Welded structure and method for manufacturing the same

Abstract

To provide a welded structure which improves fracture resistance of the welded structure by utilizing a backing strip without making execution difficult.SOLUTION: A welded structure includes a first plate-like member which has a first plate face, a second plate face and a first end face containing an inclined face at least partially, a second plate-like member which has a third plate face, a fourth plate face aligned in position with the second plate face and a second end face opposed to the first end face, a backing strip which is arranged so as to be brought into contact with the second plate face and the fourth plate face and faces a gap formed between an intersection of the first end face and the second plate face and an intersection of the second end face and the fourth plate face and welded metal filled into a space surrounded by the first end face, the second end face, and the backing strip, and is fillet-welded on the second plate face on the end part of the first plate-like member side, of both end parts of the first direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a welded structure and a method for manufacturing a welded structure. [Background technology]

[0002] For example, as described in Patent Document 1, in butt welding, a groove is formed between the components to be welded (joints) and the groove is filled with weld metal. While it is common to make the tensile strength of the weld metal higher than that of the joints, a so-called undermatched joint is also known, in which the tensile strength of the weld metal is lower than that of the joints. A backing strip is a component that prevents weld metal from leaking from the root gap during butt welding and prevents poor welding on the initial welding layer. It is joined to the joints before filling the groove with weld metal. However, at construction sites, for example, when welding the top flange of a beam, it is difficult to perform welding upward from the bottom of the joints. Therefore, as shown in Figure 11, it is common to form a weld 95 between the joints 91 and 92 and a backing strip 93 at the bottom of the groove, which is accessible from the top of the joints. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-022599 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a backing metal 93 is welded to the components at the bottom of the groove, as shown in Figure 11, even after the weld metal 94 is filled, the backing metal 93 is not bonded to the welded parts 91, 92 at the portion outside the root gap. Therefore, for example, when welding a top flange at a construction site, the backing metal is assembled and welded to the inner surface of the groove, forming a slit-like gap 93S between the backing metal 93 and the welded parts 91, 92. Furthermore, the material is discontinuous across the weld fusion line (FL) at the portion of the welded part where the groove is formed. Because the material discontinuity is inclined relative to the applied force, in-plane shear stress occurs along the discontinuity surface, increasing strain in the area (see Figure 12). Furthermore, because the tip of the gap 93S is geometrically discontinuous, strain tends to concentrate in that area. If a crack occurs due to strain concentration at the slit tip during an earthquake, the crack may propagate near the weld fusion line, where in-plane shear stress is high, and eventually lead to fracture. Furthermore, if there is a location with low toughness near the weld fusion line, there is a risk that cracks that occur at the tip of the slit will transform into brittle cracks, leading to early fracture.Furthermore, when welding is done in a factory, the assembly welding of the backing plate is done on the outer surface of the groove, but this assembly welding is generally done intermittently, so the above-mentioned strain concentration is likely to occur in the intermittent parts (parts where the weld is interrupted).

[0005] Therefore, an object of the present invention is to provide a welded structure and a method for manufacturing a welded structure that can improve the fracture resistance of the welded structure by using a backing metal without making construction difficult. [Means for solving the problem]

[0006] [1] A first plate-like member having a first plate surface facing a first side, a second plate surface facing a second side opposite to the first side, and a first end surface including at least a portion of an inclined surface inclined at an obtuse angle to the first plate surface and an acute angle to the second plate surface; a third plate surface facing the first side, a fourth plate surface facing the second side and aligned with the second plate surface; and a fourth plate surface not inclined with respect to the third and fourth plate surfaces and inclined in a first direction, which is a plate material axial direction. A welding structure including: a second plate-shaped member having a second end face opposing the first end face; a backing metal arranged to contact the second plate face and the fourth plate face, respectively, and facing a gap formed between an intersection of the first end face and the second plate face and an intersection of the second end face and the fourth plate face; and a weld metal filled in a space surrounded by the first end face, the second end face, and the backing metal, wherein the backing metal is fillet-welded to the second plate face at one of both ends in a first direction that is on the first plate-shaped member side. [2] The welding structure described in [1], wherein the backing metal is fillet welded continuously to the second plate surface at a position where the intersection of the first fusion line formed along the first end surface and the first plate surface is projected onto the second plate surface or at a position beyond that position, as viewed from the first end surface side. [3] The welded structure according to [1] or [2], wherein the tensile strength of the weld metal is lower than the tensile strength of at least the first plate-shaped member. [4] A welded structure according to any one of [1] to [3], wherein the first plate-like member is a flange of an H-shaped steel beam, a flange of an H-shaped steel column, or a column skin plate, and the second plate-like member is a diaphragm, a flange of another H-shaped steel beam, a flange of another H-shaped steel column, or a column skin plate, and the first direction is the material axis direction of the H-shaped steel beam, the H-shaped steel column, or the steel pipe column including the column skin plate. [5] A method for manufacturing a welded structure according to any one of [1] to [4], comprising: a first step of fillet-welding a backing metal to a second plate surface; and a second step of opposing the first end surface to the second end surface and bringing the backing metal into contact with a fourth plate surface, and filling a space with weld metal. A method for manufacturing a welded structure comprising: [6] A method for manufacturing a welded structure according to [5], wherein the first and second steps are carried out in a factory or on-site. [Effects of the Invention]

[0007] According to the above configuration, the plate surfaces of the first and second members that come into contact with the backing metal are aligned, so that the backing metal can be fillet welded to the first plate member before assembly, making construction easy. Fillet welding the backing metal to the first plate member integrates the backing metal with the welded portion on the groove side, preventing exposure of the tip of the gap that could become the origin of fracture during an earthquake, and shifting the strain concentration area to the assembly weld toe not only alleviates strain concentration in the area where the first plate member and the weld metal come into contact, but also prevents crack propagation along the weld fusion line and improves the fracture resistance of the welded structure. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a welded structure according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram for explaining analysis conditions for a welded structure. [Figure 3] 10 is a graph showing the maximum strength in the analysis results of the welded structure. [Figure 4] 10 is a graph showing the equivalent plastic strain at position P3 at maximum yield strength as a result of analysis of a welded structure. [Figure 5] 10 is a graph showing equivalent plastic strains at positions P1 and P4 at maximum yield strength as a result of analysis of a welded structure. [Figure 6] FIG. 1 is a contour diagram showing the distribution of equivalent plastic strain in analysis example 1. [Figure 7] FIG. 10 is a contour diagram showing the distribution of equivalent plastic strain in analysis example 2. [Figure 8] FIG. 10 is a contour diagram showing the distribution of equivalent plastic strain in analysis example 3. [Figure 9] FIG. 10 is a contour diagram showing the distribution of equivalent plastic strain in analysis example 4. [Figure 10] FIG. 10 is a contour diagram showing the distribution of equivalent plastic strain in analysis example 5. [Figure 11] FIG. 1 is a cross-sectional view showing an example of a conventional welding structure. [Figure 12] FIG. 1 is a diagram illustrating in-plane shear forces occurring along an inclined surface. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0010] FIG. 1 is a cross-sectional view showing a welded structure according to one embodiment of the present invention. In the illustrated example, the welded structure 10 is a butt weld formed between a first plate-shaped member 11 and a second plate-shaped member 12. Here, in this specification, a plate-shaped member is a member having a shape in which the length and width are large relative to the thickness, and a plate surface is a pair of faces of the plate-shaped member that include the length direction and the width direction. Furthermore, an end face is two pairs of faces of the plate-shaped member that include the thickness direction. Note that end faces 11E and 12E shown in the example of FIG. 1 are faces that include the width direction and the thickness direction of each of the first plate-shaped member 11 and the second plate-shaped member 12. The welded structure 10 is applied to, for example, the following joints. A column-beam joint in which the first plate-like member 11 is a flange or a column skin plate of an H-shaped steel beam, and the second plate-like member 12 is a diaphragm or a column skin plate attached to a steel pipe column or an H-shaped steel column. A beam-to-beam joint in which the first plate-like member 11 is a flange of an H-shaped steel beam and the second plate-like member 12 is a flange of another H-shaped steel beam A column-to-column joint in which the first plate-like member 11 is a column skin plate of a steel pipe column or a flange of an H-shaped steel column, and the second plate-like member 12 is a column skin plate of another steel pipe column or a flange of an H-shaped steel column. In the above example, the flange of the H-shaped steel beam may be either an upper flange or a lower flange. The steel pipe column may be formed of a square steel pipe or a welded box section member. The welded structure 10 is not limited to the above example, but can be widely applied to on-site butt welds.

[0011] The first plate-shaped member 11 has an upwardly facing plate surface 111, a downwardly facing plate surface 112, and an end surface 11E. The end surface 11E is an inclined surface that forms an obtuse angle with respect to the upper plate surface 111 and an acute angle with respect to the lower plate surface 112. On the other hand, the second plate-shaped member 12 has an upwardly facing plate surface 123, a downwardly facing plate surface 124, and an end surface 12E. The end surface 12E is not inclined with respect to the plate surfaces 123 and 124. The end surfaces 11E and 12E of the first plate-shaped member 11 and the second plate-shaped member 12 face each other in the X direction in the figure. When the first plate-shaped member 11 is a flange of an H-shaped steel beam, the X direction is the material axis direction of the H-shaped steel beam. As described above, since the end face 11E is an inclined face, a generally square groove (one-sided inclination) is formed between the first plate-shaped member 11 and the second plate-shaped member 12.

[0012] Here, the positions of the lower plate surfaces 112, 124 of the first plate-shaped member 11 and the second plate-shaped member 12 (the Y direction in the figure, i.e., the height direction) are aligned so as to allow contact with a backing metal, which will be described later. On the other hand, the positions of the upper plate surfaces 111, 123 are aligned in the illustrated example, but they do not necessarily have to be aligned in other examples. In other words, the plate thicknesses of the first plate-shaped member 11 and the second plate-shaped member 12 do not necessarily have to be the same. Furthermore, the end surface 11E of the first plate-shaped member 11 does not necessarily have to be formed as an inclined surface in its entirety; for example, a surface that is not inclined relative to the plate surfaces 111, 112 may be formed in the portion facing the bottom of the groove.

[0013] The backing metal 13 is arranged so as to contact the lower plate surfaces 112, 124 of the first plate-shaped member 11 and the second plate-shaped member 12, respectively, and closes the root gap of the groove formed between the first plate-shaped member 11 and the second plate-shaped member 12. Specifically, the backing metal 13 faces the gap formed between the intersection of the end surface 11E of the first plate-shaped member 11 and the plate surface 112, and the intersection of the end surface 12E of the second plate-shaped member 12 and the plate surface 124. The welded structure 10 is formed by filling the groove, i.e., the space surrounded by the end surfaces 11E, 12E and the backing metal 13, with weld metal 14. Filling the weld metal 14 melts the first plate-shaped member 11 and the second plate-shaped member 12, forming a fusion line 11F along the end surface 11E and a fusion line 12F along the end surface 12E. The weld metal 14 does not necessarily have to be filled in a single application, but may be filled in the groove by being layered multiple times.

[0014] In this embodiment, the backing metal 13 is joined to the plate surface 112 by a fillet weld 15 at the end on the first plate-shaped member 11 side of both ends in the direction in which the base materials face each other (X direction). For example, when welding beams together or a beam and a column at a construction site, assembling the first plate-shaped member 11 and the second plate-shaped member 12 using the backing metal 13 requires fillet welding to be performed in an upward position to join the backing metal 13 to the plate surface, which is difficult to perform.

[0015] Fillet weld 15 may be performed, for example, in a factory that manufactures or processes an H-shaped steel beam or the like that includes first plate-shaped member 11, or may be performed at a construction site before erection. In these processes, fillet weld 15 can be performed, for example, with the H-shaped steel beam or the like turned upside down, so welding can be performed downward from the top side of first plate-shaped member 11, making the work easy. However, to prevent deformation of the backing metal due to continuous fillet welding, fillet welds may be performed intermittently within the groove face in advance.

[0016] 1, i.e., in a cross section including the direction in which the welded parts face each other (X direction), the length L1 of contact between the plate surface 112 of the first plate-shaped member 11, which is the welded part having the inclined fusion line 11F, and the backing metal 13 is set so that, as viewed from the side of the fusion line 11F, the fillet weld 15 of the continuous weld is formed at or beyond position P2, which is the downward projection of the intersection P1 between the fusion line 11F and the upper plate surface 111. This makes it possible to induce fracture in the cross section of the base metal when a crack initiates at the fillet weld toe. Furthermore, the leg length L3 of the fillet weld 15 is preferably 4 mm or more in terms of stress transmission and thermal conditions.

[0017] By joining the backing strip 13 to the plate surface 112 of the first plate-shaped member 11 with the fillet weld 15 as described above, the gap tip, which would be a geometric discontinuity, is eliminated, preventing the backing strip and the welded material from separating during an earthquake, thereby mitigating strain concentration. Furthermore, by forming the fillet weld 15 at or beyond position P2, strain concentration at the fillet weld toe is more effectively mitigated than strain at the weld toe. Furthermore, plastic deformation of the weld can be suppressed. Furthermore, by mitigating the plastic deformation of the base material near the weld joint line, the plastic restraint effect of the low-strength portion can be enhanced. Furthermore, the length of L1 is preferably as long as possible to mitigate strain concentration near the weld root. However, a long L1 can result in a large cross-sectional defect (scallop) in the beam web, which is provided to accommodate the backing strip when welding beams together, potentially resulting in insufficient bending strength required for the member. Furthermore, if L1 is made too long, the weight of the backing plate itself will become too great, and it may become impossible to carry it by hand when attaching it to the component. Therefore, it is desirable to make the size of the scallop large enough to ensure the design strength, and to keep the length of L1 equal to or less than the size of the scallop.

[0018] According to the embodiment of the present invention described above, the positions of the lower plate surfaces 112, 124 of the first plate-shaped member 11 and the second plate-shaped member 12 are aligned and the backing metal 13 is brought into contact with these plate surfaces 112, 124, so that misalignment during installation can be absorbed even if the backing metal 13 is joined to the first plate-shaped member 11 before installation. Therefore, the fillet weld 15 can be installed, for example, with the first plate-shaped member 11 turned upside down, which does not make installation difficult.

[0019] In the above embodiment, the backing metal 13 is joined only to the first plate-shaped member 11 at the fillet weld 15, but for example, on the second plate-shaped member 12 side, a weld may be formed at the bottom of the groove, i.e., near the intersection of the end face 12E and the plate surface 124, and the backing metal 13 may be joined to both the first plate-shaped member 11 and the second plate-shaped member 12.

[0020] In the embodiments of the present invention, the relationship between the tensile strength of the welded parts (first plate-shaped member 11 and second plate-shaped member 12 in the above example) and the tensile strength of the weld metal (weld metal 14 in the above example) is not particularly limited. That is, the tensile strength of the weld metal may be higher than that of the welded parts, as in a typical example, or the tensile strength of the weld metal may be lower than that of the welded parts, resulting in an undermatched joint. While undermatched joints have advantages, they also have a weakness in that strain concentrates at the weld, making them more susceptible to fracture. However, this weakness can be overcome by combining them with the above-described embodiments of the present invention. Note that the tensile strengths of the welded parts do not need to be the same. Therefore, in the above-described embodiment, an undermatched joint is defined as a joint in which the tensile strength of weld metal 14 is at least lower than the tensile strength of first plate-shaped member 11.

[0021] Fig. 2 is a diagram for explaining the analysis conditions for the welded structure. In order to verify the effects of the embodiment of the present invention as described above, a structural analysis was carried out using a model as shown in Fig. 2. The first plate-shaped member 11 and the second plate-shaped member 12, which are the parts to be welded, both have a plate thickness t1 of 22 mm and a plate width W of 150 mm, and are rated at 780 N / mm 2 Grade steel (tensile strength 866N / mm2 ) for the weld metal 14, 590 N / mm 2 The strain relationship equivalent to the grade was converted to the true stress-true strain relationship (tensile strength 659 N / mm 2 The end face of the first plate-shaped member 11 that forms the groove is formed as an inclined surface with a groove angle of 35°. The size of the root gap between the first plate-shaped member 11 and the second plate-shaped member 12 is 7 mm. The backing metal 13 has a plate thickness t2 of 9 mm and a plate width W that is the same as the portion to be welded, and is made of a material with a tensile strength of 490 N / mm 2 Grade steel (tensile strength 594N / mm 2 ). The length L of the backing metal 13, the contact lengths L1 and L2 with the welded parts (see Figure 1), and the weld state are different for each of Analysis Examples 1 to 5 shown in Table 1. In each example, the backing metal 13 is welded to the weld metal 14 at the root gap, and in the examples marked "fillet welded" in Table 1, a fillet weld 15 (see Figure 1) is also formed. The fillet weld 15 is made of YGW11 wire (tensile strength 594 N / mm) specified in JIS Z3312. 2 ) and has a leg length of 4.5 mm.

[0022] [Table 1]

[0023] The analysis model was a half-model that considered symmetry in the Z direction (the width direction of the plate-shaped member), and a 16-node structural solid was used for the modeling elements. The analysis variables were the length and installation position of the backing plate of the weld formed by the weld metal 14. The loading method was monotonic loading, in which a forced displacement D in the X direction (positive) was applied to the X direction end of the second plate-shaped member 12. The X direction end of the first plate-shaped member 11 was constrained in the X, Y, and Z directions, and the X direction end of the second plate-shaped member 12 was also constrained in the Y and Z directions. In addition, the displacement of the symmetry plane was constrained in the Z direction. The von Mises yield criterion was used as the yield condition, and the general-purpose finite element analysis software "ANSYS 2021 R1" was used as the solver.

[0024] Figure 3 is a graph showing the maximum strength of the welded structure analysis results. The vertical axis represents the maximum strength σ max The horizontal axis represents the contact length L1 with the welded part. As shown in the graph, in both Analysis Example 1 and Analysis Example 5, the maximum strength σ of the welded structure max is the tensile strength of the weld metal (659N / mm 2 ), and exceeds the tensile strength standard value of the joined part (780N / mm 2 ), but analysis examples 2 to 5, in which the backing plate is fillet welded, have a higher maximum strength and are therefore on the safe side in terms of structural performance.

[0025] Figures 4 and 5 are graphs showing the equivalent plastic strain of the groove root P3, weld toe P1, and fillet weld toe P4 at maximum yield strength, based on the analysis results of the welded structure. The groove root P3 and fillet weld toe P4 are shown in Figure 1. In the graphs of Figures 4 and 5, the vertical axis represents equivalent plastic strain, and the horizontal axis represents the contact length L1 with the welded parts. As shown in Figure 4, in Analysis Example 2 (No. 2), compared to Analysis Example 1 (No. 1), the strain of the groove root P3 is alleviated by performing fillet welding outside the groove. Furthermore, as shown in Figure 5, in Analysis Examples 3 and 4, compared to Analysis Example 2 (No. 2), the strain of the fillet weld toe P4 is more fully alleviated than the strain of the weld toe P1 by forming a fillet weld 15 near or beyond position P2. Furthermore, plastic deformation of the weld is suppressed.

[0026] Figures 6 to 10 are contour diagrams showing the distribution of equivalent plastic strain at maximum strength in the analysis results for welded structures. As shown in Figure 6, in Analysis Example 1, strain concentration is observed in the area where the first plate-shaped member and the weld metal contact. This is because the in-plane shear force (see Figure 12) generated on the inclined surface tends to increase strain at material discontinuities, and the gap between the backing plate and the plate surface is a geometric discontinuity point where strain is most concentrated. Therefore, in Analysis Example 2, in which the backing plate is fillet-welded to the plate surface of the first plate-shaped member, as shown in Figure 7, the backing plate and the plate surface are integrated without any gaps, eliminating the exposure of the gap tip, which would be a geometric discontinuity point. This prevents the backing plate and the welded material from separating during an earthquake, thereby mitigating the concentration in the above area. Furthermore, as shown in Figure 8, in Analysis Example 3, in which the backing strip is extended toward the first plate-like member, the strain concentration around the assembly weld is moved away from the strain concentration near the weld joint line, and the plasticity of the base material near the weld joint line is alleviated, thereby enhancing the plastic constraint effect in the low-strength portion and further alleviating the strain concentration in the gap between the backing strip and the plate surface. In Analysis Example 3, the fillet weld between the backing strip and the first plate-like member is located slightly toward the groove side relative to the groove opening position (positions P1 and P2 shown in Figure 1), and the length L1 is at position P2. This allows for more mitigation of strain concentration at the fillet weld toe compared to Analysis Example 2. As shown in Figure 9, in Analysis Example 4, in which the backing strip is extended toward the first plate-like member, the strain distribution within the first plate-like member is further expanded, further alleviating the strain concentration in the area where the first plate-like member and the weld metal contact each other. On the other hand, as shown in Figure 10, in Analysis Example 5, lengths L1 and L2 are moved horizontally by the same distance, and it can be seen that in this case too, the same effect as in Analysis Example 3 is obtained. Note that the in-plane shear force increases as the difference in tensile strength between the weld metal and the base metal increases, and in particular, in undermatched joints where the strength of the weld metal is lower than the strength of the base metal, the in-plane shear force increases significantly.

[0027] These analysis results demonstrate that fillet welding the backing strip to the first plate-like member eliminates the gap edge, which is a geometric discontinuity, and prevents the backing strip from separating during an earthquake. This effectively alleviates strain concentration at the edge of gap 93S (Figure 11). Furthermore, extending the backing strip toward the first plate-like member or moving the entire backing strip toward the first member distances the strain concentration around the assembly weld from the strain concentration near the weld line, thereby alleviating plastic deformation of the base material near the weld line and enhancing the plastic restraint effect of the undermatched portion, thereby effectively alleviating strain concentration at the edge of gap 93S. The value in Analysis Example 4 (where the fillet weld is formed at or beyond P2) may be used as a guide for extending or moving the backing strip. However, as shown in Analysis Examples 2 and 3, even if the backing plate is shorter than this, the effect of mitigating strain concentration can be obtained.

[0028] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0029] 10...welded structure, 11...first plate-shaped member, 111, 112...plate surface, 11E...end surface, 11F...weld line (FL), 12...second plate-shaped member, 123, 124...plate surface, 12E...end surface, 12F...weld line (FL), 13...backing metal, 14...weld metal, 15...fillet weld.

Claims

1. a first plate-like member having a first plate surface facing a first side, a second plate surface facing a second side opposite the first side, and a first end surface at least partially including an inclined surface inclined so as to form an obtuse angle with respect to the first plate surface and an acute angle with respect to the second plate surface; a second plate-like member having a third plate surface facing the first side, a fourth plate surface facing the second side and aligned with the second plate surface, and a second end surface that is not inclined with respect to the third and fourth plate surfaces and faces the first end surface in a first direction that is a plate material axial direction; a backing metal disposed so as to be in contact with the second plate surface and the fourth plate surface, respectively, facing a gap formed between an intersection of the first end surface and the second plate surface and an intersection of the second end surface and the fourth plate surface; and a weld metal filled in a space surrounded by the first end surface, the second end surface, and the backing metal, wherein the backing metal is fillet-welded to the second plate surface only at an end of both ends in the first direction that is on the side of the first plate-shaped member; The backing metal is continuously fillet-welded to the second plate surface at a position where, when viewed from the first end face side, an intersection of a first fusion line formed along the first end face and the first plate surface is projected onto the second plate surface side, or at a position beyond that position.

2. The welded structure according to claim 1 , wherein the tensile strength of the weld metal is lower than the tensile strength of at least the first plate-shaped member.

3. the first plate-like member is a flange of an H-shaped steel beam, a flange of an H-shaped steel column, or a column skin plate; the second plate-like member is a diaphragm, a flange of another H-shaped steel beam, a flange of another H-shaped steel column, or another column skin plate; 3. The welded structure according to claim 1, wherein the first direction is a material axis direction of the H-shaped steel beam, the H-shaped steel column, or the steel pipe column including the column skin plate.

4. A welding structure described in any one of claims 1 to 3, wherein the backing metal is joined to the second plate-shaped member at a weld formed near the intersection of the second end face and the fourth plate surface.

5. A method for manufacturing a welded structure according to any one of claims 1 to 4, a first step of fillet welding the backing metal to the second plate surface; a second step of bringing the first end surface into opposition to the second end surface, bringing the backing metal into contact with the fourth plate surface, and filling the space with the weld metal; A method for manufacturing a welded structure comprising:

6. The method for manufacturing a welded structure according to claim 5 , wherein the first step and the second step are carried out in a factory or on a construction site.

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