JP6804003B1 - Formwork structure for concrete placement and central member for concrete placement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To define a stable distance between a first defining member which defines a distance between first formwork forming members facing each other and a second formwork forming member orthogonal to the first formwork forming member. SOLUTION: A concrete casting formwork 3 having a first formwork forming member 1 facing each other and a second formwork forming member 2 orthogonal to these, and a distance W1 between the first formwork forming members 1 The first defining member 10 includes a first defining member 10 and a second defining member 20 that defines a distance W2 between the first defining member 10 and the second form forming member 2. The first defining member 10 is a first form. It is arranged orthogonal to the forming member 1, and screw portions are provided at both ends, and a central screw portion 14 is provided at the center portion where the screw portions at both ends and the axis line 14a are orthogonal to each other. The central member 15 in which the axis 14a of the central thread portion 14 is orthogonal to each other on the same plane, the first rod-shaped threaded member 11 that connects to the threaded portions at both ends of the central member 15, and the central threaded portion 14 of the central member 15. A second rod-shaped screw member 22 to be connected is provided. [Selection diagram] Fig. 1

Description

The present invention relates to a concrete casting formwork structure and a concrete casting central member.

Conventionally, for example, as seen in FIG. 2 of Patent Document 1,
It has a first formwork forming member (100, 100) arranged to face each other in a plan view and a second formwork forming member (100) orthogonal to the first formwork forming member (100, 100). Formwork for concrete placement and
The first defining member (21) provided in the concrete casting formwork and defining the distance between the first formwork forming members (110, 100), the first defining member (21), and the first The second defining member (22), which defines the distance from the two formwork forming member (100),
It is a formwork structure for concrete placement equipped with
In a plan view, the first defining member (21) is
The first form-forming members (100, 100) are arranged orthogonal to the first form-forming member (100, 100), and a central screw portion is provided in the central portion (23). With the member (21)
In a plan view, the second defined member (22) is
The concrete casting formwork structure provided with the second rod-shaped screw member that makes it possible to adjust the distance between the central member and the second formwork forming member by screwing with the central screw portion of the central member is known. Has been done.

According to the concrete casting formwork structure of Patent Document 1, the first defining member (21) and the second defining member (22) are used to form the first defining member (21) and the second defining member (100). It may be possible to specify the interval with.

However, in Patent Document 1, in paragraph 0040,
"In the second embodiment configured as described above, the support member main body 21 is inserted between the formwork 100 and 100 arranged in parallel, and the fixing members formed at both ends of the support member main body 21 are formed. The support member main body 21 and the formwork 1 are provided by the bolt member 33 of 30.
00 and 100 are fixed. "
Is stated in paragraph 0042,
"In addition, the bolt member 33 of the fixing member 30 may be configured to penetrate the support member main body 21."
However, the connecting structure between the support member main body 21 and the fixing member 30 is not described, and the support member main body 21 is a member having a U-shaped cross section that opens toward the support rod member 22 side. (Paragraph 0037 of the same document and FIG. 2B), the support member main body 21 may move in the axial direction of the support rod member 22.

Therefore, the distance between the first defined member (support member main body 21) and the second formwork forming member (100) may become unstable.

Further, conventionally, as seen in FIGS. 2 to 4 of Patent Document 2, for example,
It has a first formwork forming member (12a, 12b) arranged to face each other in a plan view and a second formwork forming member (11) orthogonal to the first formwork forming member (12a, 12b). Formwork for concrete placement and
A first defining member (first separator 13) provided in the concrete casting formwork and defining the distance between the first formwork forming members (12a, 12b) and the first defining member (13). And the second defining member (second separator 14) that defines the distance between the second formwork forming member (11) and the second formwork forming member (11).
It is a formwork structure for concrete placement equipped with
A support metal fitting 21 made of a metal block in which two adjacent and orthogonal holes 22 and 23 (hole 22 is a screw hole and hole 23 is a through hole (stupid hole)) is provided.
The second defined member (14) is connected to the support metal fitting 21 by screwing one end to the screw hole 22 of the support metal fitting 21 supported on the first separator 13 by passing the first separator 13 through the through hole 23. A formwork structure for placing concrete is known in which the distance from the second formwork forming member can be adjusted.

However, in the case of Patent Document 2, the support metal fitting 21 is slidable on the first separator 13, and the axial force (thrust force or tensile force) acting on the second separator 14 makes the support metal fitting 21 first. A moment is generated to rotate the separator 13 around the axis.

Therefore, the distance between the first defined member (first separator 13) and the second formwork forming member (11) may become unstable.

Jikkenhei 6-14356 Gazette Japanese Unexamined Patent Publication No. 8-53936

The problem to be solved by the present invention is a first defining member that defines the distance between the first form forming members arranged so as to face each other, and a second form forming member that is orthogonal to the first form forming member. It is an object of the present invention to provide a formwork structure for concrete placement and a central member for concrete placement, which can specify the interval between the two and the concrete in a stable state.

In order to solve the above problems, the formwork structure for concrete placement of the present invention
In a plan view, a first formwork forming member arranged to face each other, a second formwork forming member orthogonal to the first formworking member, and a concrete casting formwork having the same formwork.
The first defining member provided in the concrete casting formwork and defining the distance between the first formwork forming members and the distance between the first defining member and the second formwork forming member are defined. 2nd regulation member and
It is a formwork structure for concrete placement equipped with
In a plan view, the first defined member is
The first form-forming members are arranged orthogonal to the first form-forming member, and screw portions are provided at both ends, and the screw portions at both ends and the axis are orthogonal to each other at the center. A central member, which is provided with a threaded portion and whose axis of the threaded portion at both ends and the axis of the central threaded portion are orthogonal to each other on the same plane.
One first rod-shaped screw member that makes it possible to adjust the distance between the central member and one first formworking member by screw-coupling with one of the screw portions at both ends of the central member.
The other first rod-shaped screw member, which makes it possible to adjust the distance between the central member and the other first formwork forming member by screwing with the other screw portion of the screw portions at both ends of the central member.
With
In a plan view, the second defined member is
A second rod-shaped screw member is provided , which makes it possible to adjust the distance between the central member and the second formwork forming member by screwing with the central screw portion of the central member .
The threaded portions at both ends have a tubular nut shape.
With respect to the axial direction of the screw portions at both ends), the central member is shorter than the distance between the first form forming members.
A connecting member connecting the first rod-shaped screw member and the first formworking member is screwed to the end of the first rod-shaped screw member on the side of the first formworking member.
The length of the screw connection between the screw portion at the end of the central member and the first rod-shaped screw member excludes the screw joint at the end of the central member in the first rod-shaped screw member and the screw connection with the connection member. Longer than the length of the part,
The central portion of the central member is characterized by having a pair of flat portions facing each other with the axes of the screw portions at both ends thereof interposed therebetween .

According to this concrete casting formwork structure
In a plan view, the first defining member that defines the distance between the first formwork forming members is
The first formwork forming members are arranged orthogonal to the first formwork forming member, and screw portions are provided at both ends, and a central screw portion whose axis is orthogonal to the screw portions at both ends is provided in the central portion. Is provided, and the central member, wherein the axis of the threaded portion at both ends and the axis of the central threaded portion are orthogonal to each other on the same plane.
One first rod-shaped screw member that makes it possible to adjust the distance between the central member and one first formworking member by screw-coupling with one of the screw portions at both ends of the central member.
The other first rod-shaped screw member, which makes it possible to adjust the distance between the central member and the other first formwork forming member by screwing with the other screw portion of the screw portions at both ends of the central member.
Because it has
The first formwork is formed by arranging the first defined member between the first formwork forming members and rotating the first rod-shaped screw member screwed to both ends of the central member with respect to the central member. The spacing between the forming members can be appropriately adjusted and specified.
In addition, in plan view, the second specified member is
Since the second rod-shaped screw member is provided so that the distance between the central member and the second formworking member can be adjusted by screwing with the central screw portion of the central member, the second rod-shaped screw member can be used as the central member. The distance between the central member and the second formwork forming member can be appropriately adjusted and specified by rotating the member.
Then, unlike the prior art, the central member has first rod-shaped screw members screwed to both ends thereof instead of being inserted, and these first rod-shaped screw members are rotated with respect to the central member to be positioned. Therefore, the distance between the first formwork forming members arranged so as to face each other can be specified in a stable state.
Further, since the central thread portion of the central member to which the second rod-shaped screw member is screwed is provided so that its axis is orthogonal to the axis of the threaded portions at both ends on the same plane, the second rod-shaped screw The axial force (thrust force or tensile force) acting on the member does not generate a moment that tries to rotate the central member around the axis of the first rod-shaped screw member, and the central member acts on the first rod-shaped screw member. Since it is screw-coupled, there is no possibility that the second rod-shaped screw member will move in the axial direction with respect to the first rod-shaped screw member.

Therefore, according to the concrete casting formwork structure of the present invention, the first formwork member that defines the distance between the first formwork forming members arranged so as to face each other is orthogonal to the first formwork forming member. The distance from the second formwork forming member can be defined in a stable state.

The front SL At the end of the first mold frame forming member side of the first rod-shaped screw member, connecting members for connecting the first rod-shaped screw member and a first mold frame member is screwed,
The length of the screw connection between the screw portion at the end of the central member and the first rod-shaped screw member excludes the screw joint at the end of the central member in the first rod-shaped screw member and the screw connection with the connection member. Since the structure is longer than the length of the portion, the axial force of the second rod-shaped screw member acting on the central member and the first rod-shaped screw member can be received by the central member and the first rod-shaped screw member in a stable state. It will be possible.

In this concrete casting formwork structure,
A ring-shaped retaining ring may be provided at the screw coupling boundary portion of the screw coupling portion between the central member and the first rod-shaped screw member.
With this configuration, the screw connection state between the central member and the first rod-shaped screw member can be fixed by a ring-shaped retaining ring, so that the distance between the first formwork forming members arranged so as to face each other is first. The defining member can be defined in a more stable state, and the distance between the first defining member and the second formwork forming member can be defined in a more stable state.

Further, in order to solve the above problems, the central member for concrete placement of the present invention is used.
A central member used in the concrete casting formwork structure of claim 1 or 2 .
With threaded portion of the cylindrical nut shape is provided at both ends of the central portion, the central threaded portion is provided with threads and the axis of said end to the central portion are orthogonal, the central screw and the axis of the threaded portion of the end portions The axis of the part is orthogonal on the same plane ,
The central portion is characterized by having a pair of flat portions facing each other with the axes of the screw portions at both ends thereof interposed therebetween .

According to this central member for concrete placement
Unlike the prior art, the first rod-shaped screw members are screwed to both ends instead of being inserted, and by rotating these first rod-shaped screw members with respect to the central member, positioning is performed, so that they face each other. It is possible to specify the distance between the first form-forming members arranged in a stable state.
Further, since the central thread portion to which the second rod-shaped screw member is screwed is provided so that its axis is orthogonal to the axis of the screw portions at both ends on the same plane, it acts on the second rod-shaped screw member. The axial force (thrust force or tensile force) to be applied does not generate a moment that tries to rotate the central member around the axis of the first rod-shaped screw member, and the central member is screwed to the first rod-shaped screw member. Therefore, there is no possibility that the second rod-shaped screw member moves in the axial direction with respect to the first rod-shaped screw member.

Therefore, according to the central member for concrete casting of the present invention, the first defining member that defines the distance between the first formwork forming members arranged so as to face each other and the first defining member that is orthogonal to the first formwork forming member. The distance between the two formwork forming members can be specified in a stable state.

It is a figure which shows the embodiment of the concrete casting formwork structure and the concrete placing central member which concerns on this invention, (a) is a plan view, (b) is the left side view of FIG. (a), (c). Is a plan view of the retaining ring 40, and (d) is also a front view. (A) (b) is a plan view which shows the application example of the embodiment of the concrete casting formwork structure and the concrete placing central member which concerns on this invention. It is a figure which shows the other embodiment, (a) is a plan view, (b) is a left side view of FIG. (a), (c) is a partial omission cc sectional view in FIG. (B).

Hereinafter, embodiments of the concrete casting formwork structure and the concrete casting central member according to the present invention will be described with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals.

As shown in FIG. 1, the concrete casting formwork structure of this embodiment is
The first formwork forming members 1 and 1 arranged to face each other in a plan view, the second formwork forming member 2 orthogonal to the first formwork forming member 1, and the concrete casting formwork 3 ,
The first defining member 10 provided in the concrete casting formwork 3 and defining the distance W1 between the first formwork forming members 1 and the first defining member 10 and the second formwork forming member 2 A second defining member 20 that defines an interval W2 is provided.

In a plan view, the first defined member 10 is
The first form-forming members 1 are arranged orthogonal to the first form-forming member 1, and the screw portions 13 are provided at both ends, and the screw portions 13 and the axis 14a at both ends are provided at the central portion 15c. A central member 15 is provided with orthogonal central screw portions 14, and the axis 13a of the screw portions 13 at both ends and the axis 14a of the central screw portion 14 are orthogonal to each other on the same plane.
By screw-coupling with one of the screw portions 13 at both ends of the central member 15, the distance W11 between the central member 15 and the one first form forming member 1 can be adjusted. Rod-shaped screw member 11 and
The other first, which makes it possible to adjust the distance W11'between the central member 15 and the other first form-forming member 1 by screw-coupling with the other screw portion of the screw portions 13 at both ends of the central member 15. It includes a bar-shaped screw member 11'.
The first defined member 10 is arranged so that the axis line 13a of the screw portion 13 is orthogonal to the first formwork forming member 1.

In a plan view, the second defined member 20 is
The second rod-shaped screw member 22 is provided so that the distance W2 between the central member 15 and the second formworking member 2 can be adjusted by screwing with the central screw portion 14 of the central member 15.

According to this concrete casting formwork structure
In a plan view, the first defining member 10 that defines the distance W1 between the first form forming members 1 is
The first form-forming members 1 are arranged orthogonal to the first form-forming member 1, and screw portions 13 are provided at both ends, and the screw portions 13 and the axis 14a at both ends are provided at the central portion 15c. A central member 15 is provided with orthogonal central screw portions 14, and the axis 13a of the screw portions 13 at both ends and the axis 14a of the central screw portion 14 are orthogonal to each other on the same plane.
By screw-coupling with one of the screw portions 13 of the screw portions 13 at both ends of the central member 15, the distance W11 between the central member 15 and the one first form forming member 1 can be adjusted. 1 rod-shaped screw member 11 and
The other third, which makes it possible to adjust the distance W11'between the central member 15 and the other first form-forming member 1 by screw-coupling with the other screw portion 13 of the screw portions 13 at both ends of the central member 15. 1 rod-shaped screw member 11'and
Because it has
The first defined member 10 is arranged between the first formwork forming members 1, and the first rod-shaped screw members 11 and 11'that are screwed to both ends (13) of the central member 15 are used as the central member 15. By rotating the first mold forming member 1, the distance W1 between the first form forming members 1 can be appropriately adjusted and specified.

Further, in a plan view, the second defined member 20 is
Since the second rod-shaped screw member 22 is provided so that the distance W2 between the central member 15 and the second formworking member 2 can be adjusted by screwing with the central screw portion 14 of the central member 15, the second rod-shaped member is provided. By rotating the screw member 22 with respect to the central member 15, the distance W2 between the central member 15 and the second formworking member 2 can be appropriately adjusted and defined.

Then, in the central member 15, the first rod-shaped screw members 11 and 11'are screwed to both end portions (13), respectively, instead of being inserted, unlike the prior art, and these first rod-shaped screw members 11 and 11'are centered. Since positioning is performed by rotating the member 15, the distance W1 between the first form-forming members 1 arranged opposite to each other can be defined in a stable state.

Further, the central screw portion 14 of the central member 15 to which the second rod-shaped screw member 22 is screwed is provided so that its axis 14a is orthogonal to the axis 13a of the screw portions 13 at both ends on the same plane. , The axial force (thrust force or tensile force) acting on the second bar-shaped screw member 22 generates a moment for rotating the central member 15 around the axis (13a) of the first bar-shaped screw members 11, 11'. Since the central member 15 is screw-coupled to the first rod-shaped screw members 11 and 11', the direction of the axis (14a) of the second rod-shaped screw member 22 with respect to the first rod-shaped screw members 11 and 11'. There is no risk of moving to.

Therefore, according to the concrete casting formwork structure of this embodiment, the first formwork member 10 that defines the distance W1 between the first formwork forming members 1 arranged so as to face each other and the first formwork. The distance W2 from the second formwork forming member 2 orthogonal to the forming member 1 can be defined in a stable state.

As shown in FIG. 1, the first rod-shaped screw member 11 (11') and the first form-forming member 1 are attached to the ends of the first rod-shaped screw members 11 and 11'on the first form-forming member 1 side. The connecting member 30 for connecting the above is screwed together.
The length L2 of the screw connection between the screw portion 13 at the end of the central member 15 and the first rod-shaped screw member 11 (11') is the screw at the end of the central member 15 in the first rod-shaped screw member 11 (11'). The length of the portion excluding the joint portion and the screw joint portion with the connection member 30 is longer than L1.

With this configuration, the axial force of the second rod-shaped screw member 22 acting on the central member 15 and the first rod-shaped screw members 11, 11'is stable in the central member 15 and the first rod-shaped screw members 11, 11'. It will be possible to catch it with.

A ring-shaped retaining ring 40 is provided at the screw coupling boundary portion of the screw coupling portion between the central member 15 and the first rod-shaped screw member 11 (11').

With this configuration, the screw connection state between the central member 15 and the first rod-shaped screw member 11 (11') can be fixed by the ring-shaped retaining ring 40, so that the first formwork is formed so as to face each other. The distance W1 between the members 1 can be defined by the first defining member 10 in a more stable state, and the distance W2 between the first defining member 10 and the second formwork forming member 2 can be defined in a more stable state. Can be specified.

As described above, the concrete placing central member 15 of this embodiment is
Threaded portions 13 are provided at both ends, and a central threaded portion 14 is provided at the central portion 15c so that the threaded portions 13 at both ends and the axis line 14a are orthogonal to each other. It is orthogonal to 14a on the same plane.

According to the concrete casting central member 15, the effects as described above can be obtained.

The concrete casting formwork structure or the concrete placing central member 15 as described above is, for example, as shown in FIG. 2A, in addition to the case where the construction as described in Patent Documents 1 and 2 described above is performed. It is also suitable for concrete casting work.

In FIG. 2A, 2 and 4 are formwork forming members for forming a concrete placing space S1 for constructing columns, and 51 and 52 are known for defining a concrete placing space S1. It is a separator (spacing member).

Reference numeral 1 denotes a formwork forming member for forming a concrete placing space S2 for constructing a wall connecting columns (S1) to each other, and 53 is a known separator (53) for defining a concrete placing space S2. Interval defining member).

For example, in the formwork configuration as shown in FIG. 2A, a known spacing defining member (for example, a separator) is provided between points A and B in order to define the spacing W5 between the outer surfaces of the columns (S1). It is difficult to provide because the distance between AB is long.

Therefore, as shown in FIG. 2B, among the spacing defining members 53 for the wall (S2), the first defining member 10 of the present embodiment is used instead of the spacing defining member 53'close to the pillar (S1). The concrete casting of the present embodiment is performed by using the second defined member 20 of the present embodiment between the first defined member 10 and the second formwork forming member 2 which is a member forming the outer surface of the pillar (S1). By constructing the installation formwork structure, the distance W2 between the first defining member 10 and the second formwork forming member 2 is defined in a stable state, thereby indirectly between the outer surfaces of the columns (S1). The interval W5 can be specified.

Known members can be used for the first formwork forming member 1 and the second formwork forming member 2, respectively. For example, plywood can be used.

Both the first rod-shaped screw member 11 and the second rod-shaped screw member 22 can be composed of known bolts, but if necessary, the intermediate portion is a hexagonal prism without screws, and it is easy to rotate with a tool. You can also do it.

The central member 15 can be made of a known material, for example, a metal such as iron. The screw portions 13 at both ends can be formed into a tubular nut shape. As shown in FIG. 1, it is desirable that the central portion 15c on which the central screw portion 14 is formed is thicker and stronger than the other portions.

The central screw portion 14 may have a bag nut shape, or may have a screw hole penetrating the central portion 15c.

The male-female relationship between the central member 15, the first rod-shaped screw member 11, and the second rod-shaped screw member 22 can be reversed.

As the connecting member 30 provided at the end of the first rod-shaped screw members 11 and 11'on the first form forming member 1 side, a known connecting member (P-con or other connecting member (for example, the above-mentioned Patent Document 2) is described. A long nut 31)) can be used.

The ring-shaped retaining ring 40 provided at the screw coupling boundary portion of the screw coupling portion between the central member 15 and the first rod-shaped screw member 11 (11') has the first rod-shaped screw member 11 (11') on the central member 15 side. Anything that can regulate the rotation in the entering direction is sufficient. For example, as shown in FIG. 1D, a ring having a tightening allowance 41 is formed and attached to the first rod-shaped screw member 11 (11'). After positioning, it can be fixed by hitting it with a hammer or the like so as to narrow the tightening allowance 41.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the gist of the present invention.

For example, the central member 15 may have a shape as shown in FIG.
Such a shape makes it easier to operate with a tool.

1: 1st formwork forming member 2: 2nd formwork forming member 3: Concrete casting formwork 10: 1st specified member 11, 11': 1st rod-shaped screw member 13: Threaded portion 13a: Axis line 14: Center Threaded part 14a: Axial line 15: Central member 15c: Central part 20: Second specified member 22: Second rod-shaped screw member 30: Connecting member 40: Retaining ring

Claims (3)

For placing concrete having a first formwork forming member (1) arranged to face each other in a plan view and a second formworking member (2) orthogonal to the first formworking member (1). Formwork (3) and
A first defining member (10) provided in the concrete casting formwork (3) and defining a distance (W1) between the first formwork forming members (1), and the first defining member (10). ) And the second defining member (20) that defines the distance (W2) between the second formwork forming member (2).
It is a formwork structure for concrete placement equipped with
In a plan view, the first defined member (10) is
The first form-forming members (1) are arranged orthogonal to the first form-forming member (1), and screw portions (13) are provided at both ends and a central portion (15c). Is provided with a central threaded portion (14) in which the threaded portions (13) at both ends and the axis (14a) are orthogonal to each other, and the axial line (13a) and the central threaded portion (14) of the threaded portions (13 ) at both ends are provided. A central member (15) whose axis (14a) is orthogonal to each other on the same plane,
By screwing with one of the screw portions (13) at both ends of the central member (15), the distance (W11) between the central member (15) and the one first formwork forming member (1) ) Is adjustable, and the first rod-shaped screw member (11)
The central member (15) and the other first formwork forming member (1) are formed by screwing with the other threaded portion (13) of the threaded portions (13) at both ends of the central member (15). The other first rod-shaped screw member (11') that makes the interval (W11') adjustable,
With
In a plan view, the second defined member (20) is
A second rod shape that makes it possible to adjust the distance (W2) between the central member (15) and the second formwork forming member (2) by screwing it to the central screw portion (14) of the central member (15). Equipped with a screw member (22)
The screw portions (13) at both ends have a tubular nut shape.
With respect to the axial direction (13a) of the screw portions (13) at both ends, the central member (15) is shorter than the distance (W1) between the first form forming members (1).
At the end of the first rod-shaped screw member (11) on the first formwork forming member (1) side, a connecting member for connecting the first rod-shaped screw member (11) and the first formwork forming member (1). (30) is screwed together
The length (L2) of the screw connection between the screw portion (13) at the end of the central member (15) and the first rod-shaped screw member (11) is the central member (15) in the first rod-shaped screw member (11). It is longer than the length (L1) of the portion excluding the screw joint portion at the end of and the screw joint portion with the connection member (30).
The central portion (15c) of the central member (15) has a pair of flat surfaces (15f, 15f) facing each other with the axis (13a) of the screw portions (13) at both ends thereof interposed therebetween. /> A formwork structure for concrete placement. Oite to claim 1,
A concrete casting formwork characterized in that a ring-shaped retaining ring (40) is provided at a screw coupling boundary portion in a screw coupling portion between the central member (15) and the first rod-shaped screw member (11). Construction. A central member (15) used in the concrete casting formwork structure of claim 1 or 2 .
With threaded portion of the cylindrical nut shape at both ends of the central portion (15c) (13) are provided, the threaded portion of said end to a central portion (15c) (13) and the central threaded portion axis (14a) is orthogonal ( 14) is provided, and the axis (13a) of the screw portion (13) at both ends and the axis (14a) of the central screw portion (14) are orthogonal to each other on the same plane .
The central portion (15c) is characterized by having a pair of flat surfaces (15f, 15f) facing each other with the axes (13a) of the screw portions (13) at both ends thereof interposed therebetween. Central member for concrete placement.

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