Joint structure

Abstract

To prevent a crack that occurs in a welding stop end of a flange from developing to lead to an early breakage of a beam end joining part.SOLUTION: A joining structure for joining a beam of an H-shaped cross section having a flange and a web to a joining target member is provided. The joining structure includes a steel end tab arranged adjacent to an end part in a width direction of the flange at an end part in a material axis direction of the beam of an H-shaped cross-section welded to the joining target member. Welding metal is filled between a first groove face formed on the flange and the joining target member, and between a second groove face formed on the end tab and the joining object member. An upper end of the second groove face is more separated from the joining target member than from an upper end of the first groove face.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to a joining structure.

Background Art

[0002] As an example of a technique related to a field-welded beam-end joint that is welded at a construction site, Patent Document 1 describes a technique in which a backing plate is abutted against the flange of an H-shaped cross-section beam, a groove face that is expanded on the opposite side of the backing plate is formed, and an end tab that compensates for the plate thickness difference between the thick plate portion and the thin plate portion included in the flange is arranged, and substantially the entire width of the flange is welded and joined with the plate thickness of the thick plate portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the beam-end joint as described above, when welded at a construction site, in order to avoid interference of the weld between the end of the flange of the H-shaped cross-section beam and the joined member such as a column or diaphragm with the web, a notch called a scallop is formed at the end of the web at the intersection with the flange. However, when a bending moment acts on the beam end during an earthquake or the like, stress and strain concentrate at the scallop bottom, and the beam-end joint may brittlely break starting from the scallop bottom. Therefore, by devising the scallop shape or the like, it has been studied to avoid crack generation from the scallop bottom that leads to early fracture. On the other hand, cracks may occur at the weld termination ends on both sides in the width direction of the flange other than the scallop bottom, but if the cracks generated at the weld termination ends also progress in the direction along the heat-affected zone of the flange where the toughness is unstable, it may lead to early fracture of the beam-end joint.

[0005] On the other hand, in beam end joints where scallops are not formed, such as those welded in a factory, cracks may occur at the weld toes on both sides of the flange in the width direction and propagate in a direction along the heat-affected zone of the flange.

[0006] Therefore, the present invention aims to provide a joint structure that can prevent cracks generated at the weld toe of a flange from propagating and leading to premature fracture of the beam end joint. [Means for solving the problem]

[0007] [1] A joining structure for joining an H-section beam having a flange and a web to a member to be joined, comprising a steel end tab positioned adjacent to the widthwise end of the flange at the axial end of the H-section beam that is welded to the member to be joined, wherein weld metal is filled between a first groove formed on the flange and the member to be joined, and between a second groove formed on the end tab and the member to be joined, and the end of the second groove on the groove-opening side is further away from the member to be joined than the end of the first groove on the groove-opening side. [2] The joint structure according to [1], wherein the distance between the end of the second groove surface on the groove-opening side and the end of the first groove surface on the groove-opening side is 10 mm or more. [3] The joining structure according to [1] or [2], wherein with respect to the member to be joined, the end of the second groove on the groove root side is spaced further apart than the end of the first groove on the groove root side. [4] The joint structure according to any one of items [1] to [3], wherein the groove angle of the second groove surface is greater than the groove angle of the first groove surface. [Effects of the Invention]

[0008] According to the above configuration, a weld is formed between the end tab and the joined member, continuous with the weld between the flange and the joined member of the H-section beam. By shifting the positions of the weld toe on the flange side and the weld toe on the end tab side, cracks that may originate from the end of the weld toe are guided towards the base material side of the flange, preventing the crack from propagating in the direction along the weld toe or heat-affected zone of the flange. Since the toughness is more stable on the base material side of the flange compared to the weld toe and heat-affected zone, cracks are less likely to turn into brittle cracks, thus preventing premature fracture of the beam end joint due to cracks. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows a joint structure according to one embodiment of the present invention. [Figure 2A] Figure 1 is an enlarged perspective view of the joint structure as seen from the upper left front side. [Figure 2B] Figure 1 is an enlarged perspective view of the joint structure as seen from the upper left front side. [Figure 3] This is a photograph showing an example of welding work in the joint structure shown in Figure 1. [Figure 4] This figure shows an example of the configuration of an end tab in one embodiment of the present invention. [Figure 5] This figure shows another example of the configuration of the end tab in one embodiment of the present invention. [Figure 6] This figure shows the dimensions of each component set in the embodiment. [Figure 7] This graph shows the stress-strain relationship of each component set in the example. [Figure 8] This graph shows the relationship between moment member angles in the examples and comparative examples. [Figure 9] This graph shows the relationship between equivalent plastic strain and distance x in the examples and comparative examples. [Figure 10] These are contour plots of (a) equivalent plastic strain and (b) shear strain for Comparative Example 1. [Figure 11] These are contour plots of (a) equivalent plastic strain and (b) shear strain for Example 1. [Figure 12] Contour diagrams of the equivalent plastic strain (a) and shear strain (b) corresponding to Example 2. [Figure 13] Contour diagrams of the equivalent plastic strain (a) and shear strain (b) corresponding to Example 3. [Figure 14] Contour diagrams of the equivalent plastic strain (a) and shear strain (b) corresponding to Example 4.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, for components having substantially the same functional configuration, the same reference numerals are assigned and redundant descriptions are omitted.

[0011] FIG. 1 is a diagram showing a joining structure according to an embodiment of the present invention. In the joining structure 1 shown in FIG. 1, an H-shaped cross-section beam 2 is joined to a column 3 and a diaphragm 31 (joined member), which are made of, for example, a square steel pipe. More specifically, the flange 21 of the H-shaped cross-section beam 2 is joined to the diaphragm 31 attached to the column 3 via a welded joint 41. A welded joint 41 is formed by filling the groove formed between the end face 211 in the material axis direction of the flange 21 and the end face 311 of the diaphragm 31 with welding metal using a backing bar 411. On the other hand, the web 22 of the H-shaped cross-section beam 2 is joined to the side face 32 of the column 3 via a welded joint (not shown). In other examples, the diaphragm 31 may not be attached to the column 3, and both the flange 21 and the web 22 may be joined to the side face 32 of the column 3 via welded joints.

[0012] Hereinafter, a joining structure including the welded joint 41 between the lower flange 21 of the H-shaped cross-section beam 2 and the diaphragm 31 will be described. However, as shown in FIG. 1, a joining structure including the welded joint 42 between the upper flange 23 of the H-shaped cross-section beam 2 and the diaphragm 33 can have a similar configuration.

[0013] At the end of the H-shaped beam 2 in the direction of the material axis, which is joined to the column 3, a scallop 5 is formed by cutting out a portion of the web 22 that is in contact with the flange 21. The scallop 5 is formed, for example, by cutting before joining the flange 21 and web 22 to the column 3. Alternatively, if the H-shaped beam 2 is an assembled H-shaped steel, the scallop 5 may be formed before welding the web 22 to the flange 21. Note that the H-shaped beam 2 is not limited to an assembled H-shaped steel, but may also be a rolled H-shaped steel. In the illustrated example, the opening edge of the scallop 5 formed on the web 22 includes arc portions 51 and 52 with different radii of curvature, and a straight portion 53 that is formed following the arc portion 52 and reaches the end face 221 of the web 22 in the direction of the material axis. The shape of the opening edge of the scallop 5 is not limited to the illustrated example, and various known shapes can be used.

[0014] Figures 2A and 2B are enlarged perspective views of the joint structure of Figure 1, viewed from the upper left front. Figure 2A shows the state before the weld metal is filled into the groove and the welded portion 41 is formed, and Figure 2B shows the state after the welded portion 41 is formed. As shown in the figures, in this embodiment, a steel end tab 6 is positioned adjacent to the end of the flange 21 in the width direction (y direction in the figure) at the end of the H-shaped cross section beam 2 in the material axis direction (x direction in the figure) that is welded to the diaphragm 31. In the illustrated example, the end tab 6 is a small plate-shaped piece formed with the same plate thickness as the flange 21, and has an upper surface 61 that is aligned with the welded surface side of the flange 21, a lower surface 62 that is aligned with the back surface on the opposite side of the welded surface of the flange 21 and is in contact with the backing plate 411 together with the flange 21, and an end surface 63 that faces the end surface 311 of the diaphragm 31 together with the end surface 211 of the flange 21.

[0015] In this embodiment, by arranging the end tab 6 as described above, a first groove G1 is formed between the end face 211 of the flange 21 and the end face 311 of the diaphragm 31, and a second groove G2 is formed between the end face 63 of the end tab 6 and the end face 311 of the diaphragm 31. In this specification, the end face 211 of the flange 21 that forms the first groove G1 is also referred to as the first groove surface, and the end face 63 of the end tab 6 that forms the second groove G2 is also referred to as the second groove surface. With respect to the diaphragm 31, which is the member to be joined, the upper end of the end face 63 of the end tab 6, which is the second groove surface, is further away from the upper end of the end face 211 of the flange 21, which is the first groove surface. Here, the upper end refers to the end of the groove surface on the groove opening side. With respect to the material axis direction of the H-shaped beam 2, the distance between the upper end of the end face 63, which is the second groove surface, and the upper end of the end face 211, which is the first groove surface, is a distance d. Due to this distance d, when weld metal is filled into the first groove G1 and the second groove G2, respectively, to form the welded joint 41 as shown in Figure 2B, a positional displacement occurs between the weld toe 412 on the flange 21 side and the weld toe 413 on the end tab 6 side, in the direction of the material axis of the H-shaped beam 2.

[0016] Figure 3 is a photograph showing an example of welding work in the joint structure of Figure 1. The first groove G1 and the second groove G2 formed as described above can be filled with weld metal in a continuous manner, for example, as shown in the photograph in Figure 3, to form a welded joint 41. Specifically, as indicated by the arrows in the photograph in Figure 3, the welding path, which proceeds sequentially from the first groove G1 side, is folded back within the second groove G2, and the end tab 6 terminates on the side of the adjacent flange 21, thereby filling the first groove G1 and the second groove G2, which is wider than the first groove G1, with weld metal. As shown in the photograph in Figure 3, the weld metal may also be filled by layering it over multiple passes.

[0017] In this embodiment, as described above, a weld is formed between the end tab 6 and the member to be joined, and the positions of the weld toe on the flange 21 and the member to be joined are offset. This prevents cracks that may originate from the end of the weld toe from propagating along the weld toe and heat-affected zone of the flange 21. More specifically, when a crack originates from the end of the weld toe of the weld joint 41 formed by filling the first groove G1 and the second groove G2 with weld metal, the crack first occurs at the intersection 414 between the weld toe 413 on the end tab 6 side and the small end face of the flange 21. However, as described above, the weld toe 413 is offset from the weld toe 412 on the flange 21 side. Therefore, the crack that originates at the intersection 414 does not propagate directly to the weld toe 412 or the heat-affected zone of the flange 21 nearby, but is instead guided towards the base material side of the flange 21. Since cracks are less likely to propagate on the base material side compared to the weld toe and heat-affected zone, premature fracture of the beam end joint due to cracks can be prevented.

[0018] Furthermore, the distance d between the upper end of the end face 63 of the end tab 6, which is the second groove surface, and the upper end of the end face 211 of the flange 21, which is the first groove surface, is preferably 10 mm or more in order to induce cracking while avoiding the heat-affected zone of the flange 21. Also, when filling the first groove G1 and the second groove G2 with weld metal in a common pass, as shown in the example in Figure 3, for example, the distance d is preferably 15 mm or less, taking into account the width that can be filled with weld metal in a single pass. However, the preferred range for the distance d is not necessarily limited to the above example, as it varies depending on the size of the member such as the H-shaped beam 2 and the welding conditions.

[0019] Furthermore, although the above example described the configuration of one end of the flange 21 in the width direction of the H-shaped beam 2, the opposite end in the width direction may be configured similarly. Also, the connection structure between the upper flange of the H-shaped beam 2 and the joined member, the diaphragm 31 or the column 3, may be configured similarly.

[0020] Figure 4 shows an example of the configuration of an end tab in one embodiment of the present invention. As described above, in this embodiment, the upper end of the end face 63 of the end tab 6, which is the second groove surface, is located at a distance d from the diaphragm 31, which is the member to be joined, compared to the upper end of the end face 211 of the flange 21, which is the first groove surface. To achieve this configuration, for example, the groove root side end of the end face 63 of the end tab 6 may also be positioned further away from the diaphragm 31 than the groove root side end of the end face 211 of the flange 21. As a result, the root gap R2 of the second groove G2 formed between the end tab 6 and the diaphragm 31 is larger than the root gap R1 of the first groove G1 formed between the flange 21 and the diaphragm 31. In this case, for example, even if the groove angles θ are the same for the first groove G1 and the second groove G2, the upper end of the end face 63 of the end tab 6 can be positioned further away from the diaphragm 31 than the upper end of the end face 211 of the flange 21.

[0021] Figure 5 shows another example of the configuration of an end tab in one embodiment of the present invention. In the example shown in Figure 5, the groove angle θ2 of the end face 63 of the end tab 6, which is the second groove surface, is greater than the groove angle θ1 of the end face 211 of the flange 21, which is the first groove surface. In this specification, the groove angle refers to the angle (acute angle side) that the groove surface makes with respect to the vertical plane. In this case, for example, even if the root gap R is the same for the first groove G1 and the second groove G2, the upper end of the end face 63 of the end tab 6, which is the second groove surface, is further away from the diaphragm 31 than the upper end of the end face 211 of the flange 21, which is the first groove surface. Alternatively, by using a combination of the examples in Figures 4 and 5, both the root gap and the groove angle in the second groove G2 may be larger than those in the first groove G1. [Examples]

[0022] The following describes the analysis results related to embodiments of the present invention. In the analysis, the dimensions of each member were set as shown in Figure 6, and the stress-strain relationship of each member was set as shown in Figure 7. The stress-strain relationship shown in Figure 7 was obtained by converting the tensile test results of the material from past experiments into a true stress-true strain relationship and using a multilinear approximation. The flange and web of the H-section beam are assumed to be joined by submagic arc welding (SAW). The flange and the member to be joined are assumed to be joined by CO2 welding. The yield stress (F) of the flange and web y ,F wy ) All values ​​are 367 N / mm 2 Assuming the beam end is fully plastic, the member angle θ p The total plastic moment is 0.00765 rad, M p The torque was set to 1705.3 kNm. Note that no scallops are formed on the web of the H-shaped beam.

[0023] As shown in Table 1, the strain relaxation effect was verified for Comparative Example 1, in which an end tab is positioned but the amount of displacement x (distance d as described in the above embodiment) between the flange and the end tab at the upper end of the groove surface is 0, and for Examples 1 to 4, in which the amount of displacement x was increased in stages. The analysis model was a 1 / 2 model considering symmetry, 8-node elements were used, and the loading method was monotonic loading that applied a forced displacement D in one direction to the beam tip. The yield condition was the von Mises yield condition, and the general-purpose nonlinear structural analysis program "Marc2021" was used for the analysis.

[0024] [Table 1]

[0025] Figure 8 is a graph showing the relationship between moment member angles in the examples and comparative examples. The difference between each example is at most about 0.5%, so there is almost no difference. Figure 9 shows the member angle of 3θ in the examples and comparative examples. pThis graph shows the equivalent plastic strain of the upper end corner of the flange groove (the intersection of the weld toe and the flange end face) element when it reaches a certain point. From the graph in Figure 9, the larger the amount of end tab displacement x, the greater the equivalent plastic strain ε. eq It can be seen that the value becomes smaller. Specifically, in Example 3 where x = 10 mm, the equivalent plastic strain is reduced by approximately 91% compared to the comparative example.

[0026] Figures 10 to 14 are contour plots of (a) equivalent plastic strain and (b) plastic shear strain for each example and comparative example. Note that end tabs are hidden in the contour plots. In the case of Comparative Example 1 shown in Figure 10, in addition to the concentration of strain at the slit tip (intersection 414 shown in Figure 2B), strain in the beam width direction is observed around the flange weld toe, and in particular, the plastic shear strain is high. In this case, it is assumed that the crack that occurs at the slit tip propagates along the flange weld toe. In contrast, in Examples 1 to 4 shown in Figures 11 to 14, a relaxation of strain at the flange weld toe can be observed in all cases. In particular, in Example 3, where a certain amount of displacement x was secured (x=10), no strain concentration around the flange weld toe was observed. In this case, it is thought that the crack that occurs at the slit tip does not propagate in the direction along the heat-affected zone where a decrease in weld toughness is expected, but is instead guided towards the base material. A similar effect can be observed in Example 4, where the shift amount x is further increased (x=30).

[0027] From the above analysis results, it was confirmed that strain is relieved by setting a displacement amount (d, as described in the above embodiment) between the flange and the end tab at the upper end of the groove surface, and that when the displacement amount is set to 10 mm or more, strain is relieved and the effect of guiding the generated crack toward the base material is particularly significant.

[0028] Preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, but the present invention is not limited to these examples. It will be obvious to those skilled in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these will naturally also be understood to fall within the technical scope of the present invention. [Explanation of Symbols]

[0029] 1...Joint structure, 2...H-shaped beam section, 21,23...Flange, 211...End face, 22...Web, 221...End face, 3...Column, 31,33...Diaphragm, 311...End face, 32...Side, 41...Welded joint, 411...Backing plate, 412,413...Weld toe, 414...Intersection, 5...Scallop, 51...First arc section, 52...Second arc section, 53...Straight section, 6...End tab, 61...Top surface, 62...Bottom surface, 63...End face, G1...First groove, G2...Second groove, R,R1,R2...Root gap, d...Distance, θ,θ1,θ2...Groove angle.

Claims

1. A joining structure for joining an H-shaped beam having flanges and webs to a member to be joined, The H-shaped beam, which is welded to the member to be joined, includes a steel end tab positioned adjacent to the end of the flange in the width direction at the end in the material axis direction, Weld metal is filled between the first groove formed on the flange and the member to be joined, and between the second groove formed on the end tab and the member to be joined, using a backing plate. With respect to the member to be joined, the end of the second groove on the groove-opening side is spaced further apart than the end of the first groove on the groove-opening side. The end tab is formed with the same thickness as the flange, and the lower surface of the end tab is in contact with the backing plate. A joint structure in which the distance between the end of the second groove on the groove-opening side and the end of the first groove on the groove-opening side is 10 mm or more.

2. The joining structure according to claim 1, wherein with respect to the member to be joined, the end of the second groove on the groove root side is spaced further apart than the end of the first groove on the groove root side.

3. The joining structure according to claim 1 or claim 2, wherein the groove angle of the second groove surface is greater than the groove angle of the first groove surface.

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