JPS58213954A - Construction of pc structure using unbond strand - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method of constructing PC structures using unbonded strands.

Generally, PC structures are constructed using unbonded strands, which are coated with unbonded grease and coated with synthetic resin on the outside, for flat slags and beams, and this type of conventional PC structure When constructing a product, if the overall length is short, as shown in Fig. 1, a crimp grip 2 is fixed to one end of the strand 1, and this is supported by a fixing plate 3 and buried in a concrete structure 4. A fixing body 5 is buried in the other end, and the other end of the strand 1 is inserted through this. After the concrete reaches a predetermined hardness, a jack (not shown) is used from the fixing body 5 side. The fixing member 5 is held under tension and fixed to the fixing member 5 using the rod 6, and after the end is cut, the hole 7 outside the fixing member 5 is filled with mortar.

In addition, if the total length is long, as shown in Fig. 2, a fixing body 5.5 similar to that described above is buried at both ends, and the strand 1 is inserted into this.
After the concrete hardens, the strand 1 is tensed with jacks from both ends, and then the holes 7.7 on both sides are filled.

However, with such conventional construction methods, during tension work,
If the strand breaks after applying a certain tensile force, or if one end of the strand becomes unattached, or if one end of the strand becomes unattached due to an unexpected external force such as a fire or interior construction after being buried under tension, etc. When the tension is suddenly released, the elasticity of the strands causes an inertial force of tens or tens of tons to be applied to the mortar buried outside the fixing body, crushing it and breaking the strands. There was a risk of it flying out.

In view of the above-mentioned problems, the present invention has been developed to unbond the strand, which has better workability than conventional strand tensioning work, and which eliminates the risk of the strand popping out even if the strand breaks or the end part becomes unfixed due to an unexpected accident. The purpose of this is to provide a method for constructing PC structures using strands, and its gist is to insert unbonded strands into concrete structures such as beams and floors, and to tension and prestress the strands. In the method for constructing a PC structure using unbonded strands that imparts The other ends of both strands are inserted into a window hole opened in the center of the concrete structure, and the strands on both sides are connected under tension within the window hole to create a prestress of 4=J. A method of constructing a PC structure using unbonded strands is provided.

Next, an embodiment of the present invention will be described with reference to FIG. 3 and the following drawings.

This embodiment relates to the construction of a so-called flat slab, in which a concrete floor 12 of a PC structure is constructed integrally with support columns 11, 11, . . . .

Using a conventional method, formwork 13 for floor 12 is constructed continuously from the upper ends of columns 11, 11, . . . , and necessary reinforcing bars 14 are installed. Parallel to the arrangement of the reinforcing bars 14, C unbonded strands are arranged, and a pair of strands 15a extend across both ends of the floor 12.

15b are connected in the longitudinal direction, and both strands 15a, 15b are connected at both end positions of the floor 12.
Crimp grips 16a and 16b are fixed to the ends of the support plates 17a and 17b to support them.

A window hole form 18 is assembled and placed in the central position of one side 12, and both strands 15a, 15b are placed within the form 18.
Insert the other end.

Strands 15a and 15b inserted into the formwork 18
is inserted into the formwork 18 through the tension fixing fitting 19 which also serves as a connection.

This tension fixing fitting 19 has a pair of strands inserted through it 7t2.
0 and -H are opened differently, and both strand insertion holes 2
A tapered portion 2°a for fitting is formed at each end of the open end side of the strand to be inserted into the tapered portion 2°, and the strand is held between the tapered portions 21 fitted thereto.

In this way, after the reinforcing bars 14 and the lands 15a, 15b are placed in the formwork 13 for the concrete floor 12, concrete 1- is placed in the formwork 13, cured for a certain period of time, and After reaching the hardness of 15a and 15b, the sheets 15a and 15b are tensed.

To tension the strands 15a, 15b, use a pair of jacks (not shown) from both ends of the tension fixing fitting 19, and pull them simultaneously from the open ends of both strands 15a, 15b (41!). Fix by +21. Thus, after tensioning, the strands 15 protrude from both ends of the tension fixing fitting 19.
Cut the unnecessary length portions a and 15b, and fill the window hole 22 with mortar 23.

In addition, in the figure, 24 is a spiral reinforcement for concrete reinforcement, and 25 is a synthetic resin coating of the strand.

The method for constructing a PC structure using unbonded strands of the present invention is configured as described above, in which a pair of strands is tensioned as a unit, and the ends of both strands are placed at the end of the concrete structure. At the same time as concrete pouring, it is buried and fixed, and d
By inserting the strand into the window hole and connecting it tensionally within the window hole, there is no need to provide a strand insertion hole at the end of the floor or beam of a concrete structure as in the past. Even in the case where conventionally both ends had to be tensioned at the same time, the tensioning work is done at the center of the floor or the like, which significantly improves work efficiency.

In addition, since the pair of strands are tensioned and connected at the center to apply prestress,
At both ends of a concrete structure, the ends of the strands should be firmly embedded in the concrete, and the structure should be able to withstand forces that occur in the opposite direction to the tension direction in the event of an unexpected accident. The strand may break or the anchor may come off due to an accident where the end anchor comes off due to incomplete work during tensioning work, or an unexpected external force due to a fire or earthquake after tensioning, and the tension in the strand is suddenly released and elastic contraction occurs. Even if the inertial force due to movement is applied in the opposite direction, there is no danger that the anchoring end will jump out of the concrete structure.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing an example of a conventional PC structure, Fig. 2 is a longitudinal cross-sectional view of another example, and Fig. 3 shows the state of strand fixation of a PC structure in which the present Shinmei method is applied. The partially enlarged sectional view and FIG. 4 are perspective views showing the connecting and fixing fittings. 11... Support column, 12... Concrete 1
Boards 15a, 15b... Strand, 16a,
16b...Crimp grip, 17a, 17b...
...Bearing plate, 19...Tension fixing fitting, 20
...Strand insertion hole, 21...Horizontal. Patent applicant: Kurosawa Kensetsu Co., Ltd. Agent: Isao Sasaki, patent attorney
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Claims (1)

[Claims] 1. In a method for constructing a PC structure using unbonded strands, the unbonded strands are inserted into concrete structures such as beams and floors, and the strands are tensioned to give prestress. When installing, one end of the pair of strands is buried in the end of the concrete structure, and the other end of both strands is inserted into a window hole opened in the center of the concrete structure. A method for constructing a PC structure using unbonded strands, characterized by applying prestress by tensioning and connecting the strands on both sides within the window hole.