Column-beam joint construction

Abstract

To provide a column beam joint structure capable of preventing a damage of a hinge part of a beam.SOLUTION: A column beam joint structure comprises a first steel bar 4 projecting from a column 2 at respective heights of an upper part and a lower part of a beam 3 and joined to a beam main bar 31 of the beam 3 by mechanical joints 61 and 62 at an end 34 of the beam 3, a second steel bar 5 projecting from the column 2 at respective heights below the upper first steel bar 4 and above the lower first steel bar 4 and having a part projecting from the column 2 situated at the end 34 of the beam 3 and a shear reinforcement bar 32 provided at the beam 3. The first steel bar 4 has higher strength and / or larger diameter than the beam main bar 31, intervals of arrangements of the shear reinforcement bar 32 are set to be smaller at a high density reinforcement area 35 at the beam 3 than other areas and the high density reinforcement area 35 is an area from a position apart for a distance between steel bar central axes of a central axis of the upper first steel bar 4 and a central axis of the lower first steel bar 4 to a central part of the beam 3 from a tension yield position 313 of the beam main bar 31, to a position of an end of the second steel bar 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a beam-column joint structure. [Background technology]

[0002] In reinforced concrete (RC) beam-column frame structures, designs typically target a beam-yielding collapse mechanism, incorporating yield hinges at the ends of beams to ensure the beam's deformation capacity. However, if an earthquake response occurs in which the main reinforcement at the beam's end yields in tension and the frame experiences large deformation, diagonal cracks in the beam-column joints may expand and the concrete may collapse, making repair difficult. Furthermore, installing splices for the beam's main reinforcement in the hinge zone at the beam's end may limit the post-yield elongation of the beam's main reinforcement, potentially preventing the required deformation capacity from being achieved. For this reason, there is a general restriction that splices should not be installed within 0.5 to 1.0 times the beam depth from the beam-end joint face. However, from the perspective of streamlining construction through precast concrete, installing splices closer to the beam's end is desirable.

[0003] Therefore, hinge relocation is sometimes performed to increase the bending strength near the end of the beam so that the main beam reinforcement yields at a position slightly away from the end of the beam, and a joint is provided at the end of the beam. For example, Patent Document 1 discloses a hinge relocation that provides cutoff reinforcing bars that protrude from the joint surface of the column and are embedded in the end of the beam, thereby increasing the bending strength near the end of the beam.Also known is a hinge relocation that provides a mechanical joint near the end of the beam, and makes the reinforcing bars joined to the mechanical joint from the end side of the beam (the side joined to the column) stronger or larger in diameter than the reinforcing bars (beam main reinforcing bars) joined from the opposite side (the center side of the beam) to have higher strength or larger diameter, or both, than the reinforcing bars (beam main reinforcing bars) joined from the opposite side (the center side of the beam), thereby increasing the bending strength near the end of the beam. In this way, by adopting hinge relocation, damage to the column-beam joint after beam yielding can be suppressed, and a beam-yielding structure with sufficient deformability can be realized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-17442 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional hinge relocation, the flexible length of the beam is shortened to ensure a non-yielding region at the end of the beam, which increases the deformation of the hinge portion (yield position) of the beam, and there is a risk of significant damage to the hinge portion of the beam.

[0006] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a column-beam joint structure that can prevent damage to the hinge portion of the beam. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the column-beam joint structure of the present invention is a column-beam joint structure in which a reinforced concrete column and a reinforced concrete beam are joined, and comprises: first reinforcing bars protruding from the column at the height of each of the upper and lower parts of the beam and joined to the main beam reinforcement of the beam at the end of the beam with mechanical joints; second reinforcing bars protruding from the column at the height below the upper first reinforcing bar and above the lower first reinforcing bar, respectively, and the protruding parts from the column are located at the end of the beam; and shear reinforcement bars provided in the beam, wherein the first reinforcing bars have higher strength and / or a larger diameter than the main beam reinforcement, and the reinforcing bar spacing of the shear reinforcement is set smaller in the high-density reinforcement region of the beam than in other regions, and the high-density reinforcement region is a region from a position away from the tensile yield position of the main beam reinforcement toward the center of the beam by the reinforcing bar central axis distance between the central axis of the upper first reinforcing bar and the central axis of the lower first reinforcing bar, to the position of the end of the second reinforcing bar.

[0008] In order to achieve the above object, the beam-column joint structure of the present invention is a beam-column joint structure in which a reinforced concrete column and a reinforced concrete beam are joined, and the beam-column joint structure comprises: reinforcing bars protruding from the column at the height of each of the upper and lower parts of the beam and joined to the main beam reinforcement of the beam at the end of the beam with mechanical joints; a steel frame joined to the column at a height between the upper reinforcing bar and the lower reinforcing bar and arranged at the end of the beam; and shear reinforcement bars provided in the beam, wherein the reinforcing bars have a higher strength and / or a larger diameter than the main beam reinforcement bars, and the reinforcing bars are set to have a smaller reinforcing bar spacing in a high-density reinforcement region of the beam than in other regions, and the high-density reinforcement region extends from a position away from the tensile yield position of the main beam reinforcement bars toward the center of the beam by the reinforcing bar central axis distance between the central axis of the upper reinforcing bar and the central axis of the lower reinforcing bar, The reinforcing bars The area extends to the end position of the

[0009] In this invention, the spacing of the shear reinforcement bars in the beam is set smaller in the high-density reinforcement area than in other areas, preventing damage to the high-density reinforcement area, which is the hinge portion of the beam. This ensures the original effect of hinge relocation, which is to prevent damage and destruction of the column-beam joint by moving the hinge position away from the end face of the beam, is achieved. In addition, it becomes possible to provide mechanical joints at the end of the beam, and in the case of precast beams, it is possible to plan precast members that are easy to manufacture, transport, and store.

[0010] Furthermore, in the beam-column joint structure according to the present invention, the amount of reinforcement of the shear reinforcement in the high-density reinforcement area may be such that the shear strength (Vsu) calculated by the following formula (1) is 1.1 times the ultimate bending shear force of the beam. Vsu=b·jt·pw·σwy···(1) b: Beam width (mm) jt: Distance between the center axes of rebars (mm) pw: Shear reinforcement ratio in the high-density reinforcement area σwy: Reference strength of shear reinforcement in high-density reinforcement area (N / mm 2 )

[0011] This configuration can prevent cracks in the concrete portion of the high-density reinforced area, which serves as the hinge portion of the beam, and can prevent damage to the high-density reinforced area. [Effects of the Invention]

[0012] According to the present invention, damage to the hinge portion of the beam can be prevented. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a vertical cross-sectional view of a beam-to-column joint according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a vertical cross-sectional view of a beam-to-column joint according to a second embodiment of the present invention. [Figure 3] (a) is a vertical cross-section of specimen No. 1 used in a cyclic loading test to confirm the performance of the beam-column joint structure, (b) is a photograph of specimen No. 1 after the cyclic loading test, and (c) is a graph showing the relationship between the load and deformation angle of specimen No. 1. [Figure 4] (a) is a vertical cross-section of specimen No. 2 used in the cyclic loading test to confirm the performance of the beam-column joint structure, (b) is a photograph of specimen No. 2 after the cyclic loading test, and (c) is a graph showing the relationship between the load and deformation angle of specimen No. 2. [Figure 5] (a) is a vertical cross-section of specimen No. 4 used in the cyclic loading test to confirm the performance of the beam-column joint structure, (b) is a photograph of specimen No. 4 after the cyclic loading test, and (c) is a graph showing the relationship between the load and deformation angle of specimen No. 4. [Figure 6] (a) is a vertical cross-section of specimen No. 6 used in the cyclic loading test to confirm the performance of the beam-column joint structure, (b) is a photograph of specimen No. 6 after the cyclic loading test, and (c) is a graph showing the relationship between the load and deformation angle of specimen No. 6. [Figure 7] (a) is a vertical cross-section of specimen No. 8 used in a cyclic loading test to confirm the performance of the beam-column joint structure, (b) is a photograph of specimen No. 8 after the cyclic loading test, and (c) is a graph showing the relationship between the load and deformation angle of specimen No. 8. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) Hereinafter, a column-beam joint structure according to an embodiment of the present invention will be described with reference to FIG. As shown in Figure 1, the beam-column joint structure 1 according to this embodiment is a joint structure between a reinforced concrete column 2 and a reinforced concrete beam 3. The beam 3 extends in one horizontal direction and is joined to the column 2 from both sides in the one horizontal direction. The area of ​​the beam 3 near the joint surface where it is joined to the column 2 is referred to as an end 34. The one horizontal direction is referred to as the X direction, and the horizontal direction perpendicular to the X direction is referred to as the Y direction.

[0015] The column 2 is a square column with a rectangular cross section. The column 2 is a precast concrete member. The column 2 has a plurality of column main reinforcements (not shown) extending in the vertical direction, a plurality of tie bars (not shown) arranged to surround the plurality of column main reinforcements, and a column concrete part 21 in which the column main reinforcements and tie bars are embedded.

[0016] The beam 3 has a rectangular cross section. The beam 3 is a precast concrete member. The beam 3 has a plurality of beam main reinforcements 31 extending in the X direction, a plurality of shear reinforcements 32 surrounding the plurality of beam main reinforcements 31, and a beam concrete section 33 in which the beam main reinforcements 31 and shear reinforcements 32 are embedded. The beam main reinforcements 31 are provided on both the upper and lower sides of the beam 3. The beam main reinforcements 31 provided on the upper side of the beam 3 are referred to as upper beam main reinforcements 311, and the beam main reinforcements 31 provided on the lower side of the beam 3 are referred to as lower beam main reinforcements 312. Details of the shear reinforcements 32 will be described later.

[0017] In the beam-column joint structure 1, a plurality of first reinforcing bars 4 and a plurality of second reinforcing bars 5 are provided which penetrate the column 2 in the X direction. The first reinforcing bars 4 and the second reinforcing bars 5 protrude from the column 2 on both sides in the X direction. The first reinforcing bars 4 are provided at the height of both the upper and lower sides of the beam 3. The first reinforcing bars 4 provided at the upper side of the beam 3 are referred to as upper first reinforcing bars 41, and the first reinforcing bars 4 provided at the lower side of the beam 3 are referred to as lower first reinforcing bars 42.

[0018] The upper first reinforcing bars 41 are arranged at the same height as the upper beam main bars 311. The upper first reinforcing bars 41 and the upper beam main bars 311 have their ends facing each other and are joined via mechanical joints 61 such as couplers. The upper first reinforcing bars 41 have higher strength and / or a larger diameter than the upper beam main bars 311. The lower first reinforcing bars 42 are arranged at the same height as the lower beam main bars 312. The lower first reinforcing bars 42 and the lower beam main bars 312 have their ends facing each other and are joined via mechanical joints 62 such as couplers. The lower first reinforcing bars 42 have a higher strength and / or a larger diameter than the lower beam main bars 312. The upper first reinforcing bars 41 and the lower first reinforcing bars 42 have the same length and protrusion dimensions from the column 2, and are joined to the beam main reinforcement bars 31 at the same position in the X direction. The upper first reinforcing bars 41 and the lower first reinforcing bars 42 are joined to the beam main reinforcement bars 31 at the end 34 of the beam 3. The distance between the central axis of the upper first reinforcing bar 41 and the central axis of the lower first reinforcing bar 42 is defined as the reinforcing bar central axis distance jt.

[0019] The second reinforcing bars 5 are provided on both the upper and lower sides between the upper first reinforcing bar 41 and the lower first reinforcing bar 42. The second reinforcing bars 5 provided on the upper side between the upper first reinforcing bar 41 and the lower first reinforcing bar 42 are referred to as upper second reinforcing bars 51, and the second reinforcing bars 5 provided on the lower side between the upper first reinforcing bar 41 and the lower first reinforcing bar 42 are referred to as lower second reinforcing bars 52. The upper second reinforcing bars 51 are arranged below the upper first reinforcing bars 41. The lower second reinforcing bars 52 are arranged above the lower second reinforcing bars 52. The upper second reinforcing bars 51 and the lower second reinforcing bars 52 have the same length and the same protruding dimension from the column 2. The upper first reinforcing bars 41, the lower first reinforcing bars 42, the upper second reinforcing bars 51 and the lower second reinforcing bars 52 each have the same protruding dimension from the column 2. The end of the upper second reinforcing bar 51 is positioned below the center of the mechanical joint, and the end of the lower second reinforcing bar 52 is positioned above the center of the mechanical joint.

[0020] The shear reinforcement bars 32 of the beam 3 have a smaller reinforcing bar spacing in a high-density reinforcement region 35 of the beam 3 than in other regions. The high-density reinforcement region 35 is a region of the beam 3 from a first position 36 to a second position 37. The first position 36 is a position in the X direction away from the tensile yield position 313 of the beam main reinforcement 31 toward the center of the beam 3 by the distance jt between the central axes of the reinforcement bars. The second position 37 is the position of the end of the upper second reinforcing bar 51 and the lower second reinforcing bar 52 in the X direction.

[0021] The reinforcement amount of the shear reinforcement 32 in the high-density reinforcement area 35 is the reinforcement amount (value of the product of pw and σwy) at which the shear strength (Vsu) calculated by the following formula (1) is 1.1 times the ultimate bending shear force of the beam 3.

[0022] Vsu=b·jt·pw·σwy(1) b: Beam width (mm) jt: Distance between the center axes of rebars (mm) pw: Shear reinforcement ratio of high density reinforcement area 35 σwy: Reference strength of the shear reinforcement 32 in the high-density reinforcement area 35 (N / mm 2 )

[0023] Next, the operation and effect of the beam-column joint structure 1 according to the present embodiment will be described. In the beam-column joint structure 1 according to the present embodiment, the spacing of the shear reinforcement bars 32 in the beam 3 is set smaller in the high-density reinforcement region 35 than in other regions, preventing damage to the high-density reinforcement region 35, which is the hinge portion of the beam. This ensures that the inherent effect of hinge relocation, which is to prevent damage or destruction of the beam-column joint by moving the hinge away from the end face of the beam, can be achieved. In addition, it becomes possible to provide a mechanical joint 6 at the end 34 of the beam 3, and if the beam 3 is a precast member, it is possible to plan a precast member that is easy to manufacture, transport, and store.

[0024] Furthermore, in the beam-column joint structure 1 according to this embodiment, the reinforcement amount of the shear reinforcement 32 in the high-density reinforcement area 35 is the reinforcement amount (the product of pw and σwy) at which the shear strength (Vsu) calculated by the above formula (1) is 1.1 times the ultimate bending shear force of the beam 3. By adopting such a configuration, cracks can be prevented in the beam concrete portion 33 in the high-density reinforcement area that serves as the hinge portion of the beam 3, and damage can be prevented.

[0025] (Second embodiment) Next, the second embodiment will be described based on the attached drawings. Components and parts that are the same as or similar to those in the first embodiment described above will be designated by the same reference numerals, and their explanation will be omitted. Only configurations that differ from the first embodiment will be described. As shown in Fig. 2, in the beam-column connection structure 1B according to the second embodiment, beams 3B extending in the X direction are joined to a column 2 from both sides in the X direction, similar to the beam-column connection structure 1 according to the first embodiment. In the beam-column connection structure 1B according to the second embodiment, reinforcing bars 7 and steel frames 8 are provided instead of the first reinforcing bars 4 and second reinforcing bars 5 of the first embodiment. In the second embodiment, the upper beam main reinforcements 311 are provided in two rows, one above the other, on the upper side of the beam 3B, and the lower beam main reinforcements 312 are provided in two rows, one above the other, on the lower side of the beam 3B.

[0026] The reinforcing bars 7 are provided in two tiers, one above the other, at the height of both the upper and lower sides of the beam 3. The reinforcing bars 7 provided on the upper side of the beam 3 are referred to as upper reinforcing bars 71, and the reinforcing bars 7 provided on the lower side of the beam 3 are referred to as lower reinforcing bars 72.

[0027] The upper reinforcing bars 71 are arranged at the same height as the upper beam main bars 311. The upper reinforcing bars 71 and the upper beam main bars 311 have their ends facing each other and are joined via mechanical joints 63 such as couplers. The upper reinforcing bars 71 have higher strength and / or a larger diameter than the upper beam main bars 311. The lower reinforcing bars 72 are arranged at the same height as the lower beam main bars 312. The lower reinforcing bars 72 and the lower beam main bars 312 have their ends facing each other and are joined via mechanical joints 64 such as couplers. The lower reinforcing bars 72 have a higher strength and / or a larger diameter than the lower beam main bars 312. The upper reinforcing bars 71 and the lower reinforcing bars 72 have the same length and protrusion dimensions from the column 2, and are joined to the beam main reinforcement bars 31 at the same position in the X direction. The upper reinforcing bars 71 and the lower reinforcing bars 72 are joined to the beam main reinforcement bars 31 at the end 34 of the beam 3. The distance between the central axis of the upper reinforcing bar 71, which is the upper of the two upper and lower rows, and the central axis of the lower reinforcing bar 72, which is the lower of the two upper and lower rows, is defined as the reinforcing bar central axis distance jt.

[0028] The steel frame 8 is arranged between the upper reinforcing bar 71 and the lower reinforcing bar 72, extending in the X direction. The steel frame 8 is an H-shaped steel or the like. One end of the steel frame 8 is joined to the column 2. The other end of the steel frame 8 protrudes further toward the center of the beam 3 than the end of the reinforcing bar 7.

[0029] In the second embodiment, the shear reinforcement bars 32 of the beam 3 have a smaller reinforcing bar spacing in the high-density reinforcement region 35B than in other regions of the beam 3. The high-density reinforcement region 35B is the region of the beam 3 from the first position 36B to the second position 37B. The first position 36 is a position in the X direction away from the tensile yield position 313 of the beam main reinforcement 31 toward the center of the beam 3 by the distance jt between the central axes of the reinforcement bars. The second position 37 is the position of the end of the upper reinforcing bar 71 and the lower reinforcing bar 72 in the X direction. That is, the second position 37 is the center position of the mechanical joint 6.

[0030] The reinforcement amount of the shear reinforcement 32 in the high-density reinforcement area 35B is the reinforcement amount (value of the product of pw and σwy) such that the shear strength (Vsu) calculated by the following formula (1) is 1.1 times the ultimate bending shear force of the beam 3B.

[0031] Vsu=b·jt·pw·σwy b: Beam width (mm) jt: Distance between the center axes of rebars (mm) pw: Shear reinforcement ratio between high density reinforcement areas 35B σwy: Reference strength of the shear reinforcement 32 in the high-density reinforcement area 35B (N / mm 2 )

[0032] The column-beam joint structure 1 according to the second embodiment has the same effects as the column-beam joint structure 1 according to the first embodiment.

[0033] In order to confirm the performance of the beam-column joint structure according to this embodiment, repeated loading tests were conducted on several specimens with different beam-column joint structures, and the results were compared for specimens No. 1, No. 2, No. 4, No. 6, and No. 8 shown below. In specimens No. 2, No. 4, and No. 6, the spacing between the reinforcing bars from the end to the area of ​​the mechanical joint was slightly smaller, but no high-density reinforcement area was provided centrally from the mechanical joint, and the reinforcing bars were evenly distributed throughout the entire length.

[0034] Specimen No. 1 shown in Figure 3 is a conventional beam-column joint structure without hinge relocation. In Specimen No. 1, the main beam reinforcement 31 penetrates the column 2. The shear reinforcement 32 of the beam 3 is evenly distributed throughout the entire length of the beam 3.

[0035] In specimen No. 2 shown in Fig. 4, a reinforcing bar 91 penetrating a column 2 is connected to the beam main reinforcement 31 at the end 34 of a beam 3 with a mechanical joint 6. The reinforcing bar 91 has a higher strength and a larger diameter than the beam main reinforcement 31. Specimen No. 2 does not have the second reinforcing bar 5 and high-density reinforcement area 35 provided in the beam-column joint structure 1 according to the first embodiment described above.

[0036] Specimen No. 4 shown in FIG. 5 has a first reinforcing bar 92 and a second reinforcing bar 93 that penetrate the column 2. The first reinforcing bar 92 is joined to the beam main reinforcement bar 31 at the end 34 of the beam 3 with a mechanical joint 6. The second reinforcing bar 93 protrudes further from the column 2 than the first reinforcing bar 92. The position in the X direction of the tip of the second reinforcing bar 93 is the same as the end of the mechanical joint 6 on the central side of the beam 3. Specimen No. 4 does not have the high-density reinforcement area 35 that is provided in the beam-column connection structure 1 according to the first embodiment described above.

[0037] In specimen No. 6 shown in FIG. 6 , a reinforcing bar 94 penetrating a column 2 is connected to the beam main reinforcement bars 31 at the end 34 of a beam 3 with a mechanical joint 6. The reinforcing bar 94 has a higher strength and a larger diameter than the beam main reinforcement bars 31. In specimen No. 6, a steel frame 95 is provided between the upper and lower reinforcing bars 94 at the end 34 of the beam 3. One end of the steel frame 95 is connected to the column 2. The position in the X direction of the other end of the steel frame 95 is the same as the position in the X direction of the end of the mechanical joint 6 on the beam main reinforcement bars 31 side. Specimen No. 6 has a configuration in which a steel frame 95 is added to specimen No. 2. Specimen No. 6 is provided with a steel frame 95 similar to that of the beam-column connection structure 1B according to the second embodiment, but does not have the high-density reinforcement region 35 provided in the beam-column connection structure 1B according to the second embodiment.

[0038] Specimen No. 8 shown in Figure 7 is a beam-column joint structure 1 of the first embodiment. A first reinforcing bar 4 and a second reinforcing bar 5 are provided to penetrate a column 2. The first reinforcing bar 4 is connected to the main beam reinforcement 31 at the end 34 of the beam 3 with a mechanical joint 6. The shear reinforcement 32 of the beam 3 has a smaller reinforcing bar spacing in the high-density reinforcement region 35 of the beam 3 than in other regions.

[0039] As shown in Figures 3 to 7, in specimens No. 2, 4, 6, and 8, the bending strength of the end 34 of beam 3 was increased compared to specimen No. 1, which resulted in extremely small fractures at the column surface, and the main beam reinforcement yielded at a position slightly away from the end 34 of beam 3. Comparing the load-displacement curve of specimen No. 1 (see Fig. 3(c)) with that of specimen No. 8 (see Fig. 7(c)), it is found that the yield strength (absolute value of load) at R<-0.03 rad. in specimen No. 1 is lower than the yield strength at around R=-0.03 rad., whereas no such decrease was observed in specimen No. 8. This indicates that specimen No. 8 has higher toughness than specimen No. 1. Furthermore, when comparing the load-displacement curve of specimen No. 2 (see Figure 4(c)) with the load-displacement curve of specimen No. 6 (see Figure 6(c)), which is specimen No. 2 with steel frame 95 attached, specimen No. 2, which does not have steel frame 95, shows a sudden drop in strength at around R = -0.04 rad., but specimen No. 6, which has steel frame 95 attached, shows deformation up to around R = -0.05 rad., indicating high toughness.

[0040] Although the embodiment of the beam-column joint structure 1 according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the spirit thereof. For example, in the above embodiment, the beams 3, 3B are joined to the column 2 from both sides in the X direction, but they may be joined from only one side in the X direction, or from at least one side in the X direction and at least one side in the Y direction. In the above embodiment, the reinforcement amount of the shear reinforcement bars 32 in the high-density reinforcement areas 35, 35B is set based on the above formula (1), but may be set as appropriate. In the above embodiment, the column 2 and the beam 3 are each a precast concrete member, but one may be a precast concrete member and the other may be constructed of cast-in-place concrete, or the method may be constructed of cast-in-place concrete. [Explanation of symbols]

[0041] 1,1B Column beam joint structure 2 pillars 3,3B beam 4 First rebar 5 Second rebar 6,61,62,63,64 Mechanical couplings 7. Reinforced concrete 8. Steel Frame 31 Main beam reinforcement 32 Shear reinforcement 34 End 35,35B High density reinforcement area 313 Tensile Yield Position

Claims

1. A column-beam joint structure in which a reinforced concrete column and a reinforced concrete beam are joined, A first reinforcing bar protruding from the column at each of the upper and lower heights of the beam and connected to the main beam reinforcement of the beam at the end of the beam with a mechanical joint; A second reinforcing bar protruding from the column at a height below the upper first reinforcing bar and above the lower first reinforcing bar, and the protruding portion from the column is located at the end of the beam; and a shear reinforcement provided in the beam, The first reinforcing bar has a higher strength and / or a larger diameter than the beam main reinforcing bar, The reinforcing interval of the shear reinforcement is set smaller in the high-density reinforcement region of the beam than in other regions, The high-density reinforcement area is a column-beam joint structure in which the area extends from a position that is the distance between the central axes of the upper first reinforcing bar and the central axis of the lower first reinforcing bar toward the center of the beam from the tensile yield position of the main beam reinforcing bar to the position of the end of the second reinforcing bar.

2. A column-beam joint structure in which a reinforced concrete column and a reinforced concrete beam are joined, Reinforcing bars protruding from the column at the height of each of the upper and lower parts of the beam and connected to the main beam reinforcement of the beam at the end of the beam with mechanical joints; a steel frame joined to the column at a height between the upper reinforcing bar and the lower reinforcing bar and disposed at the end of the beam; and a shear reinforcement provided in the beam, The reinforcing bars have a higher strength and / or a larger diameter than the beam main bars, The reinforcing interval of the shear reinforcement is set smaller in the high-density reinforcement region of the beam than in other regions, The high-density reinforcement area is a beam-column joint structure in which the area extends from the tensile yield point of the main beam reinforcement toward the center of the beam by the distance between the central axes of the upper and lower reinforcing bars to the position of the end of the reinforcing bar.

3. 3. The column-beam joint structure according to claim 1 or 2, wherein the reinforcement amount of the shear reinforcement in the high-density reinforcement area is a reinforcement amount such that the shear strength (Vsu) calculated by the following formula (1) is 1.1 times the bending ultimate shear force of the beam. Vsu=b・jt・pw・σwy...(1) b: Beam width (mm) jt: Distance between the center axes of rebars (mm) pw: Shear reinforcement ratio in the high-density reinforcement area σwy: Standard strength of shear reinforcement in high-density reinforcement area (N / mm ２ )

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