Method for repairing bridge girder

Abstract

To provide a method for repairing a corroded portion of a steel material included in a bridge girder, which can effectively suppress corrosion of a joint portion or the like between a lower flange and a vertical stiffener.SOLUTION: A method for repairing a bridge girder including a steel material 10 including an upper flange 11, a lower flange 12, and a web 13, wherein a vertical stiffener 30 made of a steel plate is joined between the upper flange 11 and the lower flange 12 in a state of surface contact with at least one of the web 13 and the lower flange 12, the method comprising: The method includes a specific step of communicating both sides of the notch 31 along the longitudinal direction of the web 13 in the 12S of the upper surface of the lower flange 12.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for repairing bridge girders, particularly bridge girders having steel structures. [Background technology]

[0002] In bridge girders with steel structures, vertical stiffeners may be installed between the upper and lower flanges and the web of the structure to provide shear buckling reinforcement.

[0003] The vertical stiffener is made of a rectangular steel plate having the height of the upper and lower flanges, with its upper end face abutting the upper flange, its lower end face abutting the lower flange, and its side end faces abutting the web. The vertical stiffener is fixed to the bridge girder by welding at least the part abutting the upper flange or the outer edge of the part abutting the web.

[0004] Although the vertical stiffeners are thinner than the web and upper and lower flanges, they corrode due to aging and salt intrusion, and if they become damaged, the load is placed directly on the web, causing it to buckle. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Usukura, Makoto et al., "Effect of Difference in Corrosion Area at the Bottom End of the Web and Stiffener on the Support Point of Plate Girder End on Its Strength Characteristics," Structural Engineering Journal A, Japan Society of Civil Engineers, 2011, Vol. 57A, pp. 724-734 Summary of the Invention [Problem to be solved by the invention]

[0006] Generally, the web of a bridge girder, the lower half of a vertical stiffener, and the bottom flange are prone to being trapped by wind and rain, and are also prone to rust. Older bridges in particular tend to use metal-to-metal connections that do not involve welding. In areas where metal-to-metal connections are used, there are small gaps (for example, less than 0.04 mm), and these areas are also prone to rust.

[0007] This rust not only weakens the vertical stiffeners, but can also corrode the weld beads at the joints between the vertical stiffeners and the web or the bottom flange, requiring on-site rewelding.

[0008] When such on-site work becomes necessary, not only does the cost of repairs increase, but the timing of repairs also becomes dependent on securing welding workers, which creates the drawback of not being able to carry out repair work at the appropriate time.

[0009] The present invention has been made to solve such problems, and aims to provide a bridge girder repair method that can suppress corrosion at the joint between the lower flange and the vertical stiffener, etc. [Means for solving the problem]

[0010] In order to achieve the above object, a bridge girder repair method according to one aspect of the present invention has the following features.

[0011] (1) A method for repairing a bridge girder comprising steel members consisting of an upper flange, a lower flange, and a web, wherein a vertical stiffener made of a steel plate is joined between the upper flange and the lower flange in a state of surface contact with at least one of the web and the lower flange, The method is characterized by having a specific process of cutting out a corroded portion that has occurred near the corner formed by the lower flange and the web at the lower end of the vertical stiffener to form a notch, and connecting both sides of the notch along the longitudinal direction of the web on the upper surface of the lower flange. According to the aspect described in (1) above, the notch formed in the upper surface of the lower flange by cutting out the corroded portion has two longitudinally connected webs, which makes it difficult for water to accumulate in the vertical stiffeners. This effectively prevents corrosion at the joint between the lower flange and the vertical stiffeners.

[0012] (2) In the bridge girder repair method described in (1), the notch is formed in a quadrant shape centered at a specific position on the lower end of the vertical stiffener; The arc-shaped portion of the quadrant may be formed to bulge outward relative to the corner. According to the aspect described in (2) above, the cutout is formed in a quadrant shape centered at a specific position on the lower end of the vertical stiffener. Since the cutting work for the arc-shaped portion of the cutout is easy, it is possible to shorten the time required for cutting the cutout while ensuring a wide water path on the upper surface of the lower flange. (3) In the bridge girder repair method described in (1) or (2), a weld bead is formed at the joint between the web and the vertical stiffener; In the identifying step, the notch may be formed so as to remove the surface of the weld bead in the width direction of the lower flange while leaving a portion of the weld bead. According to the aspect described in (3) above, the notch is formed in the width direction of the lower flange while leaving a portion of the weld bead. Therefore, welding work for connecting the weld beads can be omitted. As a result, the time required for repairing the corroded portion can be shortened. [Effects of the Invention]

[0013] According to the present invention, corrosion of the joint between the lower flange and the vertical stiffener can be effectively suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic perspective view showing a bridge girder including a main girder that is the target of the repair method of the present invention. FIG. [Figure 2]1 is a flowchart of a bridge girder repair method. [Figure 3] FIG. 1 is a perspective view showing the state of a corroded portion that is the target of a bridge girder repair method (the state before the notch forming step is performed). [Figure 4] FIG. 10 is a perspective view showing the state after the notch forming step (the state before the repair material applying step). [Figure 5] FIG. 10 is a perspective view showing the state after the repair material application step has been performed (the state before the painting step has been performed). [Figure 6] FIG. 10 is a perspective view showing the state after the painting process. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment Next, a bridge girder repair method according to a first embodiment of the present invention will be described with reference to the drawings. In the first embodiment, the target of the repair method of the present invention is a main girder 10 that constitutes a bridge girder 1, which is a steel structure. The main girder 10 has an I-shaped cross section as shown in FIG.

[0016] The bridge girder 1 constitutes a railway bridge and has multiple main girders 10 arranged in parallel at predetermined intervals across the width of the bridge girder 1, and deck slabs 20 installed on the multiple main girders 10. Note that some railway bridges have a roadbed such as sleepers directly above the upper flange 11, and in this specification, such structures are also included in the description of the "deck slab 20." Also, while the bridge girder 1 constitutes a railway bridge as an example, it may also constitute a bridge for other purposes, such as a road bridge.

[0017] The main girder 10 has an upper flange 11, a lower flange 12, and a web 13. Hereinafter, the longitudinal direction of the main girder 10 will be simply referred to as the "longitudinal direction," the direction perpendicular to the web 13 in a cross section perpendicular to the longitudinal direction (the direction in which the upper flange 11 and the lower flange 12 protrude relative to the web 13) will be referred to as the "left-right direction," and the direction parallel to the web 13 (the direction perpendicular to the left-right direction) will be referred to as the "up-down direction."

[0018] A plurality of vertical stiffeners 30 are attached to the main girder 10. Specifically, the vertical stiffeners 30 are arranged in parallel at predetermined intervals along the longitudinal direction on both the left and right sides of the web 13. The vertical stiffeners 30 are made of vertically elongated rectangular steel plates. The vertical length of each vertical stiffener 30 is the same as the vertical length of the web 13, and the horizontal length of each vertical stiffener 30 is shorter than the length from the side surface 13S of the web 13 to the tip of the lower flange 12 on the same side as the side surface 13S in the horizontal direction. However, the relationship between the vertical length of each vertical stiffener 30 and the vertical length of the web 13, and the relationship between the horizontal length of each vertical stiffener 30 and the length from the side surface 13S of the web 13 to the tip of the lower flange 12 on the same side as the side surface 13S in the horizontal direction, are not particularly limited and may be changed as appropriate.

[0019] The vertical stiffeners 30 are in contact perpendicularly with the lower surface 11S of the upper flange 11, the upper surface 12S of the lower flange 12, and the side surface 13S of the web 13. In other words, the vertical stiffeners 30 are joined to the main girder 10 on both the left and right sides of the web 13 in contact with the lower surface 11S of the upper flange 11, the upper surface 12S of the lower flange 12, and the side surface 13S of the web 13.

[0020] The vertical stiffener 30 is welded to the web 13 on both longitudinal sides over the entire vertical length. Therefore, a weld bead 32A is formed at the joint between the vertical stiffener 30 and the web 13 over the entire vertical length of the vertical stiffener 30. The vertical stiffener 30 is in metal-to-metal contact (highly accurate surface contact) with the upper flange 11 and the lower flange 12, and is not welded.

[0021] Furthermore, the bridge girder 1 is gently inclined overall. In the first embodiment, the bridge girder 1 is inclined such that the top of the bridge girder 1 is on the front side of the page in FIG. 1 and slopes downward toward the end of the bridge girder 1 on the back side of the page. Therefore, for example, when water such as rain flows onto the top surface 12S of the lower flange 12, the water flows along the top surface 12S of the lower flange 12 from the upstream, which is the top of the bridge girder 1, toward the downstream end of the bridge girder 1. Furthermore, because the vertical stiffeners 30 abut against the lower flange 12 and the web 13 without any gaps, the water flowing along the top surface 12S of the lower flange 12 is blocked by the vertical stiffeners 30, and water tends to accumulate (retain) at the corners where the vertical stiffeners 30 and the lower flange 12 intersect at right angles, and further at the corners formed by the vertical stiffeners 30, the lower flange 12, and the web 13. As a result, corrosion is particularly likely to occur in the lower flange 12 of the vertical stiffener 30 and in the vicinity of the joint with the web 13. In the first embodiment, an example will be described in which a part of the side surface 30S of the vertical stiffener 30 on the front side of the paper surface is corroded.

[0022] Next, a bridge girder repair method according to the present invention will be described. Fig. 2 is a flowchart of the bridge girder repair method according to the present invention. The bridge girder repair method according to the present invention includes a notch forming step S1 (first step), a repair material applying step S2 (second step), and a painting step S3 (third step).

[0023] In the notch forming step S1 (first step), a notch 31 is formed in a specific region 30A including the corroded portion F of the vertical stiffener 30 using a cutting tool such as a drill. Also, in the notch forming step S1 (first step), the portion of the corroded portion F other than the specific region 30A is scraped using a polishing tool such as a grinder. Therefore, the corroded portion F is removed by the notch forming step S1 (first step).

[0024] In the repair material application step S2 (second step), the repair material is applied to the application range T1 including the cutout 31. The type of repair material is not particularly limited, but in the first embodiment, the repair material is an epoxy-based repair agent containing iron powder (Devcon A: manufactured by ITW Performance Polymers & Fluids Japan Co., Ltd.). The repair material application step S2 (second step) smoothes and finishes the cut and scraped areas.

[0025] In the painting process S3 (third process), the painting area T2, which includes the painting area T1, is painted. While the type of paint used for painting is not particularly limited, in the first embodiment, the paint used for painting is configured according to the painting specifications stipulated in BMU2-7 of the SPS (Soken Paint Standard). The painting process S3 (third process) can prevent corrosion, oxidation, and abrasion of the painting area T2, while also improving its aesthetic appearance. The painting process S3 (third process) is performed after the curing period for the repair material applied in the repair material application process S2 (second process) has elapsed. The painting specifications to be applied are selected based on the intended use of the bridge, such as the F-11 painting specifications established by the Japan Road Association (public corporation) for road bridges.

[0026] Next, various steps of the bridge girder repair method will be explained using the drawings. Fig. 3 is a perspective view showing the state of the corroded portion F that is the target of the bridge girder repair method (the state before the notch forming step S1 is performed), Fig. 4 is a perspective view showing the state after the notch forming step S1 is performed (the state before the repair material applying step S2 is performed), Fig. 5 is a perspective view showing the state after the repair material applying step S2 is performed (the state before the painting step S3 is performed), and Fig. 6 is a perspective view showing the state after the painting step S3 is performed.

[0027] In the first embodiment, as shown in Fig. 3, a case will be described as an example in which a predetermined area spanning the side surface 30S of the vertical stiffener 30, the upper surface 12S of the lower flange 12, and the side surface 13S of the web 13 is corroded, so as to surround a corner C formed by the vertical stiffener 30, the web 13, and the lower flange 12. This is because, as mentioned above, water tends to accumulate near the corner C. Hereinafter, this corroded predetermined area will be referred to as a "corroded portion F." Note that in Fig. 3, the area hatched with dots is the corroded area.

[0028] Among the corroded portions F, corrosion is particularly advanced near the corners C of the vertical stiffeners 30. In other words, near the corners C of the vertical stiffeners 30, rust has occurred not only on the surface of the vertical stiffeners 30 but also inside the vertical stiffeners 30. Therefore, in the notch forming step S1 (first step), a notch 31 is formed in a specific region 30A near the corners C of the vertical stiffeners 30.

[0029] A cross section of the specific region 30A perpendicular to the longitudinal direction is formed as a quadrant of radius R1 centered at a predetermined center position A. The predetermined center position A is located a distance L1 from the corner C. The radii R1 and L1 are not particularly limited and can be set as appropriate. In the first embodiment, R1 is 30 mm and L1 is 10 mm. Note that the radius R1 and the distance L1 from the corner C to the center position A are maximum values, and the radius R1 and the distance L1 do not change even if the dimensions of the main girder 10, including the vertical stiffener 30, increase. However, if twice the sum of the radius R1 and the distance L1 exceeds the width of the vertical stiffener, an adjustment is made so that this value does not exceed the width of the vertical stiffener.

[0030] The two straight line segments of the quadrant that constitutes the specific region 30A are parallel to the left-right and up-down directions. Furthermore, the arc-shaped segments of the quadrant that constitutes the specific region 30A and the straight line segments that are parallel to the up-down direction are formed inside the vertical stiffener 30. Meanwhile, the straight line segments that are parallel to the left-right direction of the quadrant that constitutes the specific region 30A are formed on the same plane as the upper surface 12S of the lower flange 12, with which the lower end surface of the vertical stiffener 30 abuts.

[0031] Then, in the notch forming step S1, when the specific region 30A is drilled, a quadrant-shaped notch 31 penetrating the vertical stiffener 30 in the thickness direction is formed, as shown in FIG. 4 . As a result, the portion of the corroded portion F where the rust has reached the interior is removed. Furthermore, the notch 31 spatially connects the upstream side and downstream side of the vertical stiffener 30 on the upper surface 12S of the lower flange 12. In other words, both sides of the notch 13 along the longitudinal direction of the web 13 on the upper surface 12S of the lower flange 12 are connected, thereby forming a path 12R along which water that has flowed into the upper surface 12S of the lower flange 12 flows in the longitudinal direction. Therefore, water flowing from the upstream side of the vertical stiffener 30 on the upper surface 12S of the lower flange 12 flows downstream through the notch 31, making it less likely to accumulate in the vertical stiffener 30.

[0032] As described above, weld bead 32A is formed at the joint between web 13 and vertical stiffener 30. However, quadrant notch 31 is formed from a position L1 (10 mm) away from side surface 13S on the same side of web 13 of vertical stiffener 30 toward the tip. Therefore, weld bead 32A is not completely removed, at least in the range where vertical notch 31 is formed. For example, if width W1 in the left-right direction of weld bead 32A is greater than L1 (10 mm) as shown in FIG. 3, the formation of notch 31 leaves a portion of weld bead 32A on side surface 13S of web 13 in the left-right direction, and a portion of the remaining end side (not shown) of vertical stiffener 30 is removed.

[0033] Furthermore, the portions of the side surface 30S of the vertical stiffener 30 other than the specific region 30A related to the corroded portion F, the upper surface 12S of the lower flange 12, and the side surface 13S of the web 13 are polished using a polishing tool such as a grinder. In Figure 4, the areas hatched with dashed lines are the polished portions.

[0034] In the repair material application step S2, which follows the notch formation step S1, the repair material is applied to the application area T1. The application area T1 includes the inner wall surface 31A that defines the outline of the notch 31 formed in the notch formation step S1 (first step), a fixed area 13T1 (web application area 13T1) that connects to the notch 31 via the weld bead 32A on both longitudinal sides of the side surface 13S of the web 13, and a fixed area 12T1 (lower flange application area 12T1) that connects to the notch 31 via the weld bead 32A on both longitudinal sides of the upper surface 12S of the lower flange 12.

[0035] The inner wall surface 31A of the cutout 31 is slightly uneven because it is formed with a cutting tool such as a drill. Therefore, the inner wall surface 31A can be finished to be smooth by applying a repair material to the inner wall surface 31A.

[0036] The inner wall surface 31A is composed of a curved inner wall surface 31A1 that forms the arc-shaped curved surface portion of the outline of the cutout 31, upper and lower straight inner wall surfaces 31A2 that form linear flat portions parallel to the up and down direction of the outline of the cutout 31, and left and right straight inner wall surfaces 31A3 that form linear flat portions parallel to the left and right direction of the outline of the cutout 31. The curved inner wall surface 31A1 and the upper and lower straight inner wall surfaces 31A2 are formed on the vertical stiffener 30. On the other hand, the left and right straight inner wall surfaces 31A3 are formed on the same plane as the upper surface 12S of the lower flange 12.

[0037] Additionally, the web coating area 13T1 and the lower flange coating area 12T1 are slightly recessed because they have been scraped with an abrasive tool such as a grinder. If left in this state, rainwater and other moisture will accumulate in the recesses and will not be able to completely drain downstream. Therefore, it is necessary to smooth the web coating area 13T1 and the lower flange coating area 12T1 by applying a repair material to them.

[0038] The curved inner wall surface 31A1, the upper and lower straight inner wall surfaces 31A2, and the left and right straight inner wall surfaces 31A3 are connected in the circumferential direction relative to the center position A, the upper and lower straight inner wall surfaces 31A2 and the web application area 13T1 are connected along the longitudinal direction, and the left and right straight inner wall surfaces 31A3 and the lower flange application area 12T1 are connected along the longitudinal direction. Therefore, in the repair material application process S2, the repair material is applied to the entire repair material application area T1 in an integrated manner without being divided into individual sections using a brush or the like. In Figure 5, the areas filled in dark gray are the areas to which the repair material has been applied.

[0039] In particular, the repair material is applied to the left and right linear inner wall surfaces 31A3 formed to be recessed relative to the upper surface 12S of the lower flange 12, and to the lower flange application range 12T1, so that they are flush with the upper surface 12S of the lower flange 12. This is to ensure that, after the repair is completed, water that has flowed onto the upper surface 12S of the lower flange 12 flows smoothly over the upper surface 12S and exits downstream of the notch 31.

[0040] After the repair material application step S2 is completed and a certain curing period has elapsed, the repair material is applied to a painting area T2, which completely encompasses the repair material application area T1 and is wider than the repair material application area T1, as shown in Figures 5 and 6. The painting area T2 can be set as appropriate as long as it satisfies the condition that it completely encompasses the repair material application area T1. In Figure 6, the areas filled in light gray are the painted areas.

[0041] As described above, the bridge girder 1 repair method according to the first embodiment includes a bridge girder 1 having a main girder 10 (steel material) made up of an upper flange 11, a lower flange 12, and a web 13, and a vertical stiffener 30 made of a steel plate that is joined to the web 13 while abutting against the upper flange 11 and the lower flange 12 between the upper flange 11 and the lower flange 12. The repair method includes a notch forming step (specific step) of cutting out a corroded portion F that has occurred near a corner C formed by the lower flange 12 and the web 13 at the lower end of the vertical stiffener 30, forming a notch 31, and connecting both sides of the notch 31 along the longitudinal direction of the web 13 on the upper surface 12S of the lower flange 12. By connecting both sides of the notch 31 along the longitudinal direction of the web 13 on the upper surface 12S of the lower flange 12, formed by cutting out the corroded portion F, water is less likely to accumulate in the vertical stiffener 30. Therefore, corrosion of the joint between the lower flange 12 and the vertical stiffener 30 can be effectively suppressed.

[0042] Furthermore, the cutout 31 is formed in the shape of a quadrant centered at a central position A (specific position) on the lower end of the vertical stiffener 30, and the curved inner wall surface 31A1 (arcuate portion) relating to the quadrant is formed to bulge outward with respect to the corner C. In this way, because the cutout 31 is formed in the shape of a quadrant centered at a central position A (specific position) on the lower end of the vertical stiffener 30, the cutting operation of the curved inner wall surface 31A1 (arcuate portion) of the cutout 31 is easy, and therefore, the time required for the cutting operation of the cutout 31 can be shortened while ensuring a wide water path on the upper surface 12S of the lower flange 12. Furthermore, weld bead 32A is formed at the joint between web 13 and vertical stiffener 30, and in the notch forming process (specific process), notch 31 is formed in the width direction of bottom flange 12 by scraping away the surface of weld bead 32A while leaving a portion of weld bead 32A on side surface 13S of web 13. Because notch 31 is formed in the width direction of bottom flange 12 while leaving a portion of the interior of weld bead 32A, welding work to connect weld bead 32A can be omitted. As a result, the time required to repair corroded portion F can be shortened.

[0043] <Example of change> Next, a description will be given of a modified example of the repair method according to the first embodiment. The first embodiment described above can be modified as appropriate within the scope of the present invention.

[0044] In the first embodiment, the main girder 10 (steel material) that is the target of the repair method has an I-shaped cross section as shown in Fig. 1, but it may also have an H-beam structure or a box girder structure. Furthermore, the steel material that is the target of the repair method constitutes the main girder 10 of the bridge girder 1, but it may also constitute parts other than the main girder, such as cross beams.

[0045] In the first embodiment, the cross-sectional shape of the notch 31 perpendicular to the direction of travel is a quadrant, but this shape may be changed as appropriate. For example, the cross-sectional shape of the notch 31 perpendicular to the direction of travel may be a shape obtained by dividing an ellipse into four equal parts. Furthermore, the cross-sectional shape of the notch 31 perpendicular to the direction of travel may be a rectangle. However, moisture such as rainwater tends to accumulate in corners, and a quadrant shape can eliminate the cause of this accumulation.

[0046] Furthermore, in the first embodiment, the vertical stiffeners 30 and the bottom flange 12 are in contact with each other but are not welded. However, similar to the web 13, the vertical stiffeners 30 and the bottom flange 12 may be welded at their joints, with weld beads formed on both sides of the joint between the vertical stiffeners 30 and the bottom flange 12 in the direction of travel. In this case, however, it is preferable that, in the notch forming step S1, as the notches 31 are formed, the weld beads in the portions corresponding to the notches 31 are completely cut (removed) to smooth the upper surface 12S of the bottom flange 12 across both sides of the notches 31 in the longitudinal direction. This is to prevent corrosion of the vertical stiffeners 30 caused by the weld beads blocking water.

[0047] Furthermore, the area scraped in the notch forming step S1 is not particularly limited and may be changed as appropriate. However, it is preferable that the area scraped in the notch forming step S1 completely encompasses the corroded portion F. This is because the progression of corrosion can be prevented. Furthermore, the coating area T1 is not particularly limited and may be changed as appropriate. For example, the coating area T1 may be set to encompass the entire area scraped in the notch forming step S1. In addition, the coating area T2 is not particularly limited and may be changed as appropriate. However, it is preferable that the coating area T2 completely encompasses the coating area T1. This is because corrosion, oxidation, and wear can be more effectively prevented.

[0048] Although the first embodiment describes drilling the specific region 30A to form the notch 31, this is not limiting. Fusion cutting using a welding machine or cutting using a grinder may also be used. These processes may be combined. For example, drilling may be performed near the junction of the curved inner wall surface 31A1 of the notch 31 with the upper and lower linear inner wall surfaces 31A2 and near the junction of the curved inner wall surface 31A1 with the left and right linear inner wall surfaces 31A3 to form the machining reference for forming the notch 31. The reason for the "near" junction is that the left and right linear inner wall surfaces 31A3 are also the upper surface 12S of the lower flange 12. Therefore, if the junction is cut down to the non-corroded portion, the smoothness of the upper surface 12S will be lost. Therefore, the machining reference may be moved to fit within the vertical stiffener 30 depending on the area of ​​the corroded portion F.

[0049] It should be noted that the present embodiment is merely an example and does not limit the present invention in any way. Naturally, the present invention can be modified in various ways without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0050] 1...Bridge girder, 10...Main girder (steel) 11...upper flange, 12...lower flange, 13...web 11S...bottom surface, 12S...top surface, 13S...side surface 30…Vertical stiffener, 30A…Specific area 31...Notch, 31A...Inner wall surface 31A1...Curved inner wall surface, 31A2...Vertical straight inner wall surface, 31A3...Right and left straight inner wall surface 32A, 32B...weld bead T1: Application area, T2: Painting area

Claims

1. A method for repairing a bridge girder comprising steel members each consisting of an upper flange, a lower flange, and a web, wherein a vertical stiffener made of a steel plate is joined between the upper flange and the lower flange in a state of surface contact with at least one of the web and the lower flange, A bridge girder repair method characterized by including a specific process of cutting out a corroded portion that has occurred near the corner formed by the lower flange and the web at the lower end of the vertical stiffener to form a notch, and connecting both sides of the notch along the longitudinal direction of the web on the upper surface of the lower flange.

2. The bridge girder repair method according to claim 1, the notch is formed in a quadrant shape centered at a specific position on the lower end of the vertical stiffener; A bridge girder repair method, characterized in that the arc-shaped portion of the quadrant is formed to bulge outward from the corner.

3. The bridge girder repair method according to claim 1 or 2, a weld bead is formed at the joint between the web and the vertical stiffener; A bridge girder repair method characterized in that in the identifying step, the notch is formed so as to remove the surface of the weld bead in the width direction of the lower flange while leaving a portion of the weld bead.

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