JPH0416252B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applied to the ends of prestressed steel strands used as tendons for introducing stress in prestressed concrete construction methods and tension cables for cable-stayed bridges. A PC that forms a head with a bulged outer diameter for fixation.
This invention relates to a method for forming a steel strand head.

(Prior art) There are various methods for fixing stress after introducing stress when using conventional PC steel strands in prestressed concrete construction method, but all of them are wedge methods using complicated fixing tools. First of all, it lacks reliability when compared to the head-fixed method.

In the case of the head fixing method of the present invention, the head strength always exceeds the parallel part strength in a tensile test, whereas in the case of the wedge method using a conventional fixing device, most of the The strength often breaks within the parallel part and is lower than the strength of the parallel part.

Furthermore, compared to the head fixing method of the present invention, the method using a conventional fixing device significantly increases the cost and working time required for fixing.

Therefore, in the case of prestressed concrete steel bars used in the prestressed concrete construction method, similar to prestressed steel stranded wires, the pretensioning method can be easily processed by fixing the heads at both ends or by fixing the heads at one end with screws at one end. It's on. In addition, in the case of the post-tensioning method, the wire is often fixed with a screw at one end of the head, and is not fixed using a fixing tool like PC steel stranded wire.

However, due to the structure of stranded PC steel wire, it is impossible to process screws or form the head, and up until now, all methods have used fixing tools.

(Problems to be Solved by the Invention) Conventionally, as a method for fixing stress after introducing stress into a PC steel strand, a complicated fixing device was used as described above.
All of them were wedge-based.

This is because, due to the structure of PC steel strands, head forming or threading cannot be easily performed as with PC steel bars. If it is easy to form the head and thread the screws, as with PC steel rods, it becomes possible to easily and reliably fix the head or nut using only the anchor plate, without using complicated fixing tools. However, until now, it has been considered impossible to perform head forming on PC steel strands.

The reason for this is that in the case of PC steel stranded wire, the structure is made up of multiple strands twisted together, so even if you perform head forming processing on the tip of the PC steel stranded wire, the gaps between the strands will collapse and the head I can't even figure out the shape.

In view of the above points, the present invention has succeeded in forming the head of a prestressed steel stranded wire based on the results of various experiments.

(Means for Solving the Problems) The characteristics of the method for forming the head of a prestressed PC steel wire according to the present invention in order to solve the conventional problems as described above are as follows. After fitting a metal sleeve to the outer periphery of the end of the PC steel stranded wire, and heating the PC steel stranded wire and the metal sleeve at the part where the metal sleeve is fitted to a temperature that does not cause a decrease in the strength of the PC steel stranded wire, The purpose is to apply pressure from the tip and deform the end of the PC steel stranded wire together with the metal sleeve into a larger diameter.Secondly, the PC steel stranded wire is twisted by multiple strands and then cold-drawn. In addition to reducing the groove width of the threaded thread between the strands,
After the end face is plastically deformed into a nearly circular shape, the PC steel stranded wire at the fitting part of the metal sleeve and the metal sleeve are heated to a temperature close to the limit that does not cause a decrease in the strength of the PC steel stranded wire, and then the tip part is The purpose is to pressurize the ends of the PC steel stranded wire together with the metal sleeve to a larger diameter.

(Function) In this method, by fitting a metal sleeve to the PC steel strands, the strands of the PC steel strands are integrally formed without coming apart during pressure forming of the head. In addition, heating the PC steel strands to a constant temperature makes forming processing easier and reduces the occurrence of internal strain after processing. Also, the heating temperature is
Since the strength of the wire does not decrease compared to that of PC steel, the wire itself is not altered from PC steel.

Furthermore, various fracture phenomena such as delayed fracture under the head of the contact area with the anchor plate, which has been a problem with conventional PC steel bars and can occur even when it is possible to form the head of PC steel strands, can be avoided with sleeves. Since the PC steel stranded wire is protected by this and it does not come into direct contact with the anchor plate, there is no need to worry about it.

Conventionally, head anchoring or nut anchoring has been desired for the stress fixation method for PC steel stranded wires as well as for PC steel bars after stress is introduced. However, until now, head forming and thread rolling have been considered impossible due to the wire structure of PC steel. Therefore, in the case of PC steel stranded wires, the method of using a fixing device has been used in all cases.

Comparing the fixing method using a fixing tool with head or nut fixing, head or nut fixing is simpler, more reliable, cheaper, and allows easier fixing work.

Therefore, even in the case of stranded PC steel wire, by using the head forming method of the present invention, it is possible to fix the head using only the anchor plate, without using a complicated fixing device as in the past.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

In the present invention, the PC steel stranded wire to which the head forming process is performed is, as shown in Figure 1, a PC steel stranded wire 1 made by twisting a plurality of strands, and this PC steel stranded wire 1 is not shown in the figure. A stranded PC steel wire 1A is used which has been plastically deformed by cold drawing to reduce the width of the spiral groove between the strands and increase the cylindrical area of the outer periphery as shown in FIG.

Next, the head machining process for the two PC steel wires 1 and 1A will be explained in order.

First, wire 1 or 1A stranded from PC steel is cut to a required length.

As shown in FIGS. 3 to 5, a metal sleeve 2 is fitted to the tip head portion of the PC steel stranded wire 1 or 1A cut to a required length.

The PC steel stranded wire 1 or 1A (hereinafter simply referred to as 1) into which the sleeve 2 has been inserted is fed into a head forming machine and clamped by a clamp 3, as shown in FIG. When completely clamped, the heating coil 4 of the high-frequency induction heating device heats the head portion of the PC steel strand 1 including the sleeve 2 to a predetermined temperature. Heating temperature is adjusted by heating time and heating voltage. When heated to a predetermined temperature, the heating voltage is cut off by a heating timer, and then the hydraulic press cylinder (hydraulic jack) 5 is activated to form the head 6 as shown in FIG.
When the head forming process is completed, the hydraulic press cylinder 5 returns to its original position. When the hydraulic press cylinder 5 completely returns to its original position, the clamp 3 is opened and the PC steel stranded wire 1 is taken out.

This operation is repeated to form the head, and all of these operations are linked and performed automatically.

Note that the heating method for the head forming portion is not the high-frequency induction heating method, but may be a direct energization method or another heat source.

When using the prestressed steel stranded wire 1 with the head 6 formed in this way, when the prestressed steel stranded wire 1 is inserted into the hole 8 of the anchor plate 7 and fixed as shown in FIG. As shown in FIG. 9, a gourd-shaped hole 8 is provided as the plate 7, and the head 6 is inserted through the large diameter hole 8a and the head is fixed in the small diameter hole 8b. As shown in FIG. 10, a half-split anchor plate 7 is used.

(Effect of the invention) As mentioned above, the present invention was previously considered impossible.
This makes it possible to form the head of PC steel stranded wire.

Therefore, by using the method of the present invention, fixing of the head of PC steel stranded wire, which has been a concern for many years, has been realized.
The fixing costs are significantly reduced and reliable fixing is possible, making it a groundbreaking invention as a wire fixing method for PC steel, and its effects are enormous.

[Brief explanation of drawings]

Figures 1 and 2 show the process performed in the present invention.
Figures 3 and 4 are end views of the PC steel stranded wire with a metal sleeve inserted into the PC steel stranded wire, Figure 5 is a plan view of the PC steel stranded wire with a sleeve inserted, and Figure 6 is an end view of the PC steel stranded wire with a sleeve inserted. The figure is a cross-sectional view showing a schematic configuration of the head forming machine, FIG. 7 is a cross-sectional view of the head forming machine in a state where the head forming process is completed, and FIG. 8 is a plan view of an example of a state in which it is fixed to the anchor plate. Figure 9, 1st
FIG. 0 is a plan view showing examples of separate anchor plates. 1...PC steel stranded wire, 2...Sleeve, 3...
Clamp, 4... High frequency induction heating coil, 5...
Hydraulic press cylinder, 6...head.

Claims (1)

[Claims] 1. A metal sleeve is fitted around the outer periphery of the end of a PC steel stranded wire made by twisting a plurality of strands, and the PC steel stranded wire and the metal sleeve are connected to the PC steel stranded wire at the part where the metal sleeve is fitted. The head of a prestressed steel stranded wire is characterized in that the end of the prestressed steel stranded wire is heated to a temperature limit that does not cause a decrease in strength, and then pressure is applied from the tip to deform the end of the prestressed steel stranded wire together with the metal sleeve into a large diameter. Part forming processing method. 2 A PC steel stranded wire made by twisting multiple strands is cold-drawn to reduce the width of the spiral groove between the strands and to plastically deform the cross section into a nearly circular shape. A metal sleeve is fitted around the outer circumference of the end of the steel stranded wire, and the PC steel stranded wire and the metal sleeve in the part where the metal sleeve is fitted are heated to a temperature close to the limit that does not cause a decrease in the strength of the PC steel stranded wire, and then the tip is heated. Pressure is applied to the metal sleeve together with the metal sleeve.
A method for forming the head of a PC steel stranded wire, which is characterized by deforming the end of the PC steel stranded wire under pressure to a larger diameter.