maintenance of unpainted weathering steel plate beam bridges.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering, and in particular relates to a method for evaluating the technical status of the stability of the rust layer of a paint-free weathering steel plate girder bridge. Background Art

[0002] Under suitable conditions, a dense rust layer can be formed on the surface of the weathering steel matrix to prevent further erosion by external corrosive substances, thereby achieving the purpose of slowing down the corrosion rate of the steel. The dense and stable rust layer formed on the surface of weathering steel is the key to its technical and economic advantages, and is also the guarantee of its safety, durability and longevity. For the unpainted weathering steel plate girder bridge in the service stage, the technical status evaluation of the rust layer stability can provide a technical basis for the structural design of the unpainted weathering steel plate girder and the maintenance of the rust layer.

[0003] At present, the United States and Japan have proposed weathering rust layer stability evaluation methods suitable for their respective regions and climate environments. The Chinese specification proposes a classification and grading of paint layers. The above evaluation classifications are mainly qualitative evaluations based on the appearance illustrations of the rust layer. Subjective judgments dominate the evaluation process, and the evaluation results vary greatly. Domestic and foreign related studies have conducted quantitative evaluations on the corrosive properties of weathering steel rust layers, but the test steps are complex and the cost is high. For unpainted weathering steel plate girder bridges in different service environments in China, considering the impact of economy, efficiency, and universality in the in-situ test of rust layer stability, it is urgent to establish a systematic qualitative and quantitative evaluation method for the technical status of unpainted weathering steel rust layer stability. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the technical deficiencies of the current rust layer stability evaluation methods at home and abroad, and to provide a method for evaluating the technical status of the rust layer stability of a paint-free weathering steel plate girder bridge, thereby providing technical support for the rust layer stability evaluation and rust layer maintenance and management of a paint-free weathering steel plate girder bridge.

[0005] The technical solution adopted to solve the above technical problems is: a method for evaluating the technical condition of the rust layer stability of a paint-free weathering steel plate beam bridge, comprising the following steps:

[0006] Step 1: In-situ testing of bridge rust layer;

[0007] Investigate and research the basic information of the in-situ tested bridge, make a preliminary judgment on the appearance of the rust layer on the main beam by visual inspection, and conduct tape adhesion tests on the rust layer surfaces in areas with different degrees of rust to obtain the looseness of the rust layer, the diameter and number of adhesion particles;

[0008] Step 2: Determine the rust layer stability classification index;

[0009] The coverage area of ​​the rust products of the tape adhesion test sample in step 1 is counted to determine the grading index ρ of the proportion of the adhesion rust products to the test area s ; At the same time, the diameter of the larger rust particles is measured to determine the maximum rust particle diameter classification index R s ;

[0010] Step 3: Classify the stability of the rust layer at the measuring point;

[0011] Based on the visual inspection results of the rust layer appearance in step 1 and the quantitative grading index of the rust layer stability determined in step 2, the rust layer stability of the measuring points at different positions is evaluated and graded. The rust layer stability of the measuring points is graded from grade 1 to grade 4 from excellent to poor.

[0012] Step 4: Technical status evaluation of the stability of the rust layer of the entire bridge;

[0013] Based on the classification results in step 3, the technical status evaluation of the rust layer stability of the whole bridge of the unpainted weathering steel plate girder bridge is carried out. The overall score D of the rust layer stability technical status of the unpainted weathering steel plate girder bridge is determined according to formula (1):

[0014] D=D rs ×W rs +D as ×W as +D be ×W be (1)

[0015] Among them, D rs Score for the rust condition of the main beam structure, D as Score the condition of the bridge's auxiliary structures, D be Score the environmental condition of the bridge site, W rs is the weight coefficient corresponding to the rust layer condition of the main beam structure in the technical condition evaluation of the rust layer stability of the whole bridge, W as is the weight coefficient corresponding to the condition of the bridge auxiliary structure in the technical condition evaluation of the stability of the rust layer of the whole bridge, W be is the weight coefficient corresponding to the environmental condition of the bridge site in the technical condition evaluation of the stability of the rust layer of the entire bridge;

[0016] The technical condition score level of the rust layer stability of the unpainted weathering steel plate girder bridge is determined based on the overall score D, which is divided into level 1 to level 4 from excellent to poor, and the score ranges are [80,100], [60,80), [40,60), and [0,40] respectively.

[0017] In step 4 of the present invention, rs , W as , W be The values ​​are 0.55~0.65, 0.2~0.3, and 0.1~0.2 respectively.

[0018] The visual inspection method in step 1 of the present invention is to observe with the human eye or take photos with the help of a high-definition camera. The test content includes the appearance characteristics of the color, texture and roughness of the rust layer of the main beam and the distribution pattern of the rust layer in different corrosion states.

[0019] In step 1 of the present invention, the tape adhesion test on the rust layer surface obtains the looseness of the rust layer, the diameter and number of adhesion particles, and includes the following steps:

[0020] (1) According to the survey information of the tested unpainted weathering steel plate girder bridge and the appearance distribution characteristics of the rust layer, the main beam web surface, the lower surface of the main beam upper wing plate, and the upper and lower surfaces of the main beam lower wing plate were selected as the test locations;

[0021] (2) Clean and dry the surface of the rust layer to be tested, and use a cutting tool and a grid plate to grid the surface of the rust layer horizontally and vertically to form a specified grid pattern. The test uses a 6×6 grid with a cutting spacing of 3 mm. To avoid large errors in the test results, select 3 different positions in each measuring point area for repeated testing;

[0022] (3) After the test location surface is gridded, apply the pressure-sensitive tape parallel to a set of parallel lines in the grid. Apply the tape vertically and point-press to avoid back-and-forth friction. After completion, tear off the tape from the rust layer surface at a 45° angle at a steady speed.

[0023] (4) After the test is completed, take photos and record the tape samples, and store them in sealed bags according to their categories.

[0024] In step 3 of the present invention, the stability of the rust layer at the measuring point is divided into grades 1 to 4 from excellent to poor, and the classification is as follows:

[0025] (1) Grade 1: Chocolate or dark brown in color, dense and continuous texture, smooth surface, s <2%;

[0026] (2) Grade 2: Dark brown or with black rust spots, dense texture, smooth surface, R s <1mm, 2%≤ρ s <6%;

[0027] (3) Grade 3: The color varies greatly from light brown to black, the surface texture is uneven, there is stratification and shedding, and the uniformity is poor, 1mm≤R s <2mm, 2%≤ρ s <15%;

[0028] (4) Grade 4: Bright yellow to black color, obvious local color mutation, rough and uneven surface texture, obvious rust spots and pits, 1mm≤R s <2mm, 15%≤ρ s .

[0029] In step 4 of the present invention, the rust layer condition of the main beam structure is comprehensively evaluated by region, and the evaluation route is the stability of the measuring point → the component area → the main beam structure, and the rust layer condition score of the main beam structure is D rs Determined by formula (2):

[0030]

[0031] Among them, W l In order to consider the correction factor of the difference in rust layer stability caused by the distribution position of the main beam, the value for the side beam is 0.3~0.5, and the value for the secondary side beam and the middle beam is (0~0.3) / (l-2), l is the main beam number, l0 is the number of main beams, BF l WR l TF l Respectively represent the rust stability scores of the lower wing plate, web plate, and upper wing plate of the first main beam; BF l WR l TF l Determined by equations (3), (4) and (5) respectively:

[0032]

[0033] When n=1, V1=DS i1 ;

[0034] When n>1,

[0035] Among them, k is the number of measuring points in the component test area; V, m, and n are intermediate variables; i is the component number of the main beam, and j is the number of the measuring point on the component surface; DS ij It indicates the deduction value of the stability grade of the rust layer at the jth measuring point of the i-th type component. The deduction values ​​are 0, 20, 40, and 60 according to the stability grade of the rust layer at the measuring point from grade 1 to grade 4 respectively; U BF , U WR , U TF They represent the score weights of the rust layer conditions of the lower wing plate, web plate, and upper wing plate in the overall assessment of the main beam, and the value ranges are 0.6-0.8, 0.15-0.3, and 0.05-0.1, respectively. It is necessary to ensure that U BF , U WR , U TF The sum is 1.

[0036] The bridge accessory structure condition score D in step 4 of the present invention is asDepending on whether the bridge's drainage system and expansion device fail, there are four situations: if the drainage system and the expansion device work normally at the same time, the score is 100; if the drainage system works normally and the expansion device fails, the score is 90; if the drainage system fails and the expansion device works normally, the score is 40; and if the drainage system and the expansion device fail at the same time, the score is 0.

[0037] The bridge site environmental condition score D in step 4 of the present invention is be It is divided into 6 types of corrosive atmospheric environment conditions: C1, C2, C3, C4, C5, and CX, with scoring values ​​of 100, 80, 60, 40, 20, and 0 respectively.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] (1) The present invention proposes that the proportion of the adhered rust particles of the tape test sample to the test area is ρ s and the maximum rust particle diameter R s Two quantitative grading indicators, quantitative evaluation and grading of rust layer stability based on qualitative evaluation of rust layer appearance characteristics;

[0040] (2) The method for evaluating the technical condition of the rust layer stability of the unpainted weathering steel plate girder bridge of the present invention is constructed using the rust layer stability detection data of multiple unpainted weathering steel plate girder bridges in different regions of China, and takes into account the influence of the bridge's auxiliary structures and the bridge location environmental factors on the rust layer stability, and evaluates the technical condition of the rust layer stability of the entire bridge based on the objective rust layer state attributes. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of the present invention.

[0042] Figure 2 Layout of measuring points for rust layer of weathering steel beams that are free from painting.

[0043] Figure 3 This is a test diagram of the adhesion of the adhesive tape for the paint-free weathering steel plate girder bridge of the present invention.

[0044] Figure 4 Comparison chart of steel surface and sample in situ test of tape adhesion.

[0045] Figure 5 This is an evaluation example and classification index diagram for the rust layer stability grade of the weathering steel bridge in Example 1.

[0046] Figure 6 This is the evaluation diagram of the rust layer stability grade of the weathering steel bridge in Test 1.

[0047] In the figure: 1. Rust layer; 2. Steel substrate; 3. Test pressure-sensitive tape; 4. Grid cut; 5. 6×3mm grid; 6. Tear-off tape. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to these embodiments.

[0049] Example 1

[0050] like Figure 1 As shown, the technical condition evaluation method for the rust layer stability of the paint-free weathering steel plate girder bridge of the present invention comprises the following four steps:

[0051] Step 1: In-situ testing of bridge rust layer;

[0052] The basic information of the in-situ tested bridge (such as bridge structure, construction time, climate environment at the bridge location, etc.) was investigated and surveyed, and the appearance of the rust layer on the main beam was preliminarily judged by visual inspection. The rust layer surfaces in areas with different degrees of rust were selected for tape adhesion test to obtain the looseness of the rust layer, the diameter and number of adhesion particles. The visual inspection method is to observe with the human eye or take photos with the help of a high-definition camera. The test content includes the appearance characteristics of the color, texture and roughness of the rust layer on the main beam, and the distribution pattern of the rust layer in different corrosion states.

[0053] The above-mentioned rust layer surface tape adhesion test obtains the looseness of the rust layer, the diameter and number of adhesion particles, and includes the following steps:

[0054] (1) According to the survey information of the tested unpainted weathering steel plate girder bridge and the appearance distribution characteristics of the rust layer, the main beam web surface, the lower surface of the main beam upper wing plate, and the upper and lower surfaces of the main beam lower wing plate were selected as test locations. The measurement points were arranged as follows: Figure 2 As shown;

[0055] (2) Clean and dry the surface of the rust layer to be tested, and use a cutting tool and a grid plate to grid the surface of the rust layer horizontally and vertically to form a specified grid pattern. If the grid lines are skewed or deviated, they should be re-grid at adjacent positions. The test uses a 6×6 grid with a cutting spacing of 3mm. To avoid large errors in the test results, 3 different positions are selected in each measuring point area for repeated testing;

[0056] (3) After the test location surface is gridded, apply the pressure-sensitive tape parallel to a set of parallel lines in the grid. Apply the tape vertically and point-press to avoid back-and-forth friction. After completion, remove the tape from the rust layer surface at a 45° angle at a steady speed. Figure 3 As shown;

[0057] (4) After the test, take photos of the tape samples and record them. Figure 4 As shown, and store them in sealed bags.

[0058] Step 2: Determine the rust layer stability classification index;

[0059] The coverage area of ​​the rust products of the tape adhesion test sample in step 1 is counted to determine the grading index ρ of the proportion of the adhesion rust products to the test area s ; At the same time, the diameter of the larger rust particles is measured to determine the maximum rust particle diameter classification index R s ;

[0060] Step 3: Classify the stability of the rust layer at the measuring point;

[0061] Based on the visual inspection results of the rust layer appearance in step 1 (rust layer appearance legend, color, texture characteristics) and the quantitative grading index of rust layer stability determined in step 2, the rust layer stability of the rust layer at different measuring points is evaluated and graded. The rust layer stability of the measuring points is graded from excellent to poor, such as grade 1 to grade 4. Figure 5 shown.

[0062] Step 4: Technical status evaluation of the stability of the rust layer of the entire bridge;

[0063] Based on the classification results in step 3, the technical status evaluation of the rust layer stability of the whole bridge of the unpainted weathering steel plate girder bridge is carried out. The overall score D of the rust layer stability technical status of the unpainted weathering steel plate girder bridge is determined according to formula (1):

[0064] D=D rs ×W rs +D as ×W as +D be ×W be (1)

[0065] Among them, D rs Score for the rust condition of the main beam structure, D as Score the condition of the bridge's auxiliary structures, D be Score the environmental condition of the bridge site, W rs is the weight coefficient corresponding to the rust layer condition of the main beam structure in the technical condition evaluation of the rust layer stability of the whole bridge, W as is the weight coefficient corresponding to the condition of the bridge auxiliary structure in the technical condition evaluation of the stability of the rust layer of the whole bridge, W be is the weight coefficient corresponding to the environmental condition of the bridge site in the technical condition evaluation of the stability of the rust layer of the whole bridge. The values ​​of the weight coefficient are shown in Table 1;

[0066] Table 1 Weight coefficients of technical status evaluation indicators for the stability of the rust layer of the entire bridge

[0067]

[0068] The rust layer condition of the main beam structure is evaluated by region. The evaluation route is from the stability of the measuring point to the component area and then to the main beam structure. The rust layer condition score of the main beam structure is D rs Determined by formula (2):

[0069]

[0070] Among them, W l In order to consider the correction coefficient of the difference in rust layer stability caused by the distribution of the main beams, the value for the side beams is 0.3~0.5, and the value for the secondary side beams and the middle beams is (0~0.3) / (l-2), where l is the main beam number and l0 is the number of main beams. For example, for a three-main beam structure, the correction coefficient ranges for the side beams, secondary side beams and middle beams are 0.3~0.5, 0~0.3, and 0.3~0.5 respectively. l WR l TF l Respectively represent the rust layer stability scores of the lower wing plate, web plate, and upper wing plate of the lth main beam; according to the influence of the difference in the stability distribution of the rust layer in different areas of the main beam, the rust layer score weights corresponding to different components of the main beam are assigned, BF l WR l TF l Determined by equations (3), (4) and (5) respectively:

[0071]

[0072] When n=1, V1=DS i1 ;

[0073] When n>1,

[0074] Among them, k is the number of measuring points in the component test area; V, m, n are intermediate variables; i is the main beam component number, j is the component surface measuring point number; DS ij represents the deduction value of the stability grade of the rust layer at the jth measuring point of the i-th type component. The deduction values ​​are 0, 20, 40, and 60 according to the stability grades 1 to 4 of the rust layer at the measuring point, as shown in Table 2; U BF , U WR , U TF They represent the score weights of the rust layer conditions of the lower wing plate, web plate, and upper wing plate in the overall assessment of the main beam, and the value ranges are 0.6-0.8, 0.15-0.3, and 0.05-0.1, respectively. It is necessary to ensure that U BF , U WR , U TF The sum is 1.

[0075] Table 2 Deduction value of rust layer stability grade at measuring points

[0076]

[0077] The condition score of the above bridge auxiliary structure is D asThe drainage system and expansion device of the CCMD coated weathering steel plate beam bridge are key auxiliary structures that affect the formation of stable rust layer. The condition scores of the bridge auxiliary structures are shown in Table 3. According to whether the drainage system and expansion device fail, they are divided into 4 situations, where √ indicates normal working state and × indicates failure state;

[0078] Table 3 Bridge accessory structure condition scores

[0079]

[0080] The environmental assessment score of the above bridge location is D be The main environmental factors affecting the stability of the rust layer are humidity, chloride ion precipitation, and sulfur dioxide content. According to the classification standard for atmospheric corrosion environment in "Atmospheric Corrosion of Metals and Alloys Part 1: Classification, Determination and Evaluation" (GB / T 19292.1-2018), the evaluation of the conditions of six types of corrosive atmospheric environments is shown in Table 4 to characterize the influence of environmental factors at the bridge site on the stability of the rust layer.

[0081] Table 5 Evaluation of bridge site environmental conditions

[0082]

[0083] The technical condition score level of the rust layer stability of the unpainted weathering steel plate girder bridge is determined according to the overall score D, which is divided into level 1 to level 4 from excellent to poor, as shown in Table 5.

[0084] Table 5 Rust layer stability technical condition rating

[0085]

[0086]

[0087] Test 1

[0088] The evaluation method of the present invention is used to evaluate the technical status of the rust layer stability of a certain paint-free weathering steel plate girder bridge. The specific test steps are as follows:

[0089] Step 1: In-situ testing of bridge rust layer;

[0090] The paint-free weathering steel plate girder bridge was built in 2015. The structure adopts 2×28m weathering steel plate continuous composite beam bridge. The main beam is composed of 3 steel plate composite beams. The lower wing plate of the main beam is made of Q500qENH weathering steel, and the rest is made of Q345qENH weathering steel, all of which are used without painting. The bridge is located in the temperate continental monsoon climate zone, with an average annual precipitation of 596mm and an average annual sunshine hours of 2528 hours.

[0091] Through visual inspection, it was found that the rust layer on the web surface of the main beam deteriorated from top to bottom along the beam height. The rust layer near the weld was seriously detached due to the accumulation of debris and dust. The lower wing plate had unstable characteristics such as loose texture, darker color, and falling rust layer due to water erosion. Figure 6 As shown in , the rust surface of different rust degree areas was selected to test the adhesive tape adhesion;

[0092] (1) According to the structural characteristics of the unpainted weathering steel plate girder bridge and the distribution of rust layers at each test location obtained by visual observation, the main test locations include the main beam web surface, the lower surface of the upper wing plate, and the lower wing plate surface area. The specific distribution is as follows: Figure 2 As shown;

[0093] (2) Clean and dry the surface of the rust layer to be tested, and use a cutting tool and a grid plate or spacing guide device to grid the surface of the rust layer horizontally and vertically to form a specified grid pattern. The test uses a 6×6 grid with a cutting spacing of 3 mm. To avoid large errors in the test results, select 3 different positions in each measuring point area for repeated testing;

[0094] (3) After the test location surface is gridded, apply the pressure-sensitive tape parallel to a set of parallel lines in the grid. Apply the tape vertically and point-press to avoid back-and-forth friction. After completion, tear off the tape from the rust layer surface at a 45° angle at a steady speed.

[0095] (4) After the test is completed, take photos and record the tape samples, and store them in sealed bags according to their categories;

[0096] Step 2: Determine the rust layer stability classification index;

[0097] The coverage area of ​​the rust products of the tape adhesion test sample in step 1 is counted, and the proportion of the adhesion rust products to the test area is calculated. s Grading index; at the same time, measure the diameter of larger rust particles to determine the maximum rust particle diameter R s Classification index; the rust layer stability classification index in this example is shown in Table 6;

[0098] Table 6 Main beam rust layer stability classification index

[0099]

[0100] Step 3: Classify the stability of the rust layer at the measuring point;

[0101] Based on the visual inspection results of the rust layer appearance in step 1 and the quantitative grading index of the main beam rust layer stability determined in Table 6 in step 2, the rust layer stability of the three main beams was evaluated and graded. The rust layer stability of the measuring points was graded from excellent to poor. The evaluation and grading results are as follows: Figure 6 shown.

[0102] Step 4: Technical status evaluation of the stability of the rust layer of the entire bridge;

[0103] According to the difference in the stability of the rust layer in different areas of the main beam, the technical condition score weight U of the rust layer corresponding to the lower wing plate, web plate and upper wing plate of the main beam is assigned. BF , U WR , U TF They are 0.69, 0.23 and 0.08 respectively. Take the rust condition score calculation of the lower wing plate, web plate and upper wing plate of the north beam (main beam 1) of the weathering steel plate girder bridge as an example:

[0104]

[0105] TF1=100×U TF =100×0.08=8

[0106] Similarly, in the calculation, the BF2, WR2, and TF2 of the main beam (main beam 2) are 55.2, 23, and 8 respectively, and the BF3, WR3, and TF3 of the south beam (main beam 3) are 41.4, 18.4, and 8 respectively;

[0107] The rust condition score of the unpainted weathering steel plate bridge is calculated as follows:

[0108]

[0109] Determine the bridge accessory structure condition score D as :

[0110] After on-site inspection, the drainage system and expansion device of the bridge are in normal working condition, and the bridge auxiliary structure condition score is D. as is 100 points;

[0111] Bridge site environmental condition score D be :

[0112] According to the classification standard for atmospheric corrosion environment in "Corrosion of Metals and Alloys - Atmospheric Corrosion Part 1: Classification, Determination and Evaluation" (GB / T 19292.1-2018), the bridge environment belongs to the C2 environment category, and the bridge site environment assessment score is D. be 80 points;

[0113] In summary, the comprehensive evaluation of the technical status of the rust layer stability of the entire bridge is:

[0114] W in the comprehensive evaluation formula for the technical status of the rust layer stability of the entire bridge rs , W as , W beThe values ​​of are 0.6, 0.25, and 0.15 respectively. The overall technical status score D of the rust layer stability of the unpainted weathering steel plate girder bridge is calculated as follows:

[0115] D=D rs ×W rs +D as ×W as +D be ×W be =67.3×0.6+100×0.25+80×0.15=77.4

[0116] According to the grading assessment in Table 5, the bridge is a weathering steel plate girder bridge with a technical condition of rust layer stability of level 2.

Claims

1. A method for evaluating the technical status of the rust layer stability of a paint-free weathering steel plate girder bridge, characterized in that The following steps are involved: Step 1: In-situ testing of bridge rust layer; Investigate and research the basic information of the in-situ tested bridge, make a preliminary judgment on the appearance of the rust layer on the main beam by visual inspection, and conduct tape adhesion tests on the rust layer surfaces in areas with different degrees of rust to obtain the looseness of the rust layer, the diameter and number of adhesion particles; Step 2: Determine the rust layer stability classification index; The coverage area of ​​the rust products of the tape adhesion test sample in step 1 is counted to determine the grading index ρ of the proportion of the adhesion rust products to the test area s ; At the same time, the diameter of the larger rust particles is measured to determine the maximum rust particle diameter classification index R s ; Step 3: Classify the stability of the rust layer at the measuring point; Based on the visual inspection results of the rust layer appearance in step 1 and the quantitative grading index of the rust layer stability determined in step 2, the rust layer stability of the measuring points at different positions is evaluated and graded. The rust layer stability of the measuring points is graded from grade 1 to grade 4 from excellent to poor. Step 4: Technical status evaluation of the stability of the rust layer of the entire bridge; Based on the classification results in step 3, the technical status evaluation of the rust layer stability of the whole bridge of the unpainted weathering steel plate girder bridge is carried out. The overall score D of the rust layer stability technical status of the unpainted weathering steel plate girder bridge is determined according to formula (1): D=D rs ×W rs +D as ×W as +D be ×W be (1) Among them, D rs Score for the rust condition of the main beam structure, D as Score the condition of the bridge's auxiliary structures, D be Score the environmental condition of the bridge site, W rs is the weight coefficient corresponding to the rust layer condition of the main beam structure in the technical condition evaluation of the rust layer stability of the whole bridge, W as is the weight coefficient corresponding to the condition of the bridge auxiliary structure in the technical condition evaluation of the stability of the rust layer of the whole bridge, W be is the weight coefficient corresponding to the environmental condition of the bridge site in the technical condition evaluation of the stability of the rust layer of the entire bridge; The rust layer condition of the main beam structure is evaluated by comprehensive evaluation in different regions. The evaluation route is the stability of the measuring point → component area → main beam structure. The rust layer condition score of the main beam structure is D rs Determined by formula (2): Among them, W l In order to consider the correction factor of the difference in rust layer stability caused by the distribution position of the main beam, the value for the side beam is 0.3~0.5, and the value for the secondary side beam and the middle beam is (0~0.3) / (l-2), l is the main beam number, l0 is the number of main beams, BF l WR l TF l Respectively represent the rust stability scores of the lower wing plate, web plate, and upper wing plate of the first main beam; BF l WR l TF l Determined by equations (3), (4) and (5) respectively: When n=1, V1=DS i1 ; When n>1, (j=n, n is 2, 3, ... k) Among them, k is the number of measuring points in the component test area; V, m, and n are intermediate variables; i is the component number of the main beam, and j is the number of the measuring point on the component surface; DS ij It indicates the deduction value of the stability grade of the rust layer at the jth measuring point of the i-th type component. The deduction values ​​are 0, 20, 40, and 60 according to the stability grade of the rust layer at the measuring point from grade 1 to grade 4 respectively; U BF , U WR , U TF They represent the score weights of the rust layer conditions of the lower wing plate, web plate, and upper wing plate in the overall assessment of the main beam, and the value ranges are 0.6-0.8, 0.15-0.3, and 0.05-0.1, respectively. It is necessary to ensure that U BF , U WR , U TF The sum is 1; The condition score of the bridge auxiliary structure is D as According to whether the bridge drainage system and expansion device fail, there are four situations: the drainage system and expansion device work normally at the same time, with a score of 100; the drainage system works normally and the expansion device fails, with a score of 90; the drainage system fails and the expansion device works normally, with a score of 40; the drainage system and expansion device fail at the same time, with a score of 0; The bridge site environmental condition score D be It is divided into 6 types of corrosive atmosphere environment conditions: C1, C2, C3, C4, C5, and CX, with scoring values ​​of 100, 80, 60, 40, 20, and 0 respectively; The technical condition score level of the rust layer stability of the unpainted weathering steel plate girder bridge is determined based on the overall score D, which is divided into level 1 to level 4 from excellent to poor, and the score ranges are [80,100], [60,80), [40,60), and [0,40] respectively.

2. According to the method for evaluating the technical status of the rust layer stability of the unpainted weathering steel plate girder bridge according to claim 1, it is characterized in that: In step 4, W rs , W as , W be The values ​​are 0.55~0.65, 0.2~0.3, and 0.1~0.2 respectively.

3. The method for evaluating the stability of the rust layer of a paint-free weathering steel plate girder bridge according to claim 1 is characterized by: The visual inspection method in step 1 is to observe with the human eye or take photos with a high-definition camera. The test content includes the appearance characteristics of the rust layer color, texture and roughness of the main beam and the distribution pattern of the rust layer in different corrosion states.

4. The method for evaluating the stability of the rust layer of a coating-free weathering steel plate girder bridge according to claim 1 is characterized in that: The tape adhesion test on the rust layer surface in step 1 to obtain the looseness of the rust layer, the diameter and number of adhesion particles includes the following steps: (1) According to the survey information of the tested unpainted weathering steel plate girder bridge and the appearance distribution characteristics of the rust layer, the main beam web surface, the lower surface of the main beam upper wing plate, and the upper and lower surfaces of the main beam lower wing plate were selected as the test locations; (2) Clean and dry the surface of the rust layer to be tested, and use a cutting tool and a grid plate to grid the surface of the rust layer horizontally and vertically to form a specified grid pattern. The test uses a 6×6 grid with a cutting spacing of 3 mm. To avoid large errors in the test results, select 3 different positions in each measuring point area for repeated testing; (3) After the test location surface is gridded, apply the pressure-sensitive tape parallel to a set of parallel lines in the grid. Apply the tape vertically and point-press to avoid back-and-forth friction. After completion, tear off the tape from the rust layer surface at a 45° angle at a steady speed. (4) After the test is completed, take photos and record the tape samples, and store them in sealed bags according to their categories.

5. The method for evaluating the stability of the rust layer of a coating-free weathering steel plate girder bridge according to claim 1 is characterized in that: The stability of the rust layer at the measuring point in step 3 is classified into grades 1 to 4 from excellent to poor, and the classification is as follows: (1) Grade 1: Chocolate or dark brown in color, dense and continuous texture, smooth surface, s <2%; (2) Grade 2: Dark brown or with black rust spots, dense texture, smooth surface, R s <1mm, 2%≤ρ s <6%; (3) Grade 3: The color varies greatly from light brown to black, the surface texture is uneven, there is stratification and shedding, and the uniformity is poor, 1mm≤R s <2mm, 2%≤ρ s <15%; (4) Grade 4: Bright yellow to black color, obvious local color mutation, rough and uneven surface texture, obvious rust spots and pits, 1mm≤R s <2mm, 15%≤ρ s .

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