JP7495252B2 - 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 formed of a steel pipe having a rectangular cross section and including a pair of opposing first plates and a pair of opposing second plates;
a pair of wooden restraining members arranged to abut against the wide surfaces of the pair of opposing first plates, and a pair of wooden side members arranged to abut against the wide surfaces of the pair of opposing second plates and connected to the pair of restraining members;
The restraint member has a first bolt hole formed therein;
In the pair of side members, a second bolt hole is opened at a position corresponding to the first bolt hole, and a third bolt hole perpendicular to the second bolt hole is further opened,
A first bolt hole unit is formed by the corresponding first bolt hole and the corresponding second bolt hole, and a first long bolt is inserted into each of the first bolt hole units and fastened with a nut,
The second long bolts are inserted into the third bolt holes respectively and fastened with nuts.

According to this embodiment, a pair of restraining members and a pair of side members on either side of the core member formed of a steel pipe with a rectangular cross section are joined by tightening nuts on a number of first long bolts, and a number of second long bolts are further tightened on the side members, forming a highly restraining wooden restraint body made of 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 restraining members and side members from splitting and breaking in the direction perpendicular to their grain due to the stiffening force.

It is possible to assemble the restraining material and the side material to form a wooden restraint by tightening the nuts only on the first long bolts without tightening the nuts on the second long bolts. However, in this case, the axial force from the nut tightening is only introduced to the restraining material, and not to the side material, so it is not possible to form a highly rigid wooden restraint in which the axial force is introduced to the fully closed cross section (closing direction) of the wooden restraint. Therefore, in this embodiment, a third bolt hole is provided in the side material, and the second long bolt is inserted into the third bolt hole and tightened with a nut, thereby introducing the axial force to the side material as well, forming a wooden restraint in which the axial force is introduced to both the restraining material and the side material.

In this embodiment, the terms "restraint material" and "side material" may be interchanged. In this case, the above configuration may be replaced with "a wooden restraint body formed by a pair of wooden side materials arranged to abut against the wide surfaces of the pair of opposing first plates, and a pair of wooden restraint materials arranged to abut against the wide surfaces of the pair of opposing second plates and connected to the pair of side materials, a first bolt hole is opened in the side materials, a second bolt hole is opened in the pair of restraint materials at a position corresponding to the first bolt hole, and a third bolt hole perpendicular to the second bolt hole is further opened, a first bolt hole unit is formed by the corresponding first bolt hole and the second bolt hole, a first long bolt is inserted into each of the first bolt hole units and fastened with a nut, and a second long bolt is inserted into each of the third bolt holes and fastened with a nut."

Here, "rectangular cross-section steel pipe" includes both square and rectangular cross-section steel pipes. When the widths of the first and second plates (lengths perpendicular to the longitudinal direction of the core material) are the same, the cross section is square, and when the widths of the first and second plates are different, the cross section is rectangular. In addition, a rectangular cross section includes a shape in which the four corners of the rectangular cross section are rounded. In addition to square steel pipes, this steel pipe also includes four-sided box members (welded box-shaped cross-section members made of four flat steel bars) and welded box-shaped cross-section members made of two channel steel bars. By forming the core material from a rectangular cross-section steel pipe, the wavelength of the higher-order buckling mode of the core material becomes longer, and the stiffening force acting on the wooden restraint can be reduced, which makes it less likely for localized destruction of the wooden restraint to occur.

In addition, when a pair of wooden restraining members "contact the two wide surfaces of the first plate," this 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 plate-shaped 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, when there is no gap between the core material (first plate) and the restraint material, the wooden restraint material, which has a smaller Young's modulus than the core material (first plate), can deform appropriately and absorb the core material (first plate) that is being pressed in when the core material (first plate) bulges laterally and presses against the wooden restraint material from the inside, as in the case of the buckling restraint brace of this embodiment. In other words, in this embodiment in which wooden restraints are used, the 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 expecting a high restraining effect from the wooden restraint material.

In this embodiment, the side material also abuts against the second plate without any gaps. In this way, the pair of restraining materials abut against the pair of first plates without any gaps, and the pair of side materials abut against the pair of second plates without any gaps, so that the core material inside the wooden restraint body can be prevented from shifting in a direction perpendicular to the longitudinal direction of the brace. Therefore, when such a shift occurs, measures such as interposing a spacer to prevent shifting between the core material and the wooden restraint body are not necessary. The abutting surfaces of the restraining material and the side material may be joined with an adhesive and then fastened with the first long bolt. In this way, the abutting surfaces of the restraining material and the side material are joined with an adhesive and further fastened with the first long bolt, so that the adhesive surfaces, which are the abutting surfaces of the restraining material and the side material, are crimped with the first long bolt, and a buckling restrained brace can be formed with a wooden restraint body with an even higher connection strength between the restraining material and the side material.

In addition, in this embodiment, a pair of restraining members and a pair of side members are connected to each other to form a wooden restraining body with a closed structure made of four face members, and a core member made of a steel pipe with a rectangular cross section is surrounded by the wooden restraining body. Therefore, even if the buckling restrained 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 via 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 inverted relative to each other and connected with a core material sandwiched between them. In contrast, the buckling restrained brace of this embodiment can be produced by connecting a pair of side members to a pair of restraining materials to produce the wooden restraint body, and then, for example, inserting a core material into the hollow space of this wooden restraint body to produce the buckling restrained brace. This makes the production of the buckling restrained brace even easier.

Another aspect of the buckling restraint brace according to the present invention is
A core member formed of a steel pipe having a rectangular cross section and including a pair of opposing first plates and a pair of opposing second plates;
a wooden restraint body including two first restraining members arranged to abut against the respective wide surfaces of the pair of opposing first plates, and two second restraining members arranged to abut against the respective wide surfaces of the pair of opposing second plates, the wooden restraint body being formed by connecting one end of the first restraining members and a side of the second restraining members to each other in a rectangular frame shape;
The first and second restraining members each have a fourth bolt hole and a fifth bolt hole that are perpendicular to each other;
the fourth bolt hole of the first restraining member and the fifth bolt hole of the second restraining member, which are perpendicular to each other, are connected to form a third bolt hole unit, third long bolts are inserted into each of the third bolt hole units and tightened with nuts,
The fifth bolt hole of the first restraint material and the fourth bolt hole of the second restraint material, which are perpendicular to each other, are connected to form a fourth bolt hole unit, and a fourth long bolt is inserted into each of the multiple fourth bolt hole units and tightened with a nut.

According to this embodiment, a rectangular frame-shaped wooden restraint body is formed by fastening two first restraint members and two second restraint members with third and fourth bolts, and a core material made of a steel pipe with a rectangular cross section is surrounded by this wooden restraint body, thereby forming a wooden restraint body with high restraint properties by a pair of first restraint members and a pair of second restraint 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 forming a wooden restraint body by fastening both the third and fourth bolts that are perpendicular to each other with nuts, when a stiffening force acts on the wooden restraint body, it is possible to effectively prevent the restraint materials and side materials from splitting and breaking in the direction perpendicular to their grain due to this stiffening force.

Here, "a wooden restraint body formed by connecting one end of the first restraint member and the side of the second restraint member to each other in a rectangular frame shape" means that one end of the first restraint member is connected to the side of the end of the second restraint member to form a restraint member with an L-shaped cross section, and the two restraint members with L-shaped cross sections thus formed are connected to each other to form a rectangular frame-shaped wooden restraint body. In this wooden restraint body, the third long bolt and the fourth long bolt are disposed inside each restraint member of the rectangular frame-shaped wooden restraint body and are fastened with nuts. For example, when the core material is formed from a steel pipe with a square cross section, the first restraint member and the second restraint member can both be formed from restraint members of the same dimensions. Therefore, the wooden restraint body is formed from four identical restraint members, which improves the workability of the wooden restraint body and leads to reduced costs required for processing.

In another aspect of the buckling restraint brace according to the present invention, a first slit and a second slit extending in the longitudinal direction of the core material are provided at the ends of the pair of first plates and the ends of the pair of second plates, respectively,
an end reinforcing member formed of a third plate and a fourth plate perpendicular to each other and having a cross-shaped cross section perpendicular to the longitudinal direction is joined to both ends of the core material by inserting the third plate into the first slit and inserting the fourth plate into the second slit;
The wooden restraint body is characterized in that a third slit is provided at a position corresponding to the third plate and the fourth plate so as not to interfere with the third plate and the fourth plate.

According to this embodiment, slits (first slit and second slit) are opened in the first plate and the second plate of the core material having a rectangular cross section, and the third plate and the fourth plate forming the end reinforcement having a cross section are inserted into each slit, and the core material and the end reinforcement are joined by, for example, fillet welding, thereby increasing the rigidity of the end of the core material in both the inward and outward directions of the structural plane. The end reinforcement having a cross section connected to the end of the core material is attached to a gusset plate or the like of the structural plane. In this gusset plate, a fin stiffener is attached to the gusset plate, and the third plate and the gusset plate, and the fourth plate and the fin stiffener of the end reinforcement of the buckling restraint brace are joined by high tension bolts or the like via splice plates. And, by providing third slits at positions corresponding to the third and fourth plates of the end reinforcement of the wooden restraint body, interference between the third and fourth plates and the wooden restraint body can be prevented.

Another aspect of the buckling restraint brace according to the present invention is characterized in that there is a gap between the third plate and the third slit, and between the fourth plate and the third slit.

According to this embodiment, because there are gaps between the third plate and the third slit, and between the fourth plate and the third slit, when the core material or the end reinforcement expands or contracts or deforms in response to deformation of the structural surface, the expansion and contraction or deformation of the end reinforcement can be absorbed by the gaps, and there is no problem in that the third plate or fourth plate of the end reinforcement comes into contact with the wall surface of the third slit of the wooden restraint, causing damage to the wooden restraint.

For example, the amount of deformation of the structural plane during a major earthquake is left to the discretion of the designer, and the deformation and expansion of the end reinforcement material at the end of the core material of the buckling restraint brace is calculated based on the deformation of the structural plane when the story drift angle is 1/100 or when the story drift angle is 1/75. Then, for example, by setting a gap larger than this calculated deformation or expansion, it is possible to prevent the additional bending moment from acting on the wooden restraint body through the third slit.

Note that the "gap" here includes both the gap between the longitudinal ends of the third slit and the third plate or fourth plate, and the gap between the side of the third slit and the wide surfaces of the third plate and fourth plate.

Another aspect of the buckling restraint brace of the present invention is characterized in that the cross-sectional area of the rectangular frame of the core material is smaller than the cross-sectional area of the end reinforcement material.

According to this embodiment, since the cross-sectional area of the rectangular frame of the core material is smaller than the cross-sectional area of the end reinforcement, the axial rigidity of the core material can be set lower than that of the end reinforcement, and for example, the area of the core material near the end reinforcement can be made into a plasticization area that is easily plasticized. Furthermore, this plasticization area can be limited to the area of the core material near the end reinforcement.

In addition, since the area of the core material near the end reinforcement is a transition area where the cross-sectional area changes, the additional bending moment acting on the core material can be absorbed in this transition area. In this manner, in this embodiment, the additional bending moment acting on the core material is effectively absorbed in the area of the core material near the end reinforcement, and the gap provided between the end reinforcement and the wooden restraint prevents the additional bending moment acting on the core material from acting on the wooden restraint.

In another aspect of the buckling restraint brace of the present invention, at least one of the first plate and the second plate has a protrusion that protrudes and engages with an engagement hole provided in the wooden restraint body.

According to this embodiment, the protrusions extending from at least one of the first and second plates of the core material engage with the engagement holes provided in the wooden restraint, so that the core material inserted inside the wooden restraint can be prevented from being biased toward one end of the wooden restraint. This can eliminate 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 spot in terms of strength.

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 of an example of a core material that forms a buckling restraint brace according to an embodiment, illustrating the state before end reinforcements are attached to the ends of the core material. FIG. 1 is a perspective view of an example of a core material that forms a buckling restraint brace according to an embodiment, showing the state in which end reinforcements are attached to the ends of the core material. FIG. 2 is a longitudinal cross-sectional view of an example of a wooden restraint that forms a buckling restraint brace according to an embodiment, showing the restraining material and side materials that form the wooden restraint. FIG. 1 is a perspective view of an example of a wooden restraint. FIG. 11 is a longitudinal cross-sectional view of another example of a wooden restraint body that forms a buckling restraint brace according to an embodiment, showing both a first restraint member and a second restraint member that form the wooden restraint body. FIG. 1 is a perspective view of an example of a buckling restrained brace according to embodiments. FIG. 7 is a view taken along the line VII-VII of FIG. 6. FIG. 8 is a view taken along the line VIII-VIII of FIG. 6. IX-IX arrow view of FIG. 6. 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 Figures 1 and 2. Here, Figure 1 is a perspective view of an example of a core material forming a buckling restrained brace according to an embodiment, showing a state before end reinforcements are attached to the ends of the core material, and Figure 2 is a view showing a state after the end reinforcements are attached to the ends of the core material.

The core material 10 is formed of a steel pipe with a rectangular cross section (square cross section in the illustrated example) having a pair of opposing first plates 11 and a pair of opposing second plates 12. Here, the core material 10 in the illustrated example is formed of a rectangular steel pipe with a square cross section, but the core material may also have a rectangular cross section, or may be a welded box-shaped cross section member (four-sided box member) made of four flat steel pieces, a welded box-shaped cross section member made of two channel steel pieces, etc.

A first slit 14 and a second slit 15 are provided at both ends of the pair of first plates 11 and both ends of the pair of second plates 12, respectively, and extend in the longitudinal direction of the core material 10.

End reinforcements 18 with a cross-shaped cross section are attached to both ends of the core material 10. The end reinforcements 18 are formed of a fourth plate 17 and two third plates 16 made of steel, and the third plates 16 are welded to the center of the two wide faces of the fourth plate 17 so as to be perpendicular to the fourth plate 17.

The third plate 16 is inserted in the X1 direction through the first slit 14 of the first plate 11, and the fourth plate 17 is inserted in the X1 direction through the second slit 15 of the second plate 12, so that the end reinforcements 18 are attached to both ends of the core material 10 as shown in FIG. 2. More specifically, in FIG. 2, fillet welding is performed along the fitting line of the first slit 14 and the third plate 16, and similarly, fillet welding is performed along the fitting line of the second slit 15 and the fourth plate 17, so that the core material 10 and the end reinforcements 18 are welded together.

As will be explained in detail below, the cross-sectional area D1 of the end reinforcement 18 is set to be larger than the cross-sectional area D2 of the core material. Because the rectangular frame-shaped cross-sectional area D2 of the steel core material 10 is smaller than the cross-shaped cross-sectional area D1 of the steel end reinforcement 18, when the Young's modulus of both is the same, the axial rigidity of the core material 10 can be set lower than that of the end reinforcement 18, and for example, the area in the core material 10 near the end reinforcement 18 (area where the cross-sectional dimensions change) can be made into an area that is easily plasticized (plasticized area A). This plasticized area A can be limited to the area near the end reinforcement 18 in the core material 10.

In addition, the third plate 16 and the fourth plate 17 forming the end reinforcement 18 each have bolt holes 16a, 17a for bolting to a gusset plate provided on the structural surface or a fin stiffener attached to the gusset plate (see FIG. 10) via a splice plate, as described below. When the core material 10 of the buckling restraint brace 100 is attached to the gusset plate via the end reinforcement 18 so that the wide surface of the first plate 11 constituting the core material 10 is arranged parallel to the structural surface of the building, the core material 10 is formed of a steel pipe with a rectangular cross section having a second plate 12 perpendicular to the wide surface of the first plate 11 parallel to the structural surface, and the end reinforcement 18 with a cross cross section is attached to the end of the core material 10, so that the rigidity of the end of the core material 10 is increased not only in the direction inside the structural surface but also in the direction outside the structural surface.

The core material 10 and end reinforcement material 18 are 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 yield of the core material 10.

A cylindrical steel protrusion 13 protrudes from the center of the pair of first plates 11 (only the protrusion 13 of one of the first plates 11 is shown in Figs. 1 and 2). The protrusion 13 is joined to the wide surface of the first plate 11 by welding or the like. This protrusion 13 engages with an engagement hole 21a provided in the restraining material 21 of the wooden restraint body 20 (see Fig. 4) described below. The protrusion 13 may protrude from the wide surface of the second plate 12, in which case an engagement hole is provided at a corresponding position in the side material 22 of the wooden restraint body 20 (see Fig. 4) and the protrusion 13 engages therein.

<Wooden Restraints>
Next, an example of a wooden restraint body that forms the buckling restrained brace according to the embodiment will be described with reference to Figures 3 and 4. Here, Figure 3 is a vertical cross-sectional view of an example of a wooden restraint body that forms the buckling restrained brace according to the embodiment, showing both the restraining material and the side material that form the wooden restraint body, and Figure 4 is a perspective view of the example of the wooden restraint body.

The wooden restraint body 20 has a pair of restraint members 21 and a pair of side members 22. The restraint members 21 and side members 22 are each formed from a laminated wood in which laminae 21', 22' are stacked. The restraint members 21 and side members 22 may be formed from solid wood other than laminated wood, and the cross-sectional area, cross-sectional rigidity, Young's modulus, etc. of the wooden restraint body 20 are set so as to prevent the buckling restraint brace from buckling overall. 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.

A first bolt hole 23 is provided in the restraint member 21. Meanwhile, a second bolt hole 24 is provided in the pair of side members 22 at a position corresponding to the first bolt hole 23, and a third bolt hole 25 is also provided perpendicular to the second bolt hole 24.

As shown in FIG. 3, a pair of side members 22 are arranged to sandwich both ends of a pair of restraining members 21 in the X2 direction, and a first bolt hole 23 and second bolt holes 24 on either side thereof form a first bolt hole unit 26. A countersink groove 24' is provided in the second bolt hole 24, and a first long bolt 31 is inserted into the first bolt hole unit 26. A nut 33 is fastened to the screw groove at the tip of the first long bolt 31 via a washer 32 in the countersink groove 24'.

On the other hand, a countersink groove 25' is also provided in the third bolt hole 25 provided in the side member 22, and a second long bolt 34 is inserted into the third bolt hole 25, and a nut 36 is tightened in the countersink groove 25' onto the screw groove at the tip of the second long bolt 34 via a washer 35.

By assembling a pair of restraining members 21 and a pair of side members 22 into a square frame shape, a central opening 27 is formed in the center to accommodate the core member 10 with a square cross section. Adhesive is applied in advance to the contact surfaces of the restraining members 21 and the side members 22, and the first long bolts 31 are tightened with nuts 33 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 first long bolt 31 can be tightened with the nut 33 before the adhesive hardens. The adhesive surface formed by the hardening of the adhesive is firmly compressed by the tightening force applied when the first long bolt 31 is tightened with the nut 33.

In this way, a pair of restraining members 21 and a pair of side members 22 on either side of them are joined by tightening the nuts on the multiple first long bolts 31, and multiple second long bolts 34 are further tightened on the side members 22, introducing axial force in the closing direction of the square frame, forming a wooden restraining body 20 with high restraint properties by the pair of restraining members 21 and the pair of side members 22.

As shown in FIG. 4, the wooden restraint 20 is assembled as a whole by a plurality of first long bolts 31 and second long bolts 34 spaced apart in the longitudinal direction. In addition, a total of four third slits 28 that protrude outward are provided at the center positions of each side of the central opening 27, which has a square cross section, at both ends of the wooden restraint 20. As will be described in detail below, the third plate 16 and fourth plate 17 that form the end reinforcement 18 are inserted into each third slit 28 with a gap (not in contact with the third slits 28).

The pair of restraining materials 21 have engagement holes 21a at their longitudinal center positions, into which the protrusions 13 of the core material 10 engage. The protrusions 13 of the core material 10 engage with the engagement holes 21a in the wooden restraining body 20, preventing the core material 10 inserted inside the wooden restraining body 20 from biasing to one end of the wooden restraining body 20. Therefore, when the core material 10 biases to one end of the wooden restraining body 20 in this way, the other end of the wooden restraining body 20 where the core material 10 is not present does not become a weak point in terms of strength.

Next, referring to FIG. 5, another example of a wooden restraint body is shown. Here, FIG. 5 is a longitudinal cross-sectional view of another example of a wooden restraint body that forms a buckling restraint brace according to an embodiment, and shows both the first restraint member and the second restraint member that form the wooden restraint body.

The illustrated wooden restraint body 20A has a pair of first restraint members 21A and a pair of second restraint members 21B, both of which are arranged in the X2 direction so that one end 21a of the first restraint members 21A abuts against the side surface 21b of the second restraint members 21B, and are connected to each other to form a rectangular frame.

The first restraining member 21A and the second restraining member 21B shown in the figure are restraining members of the same dimensions, and therefore the wooden restraining body 20A has a square frame shape similar to the wooden restraining body 20 shown in Figures 3 and 4, and has a central opening 27 with a square cross section in the center.

The first restraining member 21A and the second restraining member 21B each have a fourth bolt hole 41 and a fifth bolt hole 42 that are mutually orthogonal. The fourth bolt hole 41 of the first restraining member 21A and the fifth bolt hole 42 of the second restraining member 21B, which are mutually orthogonal, communicate to form a third bolt hole unit 43. The fourth bolt hole 41 and the fifth bolt hole 42 are provided with countersunk grooves 41' and 42', respectively, and a third long bolt 37A is inserted into the third bolt hole unit 43. A nut 39A is tightened to the screw groove at the tip of the third long bolt 37A via a washer 38A in the countersunk groove 42'.

Meanwhile, the fifth bolt hole 42 of the first restraining member 21A and the fourth bolt hole 41 of the first restraining member 21A, which are perpendicular to each other, are connected to form a fourth bolt hole unit 44. Then, a fourth long bolt 37B is inserted into the fourth bolt hole unit 44, and a nut 39B is tightened to the screw groove at the tip of the fourth long bolt 37B via a washer 38B in the countersunk groove 42'.

When manufacturing the wooden restraint body 20A, adhesive is applied in advance to the end 21a of the first restraint member 21A and the side surface 21b of the second restraint member 21B (the contact surfaces of both), and before the adhesive hardens, the third long bolt 37A is tightened with the nut 39A, and the fourth long bolt 37B is tightened with the nut 39B.

<Buckling restraint brace>
Next, with reference to Figures 6 to 9, an example of a buckling restrained brace according to an embodiment will be described, which is formed from the previously explained core material 10 and end reinforcement material 18, and wooden restraint body 20. Here, Figure 6 is a perspective view of an example of a buckling restrained brace according to an embodiment, and Figures 7 to 9 are respectively a view taken along the lines VII-VII in Figure 6, a view taken along the lines VIII-VIII in Figure 6, and a view taken along the lines IX-IX in Figure 6.

In the buckling restraint brace 100, a core material 10 made of a square cross-section steel pipe is accommodated in the central opening 27 of the wooden restraint body 20, and the third plate 16 and the fourth plate 17 forming the end reinforcement material 18 are inserted with gaps into four third slits 28 that protrude outward at the center position of each side of the central opening 27. Here, the protrusions 13 provided on the wide surfaces of the pair of restraint members 21 forming the core material 10 engage with the engagement holes 21a provided in the pair of restraint members 21 forming the wooden restraint body 20, thereby preventing the core material 10 and the wooden restraint body 20 from moving relative to each other in the longitudinal direction.

Part of the end reinforcement 18 protrudes outward from both ends of the wooden restraint 20, and the bolt holes 16a, 17a of the third plate 16 and the fourth plate 17 face the outside.

First, the cross section of the core material 10 perpendicular to its longitudinal direction has a square frame shape, which lengthens the wavelength of the higher-order buckling mode of the core material 10, thereby reducing the stiffening force acting on the wooden restraint body 20, making it less likely that localized damage will occur to the wooden restraint body 20.

As shown in FIG. 7, the first plate 11 and the second plate 12 of the core material 10 are both in contact with the wall surface of the central opening 27 of the wooden restraint 20 without any gaps. In this way, the core material 10 is arranged inside the wooden restraint 20 without any gaps. For example, when a compressive force acts on the first plate 11 of the core material 10 and bulges laterally, and the wooden restraint 20 is pressed from the inside, the wooden restraint 20, which has a smaller Young's modulus than the first plate 11, can deform appropriately and absorb the first plate 11 that is being pressed in. In other words, in the buckling restraint brace 100 that uses the wooden restraint 20, the pair of wooden restraint members 21 and side members 22 are in contact with the two wide surfaces of the first plate 11 and the second plate 12 without any gaps, respectively, and a high restraining effect by the wooden restraint 20 can be expected while preventing damage to the restraint members 21 and side members 22.

As shown in FIG. 8, the third plate 16 and the fourth plate 17 that form the end reinforcement 18 are connected to each other via a welded portion Y formed by fillet welding. The fitting portion of the first slit 14 and the third plate 16 is also connected to each other via a welded portion Y formed by fillet welding, and similarly, the fitting portion of the second slit 15 and the fourth plate 17 is also connected to each other via a welded portion Y formed by fillet welding, thereby connecting the core material 10 and the end reinforcement 18 to each other.

As shown in FIG. 8, when the third plate 16 and the fourth plate 17 are inserted into the third slit 28 of the wooden restraint 20, a gap G1 of width t1 is provided between the third slit 28 and the third plate 16 and the fourth plate 17 on the left and right and above and below.

Furthermore, as shown in FIG. 9, a gap G2 of width t2 is provided between the longitudinal ends of the third slit 28 and the third plate 16 and the fourth plate 17.

In this way, the gaps G1 and G2 exist between the third plate 16 and the third slit 28, and between the fourth plate 17 and the third slit 28, respectively, so that when the core material 10 or the end reinforcement material 18 deforms or expands or contracts in response to deformation of the structural surface, the gaps G1 and G2 can absorb the deformation or expansion of the end reinforcement material 18. This prevents the third plate 16 or the fourth plate 17 of the end reinforcement material 18 from contacting the wall surface of the third slit 28 of the wooden restraint body 20, causing damage to the wooden restraint body 20. Note that the width t1 of the gap G1 and the width t2 of the gap G2 are set according to the amount of deformation or expansion of the core material 10 or the end reinforcement material 18, so the widths t1 and t2 may be set to different widths or to the same value.

In addition, the square frame-shaped cross-sectional area D2 of the core material 10 is set smaller than the cross-shaped cross-sectional area D1 of the end reinforcement material 18.

The axial stiffness of a member can be expressed as the product of the member's Young's modulus E and cross-sectional area D, but when the end reinforcement 18 and the core material 10 are made of the same steel material (both have the same Young's modulus E), the cross-sectional area D2 is set smaller than the cross-sectional area D1, so that the axial stiffness of the core material 10 can be set lower than that of the end reinforcement 18. This makes it possible to make the area of the core material 10 near the end reinforcement 18 into a plasticization area A (see Figure 2) that is easily plasticized, and furthermore, it is possible to limit the plasticization area A to the area near the end reinforcement 18 in the core material 10.

In addition, since the area of the core material 10 near the end reinforcement 18 is a transition area where the cross-sectional area changes, the additional bending moment acting on the core material 10 can be absorbed in this transition area. In this way, in the buckling restraint brace 100, the additional bending moment acting on the core material 10 is effectively absorbed in the area of the core material 10 near the end reinforcement 18, and the gaps G1 and G2 provided between the end reinforcement 18 and the wooden restraint 20 prevent the additional bending moment acting on the core material 10 from acting on the wooden restraint 20.

The buckling restrained brace 100 has a square cross-section core material 10 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 34, 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, the buckling restrained brace 100 does not have an out-of-balance appearance with the structural components even when applied to the structure of a wooden building.

<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. 10 and Fig. 11. Fig. 10 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. 11 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 FIG. 10 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 fourth plate 17 of the end reinforcement 18 are joined by a high tension bolt via a splice plate SP, and the fin stiffener FS and the third plate 16 of the end reinforcement 18 are joined by a high tension bolt via a splice plate SP.

As shown in Figure 11, 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.

The buckling restraint brace 100 has a gap G1 of width t1 and a gap G2 of width t2 between the end reinforcement 18 attached to the core material 10 and the wooden restraint 20. If the structural surface to which the buckling restraint brace 100 is attached is significantly deformed, these gaps G1 and G2 can absorb the deformation and expansion and contraction of the core material 10 and the end reinforcement 18. Therefore, there is no problem in that an additional bending moment acts on the wooden restraint 20, 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 12: Second plate 13: Protrusion 14: First slit 15: Second slit 16: Third plate 16a: Bolt hole 17: Fourth plate 17a: Bolt hole 18: End reinforcement material 20, 20A: Wooden restraint body 21: Restraint material (laminated wood)
21A: First restraining material (laminated wood)
21B: Second restraining material (laminated wood)
21a: engagement hole 22: side member 22': lamina 23: first bolt hole 24: second bolt hole 24': counterbore groove 25: third bolt hole 25': counterbore groove 26: first bolt hole unit 27: central opening 28: third slit 31: first long bolt 32: washer 33: nut 34: second long bolt 35: washer 36: nut 37A: third long bolt 37B: fourth long bolt 38A, 38B: washer 39A, 39B: nut 41: fourth bolt hole 42: fifth bolt hole 43: third bolt hole unit 44: fourth bolt hole unit 100: buckling restraint brace G1, G2: gap A: additional bending absorption area (plasticized area)
Y: Welded part D1: Cross-sectional area of end reinforcement D2: Cross-sectional area of core S: Frame (structural surface)
C: Pillar B: Beam GP: Gusset plate FS: Fin stiffener SP: Splice plate

Claims (6)

A core member formed of a steel pipe having a rectangular cross section and including a pair of opposing first plates and a pair of opposing second plates;
a pair of wooden restraining members arranged to abut against the wide surfaces of the pair of opposing first plates, and a pair of wooden side members arranged to abut against the wide surfaces of the pair of opposing second plates and connected to the pair of restraining members;
The restraint member has a first bolt hole formed therein;
In the pair of side members, a second bolt hole is opened at a position corresponding to the first bolt hole, and a third bolt hole perpendicular to the second bolt hole is further opened,
A first bolt hole unit is formed by the corresponding first bolt hole and the corresponding second bolt hole, and 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 long bolts are inserted into each of the multiple third bolt holes and tightened with nuts. A core member formed of a steel pipe having a rectangular cross section and including a pair of opposing first plates and a pair of opposing second plates;
a wooden restraint body including two first restraining members arranged to abut against the respective wide surfaces of the pair of opposing first plates, and two second restraining members arranged to abut against the respective wide surfaces of the pair of opposing second plates, the wooden restraint body being formed by connecting one end of the first restraining members and a side of the second restraining members to each other in a rectangular frame shape;
The first and second restraining members each have a fourth bolt hole and a fifth bolt hole that are perpendicular to each other;
the fourth bolt hole of the first restraining member and the fifth bolt hole of the second restraining member are communicated to form a third bolt hole unit, third long bolts are inserted into each of the third bolt hole units and tightened with nuts,
a fourth bolt hole unit is formed by connecting the fifth bolt hole of the first restraint member and the fourth bolt hole of the second restraint member, and a fourth long bolt is inserted into each of the fourth bolt hole units and tightened with a nut. A first slit and a second slit extending in a longitudinal direction of the core material are formed at ends of the pair of opposing first plates and ends of the pair of opposing second plates, respectively;
an end reinforcing member formed of a third plate and a fourth plate perpendicular to each other and having a cross-shaped cross section perpendicular to the longitudinal direction is joined to both ends of the core material by inserting the third plate into the first slit and inserting the fourth plate into the second slit;
3. The buckling restraint brace according to claim 1 or 2, characterized in that a third slit is provided in the wooden restraint body at a position corresponding to the third plate and the fourth plate so as not to interfere with the third plate and the fourth plate. The buckling restraint brace of claim 3, characterized in that there is a gap between the third plate and the third slit, and between the fourth plate and the third slit. The buckling restraint brace of claim 3 or 4, characterized in that the cross-sectional area of the rectangular frame of the core material is smaller than the cross-sectional area of the end reinforcement material. The buckling restraint brace according to any one of claims 1 to 5, characterized in that at least one of the first plate and the second plate has a protrusion that protrudes and engages with an engagement hole provided in the wooden restraint body.

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