JP7495249B2 - Buckling Restrained Brace - Google Patents

Description

The present invention relates to a buckling restraint brace.

Buckling-restrained braces with buckling prevention measures have been used as braces that form the framework of buildings (column-beam frameworks, roof frameworks, etc.). Buckling-restrained braces come in a variety of stiffening configurations, including a steel core stiffened only with steel plates, a steel core stiffened with RC (Reinforced Concrete), and a steel core covered with steel and mortar.

Recently, efforts have been made to improve the fire resistance and earthquake resistance of wooden buildings (wooden houses, wooden warehouses, wooden stadiums, etc.). Wooden houses inherently have advantages such as a high degree of freedom in layout and design, the soothing effect of natural wood, the moisture-regulating effect of wood, and generally lower construction costs compared to steel-framed or reinforced concrete structures depending on the building's use, such as housing. However, the above-mentioned improvements in fire resistance and earthquake resistance are one of the factors that have increased the attention of wooden buildings, including wooden houses. When the above-mentioned conventional buckling restraint brace is incorporated into the structure of such a wooden house, wooden columns and beams are mixed with buckling restraint braces with metal or concrete stiffeners, which inevitably results in an unbalanced appearance.

One possible solution to this problem would be to cover the entire buckling restraint brace with a wooden or paper panel, making the metal or concrete stiffener invisible from the outside. However, this would require a great deal of work and labor, raising concerns about increased construction costs. Furthermore, conventional buckling restraint braces tend to be heavy because they use a lot of metal, concrete, mortar, etc., and it would be structurally unbalanced to attach a heavy buckling restraint brace to the lightweight wooden beams and columns that make up a wooden house.

Therefore, a buckling restraint brace has been proposed that is suitable for use within the framework of wooden buildings, including wooden houses. Specifically, this is a buckling restraint brace that has a core material and a pair of restraint materials arranged along both sides of the core material, where the core material is made of steel and the pair of restraint materials are made of wood, and laminated lumber is used for the restraint materials, with the laminated lumber having lamina stacked parallel to the core material (see, for example, Patent Document 1).

Patent No. 4901491

In a buckling restraint brace in which a steel core material is surrounded by wooden restraint materials, when the frame is significantly deformed, for example during a major earthquake, a so-called additional bending moment (or simply, additional bending) caused by this deformation may act on the restraint materials. When this additional bending moment acts on the wooden restraint materials, there is a possibility that the restraint materials will be damaged. When the restraint materials are damaged, the buckling restraint function of the core material by the restraint materials is reduced, and the core material may buckle. Patent Document 1 does not mention measures to prevent such so-called additional bending moments from acting on the restraint materials.

The present invention was made in consideration of the above problems, and aims to provide a buckling restraint brace that is suitable for use in the framework of a wooden building or the like, and can prevent the framework from deforming significantly during a major earthquake, for example, and the so-called additional bending moment acting on the wooden restraint body, causing damage.

In order to achieve the above object, one aspect of the buckling restraint brace according to the present invention is to
A core member made of steel, comprising a first plate and a second plate perpendicular to each other, and having a cross-shaped cross section perpendicular to the longitudinal direction of the core member;
a pair of wooden restraining members arranged to abut on the two wide surfaces of the first plate, and a pair of wooden side members arranged to face the two narrow surfaces of the first plate and connected to the pair of restraining members;
First bolt holes are opened at corresponding positions of the pair of restraining members, a first bolt hole unit is formed by the corresponding first bolt holes, a first long bolt is inserted into each of the first bolt hole units and fastened with a nut,
Second bolt holes are opened at corresponding positions of the pair of side members and the restraining member, a second bolt hole unit is formed by the corresponding second bolt holes, and a second long bolt is inserted into each of the multiple second bolt hole units and tightened with a nut.

According to this aspect, a pair of restraining members are joined by tightening nuts on multiple first long bolts around a core member having a cross-shaped cross section and including a first plate and a second plate, and a pair of side members are joined by tightening nuts on multiple second long bolts together with the restraining member between them, so that a wooden restraint body with high restraint properties can be formed by a pair of restraining members and a pair of side members. This makes it possible to form a buckling restrained brace having a highly rigid wooden restraint body that is less likely to break under additional bending moments that may act. In addition, by tightening nuts on both the first long bolts and the second long bolts that are perpendicular to each other to form a wooden restraint body, when a stiffening force acts on the wooden restraint body, it is possible to effectively prevent the restraint material and the side materials from splitting and breaking in the direction perpendicular to their grain due to the stiffening force.

In addition, because the core material has a cross-shaped cross section perpendicular to its longitudinal direction, the wavelength of the higher buckling mode of the core material becomes longer, and as a result, the stiffening force acting on the wooden restraint body can be reduced, making it less likely that localized damage will occur to the wooden restraint body.

Here, a pair of wooden restraining members "contact the two wide surfaces of the first plate" means that there is no gap between the restraining members and the first plate. If there is a gap between the two, the core material may deform in a wavy manner along its length when it receives a compressive force. The crests of these waves press the restraining members from the inside, and the restraining members may be damaged by the pressing force. As the gap (height) increases, the deformation of the core material increases, and the pressing force acting on the restraining members increases. For example, in a conventional buckling restrained brace in which steel restraining members are arranged around a steel core material, if there is no gap between the core material and the restraining members, the core material that receives a compressive force will deform so as to bulge laterally according to its Poisson's ratio, and the bulging core material will press the restraining members from the inside, generating a large frictional force at the interface between the two, or the restraining members pressed by the core material may be damaged.

In contrast, by arranging wooden restraints around the core material, as in the buckling restraint brace of this embodiment, if there is no gap between the core material (first plate) and the restraint material, when the core material (first plate) bulges laterally and presses the wooden restraint material from the inside, the wooden restraint material, which has a smaller Young's modulus than the core material (first plate), deforms appropriately and can absorb the core material (first plate) that is being pressed in. In other words, in this embodiment, in which wooden restraints are used, a pair of wooden restraint materials abut against the two wide faces of the first plate without any gaps, preventing damage to the restraint material while providing a high restraining effect from the wooden restraint material.

In addition, a pair of restraining members are joined by tightening nuts on multiple first long bolts, and a pair of side members are joined by tightening nuts on multiple second long bolts together with the restraining member between them, thereby forming a wooden restraining body with high restraint of the pair of restraining members and the pair of side members. This makes it possible to form a buckling restrained brace having a highly rigid wooden restraining body that is less likely to break under additional bending moments that may act. The contact surfaces of the restraining members and the side members may be joined with an adhesive and then fastened with the second long bolt. In this way, the contact surfaces of the restraining members and the side members are joined with an adhesive and further fastened with the second long bolt, so that the adhesive surfaces that are the contact surfaces of the restraining members and the side members are crimped with the second long bolt, making it possible to form a buckling restrained brace having a wooden restraining body with even higher connection strength between the restraining members and the side members.

In this embodiment, the pair of restraining members are connected to each other by a pair of side members to form a wooden restraining body with a closed structure made of four face members, and the steel core member is surrounded by the wooden restraining body. With this configuration, even if the buckling restraint brace of this embodiment is applied to the frame of a wooden building, there is no risk of it giving an out-of-match appearance to the frame components. Here, the restraining members and side members may be made of solid wood, or may be made of laminated wood with laminated lamina.

Furthermore, in this embodiment, the wooden restraint body has a configuration in which a pair of side members are connected to a pair of restraining materials, making it easier to process the wooden restraint body. For example, the buckling restrained brace described in Patent Document 1 requires processing laminated timber to create two restraint members with an L-shaped cross section, which are then turned upside down and connected with a core member sandwiched between them. In contrast, in the buckling restrained brace of this embodiment, a wooden restraint body is created by connecting a pair of side members to a pair of restraining materials, and the buckling restrained brace can be produced by, for example, inserting a core member into the hollow space of this wooden restraint body. This makes the buckling restrained brace even easier to produce.

In another aspect of the buckling restraint brace according to the present invention, a groove is provided in the restraint material at a position corresponding to the second plate,
The second plate is accommodated in the groove.

According to this aspect, a groove is provided in the restraint material at a position corresponding to the second plate, and the second plate is accommodated in this groove, thereby forming a buckling restraint brace in which a core material with a cross-shaped cross section is accommodated inside a wooden restraint body. Here, it is preferable that the cross-sectional dimensions of the second plate and the groove are set so that a gap is formed between the second plate and the groove in both the width direction and height direction of the second plate in a cross section perpendicular to the longitudinal direction of the core material.

For example, when a second plate is joined to a first plate by fillet welding or the like, a gap exists between the second plate and the groove in the width direction, allowing the welded portion that protrudes outward from the joint corner of the first plate and second plate to be accommodated in this gap while maintaining the abutting position of the first plate and the wooden restraint body (restraint material).

In addition, by having a gap in the height direction between the upper and lower end faces of the second plate and the grooves, the wooden restraint body (its restraining material) can be reliably abutted against the wide surface of the first plate. If there was no gap in the height direction, the grooves of the wooden restraint body would get caught on the upper and lower end faces of the second plate, and the wooden restraint body (its restraining material) would not abut against the wide surface of the first plate.

Another aspect of the buckling restraint brace of the present invention is characterized in that the second plate is joined to each of the two wide faces of the first plate.

According to this embodiment, a second plate is joined to each of the two wide surfaces of a first plate by welding or the like, thereby obtaining a buckling restraint brace having a core material with a cross-shaped cross section that is easy to work with and has high joint strength. For example, the core material can be processed by joining a second steel plate, which is about half the width of the wide surfaces of the first plate, to both wide surfaces of the first steel plate by fillet welding or the like.

In another aspect of the buckling restraint brace according to the present invention, the first plate has a narrow portion at the center of the longitudinal direction where the width of the wide surface is relatively narrow, and a wide portion at the end of the longitudinal direction where the width of the wide surface is relatively wide,
The present invention is characterized in that a gap is provided between the side surface of the wide portion of the first plate and the side material.

According to this aspect, the first plate constituting the core material has a narrow portion at the center in the longitudinal direction where the wide surface is relatively narrow, and a wide portion at the end in the longitudinal direction where the wide surface is relatively wide. Since there is a gap between the side of the wide portion and the side material constituting the wooden restraint body, even if the structural member is significantly deformed, this gap absorbs the deformation of the core material, and the so-called additional bending moment is prevented from acting on the wooden restraint body. For example, the amount of deformation of the structural member during a major earthquake is left to the discretion of the designer, and the deformation amount of the end of the core material of the buckling restraint brace is calculated based on, for example, the amount of deformation of the structural member when the inter-story deformation angle is 1/100 or the amount of deformation of the structural member when the inter-story deformation angle is 1/75. Then, for example, by setting a gap larger than this calculated amount of deformation, the additional bending moment can be prevented from acting on the wooden restraint body.

In addition, by having a narrow portion at the center of the core material in the longitudinal direction and a wide portion at the end of the core material in the longitudinal direction, the narrow portion at the center can be made into a region that is easily plasticized, and the plasticization region can be limited to the narrow portion at the center. Furthermore, since the boundary region between the wide portion and the narrow portion is a change region where the planar area and cross-sectional area of the core material change, the additional bending moment acting on the core material can be absorbed in this change region. Thus, in this embodiment, the additional bending moment acting on the core material is effectively absorbed in the boundary region between the wide portion and the narrow portion of the core material, and the gap provided between the core material and the side material of the wooden restraint body prevents the additional bending moment acting on the core material from acting on the side material of the wooden restraint body.

In another aspect of the buckling restraint brace according to the present invention, the second plate extends to an end of the first plate,
The second plate has a narrow portion where the width of the wide surface is relatively narrow at a center side in a longitudinal direction thereof, and has a wide portion where the width of the wide surface is relatively wide at an end side in a longitudinal direction thereof,
The wooden restraint body is characterized in that a slit is provided at a position corresponding to the wide portion of the second plate so as not to interfere with the wide portion.

According to this embodiment, since the second plate extends to the end of the first plate and has a cross-shaped cross section even at the end of the core material, when the buckling restraint brace is attached to the gusset plate so that the wide surface of the first plate of the core material is arranged parallel to the structural surface of the building, the core material has a second plate perpendicular to the wide surface of the first plate parallel to the structural surface, so that the rigidity in the direction outside the structural surface can be increased at the end of the core material. In this way, in the gusset plate of the structural surface to which the core material with a cross-shaped cross section is attached, a fin stiffener is attached to the gusset plate, and the first plate and gusset plate of the core material of the buckling restraint brace, and the second plate and fin stiffener are each joined by a high tension bolt or the like via a splice plate. In this embodiment, like the first plate, the second plate also has a narrow portion on the center side and a wide portion on the end side in the longitudinal direction, so that the central narrow portion is accommodated in the groove of the wooden restraint body. On the other hand, the wide portion on the end side may interfere with the wooden restraint, but by providing a slit in the wooden restraint at a position corresponding to the wide surface of the second plate, interference between the wooden restraint and the wide surface on the end side of the second plate of the core material is prevented.

In another aspect of the buckling restraint brace according to the present invention, a spacer is interposed between a side surface of the narrow portion of the first plate and a wall surface of the side member,
The spacer is characterized in that a bolt hole constituting the first bolt hole unit is opened, and the first long bolt is inserted into the bolt hole.

According to this embodiment, by providing a narrow portion at the center of the first plate of the core material, a relatively large gap (larger than the gap between the wide portion at the end of the core material and the side material) exists between the narrow portion and the side material, and by interposing a spacer in this gap to close the gap, it is possible to prevent buckling of the first plate of the core material in the strong axis direction (direction parallel to the wide surface of the first plate). As described above, the narrow portions at the center of the first and second plates of the core material are plasticized regions, but by interposing a spacer between the first plate of the core material and the side material, it is possible to effectively absorb vibration energy during earthquakes, etc., by plasticizing the narrow portions of the core material while suppressing buckling of the first plate of the core material in the strong axis direction. The spacer may be made of either steel or wood.

In addition, the spacer has bolt holes that form the first bolt hole unit, and the first long bolt is inserted into this bolt hole, which prevents the spacer from moving in the longitudinal direction of the core material. Generally, because the buckling restraint brace is arranged diagonally on the structural surface, the spacer is likely to move diagonally downward, and this spacer movement can easily cause a large gap diagonally upward between the end of the spacer and the wide portion of the first plate. Therefore, the diagonally upward area of the buckling restraint brace where the spacer is not present can easily become a weak spot in terms of strength, but according to this embodiment, such spacer movement is eliminated, and no weak spots in strength due to spacer movement are created.

Another aspect of the buckling restraint brace of the present invention is characterized in that, in plan view, there is a gap between the slit and the wide portion of the second plate.

According to this embodiment, the gap between the slit and the second plate allows the gap to absorb the expansion and contraction of the core material when it expands and contracts in response to deformation of the structural surface, eliminating the problem of the wooden restraint being damaged when the expanding and contracting second plate of the core material comes into contact with the wall surface of the slit. Here, the setting of this gap is also left to the discretion of the designer, and the amount of expansion and contraction of the core material is calculated based on the set inter-story deformation angle, and for example, the gap is set to be equal to or greater than the amount of expansion and contraction of the core material. Note that the "gap" here includes the gap between the longitudinal end of the slit and the second plate, as well as the gap between the side of the slit and the wide surface of the second plate, and the gap between the side of the slit and the wide surface of the second plate can be set to the same gap as the gap between the side of the wide part of the first plate of the core material and the side material described above.

In another aspect of the buckling restraint brace of the present invention, a protrusion protrudes from the peripheral surface of the narrow portion of the first plate, and the protrusion engages with an engagement hole provided in the wooden restraint body.

According to this embodiment, the protrusions extending from the periphery of the narrow portion of the first plate of the core material engage with the engagement holes provided in the wooden restraint, thereby preventing the core material inserted inside the wooden restraint from being biased toward one end of the wooden restraint. This eliminates the problem that when the core material is biased toward one end of the wooden restraint, the other end of the wooden restraint where there is no core material becomes a weak part in terms of strength. Here, when the periphery of the narrow portion of the first plate of the core material has left and right side surfaces and upper and lower planes perpendicular to the left and right side surfaces, a form can be applied in which protrusions extend from the left and right side surfaces, respectively, and the protrusions engage with engagement holes provided in the side materials that make up the wooden restraint.

As can be seen from the above explanation, the buckling restraint brace of the present invention is suitable for use in the framework of a wooden building or the like, and can prevent damage caused by the so-called additional bending moment acting on the wooden restraint body when the framework is significantly deformed during a major earthquake, for example.

FIG. 1 is a perspective view showing an example of a core material that forms a buckling restraint brace according to an embodiment, together with a spacer. FIG. 1 is a perspective view of an example wooden restraint that forms a buckling restrained brace according to embodiments. FIG. 3 is a view taken along the line III-III of FIG. 2. FIG. 1 is a perspective view of an example of a buckling restrained brace according to embodiments. 5 is a view taken along the line VV in FIG. 4. 6 is a view taken along the line VI-VI in FIG. 4. FIG. 7 is a view taken in the direction of an arrow VII in FIG. 4 . FIG. 8 is a view taken in the direction of the arrow VIII in FIG. 4 . FIG. 1 is a diagram showing a state in which a buckling restraint brace according to an embodiment is incorporated into the frame of a wooden building or the like. FIG. 1 is a diagram illustrating the deformation of the frame during a large earthquake and the additional bending moment at the buckling-restrained brace joint caused by the deformation of the frame.

The buckling restraint brace according to the embodiment will be described below with reference to the attached drawings. Note that in this specification and the drawings, substantially identical components may be designated by the same reference numerals to avoid redundant description.

[Buckling Restrained Brace According to the Embodiment]
<Core material>
First, an example of a core material forming a buckling restrained brace according to an embodiment will be described with reference to Fig. 1. Here, Fig. 1 is a perspective view showing an example of a core material forming a buckling restrained brace according to an embodiment together with a spacer.

The core material 10 is formed of a first plate 11 made of elongated, plate-shaped flat steel, and a second plate 12 that is welded to the first plate 11 at its two wide surfaces 11c by fillet welding or the like, and its cross section perpendicular to the longitudinal direction is cross-shaped.

At the center of the first plate 11 in the longitudinal direction, a narrow portion 11b is provided, in which the width of the wide surface 11c is relatively narrow, and at the end of the first plate 11 in the longitudinal direction, a wide portion 11a is provided, in which the width of the wide surface 11c is relatively wide. In addition, in the first plate 11, the surface perpendicular to the wide surface 11c is a narrow surface 11d.

On the other hand, the second plate 12 extends to the end of the first plate 11, and the second plate has a narrow portion 12b at the center of the longitudinal direction, where the wide surface 12c has a relatively narrow width, and a wide portion 12a at the end of the longitudinal direction, where the wide surface 12c has a relatively wide width. Therefore, although the dimensions of the cross section of the core material 10 differ between the center and the end, the cross section is cross-shaped throughout its entire area. The surface of the second plate 12 that is perpendicular to the wide surface 12c is the narrow surface 12d.

The core material 10, which has a cross-shaped cross section, has narrow portions 11b, 12b at the center in the longitudinal direction in both the first plate 11 and the second plate 12, and wide portions 11a, 12a at the ends in the longitudinal direction, so that the narrow portions 11b, 12b at the center can be made into areas that are easily plasticized, and further, the plasticized areas can be limited to the narrow portions 11b, 12b at the center.

In addition, the wide portions 11a, 12a each have bolt holes 11e, 12e for bolting via a splice plate to a gusset plate provided on the structural surface or a fin stiffener (see FIG. 9) attached to the gusset plate, as described below. When the buckling restraint brace 100 is attached to the gusset plate such that the wide surface 11c of the first plate 11 constituting the core material 10 is arranged parallel to the structural surface of the building, the core material 10 has a second plate 12 that is perpendicular to the wide surface 11c of the first plate 11 that is parallel to the structural surface, thereby increasing the rigidity of the end of the core material 10 in the direction outside the structural surface.

The core material 10 is preferably made of steel with a low yield point, such as SN material (rolled steel for architectural structures) or LYP material (very low yield point steel), which improves earthquake energy absorption due to the yielding of the core material 10.

At the center of the narrow portion 11b of the first plate 11, a cylindrical steel protrusion 15 protrudes from the left and right side surfaces of the narrow portion 11b (one example of the peripheral surface of the narrow portion 11b). The protrusion 15 is joined to the side surfaces of the narrow portion 11b by welding or the like. The protrusion 15 engages with an engagement hole provided in a wooden restraint body (see FIG. 2) described below. The protrusion 15 may protrude from the upper and lower wide surfaces 11c of the narrow portion 11b. In this case, an engagement hole is provided at a corresponding position of the restraint material 21 in the wooden restraint body (see FIG. 2), and the protrusion 15 engages with this hole.

Elongated rectangular column-shaped spacers 16 are arranged in the X1 direction on the left and right sides of the narrow portion 11b of the first plate 11, and the core material 10 is housed inside the wooden restraint body described below with the spacers 16 arranged on the left and right sides of the narrow portion 11b. The spacers 16 may be either steel or wooden members. The spacers 16 may also be in a shape other than that shown in the figure, such as a cylindrical shape. The spacers 16 have multiple bolt holes 16a (three in the illustrated example) spaced apart in the longitudinal direction, through which the first long bolts described below are inserted.

<Wooden Restraints>
Next, an example of a wooden restraint body that forms a buckling restrained brace according to an embodiment will be described with reference to Figures 2 and 3. Here, Figure 2 is a perspective view of an example of a wooden restraint body that forms a buckling restrained brace according to an embodiment, and Figure 3 is a view taken along the line III-III in Figure 2.

The wooden restraining body 20 has a pair of restraining members 21 and a pair of side members 22 connecting the pair of restraining members 21, and the first plate 11 of the core material 10 is arranged in the gap 25 between the pair of restraining members 21. The pair of wooden restraining members 21 are arranged to face the two wide faces 11c (see FIG. 1) of the first plate 11, and the pair of wooden side members 22 connected to the pair of restraining members 21 are arranged to face the narrow faces 11d (see FIG. 1) of the first plate 11 of the core material 10.

The restraining material 21 and the side material 22 are formed from laminated wood in which laminae 21', 22' are stacked, but they may also be formed from solid wood. The cross-sectional area, cross-sectional rigidity, Young's modulus, etc. of the wooden restraining body 20 are set so as to prevent the buckling restraint brace from buckling as a whole. This Young's modulus is determined by the material of the wood. Examples of wood materials include cypress, red pine, larch, fir, and Yezo spruce.

As clearly shown in FIG. 3, first bolt holes 21a each having a countersunk groove 21" are provided at corresponding positions of a pair of restraining members 21, and a first bolt hole unit 21b is formed by two corresponding first bolt holes 21a. As shown in FIG. 2 and FIG. 3, in the illustrated example, two first bolt hole units 21b are provided in the width direction of the restraining member 21 and six are provided in the longitudinal direction of the restraining member 21, for a total of twelve first bolt hole units 21b.

When the first plate 11 of the core material 10 is disposed in the gap 25 between the pair of restraining members 21, each bolt hole 16a opened in the spacer 16 is positioned at a position corresponding to each first bolt hole unit 21b, and this bolt hole 16a also forms the first bolt hole unit 21b. A first long bolt 31 is inserted into the first bolt hole unit 21b and tightened with a nut 33. More specifically, a washer 32 is disposed in the countersunk groove 21" of one of the first bolt holes 21a that forms the first bolt hole unit 21b, the first long bolt 31 is inserted into the first bolt hole unit 21b through the washer 32, a washer 34 is disposed in the countersunk groove 21" of the other first bolt hole 21a, and a nut 33 is tightened to the screw groove at the tip of the first long bolt 31 that protrudes outward from the washer 34.

On the other hand, second bolt holes 22a, 21c are provided at corresponding positions of the pair of side members 22 and the restraining member 21, respectively, and the corresponding second bolt holes 22a, 21c form a second bolt hole unit 22b. The second bolt hole units 22b are provided at positions that do not interfere with the first bolt hole units 21b, and in the illustrated example, two are provided in the width direction of the side member 22 and seven are provided in the length direction of the side member 22, for a total of fourteen second bolt hole units 22b.

The second long bolt 41 is inserted into each second bolt hole unit 22b and tightened with a nut 43. More specifically, a washer 42 is disposed in the countersunk groove 22" of one of the second bolt holes 22a that form the second bolt hole unit 22b, the second long bolt 41 is inserted into the second bolt hole unit 22b via the washer 42, a washer 44 is disposed in the countersunk groove 22" of the other second bolt hole 22a, and a nut 43 is tightened into the thread groove at the tip of the second long bolt 41 that protrudes outward from the washer 44.

When tightening the second long bolt 41 with the nut 43, adhesive is applied to the contact surfaces of the restraining material 21 and the side material 22, and the second long bolt 41 is tightened with the nut 43 before the adhesive hardens.

Here, the adhesive may be a urethane adhesive or an epoxy adhesive, but it is preferable to use a urethane adhesive that takes a certain amount of time to harden (e.g., about 24 hours) so that after the adhesive is applied to the contact surface between the restraining material 21 and the side material 22, the second long bolt 41 can be tightened with the nut 43 before the adhesive hardens. The adhesive surface formed by the hardening of the adhesive is firmly compressed by the tightening force applied when the second long bolt 41 is tightened with the nut 43.

In this way, a pair of restraining members 21 are restrained together by tightening multiple first long bolts 31 with nuts 33, and a pair of side members 22 and restraining member 21 are restrained together by tightening second long bolts 41 with nuts 43 via the adhesive surfaces, forming a wooden restraining body 20 with a closed structure in which the restraining members 21 and side members 22 are firmly joined.

As clearly shown in FIG. 3, the restraint material 21 has a groove 26 that communicates with the gap 25, and the horizontally extending gap 25 and the two grooves 26 that extend vertically at its center form an opening with a cross-shaped cross section. As described above, the first plate 11 of the core material 10 is accommodated in the gap 25, and the upper and lower second plates 12 are accommodated in the upper and lower grooves 26, respectively.

The left and right side materials 22 have engagement holes 22c at the center of their longitudinal direction, into which the protrusions 15 of the core material 10 engage. The protrusions 15 of the core material 10 engage with the engagement holes 22c opened in the wooden restraint 20, preventing the core material 10 inserted inside the wooden restraint 20 from biasing to one end of the wooden restraint 20. Therefore, when the core material 10 biases to one end of the wooden restraint 20 in this way, the other end of the wooden restraint 20 where the core material 10 is not present does not become a weak point in terms of strength.

Furthermore, the spacer 16 has a bolt hole 16a that constitutes the first bolt hole unit 21b, and the first long bolt 31 is inserted into this bolt hole 16a, thereby preventing the spacer 16 from moving in the longitudinal direction of the core material 10. As will be described below with reference to FIG. 9, the buckling restraint brace is generally arranged diagonally on the structural surface, so the spacer 16 is likely to move diagonally downward, and this movement of the spacer 16 tends to create a large gap diagonally upward between the end of the spacer 16 and the wide portion 11a of the first plate 11 of the core material 10. Therefore, the diagonally upward area of the buckling restraint brace where the spacer 16 does not exist is likely to become a weak part in terms of strength, but by inserting the first long bolt 31 into the bolt hole 16a of the spacer 16 as shown in the figure, such movement of the spacer 16 is eliminated, and no weak part in terms of strength caused by the movement of the spacer 16 is created.

When the first plate 11 of the core material 10 is accommodated in the gap 25 at the end of the restraining material 21 and the second plate 12 of the core material 10 is accommodated in the groove 26, a slit 24 is provided at a position corresponding to the wide portion 12a on the end side of the second plate 12 so as not to interfere with the wide portion 12a of the second plate 12.

<Buckling restraint brace>
Next, an example of a buckling restrained brace according to an embodiment, formed of the core material 10 and wooden restraint body 20 described above, will be described with reference to Figures 4 to 8. Here, Figure 4 is a perspective view of an example of a buckling restrained brace according to an embodiment, and Figures 5 to 8 are respectively a view taken along the lines V-V in Figure 4, a view taken along the lines VI-VI in Figure 4, a view taken along the line VII in Figure 4, and a view taken along the line VIII in Figure 4.

In the buckling restraint brace 100, the first plate 11 of the core material 10 is accommodated in the gap 25 between a pair of restraining members 21, and the second plate 12 of the core material 10 is accommodated in the grooves 26 provided in each restraining member 21, so that the core material 10 with a cross-shaped cross section is disposed inside the wooden restraining body 20. The entire structure is constructed so that the wide portion 12a on the end side of the second plate 12 protrudes from the end of the wooden restraining body 20, and the bolt holes 11e, 12e of the wide portion 11a of the first plate 11 and the wide portion 12a of the second plate 12 that protrude outward face the outside.

As shown in FIG. 5, the core material 10 has a first plate 11 welded to a second plate 12 at the center of its width direction by fillet welding, and a welded portion Y protrudes outward from the joint corner between the first plate 11 and the second plate 12.

First, because the cross section of the core material 10 perpendicular to its longitudinal direction is cruciform, the wavelength of the higher-order buckling mode of the core material 10 becomes longer, and the stiffening force acting on the wooden restraint body 20 can be reduced accordingly, which makes it less likely that localized damage will occur to the wooden restraint body 20.

The pair of restraining materials 21 are in contact with the two wide surfaces of the first plate 11, and a gap G2 is provided between the second plate 12 and the groove 26 in the left-right width direction and a gap G1 is provided in the up-down height direction. Because the first plate 11 of the core material 10 and the restraining material 21 are in contact with each other without any gaps, the core material 10 receives a compressive force in the longitudinal direction and expands laterally. When the wooden restraining body 20 is pressed from the inside, the wooden restraining body 20 (the restraining material 21) which has a smaller Young's modulus than the core material 10 deforms appropriately and can absorb the core material 10 being pressed in. Therefore, damage to the restraining material 21 is suppressed, and a high restraining effect by the wooden restraining body 20 can be expected.

In addition, because there is a gap G2 between the second plate 12 and the groove 26 in the width direction, the welded portion Y that protrudes outward from the joint corner portion of the first plate 11 and the second plate 12 can be accommodated in this gap G2, while maintaining the abutting position of the first plate 11 and the wooden restraint body 20 (the restraint material 21 of the wooden restraint body 20).

Furthermore, because there is a gap G1 in the height direction between the upper and lower end faces of the second plate 12 and the groove 26, the wooden restraint body 20 (the restraint material 21) can be reliably abutted against the wide surface 11c of the first plate 11. If this height gap G1 did not exist, the groove 26 of the wooden restraint body 20 would get caught on the upper and lower end faces of the second plate 12, and the restraint material 21 would not abut against the wide surface 11c of the first plate 11.

The first plate 11 of the core material 10 is placed in the gap 25 between the pair of restraining materials 21, the second plate 12 is placed in the upper and lower grooves 26, multiple first long bolts 31 are inserted through the pair of restraining materials 21 and spacers 16 and fastened with nuts 33, and second long bolts 41 are inserted through the pair of side materials 22 and restraining materials 21 and fastened with nuts 43 to form a buckling restraint brace 100.

The buckling restrained brace 100 has a configuration in which a core material 10 with a cross-shaped cross section is surrounded by a wooden restraining body 20 formed by a pair of restraining members 21 and a pair of side members 22 that are tightly closed by tightening nuts on a number of first long bolts 31 and second long bolts 41, resulting in a buckling restrained brace with high buckling strength. Furthermore, because the steel core material 10 is surrounded by the wooden restraining body 20, even when the buckling restrained brace 100 is applied to the frame of a wooden building, it does not give an appearance that is out of proportion to the frame components.

For example, as shown in FIG. 6, in the illustrated buckling restraint brace 100, the core material 10 is housed within the gap 25 of the wooden restraint body 20 with spacers 16 arranged on the left and right sides of the first plate 11, and the protrusions 15 that protrude laterally from the side of the first plate 11 are engaged with the engagement holes 22a.

4, 6 and 7, a gap G3 of width t1 is provided between the side (narrow surface 11d) of the wide portion 11a of the first plate 11 of the core material 10 and the side material 22 of the wooden restraint body 20. Also, as shown in Figs. 4 and 8, a gap G4 of width t2 is provided in the longitudinal direction of the second plate 12 between the wide portion 12a of the second plate 12 and the slit 24 of the restraint material 21 of the wooden restraint body 20, and a gap G4 of width t1 is provided on the side of the second plate 12. In this way, by having a gap G3 between the side of the wide portion 11a of the first plate 11 and the side material 22 of the wooden restraint body 20, when the structural surface to which the buckling restraint brace 100 is attached is significantly deformed, this gap G3 absorbs the deformation of the core material 10, and the so-called additional bending moment acting on the wooden restraint body 20 can be eliminated. On the other hand, by having a gap G4 between the slit 24 and the second plate 12, when the core material 10 expands and contracts in response to deformation of the structural surface, the gap G4 can absorb this expansion and contraction of the core material 10, eliminating the problem of the expanding and contracting core material 10 (the wide portion 12a of the second plate 12) coming into contact with the wall surface of the slit 24 and causing damage to the wooden restraint body 20.

As shown in FIG. 6, the boundary area A between the wide portion 11a and the narrow portion 11b of the first plate 11 is a transition area where the planar area and cross-sectional area of the core material 10 change, and therefore serves as an additional bending absorption area where the additional bending moment acting on the core material 10 can be absorbed in this transition area. In this way, the additional bending moment acting on the core material 10 is effectively absorbed in the boundary area A between the wide portion 11a and the narrow portion 11b of the first plate 11 of the core material 10, and the gap G3 provided between the core material 10 and the side material 22 of the wooden restraint 20 prevents the additional bending moment acting on the core material 10 from acting on the side material 22 of the wooden restraint 20.

Furthermore, by providing a narrow portion 11b at the center of the first plate 11 of the core material 10, a relatively large gap G5 (larger than the gap G3 between the wide portion 11a at the end of the first plate 11 of the core material 10 and the side material 22) exists between the narrow portion 11b and the side material 22. By interposing a spacer 16 to close the gap G5, it is possible to prevent buckling in the strong axis direction (direction parallel to the wide surface 11c of the first plate 11) of the core material 10. As a result, the overall buckling of the buckling restrained brace 100 is suppressed, and the compressive strength of the buckling restrained brace 100 is improved, thereby providing an excellent seismic reinforcement effect to a frame incorporating the buckling restrained brace 100 and a building including this frame.

<Example of application of buckling restraint braces to a structure>
Next, an example of application of the buckling restrained brace to a frame will be described with reference to Fig. 9 and Fig. 10. Fig. 9 is a diagram showing a state in which a buckling restrained brace according to an embodiment is incorporated into a frame such as a wooden building. Fig. 10 is a diagram explaining deformation of the frame during a major earthquake and additional bending moment at a buckling restrained brace joint caused by deformation of the frame. The buckling restrained brace of the illustrated example may be incorporated into a frame of a steel (S) building, a frame of a reinforced concrete (RC) building, or a frame of a steel reinforced concrete (SRC) building, in addition to a frame of a wooden building.

The frame S shown in Figure 9 is formed of wooden columns C and beams B that constitute a wooden building or the like. Gusset plates GP made of flat steel are attached to the two diagonal corners. Fin stiffeners FS are welded to the surface of the gusset plates GP so that they are perpendicular to the surface. The fin stiffeners FS are joined to the gusset plates GP so that their cores L3 intersect with the intersection O between the column center L1 of the column C and the beam center L2 of the beam B. The buckling restraint brace 100 is also arranged in a line that passes through both intersections O in diagonal positions.

The gusset plate GP and the wide portion 11a of the first plate 11 of the core material 10 are joined by a high tension bolt via a splice plate SP, and the fin stiffener FS and the second plate 12 are joined by a high tension bolt via a splice plate SP.

As shown in Figure 10, when a large earthquake occurs, the structural members are deformed, and an additional bending moment shown in the following formula (1) can act on the buckling-restrained brace joints if the joints are considered to be rigid.

According to the buckling restraint brace 100, a gap G3 of width t1 is provided between the side of the wide portion 11a of the first plate 11 of the core material 10 and the side material 22 of the wooden restraint 20. This allows the gap G3 to absorb the deformation of the core material 10 and prevent additional bending moment from acting on the wooden restraint 20 when the structural surface to which the buckling restraint brace 100 is attached is significantly deformed. In addition, a gap G4 of width t2 is provided in the longitudinal direction of the second plate 12 between the second plate 12 of the core material 10 and the slit 24 of the restraint material 21 of the wooden restraint 20, and a gap G4 of width t1 is provided on the side of the second plate 12. This allows the gap G4 to absorb the expansion and contraction of the core material 10 when the core material 10 expands and contracts in response to the deformation of the structural surface, eliminating the problem that the wide portion 12a of the second plate 12 of the expanding and contracting core material 10 comes into contact with the wall surface of the slit 24, causing the wooden restraint 20 to break.

Note that the configurations described in the above embodiments may be combined with other components, and the present invention is not limited to the configurations shown here. In this regard, changes can be made without departing from the spirit of the present invention, and can be determined appropriately according to the application form.

10: Core material 11: First plate 11a: Wide portion 11b: Narrow portion 11c: Wide surface 11d: Narrow surface 11e: Bolt hole 12: Second plate 12a: Wide portion 12b: Narrow portion 12c: Wide surface 12d: Narrow surface 12e: Bolt hole 15: Protrusion 16: Spacer 16a: Bolt hole 20: Wooden restraint body 21: Restraint material (laminated wood)
21': Lamina 21": Counterbore groove 21a: First bolt hole 21b: First bolt hole unit 21c: Second bolt hole 22: Side material (laminated wood)
22': Lamina 22": Countersink groove 22a: Second bolt hole 22b: Second bolt hole unit 22c: Engagement hole 24: Slit 25: Gap 26: Groove 31: First long bolt 32: Washer 33: Nut 34: Washer 41: Second long bolt 42: Washer 43: Nut 44: Washer 100: Buckling restraint brace G1, G2, G3: Gap A: Additional bending absorption area (boundary region)
Y: Welded section S: Frame (structural surface)
C: Pillar B: Beam GP: Gusset plate FS: Fin stiffener SP: Splice plate

Claims (8)

A core member made of steel, comprising a first plate and a second plate that are mutually perpendicular and have the same length in the longitudinal direction , the first plate and the second plate being mutually perpendicular over the entire area in the longitudinal direction and having a cross-shaped cross section;
a pair of wooden restraining members arranged to abut on the two wide surfaces of the first plate, and a pair of wooden side members arranged to face the two narrow surfaces of the first plate and connected to the pair of restraining members;
First bolt holes are formed at corresponding positions of the pair of restraining members, a first bolt hole unit is formed by the corresponding first bolt holes, a first long bolt is inserted into each of the first bolt hole units and fastened with a nut,
A buckling restraint brace, characterized in that second bolt holes are opened at corresponding positions of the pair of side members and the restraint member, a second bolt hole unit is formed by the corresponding second bolt holes, and a second long bolt is inserted into each of the multiple second bolt hole units and tightened with a nut. The restraint member has a groove at a position corresponding to the second plate,
2. The buckling restrained brace of claim 1, wherein the second plate is received in the groove. The buckling restraint brace according to claim 1 or 2, characterized in that the second plate is joined to each of the two wide faces of the first plate. The first plate has a narrow portion where the width of the wide surface is relatively narrow at a center side in a longitudinal direction thereof, and has a wide portion where the width of the wide surface is relatively wide at an end side in the longitudinal direction thereof,
The buckling restraint brace according to claim 1 , wherein a gap is provided between a side surface of the wide portion of the first plate and the side member. The second plate extends to an end of the first plate,
The second plate has a narrow portion where the width of the wide surface is relatively narrow at a center side in a longitudinal direction thereof, and has a wide portion where the width of the wide surface is relatively wide at an end side in the longitudinal direction thereof,
5. A buckling restraint brace as described in claim 1, wherein the wooden restraint body has a slit at a position corresponding to the wide portion of the second plate so as not to interfere with the wide portion. a spacer is interposed between a side surface of the narrow portion of the first plate and a wall surface of the side member,
A buckling restraint brace as described in claim 4 or claim 5 dependent on claim 4, characterized in that the spacer has a bolt hole that constitutes the first bolt hole unit, and the first long bolt is inserted into the bolt hole. The buckling restraint brace according to claim 5 or claim 6 depending on claim 5, characterized in that in plan view, there is a gap between the slit and the wide portion of the second plate. The buckling restraint brace according to claim 4 and any one of claims 5 to 7 dependent on claim 4, characterized in that a protrusion projects from the peripheral surface of the narrow width portion of the first plate, and the protrusion engages with an engagement hole provided in the wooden restraint body.

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