Buckling-restrained brace

Abstract

To provide a buckling-restrained brace that can control the location of buckling in higher-order buckling modes that may occur in the core material to a desired position. [Solution] The buckling-restraining brace 100 comprises a steel, plate-shaped core material 10 and a wooden restraining body 20 formed from a pair of wooden restraining members 30, which are arranged to face at least two wide surfaces 10a of the core material 10. The core material 10 has a narrow section 11 on its longitudinal central side where the width of the wide surface 10a is relatively narrow, and a wide section 12 on its longitudinal end side where the width of the wide surface 10a is relatively wide. At least one of the pair of wide surfaces 10a of the narrow section 11 is provided with a guide groove 17 having a depth smaller than the thickness of the core material 10 to guide the buckling of the core material 10.

Description

[[Technical Field]]

[0001] The present invention relates to a buckling-restrained brace. [[Background Art]]

[0002] Conventionally, buckling-restrained braces with buckling prevention measures have been used as braces forming building frames (column-beam frames, roof frames, etc.). Various stiffening configurations exist for buckling-restrained braces, including a configuration in which a steel core material is stiffened only with steel plates around its periphery, a configuration in which a steel core material is stiffened around its periphery with RC (Reinforced Concrete), and a configuration in which a steel core material is covered around its periphery with steel material and mortar.

[0003] Nowadays, improvements in the fire resistance and seismic performance of wooden buildings (wooden houses, wooden warehouses, wooden stadiums, etc.) have been pursued. Wooden buildings inherently have advantages such as high flexibility in floor plans and designs, the healing effect of natural wood, the humidity control effect of wood, and generally lower construction costs compared to steel-framed structures and RC structures depending on the building use such as houses. The aforementioned improvements in fire resistance and seismic performance are one of the factors increasing the attention toward wooden buildings including wooden houses. When incorporating the aforementioned conventional buckling-restrained braces into the frame of such a wooden building, wooden columns and beams are mixed with buckling-restrained braces having metal or concrete stiffeners, which inevitably results in an unbalanced appearance.

[0004] Accordingly, a measure has been considered to cover the entire buckling-restrained brace with wooden or paper panels or the like so that metal or concrete stiffeners cannot be visually recognized from the outside. However, this measure requires a great deal of work labor, so there is concern about an increase in construction costs. In addition, conventional buckling-restrained braces tend to be heavy because they frequently use metal, concrete, mortar, and the like. Installing a heavy buckling-restrained brace in the lightweight wooden beams and columns constituting a wooden building is also structurally unbalanced.

[0005] Here, Patent Document 1 proposes a buckling-restrained brace suitable for use incorporated into the frame of wooden buildings, including wooden houses. Specifically, it is a buckling-restrained brace having a core material and a pair of restraining members arranged along both sides of the core material, in which the core material is made of steel and the pair of restraining members are made of wood, and laminated timber is applied to these restraining members, and the laminated timber has laminations stacked parallel to the core material. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4901491 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the buckling-restrained brace described in Patent Document 1, the resistance of the buckling-restrained brace against overall buckling can be improved by using a pair of restraining members made of wood.

[0008] Incidentally, during an earthquake, a buckling-restrained brace can buckle in a higher-order buckling mode in the direction of its weak axis. By reinforcing the core material with a wooden restraint, it is possible to suppress buckling in the higher-order buckling mode of the core material while absorbing earthquake energy through the expansion and contraction deformation of the core material. Bolt holes are provided in the ends of this core material that are joined to gusset plates or brackets that protrude from the building frame, and these bolt holes can become structural weak points in the core material.

[0009] Furthermore, in order to provide these bolt holes in a position with a predetermined edge clearance, a configuration may be applied in which a wide section with a relatively wide surface is provided at the end of the core material, and a narrow section with a relatively narrow surface is provided at the center of the core material. However, stress tends to concentrate at the boundary between the narrow and wide sections and its vicinity, which can become a structural weak point of the core material.

[0010] If the structural weakness of the core material and the location where higher-order buckling modes occur coincide, the core material will lose its strength prematurely and will not be able to adequately absorb seismic energy. Therefore, a buckling-restrained brace is desired that can control the location of buckling caused by higher-order buckling modes in the core material to a desired location, such as a location different from the structural weakness of the core material. However, the buckling-restrained brace described in Patent Document 1 does not disclose a means for controlling the location of buckling caused by higher-order buckling modes in the core material to a desired location in this manner.

[0011] This invention has been made in view of the above problems, and aims to provide a buckling-restrained brace that can control the location of buckling of higher-order buckling modes that may occur in the core material to a desired position. [Means for solving the problem]

[0012] To achieve the above objective, one embodiment of the buckling-restrained brace according to the present invention is: A steel, plate-shaped core material, The aforementioned core material has a wooden restraint body which surrounds a pair of wide surfaces and a pair of narrow surfaces and comprises at least a pair of wooden restraint members, The core material has a narrow section at its longitudinal center where the width of the wide surface is relatively narrow, and a wide section at its longitudinal end where the width of the wide surface is relatively wide. The invention is characterized in that at least one of the pair of wide surfaces of the narrow portion is provided with a guide groove having a depth smaller than the thickness of the core material, which guides the buckling of the core material.

[0013] According to this embodiment, the core material has a wide section with a relatively wide surface at its longitudinal end and a narrow section with a relatively narrow surface at its longitudinal center. At least one of the pair of wide sections of the narrow section is provided with a guide groove having a depth smaller than the thickness of the core material to guide buckling of the core material. This allows for the induction (control) of higher-order buckling modes at or near the location of the guide groove. As a result, it is possible to prevent the occurrence of higher-order buckling modes at structurally weak points such as the boundary between the width change between the wide and narrow sections of the core material and its vicinity, thereby suppressing the premature deterioration of the core material's load-bearing capacity.

[0014] Furthermore, by adjusting the depth, length, and number of guide grooves provided on the wide surface of the narrow section, the stiffness (second moment of area of ​​the core material) in the weak axis direction (the direction in which buckling of higher-order buckling modes occurs) of the narrow section can be changed, making it possible to control the wavelength of buckling of higher-order buckling modes.

[0015] In this embodiment, a steel core is surrounded by a wooden restraint body formed by a pair of wooden restraint members. With this configuration, even when the buckling-restrained brace of this embodiment is applied to the frame of a wooden building, there is no risk of it appearing inconsistent with the frame members. The restraint members may be made of solid wood or of laminated timber with laminated laminas.

[0016] Here, "a guide groove is provided on at least one of the pair of wide surfaces of the narrow section" includes both a configuration in which a guide groove is provided on only one wide surface of the narrow section and a configuration in which guide grooves are provided on both wide surfaces of the narrow section.

[0017] Furthermore, other embodiments of the buckling-restrained brace according to the present invention include: The guide grooves are provided at multiple positions corresponding to the longitudinal direction of the pair of wide surfaces of the narrow portion.

[0018] According to this embodiment, the guide grooves are provided at a plurality of positions corresponding to the longitudinal direction of the pair of wide surfaces of the narrow portion, whereby buckling in a higher-order buckling mode can be effectively induced at the plurality of positions of the core material where the corresponding two guide grooves are provided.

[0019] Another aspect of the buckling-restrained brace according to the present invention is the guide grooves are alternately provided at a plurality of positions different in the longitudinal direction of the pair of wide surfaces of the narrow portion.

[0020] According to this embodiment, the guide grooves are alternately provided at a plurality of positions different in the longitudinal direction of the pair of wide surfaces of the narrow portion, whereby buckling in a higher-order buckling mode can be effectively induced at the positions of the core member where the plurality of guide grooves different on the pair of wide surfaces are provided.

[0021] In another aspect of the buckling-restrained brace according to the present invention, the guide groove is a groove extending in a direction along the longitudinal direction.

[0022] According to this embodiment, since the guide groove is a groove extending in a direction along the longitudinal direction of the core material, buckling in a higher-order buckling mode can be effectively induced in the guide groove.

[0023] In another aspect of the buckling-restrained brace according to the present invention, the guide groove is a groove extending in a direction perpendicular to the longitudinal direction.

[0024] According to this embodiment, since the guide groove is a groove extending in a direction perpendicular to the longitudinal direction of the core material, buckling in a higher-order buckling mode can be effectively induced in the guide groove.

[0025] In another aspect of the buckling-restrained brace according to the present invention, the plurality of guide grooves are provided in the longitudinal direction at a pitch set by the wavelength of the higher-order buckling mode of the narrow portion.

[0026] According to this embodiment, by providing multiple guide grooves in the longitudinal direction of the core material at a pitch set by the wavelength of the higher-order buckling mode, buckling of the higher-order buckling mode can be effectively guided into each guide groove.

[0027] Furthermore, in other embodiments of the buckling-restrained brace according to the present invention, The width-changing boundary, which is the boundary between the wide portion and the narrow portion, and the distance between the adjacent guide groove are set to half a wavelength, or approximately half a wavelength, of the higher-order buckling mode.

[0028] According to this embodiment, by setting the distance between the width-changing boundary and the adjacent guide groove to half a wavelength or approximately half a wavelength of the higher-order buckling mode, the guide groove adjacent to the width-changing boundary can be set at a reasonable distance from the width-changing boundary without causing buckling of the higher-order buckling mode at the width-changing boundary.

[0029] Furthermore, in other embodiments of the buckling-restrained brace according to the present invention, The present invention is characterized in that, when the guide groove is a groove extending in the direction along the longitudinal direction, the distance between the longitudinal central position of the guide groove adjacent to the width change boundary and the width change boundary is set to half a wavelength or approximately half a wavelength of the higher-order buckling mode.

[0030] According to this embodiment, when the guide groove is a groove that extends in a direction along the longitudinal direction of the core material, the distance between the width change boundary and the longitudinal central position of the adjacent guide groove is set to half a wavelength or approximately half a wavelength of the higher-order buckling mode. As a result, the guide groove adjacent to the width change boundary can be set at a reasonable distance from the width change boundary without causing buckling of the higher-order buckling mode at the width change boundary.

[0031] Furthermore, in other embodiments of the buckling-restrained brace according to the present invention, Reinforcing ribs perpendicular to the wide surface at the longitudinal end of the core material are joined to the wide surface, so that the cross-sectional shape is cross-shaped. The pair of restraining members is characterized in that a slit that does not interfere with the reinforcing rib is provided at a position corresponding to the reinforcing rib.

[0032] According to this embodiment, at the longitudinal end of the core material, reinforcing ribs perpendicular to the wide surface of the core material are joined, giving it a cross-shaped cross section. Therefore, when the buckling-restrained brace is attached to the gusset plate such that the wide surface of the core material is arranged parallel to the structural plane of the building, the core material has reinforcing ribs perpendicular to the wide surface parallel to the structural plane, thus increasing the rigidity in the outward direction of the structural plane at the end of the core material. In the gusset plate of the structural plane to which such a cross-shaped core material is attached, fin stiffeners are attached to the gusset plate, and the core material of the buckling-restrained brace and the gusset plate, and the reinforcing ribs and fin stiffeners are joined to each other via splice plates using high-tension bolts or the like.

[0033] Furthermore, the restraining material is provided with slits that do not interfere with the reinforcing ribs at positions corresponding to the reinforcing ribs, and the reinforcing ribs are housed in the slits with a gap between them. This prevents or suppresses damage to the restraining material by preventing the reinforcing ribs from coming into contact with and being pressed against it during deformation of the frame and buckling-restrained brace.

[0034] Furthermore, in other embodiments of the buckling-restrained brace according to the present invention, The wide portion comprises a first wide portion at the end and a second wide portion that is relatively narrower in width than the first wide portion. The second wide portion is continuous with the narrow portion, The end of the slit is located at an intermediate position in the second wide portion, The first wide portion is characterized by having bolt holes through which bolts are inserted when the frame is bolted to it.

[0035] According to this embodiment, the wide section comprises a first wide section at the end and a second wide section that is relatively narrower than the first wide section, and bolt holes through which bolts are inserted when bolted to the frame are provided in the first wide section, thereby allowing the reinforcing ribs joined to the wide section and the bolt holes provided in the wide section to be separated as much as possible. This makes it possible to suppress interference between the tool and the reinforcing ribs when bolting bolts through the bolt holes to connect to brackets of the frame, etc.

[0036] Furthermore, in other embodiments of the buckling-restrained brace according to the present invention, The wooden restraint body is further characterized by comprising a pair of wooden side plates that connect the corresponding ends of a pair of restraint members.

[0037] According to this embodiment, the wooden restraint body further has a pair of wooden side plates that connect the corresponding ends of a pair of restraint members, thereby allowing the core material to be surrounded by a wooden restraint body with a strong closed structure. Here, the wooden restraint members and side plates can be connected by adhesive, nails, screws, bolts, or a combination thereof. [Effects of the Invention]

[0038] As can be understood from the above explanation, the buckling-restrained brace of the present invention makes it possible to control the location of buckling of higher-order buckling modes that may occur in the core material to a desired position. [Brief explanation of the drawing]

[0039] [Figure 1] This is a perspective view showing an example of a core material for forming a buckling-restrained brace according to the embodiment. [Figure 2A] This is a view along the line II-II in Figure 1, which is a longitudinal cross-sectional view taken at the location of a guide groove provided in an example of a core material. [Figure 2B] This figure corresponds to Figure 2A and is a longitudinal cross-sectional view taken at the location of the guide groove provided in another example of the core material. [Figure 3] This is a perspective view of an example of a buckling-restrained brace according to an embodiment. [Figure 4] This is a view taken along the line IV-IV in Figure 3, which is a longitudinal cross-sectional view of the end of the buckling-restrained brace according to the embodiment. [Figure 5] Figure 3 is a view along the VV arrow, and is a longitudinal cross-sectional view of the central part of the buckling-restrained brace according to the embodiment. [Figure 6] This is a schematic diagram illustrating the buckling behavior of higher-order buckling modes that occur in the core material. [Figure 7] This is a perspective view showing yet another example of a core material. [Figure 8A] This is a view taken along the line VIII-VIII in Figure 7, which is a longitudinal cross-sectional view taken at the location of a guide groove provided in yet another example of the core material. [Figure 8B] This figure corresponds to Figure 8A and is a longitudinal cross-sectional view taken at the location of a guide groove provided in yet another example of the core material. [Figure 9] This figure shows the buckling-restrained brace according to the embodiment incorporated into the frame of a wooden building or the like. [Figure 10] This figure illustrates the deformation patterns of the frame during a major earthquake and the additional bending moment at the buckling-restrained brace joints caused by the deformation of the frame. [Figure 11] This figure shows the overall buckling curve of the buckling-restrained brace. [Figure 12] This diagram illustrates buckling and stiffening forces in higher-order buckling modes of the core material. [Modes for carrying out the invention]

[0040] The buckling-restrained brace according to the embodiment will be described below with reference to the attached drawings. In this specification and drawings, substantially identical components may be denoted by the same reference numerals to avoid redundant explanations.

[0041] [Buckling-restrained brace according to an embodiment] First, an example of a buckling-restrained brace according to the embodiment will be described with reference to Figures 1 to 8. Here, Figure 1 is a perspective view showing an example of a core material forming a buckling-restrained brace according to the embodiment, Figure 2A is a view taken along the line II-II in Figure 1, and is a longitudinal cross-sectional view taken at the location of a guide groove provided in an example of the core material, and Figure 2B is a view corresponding to Figure 2A, and is a longitudinal cross-sectional view taken at the location of a guide groove provided in another example of the core material. Furthermore, Figure 3 is a perspective view of an example of a buckling-restrained brace according to the embodiment, Figure 4 is a view taken along the line IV-IV in Figure 3, and is a longitudinal cross-sectional view of the end of the buckling-restrained brace according to the embodiment, and Figure 5 is a view taken along the line VV in Figure 3, and is a longitudinal cross-sectional view of the central part of the buckling-restrained brace according to the embodiment. In addition, Figure 6 is a schematic diagram illustrating the buckling behavior of higher-order buckling modes occurring in the core material.

[0042] As shown in Figure 1, the core material 10 is formed from a long, slender, plate-shaped flat steel, and has a narrow section 11 at the center in the longitudinal direction where the width of the wide surface 10a is relatively narrow, and a wide section 12 at the end in the longitudinal direction where the width of the wide surface 10a is relatively wide, with the boundary between the narrow section 11 and the wide section 12 being a width change boundary 16.

[0043] More specifically, the wide section 12 comprises a first wide section 12A at the end and a second wide section 12B that is relatively narrower than the first wide section 12A. The width is tapered from the first wide section 12A to the second wide section 12B. Here, the wide section 12 may not have two wide sections of different widths, but rather a single wide section (wide section 12A only).

[0044] From the first wide section 12A to the second wide section 12B, a reinforcing rib 14 perpendicular to the wide surface 10a is welded to the center of the wide surface 10a, and the wide section 12 has a cross-shaped cross section.

[0045] The core material 10 has a narrow section 11 on the central side in its longitudinal direction and a wide section 12 on the end side in its longitudinal direction, thereby making the narrow section 11 on the central side a region that is easily plasticized (plasticization region).

[0046] Furthermore, in the illustrated example, reinforcing ribs 14 are attached to the wide section 12, and the rigidity of the wide section 12 is further increased, making the narrow section 11 more susceptible to plastic deformation. The additional bending moment acting on the core material 10 is effectively absorbed in the narrow section 11, which is the plastic deformation region.

[0047] The wide section 12 and the reinforcing rib 14 are provided with bolt holes 12a and 14a, respectively, for bolt connection via splice plates to gusset plates provided on the structural surface and fin stiffeners (see Figure 9) attached to the gusset plates, as described below.

[0048] When the buckling-restrained brace 100 is attached to the gusset plate such that the wide surface 10a of the core material 10 is arranged parallel to the structural plane of the building, the core material 10 has reinforcing ribs 14 perpendicular to the wide surface 10a that is parallel to the structural plane, thereby increasing the rigidity of the end of the core material 10 in the direction outward of the structural plane.

[0049] The core material 10 is preferably made of a steel material with a low yield point, such as SN material (rolled steel for building structures) or LYP material (ultra-low yield point steel), which improves the seismic energy absorption due to the yielding of the core material 10.

[0050] As shown in Figures 1 and 2A, both of the pair of wide surfaces 10a of the narrow portion 11 of the core material 10 have a depth t5 smaller than the thickness of the core material 10 (more specifically, a depth t5 smaller than half the thickness of the core material 10), and a plurality of guide grooves 17A with a length t3 extending along the longitudinal direction are provided at a predetermined pitch t4 in the longitudinal direction.

[0051] Furthermore, in the examples shown in Figures 1 and 2A, guide grooves 17A are provided at multiple positions corresponding to the longitudinal direction of the pair of wide surfaces 10a of the narrow section 11.

[0052] In the illustrated example, the guide groove 17A has a plan view shape that is a long rectangle in the longitudinal direction, but it may also be a long track shape with each corner of the rectangle curved.

[0053] Here, as shown in Figure 2B, the core material 10A may have multiple guide grooves 17A alternately provided at multiple different positions in the longitudinal direction of a pair of wide surfaces 10a of the narrow section 11.

[0054] Furthermore, although not shown in the illustration, instead of the longitudinally long guide groove 17A as in the illustrated example, a plurality of longitudinally short guide grooves may be provided at multiple corresponding positions on a pair of wide surfaces 10a of the narrow section 11, as shown in Figure 2A, or they may be provided at multiple different longitudinal positions on a pair of wide surfaces 10a of the narrow section 11, as shown in Figure 2B. Moreover, although the illustrated example has guide grooves 17A on both of the pair of wide surfaces 10a of the narrow section 11, a configuration may also exist in which guide grooves 17A are provided on only one of the wide surfaces 10a.

[0055] By providing a guide groove 17A in the narrow section 11 of the core material 10, it is possible to induce the occurrence of higher-order buckling modes at or near the location of the guide groove 17A, thereby preventing the occurrence of higher-order buckling modes at structurally weak points such as the width change boundary 16 between the wide section 12 and the narrow section 11 of the core material 10 and its vicinity, and suppressing the premature deterioration of the core material 10's load-bearing capacity.

[0056] Furthermore, by adjusting the depth, length, and number of guide grooves 17A provided on the wide surface 10a of the narrow section 11, the stiffness (second moment of area of ​​the core material) in the weak axis direction (the direction in which buckling of higher-order buckling modes occurs) of the narrow section 11 can be changed, and the wavelength of buckling of higher-order buckling modes can also be controlled.

[0057] As shown in Figures 1 and 2A, in the configuration where guide grooves 17A are provided at multiple positions corresponding to the longitudinal direction of a pair of wide surfaces 10a of the narrow section 11, the pitch t4 of each guide groove 17A is set to match half the wavelength of the higher-order buckling mode occurring in the narrow section 11, for example, as shown in Figure 6. On the other hand, as shown in Figure 2B, in the configuration where the guide grooves are provided at multiple positions in different longitudinal directions of a pair of wide surfaces 10a of the narrow section 11, the pitch t4 of each guide groove 17A is set to match the wavelength of the higher-order buckling mode occurring in the narrow section 11. As shown in Figure 6, a stiffening force P may act on the restraining member 30 from the core material 10 that has buckled in the higher-order buckling mode, but the restraining member 30 is designed to have sufficient indentation resistance to withstand the stiffening force P.

[0058] By setting the pitch t4 of each guide groove 17A in this way, it becomes easier to guide the peaks (or troughs) of the higher-order buckling mode waves into each guide groove 17A.

[0059] Furthermore, the distance t1 between the width change boundary 16, which is the boundary between the wide section 12 and the narrow section 11 in the core material 10, and the adjacent guide groove 17A (or the distance t2 between the longitudinal center position of the guide groove 17A and the width change boundary 16) is set, for example, to half a wavelength or approximately half a wavelength of the higher-order buckling mode.

[0060] In this way, by setting a distance t1 or t2 between the width-changing boundary 16 and the adjacent guide groove 17A, the guide groove 17A adjacent to the width-changing boundary 16 can be set at a reasonable distance from the width-changing boundary 16 without causing buckling of higher-order buckling modes in the width-changing boundary 16.

[0061] As shown in Figure 3, a pair of wooden restraining members 30 are arranged so as to sandwich a pair of wide surfaces 10a of the core material 10, and a pair of wooden side plates 40 are connected to the ends of the pair of restraining members 30, thereby forming a wooden restraining body 20, and a buckling restraining brace 100 is formed by surrounding the core material 10 with the wooden restraining body 20.

[0062] The restraint member 30 and the side plate 40 are connected by one or more of the following: adhesive, nails, screws, or bolts. The wooden restraint body may also be formed by only a pair of restraint members (a form without side plates), in which case the pair of restraint members are connected to each other by adhesive, nails, screws, etc.

[0063] A slit 35 is provided at the longitudinal end of the restraining member 30, and a portion of the reinforcing rib 14, which is joined to the end of the core material 10, is loosely fitted into the slit 35, thereby preventing interference between the restraining member 30 and the reinforcing rib 14.

[0064] The restraining member 30 is a laminated timber formed by laminating and bonding multiple laminas together. As will be explained in detail below, the cross-sectional area, sectional stiffness, Young's modulus, etc., of the wooden restraining body 20 are set in order to prevent overall buckling of the buckling-restrained brace. This Young's modulus is determined by the type of wood. Examples of wood types include cypress, Japanese red pine, Japanese larch, fir, and Yezo spruce.

[0065] The wooden restraint body 20 surrounds the long, narrow section 11 of the steel core material 10, thereby forming a buckling restraint brace 100 with excellent aesthetic design. Here, projections 15 are provided on both wide surfaces 10a of the narrow section 11 of the core material 10, and grooves (not shown) are provided on the wide surface of the restraint material 30 at positions corresponding to the projections 15. The projections 15 fit into both grooves, thereby preventing the core material 10 from shifting relative to the restraint material 30.

[0066] As shown in Figure 4, a gap G1 of a predetermined width is provided between the slit 35 of the restraint member 30 and the reinforcing rib 14. This gap G1 absorbs the deformation of the core material 10 (and reinforcing rib 14) when the structural surface to which the buckling restraint brace 100 is attached deforms significantly in the strong axis direction or weak axis direction, thereby preventing the reinforcing rib 14 from acting on the restraint member 30 and damaging the wooden restraint body 20.

[0067] Furthermore, in the end region of the core material 10, a gap G2 is provided between the wide portion 12 and the side plate 40 and the restraining member 30, as shown in Figure 4. This gap G2, like the gap G1, absorbs the deformation of the core material 10 and prevents the wide portion 12 of the core material 10 from acting on the side plate 40 and the restraining member 30, thereby preventing damage to the wooden restraint body 20.

[0068] On the other hand, the central region of the core material 10 is restrained by the wide surface 10a of the core material 10 contacting the wide surface of the restraining member 30, as shown in Figure 5. In contrast, a spacer 50 is interposed between the narrow surface 10b of the core material 10 and the side plate 40 to prevent the core material 10 from shifting toward the side plate 40. Here, the spacer 50 may be fixed to one of the restraining members 30 with nails, screws, or the like. Furthermore, although not shown in the figures, these members may be joined to each other by a pair of restraining members 30 and a spacer 50 with multiple bolts that pass through them.

[0069] Next, with reference to Figures 7 and 8A and 8B, yet another example of the core material will be described. Here, Figure 7 is a perspective view showing yet another example of the core material, and Figure 8A is a longitudinal cross-sectional view taken along the VIII-VIII line in Figure 7, cut at the location of the guide groove provided in yet another example of the core material.

[0070] The core material 10B shown in Figures 7 and 8A differs from the core materials 10 and 10A in that the multiple guide grooves 17B are grooves that extend in a direction perpendicular to the longitudinal direction.

[0071] The core material 10B has guide grooves 17B provided at multiple positions corresponding to the longitudinal direction of the pair of wide surfaces 10a of the narrow section 11. However, as shown in Figure 8B, the core material 10C may also have guide grooves 17B alternately provided at multiple positions in the longitudinal direction of the pair of wide surfaces 10a of the narrow section 11.

[0072] The pitch t4 of each guide groove 17B is set to match the wavelength of the higher-order buckling mode that occurs in the narrow section 11, similar to the guide groove 17A of the core material 10 shown in Figure 1.

[0073] Furthermore, the distance t2 between the width change boundary 16, which is the boundary between the wide section 12 and the narrow section 11 in the core material 10B, and the adjacent guide groove 17B is set to half a wavelength or approximately half a wavelength of the higher-order buckling mode, similar to the guide groove 17A of the core material 10 shown in Figure 1.

[0074] The core materials 10B and 10C can induce buckling of higher-order buckling modes at or near the location of the guide groove 17B, preventing buckling of higher-order buckling modes from occurring at structurally weak points such as the width change boundary 16 between the wide section 12 and the narrow section 11 of the core materials 10B and 10C and their vicinity, thereby suppressing the premature deterioration of the load-bearing capacity of the core materials 10B and 10C.

[0075] [Framework incorporating buckling-restrained braces] Next, an example of a building frame incorporating the buckling-restrained brace 100 will be described with reference to Figures 9 and 10. Here, Figure 9 shows the buckling-restrained brace according to the embodiment incorporated into the frame of a wooden building or the like. Figure 10 is a diagram illustrating the deformation of the frame during a major earthquake and the additional bending moment at the buckling-restrained brace joint caused by the deformation of the frame. Note that the buckling-restrained brace in the illustrated example may be incorporated not only into the frame of a wooden building, but also into the frame of a steel (S) building, a reinforced concrete (RC) building, or a steel-reinforced concrete (SRC) building.

[0076] The frame S shown in Figure 9 is formed by wooden columns C and beams B that make up a wooden building. Gusset plates GP made of flat steel are attached to the two diagonal corners. Fin stiffeners FS are welded to the surface of the gusset plates GP so as to be perpendicular to the surface. The fin stiffeners FS are joined to the gusset plates GP such that their center L3 intersects the intersection point O of the column center L1 of column C and the beam center L2 of beam B. The buckling-restrained braces 100 are also arranged linearly, passing through the intersection points O of both diagonally opposite positions.

[0077] The gusset plate GP and the wide portion 12 of the core material 10 are joined via a splice plate SP using high-tension bolts, and the fin stiffener FS and the reinforcing rib 14 are joined via a splice plate SP using high-tension bolts.

[0078] As shown in Figure 10, during a major earthquake, the structural plane deforms, and in the buckling-restrained brace joint, an additional bending moment shown in equation (1) below may act, assuming the joint is rigid.

[0079]

number

[0080] In the buckling-restrained brace 100, the core material 10 is restrained by a wooden restraint body 20 including a pair of wooden restraint members 30, thereby suppressing overall buckling of the buckling-restrained brace 100. Consequently, the buckling-restrained brace 100 has resistance to both overall buckling and higher-order buckling of the core material 10. Therefore, it becomes possible to form a frame S with excellent seismic resistance.

[0081] [Consideration of overall buckling] Next, we will explain a design method for preventing overall buckling of a buckling-restrained brace.

[0082] In designing buckling-restrained braces, the following equation (2) should be satisfied so that overall buckling of the buckling-restrained brace does not occur.

[0083]

number

[0084] Here, the bending moment acting at the center of the restraining member can be expressed by the following equation (3).

[0085]

number

[0086] The condition for preventing overall buckling of the wooden restraint body is that the following equation (4) is satisfied.

[0087]

number

[0088] Equation (4) is shown in Figure 11 as the overall buckling curve of the buckling-restrained brace. In Figure 11, the area above the overall buckling curve is the safety zone, and the area below is the danger zone. The design axial force of the wooden restraint, Euler load, length of the general part of the core material, and yield bending strength of the wooden restraint are set so that they fall within the safety zone. Note that the overall buckling curve of the buckling-restrained brace shown in Figure 11 is valid for both overall buckling in the weak axis direction and overall buckling in the strong axis direction of the core material.

[0089] In addition to examining the relationship between the yield bending strength of the wooden restraint and the bending moment acting on it, it is also advisable to examine that the short-term allowable bending strength of the wooden restraint is greater than the bending moment acting at the time of core material yielding (formulas omitted).

[0090] [Investigation of the failure of wooden restraints due to indentation] Next, with reference to Figure 12, we will explain the method for examining the failure of the wooden restraint body due to indentation. In the buckling-restrained brace 100, in order to prevent the wooden restraint body from failing due to the core material indenting into it, we must verify that the following equation (5) is satisfied.

[0091]

number

[0092] Here, in addition to checking the relationship between the indentation resistance of the restraining material and the stiffening force acting on it, it is also advisable to check that the short-term allowable indentation resistance of the restraining material is greater than the stiffening force acting at the time of core material yielding (formulas omitted).

[0093] Furthermore, other embodiments may be used in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited in any way to the configurations shown herein. In this regard, modifications can be made without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of symbols]

[0094] 10: Core material 10a: Wide surface 10b:Narrow side 11: Narrow section 12: Wide section 12A: First wide section (wide section) 12B: Second wide section (wide section) 12a: Bolt hole 14: Reinforcement Ribs 14a: Bolt hole 15: Protrusion 16: Boundary with width change 17,17A,17B: Guide groove 20: Wooden restraints 30: Restraint material 35: Slit 40: Side panel 50: Spacer 100: Buckling-restrained brace A: Plasticization region G1, G2: Gap P: Stiffening force S: Frame (composition) C: Pillar B: Beam GP: Gusset Plate FS: Finstiffna SP: Splice Plate

Claims

1. A steel, plate-shaped core material, The aforementioned core material has a wooden restraint body which surrounds a pair of wide surfaces and a pair of narrow surfaces and comprises at least a pair of wooden restraint members, The core material has a narrow section at its longitudinal center where the width of the wide surface is relatively narrow, and a wide section at its longitudinal end where the width of the wide surface is relatively wide. A buckling-restrained brace characterized in that at least one of the pair of wide surfaces of the narrow portion is provided with a guide groove having a depth smaller than the thickness of the core material, which guides the buckling of the core material.

2. The buckling-restrained brace according to claim 1, characterized in that the guide grooves are provided at a plurality of positions corresponding to the longitudinal direction of the pair of wide surfaces of the narrow portion.

3. The buckling-restrained brace according to claim 1, characterized in that the guide grooves are alternately provided at multiple positions in the longitudinal direction of the pair of wide surfaces of the narrow portion.

4. The buckling-restrained brace according to claim 2 or 3, characterized in that the guide groove is a groove extending in a direction along the longitudinal direction.

5. The buckling-restrained brace according to claim 2 or 3, characterized in that the guide groove is a groove extending in a direction perpendicular to the longitudinal direction.

6. The buckling-restrained brace according to claim 2 or 3, characterized in that a plurality of the guide grooves are provided in the longitudinal direction at a pitch set by the wavelength of the higher-order buckling mode of the narrow portion.

7. The buckling-restrained brace according to claim 6, characterized in that the distance between the width-changing boundary, which is the boundary between the wide portion and the narrow portion, and the adjacent guide groove is set to half a wavelength or approximately half a wavelength of the higher-order buckling mode.

8. The buckling-restrained brace according to claim 7, characterized in that, when the guide groove is a groove extending in a direction along the longitudinal direction, the distance between the longitudinal center position of the guide groove adjacent to the width change boundary and the width change boundary is set to half a wavelength or approximately half a wavelength of the higher-order buckling mode.

9. Reinforcing ribs perpendicular to the wide surface at the longitudinal end of the core material are joined to the wide surface, so that the cross-sectional shape is cross-shaped. The buckling restraint brace according to claim 7, characterized in that a slit that does not interfere with the reinforcing rib is provided at a position corresponding to the reinforcing rib of the pair of restraint members.

10. The wide portion comprises a first wide portion at the end and a second wide portion that is relatively narrower in width than the first wide portion. The second wide portion is continuous with the narrow portion, The end of the slit is located at an intermediate position in the second wide portion, The buckling-restrained brace according to claim 9, characterized in that bolt holes through which bolts are inserted when the brace is bolted to the frame are provided in the first wide portion.

11. The buckling restraint brace according to claim 2 or 3, characterized in that the wooden restraint body further comprises a pair of wooden side plates connecting the corresponding ends of a pair of restraint members.

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