JP7650177B2 - Column-beam joint core - Google Patents

Description

The present invention relates to a column-beam joint core.

A conventional beam-column joint core is a non-diaphragm construction core that uses a steel pipe with a rectangular cross section at the joint, as shown in Patent Document 1. The beam-column joint core includes a steel pipe that connects the upper steel pipe on the upper side and the lower steel pipe on the lower side, and has four side walls that form the four sides of the rectangular cross section. The thickness of the steel pipe is set to be larger than the thicknesses of the upper steel pipe and the lower steel pipe.

Japanese Patent Application Publication No. 8-302899

The ultimate strength of a non-diaphragm beam-column joint structure is determined by the smaller of the out-of-plane full plastic strength and root penetration fracture strength of the thick steel pipe at the connection. The out-of-plane full plastic strength increases as the plate thickness of the steel pipe at the connection increases. On the other hand, if the plate thickness of the steel pipe at the connection becomes too thick, the stress is not transmitted to the entire plate thickness, and the improvement in root penetration fracture strength due to the increase in plate thickness may be small.

On the other hand, the out-of-plane yield strength and out-of-plane full plastic strength increase with an increase in the thickness of the steel pipe at the connection, so the larger the beam to which it is attached, the more the plate thickness must be increased. From the perspective of improving the root penetration fracture strength, reinforcement other than increasing the plate thickness is desirable, but from the perspective of improving the out-of-plane yield strength and out-of-plane full plastic strength, it is efficient to increase the plate thickness to improve the strength, so the solutions from each perspective are contradictory.

The present invention was made to solve these problems, and aims to provide a column-beam joint core that can improve the strength of a column-beam joint structure while suppressing an increase in cross-sectional area.

The column-beam joint core according to the present invention is a column-beam joint core of the non-diaphragm construction method using a joint steel pipe with a square cross section at the joint, and is equipped with a joint steel pipe connected to an upper steel pipe on the upper side and a lower steel pipe on the lower side, and having four side walls that form the four sides of the square cross section, and inside the joint steel pipe, four steel plates are provided that are fixed to all combinations of pairs of adjacent side walls, and each steel plate is fixed with one end inclined to one side wall and the other end inclined to the other side wall when viewed from the top-bottom direction, the plate thickness of the joint steel pipe is thicker than the plate thicknesses of the upper steel pipe and the lower steel pipe, and the plate thickness of the steel plate is thinner than the plate thickness of the joint steel pipe.

The thickness of the steel pipe at the joint is thicker than that of the upper and lower steel pipes. Therefore, compared to when the thickness of the steel pipe at the joint is the same as that of the upper and lower steel pipes, the strength can be improved by making the thickness of the steel pipe at the joint thicker. In contrast, four steel plates are provided inside the steel pipe at the joint, which are fixed to all combinations of pairs of adjacent side walls. When viewed from the top and bottom, each steel plate is fixed with one end inclined to one side wall, and the other end inclined to the other side wall. Therefore, each steel plate can reinforce the four side walls of the steel pipe at the joint from the inside. When such steel plates are provided, the strength can be improved more efficiently than when the thickness of the steel pipe at the joint is simply thickened. Here, the strength of the connection in the non-diaphragm method is largely borne by the out-of-plane deformation of the side wall of the connection steel pipe, and not so much by the force flowing through the steel plate and the surface adjacent to the side wall that is subjected to out-of-plane deformation by the steel plate. In other words, since the steel plate plays an auxiliary role in the out-of-plane deformation of the connection steel pipe, even if it is thickened excessively, the effect of improving the strength obtained is low relative to the increase in the total cross-sectional area. Therefore, in order to obtain a high effect of improving the strength while suppressing the increase in the cross-sectional area, the plate thickness of the steel plate is made thinner than the plate thickness of the connection steel pipe. As a result, it is possible to improve the strength of the column-beam joint structure while suppressing the increase in the cross-sectional area.

The angle of one end of the steel plate relative to one side wall, and the angle of the other end of the steel plate relative to the other side wall, may be 45°. In this case, the symmetry of the arrangement and shape of each steel plate can be ensured. Therefore, the bearing strength of the four side walls can be improved evenly. In addition, since there is a possibility that beams will be attached to the joint from all four directions, by setting the angle at 45°, the joint can be made a general-purpose product.

A gap is formed between the corner of the joint steel pipe and the steel plate, and the distance between the outer surface of the joint steel pipe and the fixed position of the steel plate across the gap may be at least twice the plate thickness of the joint steel pipe. Depending on the shape and manufacturing method of the joint steel pipe, welding a steel plate near the corner may reduce workability and structural performance. Therefore, by keeping the distance between the outer surface of the joint steel pipe and the fixed position of the steel plate across the gap to a certain extent, at least twice the plate thickness of the joint steel pipe, the reduction in workability and structural performance can be suppressed.

The steel plate may be attached to the entire length of the steel pipe at the connection in the axial direction of the steel pipe. In this case, the effect of improving the strength can be obtained over the entire length of the steel pipe at the connection.

The steel plate may be attached to a portion of the steel pipe at the connection in the axial direction of the steel pipe. In this case, the effect of improving the strength can be obtained by limiting it to the particularly necessary parts of the steel pipe at the connection.

According to the present invention, it is possible to improve the strength of a column-beam joint structure while suppressing an increase in cross-sectional area.

FIG. 1(a) is a side view showing a column-beam joint core according to an embodiment of the present invention, and FIG. 1(b) is a view from above of the steel pipe at the joint portion of the column-beam joint core shown in FIG. 1(a). FIG. 11 is a side view showing a column-beam joint core according to a modified example. FIG. 3(a) is a side view showing a column-beam joint core according to a modified example, and FIG. 3(b) is a view showing a steel pipe at a joint portion of the column-beam joint core shown in FIG. 3(a) as viewed from above. FIG. 1 is a diagram illustrating a test specimen for analysis. FIG. 1 is a diagram showing an analysis model and analysis results. FIG. 1 is a diagram showing an analysis model and analysis results. FIG. 1 is a diagram showing an analytical model. FIG. 1 is a diagram showing an analysis model and analysis results. FIG. 13 is a diagram showing an example of manufacturing a steel pipe for a joint portion. FIG. 1 is a diagram showing an analysis model and analysis results. 1 is a table showing each condition of an analysis model.

A preferred embodiment of the present invention will be described below with reference to the drawings.

Figure 1(a) is a side view showing a column-beam joint core 200 according to an embodiment of the present invention. Figure 1(b) is a top view of the joint steel pipe of the column-beam joint core 200 shown in Figure 1(a). As shown in Figure 1(a), the column-beam joint structure 100 includes a column 1 and beams 2A and 2B joined to the column 1. The beams 2A and 2B are joined to the column 1 at a joint 3. The beams 2A and 2B have an H-shaped cross section and include upper and lower flanges 2a and 2b, and a web portion 2c that connects the flanges 2a and 2b together.

In this embodiment, a column-beam joint core 200 including a joint steel pipe 10 having a rectangular cross section made of steel is used for the joint 3. The joint steel pipe 10 is connected to an upper steel pipe 4 on the upper side and a lower steel pipe 6 on the lower side. Here, no diaphragm, which is a partition wall that spreads horizontally inside the column 1, is provided in the connection between the upper steel pipe 4 and the joint steel pipe 10, the connection between the lower steel pipe 6 and the joint steel pipe 10, or inside the joint steel pipe 10. In this way, the column-beam joint core 200 is configured as a column-beam joint core for a non-diaphragm construction method using the joint steel pipe 10.

As shown in FIG. 1(b), the joint steel pipe 10 has four side walls 11A, 11B, 11C, and 11D that constitute the four sides of the rectangular cross section. The side walls 11A and 11C face each other while being spaced apart so as to be parallel to each other. The side walls 11B and 11D are perpendicular to the side walls 11A and 11C and face each other while being spaced apart so as to be parallel to each other. The side walls 11A and 11B are arranged adjacent to each other and are connected to each other at the corners 12A. The side walls 11B and 11C are arranged adjacent to each other and are connected to each other at the corners 12B. The side walls 11C and 11D are arranged adjacent to each other and are connected to each other at the corners 12C. The side walls 11D and 11A are arranged adjacent to each other and are connected to each other at the corners 12D. The corners 12A, 12B, 12C, and 12D of the joint steel pipe 10 are rounded with a predetermined curvature. The size of the joint steel pipe 10 is not particularly limited, but may be set in the range of 150 mm to 1000 m on a side.

The manufacturing method for the joint steel pipe 10 is not particularly limited. For example, as shown in FIG. 9(a), the joint steel pipe 10 may be formed by forming a rolled material into a square shape. In this case, the ends of the rolled material are fixed together at a welded portion 24. Alternatively, as shown in FIG. 9(b), (c), (d), and (e), the joint steel pipe 10 may be formed by fixing the ends of multiple box-shaped members together at a welded portion 24.

Four steel plates 13A, 13B, 13C, 13D are provided inside the joint steel pipe 10, which are fixed to all combinations of pairs of adjacent side walls. The joint steel pipe 10 is provided with a steel plate 13A that is fixed to a pair of adjacent side walls 11A, 11B. The joint steel pipe 10 is provided with a steel plate 13B that is fixed to a pair of adjacent side walls 11B, 11C. The joint steel pipe 10 is provided with a steel plate 13C that is fixed to a pair of adjacent side walls 11C, 11D. The joint steel pipe 10 is provided with a steel plate 13D that is fixed to a pair of adjacent side walls 11D, 11A.

When viewed from the top-bottom direction, the steel plate 13 is fixed with one end inclined to one side wall portion 11, and the other end inclined to the other side wall portion 11. Specifically, when viewed from the top-bottom direction, the steel plate 13A is fixed with one end 13Aa inclined to one side wall portion 11A, and the other end 13Ab inclined to the other side wall portion 11B. When viewed from the top-bottom direction, the steel plate 13B is fixed with one end 13Ba inclined to one side wall portion 11B, and the other end 13Bb inclined to the other side wall portion 11C. When viewed from the top-bottom direction, the steel plate 13C is fixed with one end 13Ca inclined to one side wall portion 11C, and the other end 13Cb inclined to the other side wall portion 11D. When viewed from the top and bottom, one end 13Da of the steel plate 13D is fixed at an incline to one side wall portion 11D, and the other end 13Db is fixed at an incline to the other side wall portion 11A.

In this embodiment, the end 13Aa of the steel plate 13A and the end 13Db of the steel plate 13D are fixed to the center of the side wall 11A by welding. Therefore, the end 13Aa of the steel plate 13A and the end 13Db of the steel plate 13D are fixed to the side wall 11A via the same weld 14A. The end 13Ba of the steel plate 13B and the end 13Ab of the steel plate 13A are fixed to the center of the side wall 11B by welding. Therefore, the end 13Ba of the steel plate 13B and the end 13Ab of the steel plate 13A are fixed to the side wall 11B via the same weld 14B. The end 13Ca of the steel plate 13C and the end 13Bb of the steel plate 13B are fixed to the center of the side wall 11C by welding. Therefore, the end 13Ca of the steel plate 13C and the end 13Bb of the steel plate 13B are fixed to the side wall portion 11C via the same welded portion 14C. The end 13Da of the steel plate 13D and the end 13Cb of the steel plate 13C are fixed to the center position of the side wall portion 11C by welding. Therefore, the end 13Ca of the steel plate 13C and the end 13Db of the steel plate 13D are fixed to the side wall portion 11D via the same welded portion 14D.

The ends of the four steel plates 13 adjacent to each other are fixed together by a single weld 14. Before being welded, the four steel plates 13 are constructed as separate plate materials. In other words, this embodiment is different from, for example, inserting a small steel pipe with a square cross section into the joint steel pipe 10 before welding, and welding the corners of the small steel pipe to the inner surface of the joint steel pipe 10.

Here, the plate thickness tn of the joint steel pipe 10 is thicker than the plate thickness tc of the upper steel pipe 4 and the lower steel pipe 6. The plate thickness tn of the joint steel pipe 10 is the plate thickness of the side wall parts 11A, 11B, 11C, and 11D. Although not particularly limited, the plate thickness tn is set to 15 mm or more, preferably 25 mm or more, and 100 mm or less, preferably 55 mm or less. The plate thickness tc of the upper steel pipe 4 and the lower steel pipe 6 is the plate thickness of the four side wall parts of the upper steel pipe 4 and the lower steel pipe 6. Although not particularly limited, the plate thickness tc is set to 6 mm or more, preferably 9 mm or more, and 60 mm or less, preferably 40 mm or less, in the range of "plate thickness tn>plate thickness tc". The plate thickness td of the steel plates 13A, 13B, 13C, and 13D is thinner than the plate thickness tn of the joint steel pipe 10. Although not particularly limited, the plate thickness td is set to 6 mm or more, preferably 9 mm or more, and 40 mm or less, preferably 28 mm or less, in the range of "plate thickness tn>plate thickness td".

In this embodiment, the angle θ of one end of the steel plate 13 relative to one side wall portion 11, and the angle θ of the other end of the steel plate 13 relative to the other side wall portion 11 are 45°. Specifically, the angle θ of one end 13Aa of the steel plate 13A relative to one side wall portion 11A, and the angle θ of the other end 13Ab of the steel plate 13 relative to the other side wall portion 11B are 45°. The angle θ of one end 13Ba of the steel plate 13B relative to one side wall portion 11B, and the angle θ of the other end 13Bb of the steel plate 13 relative to the other side wall portion 11C are 45°. The angle θ of one end 13Ca of the steel plate 13C relative to one side wall portion 11C, and the angle θ of the other end 13Cb of the steel plate 13C relative to the other side wall portion 11D are 45°. The angle θ of one end 13Da of the steel plate 13D relative to one side wall portion 11D, and the angle θ of the other end 13Db of the steel plate 13D relative to the other side wall portion 11A are 45°.

However, the angle θ is not necessarily limited to 45°, and may be changed as appropriate depending on the attachment direction and number of beams 2. For example, the angle θ may be set to 30° or more, or 60° or less.

A gap 16 is formed between the corner 12 of the connection steel pipe 10 and the steel plate 13. Specifically, a gap 16A is formed between the corner 12A of the connection steel pipe 10 and the steel plate 13A. A gap 16B is formed between the corner 12B of the connection steel pipe 10 and the steel plate 13B. A gap 16C is formed between the corner 12C of the connection steel pipe 10 and the steel plate 13C. A gap 16D is formed between the corner 12D of the connection steel pipe 10 and the steel plate 13D.

The distance Ld between the outer surface of the joint steel pipe 10 and the weld 14, which is the fixed position of the steel plate 13 across the gap 16, is at least twice the plate thickness tn of the joint steel pipe 10. As shown in FIG. 1(b), the distance Ld of the weld 14B from the outer surface of the side wall 11A is defined by the distance between the outer surface and the weld 14B of the steel plate 13A across the gap 16A. This distance is the distance in the vertical direction to the outer surface of the side wall 11A. The distance Ld of the weld 14D from the outer surface of the side wall 11A is defined by the distance between the outer surface and the weld 14D of the steel plate 13D across the gap 16D. The distance Ld of the welds 14A, 14C from the outer surface of the side wall 11B is defined by the distance between the outer surface and the welds 14A, 14C of the steel plates 13A, 13B across the gaps 16A, 16B. The distance Ld of the welds 14B, 14D from the outer surface of the side wall 11C is defined by the distance between the outer surface and the welds 14B, 14D of the steel plates 13B, 13C across the gaps 16B, 16C. The distance Ld of the welds 14C, 14A from the outer surface of the side wall 11D is defined by the distance between the outer surface and the welds 14C, 14A of the steel plates 13C, 13D across the gaps 16C, 16D. In this embodiment, each weld 14A, 14B, 14C, and 14D is provided at the center of each side wall 11A, 11B, 11C, and 11D. Therefore, the distance Ld is approximately half the dimension of one side of the joint steel pipe 10.

As shown in FIG. 1(a), the steel plates 13A, 13B, 13C, and 13D are attached to the steel pipe 10 at the connection section over the entire length in the axial direction of the steel pipe. In other words, the steel plates 13A, 13B, 13C, and 13D extend in the axial direction of the steel pipe (up and down direction) from the upper end 10a to the lower end 10b of the steel pipe 10 at the connection section.

Alternatively, as shown in FIG. 2, the steel plates 13A, 13B, 13C, and 13D may be attached to a portion of the joint steel pipe 10 in the axial direction of the steel pipe. Specifically, the joint steel pipe 10 has a first region E1 where the steel plates 13A, 13B, 13C, and 13D are provided on the upper end 10a side, a second region E2 where the steel plates 13A, 13B, 13C, and 13D are provided on the lower end 10b side, and a third region E3 where the steel plates 13A, 13B, 13C, and 13D are not provided at a midpoint in the axial direction of the steel pipe. The first region E1 extends from the upper end 10a to below the upper flange 2a of the beams 2A and 2B. The second region E2 extends from the lower end 10b to above the lower flange 2b of the beams 2A and 2B.

The joint steel pipe 10 may be as shown in FIG. 3. In the joint steel pipe 10 shown in FIG. 1, adjacent steel plates 13 are fixed to each other via the same weld at the center of the side wall 11. Instead, in the joint steel pipe 10 shown in FIG. 3, the distance Ld is set shorter than that in FIG. 1, but in a range of at least twice the plate thickness tc. In this case, the ends of adjacent steel plates 13 are fixed to the side wall 11 while being spaced apart from each other.

Specifically, the steel plate 13A is fixed to the side wall 11A via a welded portion 14Aa near the corner 12A, and is fixed to the side wall 11B via a welded portion 14Ab. The steel plate 13B is fixed to the side wall 11B via a welded portion 14Ba near the corner 12B, and is fixed to the side wall 11C via a welded portion 14Bb. The steel plate 13C is fixed to the side wall 11C via a welded portion 14Ca near the corner 12C, and is fixed to the side wall 11D via a welded portion 14Cb. The steel plate 13D is fixed to the side wall 11D via a welded portion 14Da near the corner 12D, and is fixed to the side wall 11A via a welded portion 14Db. Other dimensional and angular relationships of the joint steel pipe 10 shown in FIG. 3 are the same as those of the joint steel pipe 10 shown in FIG. 1.

Next, we will explain the function and effect of the column-beam joint core 200 according to this embodiment.

First, as an example of a column-beam joint core using the conventional non-diaphragm method, the joint only has a thick-walled steel pipe at the joint, and no steel plate is provided inside. The ultimate strength of a column-beam joint structure using the non-diaphragm method is determined by the smaller of the out-of-plane full plastic strength and the root penetration fracture strength of the thick-walled steel pipe at the joint. The out-of-plane full plastic strength increases as the plate thickness of the steel pipe at the joint increases. On the other hand, if the plate thickness of the steel pipe at the joint becomes too thick, the stress is not transmitted to the entire plate thickness, and the improvement in the root penetration fracture strength due to the increase in plate thickness may be small (structural factor).

On the other hand, the out-of-plane yield strength and out-of-plane full plastic strength increase with an increase in the thickness of the steel pipe at the connection, so the larger the beam to which it is attached, the more the plate thickness must be increased. From the perspective of improving root penetration fracture strength, reinforcement other than increasing the plate thickness is desirable, but from the perspective of improving out-of-plane yield strength and out-of-plane full plastic strength, it is efficient to increase the plate thickness to improve strength, so the solutions from each perspective are contradictory. Thus, with conventional beam-column connection cores, there was a problem that it was difficult to obtain the desired strength by simply increasing the plate thickness of the steel pipe at the connection.

Furthermore, the Building Standards Act stipulates that steel materials with a thickness of over 40 mm must have a reduced design strength (F value). Therefore, when using steel materials with a cross-section that exceeds 40 mm in thickness, the increase in cross-sectional area is not directly reflected in the design strength. However, this does not apply if the Minister of Land, Infrastructure, Transport and Tourism certifies that steel materials with a thickness of 40 mm or more have the same performance as steel materials with a thickness of 40 mm or less. For example, there are many products on the market that are made of H-shaped steel or steel plates rolled using the TMCP process, have obtained the above-mentioned certification, and are sold with no reduction in standard strength. However, the introduction of the TMCP process tends to result in problems such as higher manufacturing costs than conventional rolling methods, and ultimately higher product costs (material factors).

In contrast, in the column-beam joint core 200 according to this embodiment, the plate thickness tn of the joint steel pipe 10 is thicker than the plate thickness tc of the upper steel pipe 4 and the lower steel pipe 6. Therefore, compared to the case where the plate thickness tn of the joint 3 is the same as the plate thickness tc of the upper steel pipe 4 and the lower steel pipe 6, the plate thickness tn of the joint steel pipe 10 is made thicker, thereby improving the bearing strength. In contrast, four steel plates 13 are provided inside the joint steel pipe 10, which are fixed to all combinations of a pair of adjacent side wall portions 11. When viewed from the top and bottom, each steel plate 13 is fixed with one end inclined to one side wall portion 11, and the other end is fixed with an inclined state to the other side wall portion 11. Therefore, each steel plate 13 can reinforce the four side wall portions 11 of the joint steel pipe 10 from the inside. When such a steel plate 13 is provided, the strength can be improved more efficiently than when the plate thickness tn of the joint steel pipe 10 is simply increased. Here, the strength of the joint 3 in the non-diaphragm construction method is borne by the out-of-plane deformation of the side wall 11 of the joint steel pipe 10 to a large extent, and is not borne by the steel plate 13 and the surface adjacent to the side wall 11 that is subjected to the out-of-plane deformation by the steel plate 13 to a large extent. In other words, since the steel plate 13 plays an auxiliary role in the out-of-plane deformation of the joint steel pipe 10, even if the thickness is increased excessively, the effect of improving the strength obtained is low relative to the increase in the total cross-sectional area. Therefore, in order to obtain a high strength improvement effect while suppressing the increase in the cross-sectional area, the plate thickness td of the steel plate 13 is made thinner than the plate thickness tn of the joint steel pipe 10. As a result, the strength of the column-beam joint structure 100 can be improved while suppressing the increase in the cross-sectional area.

In addition, in the column-beam joint core 200 according to this embodiment, there is no need to increase the plate thickness tn of the joint steel pipe 10 more than necessary, so it is possible to keep the plate thickness tn to 40 mm or less while ensuring sufficient strength, which makes it possible to prevent the introduction of the aforementioned TMCP process or the like from increasing product costs. As a result, it becomes possible to solve both the problems of structural factors and material factors mentioned above.

The angle θ of one end of the steel plate 13 relative to one side wall 11, and the angle of the other end of the steel plate 13 relative to the other side wall 11, may be 45°. In this case, the symmetry of the arrangement and shape of each steel plate 13 can be ensured. Therefore, the bearing strength of the four side walls 11 can be improved evenly. In addition, since there is a possibility that the beam 2 will be attached to the joint portion 3 from all four directions, by setting the angle θ to 45°, the joint portion 3 can be made a general-purpose product.

A gap 16 is formed between the corner 12 of the joint steel pipe 10 and the steel plate 13, and the distance Ld between the outer surface of the joint steel pipe 10 and the fixed position of the steel plate 13 across the gap 16 may be at least twice the plate thickness of the joint steel pipe 10. Depending on the shape and manufacturing method of the joint steel pipe 10, welding the steel plate 13 near the corner 12 may reduce workability and structural performance. Therefore, by keeping the distance Ld between the outer surface of the joint steel pipe 10 and the fixed position of the steel plate 13 across the gap 16 at least twice the plate thickness tc of the joint steel pipe 10, the deterioration of workability and structural performance can be suppressed.

The steel plate 13 may be attached to the entire length of the joint steel pipe 10 in the axial direction of the steel pipe. In this case, the effect of improving the strength can be obtained over the entire length of the joint steel pipe 10.

The steel plate 13 may be attached to a portion of the connection steel pipe 10 in the axial direction of the steel pipe. In this case, the steel plate 13 can be limited to necessary locations of the connection steel pipe 10, particularly the location where the H-shaped steel beam flange is attached, to obtain the effect of improving the strength.

Next, the analysis content for confirming the effect of the beam-column joint core 200 according to this embodiment will be described. As shown in Fig. 4(a), in the joint 3 of the non-diaphragm construction method, force is transmitted from the beams 2A, 2B to the column 1 via out-of-plane deformation of the side wall 11 of the joint steel pipe 10. In contrast, as shown in Fig. 4(b), a method is known for verifying the strength due to out-of-plane deformation by a unidirectional tensile test of a test specimen 250 of an element extracted from the flanges 2a of the H-shaped beams 2A, 2B and a part of the joint steel pipe 10 (Summary of the Architectural Institute of Japan Conference/Nippon Steel & Sumitomo Metal Construction Materials, JFE Steel). In the model shown in Figure 4 (b) simulating the test method, the joint steel pipe 10 and steel plate 13 were made of SN490 material, and the load plate 201 simulating the flange 2a of the beam and the welded part between the joint steel pipe 10 and the load plate 201 were made of TMCP385 material. A finite element analysis was performed, and the "tensile load" of each parameter and the "relative displacement between the load plate and the steel pipe displacement" which means the out-of-plane deformation of the steel pipe wall were compared. The results are shown in Figure 5 (c). In this case, the load plate had a thickness of 40 mm and a width of 200 mm, and the welded part between the load plate 201 and the joint steel pipe 10 was a K-shaped groove with a reinforcement height of 10 mm on one side.

As a test specimen for the comparative example, as shown in FIG. 5(a), a joint steel pipe 10 with a plate thickness tn of 41 mm and without a steel plate 13 was prepared. As a test specimen for the embodiment, as shown in FIG. 5(b), a joint steel pipe 10 with a plate thickness tn of 35 mm and a steel plate 13 with a plate thickness td of 9 mm was prepared. As a result of comparing the load-displacement relationship for these test specimens, as shown in FIG. 5(c), it is understood that both have the same load-displacement relationship. At this time, it is understood that the joint steel pipes 10 shown in FIG. 5(a) and FIG. 5(b) have the same cross-sectional area, and even if the side wall portion 11 is thinned, the bearing strength can be secured by the knee brace of the steel plate 13. In other words, it is understood that by making it a non-diaphragm joint with knee brace by the steel plate 13, it is possible to improve the bearing strength of the non-diaphragm construction joint while thinning the side wall portion 11. It can be understood that this can solve the problems related to the thickening of the structural factors and material factors mentioned above. In addition, in Figures 5(a) and (b), dimension lines are indicated with numbers. These numbers indicate the dimensional values, and the unit is "mm." For example, "402" is indicated as the dimension of one side of the connection steel pipe 10, which means that one side of the connection steel pipe 10 is "402 mm." The same applies to the subsequent figures.

Furthermore, as shown in Figure 6 (a), a specimen for a comparative example was prepared that has the same cross-sectional area as those in Figures 5 (a) and (b), with the plate thickness tn of the joint steel pipe 10 being 25 mm and the plate thickness td of the steel plate 13 being 45 mm. A comparison of the load-displacement relationship for this specimen is shown in Figure 6 (b). It can be seen that the cross section in Figure 6 (a), where the plate thickness td is greater than the plate thickness tn, has a lower load at the same displacement than the cross sections in Figures 5 (a) and (b). This is because the strength of the non-diaphragm joint with knee braces is borne by a high proportion of the out-of-plane deformation of the side wall 11, and the proportion of the force borne by the steel plate 13 and the surface adjacent to the side wall 11 that is subjected to out-of-plane deformation by the steel plate 13 is not large. Although the steel plate 13 has an effect, it only plays a supplementary role in preventing the out-of-plane deformation of the side wall 11, and it can be understood that in order to reduce the total cross-sectional area and efficiently improve the strength of the connection, the plate thickness td of the steel plate 13 must be thinner than the plate thickness td of the connection steel pipe 10. From this analysis, it can be confirmed that there is an effect of making plate thickness tn > plate thickness td, and that there is little effect of making plate thickness td > plate thickness tn.

As shown in Fig. 7(a)(b) and Fig. 8(a), specimens with the same cross-sectional area as Fig. 5(a), the plate thickness tn of the joint steel pipe 10 was unified at 35 mm, and the plate thickness td of the steel plate 13 was 11.5 mm, 17.5 mm, and 27 mm were prepared. In these specimens, the thicker the plate thickness of the steel plate 13, the closer the position where the steel plate 13 is attached to the inner corner of the joint steel pipe 10 becomes in the cross section. In this case, all the cross sections have the same cross-sectional area as the joint steel pipe 10 in Fig. 5(a) with a plate thickness tn of 41 mm and no steel plate 13. Comparing the load-displacement relationship shown in Fig. 8(b) for these specimens, it is confirmed that the load-displacement relationship is the same, and if the plate thickness tn is greater than the plate thickness td, the effect of improving the strength by providing the steel plate 13 is confirmed even if the position of the steel plate 13 approaches the inner corner of the joint steel pipe 10.

If the position of the steel plate 13 is too close to the inner corner of the joint steel pipe 10, when the joint steel pipe 10 is a rolled material (see FIG. 9(a)), it may collide with the inner corner, which may result in poor welding workability and make it difficult to ensure performance. Also, when the joint steel pipe 10 is a four-sided box (see FIG. 9(e)), there is a concern that the performance of the heat-affected zone 24a may be reduced due to the steel plate 13 intersecting with the heat-affected zone 24a of the welded portion 24 at the corner. Since the plate thickness tn is often the minimum value for manufacturing at the inner corner of the rolled material, in consideration of workability and structural performance assurance, it is desirable that the distance Ld from the outer surface of the joint to the welding position of the steel plate 13 is at least twice the plate thickness tn of the joint steel pipe 10.

As shown in Figure 10(a), the test specimen was not reinforced with a knee brace using a steel plate 13, but rather had the internal corner 25 of the connection steel pipe 10 thickened to give it the same cross-sectional area as Figure 5(a). Comparing the load-displacement relationship shown in Figure 10(b), the load-displacement relationship shown in Figure 10(a) is slightly lower at the same displacement than that shown in Figure 5(a), and no improvement in load-displacement is expected. In addition, because the plate thickness of the corner is extremely thick, it is extremely difficult to manufacture steel members with uniform material properties inside the plate thickness, and this is unsuitable as a connection member for the non-diaphragm method.

Figure 11 is a table detailing the dimensions, cross-sections, and other information of each of the test specimens mentioned above.

The present invention is not limited to the above-mentioned embodiment and modified examples. The dimensions, angles, etc. described in the above-mentioned embodiment are merely examples and may be modified as appropriate without departing from the spirit of the present invention. In addition, the shapes of the steel pipes and steel plates at the connection section may also be modified as appropriate.

1...column, 2...beam, 3...joint, 4...upper steel pipe, 6...lower steel pipe, 10...joint steel pipe, 11...side wall, 12...corner, 13...steel plate, 16...gap, 200...column-beam joint core.

Claims (6)

A column-beam joint core using a non-diaphragm construction method using a joint steel pipe having a square cross section at the joint,
The joint steel pipe is connected to an upper steel pipe on the upper side and a lower steel pipe on the lower side, and has four side wall portions that constitute the four sides of the rectangular cross section,
Four steel plates are provided inside the connection steel pipe and are fixed to all combinations of adjacent pairs of the side wall portions,
Each steel plate has one end fixed to one of the side wall portions in a slanted state when viewed from the top-bottom direction, and the other end fixed to the other side wall portion in a slanted state,
The plate thickness of the joint steel pipe is thicker than the plate thicknesses of the upper steel pipe and the lower steel pipe,
A column-beam joint core, wherein the thickness of the steel plate is thinner than the thickness of the joint section steel pipe. The column-beam joint core according to claim 1, wherein the angle of one end of the steel plate relative to one of the side walls and the angle of the other end of the steel plate relative to the other side wall are 45°. The column-beam joint core according to claim 1 or 2, in which a gap is formed between the corner of the joint steel pipe and the steel plate, and the distance between the outer surface of the joint steel pipe and the fixed position of the steel plate across the gap is at least twice the plate thickness of the joint steel pipe. The column-beam joint core according to any one of claims 1 to 3, in which the steel plate is attached to the entire length of the joint steel pipe in the axial direction of the steel pipe. The column-beam joint core according to any one of claims 1 to 3, wherein the steel plate is attached to a portion of the joint steel pipe in the axial direction of the steel pipe. The column-beam joint core according to any one of claims 1 to 5, wherein the ends of adjacent steel plates are fixed to the side wall portions in a spaced-apart relationship with each other.

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