Horizontal member for framework wall construction method

Abstract

To provide a horizontal member by a highly versatile method which does not need a special technique using general lumbering.SOLUTION: A horizontal member for a framework wall construction method includes a first layer member, a second layer member and a third layer member stacked in a plate thickness direction. The first layer member includes a first layer first member positioned on one end side in a longitudinal direction, and a first layer second member positioned closer to the other end side than the first layer first member. The second layer member includes a second layer first member and a second layer second member. The third layer member includes a third layer first member and a third layer second member. A first boundary being a boundary between the first layer first member and the first layer second member is at a position different from a second boundary being a boundary between the second layer first member and the second layer second member in the longitudinal direction. The second boundary is at a position different from a third boundary being a boundary between the third layer first member and the third layer second member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cross member for use in a wood-frame construction method. [Background technology]

[0002] Traditionally, wooden buildings using wood frame construction methods (for example, the 2x4 method) have been widely known (for example, Patent Document 1 below). In recent years, from the perspective of the SDGs, there has been a demand for long-term use of wood frame construction buildings. As part of such efforts, there is a demand for realizing skeleton infill spaces that respond to social changes, lifestyle changes, resident turnover, and other factors that are particularly noticeable in urban buildings. One element in realizing skeleton infill spaces is the construction of spaces with as large a span as possible.

[0003] Frame construction primarily uses 210-size lumber for floor framing, but the most common lumber lengths are around 14 feet (approximately 4260 mm) or 16 feet (approximately 4870 mm), with the longest types effectively limited to around 18 feet (approximately 5460 mm) or 20 feet (approximately 6080 mm). This lumber length effectively limits the spatial span, and if you want to extend the span beyond that, you will need to use technologies such as trusses, I-joists, or NLT. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-2358 Summary of the Invention [Problem to be solved by the invention]

[0005] However, technologies such as trusses, I-joists, and NLT have not been widely adopted due to a limited number of manufacturers, changes to existing installation methods, and high implementation costs. Therefore, it is hoped that floor joists can be developed using general-purpose lumber that does not require special techniques. These problems are not limited to floor joists, but are common to various horizontal members used in frame wall construction. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized, for example, in the following forms.

[0007] According to a first aspect of the present invention, there is provided a beam for use in a wood-frame construction method. The beam comprises first, second, and third layer members, which are plate-shaped members extending in the longitudinal direction and stacked in this order in the thickness direction. The first layer members comprise a first-layer first member located at one end of the longitudinal direction and a first-layer second member located at the other end of the first layer first member. The second layer members comprise a second-layer first member located at one end and a second-layer second member located at the other end of the second layer first member. The third layer members comprise a third-layer first member located at one end and a third-layer second member located at the other end of the third layer first member. The first boundary between the first layer first member and the first layer second member is located at a different position in the longitudinal direction from the second boundary between the second layer first member and the second layer second member. The second boundary is located at a different position in the longitudinal direction from the third boundary between the third layer first member and the third layer second member. The first layer member and the second layer member are integrated by nails extending in the thickness direction at least within the first layer member and the second layer member. The second layer member and the third layer member are integrated by nails extending in the thickness direction at least within the second layer member and the third layer member.

[0008] This beam can be constructed using conventional lumber for the first layer first member, first layer second member, second layer first member, second layer second member, third layer first member, and third layer second member, and these members can be fastened together with nails. As a result, the beam's multi-layer structure ensures the necessary strength while increasing the beam's overall length. Therefore, a beam longer than conventional lumber can be produced using a highly versatile method that does not require special skills. All or part of the first layer first member, first layer second member, second layer first member, second layer second member, third layer first member, and third layer second member may be used as is, or they may be cut to adjust their longitudinal length.

[0009] According to the second aspect of the present invention, in the first aspect, the longitudinal lengths of the first layer first member, the second layer second member, and the third layer first member are the same. The longitudinal lengths of the first layer second member, the second layer first member, and the third layer second member are the same and different from the longitudinal lengths of the first layer first member, the second layer second member, and the third layer first member. According to this aspect, members of the same length can be used between the first layer member, the second layer member, and the third layer member. Therefore, the manufacturing (construction) effort of the cross members can be reduced.

[0010] According to the third aspect of the present invention, in the first or second aspect, the longitudinal distance between one end of the first story and the first boundary is shorter than one-quarter of the total longitudinal length of the first story, the longitudinal distance between the other end of the second story and the second boundary is shorter than one-quarter of the total longitudinal length of the second story, and the longitudinal distance between one end of the third story and the third boundary is shorter than one-quarter of the total longitudinal length of the third story. This aspect allows the first to third boundaries (i.e., the longitudinal joints between the first, second, and third story members) to be located away from the longitudinal center. Since the closer a cross member is to the longitudinal center, the greater the bending stress. This aspect allows the joints to be located at positions where the bending stress is relatively low.

[0011] According to a fourth aspect of the present invention, in any one of the first to third aspects, the cross member is a plate-like fourth layer member extending in the longitudinal direction, and includes a fourth layer member adjacent to the third layer member in the thickness direction and stacked on the opposite side of the second layer member. The fourth layer member includes a fourth layer first member located on one end side and a fourth layer second member located on the other end side of the fourth layer first member. A fourth boundary between the fourth layer first member and the fourth layer second member is located at a different position in the longitudinal direction from the third boundary. The third layer member and the fourth layer member are integrated by nails extending in the thickness direction at least within the third layer member and the fourth layer member. According to this aspect, by making the cross member a four-layer structure, strength can be improved compared to a three-layer structure.

[0012] According to a fifth aspect of the present invention, in the fourth aspect including the second aspect, the longitudinal lengths of the first layer first member, the second layer second member, the third layer first member, and the fourth layer second member are the same. The longitudinal lengths of the first layer second member, the second layer first member, the third layer second member, and the fourth layer first member are the same and different from the longitudinal lengths of the first layer first member, the second layer second member, the third layer first member, and the fourth layer second member. This aspect provides the same effect as the second aspect.

[0013] According to a sixth aspect of the present invention, in the fourth or fifth aspect including the third aspect, the longitudinal distance between the other end of the fourth layer member and the fourth boundary is shorter than ¼ of the total length of the fourth layer member in the longitudinal direction. This aspect provides the same effects as the third aspect.

[0014] According to a seventh aspect of the present invention, in any of the first to sixth aspects, the cross member includes a first metal band attached to the side of the first layer member opposite the second layer member so as to cross the first boundary in the longitudinal direction, and a second metal band attached to the side of the third or fourth layer member opposite the second or third layer member so as to cross the third or fourth boundary in the longitudinal direction. According to this aspect, the strength of the longitudinal joint can be reinforced by the metal band.

[0015] According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the cross member includes first structural screw members extending in the plate thickness direction at least in the first and second story members on both sides of the first boundary in the longitudinal direction, and second structural screw members extending in the plate thickness direction at least in the third and second story members or at least in the fourth and third story members on both sides of the third or fourth boundary in the longitudinal direction. According to this aspect, the strength of the joint in the longitudinal direction can be reinforced by the structural screw members. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view showing a schematic structure of a building using floor joists according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an exploded view of the first, second, third and fourth layer members that make up the floor joists. [Figure 3] FIG. 10 is a diagram showing the floor joist construction procedure. [Figure 4] FIG. 2 is a partial cross-sectional view taken along the lamination direction of first to fourth layer members. [Figure 5] FIG. 10 is a diagram showing the attachment position of a reinforcing material. [Figure 6] FIG. 10 is an exploded view of a first layer member, a second layer member, and a third layer member that constitute a floor joist according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] A first exemplary embodiment of the present invention will now be described. FIG. 1 shows a schematic structure of a building 10 using floor joists 40 as an example of a cross member according to this embodiment. A plurality of floor joists 40 are spanned at intervals between joist hangers 20 arranged at both ends of the building 10. In this embodiment, the floor joists 40 have a four-layer structure. A floor 30 is constructed on the floor joists 40. The floor joists 40 have a first end 41, which is one end in the longitudinal direction, and a second end 42 opposite the first end 41. The first end 41 is a non-limiting example of "one end" or "other end" in the claims, and the second end 42 is a non-limiting example of "other end" or "one end."

[0018] FIG. 2 is an exploded view of the first, second, third, and fourth layers 50, 60, 70, and 80 that make up the four-layer floor joist 40. Each of the first, second, third, and fourth layers 50, 60, 70, and 80 is a longitudinally extending plate-like member, and is made of general-purpose lumber conforming to the lumber standards for wood-frame construction. In this embodiment, general-purpose lumber of dimension type 210 (hereinafter also referred to as 210 lumber) is used. The first, second, and third layers 50, 60, 70, and 80 can also be made of any other general-purpose lumber for wood-frame construction (e.g., dimension types 204, 206, 208, 212, etc.). The first, second, and fourth layers 50, 60, 70, and 80 are stacked in that order in the thickness direction, as described in detail below.

[0019] The first layer member 50 includes a first layer first member 51 and a first layer second member 52. The first layer first member 51 is located on the first end 41 side, and the first layer second member 52 is located on the second end 42 side. Similarly, the second layer member 60 includes a second layer first member 61 located on the first end 41 side and a second layer second member 62 located on the second end 42 side. The third layer member 70 includes a third layer first member 71 located on the first end 41 side and a third layer second member 72 located on the second end 42 side. The fourth layer member 80 includes a fourth layer first member 81 located on the first end 41 side and a fourth layer second member 82 located on the second end 42 side.

[0020] In this embodiment, the longitudinal lengths of the first layer first member 51, the second layer second member 62, the third layer first member 71, and the fourth layer second member 82 are all the same. The longitudinal lengths of the first layer second member 52, the second layer first member 61, the third layer second member 72, and the fourth layer first member 81 are also the same, and are longer than the longitudinal lengths of the first layer first member 51, the second layer second member 62, the third layer first member 71, and the fourth layer second member 82. The first layer second member 52, the second layer first member 61, the third layer second member 72, and the fourth layer first member 81 are made from 210 lumber at the size at which it is distributed, while the first layer first member 51, the second layer second member 62, the third layer first member 71, and the fourth layer second member 82 are made from 210 lumber cut to adjust their longitudinal lengths.

[0021] The first layer first member 51 and the first layer second member 52 are arranged adjacent to (in contact with) each other in the longitudinal direction, and their boundary is also referred to as the first boundary 53. The second layer first member 61 and the second layer second member 62 are arranged adjacent to (in contact with) each other in the longitudinal direction, and their boundary is also referred to as the second boundary 63. The third layer first member 71 and the third layer second member 72 are arranged adjacent to (in contact with) each other in the longitudinal direction, and their boundary is also referred to as the third boundary 73. The fourth layer first member 81 and the fourth layer second member 82 are arranged adjacent to (in contact with) each other in the longitudinal direction, and their boundary is also referred to as the fourth boundary 83.

[0022] The longitudinal positions of these boundaries are different between adjacent layers. That is, the first boundary 53 and the second boundary 63 are in different positions, the second boundary 63 and the third boundary 73 are in different positions, and the third boundary 73 and the fourth boundary 83 are in different positions. In this embodiment, due to the member lengths described above, the first boundary 53 and the third boundary 73 are in the same position, and the second boundary 63 and the fourth boundary 83 are in the same position.

[0023] A construction method for floor joists 40 will be described below with reference to FIGS. 2 to 5. First, as shown in FIG. 3(a), first layer first member 51 and first layer second member 52 are arranged adjacent to each other in the longitudinal direction. Then, as shown in FIGS. 3(b) and 3(c), second layer second member 62 is attached to first layer second member 52 by nailing. Then, second layer first member 61 is attached to first layer first member 51 and first layer second member 52 so as to be adjacent to second layer second member 62 in the longitudinal direction. FIG. 4 shows a state in which nails 43 have been driven in the thickness direction from the second layer member 60 side so as to penetrate through first layer member 50 and second layer member 60. Nail positions 64 for driving nails 43 are shown in FIG. 2. As a result, the first layer first member 51 and the first layer second member 52 are integrated via the second layer first member 61, and the second layer first member 61 and the second layer second member 62 are integrated via the first layer second member 52.

[0024] Next, as shown in FIGS. 3(d) to 3(f), a third layer first member 71 is attached to the second layer first member 61 by nailing, and a third layer second member 72 is attached to the second layer first member 61 and the second layer second member 62 so as to be adjacent to the third layer first member 71 in the longitudinal direction. FIG. 4 shows a state in which nails 44 have been driven from the third layer member 70 side in the thickness direction so as to penetrate through the second layer member 60 and the third layer member 70. FIG. 2 shows nail positions 74 for driving the nails 44. As a result, the third layer first member 71 and the third layer second member 72 are integrated via the second layer first member 61. As shown in FIG. 2, the nail positions 64 and 74 are offset in the longitudinal direction, so that the nails 43 and 44 do not interfere with each other, as shown in FIG. 4.

[0025] Next, as shown in FIGS. 3(g) to 3(i), a fourth layer second member 82 is attached to the third layer second member 72 by nailing, and a fourth layer first member 81 is attached to the third layer first member 71 and the third layer second member 72 so that the fourth layer first member 81 is adjacent to the fourth layer second member 82 in the longitudinal direction. FIG. 4 shows a state in which nails 45 have been driven from the fourth layer member 80 side in the thickness direction so as to penetrate through the third layer member 70 and the fourth layer member 80. FIG. 2 shows nail positions 84 for driving nails 45. As a result, the fourth layer first member 81 and the fourth layer second member 82 are integrated via the third layer second member 72. As shown in FIG. 2, nail positions 74 and 84 are offset in the longitudinal direction (nail position 84 is in the same longitudinal position as nail position 64), so nails 44 and 45 do not interfere with each other, as shown in FIG. 4.

[0026] This procedure integrates the first layer 50, second layer 60, third layer 70, and fourth layer 80. In this embodiment, the nails 43-45 are driven so that they extend through two of the four layers as described above, which makes it less likely for the layers to become misaligned compared to when the nails 43-45 are driven so that they extend through three or more layers. However, the nails 43-45 may also be driven so that they extend through three or four layers.

[0027] The floor joists 40 constructed in this manner may be reinforced with reinforcing materials to ensure the necessary strength. In this embodiment, metal bands and structural screw members are used as reinforcing materials. However, only one of these may be used, or both may be omitted if the necessary strength can be ensured. Figure 5 shows the installation position of the reinforcing materials. The first layer member 50 shown in the figure is viewed from the outside of the floor joist 40 (i.e., from the first layer member 50 toward the second layer member 60), and the fourth layer member 80 shown in the figure is viewed from the outside of the floor joist 40 (i.e., from the fourth layer member 80 toward the third layer member 70), with the left and right sides reversed.

[0028] In this embodiment, two first metal straps 90 and two second metal straps 91 are used as the metal straps. As shown in Fig. 5, the two first metal straps 90 are attached to the side of the first layer member 50 opposite the second layer member 60, longitudinally crossing the first boundary 53. The two second metal straps 91 are attached to the side of the fourth layer member 80 opposite the third layer member 70, longitudinally crossing the fourth boundary 83. In this embodiment, the first metal straps 90 and second metal straps 91 are attached to the floor joists 40 with nails that extend partway between the first and second layers, as viewed from the nail head.

[0029] In this embodiment, structural screws 92-94 are used. For example, pile pike screws may be used as the structural screws 92-94. As shown in FIG. 5 , four first structural screws 92 (two on each side) are driven from the first layer 50 side on both sides of the first boundary 53 in the longitudinal direction. In this embodiment, four first structural screws 92 are also driven from the opposite side (the fourth layer 80 side) at positions corresponding to both sides of the first boundary 53. In addition, four second structural screws 93 (two on each side) are driven from the fourth layer 80 side on both sides of the fourth boundary 83 in the longitudinal direction. In this embodiment, four second structural screws 93 are also driven from the opposite side (the first layer 50 side) at positions corresponding to both sides of the fourth boundary 83. Furthermore, four third structural screw members 94 are driven into the center of the floor joist 40 in the longitudinal direction from the first layer member 50 side and the fourth layer member 80 side.

[0030] In this embodiment, the structural screws 92-94 are driven so that they extend partway through the first, second, and third layers when viewed from the head. However, the structural screws 92-94 may also be driven so that they extend at least partway through the first and second layers. As shown in FIG. 5 , the driving positions of the four first structural screws 92 are in a V-shape, and this V-shape is upside down on the first layer component 50 side and the fourth layer component 80 side. This allows the first structural screws 92 driven from both sides in the plate thickness direction to be driven at approximately the same position on both sides without interfering with each other. The same applies to the driving positions of the second structural screw members 93 and the third structural screw members 94.

[0031] According to the floor joist 40 described above, ordinary lumber can be used for the first layer member 50, the second layer member 60, the third layer member 70, and the fourth layer member 80, which can be joined together with nails 43 to 45. Furthermore, two members (for example, the first layer first member 51 and the first layer second member 52) can be joined in the longitudinal direction, so the floor joist 40 has a multi-layer structure, ensuring the necessary strength while increasing the lumber length of the entire floor joist 40. Therefore, the spatial span (the distance between the joist hangers 20 in Figure 1) can be increased using a highly versatile method that does not require special technology, contributing to the realization of a skeleton infill space.

[0032] Furthermore, according to floor joist 40, the longitudinal lengths of first layer first member 51, second layer second member 62, third layer first member 71, and fourth layer second member 82 are all the same, and the longitudinal lengths of first layer second member 52, second layer first member 61, third layer second member 72, and fourth layer first member 81 are all the same. Therefore, members of the same length can be used between first layer member 50, second layer member 60, third layer member 70, and fourth layer member 80. This reduces the effort required to manufacture (construct) floor joist 40.

[0033] 2, according to the floor joist 40, the longitudinal distance between the first end 41 and the first boundary 53 of the first layer member 50 (first layer first member 51) is approximately 1 / 8 of the entire longitudinal length of the first layer member 50 (in other words, the entire length of the floor joist 40). Similarly, the longitudinal distance between the second end 42 and the second boundary 63 of the second layer member 60 (second layer second member 62), the longitudinal distance between the first end 41 and the third boundary 73 of the third layer member 70 (third layer first member 71), and the longitudinal distance between the second end 42 and the fourth boundary 83 of the fourth layer member 80 (fourth layer second member 82) are also approximately 1 / 8 of the entire length of the floor joist 40. As a result, the first boundary 53, second boundary 63, third boundary 73, and fourth boundary 83 (in other words, the longitudinal joints of each floor) are located away from the longitudinal center. Since greater bending stress occurs in floor joists 40 closer to the longitudinal center, the above configuration allows the joints to be located at positions where the acting bending stress is relatively low. This effect can also be achieved by making the longitudinal distance between the first layer first member 51, second layer second member 62, third layer first member 71, and fourth layer second member 82 shorter than 1 / 4 of the total length of floor joists 40.

[0034] The following describes the floor joist 140 according to the second embodiment, focusing only on the differences from the first embodiment. The floor joist 140 differs from the first embodiment only in that it has a three-layer structure. FIG. 6 is an exploded view of the first layer members 50, second layer members 60, and third layer members 70 that make up the three-layer floor joist 40. These first layer members 50, second layer members 60, and third layer members 70 are similar to the first layer members 50, second layer members 60, and third layer members 70 of the first embodiment, and the construction method is also similar to that of the first embodiment. This three-layer floor joist 140 can also achieve the same effects as the first embodiment.

[0035] Although the embodiments of the present invention have been described above, the above-described embodiments of the invention are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof. Furthermore, any combination or omission of each component or step described in the claims and specification is possible within the scope of solving at least part of the above-described problems or achieving at least part of the effects.

[0036] For example, floor joist 40 may be modified to have a structure of five or more layers, as long as the positions of the joints between adjacent layers in the stacking direction are different. Alternatively, floor joist 40, 140 may be modified so that three or more members are connected in the longitudinal direction in at least one layer, as long as the positions of the joints between adjacent layers in the stacking direction are different.

[0037] Furthermore, the above-described embodiment is not limited to application to floor joists, but can also be applied to various cross members (for example, ceiling joists) used in wood-frame construction. [Explanation of symbols]

[0038] 10...Buildings 20...Joist hanging 30...floors 40...Floor joists (4 layers) 41...1st end 42...Second end 43, 44, 45...nails 50...First layer member 51...First layer, first member 52...First layer, second member 53...First boundary 60...Second layer member 61...Second layer, first member 62...Second layer, second member 63...Second Boundary 64... Nail position 70...Third layer member 71...3rd layer, 1st member 72...Third layer, second member 73...The Third Boundary 74... Nail position 80...Fourth layer member 81...4th layer, 1st member 82...4th layer, 2nd member 83...The Fourth Boundary 84... Nail position 90...First metal band 91...Second metal band 92...First structural screw member 93...Second structural screw member 94...Third structural screw member 140...Floor joists (3 layers)

Claims

1. A horizontal member for a frame wall construction method, the first layer member, the second layer member, and the third layer member are plate-shaped and extend in a longitudinal direction, and are stacked in this order in a thickness direction; the first layer member includes a first layer first member located on one end side in the longitudinal direction and a first layer second member located on the other end side of the first layer first member, the second layer member includes a second layer first member located on the one end side and a second layer second member located closer to the other end side than the second layer first member, the third layer member includes a third layer first member located on the one end side and a third layer second member located closer to the other end side than the third layer first member, a first boundary between the first layer first member and the first layer second member is located at a position different from a second boundary between the second layer first member and the second layer second member in the longitudinal direction; the second boundary is at a position different from a third boundary, which is a boundary between the third layer first member and the third layer second member, in the longitudinal direction; The first layer member and the second layer member are integrated by nails extending in the thickness direction at least within the first layer member and the second layer member, The second layer member and the third layer member are integrated by nails extending in the thickness direction at least within the second layer member and the third layer member. Cross beam.

2. The cross member according to claim 1, the first layer first member, the second layer second member, and the third layer first member have the same length in the longitudinal direction; The lengths of the first layer second member, the second layer first member, and the third layer second member in the longitudinal direction are the same and are different from the lengths of the first layer first member, the second layer second member, and the third layer first member in the longitudinal direction. Cross beam.

3. The cross member according to claim 1 or claim 2, a distance in the longitudinal direction between one end of the first layer member and the first boundary is shorter than ¼ of the entire length of the first layer member in the longitudinal direction; a distance in the longitudinal direction between the other end of the second layer member and the second boundary is shorter than ¼ of the entire length of the second layer member in the longitudinal direction; The distance in the longitudinal direction between one end of the third layer member and the third boundary is shorter than ¼ of the entire length of the third layer member in the longitudinal direction. Cross beam.

4. The cross member according to claim 1 or claim 2, a fourth layer member having a plate shape extending in the longitudinal direction, the fourth layer member being adjacent to the third layer member in the plate thickness direction and stacked on the opposite side to the second layer member; the fourth layer member includes a fourth layer first member located on the one end side and a fourth layer second member located closer to the other end side than the fourth layer first member, a fourth boundary between the fourth layer first member and the fourth layer second member is located at a position different from the third boundary in the longitudinal direction; The third layer member and the fourth layer member are integrated by nails extending in the thickness direction at least within the third layer member and the fourth layer member. Cross beam.

5. A cross member according to claim 4, which includes claim 2 as a dependent element, the first layer first member, the second layer second member, the third layer first member, and the fourth layer second member have the same length in the longitudinal direction; The lengths of the first layer second member, the second layer first member, the third layer second member, and the fourth layer first member in the longitudinal direction are the same as each other and are different from the lengths of the first layer first member, the second layer second member, the third layer first member, and the fourth layer second member in the longitudinal direction. Cross beam.

6. The cross member according to claim 4, a distance in the longitudinal direction between one end of the first layer member and the first boundary is shorter than ¼ of the entire length of the first layer member in the longitudinal direction; a distance in the longitudinal direction between the other end of the second layer member and the second boundary is shorter than ¼ of the entire length of the second layer member in the longitudinal direction; a distance in the longitudinal direction between one end of the third layer member and the third boundary is shorter than ¼ of the entire length of the third layer member in the longitudinal direction; The distance in the longitudinal direction between the other end of the fourth layer member and the fourth boundary is shorter than ¼ of the entire length of the fourth layer member in the longitudinal direction. Cross beam.

7. The cross member according to claim 1 or claim 2, a first metal band attached to a side of the first layer member opposite the second layer member so as to extend longitudinally across the first boundary; a second metal band attached to a side of the third layer member opposite the second layer member so as to longitudinally cross the third boundary; Equipped with Cross beam.

8. The cross member according to claim 1 or claim 2, first structural screw members extending in the plate thickness direction at least within the first layer member and the second layer member on both sides of the first boundary in the longitudinal direction; second structural screw members extending in the plate thickness direction at least within the third layer member and the second layer member on both sides of the third boundary in the longitudinal direction; A cross member equipped with:

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