JP2011143698A - Woody plate laminating compacting joining structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joining structure that attains rigid joints and total strength with woody materials and to provide a woody frame structure that can be designed with the same calculation system as Rahmen frame in a steel structure. <P>SOLUTION: In laminating a structural plate group 1' constituting a woody plate laminate member 1, an overlapping part A is provided by alternately inserting or intersecting at an arbitrary position and arbitrary angle a structural plate group 2' of a separate woody plate laminate member 2. Then, the overlapped part is fixedly compacted by a proper compacting means until non-overlapped parts B are each integrated. The rigidity and yield strength of the overlapped part are dramatically improved by the compaction, while the non-overlapped part is provided with performance equivalent to a regular axial material. A woody frame structure is formed primarily comprising joint junction by combining regular axial materials with members of a dog leg shape, T shape, cross shape, X shape or the like which are obtained by changing the overlapping angle, overlapping position, and the like. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a joining structure that enables rigidity and full strength in a joining method using a wood material, and a wood frame structure using the joining structure.

  A method of drastically increasing rigidity and strength by impregnating and fixing resin to wood has been studied for a long time (Non-Patent Document 1), such as the shape of the base material, temperature, pressure, time, resin used, form shape, etc. By optimizing the above conditions, reinforced wood with high dimensional stability according to the characteristics of the tree species is provided, and it is used for ornaments, blade handles, door handles, sports equipment and the like. In recent years, it is also called compressed wood or consolidated wood, and fixing by only heat treatment (Non-Patent Document 2) has been established without fixing with resin, and it is also used for floor boards and table tops. It has also been proposed to use a T-shaped member (Non-Patent Document 3) obtained by overlapping and compressing plate materials as a chair frame.

  As an example of applying this reinforced wood to a building structure, it can be used as a joint, that is, as a substitute for joint hardware such as a steel gusset plate or drift pin (Patent Document 1), or in a traditional construction method. Examples include substitutes for hardwood such as hardwood plugs and dowels (for example, Non-Patent Document 4).

  In addition, as an example of strengthening the shaft material itself, a high-strength laminated material (Patent Document 2) obtained by constituting a compacted and strengthened saw plate, or a member end portion to which a joint hardware is attached, constitutes a truss structure. A technique (nonpatent literature 5) is also mentioned.

  On the other hand, among the bonding methods, in adhesive bonding, which is considered to be a rigid joint method, finger joints are applied to corner joints (Patent Documents 3 and 4), and scarf joints are applied to laminated joints. (Non-Patent Document 6).

Patent Publication 6-99412 Patent Publication 2008-44314 Patent Publication 2001-90189 Patent Publication 2001-173094 Patent Publication 2006-213689 A. J. et al. STAMM, R.M. M.M. SEBROG: Resin-Treated, Laminated, Compressed Wood, Forest Products Laboratory, R1268, USDA (1941) Iida Ikuho, Norimoto Kyo: "Restoration of Compression Set", Journal of the Wood Society, 33 (12), 929-933 (1987) Ryoichi Hasegawa, “Study on Advanced Utilization of Soft Wood (Part 1) Strength Performance of Joints Using Laminate Compression Technology”, 2005 Gifu Prefectural Research Institute for Life Technology No. 8, p59-64 (2006) Motohiro Tsuji, Akuhisa Kitamori, A. J. et al. M.M. Leijten, Kohei Komatsu: "Effects of moisture content change due to temperature and humidity on contact stress of traditional scallop-plugged joints (3rd report) Evaluation of pull-out strength performance of horn joints using cedar-compressed wood-embedded plugs" , Journal of the Wood Society, 52 (6), 358-367 (2006) Takeshi Kawauchi, et al., “Attachment Test of Bolt Joint of End-Reinforced Wooden Truss Member” Summary of Academic Lectures of the Architectural Institute of Japan (China) C-1, Structure III, September 2008, p323-324 (2008) Kimura, K. et al., "Study on All-Strength Adhesive Joints of Glulam" Summary of Annual Meeting of the Architectural Institute of Japan (Hokuriku) C-1, Structure III, August 1992, 69-70 (1992)

  An object of the present invention is to provide a wood frame structure that can be applied as a building structure by applying a consolidation technique to realize a joint structure that is rigid and full strength with a wood material. Here, the joint part of the rigid joint refers to a joint part that can calculate the deformation of the entire frame only by calculating the deformation of the member while ignoring the deformation of the joint part in the structural calculation. In addition, it refers to a joint where the joint strength exceeds the strength of the constituent members.

  Since the usual joining methods of wood members cannot be welded like metal members and resin members, joining that is rigid and strong is rare. Some joint joints can be realized by adhesive joining as in the example of Non-Patent Document 6, but not joint joint joining.

  In the furniture field and joinery field, compaction technology is applied to joints such as those described in Non-Patent Document 3, and both the rigidity and strength of the joints are superior to those of existing joints using tenon or dowels. ing. However, since the whole component is consolidated, it is not configured to satisfy the conditions of rigid joint and full strength. It is extremely rare to perform structural calculations on ordinary furniture and joinery, etc., but not only to improve rigidity and proof stress, but also to maintain a balance between deformation performance and proof strength between joints and members. Controlling the form of destruction is also an important factor for ensuring structural safety.

  On the other hand, in the construction field, various joining methods have been developed so far. However, since these are based on mechanical joining that makes full use of joint hardware, as described in Patent Document 1 and Non-Patent Document 4, the range in which reinforced wood and compressed wood are used remains a substitute for joint hardware. ing.

  Normally, joints between columns and beams are inevitable in wooden construction structures, but in order to establish a frame structure, a large force must be borne in this part, and the moment is the maximum in structural calculations. It is normal that it becomes a location. Therefore, since it is fundamental to break from the joint joint, it is desirable to give as much proof stress as possible. However, the bonding strength in mechanical bonding is usually much lower than the bending strength of the member because the presence of the joint metal itself must cause the cross section of the member to be lost. In addition, since the joint itself itself is greatly deformed by joining metal fittings or the like into the wood, what can be assumed to be a rigid joint cannot be realized in mechanical joining.

  Regarding rigidity, the only thing that can be assumed to be rigid joints can be realized by using an adhesive. However, by simply joining the beam-column joints with an adhesive, a rigid joint can be realized, but it is difficult to make it compatible with full strength. This is mainly due to the fact that split fracture occurs due to secondary stress represented by transverse tensile stress. This is an item that requires attention as the frame size increases. In other words, in joint joining, stress concentration becomes more conspicuous as the rigidity is increased due to the fit shape of the member, and the effect of stress generated in the direction perpendicular to the fiber is greatly affected.

  Thus, even if it is going to make both rigid joint and full strength by joint joining, a stress state differs greatly from the case of joint joining like a nonpatent literature 6, and cannot be realized easily. This is because wood is an orthotropic material, that is, the strength in the direction perpendicular to the fiber is extremely lower than that in the fiber direction, which is an unavoidable problem.

  In recent years, a specific joining method has been used as a wooden frame, but it is different from the rigid frame frame in a steel structure, and it is a special frame structure in which the deformation of the joint joint cannot be ignored. . When actually calculating deformation in an existing wooden rigid frame, the joint is defined as a semi-rigid joint and is accompanied by a structural calculation that takes into account the deformation of the joint. The structural calculation is dramatically more complicated than the rigid joint. In addition, some of the theoretical formulas for deformation of the joint itself are derived by researchers specializing in wood structures, but they are complex calculations that can be handled by general architects. It's hard to say.

  As described above, the current wood frame structure is in a state of being significantly restricted by the deformation performance and the proof stress of the joint joint, and therefore cannot fully utilize the deformation performance and proof strength possessed by the member. In addition, in the case of a wooden ramen frame, since the joint portion is a semi-rigid joint at the time of designing, it takes much labor in the structural calculation process. Therefore, the structural design effort can be reduced by replacing the joint with a rigid and full-strength one.

  In the first place, the ramen frame is a structural frame based on the premise that the intersection of a column and a beam is a rigid joint, as in a steel structure. There should be a ramen frame.

  Therefore, in the present invention, a technique that enables rigidity and full strength is not used as a joining method for building structures, but by a joining structure in which two members can be regarded as a continuous body, rather than a joint joining by ordinary mechanical joining. It is provided as any angled member that replaces the mouth joint. In addition, the application form applicable to furniture structure and joinery structure is shown, and finally, a wooden frame structure that can be defined as a ramen frame based on the same design concept as a steel structure is provided.

  First, the bonding structure of claim 1 will be described by taking an example of forming an L-shaped bonding structure (FIGS. 1 and 2). In this case, the wood board laminated member is defined as a member obtained by laminating and adhering components having the same shape made of wood or wood-based material. Specifically, it refers to a member made by laminating and adhering a plate material such as a rotary single plate, sliced single plate, or lamina, and various wood boards such as fiberboard and OSB. In the case of a plate laminate (so-called LVL), a relatively thick plate, it corresponds to a laminated material, but the shape of the component plate is not limited to a rectangle, a polygonal plate, a disc, What is comprised by arbitrary shapes, such as a trapezoid board, is also contained in a wooden board laminated member.

  With the upper component plate (1 ') and several corners of the component plate as a reference, the second component plate (2') is sandwiched alternately and orthogonally, and arranged in an L shape. This is compacted by 50% or more with a press machine and fixed into a predetermined shape. Here, 50% consolidation refers to the density of the overlapping portion, and is the pressure density at which the non-overlapping portions of the constituent plate groups contact each other. At the time of pressing, it is possible to apply an adhesive to the laminated surface to bond the constituent plates together, and to perform consolidation fixing by applying an appropriate heat treatment as described in Non-Patent Document 2 or Patent Document 1. Moreover, as shown in the below-mentioned Example, it is also possible to add dimensional stability by carrying out the consolidation fixation using the structural board which impregnated and dried beforehand with the synthetic resin liquid.

  The greatest feature of this joint structure is that wood fibers from two directions are intertwined in the overlapping portion, and the wood fibers are continuous at the boundary between the overlapping portion and the non-overlapping portion. Further, in the present invention, various shapes can be realized by changing the insertion angle and the overlapping position or making them orthogonal to each other, and irregular-shaped members such as a H shape, a T shape, a cross shape, and an X shape can be formed (FIG. 3).

  Claim 2 is provided as a member of these irregular shapes, and is a member that replaces the existing joint joining that enables rigid joint and / or full strength by the joining structure of claim 1.

  Until now, wood-based structural members were usually straight through materials except for curved laminated materials, but various angled members can be obtained by applying the joining structure of the present invention. Here, when the joint structure portion is rigid and full strength, the joint structure portion can be regarded as a continuous body without being regarded as a joint portion. Such an angled member exists in the steel structure, but has not been realized in the wood material.

  Consolidation of overlapping parts improves rigidity and yield strength, cross-over effect reduces anisotropy, and non-overlapping parts and overlapping parts with significantly different stiffness It is also mentioned as a feature. Thereby, the overlapping portion can resist the complex composite stress which has been a problem in Patent Documents 3 and 4, and is remarkably strengthened particularly against the split in the direction perpendicular to the fiber. In addition, the breaking point when an opening / closing moment is applied to this wood-plate laminated consolidated member is that it avoids fracture at the overlapping part due to consolidation, and moves to the boundary with the overlapping part where the moment is maximum in the non-overlapping part. Will do. At this time, the factor that determines the joint strength is the bending strength of the non-overlapping portion of the boundary. That is, the fact that the component plates are not broken at the boundary, that is, the member strength is secured at the boundary. Therefore, the joining strength can be easily calculated from the bending strength of the member.

  There is no restriction on the configuration plate shape, for example, a trapezoidal joining structure member (FIG. 4) is also effective, a rectangular wooden board laminated member and a triangular wooden board laminated member, a trapezoid wooden board laminated member and a circular wooden board laminated member Many combinations on the joining structure such as members are conceivable. Furthermore, it can be set as a member of application forms (FIG. 5), such as a square shape and P shape, by combining said joining structure in multiple places. However, since the shape of these wood board laminated consolidation members is restricted by the size of the pressing surface of the press machine, a large press machine is required to achieve a large building member.

  In addition, although the case where a component plate is additionally inserted into a non-overlapping portion and molded (FIG. 6) can be considered, even if the strength of the member is improved, the fibers of the added component plate are discontinuous at the boundary. The boundary portion is locally weak and cannot be regarded as the full strength as a joint portion. The present invention is different from Non-Patent Document 1 in that it is meaningful to maintain the full strength by dramatically improving only the overlapping portion with respect to the bending strength of the member.

  Claim 3 relates to a wood frame structure using the same. As an example using the L-shape, a frame such as a gate shape or a square shape can be formed by sufficiently securing the length of the non-overlapping portion and joining the end portions that have been jointed (FIGS. 7 and 8). ). However, as mentioned above, the size of the wood-plate laminated compaction joint member is limited by the size of the press machine. Build (Figure 9).

  In any case, in the frame structure using the wood board laminated consolidation member, the joint is mainly used, but there is no restriction on the joint method that can be adopted. Since the ease of joint processing is maintained in the non-overlapping parts due to the structural features of the wood board consolidated joint members, everything from rigid joints to pin joints can be selected according to the building scale . In addition, regarding the joint position with the other shaft material, the length distribution of the non-overlapping part is adjusted so that the longitudinal connection can be performed at the most efficient position in consideration of the moment distribution of the housing. Incorporating joints with high energy absorption is also an option. Consideration should be given so that construction errors of the entire frame can be absorbed by this joint.

  The wooden frame structure constructed according to the present invention is a form of a wooden frame structure that pursues structural mechanical rationality because the performance of the corner portion where the moment is maximum has been dramatically improved. Yes, it is a technology that realizes a completely new wooden structure that can be regarded as equivalent to a ramen frame in a steel structure.

  First, since the rigid joint is realized, it can be designed as the same rigid frame as the steel structure without calculating the deformation of the joint when calculating the structure. Moreover, since the overlap part has realized the full strength, the maximum proof stress of a wooden frame frame can be calculated with the bending strength of a non-overlap part.

  As a frame using this wooden board laminated compaction member, if it is a small-scale building, a gate-shaped three-hinge frame can be used as a pin joint (FIG. 7). Even if the building scale is large, if a strong joint with full strength is adopted for the joint, it becomes a simple and clear structure. However, the joint joint has a very high strength joint efficiency equivalent to the plastic hinge of the steel frame, and it has rigidity and toughness. By selecting a high joining method, the best form as a wood frame structure can be realized (FIG. 9). In this respect, it is significant that an existing joint can be selected without selecting a processing machine for processing the joint, and a joint according to the scale of the frame and the required performance can be selected. In general, joint joints are easier to design than joint joints, and structural calculations can be optimized by controlling joint positions. It can be provided as a new structural form to be determined.

  In addition, since it has been necessary to determine the cross-section of members such as columns and beams according to the joint strength of joints, the cross-section of members tends to be larger than that of steel structures, but the joint strength is improved. As a result, an effect of reducing the member cross section can be expected.

  In addition, if a square shape, a T shape, a cross shape, an X shape, a square shape, etc. are fully utilized, a structure in which all are formed by joint joining becomes possible (FIG. 10).

  Furthermore, assuming that the bearing walls are orthogonal to each other or a frame structure in two directions is assumed, the conventional joint joints have a complicated relationship with the hardware of the orthogonal beams, and the cross-sectional defects will be even larger, resulting in failure. However, even if a few bolt holes are processed, the effect is very small. I can say that.

  As another application, if the form shown in FIG. 8 is used as a horizontal surface, it is possible to configure a blow-out or the like in which a fire beam is omitted.

重複部の圧密度０％はいわゆるクロスラップジョイントであり、互いに交差する構成板の厚さ分だけ隙間のある状態である。重複部の圧密度に比例してこの隙間は狭くなり、５０％でちょうど非重複部同士が接触する。使用性を考慮すると、非重複部が一体化する５０％以上の圧密度が良好といえる。ただし、重複部の圧密度が８０％近辺になると、圧密を超えて、基材の破壊（木繊維の破断や分離）の発生が進行する。加えて、圧密に必要なプレス荷重が極端に高くなることから、実大サイズで実施するとプレス容量が不足するなど、製造面での困難を伴う。このことから重複部の圧密度は５０％〜７０％が良好である。一方、重複部、非重複部の剛性ならびに耐力については木材繊維の密度と比例して上昇する。重複部の剛性については接着接合によるものであることから、非圧密でも１と評価できる。一方、耐力については交差角度によって繊維直交方向成分の影響を受けるため、非圧密では重複部の耐力は非重複部の半分である。剛節か否かの判定は重複部と非重複部の剛比で行ったところ、非圧密でも剛節仮定で設計が可能であるが寸法効果に応じて局所変形の影響が懸念されることから、ここでは重複部の剛性が２倍以上で「◎」として完全に接合部の変形が無視できるものと評価した。一方、全強についての判定は重複部と非重複部の耐力比である接合効率１００％以上で「○」と評価した。このように圧密度で重複部と非重複部の剛性と耐力のバランスをコントロールすることが可能であるが、剛比ならびに接合効率においても５０％〜７０％で良好であると言える。なお、実際に圧密度を決定するに当たっては、非重複部の性能が縦継ぎする部材の剛性、耐力と同等性能になるように設定することが理想となる。First, with regard to the bonding performance of the present invention, taking the L-shaped wood board laminated consolidated member by the same number of rectangular components of the same thickness as the example, the balance between the bonded portion and the member is based on the rigidity and proof strength of the material (non-overlapping portion) As shown in the table below.

The pressure density 0% of the overlapping portion is a so-called cross lap joint, and there is a gap corresponding to the thickness of the constituent plates that intersect each other. This gap becomes narrower in proportion to the pressure density of the overlapping portion, and the non-overlapping portions are just in contact with each other at 50%. Considering usability, it can be said that a pressure density of 50% or more at which the non-overlapping parts are integrated is good. However, when the pressure density of the overlapping portion is close to 80%, the destruction of the base material (breaking or separation of the wood fiber) proceeds beyond the consolidation. In addition, since the press load necessary for compaction becomes extremely high, if it is carried out at a full size, there are difficulties in manufacturing such as insufficient press capacity. For this reason, the pressure density of the overlapping portion is preferably 50% to 70%. On the other hand, the rigidity and proof stress of the overlapping part and the non-overlapping part increase in proportion to the density of the wood fiber. Since the rigidity of the overlapping portion is based on adhesive bonding, it can be evaluated as 1 even with non-consolidation. On the other hand, since the yield strength is affected by the cross-angle direction component of the fiber, the non-consolidated portion has half the yield strength of the non-overlapping portion. Judgment of whether or not it is a rigid joint is based on the stiffness ratio of the overlapping part and the non-overlapping part, but it is possible to design with non-consolidated rigid joint assumption, but there is concern about the influence of local deformation depending on the size effect Here, it was evaluated that the rigidity of the overlapped portion was more than twice, and the deformation of the joint portion was completely negligible as “◎”. On the other hand, the determination about the total strength was evaluated as “◯” when the joining efficiency was 100% or more, which is the proof stress ratio of the overlapping portion and the non-overlapping portion. Thus, although it is possible to control the balance between the rigidity and the proof stress of the overlapping portion and the non-overlapping portion by the pressure density, it can be said that the rigidity ratio and the joining efficiency are good at 50% to 70%. When actually determining the pressure density, it is ideal to set the non-overlapping portion so that the performance of the non-overlapping portion is equivalent to the rigidity and proof strength of the member to be cascaded.

  The above is a good condition in the case of a wooden board laminated member composed of the same number and the same number of constituent plates, but the joining structure of the present invention is also used in the case of a wooden board laminated member consisting of different thicknesses or different numbers of constituent plates It can also be established. As a result, the member can cope with a combination of a beam and a column having different rigidity and proof stress. However, if the thicknesses of the deck board laminated member and the otowood board laminated member are equalized after consolidation, the pressure density of the overlapping portion is determined by the thinner total thickness of the constituent plates. In this case, if the possible range is the same as the combination of the same number of wood board laminated members, the pressure density of the overlapping part is within the range of 50% to 70%, the total thickness of the former component board and the former component board The ratio is 7: 3 or less, but it is not necessary to carry out with such an extremely different total thickness ratio of the component boards. By changing the combination, it is possible to cope with different beams and columns having different rigidity.

  Next, specific performance is shown together with the manufacturing process of a 120 mm square L-shaped member using Todomatsu. In addition, although it does not ask | require the tree seed | species of a component board in comprising a junction structure, when passing through a resin impregnation process like a present Example, it is desirable that it can be reliably impregnated to the inside of a component board. Therefore, a thin material with a relatively low specific gravity is good.

  Here, the former plate group and the second plate group have the same thickness and the same shape, and a single rotary plate having a thickness of 3.3 mm, a length of 240 mm, and a width of 120 mm was used. The impregnated resin is a phenolic resin. When hot-pressing a single plate impregnated with resin, the smaller the number of layers, the more efficiently reaching the curing temperature to the inside. Therefore, the number of overlapping portions was set to 10 and the total thickness of the overlapping portions was set to 33 mm. This was compacted to 15 mm by thickness regulation under temperature conditions suitable for softening of the wood and hardening of the phenolic resin (140 ° C. in this case) to produce an L-shaped unit plate (FIGS. 11-10). Eight L-shaped unit plates were secondarily bonded to form a 120 mm square, and the same cross section as the column beam to be longitudinally connected was secured. In the case of hot-pressing, the constituent plates are pre-impregnated with each other so that the constituent plates are bonded to each other, and at the same time, the resins on the surface layers of the constituent plates are bonded to each other and thermally cured. Adhesive performance equivalent to that when applied is obtained. Further, the secondary bonding step can be omitted by forming the required thickness in a lump using a high frequency press. Thus, when using a resin-impregnated component plate, there is an advantage in production efficiency that it is not constrained by the usable time of the adhesive that needs to be considered when using a normal adhesive, but the present invention is resin-impregnated. It is good not to stick to it but to select the compaction according to the object structure as appropriate.

  This was cascaded with a laminated material corresponding to a column beam member to obtain a moment resistance performance test specimen. Here, in order to measure the true performance of the L-shaped member, an adhesive joint using a large-sized finger joint that has been proven to be rigid and has high joint efficiency in joint joint is employed. This L-shaped specimen was applied in the opening / closing direction to obtain rigidity and proof stress. Regarding the stiffness, the calculated value of the deformation angle of only the member derived from the overlapping portion as a rigid joint was compared with the experimental value (FIG. 12). In both the opening and closing directions, the deformation amount of the experimental value was smaller than the calculated value, so that it was considered that the deformation angle of the joint was not measured, and it was confirmed that it was a rigid joint. In addition, the fracture broke at the boundary between the non-overlapping part and the overlapping part, and the yield strength (maximum moment) was equivalent to the nominal value of the laminated wood. From this, it was also confirmed that the joint strength was all strong.

  In addition, when it becomes an obtuse angle from 90 degrees, since the ratio of a transverse tensile stress component becomes small in the stress state of an overlapping part, the destruction in an overlapping part does not arise. On the other hand, when the angle is more acute than 90 °, the ratio of the transverse tensile stress component is increased, but the fiber direction of the constituent plate becomes coincident with the transverse tensile stress direction. There is no destruction.

Example of L-shaped wood board laminated consolidation member Method for constructing L-shaped wood board laminated consolidation member Example of X-shaped wood board laminated consolidation member Example of L-shaped wood board laminated consolidation member with trapezoidal component board Example of B-shaped and P-shaped wood board laminated consolidation members Method for constructing L-shaped wood board laminated consolidation member with additional construction board Example of small portal ramen frame Example of small closed frame structure Example of large-scale portal frame structure and its joints Example of wood frame structure with only joints using wood-plate laminated consolidation members Example of adjusting the thickness by secondary bonding of unit plates Load deformation curve of L-shaped wood board laminated consolidation member

DESCRIPTION OF SYMBOLS 1 ... Shell board laminated member 1 '... Upper board 2 ... Otoki board laminated member 2' ... B board 3 ... Additional component board 4 ... Gusset board, such as a steel plate 5 ... Column base metal 6 ... Drift pin group 7 ... Shaft materials such as laminated lumber 8 ... Connector group assuming wood dowels, steel bars, etc. 9 ... Wood board laminated consolidation member 10 ... L-shaped unit board A ... Overlapping part B ... Non-overlapping part

Claims (3)

  When stacking the former component group constituting the deck board laminate member, the former component group constituting the former board laminate member is inserted or intersected between the constituent plates of the former member group at an arbitrary position and at an arbitrary angle. A wood board laminated consolidation structure obtained by consolidating and fixing the overlapping portions until the non-overlapping portions of the former and the second component board group are integrated with each other.   The wood board laminated consolidation member having the joint structure according to claim 1, wherein the overlapping portion enables rigid joint and / or full strength.   A wood frame structure mainly composed of joints made of the members of claim 2 or joints made of the member of claim 2 and another shaft material.

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