Method and structure for reinforcing fulcrum of brace

Abstract

To provide a method for reinforcing a fulcrum of a brace, which can avoid fatigue fracture caused by stress concentration, by a simple configuration.SOLUTION: The method for reinforcing the fulcrum of the brace includes a second bolt hole forming step of forming a second bolt hole in the non-overlapping region, a first bolt removing step of removing some of the plurality of first bolts, a temporary tightening step of inserting a third bolt penetrating the reinforcing material into a plurality of open holes obtained by removing some of the first bolts to temporarily tighten the reinforcing material, a first fixing step of inserting the second bolt into the second bolt hole and the second through hole to fix the reinforcing material to the gusset plate, and a second fixing step of finally tightening the third bolt inserted into the plurality of open holes to fix the reinforcing material into which the second bolt is inserted to the gusset plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and structure for reinforcing the support points of braces that are placed on sole plates arranged on bridge piers, abutments, etc. and subjected to repeated loads. [Background technology]

[0002] It is known that fatigue cracks occur in steel structures such as bridge girders due to repeated loading, for example, caused by vehicles passing over them. Therefore, various reinforcement methods have been implemented to prevent fatigue cracks, such as by using bolted reinforcement structures to integrate stiffeners with angled steel bars on both sides of the stiffeners, thereby avoiding stress concentration.

[0003] For example, Patent Document 1 discloses a method for repairing and reinforcing vertical joints in steel structures such as bridges. A stiffener with a through hole formed therein is provided on the deck plate of the bridge, and reinforcing members (L-shaped steel) with bolt holes formed therein are placed on both the left and right sides of the stiffener. High-strength bolts are inserted through the through holes and bolt holes to form a bearing joint. The through holes are formed in positions where the dimension from the deck plate to the lower edge of the through hole in the stiffener is smaller by a specified dimension than the sum of the dimension from the top surface of the horizontal backing plate of the stiffener to the upper edge of the bolt hole and the diameter of the high-strength bolt. This configuration can achieve a high stress reduction effect.

[0004] Furthermore, Patent Document 2 discloses a method and structure for reinforcing the area around the bearing of a steel girder that is placed on a sole plate placed on a bridge pier or abutment and subjected to repeated loads. The reinforcing structure, for example, is composed of a stiffener and an L-shaped member, and is placed on a riveted girder that is placed on a bearing installed on a pier. The stiffener and L-shaped member are fixed with high-strength bolts with their backs facing each other in a vertical plane. With this configuration, even if a crack occurs in the lower flange on the bearing of the riveted girder, it can be effectively reinforced and the crack propagation can be suppressed. In other words, stress concentration can be suppressed even when repeated loads are applied. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6386616 [Patent Document 2] Japanese Patent Application Publication No. 2019-143368 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the methods of Patent Documents 1 and 2, multiple holes are already formed in the stiffener, and the gusset is fixed to the stiffener with bolts inserted into the multiple holes. Therefore, when attempting to reinforce the stiffener by providing new components other than the stiffener and gusset plate, the existing holes become an obstacle, leaving no space for providing new holes, making it difficult to provide reinforcement to avoid fatigue failure due to stress concentration.

[0007] Therefore, an object of the present invention is to provide a method and structure for reinforcing the support points of a brace that can avoid fatigue failure caused by stress concentration with a simple configuration. [Means for solving the problem]

[0008] In response to the above-mentioned problems, the present invention provides a method for reinforcing a brace support point, in which a pair of steel girders are arranged at an interval, and a brace provided between the upper flange of one steel girder and the lower flange of the other steel girder, a cross member provided on the lower flange side, and a stiffener provided on the web of the steel girder and having a plurality of insertion holes into which first bolts are inserted, are connected by a gusset plate, wherein the gusset plate has an overlapping region that overlaps with the stiffener in a front view of the stiffener and a non-overlapping region that does not overlap with the stiffener, and a plurality of first bolt holes are formed in the overlapping region at positions that overlap with the insertion holes in the front view, and the method includes a second bolt hole forming step of forming second bolt holes into which second bolts are inserted in the non-overlapping region, and a step of connecting the plurality of first bolts inserted into the plurality of insertion holes and the first bolt holes. The method is characterized by comprising a first bolt removal step of removing some of the first bolts; a temporary tightening step of inserting third bolts that penetrate a reinforcing material having a first region that overlaps with the overlapping region in the front view and a second region that overlaps with the non-overlapping region into a plurality of open holes formed by removing some of the first bolts in the first bolt removal step to temporarily tighten the reinforcing material; a first fixing step of inserting the second bolts into the second bolt holes formed in the second bolt hole forming step and second through holes formed in the second region at positions that overlap with the second bolt holes in the front view to fix the reinforcing material to the gusset plate; and a second fixing step of finally tightening the third bolts inserted into the plurality of open holes to fix the reinforcing material into which the second bolts have been inserted to the gusset plate.

[0009] In the first fixing step, the central axis of the second through hole is preferably positioned in a state where it is shifted upward with respect to the central axis of the second bolt hole, and the reinforcing member is pressed downward relative to the gusset plate during the process of inserting the second bolt into the second bolt hole and the second through hole, so that the lower end of the reinforcing member is in close contact with the end of the upper surface of the lower flange. Furthermore, in the first region, it is preferable that the reinforcing member is joined to the gusset plate and the stiffener by frictional bonding, and in the second region, the reinforcing member is joined to the gusset plate by pressure-bearing bonding.

[0010] The invention of the reinforcement structure for a brace support point is a reinforcement structure for a brace support point in which a pair of steel girders are arranged at a distance from each other, and a brace provided between the upper flange of one steel girder and the lower flange of the other steel girder, a cross member provided on the lower flange side, and a stiffener provided in the web of the steel girder and having a plurality of insertion holes into which first bolts and third bolts are inserted, are connected by a gusset plate, and the gusset plate has an overlapping region that overlaps with the stiffener in a front view of the stiffener and a non-overlapping region that does not overlap with the stiffener, and a plurality of first bolt holes are formed in the overlapping region at positions that overlap with the insertion holes in the front view, and the first bolt holes that overlap with the overlapping region in the front view are connected by a gusset plate. a reinforcing member having a first region and a second region overlapping the non-overlapping region; and a second bolt penetrating the gusset plate and the reinforcing member in the non-overlapping region and the second region, wherein a first through hole is formed in the first region at a position overlapping with the insertion hole in the front view, and the reinforcing member is fixed to the stiffener and the gusset plate by inserting the third bolt into the first through hole, and a second through hole is formed in the second region at a position overlapping with a second bolt hole into which the second bolt is inserted in the non-overlapping region in the front view, and the reinforcing member is fixed to the gusset plate by inserting the second bolt into the second through hole.

[0011] Here, it is preferable that the lower end of the reinforcing material is in close contact with the end of the upper surface of the lower flange. Also, it is preferable that the first region is provided with a first avoidance portion that avoids interference with a fastener for fixing the lower flange. Also, it is preferable that the second region is provided with a second avoidance portion that avoids interference with the brace. Furthermore, it is preferable that the reinforcing material has a first reinforcing plate and a second reinforcing plate that are fixed to the gusset plate. [Effects of the Invention]

[0012] In the brace support reinforcement method of the present invention configured as described above, second bolt holes are formed in the non-overlapping region of the gusset plate, and second bolts are inserted into second through holes formed at positions overlapping with the second bolt holes to secure the stiffener to the gusset plate. The first bolts are removed from the insertion holes formed in the stiffener and the first bolt holes formed in the gusset plate, and third bolts are inserted into the open holes from which the first bolts were removed and the first through holes in the stiffener to temporarily fasten the stiffener to the gusset plate. Finally, the stiffener, gusset plate, and stiffener are finally fastened with the third bolts.

[0013] In other words, the stiffener is temporarily fastened to the stiffener and gusset plate using some of the multiple insertion holes formed in the stiffener, which is an existing component. Then, the stiffener is temporarily fastened to the gusset plate via the second bolt hole formed in the gusset plate. After that, the stiffener is permanently fastened to the stiffener and gusset plate using the multiple insertion holes formed in the stiffener. This eliminates the need to form new bolt holes in the stiffener, and allows the stiffener to be fastened to the stiffener using the existing insertion holes. Therefore, fatigue failure due to stress concentration can be avoided with this simple configuration.

[0014] In addition, the invention of the reinforcement structure for the brace support point involves inserting a third bolt into a reinforcement material having a first region that overlaps with the stiffener and gusset plate, and a second region that overlaps only with the gusset plate, and fixing the reinforcement material to the stiffener and gusset plate by inserting a second bolt into the first region and inserting a third bolt into the second region.

[0015] Therefore, in the first region, existing bolt holes in the stiffener are used, and in the second region, only one hole is drilled in the gusset plate, so that the stiffener is fixed to the stiffener and the gusset plate using different types of bolts. Therefore, even if there is no space to create a new hole in the stiffener, reinforcement is possible to avoid fatigue failure caused by stress concentration. [Brief explanation of the drawings]

[0016] [Figure 1] 10A and 10B are explanatory diagrams for explaining the reinforcing structure of the brace support point of the present embodiment. [Figure 2] FIG. 1 is a perspective view illustrating a schematic configuration of a bridge. [Figure 3] (a) is a front view of the reinforcement material, and (b) is a side view of the reinforcement material. [Figure 4] FIG. 10(a) is a diagram showing a second bolt hole forming step, and FIG. 10(b) is a schematic cross-sectional view as seen in the direction of the arrow AA. [Figure 5] FIG. 10(a) is a diagram showing a first bolt removing step, and FIG. 10(b) is a schematic cross-sectional view as seen in the direction of arrow BB. [Figure 6] FIG. 1(a) is a diagram showing a temporary fastening step, and FIG. 1(b) is a schematic cross-sectional view as seen in the direction of the arrow CC. [Figure 7] 10(a) is a diagram showing a state at the start of a first fixing step, and FIG. 10(b) is a schematic cross-sectional view as seen in the direction of the arrow DD. [Figure 8] FIG. 10 is a diagram showing the positional relationship between a gusset plate and a reinforcing member. [Figure 9] 10(a) is a diagram showing a state in which a second bolt is inserted in a first fixing step, and FIG. 10(b) is a schematic cross-sectional view as seen in the direction of arrows EE. [Figure 10] FIG. 10(a) is a diagram showing a second fixing step, and FIG. 10(b) is a schematic cross-sectional view seen in the direction of the arrow FF. [Figure 11] 1A is a diagram illustrating the structure of the object to be reinforced, and FIG. 1B is a diagram illustrating the case where the reinforcement structure of the present embodiment is applied. [Figure 12] FIG. 10 is a side view of a reinforcing structure according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram illustrating a reinforcement structure of a brace support point according to this embodiment, and Fig. 2 is an explanatory diagram illustrating a schematic configuration of a bridge 1.

[0018] First, an example of the configuration of a bridge 1 will be described with reference to Figure 2. This bridge 1 includes girders 3, which are, for example, a type of steel girder. The girders 3 are bridged between an abutment and a pier 11, or between the piers 11, 11. Furthermore, a deck 12 constructed of prestressed concrete, reinforced concrete, or the like is laid on top of the multiple girders 3 that are bridged in parallel. The deck 12 may also be made of steel.

[0019] The end of the girder 3 is placed on a support 2 installed on the upper end surface 11a of the pier 11. This support 2 is mainly composed of, for example, a flat seat 23 placed on the upper end surface 11a of the pier 11, a shoe 22 installed on the seat 23, and a sole plate 21 interposed between the shoe 22 and the girder 3. Here, the seat 23 is formed from cast steel or the like, and the shoe 22 and sole plate 21 are made of steel. The end of the girder 3 is placed on the upper surface of the flat sole plate 21.

[0020] 1 and 2, the girder 3 is mainly composed of an upper flange 33 and a lower flange 31 arranged parallel to one another, and a web 32 that serves as a web connecting the upper flange 33 and the lower flange 31. The lower flange 31 is joined to the sole plate 21 by bolts 4. The upper flange 33 has a similar structure to the lower flange 31, so a detailed description thereof will be omitted.

[0021] At the end of the girder 3 placed on the sole plate 21, stiffeners 40, 40 are placed on both sides of the web plate 32. The stiffeners 40 have vertical surfaces 41 that are approximately perpendicular to the side surfaces of the web plate 32, and connect the lower flange 31 and the upper flange 33.

[0022] In the girder 3, most of the steel members are joined by welding. As shown in Fig. 1, the girders 3, 3 are also connected by joining braces 61, cross members 62, etc. to the gusset plate 50 with bolts.

[0023] If the bridge 1 is a railway bridge, for example, it will be subjected to repeated loads due to the passage of trains. Similarly, if it is a road bridge, it will also be subjected to repeated loads due to the passage of automobiles. The force acting on the deck slab 12 due to the movement of trains or automobiles is transmitted to multiple girders 3 arranged in parallel below the deck slab 12. The force acting on the girders 3 is then transmitted from the lower flange 31 to the sole plate 21. As a result, the lower flange 31 on the sole plate 21 repeatedly moves up and down due to repeated loading and unloading of forces, resulting in the formation of cracks R as shown in Figure 2. Therefore, in order to avoid such problems, a reinforcement structure must be applied.

[0024] As shown in Figure 1, the reinforcing structure around the bearing portion 2 of the steel girder is mainly composed of stiffeners 40 arranged on both sides of the web plate 32, a gusset plate 50 provided on one side of the stiffener 40 in the direction in which the lower flange 31 extends (depth direction on the paper in Figure 1), a reinforcing member 100 provided on the same side of the stiffener 40 as the gusset plate 50 and fixed to the stiffener 40 and the gusset plate 50, a third bolt (friction-connecting bolt) 143 that secures the reinforcing member 100 to the stiffener 40 and the gusset plate 50, and a second bolt (bearing-pressure connecting bolt) 142 that secures the reinforcing member 100 to the gusset plate 50.

[0025] The gusset plate 50 is arranged so that a portion of the area overlaps with the stiffener 40 in the insertion direction of the third bolt 143. Furthermore, the reinforcing member 100 is arranged so that a portion of the area overlaps with the stiffener 40 and the gusset plate 50 in the insertion direction of the third bolt 143, and another portion of the area overlaps with only the gusset plate 50.

[0026] The reinforcing structure configured in this manner is provided at the lower corner of the four upper and lower corners defined by the pair of web plates 32 and cross member 62. In other words, the reinforcing structure is provided mainly on the lower flange 31 side because it is intended to avoid fatigue failure caused by stress concentration when a load acts on the lower flange 31 due to the transmission of a load from above. However, the reinforcing structure may also be provided on the upper flange 33.

[0027] 3(a) is a front view of the reinforcing material 100, and FIG. 3(b) is a side view of the reinforcing material 100. The reinforcing material 100 is, for example, a plate-like member formed in a hexagonal shape when viewed from the front. The reinforcing material 100 has a first region A1 that overlaps with the stiffener 40 when viewed from the front of the stiffener 40, and a second region A2 that does not overlap with the stiffener 40. As shown in FIG. 1, in the insertion direction of the third bolt 143, the first region A1 overlaps with the stiffener 40 and the gusset plate 50, and the second region A2 overlaps only with the gusset plate 50.

[0028] The reinforcement material 100 is divided into a first region A1 and a second region A2 with an imaginary line L at the center. The imaginary line L is a straight line drawn for convenience to separate the first region A1 from the second region A2, and the position of the imaginary line L is determined depending on the positions of the first region A1 and the second region A2. In the following description, the side where the first region A1 is located is referred to as the rear side (the web panel 32 side), and the side where the second region A2 is located is referred to as the front side (the brace 61 and cross member 62 side).

[0029] The first region A1 has an upper edge 111, a rear edge 112, and a first avoidance portion 113. The upper edge 111 forms an end portion on the upper side of the reinforcement material 100, and the rear edge 112 forms an end portion on the rear side of the reinforcement material 100. The first avoidance portion 113 extends linearly forward from the rear edge 112 and is inclined so that it is positioned lower as it moves forward. In other words, the first avoidance portion 113 is formed to avoid interference with members such as bolt 4 (see FIG. 1 ) provided on the lower side of the reinforcement material 100. Therefore, as long as the reinforcement material 100 has a shape in which a portion of the lower side of the first region A1 is cut out, the first avoidance portion 113 may have any shape, such as an arc shape or a concave shape when viewed from above.

[0030] The first region A1 is formed with a first through hole 114 through which the third bolt 143 passes. Specifically, the first region A1 is formed with two first through holes 114 spaced apart in the up-down direction. The first through holes 114 are formed at locations that coincide with insertion holes 40a of the stiffener 40, which will be described later.

[0031] The second region A2 has a lower edge 121, a front edge 122, and a second avoidance portion 123. The lower edge 121 forms the end portion on the lower side of the reinforcing material 100, and the front edge 122 forms the end portion on the front side of the reinforcing material 100. The second avoidance portion 123 extends in a straight line from the rear edge 112 to the front side, and is inclined so that it is positioned lower as it moves forward.

[0032] The upper edge 111, rear edge 112, first avoidance portion 113, lower edge 121, front edge 122, and second avoidance portion 123 do not necessarily have to be formed in a straight line. The second avoidance portion 123 is formed to avoid interference with a member such as a brace 61 (see FIG. 1) provided on the upper side of the reinforcing material 100. Therefore, as long as the reinforcing material 100 has a shape in which the upper side of the second region A2 is partially cut out, the second avoidance portion 123 may have any shape, such as an arc shape or a concave shape when viewed from above.

[0033] In the second region A2, a second through hole 124 through which the second bolt 142 passes is formed. Specifically, in the second region A2, only one second through hole 124 is formed on the lower side. Note that the number of second through holes 124 and the positions at which the second through holes 124 are formed may be determined appropriately depending on the shape, dimensions, etc. of the reinforcing material 100.

[0034] The procedure for joining such a reinforcing member 100 to a stiffener 40 and a gusset plate 50 to form a reinforced structure will be described with reference to Figures 4 to 9. This is a procedure for increasing the strength of a structure in which a stiffener 40 and a gusset plate 50 are joined by further joining a reinforcing member 100.

[0035] <Second bolt hole forming step> In the second bolt hole forming step, second bolt holes 50b are formed in the gusset plate 50 at positions into which second bolts 142 are inserted. As shown in FIGS. 4(a) and 4(b), the stiffener 40 and the gusset plate 50 are joined by first bolts (friction-fitting bolts) 141. Three insertion holes 40a in the stiffener 40 and three first bolt holes 50a in the gusset plate 50 are formed in the vertical direction, and the first bolts 141 are inserted into the insertion holes 40a and first bolt holes 50a arranged side by side in the vertical direction. For convenience of illustration, the brace 61 is omitted from FIG. 4(b).

[0036] The gusset plate 50 has an overlapping region 51 that overlaps with the stiffener 40 along the insertion direction of the first bolt 141, and a non-overlapping region 52 that does not overlap with the stiffener 40. The first bolt hole 50a is formed in the overlapping region 51, and the second bolt hole 50b is formed in the non-overlapping region 52.

[0037] When viewed along the thickness direction of the gusset plate 50, the second bolt hole 50b is formed in a position in the non-overlapping region 52 that does not overlap with any of the stiffener 40, the brace 61, and the cross member 62. Specifically, as shown in FIG. 4(a), the second bolt hole 50b is formed on the lower side of the non-overlapping region 52, on the stiffener 40 side.

[0038] <First bolt removal step> In the first bolt removal step, some of the first bolts 141 inserted into each of the multiple insertion holes 40a and the multiple first bolt holes 50a are removed. As shown in FIGS. 5(a) and 5(b), when first bolts 141 have been inserted into each of the insertion holes 40a and the first bolt holes 50a, the uppermost first bolt 141 is left, and two first bolts 141 are removed from the lower side of the stiffener 40 and the gusset plate 50. Note that the first bolts 141 to be removed may be determined appropriately depending on the positions and numbers of the insertion holes 40a and first bolt holes 50a to be formed.

[0039] The multiple pairs of insertion holes 40a and first bolt holes 50a from which the first bolts 141 have been removed remain connected in the height direction, and multiple open holes 45 are formed by integrating the insertion holes 40a and the first bolt holes 50a. In other words, by removing the first bolts 141, multiple open holes 45 are formed that penetrate the stiffener 40 and the gusset plate 50 in the thickness direction.

[0040] <Pre-tightening step> In the temporary tightening step, third bolts 143 that penetrate the reinforcing material 100 are inserted into the plurality of open holes 45 that are created by removing some of the first bolts 141 in the first bolt removal step. As shown in Figures 6(a) and 6(b), third bolts 143 that are longer than the first bolts 141 are inserted into two open holes 45.

[0041] In the temporary tightening step, the reinforcing member 100 with the third bolt 143 inserted in the first through hole 114 is attached to the gusset plate 50 and the stiffener 40. As shown in FIG. 6(b), the reinforcing member 100 with the third bolt 143 inserted is attached to the gusset plate 50 from the side opposite to the side where the stiffener 40 is provided.

[0042] Two third bolts 143 pass through the first through holes 114, the first bolt holes 50a, and the insertion holes 40a, joining (adhering) the reinforcing material 100, the gusset plate 50, and the stiffener 40 in this order. With the third bolts 143 inserted, the reinforcing material 100 is temporarily fastened at the positions of the two first through holes 114, which are lined up one above the other. In other words, the reinforcing material 100 can move in parallel while being temporarily held in place by the first through holes 114.

[0043] <First fixation step> In the first fixing step, the second bolt 142 is inserted into the second bolt hole 50b and the second through hole 124 with the second bolt hole 50b and the second through hole 124 aligned in the insertion direction of the second bolt 142, thereby fixing the reinforcement member 100 to the gusset plate 50. As shown in FIGS. 7( a) and 7(b), when the reinforcement member 100 is supported by the gusset plate 50 by the third bolt 143, the second bolt hole 50b and the second through hole 124 are positioned at approximately the same height in the vertical direction, with their respective central axes slightly offset in the vertical direction. In this state, in order to bring the lower edge portion 121 of the reinforcement member 100 into close contact with the lower flange 31, the second bolt 142 is inserted into the second bolt hole 50b and the second through hole 124 along the direction of the hollow arrow in FIG. 7(b) and tightened, thereby fixing the reinforcement member 100 to the gusset plate 50.

[0044] That is, when the third bolt 143 is pre-tightened, the first central axis C1 of the second through hole 124 is positioned slightly above the second central axis C2 of the second bolt hole 50b (see FIG. 8 ). Starting from a state in which the first central axis C1 and the second central axis C2 are misaligned, the second bolt 142 is inserted along the direction of the arrow in FIG. 8 . As the second bolt 142 advances from the second through hole 124 to the second bolt hole 50b, downward stress (see the hatched arrow in FIG. 9 ) is generated in the reinforcement 100, and upward stress (see the hollow arrow in FIG. 9 ) is generated in the gusset plate 50. Therefore, as shown in FIGS. 9( a) and 9(b), the reinforcement 100 is pressed downward relative to the gusset plate 50. This gradually reduces the gap that existed between the lower edge portion 121 and the lower flange 31 before the insertion of the second bolt 142, and ultimately brings the lower edge portion 121 and the lower flange 31 into tight contact with each other.

[0045] <Second fixation step> In the second fixing step, the reinforcing member 100 is fixed to the stiffener 40 and the gusset plate 50. That is, the third bolts 143 are fully tightened into the two open holes 45 and the two first through holes 114 at the top and bottom of the reinforcing member 100 formed at positions overlapping the open holes 45, thereby fixing the reinforcing member 100 to the stiffener 40 and the gusset plate 50.

[0046] 10(a) and 10(b), the third bolt 143 penetrates the first region A1 of the reinforcing material 100 at two locations, and the second bolt 142 penetrates the second region A2 of the reinforcing material 100 at one location. As a result, either the second bolt 142 or the third bolt 143 is inserted into all three through holes (the first through hole 114, the second through hole 124) formed in the reinforcing material 100.

[0047] In the first region A1, the reinforcing member 100 is joined to the stiffener 40 and the gusset plate 50 by friction welding. The third bolt 143 is a bolt for friction welding. The reinforcing member 100 is joined to the stiffener 40 and the gusset plate 50 by friction welding so as to be integrated with them. This increases the joining strength between the reinforcing member 100 and the gusset plate 50, and between the gusset plate 50 and the stiffener 40.

[0048] In the second region A2, the reinforcement 100 is joined to the gusset plate 50 by a bearing joint. The second bolt 142 is a bolt for bearing joint. By bearing joint, the reinforcement 100 and the gusset plate 50 are joined together by the second bolt 142. This makes it possible to increase the joint strength with a smaller number of bolts.

[0049] In this way, the reinforcement 100 has a mixture of regions joined by friction welding and regions joined by pressure bearing welding. That is, the reinforcement 100 is joined to the gusset plate 50 by different joining methods.

[0050] 11(a) is a diagram illustrating the structure of a conventional reinforcement target that does not have a reinforcing member 100. As shown in the figure, for example, the tip of the bottom flange 31 is bent upward. This is the result of stress acting from below on the tip of the bottom flange 31. If stress is generated from below and there is a gap between the bottom flange 31 and the gusset plate 50, unless the top surface of the bottom flange 31 is held down, it will be unable to resist the stress from below and will be bent upward.

[0051] On the other hand, in the reinforcement structure according to the embodiment, the lower edge 121 of the reinforcement member 100 joined to the gusset plate 50 is in close contact with the bottom flange 31. That is, as shown in FIG. 11(b), the lower edge 121 of the reinforcement member 100 is located closer to the bottom flange 31 than the lower end of the gusset plate 50, and the lower edge 121 is in close contact with the bottom flange 31 in advance. This makes it possible to prevent deformation of the bottom flange 31 due to stress from below. Deformation of the bottom flange 31 can be suppressed.

[0052] As described above, the method for reinforcing the support points of the brace 61 according to the embodiment includes a second bolt hole forming step of forming second bolt holes 50b in the non-overlapping region 52 into which the second bolts 142 are inserted, a first bolt removal step of removing some of the first bolts 141 among the plurality of first bolts 141 inserted into the plurality of insertion holes 40a and the first bolt holes 50a, and a third bolt 143 penetrating the reinforcing member 100 having a first region A1 overlapping with the overlapping region 51 and a second region A2 overlapping with the non-overlapping region 52 in a front view, by removing some of the first bolts 141 in the first bolt removal step. the first fixing step of inserting second bolts 142 into the second bolt holes 50b formed in the second bolt hole forming step and into second through holes 124 formed in the second region A2 at positions overlapping with the second bolt holes 50b in a front view, thereby fixing the reinforcement material 100 to the gusset plate 50; and the second fixing step of finally tightening third bolts 143 inserted into the plurality of open holes 45 to fix the reinforcement material 100 into which the second bolts 142 have been inserted to the gusset plate 50.

[0053] This eliminates the need to form new holes in the stiffener 40 for passing bolts through, and allows the existing insertion holes 40a to be used to fix the reinforcing material 100 to the stiffener 40. Therefore, the simple configuration can prevent fatigue failure caused by stress concentration.

[0054] Furthermore, in the first fixing step, the central axis of the second through hole 124 is positioned in a state where it is shifted upward relative to the central axis of the second bolt hole 50b, and in the process of inserting the second bolt 142 into the second bolt hole 50b and the second through hole 124, the reinforcing member 100 is pressed downward relative to the gusset plate 50, and the lower end of the reinforcing member 100 comes into close contact with the end of the upper surface of the lower flange 31. As a result, even if an upward stress acts on the lower flange 31, the reinforcing member 100 can prevent deformation of the lower flange 31.

[0055] In the first region A1, the reinforcing member 100 is joined to the gusset plate 50 and the stiffener 40 by friction welding, and in the second region A2, the reinforcing member 100 is joined to the gusset plate 50 by pressure-bearing welding. This makes it possible to achieve a stronger joint than when joined by a uniform joining method.

[0056] The reinforcing structure also includes a reinforcing member 100 having a first region A1 that overlaps with the overlap region 51 in a front view and a second region A2 that overlaps with the non-overlapping region 52, and a second bolt 142 that penetrates the gusset plate 50 and the reinforcing member 100 in the non-overlapping region 52 and the second region A2, wherein a first through hole 114 is formed in the first region A1 at a position that overlaps with the insertion hole 40a, and the reinforcing member 100 is fixed to the stiffener 40 and the gusset plate 50 by inserting the first bolt into the first through hole 114, and a second through hole 124 is formed in the second region A2 at a position that overlaps with the second bolt hole 50b in the non-overlapping region 52, into which the second bolt 142 is inserted, and the reinforcing member 100 is fixed to the gusset plate 50 by inserting the second bolt 142 into the second through hole 124.

[0057] As a result, existing bolt holes in the stiffener 40 are utilized in the first region A1, and by drilling only one hole in the gusset plate 50 in the second region A2, different types of bolts are used to fasten the reinforcement 100 to the stiffener 40 and the gusset plate 50. Therefore, even if there is no space to create a new hole in the stiffener 40, reinforcement is possible to avoid fatigue failure due to stress concentration.

[0058] Furthermore, the lower end of the reinforcing member 100 is in close contact with the end of the upper surface of the lower flange 31. As a result, even if an upward stress acts on the lower flange 31, the reinforcing member 100 can prevent deformation of the lower flange 31.

[0059] In addition, the first region A1 is provided with a first avoidance portion 113 that avoids interference with a fastener for fixing the lower flange 31. This makes it possible to prevent the reinforcing structure including the reinforcing material 100 from being damaged from below.

[0060] Additionally, the second region A2 is provided with a second avoidance portion 123 that avoids interference with the brace 61. This makes it possible to prevent the reinforcement structure including the reinforcement material 100 from being damaged from the side.

[0061] (Variation) FIG. 12 is a side view schematically showing a reinforcing structure according to a modification of the above-described embodiment. In the above-described embodiment, the reinforcing material 100 is a single flat plate member. In the modification, instead, the reinforcing material 100 is composed of a pair of reinforcing plates, a first reinforcing plate 100a and a second reinforcing plate 100b. Specifically, as shown in FIG. 12, the pair of reinforcing plates, the first reinforcing plate 100a and the second reinforcing plate 100b, are arranged to sandwich the gusset plate 50 therebetween.

[0062] The first reinforcing plate 100a and the second reinforcing plate 100b are fixed to the gusset plate 50 by second bolts 142, and are fixed to the stiffener 40 by third bolts 143. By sandwiching the gusset plate 50 from both sides in this way, the strength of the reinforcing structure can be further improved compared to when the reinforcing member 100 is provided on only one side of the gusset plate 50.

[0063] The embodiments of the present invention have been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention. [Explanation of symbols]

[0064] 31: Lower flange 32: Web (belly) 33: Upper flange 40: Stiffener 40a: Insertion hole 45: Open hole 50: Gusset plate 50a: First bolt hole 50b: Second bolt hole 51: Overlapping area 52: Non-overlapping area 61: Brace 62: Horizontal material 100: Reinforcement material 100a: First reinforcing plate 100b: Second reinforcing plate 113: 1st avoidance part 114: First through hole 123:Second avoidance part 124: Second through hole 141: First bolt 142: Second bolt 143: 3rd bolt A1: 1st area A2:Second area

Claims

1. A method for reinforcing a brace support point in which a pair of steel girders are arranged at a distance from each other, and a brace is provided between the upper flange of one steel girder and the lower flange of the other steel girder, and a cross member is provided on the lower flange side, and a stiffener is provided in the web of the steel girder and has a plurality of insertion holes into which first bolts are inserted, is connected by a gusset plate, the gusset plate has an overlapping region that overlaps with the stiffener in a front view of the stiffener and a non-overlapping region that does not overlap with the stiffener, and a plurality of first bolt holes are formed in the overlapping region at positions that overlap with the insertion holes in the front view, a second bolt hole forming step of forming a second bolt hole in the non-overlapping region into which a second bolt is inserted; a first bolt removal step of removing some of the first bolts among the plurality of first bolts inserted into the plurality of insertion holes and the first bolt holes; a temporary fastening step of inserting third bolts penetrating a reinforcing material having a first region overlapping with the overlapping region and a second region overlapping with the non-overlapping region in the front view into a plurality of open holes obtained by removing some of the first bolts in the first bolt removal step, thereby temporarily fastening the reinforcing material; a first fixing step of fixing the reinforcing member to the gusset plate by inserting the second bolt into the second bolt hole formed in the second bolt hole forming step and a second through hole formed in the second region at a position overlapping the second bolt hole in the front view; and a second fixing step of fixing the reinforcing material into which the second bolts are inserted to the gusset plate by fully tightening the third bolts inserted into the plurality of open holes.

2. In the first fixing step, the central axis of the second through hole is positioned in a state where it is shifted upward with respect to the central axis of the second bolt hole, 2. The method for reinforcing a brace support point according to claim 1, wherein the reinforcing material is pressed downward relative to the gusset plate during the process of inserting the second bolt into the second bolt hole and the second through hole, and the lower end of the reinforcing material is brought into close contact with the end of the upper surface of the lower flange.

3. In the first region, the reinforcement is joined to the gusset plate and the stiffener by a frictional bond; 3. The method for reinforcing a brace support point according to claim 1, wherein in the second region, the reinforcing material is joined to the gusset plate by a bearing joint.

4. A pair of steel girders are arranged at an interval, and a brace is provided between the upper flange of one steel girder and the lower flange of the other steel girder, and a cross member is provided on the lower flange side, and a stiffener is provided on the web of the steel girder and has a plurality of insertion holes into which first bolts and third bolts are inserted, and the brace support reinforcement structure is connected by a gusset plate, the gusset plate has an overlapping region that overlaps with the stiffener in a front view of the stiffener and a non-overlapping region that does not overlap with the stiffener, and a plurality of first bolt holes are formed in the overlapping region at positions that overlap with the insertion holes in the front view, a reinforcing member having a first region overlapping the overlapping region in the front view and a second region overlapping the non-overlapping region; a second bolt passing through the gusset plate and the stiffener in the non-overlapping region and the second region; a first through hole is formed in the first region at a position overlapping with the insertion hole in the front view, and the third bolt is inserted into the first through hole to fix the reinforcing material to the stiffener and the gusset plate; a second through hole is formed in the second region at a position in the non-overlapping region that overlaps with a second bolt hole into which the second bolt is inserted when viewed from the front, and the second bolt is inserted into the second through hole, thereby fixing the reinforcing material to the gusset plate.

5. The brace support structure according to claim 4, characterized in that the lower end of the reinforcing member is in close contact with the end of the upper surface of the lower flange.

6. A brace support reinforcement structure as described in claim 4 or 5, characterized in that the first region is provided with a first avoidance portion that avoids interference with a fastener for fixing the lower flange.

7. 6. The reinforcement structure for a brace support point according to claim 4, wherein the second region is provided with a second avoidance portion that avoids interference with the brace.

8. 6. The reinforcing structure for a brace support point according to claim 4, wherein the reinforcing member comprises a first reinforcing plate and a second reinforcing plate fixed to the gusset plate.

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