JP7790664B2 - 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 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 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.

Patent Document 1 proposes a buckling restrained brace suitable for use within the framework of wooden buildings, including wooden houses. Specifically, this is a buckling restrained brace that has a core material and a pair of restraint members arranged along both sides of the core material. The core material 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 material.

Patent No. 4901491

The buckling restraint brace described in Patent Document 1 requires processing laminated timber to create two wooden restraint members with L-shaped cross sections, then turning them upside down and connecting them with a core material in between, making the buckling restraint brace difficult to manufacture.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a buckling restraint brace that is suitable for use in structures such as wooden buildings and is easy to manufacture.

In order to achieve the above object, one aspect of the buckling restrained brace according to the present invention is as follows:
Axial wooden restraints;
The wooden restraint material has a shaft-shaped steel core member inserted into an axial through-hole provided in the wooden restraint material.

In this embodiment, the buckling restrained brace is manufactured by inserting an axial steel core into an axial through-hole provided in an axial wooden restraint member. This allows the buckling restrained brace to be manufactured using components with a simple configuration, and the number of components is minimized, resulting in good manufacturability. Furthermore, because the core is inserted into the internal through-hole of the wooden restraint member and is surrounded by the wooden restraint member, 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 may be made of solid wood, or may be made of laminated lumber with laminated laminas or LVL (Laminated Veneer Lumber). Furthermore, the wooden restraint member may be made of a single axial member, or, for example, two axial members joined together.

In another aspect of the buckling restrained brace according to the present invention,
The wooden restraint member is made of wood and is formed by a pair of restraint plates,
The pair of restraint plates are characterized in that half-split holes that form the through holes are provided at corresponding positions on the contact surfaces thereof.

In this embodiment, the wooden restraint material is formed from a pair of wooden restraint plates with half-split holes that form through holes, which improves the manufacturability of through holes in the wooden restraint material. For example, it is not easy to bore a small-diameter through hole in the axial direction with high precision in a single shaft-shaped wooden restraint material, and the difficulty of processing becomes more pronounced as the length of the wooden restraint material increases.

Another aspect of the buckling restrained brace according to the present invention is:
The pair of restraint plates are connected to each other at the contact surfaces via an adhesive.

In this embodiment, in a configuration in which a wooden restraint material is formed from a pair of restraint plates, the pair of restraint plates are connected via adhesive, further improving the manufacturability of the wooden restraint material.

In another aspect of the buckling restrained brace according to the present invention,
The wooden restraining material is made of a driven or screwed material, and is characterized in that a split prevention means for preventing the wooden restraining material from splitting is embedded from the side of one of the restraining plates to the other of the restraining plates.

In this configuration, where a wooden restraint member is formed by a pair of restraint plates, in addition to connecting the restraint plates with an adhesive, a crack prevention device made of a driven or screwed material is embedded (embedded by driving or screwing) from the side of one restraint plate to the other, which effectively prevents the restraint plates from cracking and also functions as a fail-safe to prevent the restraint plates from separating at their contact surfaces (adhesive interfaces) in the event of a major earthquake or the like. For example, it is preferable to embed the crack prevention device in a staggered pattern along the length of the wooden restraint member.

Another aspect of the buckling restrained brace according to the present invention is:
The core material is a round steel bar.

In this embodiment, the core material is made of round steel, which is as inexpensive as possible, and this, combined with good manufacturability, reduces manufacturing costs.

Another aspect of the buckling restrained brace according to the present invention is:
The core material is characterized in that it is a steel pipe and a round bar that passes through the inside of the steel pipe.

In this embodiment, the core material is a steel pipe and a round steel bar that penetrates the inside of the steel pipe. This prevents, for example, a buckled round steel bar from directly contacting the wooden restraint material, which could cause the wooden restraint material to be pressed against the round steel bar and break.

In another aspect of the buckling restrained brace according to the present invention,
A connector having a cross-shaped cross section made of a steel plate and connected to another member is joined to both ends of the core material,
The end of the wooden restraint member is provided with a recess at a position corresponding to the connector so as not to interfere with the connector,
A portion of the connector is housed in the recess.

In this aspect, connecting bodies made of steel plates with a cross-shaped cross section that are connected to other members are joined to both ends of the core material. Therefore, when a buckling restraint brace is attached to a gusset plate and arranged on the structural surface of a building, the rigidity of the ends of the core material can be increased both inward and outward in the structural surface. In the structural surface gusset plate to which such cross-shaped connecting bodies are attached, fin stiffeners are attached to the gusset plate, and the multiple steel plates that form the connecting bodies and intersect at right angles are joined to the gusset plate and fin stiffener via splice plates using high-tension bolts or the like.

Furthermore, the ends of the wooden restraints are provided with recesses at positions corresponding to the connectors that do not interfere with the connectors, preventing the ends of the wooden restraints from being pressed by the connectors and being damaged. A gap is provided between the connectors and the recesses, and this gap is desirably set to a length that can absorb the expansion and contraction of the core material when it expands and contracts in response to deformation of the structural face. The setting of this gap is left to the discretion of the designer, and the amount of expansion and contraction of the core material is calculated based on the set story deformation angle, and the gap is set, for example, to be equal to or greater than the amount of expansion and contraction of the core material.

Furthermore, since the boundary region between the core material and the connector is a transition region where the planar and cross-sectional areas of the member change, a plastic region that is easily plasticized is formed on the core material side of this transition region, and this transition region can absorb the additional bending moment acting on the core material. An additional bending moment (or simply, additional bending) is a bending moment that can act on a wooden restraint member 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 by the core material side region of the boundary region between the core material and the connector.

As can be understood from the above explanation, the buckling restraint brace of the present invention is suitable for use in structures such as wooden buildings, and provides a buckling restraint brace with excellent manufacturability.

FIG. 1 is a perspective view of an example of a core material that forms a buckling restrained brace according to an embodiment. FIG. 10 is a perspective view of another example of a core material that forms a buckling restrained brace according to an embodiment. FIG. 1 is an exploded perspective view of an example of a wooden restraint member that forms a buckling restrained brace according to embodiments. FIG. 1 is a perspective view of an example of a buckling restrained brace according to embodiments. 5 is a cross-sectional view of an example of the end of a buckling restraint brace, taken along the line VV in FIG. 4. 6 is a cross-sectional view of an example of the central portion of a buckling restraint brace, taken along the arrows VI-VI in FIG. 4. FIG. 10 is a perspective view of another example of a buckling restrained brace according to embodiments. FIG. 10 is a perspective view of yet another example of a buckling restrained brace according to embodiments. 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. 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. 10 is a diagram showing the overall buckling line of the buckling restraint brace.

The buckling restraint brace according to the 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 Embodiment]
First, an example of a buckling-restrained brace according to an embodiment will be described with reference to Figures 1 to 6. Here, Figures 1 and 2 are both perspective views of an example of a core material forming the buckling-restrained brace according to an embodiment, and Figure 3 is an exploded perspective view of an example of a wooden restraining material forming the buckling-restrained brace according to an embodiment. Furthermore, Figure 4 is a perspective view of an example of a buckling-restrained brace according to an embodiment, Figure 5 is a cross-sectional view of an example of an end portion of the buckling-restrained brace taken along the arrows V-V in Figure 4, and Figure 6 is a cross-sectional view of an example of a central portion of the buckling-restrained brace taken along the arrows VI-VI in Figure 4.

As shown in Figure 1, the core material 10 has a shaft-shaped round steel bar 11 and a connector 15 to which both ends of the round steel bar 11 are welded.

Two shear stoppers 13 protrude from the longitudinal center of the round steel bar 11 to position the round steel bar 11 inside the wooden restraint material described below.

The connector 15 has a cross-shaped cross section, with two steel plates 17 welded to both wide sides of a single steel plate 16, and perpendicular to the steel plate 16.

The core material 10 has a round steel bar 11 at its longitudinal center, and a connector 15 at its longitudinal end that has a larger cross-sectional area and dimensions than the round steel bar 11 and is highly rigid. This allows the round steel bar 11 at the center to be a region that is easily plasticized (plasticization region A), and further allows the plasticization region A to be limited to the round steel bar 11 at the center.

Furthermore, as explained below, the steel plates 16, 17 that form the connector 15 each have bolt holes 16a, 17a 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 9). When the buckling restrained brace 100 is attached to the gusset plate so that the steel plate 16 of the connector 15 is arranged parallel to the structural face of the building, the connector 15 has a separate steel plate 17 that is perpendicular to the steel plate 16 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.

On the other hand, as shown in Figure 2, another example of core material 10A differs from core material 10 in that a round steel bar 11 is inserted inside a steel pipe 18.

Two engagement grooves 19 are provided in the center of the interior of the steel pipe 18, and two shear stoppers 13 on the round bar 11 engage with the engagement grooves 19 to position the round bar 11 relative to the steel pipe 18. Although not shown, the round bar 11 and the steel pipe 18 may each have a communicating hole at their respective centers, and a locking pin may be inserted into the communicating hole from the outside of the steel pipe 18 to position the round bar 11 relative to the steel pipe 18. The engagement grooves 19 may also be loose grooves (loose holes).

The steel pipe 18 is a component that prevents damage to the wooden restraint material when the round steel bar 11 is plastically deformed by directly pressing the deformed round steel bar 11 against the wooden restraint material.

As shown in Figure 3, the wooden restraint member 20 is formed by a pair of restraint plates 21, and half-slit holes 24 are provided at corresponding positions (central positions in the width direction) on the abutment surfaces 22 of each restraint plate to form through holes 23 (see Figure 4) in which the round steel bars 11 are accommodated.

Furthermore, the contact surfaces 22 at both ends of the restraint plate 21 are provided with half-split recesses 26 that extend in the short direction of the restraint plate 21. When a pair of restraint plates 21 are brought into contact with each other at their contact surfaces 22, the two corresponding half-split recesses 26 form a recess 25 (see Figure 4), and the steel plate 16 that forms the connector 15 is accommodated in the recess 25.

A pair of restraint plates 21 are connected to each other at their abutment surfaces 22 with the round steel bars 11 housed in the through holes 23 and the steel plates 16 housed in the recesses 25, thereby forming the wooden restraint material 20 with the core material 10 sandwiched inside.

The restraint plate 21 is made of solid wood or laminated wood, formed by stacking multiple lamina parallel to the abutment surface 22 and gluing them together. The lamination direction of the lamina may be perpendicular to the abutment surface 22, and is not particularly limited. As described in detail below, the cross-sectional area, cross-sectional rigidity, Young's modulus, etc. of the wooden restraint member 20 are set to prevent overall 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.

Although not shown in the figures, the wooden restraint member may be formed from a single axial piece of wooden material. However, since it is not easy to bore a small diameter through hole in the axial direction with high precision in such a single axial piece of wooden restraint member, it is preferable to form it from a pair of restraint plates 21 as shown in the figures, from the standpoint of ease of manufacturing the through hole and machining precision.

As shown in Figure 4, the wooden restraint member 20 is formed by bonding the contact surfaces 22 of a pair of restraint plates 21 with adhesive 30, resulting in a buckling restrained brace 100 comprising a core material 10 and wooden restraint member 20. Examples of adhesives that can be used for the adhesive 30 include urethane-based adhesives and epoxy-based adhesives.

As shown in Figure 5, at the end of the wooden restraint material 20, a predetermined gap G is provided between the through hole 23 and recess 25 and the round steel bar 11 and steel plate 16 housed therein. Here, there may be a configuration in which there is no gap G, or a configuration in which there is a gap only on the left and right sides of the steel plate 16.

In this way, by providing a gap G between the through holes 23 and recesses 25 and the round steel bars 11 and steel plates 16, when the buckling restrained brace 100 incorporated into the frame deforms during an earthquake, the round steel bars 11 and steel plates 16 come into contact with the through holes 23 and recesses 25, preventing damage to the restraint plates 21 due to pressure being applied to their wall surfaces.

On the other hand, as shown in Figure 6, in the center of the wooden restraint material 20, the round steel bar 11 is tightly fitted into the through hole 23.

Although not shown in the figure, there may be a gap between the round steel bar 11 and the through hole 23, and this gap may be blocked by unbonded material.

The buckling restraint brace 100 is manufactured by inserting round steel bars 11 into axial through-holes 23 provided on the abutment surfaces 22 of a pair of restraint plates 21, and then bonding the abutment surfaces 22 together with adhesive 30. This allows for easy manufacturing thanks to the simple configuration of components and simple connection method.

Furthermore, a pair of restraint plates 21 are connected to form a wooden restraint member 20 with a closed structure, and the core member 10 made of round steel bars 11 is surrounded by the wooden restraint member 20. Therefore, even when the buckling restraint brace 100 is applied to the frame of a wooden building, there is no risk of it appearing out of place with the structural components.

In addition, Figures 7 and 8 both show modified examples of buckling restraint braces.

The buckling restrained brace 100A shown in Figure 7 differs from the buckling restrained brace 100 in that the splitting prevention means 40, consisting of a driven or screwed material, is embedded from the side of one restraining plate 21 to the other restraining plate 21.

Materials to be driven into include nails, while materials to be screwed into include wood screws and bolts.

In the illustrated example, split prevention means 40 are provided in a staggered arrangement at the left and right positions on the top and bottom surfaces of both restraint plates 21.

In this way, in addition to connecting the restraint plates 21 with the adhesive 30, the anti-splitting means 40 is embedded from the side of one restraint plate 21 to the other restraint plate 21, which effectively prevents the restraint plates 21 from splitting and also functions as a fail-safe by preventing the restraint plates 21 from separating at the contact surfaces 22 in the event of a major earthquake, etc.

On the other hand, the buckling restraint brace 100B shown in Figure 8 differs from the buckling restraint brace 100 in that it has the core material 10A shown in Figure 2 inside.

The through hole 23 (and the half-split holes 24 that form it) are machined to dimensions that allow the steel pipe 18 to be accommodated, and the steel pipe 18 is accommodated in the through hole 23, with the round bar 11 accommodated inside the steel pipe 18.

In this way, since the wall of the through hole 23 and the round steel bars 11 do not abut against each other, it is possible to prevent, for example, a buckled round steel bar 11 from abutting directly against the wall of the through hole 23, which could cause the wooden restraint material 20 to be pressed against the round steel bars 11 and break.

[Framework incorporating buckling restraint braces]
Next, an example of a building frame incorporating a buckling restrained brace according to an embodiment will be described with reference to Figures 9 and 10. Here, Figure 9 is a diagram showing a state in which a buckling restrained brace according to an embodiment is incorporated into the frame of a wooden building or the like. Also, Figure 10 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 9 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 steel plate 16 that forms the connection body 15 between the gusset plate GP and the core material 10 is joined by a high-tension bolt via a splice plate SP, and the steel plate 17 that forms the connection body 15 between the fin stiffener FS and the splice plate SP is joined by a high-tension bolt.

As shown in Figure 10, when a large earthquake occurs, deformation of the structural plane 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 G between the round steel bars 11 of the core member 10 and the through holes 23 of the wooden restraining members 20. This gap G absorbs the deformation of the core member 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 restraining members 20. Furthermore, a gap G is also provided between the steel plates 16 of the connectors 15 and the recesses 25 of the wooden restraining members 20. This allows the gap G to absorb the expansion and contraction of the core member 10 when it expands and contracts in response to deformation of the structural surface, preventing the expanding and contracting core member 10 from contacting the wall surfaces of the recesses 25 and further compressing them, damaging the wooden restraining members 20. However, the buckling restrained brace may also have a configuration without the gap G, as described above.

[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 9 as the overall bending stress curve for the buckling-restrained brace. In Figure 9, 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 9 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.

Here, in addition to examining the relationship between the compressive strength of the restraining plate and the stiffening force acting as described above, 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).

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.

10, 10A: Core material 11: Round steel 13: Shear stopper 15: Connector 16, 17: Steel plate 16a, 17a: Bolt hole 18: Steel pipe 19: Engagement groove 20: Wooden restraint material 21: Restraint plate 22: Contact surface 23: Through hole 24: Half-split hole 25: Recess 26: Half-split recess 30: Adhesive 40: Splitting prevention means 100, 100A, 100B: Buckling restrained brace A: Plasticized region S: Frame (structural surface)
C: Pillar B: Beam GP: Gusset plate FS: Fin stiffener SP: Splice plate

Claims (2)

Axial wooden restraints;
a shaft-shaped steel core member inserted into an axial through-hole provided in the wooden restraint member;
A connector having a cross-shaped cross section made of a steel plate and connected to another member is joined to both ends of the core material,
The end of the wooden restraint member is provided with a recess at a position corresponding to the connector so as not to interfere with the connector,
A portion of the connector is housed in the recess,
The core material is a steel pipe and a round bar that penetrates the inside of the steel pipe,
This buckling restraint brace is characterized in that two loose grooves, which are engagement grooves, are provided at corresponding positions on the steel pipe, holes are provided in the round steel bar at positions corresponding to the engagement grooves, and the round steel bar is positioned relative to the steel pipe by inserting a pin into the communicating hole formed by the two engagement grooves and the holes . Axial wooden restraints;
a shaft-shaped steel core member inserted into an axial through-hole provided in the wooden restraint member;
The wooden restraint member is made of wood and is formed by a pair of restraint plates,
half-split holes that form the through holes are provided at corresponding positions on the contact surfaces of the pair of restraint plates,
the pair of restraint plates are connected at the contact surfaces via an adhesive;
a plurality of split prevention means for preventing the wooden restraining material from splitting, which are made of a material to be driven or screwed into, are disposed in a staggered pattern in the longitudinal direction of the restraining plates at left and right positions on the surfaces of both the restraining plates, and are embedded from one of the restraining plates to the other;
The core material is a steel pipe and a round bar that penetrates the inside of the steel pipe,
This buckling restraint brace is characterized in that two loose grooves, which are engagement grooves, are provided at corresponding positions on the steel pipe, holes are provided in the round steel bar at positions corresponding to the engagement grooves, and the round steel bar is positioned relative to the steel pipe by inserting a pin into the communicating hole formed by the two engagement grooves and the holes .