Reinforcement structure, reinforcement member, and reinforcement method

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

[Technical Field]

[0001] This invention relates to a reinforcing structure, a reinforcing member, and a reinforcing method having a joint between a first steel material and a second steel material. [Background technology]

[0002] Currently, as part of the highway renewal project, large-scale renovation work, such as deck slab replacement, is underway. In such cases, replacing the deck slab may result in insufficient load-bearing capacity of the existing steel girders. Reasons for insufficient load-bearing capacity of existing steel girders include an increase in dead load due to the replacement deck slab, an increase from the design live load at the time of completion to the B live load, and structural changes such as the transition from composite girders to non-composite girders. Therefore, it is expected that the demand for reinforcing existing steel girders will increase in the future. Conventionally, technologies for reinforcing steel members have been proposed, for example, the technologies disclosed in Non-Patent Document 1 and Patent Documents 1-2.

[0003] The method for reinforcing a steel I-girder described in Non-Patent Document 1 involves removing a portion of the lower part of the web connecting plate that connects the webs when replacing the lower flange connecting plate that connects the lower flanges of two steel I-girders, and then bolting a web bypass member made of metal plate to the removed portion.

[0004] The method for repairing and reinforcing steel structures described in Patent Document 1 involves forming a putty layer on the surface of a steel member using a polyurea resin putty material, and then laminating multiple fiber sheets on top of the putty layer by bonding them with resin to form multiple fiber-reinforced resin layers.

[0005] The repair method described in Patent Document 2 is a method for repairing a crack that has occurred at the toe of a joint steel member in a steel structure in which a joint steel member is welded around the surface of a steel base material by attaching a carbon fiber reinforced resin plate, wherein at least the carbon fiber reinforced resin plate is attached in a substantially U-shape to both sides of the joint steel member and to the base material surface of the toe, and at the same time, the substantially U-shaped inner surface is attached in close contact with the weld bead of the weld between the base material and the joint steel member. [Prior art documents] [Patent Documents]

[0006] [Non-Patent Document 1] Shun Matsui, Takashi Yamaguchi, Kensuke Toda, Kenji Araki, and Takashi Yamauchi, "Analytical Study on the Applicability Scope of the Web Bypass Method and the Shape of Bypass Members for Replacing the Lower Flange Connecting Plate of a Steel I-Girder," Japan Society of Civil Engineers, Transactions on Structural Engineering, Vol. 67A, 2021, pp. 323-335.

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-124553 [Patent Document 2] Japanese Patent Publication No. 2006-057352 [Overview of the project] [Problems that the invention aims to solve]

[0008] By the way, the reinforcement method described in Non-Patent Document 1 is not easy to implement because it requires forming bolt holes in the web for bolting the web bypass members together, or welding the web bypass members together.

[0009] I-section steel members are used, for example, as girder members that support bridge decks from below. However, because the deck rests on the upper flange of the I-section steel member, construction methods may be limited, such as requiring reinforcement from the underside of the upper flange. Therefore, there is a need for a technology that allows for reinforcement in a short construction time.

[0010] Furthermore, in the reinforcement method described in Non-Patent Document 1, a web bypass member made of metal plate is joined, raising concerns about a significant increase in dead load after reinforcement. Moreover, for example, a vertical stiffener may be joined to the underside of the upper flange of a steel I-girder. When reinforcing a steel member that has a joint between the upper flange and the vertical stiffener, there are difficulties in reinforcing the joint.

[0011] In the technology disclosed in Patent Document 1, even when attempting to reinforce an I-section steel member with vertical stiffeners, the vertical stiffeners prevent the continuous application of fiber sheets in the axial direction of the material. Furthermore, while the technology disclosed in Patent Document 2 is applicable to fatigue cracks, it does not relate to bending reinforcement. Therefore, in the technologies 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. Consequently, there is a need for a technology that can provide a reinforcing effect even at the joints between steel members.

[0012] Therefore, the present invention was devised in view of the above circumstances, and its objective is to provide a reinforcing structure, reinforcing member, and reinforcing method that can suppress the increase in dead load at the joint of steel members and can be easily reinforced. [Means for solving the problem]

[0013] The reinforcing structure according to the first invention is a reinforcing structure for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, comprising the steel member and a reinforcing member for reinforcing the steel member, wherein the reinforcing member has an FRP plate material in which a plurality of unidirectional fiber sheets are laminated, in which continuous reinforcing fibers are aligned in one direction and impregnated with resin, and the FRP plate material has a pair of adhesive portions formed on both sides of the second steel member and attached to the first steel member, and a bypass portion that bypasses the second steel member and connects the pair of adhesive portions, It has a notch that is cut out from the side end and into which the second steel material is inserted, and the bypass portion has a reduced portion in which the width dimension of the FRP plate material is reduced by the notch. The fiber orientation in the FRP sheet material is formed such that there is a main direction from one of the adhesive portions toward the other adhesive portion, and a direction different from the main direction. ru2 Two directions at least three directions to have Furthermore, the reduced portion is positioned to protrude outward from the widthwise edge of the first steel material. It is characterized by the following.

[0014] The reinforcing structure according to the second invention is characterized in that, in the first invention, the fiber orientation in at least two directions that are oriented in directions different from the main direction is inclined by an absolute value of 15° to 75° from the main direction and is symmetrical with respect to the main direction. The reinforcing structure according to the ninth invention is characterized in that, in the second invention, the notch is formed in a trapezoidal shape and has a pair of inclined sides and an inner side connected to the pair of inclined sides, the inner side being parallel to the main direction, one of the inclined sides being parallel to one of two directions different from the main direction, and the other inclined side being parallel to the other of two directions different from the main direction.

[0015] The reinforcing structure according to the third invention is characterized in that, in the first invention, the reinforcing member further comprises a continuous fiber material between the affixing portion and the first steel material, and a pair of the continuous fiber materials are provided spaced apart on both sides with the second steel material interposed therebetween.

[0016] The reinforcing structure according to the fourth invention is characterized in that, in the first invention, the reinforcing member further comprises an adhesive layer between the affixing portion and the first steel material, and the adhesive layer includes a high-elongation elastic resin layer.

[0017] The reinforcing structure according to the fifth invention is characterized in that, in the first invention, the thickness of the FRP plate material is formed in a tapered shape toward the end side in the main direction.

[0018] The reinforcing structure according to the sixth invention is, in the first invention, the reinforcing member has a fiber sheet affixed to the FRP plate material ,before the fiber sheet is affixed to the FRP plate material so as to straddle the reduced portion.

[0019] The reinforcing structure according to the seventh invention is characterized in that, in the sixth invention, 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 on the side opposite to the first main surface, and the fiber sheet is affixed to the first main surface.

[0020] The reinforcing structure according to the eighth invention is characterized in that, in the sixth invention or the seventh invention, 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 on the side opposite to the first main surface, and the fiber sheet is affixed to the second main surface.

[0021] No. 10The reinforcing member according to the invention is a reinforcing member for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, and comprises an FRP plate material in which a plurality of unidirectional fiber sheets are laminated, each having continuous reinforcing fibers aligned in one direction and impregnated with resin, the FRP plate material having 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 that bypasses the second steel member and connects the pair of attachment portions, It has a notch that is cut out from the side end and for inserting the second steel material, and the bypass portion has a reduced portion in which the width dimension of the FRP plate material is reduced by the notch. The fiber orientation in the FRP sheet material is formed such that there is a main direction from one of the adhesive portions toward the other adhesive portion, and a direction different from the main direction. ru2 Two directions at least three directions to have The reduced portion is configured to be positioned to protrude outward from the widthwise edge of the first steel material, and the fiber orientation in at least two directions that are oriented in directions different from the main direction is inclined at an absolute value of 15° to 75° from the main direction and is symmetrical with respect to the main direction, and the notch is formed in a trapezoidal shape and has a pair of inclined sides and an inner side connected to the pair of inclined sides, the inner side is parallel to the main direction, one of the inclined sides is parallel to one of the two directions different from the main direction, and the other inclined side is parallel to the other of the two directions different from the main direction It is characterized by the following.

[0022] The 11 The reinforcing member according to the invention is, 10 The invention comprises a fiber sheet that is attached to the FRP plate material. ,before The fiber sheet is characterized by being attached to the FRP plate material so as to straddle the reduced portion.

[0023] The 12 The reinforcing method according to the invention is a reinforcing method for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, comprising an installation step of installing a reinforcing member on the steel member, wherein the reinforcing member has an FRP plate material in which a plurality of unidirectional fiber sheets are laminated, in which continuous reinforcing fibers are aligned in one direction and impregnated with resin, and the FRP plate material has a pair of adhesive portions formed on both sides of the second steel member, and a bypass portion connecting the pair of adhesive portions, It has a notch cut out from the side edge, and the bypass portion has a reduced portion formed in which the width dimension of the FRP plate material is reduced by the notch. The fiber orientation in the FRP sheet material is such that there is a main direction from one of the bonding portions toward the other bonding portion, and a direction different from the main direction. ru2 Two directions at least three directions to have death, The aforementioned installation process is, The second steel material is inserted into the notched portion. The pair of adhesive portions are attached to the first steel material so as to bypass the second steel material using the bypass portion. The reduced portion is positioned to protrude outward from the widthwise edge of the first steel material. It is characterized by the following.

[0024] The 13The method for reinforcing steel members according to the invention is the first 12 In the invention, the reinforcing member has a fiber sheet that is attached to the FRP plate material. ,before The fiber sheet is attached to the FRP plate material so as to straddle the reduced portion, and in the installation process, the second steel material is inserted into the notch of the FRP plate material, and the FRP plate material is attached to the first steel material. The method for reinforcing a steel member according to the 14th invention is characterized in that, in the 12th invention, the fiber orientation in at least two directions that are oriented in directions different from the main direction is inclined at an absolute value of 15° to 75° from the main direction and is symmetrical with respect to the main direction, the notch is formed in a trapezoidal shape and has a pair of inclined sides and an inner side connected to the pair of inclined sides, the inner side is parallel to the main direction, one of the inclined sides is parallel to one of the two directions different from the main direction, and the other inclined side is parallel to the other of the two directions different from the main direction. [Effects of the Invention]

[0025] According to the present invention, the increase in dead load at the joint of steel members can be suppressed, and reinforcement can be easily performed. Furthermore, even in locations where sufficient anchoring length cannot be obtained due to obstacles such as bolts, backing plates, or stiffening plates, making reinforcement difficult, the reinforcing member of the present invention and the reinforcing structure using the same can be used to perform appropriate reinforcement while avoiding the obstacles. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 is a perspective view showing a partially broken bridge in which an example of the reinforcing structure in the first embodiment is provided. [Figure 2] Figure 2(a) is a cross-sectional view showing an example of a reinforcing structure in the first embodiment, and Figure 2(b) is a cross-sectional view taken along line 2A-2A in Figure 2(a). [Figure 3] Figure 3(a) is a front view showing an example of a reinforcing member in the first embodiment, and Figure 3(b) is a cross-sectional view taken along line 3A-3A in Figure 3(a). [Figure 4] Figure 4 shows an example of a reinforcement method in the first embodiment, where Figure 4(a) shows the reinforcing member before it is bonded to the flange, and Figure 4(b) shows the reinforcing member after it has been bonded to the flange. [Figure 5] Figure 5 is a cross-sectional view showing an example of a reinforcing structure in the second embodiment. [Figure 6] Figure 6(a) is a cross-sectional view showing an example of a reinforcing structure in the third embodiment, and Figure 6(b) is a cross-sectional view showing a first modified example of the reinforcing structure in the third embodiment. [Figure 7] Figure 7 is a perspective view showing a partially broken bridge in which an example of the reinforcing structure in the fourth embodiment is provided. [Figure 8] Figure 8(a) is a front view showing an example of a reinforcing structure in the fourth embodiment, and Figure 8(b) is a cross-sectional view taken along line 8A-8A in Figure 8(a). [Figure 9] Figure 9 is a plan view showing an example of an FRP sheet material in the fourth embodiment. [Figure 10] Figure 10(a) is a front view showing an example of a reinforcing member in the fourth embodiment, and Figure 10(b) is a cross-sectional view taken along line 10A-10A in Figure 10(a). [Figure 11] Figure 11 is an enlarged side view showing an example of a reinforcing structure in the fourth embodiment. [Figure 12] Figure 12 shows an example of a reinforcement method in the fourth embodiment, where Figure 12(a) shows the reinforcing member before it is bonded to the flange, and Figure 12(b) shows the reinforcing member after it has been bonded to the flange. [Figure 13] Figure 13(a) is a front view showing an example of a reinforcing structure in the fifth embodiment, and Figure 13(b) is a cross-sectional view taken along line 13A-13A in Figure 13(a). [Figure 14] Figure 14 is a cross-sectional view showing an example of a reinforcing structure in the sixth embodiment. [Figure 15] Figure 15(a) is a cross-sectional view showing an example of a reinforcing structure in the seventh embodiment, and Figure 15(b) is a cross-sectional view taken along line 15A-15A in Figure 15(a). [Figure 16] Figure 16(a) is an enlarged side view showing an example of the reinforcing structure in the seventh embodiment, and Figure 16(b) is an enlarged front view showing an example of the reinforcing structure in the seventh embodiment. [Figure 17] Figure 17(a) is a side view showing an example of the reinforcing structure in the eighth embodiment, and Figure 17(b) is a plan view showing an example of the reinforcing structure in the eighth embodiment. [Figure 18]Figure 18(a) is a side view showing an example of the reinforcing structure in the ninth embodiment, and Figure 18(b) is a plan view showing an example of the reinforcing structure in the ninth embodiment. [Figure 19] Figure 19 is a side view showing the specimen of Example 1. [Figure 20] Figure 20 is a cross-sectional view showing the specimen of Example 1. [Figure 21] Figure 21 is a plan view showing the reinforcing member in the specimen of Example 1. [Figure 22] Figure 22(a) shows the strain distribution of Comparative Example 1, Invention Example 1, and Invention Example 2 in a positive bending test, and Figure 22(b) shows the strain distribution of Comparative Example 1, Invention Example 1, and Invention Example 2 in a negative bending test. [Figure 23] Figure 23(a) shows the specimen for CASE 1 in Example 2, Figure 23(b) shows the specimen for CASE 2 in Example 2, and Figure 23(c) shows the specimen for CASE 3 in Example 2. [Figure 24] Figure 24(a) shows the positions of the strain gauges for CASE1-1, CASE2-1 to CASE2-3, and CASE3-1, and Figure 24(b) shows the positions of the strain gauges for CASE1-2, CASE1-3, CASE3-2, and CASE3-3. [Figure 25] Figure 25 shows the relationship between load and strain in Example 2. [Figure 26] Figure 26 shows the relationship between the distance from the center of the specimen and the strain in Example 2. [Figure 27] Figure 27 is a cross-sectional view showing the specimen of Example 3. [Figure 28] Figure 28 is a plan view showing the reinforcing member in the specimen of Example 3. [Figure 29] Figure 29(a) shows the adhesive layer between the steel material and the CFRP molded plate in the specimen of Example 3, and Figure 29(b) shows the adhesive layer between the steel material and the carbon fiber sheet in the specimen of Example 3. [Figure 30]Figure 30 shows the relationship between the load and the vertical displacement at the center of the span in Example 3. [Figure 31] Figure 31 shows the strain distribution for Comparative Example 2 and Example 6 of the present invention. [Figure 32] Figure 32 is a cross-sectional view showing the specimen of Example 4. [Figure 33] Figure 33 is a plan view showing the reinforcing member in Example 7 of the present invention. [Figure 34] Figure 34(a) shows an overall view of the FEM analysis model, Figure 34(b) shows a cross-sectional view of the FEM analysis model, and Figure 34(c) shows the bypass member in the FEM analysis model. [Figure 35] Figure 35 shows the axial stress ratio distribution at the center of the bottom surface of the steel plate in the FEM analysis. [Figure 36] Figure 36 shows the position of the strain gauges. [Figure 37] Figure 37 shows the load-to-span vertical deflection relationship in Example 4. [Figure 38] Figure 38 shows the strain distribution of the upper flange steel material of each specimen at 200 kN, before buckling, delamination, etc., occur in the specimen. [Modes for carrying out the invention]

[0027] Hereinafter, examples of reinforcing structures, reinforcing members, and reinforcing methods as embodiments of the present invention will be described with reference to the drawings. In each figure, the height direction is defined as the third direction Z, one planar direction intersecting, for example, perpendicular to the third direction Z is defined as the first direction X, and another planar direction intersecting, for example, perpendicular to both the third direction Z and the first direction X is defined as the second direction Y. Furthermore, the configurations in each figure are schematically described for explanatory purposes, and the size of each component, the size comparison between components, etc., may differ from those shown in the figures.

[0028] (First embodiment: Reinforcement structure 100) Figure 1 is a partially cutaway perspective view showing a bridge 9 provided with an example of the reinforcing structure 100 according to the first embodiment. Figure 2(a) is a front view showing an example of the reinforcing structure 100 according to the first embodiment, and Figure 2(b) is a cross-sectional view taken along line 2A-2A of Figure 2(a). Figure 3(a) is a front view showing an example of the reinforcing member 1 according to the first embodiment, and Figure 3(b) is a cross-sectional view taken along line 3A-3A of Figure 3(a).

[0029] The reinforcing structure 100 reinforces, for example, the existing I-shaped cross-section steel member 5 that supports the deck slab 91 of the bridge 9 from below. The reinforcing structure 100 includes the I-shaped cross-section steel member 5 and the reinforcing member 1. The I-shaped cross-section steel member 5 is used not only as a girder material for supporting the deck slab 91 but also, for example, as a beam member.

[0030] <I-shaped cross-section steel member 5> The I-shaped cross-section steel member 5 is mounted on the bridge pier 92, and the material axis direction thereof is arranged along the second direction Y. The I-shaped cross-section steel member 5 has a pair of flanges 51 and 52, a web 53 connecting the pair of flanges 51 and 52, and a vertical stiffener 54 provided between the pair of flanges 51 and 52. The flange 51 is the upper flange in the third direction Z, and the flange 52 is the lower flange. In the I-shaped cross-section steel member 5, the deck slab 91 is placed on the upper surface 51a of the flange 51. In the I-shaped cross-section steel member 5, the reinforcing member 1 is provided, for example, on the lower surface 51b of the flange 51. The vertical stiffener 54 is a stiffener that uses, for example, a steel plate and prevents buckling of the web 53.

[0031] <Reinforcing member 1> The reinforcing member 1 reinforces the I-shaped cross-section steel member 5. The reinforcing member 1 includes an FRP plate material 2, a fiber sheet 3, and an adhesive layer 4.

[0032] <FRP plate material 2> The FRP sheet material 2 is made of FRP (Fiber Reinforced Plastics), and for example, a sheet material made of CFRP (Carbon Fiber Reinforced Plastics) is used. The matrix resin of the FRP can be either a thermosetting resin or a thermoplastic resin, but a thermosetting resin such as vinyl ester resin or epoxy resin is preferred. The FRP sheet material 2 is a sheet material with a rectangular outer shape, formed with its longitudinal direction extending in the second direction Y. The FRP sheet material 2 is bonded to the lower surface 51b of the flange 51 via an adhesive layer 4. The FRP sheet material 2 has a first main surface 2a on which the adhesive surface that is bonded to the lower surface 51b of the flange 51 is formed, and a second main surface 2b on the opposite side of the first main surface 2a. In this embodiment, the first main surface 2a is the upper surface of the FRP sheet material 2, and the second main surface 2b is the lower surface of the FRP sheet material 2.

[0033] The FRP plate material 2 preferably has a ratio of the shear modulus to the axial modulus of 0.05 to 6.00, and more preferably 0.15 to 0.35. This reduces stress transmission loss in the direction perpendicular to the axis at the notched portion.

[0034] The FRP sheet material 2 has a notched portion 21 formed by cutting out from one side end in the first direction X, and a reduced portion 22 in which the dimensions of the FRP sheet material 2 are reduced by the notched portion 21. A vertical stiffener 54 is inserted into the notched portion 21. The reduced portion 22 is formed adjacent to the notched portion 21 in the first direction X. Note that the FRP sheet material 2 may have multiple notched portions 21 formed therein. Furthermore, it is preferable that unidirectional material (unidirectional fiber sheet 29, described later) is laminated in the -45 / 0 / 45° direction with respect to the axial direction so that stress is transmitted even in the notched portion.

[0035] <Fiber Sheet 3> The fiber sheet 3 may be a continuous fiber sheet such as carbon fiber, glass fiber, basalt fiber, or aramid fiber (for example, Tow Sheet®) or a sheet made by processing multiple FRP strands that have been pre-impregnated and hardened with resin into a blind-like structure (for example, Strand Sheet®). The fiber sheet 3 is formed by laminating multiple fiber sheets such as carbon fiber, with multiple layers being bonded to each other. It may be formed by impregnating and hardening the Tow Sheet or Strand Sheet with resin at the construction site, or by bonding pre-formed plates.

[0036] The fiber sheet 3 is attached to the first main surface 2a of the FRP plate material 2 so as to straddle the reduced portion 22 in the second direction Y. The fiber sheet 3 is attached to the portion of the FRP plate material 2 where the adhesive layer 4 is not provided. The fiber sheet 3 is attached so as to be of equal length on both sides in the second direction Y with respect to the center line of the reduced portion 22, but it is preferable to provide an adhesive length of at least 100 mm at both ends to ensure a stress transmission section.

[0037] <Adhesive layer 4> The adhesive layer 4 adheres the lower surface 51b of the flange 51 to the first main surface 2a of the FRP sheet material 2 and is provided between the lower surface 51b of the flange 51 and the first main surface 2a of the FRP sheet material 2. The adhesive layer 4 preferably includes a high-elongation elastic resin layer, for example, a polyurea resin layer 41 and an epoxy resin layer 42. The polyurea resin layer 41 is in contact with the flange 51 and separated from the FRP sheet material 2. At this time, the epoxy resin layer 42 is in contact with the FRP sheet material 2 and separated from the flange 51. This makes it possible to suppress the peeling of the polyurea resin layer 41 early after the yielding of the flange 51.

[0038] The polyurea resin layer 41 may be in contact with the FRP sheet 2 and separated from the flange 51. The epoxy resin layer 42 may be in contact with the flange 51 and separated from the FRP sheet 2. In this way, the polyurea resin layer 41 is bonded to the FRP sheet 2, and the epoxy resin layer 42 is in contact with the flange 51. This allows the bonding of the polyurea resin layer 41 on the FRP sheet 2 side and the application of other resin layers on the flange 51 side to be carried out simultaneously.

[0039] The adhesive layer 4 uses a well-known resin material that can bond the lower surface 51b of the flange 51 and the first main surface 2a of the FRP plate material 2 to each other. As the adhesive layer 4, for example, a high-elongation elastic resin such as acrylic resin can be used instead of the epoxy resin layer 42, or a urea-urethane resin can be used instead of the polyurea resin layer 41. A high-elongation elastic resin has a tensile modulus of 50 to 100 N / mm². 2 Furthermore, the resin has an elongation of 300% or more under maximum tensile load. The maximum tensile load elongation of the high-elongation elastic resin is preferably 300% to 1200%, more preferably 300% to 700%, and even more preferably 300% to 500%.

[0040] The adhesive layer 4 is preferably formed in advance on the FRP sheet material 2, but it may also be formed on the FRP sheet material at the construction site, or it may be formed on the lower surface 51b of the flange.

[0041] (First embodiment: An example of a reinforcement method) Next, an example of a reinforcement method in the first embodiment will be described. Figure 4 is a diagram showing an example of a reinforcement method in the first embodiment, where Figure 4(a) shows the reinforcing member 1 before it is bonded to the flange 51, and Figure 4(b) shows the reinforcing member 1 after it has been bonded to the flange 51. The reinforcement method includes an installation step of attaching the reinforcing member 1 to the I-section steel material 5.

[0042] First, as shown in Figure 4(a), in the installation process, the fiber sheet 3 is attached to the first main surface 2a so as to straddle the reduced portion 22, which is formed by a notch 21 cut out from the side edge of the FRP sheet 2, in the second direction Y. Then, in the installation process, an adhesive layer 4 is provided on the first main surface 2a of the FRP sheet 2. Finally, in the installation process, a vertical stiffener 54 is inserted into the notch 21 of the FRP sheet 2.

[0043] Next, as shown in Figure 4(b), in the installation process, the adhesive layer 4 provided on the first main surface 2a is bonded to the lower surface 51b of the flange 51.

[0044] This concludes the description of an example of a reinforcement method in the first embodiment.

[0045] According to this embodiment, the reinforcing member 1 comprises an FRP plate 2 bonded to the flange 51 and a fiber sheet 3 attached to the FRP plate 2. The FRP plate 2 has a notch 21 cut out from its side end into which a vertical stiffener 54 is inserted, and a reduced portion 22 in which the dimensions of the FRP plate 2 are reduced by the notch 21. The fiber sheet 3 is attached to the FRP plate 2 so as to straddle the reduced portion 22. That is, the notch 21 is positioned to avoid the vertical stiffener 54, and the fiber sheet 3 is positioned to compensate for the cross-sectional defect of the FRP plate 2 caused by the notch 21. Therefore, when a load is applied, stress is transmitted from the FRP plate 2 to 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. Consequently, it is possible to provide the I-section steel member 5, to which the vertical stiffener 54 is provided, with bending reinforcement effects against both positive and negative bending.

[0046] Furthermore, according to this embodiment, a vertical stiffener 54 is inserted into the notch 21 of the FRP plate material 2 to which the fiber sheet 3 is attached, and the FRP plate material 2 is bonded to the flange 51. Therefore, it is possible to perform the work on the I-section steel material 5 provided with the vertical stiffener 54 in a short amount of time.

[0047] According to this embodiment, the FRP plate material 2 has a ratio of the shear modulus value to the axial modulus value of 0.05 or more and 6.00 or less. This reduces stress transmission loss at the notch 21. Therefore, it is possible to further exhibit the bending reinforcement effect. In particular, the FRP plate material 2 has a ratio of the shear modulus value to the axial modulus value of 0.15 or more and 0.35 or less, which significantly reduces stress transmission loss at the notch 21. Therefore, it is possible to further exhibit the bending reinforcement effect.

[0048] 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 elongated elastic resin layer such as a polyurea resin layer 41. Compared to the case where bonding is done with only an epoxy resin layer, by using a highly elongated elastic resin layer such as a polyurea resin layer 41 that can be deformed more flexibly, it is possible to suppress the peeling of the FRP plate material 2 from the I-section steel material 5, maintain the reinforcing effect even under greater deformation, and exhibit the shear lag effect of the highly elongated elastic resin layer. As a result, it is possible to exert a bending reinforcement effect without the FRP plate material 2 peeling off from the I-section steel material 5.

[0049] 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. The adhesive layer 4 includes a highly elongated elastic resin layer such as a polyurea resin layer 41, and the highly elongated elastic resin layer such as the polyurea resin layer 41 contacts the flange 51 and separates from the FRP plate material 2. This makes it possible to suppress the peeling of the highly elongated elastic resin layer early after the yielding of the flange 51. As a result, the bending reinforcement effect can be further enhanced.

[0050] According to this embodiment, the reinforcing member 1 further has an adhesive layer 4 for bonding the FRP sheet material 2 to the flange 51. The adhesive layer 4 includes a highly elongated elastic resin layer such as a polyurea resin layer 41 and another resin layer such as an epoxy resin layer 42 different from the polyurea resin layer 41. The highly elongated elastic resin layer such as the polyurea resin layer 41 is bonded to the FRP sheet material 2, and the other resin layer is in contact with the flange 51. This allows the bonding of the highly elongated elastic resin layer on the FRP sheet material 2 side and the application of the other resin layer on the flange 51 side to be carried out simultaneously. Therefore, construction can be completed in a shorter time.

[0051] According to this embodiment, the fiber sheet 3 is attached to the first main surface 2a. As a result, the fiber sheet 3 is positioned further away from the neutral axis of the I-section steel material 5 than when it is attached to the second main surface 2b. Therefore, the second moment of area of ​​the reinforcing structure 100 as a whole can be increased, and the bending reinforcement effect can be further enhanced.

[0052] According to this embodiment, the FRP plate material 2 is bonded to the lower surface 51b of the upper flange 51. Therefore, even when a structure such as a floor slab 91 is provided on the upper surface 51a of the flange 51, it is possible to provide a bending reinforcement effect to the I-section steel material 5.

[0053] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 that is attached to the flange 51. This allows for a significant reduction in weight when reinforcing a steel member with a backing plate compared to when a web bypass member made of a metal plate is joined by bolts or welding. Therefore, the increase in dead load after reinforcement can be suppressed.

[0054] (Second embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the second embodiment will be described. Detailed explanations of configurations similar to those in the first embodiment described above will be omitted. Figure 5 is a cross-sectional view showing an example of the reinforcing structure 100 in the second embodiment. As shown in Figure 5, in this embodiment, the FRP plate material 2 is bonded to the upper flange 51. The fiber sheet 3 is attached to the second main surface 2b.

[0055] 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 a floor slab 91 is provided on the upper surface 51a of the flange 51, the fiber sheet 3 can exert a bending reinforcement effect on the I-section steel material 5 without being limited by the thickness of the fiber sheet 3.

[0056] (Third embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the third embodiment will be described. Figure 6(a) is a cross-sectional view showing an example of the reinforcing structure 100 in the third embodiment, and Figure 6(b) is a cross-sectional view showing a first modified example of the reinforcing structure 100 in the third embodiment. As shown in Figure 6, in this embodiment, the FRP plate material 2 is bonded to the lower flange 52. The FRP plate material 2 has a first main surface 2a on which a bonding surface is formed to be bonded to the upper surface 52a of the flange 52, and a second main surface 2b on the opposite side of 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.

[0057] As shown in Figure 6(a), the fiber sheet 3 is attached to the first main surface 2a of the FRP plate material 2.

[0058] As shown in Figure 6(b), the fiber sheet 3 is attached to the second main surface 2b of the FRP plate material 2.

[0059] In particular, according to this embodiment, the FRP plate 2 is bonded to the lower flange 52. This allows the FRP plate 2 to be bonded to the lower flange 52 without having to work in an upward position. Therefore, it is possible to reduce the burden on workers during installation.

[0060] In particular, according to the present embodiment, the fiber sheet 3 is attached to the first main surface 2a. As a result, the fiber sheet 3 is disposed at a position further away from the neutral axis of the I-section steel member 5 than in the case where the fiber sheet 3 is attached to the second main surface 2b. Therefore, the moment of inertia of area of the reinforcing structure 100 as a whole can be increased, and the bending reinforcement effect can be further exerted.

[0061] In particular, according to the present embodiment, the fiber sheet 3 is attached to the second main surface 2b. Accordingly, even when a structure such as a bridge pier 92 is provided on the lower surface 52b of the flange 52, the bending reinforcement effect can be exerted on the I-section steel member 5 without being restricted by the thickness of the fiber sheet 3.

[0062] (Fourth Embodiment: Reinforcing Structure 100) As shown in Fig. 7, Fig. 8(a) and Fig. 8(b), the reinforcing structure 100 reinforces, for example, the existing I-section steel member 5 that supports the deck slab 91 of the bridge 9 from below. The reinforcing structure 100 includes the I-section steel member 5 serving as a steel member, and the reinforcing member 1. The I-section steel member 5 is used not only as a girder member for supporting the deck slab 91, but also as a beam member, for example.

[0063] <Reinforcing Member 1> The reinforcing member 1 reinforces the I-section steel member 5. The reinforcing member 1 includes the FRP plate member 2 and the adhesive layer 4.

[0064] <FRP Plate Member 2> The FRP plate member 2 is attached to the lower surface 51b of the flange 51 via the adhesive layer 4.

[0065] As shown in Figure 9, the FRP sheet material 2 is constructed by laminating multiple unidirectional fiber sheets 29, each made of continuous reinforcing fibers such as carbon fibers, glass fibers, basalt fibers, and aramid fibers aligned in one direction and impregnated with resin. The unidirectional fiber sheets 29 are made of FRP (Fiber Reinforced Plastics), for example, CFRP (Carbon Fiber Reinforced Plastics). In the case of CFRP, the unidirectional fiber sheets 29 have a tensile strength of 2300 N / mm² as measured according to JIS A1191:2004. 2 Furthermore, it is preferable that the carbon fiber sheet has the above characteristics and an elastic modulus of 280 GPa to 450 GPa.

[0066] The matrix resin of the FRP can be either a thermosetting resin or a thermoplastic resin, but a thermosetting resin such as vinyl ester resin or epoxy resin is preferred. The FRP sheet material 2 is formed with its longitudinal direction extending in the second direction Y, and it is desirable to taper the longitudinal end 28 of the FRP sheet material 2 at an arbitrary angle in plan view from the viewpoint of avoiding stress concentration, ease of construction, and not providing unnecessary parts that do not participate in stress transmission. There are no particular restrictions on the taper angle at the end 28, but it is preferable that the angle is aligned with the orientation direction of at least two directions other than the main direction of the unidirectional fiber sheet that constitutes the FRP sheet material 2.

[0067] The FRP sheet material 2 has different fiber orientations for the unidirectional fiber sheets 29 oriented in the main direction and the other unidirectional fiber sheets 29. As a result, stress is transmitted from one adhesive portion 23a of the FRP sheet material 2 to the other adhesive portion 23b via the bypass portion 24, thereby reducing the stress on the I-section steel material 5. For example, the FRP sheet material 2 has a unidirectional fiber sheet 29 whose fiber orientation is in the second direction Y from one adhesive portion 23a to the other adhesive portion 23b (direction P1 in Figure 9, also called the "main direction"), a unidirectional fiber sheet 29 whose fiber orientation is in a direction tilted at an angle θ1 (e.g., +45°) with respect to the second direction Y (direction P2 in Figure 9), and a unidirectional fiber sheet 29 whose fiber orientation is in a direction tilted at an angle θ2 (e.g., -45°) with respect to the second direction Y (direction P3 in Figure 9). Thus, the FRP sheet material 2 has fiber orientation in at least three directions in total, namely the main direction and at least two directions different from the main direction. When it has a unidirectional fiber sheet 29 with fiber orientation in the second direction Y, it is preferable that the fiber orientation of the other at least two directions of the unidirectional fiber sheet 29 is tilted by an absolute value of approximately 15° to 75° with respect to the second direction Y, more preferably by approximately 30° to 60°, and most preferably by 45°. Furthermore, when four or more fiber orientations are adopted, fiber orientations perpendicular (90°) to the main direction may be included.

[0068] As shown in Figure 10, the FRP sheet material 2 has a pair of adhesive sections 23 (23a and 23b), a bypass section 24, and a notch section 21. The adhesive sections 23 are formed on both sides in the second direction Y, flanking the vertical stiffener 54. The adhesive sections 23 are provided with an adhesive layer 4 and are attached to the lower surface 51b of the flange 51. The bypass section 24 is formed adjacent to the adhesive sections 23 in the first direction X, and connects the pair of adhesive sections 23 by bypassing the vertical stiffener 54. The notch section 21 is formed by cutting out from one side end in the first direction X, and the notch section 21 forms a reduced section 22 in which the width dimension of the FRP sheet material 2 is reduced. The reduced section 22 is formed in the bypass section 24. The vertical stiffener 54 is inserted into the notch section 21. The notch 21 is cut out in a trapezoidal shape, for example, but its shape is arbitrary. However, it is preferable that the shape aligns with the fiber orientation of the unidirectional fiber sheet 29 that constitutes the FRP plate material 2. Furthermore, it is desirable that the fiber orientation of the unidirectional fiber sheet throughout the FRP plate material be symmetrical with respect to the principal direction.

[0069] There are no specific regulations regarding the dimensions of the FRP sheet material 2, as it is designed according to the structure being reinforced. However, the overall length is capped at approximately 2500 mm from the standpoint of workability. Furthermore, the length of the transmission section L from the ends of the pair of adhesive sections 23 (23a, 23b) provided on the FRP plate material 2 to the notched section 21 is preferably 300 mm or more, and more preferably 600 mm or more, from the viewpoint of preventing localized stress from being transmitted from one adhesive section through the bypass section 24.

[0070] As shown in Figure 11, the thickness of the FRP sheet material 2 is preferably tapered toward the end 28 in the main direction. The tapered shape may be formed by shaving or cutting the end of a plate-shaped unidirectional fiber sheet such as a rectangular parallelepiped, or by laminating multiple unidirectional fiber sheets 29 of similar shapes that differ only in size.

[0071] <Adhesive layer 4> The adhesive layer 4 adheres the lower surface 51b of the flange 51 to the adhesive portion 23 of the FRP sheet material 2 and is provided between the lower surface 51b of the flange 51 and the adhesive portion 23 of the FRP sheet material 2. The adhesive layer 4 preferably includes a high-elongation elastic resin layer, for example, an epoxy resin layer.

[0072] The adhesive layer 4 uses a well-known resin material that can bond the lower surface 51b of the flange 51 and the bonding portion 23 of the FRP plate material 2 to each other. As the adhesive layer 4, for example, instead of an epoxy resin layer, a highly elongated elastic resin such as an acrylic resin layer, a polyurea resin layer, or a urea urethane resin can also be used. A highly elongated elastic resin has a tensile modulus of 50 to 100 N / mm². 2 Furthermore, the resin has an elongation of 300% or more under maximum tensile load. The maximum tensile load elongation of the high-elongation elastic resin is preferably 300% to 1200%, more preferably 300% to 700%, and even more preferably 300% to 500%.

[0073] (Fourth embodiment: An example of a method for reinforcing steel members) Next, an example of a method for reinforcing a steel member in the fourth embodiment will be described. As shown in Figures 12(a) and 12(b), the method for reinforcing a steel member includes an installation step of installing a reinforcing member 1 on an I-shaped cross-section steel material 5.

[0074] First, as shown in Figure 12(a), an adhesive layer 4 is applied to the adhesive portion 23 during the installation process. Then, as shown in Figure 12(b), during the installation process, a pair of adhesive portions 23 are attached to the lower surface 51b of the flange 51 via the adhesive layer 4, bypassing the vertical stiffener 54 with the bypass portion 24.

[0075] This concludes the description of an example of a reinforcement method in the first embodiment.

[0076] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 that is attached to the flange 51. This allows for a significant reduction in weight when reinforcing a steel member with a backing plate compared to when a web bypass member made of a metal plate is joined by bolts or welding. Therefore, the increase in dead load after reinforcement can be suppressed.

[0077] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 in which a plurality of unidirectional fiber sheets 29 are laminated. The FRP plate material 2 has a pair of adhesive 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 adhesive portions 23 by bypassing the vertical stiffener 54. The fiber orientation in the FRP plate material 2 has a main direction from one adhesive portion 23a to the other adhesive portion 23b, and at least two directions different from the main direction. As a result, when a load is applied to the flange 51 of the I-section steel material 5, stress can be smoothly transmitted from one adhesive portion 23a to the other adhesive portion 23b via the bypass portion 24. In this way, the stress on the flange 51 can be reduced by the reinforcing member 1 bearing the stress. Therefore, it is possible to exert a bending reinforcement effect against both positive and negative bending at the joint between the flange 51 and the vertical stiffener 54 of the I-section steel material 5.

[0078] Furthermore, according to this embodiment, the adhesive 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.

[0079] Furthermore, according to this embodiment, a bypass section 24 is formed to connect the pair of adhesive sections 23 by bypassing a second steel member such as a vertical stiffener 54. This makes it possible to perform proper reinforcement while avoiding obstacles, even in locations where sufficient anchoring length cannot be obtained due to obstacles such as bolts, backing plates, or stiffener plates, making reinforcement difficult.

[0080] According to this embodiment, the fiber orientation in at least two directions, which are oriented in directions different from the principal direction, is tilted at an absolute value of 15° to 75° from the principal direction, and is symmetrical with respect to the principal direction. This enhances the isotropy of the FRP plate material 2, allowing for efficient and uniform stress transmission. As a result, it becomes possible to further exhibit bending reinforcement effects against both compression and tension.

[0081] According to this embodiment, the notch portion 21 is shaped in accordance with 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 transfer from one adhesive portion 23a to the other adhesive portion 23b via the bypass portion 24.

[0082] According to this embodiment, the reinforcing member 1 further includes an adhesive layer 4 between the adhesive portion 23 and the flange 51, and the adhesive layer 4 includes a high-elongation elastic resin layer. This makes it possible to suppress the peeling of the high-elongation elastic resin layer prematurely after the flange 51 yields. As a result, the bending reinforcement effect can be further enhanced.

[0083] According to this embodiment, the thickness of the FRP sheet material 2 is tapered toward the end 28 in the main direction. This suppresses abrupt changes in the cross-section caused by the FRP sheet material 2 and suppresses stress concentration at the end 28 of the FRP sheet material 2. As a result, stress is transmitted more smoothly from one adhesive portion 23a to the other adhesive portion 23b via the bypass portion 24.

[0084] According to this embodiment, the FRP plate material 2 has a ratio of the shear modulus value to the axial modulus value of 0.05 or more and 6.00 or less. This reduces stress transmission loss at the notch 21. Therefore, it is possible to further exhibit the bending reinforcement effect. In particular, the FRP plate material 2 has a ratio of the shear modulus value to the axial modulus value of 0.15 or more and 0.35 or less, which significantly reduces stress transmission loss at the notch 21. Therefore, it is possible to further exhibit the bending reinforcement effect.

[0085] According to this embodiment, the adhesive portion 23 of the FRP plate material 2 is attached to the lower surface 51b of the upper flange 51. Therefore, even when a structure such as a floor slab 91 is provided on the upper surface 51a of the flange 51, it is possible to provide a bending reinforcement effect to the I-section steel material 5.

[0086] (Fifth embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the fifth embodiment will be described. As shown in Figures 13(a) and 13(b), in this embodiment, the reinforcing member 1 comprises an FRP plate 2, a fiber sheet 3, and an adhesive layer 4, similar to the first embodiment. In this case, similar to the first embodiment, the fiber sheet 3 is attached to the FRP plate 2 so as to span the reduced portion 22.

[0087] (Sixth embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the sixth embodiment will be described. As shown in Figure 14, in this embodiment, the adhesive portion 23 of the FRP plate material 2 is attached to the upper surface 52a of the lower flange 52 via the adhesive layer 4.

[0088] In particular, according to this embodiment, the adhesive portion 23 of the FRP sheet material 2 is attached to the lower flange 52. This allows the FRP sheet material 2 to be bonded to the lower flange 52 without having to work in an upward position. Therefore, it is possible to reduce the burden on workers during installation.

[0089] (Sixth embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the sixth embodiment will be described. As shown in Figures 15(a), 15(b), 16(a), and 16(b), in this embodiment, the reinforcing member 1 further comprises a continuous fiber material 8 and adhesive layers 4 and 6 between the adhesive portion 23 and the flange 51, and a pair of continuous fiber materials 8 are provided spaced apart on both sides of the vertical stiffener 54. The continuous fiber material 8 reinforces the flange 51, mainly reinforcing the portion that does not become the joint between the flange 51 and the vertical stiffener 54.

[0090] <Continuous Fiber Material 8> The continuous fiber material 8 can be a continuous fiber sheet (e.g., Tow Sheet®) made of carbon fiber, glass fiber, basalt fiber, aramid fiber, etc., or a sheet (e.g., Strand Sheet®) made by processing multiple FRP strands that have been pre-impregnated and hardened with resin into a blind-like shape. The continuous fiber material 8 is made by laminating multiple fiber sheets such as carbon fiber, and bonding multiple layers to each other. It may be formed by impregnating and hardening the Tow Sheet or Strand Sheet with resin at the construction site, or by bonding pre-formed plates. The continuous fiber material 8 is composed of multiple laminated unidirectional fiber sheets in which the fiber orientation is oriented in a predetermined one direction, and the fiber orientation of all laminated unidirectional fiber sheets may be oriented in the longitudinal direction of the continuous fiber material 8.

[0091] The continuous fiber members 8 are provided spaced apart on both sides of the vertical stiffener 54. The continuous fiber members 8 are attached to the bonding portion 23 of the FRP plate 2 via an adhesive layer 6, and to the flange 51 via an adhesive layer 4.

[0092] <Adhesive layer 4> The adhesive layer 4 adheres the lower surface 51b of the flange 51 and the continuous fiber material 8 to each other and is provided between the lower surface 51b of the flange 51 and the continuous fiber material 8. The adhesive layer 4 preferably includes a high-elongation elastic resin layer, and for example, as shown in Figure 16, it includes a polyurea resin layer 41 and an epoxy resin layer 42. The polyurea resin layer 41 is in contact with the flange 51, and the epoxy resin layer 42 is in contact with the continuous fiber material 8. This makes it possible to suppress the peeling of the polyurea resin layer 41 early after the yielding of the flange 51.

[0093] Although not shown in the diagram, the polyurea resin layer 41 may be bonded to the continuous fiber material 8, and the epoxy resin layer 42 may be bonded to the flange 51. This allows the bonding of the polyurea resin layer 41 on the continuous fiber material 8 side and the application of the other resin layers on the flange 51 side to be carried out simultaneously.

[0094] The adhesive layer 4 is made of a well-known resin material that can bond the lower surface 51b of the flange 51 and the continuous fiber material 8 to each other. As the adhesive layer 4, for example, a high-elongation elastic resin such as acrylic resin can be used instead of the epoxy resin layer 42, or a urea-urethane resin can be used instead of the polyurea resin layer 41. A high-elongation elastic resin has a tensile modulus of 50 to 100 N / mm². 2 Furthermore, the resin has an elongation of 300% or more under maximum tensile load. The maximum tensile load elongation of the high-elongation elastic resin is preferably 300% to 1200%, more preferably 300% to 700%, and even more preferably 300% to 500%.

[0095] The adhesive layer 4 is preferably formed in advance on the continuous fiber material 8, but it may also be formed on the continuous fiber material 8 at the construction site, or it may be formed on the lower surface 51b of the flange 51.

[0096] <Adhesive layer 6> The adhesive layer 6 adheres the continuous fiber material 8 and the FRP plate material 2 to each other and is provided between the adhesive 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 epoxy adhesive, acrylic adhesive, or urethane adhesive can be used, but epoxy adhesive is preferred.

[0097] In particular, according to this embodiment, the reinforcing member 1 further includes a continuous fiber material 8 between the adhesive portion 23 and the flange 51, and the continuous fiber material 8 is provided in pairs on both sides of the vertical stiffener 54, spaced apart from each other. As a result, the portion that is not a joint between the flange 51 and the vertical stiffener 54 is reinforced by the continuous fiber material 8, while stress is transmitted from one adhesive portion 23 to the other adhesive portion 23 via the bypass portion 24 by the FRP plate material 2. Therefore, it is possible to achieve bending reinforcement effects against both positive and negative bending at the joint between the flange 51 and the vertical stiffener 54 and at the other portions of the I-section steel material 5.

[0098] (Seventh embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the seventh embodiment will be described. As shown in Figures 17(a) and 17(b), the reinforcing structure 100 reinforces a steel member 7 having one steel plate 71 as a first steel material and an out-of-plane gusset 72 as a second steel material joined to the one steel plate 71 by welding. The out-of-plane gusset 72 is positioned substantially perpendicular to the steel plate 71.

[0099] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 that is attached to the steel plate 71. This makes it possible to significantly reduce the weight when reinforcing a steel member with a backing plate compared to when a web bypass member made of a metal plate is joined by bolts or welding. Therefore, the increase in dead load after reinforcement can be suppressed.

[0100] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 in which a plurality of unidirectional fiber sheets 29 are laminated. The FRP plate material 2 has a pair of adhesive portions 23 formed on both sides of an out-of-plane gusset 72 and attached to the steel plate 71, and a bypass portion 24 for connecting the pair of adhesive portions 23 by bypassing the out-of-plane gusset 72. The fiber orientation in the FRP plate material 2 has a main direction from one adhesive portion 23a to the other adhesive portion 23b, and at least two directions different from the main direction. As a result, when a load is applied to the steel plate 71 of the steel member 7, stress can be smoothly transmitted from one adhesive portion 23a to the other adhesive portion 23b via the bypass portion 24. In this way, the stress on the steel plate 71 can be reduced by the reinforcing member 1 bearing the stress. Therefore, it is possible to exert a bending reinforcement effect against both positive and negative bending at the joint between the steel plate 71 and the out-of-plane gusset 72 of the steel member 7.

[0101] Furthermore, according to this embodiment, the adhesive 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.

[0102] In Figure 10, the adhesive portion 23 is sized to cover only a portion of the total width of the steel plate 71, but it may also be sized to cover the entire width of the steel plate 71.

[0103] (Eighth embodiment: Reinforcement structure 100) Next, an example of the reinforcing structure 100 in the eighth embodiment will be described. As shown in Figures 18(a) and 18(b), the reinforcing structure 100 reinforces a steel member 7 having 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. The splice plate 73 connects the two steel plates 71 to each other.

[0104] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 that is attached to the steel plate 71. This makes it possible to significantly reduce the weight when reinforcing a steel member with a backing plate compared to when a web bypass member made of a metal plate is joined by bolts or welding. Therefore, the increase in dead load after reinforcement can be suppressed.

[0105] According to this embodiment, the reinforcing member 1 has an FRP plate material 2 in which a plurality of unidirectional fiber sheets 29 are laminated. The FRP plate material 2 has a pair of adhesive portions 23 formed on both sides of the splice plate 73 and attached to the steel plate 71, and a bypass portion 24 for connecting the pair of adhesive portions 23 by bypassing the splice plate 73. The fiber orientation in the FRP plate material 2 has a main direction from one adhesive portion 23a to the other adhesive portion 23b, and at least two directions different from the main direction. As a result, when a load is applied to the steel plate 71 of the steel member 7, stress can be smoothly transmitted from one adhesive portion 23a to the other adhesive portion 23b via the bypass portion 24. In this way, the stress on the steel plate 71 can be reduced by the reinforcing member 1 bearing the stress. Therefore, it is possible to exert a bending reinforcement effect against both positive and negative bending at the joint between the steel plate 71 and the splice plate 73 of the steel member 7.

[0106] Furthermore, according to this embodiment, the adhesive portion 23 of the FRP plate material 2 is attached to the steel plate 71. This makes it possible to easily install the reinforcing member 1.

[0107] In Figure 18, the FRP sheet material attachment portion 23 is sized to cover only a portion of the total width of the steel plate 71, but it may also be sized to cover the entire width of the steel plate 71. In addition, the FRP sheet material 2 may be attached to the back surface of the steel plate 71 (the opposite side of the steel plate 71 sandwiched between the splice plate 73 in Figure 18).

[0108] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Examples]

[0109] In Example 1, a bending test was performed on the fabricated specimen to examine its bending reinforcement effect.

[0110] <Specimen> Figure 19 is a side view showing the specimen of Example 1. Figure 20 is a cross-sectional view showing the specimen of Example 1. In Example 1, specimens of Comparative Example 1, Invention Example 1, and Invention Example 2 were prepared 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. Vertical and horizontal stiffeners were also installed in the specimen. In the specimen, the width of the upper and lower flanges of the central plate girder was set to 150 mm and the plate thickness to 6 mm. In the specimen, the width of the upper and lower flanges of the plate girders at both ends was set to 200 mm and the plate thickness to 12 mm. As a result, failure occurred first in the central plate girder. In this test, all the plate girders at both ends were the same, and the test was conducted while only the central plate girder was replaced.

[0111] Table 1 shows an overview of the test specimens. In the specimen of Example 1 of the present invention, a reinforcing member was bonded to the upper flange via an adhesive layer. The reinforcing member comprises a CFRP molded plate with a notch formed therein, and a carbon fiber strand sheet attached so as to span the reduced portion where the dimensions of the CFRP molded plate are reduced by the notch. The CFRP molded plate was manufactured from a carbon fiber sheet and an epoxy resin by a hand lay-up molding method. In addition, in the specimen of Example 2 of the present invention, a carbon fiber sheet was further bonded to the lower surface of the lower flange. In Comparative Example 1, no reinforcement was performed using a reinforcing member.

[0112] [Table 1]

[0113] Table 2 shows an overview of the fiber sheets. The carbon fiber sheets in Table 2 are used in the manufacture of CFRP molded plates and are also bonded to the lower surface of the lower flange in Example 2 of the present invention. The carbon fiber strand sheets in Table 2 are attached to the reduced portion of the reinforcing members used in Example 1 and Example 2 of the present invention.

[0114] [Table 2]

[0115] Table 3 shows an overview of the resins used in the test specimens. Epoxy resins are used in the fabrication of CFRP molded plates. Polyurea putty and epoxy putty are used for bonding the flange to the CFRP molded plate. Bonding the carbon fiber strand sheets to the CFRP molded plate was performed in accordance with the "Design and Construction Manual for Repair and Reinforcement Methods of Steel Structures Using Carbon Fiber Sheets" (Highway Technology Research Institute Co., Ltd., 2013).

[0116] [Table 3]

[0117] Table 4 shows an overview of CFRP molded sheets. The elastic modulus in Table 4 is the measured value obtained by tensile testing as specified in JIS K 7165.

[0118] [Table 4]

[0119] Figure 21 is a plan view showing the reinforcing member in the specimen of Example 1. The CFRP molded plate was made flat for ease of fabrication, and a notch was made to accommodate the vertical stiffener in the center of the specimen. The size of the notch was such that it could accommodate the vertical stiffener in the center of the specimen, and the corners of the notch were made in an arc shape. The total width of the CFRP molded plate was 100 mm, and the length was 1,600 mm, which is the length that can secure an anchoring length of 200 mm from the point of thickness change (outside) of the specimen. To reinforce the cross-sectional loss of the notch, a 30 mm wide carbon fiber strand sheet was bonded to the top surface of the CFRP molded plate using epoxy resin. The bonding length of the carbon fiber strand sheet was such that the outermost layer was 200 mm from both ends of the notch, with a shift amount of 25 mm at each end of each layer.

[0120] The fiber orientation of the CFRP molded plate was set to a ratio of 1 / 2 / 1 layers in the -45 / 0 / 45° direction relative to the axial direction to ensure stress transmission even in the notched area. The number of layers was determined to increase the bending stiffness of the central part of the specimen by 25% when the upper and lower flanges were reinforced, resulting in a total of 16 layers in the [0° / ±45° / 0°] direction. The layering order was symmetrical in the thickness direction. In addition, the number of carbon fiber strand sheets in the notched area was determined to be 7 layers, so that the cross-sectional stiffness of the carbon fiber strand sheets was equal to the cross-sectional stiffness of the missing section. The carbon fiber strand sheets were bonded to the CFRP molded plate using epoxy putty.

[0121] In conventional methods for bonding CFRP molded plates to the upper flange, a polyurea putty layer is applied to the steel side. However, in this test, the polyurea putty layer was applied to the CFRP molded plate side. This allows for simultaneous work on both the CFRP molded plate and steel sides, leading to labor savings during construction. The bonding procedure involved preparing the bonding area on both the steel and CFRP molded plates. Epoxy primer was applied to the steel, and urethane primer to the CFRP molded plate, followed by the application of polyurea putty. After the epoxy primer and polyurea putty dried, the plates were bonded to the underside of the upper flange using epoxy putty. The procedure for bonding carbon fiber sheets for lower flange reinforcement was based on the "Design and Construction Manual for Repair and Reinforcement Methods of Steel Structures Using Carbon Fiber Sheets" (Highway Technology Research Institute Co., Ltd., 2013).

[0122] <Exam Overview> The test consisted of a four-point bending test with a span length of 6,000 mm, a uniform bending section of 2,500 mm, and a shear section of 1,750 mm. Loading was performed monotonically by displacement control, and the load was applied until it stopped increasing.

[0123] Furthermore, during the bending test, the strain of the upper flange was measured using strain gauges. Twenty-one strain gauges were placed on the upper surface of the flange of the specimen, with three gauges at seven locations: the center of the specimen in the direction of the material axis, and at ±100 mm, ±300 mm, and ±500 mm from the center of the specimen, perpendicular to the direction of the material axis. The strain measured was the strain of the upper flange of each specimen at 200 kN, before buckling or delamination occurred.

[0124] <Test Results: Destruction Status> Table 5 shows the maximum load, displacement at maximum load, and failure conditions for each test.

[0125] [Table 5]

[0126] In the positive bending test, the CFRP molded plate underwent compressive failure at 558kN in Example 1 of the present invention and at 555kN in Example 2 of the present invention. Therefore, while Example 1 achieved a maximum load similar to Comparative Example 1, Example 2 of the present invention, in which a carbon fiber sheet was bonded and reinforced to the lower flange, showed no damage such as delamination or fracture of the carbon fiber sheet on the lower flange even at the ultimate limit, resulting in an improved maximum load compared to Comparative Example 1.

[0127] In the negative bending test, in Example 1 of the Invention, the CFRP molded plate delaminated from the notched end at 575kN, and in Example 2 of the Invention, it delaminated from the steel-epoxy resin bond at 675kN. As the load increased, the CFRP molded plate on the non-notched side also delaminated. Furthermore, in Example 2 of the Invention, the carbon fiber sheet of the lower flange also underwent compressive failure at the ultimate limit. Therefore, in this test, the maximum loads for both Example 1 and Example 2 yielded the same results as in Comparative Example 1. In this test, the polyurea putty was placed on the CFRP molded plate side to reduce labor during construction. However, it is possible that the polyurea putty did not exhibit its delamination-suppressing effect because it delaminated brittlely between the steel and epoxy resin before the steel yielded.

[0128] <Test results: Strain of the upper flange> Figure 22(a) shows the strain distribution of Comparative Example 1, Invention Example 1, and Invention Example 2 in a positive bending test, and Figure 22(b) shows the strain distribution of Comparative Example 1, Invention Example 1, and Invention Example 2 in a negative bending test. In Figure 22, the horizontal axis represents the distance from the center of the specimen, and the vertical axis represents strain. Figure 22 shows the strain distribution of the upper flange of each specimen at 200 kN, before buckling, delamination, etc., occur in the specimen. The values ​​in the strain distribution diagram shown in Figure 22 are the average values ​​of strains read from three strain gauges arranged perpendicular to the material axis. Also, "Comparative Example 1 (Calculated Value)", "Invention Example 1 (Calculated Value)", and "Invention Example 2 (Calculated Value)" shown in Figure 22 are calculated values ​​for each test specimen, and were calculated according to beam theory. The "Design and Construction Manual for Repair and Reinforcement Methods of Steel Structures Using Carbon Fiber Sheets" (Highway Technology Research Institute Co., Ltd., 2013) indicates that when polyurea putty is used for bonding, a completely composite cross-section cannot be achieved due to the influence of the polyurea putty, and therefore the design should be carried out by multiplying the cross-sectional area of ​​the carbon fiber by a stress reduction coefficient. This stress reduction coefficient is a value determined by the number of layers of carbon fiber sheets, the bonding length, the edge treatment method, etc. However, the stress reduction coefficient for reinforcement using CFRP molded boards used in this test has not been investigated. Therefore, the fully composite cross section is used without considering the stress reduction coefficient. Furthermore, vertical and horizontal stiffeners are not considered, and the stress transfer section to the carbon fiber reinforcement (200 mm at both ends of the carbon fiber reinforcement) is considered. Only the central 1,200 mm section is treated as a reinforced cross section, and the other sections are treated as unreinforced cross sections. The calculation results are for a cross section without carbon fiber strand sheets and notches.

[0129] In the positive bending test, the distribution showed that each specimen produced a large compressive strain at its center. Furthermore, compared with Comparative Example 1, it was confirmed that stress reduction was observed at all measured points in both Invention Example 1 and Invention Example 2. Averaging the strains of all 21 strain gauges on the upper flange of each specimen, compared with Comparative Example 1, stress reduction was 13% in Invention Example 1 and 25% in Invention Example 2. From the strain distribution of Invention Example 1 and Invention Example 2, the strain was small at ±100 mm from the center, and larger at the center than at the ±100 mm point. This is thought to be because the area around ±100 mm from the center is a part of the CFRP molded plate without notches and with carbon fiber strand sheets, and the cross-sectional area of ​​the reinforcing material is larger and the cross-sectional rigidity is greater than at other points, resulting in a greater reinforcing effect and smaller strain in the upper flange. At the center of the specimen, there is a notch, so the strain is thought to be larger than the strain at the ±100 mm point. Compared to the calculated value, the strain in the upper flange at the center of the specimen is greater. However, this is because the calculated value assumes that the reinforced cross-section is a fully composite cross-section. It is expected that the calculated value will match the calculated value if the calculation is performed considering the stress reduction factor due to the polyurea resin.

[0130] In the negative bending test, similar to the positive bending test, the distribution showed that the tensile strain at the center of the upper flange of the specimen was large. Compared with Comparative Example 1, it was confirmed that the stress was reduced at all measured points. Averaging the strains of all 21 strain gauges on the upper flange of each specimen, and comparing with Comparative Example 1, the stress was reduced by 15% in Invention Example 1 and by 18% in Invention Example 2. In the negative bending test, the strain distribution of Invention Example 1 and Invention Example 2 was similar to the positive bending test, with small strains at ±100 mm from the center and larger strains at the center than at ±100 mm. When compared with calculated values, it is considered that the results will match the calculated values ​​by considering the stress reduction coefficient due to the polyurea resin, similar to the results of the positive bending test.

[0131] From the results and analysis of the bending tests described above, it was confirmed that even when the upper flange was reinforced with a notched CFRP molded plate, stress was transmitted from the notched portion to the carbon fiber strand sheet used for reinforcing the missing cross-section, and the CFRP molded plate bore the stress, resulting in a reduction in stress on the steel material. To increase the maximum load of the test specimen, the CFRP molded plate can be reinforced with a CFRP molded plate made from a carbon fiber sheet with higher strength than the carbon fiber sheet used in this test, so as not to cause compressive failure of the CFRP molded plate. [Examples]

[0132] In the negative bending test of the I-beam steel material in Example 1, it was confirmed that the CFRP molded plate delaminated before the steel material yielded. The delamination surface at this time was between the steel material and the epoxy resin, suggesting that the order of the resin layers may affect adhesion. Therefore, in Example 2, an adhesion test was conducted to confirm the effect of the position of the polyurea resin within the adhesive resin layer.

[0133] Figure 23(a) shows the specimen of CASE 1 (Example 3 of the present invention: adhesive resin layer of CFRP molded plate in Example 1 and Example 2 of the present invention) in Example 2, Figure 23(b) shows the specimen of CASE 2 (Example 4 of the present invention) in Example 2, and Figure 23(c) shows the specimen of CASE 3 (Example 5 of the present invention) in Example 2. In this test, three specimens were prepared for each case, with the presence or absence of polyurea resin and the position of the polyurea resin layer as parameters. In this test, the steel plate was 50 mm wide and 12 mm thick, and the steel plate was SS400, similar to the plate girder in the center of the bending specimen. A CFRP molded plate with a width of 50 mm and a length of 400 mm was bonded to both sides of the center of the steel plate, and a tensile test was performed at both ends.

[0134] Figure 24(a) shows the positions of the strain gauges for CASE1-1, CASE2-1 to CASE2-3, and CASE3-1, and Figure 24(b) shows the positions of the strain gauges for CASE1-2, CASE1-3, CASE3-2, and CASE3-3. For 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 Figure 24(a). Furthermore, for CASE1-1, CASE2-1 to CASE2-3, and CASE3-1, strain gauges were attached to the side of the specimen at 20 mm intervals, from the center in the axial direction of the specimen toward one end. Also, for CASE1-2, CASE1-3, CASE3-2, and CASE3-3, strain gauges were attached to both sides of the specimen at the positions shown in Figure 24(b). The material properties and construction procedures for the adhesive layer and CFRP molded board are the same as those for the bending test. The test was performed using a universal testing machine with displacement-controlled loading.

[0135] Table 6 shows the test results. In Table 6, "Ratio" indicates the ratio of the average maximum load of Invention Example 3 and Invention Example 4 (CASE 1 and CASE 2) to the average maximum load of Invention Example 5 (CASE 3).

[0136] In all specimens, delamination did not occur until the yield of the base steel sheet, and terminated after the base steel yielded. In Invention Example 4 (CASE 2), the failure site was cohesive failure where the polyurea resin layer failed, while in Invention Example 3 (CASE 1) and Invention Example 5 (CASE 3), it was delamination between the steel and epoxy resin. The maximum load increased by 8% in Invention Example 3 and 36% in Invention Example 4 compared to Invention Example 5, which does not have a polyurea layer. From the failure conditions and maximum load, it was confirmed that the adhesion performance of the CFRP molded plate is higher when a polyurea resin is present and the polyurea layer is on the steel side.

[0137] [Table 6]

[0138] Figure 25 is a diagram showing the relationship between load and strain in Example 2. The strain shown in Figure 25 is the average value of the CFRP molded plates on both sides, and the dotted line in the figure is the calculated value assuming a fully composite cross-section.

[0139] From Figure 25, in Inventive Example 5, the strain increases linearly, and the strain of CFRP at the time of base material yielding is about 1,000×10 -6 , which exhibited behavior roughly equivalent to the calculated value. On the other hand, Inventive Examples 3 and 4 showed similar behavior up to the yielding of the base steel material, but in Inventive Example 3, peeling occurred between the steel material and the epoxy resin at an early stage after base material yielding, whereas in Inventive Example 4, no peeling occurred even after base material yielding, the load and strain increased, and the test ended at about 1,000×10 -6 . In addition, the strain of Inventive Example 3 and Inventive Example 4 at the time of steel material yielding is about 400×10 -6 , which is reduced to about 0.4 times compared with Example 5, and this is considered to be an effect due to shear lag caused by the polyurea resin.

[0140] Figure 26 is a diagram showing the relationship between the distance from the center of the test specimen and strain in Example 2. Figure 26 shows the strain distribution of the CFRP molded plate at 150 kN, which is before the base material yielding of each test specimen. The dotted line in Figure 26 is the calculated value computed assuming a fully composite cross-section. In Inventive Example 5, the strain up to around 130 mm from the center of the test specimen is about 900×10 -6 , and after 130 mm, the distribution showed a sharp decrease in strain. In Inventive Example 3 and Inventive Example 4, the strain at the center of the test specimen is about 400×10 -6 , and the distribution showed that the strain decreases gently from the center of the test specimen to the end portion.

[0141] From the above, regardless of the configuration of the adhesive resin layer, delamination of the CFRP molded plate does not occur until the yielding of the base material, and the CFRP molded material bears the stress. Therefore, the reinforcing effect was exhibited in all of the present invention examples 3 to 5. However, in the present invention examples 3 and 4, the shear delay effect due to the polyurea resin is exhibited, and in particular, by arranging the polyurea layer on the steel material side in the adhesive layer as in the present invention example 4, the CFRP molded plate does not delaminate prematurely even after the yielding of the base material, and a higher reinforcing effect can be expected. [Examples]

[0142] In Example 3, similar to Example 1, a bending test was performed on the prepared specimen to examine the bending reinforcement effect.

[0143] In Example 1, the CFRP molded plate underwent compressive failure in the positive bending test. Therefore, in Example 3, a CFRP molded plate with a higher tensile strength than that used in Example 1 was used. In Example 3, the polyurea layer of the adhesive layer was placed on the steel side. In describing Example 3 below, we will mainly explain the differences from Example 1, and explain the points that are the same as in Example 1 as appropriate.

[0144] <Specimen> Figure 27 is a cross-sectional view showing the specimen of Example 3. In Example 3, specimens of Comparative Example 2 and Example 6 of the present invention were prepared using the bending mode and the presence or absence of reinforcement of the upper and lower flanges as parameters, and four-point bending tests of positive and negative bending were performed in the same manner as in Example 1.

[0145] Table 7 shows an overview of the test specimens. In the test specimen of Example 6 of the present invention, a reinforcing member was bonded to the upper flange via an adhesive layer. The reinforcing member comprises a CFRP molded plate with a notch formed therein, and a carbon fiber strand sheet attached so as to span the reduced portion of the CFRP molded plate where the dimensions have been reduced by the notch. In addition, a carbon fiber sheet was bonded to the lower surface of the lower flange. In Comparative Example 2, no reinforcement was performed using a reinforcing member.

[0146] [Table 7]

[0147] Table 8 shows an overview of the fiber sheets. The carbon fiber sheets in Table 8 are used in the manufacture of CFRP molded plates and are also bonded to the lower surface of the lower flange in Example 6 of the present invention. The carbon fiber strand sheets in Table 8 are attached to the reduced portion of the reinforcing member used in Example 6 of the present invention.

[0148] [Table 8]

[0149] The resin used for the test specimens is the same as that shown in Table 3.

[0150] Table 9 shows an overview of CFRP molded sheets. The elastic modulus in Table 9 is the measured value obtained by tensile testing as specified in JIS K 7165.

[0151] [Table 9]

[0152] Figure 28 is a plan view showing the reinforcing member in the specimen of Example 3. The CFRP molded plate was made flat for ease of fabrication, and a notch was made to accommodate the vertical stiffener in the center of the specimen. The size of the notch was such that it could accommodate the vertical stiffener in the center of the specimen, and the corners of the notch were made in an arc shape. The total width of the CFRP molded plate was 100 mm, and the length was 1,600 mm, which is the length that can secure an anchoring length of 200 mm from the point of thickness change (outside) of the specimen. To reinforce the cross-sectional loss of the notch, a 30 mm wide carbon fiber strand sheet was bonded to the top surface of the CFRP molded plate using epoxy resin. The bonding length of the carbon fiber strand sheet was such that the outermost layer was 200 mm from both ends of the notch, with a shift amount of 25 mm at each end of each layer.

[0153] The fiber orientation of the CFRP molded plate was set to a ratio of 1 / 2 / 1 layers in the -45 / 0 / 45° direction relative to the axial direction to ensure stress transmission even in the notched area. The number of layers was determined to increase the bending stiffness of the central part of the specimen by 25% when the upper and lower flanges were reinforced, resulting in a total of 24 layers ([0° / ±45° / 0°]6). The layering order was symmetrical in the thickness direction. In addition, the number of carbon fiber strand sheets in the notched area was determined to be 10 layers, so that the cross-sectional stiffness of the carbon fiber strand sheets was equal to the cross-sectional stiffness of the missing section. The carbon fiber strand sheets were bonded to the CFRP molded plate using epoxy putty.

[0154] As shown in Figure 29(a), when bonding the CFRP molded plate to the flange, a polyurea putty layer was applied to the steel material (flange) side. After the polyurea putty hardened, the CFRP molded plate was bonded to the lower surface of the upper flange using epoxy putty. As shown in Figure 29(b), the procedure for bonding the carbon fiber sheet to the flange was carried out in accordance with the "Design and Construction Manual for Repair and Reinforcement Methods of Steel Structures Using Carbon Fiber Sheets" (Highway Technology Research Institute Co., Ltd., 2013).

[0155] <Exam Overview> The test consisted of a four-point bending test with a span length of 6,000 mm, a uniform bending section of 2,500 mm, and a shear section of 1,750 mm. Loading was performed monotonically by displacement control, and the load was applied until it stopped increasing.

[0156] Furthermore, during the bending test, the strain of the upper flange was measured using strain gauges. Twenty-one strain gauges were placed on the upper surface of the flange of the specimen, with three gauges at seven locations: the center of the specimen in the direction of the material axis, and at ±100 mm, ±300 mm, and ±500 mm from the center of the specimen, perpendicular to the direction of the material axis. The strain measured was the strain of the upper flange of each specimen at 200 kN, before buckling or delamination occurred.

[0157] <Test Results: Destruction Status> Table 10 shows the maximum load for each test, the load at which the CFRP molded plate delaminated (hereinafter also referred to as the delamination load), and the failure conditions.

[0158] [Table 10]

[0159] Regarding the maximum load, it was 889kN in Comparative Example 2, while in Example 6 of the present invention it was 944kN in positive bending and 1045kN in negative bending. In Example 3, the maximum load of Example 6 of the present invention, which was reinforced with a reinforcing member, exceeded the maximum load of Comparative Example 2, which was unreinforced.

[0160] Furthermore, regarding the failure conditions, in Example 6 of the present invention, delamination 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 Example 2 of the present invention in Example 1, compressive failure occurred at 555 kN, and in the negative bending test of Example 2 of the present invention in Example 1, delamination of the CFRP molded plate occurred at 675 kN.

[0161] From the above, comparing Example 6 of the present invention with Example 2, the peel load (944kN) in the positive bending test of Example 6 was 70% higher than the breaking load (555kN) in the positive bending test of Example 2, and the peel load (830kN) in the negative bending test of Example 6 was 23% higher than the peel load (675kN) in the negative bending test of Example 2.

[0162] The tensile strength of the carbon fiber sheet used in Example 6 of the present invention is 3925 (N / mm²). 2 ) and the tensile strength of the carbon fiber sheet used in Example 1 was (2848 (N / mm²). 2 It is higher than ). As a result, neither the CFRP molded plate nor the carbon fiber sheet used for flange reinforcement showed compressive failure of the carbon fibers even under maximum load.

[0163] Regarding the peel load, it is believed that the peel load in Example 6 of the present invention was greater than the fracture load and peel load in Example 2 of the present invention because polyurea putty was placed on the steel material side when bonding the CFRP molded plate and the steel material.

[0164] In Example 6 of the present invention, the delamination mode of the CFRP molded plate was delamination from the edge of the CFRP molded plate, and the fracture surface was delamination between the CFRP molded plate and the epoxy resin.

[0165] Figure 30 shows the relationship between load and vertical displacement at the center of the span. In Example 6 of the present invention, no deformation such as delamination occurred in the positive bending test until the maximum load was reached, maintaining higher rigidity than the unreinforced version, and ultimately reaching the maximum load due to delamination. In the negative bending test, at 830kN, the CFRP molded plate on the vertical stiffener side showed a decrease in rigidity due to delamination, and at 1,000kN, the CFRP molded plate on the opposite side also showed delamination and a decrease in rigidity.

[0166] Figure 31 shows the strain distribution of the upper flange steel material for each specimen. Note that the subscript "_cal" in Figure 31, such as "Example 6_cal", represents the calculated value obtained using the fully composite cross-section. Compared to Comparative Example 2, Example 6 showed approximately 19% reduction in stress in the upper flange steel material during the positive bending test. Furthermore, it was confirmed that approximately 30% reduction in stress in the upper flange steel material was achieved during the negative bending test.

[0167] From the results and analysis of the bending tests described above, it was found that by using carbon fiber sheets with higher tensile strength, i.e., higher tensile strength for the CFRP molded plate laminated with them, compressive failure of the carbon fiber sheets did not occur even at the ultimate limit. The tensile strength of the carbon fiber sheets in Example 6 of the present invention was 3,925 (N / mm²). 2 ) and in Example 2 of the present invention, it is 2,848 (N / mm 2 Since it was 2,900 (N / mm²), the tensile strength of the carbon fiber sheet was determined to be 2,900 (N / mm²). 2 It is preferable to use the above. [Examples]

[0168] In Example 4, a bending test was performed on the fabricated specimen to examine its bending reinforcement effect.

[0169] <Specimen> Figure 32 is a cross-sectional view showing the specimen of Example 4. Figure 33 is a plan view showing the reinforcing member in Example 7 of the present invention. In Example 4, specimens of Comparative Example 3 and Example 7 of the present invention were prepared 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 plate height of 1,000 mm. Vertical and horizontal stiffeners were also installed in the specimen. In the specimen, the width of the upper and lower flanges of the central plate girder was set to 150 mm and the plate thickness to 6 mm. In the specimen, the width of the upper and lower flanges of the plate girders at both ends was set to 200 mm and the plate thickness to 12 mm. As a result, failure occurred first in the central plate girder. In this test, all the plate girders at both ends were the same, and the test was conducted while only the central plate girder was replaced.

[0170] Table 11 shows an overview of the test specimens. In the specimen of Invention Example 7, a reinforcing member was attached to the flange. In Invention Example 7, both positive bending tests and negative bending tests were performed. For the specimen used in the positive bending test, a reinforcing member was attached to the upper flange and a carbon fiber sheet was attached to the lower flange. For the specimen used in the negative bending test, a reinforcing member was attached to the lower flange and a carbon fiber sheet was attached to the upper flange. The reinforcing member was made by attaching a unidirectional CFRP molded plate to the flange, and then attaching a CFRP molded plate (hereinafter referred to as the bypass member) to this unidirectional CFRP molded plate so as to bypass the vertical stiffener. The unidirectional CFRP molded plate and the bypass member were manufactured from a carbon fiber sheet and an epoxy resin by a hand lay-up molding method. In Comparative Example 3, no reinforcement was performed using a reinforcing member.

[0171] [Table 11]

[0172] Table 12 shows an overview of the carbon fiber sheets. The carbon fiber sheets in Table 2 are medium-elasticity carbon fiber sheets. The carbon fiber sheets are used to manufacture unidirectional CFRP molded plates and bypass members, and are also bonded to flanges on the opposite side of the flange where reinforcing members are provided.

[0173] [Table 12]

[0174] Table 13 shows an overview of the resins used in the test specimens. The resins used to bond the carbon fiber sheets, unidirectional CFRP molded plates, and bypass members in this test are materials described in the "Design and Construction Manual for Repair and Reinforcement Methods of Steel Structures Using Carbon Fiber Sheets" (published by the Highway Technology Research Institute, Inc., 2020). Epoxy resins were used for the matrix resins of the unidirectional CFRP molded plates and the bypass members. High-elongation elastic putty (polyurea resin) and epoxy resin were used to bond the flanges to the unidirectional CFRP molded plates. Epoxy resin was used to bond the unidirectional CFRP molded plates to the bypass members. The steel material of the test panel portion of the steel girder specimens used in the test was SS400, with a yield strength of 293 N / mm². 2 (Test value)

[0175] [Table 13]

[0176] 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 set to 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 -45 / 0 / 45° with respect to the axial direction in a ratio of 1 / 2 / 1 layers, 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 was calculated based on the composite law and lamination theory. f The axial modulus of elasticity was also calculated. The number of layers of unidirectional CFRP molded plates was determined so that the bending stiffness of the central part of the steel girder specimen increased by 25% when the upper and lower flanges were reinforced. The number of layers of the bypass members was determined so that the tensile stiffness of the central part with the smallest cross-sectional area was the same as that of the unidirectional CFRP molded plates. The shape of the bypass members was also examined using FEM analysis. The details of the examination are shown below.

[0177]

Table 14

[0178] <Examination of Bypass Member Shape by FEM Analysis> Fig. 34(a) shows the overall view of the FEM analysis model, Fig. 34(b) shows the cross-sectional view of the FEM analysis model, and Fig. 34(c) shows the shape of the bypass member in the FEM analysis model. In the analysis model, only the flange portion was modeled, using solid elements. All materials were treated as linear materials, and the elastic modulus of the adhesive resin used the values in Table 3. Table 15 shows the material property values of the CFRP molded plate used in the analysis. Each value is based on the fiber volume content V f =0.5, and was calculated from the physical property values of the carbon fiber sheet (elastic modulus Ef=390,000N / mm 2 , Poisson's ratio νf=0.3) and the matrix resin (elastic modulus Em=2860N / mm 2 , Poisson's ratio νm=0.4). For the constraint conditions, the ends were roller-supported, and a uniaxial tensile load was applied. The analysis parameters were, as shown in Fig. 34(c), the length of the width-direction transmission section of the bypass member (CASE4: 150mm, CASE5: 300mm, CASE6: 600mm). The length of the bypass section was set to 30mm.

[0179]

Table 15

[0180] <FEM Analysis Results> Figure 35 shows the axial stress ratio distribution at the center of the underside of the steel plate in the FEM analysis model. The theoretical value was calculated from the tensile stiffness ratio of the CFRP molded plate and the steel plate. In Cases 4-6, the stress in the steel tended to be higher at the ends and in the center (800 mm from the ends) of the bypass members. Comparing Cases 4-6, the longer the transmission section, the lower the steel stress in the center tended to be. In the case of a 600 mm transmission section, the steel stress in the center is roughly in line with the theoretical value, but in the transmission section, the steel stress is below the theoretical value, resulting in many sections being over-reinforced and lacking economic viability. Also, the vertical stiffening member spacing of actual bridge steel girders is often around 1 m, and in the case of a 600 mm transmission section, adjacent bypass members interfere with each other, making it unsuitable. In the case of a 300 mm transmission section, the steel stress in the center is about 7% higher than the theoretical value, but in this model, it is generally close to the theoretical value throughout the entire section from the ends to the center. Therefore, considering economic efficiency and practical applicability in the field, a bypass member with a transmission section of 300 mm was adopted in this test.

[0181] <Exam Overview> The test consisted of a four-point bending test with a span length of 6,000 mm, a uniform bending section of 2,500 mm, and a shear section of 1,750 mm. Loading was performed monotonically by displacement control, and the load was applied until it stopped increasing.

[0182] Furthermore, during the bending test, the strain of the upper flange was measured using strain gauges. Figure 36 shows the location of the strain gauges. A total of 21 strain gauges were installed on the upper surface of the flange of the specimen, with three gauges at seven locations: the center of the specimen in the direction of the material axis, and at ±100 mm, ±300 mm, and ±500 mm from the center of the specimen, perpendicular to the direction of the material axis. The strain measured was the strain of the upper flange of each specimen at 200 kN, before buckling or delamination occurred.

[0183] <Bending test results: Test results and failure status> Table 16 shows a summary of the test results. In both the positive bending test specimens and the negative bending test specimens of Invention Example 7, the failure pattern showed that delamination between the unidirectional CFRP molded plate and the bypass member preceded the failure. In the positive bending test specimens, delamination occurred at 661 kN, and in the negative bending test specimens, delamination occurred at 850 kN.

[0184] [Table 16]

[0185] <Bending test results: Load-Span Center Vertical Deflection Relationship> Figure 37 shows the load-to-span vertical deflection relationship in Example 4. The calculated values ​​are based on an elastic modulus of 200,000 N / mm² for the steel. 2 The calculation was performed according to beam theory, ignoring vertical and horizontal stiffeners. As shown in Figure 37, the specimen used in the positive bending test of Example 7 of the present invention showed a decrease in stiffness due to delamination of the bypass member at 661 kN, prior to the yield load (calculated value) of 798 kN in Comparative Example 3. Since the bypass member used in this test was not tapered at the end, the stiffness changed due to the abrupt change in cross-sectional area at the bonded end of the bypass member. Therefore, it is thought that stress concentration occurred at the bonded end, and delamination occurred before the yield of the base steel girder.

[0186] In the negative bending test specimen of Example 7 of the present invention, the rigidity decreased due to delamination of the bypass member at 889 kN. Compared to the positive bending test specimen of Example 7 of the present invention, the delamination load was approximately 29% higher.

[0187] <Bending test results: Stress reduction effect of the upper flange> Figure 38 shows the strain distribution of the upper flange steel material of each specimen at 200 kN, before buckling, delamination, etc., occur in the specimen. As shown in Figure 38, it was confirmed that the stress was reduced in all measured cross-sections for both the specimens used in the positive bending test and the negative bending test of the present invention example 7, compared to Comparative Example 3. Averaging the strain at all 21 strain gauge points on the upper flange of each specimen and comparing it with Comparative Example 3, it was confirmed that the stress in the upper flange steel material was reduced by approximately 24% for the specimen used in the positive bending test and by approximately 26% for the specimen used in the negative bending test, obtaining a reinforcement effect that was roughly as calculated. From the above, it was confirmed that when the upper flange is reinforced with a reinforcing member using a bypass member, the stress is transmitted to the bypass member, resulting in a reduction in the stress of the steel girder specimen. [Explanation of Symbols]

[0188] 100: Reinforcement structure 1: Reinforcement member 2:FRP board material 21: Notch 22:Reduction part 23: Paste area 24: Bypass section 29: Unidirectional fiber sheet 3: Fiber sheet 4: Adhesive layer 5:I type cross section steel material 51: Flange 51a:Top surface 51b: Bottom surface 52: Flange 52a:Top surface 53: Web 54: Vertical stiffener 6: Adhesive layer 7: Steel parts 71: Steel plate 72: Out-of-plane gusset 73: Attachment plate 74: Bolt 8: Continuous fiber material 9: Bridge 91: Floor slab 92: Bridge pier X: 1st direction Y: Second direction Z: Third direction

Claims

1. A reinforcing structure for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, The invention comprises the steel member and a reinforcing member for reinforcing the steel member, The reinforcing member has an FRP plate material in which multiple unidirectional fiber sheets are laminated, each in which continuous reinforcing fibers are aligned in one direction and impregnated with resin. The aforementioned FRP sheet material is A pair of attachment portions are formed on both sides of the second steel material and attached to the first steel material, A bypass section that bypasses the second steel material and connects the pair of adhesive sections, It has a notch that is cut out from the side end and into which the second steel material is inserted, In the bypass portion, a reduced portion is formed in which the width dimension of the FRP plate material is reduced by the notch portion. The fiber orientation in the FRP sheet material has at least three directions in total: a main direction from one of the bonding portions toward the other bonding portion, and two directions different from the main direction. The reduced portion is positioned to protrude outward from the widthwise edge of the first steel material. A reinforcing structure characterized by the following.

2. The fiber orientations in at least two directions that are oriented in directions different from the principal direction are tilted by an absolute value of 15° to 75° from the principal direction and are symmetrical with respect to the principal direction. The reinforcing structure according to claim 1, characterized by the following:

3. The reinforcing member further comprises a continuous fiber material between the adhesive portion and the first steel material, The continuous fiber material is provided in pairs on both sides of the second steel material, spaced apart from each other. The reinforcing structure according to claim 1, characterized by the following:

4. The reinforcing member further comprises an adhesive layer between the adhesive portion and the first steel material, The adhesive layer includes a high-elongation elastic resin layer. The reinforcing structure according to claim 1, characterized by the following:

5. The thickness of the FRP plate material is tapered toward the end in the main direction. The reinforcing structure according to claim 1, characterized by the following:

6. The reinforcing member has a fiber sheet that is attached to the FRP plate material. The fiber sheet is attached to the FRP plate material so as to straddle the reduced portion. The reinforcing structure according to claim 1, characterized by the following:

7. 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. The fiber sheet is attached to the first main surface. The reinforcing structure according to claim 6, characterized by the above.

8. 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. The fiber sheet is attached to the second main surface. The reinforcing structure according to claim 6 or 7, characterized by the above.

9. The notch is formed in a trapezoidal shape and has a pair of inclined sides and an inner side connected to the pair of inclined sides, The inner edge is parallel to the principal direction, One of the aforementioned inclined sides is parallel to one of two directions different from the principal direction, The other inclined side is parallel to the other of two directions different from the principal direction. The reinforcing structure according to claim 2, characterized by the above.

10. A reinforcing member for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, The FRP plate material has multiple layers of unidirectional fiber sheets in which continuous reinforcing fibers are aligned in one direction and impregnated with resin. The aforementioned FRP sheet material is A pair of attachment portions are formed on both sides of the second steel material and are for attaching to the first steel material, A bypass section that bypasses the second steel material and connects the pair of adhesive sections, It has a notch that is cut out from the side end and a notch for inserting the second steel material, In the bypass portion, a reduced portion is formed in which the width dimension of the FRP plate material is reduced by the notch portion. The fiber orientation in the FRP sheet material has at least three directions in total: a main direction from one of the bonding portions toward the other bonding portion, and two directions different from the main direction. The reduced portion is configured to be positioned so as to protrude outward from the widthwise edge of the first steel material. The fiber orientations in at least two directions that are oriented in directions different from the principal direction are inclined at an absolute value of 15° to 75° from the principal direction and are symmetrical with respect to the principal direction. The notch is formed in a trapezoidal shape and has a pair of inclined sides and an inner side connected to the pair of inclined sides. The inner edge is parallel to the principal direction, One of the aforementioned inclined sides is parallel to one of two directions different from the principal direction, The other inclined side is parallel to the other of two directions different from the principal direction. A reinforcing member characterized by the following.

11. The FRP plate material has a fiber sheet that is attached to it, The fiber sheet is attached to the FRP plate material so as to straddle the reduced portion. The reinforcing member according to claim 10, characterized in that

12. A reinforcing method for reinforcing a steel member having a first steel member and a second steel member joined to the first steel member, The installation process includes installing a reinforcing member on the steel member, The reinforcing member has an FRP plate material in which multiple unidirectional fiber sheets are laminated, each sheet having continuous reinforcing fibers aligned in one direction and impregnated with resin. The aforementioned FRP sheet material is A pair of adhesive portions formed on both sides of the second steel material, A bypass section connecting the pair of aforementioned adhesive sections, It has a notch cut out from the side end, In the bypass portion, a reduced portion is formed in which the width dimension of the FRP plate material is reduced by the notch portion. The fiber orientation in the FRP sheet material has at least three directions in total: a main direction from one of the bonding portions toward the other bonding portion, and two directions different from the main direction. The installation step involves inserting the second steel material into the notch, attaching the pair of adhesive portions to the first steel material so that they bypass the second steel material via the bypass portion, and positioning the reduced portion so that it protrudes outward from the widthwise edge of the first steel material. A reinforcement method characterized by the following.

13. The reinforcing member has a fiber sheet that is attached to the FRP plate material. The fiber sheet is attached to the FRP plate material so as to straddle the reduced portion. In the installation process, the second steel material is inserted into the notch of the FRP plate, and the FRP plate is attached to the first steel material. The reinforcing method according to claim 12, characterized by the above.

14. The fiber orientation in at least two directions that are oriented in directions different from the principal direction is tilted by an absolute value of 15° to 75° from the principal direction and is symmetrical with respect to the principal direction, The notch is formed in a trapezoidal shape and has a pair of inclined sides and an inner side connected to the pair of inclined sides. The inner edge is parallel to the principal direction, One of the aforementioned inclined sides is parallel to one of two directions different from the principal direction, The other inclined side is parallel to the other of two directions different from the principal direction. The reinforcing method according to claim 12, characterized by the above.

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