WO2023163213A1

WO2023163213A1 - Joint structure

Info

Publication number: WO2023163213A1
Application number: PCT/JP2023/007316
Authority: WO
Inventors: 政樹有田; 裕一西田
Original assignee: 日本製鉄株式会社
Priority date: 2022-02-28
Filing date: 2023-02-28
Publication date: 2023-08-31

Abstract

This joint structure is for a joint where a wall of an RC building and an end of a composite beam are joined. The wall has wall concrete, the composite beam has a floor slab and a steel frame beam that supports the floor slab from below, and the floor slab has floor concrete and a plurality of reinforcing bars embedded in the floor concrete and the wall concrete. Each of the plurality of reinforcing bars includes a reinforcing bar body extending in the longitudinal direction of the steel frame beam in the floor concrete and the wall concrete, and an enlarged-diameter portion embedded in the wall concrete and having a length in the radial direction of the reinforcing bar body longer than the diameter of the reinforcing bar body. The steel frame beam is joined to the floor slab discretely or continuously in the longitudinal direction by a shear connector, the cross-sectional area ratio of the plurality of reinforcing bars satisfies equation 1, and the projected anchorage length ratio satisfies equation 2.

Description

junction structure

The present invention relates to a joint structure.
This application claims priority based on Japanese Patent Application No. 2022-029521 filed in Japan on February 28, 2022, the content of which is incorporated herein.

A semi-rigid joint has been proposed as a conventional technique, considering the effect of restraining the rotation of the joint by the reinforcing bars of the floor slab. These semi-rigid joints are generally applied to the intermediate joints of continuous beams. The intermediate joint mentioned here is a joint where the beams are arranged on both sides of the member (support member) that supports the semi-rigid jointed beam, and the floor slab continues across the support member. means
Semi-rigid joints are suitable for properties with large floor areas per floor, such as warehouses, factories, and airport terminals, located on the outskirts of cities. On the other hand, buildings located in the city center often have the following frame structure. That is, an RC core wall (hereinafter simply referred to as an RC core wall; the same applies to walls, beams, etc.) is arranged in the center of a relatively small plane. A single-span composite beam is placed between the RC wall and the RC girders of the outer frame. Buildings of this type rarely use continuous beams.

In the case of such a frame format, the reinforcing bars of the floor slab cannot be continuous across the RC wall. For this reason, the joints are generally pin joints. Therefore, the deflection of the beam becomes large, resulting in an uneconomical design.

On the other hand, at the joints between RC columns and RC beams, a method of bending and fixing the main reinforcing bars of the beams to the RC columns is used (see Patent Documents 1 and 2, for example). In the case of RC column-to-RC beam joints, the bending moment acting on the end of the beam is transferred to the column by the tensile forces of the bending anchor bars and the compressive forces of the concrete at the joint. The shear force acting on the ends of the beams is transmitted by placing the concrete of the columns and beams integrally and placing shear reinforcing bars. According to existing literature, the failure modes of RC columns due to the tensile force of bending anchoring bars of RC beams are raking out failure, side splitting failure, and local bearing failure. (local compression failure) have been reported.

Japanese Patent No. 3826354 Japanese Patent Laid-Open No. 11-148172

A method of bending (hooking) the reinforcing bars of the floor slab may also be considered when using a semi-rigid joint utilizing the reinforcing bars of the floor slab at the joint between the RC wall and the composite beam. However, when joining a steel frame beam and an RC wall, the steel frame beam and the RC wall are joined as follows because of the joining of dissimilar materials. That is, as a shear force transmission means, a shear plate is fixed to the wall concrete with a shear connector or the like. The shear plate and the steel beam web are joined with bolts.
In order to make this joint more moment-transmissible semi-rigid joint, the rebar of the composite beam floor slab is bent and anchored to the RC wall.
Also at the joints between RC walls and composite beams, there is a problem of breakage of RC walls due to the tensile force of bending fixing bars.

The present invention has been made in view of such problems, and in the joint structure of the joint where the RC wall and the end of the composite beam are joined, it is possible to suppress the destruction of the RC wall. An object of the present invention is to provide a joint structure.

In order to solve the above problems, the present invention proposes the following means.
(1) Aspect 1 of the present invention is a joint structure of a joint where an RC wall and an end of a composite beam are joined, wherein the wall has wall concrete, and the composite beam is a floor a slab and a steel beam supporting the floor slab from below, the floor slab having floor concrete and a plurality of reinforcing bars embedded in the floor concrete and the wall concrete; each of the reinforcing bars has a reinforcing bar main body extending in the longitudinal direction of the steel beam in the floor concrete and the wall concrete, and is embedded in the wall concrete, and the length of the reinforcing bar main body in the radial direction of the reinforcing bar main body is and an enlarged diameter portion longer than the diameter of the steel beam is discretely or continuously joined to the floor slab in the longitudinal direction by shear connectors, and the cross-sectional area ratio R _Ar of the plurality of reinforcing bars is This joint structure satisfies the formula (1) and the projected fixing length ratio (L _h /d _r ) satisfies the formula (2).
Here, i is the number of layers of the plurality of reinforcing bars arranged in the floor concrete, and a _{r, i} is the number of the reinforcing bars per one of the plurality of reinforcing bars in the i-th layer, which is the i-th layer from above. cross-sectional area (mm ² ) of the plurality of reinforcing bars perpendicular to the longitudinal direction, p _i is the pitch (mm) between the plurality of reinforcing bars of the i-th layer in the width direction of the floor slab, σ _ry,i is Yield stress (N/mm ² ) of the plurality of reinforcing bars of the i-th layer, σ _c is the compressive strength (N/mm ² ) of the wall concrete, L _h,i is the strength of the plurality of reinforcing bars in the i-th layer Projected fixing length (mm), which is the length of the portion fixed to the wall concrete in the longitudinal direction, _dr,i is the diameter (mm) per one of the plurality of reinforcing bars of the i-th layer. be.

The term "wall" here means a structure that extends vertically and horizontally, and that has two or more steel beams joined to one surface facing the horizontal plane. Alternatively, the wall means a structure that extends vertically and horizontally and has a width that is at least twice as large as its thickness in a plan view.

In this disclosure, the inventors conducted a large number of case studies, and as a result, in the joint structure of the joint where the RC wall and the end of the composite beam are joined, the destruction of the RC wall can be suppressed. Considered the conditions. As a result, the following conditions were found when the walls had wall concrete and the composite beams had floor concrete and a floor slab with a plurality of rebars and steel beams. That is, the condition is that the cross-sectional area ratio R _Ar of the plurality of reinforcing bars satisfies the formula (1), and the projected anchorage length ratio (L _h /d _r ) satisfies the formula (2).
Therefore, when the cross-sectional area ratio R _Ar satisfies the formula (1) and the projection fixing length ratio (L _h /d _r ) satisfies the formula (2), in the joint structure, the RC wall by three failure types Destruction can be suppressed.

(2) A second aspect of the present invention is the joint structure according to (1), wherein the diameter ratio R _dr of the plurality of reinforcing bars fixed to the wall concrete at the joint satisfies the formula (3), good too.
Here, the diameter ratio R _dr of the plurality of reinforcing bars is the diameter (−) of the plurality of reinforcing bars per unit length in the width direction.

In this disclosure, the inventors conducted a large number of case studies, and as a result, examined the conditions that can suppress bearing pressure failure in the joint structure of the joint where the RC wall and the end of the composite beam are joined. did. As a result, when the diameter ratio _Rdr of multiple reinforcing bars satisfies the formula (3), it is possible to increase the rigidity and strength of the joint while suppressing the destruction of the RC wall by three failure types in the joint structure. I found what I can do.
Therefore, when the diameter ratio _Rdr of the plurality of reinforcing bars satisfies the expression (3), it is possible to suppress deflection of the composite beam in the joint structure.

(3) A third aspect of the present invention is the joint according to (1) or (2), wherein the plurality of reinforcing bars are fixed to the wall concrete over an area equal to or larger than the effective width of the joint of the floor slab. It may be a structure.
In this disclosure, the wall is longer than the effective width in the width direction compared to a typical RC column. For this reason, in the joint structure, while fixing multiple reinforcing bars to the wall concrete up to the outermost edge within the effective width that contributes to the rigidity and strength of the joint, the fracture that may occur in the joint structure with the RC column That is, it is possible to suppress cracking of the concrete on the side (covering portion) of the fixing bar (reinforcing bar) in the wall concrete toward the outside in the width direction.

(4) Aspect 4 of the present invention is any one of (1) to (3), wherein the enlarged diameter portion extends downward from an end portion of the reinforcing bar body on the wall side with respect to the composite beam. The joint structure described in 1 may be used.
In this disclosure, the reinforcing bars can be appropriately fixed to the wall only by bending without applying special processing for mechanical fixing, and a joint structure with low cost and good workability can be obtained. .

(5) Aspect 5 of the present invention includes a shear plate joined to the wall, and bolts respectively joining the web of the steel beam, which is H-section steel, and the shear plate, wherein the web and the shear plate and the bolt hole through which the bolt is passed may be an elongated hole extending in the longitudinal direction. .

For example, a case where a pair of flanges of a steel frame beam are arranged to face each other in the vertical direction will be described. When the lower flanges of the ends of composite beams that support vertical loads are joined so as to transmit compressive force to the wall concrete by means of contact plates or welded joints, which will be described later, the ends of steel beams are flange). Therefore, the further apart the bolt is from the lower end, which is the center of rotation, the greater the amount of movement in the longitudinal direction. The bearing force is transmitted by the bolt contacting the opening peripheral edge of the bolt hole in the web or the like. In general, the bolt hole diameter is slightly larger than the bolt shaft diameter, so if the rotation of the joint is small, or if the bolt is positioned close to the center of rotation, the clearance between the bolt hole diameter and the bolt shaft diameter will prevent immediate bearing pressure. , no bearing force transmission occurs.

However, when the rotation of the joint increases, the farther the bolt is from the bottom end, which is the center of rotation, the larger the amount of bolt movement due to rotation relative to the size of the clearance, and the more likely the bolt is to bear bearing pressure. Rotation about the lower end (lower flange) of the end portion of the steel beam produces bearing force in the direction of pulling the shear plate out of the wall concrete, the farther the bolt is from the lower end, which is the center of rotation. The shear plate is fixed to the wall concrete with anchor reinforcing bars, headed studs, etc., but when the pull-out force of the anchor reinforcing bars and headed studs acts due to the bearing force, the combined force with the pull-out force of the bending anchoring bar is exerted on the wall concrete. As a result, the wall concrete is likely to break, and the load-bearing capacity of the joint is likely to be lost.

In this disclosure, since the bolt hole has an elongated hole shape extending in the longitudinal direction, the clearance between the bolt hole diameter and the bolt shaft (shaft part) diameter is large, and the composite beam receives a bending moment, and the steel beam is pushed against the shear plate. Relative movement also results in longitudinal movement of the bolt within the bolt hole.
Therefore, even if the bolt moves with respect to the wall concrete, the bolt hole and the bolt shaft will not be in a bearing state. Therefore, it is possible to suppress the pull-out due to the bearing force of the bolt acting on the anchor reinforcing bars and the headed studs that join the shear plate to the wall, thereby preventing the wall concrete from breaking.
In particular, if an external force beyond what is assumed in the design acts on the building due to some accident, there is a risk of excessive rotation at the joints. Even in such a case, it is possible to prevent multiple tensile forces from acting on the wall concrete and prevent the wall concrete from breaking.

(6) A sixth aspect of the present invention includes a shear plate joined to the wall, and bolts respectively joining the web of the steel beam, which is H-section steel, and the shear plate, wherein the web and the shear plate A bolt hole through which the bolt is passed is formed in at least one of the and the average position of the bolt hole in the height direction of the steel beam is located below the center of the steel beam in the height direction , (1) to (5).
In this disclosure, compared to when the average position (center of gravity) of the bolt holes in the height direction coincides with the center of the steel beam in the height direction, the bolts are closer to the lower flange, which is the center of rotation as a whole. Therefore, when the composite beam receives a bending moment and the steel frame beam moves relative to the shear plate, it becomes difficult for the bolt to move with respect to the wall concrete.
Therefore, even if the bolt moves relative to the wall concrete, the bolt hole and the bolt shaft will not be under pressure, and the bolt will pull out due to the bearing force acting on the anchor reinforcing bar or headed stud that joins the shear plate to the wall. can be suppressed and the destruction of the wall concrete can be prevented.

In the joint structure of the present invention, it is possible to suppress the destruction of the RC wall in the joint structure of the joint where the RC wall and the end of the composite beam are joined.

1 is a floor assembly diagram of a building in which the joint structure of one embodiment of the present invention is used; 2 is a cross-sectional view taken along a cutting line A1-A1 in FIG. 1; FIG. FIG. 3 is a cross-sectional view taken along a cutting line A2-A2 in FIG. 2; It is an enlarged view of the principal part in the shear plate of the same building. FIG. 4 is a cross-sectional view of a main part in a joint structure of a first modified example of one embodiment of the present invention; FIG. 10 is a cross-sectional view of a main part in a joint structure of a second modified example of one embodiment of the present invention; FIG. 11 is a cross-sectional view of a main part in a joint structure of a third modified example of one embodiment of the present invention; It is sectional drawing which carried out the plan view of the same building for demonstrating rake-out fixing failure. It is sectional drawing which looked at the side of the same building for demonstrating rake-out fixing failure. It is sectional drawing which looked at the side of the same building for demonstrating bearing pressure failure. FIG. 2 is a plan view of a building in which a column and an end of a composite beam are joined, for explaining lateral splitting failure. FIG. 4 is a diagram showing the effect of suppressing destruction of RC walls when the values of cross-sectional area ratios R _Ar and (L _h /d _r ) of floor reinforcing bars are limited. FIG. 10 is a diagram showing the relationship between the axial rigidity of the bending fixing bar of the wall concrete and the diameter ratio R _dr of the floor reinforcing bar when the wall thickness is 400 mm. FIG. 4 is a diagram showing the relationship between the diameter ratio R _dr of the floor reinforcement and the cross-sectional area ratio R _Ar of the floor reinforcement when the wall thickness is 400 mm. FIG. 10 is a diagram showing the relationship between the deflection of the composite beam 25 and the axial stiffness of the bending anchoring bar of the wall concrete. FIG. 5 is a diagram showing the axial stiffness of the bending anchoring bar of wall concrete with respect to the cross-sectional area ratio R _Ar of the floor reinforcing bar;

A building in which one embodiment of the joint structure according to the present invention is used will be described below with reference to FIGS. 1 to 16. FIG.

[1. Construction of a building using a joint structure]
As shown in FIGS. 1 and 2, this building 1 comprises a core wall 10, a plurality of columns 20, and composite beams 25. As shown in FIG. In addition, in FIG. 1, the composite beam 25 (a floor slab 28 to be described later) is indicated by a chain double-dashed line.
The core wall 10 has a rectangular tubular shape. The core wall 10 has a pair of first walls (walls) 11 and a pair of second walls (walls) 12 . The first wall 11 and the second wall 12 are each supporting members. A pair of 1st walls 11 and a pair of 2nd walls 12 are RC (Reinforced Concrete) structures, respectively.

As shown in FIG. 2 , the first wall 11 has wall concrete 14 , a plurality of wall rebars 15 , a base plate 16 and a plurality of headed studs 17 .
The wall concrete 14 has a rectangular plate shape when viewed in its thickness direction. The wall concrete 14 is arranged such that its thickness direction extends along the horizontal plane and extends in the up-down direction Z. As shown in FIG. In this specification, a member extending in the A direction means that the angle formed by the extending direction of the member and the A direction is 30 degrees or less. More preferably, this angle is 15 degrees or less.

The plurality of wall reinforcing bars 15 have a plurality of vertical bars 15a and a plurality of horizontal bars 15b. A plurality of vertical reinforcements 15 a and a plurality of horizontal reinforcements 15 b are embedded in the wall concrete 14 . The plurality of vertical bars 15a are arranged to be spaced apart from each other and extend in the up-down direction Z. As shown in FIG. The plurality of horizontal reinforcements 15b extend along the horizontal plane and are arranged so as to be in contact with the plurality of vertical reinforcements 15a.

As shown in FIGS. 2 and 3, base plate 16 is positioned on the outer surface of wall concrete 14 . A main surface 16b of the base plate 16 is exposed to the outside.
As shown in FIG. 2, a plurality of headed studs 17 are fixed to the main surface 16a of the base plate 16. As shown in FIG. The main surface 16a is a surface facing the inside of the wall concrete 14 . A plurality of headed studs 17 protrude from the base plate 16 towards the inside of the wall concrete 14 . A plurality of headed studs 17 are embedded in the wall concrete 14 .
As shown in FIG. 1, the pair of first walls 11 face each other in the direction along the horizontal plane.

As shown in FIG. 2, the main surface 16b of the base plate 16 is the surface of the base plate 16 opposite to the main surface 16a. A shear plate 18 is joined to the main surface 16b by welding or the like. A shear plate 18 is joined to the first wall 11 .
The shear plate 18 is formed with bolt holes 18a shown in FIG. The bolt hole 18a has an elongated hole shape extending in the longitudinal direction X of the second steel frame beam 27 described later when viewed in the thickness direction of the shear plate 18 . In this embodiment, the longitudinal direction X is a direction along the horizontal plane. However, the longitudinal direction X may be a direction that is inclined with respect to the horizontal plane.
A plurality of bolt holes 18 a are formed in the shear plate 18 . The plurality of bolt holes 18a are arranged side by side while being separated from each other in the up-down direction Z. As shown in FIG.
The number of bolt holes 18a formed in the shear plate 18 may be one.

As shown in FIG. 1 , the pair of second walls 12 are configured similarly to the pair of first walls 11 .
The second wall 12 is arranged such that its thickness direction extends along the horizontal plane and extends in the up-down direction Z. As shown in FIG. The pair of second walls 12 face each other in the direction along the horizontal plane. The pair of second walls 12 connects the ends of the first walls 11 in the width direction.
In the space within the core wall 10, an elevator shaft (not shown), a staircase, and the like are arranged.

The pillar 20 extends along the vertical direction Z. A plurality of pillars 20 are arranged around the core wall 10 at positions spaced apart from each other and from the core wall 10 . For example, the pillar 20 is RC structure. The columns may be made of steel, SRC (Steel Reinforced Concrete), CFT (Concrete-Filled Steel Tube), or the like.

As shown in FIGS. 1 and 2, the composite beam 25 has a plurality of first steel beams (steel beams) 26, a plurality of second steel beams (steel beams) 27, and a floor slab 28. there is
For example, the first steel beam 26 and the second steel beam 27 are each steel H-beams. The first steel beam 26 and the second steel beam 27 may not be H-shaped steel, but may be T-shaped steel, for example.

The first steel beams 26 span between adjacent core walls 10 and columns 20 and between adjacent columns 20, respectively, and extend in a direction along the horizontal plane, which is the longitudinal direction of the first steel beams 26. . The second steel beams 27 extend in the longitudinal direction X between the adjacent core walls 10 and the first steel beams 26 and between the adjacent first steel beams 26 .
Below, the 1st wall 11 side with respect to the composite beam 25 among the longitudinal directions X is called 1st side X1. The side of the composite beam 25 with respect to the first wall 11 in the longitudinal direction X is called a second side X2.
Since the configurations of the first steel beam 26 and the second steel beam 27 are the same, the second steel beam 27 will be described below as an example.

As shown in FIGS. 2 and 3 , the second steel beam 27 has a first flange 31 , a second flange 32 and a web 33 . The first flange 31 and the second flange 32 are arranged along the horizontal plane and face each other in the vertical direction Z. As shown in FIG. A direction perpendicular to the vertical direction Z and the longitudinal direction X is hereinafter referred to as a width direction Y. As shown in FIG.
The first flange 31 is arranged above the second flange 32 .
A web 33 is arranged between the first flange 31 and the second flange 32 . The web 33 joins the widthwise center of the first flange 31 and the widthwise center of the second flange 32 to each other.
As shown in FIG. 4, a plurality of bolt holes 33a are formed at each end of the web 33 in the longitudinal direction X (only one bolt hole 33a is shown in FIG. 4). For example, the bolt holes 33 a are circular when viewed in the thickness direction of the web 33 . The plurality of bolt holes 33a are arranged side by side while being separated from each other in the vertical direction Z. As shown in FIG.
The number of bolt holes 33a formed in the web 33 may be one.

As shown in FIGS. 2 and 3 , the floor slab 28 has a deck plate 36 , floor concrete 37 , multiple floor reinforcing bars (reinforcing bars) 38 , and multiple connecting reinforcing bars 39 .
The deck plate 36 is formed by bending a steel plate or the like. The deck plate 36 is arranged on the first flange 31 of the second steel beam 27 .
The floor concrete 37 is formed in a flat plate shape and arranged on the deck plate 36 . The multiple floor reinforcing bars 38 have multiple first floor reinforcing bars 42 and multiple second floor reinforcing bars 43 .

For example, the first floor reinforcing bar 42 is formed by bending a reinforcing bar. The first floor reinforcing bars 42 are embedded in the floor concrete 37 and the wall concrete 14 . The first floor reinforcing bar 42 has a reinforcing bar main body 42a and a bent portion (expanded diameter portion) 42b.
For example, the reinforcing bar main body 42a is formed in a cylindrical shape. The reinforcing bar body 42 a extends in the longitudinal direction X within the floor concrete 37 and the wall concrete 14 .
Here, the diameter (length in the radial direction) of the reinforcing bar main body 42a means the nominal diameter of the reinforcing bar main body 42a. The nominal diameters are, for example, 10 mm, 13 mm and 16 mm respectively in the case of deformed steel bars D10, D13 and D16 of JIS G 3112 steel bars for reinforced concrete.

The bent portion 42b extends downward from the end of the reinforcing bar main body 42a on the first side X1. The bent portion 42 b is embedded in the wall concrete 14 . That is, the wall concrete 14 is arranged on the first side X1 and the second side X2 of the bent portion 42b.
The dimension _Lv of the bent portion 42b projected in the vertical direction Z (the length of the bent portion 42b in the radial direction of the reinforcing bar main body 42a) is larger than the diameter of the reinforcing bar main body 42a. The dimension _Lv is preferably the maximum radial length of the reinforcing bar main body 42a of the bent portion 42b. The dimension _Lv of the bent portion 42b projected in the vertical direction Z is preferably 12 times or more the diameter of the reinforcing bar main body 42a.

In addition, the expanded diameter portion not only has a width expanded in the vertical direction Z (the dimension L _v obtained by projecting the bent portion 42b in the vertical direction Z) than the diameter of the reinforcing bar main body 42a, but also has a width larger than the diameter of the reinforcing bar main body 42a. It may be configured to have a width expanded in the width direction Y (the dimension of the bent portion 42b projected in the width direction Y).
The first floor reinforcing bar 42 is bent within a reference plane (XZ plane) parallel to the longitudinal direction X and the vertical direction Z, respectively. In this case, in the first floor reinforcing bar 42, the angle at which the bent portion 42b is bent with respect to the reinforcing bar main body 42a is about 90°.

The second floor reinforcing bars 43 are configured similarly to the first floor reinforcing bars 42 . The second floor reinforcing bar 43 has a reinforcing bar main body 43a and a bent portion 43b.
The reinforcing bar body 43a extends in the longitudinal direction X. As shown in FIG. The reinforcing bar main body 43a is arranged below the reinforcing bar main body 42a.
The bent portion 43b extends downward from the end of the reinforcing bar main body 43a on the first side X1. The bent portion 43 b is embedded in the wall concrete 14 .

The lower end of the bent portion 43b and the lower end of the bent portion 42b are at the same position in the up-down direction Z. As shown in FIG.
The dimension of the bent portion 43b projected in the vertical direction Z is defined in the same manner as the dimension _Lv of the bent portion 42b, and is larger than the diameter of the reinforcing bar main body 43a. Note that the lower end of the bent portion 43b and the lower end of the bent portion 42b may be arranged at different positions in the vertical direction Z from each other.

The reinforcing bar main bodies 42a of the plurality of first floor reinforcing bars 42 are arranged at the same height in the vertical direction Z. As shown in FIG. The reinforcing bar bodies 43a of the plurality of second floor reinforcing bars 43 have the same height in the vertical direction Z and are arranged below the plurality of reinforcing bar bodies 42a.
In this way, the reinforcing bar bodies 42a of the plurality of first floor reinforcing bars 42 constitute the layer ₃₈₁ of the first floor reinforcing bar 38 from above. The reinforcing bar bodies 43a of the plurality of second floor reinforcing bars 43 constitute the layer ₃₈₂ of the second floor reinforcing bar 38 from above. In this embodiment, the number of layers of the floor reinforcing bars 38 arranged in the floor concrete 37 is two. Note that the number of layers of the floor reinforcing bars 38 arranged in the floor concrete 37 is not limited.

The reinforcing bar bodies 42a of the plurality of first floor reinforcing bars 42 and the reinforcing bar bodies 43a of the plurality of second floor reinforcing bars 43 are divided into the wall concrete 14 side and the floor concrete 37 side, and these are the boundaries between the wall concrete 14 and the floor concrete 37. may be integrated using a screw type or grout injection type coupler.

The connecting reinforcing bars 39 extend in the width direction Y. As shown in FIG. A connecting reinforcing bar 391 that is part of the plurality of connecting reinforcing bars ₃₉ is in contact with the reinforcing bar bodies 42 a of the plurality of first floor reinforcing bars 42 . Note that the connecting reinforcing bars ₃₉₁ may be fixed to the reinforcing bar main bodies 42a of the plurality of first floor reinforcing bars 42 by wire mesh or welding.
The remaining connecting reinforcing bars ₃₉₂ of the plurality of connecting reinforcing bars 39 are in contact with the reinforcing bar main bodies 43 a of the plurality of second floor reinforcing bars 43 .
The connecting reinforcing bar _39-1 may be in contact with the reinforcing bar main body 42a, and the connecting reinforcing bar _39-2 may be in contact with the reinforcing bar main body 43a.

Note that the floor slab 28 may not have the deck plate 36 and the plurality of connecting reinforcing bars 39 . The number of floor reinforcing bars 38 included in the floor slab 28 may be one. In this case, the number of layers of the floor reinforcing bars 38 arranged in the floor concrete 37 is one.

A plurality of headed studs (shear connectors) 46 are fixed to the first flange 31 of the second steel beam 27 . A plurality of headed studs 46 are spaced apart from each other in the longitudinal direction X and the width direction Y. As shown in FIG. A plurality of headed studs 46 are embedded in floor concrete 37 through deck plate 36 of floor slab 28 .
As described above, the second steel beam 27 is discretely joined to the floor slab 28 in the longitudinal direction X by a plurality of headed studs 46 .
In addition, the shear connector may be a welding portion that continuously welds the first flange 31 of the second steel beam 27 and the deck plate 36 in the longitudinal direction X. In this case, the second steel beam 27 is continuously joined to the floor slab 28 in the longitudinal direction X by welding.

As shown in FIG. 2, the second flange 32 of the second steel beam 27 and the base plate 16 of the first wall 11 are joined via a contact plate 47 by welding, metal touch, or the like.
The plurality of floor reinforcing bars 38 extend over an area equal to or larger than the effective width (shown as B _eff in FIG. 3 ) in the width direction Y at the joint 51 where the first wall 11 and the end of the composite beam 25 are joined. It is anchored in concrete 14 . The effective width referred to here is defined in Non-Patent Document 1, Non-Patent Document 2, etc. below.
Non-Patent Document 1: “Eurocode 4: Design of composite steel and concrete structures - Part 1-1: General rules and rules for buildings”, December 2004, Authority: The European Union Per Regulation 305/2011, Directive 98/34/EC , Directive 2004/18/EC
Non-Patent Document 2: Architectural Institute of Japan, “Various Composite Structure Design Guidelines and Commentaries”, November 2010

Specifically, the effective width B _eff of Non-Patent Document 1 is obtained by Equation (5-3) using Equations (5-1) and (5-2).

However, L is the length of the second steel beam 27 . L _e is the length of the negative bending region (the region where the second flange (lower flange) 32 of the second steel beam 27 is compressed) on the side in contact with the joint 51 in the longitudinal direction X of the second steel beam 27; be. In the case of a semi-rigid joint, the length _Le is about 0.15 to 0.25 times the length L of the second steel frame beam 27, as in formula (5-1).

b _g is the width direction of the first flange 31 of the second steel beam 27 from the core position of the headed stud (shear connector) 46 on the second steel beam 27 to the next first steel beam 26 or the first 2 is the distance to the core position of the headed stud (shear connector) 46 on the nearer beam of the steel frame beam 27. When the headed studs 46 are arranged in two or more rows in the width direction, the distance between the core positions of the innermost headed studs 46 in the width direction _is set core the stud 46).
Similarly, when the shear connector is not a headed stud, the effective width can be obtained by the same procedure based on the center of gravity of the shear connector in the width direction.

b ₀ is the distance in the width direction of the first flange 31 of the second steel beam 27 between the headed studs 46 installed on the first flange 31 of the composite beam 25 . If the headed studs 46 are arranged in one row, the interval _b0 is zero.
b _eff,i is the effective width of the composite beam 25 per side of the floor slab 28; One side means one side of the width direction of the first flange 31 divided into both sides with the axis of the second steel beam 27 as a boundary. For a double-sided slab (floor slab 28 extends on both sides), i=2, and for a single-sided slab (floor slab 28 extends on only one side), i=1.
SI units and the like are used for the units of the length L and the like.

As shown in FIGS. 3 and 4, the web 33 of the second steel beam 27 and the shear plate 18 are joined by bolts 48 and nuts 49, respectively. More specifically, the shaft portion 48a of the bolt 48 is passed through the bolt hole 18a of the shear plate 18 and the bolt hole 33a of the web 33 of the second steel beam 27, respectively. The head 48b of the bolt 48 engages the shear plate 18 from the opposite side of the web 33. As shown in FIG.

The nut 49 engages the web 33 from the opposite side of the shear plate 18 . The nut 49 is fitted with the shaft portion 48 a of the bolt 48 . The head 48b of the bolt 48 and the nut 49 sandwich the shear plate 18 and the web 33 therebetween. Washers (not shown) are interposed between the nut 49 and the web 33 and between the head 48b of the bolt 48 and the shear plate 18. As shown in FIG.
Of the bolt holes 18a of the shear plate 18 and the bolt holes 33a of the web 33, the bolt holes 18a are assumed to be elongated. However, only the bolt hole 33a may be elongated, or the bolt holes 18a and 33a may be elongated.

As described above, the second steel beam 27 supports the floor slab 28 from below. The first steel beam 26 supports the floor slab 28 from below the floor slab 28 in the same manner as the second steel beam 27 .
In addition, generally, the length of the width direction Y of the 1st wall 11 is longer than the length of the width direction Y of a column.

As shown in FIGS. 2 and 3, the joint structure 52 of the joint portion 51 where the first wall 11 and the end portion of the composite beam 25 are joined is constructed as described above.
As shown in FIG. 1 , the joint structure 55 of the joint portion 54 where the second wall 12 and the end portion of the composite beam 25 are joined is configured for the second wall 12 as well as the first wall 11 .
The floor slab 28 may be a slab used for roofs (roof slab).
Also, the upper end of the first wall 11 preferably extends above the upper end of the composite beam 25 . It is preferable that the length by which the first wall 11 extends upward from the composite beam 25 is equal to or longer than the projected fixing length (L _h ).

In FIG. 2, the displacement of the second steel frame beam 27 when a bending moment due to a vertical load or the like acts on the composite beam 25 is indicated by a two-dot chain line. In this case, the ends of the second steel beams 27 in the longitudinal direction X rotate around their lower ends.
At this time, a tensile force acts on the floor reinforcement 38 in the longitudinal direction X of the second steel beam 27 . A second flange 32 of the second steel beam 27 compresses the base plate 16 via the contact plate 47 .

Note that the configuration of the first floor reinforcing bar 42 can be modified as follows.
As shown in FIG. 5 , the first floor reinforcing bar 65 may have a reinforcing bar body 66 and an enlarged diameter portion 67 . The enlarged diameter portion 67 is formed in an annular shape and provided at the end portion of the reinforcing bar main body 66 on the first side X1. The enlarged diameter portion 67 is fixed to the wall concrete 14 of the first wall 11 . The reinforcing bar main body 66 is configured by providing an annular second enlarged diameter portion 66b on the outer surface of a straight portion 66a extending in the longitudinal direction X. As shown in FIG. It should be noted that the enlarged diameter portion 67 may be provided not at the end portion of the reinforcing bar main body 66 but at the intermediate portion of the reinforcing bar main body 66 or the like as long as it is fixed to the wall concrete 14 .
For example, the first floor reinforcing bars 65 are made of deformed reinforcing bars. The enlarged diameter portion 67 is formed by a method of performing high-frequency induction heating with an axial compressive force applied to the reinforcing bar main body 66, rolling, or the like.

As shown in FIG. 6 , the first floor reinforcing bar 70 may have the reinforcing bar body 42 a and an enlarged diameter portion 71 . The enlarged diameter portion 71 is formed in a circular or rectangular plate shape. The enlarged diameter portion 71 is arranged coaxially with the reinforcing bar main body 42a at the end of the reinforcing bar main body 42a. The expanded diameter portion 71 may be formed by joining a part other than the reinforcing bar main body 42a by welding or the like. It may be formed by manufacturing or the like. The dimension _Lv of the expanded diameter portion 71 projected in the vertical direction Z is preferably 11 times or more the diameter of the reinforcing bar main body 42a.

As in the first floor reinforcing bar 75 shown in FIG. 7, the angle θ at which the bent portion (expanded diameter portion) 42c is bent with respect to the reinforcing bar main body 42a may be greater than approximately 90° and 180° or less. In this case, the first floor reinforcing bars 75 are preferably bent on a reference plane (XZ plane) parallel to the longitudinal direction X and the vertical direction Z, respectively.
The first

floor reinforcing bars

65, 70, 75 can also achieve the same effects as the first floor reinforcing bars 42 of the present embodiment.
In addition, regardless of the angle θ, the inner radius of the bent portion 42c is preferably three times or more the diameter of the floor reinforcement to be bent. The length of the straight portion of the bent portion 42c is 4 times or more the diameter of the floor reinforcement when the angle θ is 180°, and 6 times or more the diameter of the floor reinforcement when the angle θ is 135° or more and less than 180°. When the angle θ is 90° or more and less than 135°, it is preferably 8 times or more the diameter of the floor reinforcement.

Next, in the joint structure 52 configured as described above, the results of examining the suppression of scrape fixing failure, lateral splitting failure, and bearing pressure failure will be described.

[2. Description of scrape fixing failure, lateral splitting failure and bearing pressure failure of the joint structure]
First, scrape fixing failure, lateral splitting failure and bearing pressure failure will be described with reference to FIGS. 8 to 11. FIG. 8 to 11, the configuration is simplified and part of the display is omitted.
As shown in FIGS. 8 and 9, the rake-out anchoring failure means a failure in which the wall concrete 14 is scraped out like a cone-shaped mass R10 toward the composite beam 25, and the entire floor reinforcing bar 38 loses its bearing strength. do.

As shown in FIG. 10, the wall concrete 14 is located inside the region R1 where the first floor reinforcing bars 42 are bent. A bearing failure means a fracture in which the wall concrete 14 in the region R1 is cracked under bearing pressure when the first floor reinforcing bars 42 are pulled in the longitudinal direction X of the second steel beam 27 . When the first floor reinforcing bar 42 is pulled and moved as indicated by the two-dot chain line L1, the wall concrete 14 in the area R1 moves to the area R2. At this time, the wall concrete 14 in the region R2 is subjected to bearing pressure and cracks.

On the other hand, a joint structure 60 of a comparative example shown in FIG. 11 will be described. The joint structure 60 is a joint structure of a joint portion 62 where the RC column 61 and the end portion of the composite beam 25 are joined.
Since the column 61 is shorter in the width direction Y than the first wall 11 , when the first floor reinforcing bar 42 is pulled in the longitudinal direction X of the second steel beam 27 , the first Lateral splitting failure may occur in which the portion of the region R4, which is the side cover of the floor reinforcing bar 42, is torn toward the side of the column 61 (in the width direction Y). However, since the first wall 11 of the joint structure 52 of the present embodiment has a longer length in the width direction Y than the column 61, the wall concrete 14 serving as the lateral covering is not easily torn, and lateral splitting failure occurs. do not have.

[3. Investigation of Suppression of Bonding Structure Scraping Failure, Lateral Splitting Failure, and Bearing Pressure Failure]
[3.1. Case study conditions]
The inventors changed the specifications of the joint structure and made sample Nos. shown in Tables 1 to 3. 1 to 30 case studies were conducted. Sample no. The number of layers of floor reinforcing bars 38 from 1 to 30 is two.

For example, sample no. 1 was designed under the following design conditions.
The thickness of the first wall 11 is 400 mm. The design strength σ _c of the wall concrete 14 is 30 N/mm ² (Newtons per square millimeter). The design yield strength σ _ry,i of the floor reinforcing bars 38 is 550 N/mm ² . The diameter of the transverse bar 15b of the first wall 11 is 13 mm. The pitch in the vertical direction Z is 200 mm.

The diameter of the first floor reinforcing bar 42 is 16 mm. The pitch in the width direction Y is 150 mm. The projection fixing length is 350 mm. The projected anchorage length referred to here is the length in the longitudinal direction X of the portion of the first floor reinforcing bar 42 anchored to the wall concrete 14 (see the projected anchorage length _Lh in FIG. 2). In the first floor reinforcing bar 42, a bent portion is provided between the reinforcing bar main body 42a and the bent portion 42b. The radius inside the bend is 96 mm. In addition, the radius of the inner side of the bent portion was six times the diameter of the first floor reinforcing bar 42 . This suppressed the bearing pressure failure.
The diameter of the second floor reinforcing bar 43 is 10 mm. The pitch in the width direction Y is 200 mm. The projected fixing length is 350 mm, ensuring a cover thickness of 50 mm from the

bent portions

42b and 43b to the surface of the wall 11. FIG. The radius inside the bend is 60 mm.

In addition, sample No. From 1 to 30, the effective width B _eff was set to 1050 mm. The reinforcement area of the floor reinforcing bars 38 is 1050 mm or more, and is equal to or less than the control width of the second steel frame beam 27 .
The design yield strength of the first floor reinforcement 42 and the second floor reinforcement 43 is 550 N/mm ² and the design tensile strength is 650 N/mm ² .

　Sample No. In 1 to 30, it was determined that scraping anchorage failure occurred when the scrape anchorage failure strength according to Non-Patent Document 3 below was smaller than the tensile yield strength of the reinforcing bars within the slab effective width according to Non-Patent Document 1. In other words, it was assumed that the fracture type that gives the minimum proof stress should be selected from among scraping-fixing fracture and tensile yield. It was determined that the lateral splitting failure occurred when the proof stress of the bending fixing portion according to Non-Patent Document 4 below was smaller than the tensile yield strength of the reinforcing bars within the effective width of the slab according to Non-Patent Document 1. According to Non-Patent Document 4, bearing pressure failure can be prevented if the dimension of the bent portion satisfies the regulations of Non-Patent Document 5.

Sample no. 1 to 30, the inner radius of the bent portion was set to 6 times the diameter of the first floor reinforcing bar 42 so as to satisfy the regulation of Non-Patent Document 5. It should be noted that Non-Patent Document 4 uses the same bearing force formula regardless of the failure mode of lateral splitting failure and bearing pressure failure.
Non-Patent Document 3: Edited by Architectural Institute of Japan, “Toughness Guaranteed Seismic Design Guideline and Commentary for Reinforced Concrete Buildings”, September 2001 Non-Patent Document 4: Fujii et al. , Architectural Institute of Japan Structural Papers Report, No. 429, November 1991 Non-Patent Document 5: Architectural Institute of Japan, "Building Construction Standard Specifications and Commentary JASS5 Reinforced Concrete Construction", July 2018 Each sample No. Various parameters were investigated, from 1 to 30. The results are described below.

[3.2. Conditions for Suppressing Destruction of Fixation by Scraping]
The cross-sectional area ratio R _Ar of the floor reinforcing bars determined by the formula (6) and the projection fixing length ratio (L _h /d _r ) determined by the formula (7) were examined. The cross-sectional area ratio R _Ar of the floor reinforcing bars is the cross-sectional area ratio of the floor reinforcing bars 38 per unit length in the width direction Y of the floor slab 28 weighted by the strength ratio between the floor reinforcing bars and the wall concrete.

Here, i is the number of

layers

38 ₁ and 38 ₂ of the floor reinforcing bars 38 arranged in the floor concrete 37 . i is a natural number. In this example, i is two. The cross-sectional area ratio R _Ar of the floor reinforcing bars is the sum of the values of (( _{ar, i} /p _i )·(σ _{ry, i} /σ _c )) for all

layers

38 ₁ and 38 ₂ . Take.
a _r,i is the cross-sectional area (mm ² ) perpendicular to the longitudinal direction X of each floor reinforcing bar 38 in the i-th layer 38 _i that is the i-th layer from above. When the i-th layer _38i has a plurality of types of floor reinforcing bars 38 with different cross-sectional areas, this cross-sectional area is the average value of the cross-sectional areas of the floor reinforcing bars ₃₈ of the i-th layer 38i.
p _i (see FIG. 3 for p ₁ and p ₂ ) is the pitch (mm) in the width direction Y of the floor slab 28 between the floor reinforcing bars 38 of the i-th layer 38 _i . σ _ry,i is the design yield stress (N/mm ² ) of the floor reinforcing bars 38 of the i-th layer 38 _i . σ _c is the compressive strength (N/mm ² ) of the wall concrete 14; σ _ry,i is 550 N/mm ² .

L _h,i (mm) is the projected fixing length of each floor reinforcing bar 38 of the i-th layer 38 _i . When the composite beam 25 has one layer, the projected anchorage length L _h (mm) is the projected anchorage length of that layer. d _r,i is the diameter (mm) per one of the floor reinforcing bars 38 of the i-th layer. When the i-th layer _38i has a plurality of types of floor reinforcing bars 38 with different cross-sectional areas, dr _,i is the diameter of _the floor reinforcing bars dr _,i. is the average diameter of
When the composite beam 25 has multiple layers, the projected settlement length ratio (L _h /d _r ) is the minimum value of the projected settlement length ratio (L _h,i /d _r,i ) of each layer. .

Fig. 12 and Table 4 show the trial calculation results.
In FIG. 12 , the horizontal axis represents the cross-sectional area ratio R _Ar (mm ² /mm) of the floor reinforcing bars. The vertical axis represents the value of the projection fixing length ratio (L _h /d _r ).

For example, sample no. 1, the cross-sectional area ratio R _Ar of the floor reinforcement is 31.77 mm ² /mm. The value of (L _h /d _r ) is 21.875.
In FIG. 12, the samples determined not to cause scrape-out fixing failure are marked as "OK" by ◯ (white circle). In FIG. 12, the samples determined to cause scrape-out fixing failure are indicated by  (filled circles) as "NG".
From FIG. 12, it can be seen that if the cross-sectional area ratio R _Ar of the floor reinforcement is smaller than 30.70 and the value of (L _h /d _r ) is larger than 15.600, it can be determined that scraping and fixing failure does not occur. . That is, if the cross-sectional area ratio R _Ar of the floor reinforcement satisfies the formula (8) and the projected anchorage length ratio (L _h /d _r ) satisfies the equation (9), then in the joint structure 52, the rake anchor It was found that destruction can be suppressed.

[3.3. Conditions for Suppressing Bearing Failure and Lateral Splitting Failure]
(12) The diameter ratio R _dr of the floor reinforcing bars determined by the formula was examined.

The floor reinforcing bar diameter ratio R _dr is the diameter (−) of the floor reinforcing bar 38 per unit length in the width direction Y of the floor slab 28 . The unit length here is the pitch p _i (mm) in the width direction Y of the floor slab ₂₈ between the floor reinforcing bars 38 of the i-th layer 38 i . In this example, since i is 2, the diameter ratio R _dr of the floor reinforcing bars is the value of ((d _r,i /p _i )·(σ _ry,i /σ _c )) for all layers 38 ₁ , ₃₈₂ .
13 and 14 and Table 4 show the trial calculation results. Here, sample No. From 1 to 30, the trial calculation results for a wall thickness of 400 mm are extracted and shown.
The wall thickness is kept constant because the projection settlement length ratio (L _h /d _r ) changes when the wall thickness changes.

In FIGS. 13 and 14, the horizontal axis represents the diameter ratio R _dr (mm/mm) of the floor reinforcing bars. The vertical axis in FIG. 13 represents the value of the axial stiffness _kr of the floor reinforcement. The vertical axis in FIG. 14 represents the value of the cross-sectional area ratio R _Ar of the floor reinforcing bars.
The axial stiffness _kr can be calculated according to the non-patent document 1 by the formulas (13-1) and (13-2).

Here, E _r is the Young's modulus (N/mm ² ) of the reinforcing bar. Σar _,i is the sum (mm ² ) of the cross-sectional areas _ar,i (mm ² ) of the floor reinforcing bars 38 within the effective width of the i-th layer 38 _i , and l _j,i is the i-th layer 38 _i It is the effective length (mm) of the floor reinforcement 38 .
For example, as shown in Table 4, sample no. 1, the diameter ratio R _dr of the floor reinforcement is 2.872 mm/mm, and the axial rigidity k _r is 585.8 (kN/mm).
In FIGS. 13 and 14, ◯ marks indicate the samples determined not to cause bearing pressure failure as shown in FIG. In FIGS. 13 and 14,  marks indicate samples determined to cause bearing pressure failure as shown in FIG. In FIGS. 13 and 14, X marks indicate samples judged to cause scrape fixing failure as shown in FIGS.

From FIGS. 13 and 14, it can be seen that when the diameter ratio R _dr of the floor reinforcement is 1.57 or more, it can be determined that bearing pressure failure as shown in FIG. 11 occurs. However, the inventors have confirmed by experiments that such destruction as shown in FIG. 11 does not occur when the portion of the region R4 that becomes the side fogging is sufficiently large.
11, the first floor reinforcing bar 42 is pulled as shown in FIG. 10 and moves as indicated by a two-dot chain line L1, resulting in a region R4 that becomes the side cover of the first floor reinforcing bar 42. is torn toward the side of the pillar 61 (in the width direction Y). However, when the portion of the region R4 that becomes the side cover is sufficiently large, the first floor reinforcing bars 42 are restrained by the concrete of the region R4, so that the movement shown by the two-dot chain line L1 is difficult to occur through experiments. I found out.

That is, the joint structure 52 of the joint portion 51 where the first wall 11 and the end portion of the composite beam 25 are joined to the object of the present invention, and the joint portion where the second wall 12 and the end portion of the composite beam 25 are joined In the joint structure 55 of 54, bearing pressure failure and lateral splitting failure do not occur even when the amount of reinforcing bars is so dense that the diameter ratio R _dr of the floor reinforcing bars satisfies the formula (14).
On the other hand, as shown in FIG. 13 , as the amount of the floor reinforcing bars 38 of the composite beam 25 anchored to the wall concrete 14 is increased, in other words, as the R _dr is increased, the rotation of the joint 51 and the joint structure 52 increases. The rigidity of the reinforcing bar that resists is improved, and the deflection of the composite beam 25 is suppressed. When the diameter ratio R _dr of the floor reinforcement is 1.570 or more, the axial rigidity k _r is 400 kN/mm or more. The axial stiffness k _r is proportional to the rotational stiffness of the joint 51 . The increased rotational stiffness reduces the deflection of the composite beam 25 .

FIG. 15 shows a trial calculation example of the relationship between the axial stiffness _kr of the floor reinforcement and the deflection of the composite beam 25 . In this calculation example, the cross-sectional dimensions of the first steel beam 26 or the second steel beam 27 are 700 x 200 x 9 x 12 (beam length x flange width x web thickness x flange thickness, unit mm), and the floor slab 28 is 130 mm thick. , the length of the composite beam 25 is 10 m, and the joints 51 at both ends of the composite beam 25 have the same rotational rigidity.
According to this condition, the ratio of the deflection δ at the beam center of the composite beam 25 to the deflection δpin of the composite beam 25 whose both ends are supported by pin _joints is approximately δ/δpin=2/ It can be reduced to 3=66.7%.

Under other conditions, for example, when the beam height is 1200 mm and the beam length is 25 m, the axial stiffness _kr is 400 kN/mm, and can be reduced to approximately δ/δpin=2/5=40%. When the beam height is 400 mm and the beam length is 8 m, the axial rigidity _kr is 400 kN/mm, which can be reduced to approximately δ/δ pin = 4/5 = 80%. If the axial rigidity _kr is smaller than this, the effect of reducing the deflection becomes small. It becomes difficult to reduce the weight of the cross section of 26 or the second steel beam 27 .
In other words, since rolled H-section steel has limited options for cross-sectional dimensions, if the axial rigidity _kr is less than 400 kN/mm, reducing the weight of the first steel beam 26 or the second steel beam 27 will reduce the deflection. The weight of the cross section will be reduced, and the deflection will increase due to the weight reduction.

From the above, when the axial stiffness _kr is 400 kN/mm or more, the effect as a semi-rigid joint increases regardless of the conditions of beam thickness and beam length, and beam deflection can be effectively suppressed. As a result, when the first steel beam 26 or the second steel beam 27 is a rolled H-section steel, the cross-sectional dimension can be reduced, and the weight reduction enables material saving and economic design.
On the other hand, as the amount of the floor reinforcing bars 38 is increased, as shown in FIG.

Therefore, by satisfying the formula (14), the rigidity of the joint 51 and the joint structure 52 is increased, and by satisfying the formulas (8) and (9), the scraping and fixing failure is prevented. It is possible to increase the rotation resistance of the joint portion 51 and the joint structure 52 to the maximum within a safe range where the structure 52 is not destroyed, and suppress the deflection of the composite beam 25 .
In FIG. 14, region R11 is a region in which bearing pressure failure, lateral splitting failure, and scrape fixing failure do not occur in the case of a column-to-beam joint. The region R12 is a region where bearing failure and lateral splitting failure occur in the case of the beam-to-column joint, and where failure does not occur in the case of the wall-to-beam joint. A region R13 is a region where scrape fixing failure occurs.

FIG. 16 shows changes in the axial stiffness k _r of the floor reinforcing bars with respect to the cross-sectional area ratio R _Ar of the floor reinforcing bars. In FIG. 16, the thickness of the first wall 11 is assumed to be 400 mm.
In general, as the cross-sectional area ratio _RAr of the floor reinforcement increases, the axial rigidity _kr of the floor reinforcement also increases. When the cross-sectional area ratio R _Ar of the floor reinforcement is 13.0 or more, the axial rigidity k _r exceeds 400 kN/mm. Therefore, as described above, the effect as a semi-rigid joint is increased, and deflection of the beam can be effectively suppressed.

[4. Effects of the present embodiment]
As described above, in the joint structure 52 of the present embodiment, as a result of many case studies, the inventors have found that the first wall 11 of the RC structure and the end of the composite beam 25 are jointed. In the joint structure 52 of the portion 51, the conditions for suppressing the rake-out fixing failure were examined. As a result, when the first wall 11 has the wall concrete 14 and the composite beam 25 has the floor slab 28 with the floor concrete 37 and the floor reinforcing bars 38 and the second steel beam 27, the following conditions are satisfied: Found it. That is, the condition is that the reinforcing bar cross-sectional area ratio R _Ar satisfies the formula (8), and the projected fixing length ratio (L _h /d _r ) of the reinforcing bar satisfies the formula (9).
Therefore, when the cross-sectional area ratio R _Ar satisfies the formula (8) and the projected fixing length ratio (L _h /d _r ) satisfies the formula (9), scraping fixing failure and lateral splitting failure , and local bearing pressure failure.

The diameter ratio R _dr of the floor reinforcement satisfies the formula (14). As a result of the examination of many case studies, the inventors found that in the joint structure 52 of the joint 51 where the first wall 11 and the end of the composite beam 25 are joined, the bearing pressure failure that can occur at the column-to-beam joint We confirmed through experiments that a characteristic that does not occur at wall-to-beam joints, and investigated the conditions for improving the rigidity of joints by utilizing this. As a result, when the diameter ratio _Rdr of the reinforcing bars satisfies the formula (14), the rigidity and strength of the joint 51 are increased while suppressing the destruction of the first wall 11 of the RC structure by three types of failure in the joint structure 52. I have found that it can be improved.
Therefore, when the diameter ratio R _dr of the reinforcing bars satisfies the expression (14), bending of the composite beam 25 can be suppressed in the joint structure 52 . Specifically, the axial stiffness _kr exceeds 400 kN/mm when the reinforcing bar diameter ratio _Rdr satisfies the formula (14). Therefore, as described above, the effect as a semi-rigid joint is increased, and the deflection of the composite beam 25 can be effectively suppressed.

A plurality of floor reinforcing bars 38 are fixed to the wall concrete 14 over an area equal to or larger than the effective width of the joint 51 of the floor slab 28 . As a result, the rigidity of the floor reinforcing bars 38 of the joints 51 and the joint structure 52 calculated by the equation (14) can be increased, and the rotation resistance of the joints is increased, so the bending of the composite beam 25 is suppressed. The first wall 11 is longer than the effective width in the width direction Y compared to a general RC column. For this reason, in the joint structure 52, while fixing a plurality of floor reinforcing bars 38 to the wall concrete 14 up to the outermost edge within the effective width that contributes to the rigidity and strength of the joint 51, A possible fracture, ie, cracking of the lateral concrete of the plurality of floor reinforcing bars 38 in the wall concrete 14 toward the outside in the width direction Y can be suppressed.

The bent portion 42b extends downward from the end of the reinforcing bar main body 42a on the side of the first wall 11 with respect to the composite beam 25 . Therefore, for example, when a downward load acts on the composite beam 25, the reaction force of the tensile force acting on the reinforcing bar main body 42a acts on the wall concrete 14 as a compressive force from the inside corner of the bent portion 42b. This reaction force is balanced with the compressive force acting on the wall concrete 14 from the second flange 32 of the composite beam 25, so that the internal force of the wall concrete 14 can be more stably balanced.

The bolt hole 18a of the shear plate 18 has an elongated shape extending in the longitudinal direction X. When the second flange 32 at the end of the composite beam 25 that supports the vertical load is joined to transmit the compressive force to the wall concrete 14 by means of contact plates 47, welded joints or the like, the composite beam 25 is subjected to a bending moment. , the end of the steel beam rotates around its lower end. Therefore, the farther the bolt is from the lower end, which is the center of rotation, the larger the amount of movement in the longitudinal direction, and the greater the bearing pressure (compressive force) applied to the wall concrete.

In this disclosure, since the bolt hole 18a has an elongated hole shape extending in the longitudinal direction X, the clearance between the bolt hole 18a and the shaft portion 48a of the bolt 48 is large, and the composite beam 25 receives a bending moment and the shear plate 18 On the other hand, even if the second steel beam 27 moves relatively, the bolt 48 moves in the longitudinal direction X within the bolt hole 18a.
Therefore, even if the bolt 48 moves with respect to the wall concrete 14, the bolt hole 18a and the shaft portion 48a of the bolt 48 are not in a bearing state, and no bearing force acts on the shear plate 18 from the bolt 48. Pulling out of the anchor reinforcing bars 18 and the headed studs 17 can be suppressed, and destruction of the wall concrete 14 can be prevented.

Note that the average position of the second steel beam 27 in the height direction (the beam vertical direction of the second steel beam 27) in the plurality of bolt holes 18a is below the center of the second steel beam 27 in the height direction. may be located. In other words, the center of gravity of the multiple bolt holes 18 a may be located below the axis of the second steel beam 27 .
With this configuration, compared to the case where the average position of the plurality of bolt holes 18a in the height direction coincides with the center of the second steel frame beam 27 in the height direction, the composite beam 25 can reduce the bending moment. When the second steel frame beam 27 is moved relative to the shear plate 18 by receiving the force, the bolt 48 becomes difficult to move with respect to the wall concrete 14 .
Therefore, the amount of movement of the bolts 48 with respect to the wall concrete 14 is suppressed, and the bearing pressure applied to the wall concrete 14 by the bolts 48 can be suppressed.

As described above, one embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and the configuration can be changed, combined, or deleted without departing from the scope of the present invention. etc. are also included.
For example, in the above embodiment, the diameter ratio R _dr of the floor reinforcing bars does not have to satisfy the expression (14). The bolt holes 18 a of the shear plate 18 may be circular when viewed in the thickness direction of the shear plate 18 . The floor reinforcing bars 38 (42, 43) and the connecting reinforcing bars 39 may be round bars or deformed bars.

The joint structure can suppress anchor failure of the RC structure wall in the joint structure of the joint where the RC wall and the end of the composite beam are joined. Therefore, industrial applicability is great.

11 First wall (wall)
12 second wall (wall)
14 Wall concrete 18 Shear plate 18a Bolt hole 20 Column 25 Composite beam 26 First steel beam (steel beam)
27 Second steel beam (steel beam)
28 floor slab 37 floor concrete 38 floor reinforcing bar (reinforcing bar)
38 ₁ , 38 ₂ layers 46 Headed stud (shear connector)
48

bolt

42, 65, 70, 75 1st floor reinforcing bar (reinforcing bar)
42a, 66 Reinforcing

bar body

42b, 42c Bent portion (expanded diameter portion)
43 Second floor reinforcing bar (reinforcing bar)
51, 54

joint portion

52, 55

joint structure

67, 71 enlarged diameter portion X longitudinal direction

Claims

A joint structure of a joint where an RC wall and an end of a composite beam are joined,
the wall comprises wall concrete;
The composite beam has a floor slab and a steel beam supporting the floor slab from below,
The floor slab has floor concrete and a plurality of reinforcing bars embedded in the floor concrete and the wall concrete,
Each of the plurality of reinforcing bars includes:
a reinforcing bar body extending in the longitudinal direction of the steel beam in the floor concrete and the wall concrete;
an enlarged diameter portion embedded in the wall concrete and having a length in the radial direction of the reinforcing bar body longer than the diameter of the reinforcing bar body;
The steel beams are discretely or continuously joined to the floor slab in the longitudinal direction by shear connectors,
The cross-sectional area ratio R Ar of the plurality of reinforcing bars satisfies the formula (1),
A joint structure in which the projected fixing length ratio (L h /d r ) satisfies the formula (2).
Here, i is the number of layers of the plurality of reinforcing bars arranged in the floor concrete, and a r, i is the number of the reinforcing bars per one of the plurality of reinforcing bars in the i-th layer, which is the i-th layer from above. cross-sectional area (mm 2 ) of the plurality of reinforcing bars perpendicular to the longitudinal direction, p i is the pitch (mm) between the plurality of reinforcing bars of the i-th layer in the width direction of the floor slab, σ ry,i is Yield stress (N/mm 2 ) of the plurality of reinforcing bars of the i-th layer, σ c is the compressive strength (N/mm 2 ) of the wall concrete, L h,i is the strength of the plurality of reinforcing bars in the i-th layer Projected fixing length (mm), which is the length of the portion fixed to the wall concrete in the longitudinal direction, dr,i is the diameter (mm) per one of the plurality of reinforcing bars of the i-th layer. be.
The joint structure according to claim 1, wherein the diameter ratio R dr of the plurality of reinforcing bars fixed to the wall concrete at the joint satisfies the formula (3).
Here, the diameter ratio R dr of the plurality of reinforcing bars is the diameter (−) of the plurality of reinforcing bars per unit length in the width direction.
　The joint structure according to claim 1 or 2, wherein the plurality of reinforcing bars are fixed to the wall concrete over an area equal to or larger than the effective width of the joint of the floor slab.
The joint structure according to claim 1 or 2, wherein the enlarged diameter portion extends downward from an end portion of the reinforcing bar main body on the wall side with respect to the composite beam.
a shear plate joined to the wall;
bolts respectively joining the steel beam web and the shear plate, which are H-beams;
with
3. The joining structure according to claim 1, wherein a bolt hole formed in at least one of said web and said shear plate and through which said bolt is passed has an elongated hole shape extending in said longitudinal direction.
a shear plate joined to the wall;
bolts respectively joining the steel beam web and the shear plate, which are H-beams;
with
At least one of the web and the shear plate is formed with a bolt hole through which the bolt is passed,
The joint structure according to claim 1 or 2, wherein an average position of the bolt holes in the height direction of the steel beam is located below a center of the steel beam in the height direction.