Welded joint structure and welding method for upper and lower column members

Abstract

This invention provides a welded joint structure and welding method for upper and lower column members that offers superior constructability, economy, rationality, and reliability. [Solution] A welded joint structure for upper and lower column members, in which hollow column members arranged vertically are butt-welded together, leaving at least one unwelded section, wherein the width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow column member by the plate thickness (t) satisfies equation (1): equation (1): D / t ≤ 33√(235 / F); (F: standard strength) and the shear span ratio (L / 2D) and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt-welded joint position by the plastic section modulus of the butt-welded joint, are butt-welded together in such a way that equation (2) etc. is satisfied, thereby exhibiting a structure in which the end of the column member becomes fully plastic ahead of the butt-welded joint position. Equation (2): When (L / 2D) is 7 or more, γ > 1.02

Description

[Technical Field]

[0001] This invention belongs to the technical field of butt welding joint structures for hollow cross-section column members arranged vertically. [Background technology]

[0002] When joining hollow column members positioned vertically at a construction site using full penetration welding, it is common practice to either temporarily fix the upper and lower column members using erection pieces (and splice plates), weld the first two to three passes, then cut or remove the erection pieces, and then weld the remaining area again to finish with full penetration welding, or to divide the column member into welding areas using erection pieces (and splice plates), weld half of the divided area in several layers starting and ending at the erection piece positions, then cut or remove the erection pieces, and then weld the remaining area again to finish with full penetration welding. Therefore, in conventional welding methods as described above, the erection piece (and splice plate) acts as an obstruction, resulting in the welding process being interrupted ("welding" → "cutting or removing the erection piece" → "welding"), which is a problem due to poor work efficiency.

[0003] In recent years, as disclosed in Patent Documents 1 to 4, welding robots have been introduced to improve the efficiency of welding work, but the welding process remains fragmented into "welding" → "cutting or removal of erection piece (or erection jig)" → "welding".

[0004] Incidentally, in the middle of page 103 of Non-Patent Document 1, it is stated that it is desirable to set column joints (joints of hollow-section column members) in a location with low stress, and that it is desirable to set them at least 1.5D (where D is the outer diameter of the column) away from the top of the beam (or diaphragm). Therefore, taking this statement into consideration, in practice, the position of column joints is often set at a distance of about 1000 mm from the floor surface (above the beam). Considering the bending moment distribution caused by the shear force acting on a hollow-section column member, the bending moment at the column joint is smaller than at the column connection point. Therefore, even if the strength is lower than at the column connection point, it does not pose a problem for the overall structural performance of the building. However, in reality, the location of the column joint at construction sites is designed and constructed with full penetration welding around the entire circumference of the hollow section, ensuring performance and quality equivalent to the column-diaphragm weld at the column connection point, where the stress state is most severe and it is prone to failure and buckling. This indicates that excessive design and construction practices have been employed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-53626 [Patent Document 2] Japanese Patent Publication No. 2019-155409 [Patent Document 3] Japanese Patent Publication No. 2021-65899 [Patent Document 4] Japanese Patent Publication No. 2022-146750 [Non-Patent Document 1] Pages 102 and 103 of "Cold-Formed Square Steel Pipe Design and Construction Manual 2018 Edition," published by the Japan Building Center Foundation. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] If welding work could be performed continuously (in a single pass) without interruption, it would clearly be more beneficial, such as by dramatically increasing work efficiency.

[0007] The present invention was devised in view of the problems of the background technology described above, and its purpose is to provide a welded joint structure and welding method for upper and lower column members that is excellent in reliability as well as constructability, economy, rationality, etc., by changing the excessive design related to the position of conventional column joints (joint parts of column members with hollow cross-sections) to a rational design, for example, by performing welding work continuously (in one go) without interruption, thereby dramatically increasing work efficiency. [Means for solving the problem]

[0008] As a means to solve the above problems, the welded joint structure of the upper and lower column members according to the invention described in claim 1 is: A welded joint structure for upper and lower column members, in which hollow cross-section column members arranged vertically are butt-welded together, leaving at least one unwelded section, The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equation (1): Formula (1) D / t≦33√(235 / F) F: Reference intensity Furthermore, the column member is butt-welded such that the end of the column member becomes fully plastic before the butt-welded joint, satisfying one of the following equations (2) to (5): the shear span ratio (L / 2D) obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor by the outer diameter (D) of the hollow column member, and the stress ratio (γ) obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting on the butt-welded joint position by the plastic section modulus of the butt-welded joint. Equation (2) When (L / 2D) is 7 or greater, γ > 1.02 When equation (3) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-264.27) / -251.97 When equation (4) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-15.822) / -11.445 When (L / 2D) in formula (5) is 2.67, γ > 1.15

[0009] The welding joint structure of the upper and lower column members according to the invention described in claim 2 is a welding joint structure of upper and lower column members in which column members with hollow cross-sections arranged vertically are butt-welded with at least one non-welded part left, the width-thickness ratio obtained by dividing the outer diameter (D) of the column member with the hollow cross-section by the plate thickness (t) satisfies the following formulas (6) and (7), Formula (6) D / t > 33√(235 / F) F: reference strength Formula (7) D / t ≦ 37√(235 / F) F: reference strength and, regarding the shear span ratio (L / 2D) obtained by dividing half of the length (L) from the lower end of the upper floor beam to the upper end of the lower floor beam in the column member with the hollow cross-section by the outer diameter (D) of the column member with the hollow cross-section, and the stress ratio (γ) which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the column member with the hollow cross-section by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting on the butt-welded joint position by the plastic section modulus of the butt-welded joint part, the butt-welded joint is made to satisfy any one of the following formulas (8) to (11), thereby presenting a structure in which the end of the column member is plastically deformed completely prior to the butt joint position. Formula (8) When (L / 2D) is 7 or more, γ > 1.05 Formula (9) When (L / 2D) is 4 or more and less than 7, γ > ((L / 2D) - 28.382) / -20.334 Formula (10) When (L / 2D) is 2.67 or more and less than 4, [[ID=2,4]]γ > ((L / 2D) - 19.493) / -12.921 Formula (11) When (L / 2D) is 2.67, γ > 1.30

[0010] The invention described in claim 3 is characterized in that, in the welding joint structure of the upper and lower column members described in claim 1 or 2, the non-welded part is between the upper and lower column members and is at a position corresponding to the attachment site of the erection piece.

[0011] The invention described in claim 4 is characterized in that, in the welded joint structure of upper and lower column members described in claim 1 or 2, the lower column member is erected on the upper surface of the column-beam joint or column base.

[0012] The welding joint method for upper and lower column members according to the invention described in claim 5 is: A butt welding joint method for hollow cross-section column members arranged vertically with erection pieces, The process consists of the steps of: using the erection piece to align and temporarily fix the upper column member with respect to the lower column member; welding the upper and lower column members together; and removing the erection piece. The welding process involves butt welding the upper and lower column members, leaving a position corresponding to the mounting portion of the erection piece untouched. The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equation (1): Formula (1) D / t≦33√(235 / F) F: Reference intensity Furthermore, the structure is characterized in that the end of the column member becomes fully plastic ahead of the butt joint by performing the butt welding joint such that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, satisfies one of the following equations (2) to (5). Equation (2) When (L / 2D) is 7 or greater, γ > 1.02 When equation (3) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-264.27) / -251.97 When equation (4) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-15.822) / -11.445 Equation (5) When (L / 2D) is 2.67, γ > 1.15

[0013] The welding joint method for upper and lower column members according to the invention described in claim 6 is: A butt welding joint method for hollow cross-section column members arranged vertically with erection pieces, The process consists of the steps of: using the erection piece to align and temporarily fix the upper column member with respect to the lower column member; welding the upper and lower column members together; and removing the erection piece. The welding process involves butt welding the upper and lower column members, leaving a position corresponding to the mounting portion of the erection piece untouched. The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equations (6) and (7): Equation (6) D / t>33√(235 / F) F: Reference intensity Equation (7) D / t≦37√(235 / F) F: Reference intensity Furthermore, the structure is characterized in that the end of the column member becomes fully plastic before the butt joint, by performing the butt welding joint such that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, satisfies one of the following equations (8) to (11). Equation (8) When (L / 2D) is 7 or greater, γ > 1.05 When equation (9) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-28.382) / -20.334 When equation (10) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-19.493) / -12.921 When equation (11) (L / 2D) is 2.67, γ > 1.30

[0014] The invention described in claim 7 is characterized in that, in the welding joint method for upper and lower column members described in claim 5 or 6, the lower column member is erected on the upper surface of the column-beam joint or column base. [Effects of the Invention]

[0015] The welded joint structure and welding joint method for upper and lower column members according to the present invention provide the following effects. The FEM analysis results allowed us to more accurately demonstrate, by quantifying specifically, whether it is possible to maintain the overall structural performance of the building with minimal degradation (specifically, when it is possible to achieve a structure in which the ends of the column members are fully plastic before the butt joint) or when it is not, even if the welding work is completed without welding the positions corresponding to the mounting points of the erection pieces (leaving the openings intact). Therefore, based on the aforementioned quantified formula, it has become possible to perform welding work continuously (in a single step) without interruption, such as by eliminating the need for finishing welding work after the removal of conventional erection pieces, while remaining safe and reliable and hardly reducing the overall structural performance of the building. As a result, the amount of welding can be reduced, and welding work can be streamlined, dramatically improving work efficiency. Therefore, in addition to ease of construction, economy, and rationality, it is possible to realize a welded joint structure and welding method for upper and lower column members, as well as upper and lower column members themselves, that are extremely reliable. [Brief explanation of the drawing]

[0016] [Figure 1] This is a perspective view showing the main part of the welded joint structure of upper and lower column members according to the present invention. [Figure 2] The section X in Figure 1 is an explanatory diagram illustrating the welding joint method for upper and lower column members according to the present invention. [Figure 3]Figure A is a schematic diagram of a FEM analysis simulating a three-point bending test and the formula for the stress ratio (γ), while Figure B is the same schematic diagram and the formula for the stress ratio (β). As shown in the schematic diagrams A and B, in a three-point bending test, a moment gradient occurs where the moment is largest at the load P and smallest at the support. Similarly, when a column in a building's steel frame is subjected to horizontal force due to an earthquake, a moment gradient occurs that is determined by the balance of the horizontal force due to the earthquake and the weight of the building itself. Therefore, the stress ratios (γ) and (β) are calculated taking into account that the stress acting on the column end and column joint differs depending on the moment gradient. [Figure 4] Figures A through C are variations of the welded joint structure for the upper and lower column members according to the present invention. [Figure 5] This table categorizes column types into four ranks, from FA to FD, and summarizes the width-to-thickness ratios and other factors for each category. [Figure 6] This table shows the analytical parameters for Conventional Example 1 and for Inventions 1-1 to 1-18. [Figure 7] This table shows the analysis parameters and results for Conventional Example 1 and for Inventions 1-1 to 1-18. [Figure 8] This table shows the analytical parameters for Conventional Example 2 and for Inventions 2-1 to 2-11. [Figure 9] This table shows the analysis parameters and results for Conventional Example 2 and for Inventions 2-1 to 2-11. [Figure 10] This table shows the analytical parameters for Conventional Example 3 and for Invention 3-1 to Invention 3-8. [Figure 11] This table shows the analysis parameters and results for Conventional Example 3 and for Invention 3-1 to Invention 3-8. [Figure 12] This table shows the analytical parameters for Conventional Example 4 and for Inventions 4-1 to 4-5. [Figure 13] This table shows the analysis parameters and results for Conventional Example 4 and for Inventions 4-1 to 4-5. [Figure 14]This table shows the analytical parameters for Conventional Example 5 and the present inventions 5-1 to 5-7. [Figure 15] This table shows the analysis parameters and results for Conventional Example 5 and for Inventions 5-1 to 5-7. [Figure 16] This table shows the analytical parameters for Conventional Example 6 and the present inventions 6-1 to 6-2. [Figure 17] This table shows the analysis parameters and results for Conventional Example 6 and the present inventions 6-1 to 6-2. [Figure 18] Figure A shows a model diagram (center) of an FEM analysis for a column member with dimensions of □750×750×60, under the condition that a horizontal force is applied at 0 degrees to the center of the thickness of the through diaphragm, along with a left side view (left) and an explanatory diagram (right) showing the size of the member. Similarly, Figure B shows a model diagram (center) of an FEM analysis for a column member with dimensions of □750×750×25, under the condition that a horizontal force is applied at 0 degrees to the center of the thickness of the through diaphragm, along with a left side view (left) and an explanatory diagram (right) showing the size of the member. Note that the figures are 1 / 1 scale models, but the actual analysis model is a 1 / 4 scale model. [Figure 19] A is a detailed view of the column-through diaphragm weld in Figure 18A, and B is a detailed view of the column joint weld in Figure 18A. Similarly, C is a detailed view of the column-through diaphragm weld in Figure 18B, and D is a detailed view of the column joint weld in Figure 18B. [Figure 20] This graph shows the tensile test results (SS curves) for four material properties. [Figure 21] This graph shows the corresponding M-θ relationships between Conventional Example 1 and Inventions 1-1 to 1-18, such as Conventional Example 1 and Invention 1-1. [Figure 22] This graph shows the corresponding M-θ relationships between Conventional Example 2 and Inventions 2-1 to 2-11, such as Conventional Example 2 and Invention 2-1. [Figure 23] This graph shows the corresponding M-θ relationships between Conventional Example 3 and Invention 3-1 to Invention 3-8, such as Conventional Example 3 and Invention 3-1. [Figure 24]This graph shows the corresponding M-θ relationships between Conventional Example 4 and Inventions 4-1 to 4-5, such as Conventional Example 4 and Invention 4-1. [Figure 25] This graph shows the corresponding M-θ relationships between Conventional Example 5 and Inventions 5-1 to 5-7, such as Conventional Example 5 and Invention 5-1. [Figure 26] This graph shows the corresponding M-θ relationships between Conventional Example 6 and Inventions 6-1 to 6-2, such as Conventional Example 6 and Invention 6-1. [Figure 27] A is a graph plotting the relationship between the shear span ratio (L / 2D) and the stress ratio (γ), treating a total of 37 cases, including Invention 1-1, which correspond to Conventional Examples 1-3 for the case where the column member is □750×750×60, as FA rank. B is a graph with the relationship formulas added to an enlarged version of the stress ratio (γ) for A, specifically the range from 1.0 to 1.2 within the range of 0.8 to 2.0. [Figure 28] A is a graph plotting the relationship between the shear span ratio (L / 2D) and the stress ratio (γ), with a total of 14 cases, including Invention 3-1, corresponding to Conventional Examples 4-6 for the case where the column member is □750×750×25, treated as FB rank. B is a graph with the relationship formulas added to A. [Figure 29] This is an analytical model diagram showing the boundary conditions when the applied force is in the 0-degree direction. [Figure 30] This is a diagram showing the von Mises stress distribution during full plastic bending strength for all 10 cases, from Conventional Example 1 to Invention 1-1 to Invention 1-9. [Figure 31] The following are von Mises stress distribution diagrams at full plastic bending strength for all 10 cases, including Inventions 1-10 to 1-18 and Conventional Example 2. [Figure 32] The following are von Mises stress distribution diagrams for all 10 cases of the present invention, from 2-1 to 2-10, during full plastic bending strength. [Figure 33] The following are von Mises stress distribution diagrams at full plastic bending strength for all 10 cases, including Invention 2-11, Conventional Example 3, and Inventions 3-1 to 3-8. [Figure 34]The following are von Mises stress distribution diagrams at full plastic bending strength for a total of 10 cases: Conventional Example 4, Invention 4-1 to Invention 4-5, Conventional Example 5, and Invention 5-1 to Invention 5-3. [Figure 35] The following are von Mises stress distribution diagrams at full plastic bending strength for all seven cases: Inventions 5-4 to 5-7, Conventional Example 6, and Inventions 6-1 to 6-2. [Modes for carrying out the invention]

[0017] This invention is based on a technical concept that economically and rationally realizes a structure in which the ends of upper and lower column members are fully plasticized prior to the butt joint position in a welded joint structure of upper and lower column members. As a result of the applicant's diligent pursuit of how to reliably realize this technical concept, the present invention has discovered a method of butt welding upper and lower hollow cross-section column members while leaving one or more areas that are not welded, and has further developed this to the point of quantifying it, such as finding the applicable ranges for FA rank and FB rank. Hereinafter, embodiments (examples) of the welded joint structure and welded joint method for upper and lower column members according to the present invention will be described based on the drawings.

[0018] (Embodiment) Figure 1 shows the main part of the welded joint structure of the upper and lower column members 1, 1. Two hollow-section column members (square steel pipe columns) 1, 1, positioned vertically, are butt-welded together 2, leaving at least one unwelded section (opening) 3. In the embodiment shown in Figure 1, the welding is performed using a full-penetration welding method. The unwelded portion 3 is located between the upper and lower column members 1, 1, and corresponds to the mounting locations for the erection piece 7 and the splice plate 8. In the embodiment shown in Figure 1, the unwelded portion 3 is located at approximately the center of each of the four sides of the column member 1, for a total of four locations (see Figure 4A). However, it is not limited to this, and as illustrated in Figures 4B and 4C, the number and location of the unwelded portion 3 can be appropriately modified according to the structural design. In the embodiment shown in Figure 1, the lower column member 1 is erected on the upper surface of the column-beam joint 10 (the through diaphragm 11), but it may also be erected on the upper surface of the column base. The hollow cross-section column member 1 is, as an example, constructed with a column length (L) of 4000 mm, outer dimensions (D) of 750 x 750 mm, and a plate thickness (t) of 60 mm, with the welding position (column joint position) being at a height of approximately 1200 mm from the position of the through diaphragm 11. Herein, for convenience, the "unwelded portion" may be referred to as an "opening" in this specification. However, it should be noted that there are cases where an unwelded portion does not constitute an opening, such as when a hole is blocked by the remaining end tab from the welding process.

[0019] (Applicable scope for FA rank) Specifically, the welded joint structure of the upper and lower column members related to the FA rank is: The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equation (1): Formula (1) D / t≦33√(235 / F) F: Reference intensity Furthermore, the column member is butt-welded such that the relationship between the shear span ratio ((L / 2) / D=L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow-section column member by the outer diameter (D) of the hollow-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt-welded joint position by the plastic section modulus of the butt-welded joint, satisfies one of the following equations (2) to (5), thereby exhibiting a structure in which the end of the column member becomes fully plastic before the butt-welded joint position. Equation (2) When (L / 2D) is 7 or greater, γ > 1.02 When equation (3) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-264.27) / -251.97 When equation (4) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-15.822) / -11.445 Equation (5) When (L / 2D) is 2.67, γ > 1.15

[0020] (Applicable scope related to FB rank) Next, the welded joint structure of the upper and lower column members related to the FB rank is: The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equations (6) and (7): Equation (6) D / t>33√(235 / F) F: Reference intensity Equation (7) D / t≦37√(235 / F) F: Reference intensity Furthermore, the welded joint structure for upper and lower column members is characterized in that the end of the column member becomes fully plastic before the butt joint position, by butt welding the column member in such a way that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow column member by the outer diameter (D) of the hollow column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, satisfies one of the following equations (8) to (11). Equation (8) When (L / 2D) is 7 or greater, γ > 1.05 When equation (9) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-28.382) / -20.334 When equation (10) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-19.493) / -12.921 When equation (11) (L / 2D) is 2.67, γ > 1.30

[0021] Here, according to Ministry of Construction Notification No. 2464 of 2000, the standard strength F of steel materials determined by the Minister of Land, Infrastructure, Transport and Tourism according to the type and quality of the steel material is a value used to determine the allowable stress and material strength used in the structural design of building steel frames. The standard strength F of JIS-compliant products is determined by referring to the lower limit of the yield point specified in the JIS standard, but taking into consideration the effect of the yield ratio of steel materials in building steel frames, if 0.7 times the lower limit of the tensile strength is smaller than the lower limit of the yield point, the smaller value is to be used. On the other hand, for products certified by the Minister, the standard strength F is determined individually after the Minister of Land, Infrastructure, Transport and Tourism's certification review. The reasons for conceiving the configuration described in paragraphs

[0019] and

[0020] , and in particular for how the applicant derived formulas (1) to (5) and formulas (6) to (11), will be explained later.

[0022] In the embodiment shown in Figure 1, eight erection pieces 7 are used, one at each of the four sides of the upper and lower column members 1, 1, approximately in the center. Two splice plates 8 are arranged to sandwich the upper and lower erection pieces 7, 7 from the left and right, so a total of eight splice plates are used in four locations. The erection pieces 7 and the splice plates 8 are fastened together with fasteners such as high-strength bolts 9. Thus, the welding method for upper and lower column members 1, 1 according to the present invention is a butt welding method for hollow cross-section column members 1, 1 arranged vertically with an erection piece 7, and comprises the steps of: aligning and temporarily fixing the upper column member 1 with respect to the lower column member 1 using fasteners such as the erection piece 7, splice plate 8, and high-strength bolt 9; welding the upper and lower column members 1; and removing the splice plate 8, high-strength bolt 9, and other fasteners, as well as the erection piece 7. In the welding process described above, when welding between the upper and lower column members 1, 1, the welding method is completed with the position corresponding to the mounting area of ​​the erection piece 7 left unwelded (see reference numeral 3), as shown in Figure 2. Incidentally, reference numeral 7' in Figure 2 indicates the area where the erection piece 7 was removed.

[0023] In short, the welded joint structure of the upper and lower column members 1, 1 according to the present invention takes into account, as described in the second paragraph of paragraph

[0004] above, that "considering the bending moment distribution caused by the shear force acting on the hollow cross-section column member, the bending moment at the column joint is smaller than that at the column connection point, so even if the strength is lower than at the column connection point, there is no problem with the overall structural performance of the building." Based on this, the applicant determined that there is no problem with the structural performance even if the amount of welding at the column joint (the joint portion of the column member) is reduced to some extent. Therefore, regarding the relationship between the reduction in the amount of welding and the overall structural performance of the building, the applicant analyzed whether there is no problem with the overall structural performance of the building even if the amount of welding is reduced by not welding at the position corresponding to the mounting point of the erection piece, which has conventionally been a factor that interrupts welding work. As a result of the analysis, it was proven that there is no problem on a case-by-case basis, as described below, and the analysis was further developed to the point of quantifying this. The following explains in detail.

[0024] The analysis involved using FEM analysis to confirm whether the overall structural performance of the building would be acceptable even if unwelded sections (openings) were left unwelded. The FEM analysis model is one that simulates the most common three-point bending test used to compare the structural performance of hollow-section column members, as shown in Figure 3. The analysis parameters are shown in Figures 6 to 17.

[0025] Numerical analysis using the finite element method was performed on members having hollow cross-section column members with column joints (joining points of column members) and through diaphragms welded to the beam attachment points of the column members (see Figures 3 and 18). For each of the following types of members, the bending moment, deformation angle relationship, and full plastic bending strength of the members when horizontal external forces such as earthquakes are applied was investigated using the finite element method, with "column type (difference in width-to-thickness ratio of square steel pipes)", "shear span ratio", and "stress ratio". The "stress ratio" refers to the ratio of stresses acting on the welded joint between the column and the through diaphragm and the welded joint of the column joint, taking into account the moment gradient in the three-point bending test.

[0026] Figure 18 shows the analytical model, but this analysis is performed using a 1 / 4 model, taking into account the symmetry of the analytical model. In this numerical analysis, the hollow cross-section column members of the structural steel frame were given two shapes: outer dimensions (D) 750 × 750 mm, and plate thickness (t) 60 mm (Figure 18A) and 25 mm (Figure 18B). When the plate thickness (t) was 60 mm, the radius of curvature of the corners (outer side) was R = 210 mm, and when the plate thickness (t) was 25 mm, the radius of curvature of the corners (outer side) was R = 87.5 mm. The column length L was set to three types: 4,000 mm, 6,000 mm, and 10,500 mm, and the shear span ratio (L / 2) / D related to the three-point bending test was varied. The plate thickness of the through diaphragm was set to 60 mm when the plate thickness t of the column member was 60 mm, and to 32 mm when the plate thickness t was 25 mm. As shown in Figures 19A and C, the projection dimension of the through diaphragm from the hollow cross-section column member was set to 30 mm in each case. The shape of the weld between the column member and the through diaphragm was set with a root gap of 7 mm, a groove angle of 35 degrees on the column body, a reinforcement height of 1 / 4 of the plate thickness (t) on the through diaphragm side, and a backing plate of 9 mm x 25 mm, without considering the penetration of the weld. On the other hand, the shape of the weld at the column joint was set as shown in Figures 19B and 19D, with a groove on the upper floor column side, a root gap of 7 mm, a groove angle of 35 degrees, and a backing plate of 9 mm x 50 mm, without considering the reinforcement or penetration of the weld. The column member with a hollow cross-section (square steel pipe) is continuously formed into a circular shape from a hot-rolled coil, the seam is welded by electric resistance welding to form a circular steel pipe, and then it is sized from four directions and formed into a square steel pipe by cold roll forming. There are also cold press formed square steel pipes where thick plates are bent by pressing and the seam is welded by submerged arc welding or the like, hot roll formed square steel pipes and hot press formed square steel pipes where the steel material is roll formed or press formed in a heated state. Welded fabricated box-section columns made by welding four steel plates corresponding to each of the four square faces, commonly called a four-sided box, are common. However, this analysis model has a cross-sectional shape corresponding to the cold press formed square steel pipe BCP325 for building structures.

[0027] In addition, the material properties of the column member with a hollow cross-section (square steel pipe column) are for the flat part and the corner part respectively, and the strength level is 490 N / mm , class of cold press formed square steel pipe BCP325 for building structures. The material properties of the through diaphragm and the backing plate are those of hot rolled steel plate SN490C for building structures with a strength level of 490 N / mm 2 class. The welding metal uses the material properties of JIS Z 3312 YGW18 for numerical analysis. Based on the material property tensile test results (SS curve), the true stress-true strain values actually input into the analysis are shown in Fig. 20. The examples target steel materials of 490 N / mm 2 class, but the present invention is not limited to steel materials with a strength level of 490 N / mm 2 class, and can be applied to steel materials and welding metals with a wide range of strength levels such as 400 N / mm 2 class, 520 N / mm 2 class, 550 N / mm 2 class, 570 N / mm 2 class, 590 N / mm <00000​​​​​​​​​​​​For grades such as 325, 335, 355, and 385, the rating is 550 N / mm². 2 For graded steel, such as 385, the load capacity is 570 N / mm². 2 For grades such as 420, 430, 440, 450, 460, etc., with a load capacity of 590 N / mm². 2 For graded steel, such as 440, 500, etc., the load capacity is 780 N / mm². 2 For graded steel, such as 630 or 700, the load capacity is 1000 N / mm². 2 For graded steel, 880 is a common designation.

[0028] The aforementioned list of analysis parameters (see Figures 6 to 17) includes, as described above, parameters for comparing and examining Conventional Examples 1 to 6 with the corresponding Examples of the Present Invention (e.g., Invention 1-1), such as the "type of column (difference in the width-to-thickness ratio of the square steel pipe)", "shear span ratio", and "stress ratio" of the column joint.

[0029] Conventional examples 1 to 6, in which the column joint (the joint portion of the column member) is fully penetrated welded around the entire circumference of the cross-section and no opening is provided, (following the description in the first paragraph of paragraph number

[0004] above) have the column joint located 1000 mm (1 m) away from the through diaphragm, and the direction of application of force is set to the 0-degree direction (the direction in which the distance to the outermost edge of the cross-section of the hollow column is minimized). Other parameters are as shown in Figures 6 to 17, but for reference, the main parameters are transcribed below. Conventional Example 1 (see Figures 6 and 7) has a column length (L) of 4000 mm, a width-to-thickness ratio (D / t) of 12.5, a shear span ratio (L / 2D) of 2.67, and a stress ratio (γ) of 2.00. Conventional example 2 (see Figures 8 and 9) has a column length (L) of 6000 mm, a width-to-thickness ratio (D / t) of 12.5, a shear span ratio (L / 2D) of 4.00, and a stress ratio (γ) of 1.50. Conventional example 3 (see Figures 10 and 11) has a column length (L) of 10,500 mm, a width-to-thickness ratio (D / t) of 12.5, a shear span ratio (L / 2D) of 7.00, and a stress ratio (γ) of 1.24. Conventional example 4 (see Figures 12 and 13) has a column length (L) of 4000 mm, a width-to-thickness ratio (D / t) of 30, a shear span ratio (L / 2D) of 2.67, and a stress ratio (γ) of 2.00. Conventional example 5 (see Figures 14 and 15) has a column length (L) of 6000 mm, a width-to-thickness ratio (D / t) of 30, a shear span ratio (L / 2D) of 4.00, and a stress ratio (γ) of 1.50. Conventional example 6 (see Figures 16 and 17) has a column length (L) of 10,500 mm, a width-to-thickness ratio (D / t) of 30, a shear span ratio (L / 2D) of 7.00, and a stress ratio (γ) of 1.24.

[0030] The 18 cases related to Invention 1-1 to 1-18, which correspond to the aforementioned Conventional Example 1, clearly differ in that they have openings, as can be seen from the opening width in Figure 6. In addition, the joint position (distance) from the through diaphragm is changed. By changing the width of the opening and the joint position, the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting on the butt weld joint position by the plastic section modulus of the butt weld joint, is changed. The same applies to the following cases: a total of 11 cases relating to Invention 2-1 to Invention 2-11 corresponding to Conventional Example 2; a total of 8 cases relating to Invention 3-1 to Invention 3-8 corresponding to Conventional Example 3; a total of 5 cases relating to Invention 4-1 to Invention 4-5 corresponding to Conventional Example 4; a total of 7 cases relating to Invention 5-1 to Invention 5-7 corresponding to Conventional Example 5; and a total of 2 cases relating to Invention 6-1 to Invention 6-2 corresponding to Conventional Example 6. For more details, please refer to the numerical values ​​in each figure (explanation omitted).

[0031] <Conditions for applying horizontal force> As described above, numerical analysis was performed for each of the cases (51 cases in total) corresponding to Conventional Examples 1 to 6 and Inventions 1-1 to 6-1, etc., under the condition that a horizontal force is applied at 0 degrees (the direction in which the distance to the outermost edge of the cross-section of the hollow column is minimized) at the center of the thickness of the through diaphragm, and that the column head on the opposite side is fixed so as not to move horizontally. Incidentally, Figure 29 is an analytical model diagram showing the boundary conditions when the applied force is in the 0-degree direction. <Analysis results> Figures 21 to 26 show, in order, the relationship between bending strength M (horizontal force × length from the center of the through-diaphragm plate thickness to the opposite column head) and deformation angle θ of the hollow section column (horizontal displacement at the center of the through-diaphragm plate thickness / length from the center of the through-diaphragm plate thickness to the opposite column head), comparing Conventional Examples 1 to 6 with the corresponding cases of Invention 1-1 to Invention 6-1, etc. (51 cases in total).

[0032] In the field of structural steel construction, various methods exist for calculating full-plastic bending strength. However, in this analysis, full-plastic bending strength is defined as the bending strength M-deformation angle θ of a hollow section column, and the intersection of the initial stiffness, 1 / 3 of the initial stiffness, and the tangent to the intersection of the M-θ relationship. The yield bending strength is defined as the strength at the displacement of the intersection of the initial stiffness, 1 / 3 of the initial stiffness, and the tangent to the intersection of the M-θ relationship. Figures 30 to 35 sequentially show the von Mises stress distribution diagrams at full plastic bending strength for each case (51 cases in total), including Conventional Examples 1 to 6 and Inventions 1-1 to 6-1.

[0033] Comparing the relationship between bending strength M and deformation angle θ of hollow section columns between conventional examples 1-6 and each case of the present invention 1-1 to 6-1 (51 cases in total), it can be seen that they follow almost the same history, as shown in Figures 21 to 26, and that there is no decrease in strength or rigidity with or without openings in the column joint. However, in the comparison of full plastic bending strength, the full plastic bending strength of conventional examples 1 to 6 (M D In some cases, the full plastic bending strength is 1.000 times (see, for example, Invention 1-1 to Invention 1-14 in Figure 6), and the presence or absence of an opening in the column joint does not reduce the full plastic bending strength. In other cases, the full plastic bending strength is less than 1.000 times (see, for example, Invention 1-15 to Invention 1-18 in Figure 7), and the presence of an opening in the column joint reduces the full plastic bending strength. In Figures 7, 9, 11, 13, 15, and 17, cases showing 1.000 times are indicated with "Judgment ○", and cases showing less than 1.000 times are indicated with "Judgment ×".

[0034] In a comparison of the von Mises stress distribution diagrams during full plastic bending (see Figures 30 to 35), when comparing the conventional examples 1 to 6 with each case of the present invention 1-1 to 6-1, etc. (51 cases in total), it can be seen that in the case showing 1.000 times (see "Judgment ○"), although stress concentration occurs at the opening at the column joint, there is no difference in the overall stress distribution or the tendency for the most stress to concentrate at the weld between the hollow section column and the through diaphragm, regardless of whether there is an opening at the column joint. On the other hand, in the cases showing less than 1.000 times (see "Judgment ×" above), when comparing the stress concentration occurring at the opening of the column joint with the stress concentration occurring at the weld between the hollow section column and the through diaphragm, it appears that there is not much difference in the stress distribution at the point of greatest stress concentration. This suggests that the butt joint position may fully plasticize before the end of the column member.

[0035] Therefore, according to the welded joint structure and welding method for upper and lower column members and the upper and lower column members of the present invention, even if the welding work is completed without welding the position corresponding to the mounting part of the erection piece 7 (while leaving the opening 3), as illustrated in Figure 4A, it can be said that in the case of "Judgment ○", the FEM analysis results prove that the structural performance of the entire building can be maintained with almost no deterioration. On the other hand, in the case of the aforementioned "Judgment ×," it is understood that a person skilled in the art to construct structures related to human life should not proceed with the FEM analysis, as the results would indicate a decrease in the overall structural performance of the building.

[0036] Specifically, referring to the "section loss rate" in the table shown in Figure 7, etc., it was found that, for example, even if the opening 3 accounts for about 30% of the whole (when fully penetrated welding is performed around the entire circumference of the cross section) (section loss rate of 0.70), there are cases where there is no problem with the structural performance of the entire building (see Invention 1-4 in Figure 7, etc.), and there are also cases where there is a problem with the structural performance of the entire building even if the opening 3 accounts for about 14% of the whole (section loss rate of 0.86) (see Invention 4-1 in Figure 13, etc.).

[0037] Therefore, it was found that omitting the finishing welding work after the removal of conventional erection pieces may or may not have an adverse effect on the overall structural performance of the building, and this can be set as a boundary value (threshold) for determining whether or not it is feasible.

[0038] Therefore, the applicant treated 37 cases from Conventional Examples 1 to 3, where the column member is □750×750×60, as FA rank, out of a total of 51 cases corresponding to the aforementioned Conventional Examples 1 to 6, and plotted the relationship between the shear span ratio (L / 2D) and stress ratio (γ) in Figure 27A. Figure 27B is an enlarged excerpt of the stress ratio (γ) between 1.0 and 1.2 within the range of 0.8 to 2.0 shown in Figure 27A. Similarly, the applicant treated a total of 14 cases from Conventional Examples 4 to 6, where the column member is □750×750×25, as FB rank, and plotted the relationship between the shear span ratio (L / 2D) and stress ratio (γ) in Figure 28A. Figure 28B is an enlarged excerpt of the stress ratio (γ) between 1.0 and 1.2 within the range of 0.8 to 2.0 shown in Figure 28A.

[0039] <Basis for introducing formula (1) related to the FA rank in paragraph

[0019] above, and formulas (6) and (7) related to the FB rank in paragraph

[0020] above> (Type of column) The aforementioned FA rank related to the width-to-thickness ratio (column member is □750×750×60, 490N / mm²) 2 (Analysis performed with grade, F value 325) and the aforementioned FB rank (column member is □750×750×25, 490N / mm 2 In a FEM analysis (performed with a grade of 325 and an F-value of 325), the boundary values ​​(thresholds) between the shear span ratio (L / 2D) and stress ratio (γ) at which structural performance does not deteriorate were derived (calculated) in a FEM analysis simulating a three-point bending test. The results are shown in Figures 27 and 28 above. To reiterate, in this numerical analysis, the shape of the hollow section column body of the structural steel frame is standardized to an external dimension of DD = 750 mm square, with two types of plate thickness (t): 60 mm (Figure 18A) and 25 mm (Figure 18B). In the analysis models for both sections, the strength level of the flat and corner sections of the hollow section column member (square steel pipe column) is set to 490 N / mm². 2The cold-pressed square steel tube BCP325, a grade used for building structures, is used, and the material properties of the through diaphragm and backing plate have a strength level of 490 N / mm². 2 Numerical analysis is being conducted using the material properties of BCP325, a cold-pressed rectangular steel pipe of the same grade used for building structures. The standard strength F for BCP325 is 325. The column types when the standard strength F is 325 are as shown in the table in Figure 5. In this numerical analysis, the column type for hollow cross-section column members (square steel pipe columns) is FA rank when the plate thickness (t) is 60 mm because D / t = 12.5, and FB rank when the plate thickness (t) is 25 mm because D / t = 30. Here, the aforementioned "type of column" is classified by its susceptibility to local buckling. In route design under the Building Standards Act, hollow section column members are required to be of FA rank in Route 1 and Route 2. In Route 3, the type of column is considered and reflected in the calculation of the ultimate horizontal load-bearing capacity. FA-rank columns experience local buckling after the compression section has yielded and sufficient plastic deformation has progressed as a structural material, while FB-rank columns experience local buckling after the compression section has yielded in the weakly nonlinear region, or after some plastic deformation has progressed beyond the weakly nonlinear region. Therefore, in this invention, since it is assumed that the influence of the position and size of the opening on the load-bearing capacity at the column end differs depending on the type of column, numerical analysis was performed for two types of cross-sections: FA rank and FB rank.

[0040] Regarding the aforementioned FA rank, the applicant derived the following configuration, particularly equations (1) to (5), based on Figures 5 and 27A and 27B. Specifically, as repeated in paragraph

[0019] above, the welded joint structure of upper and lower column members is such that upper and lower column members with hollow cross-sections are butt-welded together, leaving at least one unwelded portion, The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equation (1): Formula (1) D / t≦33√(235 / F) F: Reference intensity Furthermore, the welded joint structure for upper and lower column members is characterized in that the end of the column member becomes fully plastic ahead of the butt joint position by butt welding the column member in such a way that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow column member by the outer diameter (D) of the hollow column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, satisfies one of the following equations (2) to (5). Equation (2) When (L / 2D) is 7 or greater, γ > 1.02 When equation (3) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-264.27) / -251.97 When equation (4) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-15.822) / -11.445 Equation (5) When (L / 2D) is 2.67, γ > 1.15

[0041] Next, regarding the FB rank, the applicant derived the following configuration, particularly equations (6) to (11), based on Figures 5 and 28A and 28B. Specifically, as repeated in paragraph

[0020] above, the welded joint structure of upper and lower column members is such that upper and lower column members with hollow cross-sections are butt-welded together, leaving at least one unwelded portion, The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equations (6) and (7): Equation (6) D / t>33√(235 / F) F: Reference intensity Equation (7) D / t≦37√(235 / F) F: Reference intensity Furthermore, the welded joint structure for upper and lower column members is characterized in that the end of the column member becomes fully plastic before the butt joint position, by butt welding the column member in such a way that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow column member by the outer diameter (D) of the hollow column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, satisfies one of the following equations (8) to (11). Equation (8) When (L / 2D) is 7 or greater, γ > 1.05 When equation (9) (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-28.382) / -20.334 When equation (10) (L / 2D) is 2.67 or greater and less than 4, γ>((L / 2D)-19.493) / -12.921 When equation (11) (L / 2D) is 2.67, γ > 1.30

[0042] While embodiments of the present invention have been described above with reference to the drawings, it should be noted that the present invention is not limited to the illustrated examples and includes design modifications and variations in application that are commonly practiced by those skilled in the art, without departing from the technical spirit thereof. [Explanation of Symbols]

[0043] 1 Column member 2. Welded joint 3. Parts that will not be welded (openings) 7 Erection Pieces 7' Traces of the erection piece 8 Splice Plates 9 High-strength bolts 10 Column beam joint 11 Through diaphragm

Claims

1. A welded joint structure for upper and lower column members, in which hollow column members arranged vertically are butt-welded together, leaving at least one unwelded section, The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following formula (1): Formula (1) D / t≦33√(235 / F) F: Reference intensity Furthermore, the welded joint structure for upper and lower column members is characterized in that the end of the column member becomes fully plastic ahead of the butt joint position by butt welding the shear span ratio (L / 2D), which is obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, such that the relationship between the shear span ratio (L / 2D), which is obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint position, satisfies one of the following equations (2) to (5). Equation (2) When (L / 2D) is 7 or greater, γ > 1.02 Equation (3) When (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-264.27) / -251.97 When equation (4) (L / 2D) is 2.67 or more and less than 4, γ>((L / 2D)-15.822) / -11.445 Equation (5) When (L / 2D) is 2.67, γ > 1.15

2. A welded joint structure for upper and lower column members, in which hollow column members arranged vertically are butt-welded together, leaving at least one unwelded section, The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equations (6) and (7): Formula (6) D / t>33√(235 / F) F: Reference intensity Formula (7) D / t≦37√(235 / F) F: Reference intensity Furthermore, the welded joint structure for upper and lower column members is characterized in that the end of the column member becomes fully plastic ahead of the butt joint position by butt welding the column member in such a way that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt weld joint position by the plastic section modulus of the butt weld joint, satisfies one of the following equations (8) to (11). Equation (8) When (L / 2D) is 7 or greater, γ > 1.05 Equation (9) When (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-28.382) / -20.334 When equation (10) (L / 2D) is 2.67 or more and less than 4, γ>((L / 2D)-19.493) / -12.921 Equation (11) When (L / 2D) is 2.67, γ > 1.30

3. The welded joint structure for upper and lower column members according to claim 1 or 2, characterized in that the portion that is not welded is between the upper and lower column members and is located at a position corresponding to the mounting portion of the erection piece.

4. The welded joint structure for upper and lower column members according to claim 1 or 2, characterized in that the lower column member is erected on the upper surface of the column-beam joint or column base.

5. A butt welding joint method for hollow cross-section column members arranged vertically with erection pieces, The process consists of the steps of: using the erection piece to align and temporarily fix the upper column member with respect to the lower column member; welding the upper and lower column members together; and removing the erection piece. The welding process involves butt welding the upper and lower column members, leaving a portion corresponding to the mounting area of ​​the erection piece untouched. The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following formula (1): Formula (1) D / t≦33√(235 / F) F: Reference intensity Furthermore, a welding method for joining upper and lower column members, characterized in that the end of the column member becomes fully plastic ahead of the butt joint position by performing the butt welding joint such that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt welding joint position by the plastic section modulus of the butt welding joint, satisfies one of the following equations (2) to (5). Equation (2) When (L / 2D) is 7 or greater, γ > 1.02 Equation (3) When (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-264.27) / -251.97 When equation (4) (L / 2D) is 2.67 or more and less than 4, γ>((L / 2D)-15.822) / -11.445 Equation (5) When (L / 2D) is 2.67, γ > 1.15

6. A butt welding joint method for hollow cross-section column members arranged vertically with erection pieces, The process consists of the steps of: using the erection piece to align and temporarily fix the upper column member with respect to the lower column member; welding the upper and lower column members together; and removing the erection piece. The welding process involves butt welding the upper and lower column members, leaving a portion corresponding to the mounting area of ​​the erection piece untouched. The width-to-thickness ratio obtained by dividing the outer diameter (D) of the hollow cross-section column member by the plate thickness (t) satisfies the following equations (6) and (7): Formula (6) D / t>33√(235 / F) F: Reference intensity Formula (7) D / t≦37√(235 / F) F: Reference intensity Furthermore, a welding method for upper and lower column members, characterized in that the end of the column member becomes fully plastic ahead of the butt joint position by performing the butt welding joint such that the relationship between the shear span ratio (L / 2D), obtained by dividing half the length (L) from the lower end of the beam on the upper floor to the upper end of the beam on the lower floor in the hollow cross-section column member by the outer diameter (D) of the hollow cross-section column member, and the stress ratio (γ), which is the value obtained by dividing the stress obtained by dividing the moment acting on the end of the hollow cross-section column member by the plastic section modulus of the end of the column member by the stress obtained by dividing the moment acting at the butt welding joint position by the plastic section modulus of the butt welding joint, satisfies one of the following equations (8) to (11). Equation (8) When (L / 2D) is 7 or greater, γ > 1.05 Equation (9) When (L / 2D) is 4 or greater and less than 7, γ>((L / 2D)-28.382) / -20.334 When equation (10) (L / 2D) is 2.67 or more and less than 4, γ>((L / 2D)-19.493) / -12.921 Equation (11) When (L / 2D) is 2.67, γ > 1.30

7. The welding joint method for upper and lower column members according to claim 5 or 6, characterized in that the lower column member is erected on the upper surface of the column-beam joint or column base.

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