Buckling restraint brace

Abstract

To provide a buckling restrained brace capable of maintaining a high buckling restraint force by preventing cracking of wooden restraints even when bending occurs around the brace axis of the restraint material due to out-of-plane deformation of a core.SOLUTION: A disclosed buckling restrained brace 1 includes a steel core 3, and a wooden restraints 5 arranged around it. The core 3 has two or more different cross sections in the longitudinal direction. The restraints 5 is formed by bolting two or more wooden pieces arranged to sandwich the core 3. A bolted joint 17 is constituted of at least a bolt 19, a nut 21, and a washer 23, bolts 19 are arranged in two rows along the entire axial length of the brace material on both sides of the core 3. Regarding bolted joint 17, which resists buckling around the weak axis of core 3, the bolt axial strength of bolted joint 17, which corresponds to the part of core 3 with a larger cross section, is set smaller than the bolt axial strength of the bolted joint 17, which corresponds to the part of core 3 with a smaller cross section.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a buckling restraining brace comprising a steel core material and a wooden restraining material arranged around the core material.

Background Art

[0002] In a building, a brace may be provided as a member that resists shear force during an earthquake. The brace is provided obliquely in the plane of the frame of columns and beams, and is a member that mainly resists the shear deformation of the layer caused by the earthquake load. Since axial tensile and compressive loads repeatedly act during an earthquake, the brace is required to have sufficient strength and energy absorption capacity against both loads.

[0003] Generally, when an axial compressive load acts, there is a risk of buckling in the member, and the buckling reduces the strength and deformation capacity of the member. In a brace, a reduction in strength and energy absorption capacity due to buckling may also occur. Therefore, there is a buckling restraining brace comprising a core material that resists earthquake loads and a restraining material arranged so as to cover the periphery of the core material in order to suppress the buckling deformation of the core material. FIGS. 15 and 16 show such a buckling restraining brace 31 arranged in the plane of a frame composed of columns 33 and beams 35.

[0004] The restraining material is required to have sufficient strength against the bending deformation due to the buckling of the core material, and the restraining material or the joint of the restraining material is required to have sufficient strength against the local compressive force due to the buckling deformation of the core material. FIG. 17 is a cross-sectional view of a buckling restraining brace 31 composed of a core material 37 and a restraining material 39. As the cross-sectional shape of the conventional core material 37, there are a plate (see FIG. 17(a)), a circle (see FIG. 17(b)), a cross (see FIG. 17(c)), an H shape (see FIG. 17(d)), etc. Also, the restraining material 39 covering the core material 37 is often box-shaped (see FIGS. 17(a), (c), (d)) or circular (see FIG. 17(b)).

[0005] Since the local compressive force due to the buckling deformation of the core material 37 is proportional to the compressive load acting on the core material 37 and the amount of buckling deformation of the core material, the greater the gap between the restraint material 39 and the core material 37, the higher the yield strength required for the restraint material 39. Therefore, some provide a filler material 41 such as mortar in the gap between the restraint material 39 and the core material 37 (see Fig. 17(a)). Also, there are some that apply or attach an unbonded material 43 so that the axial force of the core material 37 does not flow into the restraint material 39 (see Fig. 17(a)).

[0006] Regarding the joints between both ends of the buckling restraint brace 31 and the structure, there are a type with a bolt joint 45 joined by bolts shown in Fig. 15 and a type with a pin joint 47 joined by pins shown in Fig. 16. In either case, the width of the core material 37 near the joint is increased, high-strength steel is used, reinforcing ribs are provided, etc., to increase the yield strength of the core material and prevent plasticization, and the joint is designed not to fail first. Also, since the restraint material 39 is made of steel, local failure due to contact with the core material 37 is less likely to occur.

[0007] On the other hand, recently, due to CO 2 emission problems, the use of wood is being promoted. Since wood burns away during a fire, it may be used for building columns and beams by imparting fire resistance through non-combustible treatment, etc. In addition, there are cases where wood is used in part such as floor slabs in steel structures, and recently, the use of wood as a restraint material for braces has been under consideration.

[0008] In Patent Document 1, a buckling restraint brace is proposed that consists of a steel plate-shaped core material and a pair of wooden restraint materials arranged on both sides of the wide surface of the core material, and the two are bolted together at both axial ends. Also, Patent Document 1 proposes a buckling restraint brace in which a pair of wooden restraint materials are arranged so as to sandwich both sides of the web of an H-shaped cross-section core material.

[0009] In Patent Document 2, a buckling restraint brace is proposed, which consists of a steel plate-shaped core material, a pair of wooden restraint materials arranged on both sides of the wide surface of the core material, and a pair of wooden side plates arranged on both sides of the narrow surface of the core material and joined to the restraint plates.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] In the buckling restraint braces disclosed in Patent Documents 1 and 2, the wooden restraint materials are joined by bolts. When the core material buckles, the restraint material is pushed by the core material, and a tensile force acts on the bolt joint. At this time, there is a risk that the bolt joint (the wood or bolt around the bolt joint) may break, and the predetermined buckling restraint effect may not be obtained. In particular, since wood has a low elastic modulus, the wood at the bolt joint may be locally deformed, and as a result, the buckling deformation of the core material may increase and the local compressive force may also increase.

[0012] Therefore, a predetermined performance is required for the bolt joint, but Patent Documents 1 and 2 do not mention the necessary performance. In addition, when the core material buckles, the restraint material is pushed by the core material, and a tensile force acts on the bolt joint, and bending around the longitudinal axis of the long member acts on the restraint material. At this time, there is a risk that the restraint material may be bent and broken, and the predetermined buckling restraint effect may not be obtained.

[0013] As described above, while the use of wood is being promoted, a structure using wood as a restraint material for braces has been proposed. However, in Patent Documents 1 and 2, sufficient consideration has not been given to preventing the bending failure of the restraint material, so the restraint material may break. When the wooden restraint material breaks, the buckling restraint effect drops sharply. Therefore, it is necessary to prevent the breakage of the wood in order for the wooden restraint member to exhibit a sufficient restraint effect.

[0014] The present invention has been made to solve such problems, and even when bending around the brace material axis occurs in the restraint material due to out-of-plane deformation of the core material, it is an object of the present invention to provide a buckling restraint brace that can prevent cracking of the wooden restraint member and maintain a high buckling restraint force.

Means for Solving the Problems

[0015] (1) The buckling restraint brace according to the present invention includes a steel core material and a wooden restraint material disposed around the core material. The core material has two or more different cross-sections in the longitudinal direction. The restraint material is formed by bolt-joining two or more wooden materials arranged so as to sandwich the core material. The bolt joint portion is composed of at least a bolt, a nut, and a washer, and two rows of the bolts are arranged over the entire length in the brace material axis direction at both side surface positions of the core material. Regarding the bolt joint portion that resists buckling around the weak axis direction of the core material, the axial tensile strength of the bolt joint portion corresponding to the portion where the cross-section of the core material is large is smaller than the axial tensile strength of the bolt joint portion corresponding to the portion where the cross-section of the core material is small.

[0016] (2) Further, in the above (1), the cross-section of the core material is characterized in that it is larger at the longitudinal end than at the longitudinal center portion.

[0017] (3) Further, in the one described in the above (1) or (2), in a longitudinal range where the axial tensile strength of the bolt joint portion that resists buckling around the weak axis direction of the core material is relatively small, a reinforcing member for bending around the longitudinal member axis is provided in the restraining material.

[0018] (4) Further, in the one described in the above (3), the bending strength of the reinforcing member provided in the restraining material satisfies the following formula. M re ≧P Be (2u Be -B s ) / 4 Here, M re : Bending strength around the brace longitudinal member axis of the reinforcing member [N·mm] P Be : Axial tensile strength of the bolt joint portion that resists buckling around the weak axis direction of the core material [N] u Be : Spacing length between rows of bolt joint portions provided in two rows [mm] B s : Width in the weak axis direction of the core material [mm]

[0019] (5) Further, in the one described in the above (3), in a longitudinal range where the axial tensile strength of the bolt joint portion that resists buckling around the weak axis direction of the core material is relatively large, a reinforcing member for bending around the longitudinal member axis is provided in the restraining material, and the bending strength of the reinforcing member is less than or equal to the bending strength of the reinforcing member provided in the longitudinal range where the axial tensile strength of the bolt joint portion is relatively small.

[0020] (6) Further, in the one described in any one of the above (1) to (5), the core material is composed of flat steel, the cross section at the central portion in the longitudinal direction is rectangular, and the cross section at the end portion in the longitudinal direction is cross-shaped, the wooden member used for the restraining material is formed by adhering a plurality of flat wooden pieces, the wooden pieces are laminated in the thickness direction, and the width direction of the wooden pieces is arranged in a direction orthogonal to the width direction of the flat steel of the core material. [Effect of the Invention]

[0021] According to the present invention, even when bending around the brace member axis occurs in the wooden restraint member due to out-of-plane deformation of the core material, cracking of the restraint member can be prevented, and a high buckling restraint force can be achieved. [Brief Description of the Drawings]

[0022]

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Mode for Carrying Out the Invention

[0023] The buckling restraint brace 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1(a) is an explanatory drawing for explaining the internal structure of the buckling restraint brace 1, and shows the inside in a perspective view of the state seen from the arrow A-A direction in FIG. 2. Further, FIG. 1(b) is a view showing the state seen from the arrow B-B direction in FIG. 1(a). Furthermore, FIG. 2(a) is a view corresponding to the cross section taken along the arrow C-C in FIG. 1(a), and FIG. 2(b) is a view corresponding to the cross section taken along the arrow D-D in FIG. 1(a).

[0024] As shown in FIGS. 1 and 2, the buckling restraint brace 1 according to the present embodiment includes a steel core material 3 and a wooden restraint material 5 disposed around the core material 3. Hereinafter, each component will be described in detail.

[0025] <Core Material> The outermost ends in the longitudinal direction of the core material 3 are joints 6 with the steel frame structure. In the case of the high-strength bolt type as in this example, bolt holes 7 are provided. Also, in the case of the pin joint type, a clevis is provided at the end of the core material in the longitudinal direction. The joint 6 is often not plasticized, and the cross-sectional size may be increased at the joint 6 or high-strength steel may be used.

[0026] The cross-section of the core material varies in the longitudinal direction and has at least two or more different cross-sectional shapes. When varying the cross-sectional shape, examples include increasing the width or plate thickness in a part of the core material 3 or providing reinforcing ribs 13 so as to adjust the plasticized range or prevent plasticization in a partial range. In the present embodiment, in order to make the central portion in the longitudinal direction of the core material 3 the plasticized portion 9 and the end portion side in the longitudinal direction the plasticization prevention portion 11, the cross-section of the core material at the end portion side in the longitudinal direction is enlarged. Specifically, flat steel is used for the core material 3. The plasticized portion 9 on the central side in the longitudinal direction of the core material has a plate-shaped cross-section as it is, and the plasticization prevention portion 11 on the end portion side in the longitudinal direction of the core material has a cross-shaped cross-section with reinforcing ribs 13 provided on the flat steel. By preventing plasticization on the end portion side, the buckling length is shortened and the buckling strength of the buckling restraint brace 1 can be increased.

[0027] <Restraint material> The restraint material 5 is formed by bolt-joining two or more wooden materials arranged so as to sandwich the core material 3. It is necessary to adjust the strength and size of the restraint material 5 so that it has sufficient strength and rigidity against the bending deformation and local buckling of the core material 3.

[0028] Since the core material 3 is likely to cause out-of-plane displacement around the weak axis, when there are two wooden restraint materials 5, it is desirable to arrange the restraint material 5 on the side that suppresses the deformation around the weak axis (see Fig. 2), and when there are four restraint materials 5, it is desirable to arrange the wooden restraint materials 5 in four directions (see Fig. 4). Also, it may be formed from six or more restraint materials 5 including fine members (see Fig. 4).

[0029] Grooves 15 are formed in the restraint material 5 according to the cross-sectional shape of the core material 3, and thus the entire core material 3 can be covered. Since the plasticization prevention portion 11 of the core material 3 enlarges the cross-sectional shape of the core material as described above, the groove 15 provided in the restraint material 5 becomes larger than the plasticized portion 9, and the bending strength around the brace material axis of the restraint material 5 becomes smaller than that of the plasticized portion 9. In the present invention, in order to prevent the portion of the restraint member 5 with reduced flexural strength from undergoing flexural fracture during buckling of the core member 3, the axial tensile strength of the bolt joint 17 corresponding to this portion is made smaller than that of the bolt joint 17 of the plasticized portion 9. Details will be described later.

[0030] In addition, the wooden restraint member 5 is provided with bolt holes and countersinks for bolt joints. The bolt holes generally have a diameter that is 1 or 2 mm larger than the bolt diameter. The direction in which the core member 3 is likely to buckle depends on the cross-sectional shape of the core member 3, and the orientation of the bolt joint 17 is adjusted so that the direction in which the core member 3 is likely to buckle coincides with the axial direction of the bolt member.

[0031] In addition to sawn timber, wood-based materials such as glued laminated timber, LVL, and CLT may be used for the wooden material. Considering the initial shape irregularities of the core member 3, the size of the groove 15 may be made slightly larger than the cross-sectional shape of the core member 3.

[0032] <Bolt joint> The bolt joint 17 is composed of at least a bolt 19, a nut 21, and a washer 23, and two rows of bolts 19 are arranged over the entire length in the axial direction of the brace member at both side surface positions of the core member 3. The washer 23 uses a steel plate such as a square or circular shape, and its size is adjusted according to the target tensile strength of the bolt joint 17. In addition, an anti-loosening device for the nut 21 such as a spring washer may be provided. Two rows of bolts 19 are provided, one row on each side surface position of the core member 3 so as not to interfere with the core member 3. Since buckling of the core member 3 can occur over the entire length, it is provided over the entire length in the axial direction of the brace member of the bolt joint 17.

[0033] Regarding the bolt joint 17 that resists buckling around the weak axis direction of the core member 3, the axial tensile strength of the bolt joint 17 corresponding to the portion where the cross-section of the core member 3 is large is set to be smaller than the axial tensile strength of the bolt joint 17 corresponding to the portion where the cross-section of the core member 3 is small. In this embodiment, as described above, the central portion in the longitudinal direction of the core material 3 is the plasticized portion 9, and the end portion side in the longitudinal direction is the plasticization prevention portion 11. Therefore, since the cross-section of the core material at the end portion side in the longitudinal direction is relatively large, the axial bearing strength of the bolt at this portion is set to be smaller than that of the bolt joint portion 17 of the plasticized portion 9 on the central side in the longitudinal direction. The reason for this will be described below.

[0034] When the core material 3 is plate-shaped, the core material 3 is likely to buckle in the plate thickness direction. When the core material 3 has a flat cross-sectional shape, buckling is likely to occur in the direction with a small width. When the restraint material 5 is pushed due to the buckling of the core material 3, the bolts 19 on both side surfaces of the core material 3 resist. Therefore, for the restraint material 5, bending around the brace material axis occurs with the bolt portion as the fulcrum and the core material contact portion as the loading point. Therefore, when a bending moment greater than the bearing strength acts on the restraint material 5, the restraint material 5 may be damaged and a sufficient buckling restraint effect may not be obtained.

[0035] Since the reaction force of the bolt joint portion 17 affects the bending moment acting on the restraint material 5, by reducing the bearing strength of the bolt joint portion 17, an increase in the bending moment acting on the restraint material 5 can be suppressed, and bending failure of the restraint material 5 can be prevented. That is, it is desirable to change the bearing strength of the bolt joint portion 17 according to the bending strength of the restraint material 5 around the brace material axis.

[0036] The cross-sectional shape of the restraint material 5 affects the bending strength of the restraint material 5, and the cross-sectional shape of the restraint material 5 is affected by the groove 15 that matches the cross-sectional shape of the core material 3. Therefore, when the cross-sectional shape of the core material 3 changes in the longitudinal direction range, by changing the bearing strength of the bolt joint portion 17 accordingly, bending failure of the restraint material 5 can be prevented. Note that the bearing strength of the bolt joint portion 17 is determined by the tensile strength of the bolt 19 or the embedding strength of the bolt joint portion 17 in the wood, so it can be adjusted by the bolt diameter, bolt strength, wood strength, and contact area of the embedding portion.

[0037] Next, the upper limit of the axial bearing strength of the bolt joint portion 17 that resists buckling around the weak axis direction of the core material 3 will be described. Since the yield strength of the bolt joint 17 is reduced from the perspective of preventing the bending failure of the restraint member 5, the upper limit of the yield strength of the bolt joint 17 depends on the bending strength of the restraint member 5. When the core material 3 buckles, out-of-plane deformation occurs around the weak axis direction of the core material. Due to this out-of-plane deformation, a distributed load acts on the wooden restraint member 5 at the contact part with the core material 3, and a tensile force acts on the bolt 19 to resist it.

[0038] Due to this load, a bending moment distribution around the brace material axis as shown in Fig. 5 occurs in the restraint member 5. As shown in Fig. 6, when the part where the groove 15 is provided by the reinforcing rib 13 etc. is in the restraint member 5, the bending strength of this part is lower than that of other parts, and there is a risk of the occurrence of the bending fracture part 25 in this part due to the bending around the brace material axis described above.

[0039] Since the reaction force of the bolt 19 and the distributed load due to the buckling of the core material 3 are in equilibrium, the distributed load due to the buckling of the core material 3 is expressed by the following formula. W s =2P Be / B s Here, W s : Distributed load due to buckling of the core material per bolt pitch length [N / mm] P Be : Reaction force of the bolt joint [N] B s : Width of the core material in the weak axis direction [mm]

[0040] When a distributed load acts in the middle of a simply supported beam, the maximum value M of the bending moment max is obtained by the following formula. M max =RA(a + RA / 2w) Here, RA: Reaction force at one support point (assumed as point A) [N] a: Distance from point A to the acting end of the distributed load [mm] w: Acting distributed load [N / mm] Substituting RA = P Be and a = (u Be - B s) / 2, w = Ws = 2P Be / B s By substituting the above into the formula, the maximum value M of the bending moment shown in Fig. 5 max is expressed by the following formula. M max = P Be (2u Be - B s ) / 4 Here, P Be : Reaction force of the bolt joint [N] u Be : Spacing length between rows of bolt joints provided in two rows [mm] B s : Width in the weak axis direction of the core material [mm] The bending strength M of the restraint member 5 We is greater than or equal to the maximum value M of the bending moment, that is, M max If it is greater than or equal to M We ≧ M max is satisfied, bending failure of the restraint member 5 will not occur. Therefore, M We ≧ P Be (2u Be - B s ) / 4 By arranging the above formula with respect to P Be , the upper limit value of P Be is shown as follows. P Be ≦ 4M we / (2u Be - B s ) Here, P Be : Axial bolt strength of the bolt joint that resists buckling around the weak axis direction of the core material [N] M We : Bending strength around the brace longitudinal member axis of the wooden member [N] u Be : Spacing length between rows of bolt joints provided in two rows [mm] B s : Width in the weak axis direction of the core material [mm] As described above, when the bolt joint 17 is regarded as a fulcrum and the center side of the restraint material width in contact with the core material 3 is regarded as a loading point, by suppressing the strength of the bolt joint 17 below the upper limit shown in the above formula, bending failure of the restraint material 5 can be prevented.

[0041] In this embodiment, since the axial tensile strength of the bolt joint 17 corresponding to the portion where the cross-section of the core material 3 is large is set to be smaller than the axial tensile strength of the bolt joint 17 corresponding to the portion where the cross-section of the core material 3 is small, the breakage of the wooden restraint material 5 can be suppressed, and a high buckling restraint effect can be expected.

[0042] Hereinafter, other embodiments of the restraint material 5 will be described. When a wooden member formed by bonding a plurality of wood pieces, that is, a so-called glued laminated timber, is used as the restraint material 5, it is preferable to arrange the glued laminated timber in a direction in which the width direction of the flat steel as the core material 3 and the width direction of the wood pieces, that is, the width direction of the glued laminated timber, are orthogonal.

[0043] When the core material 3 is flat steel, since the core material 3 is likely to buckle in the plate thickness direction, the restraint material 5 is provided at a position facing the width surface of the flat steel, and a large wooden material in the core material width direction is required. Since the glued laminated timber is formed by bonding flat wooden pieces in the height direction, the dimensional adjustment in the height direction is easy. Therefore, by arranging the glued laminated timber so that the height direction thereof coincides with the width direction of the flat steel, it becomes easy to manufacture a large wooden material in the core material width direction.

[0044] A reinforcing member 27 against bending around the longitudinal member axis may be provided in the longitudinal range of the restraint material 5 where the axial tensile strength of the bolt joint 17 that resists buckling around the weak axis direction of the core material 3 is relatively small.

[0045] The bending failure of the restraint material 5 can be prevented by reducing the tensile strength of the bolt joint 17. On the other hand, if the tensile strength of the bolt joint 17 is too low, the wooden members constituting the restraint material 5 may deviate, and there is a risk that the buckling deformation of the core material 3 cannot be suppressed. Therefore, it is necessary to ensure a certain level of tensile strength of the bolt joint 17. If the tensile strength is at a level that can cause bending failure of the restraint material 5, it is necessary to reinforce the restraint material 5 to prevent bending failure.

[0046] As the reinforcing member 27, a steel plate, a steel bar, a bolt 19, etc. can be used. Fig. 7 shows an example in which a steel plate is attached to the surface of the restraint member 5 as the reinforcing member 27, and Fig. 8 shows an example in which a bolt 19 (see Fig. 8(c)) or a steel bar (see Fig. 8(b)) is passed through the wooden restraint member 5 as the reinforcing member 27. When a steel plate is used as the reinforcing member 27, as shown in Fig. 7, by joining the reinforcing member 27 to the restraint member 5 with a fastening member 29 such as a nail or a screw, it becomes possible to resist bending around the brace material axis. Also, adhesive bonding may be used instead of screw bonding.

[0047] Since the bending moment around the brace material axis generated in the restraint member 5 is affected by the bolt bearing capacity, the required bending strength of the reinforcing member 27 can also be defined by the bolt bearing capacity. That is, for the reinforcing member 27, if its bending strength is equal to or greater than the maximum value of the bending moment, it has sufficient strength to prevent the bending failure of the restraint member 5. Therefore, M re ≧M max M re ≧P Be (2u Be -B s ) / 4 Here, M re : Bending strength of the reinforcing member around the brace longitudinal material axis [N] P Be : Bolt axial bearing capacity of the bolt joint that resists buckling around the weak axis direction of the core material [N] u Be : Column spacing length of the bolt joint provided in two rows [mm] B s : Width of the core material in the weak axis direction [mm]

[0048] In the above, the reinforcing member 27 for preventing the bending failure of the restraint member 5 around the brace material axis is provided in a predetermined range in the longitudinal direction of the restraint member 5 where the bolt axial bearing capacity of the bolt joint 17 is relatively small, specifically at the longitudinal end. However, when the cross-sectional shape of the core material 3 is larger and the strength is higher than that of the restraint material 5, bending failure around the brace material axis can occur even in a range where the cross-sectional shape of the restraint material 5 is relatively large. In this case, by providing the reinforcing member 27 also in the range where the cross-sectional shape of the restraint material 5 is relatively large, bending failure can be prevented and a high buckling restraint effect can be obtained.

[0049] In this case, in the range where the cross-sectional shape of the restraint material 5 is relatively large, the bending strength of the restraint material 5 around the brace material axis is larger than that in the range where the cross-sectional shape of the restraint material 5 is relatively small. Therefore, the reinforcing member 27 to be provided can obtain a sufficient effect even with a bending strength lower than that of the reinforcing member 27 in the range where the cross-sectional shape of the restraint material 5 is relatively small.

[0050] In addition, the bolts 19 arranged in a direction orthogonal to the bolts 19 that resist buckling around the weak axis direction of the core material 3, that is, around the weak axis of the core material 3, as shown in FIG. 4, also function as the reinforcing member 27 in addition to the assembly of the restraint material 5, and thus can be used in common.

Example

[0051] A repeated loading experiment was conducted on the test body of the buckling restraint brace 1 to confirm the effect of the present invention, and the following will be described. As shown in FIGS. 9 and 10, the test body 30 is a buckling restraint brace 1 in which the core material 3 with a plasticized portion 9 having a plate cross-section and a plasticization prevention portion 11 having a cross-shaped cross-section is braced by four pieces of wood, and bolts 19 are provided in two rows in the plate thickness direction of the core plate over the entire length of the brace to prevent buckling around the weak axis of the core material 3. In addition, a joint using a drift pin and a steel plate is used in combination as a longitudinal displacement prevention of the wood located at a position facing the plate width surface of the core material 3. The No. 1 test body was used as a comparative example, and the No. 2 test body was used as an invention example. Details are shown in Table 1

[0052]

Table 1

[0053] The No. 1 specimen is also provided with bolts 19 in the plasticization prevention part 11 on the longitudinal end side, while the No. 2 specimen is not provided with bolts 19 in the plasticization prevention part 11.

[0054] The loading is to apply a repeated tensile and compressive load in the axial direction of the brace. Based on the average strain of the plasticized part 9 of the core material, it is a gradually increasing amplitude repeated load that gradually increases the amplitude by 0.5% while repeating 2 cycles for each amplitude.

[0055] Figures 11 and 12 show the load-deformation relationship of the experiment. As shown in Figure 11, for the No. 1 specimen, after 2 cycles of 0.5% and 1.0%, when compressing in the 1st cycle with a strain amplitude of 1.5%, the restraint material 5 was damaged and the load decreased.

[0056] For the No. 2 specimen, as shown in Figure 12, after 2 cycles of 0.5%, 1.0%, 1.5%, and 2.0%, when compressing in the 1st cycle with a strain amplitude of 2.5%, the restraint material 5 was damaged and the load decreased, demonstrating a higher plastic deformation capacity than the No. 1 specimen.

[0057] Figures 13 and 14 show the situation of the specimen 30 after the experiment. For the No. 1 specimen, as shown in Figure 13, a bending failure part 25 occurred at the cross-sectional part of the plasticization prevention part 11 and the wood was damaged. This is the same failure as shown in Figure 6(b), and due to this failure, the buckling restraint effect disappeared and the load decreased.

[0058] On the other hand, for the No. 2 specimen, as shown in Figure 14, there is no failure in the wood of the plasticization prevention part 11. This is because bolts 19 are not provided in the plasticization prevention part 11, so the bending moment as shown in Figure 5 does not occur in the first place. Therefore, this experiment shows that the bolts 19 have a great influence on the bending failure around the axis of the brace material of the restraint material 5, and it is confirmed that a high buckling restraint effect can be obtained by preventing the failure of the wood.

Explanation of symbols

[0059] 1 Buckling restraint brace 3 Core material 5 Restraint material 6 Joint 7 Bolt hole 9 Plasticized part 11 Plasticization prevention part 13 Reinforcing rib 15 Groove 17 Bolt joint 19 Bolt 21 Nut 23 Washer 25 Bending fracture part 27 Reinforcing member 29 Fastening material 30 Specimen 31 Buckling restraint brace (conventional) 33 Column 35 Beam 37 Core material 39 Restraint material 41 Filling material 43 Unbonded material 45 Bolt joint 47 Pin joint

Claims

1. A buckling-restrained brace comprising a steel core material and a wooden restraint material disposed around the core material, wherein the core material has two or more different cross-sections in the longitudinal direction, the restraint material is formed by bolt-joining two or more wooden materials arranged so as to sandwich the core material, the bolt-joined portion is composed of at least a bolt, a nut, and a washer, and two rows of the bolts are arranged over the entire length in the axial direction of the brace material at both side surface positions of the core material, Regarding the bolt-joined portion that resists buckling around the weak axis direction of the core material, the axial tensile strength of the bolt-joined portion corresponding to the location where the cross-section of the core material is large is smaller than the axial tensile strength of the bolt-joined portion corresponding to the location where the cross-section of the core material is small. A buckling-restrained brace characterized by this.

2. The buckling-restrained brace according to Claim 1, wherein the cross-section of the core material is larger at the longitudinal end than at the longitudinal center.

3. The buckling-restrained brace according to Claim 1 or 2, wherein a reinforcing member against bending around the longitudinal member axis is provided in the restraint material in a longitudinal range where the axial tensile strength of the bolt-joined portion that resists buckling around the weak axis direction of the core material is relatively small.

4. The buckling-restrained brace according to Claim 3, wherein the bending strength of the reinforcing member provided in the restraint material satisfies the following formula. M re ≥P Be (2u Be -B s ) / 4 Here, M re : Bending strength [N·mm] around the brace longitudinal member axis of the reinforcing member P Be : Axial tensile strength [N] of the bolt joint that resists buckling around the minor axis direction of the core material u Be : Column pitch of bolt joints provided in two columns [mm] B s : Width of the core material in the minor axis direction [mm]

5. In a longitudinal range where the axial tensile strength of the bolt-joined portion that resists buckling around the weak axis direction of the core material is relatively large, a reinforcing member against bending around the longitudinal member axis is provided in the restraint material, and the bending strength of the reinforcing member is equal to or less than the bending strength of the reinforcing member provided in the longitudinal range where the axial tensile strength of the bolt-joined portion is relatively small. The buckling-restrained brace according to Claim 3, characterized by this.

6. The core material is composed of flat steel, the cross-section at the longitudinal center is rectangular, and the cross-section at the longitudinal end is cross-shaped, The wooden member used for the restraint material is formed by adhering a plurality of flat wooden pieces, the wooden pieces are laminated in the thickness direction, and the width direction of the wooden pieces is arranged in a direction orthogonal to the width direction of the flat steel of the core material. The buckling-restrained brace according to Claim 1 or 2, characterized by this.

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