JP7670491B2 - Structures and their design and construction methods - Google Patents

Description

One embodiment of the present invention relates to a structure, such as a building, and a design method and construction method thereof.

In recent years, in structures (buildings) that require large indoor spaces, such as office buildings, hospitals, and commercial facilities, steel beams are often used to connect columns, with both ends of the steel beams covered in reinforced concrete (hybrid beams). By using hybrid beams, the number of columns can be significantly reduced compared to construction methods in which all beams are constructed from reinforced concrete, and as a result, structures with large spaces can be constructed (see Patent Documents 1 and 2).

JP 2013-170386 A JP 2001-173155 A

One of the objectives of one embodiment of the present invention is to provide a structure with hybrid beams that can be constructed at lower cost, as well as a design method and construction method for the same.

One embodiment of the present invention is a structure. The structure includes columns, beams connected to the columns, and a floor slab located on the beams. The beams include a steel frame spaced from the columns, and beam concrete that embeds the column-side ends of the steel frames. The floor slab includes slab concrete that contacts the top surface of the steel frames at the ends of the steel frames.

One embodiment of the present invention is a construction method for a structure. This construction method includes connecting a beam to a column and forming a floor slab on the beam. The beam has a steel frame and beam concrete in which the ends of the steel frame are embedded. The beam is connected to the column so that the beam concrete is located on the column side and the ends are spaced apart from the column. The floor slab includes slab concrete that contacts the top surface of the steel frame at the ends.

One embodiment of the present invention is a method for designing a structure including a column, a beam connected to the column, and a floor slab located on the beam. The beam has a steel frame separated from the column, a plurality of beam main reinforcements, a plurality of transverse reinforcements, and beam concrete. The plurality of beam main reinforcements extend in the longitudinal direction of the steel frame. The plurality of transverse reinforcements intersect with the plurality of beam main reinforcements and surround the plurality of beam main reinforcements. The beam concrete embeds the column side end of the steel frame, a portion of the plurality of beam main reinforcements, and a portion of the plurality of transverse reinforcements. The floor slab contacts the upper surface of the steel frame at the end and includes slab concrete embedding another portion of the plurality of beam main reinforcements and another portion of the plurality of transverse reinforcements. The plurality of transverse reinforcements include a plurality of steel frame end side concentrated transverse reinforcements, a plurality of steel frame center side concentrated transverse reinforcements, a plurality of first intermediate transverse reinforcements, and a plurality of second intermediate transverse reinforcements. The plurality of steel frame end side concentrated transverse reinforcements are arranged at a first density and at least a portion surrounds the end of the steel frame. The central steel concentrated horizontal reinforcement is arranged at a position farther from the column than the multiple end steel concentrated horizontal reinforcement, and is arranged at a second density. The multiple first intermediate horizontal reinforcement is arranged between the multiple end steel concentrated horizontal reinforcement and the column, and is arranged at a third density lower than the first density and the second density. The multiple second intermediate horizontal reinforcement is arranged between the end steel concentrated horizontal reinforcement and the central steel concentrated horizontal reinforcement, and is arranged at a fourth density lower than the first density and the second density. This design method includes calculating the ultimate strength of the joint surface between the beam concrete and the slab concrete, taking into account the contributions of the multiple end steel concentrated horizontal reinforcement, the multiple central steel concentrated horizontal reinforcement, the multiple first intermediate horizontal reinforcement, and the multiple second intermediate horizontal reinforcement, as well as the vertical stress component acting on the joint surface between the beam concrete and the slab concrete.

（１） One embodiment of the present invention is a method for designing a structure including a column, a beam connected to the column, and a floor slab located on the beam. The beam has a steel frame, a plurality of beam main reinforcements, a plurality of transverse reinforcements, and beam concrete. The steel frame is spaced apart from the column and has a web and a pair of flanges connected to the web. The plurality of beam main reinforcements extend in the longitudinal direction of the steel frame. The plurality of transverse reinforcements intersect with the plurality of beam main reinforcements and surround the plurality of beam main reinforcements. The beam concrete embeds the column side end of the steel frame, a portion of the plurality of beam main reinforcements, and a portion of the plurality of transverse reinforcements. The floor slab contacts the top surface of the steel frame at the end and has slab concrete embedding another portion of the plurality of beam main reinforcements and another portion of the plurality of transverse reinforcements. The plurality of transverse reinforcements include a plurality of steel frame end side concentrated transverse reinforcements, a plurality of steel frame center side concentrated transverse reinforcements, a plurality of first intermediate transverse reinforcements, and a plurality of second intermediate transverse reinforcements. The plurality of steel end concentrated transverse reinforcements are arranged at a first density and at least partially surround the end of the steel. The plurality of steel center concentrated transverse reinforcements are arranged at a position farther from the column than the steel end concentrated transverse reinforcements and arranged at a second density. The plurality of first intermediate transverse reinforcements are arranged between the plurality of steel end concentrated transverse reinforcements and the column and arranged at a third density lower than the first density and the second density. The plurality of second intermediate transverse reinforcements are arranged between the steel end concentrated transverse reinforcements and the steel center concentrated transverse reinforcements and arranged at a fourth density lower than the first density and the second density. This design method includes calculating an ultimate strength _qfr of the joint interface between the beam concrete and the slab concrete according to the following formula (1).

(1)

In formula (1), μ _eq is the friction coefficient of the joint surface. _A a _w is the sum of the cross-sectional areas of the multiple steel frame central concentrated horizontal reinforcements. _A σ _wy is the yield strength or standard strength (F value) of each of the multiple steel frame central concentrated horizontal reinforcements. _s a _w is the sum of the cross-sectional areas of the multiple second intermediate horizontal reinforcements. _s σ _wy is the yield strength or standard strength (F value) of each of the multiple second intermediate horizontal reinforcements. _o a _wy is the sum of the cross-sectional areas of the multiple steel frame end concentrated horizontal reinforcements. _o σ _wy is the yield strength or standard strength (F value) of each of the multiple steel frame end concentrated horizontal reinforcements. _e a _w is the sum of the cross-sectional areas of the multiple first intermediate horizontal reinforcements. _e σ _wy is the yield strength or standard strength (F value) of each of the multiple first intermediate horizontal reinforcements. _{σ 0} is the average vertical stress applied to the joint surface. b' is the effective width of the concrete beam at the upper flange of the pair of flanges, and l _c is the length of the concrete beam in the direction in which the steel frame extends.

Embodiments of the present invention allow for the construction of structures with large interior spaces at low cost.

FIG. 1 is a schematic perspective view of a structure according to an embodiment of the present invention. 1A and 1B are schematic side and end views of a structure according to an embodiment of the present invention. FIG. 1 is a schematic top view of a structure according to an embodiment of the present invention. FIG. 2 is a schematic end view of a beam of a structure according to an embodiment of the present invention. FIG. 2 is a schematic end view of a beam of a structure according to an embodiment of the present invention. FIG. 2 is a schematic end view of a beam of a structure according to an embodiment of the present invention. FIG. 2 is a schematic end view of a beam of a structure according to an embodiment of the present invention. 3A and 3B are schematic top and side views of an end portion of a beam of a structure according to one embodiment of the present invention. FIG. 2 is a schematic end view of a beam of a structure according to an embodiment of the present invention. 1A to 1C are schematic top, side, and end views of a beam illustrating a construction method of a structure according to one embodiment of the present invention. 1A to 1C are schematic top, side, and end views of a beam illustrating a construction method of a structure according to one embodiment of the present invention. 1A and 1B are schematic top and side views showing a construction method for a structure according to one embodiment of the present invention. 1A-1D are schematic top, end and side views of a floor slab of a structure according to one embodiment of the present invention. 1A and 1B are schematic top and side views showing a construction method for a structure according to one embodiment of the present invention. 1A and 1B are schematic top and side views showing a construction method for a structure according to one embodiment of the present invention. 1 is a schematic end view of a beam, illustrating a construction method for a structure according to one embodiment of the present invention. FIG.

Each embodiment of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in various forms without departing from the spirit of the invention, and should not be interpreted as being limited to the description of the embodiments exemplified below.

In the drawings, the width, thickness, shape, etc. of each part may be shown diagrammatically compared to the actual embodiment in order to make the explanation clearer, but this is merely an example and does not limit the interpretation of the present invention. In this specification and each figure, elements having the same function as those explained in the previous figures may be given the same reference numerals and duplicate explanations may be omitted. When describing part of an element to which a numeral is given, a lowercase alphabet is added to the numeral. When describing multiple elements having the same or similar structure in order to distinguish each of them, a hyphen and a natural number are added after the numeral. When describing multiple elements having the same or similar structure collectively, only the numerals are used.

Hereinafter, the expression "a certain structure is exposed from another structure" means that a part of a certain structure is not covered by the other structure, and includes a case where the part not covered by the other structure is covered by yet another structure.

In the following, concrete refers to a material that is made by reacting cement, one of the raw materials, with water to produce a hydrate that has hardened and no longer exhibits fluidity. On the other hand, a mixture containing cement and water that has not completely hardened and still retains fluidity will be referred to as ready-mixed concrete (also known as ready-mix concrete).

First Embodiment
In this embodiment, a structure of a structure 100 according to one embodiment of the present invention will be described. In the drawings shown below, for convenience, the description will be given assuming that a plane parallel to the horizontal ground surface is an xy plane, and that the vertical direction perpendicular to the xy plane is the z axis.

1. Overall Structure A schematic perspective view of a structure 100 is shown in Fig. 1. As shown in Fig. 1, the structure 100 basically comprises a plurality of columns 110 extending in the vertical direction (z direction), a plurality of beams 120 connected to the columns 110 and extending in the horizontal direction, and a floor slab 150 provided on the beams 120.

1-1. Columns There are no particular restrictions on the number of columns 110 as long as it is four or more, and the number and arrangement may be appropriately determined according to the size and shape of the structure 100. The columns 110 are provided on piles (not shown) and connected to foundation beams. The shape of the columns 110 (cross-sectional shape in the xy plane) is also arbitrary and may be appropriately selected from rectangular, circular, elliptical, etc. The length of the columns 110 is also designed appropriately according to the size of the structure 100 and the height of each floor.

1-2. Beams Each beam 120 is connected to a pair of columns 110. At least one of the beams 120 provided in the structure 100 is a hybrid beam. That is, at least one of the beams 120 provided in the structure 100 has a steel frame, and the steel frame is covered at both ends with reinforced concrete. Hereinafter, the concrete contained in the reinforced concrete covering the ends of the steel frame will be referred to as beam concrete. Details of hybrid beams will be described later.

All of the beams 120 in the structure 100 may be hybrid beams, or some of the beams 120 may be hybrid beams, and the other beams 120 may be beams formed entirely of reinforced concrete (reinforced concrete beams, hereafter referred to as RC beams), or beams formed of steel without reinforced concrete (steel beams). In the example shown in Fig. 1, hybrid beams are used as beams 120 connected to a pair of columns 110 (for example, a pair of the first column 110-1 and the second column 110-2, a pair of the third column 110-3 and the fourth column 110-4, a pair of the fifth column 110-5 and the sixth column 110-6) that are provided at a long interval, and RC beams are used for a pair of columns 110 (for example, a pair of the first column 110-1 and the third column 110-3, a pair of the second column 110-2 and the fourth column 110-4, a pair of the third column 110-3 and the fifth column 110-5, a pair of the fourth column 110-4 and the sixth column 110-6) that are provided at a short interval. The arrangement of the hybrid beams and the RC beams can be determined arbitrarily, but it is preferable to use a hybrid beam between a pair of columns 110 that are provided at a long interval, as in the example shown in Fig. 1. This is because hybrid beams are lighter than RC beams (here, the second beam 120-2, the fourth beam 120-4, etc.), so by using hybrid beams for beams with large spans (here, the first beam 120-1, the third beam 120-3, etc.), it is possible to provide sufficient strength to the structure 100 while ensuring a large interior space.

1-3. Floor Slab The floor slab 150 is reinforced concrete that constitutes the floor surface of each floor, and is provided on the beams 120. The floor slab 150 is provided on each floor. Note that in FIG. 1, only a part of the floor slab 150 is shown for ease of viewing. As will be described in detail later, the floor slab 150 has a deck plate that forms the floor surface, and a reinforcing truss and slab reinforcement provided on the deck plate, and can be formed of concrete in which the reinforcing truss and slab reinforcement are embedded on the deck plate. Note that there may be floors on which the floor slab 150 is not provided. Hereinafter, the concrete included in the floor slab 150 is referred to as slab concrete.

The composition of the slab concrete and the beam concrete may be the same or different. The strength of the slab concrete and the beam concrete may be the same or different. In the latter case, the strength of the slab concrete may be lower or higher than the strength of the beam concrete. The strength of the beam concrete provided at both ends of one beam 120 may also be the same or different. The strength of the concrete used in the columns 110 and RC beams may also be the same or different from the strength of the beam concrete or slab concrete.

When the strength of the slab concrete is lower than that of the beam concrete, for example, the strength of the slab concrete can be selected from the range of 21 N/ ^mm2 or ^more and 33 N/mm2 or ^less , or 24 N ^{/ mm2} or more and 27 N/mm2 or less, and the strength of the beam concrete can be selected from the range of 27 N/mm2 ^{or more} and 150 N/mm2 or ^less , 36 N/mm2 or ^more and 120 N/mm2 or less, or 36 N/mm2 or more and 48 N/ ^mm2 or less. By using the slab concrete, which has a lower strength than the beam concrete, it is possible to construct the structure 100 having a large interior space at low cost.

2. Internal structure Figures 2(A) and 2(B) show schematic side views of a beam 120 as an example of a hybrid beam, and a pair of columns 110 to which the beam 120 is connected, and Figures 3(A) and 3(B) show corresponding schematic top views. Figures 2(C) and 2(D) are schematic end views along the dashed line A-A' in Figure 2(B). In Figures 2(B) to 2(D) and Figure 3(B), the concrete included in the column 110, the beam concrete 128, and the floor slab 150 are shown with dotted lines to show the internal structure. In addition, in Figures 3(A) and 3(B), the floor slab 150 is not shown. In the following description, the direction in which the beam 120 extends is the x-direction.

2-1. Steel frame and reinforcing bar unit Each column 110 is provided with a reinforcing bar unit including at least one column main bar 112 extending vertically and a plurality of tie bars 114 arranged to surround the column main bar 112, and concrete is poured to surround this reinforcing bar unit (Fig. 2(B) and Fig. 3(B)). The number of column main bars 112 and the arrangement density of tie bars 114 are appropriately determined depending on the length and thickness of the column 110 and the required strength.

A beam 120 having a hybrid beam structure is connected to a column 110 and includes a steel frame 122 extending horizontally (FIGS. 2(A), 2(B), 3(A), and 3(B)). The steel frame 122 includes iron, and its cross-sectional shape may be H-shaped, I-shaped, T-shaped, L-shaped, or the like. Typically, an H-shaped steel beam with an H-shaped cross section can be used. When an H-shaped steel beam is used, the steel frame 122 is arranged so that two flanges extend in the horizontal plane. The steel frame 122 is arranged so as not to contact the column 110. That is, both ends of the steel frame 122 are spaced apart from the pair of columns 110, and are arranged so as not to penetrate into the reinforcing bar unit of the column 110 constructed by the column main reinforcement 112 and the hoop reinforcement 114. Since reinforced concrete including beam concrete 128 is arranged at both ends of the steel frame, the portion of the beam 120 covered by the beam concrete 128 is also called the RC section 120a (FIG. 2(A)). In addition, since no reinforced concrete is provided between the RC sections 120a, the steel frame 122 is exposed from the concrete beams 128. The portion sandwiched between the RC sections 120a is also called the S section (or steel frame section) 120b.

At least one beam main bar 126 is provided at the end of the steel frame 122, extending in a direction parallel to the longitudinal direction of the steel frame 122 (i.e., the x-direction). The at least one beam main bar 126 may include multiple beam main bars 126. A portion of this beam main bar 126 is inserted into the reinforcing bar unit of the column 110, thereby supporting and fixing the beam 120 to the column 110 (Figures 2(B) and 3(B)). An anchoring plate 126a with a larger cross-sectional area than the beam main bar 126 may be formed on the central side of the beam (opposite the column 110) of each beam main bar 126.

At the end of the steel frame 122, multiple transverse reinforcements 124 are provided, which cross the beam main reinforcements 126 and surround them (Fig. 2(B), Fig. 3(B)). Each transverse reinforcement 124 may be an integrated single ring-shaped reinforcing bar (Fig. 2(C)), or as shown in Fig. 2(D), a pair of transverse reinforcements 124-1 and 124-2 of different shapes may be combined to form a ring structure. In the latter case, for example, one transverse reinforcement 124-1 may not extend above a portion of the beam main reinforcements 126 above the steel frame 122, and the other transverse reinforcement 124-1 may be arranged to cross above this portion of the beam main reinforcements 126. The transverse reinforcements 124 firmly fix the steel frame 122 together with the beam main reinforcements 126 to the reinforcing bar unit of the column 110.

As will be described in detail later, some of the multiple horizontal reinforcements 124 do not surround the steel frame 122 and do not overlap with the steel frame 122 in the z direction. Meanwhile, other parts of the multiple horizontal reinforcements 124 surround the steel frame 122 and overlap with the steel frame 122 in the vertical direction. In addition, the multiple horizontal reinforcements 124 are arranged so that their arrangement density changes in the x direction.

Although not shown in Figs. 2(A) to 3(B), multiple insert bars may be arranged at the end of the steel frame 122 to intersect the beam main reinforcement bars 126 and surround the beam main reinforcement bars 126. The insert bars may be arranged to contact the transverse reinforcement bars 124. For example, each insert bar can be sandwiched between two adjacent transverse reinforcement bars 124 and arranged to contact one of the transverse reinforcement bars 124. The insert bars are inverted U-shaped reinforcing bars that intersect two or more beam main reinforcement bars 126 and are arranged so that the opening of the U faces downward. Some of the multiple insert bars surround part of the steel frame 122 and overlap with the steel frame 122 in the z direction. On the other hand, some of the multiple insert bars are arranged so as not to overlap with the steel frame 122 and not to surround the steel frame 122.

2-2. Concrete In the RC section 120a, a concrete beam 128 is provided (FIGS. 2(A) and 3(A)). The concrete beam 128 may be in contact with the concrete constituting the column 110. Alternatively, the concrete beam 128 and the concrete constituting the column 110 may be integrated.

Here, in the RC section 120a, a part of the steel frame 122, a part of the beam main reinforcement 126, and a part of the transverse reinforcement 124 are embedded in the beam concrete 128. More specifically, as shown in the schematic end view (FIG. 4(A)) along the dashed line A-A', a part of the steel frame 122, a part of the beam main reinforcement 126, and a part of the transverse reinforcement 124 are embedded in the beam concrete 128, and other parts of the steel frame 122, the beam main reinforcement 126, and the transverse reinforcement 124 are exposed from the beam concrete 128. For example, the top surface of the steel frame 122 is exposed from the beam concrete 128. When the steel frame 122 is an H-beam steel, the top surface of one flange (the part surrounded by a dotted ellipse in FIG. 4(A)) may be exposed from the beam concrete 128, and the top surface of the beam concrete 128 and the top surface of the flange may be located on the same plane. A portion of each horizontal reinforcement bar 124 is embedded in the beam concrete 128, and another portion is exposed from the beam concrete 128. Similarly, a portion of the multiple beam main reinforcements 126 is embedded in the beam concrete 128, and another portion is exposed from the beam concrete 128.

On the other hand, the reinforcing bars exposed from the beam concrete 128 in the RC section 120a are embedded in the slab concrete 152 included in the floor slab 150. For example, the parts of each horizontal reinforcement bar 124 exposed from the beam concrete 128 and the beam main bars 126 that are not embedded in the beam concrete 128 are embedded in the slab concrete 152. The top surface of the steel frame 122 contacts the slab concrete 152. The slab concrete 152 also contacts the beam concrete 128.

As shown in FIG. 4(A), the concrete beam 128 may be provided so that its upper surface is located on the same plane as the upper surface of the steel frame 122, or as shown in FIG. 4(B), the concrete beam 128 may be provided so that all of the upper flanges of the steel frame 122 are exposed from the concrete beam 128. In other words, the concrete beam 128 may be provided so that its upper surface is located lower than the upper surface of the steel frame 122, and part of the web connecting the pair of flanges is exposed from the concrete beam 128.

Alternatively, as shown in FIG. 5(A), the steel frame 122 may be positioned so that the top surface of the upper flange of the steel frame 122 is lower than the bottom surface of the floor slab 150 in the area that does not overlap with the concrete beam 128. In this case, a recess may be provided in the concrete beam 128, and the steel frame 122 may be exposed from the concrete beam 128 in this recess and come into contact with the concrete slab 152 (FIG. 5(B)).

Alternatively, as shown in Figures 6(A) to 6(C), all of the transverse reinforcement bars 124 and the beam main reinforcement bars 126 may be located below the bottom surface of the floor slab 150 in the area where they do not overlap with the beam concrete 128. In the example shown in Figure 6(A), a part of the upper flange of the steel frame 122 is exposed from the beam concrete 128 and contacts the slab concrete 152. In the example shown in Figure 6(B), the beam concrete 128 is provided so that a part of the web is exposed from the beam concrete 128. In the example shown in Figure 6(C), the beam concrete 128 is provided so that the upper surface of the beam concrete 128 and the upper surface of the upper flange of the steel frame 122 are substantially flush with each other.

As shown in FIG. 7, the joint surface 130 between the upper surface of the concrete beam 128 and the concrete slab 152 may have an uneven shape. The depth of the unevenness (i.e., the height of the convex portion) may be 0.5 mm to 10 mm, or 3 mm to 7 mm. By forming unevenness on the joint surface 130, the coefficient of friction between the concrete beam 128 and the concrete slab 152 can be increased, and as a result, the concrete beam 128 and the concrete slab 152 can be fixed to each other more firmly, and horizontal sliding failure can be more effectively prevented.

3. Arrangement of transverse reinforcement As described above, the transverse reinforcement 124 provided in the RC section 120a is not arranged at a uniform density in the direction in which the steel frame 122 extends, but is arranged so that there are multiple transverse reinforcement groups arranged at different arrangement densities. Schematic top views and side views of the end of the beam 120 are shown in Figures 8(A) and 8(B), respectively. As shown in these figures, the multiple transverse reinforcement 124 is composed of multiple steel frame end side concentrated transverse reinforcement 124a, multiple steel frame center side concentrated transverse reinforcement 124b, multiple first intermediate transverse reinforcement 124c, and multiple second intermediate transverse reinforcement 124d, and each of the multiple steel frame end side concentrated transverse reinforcement 124a, multiple steel frame center side concentrated transverse reinforcement 124b, multiple first intermediate transverse reinforcement 124c, and multiple second intermediate transverse reinforcement 124d forms a transverse reinforcement group. Here, the arrangement density refers to the number of horizontal reinforcement bars 124 per unit length in the extension direction of the steel frame 122.

A plurality of steel frame central concentrated lateral reinforcements 124b are arranged in the position farthest from the column 110 in each RC section 120a (i.e., on the opposite end side of the end of the steel frame 122 in each RC section 120a) to form one lateral reinforcement group. The steel frame central concentrated lateral reinforcements 124b all surround the steel frame 122 and are arranged at a relatively high arrangement density. Two adjacent lateral reinforcements 124 selected from the steel frame central concentrated lateral reinforcements 124b may be in contact with each other or may be separated from each other. There is no restriction on the number of steel frame central concentrated lateral reinforcements 124b, and it is appropriately determined according to the length of the steel frame 122 or the beam 120 in the _x direction, the length of the RC section 120a (i.e., the length of the beam concrete 128), the length of the beam main reinforcement 126 overlapping with the steel frame 122, and the like. Although not shown, one or more insert bars 125 may be provided between adjacent steel frame central concentrated lateral reinforcements 124b.

A plurality of steel frame end side concentrated lateral reinforcements 124a are arranged on the column 110 side with respect to the steel frame center side concentrated lateral reinforcements 124b in each RC section 120a, forming one lateral reinforcement group. The steel frame center side concentrated lateral reinforcements 124b may all be arranged to surround the steel frame 122, or some of the steel frame center side concentrated lateral reinforcements 124b may not overlap the steel frame 122 in the z direction. The steel frame end side concentrated lateral reinforcements 124a are also arranged with a relatively high arrangement density, which may be the same as or different from the arrangement density of the steel frame center side concentrated lateral reinforcements 124b. Two adjacent lateral reinforcements 124 selected from the steel frame end side concentrated lateral reinforcements 124a may also be in contact with each other or may be spaced apart. As with the steel frame center concentrated horizontal reinforcement bars 124b, there is no restriction on the number of steel frame end concentrated horizontal reinforcement bars 124a, and it is determined appropriately depending on the length of the steel frame 122 or the beam 120 in the x direction, the length l _c of the RC section 120a, the length l _e from the column 110 to the steel frame 122, etc. Although not shown, one or more insert bars 125 may be provided between adjacent steel frame end concentrated horizontal reinforcement bars 124a.

A plurality of first intermediate transverse reinforcements 124c are arranged on the column 110 side with respect to the concentrated transverse reinforcements 124a at the steel frame end side in each RC section 120a, forming one transverse reinforcement group. The first intermediate transverse reinforcements 124c are arranged so as not to overlap with the steel frame 122. The first intermediate transverse reinforcements 124c are arranged at a lower arrangement density than the arrangement density of the concentrated transverse reinforcements 124a at the steel frame end side and the arrangement density of the concentrated transverse reinforcements 124b at the steel frame center side. Two adjacent transverse reinforcements 124 selected from the first intermediate transverse reinforcements 124c are spaced apart from each other. There is no restriction on the number of first intermediate transverse reinforcements 124c, and it is appropriately determined according to the length of the beam 120, the length l _c of the RC section 120a, the distance l _e from the column 110 to the steel frame 122, and the like. As shown in FIG. 8(B), one or more insert bars 125 may be provided between adjacent first intermediate transverse reinforcements 124c. The insert bars 125 and the first intermediate horizontal reinforcement bars 124c may be in contact with each other or may be spaced apart.

A plurality of second intermediate transverse reinforcements 124d are arranged between the steel frame end side concentrated transverse reinforcements 124a and the steel frame center side concentrated transverse reinforcements 124b in each RC section 120a to form one transverse reinforcement group. The second intermediate transverse reinforcements 124d are arranged so as to overlap the steel frame 122. The second intermediate transverse reinforcements 124d are arranged at a lower arrangement density than the arrangement density of the steel frame end side concentrated transverse reinforcements 124a and the arrangement density of the steel frame center side concentrated transverse reinforcements 124b. The arrangement density of the second intermediate transverse reinforcements 124d may be the same as or different from the arrangement density of the first intermediate transverse reinforcements 124c. Two adjacent transverse reinforcements 124 selected from the second intermediate transverse reinforcements 124d are spaced apart from each other. There is no restriction on the number of second intermediate transverse reinforcements 124d, and it is appropriately determined according to the length of the beam 120, the length l _c of the RC section 120a, the length of the portion of the beam main reinforcement 126 overlapping with the steel frame 122, the distance between the concentrated transverse reinforcement at the steel frame end side 124a and the concentrated transverse reinforcement at the steel frame center side 124b, etc. As shown in Fig. 8 (B) , one or more insert bars 125 may be provided between adjacent second intermediate transverse reinforcements 124d. The insert bars 125 and the second intermediate transverse reinforcements 124d may be in contact with each other or may be spaced apart.

The interval or average interval between adjacent horizontal reinforcements 124 of the steel end side concentrated horizontal reinforcement 124a is smaller than the distance from the steel end side concentrated horizontal reinforcement 124a closest to the column 110 to the first intermediate horizontal reinforcement 124c furthest from the column 110, and the latter is 5 to 100 times, or 10 to 50 times, of the former. Similarly, the interval or average interval between adjacent horizontal reinforcements 124 of the steel end side concentrated horizontal reinforcement 124a is smaller than the distance from the steel end side concentrated horizontal reinforcement 124a furthest from the column 110 to the second intermediate horizontal reinforcement 124d closest to the column 110, and the latter is 5 to 100 times, or 10 to 50 times, of the former. Furthermore, the spacing or average spacing between adjacent horizontal reinforcements 124 of the steel frame central concentrated horizontal reinforcement 124b is smaller than the distance from the steel frame central concentrated horizontal reinforcement 124b closest to the column 110 to the second intermediate horizontal reinforcement 124d furthest from the column 110, and the latter is 5 to 100 times, or 10 to 50 times, the former. Therefore, when focusing on one horizontal reinforcement 124, by comparing the spacing between this horizontal reinforcement 124 and the two horizontal reinforcements 124 adjacent to it, it is possible to determine which horizontal reinforcement group this horizontal reinforcement 124 belongs to.

The load applied to the steel frame 122 is transmitted to the RC portion by the lever action of the concentrated horizontal reinforcement bars 124a at the end of the steel frame and the concentrated horizontal reinforcement bars 124b at the center of the steel frame, which makes the transmission of force from the beam 120 to the column 110 smoother, which is advantageous from a structural standpoint. This reduces damage to the RC portion. In addition, the force in the RC portion is shared by the first intermediate horizontal reinforcement bars 124c and the second intermediate horizontal reinforcement bars 124d, which restrains the beam concrete 128 and suppresses cracks in the beam concrete 128.

Second Embodiment
In this embodiment, a method for designing a structure 100 including the hybrid beam described in the first embodiment will be described. More specifically, a design method for effectively preventing horizontal slip failure caused by an external force at the joint surface 130 of the RC section 120a of the beam 120 will be described. Descriptions of configurations that are the same as or similar to the configuration described in the first embodiment may be omitted.

（２） In the design method according to this embodiment, the ultimate strength q _fr of the joint interface 130 between the concrete beam 128 and the concrete slab 152 in the RC section 120a is calculated by the following formula (2).

(2)

The variables in equation (2) are as follows (see Figures 8(A), 8(B), and the schematic end view (Figure 9) taken along the dashed line B-B' in Figure 8(B)):

（３）
ここで、μ_ｓは鉄骨１２２とスラブコンクリート１５２間の摩擦係数であり、μ_ｒｃは梁コンクリート１２８とスラブコンクリート１５２間の摩擦係数である。μ_ｓは０．３０以上０．９０以下、０．４０以上０．９０以下、０．５０以上０．９０以下、または０．５６以上０．８０以下の範囲から選択され、例えば０．５６である。梁コンクリート１２８の上面に凹凸を設けない場合にはμ_ｒｃはそれぞれ０．６λであり、凹凸を設ける場合（図７参照）にはμ_ｒｃは１．０λとする。λはコンクリートの種類に依存する係数であり、軽量コンクリートの場合には０．７５が、普通コンクリートの場合には１．０が採用される。Ｂｓはフランジの幅（鉄骨幅とも呼ばれ、鉄骨１２２のウェブの法線に平行な方向における長さ）であり、ｂはＲＣ区間１２０ａの梁コンクリート１２８の幅（ウェブの法線に平行な方向における長さ）である。ｂ´は、鉄骨１２２のフランジ位置（上側のフランジの上面の位置）でのＲＣ区間１２０ａの梁コンクリート１２８の有効幅であり、幅ｂから幅Ｂｓを引いた値である。ｌ_ｊは各ＲＣ区間１２０ａ内の鉄骨１２２の長さ（埋め込み長さ）であり、上述したように、ｌ_ｅとｌ_ｃは、それぞれｘ方向における柱１１０から鉄骨１２２までの長さとＲＣ区間１２０ａの長さである。 μ _eq is the equivalent friction coefficient, which is the friction coefficient of the joint surface 130. Since the joint surface 130 is mainly formed by the interface between the steel frame 122 and the concrete slab 152 and the interface between the concrete beam 128 and the concrete slab 152, it is assumed that the equivalent friction coefficient μ _eq is contributed by the friction coefficients of these two interfaces in accordance with their respective area ratios. Therefore, μ _eq is given by the following equation (3).

(3)
Here, _μs is the coefficient of friction between the steel frame 122 and the concrete slab 152, and _μrc is the coefficient of friction between the concrete beam 128 and the concrete slab 152. _μs is selected from the range of 0.30 to 0.90, 0.40 to 0.90, 0.50 to 0.90, or 0.56 to 0.80, and is, for example, 0.56. When no unevenness is provided on the upper surface of the concrete beam 128, _μrc is 0.6λ, and when unevenness is provided (see FIG. 7), _μrc is 1.0λ. λ is a coefficient that depends on the type of concrete, and 0.75 is used for lightweight concrete, and 1.0 is used for normal concrete. Bs is the width of the flange (also called the steel frame width, which is the length in the direction parallel to the normal line of the web of the steel frame 122), and b is the width of the concrete beam 128 of the RC section 120a (the length in the direction parallel to the normal line of the web). b' is the effective width of the concrete beam 128 in the RC section 120a at the flange position (the position of the top surface of the upper flange) of the steel frame 122, and is the value obtained by subtracting the width Bs from the width b. _lj is the length (embedded length) of the steel frame 122 in each RC section 120a, and as described above, _le and _lc are the length from the column 110 to the steel frame 122 in the x direction and the length of the RC section 120a, respectively.

_Aaw is the sum of the cross-sectional areas of the multiple steel frame central _concentrated horizontal reinforcements 124b, and _Aσwy is the yield strength or reference strength (F value) of each steel frame central concentrated horizontal reinforcement 124b. Here, the cross _- sectional area of the reinforcing bar is the area of the cross section perpendicular to the direction in which the reinforcing bar extends. Therefore, the first term in the parentheses in formula (2) represents the contribution of the steel frame central concentrated horizontal reinforcement 124b.

_s a _w is the sum of the cross-sectional areas of the multiple second intermediate transverse reinforcements 124d, and _s σ _wy is the yield strength or reference strength (F value) of each second intermediate transverse reinforcement 124d. Therefore, the second term in the brackets in Equation (2) represents the contribution of the second intermediate transverse reinforcement 124d.

_oaw is the sum of the cross _- sectional areas of the multiple steel frame end concentrated horizontal reinforcements 124a, _{and oσwy} is the yield strength or reference strength (F value) of each steel frame end concentrated horizontal reinforcement 124a. Therefore, the third term in the parentheses in formula (2) represents the contribution of the steel frame end concentrated horizontal reinforcement 124a.

（１） _sw a _w is the sum of the cross-sectional areas of the multiple insert bars 125, and _sw σ _wy is the yield strength or reference strength (F value) of each insert bar 125. Therefore, the fourth term in the parentheses in formula (2) represents the contribution of the insert bars 125. When the insert bars 125 are not used, the fourth term becomes 0, and therefore formula (2) can be rewritten as the following formula (1).

(1)

_e a _w is the sum of the cross-sectional areas of the first intermediate transverse reinforcements 124 c, and _e σ _wy is the yield strength or reference strength (F value) of each first intermediate transverse reinforcement 124 c. Therefore, the fifth term in the brackets in Equation (2) represents the contribution of the first intermediate transverse reinforcement 124 c.

σ ₀ is the average vertical stress on the interface 130. Therefore, the sixth term in the brackets of equation (2) represents the contribution of the average vertical stress on the interface 130.

As described above, the design method of the hybrid beam-equipped structure 100 according to the embodiment of the present invention includes calculating the ultimate strength q _fr at the interface (i.e., the joint surface 130) between two concretes (beam concrete 128 and slab concrete 152) present in the RC section 120a. In calculating the ultimate strength q _fr , the contribution of the transverse reinforcement 124 and the plug 125 provided in the RC section 120a and the average vertical stress acting on the joint surface 130 are taken into consideration. At this time, the equivalent friction coefficient μ _eq is used as the friction coefficient of the joint surface 130. The equivalent friction coefficient μ _eq is calculated by multiplying the friction coefficients of the interface between the steel frame 122 and the concrete slab 152 and the interface between the concrete beam 128 and the concrete slab 152 constituting the joint surface 130 by the area ratios of the respective interfaces and adding up the values. μ _eq can be selected from the range of 0.40 to 0.9 or 0.56 to 0.8, and may be, for example, 0.56 when a wide margin is required for the ultimate strength q _fr . This design method allows the ultimate shear strength at the joint surface 130 between the concrete beam 128 and the concrete slab 152 to be calculated accurately, and as a result, horizontal sliding failure at the joint surface can be effectively prevented. Therefore, even if a low-strength concrete slab 152 is used for a part of the RC section 120a and the floor slab 150, a structure 100 with excellent earthquake resistance can be provided.

Third Embodiment
In this embodiment, an example of a construction method for the structure 100 described in the first embodiment will be described. In this embodiment, a structure 100 formed by four columns 110 and four beams 120 that are hybrid beams connecting the columns 110 will be described, but the number of columns 110 and the number of beams 120 are not limited. Descriptions of configurations that are the same as or similar to those described in the first and second embodiments may be omitted.

1. Fabrication of Beam The fabrication method of the beam will be explained with reference to Fig. 10(A) to Fig. 11(C). Fig. 10(A) and Fig. 11(A) are schematic top views, and Fig. 10(B) and Fig. 11(B) are schematic side views. Fig. 10(C) and Fig. 11(C) are schematic views of the end faces along the dashed lines CC' and DD' in Fig. 10(A) and Fig. 11(A), respectively.

First, the beam reinforcement 126 and the horizontal reinforcement 124 are placed at the end of the steel frame 122 (FIGS. 10(A) to 10(C)). If necessary, the insert 125 may be placed. After that, a formwork (not shown) is installed, and ready-mixed concrete is poured into the formwork and hardened to form the beam concrete 128 (FIGS. 11(A) to 11(C)). As described in the first embodiment, the ready-mixed concrete may be poured so that, for example, the beam reinforcement 126 and a part of each horizontal reinforcement 124 installed on the lower side of the steel frame 122 are embedded, and the other parts of the beam reinforcement 126 and each horizontal reinforcement 124 installed on the upper side of the steel frame 122 are exposed. In the example described in this embodiment, the ready-mixed concrete is poured so that its upper surface is flush with the upper surface of the upper flange of the steel frame 122 (see FIG. 11(C)). When the ready-mixed concrete begins to harden, the top surface of the beam concrete 128 may be treated by brushing or other means to create irregularities.

At this time, the length of the steel frame 122, the steel frame width Bs, the width b of the concrete beam 128, the length l _e from the column 110 to the steel frame 122, the length l c of the RC section 120a, and the arrangement of the transverse reinforcement bars 124 (i.e., the number _and arrangement density of the concentrated transverse reinforcement bars 124a at the end of the steel frame, the concentrated transverse reinforcement bars 124b at the center of the steel frame, the first intermediate transverse reinforcement bars 124c, and the second intermediate transverse reinforcement bars 124d) are determined based on the ultimate shear strength required for the joint surface 130 between the concrete beam 128 and the concrete slab 152, which is obtained based on the structural calculations of the structure 100.

2. Construction of Pillars Since the construction of the pillars 110 can be performed by applying a known method, detailed explanation will be omitted, but for example, a reinforcing bar unit consisting of the column main bars 112 and the hoops 114 and the like and concrete surrounding the reinforcing bar unit may be prepared in advance to construct the pillars 110, and the reinforcing bar unit may be connected to a pile or an existing pillar 110. Alternatively, the pillars 110 may be constructed by connecting the reinforcing bar unit to a pile and then pouring concrete.

3. Installation of Beams Next, the beam 120 is installed on the column 110. As shown in the schematic top view and side view of Fig. 12(A) and Fig. 12(B), the beam 120 is lifted by a lifting machine (not shown), and the beam main reinforcements 126 exposed from both ends of the beam 120 are fitted into the column main reinforcements 112 and the hoop reinforcements 114. In this way, the beam 120 is installed on the column 110. If necessary, a column constituting an upper layer may be installed on the column 110.

As an optional configuration, one or more small beams 140 may be provided to connect a pair of steel frames 122 extending parallel to each other. The small beams 140 may also be steel frames with cross-sectional shapes such as H-shaped, I-shaped, T-shaped, and L-shaped. The strength of the small beams 140 may be smaller than the strength of the steel frames 122. In other words, the cross-sectional area of the small beams 140 may be smaller than the cross-sectional area of the steel frames 122. By providing the small beams 140, it is possible to prevent the deck plate 154, which will be described later, from bending.

4. Pouring the floor slab Next, the floor slab 150 is constructed. The floor slab 150 can also be constructed of reinforced concrete, and includes a reinforcing bar unit constructed on a metal or wooden plate material, and a slab concrete 152 in which the reinforcing bar unit is embedded. As an example, an example in which a deck plate 154 functioning as a plate material and a reinforcing bar truss 156 provided on the deck plate 154 are arranged on a steel frame 122 is shown in Figs. 13(A) to 14(B). As shown in Fig. 13(A), the deck plate 154 is a flat plate made of iron or stainless steel, and is fixed to the steel frame 122 and the small beam 140 by welding or bolts. The deck plate 154 may have an uneven shape. There is no restriction on the length of the deck plate 154, and it may be greater than or less than the interval between a pair of steel frames 122 extending parallel to each other. In the latter case, as shown in FIG. 14(A), one deck plate 154 is placed and fixed on one steel frame 122 and one minor beam 140 or on adjacent minor beams 140 .

The reinforcing bar truss 156 is a reinforcing bar unit provided on the deck plate 154. The deck plate 154 on which the reinforcing bar truss 156 has been formed may be placed on the steel frame 122, or the reinforcing bar truss 156 may be placed on the deck plate 154 placed on the steel frame 122. The configuration of the reinforcing bar truss 156 may also be selected arbitrarily. For example, as shown in Figures 13(A) to 13(C), the main components may include reinforcing bars such as upper main bars 158, lower main bars 160, lattice material 162, and hanging material 164.

The upper main reinforcement 158 and the lower main reinforcement 160 extend in one direction (for example, the x direction), and the upper main reinforcement 158 is placed on the lower main reinforcement 160. The upper main reinforcement 158 and the lower main reinforcement 160 may be arranged so as to be parallel to the long side direction of the deck plate 154, or so as to be parallel to the short side direction. The lattice material 162 is arranged between the lower main reinforcement 160 and the upper main reinforcement 158, and is fixed to the lower main reinforcement 160 and the upper main reinforcement 158 by welding or bolts. The lattice material 162 has a wave shape between the lower main reinforcement 160 and the upper main reinforcement 158, and extends in the direction in which the lower main reinforcement 160 and the upper main reinforcement 158 extend. This firmly fixes the lower main reinforcement 160 and the upper main reinforcement 158, providing high resistance to tension applied in the x direction and the vertical direction (z direction). On the other hand, the hanging member 164 extends in a direction (e.g., the y direction) that intersects with the direction in which the lower main reinforcement 160 and the upper main reinforcement 158 extend. The hanging member 164 is fixed to the deck plate 154 by welding or bolts, and is also fixed to the upper main reinforcement 158. The hanging member 164 is bent so as to have a shape that surrounds a triangle with the deck plate 154 as its bottom surface and the upper main reinforcement 158 as its apex, and is fixed to the deck plate 154 and the upper main reinforcement 158.

Next, as shown in the schematic top and side views of Figures 14(A) and 14(B), a deck plate 154 is placed on the steel frame 122 and the small beams 140. Note that instead of using the deck plate 154 and the reinforcing bar truss 156 illustrated in Figures 13(A) to 13(C), multiple reinforcing bars may be arranged in a mesh pattern on a wooden board.

After that, a formwork (not shown) for pouring the slab concrete 152 is installed, and ready-mixed concrete is poured into the formwork and allowed to harden (Figures 15(A) and 15(B)). As described above, when adjusting the strength of the slab concrete 152 to be less than the strength of the beam concrete 128, for example, the amount of cement in the ready-mixed concrete forming the slab concrete 152 may be made less than that of the beam concrete 128. Note that the columns 110 of the upper floors may be further connected before or after pouring the slab concrete 152.

As shown in the schematic end views (FIGS. 16(A) and 16(B)) along the dashed lines E-E' and F-F' in FIG. 15(A), the ready-mixed concrete that provides the slab concrete 152 is poured so as to embed the reinforcing bar truss 156. As a result, in the RC section 120a, the beam concrete 128 is poured so as to contact the slab concrete 152 and the steel frame 122, and in the S section 120b, the flange of the steel frame 122 contacts the slab concrete 152. Note that before pouring the ready-mixed concrete, multiple slab reinforcements 166 may be placed across the adjacent deck plate 154 via the beam 120 (see FIG. 16(A) and FIG. 16(B)). The multiple slab reinforcements 166 are placed on the reinforcing bar truss 156 and cross the upper main reinforcement 158, etc.

By appropriately applying the above construction methods, the structure 100 described in the first embodiment can be constructed.

The above-described embodiments of the present invention may be combined as appropriate to the extent that they are not mutually inconsistent. Any embodiment in which a person skilled in the art appropriately adds or deletes components or modifies the design is also included within the scope of the present invention as long as it contains the gist of the present invention.

Even if there are other effects and advantages different from those brought about by the above-mentioned embodiments, if they are clear from the description in this specification or can be easily predicted by a person skilled in the art, they are naturally understood to be brought about by the present invention.

100: Structure, 110: Column, 110-1: First column, 110-2: Second column, 110-3: Third column, 110-4: Fourth column, 110-5: Fifth column, 110-6: Sixth column, 112: Main column reinforcement, 114: Hoop reinforcement, 120: Beam, 120-1: First beam, 120-2: Second beam, 120-3: Third beam, 120-4: Fourth beam, 120b: S section, 122: Steel frame, 124: Horizontal reinforcement, 124a: Concentrated horizontal reinforcement on the end of the steel frame, 124b: Steel frame central concentrated horizontal reinforcement, 124c: First intermediate horizontal reinforcement, 124d: Second intermediate horizontal reinforcement, 125: Inserted reinforcement, 126: Beam main reinforcement, 126a: Fixing plate, 128: Beam concrete, 130: Joint surface, 140: Sub-beam, 150: Floor slab, 152: Slab concrete, 154: Deck plate, 156: Reinforced concrete truss, 158: Upper main reinforcement, 160: Lower main reinforcement, 162: Lattice material, 164: Suspension material, 166: Slab reinforcement

Claims (27)

Pillar,
A beam connected to the column; and a floor slab located on the beam,
The beam is
a steel frame spaced from the column; and a beam concrete in which an end of the steel frame on the column side is embedded,
the floor slab includes slab concrete in contact with an upper surface of the steel frame at the end portion;
The upper surface of the steel frame is located below or above the upper surface of the beam concrete ,
When the upper surface of the steel frame is located below the upper surface of the concrete beam, the concrete beam has a recess that exposes the upper surface of the steel frame,
A structural body in which, when the top surface of the steel frame is located above the top surface of the concrete beam, the top surface of the steel frame is exposed from the concrete beam and embedded in the concrete slab . The beam is
The steel frame further includes a plurality of beam reinforcements extending in the longitudinal direction of the steel frame, and a plurality of transverse reinforcements intersecting the plurality of beam reinforcements and surrounding the plurality of beam reinforcements,
The structure according to claim 1 , wherein each of the plurality of horizontal reinforcements is partially embedded in the beam concrete and partially exposed from the beam concrete. The structure of claim 1, wherein the strength of the slab concrete is lower than that of the beam concrete. The structure of claim 2, wherein each of the plurality of transverse reinforcements is partially embedded in the slab concrete. The plurality of beam main reinforcements include
The structure according to claim 2 , comprising: at least one beam main bar embedded in the beam concrete and spaced apart from the slab concrete; and at least one beam main bar embedded in the slab concrete and exposed from the beam concrete. The structure of claim 2, wherein the beam further includes a plurality of insert bars that intersect the plurality of beam main bars and surround the plurality of beam main bars. The plurality of transverse reinforcements include
A plurality of steel frame end side concentrated transverse reinforcements surrounding the end of the steel frame and arranged at a first density;
A plurality of steel frame central side concentrated transverse reinforcements arranged at a position farther from the column than the end side of the steel frame and arranged at a second density;
3. The structure according to claim 2, further comprising: a plurality of first intermediate horizontal reinforcements arranged between the plurality of steel frame end side concentrated horizontal reinforcements and the column at a third density lower than the first density and the second density; and a plurality of second intermediate horizontal reinforcements arranged between the plurality of steel frame end side concentrated horizontal reinforcements and the plurality of steel frame center side concentrated horizontal reinforcements and arranged at a fourth density lower than the first density and the second density. connecting a beam to a column; and forming a floor slab on the beam;
The beam is
A steel frame, and a concrete beam in which an end of the steel frame is embedded,
The beam is connected to the column so that the beam concrete is located on the column side and the end is spaced apart from the column;
the floor slab includes slab concrete in contact with an upper surface of the steel frame at the end portion;
The upper surface of the steel frame is located below or above the upper surface of the beam concrete ,
When the upper surface of the steel frame is located below the upper surface of the concrete beam, the concrete beam has a recess that exposes the upper surface of the steel frame,
A structural construction method , in which, when the top surface of the steel frame is located above the top surface of the concrete beam, the top surface of the steel frame is exposed from the concrete beam and embedded in the concrete slab . The construction method according to claim 8, in which the beam is constructed by placing a plurality of main beam reinforcements extending in the longitudinal direction of the steel frame and a plurality of transverse reinforcements intersecting the plurality of main beam reinforcements and surrounding the plurality of main beam reinforcements at the end of the steel frame, and pouring the beam concrete so as to embed the end, a portion of the plurality of main beam reinforcements, and a portion of the plurality of transverse reinforcements. The construction method according to claim 8, wherein the strength of the slab concrete is lower than that of the beam concrete. The construction method according to claim 9, wherein the beam concrete is poured so as to embed a portion of each of the plurality of transverse reinforcements in the beam concrete. The construction method according to claim 9, wherein the beam concrete is poured so that at least one of the multiple beam main reinforcements is embedded in the beam concrete and at least one of the multiple beam main reinforcements is exposed from the beam concrete. The construction method according to claim 9, wherein the fabrication of the beam further includes arranging a plurality of insert bars so as to intersect with and surround the plurality of beam main bars before pouring the beam concrete. The construction method according to claim 9, further comprising forming irregularities on the upper surface of the beam concrete before forming the floor slab. A method for designing a structure including a column, a beam connected to the column, and a floor slab located on the beam, comprising the steps of:
The beam is
A steel frame spaced from the column;
A plurality of beam reinforcements extending in the longitudinal direction of the steel frame;
a plurality of transverse reinforcements intersecting the plurality of beam main reinforcements and surrounding the plurality of beam main reinforcements; and a beam concrete in which the end of the steel frame on the column side, a portion of the plurality of beam main reinforcements, and a portion of the plurality of transverse reinforcements are embedded,
the floor slab has slab concrete in contact with the upper surface of the steel frame at the end portion and in which another part of the plurality of main beam reinforcements and another part of the plurality of transverse reinforcements are embedded;
The plurality of transverse reinforcements include
a plurality of steel frame end side concentrated transverse reinforcements arranged at a first density and at least partially surrounding the end of the steel frame;
A plurality of steel frame center concentrated transverse reinforcements arranged at a position farther from the column than the plurality of steel frame end side concentrated transverse reinforcements and arranged at a second density;
a plurality of first intermediate horizontal reinforcements arranged between the plurality of steel frame end side concentrated horizontal reinforcements and the column at a third density lower than the first density and the second density; and a plurality of second intermediate horizontal reinforcements arranged between the plurality of steel frame end side concentrated horizontal reinforcements and the plurality of steel frame center side concentrated horizontal reinforcements and arranged at a fourth density lower than the first density and the second density,
The design method includes calculating the ultimate strength of the joint surface by taking into consideration the contributions of the multiple concentrated horizontal reinforcements at the end sides of the steel frame, the multiple concentrated horizontal reinforcements at the center side of the steel frame, the multiple first intermediate horizontal reinforcements, and the multiple second intermediate horizontal reinforcements, as well as the vertical stress components acting on the joint surface between the beam concrete and the slab concrete. The design method according to claim 15, wherein the contribution of the multiple steel end concentrated horizontal reinforcements is expressed as the product of the sum of the cross-sectional areas of the multiple steel end concentrated horizontal reinforcements, the yield strength or reference strength (F value) of each of the multiple steel end concentrated horizontal reinforcements, and the friction coefficient between the beam concrete and the slab concrete. The design method according to claim 15, wherein the strength of the slab concrete is lower than the strength of the beam concrete. The design method according to claim 15, wherein the contribution of the multiple steel central concentrated horizontal reinforcements is expressed as the product of the sum of the cross-sectional areas of the multiple steel central concentrated horizontal reinforcements, the yield strength or reference strength (F value) of each of the multiple steel central concentrated horizontal reinforcements, and the friction coefficient between the beam concrete and the slab concrete. The design method according to claim 15, wherein the contribution of the first intermediate transverse reinforcement is expressed as the product of the sum of the cross-sectional areas of the first intermediate transverse reinforcement, the yield strength or reference strength (F value) of each of the first intermediate transverse reinforcement, and the friction coefficient between the beam concrete and the slab concrete. The design method according to claim 15, wherein the contribution of the second intermediate transverse reinforcement is expressed as the product of the sum of the cross-sectional areas of the second intermediate transverse reinforcement, the yield strength or reference strength (F value) of each of the second intermediate transverse reinforcement, and the friction coefficient between the beam concrete and the slab concrete. The beam further includes a plurality of insert bars that intersect the plurality of beam main bars and surround the plurality of beam main bars;
The beam concrete has a part of the plurality of insert bars embedded therein,
Another part of the plurality of insert bars is embedded in the slab concrete.
16. The design method according to claim 15, wherein the calculation of the ultimate strength further takes into account the contribution of the plurality of plug bars, which is expressed by the product of the sum of the cross-sectional areas of the plurality of plug bars, the yield strength or reference strength (F value) of each of the plurality of plug bars, and the friction coefficient between the beam concrete and the slab concrete. The design method for a structure according to any one of claims 16 to 21, wherein the coefficient of friction between the steel frame and the slab concrete is selected from the range of 0.40 to 0.90. A method for designing a structure including a column, a beam connected to the column, and a floor slab located on the beam, comprising the steps of:
The beam is
a steel frame having a web spaced apart from the column and a pair of flanges connected to the web;
A plurality of beam reinforcements extending in the longitudinal direction of the steel frame;
a plurality of transverse reinforcements intersecting the plurality of beam main reinforcements and surrounding the plurality of beam main reinforcements; and a beam concrete in which the end of the steel frame on the column side, a portion of the plurality of beam main reinforcements, and a portion of the plurality of transverse reinforcements are embedded,
the floor slab has slab concrete in contact with the upper surface of the steel frame at the end portion and in which another part of the plurality of main beam reinforcements and another part of the plurality of transverse reinforcements are embedded;
The plurality of transverse reinforcements include
a plurality of steel frame end side concentrated transverse reinforcements arranged at a first density and at least partially surrounding the end of the steel frame;
A plurality of steel frame center concentrated transverse reinforcements arranged at a position farther from the column than the plurality of steel frame end side concentrated transverse reinforcements and arranged at a second density;
a plurality of first intermediate horizontal reinforcements arranged between the plurality of steel frame end side concentrated horizontal reinforcements and the column at a third density lower than the first density and the second density; and a plurality of second intermediate horizontal reinforcements arranged between the plurality of steel frame end side concentrated horizontal reinforcements and the plurality of steel frame center side concentrated horizontal reinforcements and arranged at a fourth density lower than the first density and the second density,
The design method includes calculating an ultimate strength _qfr of a joint interface between the beam concrete and the slab concrete according to the following formula (1):

(1)
In formula (1),
μ _eq is the friction coefficient of the joining surfaces,
_A a _w is the sum of the cross-sectional areas of the multiple steel frame central concentrated horizontal reinforcements,
_A σ _wy is the yield strength or reference strength (F value) of each of the plurality of steel frame central concentrated horizontal reinforcements,
_s a _w is the sum of the cross-sectional areas of the second intermediate transverse reinforcements,
_s σ _wy is the yield strength or reference strength (F value) of each of the second intermediate transverse reinforcements;
_o a _w is the sum of the cross-sectional areas of the multiple steel frame end side concentrated transverse reinforcements,
_o σ _wy is the yield strength or reference strength (F value) of each of the plurality of steel frame end side concentrated horizontal reinforcements,
_e a _w is the sum of the cross-sectional areas of the first intermediate transverse reinforcements,
_e σ _wy is the yield strength or reference strength (F value) of each of the first intermediate transverse reinforcements;
σ ₀ is the average vertical stress on the joint surface,
b' is the effective width of the beam concrete at the upper flange position of the pair of flanges,
l _c is the length of the concrete beam in the direction of extension of the steel beam, design method. The beam further includes a plurality of insert bars that intersect the plurality of beam main bars and surround the plurality of beam main bars;
The beam concrete has a part of the plurality of insert bars embedded therein,
Another part of the plurality of insert bars is embedded in the slab concrete.
The design method includes calculating the ultimate strength q _fr according to the following equation (2):

(2)
_sw a _w is the sum of the cross-sectional areas of the multiple insert bars,
24. The design method according to claim 23, wherein _swσwy is the yield strength or reference strength (F value) of each of _the plurality of piercing bars. The friction coefficient μ _eq is expressed by the following formula:

In the above formula,
μ _s is the friction coefficient between the steel frame and the slab concrete,
_Bs is the length of the flange in a direction parallel to the normal to the web;
l _j is the length of the portion of the steel frame embedded in the beam concrete in the longitudinal direction of the steel frame,
μ _rc is the friction coefficient between the beam concrete and the slab concrete,
b is the length of the beam concrete in the direction parallel to the normal line;
The design method according to claim 23, wherein l _e is the distance from the steel frame to the column in the longitudinal direction of the steel frame. 24. The method for designing a structure according to claim 23, wherein the friction coefficient _μs between the steel frame and the slab concrete is selected from the range of 0.40 to 0.90. The design method according to claim 23, wherein the strength of the slab concrete is lower than the strength of the beam concrete.

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