Undermatched welded column joint structure and its evaluation method

Abstract

To provide a column joint structure of a soft welding type excellent in weld workability and deformability.SOLUTION: A column joint structure 10 of an undermatching weld type is provided with: an upper column member 12 and a lower column member 11 each of which has a cross section of a rectangular box shape and formed of high tensile steel; and a joint part 13 for welding an upper end part of the lower column member 11 and a lower end part of the upper column member 12 using a weld metal with lower strength than those of the column members 11, 12, wherein the high tensile steel has a yield strength Bσy of 630 MPa or more. The weld metal is set so as to meet an axial force ratio n and a determination formula prepared according to a load direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an undermatch welded column joint structure and a method for evaluating the same. [Background technology]

[0002] When welding components together, it is essential to ensure safety that the weld metal has a strength equal to or greater than that of the base material; in other words, even-match welding or over-match welding is performed. For example, according to Japan's Building Standards Act, the required strength is 355 N / mm². 2 355 N / mm² for structural steel of grade (SM520) 2 It is stipulated that weld metal having the above tensile strength should be used.

[0003] In recent years, buildings have become taller and have larger spans, and consequently, column members have become thicker and stronger. The application of 80 kg-class high-tensile steel to column members is expected, but 355 N / mm 2 There are no definitive regulations regarding the strength of the weld metal for structural steel materials with the strengths mentioned above. Following the above example, it could be said that the use of 80 kg-class weld metal is a prerequisite. However, 80 kg-class weld metal has strict constraints on welding conditions such as preheating, heat input, and interpass temperature, resulting in poor welding efficiency. Therefore, undermatch welding is being considered for corner welds and column-beam joints of high-tensile steel columns (see, for example, Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Komatsu et al., "On the evaluation of the load-bearing capacity of soft welded joints in 80 kg class box-shaped column columns", Proceedings of the Architectural Institute of Japan Kanto Branch, 1996, pp. 89-92. [Non-Patent Document 2] Awata et al., "Study on the structural performance of ultra-high-strength steel CFT members assembled by undermatching welding, Part 1," Proceedings of the Architectural Institute of Japan (China), August 2017. [Overview of the project] [Problems that the invention aims to solve]

[0005] Undermatch welding is a welding method that uses a weld metal with lower strength than the base metal. If safety can be ensured even with a lower weld metal strength, it may be possible to relax welding conditions and omit welding process management, which is expected to improve welding efficiency. However, the safety of applying undermatch welding to column joints (column-column connections) has not been verified.

[0006] The present invention aims to provide a column joint structure that can achieve both improved weldability and safety, and to provide a method for appropriately and easily evaluating the safety of an undermatched welded column joint structure. [Means for solving the problem]

[0007] The inventors of this invention, after conducting studies to achieve the above objectives, conceived the idea that the safety of a column joint structure can be evaluated according to the concept of load-bearing capacity joints. Specifically, they conceived the idea that the safety of a column joint structure can be determined based on a comparison between the load-bearing capacity of the joint (e.g., the maximum bending load of the joint) and the load-bearing capacity of the base material (e.g., the fully plastic bending load of the column member). Furthermore, based on this idea, through experiments, they obtained, as their own unique insight, a calculation formula for reasonably and easily calculating the load-bearing capacity of the joint of an undermatch welded column joint structure for columns with a box-shaped cross-section. This invention is based on such ideas and insights.

[0008] The first aspect of the present invention is an under-matched welded column joint structure comprising an upper column member and a lower column member formed of high-tensile steel and having a rectangular box-shaped cross-section, and a joint portion for welding the upper end portion of the lower column member and the lower end portion of the upper column member with a welding metal having a lower strength than that of the column member. The high-tensile steel has a yield strength of 630 MPa or more B σ y and satisfies the following formula (1.0) for the 0-degree loading direction and the following formula (1.45) for the 45-degree loading direction under the condition that the axial force ratio n satisfies 0 ≦ n ≦ 0.5: An under-matched welded column joint structure is provided.

[0009]

Number

[0010] The second aspect of the present invention is an under-matched welded column joint structure comprising an upper column member and a lower column member formed of high-tensile steel and having a rectangular box-shaped cross-section, and a joint portion for welding the upper end portion of the lower column member and the lower end portion of the upper column member with a welding metal having a lower strength than that of the column member. The high-tensile steel has a yield strength of 630 MPa or more B σ y and satisfies the following formula (2.0) for the 0-degree loading direction and the following formula (2.45) for the 45-degree loading direction under the condition that the axial force ratio n satisfies 0.5 < n ≦ 0.5(β + 1): An under-matched welded column joint structure is provided.

[0011]

Number

[0012] A third aspect of the present invention is an evaluation method for an under-match welded column joint structure, comprising an upper column member and a lower column member having a rectangular box-shaped cross-section and formed of high-tensile steel, and a joint portion that welds the upper end portion of the lower column member and the lower end portion of the upper column member with a weld metal having a lower strength than the column member, wherein the high-tensile steel has a yield strength of 630 MPa or more B σ y When it has, Under the condition where the axial force ratio n is 0 ≦ n ≦ 0.5, it is represented by the following formula (1.0.L) for the 0-degree loading direction and the following formula (1.45.L) for the 45-degree loading direction. Under the condition where the axial force ratio n is 0.5 < n ≦ 0.5(β + 1), it is represented by the following formula (2.0.L) for the 0-degree loading direction and the following formula (2.45.L) for the 45-degree loading direction, and deriving the maximum bending strength of the joint portion Based on the derived maximum bending strength of the joint portion, determining whether the joint portion can avoid breaking before the column member reaches the fully plastic state An evaluation method for an under-match welded column joint structure is provided, which includes the above steps.

[0013]

Number

[0014] According to the above, when a column member has a box-shaped cross-section, the load-bearing capacity (maximum bending strength) of the joint of an undermatched welded joint structure can be calculated relatively easily from parameters that are relatively easy for the designer of the column joint structure to obtain, such as the strength parameters of the weld metal and the design parameters of the column joint structure. Based on the calculated load-bearing capacity of the joint, it becomes possible to appropriately evaluate the safety of the column joint structure in accordance with the concept of load-bearing capacity joints, and it becomes possible to provide a column joint structure that can guarantee safety.

[0015] Furthermore, since two loading directions, a 0-degree loading direction and a 45-degree loading direction, are considered in anticipation of the response during an earthquake, it is possible to provide a column joint structure with seismic resistance. In addition, since individual calculation formulas are prepared according to the level of the axial force ratio, a reasonable evaluation can be performed considering the effect of the axial force ratio on the maximum bending strength. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a column joint structure that can achieve both improved weldability and ensured safety. Furthermore, the safety of the undermatch welded column joint structure can be reasonably and easily evaluated. [Brief explanation of the drawing]

[0017] [Figure 1] A side view of an example (0-degree loading direction) of a column structure or a test specimen thereof to which the column joint structure according to an embodiment of the present invention is applied. [Figure 2] Cross-sectional view of line II-II in Figure 1. [Figure 3] Section III-III in Figure 1. [Figure 4] This is a cross-sectional view corresponding to Figure 2 of another example (45-degree loading direction) of a test specimen of a column structure to which the column joint structure according to the embodiment of the present invention is applied. [Figure 5] A cross-sectional view of the column structure shown in Figure 4, corresponding to Figure 3. [Figure 6] A cross-sectional view showing the groove shape of a column joint structure. [Figure 7] A perspective view showing a test specimen of a column joint structure. [Figure 8] A diagram showing the procedure for taking tensile test specimens from a column joint structure. [Figure 9] A graph showing the experimental results of tensile tests on the column joint structure applied to the first column. [Figure 10] A graph showing the experimental results of tensile tests on the column joint structure applied to the second column. [Figure 11] A diagram illustrating the collapse mechanism assumed in the derivation of the formula. [Figure 12] A diagram illustrating the balance of hypothetical work assumed in the derivation of the formula. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below with reference to the drawings.

[0019] <1. Overview of the Column Joint Structure> Figures 1 to 3 show a column structure 1 to which a column joint structure 10 according to an embodiment of the present invention is applied. The column joint structure 10 mainly comprises upper and lower column members 11 and 12 and a joint 13.

[0020] The column members 11 and 12 are formed from high-tensile steel and have a box-shaped cross-section (a square outer shape with a hollow interior). The column members 11 and 12 are arranged coaxially and extend in the vertical direction. In plan view, the column members 11 and 12 have a combined outer shape when superimposed. The joint 13 welds the upper end of the lower column member 11 to the lower end of the upper column member 12. In this embodiment, a groove 14 is provided around the entire circumference of the lower end of the upper column member 12. The upper and lower column members 11 and 12 are joined by full-circumference welding and V-shaped butt welding. The groove 14 has a triangular cross-section and widens upward from the inside to the outside of the upper column member 12.

[0021] The lower part of the lower column member 11 is supported by the support structure 2 of the column structure 1. The support structure 2 is composed, for example, of a base plate 3, a pair of vertical plates 4a, 4b, a pair of horizontal plates 5a, 5b, and a plurality of rib plates 6a, 6b. The lower column member 11 and the pair of horizontal plates 5a, 5b are erected on the upper surface of the base plate 3, which is rectangular in plan view. The lower column member 11 is positioned in the center of the base plate 3. The pair of vertical plates 4a, 4b extend in the direction of the long side of the base plate 3 from the center in the short side direction of the base plate 3. Each vertical plate 4a, 4b is joined to the outer surface of the lower column member 11 at one end edge, and its other end edge reaches the short side edge of the base plate 3. The pair of horizontal plates 5a, 5b are rectangular in plan view and are placed on the upper surfaces of the pair of vertical plates 4a, 4b, respectively. Each horizontal plate 5a, 5b has one short edge joined to the outer surface of the lower column member 11, and the other short edge overlaps with the short edge of the base plate 3 in a plan view. A pair of ribs 6a, 6b protrude from both sides of the respective ends of the vertical plates 4a, 4b. Each rib 6a, 6b is formed in a trapezoidal shape, with its upper edge joined to the lower surface of the horizontal plates 5a, 5b and its lower edge joined to the upper surface of the base plate 3. However, the configuration of the support structure 2 can be changed as appropriate.

[0022] The high-tensile steel used for the column members 11 and 12 has a yield strength of 630 MPa or more. B σ y The column members 11 and 12 are formed from so-called 80 kg-class high-tensile steel or steel with a tensile strength of 80 kg or more. Because the column structure 10 has high strength, it can be suitably used as a skeletal member of a high-rise building.

[0023] On the other hand, the weld metal applied to the joint 13 has lower strength than the high-tensile steel of the column members 11 and 12. In other words, in the column joint structure 10 according to this embodiment, undermatch welding is applied to the joint 13. If even-match welding were applied, the weld metal would have a strength of 80 kg, but from the viewpoint of preventing weld cracks and ensuring the strength and toughness of the weld metal, there would be strict constraints on welding conditions such as preheating, heat input, and interpass temperature, resulting in poor welding efficiency. By applying undermatch welding, it is possible to reduce the heat input during welding and omit construction management, thereby increasing welding efficiency.

[0024] <2. Overview of the Evaluation Method Procedure> Regarding safety when applying undermatch welding, in a column-column joint having a box-shaped cross-section, even if the strength of the weld metal is lower than the strength of the column members 11 and 12 as base materials, it is considered possible to avoid a situation where the joint 13 fractures before the column members 11 and 12 reach a fully plastic state. In other words, it is considered possible to provide an undermatch welding type column joint structure 10 that can guarantee safety, in accordance with the concept of load-bearing capacity joints, which is widely used in the design of joints. The condition for preventing the joint 13 from fracturing before the column members 11 and 12 reach a fully plastic state, in accordance with the concept of load-bearing capacity joints, is expressed by the following equation (1).

[0025]

number

[0026] Regarding the right-hand side of equation (1), the specific numerical value of the joint coefficient α can preferably be 1.1, which is commonly used for members made of 490 Newton-class carbon steel. Full plastic bending strength c M p Based on known knowledge, the axial force N or axial force ratio n, the plate thickness t of column members 11 and 12, and the yield strength of column members 11 and 12 are used. B σ y It can be converted into an equation with variables such as these. Therefore, as long as the strength parameter values ​​and design parameter values ​​of column members 11 and 12 are obtained, the numerical value on the right side of equation (1) can be calculated relatively easily.

[0027] On the other hand, with respect to the left side of equation (1), the maximum bending strength of the joint 13 of the column joint structure 10 having a box-shaped cross section j M u Regarding full plastic bending strength c M pAs such, there is no formula to obtain the numerical value from the strength parameter value of the weld metal or the design parameter value of the column joint structure 10. In other words, according to the concept of load-bearing capacity joints, the maximum bending strength of the joint 13 j M u Even if we come up with the idea that if we can calculate the maximum bending strength, we can evaluate the safety when undermatch welding is applied to a column joint structure 10 having a box-shaped cross section, j M u The reality is that there is no method to calculate this value reasonably and easily.

[0028] Here, the maximum bending strength of the joint 13 j M u This is affected by the axial force N or the axial force ratio n. Furthermore, in order to ensure the seismic performance of the building, it is desirable that equation (1) be satisfied in various loading directions. When considering a column joint structure 10 having a box-shaped cross section, two loading directions to be considered are the 0-degree loading direction and the 45-degree loading direction. The 0-degree loading direction is the direction perpendicular to the side surface of the column joint structure 10. The 45-degree loading direction is the direction inclined at a 45-degree angle to the side surface of the column joint structure 10.

[0029] Based on the above, in the evaluation method for the column joint structure 10 according to this embodiment, first, from parameter values ​​that can be relatively easily obtained by the designer of the column joint structure 10, such as the strength parameter of the weld metal and the design parameter of the column joint structure 10, the maximum bending strength of the joint 13 j M u A set of calculation formulas is prepared to derive the result.

[0030] The set of calculation formulas includes multiple sets of formulas corresponding to the axial force ratio n. Each set of formulas represents the maximum bending strength assumed when a load is applied in the 0-degree loading direction. j M u The calculation formula for 0-degree loading to derive the maximum bending strength when a load is applied in the 45-degree loading direction. j M uIt includes two calculation formulas, including a calculation formula for 45-degree loading to derive the result. In this embodiment, two sets of calculation formulas are prepared depending on the level of the axial force ratio n. Therefore, the set of calculation formulas includes a total of four formulas, 2 × 2.

[0031] Once the set of calculation formulas is prepared, (1a) one set of calculation formulas is selected from the multiple sets (two sets in this example) that make up the set of calculation formulas according to the assumed axial force ratio n, and (1b) according to the two calculation formulas included in the selected set, the maximum bending strength of the joint 13 assumed when loading is applied in the 0-degree loading direction is calculated according to the design parameter values ​​of the column joint structure 10 to be evaluated and the strength parameter values ​​of the weld metal. j M u And the maximum bending strength of the joint 13 when loaded in the 45-degree loading direction j M u Calculate the result.

[0032] Next, (2) the calculated maximum bending strength j M u Based on this, it is determined whether the joint 13 will not break before the column members 11 and 12 reach a fully plastic state. That is, the calculated maximum bending strength j M u The value is compared with the value on the right side of equation (1) to determine whether the inequality in equation (1) is true or false. The maximum bending strength of the joint 13 assumed in the 0-degree loading direction. j M u Also, the maximum bending strength of the joint 13 assumed in the 45-degree loading direction j M u Furthermore, if equation (1) is satisfied, the column joint structure 10 being evaluated is deemed safe, taking seismic resistance into consideration. At least one of the maximum bending strengths j M u If equation (1) is not satisfied, the column joint structure 10 being evaluated is deemed to have no guarantee of safety.

[0033] <3. Formula for calculating the maximum bending strength of the joint> The maximum bending strength of the joint 13 is as follows: j M uThe calculation formula will be explained in more detail. Prior to deriving the calculation formula, test specimens 10A and 10B of the column joint structure 10 (see Figures 1 and 4) are manufactured. Two types of test specimens 10A and 10B are manufactured. One is the 0-degree loading test specimen 10A (see Figures 1 to 3), which is assumed to be loaded in the 0-degree loading direction. The other is the 45-degree loading test specimen 10B (see Figures 4 and 5), which is assumed to be loaded in the 45-degree loading direction. The main components of these test specimens 10A and 10B are as described above as the general configuration of the column joint structure 10.

[0034] As shown in Figures 1 to 3, in the 0-degree loading test specimen 10A, the lower column member 11 is supported by the support structure 15 in a position where one edge of the outer shape of the lower column member 11 is parallel to the long or short edge of the base plate 15a. Therefore, the pair of vertical plates 15b and 15c are joined to the center of the side surface of the lower column member 11. As shown in Figures 4 and 5, in the 45-degree loading test specimen 10B, the lower column member 11 is supported by the support structure 15 in a position where the lower column member 11 has been rotated 45 degrees around the central axis from the state shown in Figures 1 to 3. Therefore, the pair of vertical plates 15b and 15c are joined to the corners of the lower column member 11. In experiments using these test specimens 10A and 10B, the load is applied in the left-right direction of the paper as shown in Figures 2 to 4.

[0035] Furthermore, in both test specimens 10A and 10B, the lower column member 11 has a greater plate thickness than the upper column member 11, and the column joint structure 10 is a stepped joint, so that deformation is concentrated at the joint 13. The plate thickness of the lower column member 11 is 24 mm, and the plate thickness of the upper column member 12 is 12 mm. The outer dimensions of both the lower column member 11 and the upper column member 12 are 150 mm squares. In actual columns, the plate thickness is approximately 60 mm, and the outer dimensions are approximately 600 mm square.

[0036] Referring to Figure 6, groove conditions were extracted such that the equivalent plastic strain of the column joint structure of test specimens 10A and 10B and the actual column were equivalent, in order to adequately simulate the elastoplastic behavior of the actual column in experiments using test specimens 10A and 10B. As a result, the groove angle θ of test specimens 10A and 10B was set to 35 degrees, and the root gap G was set to 3 mm.

[0037] Once the design parameters for specimens 10A and 10B are determined, the collapse mechanism is then determined. To do this, the fracture lines of specimens 10A and 10B are confirmed using finite element analysis. As a result, in this example, it was confirmed that sliding deformation occurs along the groove (see Figure 11).

[0038] Next, we identify the relationship for converting the yield strength of the weld metal to the yield strength of the weld metal constrained by the column members 11 and 12. To do this, we calculate the collapse load P from the virtual work equilibrium (see Figure 12) based on the collapse mechanism determined above. Given the relationship that the work done by internal forces is equal to the work done by external forces, and the fact that the groove angle θ in this example is 35 degrees, the collapse load P is expressed by the following equation (2).

[0039]

number

[0040] Next, we set the stress distribution during full plasticity. We set the stress distribution during full plasticity using finite element analysis. The maximum bending strength considering the axial force N is: w σ u The region composed of, w σ y This is the sum of the maximum bending strengths of each region composed of these elements. The analysis is performed for both the 0-degree loading direction and the 45-degree loading direction, and stress blocks are set individually. The analysis model is the same as the one used to determine the collapse mechanism described above.

[0041] Next, it is divided into two cases according to the axial force ratio n, and for each case, based on the above stress distribution, the maximum bending resistance j M u is calculated for each of the 0-degree loading direction and the 45-degree loading direction. As a result, four calculation formulas for calculating the maximum bending resistance j M u are obtained as follows.

[0042]

Equation

[0043] Calculation formulas (1.0.L) and (1.45.L) constitute a set of calculation formulas applicable under the condition that the axial force ratio n is 0 ≤ n ≤ 0.5. Calculation formula (1.0.L) is a formula for calculating the maximum bending resistance j M u in the 0-degree loading direction. Calculation formula (1.45.L) is a formula for calculating the maximum bending resistance j M u in the 45-degree loading direction.

[0044] Calculation formulas (2.0.L) and (2.45.L) constitute a set of calculation formulas applicable under the condition that the axial force ratio n is 0.5 < n ≤ 0.5(β + 1). Calculation formula (2.0.L) is a formula for calculating the maximum bending resistance j M u in the 0-degree loading direction. Calculation formula (2.45.L) is a formula for calculating the maximum bending resistance j M u in the 45-degree loading direction.

[0045] <4. Calculation formulas for fully plastic bending resistance, etc.> Regarding the fully plastic bending resistance [[ID=四十七]] c [[ID=四十八]]M[[ID=四十九]] p [[ID=五十]]on the right side of Equation (1), similar to the maximum bending resistance [[ID=五十一]] j [[ID=五十二]]M[[ID=五十三]] u [[ID=五十四]]of the joint 13, four calculation formulas as follows are obtained according to the axial force ratio and the loading direction. [[ID=五十五]] [[ID=五十六]]

[0046] [[ID=五十七]] [[ID=五十八]] [[ID=五十九]]

Equation

[0047] Calculation formulas (1.0.R) and (1.45.R) constitute a set of calculation formulas applicable under the condition that the axial force ratio n satisfies 0 ≦ n ≦ 0.5. Calculation formula (1.0.R) is a formula for calculating the fully plastic bending resistance c M p in the 0-degree loading direction. Calculation formula (1.45.R) is a formula for calculating the fully plastic bending resistance c M p in the 45-degree loading direction. Calculation formulas (2.0.R) and (2.45.R) constitute a set of calculation formulas applicable under the condition that the axial force ratio n satisfies 0.5 < n ≦ 0.5(β + 1). Calculation formula (2.0.R) is a formula for calculating the fully plastic bending resistance c M p in the 0-degree loading direction. Calculation formula (2.45.R) is a formula for calculating the fully plastic bending resistance c M p in the 45-degree loading direction.

[0048] Note that the axial force ratio n is obtained from the following formula (3). The yield strength w σ y and tensile strength w σ u of the weld metal under the restraint of the base material are obtained from the following formulas (4) and (5) respectively based on formula (2). The reciprocal β of the yield ratio of the weld metal is obtained from the following formula (6). The joint yield resistance w N y and the joint maximum tensile resistance w N u are obtained from the following formulas (7) and (⑧) respectively. Also, the condition of the axial force ratio n: 0 ≦ n ≦ 0.5 is equivalent to the conditional formula (9) using the axial force N, and the same condition: 0.5 < n ≦ 0.5(β + 1) is also equivalent to the conditional formula (10) using the axial force N.

[0049]

Equation

[0050] Based on equations (3) to (8) and calculation formulas (1.0.L), (1.45.L), (2.0.L), (2.45.L), (1.0.R), (1.45.R), (2.0.R), and (2.45.R), the axial force N, the design parameters of the column joint structure 10 (column cross-sectional area A, column width B, and plate thickness t), and the strength parameters of the weld metal (yield point) are used. w σ y0 and tensile strength w σ u0 ) and the strength parameters of column members 11 and 12 (yield strength B σ y Once the value of ) is determined, the axial force ratio n is also determined, and the maximum bending strength of the joint section 13 j M u and full plastic bending strength c M p This can be easily calculated.

[0051] <5. Conditions for undermatched welded column joint structures> Maximum bending strength of joint section 13 j M u and full plastic bending strength c M p Once these values ​​are calculated, it is possible to determine whether the inequality shown in equation (1) is true or false. In other words, equation (1) can be rewritten into the following four determination formulas depending on the axial force ratio n and the loading direction.

[0052]

number

number

[0053] The determination formula (1.45) is obtained by using the calculation formulas (1.45.L) and (1.45.R) and transforming formula (1) in the same manner as above. The determination formula (2.0) is obtained by using the calculation formulas (2.0.L) and (2.0.R) and transforming formula (1) in the same manner as above. The determination formula (2.45) is obtained by using the calculation formulas (2.45.L) and (2.45.R) and transforming formula (1) in the same manner as above.

[0054] The designer of the column joint structure 10 only needs to obtain the parameter values related to the column joint structure 10 to be evaluated and calculate the axial force ratio n. Then, it can be determined whether it is the situation of using the set of judgment formulas (1.0) and (1.45) or the situation of using the set of judgment formulas (2.0) and (2.45).

[0055] If the axial force ratio n satisfies 0 ≦ n ≦ 0.5, judge the success or failure of the two judgment formulas (1.0) and (1.45). If the left side values of both are greater than or equal to the right side values, the column joint structure 10 to be evaluated can be evaluated as safe in terms of seismic resistance in light of the concept of holding capacity joint. If the left side value is less than the right side value in any one of the judgment formulas, the column joint structure 10 to be evaluated cannot be evaluated as safe.

[0056] The same is true when the axial force ratio n satisfies 0.5 < n ≦ 0.5(β + 1). If the left side values of both judgment formulas (2.0) and (2.45) are greater than or equal to the right side values, the column joint structure 10 to be evaluated can be evaluated as safe. If the left side value is less than the right side value in any one of the judgment formulas, the column joint structure 10 to be evaluated cannot be evaluated as safe.

[0057] By using this evaluation method in the design stage, the column joint structure 10 that satisfies both judgment formulas (1.0) and (1.45), or both judgment formulas (2.0) and (2.45), is provided to the constructor of high-rise buildings.

[0058] Even when performing under-match welding, it is possible to satisfy both judgment formulas (1.0) and (1.45), or both judgment formulas (2.0) and (,45). Therefore, a column joint structure 10 with high welding workability can be provided.

[0059] The designer of the column joint structure 10 may also consider trial and error in designing the column joint structure 10 by fine-tuning design parameters such as column width B and plate thickness t while keeping the weld metal or base material the same. In such cases, some of the variables constituting the judgment formulas (1.0), (1.45), (2.0), and (2.45) can be treated as constants. For example, w σ y0 500 N / mm 2 , w σ u0 630 N / mm 2 , B σ y 630 N / mm 2 Under the conditions, the determination formulas (1.0), (1.45), (2.0), and (2.45) can be rewritten as the following formulas (1'.0), (1'.45), (2'.0), and (2'.45). However, these proposed formulas are effective when considering the application of a 60 kg class soft welding material to an 80 kg class base material column. For example, when considering an even softer 50 kg class welding material, the collapse mechanism described in paragraph 0037 can be set using a similar method, and the collapse load P is the yield strength of the weld metal. w σ y0 By considering how many times larger it becomes, it becomes possible to apply this knowledge.

[0060]

number

number

[0061] <6. Verification of the judgment formula> The above determination formula was obtained through finite element method analysis. The inventor conducted experiments to verify its validity.

[0062] [Table 1] First, six types of test specimens were prepared. The specifications of the test specimens are shown in Table 1.

[0063] Specimens C0-H, C0-M, and C0-L were designed to be subjected to a load in the 0-degree loading direction and were constructed to have the same configuration as the first specimen 10A shown in Figures 1 to 3. Specimens C45-H, C45-M, and C45-L were designed to be subjected to a load in the 45-degree loading direction and were constructed to have the same configuration as the second specimen 10B shown in Figures 4 and 5.

[0064] In all test specimens, the material properties of the column members 11 and 12 as base materials were kept the same. The base material had a yield strength B σ y 719 N / mm 2 80 kg-class high-tensile steel was used.

[0065] Three types of weld metal were prepared. The first was an 80 kg class weld metal, which had the highest strength of the three, and was applied to test specimens C0-H and C45-H. The second was a 60 kg class weld metal, which had an intermediate strength, and was applied to test specimens C0-M and C45-M. The third was a 50 kg class weld metal, which had the lowest strength, and was applied to test specimens C0-L and C45-L.

[0066] In this experiment, the validity of decision formulas (1.0) and (1.45) is verified by setting the axial force N to 0.

[0067] [Table 2] Table 2 shows the determination by formula.

[0068] Test specimens C0-H and C45-H are comparative examples that contradict the spirit of the present invention, as even-match welding or over-match welding is applied to the joint. Test specimens C0-M and C45-M are examples that apply under-match welding to the joint and satisfy criteria (1.0) and (1.45). Test specimens C0-L and C45-L are comparative examples that apply under-match welding to the joint, but the strength of the weld metal is too low to satisfy criteria (1.0) and (1.45).

[0069] Furthermore, test specimens were prepared to obtain the tensile properties of the base metal and each weld metal. JIS Z2241 No. 5 was used for the base metal tensile test specimen, and JIS Z3111 A2 was used for the weld metal tensile test specimen. For the base metal, the specimens were taken at full pressure and perpendicular to the rolling direction. For each weld metal, in order to obtain values ​​closer to actual conditions, flat joints as shown in Figure 7 were created using materials from the same lot as the test specimens under the same welding conditions, and the specimens were taken so that the t / 2 position was centered in the cross-section of the weld, as shown in Figure 8.

[0070] The experiment was conducted according to the following experimental plan: the cross-sectional shape of the test specimen and the yield strength of the base material. B σ y Full plastic strength M based on p The corresponding amount of elastic deformation δ p Based on this, the amount of deformation for each cycle is set, ±δ p , ±2δ p , ±3δ p Each of the following was repeated twice, with alternating positive and negative loading experiments to gradually increase the load. The axial force N was set to 0. A load was applied to specimens C0-H, C0-M, and C0-L in the 0-degree loading direction. A load was applied to specimens C45-H, C45-M, and C45-L in the 45-degree loading direction.

[0071] [Table 3] The experimental results are shown in Figures 9 and 10 and Table 3.

[0072] Full plastic strength M during experimental design p For the value of , the maximum bending strength M obtained experimentally is max and minimum bending strength M min Examples were defined as those in which the absolute value of the ratio (increase in bearing capacity) was 1.1 or greater.

[0073] Test specimens C0-M and C45-M showed a strength increase rate of 1.1 or higher, indicating that even undermatched welded joints are sufficiently safe as structural components. Since test specimen C0-M satisfies criterion (1.0) and test specimen C45-M satisfies criterion (1.45), the validity of the criterion formulas was confirmed. Furthermore, the experimental value of the maximum bending strength of the joint corresponds to the calculated value derived from the calculation formula (left-hand side of the criterion formula), further confirming the validity of the criterion formulas.

[0074] Embodiments of the present invention have been described so far, but the above configurations and methods can be added, modified, and / or deleted as appropriate within the scope of the spirit of the present invention. [Explanation of Symbols]

[0075] 10. Column joint structure 11 Lower column member 12 Upper column member 13 Joint 14 Bevel

Claims

1. An upper column member and a lower column member having a rectangular box-shaped cross-section and formed from high-tensile steel, A joint is formed by welding the upper end of the lower column member and the lower end of the upper column member with a weld metal of lower strength than the upper column member and the lower column member, An undermatch welded column joint structure comprising, The aforementioned high-tensile steel has a yield strength of 630 MPa or more. Ｂ σ ｙ It has, Let B be the column width of the upper column member and the lower column member, let t be the plate thickness of the upper column member and the lower column member, and let t be the yield strength of the weld metal in a state of restraint by the upper column member and the lower column member. ｗ σ ｙ Let β be the reciprocal of the yield ratio of the weld metal. Under the condition that the axial force ratio n is 0 ≤ n ≤ 0.5, the following equation (1.0) is satisfied for the 0-degree loading direction and the following equation (1.45) is satisfied for the 45-degree loading direction. Undermatch welded column joint structure. [Math 1]

2. The weld metal, when restrained by the upper and lower column members, has a yield strength of 500 MPa or more. ｗ σ ｙ and tensile strength of 630 MPa or more ｗ σ ｕ It has, The following equation (1'.0) is satisfied in place of the above equation (1.0), and the following equation (1'.45) is satisfied in place of the above equation (1.45). The undermatch welded column joint structure according to claim 1. [Number 8]

3. An upper column member and a lower column member having a rectangular box-shaped cross-section and formed from high-tensile steel, A joint is formed by welding the upper end of the lower column member and the lower end of the upper column member with a weld metal of lower strength than the upper column member and the lower column member, An undermatch welded column joint structure comprising, The high-tensile steel has a yield strength of 630 MPa or more Ｂ σ ｙ and has Let B be the column width of the upper column member and the lower column member, let t be the plate thickness of the upper column member and the lower column member, and let t be the yield strength of the weld metal in a state of restraint by the upper column member and the lower column member. ｗ σ ｙ Let β be the reciprocal of the yield ratio of the weld metal. Under the condition that the axial force ratio n is 0.5 < n ≤ 0.5(β+1), the following equation (2.0) is satisfied for the 0-degree loading direction and the following equation (2.45) is satisfied for the 45-degree loading direction. Undermatch welded column joint structure. [Math 2]

4. The weld metal, when restrained by the upper and lower column members, has a yield strength of 500 MPa or more. ｗ σ ｙ and tensile strength of 630 MPa or more ｗ σ ｕ It has, The following equation (2'.0) is satisfied in place of equation (2.0), and the following equation (2'.45) is satisfied in place of equation (2.45). The undermatched welded column joint structure according to claim 3. [Number 9]

5. A groove is provided at the lower end of the upper column member, and the upper column member and the lower column member are butt-welded in a V-shape at the joint. The bevel angle is 35 degrees. An undermatch welded column joint structure according to any one of claims 1 to 4.

6. An upper column member and a lower column member having a rectangular box-shaped cross-section and formed from high-tensile steel, A joint is formed by welding the upper end of the lower column member and the lower end of the upper column member with a weld metal of lower strength than the upper column member and the lower column member, A method for evaluating an undermatch welded column joint structure comprising: The aforementioned high-tensile steel has a yield strength of 630 MPa or more. Ｂ σ ｙ It has, Let B be the column width of the upper column member and the lower column member, let t be the plate thickness of the upper column member and the lower column member, and let t be the yield strength of the weld metal in a state of restraint by the upper column member and the lower column member. ｗ σ ｙ Let β be the reciprocal of the yield ratio of the weld metal, Under the condition that the axial force ratio n is 0 ≤ n ≤ 0.5, the maximum bending strength of the joint is expressed by the following equation (1.0.L) for the 0-degree loading direction and the following equation (1.45.L) for the 45-degree loading direction, and under the condition that the axial force ratio n is 0.5 < n ≤ 0.5(β+1), the maximum bending strength of the joint is expressed by the following equation (2.0.L) for the 0-degree loading direction and the following equation (2.45.L) for the 45-degree loading direction. Based on the derived maximum bending strength of the joint, it is determined whether or not the joint will not break before the upper column member and the lower column member reach a fully plastic state. An evaluation method for an undermatch welded column joint structure, comprising the following features. [Math 3]

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