Reinforcement structure for steel members

Abstract

To provide a reinforcement structure that can suppress occurrence of flange local buckling in steel members.SOLUTION: A steel member reinforcement structure has webs and flanges, and receives compressive force, wherein fiber sheets are laminated and bonded to at least the flanges so that a fiber direction of the fiber sheets is along at least two directions which are a main compression direction and one direction different from the main compression direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reinforcing structure for steel members. [Background Art]

[0002] A truss bridge such as a highway is constituted by steel members including an upper chord, a lower chord, a diagonal member, and a vertical member. When an earthquake occurs, these steel members receive compressive force and may cause local buckling, so seismic reinforcement is required.

[0003] As seismic reinforcement, a reinforcement construction method of joining a steel plate (patch plate) to these steel members is known. However, this reinforcement method has problems such as an increase in dead load and re-deterioration.

[0004] On the other hand, Patent Document 1 discloses a structure in which a continuous fiber sheet is bonded to a web plate and a lower flange of a steel girder of a steel bridge via a putty layer.

[0005] In addition, Non-Patent Document 1 discloses a structure in which a carbon fiber sheet is bonded to a web plate and a flange of a short steel column having an H-shaped cross section via a high-elongation elastic putty material. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2012-52293 [Non-Patent Documents]

[0007] [Non-Patent Document 1] Yuya Hidakuma, Akira Kobayashi, Kazuo Ogaki, Shinpei Kikuchi, Tsuyoshi Miyashita, Yusuke Okuyama, "Experimental Study on Local Buckling Strength of Short Steel Columns Reinforced by Carbon Fiber Sheet Bonding", 72nd Annual Academic Lecture Meeting of the Japan Society of Civil Engineers, 2017 / 09 / 12 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] Although Patent Document 1 and Non-Patent Document 1 disclose a structure for bonding a fiber sheet to the flange of a steel member, they do not examine the effect of suppressing local buckling of the flange in the steel member, and it was not clear how to arrange the fiber sheet on the flange to suppress local buckling of the flange.

[0009] The present invention aims to provide a reinforcing structure that can suppress the occurrence of local buckling of a flange in a steel member that is subjected to compressive force substantially in the axial direction of the member. [Means for solving the problem]

[0010] The steel member reinforcing structure according to the first embodiment is a steel member reinforcing structure having a web and a flange and subjected to compressive force substantially in the axial direction of the member, wherein the fiber sheet is laminated and bonded to at least the flange such that the fiber direction of the fiber sheet is aligned with at least two directions: the main compression direction and one direction different from the main compression direction.

[0011] According to the reinforcement structure of the first embodiment, the fiber sheet is laminated and bonded to at least the flange such that the fiber direction of the fiber sheet is aligned with at least two directions: the main compression direction and one direction different from the main compression direction. As a result, the rigidity of the flange is increased not only in the main compression direction but also in the one direction different from the main compression direction. This makes it difficult for out-of-plane deformation to occur in the flange and suppresses the occurrence of local buckling of the flange in the steel member.

[0012] In the steel member reinforcing structure according to the second embodiment, in the first embodiment, the fiber sheet is laminated and bonded to the flange and the web such that the fiber direction of the fiber sheet is aligned with at least the two directions.

[0013] According to the reinforcing structure of the second embodiment, the fiber sheets are laminated and bonded to the flange and web such that the fiber direction of the fiber sheets is aligned in at least two directions. As a result, the rigidity of the web is increased not only in the main compression direction but also in one direction different from the main compression direction. This makes it difficult for out-of-plane deformation to occur in the web and also suppresses the occurrence of local buckling of the web in the steel member.

[0014] In the third embodiment, the reinforcing structure for the steel member is such that, in the first embodiment, the fiber sheet is laminated and bonded to at least the flange so as to be isotropic.

[0015] According to the third embodiment of the reinforcing structure, the fiber sheets are laminated and bonded such that the laminated state approaches isotropy with respect to at least the flange, thereby increasing the overall rigidity of the flange, including the rigidity in the main compression direction and the rigidity in one direction different from the main compression direction. As a result, out-of-plane deformation is less likely to occur in the flange, and the occurrence of local buckling of the flange in the steel member can be suppressed.

[0016] In the fourth embodiment, the reinforcing structure for a steel member is such that, in the first embodiment, the number of layers of fiber sheets bonded with the fiber direction along the one direction is 50% or more of the number of layers of fiber sheets bonded with the fiber direction along the main compression direction.

[0017] According to the reinforcing structure of the fourth embodiment, compared to the case where the number of layers of fiber sheets bonded along one fiber direction is less than 50% of the number of layers of fiber sheets bonded along the main compression direction, the rigidity in the flange in a direction different from the main compression direction is also increased. As a result, out-of-plane deformation is less likely to occur in the flange, and the occurrence of local buckling of the flange in the steel member can be suppressed.

[0018] In the steel member reinforcing structure according to the fifth embodiment, in the first embodiment, the one direction is a direction perpendicular to the principal compression direction.

[0019] According to the reinforcing structure of the fifth aspect, in the flange, not only the stiffness in the main compression direction but also the stiffness in the direction orthogonal to the main compression direction is increased. Accordingly, out-of-plane deformation is less likely to occur in the flange, and the occurrence of local buckling of the flange in the steel member can be suppressed.

[0020] In the reinforcing structure for a steel member according to the sixth aspect, in the first aspect, the fiber sheet is bonded via a high-elongation elastic putty material.

[0021] According to the reinforcing structure of the sixth aspect, since the fiber sheet is bonded via the high-elongation elastic putty material, the fiber sheet can be made to follow the deformation of the flange, and peeling of the fiber sheet is suppressed. As a result, the reinforcing effect of the fiber sheet is maintained, and the occurrence of local buckling of the flange in the steel member can be suppressed.

[0022] In the reinforcing structure for a steel member according to the seventh aspect, in the first aspect, the fiber sheet is a carbon fiber sheet.

[0023] Since the carbon fiber sheet is lightweight and has high strength, according to the reinforcing structure of the seventh aspect, an increase in dead load can be suppressed, and at the same time, the occurrence of local buckling of the flange in the steel member can be suppressed.

[0024] In the reinforcing structure for a steel member according to the eighth aspect, in the first aspect, the steel member is any one of an upper chord member, a lower chord member, a diagonal member, and a vertical member that constitutes a bridge girder portion of a truss structure supporting a floor slab in a truss bridge.

[0025] According to the reinforcing structure of the eighth aspect, the occurrence of local buckling of the flange in the steel member is suppressed in any one of the upper chord member, lower chord member, diagonal member, and vertical member that constitutes the bridge girder portion of the truss structure supporting the floor slab, so seismic reinforcement can be performed on the bridge girder portion of the truss structure. Effects of the Invention

[0026] Since the present invention adopts the above configuration, it has an excellent effect of being able to suppress the occurrence of local buckling of the flange in a steel member that receives a compressive force substantially in the axial direction of the member. [Brief explanation of the drawing]

[0027] [Figure 1] This is a cross-sectional view showing the reinforcing structure according to this embodiment. [Figure 2] (A) is a side view of a steel member with an H-shaped cross-section, and (B) is a cross-sectional view of (A) taken along the line 2B-2B. [Figure 3] (A) is a side view of a steel member with an I-shaped cross-section, and (B) is a cross-sectional view of (A) taken along the line 3B-3B. [Figure 4] (A) is a side view of a steel member with a C-shaped cross section, and (B) is a cross-sectional view of (A) taken along the line 4B-4B. [Figure 5] (A) is a side view of a steel member with a T-shaped cross-section, and (B) is a cross-sectional view of (A) taken along the line 5B-5B. [Figure 6] (A) is a side view of a steel member with a box-shaped cross-section, and (B) is a cross-sectional view of (A) taken along the line 6B-6B. [Figure 7] (A) is a side view of a steel member with an L-shaped cross-section, and (B) is a cross-sectional view of (A) taken along the line 7B-7B. [Figure 8] (A), (B), and (C) are cross-sectional views of a steel member with an L-shaped cross-section. [Figure 9] This is a side view showing a truss bridge to which steel members are applied. [Figure 10] This is a perspective view showing a fiber sheet according to this embodiment. [Figure 11] (A) is a perspective view showing another example of the fiber sheet according to this embodiment, and (B) is a diagram showing the fiber-reinforced plastic wire of the fiber sheet. [Figure 12] This is a diagram showing the test specimens used in evaluation test 1. [Figure 13] This table shows a list of the test specimens used in Evaluation Test 1. [Figure 14] This is a results table showing the evaluation results for Evaluation Test 1. [Figure 15] This is a diagram showing the test specimens used in evaluation test 2. [Figure 16]This table shows a list of the test specimens used in Evaluation Test 2. [Figure 17] This graph shows the evaluation results for the A series in Evaluation Test 2. [Figure 18] This graph shows the evaluation results for the B series in Evaluation Test 2. [Modes for carrying out the invention]

[0028] An example of an embodiment of the present invention will be described below with reference to the drawings.

[0029] <Reinforcement structure 10> The reinforcing structure 10 according to this embodiment will now be described. Figure 1 is a schematic cross-sectional view showing the reinforcing structure 10 according to this embodiment. Note that the dimensional ratios in each direction (X direction, Y direction, and Z direction in the figures) between each part shown in each figure, including Figure 1, may differ from the actual dimensional ratios.

[0030] The reinforcing structure 10 shown in Figure 1 is a structure that reinforces a steel member 90 having a web 92 and a flange 94 and subjected to compressive force substantially in the axial direction of the member, and is a structure that improves the buckling strength of the steel member 90. Specifically, the reinforcing structure 10 is a structure in which fiber sheets 40 are laminated and bonded to at least the flange 94 such that the fiber direction of the fiber sheets 40 is aligned with at least two directions: the main compression direction and one direction different from the main compression direction.

[0031] In this embodiment, the reinforcing structure 10, as shown in Figure 1, has a primer layer 20, a putty layer 30, and a plurality of fiber sheets 40. The primer layer 20, the putty layer 30, and the plurality of fiber sheets 40 are provided on the steel member 90 in this order.

[0032] The following describes the specific configuration of the steel member 90 to be reinforced and the various parts (primer layer 20, putty layer 30, and fiber sheet 40) that constitute the reinforcing structure 10.

[0033] <Steel parts 90> As shown in Figures 2 to 8, the steel member 90 has a web 92 and a flange 94 and is subjected to compressive force in approximately the axial direction of the member. Possible cross-sectional shapes of the steel member 90 include, for example, an H shape (see Figure 2), an I shape (see Figure 3), a C shape (see Figure 4), a T shape (see Figure 5), a box shape (see Figure 6), and an L shape (see Figures 7 and 8).

[0034] In Figures 2 to 8, the direction in which the steel member 90 extends is indicated by the arrow Y, the thickness direction of the web 92 and the width direction of the flange 94 are indicated by the arrow X, and the width direction of the web 92 and the thickness direction of the flange 94 are indicated by the arrow Z. The direction of extension (arrow Y direction) is the longitudinal direction of the steel member 90 and is also the axial direction of the member.

[0035] In this embodiment, the steel member 90 is a member that receives compressive force in the extending direction (arrow Y direction). That is, the main compression direction of the steel member 90 is the member axis direction.

[0036] The steel member 90 is, for example, a member used in the girder of a steel bridge. Specifically, in the truss bridge 100 shown in Figure 9, the steel member 90 is applied as one of the upper chord 106, lower chord 108, diagonal member 109, and vertical member 107 that constitute the girder portion 104 of the truss structure that supports the deck slab 102. Note that even diagonal member 109 and lower chord 108, which are tension members under normal conditions, will experience compressive forces acting in the axial direction of the member during earthquakes, etc. The steel member 90 is not limited to members used in the girder of a steel bridge, but also includes members that receive compressive forces in the extending direction (arrow Y direction) and are applied in fields such as machinery, civil engineering, and architecture.

[0037] Furthermore, the steel member 90 is made of, for example, iron or steel. Examples of iron or steel include carbon steel, which has only carbon added, and special steel, which has additives (such as nickel and chromium) added in addition to carbon.

[0038] [Steel member 90H with an H-shaped cross-section and steel member 90I with an I-shaped cross-section] In the steel member 90H with an H-shaped cross-section (see Figures 2(A) and 2(B)) and the steel member 90I with an I-shaped cross-section (see Figures 3(A) and 3(B)), the web 92 is fixed to the flange 94 at both ends in the width direction (arrow Z direction). Specifically, both edges of the web 92 in the width direction are supported at the center of the flange 94. In other words, the web 92 is a double-edge support plate with both edges supported.

[0039] Furthermore, in the steel member 90H with an H-shaped cross-section and the steel member 90I with an I-shaped cross-section, a pair of flanges 94 are provided. Each of the pair of flanges 94 protrudes from one end and the other end of the web 92 in the width direction to both sides in the thickness direction (arrow X direction) of the web 92. Therefore, the flanges 94 are free-projecting plates.

[0040] Thus, in the steel member 90H with an H-shaped cross-section and the steel member 90I with an I-shaped cross-section, the plate portion that is not supported at both ends of the plate portion that makes up each side of the cross-section of the steel member 90 constitutes the flange 94.

[0041] [Steel member 90C with a C-shaped cross-section] The steel member 90C with a C-shaped cross-section (see Figures 4(A) and 4(B)) is a so-called channel steel. In the steel member 90C with a C-shaped cross-section, the web 92 is fixed to the flange 94 at both ends in the width direction (arrow Z direction). Specifically, both edges of the web 92 in the width direction are supported by one end of the flange 94. In other words, the web 92 is a double-edge support plate with both edges supported.

[0042] Furthermore, in the steel member 90C with a C-shaped cross-section, a pair of flanges 94 are provided. Each of the pair of flanges 94 protrudes from one end and the other end of the web 92 in the width direction to one side of the web 92 in the thickness direction (arrow X direction). In other words, each of the pair of flanges 94 is supported at one end of the web 92 in the width direction (arrow X direction). Therefore, the flange 94 is a cantilever plate supported on one side.

[0043] Thus, in the steel member 90C with a C-shaped cross-section, the plate portions at both ends of the cross-section of the steel member 90 that have fewer supports constitute the flange 94.

[0044] [Steel member with T-shaped cross-section 90T] In the steel member 90T with a T-shaped cross-section (see Figure 5(A)(B)), one end of the web 92 in the width direction (arrow Z direction) is fixed to the flange 94. Specifically, one edge of the web 92 in the width direction is supported in the center of the flange 94. In other words, the web 92 is a cantilever plate supported on one side.

[0045] Furthermore, in the steel member 90T with a T-shaped cross-section, the flange 94 protrudes from one end of the web 92 in the width direction to both sides in the thickness direction (arrow X direction) of the web 92. Therefore, the flange 94 is a freely protruding plate.

[0046] Thus, in the steel member 90T with a T-shaped cross-section, the plate portion that is not supported at both ends of the cross-section of the steel member 90 constitutes the flange 94.

[0047] [Steel member 90A with box-shaped cross-section] The box-shaped steel member 90A (see Figures 6(A) and 6(B)) is used in such a way that its extending direction (Y direction) is inclined with respect to the vertical direction, or is aligned with the horizontal direction. Examples of such use include its use in the girders of a steel bridge, specifically in the truss bridge 100 shown in Figure 9, where it is used for the upper chord 106, lower chord 108, and diagonal members 109. In this embodiment, the box-shaped steel member 90A is positioned such that, for example, the Z direction shown in Figure 6(B) faces vertically upward.

[0048] In the box-shaped steel member 90A, a pair of webs 92 and flanges 94 are provided. In the box-shaped steel member 90A, the plate portions forming the upper and lower sides of the cross-section of the steel member 90 are defined as flanges 94, and the plate portions forming the right and left sides of the cross-section of the steel member 90 are defined as webs 92.

[0049] Each of the pair of webs 92 is fixed to the flange 94 at both ends in the width direction (arrow Z direction). Specifically, in each of the pair of webs 92, both edges of the web 92 in the width direction are supported by one end of the flange 94 in the width direction (arrow X direction). In other words, each of the pair of webs 92 is a double-edge support plate with both edges supported.

[0050] Furthermore, in the box-shaped steel member 90A, each of the pair of flanges 94 is fixed to the web 92 at both ends in the width direction (arrow X direction). Specifically, in each of the pair of flanges 94, both edges of the flange 94 in the width direction are supported by one end of the web 92 in the width direction (arrow Z direction). In other words, each of the pair of flanges 94 is a double-edge support plate with both edges supported.

[0051] Thus, in a steel member 90A with a box-shaped cross-section in which the number of supports at both ends is the same in the plate portion that constitutes each side of the cross-section of the steel member 90, the plate portions that constitute the upper and lower sides of the cross-section of the steel member 90 constitute the flange 94.

[0052] [Steel member with L-shaped cross-section 90L] The L-shaped steel member 90L (see Figures 7(A) and 7(B)) is used in such a configuration that its extending direction (Y direction) is inclined with respect to the vertical direction, or is aligned with the horizontal direction. Examples of such use include its use in the girders of a steel bridge, specifically in the upper chord 106, lower chord 108, and diagonal members 109 of the truss bridge 100 shown in Figure 9. In this embodiment, the L-shaped steel member 90L is arranged such that, for example, the Z direction shown in Figure 7(B) points vertically upward. Furthermore, the L-shaped steel member 90L can be arranged such that, for example, the Z direction shown in Figures 8(A), 8(B), and 8(C) points vertically upward.

[0053] In the L-shaped cross-section of the steel member 90L, the plate portion forming the upper or lower side of the cross-section of the steel member 90 is defined as the flange 94, and the plate portion forming the right or left side of the cross-section of the steel member 90 is defined as the web 92.

[0054] The web 92 is fixed at one end in the width direction (arrow Z direction) to the other end of the flange 94 in the width direction (arrow X direction). In other words, one end of the web 92 in the width direction (arrow Z direction) and one end of the flange 94 in the width direction (arrow X direction) support each other. That is, both the web 92 and the flange 94 are cantilever plates supported on one side.

[0055] Thus, in a cross-sectional L-shaped steel member 90L where the number of end supports is the same in the plate portions that make up each side of the cross-section of the steel member 90, the plate portion that makes up the upper side or the lower side of the cross-section of the steel member 90 constitutes the flange 94.

[0056] <Primer layer 20> The primer layer 20 has the function of improving the bonding (adhesion) between the surface of the steel member 90 and the layer formed on that surface (specifically, the putty layer 30). The primer layer 20 is formed by applying a primer to the surface of the steel member 90 to which the fiber sheet 40 is bonded. For example, a resin such as urethane resin is used as the primer that forms the primer layer 20. However, the primer is not limited to urethane resin, and other resins may be used, and various materials can be used.

[0057] <Putty layer 30> The putty layer 30 has the function of maintaining the bond between the fiber sheet 40 and the steel member 90. Specifically, the putty layer 30 has the function of suppressing the peeling of the fiber sheet 40 from the steel member 90 by allowing the fiber sheet 40 to follow the deformation of the steel member 90.

[0058] The putty layer 30 is formed by applying a high-elongation elastic putty material to the surface of the primer layer 20. For example, polyurea resin is used as the putty material. Here, "high elongation" refers to a material in which the elongation under maximum tensile load during hardening is 300% or more and 500% or less.

[0059] The putty material in question specifically contains a main component, a hardener, a filler, and additives, and an example of its composition is as follows.

[0060] The main component is a prepolymer containing isocyanate (e.g., 4,4'-diphenylmethane diisocyanate) as the reactive component, and is used in which the residual isocyanate at the end is adjusted to 1 to 16 parts by weight in NCO%.

[0061] Curing agent: A curing agent containing an aromatic amine (e.g., amine value 80-90) as the main component is used, calculated with an NCO:amine ratio of 1.0:0.55-0.99 parts by weight. Furthermore, a curing accelerator such as p-toluenesulfonate may also be included.

[0062] Fillers: These include silica powder, oscillating agents, etc., and are blended appropriately in amounts of 1 to 500 parts by weight.

[0063] Additives: These include colorants, viscosity modifiers, plasticizers, etc., and are blended as appropriate in amounts of 1 to 50 parts by weight.

[0064] The putty layer 30 (i.e., the putty material when hardened) has a maximum tensile elongation under load, for example, 300% to 500%, and the tensile modulus of the putty layer 30 is, for example, 50 N / mm². 2 Above, 100 N / mm 2 The following conditions apply, and the tensile strength of the putty layer 30 is, for example, 8 N / mm². 2 The above is considered correct. The thickness of the putty layer 30 is set, for example, to 0.2 mm or more and 10 mm or less.

[0065] The tensile modulus of putty layer 30 is 100 N / mm². 2 If it exceeds this value, local buckling occurs in the steel member 90, and when the flange 94 of the steel member 90 attempts to deform out of plane, the fiber sheet 40 cannot adequately follow the deformation. On the other hand, the tensile modulus of the putty layer 30 is 50 N / mm². 2 If the value is less than the specified value, the fiber sheet 40 can follow the deformation of the flange 94, but the reinforcing effect of the fiber sheet 40 cannot be sufficiently obtained.

[0066] Furthermore, if the elongation of the putty layer 30 under maximum tensile load is less than 300%, the putty layer 30 will rupture and the fiber sheet 40 will peel off when the flange 94 deforms significantly due to local buckling. On the other hand, if the elongation under maximum tensile load exceeds 500%, it becomes difficult to maintain compatibility with the tensile modulus.

[0067] Furthermore, the putty material is not limited to polyurea resin; it may also be a resin other than polyurea resin, and various materials can be used.

[0068] <Fiber Sheet 40> The fiber sheet 40 is a sheet material containing continuous fibers and functions to reinforce the steel member 90. The fiber sheet 40 is bonded to the putty layer 30 with an adhesive resin. That is, the fiber sheet 40 is bonded via a high-elongation elastic putty material.

[0069] For example, a room-temperature curing epoxy resin is used as the adhesive resin for bonding the fiber sheet 40. However, the adhesive resin is not limited to a room-temperature curing epoxy resin; for example, epoxy acrylate resin, acrylic resin, MMA resin, vinyl ester resin, unsaturated polyester resin, or photocuring resin may also be used, and various resins can be used.

[0070] As the continuous fibers used in the fiber sheet 40, for example, carbon fibers are used. That is, in this embodiment, a carbon fiber sheet is used as the fiber sheet 40. However, the continuous fibers are not limited to carbon fibers, and may also be organic fibers such as aramid, PBO (poly(p-phenylenebenzbisoxazole)), polyamide, polyarylate, and polyester, or metal fibers such as basalt fibers, glass fibers, and steel fibers, and various other fibers can be used. Furthermore, the continuous fibers are not limited to one type, but can be selected and used from multiple types.

[0071] Specifically, the fiber sheet 40 comprises a fiber layer 44 in which continuous fibers 42 are arranged in one direction (direction A in Figure 10), as shown in Figure 10, and a support layer 46 that supports the fiber layer 44. The support layer 46 is arranged on one side of the fiber layer 44 and consists of a mesh-like support sheet that supports the fiber layer 44. This support layer 46 suppresses the unraveling of the continuous fibers 42 of the fiber layer 44. Thus, in the fiber sheet 40, direction A is the fiber direction. Note that the support layer 46 may be arranged on both sides of the fiber layer 44, and a configuration without a support layer 46 is also possible if the unraveling of the continuous fibers 42 is suppressed by some method.

[0072] Here, the fiber sheet 40 is laminated and bonded to at least the flange 94 such that the fiber direction of the fiber sheet 40 is aligned with at least two directions: the main compression direction (Y direction) of the steel member 90 and one direction different from the main compression direction.

[0073] In this embodiment, the fiber sheet 40 is laminated and bonded to the flange 94 such that the fiber direction of the fiber sheet 40 is aligned with two directions: the main compression direction (Y direction) of the steel member 90 and the width direction (X direction) of the flange 94. The width direction (X direction) of the flange 94 is an example of "one direction different from the main compression direction" and an example of "a direction perpendicular to the main compression direction".

[0074] Furthermore, the "one direction different from the main compression direction" is not limited to the width direction of the flange 94, but may be a direction inclined with respect to the width direction of the flange 94. Also, the fiber sheets 40 may be laminated to the flange 94 such that their fiber directions align with three or more directions. Specifically, for example, the fiber sheets 40 can be laminated to the flange 94 such that their fiber directions align with three or more directions, including the main compression direction of the steel member 90, the width direction of the flange 94, and a direction inclined with respect to the width direction of the flange 94.

[0075] In this embodiment, as described above, the fiber sheets 40 are laminated to the flange 94 so that the fiber directions are perpendicular to each other. Therefore, when viewed in the thickness direction of the fiber sheets 40, the fiber directions are arranged at equal angular intervals. For this reason, the fiber sheets 40 are laminated and bonded to the flange 94 so that the laminated portion approaches isotropy.

[0076] Thus, "laminating the fiber sheets 40 so that they approach isotropy" means that when the fiber sheets 40 are viewed in the thickness direction, the fiber directions are arranged at equal angular intervals. Therefore, when laminating the fiber sheets 40 to the flange 94 such that the fiber directions of the fiber sheets 40 are aligned in three or more directions, it is possible to laminate the fiber sheets 40 so that they approach isotropy by arranging each fiber direction at equal angular intervals when viewed in the thickness direction of the fiber sheets 40.

[0077] Furthermore, in this embodiment, the fiber sheet 40 is bonded, for example, to the surface 94A of the flange 94 opposite to the web 92. Alternatively, the fiber sheet 40 may be bonded to the surface 94B of the flange 94 on the web 92 side. Also, the fiber sheet 40 may be bonded to both the surface 94A and the surface 94B of the flange 94.

[0078] Furthermore, the number of layers of fiber sheets 40 bonded along the width direction (X direction) of the flange 94 (hereinafter referred to as "fiber sheets 40 in the flange width direction") is set to be 50% or more of the number of layers of fiber sheets 40 arranged along the main compression direction (Y direction) of the flange 94 (hereinafter referred to as "fiber sheets 40 in the main compression direction of the flange"). Specifically, in this embodiment, for example, the number of layers of fiber sheets 40 in the flange width direction is set to be the same as the number of layers of fiber sheets 40 in the main compression direction of the flange.

[0079] Furthermore, the number of layers of fiber sheets 40 in the flange width direction only needs to be 50% or more of the number of layers of fiber sheets 40 in the flange main compression direction, and is not limited to being the same.

[0080] Furthermore, when laminating the fiber sheet 40 in the flange width direction and the fiber sheet 40 in the flange main compression direction onto the surface 94A of the flange 94, either the fiber sheet 40 in the flange width direction or the fiber sheet 40 in the flange main compression direction may be laminated first. Also, when laminating multiple sheets of each of the fiber sheet 40 in the flange width direction and the fiber sheet 40 in the flange main compression direction, one of the fiber sheets 40 may be laminated first, followed by the other, or the fiber sheets 40 in the flange width direction and the fiber sheet 40 in the flange main compression direction may be laminated alternately.

[0081] Furthermore, in this embodiment, the fiber sheet 40 is laminated and bonded to the web 92 in addition to the flange 94, such that the fiber direction of the fiber sheet 40 aligns with at least two directions: the main compression direction (Y direction) of the steel member 90 and one direction different from the main compression direction. Specifically, the fiber sheet 40 is laminated and bonded to the web 92 such that the fiber direction of the fiber sheet 40 aligns with two directions: the main compression direction (Y direction) of the steel member 90 and the width direction (Z direction) of the web 92. The width direction (Z direction) of the web 92 is an example of "one direction different from the main compression direction" and an example of "a direction perpendicular to the main compression direction".

[0082] Furthermore, the "one direction different from the main compression direction" is not limited to the width direction of the web 92, but may be a direction inclined with respect to the width direction of the web 92. Also, the fiber sheets 40 may be laminated on the web 92 such that their fiber directions align with three or more directions. Specifically, for example, the fiber sheets 40 can be laminated on the web 92 such that their fiber directions align with three or more directions, including the main compression direction of the steel member 90, the width direction of the web 92, and a direction inclined with respect to the width direction of the web 92.

[0083] In this embodiment, as described above, the fiber sheet 40 is laminated to the web 92 so that the fiber directions are perpendicular to each other. Therefore, when viewing the fiber sheet 40 in its thickness direction, the fiber directions are arranged at equal angular intervals. For this reason, the fiber sheet 40 is laminated and bonded to the web 92 so as to be close to isotropic.

[0084] The fiber sheet 40 is laminated and bonded to, for example, one of the two surfaces 92A of the web 92. Alternatively, the fiber sheet 40 may be laminated and bonded to both surfaces 92A of the web 92.

[0085] Furthermore, the number of layers of fiber sheets 40 bonded along the width direction (Z direction) of the web 92 (hereinafter referred to as "web width direction fiber sheets 40") is set to be 50% or more of the number of layers of fiber sheets 40 arranged along the main compression direction (Y direction) of the web 92 (hereinafter referred to as "web main compression direction fiber sheets 40"). Specifically, in this embodiment, the number of layers of web width direction fiber sheets 40 is set to be the same as the number of layers of web main compression direction fiber sheets 40.

[0086] Furthermore, the number of layers of fiber sheets 40 in the web width direction only needs to be 50% or more of the number of layers of fiber sheets 40 in the main compression direction of the web, and is not limited to being the same.

[0087] Furthermore, when laminating the fiber sheet 40 in the web width direction and the fiber sheet 40 in the main compression direction of the web onto the surface 92A of the web 92, either the fiber sheet 40 in the web width direction or the fiber sheet 40 in the main compression direction may be laminated first. Also, when laminating multiple sheets of the fiber sheet 40 in the web width direction and the fiber sheet 40 in the main compression direction of the web, one may be laminated multiple sheets of the other first, or the fiber sheets 40 in the web width direction and the fiber sheet 40 in the main compression direction may be laminated alternately.

[0088] Note that the fiber sheet is not limited to the fiber sheet 40 shown in Figure 10. For example, the fiber sheet 140 shown in Figures 11(A) and 11(B) may also be an example, as long as it is a fiber sheet containing fibers.

[0089] The fiber sheet 140 shown in Figures 11(A) and 11(B) is a fiber sheet (so-called strand sheet) in which multiple fiber-reinforced plastic wires 143 containing continuous fibers 142 are arranged in a curtain-like fashion along the longitudinal direction, and the wires 143 are fixed to each other with wire fixing material 145. The fiber-reinforced plastic wires 143 are formed by impregnating the continuous fibers 142 with matrix resin 147 and then curing the matrix resin 147, as shown in Figure 11(B).

[0090] Furthermore, the fiber sheet 40 can also be a fiber sheet (so-called FRP board) in which continuous fibers 42 are arranged in one direction and impregnated with resin, and the resin is cured. In this case, the resin impregnated into the fiber sheet can be a thermosetting resin such as a room-temperature curing type or thermosetting type epoxy resin, vinyl ester resin, acrylic resin, unsaturated polyester resin, or phenolic resin, or a thermoplastic resin such as a field-polymerizing type phenoxy resin, nylon, or vinylon, and preferably a thermosetting resin such as epoxy resin is used. The amount of resin impregnated into the fiber sheet 40 is 30 to 70% by weight, preferably 40 to 60% by weight.

[0091] <Construction method> Next, a construction method for applying the aforementioned reinforcing structure 10 to the steel member 90 will be described. Since the reinforcing structure 10 is formed by this construction method, it can also be considered a manufacturing method for producing the reinforcing structure 10.

[0092] This construction method includes, for example, a surface preparation step, a primer application step, a putty application step, and a fiber sheet bonding step.

[0093] In the surface preparation process, for example, sanding is performed using tools such as blasting or a disc sander. This removes existing paint films and contaminants such as rust, exposing the substrate.

[0094] In the primer application process, the aforementioned primer is applied. This forms a primer layer. Therefore, the primer application process can also be called the primer layer formation process.

[0095] In the putty application process, the aforementioned putty material is applied. This forms a putty layer. Therefore, the putty application process can also be called the putty layer formation process.

[0096] In the fiber sheet bonding process, the fiber sheet 40 is bonded to the surface of the putty layer 30 using the aforementioned adhesive resin. Specifically, for example, the adhesive resin is applied as a base coat, the fiber sheet 40 is attached to the base coat of adhesive resin, and then degassed. After that, the adhesive resin is applied as a top coat and degassed again.

[0097] A protective layer may be formed on the fiber sheet 40. In this case, a protective material such as resin constituting the protective layer is applied to the surface of the fiber sheet 40.

[0098] <Effects of this embodiment> The effects and advantages of this embodiment will now be explained.

[0099] According to the reinforcing structure 10, the fiber sheet 40 is laminated and bonded to at least the flange 94 such that the fiber direction of the fiber sheet 40 is aligned with at least two directions: the main compression direction (Y direction) of the steel member 90 and one direction different from the main compression direction.

[0100] Therefore, in the flange 94, not only is the rigidity in the main compression direction increased, but the rigidity in one direction different from the main compression direction is also increased. As a result, out-of-plane deformation is less likely to occur in the flange 94, and the occurrence of local buckling of the flange 94 in the steel member 90 can be suppressed.

[0101] In this embodiment, the one direction different from the main compression direction is the direction perpendicular to the main compression direction (specifically, the width direction of the flange 94). That is, in this embodiment, the fiber sheet 40 is laminated and bonded to the flange 94 such that the fiber direction of the fiber sheet 40 aligns with the main compression direction (Y direction) of the steel member 90 and the width direction of the flange 94.

[0102] Therefore, the rigidity of the flange 94 is increased not only in the main compression direction but also in the width direction. As a result, out-of-plane deformation is less likely to occur in the flange 94, and the occurrence of local buckling of the flange 94 in the steel member 90 can be suppressed.

[0103] Furthermore, in this embodiment, the fiber sheets 40 are laminated and bonded to the flange 94 in such a way that they approach isotropy.

[0104] Therefore, the overall rigidity of the flange 94, including the rigidity in the main compression direction and the rigidity in the width direction, is increased. As a result, out-of-plane deformation is less likely to occur in the flange 94, and the occurrence of local buckling of the flange 94 in the steel member 90 can be suppressed.

[0105] Furthermore, in this embodiment, the number of fiber sheets 40 layers in the flange width direction is set to 50% or more of the number of fiber sheets 40 layers in the flange main compression direction.

[0106] Therefore, the rigidity of the flange 94 in the width direction is increased compared to the case where the number of fiber sheets 40 layers in the flange width direction is less than 50% of the number of fiber sheets 40 layers in the flange main compression direction. As a result, out-of-plane deformation is less likely to occur in the flange 94, and the occurrence of local buckling of the flange 94 in the steel member 90 can be suppressed.

[0107] Furthermore, in this embodiment, the fiber sheet 40 is laminated and bonded to the web 92 in addition to the flange 94, such that the fiber direction of the fiber sheet 40 is aligned with at least two directions: the main compression direction (Y direction) of the steel member 90 and one direction different from the main compression direction.

[0108] Therefore, in the web 92, not only is the rigidity in the main compression direction increased, but the rigidity in one direction different from the main compression direction is also increased. As a result, out-of-plane deformation is less likely to occur in the web 92, and the occurrence of local buckling of the web 92 in the steel member 90 can also be suppressed.

[0109] Furthermore, in this embodiment, the fiber sheet 40 is bonded via a high-elongation elastic putty material. As a result, the fiber sheet 40 can follow the deformation of the flange 94, and peeling of the fiber sheet 40 is suppressed. Consequently, the reinforcing effect of the fiber sheet 40 is maintained, and the occurrence of local buckling of the flange 94 in the steel member 90 can be suppressed.

[0110] Furthermore, in this embodiment, the fiber sheet 40 is a carbon fiber sheet. Since the carbon fiber sheet is lightweight and high-strength, according to this embodiment, it is possible to suppress the occurrence of local buckling of the flange 94 in the steel member 90 while suppressing the increase in dead load.

[0111] As described above, the reinforcing structure 10 can suppress the occurrence of local buckling of the flange 94 in the steel member 90. Therefore, in the truss bridge 100 shown in Figure 9, by applying the reinforcing structure 10 to the steel member 90 which is used as one of the upper chord members 106, lower chord members 108, diagonal members 109, and vertical members 107 that constitute the bridge girder portion 104 of the truss structure that supports the deck slab 102, the bridge girder portion 104 can be seismically reinforced.

[0112] <Evaluation Test 1> In this test, the reinforcing effect of the reinforcing structure 10 according to this embodiment on the steel member 90 was evaluated. Specifically, in this test, the test specimen was reinforced with a carbon fiber sheet as described below, and a compression test was performed on the test specimen in its longitudinal direction (Y direction).

[0113] [Test specimen] As the test specimen for the steel member 90, an H-shaped section column simulating a truss bridge tension member was used, as shown in Figures 12(A) and (B). The test specimen had a longitudinal dimension L of 600 mm, and the width dimension bw of the web and the width dimension bf of the pair of flanges were 200 mm. The thickness tw of the web was 9 mm, and the thickness tf of the pair of flanges was 6 mm. SS400 steel was used.

[0114] As shown in the list in Figure 13, seven test specimens were set up with different reinforcement methods. The ultimate state of each test specimen was determined for each member using the load-bearing capacity curve from the Road Bridge Specifications. In addition, in this test, the web width-to-thickness ratio parameter R was set to a sufficiently small 0.44 in order to understand the reinforcing effect of the fiber sheet against local buckling of the flange.

[0115] [Reinforcement methods] The test specimens were reinforced using two types of sheets: a vertical sheet with the loading axis parallel to the fiber direction, and a horizontal sheet with the loading axis perpendicular to the fiber direction.

[0116] Furthermore, we conducted tests in two cases: one where the entire number of fiber sheets was laminated on one side, and another where half of the number of sheets was laminated on each side of the flange.

[0117] [Loading method] A hydraulic actuator with a loading capacity of 2000 kN was used to apply a monotonically increasing compressive load. During the installation of the test specimen, the rotation axis of the loading device was aligned with the weak axis of the H-shaped cross-section.

[0118] [Calculation of reinforcement amount] The number of layers (reinforcement amount) of vertical sheets was calculated by converting the fiber sheets to steel equivalents so that the flange width-to-thickness ratio parameter R was 0.7 or less. The number of horizontal sheets was set to be the same as or half the number of vertical sheets.

[0119] [Test Results] As shown in the results table in Figure 14, the maximum load increased for all reinforcements (a'-1 to a'-7).

[0120] Furthermore, for a'-1 to a'-5, where the number of vertically stacked sheets was the same, a tendency was observed for the maximum load to increase as the number of horizontally stacked sheets increased. This suggests that by bringing the number of horizontally stacked sheets closer to the number of vertically stacked sheets, the stacked portion of the fiber sheets became more isotropic, increasing the rigidity in the horizontal direction and thus the rigidity of the member, which suppressed the occurrence of out-of-plane deformation and buckling.

[0121] <Evaluation Test 2> In this test, the reinforcing effect of the reinforcing structure 10 according to this embodiment on the steel member 90 was evaluated using a test specimen different from that used in the aforementioned evaluation test 1. Specifically, in this test, the test specimen was reinforced with a carbon fiber sheet as described below, and a compression test was performed on the test specimen in its longitudinal direction (Y direction).

[0122] [Test specimen] As the test specimen for the steel member 90, a rectangular cross-section short column, simulating the box-shaped lower chord of a truss bridge, was used, as shown in Figures 15(A) and (B). The test specimen had a longitudinal dimension L of 600 mm. The steel type used was SS400.

[0123] As shown in the list in Figure 16, eight test specimens were prepared with varying web plate thickness, flange plate thickness, and reinforcement method. The ultimate state of each test specimen was determined for each member using the load-bearing capacity curve from the Road Bridge Specifications.

[0124] [Reinforcement methods] The test specimens were reinforced using two types of sheets: a vertical sheet with the loading axis parallel to the fiber direction, and a horizontal sheet with the loading axis perpendicular to the fiber direction. Three test specimens were prepared: an unreinforced specimen, one reinforced only with the vertical sheet, and one reinforced with a combination of the vertical and horizontal sheets.

[0125] [Loading method] A hydraulic actuator with a loading capacity of 2000 kN was used to perform compression loading with a monotonically increasing rate.

[0126] [Calculation of reinforcement amount] The number of layers (reinforcement amount) of vertical sheets was calculated by converting the fiber sheets to steel equivalents so that the flange width-to-thickness ratio parameter R was 0.7 or less. The number of horizontal sheets was set to be the same as or half the number of vertical sheets.

[0127] [Test Results] Figures 17 and 18 show the load-vertical displacement relationships obtained from the tests. The vertical axis represents the "vertical load P," and the horizontal axis represents the "vertical displacement δ," both of which are dimensionless by the yield load Py and yield displacement δy, respectively.

[0128] In the reinforced test specimens (A-1 to A-3, B-1 to B-3), the maximum load in all cases was greater than or equal to the yield load in the unreinforced specimens. Furthermore, in both the A-series and B-series, the maximum load increased more when using both vertical and horizontal sheets (A-2, A-3, B-2, B-3) than when using only vertical sheets (A-1, B-1).

[0129] Furthermore, the maximum load is greatest when the number of vertical and horizontal sheets is equal (A-2, B-2). This is presumed to be because, by bringing the number of horizontal sheets closer to the number of vertical sheets, the laminated portion of the fiber sheets approaches isotropy, increasing the rigidity in the horizontal direction and thus the rigidity of the member, which suppresses the occurrence of out-of-plane deformation and buckling.

[0130] As described above, it was confirmed that laminating and bonding not only the vertical sheets but also the horizontal sheets can suppress the occurrence of local buckling of the flange.

[0131] The present invention is not limited to the embodiments described above, and various modifications, changes, and improvements are possible without departing from the spirit of the invention.

[0132] <Note> (Aspect 1) A reinforcing structure for a steel member having a web and a flange and subjected to compressive force substantially in the axial direction of the member, The fiber sheet is laminated and bonded to at least the flange such that the fiber direction of the fiber sheet is aligned with at least two directions: the main compression direction and one direction different from the main compression direction. Reinforcement structure for the aforementioned steel member.

[0133] (Aspect 2) The fiber sheet is laminated and bonded to the flange and the web such that the fiber direction of the fiber sheet is aligned with at least the two directions. The steel member reinforcing structure described in Embodiment 1.

[0134] (Aspect 3) The fiber sheets are laminated and bonded to at least the flange so as to be isotropic. The steel member reinforcing structure according to embodiment 1 or 2.

[0135] (Aspect 4) The number of layers of fiber sheets bonded along the fiber direction in the aforementioned one direction is The fiber direction is 50% or more of the number of layers of fiber sheets bonded along the principal compression direction. A reinforcing structure for a steel member according to any one of embodiments 1 to 3.

[0136] (Appendix 5) The aforementioned first direction is a direction perpendicular to the principal compression direction. A reinforcing structure for a steel member according to any one of embodiments 1 to 4.

[0137] (Aspect 6) The aforementioned fiber sheet is bonded via a highly elongated elastic putty material. A reinforcing structure for a steel member according to any one of embodiments 1 to 5.

[0138] (Aspect 7) The aforementioned fiber sheet is a carbon fiber sheet. A reinforcing structure for a steel member according to any one of embodiments 1 to 6.

[0139] (Pattern 8) The steel member is one of the upper chord, lower chord, diagonal member, or vertical member that constitute the bridge girder portion of the truss structure supporting the deck slab in a truss bridge. A reinforcing structure for a steel member according to any one of embodiments 1 to 7. [Explanation of Symbols]

[0140] 10 Reinforcement structure 20 Primer layer 30 Putty Layers 40 Fiber Sheets 42 continuous fibers 44 fiber layers 46 Support layer 80 Amine value 90 Steel parts 92 Web 92A surface 94 Flange 94A surface 94B Surface 100 Truss Bridges 102 Floor slab 104 Bridge girder section 106 Top chord material 107 Vertical member 108 Lower string 109 Diagonal 140 fiber sheets 142 continuous fibers 143 Fiber-reinforced plastic wire 145 Wire fixing material 147 Matrix resin

Claims

1. A reinforcing structure for a steel member having a web and a flange and subjected to compressive force substantially in the axial direction of the member, The fiber sheet is laminated and bonded to at least the flange such that the fiber direction of the fiber sheet is aligned with at least two directions: the main compression direction which is substantially the axial direction of the member, and the width direction of the flange which is perpendicular to the main compression direction. The flange to which the fiber sheet is bonded has a constant thickness within the cross-section of the member. The number of layers of fiber sheets bonded with the fiber direction aligned with the width direction is 50% or more of the number of layers of fiber sheets bonded with the fiber direction aligned with the main compression direction. Reinforcement structure for the aforementioned steel member.

2. The fiber sheet is laminated and bonded to the flange and the web such that the fiber direction of the fiber sheet is aligned with at least the two directions. The steel member reinforcing structure according to claim 1.

3. The fiber sheets are laminated and bonded to at least the flange so as to be isotropic. The steel member reinforcing structure according to claim 1.

4. The fiber sheet is bonded via a high-stretch elastic putty material. The steel member reinforcing structure according to claim 1.

5. The fiber sheet is a carbon fiber sheet. The steel member reinforcing structure according to claim 1.

6. The steel member is one of the upper chord, lower chord, diagonal member, and vertical member that constitute the bridge girder portion of the truss structure that supports the deck slab in a truss bridge. The steel member reinforcing structure according to claim 1.

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