JPH0130609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing prestressed concrete members.

As is well known, prestressed concrete members are a new structural style that differs from traditional reinforced concrete structures. It is a concrete member with a structure that has a certain fixed stress state (hereinafter referred to as prestress) in its cross section.

A pretension method is known as a method for applying such a stress state, that is, prestress. This method involves applying tensile stress to a prestressed steel material made of prestressed steel wire or stranded prestressed wire and fixing it on both sides of a strong tensile table. Next, a formwork is placed around the prestressed steel material. Concrete is poured, and when the concrete has sufficiently hardened and reached the required compressive strength, the fixing devices at both ends of the prestressing steel are loosened to apply prestress to the concrete member.

By the way, since this prestressing steel material adheres to the concrete member and applies prestress to the cross section of the member, it is most important that the prestressing steel material has high adhesion strength to concrete.
For this reason, a method is generally adopted in which a large number of prestressing steel materials with as small a diameter as possible (diameter φ of 2.9 mm or less) are used.

However, when prestressing is applied using small-diameter prestressing steel like this, it is possible to ensure the adhesion strength of the prestressing steel to the concrete, but as mentioned above, there are many pieces of prestressing steel, so it takes time to fix the prestress. Problems such as the need for a special fixing device have arisen. On the other hand, if you use a method using a large diameter PC steel wire or PC steel stranded wire, the PC
Although it is possible to reduce the number of steel materials, in this case, the adhesion strength to concrete is insufficient for the tensile stress given to the prestressing steel materials.
When the fixing devices at both ends of the prestressing steel material are loosened, both ends of the prestressing steel material sink significantly into the concrete, and as a result, the areas where prestress is not applied at both ends of the concrete material become considerably large. Not only that, but a contradictory problem arises in that it becomes difficult to apply a large prestress. This phenomenon is caused by PC steel wire or
This becomes more noticeable as the diameter of the wire becomes larger than that of PC steel.

The present invention has been made in consideration of the above points, and it not only makes it possible to improve workability by reducing the number of wires by using PC steel strands having a large diameter. To provide a method for manufacturing a prestressed concrete member, which can uniformly apply a large prestress over almost the entire length of the concrete member and can obtain a large amount of prestressed concrete members at once.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 to 3 are diagrams showing a fixing metal fitting 4 used when carrying out the manufacturing method according to the present invention,
In the figure, reference numeral 1 indicates a prestressed steel stranded wire, and numeral 2 indicates an anchor plate having a female threaded hole 2a formed on the inner peripheral surface, and the female threaded hole 2a of this anchor plate 2 is larger than the prestressed steel stranded wire 1. The female screw hole 2a is formed to have a large diameter, and the internal diameter of the female screw hole 2a is tapered so as to gradually become smaller from the opening at one end toward the opening at the other end. Reference numeral 3 denotes a male thread (tapered thread) 3a on the outer circumferential surface that engages with the female thread of the female threaded hole 2a, a nut-shaped head 2b on one end, and the PC steel stranded wire 1 passing through in the axial direction. The fixing bolts 3 are cylindrical fixing bolts each having a through hole 3c, and the outer diameter of the shaft portion of the fixing bolt 3 is tapered so as to gradually become smaller toward the tip, corresponding to the female threaded hole 2a. is formed. Further, this fixing bolt 3 has a vertically divided structure into three parts as shown in FIGS. The inner diameter of the PC steel wire 1 is formed to be slightly smaller than the outer diameter of the wire 1.

Next, the manufacturing method of the present invention will be specifically explained.

First, as shown in FIG. 4, a plurality of partition plates 6 are arranged between the end plates 5a and 5b of a long formwork 5 to form a prestressed concrete member formwork 5' in one row. A plurality of prestressed molds are formed at intervals from each other, and then a prestressing plate is formed from the end plate 5a on one side to the end plate 5b on the other side so as to pass through all of the plurality of formworks 5' in the length direction. Sequentially pass wire 1 through the PC steel strands for introduction. On this occasion,
Each time one formwork 5' is penetrated, two anchor plates 2 per one PC steel strand are passed through and positioned within the formwork 5'. In this way the PC
Once the steel stranded wire 1 is penetrated, a required tensile stress is applied to the PC steel stranded wire 1 by jacking or the like, and both ends thereof are fixed to the fixing devices 7, 7.

After fixing the PC steel strands 1, the anchor plates 2 placed in each formwork 5' are placed near both ends as shown in Figure 4, and then these anchor plates are Fixing bolts 3 having a longitudinally split structure are screwed into the two female threaded holes 2a, respectively, thereby fixing each anchor plate 2 to the prestressing steel stranded wire 1. At this time, since the fixing bolt 3 is split vertically and has a split configuration, it can be attached to the anchor plate 2 in this way even after the PC steel stranded wire 1 is stretched as described above. . If such a fixing bolt 3 has a tapered thread (male thread 3a) on its outer circumferential surface, this fixation can be achieved by screwing it onto the anchor plate 2 and then screwing it into the anchor plate 2 more firmly. The diameter of the through hole 3c formed at the center of the bolt 3 is reduced, and the wire 1 is tightened more strongly than the PC steel.
It will be firmly fixed to the wire 1 using PC steel. In other words, it is possible to easily and reliably fix the fixing fitting 4 to the PC steel stranded wire 1 in which fixing means such as a threaded portion cannot be formed in the middle.

After each anchor plate 2 is fixed in its predetermined position in this way, concrete 8 is poured into each formwork 5' as shown in FIG. When this is reached, the fixing devices 7, 7 at both ends are loosened, and then the PC steel stranded wire 1 is cut from between each of the formworks 5'. Then, remove each formwork 5',
Further, by finishing both end faces, a large number of prestressed concrete members 10 with fixing fittings 4 embedded near both ends as shown in FIG. 6 can be obtained at once.

In the prestressed concrete member 10 manufactured in this way, the anchoring fittings 4 are fixed to the PC steel stranded wire 1 that applies prestress to the cross section of the member, and the anchor plates 2 are located near both ends of the concrete member 10, respectively. Since it is buried, in addition to the compressive force introduced by the adhesion of the prestressed steel stranded wire 1 itself, a compressive action on the concrete of the anchor plate 2 constituting the fixing fitting 4 is added, and therefore the prestressed steel stranded wire Both ends of the wire 1 do not sink as much as in the past, and the tensile stress given to the wire 1 from the PC steel is reliably maintained. Also, in this way, anchor plate 2 for PC steel stranded wire 1
is fixed, it is possible to give a larger tensile stress to wire 1 than the PC steel, and therefore
The number of wires 1 can be reduced accordingly compared to PC steel, thereby reducing complicated work such as fixing work at both ends.

In the above embodiment, a plurality of formworks 5' for the prestressed concrete member to be formed were formed in one row at intervals by arranging a plurality of partition plates. A large number of them may be arranged in rows and spaced apart from each other, and
After the formwork is stretched with prestressed steel wire 1,
The PC steel strands may be similarly arranged in a row along line 1. Furthermore, according to the present invention, the fixing metal fitting 4 is
Since it is extremely easy to freely fix the PC steel stranded wire 1 at any position, for example, each formwork 5', 5',
It is possible to easily deal with cases where the lengths of the ... are different, and even more effects can be achieved.

In addition, in the embodiment, the anchor plate 2
Although we have shown an example in which only the female threaded hole 2a is provided,
For example, as shown in Fig. 7, if a slit 2b communicating with the female threaded hole 2a is provided and the wire 1 can be passed through the female threaded hole 2a using the slit 2b, the PC steel Even after both ends of the stranded wire 1 are fixed to the fixing devices 7, 7, the anchor plate 2 can be fixed to the PC steel stranded wire 1.

As detailed above, according to the present invention, not only can a large number of prestressed concrete members be obtained at one time, but also the use of large-diameter prestressed steel strands reduces the number of wires and improves workability. Further, the fixing bolt has a vertically split configuration in which a tapered thread is formed on the outer peripheral surface of the prestressed steel strand and a through hole for the prestressed steel strand is formed in the shaft center, and the tapered thread of this fixing bolt is provided. Since the fixing fitting, which consists of an anchor plate that is screwed onto the PCB, is fixed and buried, a large prestress can be applied to the cross section of the member due to the introduction of compressive force due to the adhesive force of the PC steel strands. Moreover, since this anchor plate is located near both ends of the concrete member, uniform prestress is applied over almost the entire length of the concrete member, and in addition, the prestress is applied to the PC steel strands of the anchoring fitting. Since positioning and fixing can be performed extremely easily, work can be carried out efficiently, and it has excellent effects such as being able to easily accommodate concrete members of arbitrary dimensions without any modification.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the fixing fitting used in the present invention, Figs. 2 and 3 are left and right side views of the fixing fitting, and Figs. A schematic sectional view shown to explain the manufacturing method of the invention, FIG. 6 is a sectional view of a prestressed concrete member obtained by the manufacturing method of the invention, and FIG. 7 is a second embodiment showing another embodiment of the anchor plate. It is a left side view similar to the figure. 1...PC steel stranded wire, 2...Anchor plate,
2a... Female threaded hole, 2b... Slit, 3... Fixing bolt, 3a... Male thread (tapered thread), 3b
...Head, 3c...Through hole, 4...Fixing metal fitting,
5, 5'... Formwork, 5a, 5b... End plate, 6...
Partition plate, 8... concrete.

Claims (1)

[Claims] 1 A plurality of formworks 5' for the prestressed concrete member to be formed are arranged in one row and spaced apart from each other, and one or more prestressed steel strands 1 are connected to these formwork groups in the row direction. Furthermore, tensile stress is applied to this PC steel stranded wire to fix both ends thereof, and the outer periphery is placed near both ends of each of the portions of this PC steel stranded wire located in each of the above-mentioned formworks. Consisting of a vertically split fixing bolt 3 in which a tapered thread 3a is formed on the surface and a through hole 3c for the PC steel stranded wire is formed in the shaft center, and an anchor plate 2 that is screwed into the tapered thread of this fixing bolt. After fixing the fixing fittings 4, concrete 8 is poured into each of the formworks, and after the poured concrete reaches the required compressive strength, the PC steel strands are inserted between the formworks. A method for producing a prestressed concrete member, the method comprising cutting the member.