JP2009144500A - Shearing reinforcement structure for column-beam joint part of uppermost story - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve shearing strength of an upper part (portion above a hoop 6 directly under an anchor plate 20) of a column-beam joint part which is conventionally a plain concrete part when the anchor plate 20 of a main reinforcement 1 for a column is arranged at a lower part of an upper-end reinforcement 10 for a beam in a column-beam joint part of an uppermost story of a reinforced concrete building or the like. <P>SOLUTION: Main reinforcements 1 for a column located in at least four corners are projected above an anchor plate 20 for forming upper end projected parts 8. An outer periphery of the upper-end projected parts 8 are enclosed and upper-end part hoops 6A, 6B are provided, so as to form the column-beam joining part structure 50. The upper-end part hoops 6A, 6B are arranged in a necessary quantity according to an acting shearing force of the column-beam joint part. The upper-end hoop 6B is arranged right above the upper-end reinforcement 10 for the beam while the upper-end hoop 6A is arranged at the lower part of the upper-end reinforcement 10 for the beam and also near a location just above the anchor plate 20. They are selected and arranged respectively according to the necessary quantity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a shear reinforcing structure for a beam-beam joint in the uppermost layer, which is applied to the uppermost layer and the uppermost layer in which no layer is formed above the floor in a reinforced concrete structure such as a reinforced concrete structure or a steel reinforced concrete structure.

  In general, in a reinforced concrete structure, in order to fix the reinforcing bar in the concrete, the ends of the reinforcing bar are bent and processed. The end portion of the beam main reinforcing bar 10 in the uppermost column beam joint portion was bent downward to form a tip bent portion 55, and was placed in the cross section of the column 30 (see FIG. 7).

  Moreover, in the column located in the uppermost layer, the uppermost end portion of the column main reinforcement is bent 180 ° downward to form a U-shaped hook (for example, see Non-Patent Document 1 and Patent Document 1). In this case, the joint from the band just below the hook to the upper part becomes “unreinforced concrete (capital unreinforced section)”, and there was a problem that the required joint shear strength could not be ensured (hereinafter referred to as “the problem of unreinforced concrete part”). "). Non-Patent Document 1 makes two proposals (excluding proposals for column fixing stubs) to solve the problem (hereinafter referred to as “first proposal”).

  However, in those proposals, it was almost difficult to secure the anchorage length required for the column main reinforcements because of ordinary beams. Even if the necessary fixing length can be ensured, the number of reinforcing bars intersecting the column beam joint is too dense, and it is difficult to arrange the bars effectively.

  In order to avoid this, for example, a portion called a fixing stub 53 is protruded above the beam 40 (on the roof slab), and bending of the upper end of the column 30 is processed above the beam to obtain a necessary fixing length. (Hereinafter referred to as “second proposal”). In this case, the fixing stub (the upper end of the column) protrudes greatly on the roof slab, which is not preferable for waterproofing of the roof slab, makes it difficult to use the roof, and further reduces the width of the roof design. (The fixing plate 20 is used, but see FIG. 7).

  Accordingly, attempts have been made to minimize the fixing length as much as possible. For example, several so-called mechanical fixing methods have been proposed in which a fixing plate 20 (protrusions in a direction perpendicular to the reinforcing bars) is provided at the upper end portion of the column main reinforcement 1 and bending of the end portion of the column main reinforcement 1 is omitted. (FIGS. 5 to 7, Patent Documents 2 to 6).

  Non-Patent Document 2 also proposes using a mechanical fixing method that can shorten the necessary fixing length (hereinafter referred to as “third proposal”).

(1) When this mechanical fixing method is adopted, it is also proposed that the fixing plate be arranged above the uppermost bar of the beam upper bar when applying to the uppermost column beam joint (hereinafter referred to as the uppermost bar). , “Fourth proposal.” FIG. 12 of Patent Document 2, Patent Document 3).

(2) Further, when the mechanical fixing method is adopted, when it is applied to the uppermost column beam joint, if the cover thickness above the fixing plate 20 is to be secured within the beam, the fixing plate 20 is removed. Therefore, it is necessary to position the upper end of the upper end of the beam below the uppermost bar (the main reinforcing bar positioned at the uppermost position of the beam 40). As a result, an “unreinforced concrete portion 56” (FIGS. 5 and 6) having no shear reinforcement is generated above the band just below the fixing plate 20. In view of this, it has also been proposed to arrange a substantially inverted U-shaped reinforcing bar 22 from above the upper end of the beam so as to include the joint as a shear reinforcing bar for the part (hereinafter referred to as “fifth”). Proposal ", Fig. 5, Patent Document 4, Patent Document 5).

(3) Also, when the mechanical fixing method is adopted, when applied to the uppermost column beam joint, an external force that yields the column 30 acts on the column beam joint, and a large shear force acts. In some cases, if there is an unreinforced concrete part at the top of the beam-column joint, the required shear strength of the joint cannot be ensured no matter how much the bar is placed below it. It has been demanded to arrange the reinforcing bars. In order to realize this, it has been necessary to form the fixing stub 53 by projecting the column main reinforcement 1 above the beam 40 (upper part of the roof slab) (hereinafter referred to as “sixth proposal”, FIG. 7).
JP 2003-253753 A JP-A-6-57952 JP-A-4-68149 JP2003-105923A JP2004-1003009A JP 2002-276078 Edited by Architectural Institute of Japan, “Reinforced Concrete Reinforcement Guidelines and Explanation”, Architectural Institute of Japan, September 5, 1986, 2nd edition, p. 166-175 Edited by Architectural Institute of Japan, “Reinforced Concrete Reinforcement Guideline and Explanation”, Architectural Institute of Japan, November 1, 2003, 4th edition (2003 edition), p. 136, p. 196-199

(1) In the first proposal (an improvement plan of Non-Patent Document 1) that solves the problem of “unreinforced concrete part”, in most normal buildings, the necessary fixing length cannot be secured. Even if it could be secured, there were construction problems.

(2) In the second and sixth proposals (providing the fixing stub 53) for securing the necessary fixing length, as shown in the conventional example in which the fixing plate 20 is not used, the use of the rooftop is poor. The problem was also great in terms of construction and waterproofing.

(3) In the third proposal (mechanical fixing method), the problem of “unreinforced concrete” is not solved when the fixing plate is placed below the upper end of the beam. Furthermore, in the uppermost column beam joint portion of the outer column, a split crack (reference numeral 61 in FIG. 4B) is generated from the corner portion, so that the shear strength of the column beam joint portion is significantly reduced.

(4) In the fourth proposal of the prior art (the fixing plate is arranged above the uppermost streak of the beam upper end), the necessary fixing length is secured and the stirrup is placed throughout the joint. Although the problem of “unreinforced concrete” can be solved, it is necessary to increase the length of the beam in order to secure a predetermined concrete cover thickness above the fixing plate, which is difficult to implement. there were. This is because if the beam is made larger, the concrete is wasted and the height of the building must be increased unnecessarily.

(5) In the fifth proposal (with a substantially inverted U-shaped reinforcing bar), the “unreinforced concrete portion 56” (FIGS. 5 and 6) above the band just below the fixing plate 20 is used. Since there is no column main reinforcement, it is impossible to arrange a reinforcing bar that is effective as a shear reinforcement, resulting in an “unreinforced concrete” part. Therefore, although a substantially inverted U-shaped reinforcing bar 22 is arranged as the shear reinforcing bar of the part, the shear reinforcing effect cannot be expected as much as the band bar, and the entire beam-column joint required by the design is sheared. There was a problem that the yield strength was insufficient. In particular, in the case where the upper end of the beam is a two-stage reinforcement, the range of the “unreinforced concrete portion 56” where the band 6 is not arranged becomes large, so that the shear strength deficiency of the column beam joint is remarkable ( FIG. 6).
In order to ensure the required shear strength, a considerably large number of the reinforcing bars 22 and the substantially inverted U-shaped reinforcing bars 22 below the fixing plate 20 are arranged, that is, the diameter of the reinforcing bars is increased and the number of the reinforcing bars 22 is increased. Since it is necessary to increase considerably, it is difficult to arrange the bar, and there is a problem in concrete filling, and it is difficult to actually adopt it.

(6) An object of the present invention is to solve the above-mentioned problems, that is, all the problems a to d below.
a. The fixing length of the column main bars is secured within the normal beam without using fixing stubs.
b. Secure the cover thickness of the main column bars within the normal concrete cover thickness of the top beam of the beam.
c. With the structure in which the fixing plate is provided below the upper end of the beam, the problem is that the upper part of the band just below the fixing plate becomes “unreinforced concrete” and the shearing force of the joint is reduced.
d. Prevents a decrease in yield strength of the joint due to a split crack from the corner.

  In the present invention, in the case where the fixing plate at the upper end of the column reinforcement is arranged below the upper end of the beam, the upper portion of the joint of the column beam which has conventionally been an unreinforced concrete portion (above the band just below the fixing plate 20). In order to shear-reinforce the upper part of the upper end band, the column main bars located at the four corners protrude above the fixing plate to form the upper end protrusion, and surround the outer periphery of the upper end protrusion. It is to arrange the muscle. If necessary, upper end protrusions are formed on other column main bars (for example, outer column main bars other than the four corners, column main bars other than the outer periphery, etc.) to arrange the “upper end band”.

  It has been a long-standing problem in the Architectural Institute of Japan to solve the “problem of unreinforced concrete” after securing the anchorage length within the normally designed beam (Non-Patent Document 1, Non-Patent Document 1, Patent Document 2) solves all the problems by enabling the present invention to arrange a necessary amount of band reinforcement (shear reinforcement) in the part that becomes unreinforced concrete.

  Further, the “upper end strip” arranges a necessary amount (two or more pairs) of strips in accordance with the column beam joint shearing force acting. The position is selected from the vicinity immediately above the upper end of the beam, the vicinity immediately below the upper end of the beam, or the vicinity immediately above the fixing plate, or the bars are arranged at all positions.

That is, the present invention relates to the shear of the uppermost beam-column joint characterized by satisfying all of the following conditions at the joint between the column and the beam in the uppermost layer of the reinforced concrete structure in which the column main reinforcement is arranged. Reinforcement structure.
(1) A fixing plate is attached to the upper end portion of the column main reinforcement.
(2) The fixing plate is positioned below the “uppermost bar of the beam upper bar” of the beam.
(3) The upper end of the column main bar protrudes upward from the fixing plate to form an “upper end protrusion”, and the upper end of the “upper end protrusion” is a distance from the “uppermost bar of the upper end of the beam”. Project upward by H.
(4) In the “upper end projecting portion” of the column main bar, the “first upper end band” is surrounded by the outer periphery of each “upper end projecting portion” in the vicinity immediately above the “uppermost streak of the beam upper end muscle”. ”.
(5) In the “upper end projecting portion” of the column main bar, the “second projecting portion” is surrounded by the “second upper end projecting portion” below the “beam upper end rebar” and above the fixing plate. Arrange the top strip.
(6) The predetermined distance H is formed to such a length that the “first upper end band” can be arranged, and a fixing plate is not provided at the predetermined distance H.
(7) A substantially inverted U-shaped reinforcing bar formed by connecting both ends of two vertical bars arranged along the columnar main bar with a horizontal bar is the “first upper end band” in a plan view. The horizontal bar is located above the uppermost bar of the beam upper bar, and is arranged in at least one direction perpendicular to the beam upper bar or parallel to the beam upper bar.
(8) The beam is set within the normal cover thickness of the beam top bar.

  Further, in the above, in the “upper end protruding portion” of the columnar main bar, the other “third upper end band streaks surrounding the outer peripheral side of the“ upper end protruding portion ”between the fixing plate and the lower surface of the beam upper end reinforcement. Is a shear reinforcement structure of the uppermost column beam joint.

According to another aspect of the present invention, there is provided an uppermost column-beam joint characterized by satisfying all of the following conditions in a joint between a column and a beam in the uppermost layer of a reinforced concrete structure in which the column main reinforcement is arranged: This is a shear reinforcement structure.
(1) A fixing plate is attached to the upper end portion of the column main reinforcement.
(2) The fixing plate is positioned below the “uppermost bar of the beam upper bar” of the beam.
(3) The upper end of the column main bar protrudes upward from the fixing plate to form an “upper end protruding portion”.
(4) In the “upper end projecting portion” of the column main bar, the “one first projecting portion” is surrounded by the “upper end projecting portion” below the “beam upper end rebar” and above the fixing plate. 2 upper strips ".
(5) At the “upper end protrusion” of the column main bar, near the “uppermost bar of the beam upper bar” or near the “other beam upper bar”, on the outer peripheral side of each “upper end protrusion” The “other second upper end band” is arranged around.
(6) No other fixing plate is provided on the upper end protrusion.
(7) A substantially inverted U-shaped reinforcing bar formed by connecting both ends of two vertical bars arranged along the column main bar with a horizontal bar. And located in at least one direction perpendicular to the beam upper end line or parallel to the beam upper end line.
(8) The beam is set within the normal cover thickness of the beam top bar.
It is a premise that each reinforcing bar in the above has a predetermined concrete cover thickness.

  In addition, the “fixing plate” described above may have any shape or structure as long as it has a portion protruding in a direction perpendicular to the axis of the column main reinforcement in order to increase the fixing force with the concrete.

  In addition, the “beam upper bar” in the above indicates a beam main bar arranged on the upper end side among the beam main bars arranged on the upper end side and the lower end side in the normal beam direction. In addition, the upper end of the beam may be arranged in two upper and lower stages (upper and lower), and the lower part of the upper end of the beam mainly refers to the lower part of the lower part or near the lower part. It can also be in the immediate vicinity.

  In addition, the “uppermost bar of the beam upper bar” in the above refers to the upper bar of the beam when the beam upper bar is one level, and refers to the upper bar when the beam is two levels. Point to the top streaks.

  In addition, the lower part of the “beam upper bar” in the above refers to a horizontal part in which the beam upper bar functions as a structural reinforcing bar. For example, when bent downward for fixing, the bent part is excluded. It is.

In addition, in the above, in the vicinity immediately below the “uppermost bar of the beam top bar” or in the vicinity of the “other beam top bar”,
・ When there is only one beam top bar, near the upper beam of the beam (= uppermost bar) ・ When there are two beam upper bars, directly below the upper beam upper bar (= uppermost bar) Near ・ When there are three beam upper bars, it means the vicinity immediately below the upper beam upper bar (= uppermost bar) or the position immediately below the middle beam upper bar.

  Conventionally, an unreinforced concrete portion 56 is formed by forming an upper end protruding portion above the fixing plate at the column main reinforcement to which the fixing plate is attached, and arranging an “upper end strip” effective as a shear reinforcement at the upper end protruding portion. The upper part of the beam-to-column joint (the upper part from the band just below the fixing plate 20) can be shear-reinforced, and not only the “upper band” but also the column of the upper protruding part. Resistance to the shear cracks 60 and 60 generated in the beam-column joint at the upper part of the fixing plate increases the shear strength of the beam-column joint, thereby ensuring the shear strength of the beam-column joint required in the design ( FIG. 4 (a)). In addition, the column main reinforcement and the “upper end strip” that form such an upper end protrusion also resist the split cracks 61 and 61 from the corners at the uppermost column beam joint of the outer column, The joint strength can be improved. (FIG. 4B).

  In addition, by forming the upper end protruding portion of the column reinforcement, it is possible to arrange the “upper end strip” of the quantity (two or more sets) necessary for securing the shear strength of the joint.

  In addition, according to the present invention, since it is not necessary to arrange the column fixing plate on the beam upper end bar, the beam bar need not be enlarged in order to secure the cover thickness of the reinforcing bar.

  In addition, since it is possible to arrange the strips throughout the joints including the upper end protrusions of the column main bars at the column beam joints, compared to the conventional case, the strips below the fixing plate and the substantially inverted U-shape. Since the reinforcing bars can be greatly reduced, there are effects such as cost reduction and improvement of concrete filling property.

  In addition, since it is possible to place a reinforcing bar as a shear reinforcement bar on the entire joint, there is no need to project a fixing stub above the roof slab. Can be resolved.

  Moreover, since a shear strength can be further increased by using a substantially inverted U-shaped reinforcing bar in combination, a more appropriate design can be achieved. In this case, when the horizontal reinforcement 24 is arranged in the direction orthogonal to the axial direction of the beam upper end reinforcement 10 and the reinforcement reinforcement 22 is arranged, the substantially inverted U-shaped reinforcement reinforcement mainly includes the shear crack 60, 60 (FIG. 4 (a)). When the horizontal bars 24 are arranged in a direction parallel to the axial direction of the beam upper end bars 10 and the reinforcing bars 22 are arranged, the corner bars are used. This has the effect of increasing the prevention of the split cracks 61, 61 (FIG. 4B).

  In general, the present invention solves the conventional problems, and can easily secure the required joint shear strength with a small amount of reinforcing bars and simple construction, and has good concrete filling properties. A beam joint can be provided.

  An embodiment of the present invention will be described with reference to FIGS.

[1] Configuration of column beam joint 50

  An example of a construction procedure for constructing the beam-column joint (shear reinforcement structure of the uppermost beam-column joint) 50 is shown. The construction procedure is not limited to this example, and any conventional construction procedure can be adopted.

(1) The main bars 1 and 1 are built in the usual way.

(2) The lower beam bars 14 and 14 (the main reinforcing bar located on the lower end side of the beam bar), the stirrups 16 and 16 so as to intersect with the column main bars 1 and 1 by a normal method. Reinforce (beam shear reinforcement).

(3) By means of a normal method, band bars (column shear reinforcement bars) 6 and 6 are bundled and temporarily placed on beam bottom bars 14 and 14 at the beam-column joint.

(4) The fixing plate 20 is attached to the upper ends of the column main bars 1 and 1 by a normal method, and the fixing plate 20 is fixed to a predetermined height, that is, the beam upper bars (of the beam main reinforcing bars, It is located below the main rebar) 10 located on the upper end side of the beam. In this case, the fixing plates 20 and 20 are positioned a predetermined length below the upper end 2 of the column main reinforcement 1, and the fixing plates 20 and 20 are temporarily fixed and can be adjusted in position.

(5) The beam upper end bars 10 and 10 are arranged in the ribs 16 and 16 that have been arranged in advance, and intersect with the column main bars 1 and 1 by a normal method.

(6) The column main bars are such that the fixing plates 20 and 20 are at a predetermined height, and the height positions of the upper ends 2 and 2 of the column main bars 1 and 1 are at a height H from the upper surface 11 of the beam upper bar 10. 1. Adjust the position of the fixing plate 20 (FIG. 3), confirm the position, inject grout into the fixing plate 20, and fix the fixing plate 20 to the columnar bars 1, 1. Here, it is preferable that the fixing plate 20 has a predetermined concrete cover thickness and is disposed as close as possible to the beam upper-end bar 10 (as close to the lower surface 12 of the beam upper-bar bar 10).
Further, as will be described later, the height H is required to be as short as possible in order to secure the concrete cover thickness, and an amount that allows the upper end strip 6 to be arranged above the upper end of the beam 10 is necessary. . Therefore, the upper end of the upper end protruding portion 8 of the column main reinforcing bar 1 is accommodated in the concrete cover thickness, and no protrusions are formed from the upper surface of the slab like the conventional fixing stub 53 (FIG. 7) (FIG. 1, FIG. 2). Accordingly, as shown in FIG. 7, the fixing plate 20 is not further attached to the upper end protruding portion 8 of the column main reinforcing bar 1 (FIGS. 1 and 2).

  In addition, the concrete cover thickness should just ensure the minimum quantity normally prescribed | regulated by law. However, the upper surface of the concrete slab may be stretched and the slab thickness may be increased by the so-called “fracture” in the normal construction range, but this does not prevent it and belongs to the concrete cover thickness range.

(7) The bars 6 and 6 are placed at the beam-column joints below the beam top bars 10 and 10 by a normal method, and fixed to the column main bars 1 and 1 by a predetermined method (for example, a binding line). To do. In this case, at the upper end protruding portion 8 of the column main reinforcement 1, the band 6 is also arranged near the fixing plate 20, and this band is defined as the upper end band 6 </ b> A (FIG. 3A). Note that the upper end strip 6A can be positioned in the vicinity of the beam upper end strip 10 (FIGS. 3B and 3C). Further, in this case, the distance between the beam upper end line 10 and the fixing plate 20 is narrowed so that one upper end band 6A is located in the vicinity immediately above the fixing plate 20 and in the vicinity immediately below the beam upper end line 10. It can also be in a positioned state.

(8) The strip 6 is arranged above the beam upper bar 10 at the upper end protruding portion 8 of the column main bars 1 and 1. This band 6 is defined as an upper end band 6B. It is desirable that the upper end strip 6B be arranged at a position as low as possible by reducing the amount protruding upward from the upper surface 11 of the beam upper end muscle 10, for example, so as to contact the upper surface 11 of the beam upper end muscle 10. Deploy.

(9) With such a bar arrangement, the band 6B is arranged above (near the top) and the band 6A is arranged below (near the bottom) across the beam top bar 10. (FIGS. 1 and 2).

(10) It should be noted that the upper end strap 6B disposed in the vicinity immediately above the beam upper strip 10 and the upper end strip 6A disposed in the vicinity immediately above the fixing plate 20 and the fixing plate 20 are disposed below. It is desirable to arrange the strips 6 and 6 at equal intervals (equal pitch) as a whole from the viewpoint of shear reinforcement. Therefore, the upper end band 6A arranged in the vicinity immediately above the fixing plate 20 may be placed in contact with the fixing plate 20 or away from the fixing plate 20, or the arrangement position thereof is arbitrary.

(11) Subsequently, reinforcing bars 22, 22 having a substantially inverted U shape are arranged in the upper end band 6 </ b> B from above the column main reinforcement 1. The reinforcing bar 22 has two vertical bars 23, 23 arranged vertically along the columnar main bar 1, and the upper ends of the vertical bars 23, 23 are arranged at both ends of the horizontal bars 24 arranged substantially horizontally. Are connected to each other to form a reverse U-shape (FIGS. 1 and 2). Accordingly, the vertical stripes 23 and 23 and the horizontal stripe 24 are all located inside the upper end strip 6B in plan view (FIG. 1A).
The reinforcing bars 22 and 22 are arranged such that the horizontal bars 24 are arranged in a direction parallel to the axial direction of the beam upper end bars 10, and then the beam upper end bars in a direction perpendicular to the axial direction of the beam upper end bars 10. 10 is dropped from above (FIGS. 1 and 2). Accordingly, the horizontal streak 24 in the direction perpendicular to the axial direction of the beam top bar 10 is positioned on the horizontal bar 24 in a direction parallel to the axial direction of the beam top bar 10 (FIGS. 1 and 2). It should be noted that the position and number of reinforcing bars 22 and the outer diameter are selected according to the required shear strength. Usually, it may be about the same as the stirrup 16 (same diameter or 1 to 2 size large diameter).

(12) As above, arrange the bars, arrange the necessary walls and roof slabs, and install the necessary formwork (not shown) at the same time or before and after that. After the concrete 28 is solidified, an unnecessary formwork is removed to form a column beam connection structure (shear reinforcement structure of the uppermost column beam connection portion) 50 (FIGS. 1 and 2). . In the figure, 30 is the uppermost column and 40 is the uppermost beam.

[2] Other embodiments

(1) In the embodiment, the reinforcing bars 22 having a substantially inverted U shape are arranged by appropriately adjusting the number according to the shearing force acting on the beam-column joint. Further, the reinforcing bar 22 is arranged in the direction of the stress depending on the acting state in consideration of each effect. Accordingly, the reinforcing bars 22 are arranged in one or both of the “horizontal bars 24” in the “direction perpendicular to the axial direction of the beam upper bar 10” and the “direction parallel to the axial direction of the beam upper bar 10”. Further, when the action of a large shearing force is not expected, the reinforcing bar 22 can be omitted (not shown).

(2) In the above-described embodiment, the fixing plate 20 has a structure in which the fixing plate 20 is attached to the outer periphery of the deformed reinforcing bar and is fixed with a grout. In this case, the structure is arbitrary (not shown).

(3) In the above-described embodiment, the upper end protruding portion 8 is formed on the entire columnar bars 1 and 1 located on the outer periphery, but only at the columnar bars 1A and 1A located at least at the four corners (see FIGS. 1 and 2). ), Upper end protrusions 8 may be formed, and the upper end protrusions 8 may be omitted from the other column main bars 1 and 1 (not shown).

(4) In the above-described embodiment, one upper end strip 6A is arranged between the fixing plate 20 and the lower surface 12 of the beam upper strip 10 at the upper end protrusion 8. Two can also be arranged (FIG. 3B). In this case, the upper upper end strip 6 </ b> A (second upper end strip) is in contact with the lower surface 12 of the beam upper strip 10 or arranged in the vicinity of the lower surface 12. Further, the lower upper end strip 6 </ b> A (third upper end strip) is arranged near the fixing plate 20. Further, at the upper end protruding portion 8, three or more upper end strips 6 </ b> A can be disposed between the fixing plate 20 and the lower surface 12 of the beam upper end stripe 10 (not shown).
Depending on the shear strength required for the beam-column joint 50, if there is an upper end strip 6B, the upper end strip 6A can be omitted (not shown).

(5) Further, in the above embodiment, if there are as many upper end strips 6A as required, the upper end strips 6B can be omitted (FIG. 3C). In this case, the upper surface 2 of the columnar reinforcing bar 1 does not need to protrude above the beam upper bar 10, and may be located in the vicinity of the lower surface 12 of the beam upper bar 10. Further, in this case, the upper end band 6 </ b> A is located in the vicinity of the lower surface 12 of the beam upper end line 10, so that the upper end band 6 </ b> A is disposed in the vicinity of the upper surface 2 of the upper end protrusion 8.
In this case, the upper end strip 6A is arranged in the vicinity immediately above the fixing plate 20, and further in the vicinity of the lower surface 12 of the beam upper strip 10 (preferably in contact with the lower surface 12 of the beam upper strip 10). The upper end strip 6A is disposed (FIG. 3C). Therefore, when the upper end strip 6B is omitted, two upper end strips 6A are arranged between the upper end of the fixing plate 20 and the lower surface 12 of the beam upper strip 10.
Further, in this case, the reinforcing bars 22 and 22 are arranged such that the horizontal bar 24 is in a direction perpendicular to the axial direction of the beam upper end bar 10 and the horizontal bar 24 is in a direction parallel to the axial direction of the beam upper bar 10. It is desirable to arrange the reinforcing bars 22 in both directions of the reinforcing bars 22 (FIG. 1). Depending on the required performance, the reinforcing bars 22 can be arranged in only one direction of the horizontal bar 24 in a direction orthogonal to or parallel to the axial direction of the beam upper bar 10.

(6) In the above-described embodiment, the case where the beam upper bar 10 has one stage has been described. However, the present invention can also be applied to the case where the beam upper bar 10 has two or more upper and lower beams (FIGS. 3D and 3E). ). In this case, the upper end strip 6B is positioned in the vicinity of the upper end of the beam upper bar 10 at the uppermost position of the beam upper bar 10B (= the uppermost bar of the beam upper bar 10). Although the upper end band 6A is basically arranged near the fixing plate 20, it can be arranged near the lower surface 12 of the lower beam upper line 10A (FIG. 3D). Further, an upper end band 6A is arranged between the upper and lower beam upper bars 10A and 10B arranged in two upper and lower stages (FIG. 3 (d), shown by a chain line 6A), and a fixing plate 20 can also be arranged (FIG. 3). Not shown).

  When the upper end strip 6B is omitted, it is desirable to dispose the upper end strip 6A near the lower surface 12 of the beam upper strip 10B (FIG. 3E).

Test example

[1] Specimen

FIG. 8 shows specimens A and B.

(1) Specimen A
In the structure of reference 9.8 (d) on page 199 of “Non-patent Document 2”, an inverted U-shaped reinforcing bar equivalent to the present invention is also inserted in a direction parallel to the beam axis (non-patent document). Structure strengthening Patent Document 1).
・ Pillar: 400 × 400mm
-Columnar: D19-SD345
・ Beam bar: D19-SD390
・ Concrete ratio pjw = 0.3%
・ Reverse U-shaped reinforcement ratio pwv = 0.3%

(2) Specimen B
It is the structure of the Example described in FIG.
・ Column: 500x500mm
Columnar: D22-SD345
・ Beam bars: D22-SD345
・ Strip ratio pjw = 0.35%
・ Reverse U-shaped reinforcement ratio pwv = 0.34%

(3) Both specimens A and B are common in that a fixing plate is used below the upper end of the beam, but in specimen B, the first upper end band and the second upper end band are Yes, but not in Specimen A.
The band ratio pjw and the inverted U-shaped reinforcement ratio pwv were made substantially the same.
here,
Strip ratio = total cross section of the strip at the junction / (distance between the upper and lower beam bars × column width)
Reverse U-shaped reinforcing bar ratio = total cross-sectional area of reverse U-shaped reinforcing bar / cross-sectional area of column The column main bars and beam main bars (diameter × strength) per column cross-sectional area are substantially the same.

[2] Test method

An approximately 1/2 scale test specimen of the top floor T-shaped column beam joint was used, and the applied force was an interlayer deformation angle of R (5, 10, 20, 30, 40) × 10 ⁻³ rad. Of 2 cycles each and 60 × 10 ⁻³ rad. 1 cycle.

[3] Evaluation content

(1) It was evaluated how many times the ultimate bending strength (Qcmax) of the column had a safety factor with respect to the calculated value (Qcu).
A. It is possible to verify whether or not it is possible to guarantee that the ultimate bending strength of a real building is greater than the calculated value (required strength).

(2) After the maximum proof stress, it was evaluated whether the decrease in proof strength was small, that is, whether it had sufficient toughness performance.
A. It is a safe building that the proof stress does not decrease so much even after the maximum proof stress. “R80” is used as a scale for judging the performance. “R80” is the interlayer deformation angle when the proof stress is reduced to 80% of the maximum proof strength, and the larger the value, the better the toughness performance with less decrease in the proof strength.
I. Since the yield strength is suddenly reduced when the joint is subjected to shear failure, bending yielding while avoiding shear failure leads to maintenance of yield strength and securing deformation performance.

(3) Analyze the shear failure state of the joint from the failure state of the joint.

[4] Test results

(1) FIG. 9 shows a graph of load-interlayer deformation angle as a test result.
The ultimate bending strength (Qcmax) of the column is calculated (Qcu)
-Specimen A (structure strengthening Non-Patent Document 1) was "1.0 times (equivalent)"
-Specimen B (this method of construction) had a high safety factor of "about 1.15 times".
From the test results of the specimen B, it can be confirmed that the present construction method has an effect higher than expected, and even in a real building, it can be ensured that the ultimate bending strength is equal to or greater than the calculated value.
On the other hand, in the specimen A, the fact that the calculated value and the experimental value are the same cannot guarantee that the proof stress is equal to or greater than the calculated value in all the buildings that are actually constructed.
In specimen A (structure strengthened from Non-Patent Document 1), the interlayer deformation angle R = 0.032 rad. In contrast, the proof stress is drastically decreased due to the shear fracture at the joint (particularly, at the upper part of the joint, that is, in the stigma of the stigma). However, the phenomenon of joint shear failure is not observed, and the proof stress is almost maintained. The subsequent decline in yield strength is very gradual.
Focusing on the numerical value of R80, it shows that the specimen B (0.05 rad.) Has about 1.5 times higher deformation performance than the specimen A (0.032 rad.). It can be seen that the construction method results in a safe building with tenacity that is more tough against earthquakes.

(2) FIG. 10 shows a photograph of the fracture state of the joint as a test result.
Looking at the fracture condition of the specimen, the specimen A (structure strengthened from Non-Patent Document 1) is severely damaged in the upper part of the joint "capillary muscleless section" and split fracture from the corner. In the body B (the method of the present application), the degree of joint shear failure is small, and it can be seen that the entire joint including the “capital unreinforced section (unreinforced concrete portion)” sufficiently resists the shearing force.

[5] Conclusion of test

  Compared to test body A (structure strengthened from Non-Patent Document 1), test body B (the construction method of the present application) has a higher joint yield shear strength, so that the safety factor of bending strength is high, and excellent toughness with less decrease in yield strength. Since it has the performance, it can be seen that the present application method is very effective for shear reinforcement of the beam-column joint and provides a building having high earthquake resistance.

In the Example of this invention, the case where a beam is connected to the both sides of a pillar is represented, (a) is a top view, (b) is a front view. Similarly, in the embodiment of the present invention, a case where a beam is connected to one side of a column is shown, (a) is a plan view, and (b) is a front view. (A)-(e) is the Example of this invention, and is a partially expanded longitudinal cross-sectional view showing the relationship between a column main reinforcement, an upper end protrusion part, an upper end strip, and a beam upper end reinforcement. (A) (b) is a front view explaining the effect of this invention. In the conventional example of this invention, (a) is a plan view and (b) is a front view. Similarly, it is a front view of another conventional example of the present invention. Similarly, it is a front view of another conventional example of the present invention. In the test example, the structures of the test bodies A and B are shown. In a test example, a load-interlayer deformation angle curve is represented by an experiment result graph. In the test example, the destruction result of the joint portion is represented by the experimental result photograph.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Column main reinforcement 2 Upper end 6 Column reinforcement 6A Upper end strip (2nd upper end strip, 3rd upper end strip)
6B Upper end strap (first upper strip)
8 Upper end protruding portion 10 of the column main bar Upper end bar 10B Uppermost bar 10A of the upper bar of the beam Upper lower bar 11 of the upper end of the beam Upper surface 12 of the upper end of the beam Lower surface 14 of the upper bar of the beam 14 Staggered bar 20 Fixing plate 22 Reinforcing bars 23 Reinforcing bars vertical bars 24 Reinforcing bars horizontal bars 28 Concrete 30 Column 40 Beam 50 Column-beam joint structure 53 Anchor stub 55 Bend of tip (conventional example)
56 Unreinforced concrete part 60 Shear crack at the beam-column joint 61 Split crack at the beam-column joint

Claims (3)

A shear reinforcement structure for the uppermost column-beam joint characterized by satisfying all of the following conditions at the joint between the column and beam in the uppermost layer of the reinforced concrete structure in which the column main reinforcement is arranged.
(1) A fixing plate is attached to the upper end portion of the column main reinforcement.
(2) The fixing plate is positioned below the “uppermost bar of the beam upper bar” of the beam.
(3) The upper end of the column main bar protrudes upward from the fixing plate to form an “upper end protrusion”, and the upper end of the “upper end protrusion” is a distance from the “uppermost bar of the upper end of the beam”. Project upward by H.
(4) In the “upper end projecting portion” of the column main bar, the “first upper end band” is surrounded by the outer periphery of each “upper end projecting portion” in the vicinity immediately above the “uppermost streak of the beam upper end muscle”. ”.
(5) In the “upper end projecting portion” of the column main bar, the “second projecting portion” is surrounded by the “second upper end projecting portion” below the “beam upper end rebar” and above the fixing plate. Arrange the top strip.
(6) The predetermined distance H is formed to such a length that the “first upper end band” can be arranged, and a fixing plate is not provided at the predetermined distance H.
(7) A substantially inverted U-shaped reinforcing bar formed by connecting both ends of two vertical bars arranged along the columnar main bar with a horizontal bar is the “first upper end band” in a plan view. The horizontal bar is located above the uppermost bar of the beam upper bar, and is arranged in at least one direction perpendicular to the beam upper bar or parallel to the beam upper bar.
(8) The beam is set within the normal cover thickness of the beam top bar. In the “upper end protruding portion” of the column main reinforcement, another “third upper end strip” is arranged between the fixing plate and the lower surface of the beam upper end reinforcing the outer periphery of the “upper end protruding portion”. The shear reinforcement structure for the uppermost column beam joint according to claim 1. A shear reinforcement structure for the uppermost column-beam joint characterized by satisfying all of the following conditions at the joint between the column and beam in the uppermost layer of the reinforced concrete structure in which the column main reinforcement is arranged.
(1) A fixing plate is attached to the upper end portion of the column main reinforcement.
(2) The fixing plate is positioned below the “uppermost bar of the beam upper bar” of the beam.
(3) The upper end of the column main bar protrudes upward from the fixing plate to form an “upper end protruding portion”.
(4) In the “upper end projecting portion” of the column main bar, the “one first projecting portion” is surrounded by the “upper end projecting portion” below the “beam upper end rebar” and above the fixing plate. 2 upper strips ".
(5) At the “upper end protrusion” of the column main bar, near the “uppermost bar of the beam upper bar” or near the “other beam upper bar”, on the outer peripheral side of each “upper end protrusion” The “other second upper end band” is arranged around.
(6) No other fixing plate is provided on the upper end protrusion.
(7) A substantially inverted U-shaped reinforcing bar formed by connecting both ends of two vertical bars arranged along the column main bar with a horizontal bar. And located in at least one direction perpendicular to the beam upper end line or parallel to the beam upper end line.
(8) The beam is set within the normal cover thickness of the beam top bar.