JP6944818B2 - How to build a concrete body - Google Patents

Description

The present invention relates to a method for constructing a concrete body for constructing a new concrete body with a slight gap above the existing concrete body.

Conventionally, a method of supporting a bottom formwork material of a reinforced concrete body by using sand has been proposed (see Patent Documents 1 and 2).
Patent Document 1 describes a method of constructing a pillar in a reverse striking method of a building. First, a sand mold is installed on the bottom surface of the root cutting, and sand is filled in the sand mold. Next, waste concrete is cast on the surface of the filled sand, a concrete panel is laid on the waste concrete, a plastic sheet is laid on the waste concrete and the upper surface of the concrete panel, and the column main reinforcement is arranged. Next, the side formwork of the pillar is built on the waste concrete, and the concrete is placed. Next, after the concrete is hardened, the sand formwork and the side formwork members of the columns are dismantled, the filled sand is disintegrated, and the waste concrete and the concrete panel are dismantled.

Patent Document 2 describes a method of constructing a slab in the reverse striking method. First, excavate below the beam on the construction floor, spread the sand smoothly on the bottom of the excavated part, lay the base plate evenly on the spread sand, and use the formwork unit to form the beam formwork on the base plate. Assemble the slab formwork. Next, the concrete is placed by arranging reinforcement in each formwork, and after the placed concrete develops a predetermined strength, the next lower layer is excavated to collapse the paving sand and dismantle the formwork. ..
However, when constructing a concrete body with a slight gap on the existing concrete body, the methods of Patent Documents 1 and 2 require support and dismantling of the bottom formwork material for forming the concrete body to be constructed. It was difficult.

Japanese Unexamined Patent Publication No. 1-71942 Japanese Unexamined Patent Publication No. 5-79049

According to the present invention, when a concrete body is constructed with a slight gap above the existing concrete body, the bottom formwork material of the concrete body to be constructed can be easily supported, and the bottom formwork material can be used. An object of the present invention is to provide a method for constructing a concrete body that can be easily disassembled.

As a method of constructing a concrete body such as a beam with a slight gap above the floor slab, the present inventors do not support the bottom formwork material for forming the concrete body with a large-scale support work on the floor. By forming a sand layer on the upper surface of the slab and stacking the flat foam and the bottom formwork on the sand layer in this order, the predetermined height can be easily secured and the slab can be easily disassembled and removed. Focusing on it, we came to the present invention. The feature of the present invention is that the sand layer absorbs the local unevenness of the floor slab to flatten the upper surface, and a flat plate-like foam having a certain elasticity and rigidity is installed on the sand layer to make the sand layer flat. And the point that the bottom formwork material is supported by the foam. With respect to the bending of the foam, a part of the granules forming the sand layer flows, so that the bottom formwork can be maintained in a substantially flat state.

In the method for constructing a concrete body of the first invention, a new concrete body (for example, a girder 30 described later) is provided with a predetermined gap above the existing concrete body (for example, the floor slab 20 of the seismic isolation layer described later). A method for constructing a concrete body to be constructed, which is a step of laying sand on the upper surface of the existing concrete body to form a sand layer (for example, a sand layer 40 described later) (for example, steps S1 and S2 described later) and the sand layer. On the step (for example, step S3 described later) of installing a new bottom formwork material (for example, the bottom formwork material 33 described later) to be constructed, and on the bottom formwork material. A step of placing concrete (for example, step S4 described later) and a step of blowing off the sand constituting the sand layer with compressed air to form a gap between the existing concrete body and the bottom formwork material (for example). A step S6) described later and a step of disassembling the bottom formwork material (for example, steps S7 and S8 described later) are included.

Here, the predetermined gap is 20 cm or less above the existing concrete body. That is, in the present invention, a new concrete body is constructed so that the lower end surface is located in a space 20 cm or less above the existing concrete body. When constructing a new concrete body so that the lower end surface is located at a height exceeding 20 cm above the existing concrete body, the bottom formwork material is not required to adopt the method for installing the bottom formwork material of the present invention. This is because a formwork support material such as a thick-edged end may be placed underneath, and the formwork support material may be supported by a support work.
According to the present invention, a sand layer was formed on the upper surface of the existing concrete body, and the bottom formwork material was arranged on the sand layer. By using the sand layer as the support for the bottom formwork in this way, the height of the support can be considerably lowered even if the gap between the existing concrete body and the new concrete body to be constructed is narrow. The bottom formwork of a new concrete body can be easily supported.
In addition, after placing concrete, the sand in the sand layer is blown off by compressed air from a compressor or the like to form a gap between the existing concrete body and the bottom formwork, making it easy to complete the entire formwork including the bottom formwork. Can be removed.
In addition, the scattered sand can be easily removed by sucking the blown sand with a vacuum cleaner or the like.

In the method for constructing a concrete body of the second invention, in the step of forming the sand layer, a foam (for example, a foam 42 described later) is provided on the upper surface of the sand layer, and the foam and the bottom formwork material are used together. It is characterized in that a film (for example, a resin film 43 described later) is laid between the two.

According to the present invention, by providing the foam on the upper surface of the sand layer, the bottom formwork can be supported by the foam having predetermined elasticity and rigidity, so that the support work can be performed without increasing the thickness of the sand layer so much. It can be easily set to any height.
Further, since the film is laid between the sand layer and the bottom formwork material, it is possible to prevent the moisture in the cast concrete from permeating into the sand layer and hardening the sand layer.

The method for constructing a concrete body of the third invention is characterized in that, in the step of forming the sand layer, a weir material (for example, a weir material 41 described later) covering the side surface of the sand layer is installed on the upper surface of the existing concrete body. And.

According to the present invention, since the weir material covering the side surface of the sand layer is installed on the upper surface of the existing concrete body, it is possible to prevent the end portion of the sand layer from collapsing and maintain the sand layer at a predetermined height.

According to the present invention, when a concrete body is constructed with a slight gap on the existing concrete body, the bottom formwork of the concrete body to be constructed can be easily supported, and the bottom formwork can be provided. The entire formwork including it can be easily disassembled.

It is a vertical sectional view of the structure of the seismic isolated building constructed by the method of constructing the concrete body which concerns on one Embodiment of this invention. FIG. 1 is a vertical cross-sectional view and a plan view of a portion surrounded by a broken line A in FIG. It is a flowchart of the construction method of the girder of a seismic isolated building. It is explanatory drawing of the construction method of a girder (the part surrounded by the broken line B of 1 and 2). It is explanatory drawing of the construction method of a girder (the second, CC cross-sectional view of FIG. 2).

According to the present invention, as a method for constructing a concrete body (reinforced concrete beam, reinforced concrete bracket, etc.) provided on a floor slab with a slight gap, sand is spread on the upper surface of the floor slab to form a sand layer, and the sand layer is formed. A bottom formwork material is installed in the building, and concrete is placed inside the formwork material including the bottom formwork material. The slight gap referred to here is 20 cm or less above the existing concrete body, and the present invention is a case where a new concrete body is constructed so that the lower end surface is located in a space 20 cm or less above the existing concrete body. Is targeted. When constructing a concrete body at a height exceeding 20 cm above the existing concrete body, a formwork such as a thick end form under the formwork material is not adopted without adopting the method of installing the bottom formwork material of the present invention. This is because the support material can be arranged and the formwork support material can be supported by the support work.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical sectional view of a structure of a seismic isolated building 1 constructed by the method for constructing a concrete body according to an embodiment of the present invention.

The seismic isolation building 1 has five floors, and a seismic isolation layer 2 is provided between the first floor and the second floor.
A seismic isolation device 10 is provided on the floor surface of the seismic isolation layer 2. Assuming that the portion of the seismic isolation building 1 below the seismic isolation device 10 is the lower structure 3 and the portion above the seismic isolation device 10 is the upper structure 4, the seismic isolation building 1 has the seismic isolation device 10 The substructure 3 provided and the superstructure 4 supported by the seismic isolation device 10 so as to be horizontally movable are provided.
The superstructure 4 is supported by the seismic isolation device 10 so as to be horizontally movable. As a result, the superstructure 4 is seismically isolated.

In the seismic isolation building 1, the foundation part below the first floor level is made of reinforced concrete, and the part from the rise of the first floor to the floor level of the seismic isolation layer 2 is made of steel-framed reinforced concrete. The part is steel-framed reinforced concrete or reinforced concrete, and the part above the second floor is steel-framed.

FIG. 2A is a vertical cross-sectional view of the portion surrounded by the broken line A in FIG. 1, and FIG. 2B is a plan view of the portion surrounded by the broken line A in FIG.
The floor slab 20 of the seismic isolation layer 2 as an existing concrete body constituting the substructure 3 and the floor slab 20 directly above the floor slab 20 are located in the portion of the seismic isolation building 1 surrounded by the broken line A in FIG. A second floor level girder 30 constituting the superstructure 4 is provided.
The girder 30 is a reinforced concrete beam into which prestress is introduced by a post-tension method. The girder 30 has a length of three spans, and steel columns 31 are embedded on both ends of the girder 30 and supported by the seismic isolation device 10. Further, a PC steel material 32 inserted into a sheath pipe (not shown) is embedded in the girder 30, and tension force (prestress) is introduced into the PC steel material 32 after the concrete is placed in the girder 30.

The girder 30 has a large beam in the central portion, whereby the gap between the lower surface of the girder 30 and the floor slab 20 of the seismic isolation layer 2 is narrowed. Specifically, the girder 30 is constructed so that the lower end surface is located at a height position of 90 mm above the floor slab 20. Therefore, at the time of construction, a new girder 30 is constructed by leaving a slight gap on the floor slab 20 of the seismic isolation layer 2 which is an existing concrete body.

The method of constructing the girder 30 will be described with reference to FIGS. 4 and 5 according to the flowchart of FIG.
In step S1, sand is laid on the upper surface of the floor slab 20 of the seismic isolation layer 2 to form the sand layer 40, and a wooden weir material 41 covering the side surface of the sand layer 40 is formed on the upper surface of the floor slab 20 of the seismic isolation layer 2. Install.

In step S2, the flat foam 42 is placed on the upper surface of the sand layer 40, and the resin film 43 is laid on the foam 42.
In step S3, the bottom formwork 33 covering the bottom surface of the girder 30 to be constructed is built on the resin film 43. As a result, the resin film 43 is interposed between the foam 42 and the bottom formwork 33.

In the embodiment, a sand layer having a height of 53 mm is formed, a foam insulation material having a thickness of 25 mm (Styrofoam (registered trademark) manufactured by Dow Kako Co., Ltd.) is installed on the sand layer, and the upper surface of the foam insulation material is covered. It was covered with a polyethylene sheet having a thickness of 0.15 mm. For the sand layer, commercially available sand having a granular diameter of about 0.06 mm to 2 mm was used. Further, a cedar square lumber having a cross-sectional dimension of 90 mm × 90 mm was used as the weir material, and a veneer plywood having a thickness of 12 mm was used as the bottom formwork material.

In step S4, a beam reinforcing bar (not shown) is arranged on the bottom formwork 33. Next, side formwork 34 covering the side surface of the girder 30 is built at both ends of the bottom formwork 33, and then concrete is cast in the space surrounded by the bottom formwork 33 and the side formwork 34. Set up.
In step S5, the side formwork member 34 is disassembled after the concrete is hardened.

In step S6, the sand constituting the sand layer 40 is blown off by the compressed air of the compressor to form a gap between the floor slab 20 of the seismic isolation layer 2 and the bottom formwork 33.
In step S7, the blown sand is sucked and collected with a vacuum cleaner (vacuum).
In step S8, the bottom formwork 33, the foam 42, and the resin film 43 are disassembled and removed.

According to this embodiment, there are the following effects.
(1) A sand layer 40 was formed on the floor slab 20 of the seismic isolation layer 2, and the bottom formwork 33 was placed on the sand layer 40. By using the sand layer 40 for the support of the bottom formwork 33 in this way, even if the gap between the floor slab 20 of the seismic isolation layer, which is an existing concrete body, and the girder 30 to be constructed is narrow, the support work Since the height of the canopy can be made considerably low, the bottom formwork 33 of the girder 30 can be easily supported.
The present invention is a method for constructing a new concrete body, a girder 30, with a slight gap above the floor slab 20 which is an existing concrete body, and for removing the bottom formwork 33 of the girder 30, the floor. It was necessary to remove the sand layer 40 laid on the upper surface of the slab 20. Therefore, after the concrete was placed, the sand in the sand layer was blown off by the compressed air of the compressor to form a gap between the floor slab 20 of the seismic isolation layer 2 and the girder 30, so that the bottom formwork 33 can be easily removed. be able to.
In addition, by sucking the sand blown off from the vacuum cleaner, the scattered sand can be easily collected and removed.

(2) By providing the foam 42 on the upper surface of the sand layer 40, the support work can be easily set to an arbitrary height without increasing the thickness of the sand layer 40 so much.
Further, since the resin film 43 was laid between the foam 42 and the bottom formwork 33, the moisture in the cast concrete permeated into the sand layer 40 under the foam 42 and the sand layer 40 was cured. Can be prevented. Further, by preventing the moisture of the concrete from penetrating into the foam 42, it is possible to prevent the structural characteristics of the foam 42 from deteriorating.
Further, a bottom for constructing a new concrete by combining a flat plate-shaped foam 42 having a constant elastic rigidity and a sand layer that absorbs unevenness on the upper surface of the floor slab 20 under the foam 42. By supporting the formwork material 33, the bottom formwork material 33 can be easily supported at a predetermined height position.

(3) Since the weir material 41 covering the side surface of the sand layer 40 is installed on the upper surface of the floor slab 20 of the seismic isolation layer 2, it is possible to prevent the end portion of the sand layer 40 from collapsing.

The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the range in which the object of the present invention can be achieved are included in the present invention.
For example, in the present embodiment, the present invention is applied to a reinforced concrete girder 30, but the present invention is not limited to this, and the present invention can also be applied to a reinforced concrete slab and a steel-framed reinforced concrete beam.
Further, in the present embodiment, the present invention is applied to the construction of the girder 30 of the seismic isolation layer, but the present invention is not limited to this, and the bracket made of reinforced concrete for fixing the damping device between the floor slabs above and below the seismic isolation layer is used. May be applied to construction.
Further, in the present embodiment, the present invention is applied to the seismic isolation layer, but the present invention is not limited to this, and may be applied to floors other than the seismic isolation layer.
Further, in the present embodiment, the resin film 43 is laid between the foam 42 and the bottom formwork 33, but for example, when the amount of concrete to be cast is small, the resin film may not be provided.

1 ... Seismic isolation building 2 ... Seismic isolation layer 3 ... Substructure 4 ... Superstructure 10 ... Seismic isolation device 20 ... Seismic isolation layer floor slab (existing concrete body)
30 ... Girder (new concrete body) 31 ... Steel columns 32 ... PC steel 33 ... Bottom formwork 34 ... Side formwork 40 ... Sand layer 41 ... Weir material 42 ... Foam 43 ... Resin film

Claims (2)

It is a method of constructing a concrete body that constructs a new concrete body with a predetermined gap above the existing concrete body.
A step of laying sand on the upper surface of the existing concrete body to form a sand layer, providing a foam on the upper surface of the sand layer, and laying a film on the foam .
The process of installing a new concrete bottom formwork to be constructed on the film,
The process of placing concrete on the bottom formwork and
A step of blowing off the sand constituting the sand layer with compressed air to form a gap between the existing concrete body and the bottom formwork material.
A method for constructing a concrete body, which comprises a step of disassembling the bottom formwork material. In the step of forming the sand layer, method for constructing a concrete body according to claim 1, characterized in that installing a weir member which covers the side surface of the sand layer on the upper surface of the existing concrete body.

Images