JPS6315421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for joining reinforcing bars using a coupler.

It is known to coaxially join reinforcing bars via couplers. To illustrate a conventional joint of this kind, the one shown in FIG. 1 is a lock nut type joint, in which a pair of threaded reinforcing bars 1 to be connected are joined by a coupler 2 and a lock nut 3. The one shown in FIG. 2 is a tension type lock nut joint, in which an annular member 4 is interposed between the coupler 2 and the lock nut 3, and the annular member 4 is compressed in the radial direction to give retrograde deformation in the axial direction. This provides a strong axial force between lock nut 2 and lock nut 3. The one shown in FIG. 3 is a crimp type joint in which the coupler 2 is compressed in the radial direction to crimp the coupler 2 and the reinforcing bar 1 together.

Each of these conventional joints has its own characteristics and is used in the right place with the right material, but in order to use such joint reinforcing bars in buildings and structures that require the highest safety, such as those related to nuclear power, it is necessary to comply with Building Standards Act 38. It must be certified based on the Article. In order to receive this certification, a building must pass the performance criteria of the Building Center of Japan RPCJ Committee.

Among the above standards, in the ``yield characteristic test'' for the ``A joint'', which is a fully strong joint that can transmit the yield point stress of reinforcing bars with sufficient margin, Apply a load that causes a strain (2δY) that is twice the strain (δY) at a load equivalent to , and apply a load equivalent to 50% of the JIS minimum yield point on the compression side, repeat 4 times,
The second residual strain is 0.3mm or less and 0.5δY or less. ” is stipulated.

However, the conventional method described above could not meet this standard. That is, the yield characteristic test results for the lock nut type joint shown in Fig.
As shown in the figure, in the SD32 reinforcing steel, the residual strain Δε
() was 0.38mm. As is clear from FIG. 4, the stress-strain line is significantly curved at the boundary between the tension side and the compression side. This is considered to be because the tensile force F between the coupler 2 and the lockite 3 is insufficient, causing looseness between the coupler 2 and the reinforcing bar 1. In other words, mill scale remains on the surface of the reinforcing bar in the threaded Fuji reinforcing bar 1, the thread pitch is large and varies due to manufacturing, and the tension between the male and female threads due to the tension between the coupler 2 and the lock nut is greater than that of the coupler 2. This is due to the fact that the necessary axial force cannot be obtained because it gradually decreases from the ends to the center, and that the tightening torque of the lock nut 3 varies and has a limit.

Therefore, it is thought that the above problems can be solved by strongly tightening the lock nut 3, but in reality, a high-output, large-capacity tightening machine is required to tighten it to meet the standard value, and the work is difficult. This makes it difficult to employ in field work due to poor performance.

The same can be said of the parts shown in Figs. 2 and 3, and in addition, in the part shown in Fig. 2, the length of the annular member 4 must be increased in order to obtain a strong tensile force. First, the overall length of the joint becomes longer, and the annular member 4 is required, leading to an increase in the number of parts. Although the one shown in Figure 3 is called crimping, strictly speaking, there is play between some of the screw threads and the valleys, and it cannot pass the above-mentioned strict standards.

As described above, there are no current mechanical joints that meet the above standards, and currently only joints made by gas pressure welding, arc welding, etc. meet this standard.

However, since gases, arcs, etc. are accompanied by flames, their use is restricted and there are quality problems, so there is a strong need for the development of mechanical joints.

Therefore, the present invention was devised in view of the above problems, and an object of the present invention is to provide a method for joining reinforcing bars using couplers, which can achieve the above standards with extremely simple on-site work. Therefore, the feature is that the reinforcing bars are coaxially joined by threading the male threaded part of the end of the reinforcing bar into the female threaded part of the coupler, and after screwing the nut member into the male threaded part, the above-mentioned After that, the nut member is brought into contact with both end faces of the coupler to temporarily join the reinforcing bars coaxially, and then the outer peripheral surface of the coupler is compressed to cause retrograde deformation in the radial and axial directions of the coupler. The main point is to press the female threaded portion and the male threaded portion together, and to apply compressive stress in the axial direction to the abutment surfaces of the nut member and the coupler for final joining.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 5, reference numeral 10 denotes a threaded reinforcing bar, and a large number of threaded bars 1 are arranged along the longitudinal direction on the outer peripheral surface of the reinforcing bar 10.
The male screw portion 12 is formed by arranging one group as a whole to form a series of male screws.

Reference numeral 13 denotes a coupler. The coupler 13 is formed into a cylindrical shape, and a female threaded portion 14 screwed into the male threaded portion 12 is provided in the through hole thereof.

A nut member 15 has a hexagonal outer peripheral surface and has the same female thread as the female thread part 14.

Next, a method for coaxially joining reinforcing bars 10 using the coupler 13 and nut member 15 will be described.

First, the nut member 15 is screwed into a predetermined position using the male threaded portion 12 at the end of the reinforcing bar 10. Next, the male screw portion 12 at the end of the reinforcing bar 10 to which the nut member 15 is screwed is screwed together from both ends of the female screw portion 14 of the coupler 13.
Then, screw the coupler 13 to approximately the center. Next, tighten the nut members 15 at both ends of the coupler 13 by hand (tightening by hand using a hexagon spanner).
Tighten the coupler so that it contacts both end surfaces of the coupler 13.
As a result, the reinforcing bars 10 are temporarily joined coaxially via the coupler 13.

This temporary connection can eliminate play in the tension direction between the reinforcing bars 10 and the threaded parts 12 and 14 of the coupler 13, and the slight tensile load acting on the reinforcing bars 10 is transmitted to the other reinforcing bars 10 via the coupler 13. ,
The compressive load will be transmitted via the nut member 15 and the coupler 3.

After the temporary bonding is completed, the outer circumferential surface of the coupler 13 is compressed in the radial direction by a crimping device (not shown). This compression device consists of a half-split compression section that clamps the outer peripheral surface of the coupler 13, a hydraulic cylinder that operates the half-compression section, and the like.
Due to this compression of the coupler 13, the coupler 13 contracts and deforms in the radial direction, and the female threaded portion 14 and the male threaded portion 1
2 are pressed together, and the coupler 13 also tends to deform in the axial direction. However, since both ends in the axial direction are restrained by the nut member 15, the coupler 1
3 and the nut member 15, a strong compressive stress o ₁ is generated between the nut member 15 and the nut member 15. That is, this stress o ₁ is the reinforcing bar 10
gives rise to a tensile stress o ₂ .

Therefore, due to the crimping of the coupler 13 and the cooperative action of the tensile force of the joint 13 and the nut member 15, the female threaded part 14 and the male threaded part 12 are strongly fitted together, and there is no play between them. The main bonding is completed.

FIG. 6 shows the results of a yield characteristic test of the joint according to the embodiment of the present invention, in which SD35 was used as the reinforcing bar 10.

According to the figure, the residual strain Δε() is 0.26 mm, which is 0.3 mm or less, which is the performance criterion for A joints set by the RPCJ Committee of the Building Center of Japan.

The reason why such high performance is obtained is that both reinforcing bars 10 are integrally joined via the nut member 15 and the coupler 13 without causing play in the axial direction. This is also clear from the fact that the stress-strain line in FIG. 6 is expressed as a continuous line without any inflection points on the compression side and the tension side. Such a strong and integral bond cannot be easily obtained by a simple lock nut type, a simple tension type, or a simple crimp type, nor can it be obtained by a simple combination, but can be achieved by organic bonding as in the present invention. It's something you get.

That is, due to the cooperation of the crimping force and the axial force, the reinforcement 10,
The coupler 13 and the nut member 15 are integrally connected, and the play between the female threaded portion 14 and the male threaded portion 12 is completely eliminated. The result was an excellent performance that had never been achieved before.

As described in detail above, according to the present invention, there is no need to forcefully tighten the nut member, so on-site work can be performed extremely easily, and the joint and the reinforcing bar can be integrally joined by a simple crimping operation, which has not been achieved until now. It has the remarkable effect of being able to pass the difficult yield characteristic test of the Japan Building Center.

[Brief explanation of the drawing]

Figures 1, 2, and 3 are cross-sectional views showing conventional joint systems, Figure 4 is a stress-strain diagram due to repeated loading of a conventional block nut type joint, and Figure 5 is a side view of a joint according to the present invention. A partial sectional view and FIG. 6 are stress-strain diagrams. 10...Reinforcement bar, 11...Binding, 12...Male thread part, 13...Coupler, 14...Female thread part, 15...
...Natsuto parts.

Claims (1)

[Claims] 1. In a device that coaxially joins reinforcing bars by screwing the male threaded part of the end of the reinforcing steel into the female threaded part of the coupler, a nut member is screwed into the male threaded part and then screwed into the female threaded part, and then the The nut member is brought into contact with both end faces of the coupler to temporarily join the reinforcing bars coaxially, and then the outer circumferential surface of the coupler is compressed to give the joint retrograde deformation in the radial and axial directions to separate the female threaded part and the male threaded part. A method for joining reinforcing bars using a coupler, characterized in that the main joining is performed by crimping the nuts and applying compressive stress in the axial direction to the contact surfaces of the nut member and the joint.