Column-beam joint structure

Abstract

To provide a column beam joint structure that can reduce the risk of damage such as cracks occurring at the joint where a flat beam and an orthogonal beam intersect due to twisting that occurs between the flat beam and the orthogonal beam during an earthquake or the like.SOLUTION: In a joint structure 100, a column 10, a flat beam 20 having a beam width wider than a column width of the column 10, and an orthogonal beam 30 that is orthogonal to the column 10 and the flat beam 20 and has beam width of less than or equal to the width of the beam are connected. There are arranged a plurality of beam main reinforcements 31 extending linearly in the longitudinal direction of the orthogonal beam 30 throughout the orthogonal beam 30 continuously through an overhanging portion 41 which is the joint portion with the flat beam 20 inside of the column 10 and the orthogonal beam 30 and a plurality of auxiliary bars 33 protruding from the outside of the beam width of the flat beam 20 into the orthogonal beam 30 through the overhanging portion 41 from the column 10 and extending linearly in the longitudinal direction of the orthogonal beam 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a structure at a joint between a column, a flat beam, and an orthogonal beam. [Background technology]

[0002] In buildings with reinforced concrete rigid frame structures, a flat beam construction method has been proposed that uses flat beams with a width wider than the width of the columns. This flat beam construction method keeps the beam depth small and allows an open space to be created under the beams, making it possible to ensure sufficient interior height while lowering the overall height of the building (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-85189 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional flat beam construction method, there was a risk of damage such as cracks occurring at the joints where the flat beams and the orthogonal beams intersect due to twisting that occurs between the flat beams and the orthogonal beams during earthquakes, etc.

[0005] In consideration of the above, the present invention aims to provide a column-beam joint structure that can reduce the risk of damage such as cracks occurring at the joint where a flat beam and an orthogonal beam intersect due to torsion that occurs between the flat beam and the orthogonal beam during an earthquake, etc. [Means for solving the problem]

[0006] The present invention provides a joint structure in which a column, a flat beam having a beam width wider than the column width of the column, and an orthogonal beam perpendicular to the column and the flat beam and having a beam width equal to or less than the beam depth are connected, and is characterized in that a plurality of orthogonal beam main reinforcements extend linearly in the longitudinal direction of the orthogonal beam continuously throughout the interior of the column and the orthogonal beam via the joint with the flat beam, and a plurality of auxiliary reinforcements protrude from the column from the joint outside the beam width of the flat beam into the interior of the orthogonal beam and extend linearly in the longitudinal direction of the orthogonal beam.

[0007] According to the present invention, the presence of the auxiliary reinforcement makes it possible to suppress damage such as cracks at the joint where the flat beam and the orthogonal beam intersect due to torsion occurring between the flat beam and the orthogonal beam during an earthquake, etc. In addition, since the auxiliary reinforcement protrudes into the orthogonal beam by a predetermined length greater than the beam width of the flat beam, even if the orthogonal beam is damaged by torsion, the damaged part is at least a predetermined length away from the joint interface between the flat beam and the orthogonal beam, making it possible to easily repair the damage.

[0008] In the present invention, when the beam depth of the orthogonal beam is D, it is preferable that the reinforcing bars protrude from the outer side of the beam width of the flat beam by a distance of D / 10 or more and D or less.

[0009] The reason why the protruding length of the auxiliary reinforcement is preferable to be D / 10 is based on the fact that, as described below, the inventors produced a test specimen in which the protruding length of the auxiliary reinforcement was D / 4 and conducted an alternating positive and negative load test on this test specimen, and found that no penetrating cracks were found in the orthogonal beams, meaning that there was still room for cracking in the test specimen.

[0010] On the other hand, the protruding length of the auxiliary reinforcement is equal to or less than D because if the protruding length exceeds D, there is a risk that the torsion of the flat beam will not be sufficiently transmitted to the orthogonal beam.

[0011] In the present invention, when the beam depth of the orthogonal beam is D, it is preferable that the reinforcing bars protrude from the outside of the beam width of the flat beam by a distance of D / 4 or more and D or less.

[0012] This is based on the fact that, as mentioned above, when alternating positive and negative load tests were conducted on specimens with a protruding length of the auxiliary reinforcement of D / 4, no penetrating cracks were found in the orthogonal beams. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view in an XY plane of a column-beam joint structure according to an embodiment of the present invention. [Diagram 2] Schematic cross-sectional view taken along line II-II in Figure 1. [Diagram 3] Schematic cross-sectional view taken along line III-III in Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A column-beam joint structure 100 according to an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 3. Note that Fig. 1 to Fig. 3 are diagrams for explaining the present embodiment in a schematic manner, and the dimensions are exaggerated.

[0015] The column-beam joint structure 100 is an integrally constructed reinforced concrete (RC) structure including a column 10, a flat beam 20, an orthogonal beam 30 perpendicular to the column 10, and a joint 40 formed by joining these at their intersection. The column-beam joint structure 100 or a structure including the column-beam joint structure 100 may be made of cast-in-place concrete or half-precast concrete.

[0016] The flat beam 20 is a flat beam having a beam width wider than the beam depth, and the beam width is wider than the column width of the column 10. The ratio of the beam width of the flat beam 20 to the column width of the column 10 is preferably 3 or less. The orthogonal beam 30 is a non-flat beam having a beam depth equal to or greater than the beam width. The beam width of the orthogonal beam 30 is preferably 1 / 3 or less of the beam width of the flat beam 20. In addition, the beam depth of the orthogonal beam 30 is preferably equal to or greater than the beam depth of the flat beam 20.

[0017] The part of the flat beam 20 that protrudes outward from the side surface of the column 10 in the beam width direction of the flat beam 20 from the joint 40 serves as a protruding part 41. This protruding part 41 corresponds to the joint with the flat beam of the present invention.

[0018] The portion of the protruding portion 41 that protrudes outward from the side surface of the orthogonal beam 30 forms a beam joint 42 formed by the intersection of the flat beam 20 and the orthogonal beam 30. It is preferable that the dimension of the portion of the protruding portion 41 that protrudes from the side surface of the column 10 is equal to or smaller than the column width and column height, and equal to or smaller than twice the beam height of the flat beam 20.

[0019] Here, we will explain the case where the axis Oc of the column 10 and the axis Og of the flat beam 20 intersect, i.e., the column 10 is joined to the flat beam 20 without eccentricity, but there may be eccentricity between them, i.e., the column 10 is joined to the flat beam 20 with an offset thereto.

[0020] In addition, here, we will explain the case where the axis Oc of the column 10 and the axis Or of the orthogonal beam 30 intersect, i.e., the column 10 is joined to the orthogonal beam 30 without eccentricity, but there may be eccentricity between them, i.e., the column 10 may be joined to one side relative to the orthogonal beam 30.

[0021] In the following description, the direction in which the axis Og of the flat beam 20 extends is the X-axis direction, the direction in which the axis Oc of the column 10 extends is the Z-axis direction, and the direction in which the axis Or of the orthogonal beam 30 extends, perpendicular to the X-axis and Z-axis, is the Y-axis direction.

[0022] In the column 10, a plurality of linear column main reinforcements 11 extending in the Z-axis direction and a plurality of square-shaped hoop reinforcements (shear reinforcement) 12 surrounding the outer periphery of these column main reinforcements 11 and spaced apart in the Z-axis direction are arranged. The column main reinforcements 11 extend within the adjacent columns 10 in the Y-axis direction via joints 40.

[0023] A plurality of linear beam main reinforcements 21 extending in the X-axis direction are arranged in the flat beam 20. The beam main reinforcements 21 may be arranged at equal intervals in the Y-axis direction, but are preferably arranged so that the intervals are narrower inside the column compared to outside the column. The beam main reinforcements 21 extend in the flat beams 20 adjacent in the X-axis direction via the joints 40 and the protruding parts 41.

[0024] In addition, in the flat beam 20, a plurality of square-shaped stirrups (shear reinforcement bars) 22 are arranged at intervals in the X-axis direction, surrounding the outer periphery of the beam main reinforcement bars 21. Although not shown, it is preferable that core bars are also arranged to connect the stirrups 22 in the middle in the Z-axis direction.

[0025] Furthermore, in the column 10 and the protruding portion 41, in the portion outside the beam width of the orthogonal beam 30 in the column depth, one torsion reinforcement bar 23 is arranged so as to surround each of the multiple beam main reinforcements 21. Note that each of the multiple torsion reinforcements 23 may be arranged at intervals in the X-axis direction.

[0026] The torsional reinforcement 23 is divided into two pieces, each of which is U-shaped. The torsional reinforcement 23 is arranged from the end face side of the flat beam 20 on the orthogonal beam 30 side toward the inside of the joint 40 so as to surround the outside of the beam main reinforcement 21.

[0027] Furthermore, in the area of ​​the flat beam 20 that is outside the column height, i.e., in the beam joint 42 that is outside the side of the column 10 in the Y-axis direction, multiple L-shaped shear reinforcement bars 24 are arranged at intervals in the X-axis direction to surround the outside of multiple beam main reinforcements 21.

[0028] It is preferable that the shear reinforcement 24 is arranged over the entire outer side of the column height of the flat beam 20, but it may be arranged only within the range of the outer side of the column height of the flat beam 20 that is necessary for cross-sectional calculations.

[0029] In the orthogonal beams 30, a plurality of linear beam main reinforcements 31 are arranged, which penetrate the joints 40 and the protruding parts 41 and extend continuously in the Y-axis direction throughout the two adjacent orthogonal beams 30. The beam main reinforcements 31 correspond to the beam main reinforcements of the present invention. In addition, in the orthogonal beams 30, except for the joints 40 and the protruding parts 41, a plurality of square-shaped hoop reinforcements (shear reinforcement reinforcements) 32 are arranged at intervals in the Y-axis direction, surrounding the outer periphery of the plurality of beam main reinforcements 31.

[0030] Furthermore, in addition to the beam main reinforcement 31, the orthogonal beam 30 is provided with linear reinforcing bars 33 extending in the Y-axis direction via the joints 40 and the protruding portions 41. These reinforcing bars 33 correspond to the reinforcing bars of the present invention. The reinforcing bars 33 protrude into the orthogonal beam 30 by a predetermined length X beyond the beam width of the flat beam 20. For example, when the beam depth of the orthogonal beam 30 is D, the predetermined length X is D / 10 or more and D or less, and more preferably D / 4 or more and D or less.

[0031] The reinforcing bars 33 are spaced apart in the X-axis direction, here at the same intervals as the beam main reinforcing bars 21, and are spaced apart in the Y-axis direction, here at intervals narrower than the intervals of the beam main reinforcing bars 31 so as to be located between the beam main reinforcing bars 21. The reinforcing bars 33 have anchoring parts 33a at both ends. The amount of reinforcing bars 33 may be equal to or greater than the minimum amount of reinforcing bars determined from the desired allowable torsional stress.

[0032] Additionally, within the protruding portion 41, a number of U-shaped bar bars (torsion reinforcement bars) 34 are arranged at intervals in the Y-axis direction so as to surround the multiple reinforcing bars 33 and the beam main reinforcement bars 31. Here, the bar bars 34 are arranged so as to extend downward from the upper surface side that contacts the beam main reinforcement bars 31 at the upper end, so as to contact the reinforcing bars 33 at the lower end. However, the bar bars 34 do not have to be arranged.

[0033] In this way, the presence of the auxiliary reinforcement 33 and also the hairpin reinforcement 34 makes it possible to prevent damage such as cracks from occurring at the intersection of the flat beam 20 and the orthogonal beam 30 due to twisting that occurs between the flat beam 20 and the orthogonal beam 30 during an earthquake, etc.

[0034] In addition, since the auxiliary reinforcement 33 protrudes into the orthogonal beam 30 by a predetermined length X beyond the beam width of the flat beam 20, even if the orthogonal beam 30 is damaged due to twisting, the damaged area will be at least the predetermined length X away from the joint interface between the flat beam 20 and the orthogonal beam 30, making it possible to easily repair the damage.

[0035] The inventors produced a test specimen in which the protruding length X of the reinforcing bars 33 was set to D / 4. Then, the flat beams 20 and the orthogonal beams 30 of this test specimen were subjected to 10 cycles of alternating positive and negative load tests of 1 / 50·rad in sequence.

[0036] As a result, no through cracks (structural cracks) were found in the orthogonal beam 30, and the maximum crack width was 0.06 mm. This shows that if the protruding length X of the reinforcing bars 33 is D / 4, it is possible to sufficiently prevent damage to the orthogonal beam 30 due to torsion. And, since there was still room for cracks in the test specimen, it is presumed that if the protruding length X of the reinforcing bars 33 is about D / 10, it is possible to prevent damage to the orthogonal beam 30 due to torsion.

[0037] On the other hand, if the protruding length X of the flat beam 20 of the reinforcing bar 33 is too long, the torsion of the flat beam 20 may not be sufficiently transmitted to the orthogonal beam 30. Therefore, it is presumed that the protruding length X of the reinforcing bar 33 is preferably equal to or less than D so that the torsion of the flat beam 20 is sufficiently transmitted to the orthogonal beam 30.

[0038] The present invention is not limited to the beam-column joint structure 100 specifically described in the above embodiment, and can be modified as appropriate within the scope of the claims.

[0039] For example, although the structure in which the upper surfaces of the flat beam 20 and the orthogonal beam 30 coincide has been described, the present invention may be applied to a structure in which the lower surfaces of the flat beam 20 and the orthogonal beam 30 coincide. In this case, since the lower end bar of the beam main reinforcement 21 of the flat beam 20 is located lower than the lower end bar of the beam main reinforcement 21 of the orthogonal beam 30, the torsional reinforcement bar may be inserted from the lower surface side of the flat beam 20 to restrain the lower end bar of the beam main reinforcement 21 of the flat beam 20.

[0040] Although the structure in which the flat beam 20 and the orthogonal beam 30 intersect in a cross shape in a plan view has been described, the present invention may be applied to a structure in which the flat beam 20 and the orthogonal beam 30 are connected in a U-shape in a plan view. In this case, for example, the axis Oc of the column 10 and the axis Or of the orthogonal beam 30 do not intersect, and the outer surfaces of the column 10 and the orthogonal beam 30 are flush with each other. The beam main reinforcement 21 may have an anchoring portion at the end of the outer surface of the flat beam 20 that is flush with the outer surface of the column 10.

[0041] Furthermore, it may be applied to a structure in which the flat beam 20 and the orthogonal beam 30 are connected in an L-shape in a plan view. In this case, the reinforcing bar 33 may be protruded from the inside of the column 10 via the protruding portion 41 to one orthogonal beam 30 by a predetermined length X. [Explanation of symbols]

[0042] 10...column, 11...main column bars, 12...hoop bars (shear reinforcement), 20...flat beam, 21...main beam bars, 22...stirrup bars (shear reinforcement), 23...torsion reinforcement, 24...shear reinforcement, 30...orthogonal beam, 31...main beam bars, 32...hoop bars (shear reinforcement), 33...auxiliary bars, 34...hairpin bars (torsion reinforcement), 40...joint, 41...projection part (joint with flat beam), 42...beam joint, 100...column-beam joint structure, D...beam depth of orthogonal beam, Oc...axis center of column, Og...axis center of flat beam, Or...axis center of orthogonal beam, X...projection length.

Claims

1. A joint structure in which a column, a flat beam having a beam width wider than the column width of the column, and an orthogonal beam perpendicular to the column and the flat beam and having a beam width equal to or less than the beam depth are connected, A plurality of beam main reinforcements extending linearly in the longitudinal direction of the orthogonal beam continuously through the joint between the column and the orthogonal beam and the flat beam throughout the entire orthogonal beam; A column-beam joint structure characterized in that a plurality of auxiliary reinforcements are arranged from the column through the joint, protruding from the outside of the beam width of the flat beam to the inside of the orthogonal beam and extending linearly in the longitudinal direction of the orthogonal beam.

2. The column-beam joint structure according to claim 1, characterized in that, when the beam depth of the orthogonal beam is D, the auxiliary reinforcement protrudes from the outside of the beam width of the flat beam by more than D / 10 and less than D.

3. The column-beam joint structure according to claim 1, characterized in that, when the beam depth of the orthogonal beam is D, the auxiliary reinforcement protrudes from the outside of the beam width of the flat beam by a distance of D / 4 or more and D or less.

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