Buckling-restrained brace and method for manufacturing the same

Abstract

Provided are a buckling-restrained brace that improves the energy absorption performance by means of an axial force tube and is easy to manufacture in a factory, and a method for manufacturing the same. 【Solution means】An axial force tube that bears an axial force, a stiffening tube into which the axial force tube is inserted internally so as to cover the outer circumference of the axial force tube, a set of end plates joined to both ends so as to close both ends of the axial force tube, and a set of cross plates joined to both ends of the axial force tube via the end plates and serving as fixing parts to a building structure frame. The plate thickness t e (mm) of the end plate is set to be not less than the value calculated by the following formula (1). It is a buckling-restrained brace. P ey =2×(1 + √2)×t e 2 ×σ ey +π×t p ×(r - t p / 2)σ py ……(1) Here, P ey (N): the yield load of the end plate, r(mm): the outer radius of the axial force tube, σ ey (N / mm 2 ): the yield stress of the end plate, π: pi, t p (mm): the plate thickness of the axial force tube, σ py (N / mm 2 ): the yield stress of the axial force tube.

Description

[Technical Field]

[0001] This invention relates to a buckling-restrained brace installed in a building structure, and a method for manufacturing the same. [Background technology]

[0002] Various types of buckling-restrained braces have been developed that are installed diagonally on the frame of a building structure consisting of columns and beams, and that prevent buckling when subjected to compressive axial force.

[0003] A buckling-restrained brace, for example, like the double-tube steel brace material disclosed in Patent Document 1, has an axial force tube positioned at the center of the buckling-restrained brace and a stiffening tube that encloses the outer circumference of the axial force tube and into which the axial force tube is inserted. The axial force tube receives the axial force acting on the buckling-restrained brace, and the stiffening tube restrains the buckling deformation of the axial force tube.

[0004] When a compressive force acts on the axial force pipe of a buckling-restrained brace during an earthquake, buckling deformation occurs in the axial force pipe. However, buckling is suppressed by stiffening pipes arranged to surround the outer circumference of the axial force pipe. This allows for increased strength of the brace material and a reduction in cross-section compared to a design without stiffening pipes. Furthermore, when repeated loads act on the axial force pipe of a buckling-restrained brace during an earthquake, causing the axial force pipe to yield and undergo plastic deformation, the rapid decrease in strength due to plastic deformation of the axial force pipe is suppressed. As a result, the energy absorption effect due to the plastic deformation of the axial force pipe is exerted against repeated loads, absorbing earthquake energy acting on the building structure, thus enabling an economical and highly safe seismic-resistant design.

[0005] In a buckling restraint brace, it is common to provide joining members for joining to gusset plates or the like provided on the frame of a building structure at both ends of the axial force pipe. The joining member of the double steel pipe type brace material disclosed in Patent Document 1 is composed of joining pipes welded to both ends of the axial force pipe and a cross plate welded to the joining pipes, and the cross plate serves as a fixing portion to the frame of the building structure. In the double steel pipe type brace material disclosed in Patent Document 1, in order to increase the strength of the joint between the cross plate and the joining pipe, a notch is formed in the cross plate, and the joining pipe is inserted into this notch, and the two are welded together.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Here, in the buckling restraint brace disclosed in Patent Document 1, since the joining pipe is inserted into the stiffening pipe and welded to the end of the axial force pipe inside the stiffening pipe, the length of the axial force pipe is shorter than that of the stiffening pipe. Therefore, depending on the shape of the frame composed of columns and beams of a building structure, it may not be possible to sufficiently secure the length of the axial force pipe. In this case, the buckling restraint brace cannot be installed in the building structure, and the building structure cannot be made into a vibration control structure.

[0009] Furthermore, in the buckling-restrained brace disclosed in Patent Document 1, the welding length required at the joint between the connecting pipe and the cross plate is equal to the length of the portion of the connecting pipe that is inserted into the notch of the cross plate. Therefore, the distance between the bolt holes provided in the cross plate for bolting the cross plate to the frame of the building structure and the end of the axial force pipe increases by the amount of the welding length, and as a result, the length of the axial force pipe is shortened.

[0010] The axial force tubes of buckling-restrained braces absorb energy through repeated plastic deformation caused by expansion and contraction loads resulting from seismic forces. As mentioned above, if the length of the axial force tubes is shortened, the amount of seismic energy absorbed by the buckling-restrained braces decreases accordingly. As a result, it becomes necessary to reinforce the columns and beams of the building structure against seismic forces, making economical design impossible.

[0011] The present invention was made to solve the above-mentioned problems, and aims to provide a buckling-restrained brace and a method for manufacturing the same, which improves the energy absorption performance by the axial force pipe and facilitates factory manufacturing, by making the shape of the joint between the axial force pipe of the buckling-restrained brace and the joining members provided at both ends of the axial force pipe and joined to the frame of the building structure such that the length of the axial force pipe can be increased relative to the total length of the buckling-restrained brace. [Means for solving the problem]

[0012] The means to solve the above problems are as follows: [1] A buckling-restrained brace comprising: an axial force tube that bears axial force; a stiffening tube into which the axial force tube is inserted so as to cover the outer circumference of the axial force tube; a pair of end plates joined to both ends of the axial force tube so as to close both ends of the axial force tube; and a pair of cross plates joined to both ends of the axial force tube via the end plates, which serve as fixing parts to the frame of a building structure. [2] The buckling-restrained brace according to [1], wherein a notch is provided on the outer edge of the end plate, the inner surface of the axial force tube is fitted into the notch, and the axial force tube and the end plate are welded together using a groove formed by the notch of the end plate and the end face of the axial force tube. [3] The buckling-restrained brace according to [1], wherein a backing plate is provided on the side surface of the end plate on the side facing the axial force pipe, in a state that it abuts against the inner surface of the axial force pipe, and the axial force pipe and the end plate are welded together using a groove formed by the side surface of the end plate, the backing plate, and the end face of the axial force pipe. [4] The buckling-restrained brace according to any one of [1] to [3], wherein the stiffening pipe is fixed to the axial force pipe by a stiffening pipe fixing part provided at one location along the length of the stiffening pipe. [5] The stiffening pipe fixing portion is configured such that the stiffening pipe is welded to the axial force pipe using welding holes provided in the stiffening pipe, as described in [4], a buckling-restrained brace. [6] The stiffening pipe fixing portion is configured such that one end of the stiffening pipe is welded to the end plate which is joined to one end of the axial force pipe, as described in [4], a buckling-restrained brace. [7] A buckling-restrained brace according to any one of [1] to [3], wherein a suspension piece is provided on the outer surface of the stiffening pipe. A method for manufacturing a buckling-restrained brace as described in any of [8] [1] to [3], At least one of the pair of end plates is formed to have a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening pipe. The axial force tube is inserted into the stiffening tube from the side to which the end plate, which has a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening tube, is joined. A method for manufacturing a buckling-restrained brace, comprising: next, joining the cross plate to the end plate having a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening pipe. [Effects of the Invention]

[0013] According to the buckling-restrained brace and its manufacturing method of the present invention, a cross plate, which serves as the fixing portion to the frame of a building structure, is joined to both ends of the axial force pipe via end plates that are joined so as to close both ends of the axial force pipe. Therefore, the distance between the bolt holes provided in the cross plate for bolting the cross plate to the frame of the building structure and the ends of the axial force pipe can be reduced.

[0014] As a result, the length of the axial force pipe relative to the total length of the buckling-restrained brace can be increased. This increases the amount of seismic energy absorbed by the plastic deformation that occurs in the axial force pipe when seismic forces act on it. Therefore, the building structure can be made into a structure with high vibration damping, improving the overall economic efficiency of the building structure. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1(a) is a side view showing a buckling-restrained brace according to one embodiment of the present invention, and Figures 1(b) and 1(c) are cross-sectional views of the buckling-restrained brace shown in Figure 1(a) along the IB-IB line and the IC-IC line, respectively. [Figure 2] Figure 2 is an enlarged view of the main part of the buckling-restrained brace shown in Figure 1(a). [Figure 3] Figure 3 is an enlarged view of the main part of the buckling-restrained brace shown in Figure 1(a). [Figure 4] Figure 4 is a cross-sectional view showing an example of the connection configuration between the axial force pipe and the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 5] Figure 5 is a cross-sectional view showing another example of the connection configuration between the axial force pipe and the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 6] Figure 6 is a cross-sectional view showing yet another example of the connection configuration between the axial force pipe and the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 7] Figure 7 is a cross-sectional view showing yet another example of the connection configuration between the axial force pipe and the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 8] Figure 8 is a cross-sectional view showing yet another example of the connection configuration between the axial force pipe and the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 9] Figures 9(a) and 9(b) are a cross-sectional view and a side view of a buckling-restrained brace, respectively, showing an example of a stiffening pipe fixing portion of a buckling-restrained brace according to one embodiment of the present invention. [Figure 10]Figure 10 is a cross-sectional view of a buckling-restrained brace, showing another example of the stiffening pipe fixing portion of a buckling-restrained brace according to one embodiment of the present invention. [Figure 11] Figure 11 is a side view showing an example of a suspension piece for a buckling-restrained brace according to one embodiment of the present invention. [Figure 12] Figure 12 is a schematic perspective view showing the out-of-plane deformation occurring in the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 13] Figures 13(a) and 13(b) are side views showing a test specimen used in a loading test to confirm the amount of out-of-plane deformation occurring in the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 14] Figure 14 is a graph showing the results of a loading test to confirm the amount of out-of-plane deformation occurring in the end plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 15] Figure 15 is a graph showing an example of the strain distribution occurring at the end of the axial force pipe of a buckling-restrained brace according to one embodiment of the present invention. [Figure 16] Figure 16 is a graph showing an example of the strain distribution occurring at the end of the cross plate of a buckling-restrained brace according to one embodiment of the present invention. [Figure 17] Figure 17 is a side view showing the length of the expansion and contraction range in which a relative displacement occurs between the axial force pipe and the stiffening pipe when the axial force pipe of a buckling-restrained brace according to one embodiment of the present invention expands and contracts under load. [Figure 18] Figure 18 is a side view showing the length of the expansion and contraction range in which a relative displacement occurs between the axial force pipe and the stiffening pipe when the axial force pipe of a buckling-restrained brace according to one embodiment of the present invention expands and contracts under load. [Figure 19] Figure 19 is a graph showing an example of the stress-strain relationship of the axial force pipe of a buckling-restrained brace according to one embodiment of the present invention. [Figure 20] Figure 20 is a graph showing another example of the stress-strain relationship of the axial force pipe of a buckling-restrained brace according to one embodiment of the present invention. [Figure 21]Figures 21(a) and 21(b) are graphs showing an example of the relative displacement between the axial force pipe and the stiffening pipe of a buckling-restrained brace according to one embodiment of the present invention. [Figure 22] Figure 22 shows the relationship between the outer diameter of the axial force pipe and the inner diameter of the stiffening pipe of a buckling-restrained brace according to one embodiment of the present invention. [Figure 23] Figure 23 shows an example of the procedure for manufacturing a buckling-restrained brace according to one embodiment of the present invention. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments of the buckling-restrained brace and its manufacturing method according to the present invention will be described with reference to the drawings. [Buckling Restraint Brace] Figure 1(a) shows a side view of a buckling-restrained brace 1 according to one embodiment of the present invention. Figures 1(b) and 1(c) show cross-sectional views of the buckling-restrained brace 1 shown in Figure 1(a) along the IB-IB and IC-IC lines, respectively.

[0017] As shown in Figures 1(a) to 1(c), the buckling-restrained brace 1 comprises an axial force pipe 11, a stiffening pipe 12, a pair of end plates 13, and a pair of cross plates 14. The axial force pipe 11 is made of a cylindrical steel pipe and bears the axial force input to the buckling-restrained brace 1. The stiffening pipe 12 is also made of a cylindrical steel pipe, and the axial force pipe 11 is inserted into the stiffening pipe 12 so that the stiffening pipe 12 covers the outer circumference of the axial force pipe 11. The end plates 13 are made of disc-shaped steel plates and are welded to both ends of the axial force pipe 11 so as to close both ends of the axial force pipe 11. The cross plates 14 are made by combining steel plates to form a cross cross section and are welded to both ends of the axial force pipe 11 via the end plates 13, becoming the fixing part to the frame of the building structure (not shown). Specifically, the building structure is provided with a frame-side cross plate 21 at a position opposite to the cross plate 14 of the buckling-restrained brace 1. The buckling-restrained brace 1 is then fixed to the building structure by friction joining the cross plate 14 of the buckling-restrained brace 1 and the frame-side cross plate 21 of the building structure using splice plates 22 and high-strength bolts. The stiffening pipe 12 is fixed to the axial force pipe 11 by a stiffening pipe fixing part (described later) provided at one point along the length of the stiffening pipe 12.

[0018] Figures 2 and 3 show enlarged views of the main parts of the buckling-restrained brace 1 shown in Figure 1(a).

[0019] As shown in Figures 2 and 3, the end plates 13, which are welded to both ends of the axial force pipe 11, are inserted into the stiffening pipe 12 together with the axial force pipe 11, and the outer diameter of the end plates 13 is less than or equal to the outer diameter of the axial force pipe 11. A notch 13a is provided on the outer edge of the end plate 13 by machining, and the inner surface of the axial force pipe 11 is fitted into this notch 13a. In this state, a groove is formed from the notch 13a of the end plate 13 and the end face of the axial force pipe 11, and the axial force pipe 11 and the end plate 13 are welded together using this groove. The surface of the weld metal W in the weld joint between the axial force pipe 11 and the end plate 13 is kept from contacting the inner surface of the stiffening pipe 12.

[0020] It is preferable that the portion of the notch 13a of the end plate 13 facing the end face of the axial force pipe 11 be an inclined surface that forms an inclination angle θ1 with respect to the radial direction of the end plate 13. This inclined surface provides a groove angle to the weld joint between the axial force pipe 11 and the end plate 13. The flat portion of the notch 13a of the end plate 13, other than the inclined surface, serves as a backing for the weld metal W. It is preferable that the overlap length L1 between the flat portion of the notch 13a of the end plate 13 and the fitting portion with the axial force pipe 11 be 5 to 10 mm. The length L2 of the flat portion of the notch 13a of the end plate 13, excluding the fitting portion with the axial force pipe 11, becomes the root gap of the weld joint between the axial force pipe 11 and the end plate 13.

[0021] Furthermore, as shown in Figures 2 and 3, the width of the cross plate 14 differs between the base portion 14a, which is joined to the end plate 13, and the tip portion 14b, which is joined to the cross plate 21 on the frame side of the building structure, with the latter being larger.

[0022] Preferably, the width of the base 14a of the cross plate 14 that is joined to the end plate 13 is set to be 20 mm or more smaller than the diameter of the end plate 13. This ensures that a welding allowance h of 10 mm or more is secured for wrap welding between the outer edge of the end plate 13 and the base 14a of the cross plate 14. Furthermore, the width of the base 14a of the cross plate 14 is kept constant, and the length L3 of the base 14a in the longitudinal direction of the buckling-restrained brace 1 is set to be large enough so that the cross plate 14 does not come into contact with the stiffening pipe 12 when the axial force pipe 11 is compressed and shrinks.

[0023] The width of the tip 14b of the cross plate 14 that is joined to the cross plate 21 on the building structure side is kept constant and set to be approximately the same as the width of the cross plate 21 on the building structure side. This makes it possible to frictionally join the cross plate 14 of the buckling-restrained brace 1 and the cross plate 21 on the building structure side at the tip 14b of the cross plate 14 using the splice plate 22 and high-strength bolts.

[0024] Furthermore, a slanted portion 14c is provided between the base 14a and the tip 14b of the cross plate 14 to change the width of the cross plate 14. The inclination angle θ of the side surface of the cross plate 14 at the slanted portion 14c a It is preferable that the angle be 45° or less. This allows for smooth transmission of axial force between the axial force pipe 11 of the buckling-restrained brace 1 and the building structure.

[0025] Figures 4 to 7 show cross-sectional views of other examples of the connection configuration between the axial force tube 11 and the end plate 13 of the buckling-restrained brace 1.

[0026] In the example shown in Figure 4, an inclination angle θ2 is also provided on the end face of the axial force pipe 11 that faces the inclined surface of the notch 13a of the end plate 13. The inclined surface of the notch 13a of the end plate 13 and the end face of the axial force pipe 11 provide a groove angle in the weld joint between the axial force pipe 11 and the end plate 13. In this case, it is desirable that the inclination angle θ1 of the inclined surface of the notch 13a of the end plate 13 be 10° to 20°, the inclination angle θ2 of the end face of the axial force pipe 11 be 30° to 40°, and the root gap L2 of the weld joint between the axial force pipe 11 and the end plate 13 be 3 to 7 mm.

[0027] In the example shown in Figure 5, the end face of the axial force pipe 11 facing the inclined surface of the notch 13a of the end plate 13 does not have an inclination angle. In this case, it is desirable that the inclination angle θ1 of the inclined surface of the notch 13a of the end plate 13 be 30° to 40°, and the root gap L2 of the groove of the welded joint between the axial force pipe 11 and the end plate 13 be 3 to 7 mm.

[0028] The example shown in Figure 6 is the same as the example shown in Figure 4, but with a step of 1 mm or less between the flat portion of the notch 13a of the end plate 13, which will be the root gap L2 of the weld joint between the axial force pipe 11 and the end plate 13, and the fitting portion with the axial force pipe 11. Similarly, the example shown in Figure 7 is the same as the example shown in Figure 5, but with a step of 1 mm or less between the flat portion of the notch 13a of the end plate 13, which will be the root gap L2 of the weld joint between the axial force pipe 11 and the end plate 13, and the fitting portion with the axial force pipe 11. By providing a step in the flat portion of the notch 13a of the end plate 13 in this way, it becomes easier to adjust the root gap L2 of the weld joint between the axial force pipe 11 and the end plate 13 to a predetermined length. In addition, the gap between the inner surface of the axial force pipe 11 and the flat portion of the notch 13a of the end plate 13 becomes smaller, making the weld joint between the axial force pipe 11 and the end plate 13 more reliable. In particular, if the actual inner diameter of the axial force tube 11 is smaller than the specified value, the gap between the inner surface of the axial force tube 11 and the flat portion of the notch 13a of the end plate 13 is adjusted by the above-mentioned step, which allows the inner surface of the axial force tube 11 to fit smoothly into the notch 13a of the end plate 13.

[0029] Figure 8 shows a cross-sectional view of yet another example of the connection configuration between the axial force pipe 11 and the end plate 13 of the buckling-restrained brace 1.

[0030] In the example shown in Figure 8, the end plate 13 does not have a notch 13a. A backing plate 13b is provided on the side of the end plate 13 facing the axial force pipe 11, in contact with the inner surface of the axial force pipe 11. The axial force pipe 11 is welded to the end plate 13 using a groove formed by the side of the end plate 13, the backing plate 13b, and the end face of the axial force pipe 11. An inclination angle θ2 is provided on the end face of the axial force pipe 11 that is facing the side of the end plate 13. Thus, the groove of the weld between the axial force pipe 11 and the end plate 13 is provided by the side of the end plate 13 and the end face of the axial force pipe 11.

[0031] In the configuration shown in Figure 8, a backing plate 13b needs to be provided separately, but machining to create a notch 13a in the end plate 13 is unnecessary. When the yield strength of the buckling-restrained brace 1 is large and the outer diameter of the end plate 13 is large, the cost of machining to create a notch 13a in the end plate 13 becomes high, but by adopting the configuration shown in Figure 8, this machining becomes unnecessary, improving cost-effectiveness.

[0032] Figures 9(a) and 9(b) show a cross-sectional view and a side view, respectively, of the area surrounding the stiffening pipe fixing portion 15 of the buckling-restrained brace 1.

[0033] In the examples shown in Figures 9(a) and 9(b), the stiffening pipe 12 is fixed to the axial force pipe 11 by a stiffening pipe fixing part provided at one point along the length of the stiffening pipe 12. The stiffening pipe fixing part is constructed by welding the stiffening pipe 12 to the axial force pipe 11 by plug welding 15 using a welding hole 12a provided in the stiffening pipe 12.

[0034] Specifically, as shown in Figures 9(a) and 9(b), a fixing plate 11a is welded to the center of the axial force pipe 11 in the longitudinal direction. A welding hole 12a is also provided in the center of the stiffening pipe 12 in the longitudinal direction. The diameter of this welding hole 12a is preferably 20 to 40 mm. The stiffening pipe fixing section is then constructed by fixing the fixing plate 11a of the axial force pipe 11 and the welding hole 12a of the stiffening pipe 12 by plug welding 15.

[0035] It is desirable that the stiffening pipe fixing points be provided at 2 to 3 locations in the circumferential direction at the center of the longitudinal direction of the axial force pipe 11. By fixing the axial force pipe 11 and the stiffening pipe 12 by plug welding 15 in this way, the gap between the outer surface of the axial force pipe 11 and the inner surface of the stiffening pipe 12 can be made uniform in the circumferential direction, and the stiffening effect of the stiffening pipe 12 on the axial force pipe 11 can be reliably exerted. In addition, by fixing the positions of the axial force pipe 11 and the stiffening pipe 12, if the buckling-restrained brace is installed at an angle, it is possible to prevent the stiffening pipe 12 from shifting downward, causing its end to come into contact with the end face of the cross plate 14 and damaging the paint, thus preventing problems such as damage. Furthermore, because the joint is locally made by plug welding, the gap between the outer surface of the axial force pipe 11 and the inner surface of the stiffening pipe 12 is in communication at the stiffening pipe fixing point, making it easier to remove rainwater and dust that may enter the gap between the axial force pipe 11 and the stiffening pipe 12.

[0036] Figure 10 shows a cross-sectional view of another example of the stiffening pipe fixing section of the buckling-restrained brace 1.

[0037] In the example shown in Figure 10, the stiffening pipe fixing section is constructed by welding one end of the stiffening pipe 12 to an end plate 13 that is joined to one end of the axial force pipe 11.

[0038] Specifically, as shown in Figure 10, a stiffening pipe weld 13c is provided on the outer circumference of the end plate 13 by machining, and the inner surface of the stiffening pipe 12 is in contact with the outer circumference of this stiffening pipe weld 13c. A portion of the outer circumference of the stiffening pipe weld 13c protrudes axially outward from the end face of the stiffening pipe 12, and the end face of the stiffening pipe 12 and the stiffening pipe weld 13c of the end plate 13 are fixed together by fillet welding 16. In addition, a notch 13a is provided on the outer edge of the end plate 13 by machining, and the inner surface of the axial force pipe 11 is fitted into this notch 13a. In this state, a groove is formed from the notch 13a of the end plate 13 and the end face of the axial force pipe 11, and the axial force pipe 11 and the end plate 13 are welded together using weld metal W using this groove.

[0039] In this way, the axial force pipe 11 and the stiffening pipe 12 are fixed together by fillet welding 16 via the end plate 13, which makes the gap between the outer surface of the axial force pipe 11 and the inner surface of the stiffening pipe 12 uniform in the circumferential direction, ensuring that the stiffening effect of the stiffening pipe 12 on the axial force pipe 11 is reliably exerted. Furthermore, by fixing the positions of the axial force pipe 11 and the stiffening pipe 12, when the buckling-restrained brace is installed at an angle, it is possible to prevent the stiffening pipe 12 from shifting downwards, causing its end to come into contact with the end face of the cross plate 14 and damaging the paint, thus preventing problems such as paint damage. Additionally, when the buckling-restrained brace 1 is installed at an angle in a building structure, positioning the buckling-restrained brace 1 so that the stiffening pipe fixing part 16 is on the upper side of the buckling-restrained brace 1 prevents rainwater, dust, etc. from entering the interior of the buckling-restrained brace 1. In particular, if the buckling-restrained brace 1 is installed outdoors and is subject to wind and rain, configuring the stiffening pipe fixing section as shown in Figure 10 is effective for the preservation of the buckling-restrained brace 1.

[0040] Figure 11 shows a side view of an example in which a suspension piece 17 is provided on a buckling-restrained brace 1.

[0041] As shown in Figure 11, a suspension piece 17 is provided on the outer surface of the stiffening pipe 12 of the buckling-restrained brace 1. The suspension piece 17 has a hole for passing a shackle or the like for suspension.

[0042] This method facilitates the lifting of the buckling-restrained brace 1 using a crane or similar equipment when installing it on the frame of a building structure. This shortens the installation process and improves safety when installing the buckling-restrained brace 1 on a building structure.

[0043] It is desirable that the suspension pieces 17 be provided in pairs, at equal intervals on both sides of the center of the buckling-restrained brace 1 in the longitudinal direction. This enhances the stability of the buckling-restrained brace 1 when it is suspended, thereby further improving safety. [Thickness of end plates] Figure 12 schematically shows the situation in which out-of-plane deformation occurs in the end plate 13 of the buckling-restrained brace 1 according to the present invention.

[0044] The end plate 13 of the buckling restraint brace 1 according to this embodiment is joined at one side surface to the cross-shaped cross section of the cross plate 14 and at the other side surface to the circular cross section of the axial force tube 11. Therefore, as shown in FIG. 12, when a tensile load acts on the buckling restraint brace 1 due to seismic force, a local tensile force acts from the cross plate 14 on the end plate 13, causing non-uniform out-of-plane deformation. At this time, as indicated by the ○ mark in FIG. 12, bending occurs at the joint of the end plate 13 with the cross plate 14, generating a large stress. It is necessary to set the plate thickness of the end plate 13 so that damage does not occur to the end plate 13 at this time.

[0045] In the buckling restraint brace 1, the collapse mechanism of the end plate 13 is composed of bending yielding in the yield line portion of the end plate 13 and axial yielding at the end of the axial force tube 11. When deriving the out-of-plane yield strength evaluation formula of the end plate 13 using the yield line theory based on this collapse mechanism, it becomes as shown in the following formula (1).

[0046] P ey =2×(1 + √2)×t e 2 ×σ ey +π×t p ×(r - t p / 2)σ py ……(1) Here, P ey (N): The yield load of the end plate 13, r (mm): The outer radius of the axial force tube 11, σ ey (N / mm 2 ): The yield stress of the end plate 13, π: Pi, t e (mm): The plate thickness of the end plate 13, t p (mm): The plate thickness of the axial force tube 11, σ py s (N / mm 2 ): The yield stress of the axial force tube 11.

[0047] Next, in order to confirm the out-of-plane deformation amount that occurs in the end plate 13 of the buckling restraint brace 1 according to the present invention, as well as the strain degree that occurs at the end of the axial force tube 11 and the end of the cross plate 14 joined to the end plate 13, a loading test was conducted, and this will be described below.

[0048] Figures 13(a) and 13(b) show side views of the test specimens used in this loading test.

[0049] As shown in Figures 13(a) and 13(b), the specimen used in this loading test is configured such that the buckling-restrained brace 1 includes the end plate 13 and the joint portion between the axial force pipe 11 and the cross plate 14 joined to both sides thereof.

[0050] In the test specimen used in this loading test, the material of the end plate 13 was SN490B as specified in Japanese Industrial Standard JIS G3136 (Rolled Steel for Building Structures), and the thickness of the end plate 13 was t e The diameter was set to 12 mm. The material of the axial force pipe 11 is STK400 as specified in Japanese Industrial Standard JIS G3444 (Carbon steel pipes for general structural use), the outer diameter Φ of the axial force pipe 11 is 216.3 mm, and the plate thickness t of the axial force pipe 11 is 216.3 mm. p The thickness was set to 5.8 mm. The material of the cross plate 14 was SN490B, the width of the cross plate 14 was 210 mm x 210 mm, and the thickness of the cross plate 14 was 16 mm.

[0051] Then, a tensile load was applied to the above-mentioned test specimen, and a loading test was conducted under the condition that this tensile force was gradually increased. The amount of out-of-plane deformation (mm) that occurred in the end plate 13 of the test specimen, as well as the degree of strain (%) that occurred in the end of the axial force tube 11 and the end of the cross plate 14 joined to the end plate 13, were confirmed. In addition, numerical analysis using the finite element method was performed on an analytical model simulating the above-mentioned test specimen under the same loading conditions.

[0052] Figure 14 shows the relationship between the tensile load F (kN) obtained from the above loading test and numerical analysis and the out-of-plane deformation (mm) occurring in the end plate 13 of the test specimen. In Figure 14, the thick solid line represents the experimental value, the thin solid line represents the analytical value, the thick dashed line is a bilinear approximation of the experimental value curve, and the thin dashed line is a bilinear approximation of the analytical value curve. Yield load P of the end plate 13 yFor each of the lines (thick dashed line and thin dashed line) that approximate the experimental or analytical curves using bilinear approximation, the value of the tensile load F(kN) at the intersection of the initial slope and the secondary slope is shown. In Figure 14, the ● and ○ marks indicate that the tensile load F(kN) on the experimental curve (thick solid line) or the analytical curve (thin solid line) is P y , 2 / 3P y , and 1 / 3P y These are plots of the points that result in each of these conditions.

[0053] As shown in Figure 14, the initial stiffness of the end plate 13 shows a good correspondence between the experimental and analytical values, but the yield load P of the end plate 13... y The analytical value is approximately 14% smaller than the experimental value.

[0054] Figure 15 shows that the tensile load F (kN) obtained from the above loading test and numerical analysis is P y , 2 / 3P y , 1 / 3P y The distribution of strain (%) generated at the end of the axial force pipe 11 of the test specimen is shown for each case. The horizontal axis of Figure 15 shows the 0° position and the 90° position, which are the joints between the end plate 13 and the cross plate 14, and the positions in between, for a quarter of the cross section of the axial force pipe 11.

[0055] As shown in Figure 15, the tensile load F (kN) is P y In this case, significant strain occurs in the axial force tube 11 near 0° and 90°, which are the joints between the end plate 13 and the cross plate 14, indicating that the end plate 13 is deformed out of plane and yielding occurs in the axial force tube 11. Also, the tensile load F (kN) is 2 / 3P y and 1 / 3P y In this case, the strain of the axial force pipe 11 is small, indicating that the end plate 13 is exhibiting sufficient rigidity to distribute the stress generated in the axial force pipe 11.

[0056] Figure 16 shows that the tensile load F (kN) obtained from the above loading test and numerical analysis is P y , 2 / 3P y , 1 / 3P yThis shows the distribution of strain (%) at the end of the cross plate 14 of the test specimen. Figure 16 shows the distribution of axial strain of the cross plate 14 at a position 20 mm away from the surface of the end plate 13. The horizontal axis of Figure 16 is set to 0 at the intersection of the cross plate 14 and to -1 or 1 at the tip of the cross plate 14 in the width direction.

[0057] As shown in Figure 16, the strain generated at the end of the cross plate 14 increases towards the front end in the width direction of the cross plate 14. The tensile load F (kN) is P y In this case, the analytical value of the strain generated at the end of the cross plate 14 is larger than the experimental value. This is similar to how the analytical value of the out-of-plane deformation of the end plate 13 shown in Figure 14 indicates a state where the yield of the end plate 13 has progressed further than the experimental value. Thus, the analytical value of the strain generated at the end of the cross plate 14 indicates a state where the yield of the end plate 13 occurs earlier than the experimental value. However, within the elastic range, the initial stiffness and strain distribution of the end plate 13 show a good correspondence between the experimental and analytical values, and the analytical value is on the safe side, so it is possible to evaluate the load-bearing capacity of the end plate 13 using the analytical value.

[0058] Table 1 shows a comparison of the experimental, analytical, and calculated yield load values ​​of the end plate 13 using equation (1) above.

[0059] [Table 1]

[0060] The experimental yield load of the end plate 13 is 0.95 times the calculated value using equation (1) above, indicating a good correspondence between the experimental and calculated values. On the other hand, the analytical yield load of the end plate 13 is smaller than the experimental value, and this analytical value is 0.83 times the calculated value using equation (1) above.

[0061] The buckling-restrained brace 1 should be designed such that the end plate 13 remains within the elastic range when the axial force pipe 11 reaches its yield strength. Therefore, the yield load P of the end plate 13 obtained by the yield line theory in equation (1) above is appropriate. ey Multiplying the calculated value of (N) by a discount factor of 2 / 3 (=1 / 1.5), the short-term allowable tensile strength P of the end plate 13 is obtained as shown in equation (2) below. a (N) is calculated. Then, as shown in equation (3) below, the short-term allowable tensile strength P of the end plate 13 is calculated. a (N) is the yield strength P of the axial force pipe 11. py It is safer to design it so that it is greater than (N). Using this discount factor, the yield load P of the end plate 13 obtained by the numerical analysis described above can be determined. y Even in this case, a sufficiently safe result can be obtained.

[0062] P a =P ey / 1.5 ……(2) P a ≥P py ...(3) Required plate thickness t for end plate 13 e The calculation (mm) is first performed using the yield strength P of the axial force pipe 11. py (N) is obtained, and the short-term allowable tensile strength P of the end plate 13 is obtained by the above equation (3). a Set (N). Then, according to equation (2) above, the yield load P of the end plate 13. ey (N) is calculated, and the plate thickness t of the end plate 13 is calculated using the above formula (1). e The procedure involves calculating (mm).

[0063] Table 2 shows the required plate thickness t for the end plate 13 according to equations (1) to (3) above. e An example of calculating (mm) is shown.

[0064] [Table 2]

[0065] However, in the calculation example shown in Table 2, the material of the axial force pipe 11 was JFE-LY225S, a low yield strength steel pipe for building structures manufactured by JFE Steel Corporation. The material of the end plate 13 was SN490C as specified in Japanese Industrial Standard JIS G3136 (Rolled steel for building structures).

[0066] As shown in Table 2, the yield strength P of the axial force pipe 11 py The larger (N) is, the greater the required plate thickness t for the end plate 13. e (mm) will increase.

[0067] The plate thickness t of the end plate 13 shown in Figures 3 to 7 is the required plate thickness t for the end plate 13, which was calculated by the above method. e By setting the thickness to (mm) or more, the end plate 13 can be kept within the elastic range when the axial force pipe 11 reaches its yield strength. This suppresses out-of-plane deformation of the end plate 13, reduces stress concentration at the joint between the end plate 13, the axial force pipe 11, and the cross plate 14, and ensures the safety of the joint.

[0068] Figures 17 and 18 are side views showing the length L (mm) of the expansion and contraction range in which relative displacement occurs between the axial force pipe 11 of the buckling-restrained brace 1 and the stiffening pipe 12 due to expansion and contraction under load. Figure 17 shows an example in which the stiffening pipe fixing part for fixing the stiffening pipe 12 to the axial force pipe 11 is provided in the center of the axial force pipe 11 in the longitudinal direction, as shown in Figures 9(a) and 9(b). Figure 18 also shows an example in which the stiffening pipe fixing part for fixing the stiffening pipe 12 to the axial force pipe 11 is provided at one end of the axial force pipe 11, as shown in Figure 10.

[0069] When an axial load is applied to the axial force pipe 11, axial strain occurs in the axial force pipe 11, causing it to expand and contract, whereas no axial load is applied to the stiffening pipe 12, and therefore no expansion or contraction occurs in the stiffening pipe 12. At this time, the relative displacement between the axial force pipe 11 and the stiffening pipe 12 is zero at the stiffening pipe fixing point. Then, at the end face of the axial force pipe 11, which is at a distance of length L (mm) from the stiffening pipe fixing point, a relative displacement δ (mm) occurs relative to the stiffening pipe 12, with a magnitude proportional to the length L (mm) of the expansion and contraction range.

[0070] When the axial force pipe 11 is subjected to an axial load, if ε is the axial strain generated in the axial force pipe 11, the relative displacement δ (mm) between the end face of the axial force pipe 11 and the stiffening pipe 12 is expressed by the following equation (4).

[0071] δ = ε × L ……(4) Figures 19 and 20 show examples of hysteresis curves of the stress-strain relationship of the axial force tube 11, obtained as a result of a loading test in which alternating positive and negative axial loads were applied to the buckling-restrained brace 1. In Figures 19 and 20, the horizontal axis represents the strain (%) of the axial force tube 11, and the vertical axis represents the stress (N / mm²) of the axial force tube 11. 2 This indicates that...

[0072] Figure 19 shows an example in which the axial force pipe 11 uses JFE-LY225S, a low yield-point steel pipe for building structures manufactured by JFE Steel Corporation. In the example shown in Figure 19, the alternating positive and negative loads applied axially to the buckling-restrained brace 1 were controlled based on the strain generated in the axial force pipe 11, and the load was repeatedly applied until the strain was ±2.0%. As a result, the stress-strain relationship of the axial force pipe 11 showed a stable hysteresis curve, and it was confirmed that the axial force pipe 11 exhibited high energy absorption capacity in the range of strain up to ±2.0%.

[0073] Figure 20 shows an example in which STKN400B, as specified in Japanese Industrial Standard JIS G3444 (Carbon Steel Pipes for General Structural Use), is used for the axial force pipe 11. In the example shown in Figure 20, the alternating positive and negative loads applied axially to the buckling-restrained brace 1 were controlled based on the strain generated in the axial force pipe 11, with loads applied for one cycle each resulting in strains of ±0.25%, ±0.5%, ±0.75%, ±1.0%, ±1.25%, and ±1.5%. As a result, the stress-strain relationship of the axial force pipe 11 showed a stable hysteresis curve, and it was confirmed that the axial force pipe 11 exhibited high energy absorption capacity in the strain range up to ±1.5%.

[0074] Based on these results, when the buckling-restrained brace 1 is used as a vibration damping member that exhibits energy absorption capacity during an earthquake, the maximum strain ε of the axial force pipe 11 of the buckling-restrained brace 1 max(%) is preferably determined as follows, for example, as shown in formula (5) or (6) below. 1) When using JFE-LY225S or JFE-LY100S low yield strength steel pipes for building structures manufactured by JFE Steel Corporation for the axial force pipe 11. ε max = ±2.0% ……(5) 2) When using STKN400B or STKN490B as specified in Japanese Industrial Standard JIS G3475 (Carbon Steel Pipes for Building Structures), or STK400 or STK490 as specified in Japanese Industrial Standard JIS G3444 (Carbon Steel Pipes for General Structural Use) for the axial force pipe 11. ε max = ±1.5% ……(6) Furthermore, when the buckling-restrained brace 1 is used as an earthquake-resistant brace within the elastic range of the axial force pipe 11, the maximum strain ε of the axial force pipe 11 of the buckling-restrained brace 1 max The percentage (%) is preferably ±0.2% or less.

[0075] Then, from equation (4) above, the maximum value of the relative displacement δ between the end face of the axial force pipe 11 and the stiffening pipe 12 is obtained. max (mm) is given by equation (7) below.

[0076] δ max =ε max ×L ……(7) Figures 21(a) and 21(b) show an example of the relative displacement δ (mm) between the axial force pipe 11 and the stiffening pipe 12 of a buckling-restrained brace 1 according to one embodiment of the present invention.

[0077] Figure 21(a) shows the state near the joint between the end plate 13 and the axial force pipes 11 and cross plate 14 joined to both sides of the end plate 13 when no axial load is acting on the axial force pipe 11. At this time, the following relationship (8) holds.

[0078] c = a + b = h / tanθ a +b ……(8) Here, h (mm): welding allowance between the end plate 13 and the cross plate 14, a (mm): horizontal length of the oblique end of the cross plate 14 relative to the welding allowance h (mm) between the end plate 13 and the cross plate 14, b (mm): base length of the cross plate 14, θ a (°): This is the inclination angle of the end face of the cross plate 14.

[0079] Figure 21(b) shows the state in which an axial compressive load acts on the axial force pipe 11, causing the axial force pipe 11 to contract and the outer side of the end plate 13 to be displaced inward from the stiffening pipe 12. The maximum value of the relative displacement δ (mm) between the axial force pipe 11 and the stiffening pipe 12 at this time is shown. max (mm) is as shown in equation (7) above. The maximum value of this relative displacement δ (mm) is δ max If (mm) is within the range that satisfies equation (9) below, it is possible to prevent the stiffening pipe 12 and the cross plate 14 from coming into contact and being damaged.

[0080] c>δ max ...(9) It is preferable to set the size of the welding allowance h (mm) between the end plate 13 and the cross plate 14 so as to satisfy the relationship shown in equation (10) below. This ensures that the welding cross-section between the end plate 13 and the cross plate 14 is sufficiently large, thereby guaranteeing the joint strength between the end plate 13 and the cross plate 14.

[0081] h≧10(mm) ……(10) Furthermore, as described above, a slanted portion 14c is provided between the base portion 14a and the tip portion 14b of the cross plate 14 to change the width of the cross plate 14. The inclination angle θ of the side surface of the cross plate 14 at the slanted portion 14c aIt is preferable to set (°) such that it satisfies the relationship shown in equation (11) below. In this way, the axial force of the axial force pipe 11 is evenly distributed to the cross plate 14, the variation in shear force acting on the high-strength bolts that connect the cross plate 14 to the frame-side cross plate 21 of the building structure is suppressed, and the joining force of the high-strength bolt friction joint is made reliable. As a result, the area of ​​the cross plate 14 can be reduced as much as possible, reducing the weight of the member and preventing interference between the cross plate 14 and other members.

[0082] θ a ≤45(°) ……(11) Table 3 shows an example of a cruciate plate 14 of the buckling-restrained brace 1 designed based on the above equations. Equations (5) to (9) above prevent damage due to contact between the stiffening pipe 12 and the cruciate plate 14, allowing the buckling-restrained brace 1 to exhibit stable energy absorption capabilities during an earthquake, thereby realizing a safe and economical building structure with high vibration damping performance.

[0083] [Table 3]

[0084] Figure 22 shows the relationship between the outer diameter D1 (mm) of the axial force pipe 11 and the inner diameter D2 (mm) of the stiffening pipe 12 of the buckling-restrained brace 1 according to one embodiment of the present invention.

[0085] If the difference between the outer diameter D1 (mm) of the axial force pipe 11 and the inner diameter D2 (mm) of the stiffening pipe 12 is too small, the excess weld material between the axial force pipe 11 and the end plate 13 will interfere with the inner surface of the stiffening pipe 12, hindering the smooth expansion and contraction of the axial force pipe 11.

[0086] To prevent such problems, it is preferable to set the outer diameter D1 (mm) of the axial force pipe 11 and the inner diameter D2 (mm) of the stiffening pipe 12 so as to satisfy the relationship shown in equation (12) below.

[0087] D2-D1≧6(mm) ……(12) Furthermore, if the difference between the outer diameter D1 of the axial force pipe 11 and the inner diameter D2 of the stiffening pipe 12 is too large, the stiffening pipe 12 will not be able to adequately restrain the deformation of the axial force pipe 11 when an axial load is applied to it. As a result, buckling of the axial force pipe 11 will become significant in response to repeated axial loads during an earthquake, reducing its resistance to axial loads, and preventing the buckling-restrained brace 1 from fully exhibiting its energy absorption capacity.

[0088] Therefore, in order to fully utilize the energy absorption capacity of the buckling-restrained brace 1, it is preferable to set the outer diameter D1 (mm) of the axial force pipe 11 and the inner diameter D2 (mm) of the stiffening pipe 12 to satisfy the relationship shown in equation (13) below.

[0089] D2-D1 ≤ 25 (mm) ……(13) Combining equations (12) and (13) above, it is preferable to set the outer diameter D1 (mm) of the axial force pipe 11 and the inner diameter D2 (mm) of the stiffening pipe 12 so as to satisfy the relationship shown in equation (14) below.

[0090] 6(mm)≦D2-D1≦25(mm)……(14) Furthermore, equations (13) and (14) above apply when the buckling-restrained brace 1 is used in a commonly employed dimension, specifically when the lengths of the axial force pipe 11 and stiffening pipe 12 are between 4,000 and 14,000 mm. If the lengths of the axial force pipe 11 and stiffening pipe 12 are greater than this, it is desirable to set the upper limit of (D2-D1) in equations (13) and (14) above to less than 25 mm in order to fully utilize the energy absorption capacity of the buckling-restrained brace 1.

[0091] Furthermore, in order to prevent the stiffening pipe 12 from bending and buckling, it is preferable to design the stiffening pipe 12 to satisfy the following equation (15), taking into account the gap e (mm) between the axial force pipe 11 and the stiffening pipe 12 and the buckling length l (mm) of the axial force pipe 11.

[0092]

number

[0093] However, in equation (15) above,

[0094]

number

[0095]

number

[0096] P R (N): Design axial force of stiffening pipe 12, b M b1 (N·mm): Short-term allowable bending strength of stiffening pipe 12, E(N / mm) 2 ): Young's modulus of stiffening pipe 12, I b (mm 4 ): Second moment of area of ​​the stiffening pipe 12, l (mm): buckling length of the axial force pipe 11, e (mm): gap between the axial force pipe 11 and the stiffening pipe 12, ν0 (mm): initial deflection of the stiffening pipe (=l / 1000).

[0097] Furthermore, equation (15) above is a calculation formula derived based on the design method described in Non-Patent Document 1.

[0098] Table 4 shows an example of designing the stiffening pipe 12 based on the above equations. Equations (15) to (17) above allow for the appropriate setting of the gap e (mm) between the axial force pipe 11 and the stiffening pipe 12 according to the length l (mm) of the axial force pipe 11. This enables the buckling-restrained brace 1 to exhibit stable energy absorption capabilities during an earthquake, resulting in a safe and economical building structure with high vibration damping performance.

[0099] [Table 4]

[0100] [Manufacturing method for buckling-restraint braces] Figure 23 shows an example of the procedure for manufacturing a buckling-restrained brace 1 according to one embodiment of the present invention.

[0101] The manufacturing method for the buckling-restrained brace of this embodiment is a method for manufacturing the buckling-restrained brace 1 described above. The buckling-restrained brace 1 manufactured by this manufacturing method is formed such that at least one of the pair of end plates 13 has a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening pipe 12.

[0102] As shown in Figure 23, in the manufacturing method of the buckling-restrained brace of this embodiment, first, in step S1, end plates 13 are welded to both ends of the axial force tube 11. Next, in step S2, the outer surface of the axial force tube 11 is painted. Next, in step S3, the inner surface of the stiffening tube 12 is painted. Next, in step S4, the axial force tube 11 is inserted into the stiffening tube 12 from the side to which the end plates 13, which have a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening tube 12, are joined. Next, in step S5, the stiffening tube 12 is fixed to the axial force tube 11 with a stiffening tube fixing part. Next, in step S6, cross plates 14 are welded to the end plates 13 on both sides of the axial force tube 11. Next, in step S7, the outer surface of the stiffening tube 12 and the cross plates 14 are painted.

[0103] In step S6 described above, the cross plate 14 is welded to both end plates 13 of the axial force pipe 11 simultaneously. However, instead, in step S6, only one of the end plates 13 of the axial force pipe 11 may be welded. In this case, in step S6, one of the pair of end plates 13 is selected to have a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening pipe 12, and joined to the cross plate 14. The joining of the other end plate 13 of the pair to the cross plate 14 can be performed at any stage prior to step S5 described above.

[0104] As described above, the method for manufacturing the buckling-restrained brace of this embodiment is completed. [Explanation of Symbols]

[0105] 1. Buckling-restrained brace 11 Axial force tube 11a Fixed plate 12 Stiffening tube 12a Welding hole 13 End plate 13a Notch 13b Backing plate 13c Stiffening pipe weld 14 Cross Plate 14a base 14b Tip 14c Slope 15. Plug welding (for fixing stiffened pipes) 16. Fillet welding (for fixing stiffening pipes) 17 Hanging Pieces W Weld Metal 21. Cross plate on the frame side 22 Connection plate

Claims

1. An axial force pipe that bears the axial force, A stiffening pipe is provided, with the axial force pipe inserted inside, so as to cover the outer circumference of the axial force pipe. A pair of end plates are joined to both ends of the axial force pipe so as to close both ends of the axial force pipe, It has a set of cross plates that are joined to both ends of the axial force pipe via the end plates and serve as fixing points to the frame of the building structure, A notch is provided in the outer edge of the end plate, and when the axial force pipe and the end plate are welded together using a groove formed by the notch and the end face of the axial force pipe, the inner surface of the axial force pipe is superimposed on the notch and fitted into the groove, with the notch acting as a backing for the groove. A buckling-restrained brace in which the axial force tube and the end plate are welded together in the aforementioned state.

2. The buckling-restrained brace according to claim 1, wherein the overlap length of the fitting portion between the end plate and the axial force tube is 5 to 10 mm.

3. The buckling-restrained brace according to claim 1 or 2, wherein a step is provided between the portion of the notch that forms the root gap of the groove and the portion that fits with the axial force pipe.

4. The buckling-restrained brace according to claim 1 or 2, wherein the stiffening pipe is fixed to the axial force pipe by a stiffening pipe fixing portion provided at one location along the length of the stiffening pipe.

5. The buckling-restrained brace according to claim 4, wherein the stiffening pipe fixing portion is configured such that the stiffening pipe is welded to the axial force pipe using welding holes provided in the stiffening pipe.

6. The buckling-restrained brace according to claim 4, wherein the stiffening pipe fixing portion is formed by welding one end of the stiffening pipe to the end plate which is joined to one end of the axial force pipe.

7. The buckling-restrained brace according to claim 1 or 2, wherein a suspension piece is provided on the outer surface of the stiffening pipe.

8. A method for manufacturing a buckling-restrained brace according to claim 1 or 2, At least one of the pair of end plates is formed to have a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening pipe. The axial force tube is inserted into the stiffening tube from the side to which the end plate, which has a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening tube, is joined. A method for manufacturing a buckling-restrained brace, comprising: next, joining the cross plate to the end plate having a planar shape smaller than the cross-sectional shape of the inner circumference of the stiffening pipe.

9. A method for manufacturing a buckling-restrained brace according to claim 1 or 2, When welding the axial force pipe and the end plate using a groove formed by the notch and the end face of the axial force pipe, the inner surface of the axial force pipe is fitted into the notch with the notch acting as a backing for the groove. A method for manufacturing a buckling-restrained brace, comprising welding the axial force pipe and the end plate together in the aforementioned state.

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