JP7754566B2 - Buckling Restrained Brace - Google Patents

Description

The present invention relates to a buckling-restrained brace.

Buckling-restrained braces with buckling prevention measures have traditionally been used as braces to form building frames (column-beam frames, roof frames, etc.). Buckling-restrained braces come in a variety of stiffening configurations, including a steel core reinforced only with steel plates, a steel core reinforced 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 floor plan and design, the soothing effects of natural wood, the moisture-regulating properties of wood, and, depending on the building's intended use (such as residential), generally lower construction costs compared to steel-frame or reinforced concrete structures. However, the improved fire resistance and earthquake resistance mentioned above is one factor that is driving increased interest in wooden houses and other wooden buildings. When the above-mentioned conventional buckling restrained braces are incorporated into the frame of such a wooden house, wooden columns and beams are mixed with buckling restrained braces with metal or concrete stiffeners, which inevitably results in an unbalanced appearance.

One possible solution is to cover the entire buckling restrained brace with a wooden or paper panel, making the metal or concrete stiffener invisible from the outside. However, this requires a great deal of work, which raises concerns about increased construction costs. Furthermore, conventional buckling restrained braces tend to be heavy because they make extensive use of metal, concrete, mortar, etc., and installing heavy buckling restrained braces inside the lightweight wooden beams and columns that make up a wooden house is structurally unbalanced.

In response, a buckling-restrained brace suitable for use within the framework of wooden buildings, including wooden houses, has been proposed. Specifically, this buckling-restrained brace has a core member and a pair of restraint members arranged along both sides of the core member. The core member is made of steel, and the pair of restraint members are made of wood. These restraint members are made of laminated lumber, with the lamina stacked parallel to the core member (see, for example, Patent Document 1).

Patent No. 4901491

The wooden restraint members surrounding the steel core member that forms the buckling-restrained brace are composed of a pair of restraint plates facing the two wide surfaces of the core member, and a pair of side plates connecting the ends of the pair of restraint plates. However, buckling-restrained braces pose an issue when, for example, during a major earthquake, the frame and the buckling-restrained braces incorporated into the frame undergo significant outward deformation, causing the core member to push against the restraint plates, and the restraint plates pushed into the core member to pull on the side plates, resulting in cracks in the side plates. Patent Document 1 does not mention any measures to prevent cracks in the side plates caused by the restraint plates pushed into the core member pulling on the side plates when the buckling-restrained brace undergoes such outward deformation.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a buckling restrained brace that is suitable for use within the framework of a wooden building or the like, and that can prevent cracks from occurring in the side panels pulled by the restraining plates when the framework and buckling restrained brace deform outside the structural plane during a major earthquake, for example, and the core material that forms the buckling restrained brace presses into the restraining plates that form the wooden restraining member.

In order to achieve the above object, one aspect of the buckling restrained brace according to the present invention is as follows:
A steel plate-shaped core material,
a wooden restraining member formed by a pair of wooden restraining plates arranged so as to face the two wide surfaces of the core material, and a pair of wooden side plates arranged so as to face the two narrow surfaces of the core material and connected to the pair of restraining plates;
The ends of the pair of restraining plates are connected by an end restraining member.

In this embodiment, the wooden restraint member is formed together with a pair of wooden side panels. The ends of the pair of wooden restraint panels are connected and reinforced by end restraint members. This makes it possible to prevent cracks (splitting) that may occur at the ends of the side panels connected at positions corresponding to the ends of the pair of restraint panels that receive the strongest pushing force from the core material when the frame and buckling restrained brace are deformed outside the structural plane.

In this embodiment, a pair of restraint plates are connected by a pair of side panels, forming a wooden restraint member with a closed structure made of four face panels, and the steel core member is surrounded by the wooden restraint member. With this configuration, even when the buckling restrained brace of this embodiment is applied to the frame of a wooden building, there is no risk of it appearing out of place with the frame components. Here, the wooden restraint member and side panels may be made of solid wood, or may be made of laminated lumber with laminated lamina.

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

In another aspect of the buckling restrained brace according to the present invention,
The end restraint member is a rivet.

In this embodiment, the end restraint members are clamps, which allow the ends of a pair of restraint plates to be firmly fixed together using commonly available, inexpensive materials, thereby making it possible to prevent cracks from occurring at the ends of the side plates.

In another aspect of the buckling restrained brace according to the present invention,
The two piercing portions of the clamp are driven into and fixed to the pair of restraint plates, or the two piercing portions of the clamp are inserted into fixing holes opened in the pair of restraint plates and adhesively fixed.

In this embodiment, the fastener can be fixed to the restraint plate either by hammering the piercing portion of the fastener into place, or by inserting the piercing portion into a fixing hole in the restraint plate and adhesively fixing the fastener. In either case, the fastener can be firmly fixed to the end of the restraint plate.

For example, in a configuration in which the piercing portion of the fastener is driven in and fixed, the fastener can be easily fixed to the end of the restraining plate. Here, the piercing portion of the fastener is pierced into the end of the side plate, and then into the end of the restraining plate. In other words, the two piercing portions of the U-shaped fastener are pierced near both ends of the side plate, and then into the end faces of the pair of restraining plates, so that the ends of both the side plate and the pair of restraining plates are fixed via the fastener.

On the other hand, in a configuration in which the piercing portion is inserted into a fixing hole in the restraining plate and adhesively fixed, there is no risk of damaging the side plate or the edge of the restraining plate due to the force of driving the nail, and the initial rigidity of both the side plate and the restraining plate around the point of fixation by the nail can be maintained. In other words, fixing holes that communicate with both are fixed near both ends of the side plate and on the end faces of the pair of restraining plates, and the piercing portion of the nail is inserted into the fixing hole and adhesively fixed, so that the piercing portion is adhesively fixed to both the side plate and the restraining plate, and the edges of both the side plate and the pair of restraining plates are fixed via the nail.

In another aspect of the buckling restrained brace according to the present invention,
The end restraint material is one or more strip-shaped steel plates or fiber reinforcement materials that span a pair of restraint plates, and the steel plates or fiber reinforcement materials are connected to the pair of restraint plates, or the pair of restraint plates are indirectly connected to each other by connecting multiple steel plates or multiple fiber reinforcement materials to each other.

In this embodiment, the end restraint member is one or more strips of steel plate or fiber reinforcement material that span the pair of restraint plates, thereby firmly reinforcing the ends of the restraint plates by wrapping around the pair of restraint plates and the pair of side panels (wooden restraint members). Here, the steel plate or fiber reinforcement material may be wrapped around the pair of restraint plates and directly connected to the ends of the restraint plates, or, for example, two steel plates may be wrapped around the wooden restraint member and the ends of the two steel plates may be connected to indirectly restrain (reinforce) the ends of the restraint plates. Examples of fiber reinforcement materials include fiber-reinforced plastic plates such as carbon fiber reinforced plastic plates (CFRP) and glass fiber reinforced plastic plates (GFRP), and fiber-reinforced plastic sheets such as carbon fiber reinforced plastic sheets and glass fiber reinforced plastic sheets.

In another aspect of the buckling restrained brace according to the present invention,
a non-contact groove that does not come into contact with the wide surface of the core material is provided at an end of the restraint plate;
The area of the restraint plate other than the non-contact groove is in contact with the wide surface of the core material.

According to this aspect, the end of the restraint plate is provided with a non-contact groove that does not come into contact with the wide surface of the core material, and the area of the restraint plate other than the non-contact groove is in contact with the wide surface of the core material. Therefore, when the frame and the buckling restrained brace deform outward from the structural plane, the non-contact groove is provided at the end of the restraint plate that receives the strongest pushing force from the core material. This eliminates or reduces contact between the core material and the restraint plate, making it possible to suppress cracks that may occur at the end of the side plate connected to the position corresponding to the end of the restraint plate. In particular, the combination of the previously described configuration in which the ends of the pair of restraint plates (and the ends of the side plates) are connected by end restraint members and the configuration in which the non-contact grooves at the end of the restraint plate do not come into contact with the wide surface of the core material further enhances the suppression of cracks that may occur at the end of the side plate. Here, non-contact grooves are provided at each end of the pair of restraint plates facing the two wide surfaces of the core material, in areas where the core material may come into contact with the restraint plate when the buckling restrained brace deforms outward from the structural plane.

The non-contact grooves at the ends of the restraint plate eliminate or reduce contact (prevent strong contact) between the ends of the restraint plate and the core material, while the areas of the restraint plate other than the non-contact grooves come into contact with the core material, ensuring that the restraint plate prevents the core material from buckling.

In another aspect of the buckling restrained brace according to the present invention,
the core material has a narrow portion at a center side in a longitudinal direction where the width of the wide surface is relatively narrow, and a wide portion at an end side in a longitudinal direction where the width of the wide surface is relatively wide,
The non-contact groove extends from an edge of the restraint plate to a position corresponding to the boundary between the wide portion and the narrow portion of the core material.

In this embodiment, 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. This allows the narrow portion at the center to be a region that is easily plasticized, and further allows the plasticization region to be limited to the narrow portion at the center. Furthermore, the boundary region between the wide portion and the narrow portion is a transition region where the planar area and cross-sectional area of the core material change, so the additional bending moment acting on the core material can be absorbed in this transition region. The additional bending moment (or simply, additional bending) refers to the bending moment that can act on the wooden restraint material due to large deformation of the frame and buckling restrained brace, for example, during a major earthquake. In this way, in this embodiment, the additional bending moment acting on the core material can be effectively absorbed in the boundary region between the wide portion and narrow portion of the core material.

While the core material has wide and narrow sections, the restraining plate has non-contact grooves extending from its edge to a position corresponding to the boundary between the wide and narrow sections of the core material, which makes it possible to highly reliably prevent the core material from contacting (pushing into) the end of the restraining plate.

In another aspect of the buckling restrained brace according to the present invention,
a steel plate accommodating groove is provided in an inner surface of the side plate in a corresponding range corresponding to the non-contact groove between the pair of restraint plates,
a reinforcing steel plate spanning each side surface of the pair of restraint plates is fixed to each side surface of the pair of restraint plates,
The reinforcing steel plate is accommodated in the steel plate accommodation groove without contacting the inner wall surface of the steel plate accommodation groove.

According to this aspect, a steel plate accommodation groove is provided on the inner surface of the side plate in a range corresponding to the non-contact groove between the pair of restraint plates, and the reinforcing steel plate, which straddles the side surfaces of each of the pair of restraint plates and is fixed to each of the pair of restraint plates, is accommodated in the steel plate accommodation groove without contacting the inner wall surface of the steel plate accommodation groove. This allows the reinforcing steel plate, which is fixed to the restraint plate and does not contact the side plate, to effectively resist tension from the side plate. This, combined with the non-contact grooves provided at the ends of the restraint plates, makes it possible to more effectively suppress cracks that may occur in the side plate. Furthermore, because the reinforcing steel plate does not contact the inner wall surface of the steel plate accommodation groove, there is no risk of the reinforcing steel plate pressing against the side plate and inducing cracks.

In another aspect of the buckling restrained brace according to the present invention,
The fiber direction of the corresponding range of the side plate corresponding to the non-contact groove of the restraint plate is the short direction of the side plate, and the fiber direction outside the corresponding range is the long direction of the side plate.

In this aspect, the fiber direction of the corresponding range of the side panel that corresponds to the non-contact grooves of the restraining plate is aligned with the short side of the side panel. This means that the wood's high-strength fiber direction is aligned along (or to some extent along) the direction of cracks that may occur in the side panel due to tension from the restraining plate (the short side of the side panel), allowing the side panel to provide high resistance to cracks. On the other hand, the fiber direction of the side panel outside the corresponding range at the end is aligned along the length of the side panel. This means that the wood's high-strength fiber direction is aligned in the center of the side panel, where bending is most pronounced, allowing the side panel to have high bending strength against bending in the center.

In another aspect of the buckling restrained brace according to the present invention,
The side plates are characterized in that piercing means extending toward the pair of restraining plates are pierced into corresponding areas of the side plates that correspond to the non-contact grooves of the restraining plates.

In this aspect, the piercing means extending toward the pair of restraining plates pierces the side plates in the corresponding ranges of the non-contact grooves of the restraining plates. More specifically, the piercing means pierces in the direction (or to some extent in the direction) of cracks that may occur in the side plates due to tension from the restraining plates (the short direction of the side plates). This allows the piercing means to provide high resistance to cracks. Examples of piercing means include screws, nails, and bolts, including lag screw bolts.

In another aspect of the buckling restrained brace according to the present invention,
First bolt holes are opened at corresponding positions of the pair of restraint plates, and first bolt hole units are formed by the corresponding first bolt holes, and first long bolts are inserted into each of the plurality of first bolt hole units and fastened with nuts,
Second bolt holes are opened at corresponding positions of the pair of side plates and the restraint plate, and second bolt hole units are formed by the corresponding second bolt holes, and second long bolts are inserted into each of the multiple second bolt hole units and tightened with nuts.

In this embodiment, a pair of restraint plates are joined by tightening nuts on multiple first-length bolts, and a pair of side plates are joined together with the restraint plate between them by tightening nuts on multiple second-length bolts. This allows for the formation of a wooden restraint member that provides high restraint for the pair of restraint plates and the pair of side plates. This makes it possible to form a buckling-restrained brace with a highly rigid wooden restraint member that is less likely to break under additional bending moments that may act.

In another aspect of the buckling restrained brace according to the present invention,
The contact surfaces of the restraint plate and the side plate are joined with an adhesive and fastened by the second long bolts.

In this embodiment, the contact surfaces of the restraint plate and side plate are joined with adhesive and further tightened with second-long bolts. This allows the adhesive surfaces, which are the contact surfaces between the restraint plate and side plate, to be crimped with the second-long bolts, resulting in the formation of a buckling restrained brace with wooden restraint members that has even stronger connection strength between the restraint plate and side plate.

In another aspect of the buckling restrained brace according to the present invention,
a reinforcing rib orthogonal to the wide surface of the end of the core material in the longitudinal direction is joined to the wide surface, forming a cross-shaped cross section;
The wooden restraint member is characterized in that a slit is provided at a position corresponding to the reinforcing rib so as not to interfere with the reinforcing rib.

In this embodiment, the longitudinal ends of the core material have a cross-shaped cross section due to the reinforcing ribs that are perpendicular to the wide faces of the core material. Therefore, when a buckling restrained brace is attached to a gusset plate with the wide faces of the core material arranged parallel to the structural face of the building, the core material has reinforcing ribs that are perpendicular to the wide faces that are parallel to the structural face, thereby increasing the rigidity of the ends of the core material in the outward direction of the structural face. In the gusset plates of the structural face to which the core material with a cross cross section is attached, fin stiffeners are attached to the gusset plates, and the core material of the buckling restrained brace and gusset plate, and the reinforcing ribs and fin stiffeners are each joined via splice plates using high-tension bolts or the like. In this embodiment, slits are provided in the wooden restraining material at positions corresponding to the reinforcing ribs, and these slits are configured to prevent interference between the wooden restraining material and the reinforcing ribs.

Another aspect of the buckling restrained brace according to the present invention is:
In plan view, a gap is formed between the slit and the reinforcing rib.

According to this configuration, the gap between the slit and the reinforcing rib allows the core material to absorb expansion and contraction in response to structural deformation. This eliminates the problem of the expanding and contracting core material coming into contact with the wall of the slit, leading to damage to the wooden restraint material. The design of this gap is also left to the designer's discretion. The amount of expansion and contraction of the core material is calculated based on the set story deformation angle. 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 reinforcing rib, as well as the gap between the side of the slit and the reinforcing rib. The gap between the side of the slit and the reinforcing rib can be set to the same size as the gap between the side of the wide portion of the core material and the side panel. Furthermore, the non-contact grooves in the restraint plate create a separate gap between the core material and the restraint plate. This gap is set large enough so that the core material does not press strongly against or come into contact with the restraint plate when the buckling-restrained brace deforms during a major earthquake.

In addition, another aspect of the buckling restrained brace according to this aspect is as follows:
The present invention is characterized in that an insert plate is interposed between the wide surface of the core material and the restraining plate.

In this embodiment, higher-order buckling deformation of the core material causes localized compressive forces to act from the core material on the restraining plate, preventing damage to the restraining plate due to these localized forces. By interposing an insert plate between the wide surface of the core material and the restraining plate, the force acting from the convex portion of the higher-order buckling deformation of the core material is first transmitted to the insert plate, which then spreads within the insert plate, and the force diffused within the insert plate acts on the wooden restraining plate. This effectively prevents damage to the wooden restraining plate due to multiple localized forces acting from the core material.

As can be seen from the above explanation, the buckling restrained brace of the present invention is suitable for use within the framework of wooden buildings and the like. For example, during a major earthquake, the framework and buckling restrained brace may deform outward from the structural plane, causing the core material forming the buckling restrained brace to press into the restraining plates that form the wooden restraining member, preventing cracks from occurring in the side panels pulled by the restraining plates.

FIG. 1 is a perspective view showing an example of a core material that forms the buckling restrained brace according to the first embodiment, together with a spacer. FIG. 2 is a perspective view of an example of a wooden restraint member that forms the buckling restrained brace according to the first embodiment. FIG. 2 is a perspective view of an example of a buckling restrained brace according to the first embodiment. FIG. 4 is a view taken in the direction of an arrow IV in FIG. 3 . FIG. 4 is a view taken along the arrows VV in FIG. 3. 6 is a view taken along the line VI-VI in FIG. 3. FIG. 7 is a view taken along the line VII-VII in FIG. 3. FIG. 8 is a view taken along the arrows VIII-VIII in FIG. 3. FIG. 10 is a perspective view showing a first modified example of a wooden restraint material. FIG. 10 is a perspective view showing a second modified example of the wooden restraint material. FIG. 10 is a perspective view showing a third modified example of a wooden restraint material. FIG. 10 is a perspective view showing a fourth modified example of a wooden restraint material. FIG. 10 is a perspective view showing a fifth modified example of a wooden restraint material. FIG. 10 is a perspective view showing a sixth modified example of a wooden restraint material. FIG. 1 is a diagram showing a state in which the buckling restraint brace according to the first embodiment is incorporated into the frame of a wooden building or the like. 1 is a diagram illustrating the deformation of the frame during a major earthquake and the additional bending moment at the buckling-restrained brace joint due to the deformation of the frame. FIG. 11 is a perspective view showing an example of a core material that forms a buckling restrained brace according to a second embodiment, together with a spacer. FIG. 10 is a longitudinal cross-sectional view of an example of a buckling restrained brace according to a second embodiment. 19 is an enlarged view of part XIX in FIG. 18, which explains how the force acting locally from the convex portion on the surface of the core material is diffused through the insertion plate and transmitted to the restraint plate. FIG. 10 is a diagram showing the overall buckling line of the buckling restraint brace.

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

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

The core material 10 is formed from a long, slender, plate-shaped flat steel. It has a narrow portion 13 at its longitudinal center, where the wide surface 11a is relatively narrow, and wide portions 12 at its longitudinal ends, where the wide surface 11a is relatively wide. Furthermore, reinforcing ribs 14 perpendicular to the wide surface 11a are welded to the wide surface 11a at the longitudinal ends of the core material 10, giving it a cross-shaped cross section.

By having a narrow width section 13 at the center of the core material 10 in the longitudinal direction and wide width sections 12 at the ends in the longitudinal direction, the narrow width section 13 at the center can be made into a region that is easily plasticized, and further, the plasticized region can be limited to the narrow width section 13 at the center.

Furthermore, as described below, the wide portion 12 and the reinforcing rib 14 each have bolt holes 12a, 14a for bolting via a splice plate to a gusset plate provided on the structural face or a fin stiffener attached to the gusset plate (see Figure 11). When the buckling restrained brace 100 is attached to a gusset plate so that the wide surface 11a of the core material 10 is arranged parallel to the structural face of the building, the core material 10 has reinforcing ribs 14 that are perpendicular to the wide surface 11a that is parallel to the structural face, thereby increasing the rigidity of the end of the core material 10 in the outward direction of the structural face.

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 (extremely low yield point steel), which improves seismic energy absorption due to the yielding of the core material 10.

At the center of the narrow portion 13 of the core material 10, cylindrical steel protrusions 15 protrude from the left and right side surfaces of the narrow portion 13 (one example of the peripheral surface of the narrow portion 13). The protrusions 15 are joined to the side surfaces of the narrow portion 13 by welding or other means. The protrusions 15 engage with engagement holes provided in the wooden restraint material (see Figure 2) described below. The protrusions 15 may also protrude from the upper and lower planes of the narrow portion 13. In this case, engagement holes are provided in the wooden restraint material (see Figure 2) at corresponding positions in the restraint plates 21, into which the protrusions 15 engage.

Elongated, rectangular column-shaped spacers 16 are arranged in the X1 direction on both sides of the narrow portion 13, and the core material 10 is housed inside the wooden restraint material described below with the spacers 16 arranged on both sides of the narrow portion 13. The spacers 16 may be either steel or wooden members. The spacers 16 may also have a shape other than that shown in the illustration, such as a cylindrical shape. The spacer 16 has multiple bolt holes 16a (three in the illustrated example) spaced apart along its length, through which first long bolts described below are inserted.

<Wooden restraint material>
Next, an example of a wooden restraint member that forms the buckling restrained brace according to the first embodiment will be described with reference to Fig. 2. Here, Fig. 2 is a perspective view of an example of a wooden restraint member that forms the buckling restrained brace according to the first embodiment.

The wooden restraint member 20 has a pair of restraint plates 21 and a pair of side plates 22 connecting the pair of restraint plates 21, with the core material 10 disposed in the gap 25 between the pair of restraint plates 21. The pair of wooden restraint plates 21 are disposed so as to face the two wide surfaces 11a (see Figure 1) of the core material 10, and the pair of wooden side plates 22 connected to the pair of restraint plates 21 are disposed so as to face the two narrow surfaces 11b (see Figure 1) of the core material 10.

A pair of restraint plates 21 each have a counterbore-equipped first bolt hole 21a at corresponding positions, and two corresponding first bolt holes 21a form a first bolt hole unit 21b. In the illustrated example, two first bolt hole units 21b are provided in the width direction of the restraint plate 21 and six are provided in the length direction of the restraint plate 21, for a total of twelve first bolt hole units 21b.

When the core material 10 is placed in the gap 25 between the pair of restraint plates 21, each bolt hole 16a opened in the spacer 16 is positioned at a position corresponding to each first bolt hole unit 21b, and these bolt holes 16a also form 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 placed in the counterbore of one of the first bolt holes 21a that form the first bolt hole unit 21b, the first long bolt 31 is inserted into the first bolt hole unit 21b via the washer 32, a washer 34 is placed in the counterbore of the other first bolt hole 21a, and the nut 33 is tightened onto the threaded groove at the tip of the first long bolt 31 that protrudes outward from the washer 34.

Meanwhile, second bolt holes 22a, 21c are opened at corresponding positions on the pair of side plates 22 and the restraint plate 21, respectively, and the corresponding second bolt holes 22a, 21c form second bolt hole units 22b. The second bolt hole units 22b are located in positions that do not interfere with the first bolt hole units 21b; in the illustrated example, two are provided in the width direction of the side plate 22 and seven are provided in the length direction of the side plate 22, for a total of fourteen second bolt hole units 22b.

A 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 placed in the counterbore 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 placed in the counterbore of the other second bolt hole 22a, and a nut 43 is tightened onto the thread groove at the tip of the second-long bolt 41 that protrudes outward from the washer 44.

In addition, when tightening the second-long bolts 41 with the nuts 43, adhesive is applied to the contact surfaces of the restraint plate 21 and the side plate 22, and the second-long bolts 41 are tightened with the nuts 43 before the adhesive hardens.

The adhesive used here can be a urethane-based adhesive or an epoxy-based adhesive, but it is preferable to use a urethane-based adhesive that takes a certain amount of time to harden (for example, about 24 hours), so that after the adhesive is applied to the contact surface between the restraint plate 21 and the side plate 22, the second-long bolts 41 can be tightened with the nuts 43 before the adhesive hardens. The adhesive surface formed when the adhesive hardens is firmly compressed by the tightening force applied when the second-long bolts 41 are tightened with the nuts 43.

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

If high joint strength such as that shown in the illustrated example is not required, the wooden restraint member 20 may be formed by bonding a pair of restraint plates 21 and a pair of side plates 22 together using only adhesive.

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

Furthermore, the spacer 16 has a bolt hole 16a that constitutes the first bolt hole unit 21b, and a first long bolt 31 is inserted through this bolt hole 16a, thereby preventing the spacer 16 from moving in the longitudinal direction of the core material 10. As will be explained below with reference to Figure 11, buckling restrained braces are generally arranged diagonally on the structural plane, so the spacer 16 is prone to moving diagonally downward. This movement of the spacer 16 can easily create a large gap diagonally upward between the end of the spacer 16 and the wide portion 12 of the core material 10. Therefore, the diagonally upward region of the buckling restrained brace where the spacer 16 is not present is likely to become a weak spot. However, by inserting a first long bolt 31 through the bolt hole 16a of the spacer 16 as shown in the figure, this movement of the spacer 16 is eliminated, and no weak spot due to the movement of the spacer 16 occurs.

As is clear from Figure 2, although the ends of the pair of restraint plates 21 are fixed to the side plates 22 via adhesive, they are not fixed by the second long bolts 41, and therefore it is difficult to say that a strong closed structure is formed at the ends of the wooden restraint member 20.

As a result, when buckling restraint braces are incorporated into a frame and are deformed outside the structural plane during an earthquake, cracks (splitting) may occur at the ends of the side panels 22 connected to positions corresponding to the ends of the pair of restraint plates 21 that receive the strongest pushing force from the core material 10.

As shown in Figure 2, the ends of a pair of restraint plates 21 are connected together by multiple rivets 29A (an example of end restraint members).

The clamp 29A is a metal fitting that is U-shaped overall, with a straight connecting portion 29a and two piercing portions 29b formed by bending the connecting portion 29a at right angles at both ends.

The two piercing portions 29b of the U-shaped clamps 29A are pierced near both ends of the side panel 22, and then further pierced into the end faces of the pair of restraining plates 21, thereby securing both ends of the side panel 22 and the pair of restraining plates 21 via the clamps 29A. In the illustrated example, three clamps 29A are driven into each end of the left and right side panels 22, forming a strong closed structure at both ends of the wooden restraining member 20.

Here, the method of fixing the clamp 29A may be by hammering it in, or by inserting the piercing portion 29b into a fixing hole (not shown) opened in the end face of the restraint plate 21 and adhesively fixing it with adhesive. More specifically, fixing holes that communicate with both sides are provided near both ends of the side plate 22 and in the end faces of the pair of restraint plates 21, and the piercing portion 29b is inserted into these communicating fixing holes and adhesively fixed with adhesive filled in the fixing holes. Here, as described above, a urethane-based adhesive or an epoxy-based adhesive is used as the adhesive.

In addition, non-contact grooves 23 are provided at both ends of the restraint plate 21 so that they do not come into contact with the wide surface 11a of the core material 10 housed in the gap 25. The area of the restraint plate 21 other than the non-contact grooves 23 (the central area) comes into contact with the wide surface 11a of the core material 10. This configuration and the effects it provides are described in detail below.

The restraining plate 21 and side plate 22 may be made of either solid wood or wood materials, including laminated lumber made of laminated lamina. As described in detail below, the cross-sectional area, cross-sectional rigidity, Young's modulus, etc. of the wooden restraining member 20 are set to prevent global buckling of the buckling-restrained brace. This Young's modulus is determined by the wood material. Examples of wood materials include cypress, red pine, larch, fir, and Yezo spruce.

At the end of the restraint plate 21, a slit 24 is provided at a position that corresponds to the reinforcing rib 14 when the core material 10 is placed in the gap 25, so that it does not interfere with the reinforcing rib 14. Additionally, multiple additional clamps 29A' are hammered into the periphery of the slit 24 in the restraint plate 21, reinforcing the area around the slit 24. Note that the clamps 29A' are optional components and are not required components.

<Buckling restraint brace>
Next, an example of a buckling-restrained brace according to the first embodiment, formed using the core material 10 and wooden restraint material 20 described above, will be described with reference to Figures 3 to 14. Here, Figure 3 is a perspective view of an example of a buckling-restrained brace according to the first embodiment. Also, Figures 4, 5, 6, 7, and 8 are a view taken along the arrow IV in Figure 3, a view taken along the arrow V-V in Figure 3, a view taken along the arrow VI-VI in Figure 3, a view taken along the arrow VII-VII in Figure 3, and a view taken along the arrow VIII-VIII in Figure 3, respectively.

The buckling restraint brace 100 is constructed so that wooden restraint members 20 surround the narrow section 13 and part of the wide section 12 of the core member 10, and the cross-shaped end of the wide section 12 extends beyond the end of the wooden restraint member 20. The bolt holes 12a, 14a of the wide section 12 and reinforcing rib 14 that extend outward face the exterior.

A core material 10 is placed in the gap 25 between a pair of restraint plates 21, multiple first long bolts 31 are inserted through the pair of restraint plates 21 and spacers 16 and tightened with nuts 33, second long bolts 41 are inserted through the pair of side plates 22 and restraint plates 21 and tightened with nuts 43, and the ends of the pair of restraint plates 21 are connected by clamps 29A driven into the outside of the side plates 22, thereby forming a buckling restrained brace 100. As shown in the figure, the extension direction of the first long bolts 31 is the weak axis direction of the core material 10, and the extension direction of the second long bolts 41 is the strong axis direction of the core material 10.

The buckling-restrained brace 100 has a structure in which the core material 10 is surrounded by wooden restraint members 20, which are formed by a pair of restraint plates 21 and a pair of side plates 22 that are tightly closed by tightening nuts on a number of first-length bolts 31 and second-length bolts 41, resulting in a buckling-restrained brace with high buckling strength. Furthermore, by connecting the ends of the pair of restraint plates 21 with clamps 29A, the buckling-restrained brace has a strong closed structure at the ends. Furthermore, because the steel core material 10 is surrounded by wooden restraint members 20, the buckling-restrained brace 100 does not appear out of place with the structural components, even when applied to the frame of a wooden building.

In the illustrated buckling restraint brace 100, the core material 10 is housed within the gap 25 of the wooden restraint material 20, with spacers 16 arranged on the left and right sides of the narrow portion 13, and the protrusions 15 extending laterally from the sides of the narrow portion 13 are engaged with the engagement holes 22c.

A gap G1 of width t1 is provided between the side of the wide portion 12 of the core material 10 and the side panel 22 of the wooden restraint material 20.

In addition, a non-contact groove 23 is formed at the end of the restraint plate 21 to prevent the restraint plate 21 from abutting against the wide portion 12 of the core material 10, and a gap G3 of height t2 is provided between the non-contact groove 23 and the wide portion 12. As shown in detail in Figure 7, this non-contact groove 23 is provided in a range from the edge of the restraint plate 21 to a position corresponding to the additional bending absorption area A of the core material 10 (boundary region A between the wide portion 12 and narrow portion 13).

As shown in Figures 7 and 8, the boundary region A between the wide section 12 and the narrow section 13 is a transition region 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 region. In this way, the additional bending moment acting on the core material 10 is effectively absorbed in the boundary region A between the wide section 12 and the narrow section 13 of the core material 10, and the gap G1 provided between the core material 10 and the side panel 22 of the wooden restraint member 20 prevents the additional bending moment acting on the core material 10 from acting on the side panel 22 of the wooden restraint member 20.

Furthermore, between the reinforcing rib 14 and the slit 24 in the restraining plate 21 of the wooden restraining member 20, a gap G2 of width t3 is provided in the longitudinal direction of the reinforcing rib 14 and width t1 is provided to the side of the reinforcing rib 14. In this way, by providing gap G1 between the side surface of the wide section 12 and the side plate 22 of the wooden restraining member 20, if the structural surface to which the buckling restrained brace 100 is attached undergoes significant deformation, this gap G1 absorbs the deformation of the core material 10, preventing so-called additional bending moment from acting on the wooden restraining member 20. On the other hand, the presence of gap G2 between the slit 24 and the reinforcing rib 14 allows gap G2 to absorb the expansion and contraction of the core material 10 when it expands and contracts in response to deformation of the structural surface, eliminating the problem of the expanding and contracting core material 10 coming into contact with the wall of the slit 24 and causing damage to the wooden restraining member 20.

As shown in Figures 4 and 5, in the buckling restraint brace 100, non-contact grooves 23 are provided in the restraint plate 21 over the range from its edge to a position corresponding to the additional bending absorption area A of the core material 10. Meanwhile, as shown in Figure 6, the area of the restraint plate 21 other than the non-contact grooves 23 is in contact with the narrow portion 13 of the core material 10.

With the above configuration, when the frame S (see Figure 11) and buckling restraint brace 100 are deformed outside the structural plane, the non-contact grooves 23 eliminate or reduce contact (prevent strong contact) between the core material 10 and the restraint plate 21 at the end of the restraint plate 21, which is likely to receive the strongest pushing force from the core material 10.

In this way, by eliminating or reducing the pressure from the core material 10 on the restraint plate 21, it is possible to suppress cracks that may occur at the ends of the side panels 22 connected at positions corresponding to the ends of the restraint plate 21. When the restraint plate 21 is pressed into the core material 10, cracks that occur in the side panels 22 due to tension from the pressed-in restraint plate 21 tend to occur more prominently in the short direction or a direction close to the short direction in the longitudinal cross section of the wooden restraint material 20, as shown in Figures 4 and 5, but this cracking is effectively eliminated.

In the illustrated example, the ends of a pair of restraint plates 21 are connected (reinforced) by clamps 29A driven into the outside of the side plates 22. This reinforcement structure, combined with the non-contact grooves 23 that eliminate or reduce contact between the core material 10 and the restraint plates 21, further enhances the effectiveness of preventing cracking of the side plates 22 due to tension from the restraint plates 21.

In addition, the non-contact grooves 23 at the ends of the restraint plates 21 eliminate or reduce contact between the ends of the restraint plates 21 and the core material 10, while the areas of the restraint plates 21 other than the non-contact grooves 23 (the central areas) come into contact with the core material 10, ensuring that the restraint plates 21 can prevent the core material 10 from buckling.

As shown in Figures 7 and 8, by providing a narrow section 13 at the center of the core material 10, a relatively large gap G4 (larger than the gap G1 between the wide section 12 at the end of the core material 10 and the side panel 22) exists between the narrow section 13 and the side panel 22. By interposing a spacer 16 in this gap G4 and closing the gap G4, buckling in the strong axis direction of the core material 10 (a direction parallel to the wide surface 11a of the core material 10) can be prevented. This suppresses overall buckling of the buckling-restrained brace 100 and improves the compressive strength of the buckling-restrained brace 100, thereby providing excellent seismic reinforcement for frames incorporating the buckling-restrained brace 100 and buildings that include this frame.

Next, with reference to Figures 9 to 14, we will explain first to fifth variants of the wooden restraint material that forms the buckling restrained brace 100. Each variant of the wooden restraint material here has a distinctive side panel.

First, the wooden restraint material 20A shown in Figure 9 has two strip-shaped steel plates 29B (another example of an end restraint material) wrapped around the ends of the wooden restraint material 20A, and by connecting the ends of the two steel plates 29B together, the ends of the pair of restraint plates 21 are indirectly restrained (reinforced) together. Here, in the illustrated example, the wooden restraint material 20A has the end of the wooden restraint material 20A reinforced with one strip-shaped steel plate 29B, but the end of the wooden restraint material 20A may also be reinforced with two or more strip-shaped steel plates 29B.

In this way, by restraining the ends of the pair of restraint plates 21 with the strip-shaped steel plate 29B, it is possible to suppress cracks that may occur in the side plate 22 due to tension from the restraint plates 21.

The wooden restraint material 20B shown in Figure 10 has two strip-shaped fiber reinforcement materials 29C (another example of an end restraint material) wrapped around the ends of the wooden restraint material 20B, and the ends of the two fiber reinforcement materials 29C are connected to each other, thereby indirectly restraining (reinforcing) the ends of a pair of restraint plates 21. Here, in the illustrated example, the wooden restraint material 20C has the ends of the wooden restraint material 20B reinforced with two strip-shaped fiber reinforcement materials 29C, but the ends of the wooden restraint material 20B may also be reinforced with one, three or more strip-shaped fiber reinforcement materials 29C.

In this way, by restraining the ends of the pair of restraint plates 21 with the strip-shaped fiber reinforcement 29C, cracks that may occur in the side plates 22 due to tension from the restraint plates 21 can be suppressed.

The wooden restraint material 20C shown in Figure 11 has a side panel 22A that includes a central side panel 26 and end side panels 27 at both ends of the central side panel 26, and the central side panel 26 and the end side panels 27 are connected with adhesive or the like.

The end side plates 27 are located in a range corresponding to the non-contact grooves 23 of the restraint plate 21, and the wood grain direction of the end side plates 27 is oriented in the short direction of the side plate 22A. On the other hand, the wood grain direction of the center side plate 26 is arranged in the long direction of the side plate 22A.

In addition, the ends of the pair of restraint plates 21 are connected (reinforced) by multiple (three in the illustrated example) clamps 29A driven into the outside of the end side plates 27.

In this way, the fiber direction of the end side panels 27 of the side panels 22A that are in the corresponding ranges to the non-contact grooves 23 of the restraining plate 21 is aligned in the short direction of the side panels 22A. This means that the strong fiber direction of the wood is oriented in the direction (or to some extent in the direction) that would cause cracks in the end side panels 27 due to tension from the restraining plate 21 (the short direction of the side panels 22A), enabling the end side panels 27 to provide high resistance to cracks. On the other hand, the fiber direction of the central side panels 26 of the side panels 22A that are outside the corresponding ranges to the end panels is oriented in the long direction of the central side panels 26. This means that the strong fiber direction of the wood is oriented in the central portion of the side panels 22A where bending is most pronounced, providing high bending strength against bending in the central portion.

Furthermore, by connecting the ends of the pair of restraint plates 21 with clamps 29A, a strong closed structure can be formed at the end of the wooden restraint material 20C. Instead of clamps 29A, as shown in Figures 9 and 10, the end of the wooden restraint material can be wrapped around a strip of steel plate 29B or a strip of fiber reinforcement material 29C, thereby forming a strong closed structure at the end.

On the other hand, the wooden restraint material 20D shown in Figure 12 has multiple (three in the illustrated example) piercing means 28 extending toward the pair of restraint plates (in the short direction of the side plates 22B) pierced into the side plates 22B in the range corresponding to the non-contact grooves 23 of the restraint plates 21. Here, the piercing means 28 can be screws, nails, bolts including lag screw bolts, etc.

In addition, the ends of the pair of restraint plates 21 are connected (reinforced) by multiple (three in the illustrated example) clamps 29A driven into the outside of the side plate 22B.

In this way, the piercing means 28 extending toward the pair of restraining plates pierces the side plate 22B in a range that corresponds to the non-contact groove 23 of the restraining plate 21. More specifically, the piercing means 28 pierces in a direction that follows (or is somewhat parallel to) the direction of cracks that may occur in the side plate 22B due to tension from the restraining plate 21 (the short side direction of the side plate). This allows the piercing means 28 to provide high resistance to cracks. Furthermore, because the ends of the pair of restraining plates 21 are connected by clamps 29A, a strong closed structure can be formed at the end of the wooden restraining material 20D.

On the other hand, the wooden restraint member 20E shown in Figure 13 has a steel plate accommodating groove 22e that is rectangular in plan view from the inside, located on the inner surface of the side plate 22C (the surface facing the non-contact groove 23) in a corresponding area that corresponds to the non-contact groove 23 between the pair of restraint plates 21. A reinforcing steel plate 45 that is rectangular in plan view and spans each side surface is fixed to each side surface of the pair of restraint plates 21. For example, the reinforcing steel plate 45 is fixed to the side surfaces of the pair of restraint plates 21 by adhesive, drill screws, or both.

Here, the planar dimensions of the reinforcing steel plate 45 are set smaller than the planar dimensions of the steel plate storage groove 22e, and further, the thickness of the reinforcing steel plate 45 is set thinner than the groove depth of the steel plate storage groove 22e.

When a reinforcing steel plate 45 is fixed to the side surfaces of a pair of restraint plates 21 and the pair of restraint plates 21 and side plates 22 are connected so that the reinforcing steel plate 45 is accommodated in the steel plate accommodation groove 22e, the reinforcing steel plate 45, which has dimensions smaller than the planar dimensions and depth of the steel plate accommodation groove 22e, is accommodated in the steel plate accommodation groove 22e without coming into contact with the inner wall surface of the steel plate accommodation groove 22e.

On the left and right sides of the pair of restraint plates 21, reinforcing steel plates 45 are accommodated in the steel plate accommodation grooves 22e without contacting the side plates 22C, and the pair of side plates 22C are connected to the pair of restraint plates 21, thereby forming the wooden restraint member 20E.

In this way, the reinforcing steel plate 45, which does not contact the side plate 22C, is fixed to the side surfaces of the pair of restraint plates 21, allowing the reinforcing steel plate 45 to withstand tension from the side plate 22 with high resistance. At this time, because the reinforcing steel plate 45 does not contact the inner wall surface of the steel plate storage groove 22e, there is no risk of the reinforcing steel plate 45 pressing against the side plate 22C and causing cracks.

On the other hand, the wooden restraint material 20F shown in Figure 14 is configured such that multiple nails 29A are driven into the ends of a pair of restraint plates 21 to connect the ends of the pair of restraint plates 21, and then side panels 22 are fixed to the outside of the restraint plates 21 via adhesive.

In this way, by arranging the side plates 22 on the outside of the multiple rivets 29A connecting the ends of the restraint plates 21, the rivets 29A can be hidden from view from the outside, which not only prevents the side plates 22 from cracking due to tension from the restraint plates 21, but also results in a wooden restraint member 20F with excellent external design.

In the wooden restraint materials 20A, 20B, 20C, 20D, 20E, and 20F according to the first through sixth variations, the ends of the pair of restraint plates 21 are connected by the end restraint member 29A. Furthermore, the pair of restraint plates 21 have non-contact grooves 23 at both ends that eliminate or mitigate the pressure exerted by the wide portion 12 of the deforming core material 10. In addition, the ends of the side plates 22A and 22B are reinforced against cracks with end side plates 27, multiple piercing means 28, and reinforcing steel plates 45, with the fiber direction aligned with the crack direction. This makes it possible to more effectively eliminate cracks that may occur in the side plates 22, 22A, 22B, and 22C.

<Example of application of buckling restraint braces to a frame>
Next, an example of application of a buckling restrained brace to a frame will be described with reference to Figures 15 and 16. Here, Figure 15 is a diagram showing the buckling restrained brace according to the first embodiment incorporated into the frame of a wooden building or the like. Also, Figure 16 is a diagram explaining the deformation of the frame during a major earthquake and the additional bending moment at the buckling restrained brace joint resulting from the deformation of the frame. Note that the buckling restrained brace shown in the example may be incorporated into the frame of a steel (S) building, a reinforced concrete (RC) building, or a steel reinforced concrete (SRC) building, in addition to the frame of a wooden building.

The frame S shown in Figure 15 is formed from wooden columns C and beams B that make up 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 linearly, passing through both diagonal intersections O.

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

As shown in Figure 16, when a large earthquake occurs, deformation of the structural members can cause an additional bending moment, as shown in equation (1) below, to act on the buckling-restrained brace joints, assuming that the joints are rigid.

The buckling restrained brace 100 has a gap G1 of width t1 between the side of the wide section 12 of the core material 10 and the side panel 22 of the wooden restraint member 20. This gap G1 absorbs deformation of the core material 10 when the structural surface to which the buckling restrained brace 100 is attached undergoes significant deformation, preventing additional bending moments from acting on the wooden restraint member 20. Furthermore, a gap G2 of width t2 is provided between the reinforcing rib 14 and the restraint plate 21 of the wooden restraint member 20 in the longitudinal direction of the reinforcing rib 14 and on the side of the reinforcing rib 14. This allows the gap G2 to absorb expansion and contraction of the core material 10 when it expands and contracts in response to deformation of the structural surface, eliminating the problem of the expanding and contracting core material 10 coming into contact with the wall of the slit 24 and causing damage to the wooden restraint member 20. Furthermore, the ends of the restraint plates 21, which are likely to receive the strongest pushing force from the core material 10, are connected by multiple end restraint members 29A, and gaps G3 are formed by non-contact grooves 23 at these ends. Gap G3 eliminates or reduces contact between the core material 10 and the restraint plates 21, effectively preventing cracks from occurring at the ends of the side plates 22 connected at positions corresponding to the ends of the restraint plates 21.

[Buckling Restrained Brace According to the Second Embodiment]
Next, an example of a core material forming a buckling restrained brace according to the second embodiment will be described with reference to Figures 17 to 19. Here, Figure 17 is a perspective view showing an example of a core material forming a buckling restrained brace according to the second embodiment together with a spacer, and Figure 18 is a longitudinal cross-sectional view of an example of a buckling restrained brace according to the second embodiment. Furthermore, Figure 19 is an enlarged view of part XIX in Figure 18, which illustrates how a force acting locally from a convex portion on the surface of the core material is diffused via an insertion plate and transmitted to the restraining plate.

The buckling restrained brace 100A differs from the buckling restrained brace 100 in that an insert plate 17 is interposed between the wide surface 11a of the core material 10 and the restraint plate 21. The insert plate 17 may be either a steel plate or a wooden plate, and the wooden plate may be, for example, laminated veneer lumber (LVL). Note that in this embodiment, the protrusions 15 may also extend beyond the upper and lower planes of the narrow portion 13.

On the wide surface of the inner plate 17, a slit 18 is opened at the longitudinal end at a position corresponding to the reinforcing rib 14 of the core material 10 so as not to interfere with the reinforcing rib 14. The inner plate 17 also has a bolt hole 17a opened at a position corresponding to the bolt hole 16a opened in the spacer 16, through which the first long bolt 31 shown in Figure 2 is inserted.

With the buckling-restrained brace 100A, as shown in Figure 19, higher-order buckling deformation of the core material 10 causes a localized compressive force P to act from the core material 10 on the restraining plate 21. This localized force P can lead to damage to the wooden restraining plate 21. Therefore, by interposing an inner plate 17 between the wide surface 11a of the core material 10 and the restraining plate 21, the force P acting from the convex portion 10a of the higher-order buckling deformation of the core material 10 is first transmitted to the inner plate 17. The transmitted force P then spreads within the inner plate 17, and the force dispersed within the inner plate 17 acts on the wooden restraining plate 21 as a dispersed force q. This effectively prevents damage to the wooden restraining plate 21 due to multiple localized forces P acting from the core material 10.

[Study of overall buckling]
Next, we will explain the design method for preventing global buckling of buckling-restrained braces.

When designing a buckling-restrained brace, the following equation (2) must be satisfied to prevent global buckling of the buckling-restrained brace.

Here, the bending moment acting on the center of the restraint plate can be expressed by the following equation (3).

The condition for preventing global buckling of the wooden restraint member is to satisfy the following equation (4).

Equation (4) is shown in Figure 20 as the overall bending stress curve for the buckling-restrained brace. In Figure 20, the upper side of the overall bending stress curve is the safe zone, and the lower side is the dangerous zone. The design axial force of the wooden restraint member, Euler load, length of the general part of the core member, and yield bending strength of the wooden restraint member are set so that they fall within the safe zone. Note that the overall bending stress curve for the buckling-restrained brace shown in Figure 20 applies to both overall buckling in the weak axis direction of the core member and overall buckling in the strong axis direction.

In addition to examining the relationship between the yield bending strength of the wooden restraint material and the acting bending moment as described above, it is also advisable to examine whether the short-term allowable bending strength of the wooden restraint material will be greater than the bending moment acting when the core material yields (formula omitted).

<Study on the compressive failure of wooden restraint materials>
Next, we will explain how to evaluate the failure of wooden restraints due to the core material penetrating into the wooden restraint. To prevent the wooden restraint from failing due to the core material penetrating into the wooden restraint, we verify that the following formula (5) is satisfied.

In addition to examining the relationship between the compressive strength of the restraining plate and the stiffening force acting on it, it is also advisable to examine whether the short-term allowable compressive strength of the restraining plate will be greater than the stiffening force acting when the core material yields (formula omitted).

<Consideration of specifications for the first long bolt (weak axis direction bolt) and the second long bolt (strong axis direction bolt)>
Next, a method for setting the specifications of the first long bolts (weak axis direction bolts) and the second long bolts (strong axis direction bolts) will be described.

When setting the specifications for the first long bolts (weak axis direction bolts) and second long bolts (strong axis direction bolts), the sum of the yield strengths of each long bolt must be set to be equal to or greater than the sum of the reinforcing forces acting on the wooden restraint material, and the specifications of each long bolt (yield stress, number, effective cross-sectional area (effective cross-sectional area per bolt and total effective cross-sectional area due to the number of bolts), etc.) must be determined so as to satisfy the following formula (6).

Note that other embodiments may be possible in which other components are combined with the configurations described in the above embodiments, and the present invention is in no way 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 depending on the application form.

DESCRIPTION OF SYMBOLS 10: Core material 11a: Wide surface 11b: Narrow surface 12: Wide portion 12a: Bolt hole 13: Narrow portion 14: Reinforcing rib 14a: Bolt hole 15: Protrusion 16: Spacer 16a: Bolt hole 17: Insertion plate 17a: Bolt hole 20, 20A, 20B, 20C, 20D, 20E: Wooden restraining material 21: Restraining plate 21a: First bolt hole 21b: First bolt hole unit 21c: Second bolt hole 22, 22A, 22B, 22C: Side plate 22a: Second bolt hole 22b: Second bolt hole unit 22c: Engagement hole 22d: Steel plate accommodating groove 23: Non-contact groove 24: Slit 25: Gap 26: Central side plate 27: End side plate 28: Piercing means 29A: Hook (end restraining material)
29A': Steel plate 29B: Steel plate (end restraining material)
29C: Fiber reinforcement material (end restraint material)
29a: Connecting portion 29b: Piercing portion 31: First long bolt 32: Washer 33: Nut 34: Washer 41: Second long bolt 42: Washer 43: Nut 44: Washer 45: Reinforcing steel plate 100, 100A: Buckling restraint brace G1, G2, G3, G4, G5: Gaps A: Additional bending absorption area (boundary region)
S: Frame (frame)
C: Pillar B: Beam GP: Gusset plate FS: Fin stiffener SP: Splice plate

Claims (3)

A steel plate-shaped core material,
a wooden restraining member formed by a pair of wooden restraining plates arranged so as to face the two wide surfaces of the core material, and a pair of wooden side plates arranged so as to face the two narrow surfaces of the core material and connected to the pair of restraining plates;
The ends of the pair of restraint plates are connected by end restraint members, which are clamps ,
A buckling restraint brace characterized in that the two piercing portions of the clamp are inserted into fixing holes opened in the pair of restraint plates and fixed by adhesive . a non-contact groove that does not come into contact with the wide surface of the core material is provided at an end of the restraint plate;
2. The buckling restraint brace according to claim 1 , wherein the area of the restraint plate other than the non-contact groove is in contact with the wide surface of the core material. the core material has a narrow portion at a center side in a longitudinal direction where the width of the wide surface is relatively narrow, and a wide portion at an end side in a longitudinal direction where the width of the wide surface is relatively wide,
3. The buckling restraint brace according to claim 2 , wherein the non-contact groove extends from an edge of the restraint plate to a position corresponding to the boundary between the wide portion and the narrow portion of the core material.