Joint structure

Abstract

This invention provides a joint structure that can improve bending rigidity using a method different from the conventional approach of increasing the thickness of the through diaphragm. [Solution] The joining structure 1 is a joining structure in which an upper member 11 and a lower member 12 are joined via a through diaphragm 13, wherein the upper member 11 has a cross-sectional shape different from that of the lower member 12, and in a plan view, the four corners of the upper member 11 overlap with those of the lower member 12.

Description

[Technical Field]

[0001] The present invention relates to a joining structure in which an upper member and a lower member are joined via a through diaphragm. [Background technology]

[0002] In steel-framed buildings, when the diameter of columns changes between floors, a variable-width joint system with a thickened diaphragm is used as one of the joint types. Reducing the column diameter saves material, which has the advantage of reducing costs and GHG (Green House Gas: greenhouse gases such as CO2). As shown in Non-Patent Literature 1 below, the application condition for this variable-width joint system is that the diaphragm does not collapse until the column collapses. The collapse of the diaphragm is the minimum load-bearing capacity of the joint, which can be determined by yield line theory assuming an arbitrary collapse mechanism (hereinafter, j M u ) and the collapse of the column is due to the full plastic moment of the upper column (hereinafter, c M p ) is determined by. That is, j M u ≧ c M p Satisfying this condition is a requirement for applying the differential width joint type. Non-patent documents 2 and 3 below disclose the load-bearing capacity evaluation that forms the basic concept of Non-patent document 1.

[0003] Patent Document 1 discloses a method for designing the plate thickness of a through diaphragm in a variable-width joint type, wherein the plate thickness satisfies a predetermined load-bearing capacity evaluation formula and a defined stiffness evaluation formula. Patent Document 1 also discloses three arrangements for the upper and lower columns: a center-aligned arrangement (Figures 1 and 2 of Patent Document 1), a one-way eccentric arrangement (Figures 3 and 4 of Patent Document 1), and a two-way eccentric arrangement (Figures 5 and 6 of Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-028997 [Non-patent literature]

[0005] [Non-Patent Document 1] Architectural Institute of Japan: Steel structure joint design guidelines 4th edition (2021) [Non-Patent Document 2] Tsuyoshi Tanaka, Masao Terashima, and Mototsugu Tabuchi: Evaluation of the load-bearing capacity of through diaphragms in irregular-width rectangular steel pipe column-beam joints, Annual Proceedings of Steel Structures, Vol. 16, (2008), pp. 95-102. [Non-Patent Document 3] Seiji Miyoshi, Tsuyoshi Tanaka, Mototsugu Tabuchi, Masao Terashima: Out-of-plane bending strength of through diaphragm in irregular-width rectangular steel pipe column-beam joint, Proceedings of the Architectural Institute of Japan Annual Meeting, (2011), pp. 1087-1088. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Patent Document 1 improves bending rigidity by increasing the thickness of the diaphragm. However, increasing the plate thickness increases the amount of steel used, thus increasing costs. Furthermore, depending on the standard, it may be necessary to reduce strength due to the increased plate thickness, or the availability of materials may become an issue if one changes to TMCP steel, which does not require strength reduction. Therefore, other methods that can improve bending rigidity are needed.

[0007] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide a joint structure that can improve bending rigidity using a method different from the conventional method of increasing the thickness of the through diaphragm. [Means for solving the problem]

[0008] Through various studies conducted by the inventors, the following new findings were obtained. Specifically, when bending is applied to the joint structure, the stress (compressive or tensile force) is maximum at the four corners of the cross-section of the upper member. Therefore, by overlapping the four corners of the upper member with the lower member in a plan view, stress can be transmitted between the upper and lower members at the four corners without out-of-plane bending deformation of the through diaphragm, thereby mitigating the indentation of the through diaphragm by the upper member and improving bending rigidity. The present invention was made based on these new findings.

[0009] In one embodiment, the joining structure according to the present invention is a joining structure in which an upper member and a lower member are joined via a through diaphragm, wherein the upper member has a cross-sectional shape different from that of the lower member, and in a plan view, the four corners of the upper member overlap with those of the lower member. [Effects of the Invention]

[0010] According to one embodiment of the joint structure of the present invention, in a plan view, the four corners of the upper member overlap with the lower member, so the bending rigidity can be improved by a method different from the conventional method of increasing the plate thickness of the through diaphragm. [Brief explanation of the drawing]

[0011] [Figure 1] This is a plan view showing a joint structure according to an embodiment of the present invention. [Figure 2] This is a front view showing the joint structure in Figure 1. [Figure 3] This graph illustrates the preferred ratio AR in the joint structure shown in Figure 1. [Figure 4] This is a plan view showing a first modified example of the joint structure in Figure 1. [Figure 5] This is a plan view showing a second modified example of the joint structure in Figure 1. [Figure 6] This is a plan view showing a third modified example of the joint structure in Figure 1. [Figure 7] This is a perspective view showing a column joint structure with varying widths, including the joint structure shown in Figure 1. [Figure 8]Figure 7 is a perspective view showing a first modified example of the column joint structure with varying widths. [Figure 9] Figure 8 is a perspective view showing the beam connected to the column joint structure with varying widths. [Figure 10] Figure 7 is a perspective view showing a second modified example of the column joint structure with varying widths. [Figure 11] Figure 10 is a perspective view showing the beam connected to the column joint structure with varying widths. [Figure 12] This is a perspective view showing the first aspect of the analytical model used in the example. [Figure 13] This is an explanatory diagram showing the first aspect of the analysis model in Figure 12. [Figure 14] This is a perspective view showing a second aspect of the analytical model used in the example. [Figure 15] This is an explanatory diagram showing the second aspect of the analysis model in Figure 14. [Figure 16] This graph shows the nominal stress-nominal strain relationship set in the example. [Figure 17] This is a contour map of the equivalent stress in analysis models No. 2 and 4. [Figure 18] This is an explanatory diagram showing the conventionally proposed collapse patterns. [Figure 19] This is an explanatory diagram showing the normalized deformation angle at the time of member yielding. [Figure 20] This is an explanatory diagram showing the definitions of yield moment and deformation angle. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention will be described below with reference to the drawings. The present invention is not limited to each embodiment, and can be materialized by modifying the components without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in each embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined.

[0013] First, the joining structure 1 according to an embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a plan view showing the joining structure 1 according to an embodiment of the present invention, and Figure 2 is a front view showing the joining structure 1 of Figure 1.

[0014] As shown in Figures 1 and 2, the joint structure 1 according to an embodiment of the present invention is one in which an upper member 11 and a lower member 12 are joined via a through diaphragm 13. The entire lower end circumference of the upper member 11 may be joined to the upper surface of the through diaphragm 13, and the entire upper end circumference of the lower member 12 may be joined to the lower surface of the through diaphragm 13. The joining may be performed by welding.

[0015] As shown in Figure 1, the upper member 11 has a different cross-sectional shape from that of the lower member 12. The cross-sectional shape is the shape of the cross-section in a plane perpendicular to the material axis direction. In the joint structure 1 of this embodiment, as shown in Figure 1, the four corners 11c (four corners or edges) of the upper member 11 overlap with the lower member 12 in a plan view. In other words, the lower member 12 is positioned below the four corners 11c of the upper member 11.

[0016] When bending is applied to the joint structure 1, the stress (compressive or tensile force) is maximized at the four corners 11c of the upper member 11 within the cross-section of the upper member 11. For example, in Figure 2, when a load Lo is applied to the upper member 11 from left to right, the compressive force CP is maximized at the right corner 11c in the figure, and the tensile force TF is maximized at the left corner 11c in the figure. As in this embodiment, by overlapping the four corners 11c of the upper member 11 with the lower member 12 in a plan view, stress can be transmitted between the upper member 11 and the lower member 12 at the four corners 11c without going through out-of-plane bending deformation of the through diaphragm 13, the indentation of the through diaphragm 13 by the upper member 11 can be mitigated, and the bending rigidity can be improved.

[0017] If it is assumed that at least one of the four corners 11c does not overlap with the lower member 12, depending on the direction of the load Lo applied to the upper member 11, the out-of-plane bending stiffness of the through diaphragm 13 may be insufficient, and stress may not be sufficiently transmitted between the upper member 11 and the lower member 12. However, by overlapping (all of) the four corners 11c of the upper member 11 with the lower member 12 as in the present embodiment, even if the load Lo is applied to the upper member 11 from various directions, stress can be sufficiently transmitted between the upper member 11 and the lower member 12 without going through the out-of-plane bending deformation of the through diaphragm 13 (regardless of the out-of-plane bending stiffness). That is, according to the configuration of the present embodiment, it can cope with the load Lo in various directions.

[0018] It is only necessary that the plate thickness range of the four corners 11c of the upper member 11 overlaps with at least a part of the plate thickness range of the lower member 12. It is preferable that the four corners 11c of the upper member 11 overlap with the lower member 12 within the range that falls within the limit tolerance for joint deviation described in "(12) Joint deviation e" in "Appendix 6." and "Steel Structure Precision Inspection Standard Appendix Table 3" of "Japanese Architectural Standard Specification JASS6 Steel Construction Works" (issued by Architectural Institute of Japan, 11th edition, issued in January 2018). The four corners 11c of the upper member 11 refer to four regions located at positions farthest from the center point in the cross section of the upper member 11.

[0019] As shown in Fig. 1, the cross-sectional shape of the upper member 11 of the present embodiment is a shape having a long-side direction 11L and a short-side direction 11S. The long-side direction 11L and the short-side direction 11S are directions orthogonal to each other. The upper member 11 has a pair of opposing plate elements 11f that are arranged spaced apart from each other in the long-side direction 11L and extend in the short-side direction 11S. The side length D in the long-side direction 11L of the upper member 11 u is the diameter or width D of the lower member 12 pEqually, as shown in Figure 1, in a plan view, a pair of opposing plate elements 11f extending in the short-side direction 11S of the upper member 11 overlap with the plate element 12f of the lower member 12. By adopting this configuration, stress can be transmitted more reliably between the upper member 11 and the lower member 12 without out-of-plane bending deformation of the through diaphragm 13, thereby more reliably improving bending rigidity. In this specification, the dimensions of a shape having a longitudinal direction and a transverse direction, such as a rectangle, are referred to as side length, and the dimensions of any shape not limited to such shapes are referred to as diameter or width. The terms diameter or width also include side length.

[0020] As particularly shown in Figure 1, in the joint structure 1 of this embodiment, the upper member 11 and the lower member 12 are rectangular steel pipes. The cross-sectional shape of the upper member 11 is a rectangle with a long side direction 11L and a short side direction 11S, and the cross-sectional shape of the lower member 12 is a square. When the upper member 11 is a rectangular steel pipe, the plate element 11f is composed of a flat plate portion, and the four corners 11c are composed of corner portions. In Figure 1, the plate element 11f is mainly shown to be perpendicular at the four corners (four corners 11c) of the upper member 11. However, as shown on the left side of the figure, the corner portion may be composed of an arc-shaped portion having a predetermined radius of curvature. When the line segment connecting the starting point of curvature P1 on the outer surface of the upper member 11 and the starting point of curvature P2 on the inner surface of the upper member 11 in the cross-section of the upper member 11 is called the switching line CL, the corner portion is the region between the pair of switching lines CL. The switching line CL is included in the corner portion. In particular, the switching line CL located on the plate element 11f extending in the short-side direction 11S of the upper member 11 is included in the corner. When the switching line CL located on the plate element 11f extending in the short-side direction 11S of the upper member 11 overlaps with at least a portion of the plate thickness range of the lower member 12, it is understood that the corner of the upper member 11 overlaps with the lower member 12. It is preferable that point P3 located at the center of the plate thickness of the plate element 11f on the switching line CL overlaps with the plate thickness range of the lower member 12. When the plate elements 11f are perpendicular, the corner is defined as the region where the two plate elements 11f intersect (the region highlighted by shading in Figure 1). Even in this case, the boundary line of the corner (the extension of the inner surface of the plate element 11f) is included in the corner, and when the boundary line located on the plate element 11f extending in the short-side direction 11S of the upper member 11 overlaps with at least a part of the plate thickness range of the lower member 12, it is understood that the corner of the upper member 11 overlaps with the lower member 12. Furthermore, it is preferable that the point located at the center of the plate thickness of the plate element 11f on the same boundary line overlaps with the plate thickness range of the lower member 12. Also, when the upper member 11 is a rectangular steel pipe, the side length D in the long-side direction 11L of the upper member 11 u This is the dimension between the thickness centers of plate elements 11f that are separated from each other in the short side direction 11S. Also, the side length B of the upper member 11 in the short side direction 11S. u This is the dimension between the thickness centers of plate elements 11f that are separated from each other in the long side direction 11L. The corners of the lower member 12, the plate elements and diameter or width Dp The same applies to this matter.

[0021] In Figure 1, the upper member 11 is positioned biased towards the short side direction 11S such that, in a plan view, one of the pair of plate elements 11f extending in the long side direction 11L of the upper member 11 overlaps with the plate element 12f of the lower member 12. However, the relative positional relationship between the upper member 11 and the lower member 12 in the short side direction 11S may be changed.

[0022] Next, Figure 3 is a graph illustrating the preferred ratio AR in the joint structure 1 of Figure 1. In the joint structure 1 of this embodiment, the side length B of the short side direction 11S of the upper member 11 is... u (See Figure 1) Side length D in the long side direction 11L u (See Figure 1) Ratio AR(D u / B u (Aspect ratio), and reference through diaphragm thickness t x The thickness of the through diaphragm 13 relative to the diaphragm t d (See Figure 2) Ratio t d / t x It is preferable that the following equation A is satisfied. In considering the ratio AR, the side length B is the side length of the short side direction 11S of the upper member 11 in Figure 1. u The longer side direction is 11L and the side length D u The value was reduced from its original state (the ratio AR was increased from 1.0).

[0023]

number

[0024] However, the application conditions for formula A are the side length D of the long side direction 11L of the upper member 11. u The diameter or width D of the lower member 12 p Equal to the side length B of the short side direction 11S of the upper member 11. u (B u <D u This is the case where the variable is the side length B of the upper member 11. u ,D uWhen they are equal to each other, the ratio AR is 1.0, and in this case the diameter or width (side length B) of the upper member 11 is equal to the diameter or width (side length B). u ,D u ) matches the diameter or width of the lower member 12, so the thickness t of the through diaphragm 13 d Theoretically, this can be set to a value very close to 0. Also, α = 0.219, and the reference through diaphragm thickness t x The diameter or width D of the lower member 12 p In a standard joint structure in which a standard lower rectangular steel pipe having a square cross-section of the same diameter or width as the standard lower rectangular steel pipe and a standard upper rectangular steel pipe having a square cross-section with a diameter or width 50 mm smaller than the diameter or width of the standard lower rectangular steel pipe are joined via a standard through diaphragm, the joint load capacity j M u and the full plastic moment of the upper reference square steel pipe c M p This is the minimum standard through-diaphragm thickness that satisfies equation B below. By satisfying equation B, the through-diaphragm 13 will not collapse until the upper member 11 collapses. Full plastic moment c M p This is calculated based on Equation 13 described below. Joint strength j M u This is calculated based on equations 14-21 described below.

[0025]

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[0026] Figure 3 shows the ratio AR(D) on the vertical axis. u / B u ) and the horizontal axis is compared t d / t x This is the resulting graph. Equation A above indicates that when the ratio AR is greater than 1, the ratio AR lies in the triangular region below the solid line that extends upward to the right in Figure 3.

[0027] In the joining structure 1 of this embodiment, it is preferable that the following formula C is further satisfied, where β = 1.167.

[0028]

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[0029] Equation C above indicates that when the ratio AR is greater than 1, the ratio AR lies in the region below the dashed line extending horizontally in Figure 3. When equations A and C are satisfied, the ratio AR is included in the shaded trapezoidal region in Figure 3. Furthermore, from the viewpoint of more reliably improving bending stiffness, the ratio t d / t x There is no need to set an upper limit, but the thickness t of the through diaphragm 13 d The diaphragm thickness t is passed through the reference. x Compared from the perspective of setting the following: d / t x It may be 1 or less.

[0030] Next, Figure 4 is a plan view showing a first modified example of the joint structure 1 of Figure 1. In the embodiment shown in Figure 1, the cross-sectional shape of the lower member 12 was described as being square, but the cross-sectional shape of the lower member 12 may be changed. As shown in Figure 4, the cross-sectional shape of the lower member 12 may be rectangular. In this case, the side length D of the long side direction 11L of the upper member 11 is... u The side length D of the lower member 12 in the short side direction 12S p This is made equal to the above. As shown in Figure 4, the upper member 11 and the lower member 12 may be arranged coaxially. The center position of the short side direction 11S of the upper member 11 and the center position of the long side direction 12L of the lower member 12 may coincide.

[0031] Next, Figure 5 is a plan view showing a second modified example of the joint structure 1 of Figure 1. In the embodiment shown in Figure 1, the upper member 11 was described as a rectangular steel pipe, but as shown in Figure 5, the upper member 11 may be made of other members such as H-shaped steel. When the upper member 11 is made of H-shaped steel, the plate element 11f is made of flange 11a, and the four corners 11c are made of both ends of flange 11a. Also, the side length D of the long side direction 11L of the upper member 11 uThe dimension is defined as the distance between the centers of the plate thickness of the flange 11a. In the illustrated embodiment, the lower member 12 is a rectangular steel pipe with a rectangular cross-sectional shape. The width W of the flange 11a is the side length D of the shorter side direction 12S of the lower member 12. p It is shorter than that. The width W of flange 11a is the dimension between the outer ends of flange 11a.

[0032] Next, Figure 6 is a plan view showing a third modified example of the joint structure 1 of Figure 1. In the embodiment shown in Figure 1, the cross-sectional shape of the upper member 11 was described as having a long side direction 11L and a short side direction 11S, but depending on the shape of the lower member 12, the cross-sectional shape of the upper member 11 may not have a long side direction 11L and a short side direction 11S. As shown in Figure 6, the cross-sectional shape of the upper member 11 may be square and the cross-sectional shape of the lower member 12 may be circular. Such an embodiment is also included in embodiments in which the upper member 11 has a cross-sectional shape different from that of the lower member 12. As shown in Figure 6, when the upper member 11 is a square steel pipe and the lower member 12 is a circular steel pipe, it is preferable that the diagonal distance of the outer dimensions of the upper member 11 is equal to the diameter or width of the outer dimensions of the lower member 12, or that the diagonal distance of the inner dimensions of the upper member 11 is equal to the diameter or width of the inner dimensions of the lower member 12. By configuring it in this way, regardless of whether the thickness of the upper member 11 is equal to or different from the thickness of the lower member 12, the four corners 11c of the upper member 11 can be more reliably made to overlap with the lower member 12.

[0033] Next, Figure 7 is a perspective view showing a column joint structure of different widths 2, which includes the joint structure 1 of Figure 1. The joint structure 1 of Figure 1 may be included in the column joint structure of different widths 2 as shown in Figure 7. In the column joint structure of different widths 2, the column 21 of the upper floor and the column 22 of the lower floor are joined via a joint 23. The joint 23 has an upper diaphragm 23a, a rectangular joint panel 23b whose upper surface is joined to the lower surface of the upper diaphragm 23a, and a lower diaphragm 23c whose upper surface is joined to the lower surface of the joint panel 23b. The lower end of the column 21 of the upper floor is joined to the upper surface of the upper diaphragm 23a, and the upper end of the column 22 of the lower floor is joined to the lower surface of the lower diaphragm 23c.

[0034] The upper floor columns 21 are made of rectangular steel pipes with a rectangular cross-section, while the lower floor columns 22 and connecting panels 23b are made of rectangular steel pipes with a square cross-section. The diameter or width of the upper floor columns 21 in the short-side direction is smaller than the diameter or width of the lower floor columns 22. The diameter or width of the connecting panels 23b is approximately the same as the diameter or width of the lower floor columns 22. In such a column-joint structure with different widths 2, the upper member 11 in Figure 1 may be the upper floor column 21, the lower member 12 in Figure 1 may be the connecting panel 23b, and the through diaphragm 13 in Figure 1 may be the upper diaphragm 23a. Although not shown, the joint 23 may be made of only one diaphragm. In this case, the upper member 11 in Figure 1 may be the upper floor column 21, and the through diaphragm 13 in Figure 1 may be the diaphragm constituting the joint 23.

[0035] In the embodiment shown in Figure 7, the lower floor column 22 and the connecting panel 23b are arranged coaxially with each other. In addition, one of the pair of plate elements extending in the long-side direction of the upper floor column 21 is positioned to overlap with the plate element of the connecting panel 23b.

[0036] Next, Figure 8 is a perspective view showing a first modified example of the uneven-width column joint structure 2 of Figure 7. As shown in the embodiment in Figure 8, the upper floor column 21 and joint panel 23b may be made of rectangular steel pipes with a rectangular cross-section, and the lower floor column 22 may be made of rectangular steel pipes with a square cross-section. In the embodiment shown in Figure 8, the diameter or width of the upper floor column 21 and joint panel 23b are approximately the same. The diameter or width of the joint panel 23b in the short-side direction is smaller than the diameter or width of the lower floor column 22. In such an uneven-width column joint structure 2, the upper member 11 in Figure 1 may be the joint panel 23b, the lower member 12 in Figure 1 may be the lower floor column 22, and the through diaphragm 13 in Figure 1 may be the lower diaphragm 23c.

[0037] In the embodiment shown in Figure 8, the upper floor column 21 and the connecting panel 23b are arranged coaxially with each other. In addition, one of the pair of plate elements extending in the long-side direction of the connecting panel 23b is positioned to overlap with the plate element of the lower floor column 22.

[0038] Next, Figure 9 is a perspective view showing the state in which a beam 24 is joined to the column joint structure 2 of different widths shown in Figure 8. As shown in Figure 9, a beam 24 may be joined to the joint 23. Although not limited to this, in an embodiment in which the joint panel 23b (upper member 11) is positioned biased in the short-side direction such that one of the pair of plate elements extending in the long-side direction of the joint panel 23b (upper member 11) overlaps with a plate element of the column 22 (lower member 12) of the lower floor, as shown in Figures 8 and 9, three beams 24 may be joined to the joint 23.

[0039] Next, Figure 10 is a perspective view showing a second modified example of the uneven-width column joint structure 2 of Figure 7. In the embodiment shown in Figure 10, the upper floor column 21 and joint panel 23b are made of rectangular steel pipes with a rectangular cross-section, and the lower floor column 22 is made of rectangular steel pipes with a square cross-section. The diameter or width of the upper floor column 21 in the long side direction is approximately the same as the diameter or width of the joint panel 23b in the short side direction, and the diameter or width of the joint panel 23b in the long side direction is approximately the same as the diameter or width of the lower floor column 22. In such an uneven-width column joint structure 2, the upper member 11 in Figure 1 may be the upper floor column 21, the lower member 12 in Figure 1 may be the joint panel 23b, and the through diaphragm 13 in Figure 1 may be the upper diaphragm 23a. Furthermore, the upper member 11 in Figure 1 may be a connecting panel 23b, the lower member 12 in Figure 1 may be a column 22 on the lower floor, and the through diaphragm 13 in Figure 1 may be a lower diaphragm 23c.

[0040] In the embodiment shown in Figure 10, the upper floor column 21, the connecting panel 23b, and the lower floor column 22 are arranged coaxially. The center position of the upper floor column 21 in the short-side direction coincides with the center position of the connecting panel 23b in the long-side direction. Also, the center position of the connecting panel 23b in the short-side direction coincides with the center position of the lower floor column 22 in the width direction.

[0041] Next, Figure 11 is a perspective view showing the state in which beams 24 are joined to the column joint structure 2 of different widths shown in Figure 10. Although not limited to this, as shown in Figures 10 and 11, in an embodiment in which the upper floor column 21, joint panel 23b and lower floor column 22 are arranged coaxially, four beams 24 may be joined to the joint 23.

[0042] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Examples]

[0043] The present invention will be described more specifically below with reference to examples. The present invention is not limited to these examples.

[0044] The inventors conducted simulation tests of the joint structure using a general-purpose finite element analysis (FEA) program. Analysis models No. 1 to 4, whose general shapes are shown in Figures 12 and 13, and Figures 14 and 15, were created. Table 1 below shows the conditions for analysis models No. 1 to 4. All analysis models No. 1 to 4 are joint structures in which an upper rectangular steel pipe (upper member) and a lower rectangular steel pipe (lower member) are joined via a through diaphragm. For the lower rectangular steel, a rectangular steel pipe with a square cross-section was used in all analysis models No. 1 to 4. For the upper rectangular steel, a rectangular steel pipe with a square cross-section was used in analysis models No. 1 and 2, while a rectangular steel pipe with a rectangular cross-section was used in analysis models No. 3 and 4. In analysis models No. 1 and 2, the upper and lower square steel sections are arranged coaxially (see Figure 13), while in analysis models No. 3 and 4, the four corners of the upper square steel section overlap with the lower square steel section in a plan view (see Figure 15).

[0045] [Table 1]

[0046] The boundary conditions for the analysis model were a pin roller support at the upper end and a fixed end at the lower end. A displacement incremental analysis was performed by applying a forced displacement (100 mm) in one direction while maintaining an axial compressive force at the upper end support point with an axial force ratio of 0.3. The nominal stress-nominal strain relationship of the material was assumed to be of the perfect elastoplastic type, as shown in Figure 16, and this was converted to a true stress-true strain relationship for use in the analysis.

[0047] The nominal yield strength of the square steel pipe is 295 (N / mm²). 2 The nominal yield strength of the through diaphragm, weld metal, and backing plate is set to 325 (N / mm²). 2 ) and all elastic moduli are set to 205,000 (N / mm²). 2 As described above, in analysis models No. 3 and 4, the upper rectangular steel pipe is assumed to be rectangular, and the load is applied in the direction of the weak axis (short side). To simplify the analysis model, it was assumed that there is no curvature at the corners of the rectangular steel pipe, and that each plate element is orthogonal.

[0048] Table 2 below shows the parameters used for analysis models No. 1 and 2. Analysis model No. 1 is a variable-width joint structure that is deemed designable according to the Steel Structure Joint Design Guidelines (Non-Patent Literature 1), and is the target model. Analysis model No. 2 is a variable-width joint structure that is deemed undesignable according to the Steel Structure Joint Design Guidelines (Non-Patent Literature 1), and is the model for comparison.

[0049] [Table 2]

[0050] Similarly, the parameters used for analysis models No. 3 and 4 (examples) are shown in Table 3 below. Analysis models No. 3 and 4 employ the same diaphragm thickness as analysis model No. 2, which is deemed unsuitable for design according to the Steel Structure Joint Design Guidelines (Non-Patent Literature 1).

[0051] [Table 3]

[0052] Figure 17 shows contour plots for the equivalent stress in analysis models No. 2 and 4 at maximum load capacity, separated into plan view and elevation view. The through diaphragm and weld metal have a load of 325 (N / mm²). 2 It was determined that they had surrendered, and the upper and lower square steel pipes were 295 (N / mm²). 2 It was determined that they had surrendered. Furthermore, the plan view contour diagram was made visible by removing the upper rectangular steel pipe.

[0053] In analysis model No. 2, yield regions were observed not only throughout the entire diaphragm but also in a portion of the upper rectangular steel pipe, suggesting a conventionally proposed collapse pattern (see Figure 18). In contrast, analysis model No. 4 showed collapse mechanisms in both the diaphragm and the lower rectangular steel pipe, even at positions overlapping with the upper member in a plan view. This analysis confirmed that overlapping the four corners of the upper rectangular steel pipe with the lower member resulted in a linear axial stress transmission path. Subsequently, the behavior (stiffness) of the entire joint when this deformation remained within the elastic range was examined, and a significant effect was observed in analysis model No. 3.

[0054] Here, let M (kNm) be the moment at the fixed end position, and M' (kNm) be the moment at the center of the through diaphragm's plate thickness. In this study, M' is the yield moment of the upper square steel. uy At the point when it reaches, or when M is the yield moment M of the lower square steel pipe py The deformation angles of the entire member at the point where the yield moment was reached were compared (Figure 19). However, the yield moment was assumed to be 85% of the total plastic moment calculated considering the axial force (see equations 3-1 to 4-2 below). The comparison of moments and the position where yield determination was made in each model are summarized in Table 4 below.

[0055] [Table 4]

[0056] Furthermore, the deformation angle θ of the entire group being compared was calculated as follows to eliminate the influence of cross-sectional properties.y The standardization was performed by dividing by [a certain factor].

[0057] <θ y Calculation procedure > The model is divided into upper and lower sections at the center of the through-diaphragm's plate thickness, with the cross-sections of each section having the dimensions shown in Table 1. It is assumed that there is a rigid connection at the location of the through-diaphragm, and M' is the yield moment M of the upper rectangular steel pipe. uy At the point when it reaches, or when M is the yield moment M of the lower square steel pipe py The horizontal displacement δ at the loading point when it reaches this point. y The horizontal displacement δ is calculated. y In calculating (Equation 7), the transition of the second moment of area of ​​the upper and lower square steel pipes is taken into consideration (Equations 5, 6), and only the bending component is considered. The horizontal displacement δ obtained in this way y The value obtained by dividing by the total length of the member is θ y (See Figure 20).

[0058] θ y The formula used in the calculation is shown below.

[0059]

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[0060]

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[0061]

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[0062]

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[0063]

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[0064]

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[0065]

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[0066]

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[0067] M uy : Yield moment of the upper rectangular steel pipe M upc : Full plastic moment considering the axial force of the upper rectangular steel pipe M py : Yield moment of the lower rectangular steel pipe M ppc : Full plastic moment considering the axial force of the lower rectangular steel pipe M: Bending moment at a fixed end position M': Bending moment at the center of the thickness of the through diaphragm L u : Upper material length (distance from the loading point to the center of the through diaphragm's plate thickness) L p : Lower material length (distance from the fixed end to the center of the thickness of the through diaphragm plate) I u : Second moment of area of ​​the upper rectangular steel pipe I p : Second moment of area of ​​the lower rectangular steel pipe D u : The length of the upper rectangular steel pipe in the long side direction B u : Side length in the short side direction of the upper rectangular steel pipe t u : Plate thickness of the upper rectangular steel pipe D p : Diameter or width of the lower square steel pipe t p : Plate thickness of the lower square steel pipe δ y : Horizontal displacement of the loading point at the time of member yielding E: Modulus of elasticity θ y : Deformation angle of the entire member when the member yields

[0068] Total plastic moment M in the weak axis direction of a rectangular-sectioned square steel pipe upc and the total plastic moment M of a square-sectioned square steel pipe ppc were calculated based on the following method.

[0069] <M upc and M ppc Calculation method> Total plastic moment M in the weak axis direction of a rectangular-sectioned square steel pipe upc is calculated based on the following Equation 9. In Equation 9, D u is the side length in the long side direction of the upper square steel pipe, B u is the side length in the short side direction of the upper square steel pipe, t u is the plate thickness of the upper square steel pipe, R u is the corner curvature radius of the upper square steel pipe, c σ y is the yield stress of the square steel pipe.

[0070] [Numerical formula]

[0071] y in Equation 9 uo is the distance between the centroid and the neutral axis of the upper square steel pipe, and was calculated based on the following Equation 10. In Equation 10, N is axial force.

[0072] [Numerical formula]

[0073] Total plastic moment M of a square-sectioned square steel pipe ppc is calculated based on the following Equation 11. In Equation 11, D p is the side length of the lower square steel pipe, t p is the plate thickness of the lower square steel pipe, R p is the corner curvature radius of the lower square steel pipe, c σ yThis is the yield stress of a rectangular steel pipe.

[0074]

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[0075] y in Equation 11 po is the distance between the centroid and the neutral axis of the lower rectangular steel pipe, and is calculated based on the following equation 12. In equation 12, N is the axial force.

[0076]

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[0077] Table 5 shows the normalized deformation angles at member yield obtained for each analysis model. Analysis model No. 1 is a joint structure whose design is permitted in the Steel Structure Joint Design Guidelines (Non-Patent Literature 1), so in this study, this deformation angle was used as the basis for comparison. Analysis model No. 2 is a joint structure in which the through diaphragm plate thickness has been reduced, as deemed unacceptable in the design guidelines. The normalized deformation angle of analysis model No. 2 was 16.40% higher than that of analysis model No. 1. From this, it was confirmed that the bending stiffness of analysis model No. 2 was lower than that of analysis model No. 1. Analysis models No. 3 and 4 are models in which the through diaphragm plate thickness is the same as that of analysis model No. 2, and the four corners of the upper member overlap the lower member in a plan view. It was confirmed that the normalized deformation angle of analysis model No. 3 was limited to an increase of 2.70% compared to analysis model No. 1. This confirms that, in a plan view, overlapping the four corners of the upper member with the lower member allows for improved bending rigidity using a method different from the conventional approach of increasing the plate thickness of the through diaphragm.

[0078] [Table 5]

[0079] On the other hand, in the case of analysis model No. 4, the yield strength decreased before member yielding. This was thought to be due to the collapse of the through diaphragm. In this study, it was determined that the increase in the normalized deformation angle was 5% or less compared to analysis model No. 1, and that the required stiffness was almost secured. In Figure 3, analysis model No. 3, which meets the above criteria, and the joint structure that has no discontinuity in the cross-section between the upper and lower sections and possesses sufficient stiffness (a joint structure in which upper and lower square steel pipes of the same width are arranged coaxially, and the ratio AR of this joint structure is 1.0) are shown with a "○" (circle), and analysis model No. 4, which does not meet the above criteria, is shown with a "×" (cross). It should be noted that in the joint structure that has no discontinuity in the cross-section between the upper and lower sections and possesses sufficient stiffness, it was thought that local rotation at the position of the through diaphragm would not occur even if the plate thickness of the through diaphragm was small because there was no discontinuity in the cross-section. For this reason, it was considered clear that the stiffness would exceed the target value in this joint structure.

[0080] Based on the following, the organization shown in Figure 3 was performed. • All lower rectangular steel pipes are assumed to have the same square cross-section (in this study, the diameter of the lower rectangular steel pipes was set to 350 mm and the plate thickness of the lower rectangular steel pipes to 12 mm). • Side length D in the long side direction of the upper rectangular steel pipe u The diameter D of the lower square steel pipe p It is equivalent to the above. • Side length B in the short side direction of the upper rectangular steel pipe u Side length D in the direction of the longer side u Ratio AR(D u / B u The vertical axis is defined as AR=1.0, which means that the cross-sectional shapes of the lower and upper rectangular steel pipes are the same. • Joint strength in the following standard joint structures j M u and the full plastic moment of the upper reference square steel pipe c M p Toga j M u ≧ c M p The minimum standard through diaphragm thickness that satisfies this condition is t x And this t x Through each analysis model, the diaphragm thickness td The normalized value (t) obtained by dividing by d / t x The horizontal axis is defined as ). The standard joint structure shall be as follows: -Reference lower rectangular steel pipe: The lower rectangular steel pipe of the analysis model will have the same cross-section (square) (in this study, the diameter of the reference lower rectangular steel pipe was set to 350 mm and the plate thickness of the reference lower rectangular steel pipe was set to 12 mm). -Reference upper rectangular steel pipe: The reference lower rectangular steel pipe has a square cross-section with a diameter difference of 50 mm (in this study, the diameter of the reference upper rectangular steel pipe was set to 300 mm and the plate thickness of the reference upper rectangular steel pipe was set to 12 mm). - A central column type will be used (the upper and lower rectangular steel pipes will be arranged coaxially). - Reference through diaphragm thickness t x Let it be 25mm.

[0081] Standard through diaphragm thickness t x The full plastic moment when determining c M p and joint strength j M u The calculation was performed based on the following method.

[0082] < c M p and j M u How to calculate it > Standard through diaphragm thickness t x The full plastic moment when determining c M p This is calculated based on the following equation 13. In equation 13, t u D is the plate thickness of the upper rectangular steel pipe, u ,B u is the diameter of the upper rectangular steel pipe, R u This is the radius of curvature of the corner of the upper rectangular steel pipe, c σ y is the yield stress of the square steel pipe, and y uo is the distance between the centroid and the neutral axis of the upper rectangular steel pipe, and is calculated based on Equation 10 above. Reference through diaphragm thickness t x When determining the upper rectangular steel pipe, since it is square, B u=D u Let's assume that.

[0083]

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[0084] Joint strength j M u This is calculated using the yield stress of the upper rectangular steel pipe and the yield stress of the through diaphragm. More specifically, the joint strength j M u This is calculated based on the following equations 14-21.

[0085]

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[0086] In Equation 14, j M ua This is the joint strength when the neutral axis is located on the plate of the lower rectangular steel pipe. j M ub This is the joint strength when the neutral axis passes through the upper square steel pipe. Equation 14 j M ua and j M ub This is calculated based on the following equations 15 and 16. In equations 15 and 16, s m p This is the total plastic moment per unit length at the yield line located at the top of the lower rectangular steel pipe, D m p D is the total plastic moment per unit length in a through diaphragm, p D is the diameter of the lower square steel pipe. u x is the diameter of the upper rectangular steel pipe, l is the difference in size between the upper and lower rectangular steel pipes, and x is a variable that determines the axial yield strain region in the upper rectangular steel pipe. u n y is the axial yield load per unit length in the upper rectangular steel pipe, y is the distance between the neutral axis and one side of the upper rectangular steel pipe, and N is the axial force.

[0087]

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[0088]

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[0089] Equations 15 and 16 D m P This is calculated based on the following equation 17. In equation 17, d σ y is the yield stress of the through diaphragm, and t x This is the thickness of the through diaphragm.

[0090]

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[0091] Equations 15 and 16 s m p This is calculated based on the following equation 18. In equation 18, D m p This is the total plastic moment per unit length in a through diaphragm, p m p This is the full plastic moment per unit length in the lower rectangular steel pipe.

[0092]

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[0093] Equation 18 p m p This is calculated based on the following equation 19. In equation 19, c σ y is the yield stress of a rectangular steel pipe, and t p This is the plate thickness of the lower rectangular steel pipe.

[0094]

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[0095] Equations 15 and 16 u n y This is calculated based on the following equation 20. In equation 20, c σ y is the yield stress of a rectangular steel pipe, and t u This is the plate thickness of the upper rectangular steel pipe.

[0096]

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[0097] The value of l in equations 15 and 16 is calculated based on the following equation 21. In equation 21, D p D is the diameter of the lower square steel pipe. u This is the diameter of the upper rectangular steel pipe.

[0098]

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[0099] In Figure 3, the region below the line passing through the two points (0,1) representing a joint structure with no discontinuity in the cross-section between the upper and lower sections and sufficient rigidity (a joint structure in which upper and lower rectangular steel pipes of the same width are arranged coaxially) and the plot of analysis model No. 3 (19 / 25, 350 / 300) = (0.76, 1.167) where bending rigidity was confirmed, is the region with ratio AR(D u / B u It was thought that sufficient bending rigidity could be ensured if ) was present. Furthermore, since it was assumed that the upper rectangular steel pipe had a different cross-sectional shape from the lower member, it was thought that the ratio AR should be greater than 1. From these, it was derived that it is preferable to satisfy the following equation A, where α = 0.219.

[0100]

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[0101] Also, ratio AR(D u / Bu ) is the ratio AR(D) of analysis model No. 3 u / B u It was thought that if it was smaller than ), sufficient bending stiffness could be more reliably ensured. From this, it was derived that it is preferable to further satisfy the following equation C, where β = 1.167.

[0102]

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[0103] 1:Joint structure 11: Upper member 11L: Long side direction 11S: Short side direction 11c: Four corners 11f: Plate element 12: Lower part 13: Through diaphragm

Claims

1. A joining structure in which an upper member and a lower member are joined via a through diaphragm, The upper member has a cross-sectional shape different from that of the lower member. In a plan view, the four corners of the upper member overlap with the lower member. Joint structure.

2. The cross-sectional shape of the upper member has a long side direction and a short side direction, The upper member has a pair of opposing plate elements that are spaced apart from each other in the direction of the longer side and extend in the direction of the shorter side, The length of the upper member in the direction of its long side is equal to the diameter or width of the lower member. In a plan view, a pair of opposing plate elements extending in the direction of the shorter side of the upper member overlap with the plate elements of the lower member. The joining structure according to claim 1.

3. The upper and lower members are rectangular steel pipes. The cross-sectional shape of the upper member is a rectangle having a long side direction and a short side direction, The cross-sectional shape of the lower member is square. The joining structure according to claim 2.

4. The side length B of the upper member in the short side direction u The side length D in the direction of the long side u Ratio A.R. (D u / B u ), and the reference diaphragm thickness t x The thickness t of the through diaphragm relative to the above d ratio t d / t x The following equation A is satisfied, [Math 1] The joining structure according to claim 3. however, α = 0.219, Reference diaphragm thickness t x is defined, in a reference joint structure in which a reference lower square steel pipe having a square cross section with the same diameter or width as the diameter or width of the lower member and a reference upper square steel pipe having a square cross section with a diameter 50 mm smaller than the diameter or width of the reference lower square steel pipe are joined via a reference through-diaphragm, the joint proof stress j M u and the full plastic moment of the reference upper square steel pipe c M p is the minimum thickness of the reference through-diaphragm that satisfies the following formula B. [Math 2]

5. The joining structure according to claim 4, further satisfying the following formula C. [Math 3] However, β = 1.

167.

6. The upper member is a rectangular steel pipe, The lower member is a circular steel pipe, The diagonal distance of the outer dimensions of the upper member is equal to the diameter or width of the outer dimensions of the lower member, or the diagonal distance of the inner dimensions of the upper member is equal to the diameter or width of the inner dimensions of the lower member. The joining structure according to claim 1.

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