Buckling restraint brace and strength design method of filling material

Abstract

To provide a buckling-restrained brace that can inhibit a filler material from crushing, and a method for designing the strength of the filler material of the buckling-restrained brace.SOLUTION: The buckling-restrained brace comprises: a long and plate-shaped core material 10; a restraining member 20 covering the outer circumference of the core material 10 with both ends of the core material protruding; and a filling material 30 filling the space between the core material 10 and the restraining member 20. When the out-of-plane deformation of the core material 10 reaches the maximum allowable deformation, the crushing strength of the filling material 30 is greater than or equal to the maximum compressive stress generated in the filling material 30.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a buckling restraint brace and a method for designing the strength of a filler material.

Background Art

[0002] A buckling restraint brace may be used for vibration control applications in buildings. As a buckling restraint brace, there is one including a long and plate-shaped core material, a restraint member that covers the outer periphery with both ends of the core material protruding, and a filler material filled between the core material and the restraint member. When a compressive axial force is generated in the core material due to the vibration load during an earthquake and the core material is displaced in the plate thickness direction, the load is transmitted to the restraint member by the filler material, and the restraint member receives the load, thereby suppressing the progress of buckling of the core material. By preventing the buckling of the core material from progressing, the vibration control effect against earthquakes is improved. During an earthquake, a compressive load is input to the filler material filled between the restraint member and the core material. As a conventional example of such a buckling restraint brace, for example, there is one disclosed in Patent Document 1. In the buckling restraint brace of Patent Document 1, with the aim of providing necessary energy absorption while increasing rigidity and enabling cost reduction, it has a core material and a restraint material, and an energy absorption portion having a smaller second moment of cross-section than others is provided in a part of the longitudinal direction of the core material. One or more structural slits are provided along the longitudinal direction in this energy absorption portion, and the width dimensions of a plurality of core material divided portions separated by the structural slits are made different from each other. In this buckling restraint brace, by making the width dimensions of the plurality of core material divided portions different, the buckling mode of the core material due to the compressive axial force during an earthquake is controlled, and the compressive load acting on the filler material is dispersed in the longitudinal direction so that a local compressive load is not input to the filler material. That is, in the buckling restraint brace of Patent Document 1, the compressive load received by the filler material is reduced by devising the shape of the core material. In addition, in the buckling restraint brace of Patent Document 1, since it is necessary to form an opening in the plasticized portion of the core material, there is a concern about a decrease in axial bearing capacity and a deterioration in productivity compared to the case where no opening is formed.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-229572 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] In the buckling restraint brace of the above Patent Document 1, although the dispersion of the compressive load acting on the filler is achieved, the strength against the crushing of the filler is not considered. Therefore, when a part of the core material is displaced in the plate thickness direction, depending on the magnitude of the compressive load after dispersion, the filler may be crushed. When the filler is crushed, the core material is not restrained, and the buckling of the core material accompanying the vibration during an earthquake progresses, resulting in a problem that the vibration damping effect by the buckling restraint brace cannot be obtained.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a buckling restraint brace capable of suppressing the crushing of a filler and a method for designing the strength of the filler of the buckling restraint brace. [Means for Solving the Problems]

[0006] <1>The buckling restraint brace according to Aspect 1 of the present invention includes a long and plate-shaped core material, a restraint member that covers the outer periphery of the core material with both ends of the core material protruding, a filler filled between the core material and the restraint member, and an unbonded material interposed between the core material and the filler so that relative movement between the core material and the filler is possible. The crushing strength, which is the compressive strength of the filler, is equal to or greater than the maximum compressive stress generated in the filler when the core material is most greatly deformed out of plane in the plate thickness direction of the core material within the thickness range of the unbonded material and comes into contact with the filler. The filler is in close contact with the entire circumference of the unbonded material in a cross section orthogonal to the longitudinal direction of the core material.

[0007] According to the present invention, the crushing strength of the filler is equal to or greater than the maximum compressive stress. The maximum compressive stress is the compressive stress generated in the filler when the core material undergoes the largest out-of-plane deformation in the plate thickness direction of the core material within the thickness range of the unbonded material and contacts the filler. Thereby, when the core material is deformed by the compressive axial force, as long as the amount of deformation is equal to or less than the amount of deformation of the core material that generates the above maximum compressive stress, it is possible to suppress the crushing of the filler.

[0008] <2>The buckling restraint brace according to Embodiment 2 of the present invention is the buckling restraint brace according to Embodiment 1, wherein the core material includes a plasticized portion located at the center in the longitudinal direction, and the plasticized portion is narrower in width than the portion protruding from the restraint member.

[0009] According to the present invention, the core material includes a plasticized portion that is located at the center in the longitudinal direction and is narrower in width than the portion protruding from the restraint member. Thereby, for example, when a compressive axial force is applied by an earthquake or the like in the longitudinal direction of the buckling restraint brace, the plasticized portion of the core material can be deformed out of plane by the compressive axial force.

[0010] <3>The buckling restraint brace according to Embodiment 3 of the present invention is the buckling restraint brace according to Embodiment 2, wherein the plasticized portion has no opening.

[0011] According to the present invention, for example, unlike the case where an opening is formed in the plasticized portion, since the cross-sectional area in the direction orthogonal to the longitudinal direction can be maintained at the maximum area corresponding to the outer shape of the plasticized portion, the axial load-bearing capacity of the plasticized portion against the tensile load along the longitudinal direction is not reduced. In addition, since the second moment of inertia of the cross section of the plasticized portion can be increased, the bending rigidity of the plasticized portion can be increased compared to the case where an opening is formed in the plasticized portion. Furthermore, since the plasticized portion has a closed surface without an opening, a confined effect can be appropriately generated on the filler located around the plasticized portion. Therefore, the load-bearing capacity of the filler can be improved compared to the case where an opening is formed in the plasticized portion.

[0012] <4>The buckling restraint brace according to Aspect 4 of the present invention is the buckling restraint brace according to any one of Aspects 1 to 3, wherein the restraint member is cylindrical.

[0013] According to this invention, the restraint member is cylindrical. Thereby, for example, the load applied to the filler due to the deformation of the core material can be dispersed over a wide area of the filler. Therefore, for example, even if a large load is concentrated on a part of the filler due to the deformation of the core material, it is possible to suppress the occurrence of local stress in the filler. Therefore, it is possible to further suppress the filler from being crushed.

[0014] <5>The buckling restraint brace according to Aspect 5 of the present invention is the buckling restraint brace according to any one of Aspects 1 to 4, wherein the plate thickness of the core material is 12 mm or more and 16 mm or less, and the crushing strength of the filler is 21 N / mm 2 or more.

[0015] According to this invention, the plate thickness of the core material is 12 mm or more and 16 mm or less. In this way, by making the plate thickness of the core material relatively small, it is possible to obtain a buckling restraint brace with a small axial bearing capacity applicable to small-scale buildings. The crushing strength of the filler is 21 N / mm 2 or more. Thereby, in a buckling restraint brace for a small-scale building in which the plate thickness of the core material is relatively small, it is possible to suppress the crushing of the filler and appropriately restrain the core material.

[0016] <6>The buckling restraint brace according to Aspect 6 of the present invention is the buckling restraint brace according to Aspect 2, wherein the core material includes a pair of width-changing portions adjacent to both sides of the plasticized portion, and in the pair of width-changing portions, the plate width on the end side is larger than the plate width on the plasticized portion side, and the angle formed by the inclined plane forming the end face in the plate width direction in the width-changing portion and the longitudinal direction is 30 degrees or more.

[0017] According to the present invention, the core material includes a pair of width-changing portions adjacent to both sides of the plasticized portion. In the pair of width-changing portions, the plate width at the end portion side is larger than the plate width at the plasticized portion side, and the angle formed by the inclined plane forming the end face in the plate width direction in the width-changing portion and the longitudinal direction is 30 degrees or more. Thereby, for example, the compressive load applied to the core material can be efficiently transmitted to the plasticized portion through the width-changing portion.

[0018] <7>The method for designing the strength of the filler according to Aspect 7 of the present invention is a method for designing the strength of the filler in a buckling restraint brace including a long and plate-shaped core material, a restraint member covering the outer periphery of the core material with both ends of the core material protruding, a filler filled between the core material and the restraint member, and an unbonded material interposed between the core material and the filler so that relative movement between the core material and the filler is possible. The crushing strength, which is the compressive strength of the filler, is set to be equal to or greater than the maximum compressive stress generated in the filler when the core material undergoes the largest out-of-plane deformation in the plate thickness direction of the core material within the thickness range of the unbonded material and comes into contact with the filler. The filler is characterized in that it is in close contact with the entire circumference of the unbonded material in a cross section perpendicular to the longitudinal direction of the core material.

[0019] According to the present invention, the crushing strength of the filler is set to be equal to or greater than the maximum compressive stress. Thereby, when the core material is deformed by an amount equal to or less than the deformation amount of the core material that generates the above maximum compressive stress, it is possible to suppress the crushing of the filler.

Effects of the Invention

[0020] According to the present invention, it is possible to provide a buckling restraint brace capable of suppressing the crushing of the filler and a method for designing the strength of the filler of the buckling restraint brace.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0022] Hereinafter, with reference to the drawings, the buckling restraint brace 100 according to an embodiment of the present invention will be described. The buckling restraint brace 100 is used, for example, to reinforce a structure composed of columns and beams in a building. As shown in FIGS. 1 to 4, the buckling restraint brace 100 includes a core material 10, a restraint member 20, a filling material 30, and an unbonding material 40.

[0023] The core material 10 is, for example, a long and plate-shaped member made of a steel plate. The core material 10 reinforces the building by having both ends attached to the structure of the building. The core material 10 is formed from a steel plate (flat steel). It is preferable that the core material 10 is formed of a steel material with a low yield point such as an SN material (rolled steel for building structures) or an LYP material (extra-low yield point steel material). In this case, the earthquake energy absorption property due to the yield of the core material 10 becomes good.

[0024] As shown in FIG. 1, the core material 10 includes a narrow-width portion 11, a wide-width portion 12, a width-changing portion 13, and a core material stiffening member 14. Hereinafter, when not distinguishing between the narrow-width portion 11, the wide-width portion 12, the width-changing portion 13, and the core material stiffening member 14 with respect to the core material 10, it will be referred to as the core material 10 in the drawing or by name. The narrow-width portion 11 is located at the center in the longitudinal direction of the core material 10. The wide-width portions 12 are located at both ends in the longitudinal direction of the core material 10. The wide-width portion 12 has a wider plate width than the narrow-width portion 11. The wide-width portion 12 is shorter in the longitudinal direction than the narrow-width portion 11. In the present embodiment, the wide-width portion 12 has a constant width length, but it may have a shape in which the width length gradually increases toward the end.

[0025] In this embodiment, the core material 10 has a plasticized portion 10P that is located in the center of the core material 10 in the longitudinal direction and is narrower than the portion protruding from the restraining member 20 described later. That is, the center of the core material 10 in the longitudinal direction is a narrow portion 11, and the ends in the longitudinal direction are wide portions 12, so that the center of the core material 10 in the longitudinal direction (narrow portion 11) is a region that is easily plasticized. Hereinafter, the region of the core material 10 that is easily plasticized (narrow portion 11) is referred to as the plasticized portion 10P. For example, when a compressive axial force is applied in the longitudinal direction of the buckling restrained brace 100 due to an earthquake or the like, the plasticized portion 10P of the core material 10 is deformed out-of-plane by the compressive axial force, as shown in FIG. 5.

[0026] 1 and 2, a core stiffening member 14 is joined to the wide width portion 12. The core stiffening member 14 is provided on the front and back surfaces (surfaces facing the thickness direction of the core material 10 excluding the core stiffening member 14) of the wide width portion 12. In the portion where the core stiffening member 14 is arranged in the longitudinal direction, the core material 10 has a cross-shaped cross section perpendicular to the longitudinal direction, as shown in FIG. Bolt holes (not shown) are formed in the wide portion 12 and the core stiffening member 14. The buckling restraint brace 100 is attached to a building by bolts (not shown) that are inserted into the bolt holes.

[0027] As shown in FIG. 1, the width changing portion 13 is a boundary region between the wide width portion 12 and the narrow width portion 11. The width of the width changing portion 13 changes along the longitudinal direction. The width of the width changing portion 13 continuously decreases from the wide width portion 12 side toward the narrow width portion 11 side, and a tapered surface 13T (corresponding to an inclined plane) is formed on both ends of the width changing portion 13. The width changing portion 13 absorbs, for example, an additional bending moment acting on the core material 10. The angle A between the tapered surface 13T in the width changing portion 13 and the longitudinal direction is preferably 30 degrees or more. This allows the compressive load input from the wide width portion 12 to be efficiently transmitted to the narrow width portion 11.

[0028] In this embodiment, the plate thickness of the core material 10 is, for example, 12 mm or more and 16 mm or less. In this embodiment, the plate thickness of the core material 10 refers to the plate thickness of the core material 10 excluding the core material stiffening member 14. Further, the maximum allowable deformation amount of the core material 10 is the deformation amount when the core material 10 is most greatly deformed out of plane in the plate thickness direction within the range of the thickness 40t of the unbonded material 40 (described later) shown in FIG. 5.

[0029] The core material stiffening member 14 is a plate-like member made of a steel plate. As shown in FIGS. 1 and 2, the core material stiffening member 14 is vertically arranged on both side surfaces in the plate thickness direction of the wide-width portion 12 at the longitudinal ends of the core material 10. Thereby, both ends of the core material 10 are reinforced, and it is possible to prevent the portion of the core material 10 where the core material stiffening member 14 is arranged in the longitudinal direction from bending in the plate thickness direction. In this embodiment, the plate thickness of the core material stiffening member 14 is preferably, for example, the same as that of the core material 10 excluding the core material stiffening member 14, which is 12 mm or more and 16 mm or less.

[0030] The restraining member 20 is a member that covers the outer periphery of the core material 10 with both ends of the core material 10 protruding. In this embodiment, the restraining member 20 is, for example, cylindrical. In other words, the portions other than both ends of the core material 10 are accommodated inside the cylindrical restraining member 20. By this, for example, the load applied to the filling material 30 due to the deformation of the core material 10 can be dispersed by the filling material 30. The restraining member 20 is made of, for example, a steel material. The length of the restraining member 20 in the longitudinal direction is shorter than the length of the core material 10 in the longitudinal direction. Therefore, both ends of the core material 10 in the longitudinal direction protrude from the restraining member 20.

[0031] The filling material 30 is filled inside the restraining member 20. The filling material 30 is filled between the core material 10 and the restraining member 20. The filling material 30 is concrete, mortar, or the like. The restraining member 20 and the filling material 30 restrict the deformation (in-plane buckling or out-of-plane buckling) of the core material 10 in the direction excluding the longitudinal direction. In order to prevent the filling material 30 from leaking out from the ends of the restraining member 20, both ends of the restraining member 20 are closed by lids (not shown).

[0032] In this embodiment, the crushing strength of the filling material 30 is equal to or greater than the maximum compressive stress generated in the filling material 30 when the out-of-plane deformation amount of the core material 10 reaches the allowable maximum deformation amount. Here, the maximum compressive stress is the stress indicating the maximum value among the stresses generated with a distribution in the filling material 30. In this embodiment, the crushing strength of the filling material 30 is, for example, 21 N / mm 2 or more. The crushing strength of the filling material 30 can be measured by a mortar strength test specified in JASS·5 (Construction Standard Specification, Explanation of Chapter 5 (Reinforced Concrete)).

[0033] In this embodiment, the plasticized portion 10P has no opening. In other words, the filling material 30 is filled between the plasticized portion 10P of the core material 10 and the restraint member 20 without any gap. By this, a confined effect is generated in the filling material 30 located around the plasticized portion 10P, and the bearing capacity of the filling material 30 located around the plasticized portion 10P can be further improved.

[0034] As shown in FIGS. 3 and 4, the unbonded material 40 is interposed between the core material 10 and the filling material 30, and allows relative movement between the core material 10 and the filling material 30 by elastically deforming as the core material 10 deforms. By this, the unbonded material 40 restricts the core material 10 and the filling material 30 from behaving integrally in the longitudinal direction. Thereby, the filling material 30 holds the core material 10 so that the axial force of the core material 10 is not transmitted to the restraint member 20, that is, so that the core material 10 can relatively move in the longitudinal direction with respect to the restraint member 20.

[0035] (Strength Design Method of Filling Material 30) Next, a strength design method of the filling material 30 in the buckling restraint brace 100 according to this embodiment will be described. That is, in the strength design method of the filling material 30 according to this embodiment, the crushing strength of the filling material 30 is set to be equal to or greater than the maximum compressive stress generated in the filling material 30 when the out-of-plane deformation amount of the core material 10 reaches the allowable maximum deformation amount.

[0036] Specifically, for example, the compressive axial force applied to the buckling restraint brace 100 is P d,w , and the contact width between the core material 10 and the filling material 30 is lc Let the width of the core material be B c Then, the compressive stress applied to the filler 30 is expressed by the following formula. P d,w / (l c ·B c )

[0037] Based on the above formula, for example, when the compressive axial force P d,w is 100,000 N, the contact width l c is 22 mm, and the width B of the core material c is 200 mm, the compressive axial force applied to the filler 30 is expressed by the following formula. 100,000 / 22 / 200 = 22.7 N / mm 2 In the case as described above, determine the crushing strength of the filler to be 22.7 N / mm 2 When designing the strength of the filler, calculate the maximum compressive stress generated in the filler 30 based on the compressive axial force assumed when the buckling restraint brace 100 is arranged in the building, and determine the crushing strength of the filler 30. The strength of the filler 30 is designed by the above method.

[0038] The maximum compressive stress generated in the filler 30 can also be obtained by the finite element method (FEM). In this case, calculate the compressive stress distribution generated in the filler 30 when the core material 10 buckles in a predetermined buckling mode, and the maximum compressive stress among the compressive stress distributions can be used as the maximum compressive stress. Furthermore, the compressive stress distribution generated in the filler 30 for each of the multiple buckling modes can be calculated, and the maximum compressive stress among them can also be used as the maximum compressive stress.

[0039] As described above, according to the buckling restraint brace 100 according to the present embodiment, the crushing strength of the filler 30 is equal to or greater than the maximum compressive stress. The maximum compressive stress is the maximum compressive stress when the out-of-plane deformation amount of the core material 10 reaches the allowable maximum deformation amount. Thereby, when the core material 10 is deformed by the compressive axial force, as long as the deformation amount is equal to or less than the allowable maximum deformation amount, it is possible to suppress the filler 30 from being crushed.

[0040] ​Further, the core material 10 includes a plasticized portion 10P that is located at the center in the longitudinal direction and is narrower in width than the portion protruding from the restraint member 20, and the plasticized portion 10P has no opening. Thus, for example, unlike the case of forming an opening in the plasticized portion 10P, the cross-sectional area in the direction orthogonal to the longitudinal direction can be maintained at the maximum area corresponding to the outer shape of the plasticized portion 10P, so that the axial bearing capacity of the plasticized portion 10P against the tensile load along the longitudinal direction is not reduced. Also, since the second moment of inertia of the cross-section of the plasticized portion 10P can be increased, the bending rigidity of the plasticized portion 10P can be increased compared to the case of forming an opening in the plasticized portion 10P. Further, since the plasticized portion 10P has a closed surface without an opening, the confined effect can be appropriately generated on the filler 30 located around the plasticized portion 10P. Therefore, the bearing capacity of the filler 30 can be improved compared to the case of forming an opening in the plasticized portion 10P.

[0041] Further, an unbonded material 40 is further provided, which is interposed between the core material 10 and the filler 30 and allows relative movement between the core material 10 and the filler 30 by elastically deforming as the core material 10 deforms. Thus, even when an out-of-plane deformation of the core material 10 occurs, the unbonded material 40 elastically deforms, so that the filler 30 can be prevented from deforming following the out-of-plane deformation of the core material 10. The maximum allowable deformation amount of the core material 10 is the deformation amount when the core material 10 undergoes the largest out-of-plane deformation in the plate thickness direction within the range of the thickness 40t of the unbonded material 40. Thereby, even when the core material 10 deforms, as long as the deformation amount is equal to or less than the maximum allowable deformation amount, the maximum compressive stress generated in the filler 30 is within the crushing strength, so that the filler 30 can be prevented from being crushed.

[0042] Further, the restraint member 20 has a cylindrical shape. Thus, for example, the load applied to the filler 30 due to the deformation of the core material 10 can be dispersed over a wide area of the filler 30. Therefore, for example, even if a large load is concentrated on a part of the filler 30 due to the deformation of the core material 10, the occurrence of local stress in the filler 30 can be suppressed. Therefore, the filler 30 can be further prevented from being crushed.

[0043] Also, the plate thickness of the core material 10 is 12 mm or more and 16 mm or less. By making the plate thickness of the core material 10 relatively small in this way, it is possible to obtain the buckling restraint brace 100 with a small axial bearing capacity applicable to small-scale buildings. The crushing strength of the filling material 30 is 21 N / mm 2 or more. Thereby, in the buckling restraint brace 100 for small-scale buildings where the plate thickness of the core material 10 is relatively small, crushing of the filling material 30 can be suppressed and the core material 10 can be appropriately restrained.

[0044] Also, the core material 10 includes a plasticizing portion 10P that is located at the center in the longitudinal direction and is narrower in width than the portion protruding from the restraining member 20. Further, the core material 10 includes a pair of width-changing portions 13 that are adjacent to both sides of the plasticizing portion 10P and have a shape in which the plate width becomes larger toward the end portion side. The angle formed between the inclined plane forming the end face in the plate width direction in the width-changing portion 13 and the longitudinal direction is 30 degrees or more. Thereby, for example, the compressive axial force applied to the core material 10 can be efficiently transmitted to the plasticizing portion 10P via the width-changing portion 13.

[0045] Also, the crushing strength of the filling material 30 is set to be equal to or greater than the maximum compressive stress generated in the filling material 30 when the out-of-plane deformation amount of the core material 10 reaches the allowable maximum deformation amount. Thereby, when the core material 10 deforms with a deformation amount equal to or less than the allowable maximum deformation amount due to the compressive axial force, it is possible to suppress the filling material 30 from being crushed.

[0046] Note that the technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, although it has been described that the restraining member 20 is preferably cylindrical, it may be square cylindrical as needed. Also, the restraining member 20 may be formed by connecting a plurality of members. Further, although the plasticizing portion 10P has been exemplified as having a constant cross-sectional shape in the longitudinal direction in the direction orthogonal to the longitudinal direction, the plasticizing portion 10P may have a cross-sectional shape different from other portions in a part of the longitudinal direction. Furthermore, although it is preferable not to form an opening in the plasticizing portion 10P, an opening may be formed in the plasticizing portion 10P.

[0047] In addition, within the scope not departing from the gist of the present invention, it is possible to appropriately replace the components in the above-described embodiment with well-known components, and the above-described modified examples may be appropriately combined.

Explanation of Reference Numerals

[0048] 10 Core material 10P Plasticized portion 11 Narrow portion 12 Wide portion 13 Width change portion 14 Core material stiffening member 20 Restraining member 30 Filling material 40 Unbonding material 100 Buckling restraining brace

Claims

1. A long, plate-shaped core material; a restraining member that covers an outer periphery of the core material with both ends of the core material protruding; A filler material is filled between the core material and the restraining member; an unbond material interposed between the core material and the filler material so as to allow relative movement between the core material and the filler material; Equipped with The compressive strength of the filler is equal to or greater than the maximum compressive stress generated in the filler when the out-of-plane deformation of the core material reaches the maximum allowable deformation, The compressive stress generated in the filler is a compressive stress exerted by the core material on the filler due to a pressing force acting on the filler through the unbond material as the core material approaches the filler due to out-of-plane deformation, The maximum allowable deformation amount is a deformation amount when the core material is deformed most greatly out-of-plane in the plate thickness direction within the thickness range of the unbonded material, The filler material is in close contact with the entire periphery of the unbonded material in a cross section perpendicular to the longitudinal direction of the core material. A buckling restrained brace characterized by:

2. The core material has a plasticized portion located at the center in the longitudinal direction, The plasticized portion is narrower than a portion protruding from the restraining member.

2. The buckling restrained brace of claim 1.

3. The restraining member is cylindrical.

2. The buckling restrained brace of claim 1.

4. The thickness of the core material is 12 mm or more and 16 mm or less, The crushing strength of the filler is 21 N / mm ２ That's all.

4. The buckling restrained brace of claim 1.

5. The core material has a pair of width changing portions adjacent to both sides of the plasticized portion. Further comprising: The pair of width changing portions have a plate width on the end side larger than a plate width on the plasticized portion side, The angle between the inclined plane forming the end face in the plate width direction at the width changing portion and the longitudinal direction is 30 degrees or more.

3. The buckling restrained brace of claim 2.

6. A long, plate-shaped core material; a restraining member that covers an outer periphery of the core material with both ends of the core material protruding; A filler material is filled between the core material and the restraining member; an unbond material interposed between the core material and the filler material so as to allow relative movement between the core material and the filler material; A method for designing the strength of the filler in a buckling restrained brace comprising: The compressive strength of the filler is set to be equal to or greater than the maximum compressive stress generated in the filler when the out-of-plane deformation amount of the core material reaches the maximum allowable deformation amount, The compressive stress generated in the filler is a compressive stress exerted by the core material on the filler due to a pressing force acting on the filler through the unbond material as the core material approaches the filler due to out-of-plane deformation, The maximum allowable deformation amount is a deformation amount when the core material is deformed most greatly out-of-plane in the plate thickness direction within the thickness range of the unbonded material, The filler material is in close contact with the entire periphery of the unbonded material in a cross section perpendicular to the longitudinal direction of the core material. A method for designing the strength of a filler.

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