JPH01316216A - Manufacture of precast concrete member - Google Patents

Abstract

PURPOSE:To form the ducts of sheath parts in a precast concrete member and consequently manufacture the precast concrete member, which is favorable from the view point of structural yield point, by a method wherein elastic tubular bodies, on the outer peripheral surface of each of which a spiral cut is provided, are set at the arrangement positions of reinforcing steel material in a concrete form for manufacturing a precast concrete member and, after that, concrete is placed in the concrete form and finally the elastic tubular bodies are pulled out under the state that the placed concrete is under un-solidified state. CONSTITUTION:Elastic tubular bodies 2 are set at sheath parts for inserting the main reinforcing bar of a column in a concrete form 1 and the ends of each tubular body 2 are fixed to the concrete form 1 so as not to allow to shift the position of said tubular body 2. After the arrangement of necessary reinforcing bars such as hoop reinforcing bars and the like is done, concrete 5 is filled in the concrete form. Just after the centrifugal casting of the concrete, by pulling both the ends or one end side of each of the tubular bodies, each of said tubular bodies 2 is cut off along a spiral cut 3 so as to be turned into a sheet of strip in order to be easily pulled out of the placed concrete 5, resulting in forming the ducts of sheath parts in the impressions of the pulled-out tubular bodies.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing precast concrete members such as construction columns and beams.

(Prior art) When connecting the main reinforcements of upper and lower floors of precast concrete columns of a building using the sheath reinforcement method, when forming the sheath part for the main reinforcement of precast concrete beams and walls,
Alternatively, when forming a sheath part for a prestressed strand of a precast concrete beam or a steel bar, conventionally, by driving a thin-walled steel sheath pipe into a predetermined position,
The sheath part was being molded.

(Problems to be Solved by the Invention) In the conventional method, a sheath line is inserted into a thin-walled steel sheath pipe cast into a precast concrete member, and then grout mortar is injected into the sheath pipe.
The boundary between the grout mortar in the sheath and the component concrete is a thin-walled steel sheath pipe! ! ! Because the sheath is edged, the grout in the sheath and the concrete of the main body of the sheath are insufficiently integrated, causing many problems in terms of structural strength.

The present invention has been proposed in view of the problems of the prior art, and its purpose is to improve grouting material injected into cavities for installing main reinforcing bars, prestressed strands, or steel bars. It is an object of the present invention to provide a method for manufacturing a precast concrete member which is advantageous in terms of structural strength and whose integrity with the concrete member is significantly improved.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the method for manufacturing a precast concrete member according to the present invention includes the following steps:
An elastic tubular body having a spiral cut on its outer peripheral surface is set, concrete is poured into the formwork, and the elastic tubular body is pulled out when the poured concrete has not yet hardened. ing.

When the above method is carried out by centrifugal molding, the elastic tubular body is pulled out immediately after filling the mold with concrete 1 and performing centrifugal molding.

In addition, when performing the above method by simply placing concrete in a formwork without using centrifugal forming, when the compressive strength of the poured concrete reaches approximately 5.0 kg/ctA or more, the elastic tubular body is removed. It is something to pull out.

(Function) As described above, in the present invention, a spiral shape is formed on the outer peripheral surface of a formwork for forming a sheath portion for inserting the reinforcing steel material at the position where the reinforcing steel material is placed in the formwork for manufacturing precast concrete members. An elastic tubular body provided with a notch is set, concrete is poured into the formwork for producing a precast concrete member, and the elastic tubular body is pulled out when the poured concrete is in an unsolidified state.

At this time, since the elastic tubular body is provided with a spiral cut on its outer peripheral surface, it is cut along the cut by being subjected to a tensile force, and becomes one continuous strip.
It is easily pulled out from poured concrete, creating a cavity within the concrete.

Since the spiral notch provided on the outer peripheral surface of the elastic tubular body is filled with the poured concrete, one continuous strip is cut along the notch by pulling the tubular body. When pulled out from poured concrete as a piece,
Spiral ridges are formed on the inner peripheral surface of the concrete.

When the above method is carried out by centrifugal forming, the poured concrete is consolidated by centrifugal force, so even if the elastic tubular body is pulled out immediately after centrifugal forming, the shape of the cavity is sufficiently maintained.

Also, at this time, the adhesion force between the poured concrete and the elastic tubular body is low, and the strips cut along the spiral cut of the tubular body are easily peeled off from the concrete surface, and the tubular body is easily pulled out. It will be destroyed.

When performing the above method by simply pouring concrete into formwork without performing centrifugal forming, when the compressive strength of the poured concrete reaches approximately 5 kg/cd or more, the elastic tubular bodies are sequentially pulled out. By punching, a cavity of the sheath is formed in the precast concrete member.

(Example) The present invention will be explained below with reference to the illustrated example.

(1) is a formwork for manufacturing precast concrete column members,
(2) is an elastic tubular body made of a rubber tube or the like, and a spiral cut (3) with a V-shaped cross section is provided on the outer peripheral surface.

Then, the elastic tubular body (2) is set in the sheath part for inserting the column main reinforcement in the formwork (1), and the end part is aligned with the formwork (1) so that the position of the tubular body (2) does not shift. ) is fixed.

Next, after arranging necessary reinforcing bars such as hoop reinforcements (4), concrete (5) is filled, and immediately after centrifugal forming, the tubular body (2) is pulled from both ends or from one end side. , the tubular body (2) has the spiral cut (3
), the strip is easily pulled out of the poured concrete (5), and the cavity of the sheath portion is formed in the trace.

At this time, since the poured concrete (5) has been consolidated by centrifugal forming, immediately after centrifugal forming, the elastic tubular body (2)
) Even if the tube is pulled out, the cavity retains its shape, and at this time, the adhesion between the concrete and the elastic tubular body (2) is small, and the spiral cut (3) in the tubular body (2) The strips produced by cutting along the strips are easily peeled off from the concrete surface, and the elastic tubular body (2) can be easily pulled out.

In addition, the elastic tubular body (2) has a V-shaped cross-sectional spiral cut (
3) is filled with a part of the cast concrete (5), and a protruding ridge with a V-shaped cross section is integrated into the inner peripheral surface of the cavity of the sheath part of the precast concrete column member created by pulling out the tubular body (2). is formed into.

In addition, when forming a precast concrete column member by simply placing concrete in the formwork without using centrifugal forming, the compressive strength of the poured concrete is 5 k, g.
/c- or more, by pulling out the elastic tubular body, a precast concrete column member having a hollow part in the sheath part with a spiral ridge with a ■-shaped cross section protruding from the inner peripheral surface is formed. molded.

(Effects of the Invention) According to the present invention, as described above, there is no need to set a sheath pipe made of thin-walled steel pipe at the location of the reinforcing material in the formwork for manufacturing precast concrete members, as in the past, and the spiral A continuous spiral protrusion is formed on the inner circumferential surface by setting an elastic tubular body provided with a shaped cut and pouring concrete, and then pulling out the tubular body while the poured concrete is still unhardened. Since the cavity of the sheath part having ridges is formed, the grout material in the cavity and the main concrete of the precast concrete member are in direct contact and integrated via the spiral ridges, and thus Compared to the conventional sheath pipe system, the integrity of the concrete and grout material in the precast concrete member is significantly improved, which is advantageous in terms of structural strength.

The invention according to claim 2 provides that when the method is carried out by centrifugal molding, the concrete in the form is consolidated by centrifugal force, and the sheath cavity can be sufficiently retained in shape even when the elastic tubular body is pulled out. This is because the elastic tubular body is pulled out immediately after centrifugal forming, and the adhesion between the poured concrete and the elastic tubular body is low at this time, making it easy to pull out the tubular body. Therefore, it is possible to improve manufacturing efficiency.

The invention according to claim 3 provides that when the above method is carried out by simply placing concrete in a formwork without using centrifugal forming, when the compressive strength of the poured concrete becomes about 5.0 kg/C+a or more, The elastic tubular body can be pulled out of the poured concrete and manufacturing efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional plan view showing the implementation status of one embodiment of the method for manufacturing precast concrete members according to the present invention, and FIG.
The figure is a plan view of the elastic tubular body. (1) -- Formwork for manufacturing precast concrete column members (2) - Elastic tubular body (3) - Single spiral cut (5) - Concrete agent and patent attorney Shige Okamoto 2 flashes

Claims (2)

[Claims] (1) Set an elastic tubular body with a spiral cut on its outer circumferential surface at the position where the reinforcing steel material is to be placed in a formwork for manufacturing precast concrete members, pour concrete into the formwork, and pour the concrete into the formwork. A method for producing a precast concrete member, characterized in that the elastic tubular body is pulled out in a state where the concrete has not yet solidified. (2) The method for manufacturing a precast concrete member according to claim (1), wherein when the member is centrifugally formed, the elastic tubular body is pulled out immediately after filling a mold with concrete and centrifugally forming the member. (3) When forming the above-mentioned member by simply placing concrete in a formwork without using centrifugal forming, when the compressive strength of the poured concrete reaches approximately 5.0 kg/cm^2 or more, the above-mentioned elasticity The method for manufacturing a precast concrete member according to claim (1), wherein the tubular body is pulled out.