JP2023067785A - Reinforcing structure, reinforcing member, and reinforcing method - Google Patents

Abstract

To provide a reinforcing member of a steel member capable of preventing dead load at joints of steel members from increasing, and facilitating reinforcement.SOLUTION: A reinforcing structure 100 in an embodiment comprises a cross-sectional I-shaped steel girder 5 having a flange 51 and a vertical stiffener 54 to be joined to the flange 51, and a reinforcing member 1 for reinforcing the cross-sectional I-shaped steel girder 5. The reinforcing member 1 has an FRP plate material 2 in which a plurality of unidirectional fiber sheets is laminated. The FRP plate material 2 is formed with a pair of attached portions 23 formed on both sides of the vertical stiffener 54 and attached to the flange 51, and a bypass portion 24 for connecting the pair of attached portions 23 by bypassing the vertical stiffener 54. A fiber orientation in the FRP plate material 2 has a main direction from one attachment portion 23a to the other attachment portion 23b and at least two directions different from the main direction.SELECTED DRAWING: Figure 8

Description

There is an application for exception to loss of novelty

The present invention relates to a reinforcing structure, a reinforcing member, and a reinforcing method having joints between a first steel material and a second steel material.

Currently, as part of the expressway renewal project, large-scale renewal work such as floor slab replacement is underway. At that time, the existing steel girders may not have sufficient load-bearing capacity due to the replacement of the floor slabs. The reasons for the insufficient load-bearing capacity of existing steel girders include an increase in dead load due to floor slabs after replacement, an increase in live load from the design live load at the time of completion to B live load, and structural changes from composite girders to non-composite girders. etc. Therefore, the demand for reinforcement of existing steel girders is expected to increase in the future. Conventionally, techniques disclosed in, for example, Non-Patent Document 1 and Patent Documents 1 and 2 have been proposed as techniques for reinforcing steel members.

In the method of reinforcing steel I girders in Non-Patent Document 1, when replacing the lower flange connecting plate that connects the lower flanges of two steel I girders, a part of the lower side of the web connecting plate that connects the webs is replaced. A web bypass member made of a metal plate is bolted to the removed portion.

The method for repairing and reinforcing a steel structure in Patent Document 1 includes a step of forming a putty layer on the surface of a steel member with a polyurea resin putty material, and laminating a plurality of fiber sheets on the putty layer by bonding them with a resin. , to form a plurality of fiber reinforced resin layers.

In the repair method of Patent Document 2, in a steel structure in which a joint steel member is turn-welded out of the plane of a steel base material, a crack occurring at the toe portion of the joint steel member is repaired with a carbon fiber reinforced resin plate. At the same time as attaching at least the carbon fiber reinforced resin plate to both side surfaces of the joint steel member and the base material surface of the toe portion in a substantially U-shape, The inner surface of the shape is attached in close contact with the weld bead of the weld between the base material and the joint steel member.

Shun Matsui, Takashi Yamaguchi, Kensuke Toda, Kenji Araki, Takashi Yamauchi, "Analytical study on the application range of the web bypass method and the shape of the bypass member for replacing the flange connecting plate under the steel I girder", The Japan Society of Civil Engineers, Journal of Structural Engineering Vol.67A, 2021, P.323-335

JP 2015-124553 A JP 2006-057352 A

By the way, in the reinforcing method of Non-Patent Document 1, it is necessary to form a bolt hole in the web for bolting the web bypass member and to weld the web bypass member, so the construction is not easy.

The I-section steel material is used, for example, as a girder member that supports the floor slab of a bridge from below. However, since the floor slab is placed on the upper flange of the I-section steel material, construction may be limited, such as reinforcing the upper flange from the lower surface side. Therefore, there is a demand for a technique that enables reinforcement in a short construction time.

Further, in the reinforcing method of Non-Patent Document 1, since the web bypass member made of a metal plate is joined, there is concern that the dead load after the reinforcement will increase significantly. In addition, vertical stiffeners may be joined to the underside of the upper flanges, for example of steel I girders. When reinforcing a steel member having a joint between an upper flange and a vertical stiffener, it is difficult to reinforce the joint.

In the technique disclosed in Patent Document 1, even if an attempt is made to reinforce an I-section steel material provided with vertical stiffeners, the vertical stiffeners cannot stick fiber sheets continuously in the material axis direction. Moreover, although the technology disclosed in Patent Document 2 can be applied to fatigue cracks, it does not relate to bending reinforcement. Therefore, in the techniques disclosed in Patent Documents 1 and 2, when reinforcing a steel member having a joint between the upper flange and the vertical stiffener, it is difficult to reinforce the joint. Therefore, there is a demand for a technique that can exert a reinforcing effect even at joints between steel materials.

Accordingly, the present invention has been devised in view of the circumstances described above, and its object is to suppress an increase in dead load at joints of steel members and to facilitate reinforcement. It is an object of the present invention to provide a reinforcing structure, a reinforcing member, and a reinforcing method.

A reinforcing structure according to a first aspect of the invention is a reinforcing structure for reinforcing a steel member having a first steel material and a second steel material joined to the first steel material, wherein the steel member and the steel member are reinforced. and a reinforcing member for , a pair of attachment portions formed on both sides of the second steel member and attached to the first steel member, and a bypass portion connecting the pair of attachment portions by bypassing the second steel member. The fiber orientation formed in the FRP plate is characterized by having a main direction from one attachment portion to the other attachment portion and at least two directions different from the main direction.

A reinforcing structure according to a second invention is the reinforcing structure according to the first invention, wherein the fiber orientation in at least two directions oriented in directions different from the main direction is inclined at an absolute value of 15 ° to 75 ° from the main direction, It is characterized by being symmetrical with respect to the main direction.

A reinforcing structure according to a third aspect of the invention is, in the first aspect, wherein the reinforcing member further includes a continuous fiber material between the attachment portion and the first steel material, and the continuous fiber material includes the second steel material. It is characterized by providing a pair on both sides with a space therebetween.

A reinforcing structure according to a fourth invention is the reinforcing member in the first invention, wherein the reinforcing member further includes an adhesive layer between the attachment portion and the first steel material, and the adhesive layer comprises a high elongation elastic resin layer. characterized by comprising

A reinforcing structure according to a fifth invention is characterized in that in the first invention, the thickness of the FRP plate material is tapered toward the end portion side in the main direction.

A reinforcement structure according to a sixth invention is the reinforcement structure according to the first invention, wherein the reinforcing member has a fiber sheet attached to the FRP plate material, and the FRP plate material is notched from a side end and the second steel material is inserted. and a reduced portion in which the size of the FRP plate is reduced by the cutout, and the fiber sheet is attached to the FRP plate so as to straddle the reduced portion. Characterized by

A reinforcing structure according to a seventh invention is the reinforcement structure according to the sixth invention, wherein the FRP plate material has a first main surface on which the bonding surface of the first steel material is formed, and a second main surface opposite to the first main surface. , and the fiber sheet is attached to the first main surface.

A reinforcing structure according to an eighth invention is the reinforcement structure according to the sixth invention or the seventh invention, wherein the FRP plate material has a first main surface on which the bonding surface of the first steel material is formed, and a first main surface on the opposite side of the first main surface. and two main surfaces, and the fiber sheet is attached to the second main surface.

A reinforcing member according to a ninth aspect of the invention is a reinforcing member for reinforcing a steel member having a first steel material and a second steel material joined to the first steel material, wherein continuous reinforcing fibers are pulled in one direction. It has an FRP plate material in which a plurality of unidirectional fiber sheets that are aligned and impregnated with resin are laminated, and the FRP plate material is formed on both sides of the second steel material and is attached to the first steel material. A pair of attached portions and a bypass portion for bypassing the second steel material and connecting the pair of attached portions are formed, and the fiber orientation in the FRP plate material is from one of the attached portions to the other. It has a main direction toward the attachment portion and at least two directions different from the main direction.

A reinforcing member according to a tenth aspect of the present invention is a reinforcing member according to the ninth aspect of the present invention, which has a fiber sheet attached to the FRP plate material, and the FRP plate material is cut out from a side end and a notch portion into which the second steel material is inserted. and a reduced portion in which the size of the FRP plate material is reduced by the notch portion, and the fiber sheet is attached to the FRP plate material so as to straddle the reduced portion.

A reinforcing method according to an eleventh aspect of the present invention is a method for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, wherein the steel member is provided with the reinforcing member. The reinforcing member has an FRP plate material in which a plurality of unidirectional fiber sheets in which continuous reinforcing fibers are aligned in one direction and are impregnated with resin are laminated, and the FRP plate material is the second 2. A pair of attached portions formed on both sides of the steel material and a bypass portion connecting the pair of attached portions are formed, and the fiber orientation in the FRP plate material is from one of the attached portions to the other. a main direction toward the affixing portion and at least two directions different from the main direction; It is characterized by sticking the said sticking part.

A method for reinforcing a steel member according to a twelfth invention is, in the eleventh invention, wherein the reinforcing member has a fiber sheet attached to the FRP plate, and the FRP plate is notched from a side end and the second It has a notch into which a steel material is inserted, and a reduced portion in which the size of the FRP plate is reduced by the notch, and the fiber sheet is attached to the FRP plate so as to straddle the reduced portion. In the installation step, the second steel member is inserted into the notch portion of the FRP plate member, and the FRP plate member is attached to the first steel member.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the increase in the dead load in the joint part of a steel member, and to reinforce easily. Furthermore, even if there are obstacles such as bolts, backing plates, stiffening plates, etc., and it is difficult to reinforce a place where a sufficient fixing length cannot be obtained, the reinforcing member of the present invention and a reinforcing structure using the same can prevent obstacles. You can do proper reinforcement while avoiding things.

FIG. 1 is a partially broken perspective view of a bridge provided with an example of a reinforcing structure according to the first embodiment. FIG. 2(a) is a cross-sectional view showing an example of the reinforcing structure in the first embodiment, and FIG. 2(b) is a cross-sectional view taken along line 2A-2A in FIG. 2(a). FIG. 3(a) is a front view showing an example of a reinforcing member in the first embodiment, and FIG. 3(b) is a sectional view taken along line 3A-3A in FIG. 3(a). 4A and 4B are diagrams showing an example of a reinforcing method in the first embodiment, FIG. 4A is a diagram showing a reinforcing member before being adhered to a flange, and FIG. FIG. 10 is a diagram showing the reinforcing member after being reinforced; FIG. 5 is a cross-sectional view showing an example of a reinforcing structure in the second embodiment. FIG. 6(a) is a cross-sectional view showing an example of the reinforcing structure in the third embodiment, and FIG. 6(b) is a cross-sectional view showing a first modified example of the reinforcing structure in the third embodiment. FIG. 7 is a partially broken perspective view showing a bridge provided with an example of a reinforcing structure according to the fourth embodiment. FIG. 8(a) is a front view showing an example of the reinforcing structure in the fourth embodiment, and FIG. 8(b) is a sectional view taken along line 8A-8A in FIG. 8(a). FIG. 9 is a plan view showing an example of the FRP plate material in the fourth embodiment. FIG. 10(a) is a front view showing an example of a reinforcing member in the fourth embodiment, and FIG. 10(b) is a sectional view taken along line 10A-10A in FIG. 10(a). FIG. 11 is a side view showing an enlarged example of the reinforcement structure in the fourth embodiment. 12A and 12B are diagrams showing an example of a reinforcing method in the fourth embodiment, FIG. 12A is a diagram showing the reinforcing member before being adhered to the flange, and FIG. FIG. 10 is a diagram showing the reinforcing member after being reinforced; FIG. 13(a) is a front view showing an example of the reinforcement structure in the fifth embodiment, and FIG. 13(b) is a sectional view taken along line 13A-13A in FIG. 13(a). FIG. 14 is a cross-sectional view showing an example of a reinforcing structure in the sixth embodiment. FIG. 15(a) is a cross-sectional view showing an example of a reinforcing structure in the seventh embodiment, and FIG. 15(b) is a cross-sectional view taken along line 15A-15A in FIG. 15(a). FIG. 16(a) is an enlarged side view showing an example of the reinforcing structure in the seventh embodiment, and FIG. 16(b) is an enlarged front view showing an example of the reinforcing structure in the seventh embodiment. be. FIG. 17(a) is a side view showing an example of the reinforcing structure in the eighth embodiment, and FIG. 17(b) is a plan view showing an example of the reinforcing structure in the eighth embodiment. FIG. 18(a) is a side view showing an example of the reinforcement structure in the ninth embodiment, and FIG. 18(b) is a plan view showing an example of the reinforcement structure in the ninth embodiment. FIG. 19 is a side view showing the specimen of Example 1. FIG. FIG. 20 is a cross-sectional view showing a test piece of Example 1. FIG. 21 is a plan view showing a reinforcing member in the test piece of Example 1. FIG. FIG. 22(a) is a diagram showing the strain distribution of Comparative Example 1, Inventive Example 1, and Inventive Example 2 in the positive bending test, and FIG. 22(b) is Comparative Example 1 in the negative bending test, the present invention FIG. 3 is a diagram showing strain distributions of Example 1 and Inventive Example 2; 23(a) is a diagram showing a specimen of CASE1 in Example 2, FIG. 23(b) is a diagram showing a specimen of CASE2 in Example 2, and FIG. FIG. 10 is a diagram showing a specimen of CASE 3 in Example 2; FIG. 24(a) is a diagram showing the positions of strain gauges in CASE1-1, CASE2-1 to CASE2-3 and CASE3-1, and FIG. 2 and CASE 3-3 strain gauge positions. 25 is a diagram showing the relationship between load and strain in Example 2. FIG. 26 is a diagram showing the relationship between the distance from the center of the specimen and the strain in Example 2. FIG. 27 is a cross-sectional view showing a test piece of Example 3. FIG. 28 is a plan view showing a reinforcing member in the test piece of Example 3. FIG. 29(a) is a diagram showing an adhesive layer between the steel material and the CFRP molded plate in the specimen of Example 3, and FIG. 29(b) is a diagram showing the adhesion layer between the steel material and the carbon fiber sheet in the specimen of Example 3. FIG. 10 is a diagram showing an adhesive layer; 30 is a diagram showing the relationship between the load and the span center vertical displacement in Example 3. FIG. 31 is a diagram showing strain distributions of Comparative Example 2 and Inventive Example 6. FIG. FIG. 32 is a cross-sectional view showing a specimen of Example 4. FIG. 33 is a plan view showing a reinforcing member in Inventive Example 7. FIG. FIG. 34(a) shows an overall view of the FEM analysis model, FIG. 34(b) shows a sectional view of the FEM analysis model, and FIG. 34(c) shows a bypass member in the FEM analysis model. FIG. 35 shows an axial stress ratio distribution map at the center of the lower surface of the steel plate in FEM analysis. FIG. 36 shows a positional diagram of strain gauges. 37 shows the load-span center vertical deflection relationship in Example 4. FIG. FIG. 38 shows the strain distribution of the upper flange steel material of each test piece at 200 kN before buckling, delamination, etc. of the test piece occurs.

An example of a reinforcing structure, a reinforcing member, and a reinforcing method according to embodiments of the present invention will be described below with reference to the drawings. In each figure, the height direction is defined as a third direction Z and intersects with the third direction Z. , for example, a second direction Y is another orthogonal plane direction. Also, the configuration in each drawing is schematically described for explanation, and for example, the size of each configuration and the comparison of the size of each configuration may differ from those in the drawings.

(First embodiment: reinforcement structure 100)
FIG. 1 is a partially broken perspective view showing a bridge 9 provided with an example of a reinforcing structure 100 according to the first embodiment. FIG. 2(a) is a front view showing an example of the reinforcing structure 100 in the first embodiment, and FIG. 2(b) is a cross-sectional view taken along line 2A-2A in FIG. 2(a). FIG. 3(a) is a front view showing an example of the reinforcing member 1 in the first embodiment, and FIG. 3(b) is a sectional view taken along line 3A-3A in FIG. 3(a).

The reinforcement structure 100 reinforces the existing I-section steel material 5 that supports the floor slab 91 of the bridge 9 from below, for example. The reinforcement structure 100 includes an I-section steel material 5 and a reinforcement member 1 . The I-section steel material 5 is used not only as a girder material for supporting the floor slab 91 but also as a beam material, for example.

<I-type cross section steel 5>
The I-section steel material 5 is placed on the bridge pier 92, and the material axis direction is arranged along the second direction Y. As shown in FIG. The I-section steel member 5 has a pair of flanges 51,52, a web 53 connecting the pair of flanges 51,52, and a vertical stiffener 54 provided between the pair of flanges 51,52. The flange 51 is the upper flange in the third direction Z, and the flange 52 is the lower flange. The floor slab 91 is placed on the upper surface 51 a of the flange 51 of the I-section steel material 5 . The I-section steel material 5 is provided with the reinforcing member 1 on the lower surface 51b of the flange 51, for example. The vertical stiffener 54 is, for example, a steel plate and is a stiffener for preventing buckling of the web 53 .

<Reinforcing member 1>
The reinforcing member 1 reinforces the I-section steel material 5 . A reinforcing member 1 includes an FRP plate 2 , a fiber sheet 3 and an adhesive layer 4 .

<FRP plate material 2>
The FRP plate material 2 is made of FRP (Fiber Reinforced Plastics), for example, a CFRP (Carbon Fiber Reinforced Plastics) plate material is used. Either thermosetting resin or thermoplastic resin can be used as the matrix resin of FRP, but vinyl ester resin and epoxy resin, which are thermosetting resins, are preferable. The FRP plate member 2 is a plate member having a rectangular outer shape, and is formed so that its longitudinal direction extends in the second direction Y. As shown in FIG. The FRP plate material 2 is adhered to the lower surface 51b of the flange 51 with the adhesive layer 4 interposed therebetween. The FRP plate material 2 has a first principal surface 2a on which a bonding surface to be adhered to the lower surface 51b of the flange 51 is formed, and a second principal surface 2b opposite to the first principal surface 2a. In this embodiment, the first main surface 2a is the upper surface of the FRP plate material 2, and the second main surface 2b is the lower surface of the FRP plate material 2. As shown in FIG.

The FRP plate material 2 preferably has a ratio of the value of the shear elastic modulus to the value of the axial elastic modulus of 0.05 or more and 6.00 or less, more preferably 0.15 or more and 0.35 or less. Thereby, the stress transmission loss in the axis-perpendicular direction at the notch portion can be reduced.

The FRP plate material 2 has a notch portion 21 formed by notching one side end in the first direction X, and a reduced portion 22 in which the size of the FRP plate material 2 is reduced by the notch portion 21 . A vertical stiffener 54 is inserted into the notch 21 . The reduced portion 22 is formed adjacent to the notch portion 21 in the first direction X. As shown in FIG. Note that the FRP plate material 2 may have a plurality of notch portions 21 formed therein.
Moreover, it is preferable that unidirectional members (unidirectional fiber sheets 29 described later) are laminated in directions of −45/0/45° with respect to the axial direction so that stress can be transmitted even in the cutout portions.

<Fiber sheet 3>
The fiber sheet 3 is a continuous fiber sheet (for example, tow sheet (registered trademark)) such as carbon fiber, glass fiber, basalt fiber, aramid fiber, or a plurality of FRP strands impregnated with resin and cured in advance and processed into a blind shape. A sheet (for example, Strand Sheet (registered trademark)) is used. The fiber sheet 3 is formed by, for example, laminating a plurality of fiber sheets such as carbon fiber, and bonding the plurality of layers to each other. Alternatively, a plate-shaped member may be bonded in advance.

The fiber sheet 3 is attached to the first main surface 2a of the FRP plate 2 so as to straddle the reduced portion 22 in the second direction Y. As shown in FIG. The fiber sheet 3 is attached to a portion of the FRP plate 2 where the adhesive layer 4 is not provided. The fiber sheet 3 is affixed so as to have a uniform length in the second direction Y with respect to the center line of the reduced portion 22. In order to secure a stress transmission section, the adhesion length should be at least 100 mm or more at both ends. It is preferable to keep

<Adhesive layer 4>
The adhesive layer 4 bonds the lower surface 51 b of the flange 51 and the first main surface 2 a of the FRP plate 2 to each other, and is provided between the lower surface 51 b of the flange 51 and the first main surface 2 a of the FRP plate 2 . The adhesive layer 4 preferably includes a high-stretch elastic resin layer, and includes, for example, a polyurea resin layer 41 and an epoxy resin layer 42 . The polyurea resin layer 41 contacts the flange 51 and is separated from the FRP plate material 2 . At this time, the epoxy resin layer 42 is brought into contact with the FRP plate 2 and separated from the flange 51 . This can prevent the polyurea resin layer 41 from peeling off early after the flange 51 yields.

The polyurea resin layer 41 may be in contact with the FRP plate 2 and may be separated from the flange 51 . The epoxy resin layer 42 contacts the flange 51 and is separated from the FRP plate material 2 . Thus, the polyurea resin layer 41 adheres to the FRP plate 2 and the epoxy resin layer 42 contacts the flange 51 . As a result, the operation of bonding the polyurea resin layer 41 on the FRP plate material 2 side and the operation of applying another resin layer on the flange 51 side can be performed simultaneously.

The adhesive layer 4 is made of a well-known resin material capable of adhering the lower surface 51b of the flange 51 and the first main surface 2a of the FRP plate 2 to each other. As the adhesive layer 4, for example, an acrylic resin can be used instead of the epoxy resin layer 42, and a high elongation elastic resin such as urea urethane resin can be used instead of the polyurea resin layer 41. FIG. The high elongation elastic resin is a resin having a tensile modulus of elasticity of 50 to 100 N/mm ² and an elongation at maximum tensile load of 300% or more. The maximum tensile load elongation of the high elongation elastic resin is preferably 300% to 1200%, more preferably 300% to 700%, and still more preferably 300% to 500%.

The adhesive layer 4 is preferably formed in advance on the FRP plate material 2, but may be formed on the FRP plate material at the construction site, or may be formed on the flange lower surface 51b.

(First embodiment: an example of a reinforcing method)
Next, an example of the reinforcement method in 1st Embodiment is demonstrated. 4A and 4B are diagrams showing an example of a reinforcing method in the first embodiment, FIG. 4A is a diagram showing the reinforcing member 1 before bonding to the flange 51, and FIG. 51 shows the reinforcing member 1 after gluing to 51; FIG. The reinforcing method includes an installation step of providing the reinforcing member 1 to the I-section steel material 5 .

First, as shown in FIG. 4( a ), in the installation step, the notch 21 cut out from the side end of the FRP plate 2 straddles the reduced portion 22 in which the dimension of the FRP plate 2 is reduced in the second direction Y. The fiber sheet 3 is attached to the first main surface 2a as shown. Then, in the installation step, the adhesive layer 4 is provided on the first main surface 2 a of the FRP plate material 2 . Then, in the installation step, the vertical stiffener 54 is inserted into the notch 21 of the FRP plate 2 .

Next, as shown in FIG. 4B, in the installation step, the adhesive layer 4 provided on the first main surface 2a is adhered to the lower surface 51b of the flange 51. Next, as shown in FIG.

An example of the reinforcement method in 1st Embodiment is completed by the above.

According to this embodiment, the reinforcing member 1 has the FRP plate material 2 adhered to the flange 51 and the fiber sheet 3 attached to the FRP plate material 2, and the FRP plate material 2 is notched from the side end. and a cutout portion 21 into which a vertical stiffener 54 is inserted, and a reduced portion 22 in which the size of the FRP plate material 2 is reduced by the cutout portion 21, and the fiber sheet 3 straddles the reduced portion 22. , is attached to the FRP plate material 2 . That is, the notch 21 is arranged so as to avoid the vertical stiffener 54 , and the fiber sheet 3 is arranged so as to compensate for the cross-sectional loss of the FRP plate material 2 caused by the notch 21 . Therefore, when a load is applied, stress is transmitted to the FRP plate 2 and the fiber sheet 3 for reinforcing the defective cross section, and the reinforcing member 1 bears the stress, thereby reducing the stress on the flange 51 . Therefore, it is possible to make the I-section steel material 5 provided with the vertical stiffener 54 exert a bending reinforcing effect against both positive bending and negative bending.

Further, according to this embodiment, the vertical stiffener 54 is inserted into the notch 21 of the FRP plate 2 to which the fiber sheet 3 is attached, and the FRP plate 2 is adhered to the flange 51 . Therefore, it is possible to construct the I-section steel material 5 provided with the vertical stiffener 54 in a short time.

According to this embodiment, the FRP plate 2 has a ratio of the value of the shear elastic modulus to the value of the axial elastic modulus of 0.05 or more and 6.00 or less. Thereby, the stress transmission loss at the notch 21 can be reduced. Therefore, it is possible to further exhibit the bending reinforcing effect. In particular, the FRP plate material 2 has a ratio of the value of the shear elastic modulus to the value of the axial elastic modulus of 0.15 or more and 0.35 or less, so that the stress transmission loss at the notch 21 can be greatly reduced. can. Therefore, it is possible to further exhibit the bending reinforcing effect.

According to this embodiment, the reinforcing member 1 further has an adhesive layer 4 for bonding the FRP plate material 2 to the flange 51, and the adhesive layer 4 includes a highly elastic resin layer such as a polyurea resin layer 41. . By using a highly elastic resin layer such as a polyurea resin layer 41 that can be deformed more flexibly than in the case of bonding with only an epoxy resin layer, the separation of the FRP plate material 2 from the I-shaped cross section steel material 5 can be prevented. It is possible to suppress the deformation, maintain the reinforcing effect against larger deformation, and exhibit the shear retarding effect of the high elongation elastic resin layer. Therefore, the FRP plate material 2 does not separate from the I-section steel material 5, and the bending reinforcing effect can be exhibited.

According to this embodiment, the reinforcing member 1 further has an adhesive layer 4 for adhering the FRP plate material 2 to the flange 51, and the adhesive layer 4 includes a high elongation elastic resin layer such as a polyurea resin layer 41. , the polyurea resin layer 41 or the like contacts the flange 51 and separates from the FRP plate material 2 . As a result, it is possible to suppress early separation of the high-stretch elastic resin layer after the flange 51 yields. For this reason, it becomes possible to exhibit the bending reinforcement effect further.

According to this embodiment, the reinforcing member 1 further has an adhesive layer 4 for bonding the FRP plate material 2 to the flange 51, and the adhesive layer 4 includes a high elongation elastic resin layer such as a polyurea resin layer 41, Other resin layers such as an epoxy resin layer 42 different from the polyurea resin layer 41 are included, and the high elongation elastic resin layer such as the polyurea resin layer 41 is adhered to the FRP plate 2, and the other resin layers 51 is contacted. As a result, the work of bonding the high-stretch elastic resin layer on the FRP plate material 2 side and the work of applying another resin layer on the flange 51 side can be performed simultaneously. Therefore, construction can be completed in a shorter time.

According to this embodiment, the fiber sheet 3 is attached to the first main surface 2a. As a result, the fiber sheet 3 is arranged at a position farther apart from the neutral axis of the I-section steel material 5 than when the fiber sheet 3 is attached to the second main surface 2b. Therefore, the moment of inertia of the area of the reinforcing structure 100 as a whole can be increased, and the bending reinforcing effect can be further exhibited.

According to this embodiment, the FRP plate material 2 is adhered to the lower surface 51b of the upper flange 51 . Therefore, even when a structure such as the floor slab 91 is provided on the upper surface 51 a of the flange 51 , the I-section steel material 5 can exhibit a bending reinforcing effect.

According to this embodiment, the reinforcing member 1 has the FRP plate material 2 attached to the flange 51 . As a result, when the steel member is reinforced with the backing plate, the weight can be significantly reduced as compared with the case where the web bypass member made of the metal plate is joined by bolts or welding. Therefore, an increase in dead load after reinforcement can be suppressed.

(Second embodiment: reinforcement structure 100)
Next, an example of the reinforcement structure 100 in 2nd Embodiment is demonstrated. Hereinafter, detailed descriptions of the same configurations as those of the above-described first embodiment will be omitted. FIG. 5 is a cross-sectional view showing an example of the reinforcing structure 100 in the second embodiment. As shown in FIG. 5, in this embodiment, the FRP plate material 2 is adhered to the upper flange 51 . The fiber sheet 3 is attached to the second main surface 2b.

In particular, according to this embodiment, the fiber sheet 3 is attached to the second main surface 2b. As a result, even when a structure such as the floor slab 91 is provided on the upper surface 51a of the flange 51, the bending reinforcement effect is obtained for the I-section steel material 5 without being subject to the thickness limitation of the fiber sheet 3. It is possible to demonstrate

(Third Embodiment: Reinforcing Structure 100)
Next, an example of the reinforcement structure 100 in 3rd Embodiment is demonstrated. FIG. 6(a) is a cross-sectional view showing an example of the reinforcing structure 100 in the third embodiment, and FIG. 6(b) is a cross-sectional view showing a first modified example of the reinforcing structure 100 in the third embodiment. . As shown in FIG. 6, in this embodiment, the FRP plate material 2 is adhered to the lower flange 52 . The FRP plate 2 has a first main surface 2a formed with a bonding surface to be adhered to the upper surface 52a of the flange 52, and a second main surface 2b opposite to the first main surface 2a. In this embodiment, the first main surface 2a is the lower surface of the FRP plate material 2, and the second main surface 2b is the upper surface of the FRP plate material 2. As shown in FIG.

As shown in FIG. 6(a), the fiber sheet 3 is attached to the first main surface 2a of the FRP plate material 2. As shown in FIG.

As shown in FIG. 6(b), the fiber sheet 3 is attached to the second main surface 2b of the FRP plate material 2. As shown in FIG.

In particular, according to this embodiment, the FRP plate material 2 is adhered to the lower flange 52 . As a result, the FRP plate material 2 can be adhered to the lower flange 52 without requiring upward work. Therefore, it is possible to reduce the burden on the worker during construction.

In particular, according to this embodiment, the fiber sheet 3 is attached to the first main surface 2a. As a result, the fiber sheet 3 is arranged at a position farther apart from the neutral axis of the I-section steel material 5 than when the fiber sheet 3 is attached to the second main surface 2b. Therefore, the moment of inertia of the area of the reinforcing structure 100 as a whole can be increased, and the bending reinforcing effect can be further exhibited.

In particular, according to this embodiment, the fiber sheet 3 is attached to the second main surface 2b. As a result, even when a structure such as the pier 92 is provided on the lower surface 52b of the flange 52, the bending reinforcement effect can be obtained for the I-section steel material 5 without being subject to the thickness limitation of the fiber sheet 3. It is possible to demonstrate.

(Fourth embodiment: reinforcing structure 100)
As shown in FIGS. 7, 8(a) and 8(b), the reinforcing structure 100 reinforces the existing I-section steel material 5 that supports the floor slab 91 of the bridge 9 from below, for example. The reinforcement structure 100 includes an I-section steel material 5 as a steel member and a reinforcement member 1 . The I-section steel material 5 is used not only as a girder material for supporting the floor slab 91 but also as a beam material, for example.

<Reinforcing member 1>
The reinforcing member 1 reinforces the I-section steel material 5 . A reinforcing member 1 includes an FRP plate material 2 and an adhesive layer 4 .

<FRP plate material 2>
The FRP plate 2 is attached to the lower surface 51b of the flange 51 with the adhesive layer 4 interposed therebetween.

As shown in FIG. 9, the FRP plate material 2 is formed by laminating a plurality of unidirectional fiber sheets 29 in which continuous reinforcing fibers such as carbon fiber, glass fiber, basalt fiber, and aramid fiber are aligned in one direction and impregnated with resin. consists of The unidirectional fiber sheet 29 is made of FRP (Fiber Reinforced Plastics), for example CFRP (Carbon Fiber Reinforced Plastics). When CFRP is used, the unidirectional fiber sheet 29 is preferably a carbon fiber sheet having a tensile strength of 2300 N/mm ² or more and an elastic modulus of 280 GPa to 450 GPa as measured by JIS A1191:2004. .

Either thermosetting resin or thermoplastic resin can be used as the matrix resin of FRP, but vinyl ester resin and epoxy resin, which are thermosetting resins, are preferable. The FRP plate material 2 is formed so that its longitudinal direction extends in the second direction Y, and the longitudinal ends 28 of the FRP plate material 2 avoid stress concentration, workability, and do not provide unnecessary portions that do not participate in stress transmission. From a point of view, it is desirable to taper the end portion 28 at an arbitrary angle in plan view. The taper angle of the end portion 28 is not particularly limited, but it is preferably an angle along at least two orientation directions other than the main direction of the unidirectional fiber sheets forming the FRP plate 2 .

In the FRP plate 2, the fiber orientation of the unidirectional fiber sheet 29 oriented in the main direction and the fiber orientation of the other unidirectional fiber sheets 29 are different. As a result, stress is transmitted from one attachment portion 23a of the FRP plate 2 to the other attachment portion 23b via the bypass portion 24, and the stress on the I-section steel member 5 can be reduced. For example, the FRP plate material 2 has a unidirectional fiber sheet 29 whose fiber orientation is the second direction Y from one attachment portion 23a to the other attachment portion 23b (the P1 direction in FIG. 9, also called the "main direction"). and a unidirectional fiber sheet 29 whose fibers are oriented in a direction (P2 direction in FIG. 9) inclined by an angle θ1 (for example +45°) with respect to the second direction Y, and an angle θ2 (for example −45°), and a unidirectional fiber sheet 29 having a fiber orientation in the inclined direction (P3 direction in FIG. 9). Thus, the FRP plate material 2 has fiber orientation in at least three directions, that is, the main direction and at least two directions different from the main direction, and the unidirectional fiber sheet 29 having the fiber orientation in the second direction Y is formed. If so, the fiber orientations of the unidirectional fiber sheet 29 in at least two other directions are preferably tilted by an absolute value of about 15° to 75° with respect to the second direction Y, and tilted by about 30° to 60°. more preferably, and most preferably inclined at 45°.
In addition, when taking fiber orientation of 4 axes or more, the fiber orientation of the orthogonal|vertical (90 degree) direction may be included in a main direction.

As shown in FIG. 10, the FRP plate material 2 has a pair of attachment portions 23 (23a and 23b), a bypass portion 24, and a notch portion 21. As shown in FIG. The attachment portions 23 are formed on both sides in the second direction Y with the vertical stiffener 54 interposed therebetween. The attachment portion 23 is provided with the adhesive layer 4 and is attached to the lower surface 51 b of the flange 51 . The bypass portion 24 is formed adjacent to the attachment portion 23 in the first direction X, bypasses the vertical stiffener 54 and connects the pair of attachment portions 23 . The notch portion 21 is formed by notching one side end in the first direction X, and the notch portion 21 forms a reduced portion 22 in which the width dimension of the FRP plate material 2 is reduced. The reduced portion 22 is formed in the bypass portion 24 . A vertical stiffener 54 is inserted into the notch 21 . The notch 21 is cut out, for example, in a trapezoidal shape. Although the shape is arbitrary, it is preferable that the shape conforms to the fiber orientation of the unidirectional fiber sheet 29 that constitutes the FRP plate 2 . In addition, it is desirable that the fiber orientation of the unidirectional fiber sheet in the entire FRP plate is line symmetrical with respect to the main direction.

Various dimensions of the FRP plate material 2 are not specified because the FRP plate material 2 is designed depending on the structure to be reinforced.
In addition, the length of the transmission section L from the ends of the pair of affixed portions 23 (23a, 23b) provided on the FRP plate 2 to the notch portion 21 is transmitted from one of the affixed portions through the bypass portion 24. From the viewpoint of preventing the stress applied locally, the length is desirably 300 mm or more, and more desirably 600 mm or more.

As shown in FIG. 11, the thickness of the FRP plate material 2 is preferably tapered toward the end 28 side in the main direction. The tapered shape may be formed by scraping or cutting the end of a plate-shaped unidirectional fiber sheet such as a rectangular parallelepiped, or by stacking a plurality of unidirectional fiber sheets 29 having similar shapes that differ only in size. may be formed by

<Adhesive layer 4>
The adhesive layer 4 bonds the lower surface 51 b of the flange 51 and the attachment portion 23 of the FRP plate 2 to each other, and is provided between the lower surface 51 b of the flange 51 and the attachment portion 23 of the FRP plate 2 . The adhesive layer 4 desirably contains a high elongation elastic resin layer, for example, an epoxy resin layer.

The adhesive layer 4 is made of a well-known resin material capable of bonding the lower surface 51b of the flange 51 and the attachment portion 23 of the FRP plate 2 to each other. As the adhesive layer 4, for example, instead of the epoxy resin layer, an acrylic resin layer, a polyurea resin layer, a urea urethane resin, or other highly elastic resin may be used. A high elongation elastic resin is a resin having a tensile modulus of elasticity of 50 to 100 N/mm ² and an elongation at maximum tensile load of 300% or more. The maximum tensile load elongation of the high elongation elastic resin is preferably 300% to 1200%, more preferably 300% to 700%, and still more preferably 300% to 500%.

(Fourth Embodiment: An example of a method for reinforcing a steel member)
Next, an example of a reinforcing method for steel members in the fourth embodiment will be described. As shown in FIGS. 12( a ) and 12 ( b ), the steel member reinforcement method includes an installation step of installing the reinforcement member 1 on the I-section steel material 5 .

First, as shown in FIG. 12( a ), in the installation step, the adhesive layer 4 is provided on the attachment portion 23 . Then, as shown in FIG. 12(b), in the installation process, a pair of attaching portions 23 are attached to the lower surface 51b of the flange 51 via the adhesive layer 4 so as to bypass the vertical stiffener 54 by the bypass portion 24. wear.

An example of the reinforcement method in 1st Embodiment is completed by the above.

According to this embodiment, the reinforcing member 1 has the FRP plate material 2 attached to the flange 51 . As a result, when the steel member is reinforced with the backing plate, the weight can be significantly reduced as compared with the case where the web bypass member made of the metal plate is joined by bolts or welding. Therefore, an increase in dead load after reinforcement can be suppressed.

According to this embodiment, the reinforcing member 1 has an FRP board 2 in which a plurality of unidirectional fiber sheets 29 are laminated. and a bypass portion 24 for connecting the pair of attached portions 23 by detouring the vertical stiffener 54, and the fiber orientation in the FRP plate material 2 is It has a main direction from the sticking portion 23a to the other sticking portion 23b and at least two directions different from the main direction. As a result, when a load acts on the flange 51 of the I-section steel material 5, stress can be smoothly transmitted from one attachment portion 23a to the other attachment portion 23b via the bypass portion 24. In this way, the stress on the flange 51 can be reduced by the reinforcing member 1 taking charge of the stress. For this reason, it is possible to exert a bending reinforcing effect against both positive bending and negative bending at the joint between the flange 51 and the vertical stiffener 54 in the I-section steel material 5 .

Further, according to this embodiment, the attachment portion 23 of the FRP plate material 2 is attached to the flange 51 . This makes it possible to easily reinforce the steel member with the reinforcing member 1 .

Furthermore, according to the present embodiment, a bypass portion 24 for connecting the pair of attachment portions 23 by detouring the second steel material such as the vertical stiffener 54 is formed. As a result, even in locations where it is difficult to reinforce due to the presence of obstacles such as bolts, backing plates, stiffening plates, etc., it is possible to perform appropriate reinforcement while avoiding obstacles. can.

According to the present embodiment, the fiber orientations in at least two directions that are oriented in directions different from the main direction are inclined at an absolute value of 15° to 75° from the main direction, and are line symmetrical about the main direction. It's becoming As a result, the isotropy of the FRP plate material 2 can be enhanced, and stress can be efficiently and uniformly transmitted. For this reason, it is possible to further exhibit the bending reinforcing effect against both compression and tension.

According to this embodiment, the notch 21 has a shape along the fiber orientation of the unidirectional fiber sheet 29 . This maintains the continuity of the fibers oriented in the direction along the notch, enabling smooth stress transmission from one attachment portion 23a to the other attachment portion 23b via the bypass portion 24. becomes.

According to this embodiment, the reinforcing member 1 further includes an adhesive layer 4 between the attachment portion 23 and the flange 51, and the adhesive layer 4 includes a high-stretch elastic resin layer. As a result, it is possible to suppress early separation of the high-stretch elastic resin layer after the flange 51 yields. For this reason, it becomes possible to exhibit the bending reinforcement effect further.

According to this embodiment, the thickness of the FRP plate material 2 is tapered toward the end portion 28 side in the main direction. As a result, sudden changes in the cross section due to the FRP plate material 2 can be suppressed, and stress concentration at the end portions 28 of the FRP plate material 2 can be suppressed. For this reason, the stress is transmitted more smoothly from one sticking portion 23a to the other sticking portion 23b via the bypass portion 24. As shown in FIG.

According to this embodiment, the FRP plate 2 has a ratio of the value of the shear elastic modulus to the value of the axial elastic modulus of 0.05 or more and 6.00 or less. Thereby, the stress transmission loss at the notch 21 can be reduced. Therefore, it is possible to further exhibit the bending reinforcing effect. In particular, the FRP plate material 2 has a ratio of the value of the shear elastic modulus to the value of the axial elastic modulus of 0.15 or more and 0.35 or less, so that the stress transmission loss at the notch 21 can be greatly reduced. can. Therefore, it is possible to further exhibit the bending reinforcing effect.

According to this embodiment, the attachment portion 23 of the FRP plate material 2 is attached to the lower surface 51 b of the upper flange 51 . Therefore, even when a structure such as the floor slab 91 is provided on the upper surface 51 a of the flange 51 , the I-section steel material 5 can exhibit a bending reinforcing effect.

(Fifth embodiment: reinforcing structure 100)
Next, an example of the reinforcement structure 100 in 5th Embodiment is demonstrated. As shown in FIGS. 13(a) and 13(b), in this embodiment, the reinforcing member 1 includes an FRP plate 2, a fiber sheet 3, and an adhesive layer 4, as in the first embodiment. Prepare. In this case, as in the first embodiment, the fiber sheet 3 is attached to the FRP plate material 2 so as to straddle the reduced portion 22 .

(Sixth embodiment: reinforcement structure 100)
Next, an example of the reinforcement structure 100 in 6th Embodiment is demonstrated. As shown in FIG. 14, in the present embodiment, the attachment portion 23 of the FRP plate material 2 is attached to the upper surface 52a of the lower flange 52 with the adhesive layer 4 interposed therebetween.

In particular, according to this embodiment, the attachment portion 23 of the FRP plate material 2 is attached to the lower flange 52 . As a result, the FRP plate material 2 can be adhered to the lower flange 52 without requiring upward work. Therefore, it is possible to reduce the burden on the worker during construction.

(Sixth embodiment: reinforcement structure 100)
Next, an example of the reinforcement structure 100 in 6th Embodiment is demonstrated. As shown in FIGS. 15(a), 15(b), 16(a), and 16(b), in this embodiment, the reinforcing member 1 has a continuous fiber between the attachment portion 23 and the flange 51. Further comprising a material 8 and adhesive layers 4, 6, the continuous fibrous material 8 is provided in a pair spaced apart on both sides of the vertical stiffener 54 therebetween. The continuous fiber material 8 reinforces the flange 51, and mainly reinforces the portion where the flange 51 and the vertical stiffener 54 are not connected.

<Continuous fiber material 8>
The continuous fiber material 8 is a continuous fiber sheet (for example, tow sheet (registered trademark)) such as carbon fiber, glass fiber, basalt fiber, aramid fiber, or a plurality of FRP strands impregnated with resin and cured in advance and processed into a blind shape. A sheet (for example, Strand Sheet (registered trademark)) is used. The continuous fiber material 8 is formed by, for example, laminating a plurality of fiber sheets such as carbon fibers and adhering the plurality of layers to each other. Alternatively, it may be preformed into a plate shape and adhered. The continuous fiber material 8 is constructed by laminating a plurality of unidirectional fiber sheets in which the fiber orientation is oriented in a predetermined direction. may be oriented.

The continuous fiber materials 8 are provided on both sides of the vertical stiffener 54 so as to be spaced apart from each other. The continuous fiber material 8 is attached to the attaching portion 23 of the FRP plate material 2 via the adhesive layer 6 and is attached to the flange 51 via the adhesive layer 4 .

<Adhesive layer 4>
The adhesive layer 4 bonds the lower surface 51 b of the flange 51 and the continuous fiber material 8 to each other, and is provided between the lower surface 51 b of the flange 51 and the continuous fiber material 8 . The adhesive layer 4 desirably includes a high elongation elastic resin layer, and includes, for example, a polyurea resin layer 41 and an epoxy resin layer 42 as shown in FIG. The polyurea resin layer 41 contacts the flange 51 and the epoxy resin layer 42 contacts the continuous fibrous material 8 . This can prevent the polyurea resin layer 41 from peeling off early after the flange 51 yields.

Although illustration is omitted, the polyurea resin layer 41 may be adhered to the continuous fiber material 8 and the epoxy resin layer 42 may be adhered to the flange 51 . As a result, the operation of bonding the polyurea resin layer 41 on the continuous fiber material 8 side and the operation of applying another resin layer on the flange 51 side can be performed simultaneously.

The adhesive layer 4 is made of a well-known resin material capable of adhering the lower surface 51b of the flange 51 and the continuous fiber material 8 to each other. As the adhesive layer 4, for example, an acrylic resin can be used instead of the epoxy resin layer 42, and a high elongation elastic resin such as urea urethane resin can be used instead of the polyurea resin layer 41. FIG. The high elongation elastic resin is a resin having a tensile modulus of elasticity of 50 to 100 N/mm ² and an elongation at maximum tensile load of 300% or more. The maximum tensile load elongation of the high elongation elastic resin is preferably 300% to 1200%, more preferably 300% to 700%, and still more preferably 300% to 500%.

The adhesive layer 4 is preferably formed on the continuous fiber material 8 in advance, but may be formed on the continuous fiber material 8 at the construction site, or may be formed on the lower surface 51 b of the flange 51 .

<Adhesive layer 6>
The adhesive layer 6 bonds the continuous fiber material 8 and the FRP plate material 2 together, and is provided between the attachment portion 23 and the continuous fiber material 8 . The adhesive layer 6 is not particularly limited as long as it can firmly bond the continuous fiber material 8 and the FRP plate material 2, and any adhesive such as an epoxy adhesive, an acrylic adhesive, or a urethane adhesive can be used. is preferably an epoxy adhesive.

In particular, according to this embodiment, the reinforcing member 1 further comprises a continuous fiber material 8 between the affixing portion 23 and the flange 51 , the continuous fiber material 8 being arranged on both sides of the vertical stiffener 54 . A pair is provided spaced apart. As a result, the continuous fiber material 8 reinforces the portion that is not the joint between the flange 51 and the vertical stiffener 54, and the FRP plate material 2 extends from one attachment portion 23 through the bypass portion 24 to the other attachment portion. 23 is stress-transmitted. For this reason, it is possible to exert a bending reinforcing effect against both positive bending and negative bending at the joints between the flange 51 and the vertical stiffener 54 in the I-section steel material 5 and at the places other than the joints.

(Seventh embodiment: reinforcing structure 100)
Next, an example of the reinforcement structure 100 in 7th Embodiment is demonstrated. As shown in FIGS. 17(a) and 17(b), the reinforcing structure 100 includes one steel plate 71 as a first steel member and an out-of-plane gusset as a second steel member joined to the one steel plate 71 by welding. 72 and reinforce the steel member 7. The out-of-plane gussets 72 are arranged substantially perpendicular to the steel plate 71 .

According to this embodiment, the reinforcing member 1 has the FRP plate material 2 attached to the steel plate 71 . As a result, when the steel member is reinforced with the backing plate, the weight can be significantly reduced as compared with the case where the web bypass member made of the metal plate is joined by bolts or welding. Therefore, an increase in dead load after reinforcement can be suppressed.

According to this embodiment, the reinforcing member 1 has an FRP board 2 in which a plurality of unidirectional fiber sheets 29 are laminated. A pair of affixed portions 23 to be affixed and a bypass portion 24 for connecting the pair of affixed portions 23 bypassing the out-of-plane gusset 72 are formed. It has a main direction from the portion 23a to the other sticking portion 23b and at least two directions different from the main direction. As a result, when a load acts on the steel plate 71 of the steel member 7, stress can be smoothly transmitted from one attachment portion 23a through the bypass portion 24 to the other attachment portion 23b. Thus, the stress of the steel plate 71 can be reduced by the reinforcement member 1 taking charge of the stress. For this reason, it is possible to exert a bending reinforcement effect against both positive bending and negative bending at the joint between the steel plate 71 and the out-of-plane gusset 72 in the steel member 7 .

Further, according to this embodiment, the attachment portion 23 of the FRP plate material 2 is attached to the steel plate 71 . This makes it possible to easily reinforce the steel member with the reinforcing member 1 .

10, the attachment portion 23 has a size to cover a part of the entire width of the steel plate 71, but may have a size to cover the entire width of the steel plate 71. FIG.

(Eighth embodiment: reinforcement structure 100)
Next, an example of the reinforcement structure 100 in 8th Embodiment is demonstrated. As shown in FIGS. 18A and 18B, the reinforcing structure 100 includes two steel plates 71 as first steel members and a splice plate 73 as a second steel member joined to the steel plates 71 by bolts 74. and reinforces the steel member 7 having. The splicing plate 73 connects the two steel plates 71 together.

According to this embodiment, the reinforcing member 1 has the FRP plate material 2 attached to the steel plate 71 . As a result, when the steel member is reinforced with the backing plate, the weight can be significantly reduced as compared with the case where the web bypass member made of the metal plate is joined by bolts or welding. Therefore, an increase in dead load after reinforcement can be suppressed.

According to this embodiment, the reinforcing member 1 has the FRP plate material 2 in which a plurality of unidirectional fiber sheets 29 are laminated. A pair of affixing portions 23 to be affixed and a bypass portion 24 for connecting the pair of affixing portions 23 bypassing the splicing plate 73 are formed. It has a main direction from the portion 23a to the other sticking portion 23b and at least two directions different from the main direction. As a result, when a load acts on the steel plate 71 of the steel member 7 , stress can be smoothly transmitted from one attachment portion 23 a to the other attachment portion 23 b via the bypass portion 24 . Thus, the stress of the steel plate 71 can be reduced by the reinforcement member 1 taking charge of the stress. Therefore, it is possible to exert a bending reinforcing effect against both positive bending and negative bending at the joint between the steel plate 71 and the splicing plate 73 in the steel member 7 .

Further, according to this embodiment, the attachment portion 23 of the FRP plate material 2 is attached to the steel plate 71 . This makes it possible to easily construct the reinforcing member 1 .

18, the attachment portion 23 of the FRP plate material has a size to cover a part of the full width of the steel plate 71, but may have a size to cover the full width of the steel plate 71. FIG. In addition, the FRP plate material 2 may be attached to the back surface of the steel plate 71 (the opposite surface sandwiching the splicing plate 73 and the steel plate 71 in FIG. 18).

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

In Example 1, a bending test was performed on the prepared specimen to examine the bending reinforcing effect.

<Specimen>
FIG. 19 is a side view showing the specimen of Example 1. FIG. FIG. 20 is a cross-sectional view showing a test piece of Example 1. FIG. In Example 1, specimens of Comparative Example 1, Inventive Example 1, and Inventive Example 2 were produced using the bending mode and the presence or absence of reinforcement of the upper and lower flanges as parameters. The specimen was an I-section steel material with a total length of 6,300 mm and a web height of 1,000 mm. Also, a vertical stiffener and a horizontal stiffener were installed in the specimen. The specimen had a width of 150 mm at the upper and lower flanges of the central plate girder and a thickness of 6 mm. The specimen had a width of 200 mm at the upper and lower flanges of the plate girders at both ends, and a thickness of 12 mm. This preceded the failure in the central plate girder. In this test, the same plate girders at both ends were used, and the test was performed while only the center plate girders were replaced.

Table 1 shows the outline of the specimen. In the test piece of Inventive Example 1, a reinforcing member was adhered to the upper flange via an adhesive layer. The reinforcing member includes a CFRP molded plate having a notch, and a carbon fiber strand sheet attached so as to straddle the reduced size portion of the CFRP molded plate due to the notch. A CFRP molded plate was produced from a carbon fiber sheet and an epoxy resin by a hand lay-up molding method. In addition, in the specimen of Inventive Example 2, a carbon fiber sheet was further adhered to the lower surface of the lower flange. In Comparative Example 1, no reinforcing member was used for reinforcement.

Table 2 shows an overview of the fiber sheets. The carbon fiber sheets in Table 2 are used to produce a CFRP molded plate, and are also adhered to the lower surface of the lower flange of Inventive Example 2. The carbon fiber strand sheets in Table 2 are attached to the contracted portion of the reinforcing member used in Inventive Examples 1 and 2.

Table 3 shows an overview of the resins used for the specimens. Epoxy-based resins are used to produce CFRP molded plates. Polyurea putty and epoxy putty are used for adhesion between the flange and the CFRP molded plate. The bonding between the carbon fiber strand sheet and the CFRP molded plate was performed based on the "Repair/Reinforcement Method for Steel Structures Using Carbon Fiber Sheets Design and Construction Manual" (Highway Technical Research Institute, 2013).

Table 4 shows an outline of the CFRP molded plate. The elastic moduli in Table 4 are actual values measured by a tensile test specified in JIS K7165.

21 is a plan view showing a reinforcing member in the test piece of Example 1. FIG. The shape of the CFRP molded plate was a flat plate in consideration of the simplicity of fabrication, and a notch was made to avoid the vertical stiffener at the center of the specimen. The size of the notch was set so that the vertical stiffener at the center of the specimen could pass through, and the corners of the notch were arc-shaped. The CFRP molded plate had a total width of 100 mm and a length of 1,600 mm, which is a length that ensures a fixing length of 200 mm from the plate thickness change point (outside) of the specimen. A carbon fiber strand sheet with a width of 30 mm was adhered to the upper surface of the CFRP molded plate using an epoxy resin in order to reinforce the cross-sectional defect of the notch. The adhesion length of the carbon fiber strand sheet was set to 200 mm from both ends of the notch of the outermost layer, and the shift amount was set to 25 mm at both ends of each layer.

The fiber orientation of the CFRP molded plate is set to a ratio of 1/2/1 layers in the -45/0/45° direction with respect to the axial direction so that stress can be transmitted even in the notch part. The flexural rigidity of the central portion of the specimen was determined to increase by 25%, and the number of laminations was [0°/±45°/0°] ₄ (16 layers in total). The stacking order was symmetrical in the plate thickness direction. The number of layers of the carbon fiber strand sheet in the notch portion was determined so that the cross-sectional rigidity of the carbon fiber strand sheet was equal to the cross-sectional rigidity of the defect cross section, and was seven layers. The carbon fiber strand sheet was adhered to the CFRP molded plate using epoxy putty.

For adhesion of the CFRP molded plate to the upper flange, a polyurea putty layer was provided on the steel material side in the conventional method, but in this test, a polyurea putty layer was provided on the CFRP molded plate side. By doing so, the CFRP molding plate side and the steel material side can be worked at the same time, which leads to labor saving in construction. As for the bonding procedure, both the steel material and the CFRP molded plate were cleaned in the bonding range, the steel material was coated with epoxy primer, and the CFRP molded plate was coated with urethane primer and then polyurea putty. After drying the epoxy primer and polyurea putty, the epoxy putty was used to adhere to the lower surface of the upper flange. The procedure for bonding the carbon fiber sheet to reinforce the lower flange was performed based on the "Repair and Reinforcement Construction Method for Steel Structures Using Carbon Fiber Sheets Design and Construction Manual" (Highway Research Institute, 2013).

<Test overview>
The test was a four-point bending test with a span length of 6,000 mm, a constant bending section of 2,500 mm, and a shear section of 1,750 mm. The loading was monotonic loading by displacement control, and the loading was continued until the load stopped increasing.

Moreover, the strain of the upper flange was measured with a strain gauge in the bending test. Three strain gauges were placed on the upper surface of the flange of the specimen at the center of the specimen in the material axis direction, and at ±100 mm, ±300 mm, and ±500 mm from the center of the specimen at a total of 7 points in the direction perpendicular to the material axis. 21 sheets were installed. The strain measured was the strain of the upper flange of each test piece at 200 kN before buckling or peeling occurred.

<Test result: Destruction status>
Table 5 shows the maximum load, displacement at maximum load, and fracture conditions for each test.

In the positive bending test, the CFRP molded plate underwent compression failure at 558 kN for Invention Example 1 and at 555 kN for Invention Example 2. For this reason, in present invention example 1, the maximum load was about the same as in comparative example 1, but in present invention example 2, in which the carbon fiber sheet was adhered and reinforced to the lower flange, the carbon fiber sheet on the lower flange peeled off even at the end. , the maximum load was higher than that of Comparative Example 1, partly because damage such as breakage was not confirmed.

In the negative bending test, the CFRP molded plate peeled from the notched end between the steel material and the epoxy resin at 575 kN for Example 1 of the present invention, and at 675 kN for Example 2 of the present invention. The CFRP molded plate on the side without was also peeled off afterwards. In addition, in Inventive Example 2, the carbon fiber sheet of the lower flange was also compression-broken at the end. Therefore, in this test, the maximum load of Inventive Example 1 and Inventive Example 2 was the same as that of Comparative Example 1. In this test, the position of the polyurea putty was placed on the side of the CFRP molded plate for labor saving in construction. However, there is a possibility that brittle exfoliation occurred between the steel material and the epoxy resin before the steel material yielded, and the polyurea putty did not exert its exfoliation suppressing effect.

<Test result: distortion of upper flange>
FIG. 22(a) is a diagram showing the strain distribution of Comparative Example 1, Inventive Example 1, and Inventive Example 2 in the positive bending test, and FIG. 22(b) is Comparative Example 1 in the negative bending test, the present invention FIG. 3 is a diagram showing strain distributions of Example 1 and Inventive Example 2; In FIG. 22, the horizontal axis is the distance from the center of the specimen, and the vertical axis is the strain. FIG. 22 shows the upper flange strain distribution of each test piece at 200 kN before buckling, peeling, etc. occurs in the test piece.
The values of the strain distribution diagram shown in FIG. 22 are average strain values read from three strain gauges arranged in the direction perpendicular to the material axis. In addition, "Comparative Example 1 (calculated value)", "Inventive Example 1 (calculated value)", and "Inventive Example 2 (calculated value)" shown in FIG. Calculated according to theory. Repair and Reinforcement Method of Steel Structures Using Carbon Fiber Sheets Design and Construction Manual” (Highway Technology Research Institute Co., Ltd., 2013), when polyurea putty is used for bonding, the effect of polyurea putty is to create a completely synthetic cross section. Therefore, it is indicated that the cross-sectional area of the carbon fiber is multiplied by the stress reduction factor for design. This stress reduction factor is a value determined by the number of laminated carbon fiber sheets, bonding length, edge treatment method, etc., but the stress reduction factor for reinforcement by the CFRP molded plate used in this test has not been examined. Therefore, in addition to using a completely composite cross section without considering the stress reduction factor, the stress transfer section to the carbon fiber reinforcement (200 mm at both ends of the carbon fiber reinforcement) is set without considering vertical stiffeners and horizontal stiffeners. Considering this, only the central 1,200 mm section is a reinforced cross section and the other sections are non-reinforced cross sections, and is a calculation result for a cross section without a carbon fiber strand sheet and a notch.

In the positive bending test, the distribution was such that a large compressive strain occurred in each specimen and the center of the specimen. In addition, compared with Comparative Example 1, it can be confirmed that the stress is reduced at all points measured in both Inventive Examples 1 and 2, and the average strain of all 21 strain gauges on the upper flange of each specimen However, when compared with Comparative Example 1, the stress was reduced by 13% in Inventive Example 1 and by 25% in Inventive Example 2. From the strain distributions of Inventive Example 1 and Inventive Example 2, the strain was small at the points ±100 mm from the center, and the strain at the center was greater than the strain at the points ±100 mm. This is the part where there is no notch in the CFRP molded plate and where there is a carbon fiber strand sheet around ±100 mm from the center. It is thought that the strain at the center of the specimen was small, and that the strain was greater than the strain at the ±100 mm point because there was a notch in the center of the specimen. Compared to the calculated value, the strain of the upper flange at the center of the specimen is larger, but this is a calculated value when the reinforced cross section is assumed to be a completely synthetic cross section, so the calculation takes into account the stress reduction factor due to the polyurea resin. is considered to match the calculated value by performing

Similar to the positive bending test, the negative bending test also has a distribution in which the upper flange tensile strain in the center of the specimen is large. When the strains of all 21 strain gauges on the upper flange of the specimen were averaged and compared with Comparative Example 1, the stress was reduced by 15% in Inventive Example 1 and by 18% in Inventive Example 2. In the negative bending test, the strain distributions of Inventive Example 1 and Inventive Example 2 were similar to the positive bending test, with small strain at points ±100 mm from the center and greater strain at points ±100 mm at the center. . When compared with the calculated value, it is considered that the calculated value matches the calculated value by performing the calculation considering the stress reduction coefficient due to the polyurea resin as in the positive bending test result.

From the above bending test results and analysis, even when the upper flange is reinforced with a CFRP molded plate with a notch, stress is transmitted to the carbon fiber strand sheet for reinforcing the defect cross section at the notched portion, and the CFRP molded plate is strengthened. It was confirmed that the stress of the steel material was reduced by taking charge of the stress. In order to increase the maximum load of the test piece, the CFRP molded plate should be reinforced with a CFRP molded plate made of a carbon fiber sheet having a higher strength than the carbon fiber sheet used in this test so that the CFRP molded plate does not break due to compression.

In the negative bending test of the I-shaped steel material of Example 1, it was confirmed that the CFRP molded plate separated before the steel material yielded. The peeling surface at this time was between the steel material and the epoxy resin, suggesting the possibility that the order of the resin layers affected adhesion. Therefore, in Example 2, an adhesion test was conducted to confirm the influence of the position of the polyurea resin in the adhesive resin layer.

FIG. 23(a) is a diagram showing a specimen of CASE 1 (Invention Example 3: the adhesive resin layer of the CFRP molded plate in Inventive Example 1 and Inventive Example 2) in Example 2, and FIG. ) is a diagram showing a specimen of CASE 2 (Invention Example 4) in Example 2, and FIG. 23C is a diagram showing a specimen of CASE 3 (Invention Example 5) in Example 2. FIG. In this test, three specimens were prepared using the presence or absence of the polyurea resin and the position of the polyurea resin layer as parameters. In this test, the steel plate width is 50 mm and the plate thickness is 12 mm. did the test.

FIG. 24(a) is a diagram showing the positions of strain gauges in CASE1-1, CASE2-1 to CASE2-3 and CASE3-1, and FIG. 2 and CASE 3-3 strain gauge positions. In CASE1-1, CASE2-1 to CASE2-3, and CASE3-1, strain gauges were attached to both sides of the specimen at the positions shown in FIG. 24(a). Furthermore, in CASE 1-1, CASE 2-1 to CASE 2-3, and CASE 3-1, strain gauges were attached to the side surface of the specimen at intervals of 20 mm from the center toward one end in the material axial direction of the specimen. In CASE1-2, CASE1-3, CASE3-2, and CASE3-3, strain gauges were attached to both surfaces of the specimen at positions shown in FIG. 24(b). The adhesive layer, the material properties of the CFRP molded plate and the construction procedure are the same as the bending test. A universal testing machine was used for the test, and loading was carried out under displacement control.

Table 6 shows the test results. The "ratio" in Table 6 indicates the ratio of the average maximum load of Invention Examples 3 and 4 (CASE 1 and CASE 2) to the average maximum load of Invention Example 5 (CASE 3).

In all specimens, delamination did not occur until the base material steel plate yielded and ended after the base material yielded. The breaking point was cohesive failure where the polyurea resin layer was broken in Inventive Example 4 (CASE 2), and in Inventive Example 3 (CASE 1) and Inventive Example 5 (CASE 3) there was delamination between the steel material and the epoxy resin. The maximum load increased by 8% in Inventive Example 3 and by 36% in Inventive Example 4 compared to Inventive Example 5, which did not have a polyurea layer. It was confirmed that when the polyurea layer is on the steel material side, the adhesion performance of the CFRP molded plate becomes higher.

25 is a diagram showing the relationship between load and strain in Example 2. FIG. The strain shown in FIG. 25 is the average value of the CFRP molded plates on both sides, and the dotted line in the figure is the calculated value with a completely synthetic cross section.

As shown in FIG. 25, the strain increased linearly in Example 5 of the present invention, and the CFRP strain was about 1,000×10 ⁻⁶ at the time of yielding of the base material, which was approximately the same behavior as the calculated value.
On the other hand, Inventive Examples 3 and 4 exhibited similar behavior until the base material steel yielded, but in Inventive Example 3, peeling occurred between the steel material and the epoxy resin early after the base material yielded, whereas the present invention exhibited the same behavior. In Example 4, the load and strain increased without causing delamination even after the base material yielded, ending at about 1,000×10 ^-6 . In addition, the strain at the time of yielding the steel materials of Inventive Examples 3 and 4 was about 400×10 ⁻⁶ , which was reduced to about 0.4 times as compared with this Example 5. This is considered to be the effect of the shear delay caused by

26 is a diagram showing the relationship between the distance from the center of the specimen and the strain in Example 2. FIG. FIG. 26 shows the strain distribution of the CFRP molded plate at 150 kN before yielding the base material of each specimen. The dotted line in FIG. 26 is a calculated value calculated as a completely synthetic cross section.
In Example 5 of the present invention, the strain was about 900×10 ⁻⁶ from the center of the test piece to about 130 mm, and the distribution showed a sharp drop in strain after 130 mm. In Inventive Examples 3 and 4, the strain at the center of the specimen was about 400×10 ⁻⁶ , and the distribution of strain gradually decreased from the center to the end of the specimen.

From the above, regardless of the configuration of the adhesive resin layer, until the base material yields, the CFRP molded plate does not peel off and the CFRP molded material bears the stress. However, in Inventive Examples 3 and 4, the shear delay effect due to the polyurea resin was exhibited. Also, the CFRP molded plate does not peel off at an early stage, and a higher reinforcing effect can be expected.

In Example 3, similarly to Example 1, a bending test was performed on the prepared specimen to examine the bending reinforcing effect.

In Example 1, the CFRP molded plate was subjected to compression failure in the positive bending test. Therefore, in Example 3, a CFRP molded plate having a tensile strength higher than that of the CFRP molded plate used in Example 1 was used. Moreover, in Example 3, the polyurea layer of the adhesive layer was arranged on the steel material side. In the following description of the third embodiment, differences from the first embodiment will be mainly described, and descriptions of the same points as the first embodiment will be omitted as appropriate.

<Specimen>
27 is a cross-sectional view showing a test piece of Example 3. FIG. In Example 3, the bending mode and the presence or absence of reinforcement of the upper and lower flanges were used as parameters to prepare specimens of Comparative Example 2 and Inventive Example 6, and the four-point bending test of positive bending and negative bending was performed in the same manner as in Example 1. did

Table 7 shows the outline of the specimen. In the specimen of Inventive Example 6, a reinforcing member was adhered to the upper flange via an adhesive layer. The reinforcing member includes a CFRP molded plate having a notch, and a carbon fiber strand sheet attached so as to straddle the reduced size portion of the CFRP molded plate due to the notch. Also, a carbon fiber sheet was adhered to the lower surface of the lower flange. In Comparative Example 2, no reinforcing member was used for reinforcement.

Table 8 shows an overview of the fiber sheets. The carbon fiber sheets in Table 8 are used to produce a CFRP molded plate, and are also adhered to the lower surface of the lower flange of Inventive Example 6. The carbon fiber strand sheet in Table 8 is attached to the contracted portion of the reinforcing member used in Inventive Example 6.

The resin used for the specimen is the same as in Table 3.

Table 9 shows an outline of the CFRP molded plate. The elastic moduli in Table 9 are actual values measured by a tensile test specified in JIS K7165.

28 is a plan view showing a reinforcing member in the test piece of Example 3. FIG. The shape of the CFRP molded plate was a flat plate in consideration of the simplicity of fabrication, and a notch was made to avoid the vertical stiffener at the center of the specimen. The size of the notch was set so that the vertical stiffener at the center of the specimen could pass through, and the corners of the notch were arc-shaped. The CFRP molded plate had a total width of 100 mm and a length of 1,600 mm, which is a length that ensures a fixing length of 200 mm from the plate thickness change point (outside) of the specimen. A carbon fiber strand sheet with a width of 30 mm was adhered to the upper surface of the CFRP molded plate using an epoxy resin in order to reinforce the cross-sectional defect of the notch. The adhesion length of the carbon fiber strand sheet was set to 200 mm from both ends of the notch of the outermost layer, and the shift amount was set to 25 mm at both ends of each layer.

The fiber orientation of the CFRP molded plate is set to a ratio of 1/2/1 layers in the -45/0/45° direction with respect to the axial direction so that stress can be transmitted even in the notch part. The flexural rigidity of the central portion of the specimen was determined to increase by 25%, and the number of laminations was [0°/±45°/0°] ₆ (24 layers in total). The stacking order was symmetrical in the plate thickness direction. Also, the number of layers of the carbon fiber strand sheet in the notch portion was determined so that the cross-sectional rigidity of the carbon fiber strand sheet was equal to the cross-sectional rigidity of the defect cross section, and was set to 10 layers. The carbon fiber strand sheet was adhered to the CFRP molded plate using epoxy putty.

As shown in FIG. 29(a), when the CFRP molded plate was adhered to the flange, a polyurea putty layer was provided on the steel material (flange) side. After curing the polyurea putty, the CFRP molded plate was adhered to the lower surface of the upper flange using epoxy putty. As shown in Fig. 29(b), the procedure for bonding the carbon fiber sheet to the flange is described in "Repair/Reinforcement Method for Steel Structures Using Carbon Fiber Sheet Design/Construction Manual" (Highway Research Institute, 2013). based on

<Test overview>
The test was a four-point bending test with a span length of 6,000 mm, a constant bending section of 2,500 mm, and a shear section of 1,750 mm. The loading was monotonic loading by displacement control, and the loading was continued until the load stopped increasing.

Moreover, the strain of the upper flange was measured with a strain gauge in the bending test. Three strain gauges were placed on the upper surface of the flange of the specimen at the center of the specimen in the material axis direction, and at ±100 mm, ±300 mm, and ±500 mm from the center of the specimen at a total of 7 points in the direction perpendicular to the material axis. 21 sheets were installed. The strain measured was the strain of the upper flange of each test piece at 200 kN before buckling or peeling occurred.

<Test result: Destruction status>
Table 10 shows the maximum load of each test, the load when the CFRP molded plate was peeled (hereinafter also referred to as peeling load), and the state of destruction.

The maximum load was 889 kN in Comparative Example 2, while it was 944 kN in positive bending and 1045 kN in negative bending in Example 6 of the present invention. The load exceeded the maximum load of Comparative Example 2 without reinforcement.

As for the state of destruction, in Example 6 of the present invention, peeling of the CFRP molded plate occurred at 944 kN in the positive bending test and at 830 kN in the negative bending test. Referring to Table 5, in the positive bending test of Inventive Example 2 of Example 1, compression failure occurred at 555 kN, and in the negative bending test of Inventive Example 2 of Example 1, peeling of the CFRP molded plate occurred at 675 kN.

From the above, when comparing Inventive Example 6 and Inventive Example 2, the peel load (944 kN) in the positive bending test of Inventive Example 6 is 70% higher than the breaking load (555 kN) in the positive bending test of Inventive Example 2. However, the peel load (830 kN) in the negative bending test of Inventive Example 6 was improved by 23% from the peel load (675 kN) in the negative bending test of Inventive Example 2.

The tensile strength of the carbon fiber sheet used in Inventive Example 6 is 3925 (N/mm ² ), which is higher than the tensile strength of the carbon fiber sheet used in Example 1 (2848 (N/mm ² )). As a result, neither the CFRP molded plate nor the flange-reinforced carbon fiber sheet suffered from compression fracture of the carbon fibers even under the maximum load.

Regarding the peeling load, the peeling load in Inventive Example 6 was larger than the breaking load and the peeling load in Inventive Example 2 because the polyurea putty was placed on the steel material side when the CFRP molded plate and the steel material were bonded. Conceivable.

The mode of peeling of the CFRP molded plate of Inventive Example 6 was peeling from the edge of the CFRP molded plate, and the fracture surface was peeling between the CFRP molded plate and the epoxy resin.

FIG. 30 is a diagram showing the relationship between load and span center vertical displacement. In Example 6 of the present invention, deformation such as peeling did not occur until the maximum load was applied in the forward bending test, and the maximum load was reached while maintaining a higher rigidity than that of no reinforcement, and the test ended with peeling. In the negative bending test, the CFRP molded plate on the vertical stiffener side peeled off at 830 kN and the rigidity decreased, and at 1,000 kN, the CFRP molded plate on the opposite side peeled off and the rigidity decreased.

FIG. 31 shows the strain distribution of the upper flange steel material of each specimen. Note that the suffix "_cal" in, for example, "Invention Example 6_cal" shown in FIG. 31 is a calculated value calculated as a completely synthesized cross section. Compared to Comparative Example 2, Inventive Example 6 reduced the stress of the upper flange steel material by about 19% in the positive bending test. Also, in the negative bending test, it was confirmed that the stress of the upper flange steel material was reduced by about 30%.

From the results and analysis of the above bending test, it was found that by using a carbon fiber sheet with a higher tensile strength, that is, a CFRP molded plate laminated with this, the carbon fiber sheet did not suffer compression failure even at the end. rice field. The tensile strength of the carbon fiber sheet was 3,925 (N/mm ² ) in Inventive Example 6 and 2,848 (N/mm ² ) in Inventive Example 2. It is preferable to use a sheet having a tensile strength of 2,900 (N/mm ² ) or more.

In Example 4, a bending test was performed on the prepared specimen to examine the bending reinforcing effect.

<Specimen>
FIG. 32 is a cross-sectional view showing a specimen of Example 4. FIG. 33 is a plan view showing a reinforcing member in Inventive Example 7. FIG. In Example 4, specimens of Comparative Example 3 and Inventive Example 7 were produced using the bending mode and the presence or absence of reinforcement of the upper and lower flanges as parameters. The specimen was an I-section steel material with a total length of 6,300 mm and a web height of 1,000 mm. Also, a vertical stiffener and a horizontal stiffener were installed in the specimen. The specimen had a width of 150 mm at the upper and lower flanges of the central plate girder and a thickness of 6 mm. The specimen had a width of 200 mm at the upper and lower flanges of the plate girders at both ends, and a thickness of 12 mm. This preceded the failure in the central plate girder. In this test, the same plate girders at both ends were used, and the test was performed while only the center plate girders were replaced.

Table 11 shows the outline of the specimen. In the specimen of Inventive Example 7, a reinforcing member was attached to the flange. In Example 7 of the present invention, a positive bending test and a negative bending test are performed. A specimen subjected to the positive bending test had a reinforcing member attached to the upper flange and a carbon fiber sheet attached to the lower flange. A specimen subjected to a negative bending test had a reinforcing member attached to the lower flange and a carbon fiber sheet attached to the upper flange. For the reinforcing member, a unidirectional CFRP molded plate was attached to the flange, and a CFRP molded plate (hereinafter referred to as bypass member) was attached to the unidirectional CFRP molded plate so as to bypass the vertical stiffener. A unidirectional CFRP molded plate and a bypass member were produced from a carbon fiber sheet and an epoxy resin by a hand layup molding method. In Comparative Example 3, no reinforcing member was used for reinforcement.

Table 12 shows an overview of the carbon fiber sheets. As the carbon fiber sheets in Table 2, medium elastic carbon fiber sheets were used. Carbon fiber sheets are used to make unidirectional CFRP molded plates, bypass members, and are glued to flanges opposite to flanges on which reinforcing members are provided.

Table 13 shows an overview of the resins used for the specimens. The carbon fiber sheet used in this test, the unidirectional CFRP molded plate, and the resin used for bonding the bypass member are "Repair/reinforcement method for steel structures using carbon fiber sheets Design and construction manual" (Expressway Technical Research Co., Ltd. Institute, 2020). Epoxy-based resin was used for the matrix resin of the unidirectional CFRP molded plate and the matrix resin of the bypass member. A high elongation elastic putty (polyurea resin) and an epoxy resin were used to bond the flange and the unidirectional CFRP molded plate. Epoxy resin was used to bond the unidirectional CFRP molded plate and the bypass member. The steel material of the test panel portion of the steel girder specimen used for the test was SS400, and the yield strength was 293 N/mm ² (test value).

Table 14 shows an overview of the unidirectional CFRP molded plate and the bypass member. The fiber orientation of the unidirectional CFRP molded plate was 0° with respect to the axial direction, and 20 layers of carbon fiber sheets were laminated. The fiber orientation of the bypass member was set to a ratio of 1/2/1 layers in -45/0/45° directions with respect to the axial direction so as to transmit stress in the width direction, and 10 layers of carbon fiber sheets were laminated. The thickness (plate thickness) of the CFRP molded plate in Table 14 is a measured value. Based on the plate thickness and the values shown in Tables 12 and 13, the fiber volume content V _f and the axial elastic modulus were calculated based on the law of combination and lamination theory. The number of laminated unidirectional CFRP molded plates was determined so that the bending rigidity of the central part of the steel girder specimen increased by 25% when the upper and lower flanges were reinforced. Also, the number of laminations of the bypass member was determined so that the tensile stiffness at the central portion with the smallest cross-sectional area was the same as the tensile stiffness of the unidirectional CFRP molded plate. Also, the shape of the bypass member was examined using FEM analysis. The details of the study are shown below.

<Examination of shape of bypass member by FEM analysis>
34(a) shows an overall view of the FEM analysis model, FIG. 34(b) shows a sectional view of the FEM analysis model, and FIG. 34(c) shows the shape of the bypass member in the FEM analysis model. The analysis model was modeled only for the flange part and modeled with solid elements. All the materials were linear materials, and the values shown in Table 3 were used for the elastic modulus of the adhesive resin. Table 15 shows material property values of the CFRP molded plate used for the analysis. Each value is a carbon fiber sheet (elastic modulus Ef = 390,000 N/mm ² , Poisson's ratio νf = 0.3) and a matrix resin (elastic modulus Em = 2860 N/mm ² with a fiber volume content V _f = 0.5). , Poisson's ratio νm=0.4). Constraint conditions were that the ends were supported by rollers and a uniaxial tensile load was applied. As shown in FIG. 34(c), the analysis parameter was the length of the width direction transmission section of the bypass member (CASE4: 150 mm, CASE5: 300 mm, CASE6: 600 mm). Moreover, the length of the bypass section was set to 30 mm.

<FEM analysis result>
FIG. 35 shows an axial stress ratio distribution map at the center of the lower surface of the steel plate in the FEM analysis model. The theoretical value was calculated from the tensile rigidity ratio of the CFRP molded plate and the steel plate. In CASEs 4 to 6, the stress of the steel tended to increase at the ends and the center (800 mm from the ends) of the bypass member. A comparison of CASEs 4 to 6 showed a tendency that the longer the transmission section, the smaller the central steel material stress. In the case of the transmission section of 600 mm, the central steel stress is roughly the same as the theoretical value. In addition, the distance between vertical stiffeners in steel girders of actual bridges is often about 1 m, and in the case of a transmission section of 600 mm, adjacent bypass members interfere with each other, making this method inapplicable. In the case of the transmission section of 300 mm, the center steel stress is about 7% larger than the theoretical value, but in this model, the entire section from the ends to the center is generally close to the theoretical value. Therefore, in consideration of economy and on-site applicability, a bypass member with a transmission section of 300 mm was adopted in this test.

<Test overview>
The test was a four-point bending test with a span length of 6,000 mm, a constant bending section of 2,500 mm, and a shear section of 1,750 mm. The loading was monotonic loading by displacement control, and the loading was continued until the load stopped increasing.

Moreover, the strain of the upper flange was measured with a strain gauge in the bending test. FIG. 36 shows a positional diagram of strain gauges. Three strain gauges were placed on the upper surface of the flange of the specimen at the center of the specimen in the material axis direction, and at ±100 mm, ±300 mm, and ±500 mm from the center of the specimen at a total of 7 points in the direction perpendicular to the material axis. 21 sheets were installed. The strain measured was the strain of the upper flange of each test piece at 200 kN before buckling or peeling occurred.

<Bending test results: test results and breaking conditions>
Table 16 shows a list of test results. The state of destruction is the result of precedence of delamination between the unidirectional CFRP molded plate and the bypass member in both the positive bending test specimen of Inventive Example 7 and the negative bending test specimen of Inventive Example 7. The bypass member was peeled off at 661 kN in the specimen and at 850 kN in the positive bending test specimen.

<Bending test results: load-span center vertical deflection relationship>
37 shows the load-span center vertical deflection relationship in Example 4. FIG. The calculated value was calculated according to beam theory, with the modulus of elasticity of steel being 200,000 N/mm ² and ignoring vertical stiffeners and horizontal stiffeners. As shown in FIG. 37, the positive bending test specimen of Inventive Example 7 showed a behavior in which the stiffness decreased due to the detachment of the bypass member at 661 kN before the yield load (calculated value) of Comparative Example 3 of 798 kN. Since the bypass member used in this test was not subjected to taper processing or the like at the end portion, the rigidity changes due to a sudden change in cross section of the bonded end portion of the bypass member. Therefore, it is considered that stress concentration occurred at the bonded ends, and delamination occurred before the base material steel girders yielded.

The specimen in the negative bending test of Inventive Example 7 showed a decrease in rigidity due to the detachment of the bypass member at 889 kN. When compared with the positive bending test specimen of Inventive Example 7, the peel load was increased by about 29%.

<Bend test result: stress reduction effect of upper flange>
FIG. 38 shows the strain distribution of the upper flange steel material of each test piece at 200 kN before buckling, delamination, etc. of the test piece occurs. As shown in FIG. 38, compared to Comparative Example 3, both the specimen for the positive bending test of Inventive Example 7 and the specimen for the negative bending test of Inventive Example 7 reduced the stress in all measured cross sections. was confirmed. By averaging the strain of all 21 strain gauges on the upper flange of each specimen and comparing with Comparative Example 3, the positive bending test specimen was about 24%, and the negative bending test specimen was about 26% of the upper flange steel material. It was confirmed that the stress was reduced, and the reinforcing effect was obtained as calculated. From the above, it was confirmed that when the upper flange was reinforced with a reinforcement member using a bypass member, the stress on the steel girder specimen was reduced by transmitting the stress to the bypass member.

100 : Reinforcing structure 1 : Reinforcement member 2 : FRP plate material 21 : Notch 22 : Reduced part 23 : Attachment part 24 : Bypass part 29 : Unidirectional fiber sheet 3 : Fiber sheet 4 : Adhesive layer 5 : I-shaped cross section steel material 51 : Flange 51a : Upper surface 51b : Lower surface 52 : Flange 52a : Upper surface 53 : Web 54 : Vertical stiffener 6 : Adhesive layer 7 : Steel member 71 : Steel plate 72 : Out-of-plane gusset 73 : Splice plate 74 : Bolt 8 : Continuous fiber material 9 : Bridge 91 : Floor slab 92 : Pier X : First direction Y : Second direction Z : Third direction

Claims (12)

A reinforcing structure for reinforcing a steel member having a first steel material and a second steel material joined to the first steel material,
comprising the steel member and a reinforcing member for reinforcing the steel member;
The reinforcing member has an FRP plate material in which a plurality of unidirectional fiber sheets in which continuous reinforcing fibers are aligned in one direction and are impregnated with resin are laminated,
The FRP plate material is
a pair of attachment portions formed on both sides of the second steel material and attached to the first steel material;
a bypass portion that bypasses the second steel material and connects the pair of attachment portions,
The reinforcing structure, wherein the fiber orientation in the FRP plate material has a main direction from one of the attached portions to the other of the attached portions and at least two directions different from the main directions. The fiber orientations in at least two directions that are oriented in directions different from the main direction are inclined at an absolute value of 15° to 75° from the main direction, and are symmetrical about the main direction. The reinforcing structure according to claim 1, characterized by: The reinforcing member further includes a continuous fiber material between the attachment portion and the first steel material,
The reinforcing structure according to claim 1, wherein a pair of said continuous fiber materials are provided on both sides of said second steel material with a space therebetween. The reinforcing member further includes an adhesive layer between the attachment portion and the first steel material,
The reinforcing structure according to claim 1, wherein the adhesive layer includes a high elongation elastic resin layer. The reinforcing structure according to claim 1, wherein the thickness of the FRP plate material is tapered toward the end portion side in the main direction. The reinforcing member has a fiber sheet attached to the FRP plate,
The FRP plate material is
having a notch portion cut from a side end into which the second steel material is inserted, and a reduced portion in which the size of the FRP plate is reduced by the notch portion,
The reinforcing structure according to claim 1, wherein the fiber sheet is attached to the FRP plate so as to straddle the reduced portion. The FRP plate has a first main surface on which the bonding surface of the first steel material is formed, and a second main surface opposite to the first main surface,
The reinforcing structure according to claim 6, wherein said fiber sheet is attached to said first main surface. The FRP plate has a first main surface on which the bonding surface of the first steel material is formed, and a second main surface opposite to the first main surface,
The reinforcing structure according to claim 6 or 7, wherein the fiber sheet is attached to the second main surface. A reinforcing member for reinforcing a steel member having a first steel material and a second steel material joined to the first steel material,
Having an FRP plate material in which a plurality of unidirectional fiber sheets in which continuous reinforcing fibers are aligned in one direction and are impregnated with resin are laminated,
The FRP plate material is
a pair of attachment portions formed on both sides of the second steel material and attached to the first steel material;
a bypass portion for bypassing the second steel material and connecting the pair of attachment portions;
The reinforcing member, wherein the fiber orientation in the FRP plate material has a main direction from one of the attached portions to the other of the attached portions and at least two directions different from the main directions. Having a fiber sheet attached to the FRP plate,
The FRP plate material is
having a notch portion cut from a side end into which the second steel material is inserted, and a reduced portion in which the size of the FRP plate is reduced by the notch portion,
10. The reinforcing member according to claim 9, wherein the fiber sheet is attached to the FRP plate so as to straddle the reduced portion. A reinforcing method for reinforcing a steel member having a first steel material and a second steel material joined to the first steel material, comprising:
An installation step of installing a reinforcing member on the steel member,
The reinforcing member has an FRP plate material in which a plurality of unidirectional fiber sheets in which continuous reinforcing fibers are aligned in one direction and are impregnated with resin are laminated,
The FRP plate material is
a pair of attachment portions formed on both sides of the second steel material;
a bypass portion connecting the pair of attachment portions is formed,
The fiber orientation in the FRP plate has a main direction from one attachment portion to the other attachment portion and at least two directions different from the main direction,
The reinforcing method, wherein the installing step includes attaching the pair of attaching portions to the first steel member so as to bypass the second steel member by the bypass portion. The reinforcing member has a fiber sheet attached to the FRP plate,
The FRP plate material is
having a notch portion cut from a side end into which the second steel material is inserted, and a reduced portion in which the size of the FRP plate is reduced by the notch portion,
The fiber sheet is attached to the FRP plate so as to straddle the reduced portion,
12. The reinforcing method according to claim 11, wherein, in the installation step, the second steel member is inserted into the notch portion of the FRP plate member, and the FRP plate member is attached to the first steel member.

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