JP2022014761A - Manufacturing method for movable space holder and pretension pc product - Google Patents

Abstract

To provide a manufacturing method for a movable space holder that does not have an adverse effect due to a bending stress being transmitted when a pretension PC product having a convex and concave is removed and can be manufactured at low cost, and the pretension PC product using the movable space holder.SOLUTION: A space holder 1 which is installed on both sides of a concrete product (10) to hold a space between the PC steel materials (11) when prestress is applied to the concrete product by the pretension method includes a space holding part 6 through which the PC steel material (11) is inserted to hold a space, a pair of columns 3 and 3 supporting the space holding part 6, and a lower connecting part 4 that connects the legs of the pair of columns 3 and 3 to each other. Height changing means (7) in which the space holding part 6 is configured to be vertically movable with respect to the column 3 and the height of the PC steel material (11) is changed by connecting a space holding part 6 and the lower connecting part 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a movable spacing holder that is installed beside the concrete product to maintain the spacing between the PC steel materials when prestressing the concrete product by the pretension method, and a method for manufacturing the pretension product using the movable spacing holder. ..

Conventionally, when prestressing a concrete product by a pretension method, as shown in FIG. 8A, a PC steel material in which one end of the PC steel material 11 is fixed to a fixed object 12 and inserted into the concrete product (10). The PC steel material 11 is spread and inserted from the fixed object 12 with a fixed space holder 13 in a fan shape according to the space of 11. Then, prestress was introduced by tensioning the other end side of the PC steel 11 with a tension jack (not shown) in the fixed object 12 via the fixed spacing holder 13 in the same manner. Hereinafter, the concrete product in which prestress is introduced by the prestressed method is referred to as a prestressed concrete (prestressed concrete) product 10.

At this time, as shown in FIG. 9A, when the tension force of the PC steel material 11 is relaxed by demolding, the pretension PC product 10 is pulled to the fixed side as shown in FIG. 9B. Will move. Therefore, as shown in FIG. 9, when the pretension PC product 10 has irregularities, as shown in FIG. 8 (b), the PC steel material 11 is moved during demolding in a tense state in which a tension force is applied. It was necessary to lift the pretension PC product 10 to a height at which unevenness does not interfere with the surface. However, if it is lifted upward in a tense state, a downward vector component corresponding to the tension force acts via the PC steel material 11, and bending stress is transmitted to the pretension PC product 10, which may have an adverse effect such as cracking. was there.

As a method for manufacturing a pretensioned PC product that applies prestress to a concrete product by a pretension method, for example, in Patent Document 1, a PC steel material is placed on a formwork to apply tension, and then concrete is placed. A method for manufacturing a pretensioned PC product, which is demolded after curing, releases the tension of the PC steel material in the demolded state, and introduces prestress, is disclosed (claims of Patent Document 1). 1. See the 14th line in the upper left column of the specification, the 16th line in the lower left column, and FIGS. 1 to 3 of the drawing).

However, in the method for manufacturing a pretensioned PC product described in Patent Document 1, when the pretensioned PC product is lifted upward in a tense state, a downward vector component corresponding to the tension force acts on the pretensioned PC product via the PC steel material. No consideration was given to the problem of bending stress being transmitted and having an adverse effect.

Further, in Patent Document 2, a formwork 1 having a surface formwork 3 and a protruding formwork 5 which is installed on the surface formwork 3 and has elasticity and is separate from the surface formwork 3 is used. A method for manufacturing a precast concrete member having a step of placing concrete 17 on the protruding formwork 5 side of the surface formwork 3 and a step of removing the surface formwork 3 and the protruding formwork 5 after the concrete 17 is hardened. It is disclosed (see claim 1 of the scope of patent claims in Patent Document 2, paragraphs [0029] to [0048] of the specification, FIG. 4 of the drawing).

In the method for manufacturing a precast concrete member described in Patent Document 2, since the protruding formwork 5 is not fixed to the surface formwork 3, bending stress is transmitted to the precast concrete member (pretension PC product), which has an adverse effect. The problem can be solved. However, the method for manufacturing a precast concrete member described in Patent Document 2 requires an air pressure adjusting means and requires that the protruding formwork 5 be separate from the surface formwork 3 made of an elastic material. There was a problem that the manufacturing cost was high.

Japanese Unexamined Patent Publication No. 62-77906 Japanese Unexamined Patent Publication No. 2016-14290

Therefore, the present invention has been devised in view of the above-mentioned problems, and an object thereof is that there is no possibility that bending stress is transmitted at the time of demolding a pretensioned PC product having irregularities, which has an adverse effect. Further, it is an object of the present invention to provide a movable spacing holder that can be manufactured at low cost and a method for manufacturing a pretension PC product using the movable spacing holder.

The movable spacing holder according to claim 1 is a spacing holder that is installed on both sides of the concrete product to maintain the spacing between the PC steel materials when prestressing the concrete product by the pretension method. The space holding portion includes a space holding portion for inserting a PC steel material to hold the space, a pair of columns for supporting the space holding portion, and a connecting portion for connecting the legs of the pair of columns. It is configured to be movable up and down with respect to the support column, and is characterized by having a height changing means for connecting the space holding portion and the connecting portion to change the height of the PC steel material.

The movable spacing holder according to claim 2 is the movable spacing holder according to claim 1, wherein the height changing means is a manual height changing means capable of manually changing the height. And.

The method for manufacturing a prestressed PC product according to claim 3 is a method for manufacturing a prestressed PC product by applying prestress to a concrete product having irregularities by a prestressing method using a PC steel material to manufacture the prestressed PC product. According to claim 1 or 2, in the tensioning step of tensioning the PC steel material, a fixed spacing holder is installed at a height at which the unevenness of the prestressed PC product does not interfere with the formwork, and inside the fixed space holder. A movable spacing holder is installed, and the prestressed PC product is lifted upward to remove the mold while tensioning by bypassing the PC steel material tensioning route downward near the formwork of the concrete product. In the step, the height of the PC steel material is changed to a height at which the unevenness of the prestressed PC product does not interfere with the formwork by using the height changing means of the movable spacing holder, and the mold is removed. It is characterized by.

According to the inventions according to claims 1 to 3, not only is there no adverse effect on the prestressed PC product because unnecessary stress such as bending stress does not act on the PC steel material when the prestressed PC product is demolded. Prestressed PC products can be manufactured at low cost without increasing the production cost of the formwork.

In particular, according to the second aspect of the present invention, the height of the space holding portion and the connecting portion can be changed manually, a special device such as a hydraulic jack is not required, and maintenance and running cost of the device are not required. Pretension PC products can be manufactured at a lower cost.

1A and 1B are views showing a movable spacing holder according to an embodiment of the present invention, in which FIG. 1A is a front view and FIG. 1B is a plan view. FIG. 2 is a right side view showing the movable spacing holder of the same. FIG. 3 is a schematic view showing an outline of a method for manufacturing a pretensioned PC product according to an embodiment of the present invention, in which (a) is a state in which the pretensioned PC product is lifted before demolding and (b) is a state in which the pretensioned PC product is lifted during demolding. It is a figure which shows. FIG. 4 is an enlarged view of part A in FIG. 3 (a). FIG. 5 is a front view showing the state of the movable spacing holder before demolding as above. FIG. 6 is an enlarged view of part B of FIG. 3 (b). FIG. 7 is a front view showing the state of the movable spacing holder at the time of the same demolding. 8A and 8B are schematic views showing an outline of a conventional method for manufacturing a pretensioned PC product, in which FIG. 8A shows a state in which the pretensioned PC product is lifted before demolding and FIG. 8B shows a state in which the pretensioned PC product is lifted during demolding. .. 9A and 9B are views for explaining the problems of the conventional method of manufacturing a pretensioned PC product, in which FIG. 9A shows a state in which the pretensioned PC product is lifted at the time of demolding, and FIG. It is a figure which shows that a tension PC product moves to a fixed side.

Hereinafter, an embodiment of a method for manufacturing a movable spacing holder and a pretension PC product according to the present invention will be described in detail with reference to the drawings.

[Movable space holder]
First, the movable spacing holder 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. 1A and 1B are views showing a movable spacing holder 1 according to an embodiment of the present invention, in which FIG. 1A is a front view and FIG. 1B is a plan view. Further, FIG. 2 is a right side view showing the movable spacing holder 1.

The movable spacing holder 1 is installed on both sides of the pretension PC product 10 when prestress is applied to the concrete product (pretension PC product 10) by the pretension method, and is a spacing for maintaining the spacing between the PC steel materials 11. It is a holder (see also FIG. 3). As shown in FIGS. 1 and 2, the movable spacing holder 1 includes a pair of left and right base rails 2 and 2, and a pair of left and right columns 3 and 3 erected on the base rails 2 and 2. It is equipped with.

Further, the pair of left and right columns 3 and 3 are connected by a lower connecting portion 4 made of a steel material connecting the lower ends of both, and an upper connecting portion 5 made of a steel material connecting the upper portions, and are connected by a rectangular frame in front view. It is combined in a shape.

A space holding portion 6 configured to be vertically movable with respect to the support column 3 is provided between the pair of left and right columns 3, 3, and the height of the space holding unit 6 and the lower connecting portion 4 is changed. It is connected by a lever block (registered trademark) 7 which is a means so that the height can be freely changed.

(Base rail)
The base rail 2 is a member mainly composed of a base rail main body 20 made of a steel material such as H-shaped steel, and is fixed to the floor of a manufacturing yard by post-installed anchors such as hole-in anchors. This is to prevent the movable spacing holder 1 from tipping over due to the tension force transmitted via the PC steel material 11.

Further, as shown in FIG. 2, a support column 3 is erected in the center of the base rail main body 20 in the longitudinal direction, and diagonal members 21 are attached to both ends of the base rail main body 20 in the longitudinal direction. It is reinforced.

(Post)
In the column 3, a slit 31 is formed between the two column steel materials 30 and 30, and the interval holding portion 6 is interposed in the slit 31, so that the interval holding portion 6 is slidably configured up and down. ing.

As shown in FIG. 2, the diagonal member 21 is bolted to the upper portion of the support column steel 30 to prevent the support column 3 from being pulled down along the PC steel material 11.

(Lower connection part)
The lower connecting portion 4 includes a lower connecting portion main body 40 made of a steel material, and the lower connecting portion main body 40 is laid in the center of the base rail main body 20 in the longitudinal direction in a direction orthogonal to the base rail main body 20.

Further, a pair of brackets 41, 41 for hooking one end of the lever block (registered trademark) 7 are attached on the axis of the lower connecting portion main body 40. Like the base rail 2, the bracket 41 is fixed to the floor of the manufacturing yard with post-installed anchors such as hole-in anchors. This is to counter the reaction force when pulling down the tensioning route of the PC steel material 11.

(Upper connection part)
As shown in FIG. 1, the upper connecting portion 5 is mainly composed of an upper connecting portion main body 50 made of a steel material, and both ends of the upper connecting portion main body 50 in the longitudinal direction are joined to the supporting steel material 30 of the supporting column 3. .. The inside corner of the joint portion between the upper connecting portion main body 50 and the support steel material 30 is reinforced by a reinforcing plate 51 in order to increase the rigidity. This is to prevent the rectangular frame including the columns 3, 3 and the lower connecting portion 4 and the upper connecting portion 5 from being deformed into a parallel four-sided shape.

(Interval holding part)
As shown in FIG. 1, the space holding portion 6 is a portion where a plurality of steel material insertion holes 61 through which the PC steel material 11 is inserted are formed in the space holding portion main body 60 to which the channel steel is joined by the web portion. It has a function of maintaining the space between the PC steel materials 11 at the space between the steel material insertion holes 61.

Further, a pair of projecting brackets 62 are formed downward at the lower end of the space holding portion main body 60, and one end of the lever block (registered trademark) 7 is hooked to the projecting brackets 62.

(Means for changing height)
As shown in FIGS. 1 and 2, a lever block (registered trademark) 7 is provided as a height changing means for connecting the space holding portion 6 and the lower connecting portion 4 to change the height of the PC steel material 11. However, the height changing means according to the present invention is any means as long as it is a means such as a hydraulic jack that connects the space holding portion 6 and the lower connecting portion 4 to pull down the tensioning route of the PC steel material 11 in a state where tension is applied. It is possible to adopt it.

However, like the lever block (registered trademark) 7 and the chain block exemplified as the height changing means according to the present embodiment, the principle of the pulley is applied and the PC steel material 11 in a state where tension is manually applied is stretched. It is preferable that it is a manual height changing means that can lower the route. This is because if the device is a manual device, maintenance and running costs of the device are not required, and the pretension PC product 10 can be manufactured at low cost.

[Manufacturing method of pretension PC products]
Next, a method for manufacturing a pretensioned PC product according to an embodiment of the present invention will be described with reference to FIGS. 3 to 7. FIG. 3 is a schematic view showing an outline of a method for manufacturing a pretensioned PC product according to an embodiment of the present invention, in which (a) is a state in which the pretensioned PC product is lifted before demolding and (b) is a state in which the pretensioned PC product is lifted during demolding. It is a figure which shows. Further, FIG. 4 is an enlarged view of part A of FIG. 3A, and FIG. 5 is a front view showing a state of the movable spacing holder before demolding of FIG. 4. FIG. 6 is an enlarged view of part B of FIG. 3 (b), and FIG. 7 is a front view showing a state of the movable spacing holder at the time of demolding of FIG.

(Tension process)
First, in the method for manufacturing a pre-tensioned PC product according to the present embodiment, a tensioning step is performed in which the PC steel material 11 is tensioned with one end fixed to the fixed object 12 by using a tension jack or the like.

At this time, in the method for manufacturing the pretensioned PC product according to the present embodiment, unlike the conventional method, as shown in FIGS. 3 (a), 4 and 5, the unevenness of the pretensioned PC product 10 having the unevenness is a mold. A fixed spacing holder 13 is installed at a height that does not interfere with the frame 10', and the tensioning route of the PC steel material 11 is lifted (see also FIG. 9). Then, the above-mentioned movable spacing holder 1 is installed inside the tension PC product 10 (the side close to the pretension PC product 10), and the PC steel material 11 is stretched in a state of being detoured around the formwork 10'and pulled down. And get nervous (see FIGS. 3 (a) and 4).

Specifically, the PC steel material 11 is inserted into the steel material insertion hole 61 of the above-mentioned spacing holding portion 6, the lever block (registered trademark) 7 is manually contracted, the spacing holding portion 6 is pulled toward the lower connecting portion 4, and the lever is used. The block (registered trademark) 7 is tense in a state of being detoured downward against the tension of the PC steel material 11.

(Casting process)
Next, in the method for manufacturing a pretensioned PC product according to the present embodiment, a placing step of placing concrete in the formwork 10'of the pretensioned PC product 10 is performed.

However, in this step, as described above, the movable spacing holder 1 is installed inside the fixed spacing holder 13, and the movable spacing holder 1 is used to mold the height of the PC steel material 11. Concrete is placed in the formwork 10'while it is pulled down near the frame 10'.

(Demolding process)
Next, in the method for manufacturing a pretensioned PC product according to the present embodiment, after the strength of the placed concrete is developed, the pretensioned PC product 10 is lifted upward by using a lifting machine such as a portal crane to remove it. Perform the mold removal process.

In this step, as shown in FIGS. 3 (b), 6 and 7, the PC steel 11 is subjected to the unevenness of the pretension PC product 10 by using the lever block (registered trademark) 7 of the movable spacing holder 1. The height of the fixed spacing holder 13 that does not interfere with the mold 10'is changed and the mold is removed.

Specifically, a pretension PC product using a lifting machine or the like with the lever block (registered trademark) 7 manually loosened while the PC steel material 11 is under tension and the space holding portion 6 is freed. Lift 10 upwards.

At this time, originally, the fixed spacing holder 13 was used to stretch the pretension PC product 10 to a height at which the unevenness of the pretension PC product 10 did not interfere with the formwork 10', and stretched the stretched route of the PC steel 11 in a state of being tense. Therefore, by freeing the space holding portion 6 of the movable space holder 1 that has pulled down the PC steel material 11, the tension force of the PC steel material 11 is relaxed as the pretension PC product 10 rises. Therefore, it is possible to solve the problem that bending stress is transmitted to the pretension PC product 10 via the PC steel material 11 when the pretension PC product 10 is lifted, which has an adverse effect such as cracking.

According to the movable spacing holder 1 and the method for manufacturing a pretensioned PC product using the movable spacing holder 1 according to the above-described embodiment, bending stress or the like is unnecessary via the PC steel material 11 when the pretensioned PC product 10 is removed from the mold. No stress is applied and the pretension PC product 10 is not adversely affected.

Moreover, according to the method for manufacturing a pretensioned PC product using the movable spacing holder 1, a mold having a high manufacturing cost such that a part of the mold is made into an elastic body as in Patent Document 2 is used. Since there is no need, the pretension PC product 10 can be manufactured at low cost.

Further, the height changing means of the movable spacing holder 1 is a manual height changing means such as a lever block (registered trademark) 7 which can manually change the height. Therefore, according to the movable spacing holder 1, a special device such as a hydraulic jack is not required, maintenance of the device and running cost are not required, and a pretension PC product can be manufactured at a lower cost.

The method of manufacturing a pretensioned PC product using the movable spacing holder 1 according to the embodiment of the present invention and the movable spacing holder 1 according to the embodiment of the present invention has been described in detail above. However, all of the above-mentioned or illustrated embodiments show only one embodiment embodied in carrying out the present invention. Therefore, the technical scope of the present invention should not be construed in a limited manner by these.

10: Pretension PC product 10': Formwork 11: PC steel 12: Fixed object 13: (Fixed) spacing holder 1: Movable spacing holder 2: Base rail 20: Base rail body 21: Oblique member 3 : Support 30: Support steel 31: Slit 4: Lower connecting part (connecting part)
40: Lower connecting part main body 41: Bracket 5: Upper connecting part 50: Upper connecting part main body 51: Reinforcing plate 6: Spacing holding part 60: Spacing holding part main body 61: Steel material insertion hole 62: Protruding bracket 7: Lever block (registered) Trademark) (Means for changing height)

Claims (3)

It is a spacing holder that is installed on both sides of the concrete product to maintain the spacing between the PC steel materials when prestressing the concrete product by the pretension method.
It is provided with an interval holding portion for inserting the PC steel material to hold the interval, a pair of columns for supporting the interval holding portion, and a connecting portion for connecting the legs of the pair of columns.
The space holding portion is configured to be vertically movable with respect to the support column, and is characterized by having a height changing means for connecting the space holding portion and the connecting portion to change the height of the PC steel material. Movable space holder. The movable spacing holder according to claim 1, wherein the height changing means is a manual height changing means capable of manually changing the height. It is a manufacturing method of a pretensioned PC product that manufactures a pretensioned PC product by applying prestress to a concrete product having irregularities by a pretension method using a PC steel material.
In the tensioning step of tensioning the PC steel material, a fixed spacing holder is installed at a height at which the unevenness of the prestressed PC product does not interfere with the formwork, and the movable device according to claim 1 or 2 is installed inside the fixed spacing holder. A formula spacing holder was installed, and the PC steel material was laid down near the formwork of the concrete product, and the tension was increased.
In the demolding step of lifting the pretensioned PC product upward and removing the mold, the height of the PC steel material is adjusted by the unevenness of the pretensioned PC product by using the height changing means of the movable spacing holder. A method for manufacturing pre-tensioned PC products, which is characterized by changing the height so that it does not interfere with the mold and removing the mold.

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