Steel bridge preventive maintenance structure and steel bridge preventive maintenance method

Abstract

To provide an inexpensive and highly efficient steel bridge preventive maintenance structure and a steel bridge preventive maintenance method.SOLUTION: In the preventive maintenance structure of the steel bridge, the lower flange 11 and the sole plate 32 have a gap therebetween due to the formation of the welded portion 33 over the outer periphery of the sole plate 32, and the gap is maintained in the inter-diameter side region A adjacent to the welded portion 33 in the lower flange 11 and the sole plate 32 in a state where the male screw portion of the bolt T is screwed into the female screw portions formed in both the lower flange 11 and the sole plate 32.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a steel bridge preventive maintenance structure and a steel bridge preventive maintenance method. [Background technology]

[0002] Conventionally, there is known a steel bridge equipped with a sole plate fixed between the bridge girder and the bearing by fillet welding and mounting bolts (see, for example, Patent Document 1). This steel bridge has a problem in that fatigue cracks occur at stress-concentrated points in the welds when subjected to repeated loads from the passage of vehicles over a long period of time.

[0003] The steel bridge preventive maintenance method described in Patent Document 1 includes a first step of horizontally cutting the welded portion with a disc grinder to separate the sole plate from the lower flange of the bridge girder, and a second step of replacing the mounting bolts that fasten the sole plate to the lower flange with ones strong enough that fillet welding is not required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-346518 Summary of the Invention [Problem to be solved by the invention]

[0005] The sole plates of steel bridges are attached to the bottom flange by rivets, high-strength bolts, or welding for the purpose of smooth load transfer from the bridge girder to the bearing. Among these, sole plates attached by welding have been reported to suffer from fatigue cracks around the welds, primarily due to a decrease in the movable function of the bearing, which generates high compressive stress near the front of the sole plate weld. Patent Document 1 describes a preventive maintenance measure to eliminate welded joints with low fatigue strength. However, when separating the sole plate from the bottom flange of the bridge girder, it is necessary to operate a disc grinder to avoid damaging the bottom flange, which reduces work efficiency. Furthermore, the mounting bolts that fasten the sole plate to the bottom flange must be replaced, which increases costs.

[0006] Therefore, there is a demand for a preventive maintenance structure and method for steel bridges that are inexpensive and have high work efficiency. [Means for solving the problem]

[0007] The characteristic configuration of the steel bridge preventive maintenance structure of the present invention is a preventive maintenance structure for a steel bridge comprising a bridge girder, a bearing portion that supports the bridge girder, and a sole plate arranged between the lower flange of the bridge girder and the upper shoe of the bearing portion, wherein a gap is formed between the lower flange and the sole plate due to a weld formed around the outer periphery of the sole plate, and the gap is maintained in the span side area adjacent to the weld on the lower flange and the sole plate by having the male thread portion of a bolt screwed into the female thread portion formed on both the lower flange and the sole plate.

[0008] In this configuration, the lower flange and the sole plate are welded together by a fillet weld that runs around the outer periphery of the sole plate, and bolts are attached to the span-side area of ​​the weld to maintain a gap between the lower flange and the sole plate. As a result, relative displacement between the lower flange and the sole plate, which can cause fatigue cracks in the weld, is suppressed, and high compressive stresses can be prevented from occurring near the front of the sole plate weld.

[0009] In addition, because this configuration has female threads on both the lower flange and the sole plate, there is no need to provide a separate component to prevent the lower flange from sinking when the bolts are screwed in. Furthermore, the work of machining the female threads on the flange and sole plate can be done from the top side of the lower flange, which increases work efficiency. In addition, because the bolts suppress relative displacement while leaving the welds intact, this can be constructed inexpensively as a preventive maintenance measure for existing steel bridges.

[0010] In this way, it is an inexpensive and highly efficient steel bridge preventive maintenance structure.

[0011] Another characteristic feature is that the span side region is adjacent to the web of the bridge girder.

[0012] The web of a bridge girder is a part that bears the dynamic load of vehicles and other vehicles, and compressive stress is likely to occur in the welds on the span side of the web. By locating the span side area where the bolts are placed adjacent to the web, as in this configuration, the relative displacement between the lower flange and the sole plate can be effectively suppressed, reducing the compressive stress on the welds. As a result, the lifespan of the steel bridge is extended.

[0013] Another characteristic feature is that a plurality of the bolts are arranged along the web.

[0014] By arranging multiple elements adjacent to and along the web as in this configuration, the relative displacement between the lower flange and the sole plate can be further suppressed, thereby extending the fatigue life of the welded portion.

[0015] Another characteristic feature is that the web and the lower flange are fixed by welding, and a spacer is arranged between the head of the bolt and the lower flange to maintain the distance between them.

[0016] By placing a spacer at the welded portion between the web and the lower flange to maintain the distance between the bolt head and the lower flange, as in this configuration, the spacer end shape can be easily machined to match the shape of the welded portion, allowing the bolt to be positioned closer to the web, effectively extending the fatigue life of the weld.

[0017] Another characteristic feature is that a resin coating is formed on the surface of the male thread portion.

[0018] As in this configuration, by providing a resin coating on the surface of the male threaded portion of the bolt, minute relative displacement at the mating point between the male threaded portion and the female threaded portion is suppressed, and the bolt is prevented from loosening, ensuring that the gap between the lower flange and the sole plate is maintained.

[0019] A characteristic feature of the preventive maintenance method for steel bridges according to the present invention is that it is a preventive maintenance method for steel bridges comprising a bridge girder, a support portion supporting the bridge girder, and a sole plate arranged between the lower flange of the bridge girder and the upper shoe of the support portion, wherein the lower flange and the sole plate have a gap formed between them due to a weld around the outer periphery of the sole plate, and includes the following steps: a first step of forming a through hole between the lower flange and the sole plate in the span-side region of the weld in the lower flange and the sole plate; a second step of forming a female thread on the inner surface of the through hole; and a third step of maintaining the gap by screwing the male thread portion of a bolt into the female thread portion formed in both the lower flange and the sole plate.

[0020] This method achieves the same effects as the above-mentioned steel bridge preventive maintenance structure. In addition, because all steps from the first to the third can be performed from the top side of the lower flange, preventive maintenance measures can be easily implemented even by those with low levels of skill. [Brief explanation of the drawings]

[0021] [Figure 1] This is an external perspective view of a steel bridge. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] This is a side view of the bearing section viewed from a direction perpendicular to the bridge axis of the steel bridge. [Figure 5] FIG. 2 is a top view of the lower flange of the steel bridge preventive maintenance structure according to the present embodiment. [Figure 6A] FIG. 2 is an enlarged view of the steel bridge preventive maintenance structure according to the present embodiment, as viewed from the bridge axis direction. [Figure 6B] FIG. 2 is an enlarged view of the steel bridge preventive maintenance structure according to the present embodiment, viewed from a direction perpendicular to the bridge axis. [Figure 7] FIG. 10 is a list of comparative examples and the present embodiment. [Figure 8] 10 shows simulation results for a comparative example and this embodiment. [Figure 9] FIG. 10 is an enlarged view of a steel bridge preventive maintenance structure according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of a steel bridge preventive maintenance structure and a steel bridge preventive maintenance method according to the present invention will be described with reference to the drawings. In this embodiment, a bridge 100 on which railway vehicles run will be used as an example of a steel bridge. However, the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the gist thereof.

[0023] As shown in Figure 1, a bridge 100 is a structure on a railway transportation route that crosses over rivers, valleys, lakes, straits, or other roads, railways, or waterways that pose obstacles to transportation, and also includes viaducts constructed continuously in spaces above roads or rivers. In this embodiment, the bridge 100 will be described as a simple girder bridge or a continuous girder bridge, but is not particularly limited as long as it is a steel bridge equipped with welded joints in the sole plates 32 described below. Hereinafter, the portion of the bridge axis X that faces away from the abutment toward another abutment or pier will be referred to as the span side X1, and the opposite side will be referred to as the girder end side X2.

[0024] The bridge 100 comprises multiple bridge girders 1 spanning between piers and abutments (not shown, hereafter referred to as "abutments, etc.") comprising the substructure, and a concrete deck 2 laid on top of the multiple bridge girders 1 to form the roadway on which railroad vehicles travel. The bridge girders 1 are composed of simple girders, continuous girders, or Gerber girders. The bridge girders 1 and concrete deck slab 2 form the superstructure that bears the running load of the railroad vehicles, and a bearing 3 that supports the bridge girders 1 is installed between the bridge girders 1 and the substructure, such as the abutments. The bearing 3 is a mechanism that transmits the load of the superstructure to the substructure, and is structured to allow the superstructure to expand and contract due to elastic deformation, etc., and to rotate freely due to deflection. The bearing 3 may be a fixed bearing that restricts horizontal movement, or a movable bearing that is movable only in a specific direction.

[0025] The bridge girder 1 is made of steel girders including I-shaped girders, and has a bottom flange 11, an top flange 12, and a plate-like web 13 connecting the bottom flange 11 and the top flange 12. A bearing 3 is fixed to the bottom flange 11 on the girder end side X2 of each of the multiple bridge girders 1, and multiple reinforcing steel members 13a are arranged on the web 13 along the bridge axis X. The multiple bridge girders 1 are also connected by supports 14 and bracing members 14. The bridge girders 1 are not limited to I-shaped girders, but may be H-shaped girders, box girders, T-shaped girders, or the like. While FIG. 1 shows the girder end side X2 where the abutment is located, the bearing 3 may also be provided on a pier located between a pair of abutments.

[0026] 2 to 4 show examples of the bearing 3, but the structure is not limited to these. As shown in FIGS. 2 and 3, the metal bearing 3 includes a bearing 31 and a sole plate 32 that is disposed between the bearing 31 and the lower flange 11 and is fillet-welded to the lower flange 11. The sole plate 32 is attached to the lower flange 11 for the purpose of smooth load transfer from the bridge girder 1 to the bearing 3. The sole plate 32 is attached to the lower flange 11 by rivets in a riveted bridge, and by high-strength bolts or welding in a welded bridge. However, this embodiment targets a welded bridge 100 in which fatigue cracks occur around the sole plate weld, rather than a riveted bridge.

[0027] As shown in Figure 4, bearing 31 has upper shoe 31a, bearing plate 31b, and lower shoe 31c. In this embodiment, bearing 31 is a steel bearing having bearing plate 31b, which transmits vertical loads transmitted from the superstructure to the substructure, follows expansion and contraction and rotation of the superstructure due to live loads, stress changes, etc., and absorbs relative horizontal and rotational displacements between the superstructure and substructure. Note that bearing 31 is not limited to a steel bearing having bearing plate 31b, and may be a steel bearing such as a pin bearing or a rubber bearing.

[0028] As shown in Figures 2 and 3, the upper shoe 31a, sole plate 32, and lower flange 11 are fixed together by multiple (eight in this embodiment) mounting bolts Ba. The outer periphery of the sole plate 32 is welded to the lower flange 11. As a result, a gap S is formed between the lower flange 11 and the sole plate 32 due to a weld 33 formed around the outer periphery of the sole plate 32 (see also Figures 5, 6A, and 6B). The lower shoe 31c is fixed to an abutment or the like by multiple (four in this embodiment) mounting bolts Bb, and the bearing plate 31b is designed to absorb horizontal and rotational displacement. For convenience, the weld 33 is shown with diagonal lines in Figures 4, 5, 6A, and 6B, and the male thread Ta of the ordinary bolt T and the female threads 11a and 32a formed on both the lower flange 11 and the sole plate 32 are shown in perspective. 5 are disposed below the lower flange 11, but are shown by solid lines for convenience. The dashed circle in the center shown in FIG. 5 is the fitting portion between the sole plate 32 and the upper shoe 31a.

[0029] In this embodiment, as shown in Figures 3 and 4, the lower end of the web 13 (including the reinforcing steel 13a) is also welded to the bottom flange 11 to form a web weld 13b, and although not shown, the upper end of the web 13 (including the reinforcing steel 13a) is also welded to the top flange 12. Fatigue cracks have been reported to occur at welds in bridges 100, with the main crack initiation locations being (1) the bottom flange toe of the span side X1 of the sole plate 32, (2) the root (near the center of the weld 33), (3) the web toe of the web weld 13b, and (4) the bottom flange toe of the web weld 13b. It is believed that a decrease in the mobility of the bearing 3 causes high compressive stresses in (1) the bottom flange toe and (2) the root of the span side X1 of the sole plate 32, and that the compressive stresses are exacerbated by the gap S between the bottom flange 11 and the sole plate 32. In fact, the applicant conducted a survey of 854 bearings in steel bridges and found that cracks at (1) the toe on the bottom flange side and (2) the root accounted for 24% of the surveyed population, and cracks at (3) and (4) the web weld 13b accounted for just under 2% of the surveyed population. Therefore, in this embodiment, a steel bridge preventive maintenance structure and a steel bridge preventive maintenance method for the front weld 33a on the span side X1 of the sole plate 32 will be described in detail below.

[0030] As shown in FIG. 6B , in a span-side region A adjacent to the front weld 33a of the weld 33 in the lower flange 11 and the sole plate 32, a gap S is maintained by threading a male thread Ta of a standard bolt T (an example of a bolt) into female threads 11a, 32a (tapped holes) formed in both the lower flange 11 and the sole plate 32. In this embodiment, instead of using a hole in the lower flange 11 as a loose hole and sinking the lower flange 11 with a standard bolt T to eliminate the gap S, tapping holes are formed in both the lower flange 11 and the sole plate 32 to suppress both the opening / closing displacement and horizontal shear displacement of the gap S. In particular, because it is sufficient to drill a tapped hole from the top surface of the lower flange 11 and thread the standard bolt T, work efficiency can be improved.

[0031] That is, in this embodiment, with the fillet weld of the sole plate 32 to the lower flange 11 remaining, ordinary bolts T that maintain the gap S between the lower flange 11 and the sole plate 32 are installed in the span-side region A adjacent to the front weld 33a of the weld 33 on the lower flange 11 and the sole plate 32. As a result, relative displacement between the lower flange 11 and the sole plate 32, which can cause fatigue cracks in the front weld 33a, is suppressed, and the problem of high compressive stress occurring in the front weld 33a of the sole plate 32 can be prevented.

[0032] Furthermore, in this embodiment, since the female threads 11a, 32a are provided on both the lower flange 11 and the sole plate 32, there is no need to provide a separate member to prevent the lower flange 11 from sinking when the ordinary bolts T are screwed in. Furthermore, the work of machining the female threads 11a, 32a on the lower flange 11 and the sole plate 32 can be performed from the upper surface side of the lower flange (the upper surface of the lower flange 11), which increases work efficiency. In addition, since the relative displacement is suppressed by the ordinary bolts T while leaving the welded portions 33 in place, this can be constructed inexpensively as a preventive maintenance measure for an existing bridge 100. In this way, a steel bridge preventive maintenance structure is provided that is inexpensive and has high work efficiency.

[0033] As shown in Figures 5 and 6A, the span-side region A adjacent to the front weld 33a of the weld 33 in the bottom flange 11 and the sole plate 32 is adjacent to the web 13 of the bridge girder 1. In this span-side region A, multiple (four on each side in this embodiment) ordinary bolts T are arranged along both sides of the web 13. Here, "the span-side region A adjacent to the front weld 33a" means that the center of the head Tb of the ordinary bolt T closest to the span side X1 is located within a predetermined distance (e.g., 10 to 30 mm) from the span-side X1 toe of the sole plate 32. Also, "the span-side region A is adjacent to the web 13 of the bridge girder 1" means that the center of the head Tb of the ordinary bolt T is located within a predetermined distance (e.g., 10 to 30 mm) from the web 13.

[0034] The web 13 of the bridge girder 1 is a portion that bears the dynamic load of a vehicle, and compressive stress is likely to occur in the front welded portion 33a on the span side X1 of the web 13. As in this embodiment, by arranging the span side region A, where multiple ordinary bolts T are arranged, adjacent to the web 13, the relative displacement between the bottom flange 11 and the sole plate 32 can be effectively suppressed, thereby reducing the compressive stress applied to the front welded portion 33a. As a result, the lifespan of the bridge 100 is extended. Moreover, by arranging multiple ordinary bolts T along the web 13 while adjacent to the web 13, the relative displacement between the bottom flange 11 and the sole plate 32 can be further suppressed, and the fatigue life of the front welded portion 33a can be extended.

[0035] As described above, the web 13 and the bottom flange 11 are fixed by welding. As shown in FIG. 6A , the web weld 13b (welded portion) protrudes to the left and right. Therefore, if only the ordinary bolt T is used, the web weld 13b would get in the way and make it difficult to approach the web 13. Therefore, in this embodiment, a spacer 4 is disposed between the head Tb of the ordinary bolt T and the bottom flange 11 to maintain the distance between them. This spacer 4 has a notch 41 on the underside of the metal plate facing the web weld 13b so as not to interfere with the web weld 13b. By disposing the spacer 4 at the web weld 13b (welded portion) between the web 13 and the bottom flange 11, which maintains the distance between the head Tb of the ordinary bolt T and the bottom flange 11, the spacer 4 can be easily machined to match the shape of the web weld 13b (welded portion), allowing the ordinary bolt T to be positioned closer to the web 13. As a result, the fatigue life of the weld 33 can be effectively extended.

[0036] Next, using Figures 7 and 8, we will explain the optimal range of the span-side region A where multiple ordinary bolts T are arranged. For simplicity, Figure 7 omits the welded portion 33 shown in Figure 5, and the reference numerals are also omitted. As shown in Figure 7, the comparative example is a case without any countermeasures, without the span-side region A. Examples a to d are cases in which ordinary bolts T are installed along both sides of the web 13 as close to the web 13 as possible. Example a is a case in which a single row of ordinary bolts T is installed closest to the front welded portion 33a. Examples b to d are cases in which bolt rows are added one row at a time toward the girder end X2, as compared to Example a. Example d is a case in which a bolt arrangement that can be standardized for many actual bridges is assumed, based on the dimensions of the sole plate 32 of a typical steel bridge. The reason for positioning the ordinary bolts T close to the web 13 is that most weld cracks occur near the web 13, and we aimed to suppress the displacement of the gap S near the web 13. In addition, in Examples e to f, the number of bolts in the front row near the welded portion 33 of Example d was increased to four and six, respectively, in order to evaluate the effect of increasing the number of normal bolts T in the width direction of the sole plate 32.

[0037] The analysis was an elastic analysis using the general-purpose finite element analysis software Abaqus 2021. Considering that the gap displacement near the root of the front weld 33a is correlated with the stress generated near the front weld 33a, in this analysis the condition for the bearing 3 where the stress generated near the front weld 33a is thought to be the greatest was to connect the upper shoe 31a, sole plate 32 and lower shoe 31c, restraining the horizontal movement and rotation of the bearing 31, and also connecting the upper shoe 31a and sole plate 32. The main specifications of the bridge analyzed are as shown in Table 1. [Table 1]

[0038] Figure 8 shows the analysis results, showing the maximum value of the resultant displacement at the center of the web 13 thickness for each case. Comparing the comparative example with examples a to d reveals that the greater the number of standard bolts T installed, the lower the resultant displacement. The resultant displacement was approximately 0.02 mm in the comparative example, but was reduced to just under 0.01 mm (44%) in example d. According to the displacement-based fatigue strength evaluation method described in "Kazuo Tateishi, Naohiro Hayata, Tsuyoshi Hanji, and Masaru Shimizu: Displacement-Based Fatigue Strength Evaluation Method for Root Cracks in Fillet Welded Joints," Journal of the Japan Society of Civil Engineers, A1, Vol. 71, No. 3, pp. 315-326, 2015, the fatigue life of the root of the front weld 33a is inversely proportional to the cube of the magnitude of the resultant displacement. Therefore, if the resultant displacement is reduced to 44% (a 56% reduction), the fatigue life of the root of the front weld 33a is expected to be extended by 11.7 times. On the other hand, for Examples e to f, in which the number of bolts closest to the front weld 33a was increased in the width direction of the sole plate 32 compared to Example d, the resultant displacement was almost the same as that of Example d. From this, it can be said that there is almost no effect in increasing the number of ordinary bolts T in the width direction of the sole plate 32. From the above, even in Example a, in which one row of ordinary bolts T was installed in the position closest to the front weld 33a, an effect of 65% (a 35% reduction) was obtained, demonstrating the advantageous effect of this embodiment.

[0039] The preventive maintenance method for a steel bridge in this embodiment is a preventive maintenance method for a steel bridge comprising a bridge girder 1, a bearing portion 3 supporting the bridge girder 1, and a sole plate 32 arranged between the lower flange 11 of the bridge girder 1 and the upper shoe 31a of the bearing portion 3, wherein the lower flange 11 and the sole plate 32 have a gap S between them due to a weld portion 33 around the outer periphery of the sole plate 32, and includes the following steps: a first step of forming a through hole between the lower flange 11 and the sole plate 32 in the span side region A of the weld portion 33 in the lower flange 11 and the sole plate 32; a second step of forming female thread portions 11a, 32a on the inner surface of the through hole; and a third step of maintaining the gap S by screwing the male thread portion Ta of a normal bolt T into the female thread portions 11a, 32a formed on both the lower flange 11 and the sole plate 32.

[0040] As shown in FIGS. 6A and 6B , in the first step, a pilot hole appropriate for the diameter of the female threads 11a, 32a is drilled using a drill (not shown), and in the second step, a cutting tap (not shown) is inserted to remove the roots of the threads, thereby forming the female threads 11a, 32a. In the first step, the pilot hole is preferably drilled to an extent that the upper shoe 31a is exposed, and in the second step, the female threads 11a, 32a are preferably formed to a length approximately equal to the under-neck length of the ordinary bolt T. Next, in the third step, the male threads Ta of the ordinary bolt T are threadedly engaged with the female threads 11a, 32a, thereby maintaining the gap S. Note that the first and second steps are not limited to cutting tapping, and may also be rolling tapping, which expands the metal in the pilot hole to create the crests and roots of the threads.

[0041] This method achieves the same effects as the above-mentioned steel bridge preventive maintenance structure. In addition, because all steps from the first to the third can be performed from the top side of the lower flange, preventive maintenance measures can be easily implemented even by those with low levels of skill.

[0042] [Other embodiments] (1) The bridge 100 is not limited to a route on which railroad vehicles travel, but may also be used for other routes such as roads and waterways. (2) As shown in Figure 9, a resin coating C may be formed on the surface of the male thread portion Ta of the ordinary bolt T. By providing the resin coating C on the surface of the male thread portion Ta of the ordinary bolt T in this way, minute relative displacement at the engagement portion between the male thread portion Ta and the female thread portion 11a is suppressed, and the ordinary bolt T is prevented from loosening, and the gap S between the lower flange 11 and the sole plate 32 can be reliably maintained. (3) There are no particular restrictions on the standard of the ordinary bolt T. In this embodiment, an M16 bolt with a JIS metric coarse thread, strength class 10.9, and neck length of 35 mm is used, but bolts of other strength classes, neck lengths, and nominal diameters may also be used, and may be selected appropriately depending on the force acting on the ordinary bolt T. The neck length of the ordinary bolt T is determined from the bottom flange 11, the gap S between the sole plate 32 and the bottom flange 11, the threaded length into the sole plate 32, and the total thickness of the spacer 4. Note that the bolt is not limited to the ordinary bolt T, as long as it can ensure a length within the specified threaded engagement range. (4) It is preferable to provide the same number of ordinary bolts T in the span side region A symmetrically along both sides of the web 13, but depending on the installation environment, they may be provided asymmetrically along both sides of the web 13, or different numbers may be used. Also, it is preferable to provide two or more ordinary bolts T at equal intervals along each side of the web 13, but two or more ordinary bolts T may be provided at unequal intervals, or one ordinary bolt T may be provided on each side. (5) If the ordinary bolts T can be arranged along the web 13, the spacers 4 in the above-described embodiment may be omitted. In this case, the ordinary bolts T may be provided at a slight distance from the web 13. [Industrial Applicability]

[0043] The present invention can be used in preventive maintenance structures and methods for steel bridges installed on railways, roads, etc. [Explanation of symbols]

[0044] 1: Bridge girder 3: Bearing part 4: Spacer 11: Lower flange 11a: Female thread 13: Web 13b: Web welded section (welded fixed section) 31: Bearing part 31a: Kamikutsu 32: Sole plate 32a: Female thread 33: Welded section 100: Bridge A: Span side area C: Resin coating S: Gap T: Standard bolt Ta: Male thread Tb: head X: Bridge axis X1: Span side

Claims

1. A preventive maintenance structure for a steel bridge comprising a bridge girder, a bearing portion supporting the bridge girder, and a sole plate disposed between the lower flange of the bridge girder and the upper shoe of the bearing portion, a gap is formed between the lower flange and the sole plate by forming a welded portion around the outer periphery of the sole plate; A steel bridge preventive maintenance structure in which the gap is maintained in the span side area adjacent to the weld on the lower flange and the sole plate by threading the male thread portion of a bolt into the female thread portion formed on both the lower flange and the sole plate.

2. The steel bridge preventive maintenance structure according to claim 1 , wherein the span-side region is adjacent to a web of the bridge girder.

3. The steel bridge preventive maintenance structure according to claim 2 , wherein a plurality of the bolts are arranged along the web.

4. The web and the lower flange are fixed by welding, 4. The steel bridge preventive maintenance structure according to claim 3, wherein a spacer is disposed between the head of the bolt and the lower flange to maintain a distance therebetween.

5. 5. A steel bridge preventive maintenance structure according to claim 1, wherein a resin coating is formed on the surface of the male thread portion.

6. A preventive maintenance method for a steel bridge comprising a bridge girder, a bearing portion supporting the bridge girder, and a sole plate disposed between a lower flange of the bridge girder and an upper shoe of the bearing portion, wherein a gap is formed between the lower flange and the sole plate by a weld portion extending along the outer periphery of the sole plate, a first step of forming a through hole extending from the lower flange to the sole plate in a span-side region of the welded portion of the lower flange and the sole plate; a second step of forming a female thread portion on the inner surface of the through hole; A steel bridge preventive maintenance method including a third step of maintaining the gap by screwing the male thread portion of a bolt into the female thread portion formed on both the lower flange and the sole plate.

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