Reinforcement structure for steel member

Abstract

To provide a reinforcement structure for steel members capable of improving strength of the steel member subjected to compressive force against overall buckling.SOLUTION: In an embodiment, a reinforcement structure 10 for a steel member having a web 52 and a flange 51 and subjected to compressive force in a member axial direction Z comprises an FRP molded material 2 bonded to the flange 51. The FRP molded material 2 is arranged to protrude beyond an end of the flange 51 in a member width direction X. A fiber direction of the FRP molded material 2 is oriented in at least one direction parallel to the member axial direction Z and one direction different from the member axial direction Z. A cross-sectional shape of the FRP molded material 2 perpendicular to the member axial direction Z is L-shaped. The FRP molded material 2 is bonded to the flange 51 via a high-elongation elastic putty material 41.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a reinforcing structure for a steel member that has a web and a flange and is subjected to a compressive force in the axial direction of the member. [Background technology]

[0002] Truss bridges on expressways and other structures are composed of steel members such as upper chords, lower chords, diagonal members, and vertical members. These steel members require seismic reinforcement because they are susceptible to compressive forces in the event of an earthquake and may buckle as a whole.

[0003] The reinforcing structure of Patent Document 1 comprises an I-section steel girder having a flange and a vertical stiffener joined to the flange, and a reinforcing member for reinforcing the I-section steel girder. The reinforcing member has an FRP plate material in which multiple unidirectional fiber sheets are laminated, and the FRP plate material has a pair of attachment sections formed on both sides of the vertical stiffener and attached to the flange, and a bypass section that bypasses the vertical stiffener and connects the pair of attachment sections.

[0004] The reinforcing structure of Patent Document 2 is a reinforcing structure for a steel member that has a web and a flange and is subjected to a compressive force, in which the fiber sheet is laminated and adhered to at least the flange so that the fiber direction of the fiber sheet is along at least two directions: the main compression direction and one direction different from the main compression direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-67785 [Patent Document 2] Japanese Patent Publication No. 2024-18525 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology disclosed in Patent Document 1 reinforces steel members against bending by bypassing stress acting on the flange with an FRP plate material that has notches formed to circumvent the vertical stiffener. The technology disclosed in Patent Document 2 reinforces steel members against buckling by laminating and attaching reinforcing fibers to the flange of the steel member or to the flange and web of the steel member so that the fiber direction is different from the member axial direction, but this technology primarily reinforces against local buckling. Therefore, there is a need for a technology that can reinforce steel members against global buckling in order to further improve the seismic resistance of steel structures that use steel members, such as truss bridges.

[0007] Therefore, the present invention has been devised in consideration of the above-mentioned circumstances, and its object is to provide a reinforcement structure for steel members that can improve the resistance to overall buckling of steel members subjected to compressive force. [Means for solving the problem]

[0008] The reinforcement structure for a steel member of the present invention is a reinforcement structure for a steel member that has a web and a flange and is subjected to a compressive force in the axial direction of the member, and is characterized in that it comprises an FRP molding material adhered to the flange, and the FRP molding material is positioned so as to extend beyond the end of the flange in the width direction of the member. [Effects of the Invention]

[0009] According to the present invention, the FRP molding material is arranged to extend beyond the end of the flange in the width direction of the member. This allows the secondary radius of area of ​​the steel member to be increased. This in turn reduces the slenderness ratio parameter around the weak axis. As a result, the strength against global buckling can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side view showing a truss bridge to which the steel members are applied. [Figure 2]FIG. 2(a) is a cross-sectional view showing an example of a reinforcing structure in the first embodiment, and FIG. 2(b) is an enlarged cross-sectional view of FIG. 2(a). [Figure 3] FIG. 3(a) is a cross-sectional view showing an example of a reinforcement structure in the second embodiment, and FIG. 3(b) is a cross-sectional view showing an example of a reinforcement structure in the third embodiment. [Figure 4] FIG. 4(a) is a cross-sectional view showing an example of a reinforcement structure in the fourth embodiment, and FIG. 4(b) is a cross-sectional view showing an example of a reinforcement structure in the fifth embodiment. [Figure 5] FIG. 5(a) is a cross-sectional view showing an example of a reinforcement structure in the sixth embodiment, and FIG. 5(b) is a cross-sectional view showing an example of a reinforcement structure in the seventh embodiment. [Figure 6] Figure 6(a) is a cross-sectional view showing an example of a reinforcement structure in the eighth embodiment, Figure 6(b) is a cross-sectional view showing an example of a reinforcement structure in the ninth embodiment, and Figure 6(c) is a cross-sectional view showing an example of a reinforcement structure in the tenth embodiment. [Figure 7] FIG. 7(a) is a side view showing the steel member used in the example, and FIG. 7(b) is a cross-sectional view taken along line BB of FIG. 7(a). [Figure 8] FIG. 8 is a table showing an overview of the specimens used in the examples. [Figure 9] Figure 9(a) is a cross-sectional view of the CASE 2 specimen, Figure 9(b) is a cross-sectional view of the CASE 3 and 4 specimens, Figure 9(c) is a cross-sectional view of the CASE 5 specimen, and Figure 9(d) is a photograph of the CASE 5 specimen. [Figure 10] FIG. 10 is a table showing the material properties of the CFRP molding materials used in the examples. [Figure 11] FIG. 11(a) is a diagram showing the alternating loading patterns applied to the specimens of Cases 0 to 3 and 5, and FIG. 11(b) is a diagram showing the alternating loading pattern applied to the specimen of Case 4. [Figure 12] FIG. 12 is a diagram showing the maximum compressive and tensile loads and the ultimate yield strength Pu / Py0 relative to the full plastic yield strength in the examples. [Figure 13]FIG. 13 is a table showing the test results in the examples. [Figure 14] 14(a) to 14(c) are diagrams showing the load-displacement relationship in the example. [Figure 15] FIG. 15 is a diagram showing an envelope of the load-displacement relationship in the example. [Figure 16] FIG. 16 is a photograph showing the specimens after the test in the example, where FIG. 16(a) shows the specimen of CASE 0, FIG. 16(b) shows the specimen of CASE 1, and FIG. 16(c) shows the specimen of CASE 2. [Figure 17] FIG. 17 is a photograph showing the specimens after the test in the example, where FIG. 17(a) shows the specimen of CASE 3, FIG. 17(b) shows the specimen of CASE 4, and FIG. 17(c) shows the specimen of CASE 5. [Figure 18] FIG. 18 is a diagram showing the relationship between displacement and cumulative energy absorption in the example. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments for carrying out a reinforcement structure for a steel member to which the present invention is applied will be described in detail with reference to the drawings.

[0012] First Embodiment As shown in Figure 1, the reinforcement structure for steel members according to this embodiment is intended to reinforce steel members that are subjected to compressive force in the axial direction of the members. The steel members in the reinforcement structure are, for example, any of upper chord members 106, lower chord members 108, diagonal members 109, and vertical members 107 that constitute a bridge girder portion 104 of a truss structure that supports a deck slab 102 in a truss bridge 100. By applying the reinforcement structure to the steel members, the bridge girder portion 104 can be seismically reinforced.

[0013] As shown in FIGS. 2(a) and 2(b), the member width direction X of the steel member 5, the member height direction Y of the steel member 5, and the member axis direction Z of the steel member 5 are defined. The reinforcing structure 10 of the steel member is for reinforcing the steel member 5 that receives a compressive force in the member axis direction Z. The cross-sectional shape of the steel member 5 perpendicular to the member axis direction Z is an open cross-sectional shape. For example, an H-shaped steel is used as the steel member 5. The steel member 5 has a web 52 and a pair of flanges 51. The web 52 is provided at the center of the member width direction X of the flange 51 and connects the pair of flanges 51.

[0014] <FRP molded material 2> The reinforcing structure 10 of the steel member includes an FRP molded material 2 adhered to the flange 51. The FRP molded material 2 is disposed so as to protrude from the end of the flange 51 in the member width direction X.

[0015] For example, a CFRP molded material made of a carbon fiber sheet is used as the FRP molded material 2. The FRP molded material 2 is composed of a plurality of one-direction fiber sheets in which continuous reinforcing fiber sheets such as carbon fiber sheets are aligned in one direction and impregnated with resin. The one-direction fiber sheet is made of FRP (Fiber Reinforced Plastics) and CFRP (Carbon Fiber Reinforced Plastics). When it is made of CFRP, the one-direction fiber sheet has a tensile strength measured in accordance with JIS A1191:2004 of 2300 N / mm 2 Preferably, it is a carbon fiber sheet having the above properties and an elastic modulus of 280 GPa to 450 GPa. The continuous reinforcing fibers used in the one-direction fiber sheet are not limited to carbon fibers, and may be, for example, organic fibers such as aramid, PBO (polyparaphenylene benzobisoxazole), polyamide, polyarylate, and polyester, basalt fibers, glass fibers, etc., and various fibers can be used. Also, the continuous fibers are not limited to one type, and a plurality of types can be selected and used.

[0016] The fiber direction of the FRP molding material 2 is oriented at least in a direction parallel to the component axis direction Z of the steel component 8 and in a direction different from the component axis direction Z (for example, a direction perpendicular to the component axis direction Z). Therefore, the FRP molding material 2 is preferably a laminate in which two or more layers of unidirectional fiber sheets are stacked, and the layer stacked so that the layers stacked so that the fiber direction is oriented in the component axis direction is at least one layer stacked so that the fiber direction is different from the component axis.

[0017] The matrix resin of the FRP molding material 2 can be either a thermosetting resin or a thermoplastic resin, but vinyl ester resin or epoxy resin, which are thermosetting resins, are preferred.

[0018] The length of the FRP molding material 2 in the member axial direction Z is preferably at least half the length of the steel member 5 in the member axial direction Z. Most preferably, the length of the FRP molding material 2 in the member axial direction Z is the same as the length of the steel member 5 in the member axial direction Z, but due to physical interference with gusset plates and other steel members at the connection points of the steel members, the length is more preferably at least 80% of the member axial direction Z. If the length of the FRP molding material 2 in the member axial direction Z is short, local buckling may occur first in the flanges 51 where the FRP molding material 2 is not bonded, which could result in a decrease in seismic resistance. However, by increasing the length of the FRP molding material 2 in the member axial direction Z, it is possible to prevent the occurrence of local buckling first in the flanges 51 in the unbonded areas.

[0019] The center of the FRP molding 2 in the member axial direction Z is preferably placed at the center of the steel member 5 in the member axial direction Z.

[0020] The FRP molded materials 2 are bonded to the inner surfaces of a pair of flanges 51. The FRP molded materials 2 are arranged line-symmetrically with respect to a neutral axis X1 along the width direction X of the steel member 5. The FRP molded materials 2 are arranged line-symmetrically with respect to a neutral axis Y1 along the height direction Y of the steel member 5.

[0021] The cross-sectional shape perpendicular to the member axis direction of the FRP molded member 2 is, for example, L-shaped. Since the FRP molded member 2 is formed into an L-shape by bending a flat FRP molded member, the corner portion of the FRP molded member 2 is curved with a predetermined curvature. The FRP molded member 2 has a first flat portion 21 adhered to the flange 51 and an overhanging portion 22 protruding from the end of the flange 51 in the member width direction X. The overhanging portion 22 has a portion that is bent and raised in a direction away from the neutral axis X1 of the steel member 5 with respect to the first flat portion 21.

[0022] Although there are no particular restrictions on the bending radius and bending angle of the curved portion of the FRP molded member 2, it is preferable that the former is R16 mm or more, and it is preferable that the latter is in the range of 0° to ±90°. For the first flat portion 21, it is preferable that its adhesion length L is 1 / 2 or more of the adhesion portion W of the flange 51, and more preferably 2 / 3 or more.

[0023] As shown in Fig. 2(b), the length B of the FRP molded member 2 in the member width direction X is longer than the height H of the FRP molded member 2 in the member width direction X. Thereby, the width-thickness ratio of the flange can be reduced, and local buckling can be suppressed. Regarding the height H of the FRP molded member 2, it is preferable to satisfy the following formula (1). (T1 + T2 + t) < H ≦ 1 / 2B ··· Formula (1) T1: Thickness of the FRP molded member 2 T2: Thickness of the adhesive layer 4 t: Thickness of the flange 51 B: Length of the FRP molded member 2 in the member width direction X

[0024] <Adhesive layer 4> The FRP molding material 2 is bonded to the flange 51 via an adhesive layer 4. The adhesive layer 4 includes, for example, a high-elongation elastic putty material 41 and an adhesive material 42, but at least the adhesive material 42 is essential and is preferably used in combination with the high-elongation elastic putty material 41 in a laminated form. In this embodiment, the adhesive layer 4 is bonded to the flange 51 via the high-elongation elastic putty material 41, but to improve the adhesive strength with the adhesive layer 4, a primer is also applied in advance to the bonding surface of the flange 51 where the adhesive layer 4 is bonded (not shown)

[0025] The high-elongation elastic putty material 41 has the function of preventing the FRP molding material 2 from peeling off from the steel member 5 by allowing the FRP molding material 2 to follow the deformation of the steel member 5. As the high-elongation elastic putty material 41, for example, epoxy resin, acrylic resin, polyurethane resin, urea-urethane resin, etc. are used, with polyurethane resin and urea-urethane resin being preferred.

[0026] The high-elongation elastic putty material 41 has a tensile modulus of elasticity of 50 to 100 N / mm 2 The resin has an elongation at maximum tensile load of 300% or more. The maximum tensile load elongation of the high elongation elastic putty material 41 is preferably 300% to 1200%, more preferably 300% to 700%, and even more preferably 300% to 500%.

[0027] High-elongation elastic putty material 41 has a tensile modulus of 100 N / mm 2 If the tensile modulus of elasticity of the high-elongation elastic putty material 41 is greater than 50 N / mm, the FRP molding material 2 cannot sufficiently follow the deformation when local buckling occurs in the steel member 5 and the flange 51 of the steel member 5 attempts to deform out of plane. 2 If the thickness is less than 1 / 2 mm, the FRP molding material 2 can follow the deformation of the flange 51, but the reinforcing effect of the FRP molding material 2 cannot be obtained sufficiently.

[0028] Furthermore, if the elongation at maximum tensile load of the high-elongation elastic putty material 41 is less than 300%, the high-elongation elastic putty material 41 will break and peel off the FRP molding material 2 if the flange 51 is significantly deformed due to local buckling. On the other hand, if the elongation at maximum tensile load exceeds 1200%, it becomes difficult to coexist with the tensile modulus of elasticity.

[0029] The tensile strength of the high elongation elastic putty material 41 is, for example, 8 N / mm 2 The thickness of the high elongation elastic putty material 41 is set to, for example, 0.2 mm or more and 10 mm or less.

[0030] The adhesive 42 has a function of increasing adhesiveness to the high-elongation elastic putty material 41 or the steel member 5. As the adhesive 42, an epoxy resin, an acrylic resin, or the like is used.

[0031] 2(b), for example, the high-elongation elastic putty material 41, the adhesive material 42, and the FRP molding material 2 are provided in this order on the flange 51. In this case, it is possible to prevent the high-elongation elastic putty material 41 from peeling off early after the flange 51 yields.

[0032] Although not shown, in the present invention, for example, the adhesive 42, the high-elongation elastic putty 41, and the FRP molding material 2 may be provided in this order on the flange 51. In this case, the work of adhering the high-elongation elastic putty 41 on the FRP molding material 2 side and the work of applying the adhesive 42 on the flange 51 side can be performed simultaneously.

[0033] Furthermore, before providing the adhesive layer 4, it is advisable to expose the steel substrate by scraping the adhesive surface of the flange 51, for example, in order to improve adhesive strength.

[0034] <Fiber sheet 3> The reinforcement structure 10 for steel members may further have fiber sheets 3 bonded to both sides of the web 52. This makes it possible to suppress the occurrence of local buckling of the web 52.

[0035] The fiber sheet 3 is a sheet material containing continuous fibers and functions to reinforce the steel member 5. In the reinforcing structure 10, a primer (not shown), a high-elongation elastic putty (not shown), an adhesive (not shown), and the fiber sheet 3 are applied to the web 52 in this order. That is, the fiber sheet 3 is impregnated and bonded to the web 52 with an adhesive via, for example, a high-elongation elastic putty. In this case, the high-elongation elastic putty used to bond the fiber sheet 3 is the same as the high-elongation elastic putty 41 used to bond the FRP molding material 2, and the adhesive used to bond the fiber sheet 3 is an adhesive for a fiber sheet bonding method (for example, FR-E3P manufactured by Nippon Steel Chemical & Material Co., Ltd.). Note that, although it is preferable to use a combination of an adhesive and a high-elongation elastic putty to bond the fiber sheet 3, it is also possible to use only the adhesive.

[0036] For example, a room temperature curing epoxy resin is used as the adhesive used to bond the fiber sheet 3. However, the adhesive is not limited to a room temperature curing epoxy resin, and various resins can be used, such as an epoxy acrylate resin, an acrylic resin, an MMA resin, a vinyl ester resin, an unsaturated polyester resin, or a photocurable resin.

[0037] The continuous fibers used in the fiber sheet 3 are, for example, carbon fibers. That is, in this embodiment, a carbon fiber sheet is used as the fiber sheet 3. The continuous fibers are not limited to carbon fibers, and various fibers can be used, such as organic fibers such as aramid, PBO (polyparaphenylenebenzbisoxazole), polyamide, polyarylate, and polyester, basalt fibers, and glass fibers. Furthermore, the continuous fibers are not limited to one type, and multiple types can be selected and used.

[0038] Next, the effects of this embodiment will be described.

[0039] According to this embodiment, the FRP molding material 2 is arranged to protrude beyond the end of the flange 51 in the width direction of the member. This allows the secondary radius of area of ​​the steel member 5 to be increased. This allows the slenderness ratio parameter about the weak axis to be reduced. As a result, the strength against global buckling can be improved.

[0040] According to this embodiment, the FRP molded material 2 is adhered to the flange 51. The FRP molded material 2 is lightweight and has high strength, and therefore can suppress the occurrence of global buckling of the flange 51 in the steel member 5 while suppressing an increase in dead load.

[0041] According to this embodiment, the fiber direction of the FRP molding material 2 is oriented in a direction parallel to the component axial direction Z and a direction different from the component axial direction Z. This increases the rigidity of the flange 51 not only in the main compression direction but also in other directions. This makes it difficult for out-of-plane deformation to occur in the flange 51, and can suppress the occurrence of global buckling of the flange 51 in the steel component 5.

[0042] According to this embodiment, the cross-sectional shape of the FRP molding material 2 perpendicular to the member axis direction Z is L-shaped, and the FRP molding material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 protruding from the end of the flange 51 in the member width direction X, and the protruding portion 22 has a part that stands up in a direction away from the neutral axis X1 relative to the first flat plate portion 21. This increases the bending rigidity of the steel member 5 around the neutral axis X1, and therefore makes it possible to suppress the occurrence of local buckling of the flange 51.

[0043] According to this embodiment, the FRP molding 2 is bonded to the flange 51 via a high-elongation elastic putty material 41. Bonding via a highly flexible high-elongation elastic putty material 41, such as a polyurethane resin layer, prevents the FRP molding 2 from peeling off from the steel member 5, maintains its reinforcing effect even with greater deformation, and allows the shear lag effect of the high-elongation elastic putty material 41 to be exerted. This allows the FRP molding 2 to exert its reinforcing effect against global buckling without peeling off from the steel member 5.

[0044] According to this embodiment, the FRP molding material 2 is a CFRP molding material made of a carbon fiber sheet, and by using carbon fiber that has excellent strength and rigidity, the reinforcing effect per thickness is increased.

[0045] According to this embodiment, the steel member 5 is any one of the upper chord member 106, the lower chord member 108, the diagonal member 109, and the vertical member 107 that constitute the bridge girder portion 104 of the truss structure that supports the deck slab 102 in the truss bridge 100. As a result, by applying the reinforcing structure 10 to the steel member 5, the bridge girder portion 104 can be seismically reinforced.

[0046] Second Embodiment Next, a second embodiment will be described. Differences from the above-described embodiment will be mainly described below. As shown in Fig. 3(a), in this embodiment, the FRP molding material 2 is adhered to the outer surface of the flange 51. As a modification of this embodiment, the FRP molding material 2, which is divided into two parts about the axis Y1, may be integrated.

[0047] <Third embodiment> Next, a third embodiment will be described. As shown in Fig. 3(b), in the third embodiment, the protruding portion 22 of the FRP molding material 2 has a portion that stands up in a direction approaching the neutral axis X1 of the steel member 5.

[0048] According to this embodiment, the cross-sectional shape of the FRP molding material 2 perpendicular to the member axis direction Z is L-shaped, and the FRP molding material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 that protrudes from the end of the flange 51 in the member width direction X, and the protruding portion 22 has a portion that stands up in a direction approaching the neutral axis X1 relative to the first flat plate portion 21. This increases the bending rigidity of the steel member 5 around the neutral axis X1, and therefore makes it possible to suppress the occurrence of local buckling of the flange 51.

[0049] <Fourth embodiment> Next, a fourth embodiment will be described. As shown in FIG. 4(a), in this embodiment, the cross section of the FRP molding material 2 perpendicular to the component axis direction Z is linear. The FRP molding material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 that protrudes from the end of the flange 51 in the component width direction X. The protruding portion 22 has a portion parallel to the first flat plate portion 21. As a modification of this embodiment, the FRP molding material 2 may be disposed on the outer surface of the flange 51, as in the second embodiment shown in FIG. 3(a), or the FRP molding material 2 may be divided into two pieces about the axis Y1 and integrated.

[0050] Fifth Embodiment Next, a fifth embodiment will be described. As shown in Fig. 4(b), in this embodiment, the cross-sectional shape of the FRP molded material 2 perpendicular to the member axial direction Z is T-shaped. The FRP molded material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 that protrudes from the end of the flange 51 in the member width direction X. The protruding portion 22 has a portion parallel to the first flat plate portion 21 and portions that stand upright relative to the first flat plate portion 21 in directions approaching and away from the neutral axis X1 of the steel member 5.

[0051] According to this embodiment, the cross-sectional shape of the FRP molding material 2 perpendicular to the member axis direction Z is T-shaped, and the FRP molding material 2 has a first flat plate portion 21 that is bonded to the flange 51 and a protruding portion 22 that protrudes from the first flat plate portion 21 beyond the end of the flange 51, and the protruding portion 22 has a portion that stands up in a direction away from the neutral axis X1. This increases the bending rigidity of the steel member 5 around the neutral axis X1, and therefore makes it possible to suppress the occurrence of local buckling of the flange 51. Note that this embodiment can also be modified in the same way as the fourth embodiment.

[0052] Sixth Embodiment Next, a sixth embodiment will be described. As shown in FIG. 5(a), in this embodiment, the cross-sectional shape of the FRP molded material 2 perpendicular to the axial direction of the member is crank-shaped. The FRP molded material 2 is formed into a crank shape by bending a flat FRP molded material, so that the corners of the FRP molded material 2 are curved with a predetermined curvature. The FRP molded material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 protruding from the end of the flange 51 in the width direction X of the member. The protruding portion 22 has a portion bent from the first flat plate portion 21 in a direction away from the neutral axis X1 of the steel member 5 and standing up, and a portion bent from the standing portion in a direction away from the first flat plate portion 21 and parallel to the first flat plate portion 21.

[0053] According to this embodiment, the cross-sectional shape of the FRP molding material 2 perpendicular to the member axis direction Z is crank-shaped, and the FRP molding material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 that protrudes from the first flat plate portion 21 beyond the flange of the FRP molding material 2, and the protruding portion 22 has a portion that stands up in a direction away from the neutral axis X1. This increases the bending rigidity of the steel member 5 around the neutral axis X1, thereby suppressing the occurrence of local buckling of the flange 51. Note that this embodiment can also be modified in the same way as the second embodiment.

[0054] Seventh Embodiment Next, a seventh embodiment will be described. As shown in FIG. 5(b), in this embodiment, the cross-sectional shape of the FRP molded material 2 perpendicular to the axial direction of the member is U-shaped. Because the FRP molded material 2 is formed by bending a flat FRP molded material into a U-shape, the corners of the FRP molded material 2 are curved with a predetermined curvature. The FRP molded material 2 has a first flat plate portion 21 bonded to the flange 51 and a protruding portion 22 that protrudes from the end of the flange 51 in the width direction X of the member. The protruding portion 22 has a portion that is bent from the first flat plate portion 21 in a direction away from the neutral axis X1 of the steel member 5 and stands up, and a portion that is bent from the protruding portion in a direction approaching the first flat plate portion 21 and is parallel to the first flat plate portion 21.

[0055] According to this embodiment, the cross-sectional shape of the FRP molding material 2 perpendicular to the member axis direction Z is U-shaped, and the FRP molding material 2 has a first flat plate portion 21 parallel to the flange 51 and a protruding portion 22 that protrudes from the first flat plate portion 21 beyond the flange of the FRP molding material 2, and the protruding portion 22 has a portion that stands up in a direction away from the neutral axis X1. This increases the bending rigidity of the steel member 5 around the neutral axis X1, and therefore makes it possible to suppress the occurrence of local buckling of the flange 51. Note that this embodiment can also be modified in the same way as the fourth embodiment.

[0056] Eighth Embodiment Next, an eighth embodiment will be described. As shown in Fig. 6(a), in this embodiment, for example, a channel steel is used as the steel member 5. The steel member 5 has a web 52 and a pair of flanges 51. The web 52 is provided at the end of the flange 51 in the member width direction X, and connects the pair of flanges 51.

[0057] Ninth Embodiment Next, a ninth embodiment will be described. As shown in Fig. 6(b), in this embodiment, for example, an angle iron is used as the steel member 5. The steel member 5 has a web 52 and a flange 51. The web 52 is provided at an end of the flange 51 in the member width direction X.

[0058] Tenth Embodiment Next, a tenth embodiment will be described. As shown in Fig. 6(c), in this embodiment, the steel member 5 is, for example, a T-shaped steel. The steel member 5 has a web 52 and a flange 51. The web 52 is provided at the center of the flange 51 in the member width direction X. As a modification of this embodiment, the FRP molding material 2 may also be adhered to the web 52. [Example]

[0059] Axial compressive load carrying capacity tests were conducted using long-column specimens with H-shaped cross sections that are approximately one-third the size of the actual bridge. The dimensions of the specimens were set as shown in Fig. 7, taking into consideration the width-thickness ratio parameters and slenderness ratio parameters of tension diagonal members that require seismic reinforcement in the actual bridge.

[0060] As shown in Fig. 8, six specimens were prepared with different reinforcement methods (CASE0 to CASE5). Among the width-thickness ratio parameters R of CASE2 to CASE5, the width-thickness ratio parameter R of the flange f <0.7, and the width-thickness ratio parameter R w The reinforcement amounts of the carbon fiber sheet and the CFRP extrusion were set in steel equivalent terms so that the tensile strength was <0.7. The axial lengths of the carbon fiber sheet and the CFRP extrusion used for reinforcement were the same as the longitudinal length of the H-beam. The specimens of CASE 0 to CASE 4 correspond to comparative examples, and the specimen of CASE 5 corresponds to an example of the present invention.

[0061] The CASE0 and CASE1 specimens are specimens in which the web and flange of the H-shaped steel are not particularly reinforced.

[0062] As shown in Figure 9(a), the CASE 2 specimen had carbon fiber sheets 73 bonded to a pair of flanges 71 of the H-shaped steel. As shown in Figure 9(b), the CASE 3 and CASE 4 specimens had carbon fiber sheets 73 bonded to the web 752 and pair of flanges 751 of the H-shaped steel. The fibers of the carbon fiber sheets 73 were oriented vertically along the axial direction of the H-shaped steel and horizontally along the direction perpendicular to the axis of the H-shaped steel. The carbon fiber sheets 73 in CASE 2 to CASE 4 were stacked in six layers, with three layers alternately stacked vertically and horizontally. In the CASE 2 specimen, six layers of carbon fiber sheets 73 were bonded to the inner surfaces of the pair of flanges 751. In the CASE 3 and CASE 4 specimens, six layers of carbon fiber sheets 73 were bonded to both sides of the web 752 and the inner surfaces of the pair of flanges 751. In the specimens of CASE 2 to CASE 4, the end of the carbon fiber sheet 73 was aligned with the end of the flange 751 in the width direction of the member and bonded.

[0063] As shown in Figures 9(c) and 9(d), the specimen for CASE 5 had CFRP extrusions 72 bonded to the inner surfaces of a pair of flanges 751 of an H-shaped steel beam, and carbon fiber sheets 73 bonded to the web. The CFRP extrusions 72 were bent so that their cross-sectional shape along the axial direction of the member was L-shaped, and they were positioned so that they protruded beyond the ends of the flanges 751. The carbon fiber sheets used for the CFRP extrusions 72 were stacked in six layers vertically and three layers horizontally, for a total of nine layers. Figure 10 shows the properties of the material used for the CFRP extrusions. The carbon fiber sheets 73 bonded to the web 752 of CASE 5 were stacked in two layers, alternating one layer vertically and one layer horizontally, for a total of four layers. For the specimen for CASE 5, four layers of carbon fiber sheets 73 were bonded to both sides of the web. Vf in Figure 10 indicates the fiber volume content, and Vf = 30%.

[0064] The tests were carried out using a 3,000kN universal testing machine, with special pin supports installed at both ends to allow for alternating compression and tension loading. The specimens for CASE0 to CASE3 and CASE5 were subjected to alternating loading of 1δy to 4δy once each (loading pattern shown in Figure 11(a)), while the specimen for CASE4 was subjected to alternating loading of 1δy to 4δy three times each (loading pattern shown in Figure 11(b)). δy in Figure 11 is the yield displacement in an unreinforced state, which is 2.7mm.

[0065] Figure 12 shows the maximum compressive and tensile loads in the examples, and the ultimate strength P u / P y0 12 is a diagram showing the P u are the maximum loads for tension and compression, respectively, and P y0 indicates the fully plastic axial force. Also, Figure 13 is a table comparing the test results of specimens CASE 1 to 5 with CASE 0. Figure 14 shows the load-displacement relationships of specimens CASE 1 to 5. Figure 15 shows the envelope of the load-displacement peaks of specimens CASE 1 to 5. The horizontal axis in Figures 13 to 15 is the value obtained by non-dimensionalizing the displacement δ with the yield displacement δy. In Figures 12 to 15, compression is indicated by negative values ​​and tension is indicated by positive values.

[0066] As shown in Figures 12 to 15, the maximum compressive loads of the specimens CASE 2 to CASE 5 reinforced with CFRP sheets increased by 1.20 to 1.72 times compared to the specimen CASE 0. On the other hand, although the width-thickness ratio parameter of the specimen CASE 1 was larger than that of the specimen CASE 0, the maximum compressive load of CASE 1 was smaller than that of CASE 0.

[0067] Furthermore, when comparing the CASE 2 specimen with the CASE 3 specimen, the CASE 2 specimen had a larger buckling load near -1δy, and the degree of load reduction was also smaller than that of the CASE 3 specimen. Thus, despite the CASE 3 specimen having reinforced both the web plate and flange, it buckled earlier and lost strength than the CASE 2 specimen, which only had the flange reinforced. This is thought to be because the reinforcement of the web plate reduced the secondary radius of area around the weak axis of the H-shaped steel, which in turn increased the slenderness ratio parameter λc around the Y-axis (weak axis), resulting in a decrease in the strength against global buckling.

[0068] Assuming that the entire steel section of the specimen yields, the full plastic axial force P y0 As shown in Figure 13, the ratios of the full plastic axial force to the compressive load of the specimens in Cases 0 and 1 were 0.65 to 0.70. The ratios of the full plastic axial force to the compressive load of the specimens in Cases 2 to 4 were 1.14 to 1.42. In particular, the ratio of the full plastic axial force to the compressive load of the specimen in Case 5 was 1.57, which was higher than those in Cases 2 to 4, confirming that the strength of the specimen in Case 5 against global buckling was improved. This is thought to be because the CFRP moldings in the specimen in Case 5 protruded beyond the flange end, resulting in a larger secondary radius of area of ​​the steel members compared to the specimens in Cases 0 to 4, resulting in a smaller slenderness ratio parameter λc around the Y-axis (weak axis) (below 1.0).

[0069] Furthermore, as shown in Figs. 13, 16 and 17, the failure mode of all the specimens of CASE0 to CASE5 was that local buckling occurred after global buckling.

[0070] Figure 18 shows the results of calculating cumulative energy absorption based on this test. The cumulative energy absorption was calculated based on the area enclosed by the hysteresis loop of the load-displacement relationship. The horizontal axis in Figure 18 represents the displacement δ non-dimensionalized by the yield displacement δy. As shown in Figure 18, the cumulative energy absorption of the CASE 5 specimen was greater than that of CASE 0 to 4. Therefore, improved seismic performance was confirmed for the CASE 5 specimen.

[0071] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Furthermore, the present invention can be embodied in various novel forms in addition to the above-described embodiments. Therefore, various omissions, substitutions, and modifications are possible in the above-described embodiments without departing from the spirit and scope of the present invention. Such novel forms and modifications are included within the scope and spirit of the present invention, as well as within the scope of the inventions set forth in the claims and equivalents of the inventions set forth in the claims. [Explanation of symbols]

[0072] 10: Reinforcement structure of steel members 2:FRP molding material 21: 1st flat plate part 22: Protruding part 3: Fiber sheet 4: Adhesive layer 41: High-stretch elastic putty material 42: Primer material 5: Steel parts 51: Flange 52: Web 82: Flange 90: Steel parts 94: Flange 100: Truss bridge 102: Floor slab 104: Bridge girder part 106:Top chord material 107:Vertical member 108: Lower chord 109: oblique material

Claims

1. A reinforcement structure for a steel member having a web and a flange and subjected to a compressive force in the member axial direction, an FRP molding material bonded to the flange, The FRP molding material is arranged so as to protrude beyond the end of the flange in the width direction of the member. A reinforced structure of steel members characterized by the above.

2. The fiber direction of the FRP molding material is oriented in a direction parallel to the member axial direction and a direction different from the member axial direction.

2. The reinforced structure of claim 1, wherein:

3. The cross-sectional shape of the FRP molding material perpendicular to the member axial direction is at least one of a straight line, an L-shape, a T-shape, a crank shape, and a U-shape.

2. The reinforced structure of claim 1, wherein:

4. The FRP molding material is bonded to the flange via a high-elongation elastic putty material.

2. The reinforced structure of claim 1, wherein:

5. The FRP molding material is a CFRP molding material made from a carbon fiber sheet.

2. The reinforced structure of claim 1, wherein:

6. In a truss bridge, the steel member is one of the upper chord, lower chord, diagonal member, and vertical member that make up the bridge girder part of the truss structure that supports the deck slab.

2. The reinforced structure of claim 1, wherein:

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