JP2020159035A - Underground skeleton structure - Google Patents

Abstract

To provide an underground skeleton structure that prevents downward displacement of a reinforced concrete beam with respect to a steel-framed reinforced concrete column without attaching additional members such as shear connectors.SOLUTION: There is provided an underground skeleton structure comprising a steel-framed reinforced concrete column 2 including a steel frame made of H-shaped steel 21, and a reinforced concrete beam 3 extending only in the weak axis direction in the cross section of the H-shaped steel 21 and joined to the steel-framed reinforced concrete column 2. At least a part of a reinforcing bar 311A constituting a main reinforcing bar 311 of the reinforced concrete beam 3 is inserted into a through hole 214 formed in a web 213 of the H-shaped steel 21.SELECTED DRAWING: Figure 2

Description

The present invention relates to an underground skeleton structure.

Conventionally, the reverse striking method (construction pillar construction method) has been widely adopted for the structure of the underground floor of a skyscraper. In the reverse striking method, the foundation pedestal is usually constructed at the column formation position of the underground skeleton, and the main or temporary columns such as steel pipes, H-shaped steel, and cross H-shaped steel are constructed at the true position of the foundation pedestal. (Also called a pillar) is built, and while the upper skeleton is built on the structural pillar, the lower skeleton is built by counter-strike in parallel with it. In the conventional reverse striking method, it is common that the columns on the underground floor of a skyscraper are made of steel-framed reinforced concrete. In this case, for example, a steel frame such as cross-H-section steel with a reinforcing member such as a gusset, bracket, or stiffener attached at the beam mounting position is used as a structural pillar, and the earth drill method, benot method, and reverse circulation drill method are used. The lower part of the structural pillar is embedded in the foundation pillar by such means, and the SRC pillar is constructed by reverse striking.

Here, in Patent Document 1, cement milk is injected into the lower part of a small-diameter vertical hole formed at a beam forming position of an underground skeleton to build a structure pillar of rolled H-shaped steel to form a foundation pillar and a structure. The process of fixing the lower part of the pillar to the foundation pillar, and the part of the beam main bar of the RC beam is positioned around the part of the structural pillar corresponding to the beam formation position of each floor while sequentially cutting the ground, and vice versa. The process of forming only the RC beams, RC floors and the short parts of the corresponding SRC pillars by striking, and the pillar reinforcing bars are placed around the structural pillars that roughly correspond to the room space on each floor, and the floor below the underground skeleton. A reverse striking method including a step of placing concrete around the structural pillar and the pillar reinforcing bar to form an SRC pillar having the structural pillar as the main steel frame is described in order from the upper floor to the upper floor. This eliminates the need to manufacture structural pillars at a steel frame factory, improves the connection between the SRC columns of the underground frame and the RC beams, and improves workability.

Further, in Patent Document 1, in order to prevent the RC beam and the RC floor from being displaced downward due to the load, a bulging portion at the tip, for example, in the portion of the structural pillar corresponding to the formation position of the RC beam in the underground skeleton. It is also described to fix a shear connector such as a headed stud on which is formed. In the reverse striking method described in Patent Document 1, SRC columns having the structural pillars as pillar steel frames are formed around the structural pillars substantially corresponding to the room space on each floor, and act on the RC beams and the RC floor. Since the load is supported by the RC portion of the SRC column, the shear connector can be easily configured and can be installed before and after the construction of the structural column at the construction site.

Japanese Unexamined Patent Publication No. 5-156654

However, when the shear connector is attached by the reverse striking method described in Patent Document 1, even if the configuration is simple, the main bar of the RC beam and the shear connector will intersect at the column-beam joint, so that the shear connector will intersect at the site. There was a possibility that the process of bar arrangement and concrete placement would be complicated.

Therefore, the present invention provides a new and improved underground skeleton structure capable of preventing a downward displacement of a reinforced concrete beam with respect to a steel-framed reinforced concrete column without attaching an additional member such as a shear connector. With the goal.

According to a certain aspect of the present invention, an underground skeleton structure including a steel-framed reinforced concrete column including a steel frame made of H-shaped steel and a reinforced concrete beam extending only in the weak axis direction in the cross section of the H-shaped steel and joined to the steel-framed reinforced concrete column. Is provided. At least a part of the reinforcing bars constituting the main reinforcing bars of the reinforced concrete beam is inserted into the through holes formed in the web of the H-section steel. The H-section steel may form a structural pillar whose lower portion is embedded in the foundation pillar. Further, the diameter of the through hole may be twice or less the diameter of the reinforcing bar. Further, a plurality of through holes are arranged side by side in the horizontal direction, and the distance between adjacent through holes may be 2.5 times or more the diameter of the reinforcing bar.

According to the above configuration, the through holes formed in the web of the H-section steel function as the gibber (slip prevention) of the reinforced concrete beam, so that the reinforced concrete for the reinforced concrete column without attaching an additional member such as a shear connector. It is possible to prevent the beam from shifting downward. Further, the gibber effect of the through hole can be expected to further increase the strength by passing a reinforcing bar through the through hole. That is, by passing the reinforcing bar of the reinforced concrete beam through the through hole, a stronger column and beam slip prevention mechanism can be constructed.

It is sectional drawing of the underground skeleton structure which concerns on one Embodiment of this invention. It is an enlarged view of the vicinity of the steel-framed reinforced concrete column of FIG. 2 is a cross-sectional view of FIG. 2 in different directions.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

FIG. 1 is a simplified cross-sectional view of an underground skeleton structure according to an embodiment of the present invention. As shown in FIG. 1, the underground skeleton structure 1 includes a steel-framed reinforced concrete column 2, a reinforced concrete beam 3, a reinforced concrete floor 4, and a reinforced concrete wall 5. The reinforced concrete beam 3 is joined to the reinforced concrete column 2, and the reinforced concrete floor 4 is joined to the reinforced concrete beam 3 and the reinforced concrete wall 5. The steel-framed reinforced concrete column 2 includes a steel frame made of H-shaped steel 21.

As shown in the figure, in the present embodiment, the reinforced concrete beam 3 extends only in the weak axis direction (y direction in the drawing) in the cross section of the H-shaped steel 21. Here, in the present specification, the weak axis direction in the cross section of the member means the direction of the axis of symmetry of the cross section in which the moment of inertia of area is minimized. In the case of the H-section steel 21, the direction of the axis that passes through the center of the web and is perpendicular to the web in the cross section is the weak axis direction. As a result, as will be described later, the main bar of the reinforced concrete beam 3 extends only in the weak axis direction of the H-shaped steel 21, and at least a part of the reinforcing bars constituting the main bar is inserted into the through hole formed in the web of the H-shaped steel 21. It becomes possible to do.

In the underground skeleton structure 1, the reinforced concrete beam 3 does not extend in the x direction in the figure orthogonal to the y direction in the figure, that is, in the strong axis direction in the cross section of the H-shaped steel 21. However, in the underground skeleton structure 1, since the reinforced concrete floor 4 is constructed while sequentially cutting the ground, the ground can be used as a support at the time of construction. Therefore, in constructing the underground skeleton structure 1, it is easy to construct the reinforced concrete floor 4 even if the reinforced concrete beam 3 does not extend in the x direction. Further, in the underground skeleton structure 1, a large horizontal load generated at the time of an earthquake or the like is released to the ground through the reinforced concrete wall 5, so that the reinforced concrete beam 3 does not extend in the x direction is the load capacity of the underground skeleton structure 1. Has no substantial effect on sex.

In constructing the underground skeleton structure 1 as described above, first, the H-shaped steel 21 is built in a vertical hole excavated in the ground. For example, by injecting cement milk into the lower part of the vertical hole and then building the H-shaped steel 21 in the vertical hole, a structural pillar whose lower part is embedded in the foundation pedestal is formed. Next, the steel-framed reinforced concrete columns 2, the reinforced concrete beams 3, and the reinforced concrete floor 4 that constitute the room space of each floor of the underground skeleton structure 1 are constructed while sequentially cutting the ground. Specifically, column reinforcing bars are arranged around the H-shaped steel 21, beam reinforcing bars and floor reinforcing bars are arranged on the ground exposed by root cutting, and then concrete is cast around the respective steel frames and reinforcing bars. Set up. As described above, since the ground can be used as a support at the time of construction, the reinforced concrete floor 4 can be easily constructed even if the reinforced concrete beam 3 does not extend in the x direction in the drawing.

FIG. 2 is an enlarged view of the vicinity of the steel-framed reinforced concrete column in the underground skeleton structure shown in FIG. 1, and FIG. 3 is a cross-sectional view of FIG. 2 in different directions. In FIGS. 2 and 3, the cross sections of the respective figures are shown by lines II-II and III-III, respectively. As shown in the figure, the steel-framed reinforced concrete columns 2 are formed around the H-shaped steel 21 constituting the steel frame, the column reinforcing bars 22 arranged around the H-shaped steel 21, and the H-shaped steel 21 and the column reinforcing bars 22. Includes the concrete 23 to be cast. The H-section steel 21 is composed of flanges 211, 212 and web 213, and a plurality of through holes 214 are formed in the web 213. In the case of the present embodiment, two through holes 214 are arranged side by side in the horizontal direction, and in the case of the one shown in FIG. 3, a set of two through holes 214 and 214 is provided in a plurality of stages at different heights. There is. Here, the weak axis direction (y direction in the drawing, common to FIG. 1) in the cross section of the H-section steel 21 is the direction of the axis that passes through the center of the web 213 and is perpendicular to the web 213. Therefore, the through hole 214 formed in the web 213 opens in the weak axis direction of the H-shaped steel 21.

Further, as shown in the drawing, the reinforced concrete beam 3 includes a beam reinforcing bar 31 and a concrete 32 cast around the beam reinforcing bar 31. The beam reinforcing bar 31 includes a main reinforcing bar 311 and a rib reinforcing bar 312. As described above, in the present embodiment, since the reinforced concrete beam 3 extends only in the weak axis direction in the cross section of the H-shaped steel 21, the main bar 311 of the reinforced concrete beam 3 also extends only in the weak axis direction in the cross section of the H-shaped steel 21, and the main bar 311 It becomes possible to insert the reinforcing bar 311A constituting the above through the through hole 214 formed in the web 213 of the H-shaped steel 21. In this way, by inserting the reinforcing bar 311A constituting the main bar 311 of the reinforced concrete beam 3 into the through hole 214, the through hole 214 prevents the reinforced concrete beam 3 from shifting downward with respect to the steel-framed reinforced concrete column 2 due to the load. Functions as a gibber (anti-slip).

Here, after the concrete 23 of the steel-framed reinforced concrete column 2 and the concrete 32 of the reinforced concrete beam 3 are cast, both the H-shaped steel 21 and the reinforcing bar 311A are fixed in the concrete. Therefore, the through hole 214 can function as a gibber even when there is a gap between the reinforcing bar 311A and the through hole 214. Specifically, for example, if the diameter of the through hole 214 is twice or less the diameter of the reinforcing bar 311A, the through hole 214 can function as a gibber.

In the illustrated example, another reinforcing bar 311B constituting the main bar 311 is not inserted through the through hole 214. As described above, in the present embodiment, at least a part of the reinforcing bars constituting the main reinforcing bar 311 of the reinforced concrete beam 3 may be inserted through the through hole 214. In another embodiment, all the reinforcing bars constituting the main reinforcing bar of the reinforced concrete beam may be inserted through the through holes formed in the web of the H-section steel.
Further, the distance d between adjacent through holes 214 and 214 arranged side by side in the horizontal direction (distance between the peripheral edges of the through holes 214) is 2.5 times or more the diameter of the main bar 311 from the viewpoint of ensuring the fixation of the reinforcing bar. Is desirable. The spacing between these through holes 214 and 214 is such that the aggregate of concrete is sufficiently filled between the plurality of reinforcing bars, and the concrete between the reinforcing bars exerts a predetermined strength more stably. The required interval. When the distance between the adjacent through holes 214 and 214 is 2.5 times or more, the concrete aggregate is sufficiently filled between the reinforcing bars, so that the fixing of the reinforcing bars can be secured more stably. This makes it possible to more stably prevent early split fracture and adhesion fracture due to insufficient strength of concrete between the reinforcing bars. The upper limit of the distance between adjacent through holes is not particularly specified, but it is appropriately set within the possible range according to various conditions such as the width of the web of the H-section steel, the size of the through holes, and the diameter of the reinforcing bar. be able to.

According to the configuration of the present embodiment as described above, the reinforced concrete beam 3 is loaded against the steel-framed reinforced concrete column 2 without using a reinforcing member for beam mounting such as a shear connector, a gusset, a bracket, and a stiffener. It is possible to prevent it from shifting downward. By eliminating the need for a reinforcing member for attaching the beam, for example, the beam reinforcing bar 31 and the shear connector do not intersect at the column-beam joint, and the process of bar arrangement and concrete placement at the site is simplified. Further, since the reinforcing member for mounting the beam does not protrude from the cross section of the H-shaped steel, the hole diameter can be minimized when the H-shaped steel is built into the vertical hole excavated in the ground.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 ... Underground skeleton structure, 2 ... Reinforced concrete columns, 3 ... Reinforced concrete beams, 4 ... Reinforced concrete floors, 5 ... Reinforced concrete walls, 21 ... H-shaped steel, 213 ... Web, 214 ... Through holes, 22 ... Reinforcing bars, 31 ... Beams Reinforcing bar, 311 ... Main bar group, 311A, 311B ... Reinforcing bar.

Claims (4)

Steel-framed reinforced concrete columns including steel frames made of H-shaped steel,
It is provided with a reinforced concrete beam that extends only in the weak axis direction in the cross section of the H-section steel and is joined to the steel-framed reinforced concrete column.
An underground skeleton structure in which at least a part of the reinforcing bars constituting the main reinforcing bar of the reinforced concrete beam is inserted into a through hole formed in the web of the H-shaped steel. The underground skeleton structure according to claim 1, wherein the H-section steel forms a structural pillar whose lower portion is embedded in a foundation pedestal. The underground skeleton structure according to claim 1 or 2, wherein the diameter of the through hole is not more than twice the diameter of the reinforcing bar. The one according to any one of claims 1 to 3, wherein a plurality of the through holes are arranged side by side in the horizontal direction, and the distance between the adjacent through holes is 2.5 times or more the diameter of the reinforcing bar. Underground skeleton structure.

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