JP6644933B1 - Method of manufacturing precast PC slab - Google Patents

Abstract

An object of the present invention is to provide a method of manufacturing a precast PC slab, which can reduce the amount of work and cost as compared with the related art, and can improve quality and safety. In a method of manufacturing a pretensioned precast PC slab, a box-cutting portion is provided at a predetermined distance from an end of the precast PC slab, continues to a surface of the slab, and exposes a PC steel material. 4 is provided. An unbonded section where the adhesion between the PC steel material 2 and the cast concrete 3 is cut is provided between the box punching portion 4 and the end of the floor slab 1, and after the concrete 3 is cured, the tension introduced into the PC steel material 2 is released. Thus, prestress is introduced into the concrete 3 of the floor slab 1. Thereafter, the portion of the PC steel material 2 exposed in the box blank is cut, and the box blank 4 is closed with the filler 5. When the tension of the PC steel material 2 is released, the tension of the PC steel material 2 exposed in the box punching portion 4 is reliably released, and the PC steel material 2 can be safely cut in the box punching portion 4. [Selection] Figure 2

Description

  The present invention relates to a method of manufacturing a precast PC slab for introducing prestress by a pretension method, and is used, for example, for manufacturing a precast PC slab for a bridge or a precast PC slab for a building.

  For example, in road bridges such as highways, the aging of conventional reinforced concrete slabs is progressing, and replacement with a more durable prestressed concrete slab is being studied. In that case, a precast PC slab is often used.

  FIG. 3 shows a method of manufacturing a precast PC floor slab 1 which is conventionally generally performed when prestress is introduced by a pretension method. In order to secure the cover of the PC steel material 2, FIG. As shown in (a), a notch 11 is provided at the end of the floor slab.

  After the concrete 3 is poured into the formwork and cured in a state where the PC steel 2 is tensioned, the PC steel 2 is cut at the notch 11, and the filler 12 is post-cut into the notch 11. The filling confirmation inspection is performed for all the notches 11.

  In addition, there are inventions described in Patent Literature 1 and Patent Literature 2, for example, regarding introduction of prestress by a pretension method.

  Patent Document 1 discloses a method for manufacturing a continuous structure of concrete supported at at least three places, in which a tendon for negative bending moment resistance is linearly arranged on the upper edge side of the structure, and the tendon arranged is concrete. Provide an attached portion that adheres to and an unbonded portion that does not adhere, the attached portion is mainly disposed in a section where a negative bending moment occurs, and the unbonded portion that does not adhere is disposed in a section where a negative bending moment does not occur, Pre-stress is introduced into the tendon by the pre-tension method, and after the concrete of the structure is cured, the tendon after the tension is cut at the unbonded section where no negative bending moment is generated between the intermediate struts. A method for producing a continuous concrete structure is disclosed.

  Patent Literature 2 discloses that a tension member of a pretensioned PC member to which a prestressing force is applied is cut at a required point in the middle of the member or before concrete is poured into a required section of the tension member. A method for adjusting the prestressing force of a pretension type PC member, wherein a prestressing force is released from this portion or a prestressing force is not generated by applying a slipping agent such as asphalt in advance and placing it. It has been disclosed.

JP 2008-127954 A Japanese Patent Publication No. 40-028419

  Conventionally, in the case of the system shown in FIG. 3 which is generally performed, a formwork for post-implanting a filler into a notch provided at an end portion of a floor slab is required, which increases the amount of work and cost. In addition, when post-filling the filler, visual confirmation cannot be performed, and therefore, there is a concern about defective filling. After removal from the mold, since the post-punched portion of the floor slab end is exposed, there is a risk that the filler in the post-punched portion may fall off.

  Further, in the case of the invention described in Patent Document 1, in order to cut a PC steel wire disposed inside a continuous concrete structure at an intermediate span, a box-free space for cutting without concrete is formed. Cut the PC steel wire inside the space. Before the cutting, the tension of the jack is released, but the tension remains in the PC steel wire inside the box empty space, and in paragraph 0014 of Patent Document 1, "the PC for negative bending resistance is generated by the heat of the burner. When the steel wire 31 is gradually heated and cut, the tension of the PC steel wire 31 can be gradually released as compared with the case where the steel wire 31 is cut instantaneously with a blade, which is safe. " However, it is conceivable that by cutting a PC steel wire in a tensioned state in the boxed space, an impact is given to a cross section of the boxed space and cracks are caused from corners and the like.

  In the invention described in Patent Document 2, a steel tube or a sheath buried in concrete is used to provide a through-hole opening on the side of the PC member, and an electric cutting rod is inserted into the through-hole to cut the PC member. Since the member is in a tensioned state at the through hole position, there is a possibility that the concrete around the cutting position may be damaged at the time of cutting, as in the invention described in Patent Document 1.

  The present invention has been made to solve the problems in the prior art as described above, and can reduce the amount of work and cost as compared with the prior art, and can improve the quality and safety of a precast PC slab. It is an object of the present invention to provide a method for producing the same.

  In the present invention, concrete is poured into a formwork in a state where tension is introduced into a plurality of PC steel materials arranged in one direction in a floor slab, and after the concrete is cured, the tension introduced into the PC steel material is reduced. In the method for producing a pretensioned precast PC slab, which is released and introduces prestress into the concrete of the slab, at a position spaced a predetermined distance from an end of the precast PC slab, to a surface position of the slab. A box punching section is provided continuously and the PC steel material is exposed, and an unbond section is provided from the box punching section to an end of the floor slab to cut off the adhesion of the PC steel material and the cast concrete, and cure the concrete. Thereafter, by releasing the tension introduced into the PC steel, a prestress was introduced into the concrete of the floor slab, and thereafter, the PC slab was exposed in the box punched portion. Min was cut, is characterized in that closed by filler the box cut-out portion.

  The box emptying portion is provided at a position at a predetermined distance from an end of the precast PC slab to a depth at which the PC steel material is exposed vertically from the surface of the slab. In addition, the PC steel material from the box emptying portion to the end of the floor slab is an unbonded section, and a sheath or the like is provided outside the PC steel material to cut off the adhesion to the concrete.

  After curing the concrete, the tension introduced into the PC steel is released, and prestress is introduced into the concrete of the floor slab. Thereafter, the PC steel material is cut in the box punching section, the cut PC steel material is removed, and a filler is injected into the box punching section to close the box.

  When an unbonded section is provided from the boxed part to the end and the tension is released, the part of the PC steel material exposed to the boxed part is also securely released. There is no impact even if cut, and it is safe. It is easy to treat the PC steel material at the end after the prestress is introduced into the concrete, and there is no need to prepare a formwork for post-punching because of the boxless shape.

  As the filler to be injected into the box punching section, for example, non-shrink mortar can be used. The filler to be injected into the box punching section is not particularly limited as long as there is no problem in strength and durability, but if non-shrink mortar is used, the shrinkage inside the box punching section is suppressed and it adheres to the inner surface of the box punching section And more secure.

  According to the method for manufacturing a precast PC slab of the present invention, the notch portion provided at the end of the conventional precast PC slab becomes unnecessary by providing a box cutout for cutting the PC steel material. No formwork for punching is required.

  Since the filling material can be visually confirmed at the time of post-implanting the filling material in the box blank portion, the risk of defective filling is reduced. Since the filler in the post-implanted portion is not exposed and is accommodated in the box punching portion, there is no risk that the filler is peeled off. As a whole, the processing of the end portion of the precast PC slab becomes easy, and the amount of work and cost can be reduced.

  In addition, by providing a box punching part at a predetermined position from the end of the floor slab and forming an unbonded section from the box punching part to the end of the floor slab, when the tension on the PC steel material is released, it is exposed to the box punching part. Since the tension of the PC steel material is reliably released, there is no impact when cutting the PC steel material inside the box punching part, and it is possible to work safely without damaging the concrete in the box punching part. it can. The processing after cutting the PC steel material in the box blanking portion is also easy, and the PC steel material and the unbonded member may be removed from the end of the floor slab, and the filler may be injected into the box blanking portion.

It is the perspective view which showed roughly one Embodiment of the precast PC slab in the manufacturing method of the precast PC slab of this invention. 1A and 1B show an outline of an end structure of a precast PC floor slab in the embodiment of FIG. 1, wherein FIG. 1A is a cross-sectional view of a state in which a PC steel material is tensioned and concrete is poured and cured, and FIG. After releasing the tension and introducing the prestress, a cross-sectional view of a state in which the PC steel material is cut, (c) is a cross-sectional view in a state in which the PC steel material at the end and the unbonded member are removed after cutting the PC steel material, (d) is a cross-sectional view showing a state in which a filler is injected into a portion from which the box punching portion and the unbonded member have been removed. It shows the outline of the end structure in the method of manufacturing a precast PC slab of the conventional pretension method, (a) is a cross-sectional view after cutting a PC steel material, (b) is a filler material in a notch portion. It is sectional drawing after injection | pouring.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

  FIG. 1 schematically shows an embodiment of a precast PC slab 1 manufactured by the method for manufacturing a precast PC slab 1 of the present invention. Inside the precast PC slab 1, a PC steel material and a reinforcing bar are arranged (not shown).

  In the side frame at one end of the precast PC floor slab, there is a mark obtained by treating the end of the PC steel material, which is filled with the filler 5. At the front and rear ends of the surface of the precast PC slab 1, a plurality of box punches 4 are arranged in the bridge axis direction, and a filler 5 is injected into each box punch 4.

  FIG. 2 is a schematic diagram showing a structure of an end portion of the floor slab in the precast PC slab 1 in the embodiment of FIG. FIG. 2 (a) is a cross-sectional view after the concrete is cast by stretching the PC steel material and cured. In the precast PC slab 1, a PC steel material 2 passes vertically. At the end of the floor slab, a box punch 4 is provided in the vertical direction from the surface of the floor slab to a depth at which the PC steel material 2 penetrating the floor slab is exposed.

  A sheath 6 and the like are provided on the outside of the PC steel material 2 from the box blanking portion 4 to the end of the floor slab, and the PC steel material 2 and the concrete 3 are cut off to form an unbonded section. As a material used for unbonding, for example, a sheath made of polyethylene may be used. In addition, any material may be used as long as it can eliminate the adhesion between the PC steel material and the concrete and has no problem in strength and durability.

  FIG. 2 (b) shows a cross-sectional view of the PC steel material 2 exposed at the box punching portion 4 when cut. After releasing the tension of the PC steel material 2 and introducing prestress into the concrete 3, a cutting machine is inserted into the box punching portion 4 to cut the PC steel material 2.

  The box punching part 4 is provided at a predetermined position from the end of the floor slab, and the unbonded section from the box punching part 4 to the end of the slab is exposed to the box punching part 4 when the tension on the PC steel material 2 is released. Since the tension of the PC steel material 2 is released, the PC steel material 2 is safely cut without cutting when the PC steel material 2 is cut in the box punching section 4.

  FIG. 2C is a cross-sectional view after the end of the PC steel material 2 and the sheath 6 have been removed. After cutting the PC steel material 2, the PC steel material 2 and the sheath 6 from the box blanking part 4 to the end of the floor slab are removed. After cutting the PC steel material 2, it is easy to simply remove the PC steel material 2 and the sheath 6 from the end of the floor slab.

  FIG. 2D is a cross-sectional view showing a state in which the filler 5 is injected into the box punching portion 4 and a portion where the sheath 6 from the box punching portion 4 to the end of the floor slab is pulled out. What is necessary is just to post-punch the filler 5 from the box blanking part 4, and the formwork for post-punching is unnecessary.

[Manufacturing procedure of precast PC floor slab 1]
One embodiment of the method for manufacturing the precast PC slab 1 of the present invention will be described with reference to FIG. However, the present invention is not limited to the procedure described below.

(1) Cleaning and preparation of the formwork The dimensions and shape of the formwork of the precast PC floor slab 1 are checked. Clean the formwork and place the formwork in place.

(2) Reinforcing bars Rebars are placed and fixed in the formwork of the precast PC slab.

(3) Placing the formwork and PC steel 2 Fix the reinforcing steel placed in (2) and place the PC steel 2. After fixing the reinforcing steel and the PC steel material 2, the formwork of the precast PC floor slab 1 is assembled. In addition, a block for providing the box emptying part 4 is arranged at a position spaced a predetermined distance from the end of the precast PC floor slab 1.

  The block for providing the box punching portion 4 can be removed after the concrete 3 has been cast thereafter, and it is sufficient that the concrete has a box punching shape. For example, a block provided with waterproofing on the outside of the styrene foam may be used.

  For the PC steel 2, a polyethylene sheath 6 is wound around the outside of the PC steel 2 so as to cut off the concrete 3 and the PC steel 2 in order to make an unbonded section from the portion exposed by the box punching section 4 to the end of the floor slab. I do.

(4) Tensioning the PC steel material 2 For example, a hydraulic jack or the like is connected to the end of the PC steel material 2 to apply a tension to the PC steel material 2 (FIG. 2 (a)). The tension may be introduced by any means other than the hydraulic jack as long as the tension can be introduced into the PC steel material 2.

(5) Casting concrete 3 Concrete 3 of predetermined quality is cast in the formwork and the surface is adjusted.

(6) Curing Surround the outside of the formwork with curing equipment and perform steam curing. As the conditions for the steam curing, for example, if the steam curing at 50 ° C. is performed for 5 hours or more, the quality may be stable.

(7) Demolding and introduction of prestress After the curing is completed and the curing equipment is removed, the tension of the PC steel 2 is released and prestress is introduced into the concrete 3 of the PC slab 1. The form of the PC floor slab 1 is removed and stored at a predetermined position.

(8) Providing a boxed part 4 A block buried in a predetermined position is removed from an end of the precast PC slab 1 to form a boxed part 4 for exposing the PC steel material 2 and the PC steel material 2 is cut. Make a box-shaped hole for

(9) Cutting of the PC steel material 2 A machine capable of cutting the PC steel material 2 such as a plasma cutting machine is inserted into the box punching section 4, and the PC steel material 2 is cut (FIG. 2 (b)). The cut PC steel material 2 and sheath 6 are pulled out from the end of the floor slab (FIG. 2 (c)).

(10) Injection of Filler 5 into Box Draft 4 Filler 5 is injected from the box cutout 4 to fill the inside of the box cutout 4 (FIG. 2 (d)). The filler 5 is not particularly limited as long as there is no problem in strength and durability, but for example, non-shrink mortar is preferable.

DESCRIPTION OF SYMBOLS 1 ... Precast PC floor slab, 2 ... PC steel material, 3 ... Concrete, 4 ... Box empty part, 5 ... Filling material, 6 ... Sheath,
11 Notch, 12 Filler

Claims (2)

  In a state where tension is introduced into a plurality of PC steel materials parallel to one direction of the floor slab, concrete is poured into the formwork, and after curing of the concrete, the tension introduced into the PC steel material is released, In the method for producing a pretensioned precast PC slab, which introduces prestress into the concrete of the slab, at a position spaced from an end of the precast PC slab by a predetermined distance, continuously to a surface position of the slab, An unbonded section where the PC steel material is exposed is provided, and an unbonded section in which the PC steel material and the cast concrete are cut off is provided from the box punched portion to the end of the floor slab. By releasing the tension introduced into the steel material, prestress is introduced into the concrete of the floor slab, and thereafter, the portion of the PC steel material exposed in the box blank portion is cut. The method of precast PC slab, characterized in that for closing the filler the box cut-out portion. The method for manufacturing a precast PC slab according to claim 1, wherein a non-shrink mortar is used as the filler.

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