JP2005054513A - Post-tensioning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a post-tensioning method improving the durability of a structure by suitably preventing a prestressed concrete tension material from rusting. <P>SOLUTION: In this post-tensioning method, the prestressed concrete tension material is inserted through a through hole formed in the structure, and in the tensed state of the prestressed concrete tension material, its end is anchored to the structure, and the air-gap of the through hole is filled with a filler. A rust preventive coated prestressed concrete strand 12A formed by filling synthetic resin 15 in an air-gap 19 between the respective element wires 17 of a prestressed concrete strand 14 formed by stranding a plurality of elements wires 17 formed of prestressed concrete steel wires, and covering the outer periphery with synthetic resin 16, is used as the prestressed concrete tension material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a post-tension method for applying prestress to a prestressed concrete structure.

  Conventionally, a post-tension method is known as a method for applying prestress to a prestressed concrete structure (hereinafter referred to as a PC structure).

In this post-tensioning method, concrete is cast with the sheath 1 disposed inside the mold, and after it is hardened, as shown in FIG. 2 is inserted, one or both ends of the PC tendon 2 are pulled to tension the PC tendon 2, and both ends are fixed to the concrete structure 3, and a filler 4 such as cement milk is placed inside the sheath 1. By injecting into the concrete structure, the strained PC tendon 2 is fixed to the concrete structure 3, and prestress is applied to the concrete structure 3 (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 08-100530

  However, in the conventional technology as described above, the filling material such as cement milk is not sufficiently filled, and as shown in FIG. 8, a gap a is formed in the sheath 1, that is, inside the insertion hole, and the PC tension material There was a problem that the portion exposed in the gap a of 2 touched air to cause rust, and the strength and durability of the structure were impaired.

  In order to prevent such voids from being generated, a method of performing high-pressure injection or evacuation of grout has been implemented, but adding such a high-pressure injection or evacuation process increases costs and costs. There is also the problem of becoming high.

  SUMMARY OF THE INVENTION In view of the above-described problems of the prior art, an object of the present invention is to provide a post-tension method capable of suitably preventing rusting of a PC tension material, improving the durability of a structure, and implementing it at low cost.

  The invention according to claim 1 for solving the conventional problem as described above is such that after the PC tendon is inserted into the insertion hole formed in the structure, the end of the PC tendon is tensioned. In the post-tension method in which the portion is fixed to the structure and the gap of the insertion hole is filled with a filler, the PC tension member is made of a PC twisted wire obtained by twisting a plurality of strands made of PC steel wire. The space between the strands is filled with a synthetic resin, and a rust-proof coated PC strand whose outer periphery is coated with a synthetic resin is used.

  In addition to the structure of claim 1, the rust-proof coated PC strand is filled with a soft or hard thermoplastic synthetic resin rust preventive material in the internal space between the strands of the PC twisted wire. In addition, the outer periphery of the PC twisted wire is covered with the rust-proofing material of the soft or hard thermoplastic synthetic resin rust-proofing material.

  In addition to the structure of claim 1, the rust-proof coated PC strand is filled with a soft thermoplastic synthetic resin rust preventive material in each internal space between the strands of the PC twisted wire. The outer periphery of the PC twisted wire is primarily coated with the soft thermoplastic synthetic resin rust preventive material, and is fused to the outer periphery of the primary coating to be coated with the hard thermoplastic synthetic resin rust preventive material. Features.

  The invention according to claim 4 is characterized in that, in addition to the structure of claim 2 or 3, the soft thermoplastic synthetic resin rust preventive material is a polyethylene-based synthetic resin material.

  The invention described in claim 5 is characterized in that, in addition to the structure of claim 2 or 3, the hard thermoplastic synthetic resin rust preventive material is a nylon-based or saturated polyester-based synthetic resin material.

  The post-tension method according to the present invention suitably prevents rusting of the PC tendon material even if a gap is formed in the insertion hole, and increases the durability of the structure.

  In addition, when a filler such as cement milk is injected, a process such as evacuation can be omitted, and the cost is reduced.

  Next, an embodiment of the post-tension method according to the present invention will be described.

  FIG. 1 shows a state in which prestress is applied to a concrete structure by a post-tension method, and reference numeral 10 in the figure is a concrete structure.

  The concrete structure 10 has an insertion hole formed by the sheath 11 over its entire length, and the PC tension member 12 is inserted into the insertion hole to be tensioned, and both ends thereof are fixed to the concrete structure 10 and the insertion hole is inserted. Prestress is imparted by filling the inner space with the filler 13.

  The PC tendon 12 uses a rust-proof coated PC strand 12A as shown in FIG.

  The anticorrosion-coated PC strand 12A is provided with an internal filling 15 in which an internal space of a so-called seven-stranded PC twisted wire 14 is filled with a thermoplastic synthetic resin material, and a coating 16 of the same synthetic resin material is provided on the outer periphery. Has been made.

  As shown in FIG. 3, the PC twisted wire 14 is composed of seven single strands in which six side wires 17 b, 17 b... Are spirally wound around the outer periphery of one core wire 17 a and twisted. The inter-single-wire internal voids 18, 18,... Surrounded by 17a and surrounding side lines 17b, 17b.

  The inner filling 15 and the coating 16 are integrally formed of the same resin material, and the outer periphery of the core wire 17a and the side wires 17b, 17b.

  As the thermoplastic synthetic resin, a soft thermoplastic synthetic resin material such as a polyethylene synthetic resin, or a hard thermoplastic synthetic resin rust preventive material such as a saturated polyester synthetic resin can be used.

  Moreover, you may use the anticorrosion coating PC strand 12B shown in FIG.

  The rust-proof coated PC strand 12B has a coating 16 on the outer periphery of the rust-proof coated PC strand 12A shown in FIG. 2 as a primary coating, and has an outer coating (secondary coating) 19 on the outer periphery. In addition, the same code | symbol is attached | subjected to the part same as the 1st Example mentioned above, and the description is abbreviate | omitted.

  In this rust-proof coated PC strand 12B, a soft thermoplastic synthetic resin material such as polyethylene synthetic resin is used as the material of the primary coating 16, and a hard thermoplastic synthetic material such as saturated polyester or nylon is used as the material of the outer periphery coating 19. Use resin rust prevention material.

  In addition to the above-described embodiment, the PC tension member 12 is injected with a rust-proof filler 20 made of synthetic resin through a gap between the single strands of the PC stranded wire 14 as shown in FIG. After filling the inside voids 18, the outer periphery of the PC twisted wire 14 was coated 21 with a soft thermoplastic synthetic resin material such as a polyethylene synthetic resin or a hard thermoplastic synthetic resin rust preventive material such as a saturated polyester synthetic resin. The rust-preventing coated PC strand 12D (see FIG. 5) or the coating 21 on the outer periphery of the rust-preventing coated PC strand 12C shown in FIG. 5 is used as the primary coating and the outer coating (secondary coating) 22 is provided on the outer periphery. 6) etc. may be used.

  Further, the anticorrosion-coated PC strands 12A to 12D can be provided with uneven portions on the surface portion of the outer periphery coating, and by providing the uneven portions, adhesion between the PC tension material 12 and the filler can be enhanced. .

  Next, the construction of this post tension method will be described.

  In this post-tension method, first, a formwork for placing concrete is installed, and a sheath 11 is disposed therein. In this state, concrete is placed in the formwork, and the sheath 11 over the entire length, that is, A concrete structure 10 having an insertion hole is formed, and the concrete structure 10 is cured and cured.

  Further, grout hoses 21 and 21 are vertically connected to the sheath 11, and an end of the grout hose 23 protrudes from the upper surface of the concrete structure 10. A supply pump (not shown) communicates with the grout hose 23, and a filler (grout) 13 such as cement milk is supplied by the supply pump.

  After the concrete structure 10 is sufficiently cured, the formwork is removed, and the PC tendon 12 is inserted into the sheath 11, that is, the insertion hole disposed inside the concrete structure 10.

  Then, both ends of the PC tendon 12 are attached to the jack, and the PC tendon 12 is tensioned by pulling a reaction force against the end of the concrete structure 10.

  Next, the PC tension member 12 is fixed to the end portion of the concrete structure 10, that is, the fixing plate 24 using a fixing tool such as a wedge 25 while the end portion of the PC tension member 12 is tensioned.

  Then, the supply pump is operated to inject a filler (grout) 13 such as cement milk into the sheath 11 to fix the synthetic resin 16 (20) covering the outer periphery of the PC tendon 12 and the filler 13 to the PC. A structure is formed.

  In addition, in the filling material injection, the material is injected only by pumping without performing vacuuming or the like.

  If injection is performed only by a pump without performing vacuuming or the like in this way, a void is formed in the sheath 11, that is, the filling material 13 such as cement milk in the insertion hole, and a void of the PC tendon is formed in the void. The outer periphery is exposed.

  However, the used PC tendon 12 is coated with a synthetic resin 16 (19, 21, 22) on the outer periphery, and is rust-prevented by filling the gap 18 between the strands 17 and 17 with the synthetic resin 15. It is exposed to the air gap in the sheath 11 so that it does not rust even when exposed to air.

  Even if the outer peripheral surface of the PC tendon 12 is condensed, there is no problem because the outer periphery is covered with the synthetic resin 16 (19, 21, 22).

  On the other hand, even if some gaps are generated in the sheath 11, that is, in the insertion hole, the PC tendon 12 is fixed to the concrete structure 10 through the filler 13 with sufficient strength.

  In addition, although the above-mentioned Example demonstrated the example which used the 7 twist PC twisted wire for the PC tension | tensile_strength material, you may use many twisted PC twist wires, such as 19 twist.

  The post-tension method can be applied to all structures to which prestress is introduced.

It is sectional drawing which shows the state which gave the prestress to the concrete structure by the post tension method concerning this invention. It is sectional drawing which shows the 1st example of the antirust coating PC strand in FIG. It is sectional drawing which shows the PC twisted wire before the antirust process of an antirust coating PC strand same as the above. It is sectional drawing which shows the 2nd example of a rust prevention coating | coated PC strand same as the above. It is sectional drawing which shows the 3rd example of a rust prevention coating | coated PC strand same as the above. It is sectional drawing which shows the 4th example of a rust prevention coating | coated PC strand same as the above. It is sectional drawing which shows the state which gave the prestress to the concrete structure by the conventional post tension method. It is a partial expanded sectional view which shows the filling state of a filler.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Concrete structure 11 Sheath 12 PC tension material 12A-12D Rust prevention coating PC strand 13 Filler (grouting)
14 PC twisted wire 15 Internal filling 16 Coating 17A Core wire 17a Side wire 18 Internal void 19 Outer coating (secondary coating)
20 Antirust filler 21 Outer coating (primary coating)
22 Outer coating (secondary coating)
23 Grout hose 24 Fixing plate 25 Wedge (fixing tool)

Claims (5)

After inserting the PC tension material into the insertion hole formed in the structure, the end of the PC tension material is fixed to the structure while the PC tension material is tensioned, and the gap of the insertion hole is filled with the filler. In the post-tension method
For the PC tension material, use a rust-proof coated PC strand in which a gap between the strands of a PC twisted wire obtained by twisting a plurality of strands is filled with a synthetic resin and the outer periphery is covered with a synthetic resin. The post-tension method that features   The anticorrosion-coated PC strand is filled with a soft or hard thermoplastic synthetic resin anticorrosive material in the internal space between the strands of the PC twisted wire, and the outer periphery of the PC twisted wire is covered with the soft or hard heat. The post-tension method according to claim 1, wherein the antirust coating is made of a plastic synthetic resin antirust material.   The anticorrosion-coated PC strand is filled with a soft thermoplastic synthetic resin anticorrosive material in the internal space between the strands of the PC twisted wire, and the soft thermoplastic synthetic resin anticorrosive material around the outer periphery of the PC twisted wire. The post-tensioning method according to claim 1, wherein the primary coating is applied and the outer periphery is coated with a hard thermoplastic synthetic resin rust preventive material after being fused to the outer periphery of the primary coating.   The post-tension method according to claim 2 or 3, wherein the soft thermoplastic synthetic resin rust preventive material is a polyethylene-based synthetic resin material.   The post-tension method according to claim 2 or 3, wherein the hard thermoplastic synthetic resin rust preventive material is a nylon-based or saturated polyester-based synthetic resin material.

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