JP2015025299A - Crack extension prevention device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crack extension prevention device and method that can be applied to a crack made in a general region (for example, a flat plate part) of a structure and can prevent the crack from extending only by fastening a bolt.SOLUTION: A crack extension prevention device includes: one or a plurality of reinforcement members 12 which extend along one surface or both surfaces of a part 4 to be reinforced across a crack 3; and a fastening member 14 which fastens the reinforcement member 12 to the part 4 to be reinforced on both sides across the crack 3. Each reinforcement member 12 has a pair of anchoring parts 13a which are in contact with a surface of the part 4 to be reinforced across the crack 3 and anchored integrally to the surface of the part 4 to be reinforced with fastening force T by the fastening member 14; and a deformation part 13b which holds the pair of anchoring parts 13a with the part 4 to be reinforced and deforms with the fastening force T by the fastening member 14 to press each anchoring part 13a against the crack 3 along the surface of the part 4 to be reinforced.

Description

  The present invention relates to a crack growth preventing apparatus and method for preventing the growth of a crack generated in a structure.

For example, in a structure such as a bridge or a crane, a crack may occur on the surface or inside of the structure due to a fatigue phenomenon due to repeated stress during service or an excessive stress due to an earthquake or the like.
In such a case, for example, Patent Documents 1 to 4 have been proposed as means for preventing the development of a crack generated in the structure.

  Patent Literature 1 discloses a method for reinforcing steel piers in which a column member and a beam member are connected to each other with a temperature difference between the column member and the beam member. A prestressing force is generated in a direction that is offset by an internal force that acts on or near the connecting portion of the beam member.

  Patent Document 2 “Reinforcing Structure Excellent in Stopping Brittle Crack Propagation” is that a tensile strain is applied to the reinforcing plate in advance by the reinforcing plate straddling the brittle crack and the coupling means for connecting the reinforcing plate to the base material. Is. This application is by heating or mechanical tension.

  Patent Document 3 “Repair / Reinforcement Structure for Cracks from Fillet Welded Parts of Steel Bridge Sole Plate” is on the side opposite to the fillet welded part of the sole plate of the main girder flange, parallel to the flange of the main girder. Apply the extending reinforcing plate, apply the presser material to the reinforcing plate from the opposite side of the main girder flange, sandwich the reinforcing plate between the main girder flange and the presser material, and tighten with the high strength bolts. A stiffener or web is fastened with a high-strength bolt.

  Patent Document 4 “Steel Reinforcement Method and Steel-Concrete Composite Panel Used in the Construction Method” is a method of placing fiber reinforced concrete on the top surface of a striped steel plate on the deck plate of the steel floor slab from which the pavement has been removed. The steel-concrete composite panel is integrated and fixed, and the steel-concrete composite panel is fixed to the deck plate.

JP 2004-68402 A Japanese Patent No. 4909237 JP 2000-288726 A JP 2011-42985 A

The conventional means (crack growth preventing means) described above has the following problems.
In the means of Patent Document 1, it is difficult to maintain a temperature difference due to heat transfer between the portion to be reinforced (column member and beam member) and the reinforcing member. Moreover, it is difficult to fasten the high-temperature reinforcing member with a bolt or the like.
With the means of Patent Document 2, it is difficult to install a device that mechanically applies a tensile force at a repair site of a structure. Moreover, there is a high possibility that welding a member will be a starting point for destruction.
The means of Patent Document 3 is limited to the case where there is a member (in this example, the end stiffener or web of the main girder) that fastens the reinforcing plate with a high-strength bolt to the structure.
The means of patent document 4 is restricted to the deck plate of a steel deck.

  For this reason, it has been difficult to apply to a crack generated in a general portion (for example, a flat plate portion) of a structure such as a bridge or a crane.

  The present invention has been developed to solve the above-described problems. That is, the object of the present invention can be applied to a crack generated in a general part of a structure (for example, a flat plate portion), and can prevent crack propagation by only fastening a bolt and preventing crack propagation. It is to provide an apparatus and method.

According to the present invention, there is provided a crack growth preventing apparatus for preventing the development of a crack generated in a reinforced portion of a structure,
One or more reinforcing members extending along one or both sides of the reinforced portion across the crack; and
A fastening member that fastens the reinforcing member to the reinforced portion on both sides straddling the crack; and
Each reinforcing member is in close contact with the surface of the reinforced portion across the crack, and a pair of fixing portions that are integrally fixed to the surface of the reinforced portion by the clamping force of the fastening member;
A pair of the fixing portions sandwiched between the reinforced portion and a deforming portion that deforms by the clamping force of the fastening member and presses the fixing portions along the surface of the reinforced portion toward the crack; , And a crack propagation preventing device is provided.

  The reinforcing member includes an integral member or a pair of fixing portions and a single deformation portion.

  The adhering portion has a claw portion that is engaged with the surface of the reinforced portion by a tightening force of the fastening member and increases a coefficient of friction with the reinforced portion.

  The to-be-reinforced portion has a protrusion or a groove that fits with the fixing portion and integrally fixes the fixing portion.

  The fastening member is a bolt that is screwed into a female screw hole provided in the reinforced portion, or a bolt and a nut that fasten both ends of the reinforcing member and the reinforced portion through a through hole provided in the reinforced portion. It is.

  The bolt is a high-strength bolt that integrally fixes the fixing portion to the surface of the reinforced portion by friction bonding.

Further, according to the present invention, there is provided a crack propagation preventing method for preventing the crack from occurring in the reinforced portion of the structure,
One or more reinforcing members;
A fastening member for fastening both ends of the reinforcing member to the reinforced portion, and
Each reinforcing member has a pair of fixed portions and deformed portions,
(A) The one or more reinforcing members are disposed along one or both sides of the reinforced portion across the crack,
(B) A pair of the fixing portions are sandwiched between the deformable portion and the reinforced portion,
(C) The pair of fixing portions are closely attached to the surface of the reinforced portion across the crack,
(D) The fastening member fastens the reinforcing member to the reinforced portion on both sides across the crack,
(E) The fixing portion is integrally fixed to the surface of the reinforced portion by the tightening force of the fastening member,
(F) A crack propagation preventing method is provided, wherein the deforming portion is deformed by a tightening force of the fastening member, and the fixing portions are pressed toward the crack along the surface of the reinforced portion. The

  According to the apparatus and method of the present invention, each reinforcing member has a pair of fixed portions and a deformed portion, so that the pair of fixed portions are sandwiched between the deformed portion and the reinforced portion of the structure, The pair of fixing portions can be brought into close contact with the surface of the reinforced portion across the crack, and the reinforcing member can be fastened to the reinforced portion on both sides of the crack with the fastening member. As a result, the fixing portion is integrally fixed to the surface of the structure by the tightening force of the fastening member, and the deformation portion is deformed by the tightening force of the fastening member so that each fixing portion is cracked along the surface of the structure. Can be pressed toward

Since this pressing force works in the direction in which the crack closes, the external force cancels the action of opening the crack and propagating it, thereby preventing crack propagation.
Therefore, the present invention can be applied to a crack generated in a general portion (for example, a flat plate portion) of the structure, and only the fastening member (bolt) can be fastened to prevent the crack from progressing.

It is a schematic diagram (B) of the crack generation example (A) and the crack propagation preventing device of the present invention. It is 1st Embodiment figure of the crack growth prevention apparatus of this invention. It is a flowchart of the crack growth prevention method of the present invention. It is 2nd Embodiment figure of the crack growth prevention apparatus of this invention. It is 3rd Embodiment figure of the crack growth prevention apparatus of this invention. It is 4th Embodiment figure of the crack growth prevention apparatus of this invention. It is 5th Embodiment figure of the crack growth prevention apparatus of this invention. It is a figure which shows the specific example of the surface of an adhering part and a to-be-reinforced part.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a schematic diagram (B) of an example (A) of crack 3 generation and a crack growth preventing device 10 of the present invention.

In FIG. 1A, 1 is a structure such as a bridge or a crane, 2 is a flat plate portion constituting the structure 1, and 3 is a crack generated in the flat plate portion 2.
Hereinafter, the portion of the structure 1 including the crack 3 (the flat plate portion 2 in this example) is simply referred to as a “reinforced portion” and indicated by reference numeral 4.
In addition, the to-be-reinforced part 4 is not limited to the flat plate part 2, A block etc. of a cast member may be sufficient. Moreover, the crack 3 is not limited to what penetrated the to-be-reinforced part 4 in the thickness direction, and may exist only in the surface or the inside.

  As shown in FIG. 1B, the crack propagation preventing device 10 of the present invention includes a reinforcing member 12 and a fastening member 14.

  In this drawing, the reinforcing member 12 is single and extends along one side of the portion to be reinforced 4 of the structure 1 across the crack 3. Note that a plurality (for example, two) of the reinforcing members 12 may be provided and disposed along both surfaces of the reinforced portion 4 across the crack 3. Bolt holes through which the bolts are passed are provided at both ends (left and right in the drawing) of the reinforcing member 12 positioned across the crack 3. The bolt holes at both ends may be single or plural.

  A similar bolt hole or female screw hole is provided in advance in the portion to be reinforced 4 at a position facing the bolt hole of the reinforcing member 12 across the crack 3.

In this drawing, the fastening member 14 is four bolts, and fastens the reinforcing member 12 to the reinforced portion 4 on both sides straddling the crack 3.
In this example, the fastening member 14 is a bolt and a nut (not shown) that fasten both ends of the reinforcing member 12 and the reinforced portion 4 through the through-holes provided in the reinforced portion 4. It may be a bolt that is screwed into a female screw hole provided in the reinforcing portion 4.

FIG. 2 is a first embodiment of the crack growth preventing apparatus 10 of the present invention. In this figure, (A) shows the fastening member 14 before fastening, and (B) shows the fastening member 14 after fastening.
In FIG. 2A, the two reinforcing members 12 extend along both surfaces of the reinforced portion 4 across the crack 3. Further, in this example, the fastening member 14 is a bolt 15 a and a nut 15 b that fasten both ends of the reinforcing member 12 and the reinforced portion 4 through through holes provided in the reinforced portion 4. The bolt 15a is preferably a high-strength bolt, and a fixing portion 13a (described later) is integrally fixed to the surface of the reinforced portion 4 by friction bonding.

  Each reinforcing member 12 has a pair of fixed portions 13a and deformed portions 13b. In this example, the pair of fixing portions 13a and the deforming portion 13b are integral members. Bolt holes through which the bolts 15a are passed are provided at both ends of the reinforcing member 12 (left and right in the figure).

  The pair of fixing portions 13a are in close contact with the surface (both sides in this case) of the reinforced portion 4 across the crack 3, and are integrally fixed to the surface of the reinforced portion 4 by the tightening force T by the fastening member 14. The The friction coefficient μ between the surface of the portion to be reinforced 4 and the fixing portion 13a is at least 0.2 or more, preferably 1.0 or more.

  The deformable portion 13b sandwiches a pair of fixed portions 13a between the reinforced portion 4 and deforms by the tightening force T by the fastening member 14 so that each fixed portion 13a is cracked along the surface of the reinforced portion 4. It pushes towards 3. The deformation of the deformation portion 13b may be elastic deformation or elasto-plastic deformation including elastic deformation.

  FIG. 3 is a flowchart of the crack propagation preventing method of the present invention. As shown in this figure, the method of the present invention comprises steps (steps) S1 to S7.

In step S <b> 1, one or a plurality of reinforcing members 12 and a fastening member 14 that fastens both ends of the reinforcing member 12 to the reinforced portion 4 are prepared.
In step S <b> 2, one or a plurality of reinforcing members 12 are disposed along one side or both sides of the reinforced portion 4 across the crack 3.
In step S <b> 3, a pair of fixing portions 13 a is sandwiched between the deformable portion 13 b and the reinforced portion 4.
In step S <b> 4, the pair of fixing portions 13 a are brought into close contact with the surface of the reinforced portion 4 across the crack 3.
In step S <b> 5, both ends of the reinforcing member 12 are fastened to the reinforced portion 4 by the fastening member 14.
In step S <b> 6, the fixing portion 13 a is integrally fixed to the surface of the reinforced portion 4 with the tightening force T by the fastening member 14. The fastening force T by the fastening member 14 is preferably the fastening force T of the high strength bolt.
In step S7, the deforming portion 13b is deformed by the tightening force T (high-strength bolt tightening force T) by the fastening member 14, and the fixing portions 13a are pressed toward the crack 3 along the surface of the reinforced portion 4. .
Steps S5 to S7 are repeatedly performed until a desired tightening force T (high-strength bolt tightening force T) is reached.

FIG. 2B shows the state after the fastening member 14 is fastened, that is, the state of step S7.
If it deform | transforms so that the both ends of the reinforcement member 12 may approach the surface of the to-be-reinforced part 4 by step S7, the space | interval of the fixing point of a pair of fixing | fixed part 13a will become shorter than before fastening. That is, as long as the fixing portion 13a does not slide (fixed) to the surface of the reinforced portion 4, the reinforcing member 12 is deformed in an arc shape, so that the length before the deformation becomes the length of the arc string after the deformation. The distance between the fixing points of the pair of fixing portions 13a is shorter than that before fastening by a length corresponding to the difference.
Therefore, each fixing portion 13a can be pressed along the surface of the reinforced portion 4 toward the crack 3 by the deformation of the deformation portion 13b.

Further, in this state, even if an external force in the direction of opening the crack 3 acts, the crack 3 is supported in the closing direction up to a force corresponding to μT per side, so that the crack 3 can be prevented from progressing. .
Therefore, in the case of FIG. 2 (B), with respect to the external force in the direction of opening the crack 3, the two reinforcing members 12 support the force corresponding to 2 μT, which is doubled in both directions in the direction of closing the crack 3. can do.
Further, when the number of bolts n at both ends is plural, it is possible to support even a force corresponding to n times.

4A and 4B are diagrams showing a second embodiment of the crack growth preventing device 10 according to the present invention, in which FIG. 4A is a welding process, FIG. 4B is a state before the fastening member 14 is fastened, and FIG. Is shown.
In this example, the crack surface is welded before attaching the reinforcing member 12 in FIG. In this welding, the inside cannot be repaired by welding, and the crack 3 may remain inside.
In this example, in addition to repair by welding, reinforcement by the reinforcing member 12 is performed.
Other configurations are the same as those of the first embodiment. That is, FIG. 4B is the same as FIG. 3A, and FIG. 4C is the same as FIG.

With the above-described configuration, even if the crack 3 remains inside in FIG. 4A, even if an external force in the direction of opening the crack 3 acts in the state of FIG. Since a force corresponding to μT per side is supported in the closing direction, the crack 3 can be prevented from progressing.
Accordingly, in the case of FIG. 4C, the two reinforcing members 12 support the external force in the direction of opening the crack 3 to a force corresponding to 2 μT, which is doubled in both directions in the direction of closing the crack 3. can do.
FIG. 4 shows the crack growth preventing device 10 of the first embodiment, but the configuration of the crack growth preventing device 10 is not limited to the first embodiment, and in other embodiments. It may be the crack growth prevention device 10 shown.

5A and 5B are diagrams of a third embodiment of the crack growth preventing device 10 according to the present invention, in which FIG. 5A shows before the fastening member 14 is fastened, and FIG. 5B shows after the fastening member 14 has been fastened.
In FIG. 5A, a single reinforcing member 12 extends along one side of the reinforced portion 4 across the crack 3.
Other configurations are the same as those of the first embodiment.

FIG. 5B shows a state after the fastening member 14 is fastened, that is, the state of step S7.
In this example, the fixing portion 13a acts only on one side of the portion to be reinforced 4, so that the external force in the direction of opening the crack 3 supports up to a force equivalent to μT per side in the direction of closing the crack 3. Can do.

6A and 6B are diagrams of a fourth embodiment of the crack growth preventing device 10 of the present invention, in which FIG. 6A shows before the fastening member 14 is fastened and FIG. 6B shows after the fastening member 14 has been fastened.
In FIG. 6A, the two reinforcing members 12 extend along both surfaces of the portion to be reinforced 4 across the crack 3 as in the first embodiment.

In this example, each reinforcing member 12 includes a pair of fixing portions 13a and a single deformation portion 13b, and the fixing portions 13a and the deformation portions 13b are separate parts.
Bolt holes through which the bolts 15a are passed are provided at both ends of the reinforcing member 12 (left and right in the figure). The bolt holes at both ends may be single or plural. Further, in this example, the bolt holes are provided in both the fixing portion 13a and the deforming portion 13b. However, the bolt holes may be provided only in the deforming portion 13b, and the fixing portion 13a may be positioned inside thereof.

In this example, the deforming portion 13b is a flat plate having a constant thickness, and the fixing portion 13a can be configured as a tapered washer whose thickness changes. Therefore, this configuration facilitates the production of the reinforcing member 12 (fixed portion 13a and deformed portion 13b), is suitable for mass production, and can be expected to reduce costs.
In addition, this invention is not limited to this structure, You may change the thickness of the deformation | transformation part 13b suitably as needed.
Other configurations and functions of the fixing portion 13a and the deformation portion 13b are the same as those in the first embodiment.

FIG. 6B shows the state after the fastening member 14 is fastened, that is, the state of step S7.
If it deform | transforms so that the both ends of the reinforcement member 12 may approach the surface of the to-be-reinforced part 4 by step S7, the space | interval of the fixing point of a pair of fixing | fixed part 13a will become shorter than before fastening.
That is, as long as the fixing portion 13a does not slide (fixed) to the surface of the reinforced portion 4, the reinforcing member 12 is deformed in an arc shape, so that the length before the deformation becomes the length of the arc string after the deformation. The distance between the fixing points of the pair of fixing portions 13a is shorter than that before fastening by a length corresponding to the difference.
Therefore, each fixing portion 13a can be pressed along the surface of the reinforced portion 4 toward the crack 3 by the deformation of the deformation portion 13b.

Further, in this state, even if an external force in the direction of opening the crack 3 acts, the crack 3 is supported in the closing direction up to a force corresponding to μT per side, so that the crack 3 can be prevented from progressing. .
Therefore, in the case of FIG. 2 (B), with respect to the external force in the direction of opening the crack 3, the two reinforcing members 12 support the force corresponding to 2 μT, which is doubled in both directions in the direction of closing the crack 3. can do.

FIGS. 7A and 7B are diagrams of a fifth embodiment of the crack growth preventing device 10 according to the present invention, in which FIG. 7A shows before the fastening member 14 is fastened, and FIG. 7B shows after the fastening member 14 has been fastened.
In FIG. 7A, a single reinforcing member 12 extends along one side of the portion to be reinforced 4 across the crack 3.
Other configurations are the same as those of the fourth embodiment.

FIG. 7B shows the state after the fastening member 14 is fastened, that is, the state of step S7.
In this example, the fixing portion 13a acts only on one side of the portion to be reinforced 4, so that the external force in the direction of opening the crack 3 supports up to a force equivalent to μT per side in the direction of closing the crack 3. Can do.

  FIG. 8 is a diagram illustrating specific examples of the surfaces of the fixing portion 13 a and the portion to be reinforced 4. Although FIG. 8 shows the configuration of the fifth embodiment, other embodiments may be used.

In FIG. 8A, the fixing portion 13 a has a claw portion 16. The claw portion 16 is preferably formed integrally with the fixing portion 13a and has a pointed shape in contact with the surface of the reinforced portion 4. Further, the claw portion 16 should have high hardness by quenching or the like.
With this configuration, the claw portion 16 is engaged with the surface of the reinforced portion 4 by the tightening force T (high-strength bolt tightening force T) of the fastening member 14 and increases the coefficient of friction μ with the reinforced portion 4. It is like that.
For example, with this configuration, the friction coefficient μ between the surface of the portion to be reinforced 4 and the fixing portion 13a can be at least 1.0 or more, and the crack 3 in the first to fifth embodiments described above is closed. The supporting force to support can be increased.

In FIG. 8 (B), the to-be-reinforced part 4 has a concave groove 4a on its surface. The concave groove 4a is preferably formed by additional machining when a bolt hole or a female screw hole is provided in advance in the portion to be reinforced 4 in order to reinforce the crack 3.
The concave groove 4a is fitted to a portion of the fixing portion 13a that engages with the portion to be reinforced 4, so that the fixing portion 13a is integrally fixed.

In FIG. 8C, the reinforced portion 4 has a protrusion 4b on its surface. The protrusion 4b is preferably attached by bolt fastening, rivet or welding when a bolt hole or a female screw hole is provided in advance in the portion to be reinforced 4 in order to reinforce the crack 3.
The protrusion 4b is fitted to a portion of the fixing portion 13a that engages with the portion to be reinforced 4, thereby fixing the fixing portion 13a integrally.

8 (B) and 8 (C) can essentially prevent slippage of the fixing portion 13a with respect to the surface of the reinforced portion 4, and close the crack 3 in the first to fifth embodiments described above. The supporting force to support in the direction can be greatly increased.
In addition, you may use together the structure of FIG. 8 (A) (B) (C).

  According to the above-described apparatus and method of the present invention, each reinforcing member 12 has a pair of fixing portions 13a and a deforming portion 13b, so that there is a pair between the deforming portion 13b and the portion to be reinforced 4 of the structure 1. Are attached to the surface of the reinforced portion 4 across the crack 3, and the fastening member 14 covers the reinforcing member 12 on both sides of the crack 3. The reinforcing part 4 can be fastened. As a result, the fixing portion 13a is integrally fixed to the surface of the structure 1 by the tightening force T by the fastening member 14, and the deforming portion 13b is deformed (elastically deformed or elastic-plastically deformed) by the tightening force T by the fastening member 14. ) And the respective fixing portions 13a can be pushed along the surface of the structure 1 toward the crack 3.

Since this pressing force acts in the direction in which the crack 3 is closed, the external force cancels the action of opening the crack 3 and propagating it, thereby preventing crack propagation.
Therefore, it can be applied to a crack 3 generated in a general part (for example, the flat plate portion 2) of the structure 1, and only the fastening member 14 (bolt 15a) can be fastened to prevent the crack 3 from progressing. .

  In addition, this invention is not limited to embodiment mentioned above, is shown by description of a claim, and also includes all the changes within the meaning and range equivalent to description of a claim.

μ Friction coefficient, T tightening force,
1 structure, 2 flat plate, 3 crack,
4 Reinforced part, 4a Groove, 4b Protruding part,
10 crack growth prevention device, 12 reinforcing member,
13a fixing part, 13b deformation part,
14 fastening member, 15a bolt (high strength bolt),
15b nut, 16 claws

Claims (7)

A crack growth prevention device for preventing the development of a crack generated in a reinforced portion of a structure,
One or more reinforcing members extending along one or both sides of the reinforced portion across the crack; and
A fastening member that fastens the reinforcing member to the reinforced portion on both sides straddling the crack; and
Each reinforcing member is in close contact with the surface of the reinforced portion across the crack, and a pair of fixing portions that are integrally fixed to the surface of the reinforced portion by the clamping force of the fastening member;
A pair of the fixing portions sandwiched between the reinforced portion and a deforming portion that deforms by the clamping force of the fastening member and presses the fixing portions along the surface of the reinforced portion toward the crack; A crack propagation preventing device characterized by comprising:   The crack propagation preventing device according to claim 1, wherein the reinforcing member includes an integral member or a pair of fixing portions and a single deformation portion.   The said fixing | fixed part has a nail | claw part which bites into the surface of the said to-be-reinforced part with the clamping force by the said fastening member, and increases a friction coefficient with the to-be-reinforced part. Crack growth prevention device.   The crack propagation preventing device according to claim 1, wherein the reinforced portion includes a protrusion or a concave groove that is fitted to the fixing portion and integrally fixes the fixing portion.   The fastening member is a bolt that is screwed into a female screw hole provided in the reinforced portion, or a bolt and a nut that fasten both ends of the reinforcing member and the reinforced portion through a through hole provided in the reinforced portion. The crack growth preventing device according to claim 1, wherein:   The crack propagation preventing device according to claim 5, wherein the bolt is a high-strength bolt that integrally fixes the fixing portion to the surface of the reinforced portion by friction bonding. A crack growth prevention method for preventing the development of a crack generated in a reinforced portion of a structure,
One or more reinforcing members;
A fastening member for fastening both ends of the reinforcing member to the reinforced portion, and
Each reinforcing member has a pair of fixed portions and deformed portions,
(A) The one or more reinforcing members are disposed along one or both sides of the reinforced portion across the crack,
(B) A pair of the fixing portions are sandwiched between the deformable portion and the reinforced portion,
(C) The pair of fixing portions are closely attached to the surface of the reinforced portion across the crack,
(D) The fastening member fastens the reinforcing member to the reinforced portion on both sides across the crack,
(E) The fixing portion is integrally fixed to the surface of the reinforced portion by the tightening force of the fastening member,
(F) A crack propagation preventing method, wherein the deforming portion is deformed by a tightening force of the fastening member, and the fixing portions are pressed toward the crack along the surface of the reinforced portion.

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