JPS6239211Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an unbonded PC steel bar used in a construction method that applies prestress to concrete using a post-tension method.

Conventionally, as a post-tension type PC construction method that introduces prestress after concrete is poured, the method shown in Figure 6 or Figure 7 has been popular. That is, the method shown in FIGS. 6A and B uses a steel rod 11 partially carved with screws 12, 12 at both ends, and a sheath 13 separately formed from a thin metal plate or the like. , the sheath 13 is placed in the concrete 10 during concrete pouring. After the concrete 10 has hardened, the PC steel rod 11 is inserted into the sheath 13, and then tension is applied to the PC steel rod 11 from both ends using tension jacks, etc., and in this state, it is screwed into the threaded portions 12 at both ends. The nuts 14, 14 are then tightened to fix them to the end face of the concrete 10 via the fixing plates 15, 15. However, according to this method, it is necessary to inject the graft 16 into the gap between the sheath 13 and the PC steel rod 11, resulting in poor workability.
In addition, after the PC steel bar 11 is formed by rolling or the like, threading is performed over a predetermined range at both ends to enable tension and fixation. Ta.

In addition, the method shown in FIG. 7 involves applying grease to the surface of the PC steel stranded wire 21 in advance and covering it with a sheath of kraft paper or polyethylene to form the unbonded part 22.
Using a steel wire, embed it directly in the concrete 10, and after the concrete 10 hardens, use tension fixing tools 23, 23, tension jacks, etc. to tighten the PC.
The steel wire is taut to make it stick. According to this method, grouting work is omitted, which simplifies the work. However, in this case as well, the unbonded PC steel wire is difficult to manufacture because threading and other processes are applied to the predetermined ranges at both ends of the unbonded PC steel wire for tensioning and fixing after forming the steel strand. The work of forming the unbonded portion 22 by applying grease and adhering the sheath to the unbonded portion 22 is also troublesome, and due to these, disadvantages such as high cost remain.

In view of these circumstances, the present invention can be applied to a simple construction method in which prestressing steel with unbonded material attached is directly embedded in concrete and tensioned and fixed after the concrete hardens.
To provide an unbonded PC steel bar which can easily produce a structure in which the main body of the PC steel bar as a PC steel material is equipped with screws for tensioning and fixing, and an unbonded material is attached, and which can reduce costs.

That is, the present invention comprises a prestressed steel bar main body in which a thread is formed over the entire length by rolling, and an unbonded part formed by attaching an unbonding material to the threaded valley of the prestressed steel bar main body. be. Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

In FIGS. 1 and 2, reference numeral 1 denotes a PC steel bar body, which has a screw 2 along its entire length, and the screw 2 is formed by rolling at the same time as the PC steel bar body is formed. That is, a so-called threaded steel bar is used for the PC steel bar body 1, which is a primary product obtained by rolling and is inexpensive. This PC
An unbonded part 3 is formed by applying an unbonded material such as a synthetic resin to the valley part of the screw 2 of the steel rod body 1. This unbonding part 3 is to avoid adhesion between the PC steel bar body 1 and concrete in the prestress introduction construction described later, and to allow the PC steel bar body 1 to elongate due to tension after concrete hardens. It is painted to fill the valleys. The ridge portion 2a of the screw 2 is sufficiently narrower than the unbonded portion 3. Furthermore, if necessary, a vinyl capping 4 may be applied to the outer periphery of the PC steel bar provided with the unbonded portion 3.

FIG. 3 shows another example of the unbonded portion, in which an unbonded portion 3' is formed by attaching a spring made of steel or the like to the valley of the screw 2 of the PC steel bar body 1. Other structures are similar to the embodiment shown in FIG.

When producing a prestressed concrete member using this unbonded PC steel rod, prestressing can be easily introduced as shown in FIGS. 4 and 5.

That is, first, when pouring concrete 10,
The above-mentioned unbonded PC steel rod is directly embedded in concrete 10 (see Fig. 4). Next, after the concrete 10 has hardened, the unbonded portions 3 (or 3') are peeled off from the PC steel bar body 1 at both end portions of the unbonded PC steel bar protruding from the end face of the concrete 10, thereby screwing the PC steel bar body 1. 2, and screw nuts 5 and 5 here. Next, the PC steel bar main body 1 is tensioned from both ends using predetermined tensioning jacks (not shown), and after applying a suitable tension force, the nuts 5 are rotated to tighten both end surfaces of the concrete 10. (See Figure 5). In this case, a fixing plate (not shown) may be interposed between the end face of the concrete 10 and the nuts 5, 5. In this way, the prestress introduction is completed.

As described above, the unbonded PC steel bar of the present invention is formed by rolling to form a PC steel bar body with threads along its entire length, and the unbonded material is attached to the valleys of the threads. It can be applied to an extremely simple prestress introduction method in which it is embedded in concrete, tensioned from both ends after the concrete hardens, and tightened with nuts. Moreover, the screws necessary for tensioning and fixing are formed at the same time as the steel rod body is formed, and the unbonded material can be easily attached using the screws, making it easy to form and process the unbonded PC steel rod. , costs can be significantly reduced. Furthermore, by having a screw formed on the entire length,
Even when cutting a pre-formed long steel bar body to the desired length, there is no problem in attaching the unbonded material, and the tension work to introduce prestress can be done no matter where the cut is made. This makes it possible to improve the workability and workability of unbonded PC steel bars.

[Brief explanation of the drawing]

Fig. 1 is a partially sectional front view showing an embodiment of the unbonded PC steel rod of the present invention, and Fig. 2 is a -
3 is a partially sectional front view showing another embodiment; FIGS. 4 and 5 are schematic sectional views showing prestress introduction in order of operation; FIG.
Figures A, B and Figure 7 are schematic diagrams showing conventional examples, respectively. 1...PC steel bar body, 2...Screw, 3, 3'...
Unbonded part.

Claims (1)

[Scope of utility model registration request] PC with screws formed over the entire length by rolling
1. An unbonded PC steel bar comprising a steel bar body and an unbonded part formed by attaching an unbonding material such as a resin or a steel spring to the threaded valley of the PC steel bar body.