Main beam-small beam joining structure and main beam-small beam joining method

Abstract

To practically join a main beam and small beams even when a gap between the main beam and the small beams is small.SOLUTION: A joining structure 100 for joining a main beam 10 and a pair of small beams 20 with a shorter beam depth than the main beam comprises: an upper side splice plate for joining upper flanges of the small beams; a pair of joining plates for joining a web of the main beam and webs of the pair of small beams; a pair of haunches 70 which are arranged below lower flanges of the small beams; and lower side splice plates which are arranged below the pair of haunches and a lower flange of the main beam and join the pair of haunches. A lower face of the lower flange of the main beam and lower faces of the haunches are arranged at the same height, the lower flanges of the small beams are formed with notches viewed in a vertical direction, horizontal pieces of the haunches and the lower side splice plate are stacked and bolt-joined, and the notches are formed above a bolt which joints the horizontal pieces and the lower side splice plate.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a joint structure between a main beam and a sub-beam, and a method for joining the main beam and the sub-beam. [Background technology]

[0002] In steel-framed buildings, the floor structure of each floor is formed by connecting minor beams to the main beams. The main beams are connected to steel columns and bear earthquakes, wind, floor loads, etc., while minor beams are connected to the main beams without being directly connected to columns, and mainly support the floor load and transmit the load to the main beams. The main beams are rigidly connected to the steel columns, for example, and minor beams perpendicular to the main beams are pin-connected to one or both sides of the main beams, thereby connecting the columns, main beams, and minor beams to each other.

[0003] In general, the joining of the sub-beam to the girder is performed by first welding the bracket or gusset plate to the flange and web of the girder, and then bolting the bracket and the sub-beam with high-strength bolts via a splice plate. Here, the bracket is formed of a shaped steel material (H-shaped steel, etc.) of the same dimensions as the sub-beam, and is welded to, for example, the upper flange or web of the girder. When joining the bracket to the girder in this way, it is necessary to process the end of the bracket so that it abuts against the flange or web of the girder, and there is a problem that this complicated end processing requires time and effort. Furthermore, in standard joints (standard joints) between the girder and the sub-beam, the length of the bracket tends to be long (for example, 1 m or more from the column center), and brackets are often joined to the left and right of the corresponding position in the longitudinal direction of the girder, and there is also a problem that the transportation efficiency is extremely poor because the girder and bracket are usually welded to the factory and then this unit is transported to the site.

[0004] Here, Patent Document 1 proposes a joint structure between a main beam and a secondary beam that does not require the above-mentioned bracket. Specifically, the upper flange of the secondary beam is bolted to the underside of a portion protruding laterally from the upper flange of the main beam in an upper joint plate that is bolted to the upper surface of the upper flange of the main beam, the lower flange of the secondary beam is bolted to the underside of a lower joint plate that is welded to the web of the main beam and protrudes laterally from the web, and the lower joint plate is reinforced by being joined at its underside to a rib member joined to the main beam, and the rib member is a flat plate that is welded to the web and lower flange of the main beam and is located in the middle of the lower joint plate in the width direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6266269 Summary of the Invention [Problem to be solved by the invention]

[0006] The joint structure between the main girder and secondary beam described in Patent Document 1 handles the shear force acting from the secondary beam and the lower joint plate using only the shear resistance force of the rib member. Therefore, for example, as the step between the main girder and secondary beam becomes smaller and the height of the rib member becomes lower, the thickness of the rib member must be increased. Therefore, when the step between the main girder and secondary beam is small, it is difficult to achieve a practical joint structure.

[0007] The present invention aims to provide a joint structure between a main beam and a secondary beam that is simple in structure and that can practically join the main beam and secondary beam even when the step between the main beam and secondary beam is small, and a method for joining the main beam and secondary beam. [Means for solving the problem]

[0008] One aspect of the joint structure between a main beam and a sub-beam according to the present invention is as follows: A joint structure for a main beam and a sub-beam, which joins a main beam extending in a first direction and a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, An upper splice plate extending in the second direction and placed on the upper flanges of the pair of sub-beams and the upper flanges of the main beam to join the upper flanges of the pair of sub-beams; A pair of joining plates arranged so that a plate thickness direction is along the first direction and joining the web of the main girder and the webs of the pair of small beams; A pair of haunches disposed below the lower flanges of the pair of joists and joined to the pair of joists; A lower splice plate extending in the second direction and disposed below the pair of haunches and the lower flange of the girder to join the pair of haunches together, The upper surface of the upper flange of the main beam and the upper surfaces of the upper flanges of the pair of small beams are disposed at the same height, The lower flange of the main beam is disposed below the lower flanges of the pair of sub beams, The pair of haunches are A vertical piece is arranged so that the plate thickness direction is along the first direction, is joined to the pair of small beams, and extends downward; A horizontal piece is arranged so that the plate thickness direction is along the vertical direction and is joined to the vertical piece, The lower surface of the lower flange of the girder and the lower surface of the horizontal piece are disposed at the same height; The lower flanges of the pair of small beams have notches formed in areas that overlap with the horizontal pieces when viewed in the vertical direction, The horizontal piece and the lower splice plate are overlapped in the vertical direction and bolted together; The notch is formed above a bolt that joins the horizontal piece and the lower splice plate when viewed in the vertical direction.

[0009] According to this aspect, the main girder and the sub-girder are bolted together via the lower splice plate and the haunch, and thus the processing time can be reduced as a simple structure. In addition, according to this aspect, complicated processing of the bracket is not required, and the processing time of the bracket is not required. Furthermore, in this aspect, since full penetration welding or the like is not required, the time and effort related to construction is significantly reduced. In addition, in this aspect, the haunch can be placed on the lower splice plate joined to the lower flange of the main girder, so that the workability and efficiency during construction can be improved. In addition, in this aspect, the lower flanges of the pair of sub-girders are formed with notches, so that the lower flanges of the sub-girders do not get in the way when the haunch and the lower splice plate are bolted together. Since the lower flanges are provided with notches, it is easy to insert bolts and tools from above. The worker can work downward and tighten the bolts using tools, so that the work efficiency during construction can be improved. In this embodiment, since the lower flange of the secondary beam does not get in the way, the secondary beam and the main beam can be joined practically even if the step between the main beam and the secondary beam is small.

[0010] According to this aspect, the upper flange of the girder and the upper splice plate are not joined, so the labor required for construction is reduced. Also, according to this aspect, the upper flange of the girder and the upper splice plate are not joined by bolts, so there is no need to form bolt holes in the upper flange. Therefore, the labor required for processing is reduced, there is no reduction in strength due to loss of the opening, and there is no need to consider cross-sectional loss. Also, according to this aspect, the upper flange of the girder and the upper splice plate are not welded, so the labor required for welding construction is reduced.

[0011] In another aspect of the present invention, The pair of haunches extend in the second direction farther from the girder than the lower splice plate, In the second direction, the protruding length from the end of the lower splice plate to the ends of the pair of haunches is greater than or equal to the length in the vertical direction from the lower flanges of the pair of sub-beams to the lower surface of the horizontal piece.

[0012] According to this aspect, the overhang length of the pair of haunches is increased to ensure the shear strength. This allows the pair of haunches to receive the shear force transmitted from the lower flange of the sub-beam and transmit it to the lower splice plate via the pair of haunches. In addition, in this aspect, the shear strength can be changed by changing the plate thickness of the pair of haunches.

[0013] In another aspect of the present invention, The lower flanges of the pair of sub-beams include protruding portions that protrude from the webs of the pair of sub-beams in the first direction in portions adjacent to the cutout portions, The vertical pieces of the pair of haunches and the protruding portions of the lower flanges of the pair of sub-beams are fillet welded.

[0014] According to this aspect, when forming the notch in the bottom flange of the sub-beam, the part of the bottom flange of the sub-beam close to the web is left, and the remaining part can be used as the protruding part. The protruding part protruding in the first direction from the web of the sub-beam and the vertical pieces of the pair of haunches are joined by fillet welding, so that welding can be performed with reduced labor.

[0015] One aspect of the joint structure between a main beam and a sub-beam according to the present invention is as follows: A joint structure for a main beam and a sub-beam, which joins a main beam extending in a first direction and a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, A lower splice plate extending in the second direction and disposed below the lower flanges of the pair of sub-beams and the lower flanges of the main beam, and joining the lower flanges of the pair of sub-beams together; A pair of joining plates arranged so that a plate thickness direction is along the first direction and joining the web of the main girder and the webs of the pair of small beams; A pair of haunches disposed above the upper flanges of the pair of joists and joined to the pair of joists; An upper splice plate extending in the second direction and placed on the pair of haunches and the upper flange of the girder to join the pair of haunches together; The lower surface of the lower flange of the main beam and the lower surfaces of the lower flanges of the pair of sub beams are disposed at the same height, The upper flange of the main beam is disposed above the upper flanges of the pair of sub beams, The pair of haunches are A vertical piece is arranged so that the plate thickness direction is along the first direction, is joined to the pair of small beams, and extends upward; A horizontal piece is arranged so that the plate thickness direction is along the vertical direction and is joined to the vertical piece, The upper surface of the upper flange of the girder and the upper surface of the horizontal piece are disposed at the same height; The upper flanges of the pair of small beams have notches formed in areas that overlap with the horizontal pieces when viewed in the vertical direction, The horizontal piece and the upper splice plate are overlapped in the vertical direction and bolted together; The cutout portion is formed below the bolt that joins the horizontal piece and the upper splice plate when viewed in the vertical direction.

[0016] According to this aspect, the main girder and the sub-girder are bolted together via the upper splice plate and the haunch, resulting in a simple structure and reducing the amount of work required. In addition, according to this aspect, complicated bracket processing is not required, and the processing of the bracket is not required. Furthermore, in this aspect, complete penetration welding and the like are not required, so the amount of work required for construction is significantly reduced. In addition, in this aspect, the lower flange of the sub-girder can be placed on the lower splice plate joined to the lower flange of the main girder, so that the work efficiency during construction can be improved. In addition, in this aspect, the upper flanges of the pair of sub-girders are formed with notches, so that the upper flanges of the sub-girders do not get in the way when the haunch and the upper splice plate are bolted together. The provision of the notches in the upper flanges makes it easy to install the bolts. The worker can work downward and tighten the bolts using tools, so that the work efficiency during construction can be improved. In this embodiment, since the upper flange of the secondary beam does not get in the way, the secondary beam and the main beam can be joined practically even if the step between the secondary beam and the main beam is small.

[0017] According to this aspect, the upper flange of the girder and the upper splice plate are not joined, so the labor required for construction is reduced. Also, according to this aspect, the upper flange of the girder and the upper splice plate are not joined by bolts, so there is no need to form bolt holes in the upper flange. Therefore, the labor required for processing is reduced, there is no reduction in strength due to loss of the opening, and there is no need to consider cross-sectional loss. Also, according to this aspect, the upper flange of the girder and the upper splice plate are not welded, so the labor required for welding construction is reduced.

[0018] In another aspect of the present invention, The pair of haunches extend in the second direction farther from the girder than the upper splice plate, In the second direction, the length from the end of the upper splice plate to the ends of the pair of haunches is greater than or equal to the length from the upper flanges of the pair of sub-beams to the upper surface of the horizontal piece in the vertical direction.

[0019] According to this aspect, the overhang length of the pair of haunches is increased to ensure the shear strength. This allows the pair of haunches to receive the shear force transmitted from the upper flange of the sub-beam and transmit it to the upper splice plate via the pair of haunches. In addition, in this aspect, the shear strength can be changed by changing the plate thickness of the pair of haunches.

[0020] In another aspect of the present invention, The upper flanges of the pair of sub-beams include protruding portions that protrude from the webs of the pair of sub-beams in the first direction in portions adjacent to the cutout portions, The vertical pieces of the pair of haunches and the protruding portions of the upper flanges of the pair of sub-beams are fillet welded.

[0021] According to this aspect, when forming the notch in the upper flange of the sub-beam, the portion of the upper flange of the sub-beam close to the web is left, and the remaining portion can be used as the protruding portion. The protruding portion protruding in the first direction from the web of the sub-beam and the vertical pieces of the pair of haunches are joined by fillet welding, so that welding can be performed with reduced construction labor.

[0022] One aspect of the method for joining a main beam and a sub-beam according to the present invention is to A method for joining a main beam and a sub-beam, the method comprising the steps of: joining a main beam extending in a first direction to a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, the method comprising the steps of: The lower flanges of the pair of small beams have notches formed at the ends closer to the main beam in the longitudinal direction of the pair of small beams, A pair of haunches arranged below the lower flanges of the pair of sub-beams are respectively joined to the ends of the pair of sub-beams that are closer to the main beam in the longitudinal direction, A lower splice plate is joined to the lower flange of the girder, the lower splice plate extending in the second direction, disposed below the lower surface of the lower flange of the girder, and protruding on both sides of the girder; placing the pair of haunches on the lower splice plate; bolting the pair of haunches and the lower splice plate together; joining a web of the main girder to a web of the pair of sub-girders; placing an upper splice plate extending in the second direction on the upper flanges of the pair of minor beams and the upper flange of the major beam; and a step of bolting the upper flanges of the pair of sub-beams to the upper splice plate.

[0023] According to this aspect, the main girder and the sub-girder are bolted together via the lower splice plate and the haunch, and thus the processing time can be reduced as a simple structure. In addition, according to this aspect, complicated processing of the bracket is not required, and the processing time of the bracket is not required. Furthermore, in this aspect, since full penetration welding or the like is not required, the time and effort related to construction is significantly reduced. In addition, in this aspect, the haunch can be placed on the lower splice plate joined to the lower flange of the main girder, so that the workability and efficiency during construction can be improved. In addition, in this aspect, the lower flanges of the pair of sub-girders are formed with notches, so that the lower flanges of the sub-girders do not get in the way when the haunch and the lower splice plate are bolted together. Since the lower flanges are provided with notches, it is easy to insert bolts and tools from above. The worker can work downward and tighten the bolts using tools, so that the work efficiency during construction can be improved. In this embodiment, since the lower flange of the secondary beam does not get in the way, the secondary beam and the main beam can be joined practically even if the step between the main beam and the secondary beam is small.

[0024] One aspect of the method for joining a main beam and a sub-beam according to the present invention is to A method for joining a main beam and a sub-beam, the method comprising the steps of: joining a main beam extending in a first direction to a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, the method comprising the steps of: The upper flanges of the pair of small beams have notches formed at the ends closer to the main beam in the longitudinal direction of the pair of small beams, A pair of haunches arranged above the upper flanges of the pair of sub-beams are respectively joined to the ends of the pair of sub-beams that are closer to the main beam in the longitudinal direction, A lower splice plate is joined to the lower flange of the girder, the lower splice plate extending in the second direction, disposed below the lower surface of the lower flange of the girder, and protruding on both sides of the girder; placing the lower flanges of the pair of joists on the lower splice plate; bolting the lower flanges of the pair of joists to the lower splice plate; joining a web of the main girder to a web of the pair of sub-girders; placing an upper splice plate extending in the second direction on the pair of haunches and an upper flange of the girder; and a step of bolting the pair of haunches and the upper splice plate together.

[0025] According to this aspect, the main girder and the sub-girder are bolted together via the upper splice plate and the haunch, resulting in a simple structure and reducing the amount of work required. In addition, according to this aspect, complicated bracket processing is not required, and the processing of the bracket is not required. Furthermore, in this aspect, complete penetration welding and the like are not required, so the amount of work required for construction is significantly reduced. In addition, in this aspect, the lower flange of the sub-girder can be placed on the lower splice plate joined to the lower flange of the main girder, so that the work efficiency during construction can be improved. In addition, in this aspect, the upper flanges of the pair of sub-girders are formed with notches, so that the upper flanges of the sub-girders do not get in the way when the haunch and the upper splice plate are bolted together. The provision of the notches in the upper flanges makes it easy to install the bolts. The worker can work downward and tighten the bolts using tools, so that the work efficiency during construction can be improved. In this embodiment, since the upper flange of the secondary beam does not get in the way, the secondary beam and the main beam can be joined practically even if the step between the secondary beam and the main beam is small. Effect of the Invention

[0026] As can be understood from the above explanation, according to the present invention, it is possible to provide a joint structure between a main beam and a secondary beam, and a joint method between a main beam and a secondary beam, which has a simple structure and is capable of practically joining the main beam and the secondary beam even when the step between the main beam and the secondary beam is small. [Brief description of the drawings]

[0027] [Figure 1] FIG. 2 is a side view of an example of a joint structure between a main beam and a secondary beam according to the first embodiment, seen from a midpoint of the main beam. [Diagram 2] 2 is a cross-sectional view showing a section taken along line II-II in FIG. [Diagram 3] FIG. 1 is an exploded perspective view showing the upper splice plate, joist, haunch, and lower splice. [Figure 4] 4 is a cross-sectional view showing a cut surface along the line IV-IV in FIG. [Diagram 5] FIG. 11 is a side view of an example of a joint structure between a main beam and a secondary beam in the second embodiment, seen from a midpoint of the main beam. [Figure 6] FIG. 11 is a side view of an example of a joint structure between a main beam and a secondary beam in the third embodiment, seen from a midpoint of the main beam. [Figure 7] FIG. 13 is a cross-sectional view showing a cut surface along the XY plane of an example of a joint structure between a main beam and a secondary beam according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, a joint structure and a joint method for a main beam and a sub-beam according to an embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, substantially the same components are designated by the same reference numerals to avoid redundant description.

[0029] [Beam-beam joint structure 100 according to the first embodiment] An example of a joint structure 100 between a girder 10 and a sub-beam 20 according to the first embodiment will be described with reference to Figs. 1 to 4. Fig. 1 is a side view of an example of a joint structure 100 between a girder 10 and a sub-beam 20 according to the first embodiment, seen from a midway position of the girder 10. Fig. 2 is a cross-sectional view showing a cut surface along line II-II in Fig. 1. Fig. 3 is an exploded perspective view showing an upper splice plate 30, a sub-beam 20, a haunch 70, and a lower splice plate 40. Fig. 4 is a cross-sectional view showing a cut surface along line IV-IV in Fig. 1. In each figure, arrows indicating X-axis direction, Y-axis direction, and Z-axis direction which are orthogonal to each other are illustrated. The X-axis direction and the Y-axis direction are along the horizontal direction. The Z-axis direction is along the vertical direction. The Y-axis direction is an example of a first direction, and the X-axis direction is an example of a second direction.

[0030] The joint structure 100 shown in Figs. 1 to 3 is a joint structure between a main girder 10 and a secondary beam 20 having different beam depths. The secondary beam 20 has a shorter beam depth than the main girder 10. The joint structure 100 includes a joint having structural performance that can be regarded as a rigid joint. In a plan view, a pair of secondary beams 20 are arranged on both sides of the main girder 10. The main girder 10 extends in the Y-axis direction, and the pair of secondary beams 20 extend in the X-axis direction. The main girder 10 and the pair of secondary beams 20 are arranged so as to be perpendicular to each other.

[0031] <Major beam 10 and small beam 20> The main girder 10 and the pair of secondary beams 20 are formed of H-shaped steel. The main girder 10 has a web 11, an upper flange 12, and a lower flange 13. The secondary beam 20 has a web 21, an upper flange 22, and a lower flange 23. The upper surface 12a of the upper flange 12 and the upper surface 22a of the upper flange 22 are flush with each other. The lower surface 13b of the lower flange 13 is disposed lower than the lower surface 23b of the lower flange 23. The lower surface 13b of the lower flange 13 and the lower surface 23b of the lower flange 23 have a step L1 in the Z-axis direction. The step L1 is the difference in height between the lower surface 23b and the lower surface 13b in the Z-axis direction.

[0032] <Upper splice plate 30> The joint structure 100 includes an upper splice plate 30 arranged above the girder 10, a lower splice plate 40 arranged below the girder 10, a pair of gusset plates 50 joined to the web 11 of the girder 10, and a pair of haunches 70 arranged below the pair of minor beams 20. The upper splice plate 30 and the lower splice plate 40 are arranged perpendicular to the girder 10 in a plan view, and extend along the longitudinal direction of the pair of minor beams 20. The plate thickness direction of the upper splice plate 30 and the lower splice plate 40 is along the Z-axis direction.

[0033] <Hunch 70> As shown in Figures 3 and 4, the haunch 70 is T-shaped. The haunch 70 has a web 71 and a flange 72. The haunch 70 is a steel frame member having a predetermined length in the X-axis direction. The thickness direction of the web 71 is along the Y-axis direction. The thickness of the web 71 may be the same as the thickness of the web 21. The thickness direction of the flange 72 is along the Z-axis direction. The thickness of the flange 72 may be the same as the thickness of the lower flange 23. The width of the flange 72 along the Y-axis direction may be the same as the width of the lower flange 23 along the Y-axis direction. The flange 72 is formed with a bolt hole penetrating in the thickness direction.

[0034] The haunch 70 is disposed below the bottom flange 23 of the minor beam 20. As described below, the upper end of the web 71 of the haunch 70 is welded to the bottom surface 23b of the bottom flange 23 of the minor beam 20. The bottom surface 72b of the flange 72 of the haunch 70 is flush with the bottom surface 13b of the bottom flange 13 of the major beam 10.

[0035] <Lower splice plate 40> 1, 3 and 4, the lower splice plate 40 is disposed below the lower surface 13b of the lower flange 13 of the girder 10 and the lower surface 72b of the flange 72 of the haunch 70. The upper surface 40a of the lower splice plate 40 abuts the lower surface 13b of the lower flange 13 and the lower surface 72b of the flange 72.

[0036] <Welding of the lower splice plate 40 and the lower flange 13> The lower splice plate 40 is welded to the bottom flange 13 of the girder 10. Both longitudinal ends of the lower splice plate 40 are welded to the lower surface 13b of the bottom flange 13. The weld WL1 is a weld line between the lower splice plate 40 and the bottom flange 13. For example, the weld WL1 is a weld formed by fillet welding.

[0037] The length of the weld WL1 along the X-axis direction is, for example, equal to or greater than the width of the secondary beam 20 along the Y-axis direction. The length of the weld WL1 along the X-axis direction is, for example, equal to or less than the width of the main beam 10 along the X-axis direction. The size of the weld WL1, which is a fillet weld, is, for example, 70% or more of the thinner of the plate thickness of the lower flange 13 of the main beam 10 or the plate thickness of the lower splice plate 40. The size of the weld WL1 is the shorter of the leg length along the Y-axis direction or the leg length along the Z-axis direction.

[0038] <Bolt connection between the lower splice plate 40 and the flange 72 of the haunch 70> The lower splice plate 40 is disposed so as to protrude on both sides of the girder 10 in the X-axis direction. The flange 72 of the haunch 70 is placed on the lower splice plate 40. The upper surface 40a of the lower splice plate 40 abuts against the lower surface 72b of the flange 72 of the haunch 70. The flange 72 and the lower splice plate 40 are bolted together using bolts 45. A person skilled in the art can design the diameter and number of bolts 45 as appropriate.

[0039] <Relationship between the upper splice plate 30 and the upper flange 12 of the girder 10> The upper splice plate 30 is disposed on the upper surface 12a of the upper flange 12 of the girder 10. The lower surface 30b of the upper splice plate 30 abuts against the upper surface 12a of the upper flange 12. The upper splice plate 30 is simply placed on the upper flange 12 and is not joined to the girder 10.

[0040] <Bolt connection between the upper splice plate 30 and the upper flange 22 of the sub-beam 20> The upper splice plate 30 is disposed so as to protrude on both sides of the main girder 10 in the X-axis direction. The upper splice plate 30 is placed on the upper flange 22 of the secondary beam 20. The lower surface of the upper splice plate 30 abuts against the upper flange 22 of the secondary beam 20. The upper flange 22 and the upper splice plate 30 are bolted together using bolts 35.

[0041] <Gusset plate 50> The gusset plate 50 is formed so as to protrude from the girder 10 in a plan view. The plate thickness direction of the gusset plate 50 is arranged in the longitudinal direction of the girder 10. The gusset plate 50 is welded to the lower surface 12b of the upper flange 12 of the girder 10, the side surface 11a of the web 11, and the upper surface 13a of the lower flange 13.

[0042] The gusset plate 50 protrudes outward beyond the upper flange 12 and the lower flange 13 in the X-axis direction. The gusset plate 50 is disposed so as to overlap the web 21 of the sub-beam 20 in the Y-axis direction. The gusset plate 50 abuts against the web 21 in the Y-axis direction. The gusset plate 50 and the web 21 are bolted together using bolts 55. The gusset plate 50 is not joined to the upper flange 22 and the lower flange 23 of the sub-beam 20.

[0043] <Notch 90 of the lower flange 23 of the beam 20> As shown in Figs. 1 to 4, a notch 90 is formed in the lower flange 23 of the sub-beam 20. The notch 90 is formed at an end of the sub-beam 20 in the X-axis direction. The notch 90 is formed at a position overlapping with the bolt 45 when viewed in the Z-axis direction. The bolt 45 is a bolt for joining the flange 72 of the haunch 70 and the lower splice plate 40. The notch 90 may be an opening that penetrates the lower flange 23 in the plate thickness direction.

[0044] The notch 90 may be formed at a position overlapping with the bolt 35 in the Z-axis direction. The bolt 35 is a bolt that joins the upper flange 22 and the upper splice plate 30 together.

[0045] The size of the cutout portion 90 is preferably the minimum necessary. The size of the cutout portion 90 may be sufficient as long as the bolt 45 and the bolt tightening tool can be inserted therein.

[0046] <Protruding portion 24 adjacent to cutout portion 90> The lower flange 23 includes an overhanging portion 24 adjacent to the cutout portion 90. The overhanging portion 24 is a part of the lower flange 23 remaining after the cutout portion 90 is machined. The overhanging portion 24 is a portion of the lower flange 23 that is close to the web 21. The overhanging length of the overhanging portion 24 in the Y-axis direction is, for example, 70% or more of the thinner of the plate thickness of the lower flange 23 of the joist 20 or the plate thickness of the web 71 of the haunch 70. The overhanging portion 24 overhangs on both sides from the web 21 in the Y-axis direction.

[0047] <Welding of Beam 20 and Haunch 70> As shown in Figs. 1 and 4, the upper end of the web 71 of the haunch 70 is welded to the lower surface 23b of the lower flange 23 of the sub-beam 20. The weld WL2 is a weld line between the lower flange 23 and the web 71. The weld WL2 is a fillet weld between the lower surface 23b of the lower flange 23 and the side surface 71b of the web 71. In the portion adjacent to the cutout 90, the weld WL2 joins the lower surface of the overhanging portion 24 of the sub-beam 20 and the side surface 71b of the web 71. As described above, the overhang length of the overhanging portion 24 in the Y-axis direction is equal to or greater than the leg length of the weld WL2.

[0048] <Extra length L2 of haunch 70> 1 to 3, the haunch 70 projects in the X-axis direction farther from the girder 10 than the lower splice plate 40. In the X-axis direction, the end 70b of the haunch 70 is located farther from the girder 10 than the end 40c of the lower splice plate 40. Of the ends 70a, 70b of the haunch 70 in the X-axis direction, the end 70b is the one farther from the girder 10. The end 70a is the end closer to the girder 10 than the end 70b.

[0049] The extra length L2 of the haunch 70 is equal to or longer than the step L1. The step L1 is the step between the lower surface 23b of the lower flange 23 of the secondary beam 20 and the lower surface 13b of the lower flange 13 of the primary beam 10. The extra length L2 is the length between the end 40c and the end 70b in the X-axis direction, and is the length between the end 40c and the end 70b that are closer to each other.

[0050] Next, a resistance mechanism against bending moment and shear force acting on the joint structure 100 will be described.

[0051] The bending moment that generally acts on the upper flange 22 and the upper splice plate 30 in the connection structure 100 due to the floor load supported by the sub-beam 20 is resisted by a bending resistance mechanism of the bolts 35 that bolt-connect the upper flange 22 and the upper splice plate 30. This bending moment is a moment about the Y-axis. On the other hand, the shear force that generally acts on the connection structure 100 is resisted by the shear resistance mechanism of the bolts 55 that bolt-connect the gusset plate 50 and the web 21 and the shear resistance mechanism of the gusset plate 50.

[0052] In this way, a design based on a clear design formula that separates the bending resistance mechanism and the shear resistance mechanism can be realized, and there is no need to construct a new design theory for structural design.

[0053] [Method of joining the main beam 10 and the sub beam 20 according to the first embodiment] Next, a method for joining the girder 10 and the minor beams 20 will be described. The method for joining the girder 10 and the minor beams 20 is a method for joining the girder 10 to a pair of minor beams 20 that are shorter in depth than the girder 10, are arranged on both sides of the girder 10, and are perpendicular to the girder 10. By this method for joining the girder 10 and the minor beams 20, a joint structure 100 can be constructed.

[0054] In the method for joining the girder 10 and the secondary beam 20, first, a process of welding the lower splice plate 40 to the girder 10 is performed. For example, in a factory, the lower splice plate 40 is welded to the bottom flange 13 of the girder 10. The lower splice plate 40 is arranged so as to be perpendicular to the longitudinal direction of the girder 10 in a plan view. The lower splice plate 40 is arranged so as to abut against the bottom surface 13b of the bottom flange 13 of the girder 10, and is arranged so as to protrude on both sides in the width direction of the girder 10, and is welded to the bottom flange 13. Note that the "bottom surface 13b of the bottom flange 13" referred to here refers to the bottom surface of the flange that is arranged on the bottom when constructed at a construction site.

[0055] Next, a process of welding the gusset plate 50 to the girder 10 is performed. The gusset plate 50 is arranged so as to be perpendicular to the web 11 of the girder 10, and the gusset plate 50 is welded to the girder 10. For example, the gusset plate 50 is welded to the girder 10 in a factory. The gusset plate 50 is welded to the lower surface 12b of the upper flange 12, the side surface 11a of the web 11, and the upper surface 13a of the lower flange 13. The gusset plate 50 is arranged so as to protrude from the girder 10 in the width direction of the girder 10.

[0056] Next, a step of forming the notch portion 90 in the bottom flange 23 of the joist 20 is performed. A predetermined range of the bottom flange 23 is cut and removed at the longitudinal end of the bottom flange 23. For example, the cutout portion 90 is formed by cutting the bottom flange 23 at a factory. After the cutout portion 90 is formed, the protruding portion 24 remains.

[0057] Next, a process of welding the haunch 70 to the sub-beam 20 is performed. The haunch 70 is arranged so that the longitudinal direction of the haunch 70 and the longitudinal direction of the lower flange 23 are in the same direction, and the upper end of the web 71 of the haunch 70 is welded to the lower surface 23b of the lower flange 23 of the sub-beam 20. After the widthwise and longitudinal positions of the sub-beam 20 and the haunch 70 are aligned, the lower surface 23b of the lower flange 23 and the side surface 71a of the web 71 are fillet welded. In the portion where the notch 90 is formed, the overhanging portion 24 and the web 71 are welded. The upper end of the web 71 is the end that is located on the upper side (closer to the lower flange 23) at the construction site. Similarly, the lower surface 23b of the lower flange 23 is the lower surface at the construction site. The welded portion WL2 is formed by welding the web 71 to the lower flange 23. For example, when welding is performed at a factory, welding can be performed by turning the parts upside down.

[0058] The order of the steps may be changed as appropriate, or a plurality of steps may be performed simultaneously. The girder 10 to which the lower splice plate 40 and the gusset plate 50 are welded is transported to the site and joined to the column.

[0059] Next, a step of placing a pair of haunches 70 on the lower splice plate 40 is performed. The flanges 72 of the haunches 70 are placed on the portion of the lower splice plate 40 that protrudes beyond the girder 10 in the width direction of the girder 10. The lower surface 72b of the flanges 72 is placed on the upper surface 40a of the lower splice plate 40. The lower splice plate 40 and the flanges 72 are overlapped in the Z-axis direction. By placing the haunches 70 on the lower splice plate 40, the ends of the sub-beams 20 in the longitudinal direction are supported by the lower splice plate 40 via the haunches 70.

[0060] Next, a process is performed in which the flanges 72 of the pair of haunches 70 are bolted to the lower splice plate 40. Here, the bolts 45 are inserted into bolt holes formed in the flanges 72 and the lower splice plate 40 to perform the bolting.

[0061] An operator can insert his / her hand into the notch 90 from above to perform work. The operator can insert the bolt 45 through the notch 90 and insert the bolt 45 into the bolt hole from below the lower splice plate 40. The operator positions the head of the bolt 45 below the lower splice plate 40 and inserts the shaft of the bolt 45 into the bolt hole so that it protrudes upward from the flange 72. The operator can attach a nut to the shaft of the bolt 45 that protrudes above the flange 72. The operator can insert a tool into the notch 90 from above to tighten the nut. The operator can look down from above to visually check the nut and bolt 45. The lower flange 23 does not get in the way when the operator works.

[0062] Next, a process of bolting the pair of gusset plates 50 and the web 21 of the sub-beam 20 is performed. Here, the bolts 55 are inserted into bolt holes formed in the gusset plates 50 and the web 21 to perform the bolting.

[0063] Next, a process is performed in which the upper splice plate 30 is placed on the upper surface 12a of the upper flange 12 of the main girder 10 and the upper surfaces 22a of the upper flanges 22 of the pair of secondary beams 20. Here, the upper splice plate 30 is disposed so as to be perpendicular to the longitudinal direction of the main girder 10 in a plan view. The upper splice plate 30 is placed across the upper flanges 12 of the main girder 10 and on the upper flanges 22 of the secondary beams 20 on both sides.

[0064] Next, a process is performed in which the upper flanges 22 of the pair of secondary beams 20 are bolted to the upper splice plate 30. Here, bolts 35 are inserted into bolt holes formed in the upper flanges 22 and the upper splice plate 30 to perform bolt fastening. By performing each of these processes, the pair of secondary beams 20 can be rigidly joined to the main girder 10.

[0065] As described above, the order of each process may be changed as appropriate, or the processes may be performed simultaneously. For example, the process of bolting the upper flanges 22 of the pair of sub-beams 20 to the upper splice plate 30 may be performed first, followed by the process of bolting the pair of gusset plates 50 to the webs 21 of the sub-beams 20. In addition, one of the pair of sub-beams 20 may be joined to the girder 10, and then the other sub-beam 20 may be joined to the girder 10. In addition, the pair of sub-beams 20 may be joined to the girder 10 at the same time.

[0066] (Actions and Effects of the Joint Structure 100 According to the First Embodiment) The joint structure 100 is a joint structure between a main girder 10 extending in a Y-axis direction (first direction) and a pair of sub-beams 20 that are shorter in beam depth than the main girder 10 and extend on either side of the main girder 10 in an X-axis direction (second direction) perpendicular to the Y-axis direction, and includes an upper splice plate 30 that extends in the X-axis direction and is placed on the upper flanges 22 of the pair of sub-beams 20 and the upper flanges 12 of the main girder 10 to join the upper flanges 22 of the pair of sub-beams 20 together; The present invention relates to a beam structure including a pair of gusset plates (joint plates) 50 arranged such that the plate thickness direction is along the Y-axis direction and joining the web 11 of the main girder 10 and the webs 21 of the pair of sub-beams 20, a pair of haunches 70 arranged below the bottom flanges 23 of the pair of sub-beams 20 and joined to the pair of sub-beams 20, and a lower splice plate 40 extending in the X-axis direction and arranged below the pair of haunches 70 and the bottom flange 13 of the main girder 10 to join the pair of haunches 70 together. The upper surface 22a of the upper flange 22 of the main beam 10 and the upper surfaces 22a of the upper flanges 22 of the pair of sub-beams 20 are disposed at the same height, the lower flange 13 of the main beam 10 is disposed lower than the lower flanges 23 of the pair of sub-beams 20, the pair of haunches 70 are disposed so that the plate thickness direction is along the Y-axis direction, and are joined to the pair of sub-beams and include a web (vertical piece) 71 extending downward, and a flange (horizontal piece) 72 disposed so that the plate thickness direction is along the Z-axis direction and joined to the web 71. The lower surface 13b of the lower flange 13 of the main girder 10 and the lower surface 72b of the flange 72 are arranged at the same height, the lower flanges 23 of the pair of secondary beams 20 have cutout portions 90 formed in areas overlapping with the flanges 72 when viewed in the Z-axis direction, the flanges 72 and the lower splice plate 40 are overlapped in the Z-axis direction and bolted together, and the cutout portions 90 are formed above the bolts 45 that join the flanges 72 and the lower splice plate 40 when viewed in the Z-axis direction.

[0067] According to the joint structure 100 of this embodiment, the girder 10 and the sub-girder 20 are bolted together via the lower splice plate 40 and the haunch 70, and the structure is simple, reducing the amount of work required. In addition, according to the joint structure 100 of this embodiment, complicated bracket processing is not required, and the amount of work required for processing the bracket is not required. Furthermore, in the joint structure 100 of this embodiment, full penetration welding and the like are not required, so the amount of work required for construction is significantly reduced. In addition, in the joint structure 100 of this embodiment, the haunch 70 can be placed on the lower splice plate 40 joined to the lower flange 13 of the girder 10, so that the workability during construction can be improved. In addition, in the joint structure 100 of this embodiment, the lower flange 23 of the pair of sub-girders 20 has a notch portion 90 formed therein, so that the lower flange 23 of the sub-girder 20 does not get in the way when the haunch 70 and the lower splice plate 40 are bolted together. The provision of the notch 90 in the lower flange 23 makes it easy to insert the bolts 45 and tools from above the lower flange 23. The worker can work facing downward and tighten the bolts using tools, improving work efficiency during construction. In the joint structure 100 of this embodiment, the lower flange 23 of the secondary beam 20 does not get in the way, so that the main beam 10 and secondary beam 20 can be joined practically even if the step L1 between the main beam 10 and secondary beam 20 is small.

[0068] According to the joint structure 100 of this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30 are not joined, so that the labor required for construction is reduced. Also, according to the joint structure 100 of this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30 are not joined by bolts, so that it is not necessary to form bolt holes in the upper flange 12. Therefore, the processing labor is reduced, and there is no reduction in strength due to loss of the opening, and it is not necessary to consider cross-sectional loss. Also, according to the 100 of this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30 are not welded, so that the labor required for welding construction is reduced. The joint structure 100 according to the embodiment is a joint having structural performance that can be considered as a rigid joint.

[0069] According to the joint structure 100 of this embodiment, the weld WL1 between the lower flange 13 of the girder 10 and the lower splice plate 40 only needs to have a strength sufficient to support the weight of the lower splice plate 40 (or the weight of the lower splice plate 40, the sub-beam 20, and the haunch 70) by balancing the support pressure due to the bending moment on both sides of the girder 10 caused by a long-term load. As a result, the weld WL1 can ensure sufficient strength as long as it has a weld length that does not result in a short bead (for example, a weld length of 40 mm or more), so that the joint structure 100 of this embodiment does not require consideration of the weld strength. The weld length of the weld WL1 is equal to or greater than the width of the sub-beam 20 and equal to or less than the width of the girder 10.

[0070] In addition, in the joint structure 100, the pair of haunches 70 extend in the X-axis direction farther from the main girder 10 than the lower splice plate 40, and the excess length L2, which is the extension length from the end 40c of the lower splice plate 40 to the end 70b of the pair of haunches 70 in the X-axis direction, is greater than or equal to the step L1, which is the length from the lower flanges 23 of the pair of sub-beams 20 to the lower surfaces 72b of the flanges 72 in the vertical direction.

[0071] According to the joint structure 100 of this embodiment, the shear strength can be ensured by lengthening the excess length L2, which is the overhang length of the pair of haunches 70. This allows the shear force transmitted from the lower flange 23 of the sub-beam 20 to be received by the pair of haunches 70 and transmitted to the lower splice plate 40 via the pair of haunches 70. Furthermore, in the joint structure 100 of this embodiment, the shear strength can be changed by changing the plate thickness of the webs 71 of the pair of haunches 70.

[0072] In addition, in the joint structure 100, the lower flanges 23 of the pair of sub-beams 20 include protruding portions 24 that protrude in the Y-axis direction from the webs 21 of the pair of sub-beams 20 in the portion adjacent to the cutout portion 90, and the webs 71 of the pair of haunches 70 and the protruding portions 24 of the lower flanges 23 of the pair of sub-beams 20 are fillet welded.

[0073] According to the joint structure 100 of this embodiment, when forming the notch portion 90 in the bottom flange 23 of the sub-beam 20, by leaving a portion of the bottom flange 23 of the sub-beam 20 close to the web 21, this remaining portion can be used as the protruding portion 24. The protruding portion 24 protruding in the Y-axis direction from the web 21 of the sub-beam 20 and the webs 71 of the pair of haunches 70 are joined by fillet welding, thereby reducing the welding work.

[0074] In addition, in the joint structure 100, the plate thickness direction is arranged along the longitudinal direction of the main girder 10, and the pair of gusset plates 50 are welded to the lower surface 12b of the upper flange 12 of the main girder 10, the side surface 11a of the web 11, and the upper surface 13a of the lower flange 13, and extend on both sides of the main girder 10, and the webs 21 of the pair of secondary beams 20 are each bolted to the pair of gusset plates 50.

[0075] According to the joint structure 100 of this embodiment, the gusset plate 50 welded to the main girder 10 and the web 21 of the secondary girder 20 are bolted together, resulting in a simple configuration that can reduce the labor required for construction. As described above, according to the joint structure 100 of this embodiment, processing of the bracket is not required, and the labor required for processing the bracket is not required. Furthermore, since the joint structure 100 of this embodiment does not require full penetration welding or the like, the labor required for welding construction is significantly reduced.

[0076] (Functions and Effects of the Joining Method According to the First Embodiment) The joining method according to the present embodiment is a method for joining a girder 10 extending in the Y-axis direction to a pair of minor beams 20 that have a shorter beam depth than the girder 10 and extend on both sides of the girder 10 in the X-axis direction perpendicular to the Y-axis direction, in which a notch 90 is formed in the bottom flanges 23 of the pair of minor beams 20 at ends closer to the girder 10 in the longitudinal direction of the pair of minor beams 20, a pair of haunches 70 arranged below the bottom flanges 23 of the pair of minor beams 20 are joined to ends closer to the girder 10 in the longitudinal direction of the pair of minor beams 20, and the bottom flanges 13 of the girder 10 have a pair of haunches 70 extending in the X-axis direction and extending in the X-axis direction. The lower splice plate 40 is disposed under the lower surface 13b of the lower flange 13 of the girder 10 and protrudes on both sides of the girder 10. The method includes the steps of placing a pair of haunches 70 on the lower splice plate 40, bolting the pair of haunches 70 to the lower splice plate 40, joining the web 11 of the girder 10 to the webs 21 of the pair of minor beams 20, placing an upper splice plate 30 extending in the X-axis direction on the upper flanges 22 of the pair of minor beams 20 and the upper flange 12 of the girder 10, and bolting the upper flanges 22 of the pair of minor beams 20 to the upper splice plate 30.

[0077] According to the joining method of this embodiment, the girder 10 and the sub-girder 20 are bolted together via the lower splice plate 40 and the haunch 70, and the structure is simple, so that the processing labor can be reduced. In addition, according to this embodiment, complicated processing of the bracket is not required, and the processing of the bracket is not laborious. Furthermore, in this embodiment, since full penetration welding or the like is not required, the labor involved in construction is significantly reduced. In addition, in this embodiment, the haunch 70 can be placed on the lower splice plate 40 joined to the lower flange 13 of the girder 10, so that the workability during construction can be improved. In addition, in this embodiment, the lower flanges 23 of the pair of sub-girders 20 are formed with the notches 90, so that the lower flanges 23 of the sub-girders 20 do not get in the way when the haunch 70 and the lower splice plate 40 are bolted together. Since the lower flanges 23 are provided with the notches 90, the bolts 45 and tools can be easily inserted from above the lower flanges 23. The worker can work facing downward and tighten the bolts using tools, improving the efficiency of the work during construction. In this embodiment, the lower flange 23 of the sub-beam 20 does not get in the way, so that the main girder 10 and the sub-beam 20 can be joined practically even if the step between the main girder 10 and the sub-beam 20 is small.

[0078] In addition, the joining method of this embodiment includes a step of placing the upper splice plate 30 on the upper surface 12a of the upper flange 12 of the main beam 10 and the upper surfaces 22a of the upper flanges 22 of a pair of secondary beams 20, and a step of bolting the upper flanges 22 of the pair of secondary beams 20 to the upper splice plate 30.

[0079] According to this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30 are not joined, so the labor required for construction is reduced. Also, according to this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30 are not joined by bolts, so there is no need to form bolt holes in the upper flange 12. Therefore, the labor required for processing is reduced, there is no reduction in strength due to loss of the opening, and there is no need to consider loss of cross section. Also, according to this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30 are not welded, so the labor required for welding construction is reduced.

[0080] [Second embodiment of beam-beam joint structure 100B] Next, an example of a joint structure 100B between a girder 10 and a sub-beam 20 according to the second embodiment will be described with reference to Fig. 5. Fig. 5 is a side view of an example of the joint structure 100B between a girder 10 and a sub-beam 20 according to the second embodiment, seen from a midway position of the girder. The joint structure 100B according to the second embodiment shown in Fig. 5 differs from the joint structure 100 according to the first embodiment in that it includes a stiffener 60 and a splice plate 50B instead of the gusset plate 50. Note that in the description of the second embodiment, the same description as in the first embodiment will be omitted.

[0081] The joint structure 100B includes a pair of stiffeners 60. The pair of stiffeners 60 are welded to the girder 10. The stiffeners 60 are plate-shaped, and the plate thickness direction of the stiffeners 60 is along the longitudinal direction of the girder 10. The stiffeners 60 are welded to the lower surface 12b of the upper flange 12, the side surface 11a of the web 11, and the upper surface 13a of the lower flange 13. The stiffeners 60 are arranged so as to protrude on both sides in the X-axis direction from the web 11. The stiffeners 60 do not protrude outward beyond the upper flange 12 and the lower flange 13 in the X-axis direction. The stiffeners 60 are welded to the girder 10, for example, in a factory.

[0082] The joint structure 100B includes a pair of splice plates 50B. The pair of splice plates 50B may be a pair of splice plates for a pair of webs. The pair of splice plates 50B are arranged in the longitudinal direction of the main beam 10 so as to sandwich the stiffener 60 and the web 21 of the sub-beam 20 from both sides. The stiffener 60 and the web 21 are sandwiched by the splice plates 50B from both sides in the plate thickness direction.

[0083] Bolts are inserted through bolt holes formed in the stiffener 60 and the pair of splice plates 50B, and the stiffener 60 and the pair of splice plates 50B are bolted together. Similarly, bolts 55 are inserted through bolt holes formed in the web 21 of the sub-beam 20 and the pair of splice plates 50B, and the web 21 and the pair of splice plates 50B are bolted together. The main girder 10 and the sub-beam 20 are rigidly joined together via the stiffener 60 and the pair of splice plates 50B.

[0084] (Actions and Effects of Joint Structure 100B According to Second Embodiment) The joint structure 100B according to the second embodiment has the same effect as the joint structure 100 according to the first embodiment. The joint structure 100B may be a structure in which the stiffener 60 welded to the main girder 10 and the web 21 of the sub-girder 20 are bolted together via the splice plate 50B.

[0085] [Joint structure 100C between main beam and sub-beam according to the third embodiment] Next, an example of a joint structure 100C between a main beam 10 and a sub beam 20 according to the third embodiment will be described with reference to Fig. 6. Fig. 6 is a side view of an example of a joint structure 100C between a main beam 10 and a sub beam 20B according to the third embodiment, seen from a midway position of the main beam. The joint structure 100C according to the third embodiment shown in Fig. 6 is obtained by turning the joint structure 100 according to the first embodiment upside down. Note that in the description of the third embodiment, descriptions similar to those of the first and second embodiments will be omitted.

[0086] The joint structure 100C shown in FIG. 6 is a joint structure between a main beam 10 and a secondary beam 20B having different beam depths. The beam depth of the secondary beam 20B is shorter than the beam depth of the main beam 10. The joint structure 100 includes a joint having structural performance that can be regarded as a rigid joint. In a plan view, a pair of secondary beams 20B are arranged on both sides of the main beam 10. The main beam 10 extends in the Y-axis direction, and the pair of secondary beams 20B extend in the X-axis direction. The main beam 10 and the pair of secondary beams 20B are arranged so as to be perpendicular to each other.

[0087] <Major beam 10 and minor beam 20B> The girder 10 and the pair of minor beams 20B are formed of H-shaped steel. The girder 10 has a web 11, an upper flange 12, and a lower flange 13. The minor beam 20B has a web 21, an upper flange 22B, and a lower flange 23B. The lower surface 13b of the lower flange 13 of the girder 10 and the lower surface 23b of the lower flange 23B of the minor beam 20B are flush with each other. The upper surface 12a of the upper flange 12 is disposed above the upper surface 22a of the upper flange 22B. In other words, the upper surface 22a of the upper flange 22B is disposed below the upper surface 12a of the upper flange 12. The upper surface 12a of the upper flange 12 and the upper surface 22a of the upper flange 22B have a step L3 in the Z-axis direction. The step L3 is the difference in height between the upper surface 22a and the upper surface 12a in the Z-axis direction.

[0088] <Upper splice plate 30B> The joint structure 100B includes an upper splice plate 30B arranged above the girder 10, a lower splice plate 40B arranged below the girder 10, a pair of gusset plates 50C joined to the web 11 of the girder 10, and a pair of haunches 70B arranged above the pair of minor beams 20B. The upper splice plate 30B and the lower splice plate 40B are arranged perpendicular to the girder 10 in a plan view and extend along the longitudinal direction of the pair of minor beams 20B. The plate thickness direction of the upper splice plate 30B and the lower splice plate 40B is along the Z-axis direction.

[0089] <Haunch 70B> The haunch 70B is T-shaped. The haunch 70B has a web 71 and a flange 72. The haunch 70B is a steel frame member having a predetermined length in the X-axis direction. The thickness direction of the web 71 is along the Y-axis direction. The thickness of the web 71 may be the same as the thickness of the web 21. The thickness direction of the flange 72 is along the Z-axis direction. The thickness of the flange 72 may be the same as the thickness of the upper flange 22B. The width of the flange 72 along the Y-axis direction may be the same as the width of the upper flange 22B along the Y-axis direction. The flange 72 is formed with a bolt hole penetrating in the thickness direction.

[0090] The haunch 70B is disposed above the upper flange 22B of the minor beam 20B. As described below, the lower end of the web 71 of the haunch 70B is welded to the upper surface 22a of the upper flange 22B of the minor beam 20B. The upper surface 72a of the flange 72 of the haunch 70B is flush with the upper surface 12a of the upper flange 12 of the main beam 10. The haunch 70B has an upper surface 72a that is flush with the upper surface 12a of the upper flange 12 of the main beam 10. The step L3 may be the difference in height between the upper surface 22a and the upper surface 72a in the Z-axis direction.

[0091] <Lower splice plate 40B> The lower splice plate 40B is disposed below the lower surface 13b of the lower flange 13 of the girder 10. The upper surface 40a of the lower splice plate 40B abuts against the lower surface 13b of the lower flange 13.

[0092] <Bolt connection between the lower splice plate 40B and the lower flange 23B of the beam 20B> The lower splice plate 40B is disposed so as to protrude on both sides of the main girder 10 in the X-axis direction. The lower flange 23B of the secondary beam 20B is placed on the lower splice plate 40B. The upper surface 40a of the lower splice plate 40B abuts against the lower surface 23b of the lower flange 23B of the secondary beam 20B. The lower flange 23B and the lower splice plate 40B are bolted together using bolts 45. The diameter and number of bolts 45 can be designed appropriately by a person skilled in the art.

[0093] <Relationship between the upper splice plate 30B and the upper flange 12 of the girder 10> The upper splice plate 30B is disposed on the upper surface 12a of the upper flange 12 of the girder 10. The lower surface 30b of the upper splice plate 30B abuts against the upper surface 12a of the upper flange 12. The upper splice plate 30B is simply placed on the upper flange 12 and is not joined to the girder 10.

[0094] <Bolt connection between upper splice plate 30B and flange 72 of haunch 70B> The upper splice plate 30B is disposed so as to protrude on both sides of the girder 10 in the X-axis direction. The upper splice plate 30B is placed on the flange 72 of the haunch 70B. The lower surface 30b of the upper splice plate 30B abuts against the flange 72 of the haunch 70B. The flange 72 and the upper splice plate 30B are bolted together using bolts 35.

[0095] <Gusset plate 50C> Like the gusset plate 50, the gusset plate 50C is formed to protrude from the girder 10 in a plan view. The plate thickness direction of the gusset plate 50C is arranged in the longitudinal direction of the girder 10. The gusset plate 50C is welded to the lower surface 12b of the upper flange 12 of the girder 10, the side surface 11a of the web 11, and the upper surface 13a of the lower flange 13.

[0096] The gusset plate 50C protrudes outward beyond the upper flange 12 and the lower flange 13 in the X-axis direction. The gusset plate 50C is disposed so as to overlap the web 21 of the sub-beam 20B in the Y-axis direction. The gusset plate 50C abuts against the web 21 in the Y-axis direction. The gusset plate 50C and the web 21 are bolted together using bolts 55. The gusset plate 50C is not joined to the upper flange 22B and the lower flange 23B of the sub-beam 20.

[0097] <Notch 90B of upper flange 22B of small beam 20B> A notch 90B is formed in the upper flange 22B of the sub-beam 20B. The notch 90B is formed at an end of the sub-beam 20B in the X-axis direction. The notch 90B is formed at a position overlapping with the bolt 35 when viewed in the Z-axis direction. The bolt 35 is a bolt for joining the flange 72 of the haunch 70B and the upper splice plate 30B. The notch 90B may be an opening penetrating the upper flange 22B in the plate thickness direction.

[0098] The cutout portion 90B may be formed at a position overlapping with the bolt 45 in the Z-axis direction. The bolt 45 is a bolt that joins the lower flange 23B and the lower splice plate 40B together.

[0099] The size of the cutout portion 90B is preferably the minimum necessary. The size of the cutout portion 90B may be large enough to allow the bolt 35 and a bolt tightening tool to be inserted therein.

[0100] <Protruding portion 24B adjacent to cutout portion 90B> The upper flange 22B includes a protruding portion 24B adjacent to the cutout portion 90B. The protruding portion 24B is a part of the upper flange 22B remaining after the cutout portion 90B is machined. The protruding portion 24B is a portion of the upper flange 22B that is close to the web 21. The protruding length of the protruding portion 24B in the Y-axis direction is, for example, 70% or more of the thinner of the plate thickness of the upper flange 22B of the joist 20 or the plate thickness of the web 71 of the haunch 70B. The protruding portion 24B protrudes from both sides from the web 21 in the Y-axis direction.

[0101] <Welding of small beam 20B and haunch 70B> The lower end of the web 71 of the haunch 70B is welded to the upper surface 22a of the upper flange 22B of the sub-beam 20. The weld WL3 is a weld line between the upper flange 22B and the web 71. The weld WL3 is a fillet weld between the upper surface 22a of the upper flange 22B and the side surface 71b of the web 71. In a portion adjacent to the cutout portion 90B, the weld WL3 joins the upper surface of the overhanging portion 24B of the sub-beam 20B and the side surface 71b of the web 71. As described above, the overhang length in the Y-axis direction of the overhanging portion 24B is equal to or greater than the leg length of the weld WL3.

[0102] [Method of joining the main beam 10 and the sub beam 20B according to the third embodiment] Next, a method for joining the girder 10 and the minor beams 20B will be described. The method for joining the girder 10 and the minor beams 20B is a method for joining the girder 10 and a pair of minor beams 20B that are shorter in depth than the girder 10, are arranged on both sides of the girder 10, and are perpendicular to the girder 10. By this method for joining the girder 10 and the minor beams 20B, a joint structure 100B can be constructed.

[0103] In the method of joining the girder 10 and the secondary beams 20B, first, a process of welding the lower splice plate 40B to the girder 10 is performed. For example, in a factory, the lower splice plate 40B is welded to the bottom flange 13 of the girder 10. The lower splice plate 40B is arranged so as to be perpendicular to the longitudinal direction of the girder 10 in a plan view. The lower splice plate 40B is arranged so as to abut against the lower surface 13b of the bottom flange 13 of the girder 10, and is arranged so as to protrude on both sides in the width direction of the girder 10, and is welded to the bottom flange 13.

[0104] Next, a process of welding the gusset plate 50C to the girder 10 is performed. The gusset plate 50C is arranged so as to be perpendicular to the web 11 of the girder 10, and the gusset plate 50C is welded to the girder 10. For example, the gusset plate 50C is welded to the girder 10 in a factory. The gusset plate 50C is welded to the lower surface 12b of the upper flange 12, the side surface 11a of the web 11, and the upper surface 13a of the lower flange 13. The gusset plate 50C is arranged so as to protrude from the girder 10 in the width direction of the girder 10.

[0105] Next, a step of forming the notch portion 90B in the upper flange 22B of the sub-beam 20B is performed. At the longitudinal end of the upper flange 22B, a portion of the upper flange 22B within a predetermined range is cut and removed. For example, in a factory, the portion of the upper flange 22B is cut to form the notch portion 90B. After the notch portion 90B is formed, the protruding portion 24B remains.

[0106] Next, a process of welding the haunch 70B to the sub-beam 20B is performed. The haunch 70B and the upper flange 22B are arranged so that their longitudinal directions are the same, and the lower end of the web 71 of the haunch 70B is welded to the upper surface 22a of the upper flange 22B of the sub-beam 20B. After the sub-beam 20B and the haunch 70B are aligned in the width direction and the longitudinal direction, the upper surface 22a of the upper flange 22B and the side surface 71a of the web 71 are fillet welded. In the portion where the notch 90B is formed, the overhanging portion 24B and the web 71 are welded. The lower end of the web 71 is the end that is located on the lower side (closer to the upper flange 22B) at the construction site. Similarly, the upper surface 22a of the upper flange 22 is the lower surface at the construction site. The welded portion WL3 is formed by welding the web 71 to the upper flange 22B. For example, when welding is performed at a factory, the welding can be performed by turning the parts upside down.

[0107] Next, a step of placing a pair of sub-beams 20B on the lower splice plate 40B is performed. The lower flange 23B of the sub-beam 20B is placed on the portion of the lower splice plate 40B that protrudes beyond the main beam 10 in the width direction of the main beam 10. The lower surface 72b of the lower flange 23B is placed on the upper surface 40a of the lower splice plate 40B. The lower splice plate 40B and the lower flange 23B are overlapped in the Z-axis direction. By placing the haunch 70B on the lower splice plate 40B, the longitudinal end of the sub-beam 20B is supported by the lower splice plate 40B.

[0108] Next, a process of bolting the lower flanges 23B of the pair of sub-beams 20B to the lower splice plate 40B is performed. Here, bolts 45 are inserted into bolt holes formed in the lower flanges 23B to perform the bolting.

[0109] Next, a process of bolting the pair of gusset plates 50C and the web 21 of the sub-beam 20B is performed. Here, the bolts 55 are inserted into bolt holes formed in the gusset plate 50C and the web 21 to perform the bolting.

[0110] Next, a process is performed in which the upper splice plate 30B is placed on the upper surface 12a of the upper flange 12 of the girder 10 and the upper surfaces 72a of the flanges 72 of the pair of haunches 70B. Here, the upper splice plate 30B is arranged so as to be perpendicular to the longitudinal direction of the girder 10 in a plan view. The upper splice plate 30B is placed across the upper flange 12 of the girder 10 and on the flanges 72 of the haunches 70B on both sides.

[0111] Next, a process of bolting flanges 72 of the pair of haunches 70B to the upper splice plate 30B is performed. Here, bolts 35 are inserted into bolt holes formed in the flanges 72 and the upper splice plate 30B to perform bolting.

[0112] For example, a worker can insert his / her hand into the notch portion 90B from below to work. The bolt 35 can be inserted through the notch portion 90B and inserted into the bolt hole from below the flange 72. The worker places the head of the bolt 35 below the flange 72, inserts the shaft of the bolt 35 into the bolt hole, and makes it protrude upward from the upper splice plate 30B. The worker can attach a nut to the shaft of the bolt 35 protruding above the upper splice plate 30. The worker can look down from above and visually confirm the nut and bolt 35. The lower flange 23 does not get in the way when the worker works. When the step L3 is small, if the upper flange 22B of the sub-beam 20B is present below the bolt hole of the flange 72, this part may get in the way. In the joint structure 100C, the notch portion 90B is formed, so that the upper flange 22B does not get in the way when the bolt 35 is inserted.

[0113] By carrying out each of these steps, the pair of minor beams 20B can be rigidly joined to the major beam 10.

[0114] (Actions and Effects of Joint Structure 100C According to Third Embodiment) The joint structure 100C is a joint structure between a main girder 10 extending in the Y-axis direction and a pair of minor beams 20B that are shorter than the main girder 10 and extend on both sides of the main girder 10 in the X-axis direction perpendicular to the Y-axis direction. The joint structure 100C is a joint structure between a main girder 10 and a minor beam 20B, the joint structure including a lower splice plate 40B extending in the X-axis direction and disposed below the bottom flanges 23B of the pair of minor beams 20B and the bottom flange 13 of the main girder 10, and joining the bottom flanges 23B of the pair of minor beams 20B together; The pair of gusset plates 50C are arranged along the Y-axis direction and connect the web 11 of the main girder 10 and the webs 21 of the pair of sub-beams 20B, a pair of haunches 20B are arranged above the upper flanges 22B of the pair of sub-beams 20B and connected to the pair of sub-beams 20B, and an upper splice plate 30B extends in the X-axis direction and is placed on the pair of haunches 20B and the upper flanges 12 of the main girder 10 to connect the pair of haunches 70B together. The lower surface 13b of the flange 13 and the lower surfaces 23b of the lower flanges 23B of the pair of sub-beams 20B are disposed at the same height, the upper flange 12 of the main girder 10 is disposed above the upper flanges 22B of the pair of sub-beams 20B, the pair of haunches 70B are disposed so that the plate thickness direction is along the Y-axis direction, are joined to the pair of sub-beams 20B, and have webs 71 extending upward, and flanges 72 are disposed so that the plate thickness direction is along the Z-axis direction and are joined to the webs 71. The upper surface 12a of the upper flange 12 and the upper surface 72a of the flange 72 are disposed at the same height, and the upper flange 22B of the pair of small beams 20B has a notch portion 90B formed in a region overlapping with the flange 72 when viewed in the Z-axis direction. The flange 72 and the upper splice plate 30B are overlapped in the Z-axis direction and bolted together, and the notch portion 90B is formed below the bolt 35 that joins the flange 72 and the upper splice plate 30B when viewed in the Z-axis direction.

[0115] According to the joint structure 100C of this embodiment, the girder 10 and the sub-beam 20B are bolted together via the upper splice plate 30B and the haunch 70B, and the structure is simple, reducing the amount of work required. In addition, according to the joint structure 100C of this embodiment, complicated bracket processing is not required, and the time required for processing the bracket is not required. Furthermore, in the joint structure 100C of this embodiment, since full penetration welding and the like are not required, the time required for construction is significantly reduced. In addition, in this embodiment, the lower flange 23B of the sub-beam 20B can be placed on the lower splice plate 40B joined to the lower flange 13 of the girder 10, so that the workability during construction can be improved. In addition, in the joint structure 100C of this embodiment, the upper flange 22B of the pair of sub-beams 20B is formed with the notch portion 90B, so that the upper flange 22B of the sub-beam 20B does not get in the way when the haunch 70B and the upper splice plate 30B are bolted together. The cutout portion 90B in the upper flange 22B makes it easy to install the bolt 35. The worker can work facing down and tighten the bolt using a tool, improving the work efficiency during construction. In the joint structure 100C of this embodiment, the upper flange 22B of the secondary beam 20B does not get in the way, so that the main beam 10 and the secondary beam 20B can be joined practically even if the step L3 between the main beam 10 and the secondary beam 20B is small.

[0116] According to the joint structure 100C of this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30B are not joined, so the labor required for construction is reduced. Also, according to the joint structure 100C of this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30B are not joined by bolts, so there is no need to form bolt holes in the upper flange 12. Therefore, the processing labor is reduced, there is no reduction in strength due to loss of the opening, and there is no need to consider cross-sectional loss. Also, according to the joint structure 100C of this embodiment, the upper flange 12 of the girder 10 and the upper splice plate 30B are not welded, so the labor required for welding construction is reduced.

[0117] In addition, in the joint structure 100C, the pair of haunches 70B extend farther from the main girder 10 in the X-axis direction than the upper splice plate 30B, and the excess length L4, which is the length from the end 30c of the upper splice plate 30B to the end 70b of the pair of haunches 70B in the X-axis direction, is greater than or equal to the step L3, which is the length from the upper flanges 22B of the pair of sub-beams 20B to the upper surfaces 72a of the flanges 72 in the Z-axis direction.

[0118] According to the joint structure 100C of this embodiment, the overhang length L4 of the pair of haunches 70B is increased to ensure the shear strength. This allows the pair of haunches 70B to receive the shear force transmitted from the upper flange 22B of the sub-beam 20B, and transmit it to the upper splice plate 30B via the pair of haunches 70B. In addition, in the joint structure 100C of this embodiment, the shear strength can be changed by changing the plate thickness of the web 71 of the pair of haunches 70B.

[0119] In addition, in the joint structure 100C, the upper flanges 22B of the pair of sub-beams 20B include protruding portions 24B protruding in the Y-axis direction from the webs 71 of the pair of sub-beams 20B in the portion adjacent to the cutout portion 90B, and the webs 71 of the pair of haunches 70B and the protruding portions 24B of the upper flanges 22B of the pair of sub-beams 20B are fillet welded.

[0120] According to the joint structure 100C of this embodiment, when forming the notch portion 90B in the upper flange 22B of the sub-beam 20B, a portion of the upper flange 22B of the sub-beam 20B close to the web 21 is left, and this remaining portion can be used as the protruding portion 24B. The protruding portion 24B protruding in the Y-axis direction from the web 21 of the sub-beam 20B and the web 71 of the pair of haunches 70B are joined by fillet welding, thereby reducing the welding work.

[0121] (Functions and Effects of the Joining Method According to the Second Embodiment) The joining method according to the present embodiment is a method for joining a girder 10 extending in the Y-axis direction to a pair of minor beams 20B that have a shorter beam depth than the girder 10 and extend on both sides of the girder 10 in the X-axis direction perpendicular to the Y-axis direction, in which a notch 90B is formed in the upper flanges 22B of the pair of minor beams 20B at ends closer to the girder 10 in the longitudinal direction of the pair of minor beams 20B, a pair of haunches 20B arranged above the upper flanges 22B of the pair of minor beams 20B are joined to ends closer to the girder 10 in the longitudinal direction of the pair of minor beams 20B, and a pair of haunches 20B arranged above the upper flanges 22B of the pair of minor beams 20B are joined to the lower flanges 13 of the girder 10, the haunches 20B extending in the X-axis direction and the A lower splice plate 40B is positioned under the lower surface 13b of the lower flange 13 and is joined to both sides of the main girder 10, and the method includes the steps of placing the lower flanges 23B of a pair of secondary beams 20B on the lower splice plate 40B, bolting the lower flanges 23B of the pair of secondary beams 20B to the lower splice plate 40B, joining the web 11 of the main girder 10 to the webs 21 of the pair of secondary beams 20B, placing the upper splice plate 30B extending in the X-axis direction on the pair of haunches 70B and the upper flanges 12 of the main girder 10, and bolting the pair of haunches 70B to the upper splice plate 30B.

[0122] According to the joining method of this embodiment, the girder 10 and the sub-beam 20B are bolted together via the upper splice plate 30B and the haunch 70B, and the structure is simple, so that the processing labor can be reduced. In addition, according to this embodiment, complicated processing of the bracket is not required, and the processing of the bracket is not time-consuming. Furthermore, in this embodiment, since full penetration welding and the like are not required, the labor required for construction is significantly reduced. In addition, in this embodiment, the lower flange 23B of the sub-beam 20B can be placed on the lower splice plate 40B joined to the lower flange 13 of the girder 10, so that the workability during construction can be improved. In addition, in this embodiment, the upper flange 22B of the pair of sub-beams 20B is formed with the notch portion 90B, so that the upper flange 22B of the sub-beam 20B does not get in the way when the haunch 70B and the upper splice plate 30B are bolted together. Since the upper flange 22B is provided with the notch portion 90B, the bolt 35 can be easily attached. The worker can work facing downward and tighten the bolts using tools, which improves the efficiency of the work during construction. In this embodiment, since the upper flange 22B of the minor beam 20B does not get in the way, the major beam 10 and the minor beam 20B can be joined practically even if the step L3 between the major beam 10 and the minor beam 20B is small.

[0123] [Beam-beam joint structure 100D according to the fourth embodiment] Next, an example of a joint structure 100D between a main beam 10 and a secondary beam 20 according to the fourth embodiment will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view showing a cut surface along the XY plane of an example of the joint structure 100D between a main beam 10 and a secondary beam 20 according to the fourth embodiment. The joint structure 100D according to the fourth embodiment shown in Fig. 7 differs from the joint structure 100 according to the first embodiment in that a lower splice plate 40D having a widened portion 41 is provided instead of the lower splice plate 40. Note that in the description of the fourth embodiment, the same description as in the first to third embodiments will be omitted.

[0124] The joint structure 100D includes a lower splice plate 40D. The lower splice plate 40D has a widened portion 41. The widened portion 41 is disposed in the center of the lower splice plate 40D in the longitudinal direction. A width W2 of the widened portion 41 in the Y-axis direction is greater than widths W1 of both ends of the lower splice plate 40D in the longitudinal direction.

[0125] The width W1 of each end of the lower splice plate 40D is equal to, for example, the width of the lower flange 23 of the sub-beam 20. The width W2 of the widened portion 41 is greater than the width of the lower flange 23.

[0126] An end of the widened portion 41 in the Y-axis direction is welded to the lower surface of the bottom flange 13 of the girder 10. A weld WL4 between the widened portion 41 and the bottom flange 13 is a fillet weld. The weld WL4 is a weld line that welds the bottom flange 13 and the lower splice plate 40D together, and extends in the X-axis direction. The weld WL4 is located outward in the Y-axis direction from the end of the bottom flange 23 in the width direction.

[0127] The length of the weld WL4 along the X-axis direction is, for example, equal to or greater than the width W1 of the secondary beam 20 along the Y-axis direction. The length of the weld WL4 along the X-axis direction is, for example, equal to or less than the width of the main beam 10 along the X-axis direction. The size of the weld WL4, which is a fillet weld, is, for example, 70% or more of the thinner of the plate thickness of the lower flange 13 of the main beam 10 or the plate thickness of the lower splice plate 40D. The size of the weld WL4 is the shorter of the leg length along the Y-axis direction or the leg length along the Z-axis direction.

[0128] The joint structure 100D according to the fourth embodiment also provides the same effects as those of the joint structure 100 according to the first embodiment.

[0129] In addition, the present invention is not limited to the configuration shown here, and may be implemented in other embodiments in which other components are combined with the configurations and the like of the above-mentioned embodiment. In this regard, the present invention may be modified within the scope of the gist of the present invention, and may be appropriately determined according to the application form.

[0130] In the joint structure 100 according to the above embodiment, a case where the upper splice plate 30 is not joined to the upper flange 12 of the girder 10 is illustrated, but the upper splice plate 30 may be joined to the upper flange 12 of the girder 10. When the upper splice plate 30 is not joined to the upper flange 12, the construction work can be reduced.

[0131] (Modification) In the joint structure 100 according to the embodiment, for example, the upper surface 40a of the lower splice plate 40 and the side surface of the lower flange 13 of the girder 10 may be joined by fillet welding. In the joint structure 100, a welded portion may be formed by fillet welding in the gap between the side surface of the lower flange 13 and the end surface of the lower flange 23 of the sub-beam 20. The side surface of the lower flange 13 is a side surface extending in the longitudinal direction (Y-axis direction) of the girder 10. The end surface of the lower flange 23 of the sub-beam 20 is an end surface in the longitudinal direction (X-axis direction) of the sub-beam 20 and is along the Y-axis direction. The welded portion between the upper surface 40a of the lower splice plate 40 and the side surface of the lower flange 13 of the girder 10 extends in the Y-axis direction, and the welded portion has a weld length of, for example, 40 mm or more and less than the width of the sub-beam 20.

[0132] In addition, in the joint structure 100, the case where the haunch 70 is formed on the lower side of the sub-beam 20 has been illustrated, but the haunches 70, 70B may be formed on both the upper and lower sides of the sub-beam 20.

[0133] In addition, in the joint structure 100, the pair of minor beams 20 have the same beam depth, but the pair of minor beams 20 may have different beam depths. In this case, the heights of the webs 71 of the haunches 70 along the Z-axis direction are different. [Explanation of symbols]

[0134] 100, 100B, 100C, 100D: Joint structure (joint structure of a main beam and a pair of small beams) 10: Large beam 11: Web (beam web) 12: Top flange (top flange of girder) 13; Bottom flange (bottom flange of girder) 13b: Bottom surface (bottom surface of bottom flange) 20,20B: Small beam 21: Web (beam web) 22, 22B: Upper flange (upper flange of sub-beam) 23, 23B: Bottom flange (bottom flange of sub-beam) 24, 24B: protruding part 30, 30B: Upper splice plate 30c: End of upper splice plate 40, 40B: Lower splice plate 40c: End of lower splice plate 50, 50C: Gusset plate (joint plate) 50B: Splice plate (web splice plate) 60: Stiffener 70,70B: Pair of corbels 70b: Ends of a pair of corbels 71: Web (vertical piece) 72: Flange (horizontal piece) 90,90B: Notch part L1: Step (length from the bottom flange of the sub-beam to the bottom surface of the horizontal piece of the haunch) L2: Extra length (overhang length from the end of the lower splice plate to the end of the haunch) L3: Step (length from the top flange of the sub-beam to the top surface of the horizontal piece of the haunch) L4: Extra length (overhang length from the end of the upper splice plate to the end of the haunch) X: X-axis direction (second direction) Y: Y axis direction (first direction) Z: Z-axis direction (vertical direction)

Claims

1. A joint structure for a main beam and a sub-beam, the joint structure including a main beam extending in a first direction and a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, An upper splice plate extending in the second direction and placed on the upper flanges of the pair of sub-beams and the upper flanges of the main beam to join the upper flanges of the pair of sub-beams; A pair of joining plates are arranged so that a plate thickness direction is along the first direction and join the web of the main girder and the webs of the pair of small beams; A pair of haunches disposed below the lower flanges of the pair of joists and joined to the pair of joists; A lower splice plate extending in the second direction and disposed below the pair of haunches and the lower flange of the girder to join the pair of haunches together, The upper surface of the upper flange of the main beam and the upper surfaces of the upper flanges of the pair of small beams are disposed at the same height, The lower flange of the main beam is disposed below the lower flanges of the pair of sub beams, The pair of haunches are A vertical piece is arranged so that the plate thickness direction is along the first direction, is joined to the pair of small beams, and extends downward; A horizontal piece is arranged so that the plate thickness direction is along the vertical direction and is joined to the vertical piece, The lower surface of the lower flange of the girder and the lower surface of the horizontal piece are disposed at the same height; The lower flanges of the pair of small beams have notches formed in areas that overlap with the horizontal pieces when viewed in the vertical direction, The horizontal piece and the lower splice plate are overlapped in the vertical direction and bolted together; A joint structure between a main beam and a secondary beam, characterized in that the notch portion is formed above the bolt that joins the horizontal piece and the lower splice plate when viewed in the vertical direction.

2. The pair of haunches extend in the second direction farther from the girder than the lower splice plate, 2. The joint structure of claim 1, wherein the overhang length from the end of the lower splice plate to the end of the pair of haunches in the second direction is equal to or greater than the length from the lower flanges of the pair of sub-beams to the lower surface of the horizontal piece in the vertical direction.

3. The lower flanges of the pair of sub-beams include protruding portions that protrude from the webs of the pair of sub-beams in the first direction in portions adjacent to the cutout portions, 3. The joint structure of a main beam and a secondary beam according to claim 1, wherein the vertical pieces of the pair of haunches and the protruding portions of the lower flanges of the pair of secondary beams are fillet welded.

4. A joint structure for a main beam and a sub-beam, the joint structure including a main beam extending in a first direction and a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, A lower splice plate extending in the second direction and disposed below the lower flanges of the pair of sub-beams and the lower flanges of the main beam, and joining the lower flanges of the pair of sub-beams together; A pair of joining plates are arranged so that a plate thickness direction is along the first direction and join the web of the main girder and the webs of the pair of small beams; A pair of haunches disposed above the upper flanges of the pair of joists and joined to the pair of joists; An upper splice plate extending in the second direction and placed on the pair of haunches and the upper flange of the girder to join the pair of haunches together, The lower surface of the lower flange of the main beam and the lower surfaces of the lower flanges of the pair of sub beams are disposed at the same height, The upper flange of the main beam is disposed above the upper flanges of the pair of sub beams, The pair of haunches are A vertical piece is arranged so that a plate thickness direction is along the first direction, is joined to the pair of small beams, and extends upward; A horizontal piece is arranged so that the plate thickness direction is along the vertical direction and is joined to the vertical piece, The upper surface of the upper flange of the girder and the upper surface of the horizontal piece are disposed at the same height; The upper flanges of the pair of small beams have notches formed in areas that overlap with the horizontal pieces when viewed in the vertical direction, The horizontal piece and the upper splice plate are overlapped in the vertical direction and bolted together; A joint structure between a main beam and a secondary beam, characterized in that the cutout portion is formed below the bolt that joins the horizontal piece and the upper splice plate when viewed in the vertical direction.

5. The pair of haunches extend in the second direction farther from the girder than the upper splice plate, 5. The joint structure of claim 4, wherein the length from the end of the upper splice plate to the end of the pair of haunches in the second direction is equal to or greater than the length from the upper flanges of the pair of sub-beams to the upper surface of the horizontal piece in the vertical direction.

6. The upper flanges of the pair of sub-beams include protruding portions that protrude from the webs of the pair of sub-beams in the first direction in portions adjacent to the cutout portions, 6. The joint structure of a main beam and a secondary beam according to claim 4, wherein the vertical pieces of the pair of haunches and the protruding portions of the upper flanges of the pair of secondary beams are fillet welded.

7. A method for joining a main beam and a sub-beam, the method comprising the steps of: joining a main beam extending in a first direction to a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, the method comprising the steps of: The lower flanges of the pair of small beams have notches formed at the ends closer to the main beam in the longitudinal direction of the pair of small beams, A pair of haunches arranged below the lower flanges of the pair of sub-beams are respectively joined to the ends of the pair of sub-beams that are closer to the main beam in the longitudinal direction, A lower splice plate is joined to the lower flange of the girder, the lower splice plate extending in the second direction, disposed below a lower surface of the lower flange of the girder, and protruding on both sides of the girder; placing the pair of haunches on the lower splice plate; bolting the pair of haunches and the lower splice plate together; joining a web of the main girder to webs of the pair of sub-girders; placing an upper splice plate extending in the second direction on the upper flanges of the pair of minor beams and the upper flange of the major beam; and a step of bolting the upper flanges of the pair of sub-beams to the upper splice plate.

8. A method for joining a main beam and a sub-beam, the method comprising the steps of: joining a main beam extending in a first direction to a pair of sub-beams having a shorter beam depth than the main beam and extending on both sides of the main beam in a second direction perpendicular to the first direction, the method comprising the steps of: The upper flanges of the pair of small beams have notches formed at the ends closer to the main beam in the longitudinal direction of the pair of small beams, A pair of haunches arranged above the upper flanges of the pair of sub-beams are respectively joined to the ends of the pair of sub-beams that are closer to the main beam in the longitudinal direction, A lower splice plate is joined to the lower flange of the girder, the lower splice plate extending in the second direction, disposed below a lower surface of the lower flange of the girder, and protruding on both sides of the girder; placing the lower flanges of the pair of joists on the lower splice plate; bolting the lower flanges of the pair of joists to the lower splice plate; joining a web of the main girder to webs of the pair of sub-girders; placing an upper splice plate extending in the second direction on the pair of haunches and an upper flange of the girder; and a step of bolting the pair of haunches and the upper splice plate together.

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