JP2746072B2 - Butt welding method of reinforcing steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of butt welding two unrestricted ends of two reinforcing bars whose ends are restrained by concrete.

[0002]

2. Description of the Related Art Butt welding has been widely used as a method of joining rebars at locations where joining by pressure welding is not possible because joining by joints is insufficient in performance.

[0003]

Conventionally, in the case of butt welding, the effect of the shrinkage of the reinforcing bar due to welding has not been taken into account. It will remain as internal stress, upsetting the design assumption that there is no initial internal stress in the reinforcing bar. This shrinkage strain increases as the constraint at the end of the reinforcing bar increases, and increases as the reinforcing bar at the unconstrained portion becomes shorter. Conventionally, contraction distortion is ignored as not so large, or the number of distribution muscles is increased in anticipation of contraction distortion to cope with it. However, when the rebar ends are completely constrained by the reverse striking method or the like and the rebars in the unconstrained portions are short, the shrinkage strain becomes a size that cannot be ignored.

An object of the present invention is to provide a butt welding method that does not leave shrinkage strain.

[0005]

SUMMARY OF THE INVENTION According to the present invention, in a butt welding of unconstrained ends of two rebars whose ends are constrained by concrete, (A) the ends of the rebars are trimmed to a predetermined length, A step of fitting a ring-shaped backing metal so as to straddle the ends of the two rebars; (B) a straight steel material having rebar grippers at both ends is placed on the restraining side of each rebar by the rebar grippers; Fixing, and butt-welding in a state in which each reinforcing bar is curved to opposite sides by a reinforcing bar pulling means and a reinforcing bar pushing means provided one each in the middle of the linear steel material so as to widen a gap between the ends of the reinforcing bars; (C) A step of butt-welding the reinforcing bar, comprising the step of removing the linear steel material from the reinforcing bar after the weld is cooled.

The most important point of the present invention is that the unconstrained portions of the two rebars are curved to the opposite sides to perform butt welding with the gap between the rebar ends slightly widened. The length expanded by bending is a length commensurate with the length at which the rebar contracts due to welding. Therefore, when the welded portion cools after welding, the contraction of the rebar is absorbed by the curved portion, and the two rebars are joined in a straight line. Even if the unrestricted portions of the two rebars are bent to the same side and welded, the two rebars that are welded become linear after cooling. This method must be avoided because it results in residual distortion.

In the present invention, a simple jig is used to bend an unconstrained portion of a reinforcing bar. This jig is mainly made of one steel material having higher rigidity than a reinforcing bar, has a reinforcing bar grip portion at both ends, and has a reinforcing bar pulling unit and a reinforcing bar pushing unit in the middle. Fixing the rebar holding parts at both ends to the rebar on the restraint side, taking the reaction force to the concrete via the rebar, and bending the unconstrained portions of the two rebars to the opposite sides by the rebar pulling means and the rebar pushing means. is there.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows a state in which a jig used in the present invention is attached to a reinforcing bar to be butt-welded, and FIG.
(B) is a longitudinal sectional view of a reinforcing bar gripping part, (c) is a longitudinal sectional view of a reinforcing bar pushing means, and (d) is a longitudinal sectional view of a reinforcing rod pulling means.

In this example, the main material of the jig 1 is a channel steel 2
Are used, and rebar gripping parts 4, 4 are fixed to both ends thereof with screws or bolts. In the middle, a rebar pushing means 5 and a rebar pulling means 6 are similarly fixed with screws or bolts. As shown in FIG. 1 (b), the reinforcing bar gripping portion 4 is composed of an iron plate 8, a supporting plate, and a grooved steel side gripping metal 4B. 3 is fixed to the reinforcing steel bar 3. As shown in FIG. 1 (c), the rebar pushing means 5 is composed of an iron plate 8, a nut 10 welded to the iron plate 8, and a bolt 9 screwed to the nut 10, while the rebar 3 has a groove-shaped steel-side receiving hardware 5B. Are attached by bolting to the rebar-side holding hardware 5A, and the tip of the nut 10 is in contact with the channel steel-side receiving hardware 5B. As shown in FIG. 1 (d), the reinforcing bar tension means 6 comprises an iron plate 8, a nut 10 welded to the iron plate 8, a bolt 9 screwed to the nut 10, and a tension metal member 6B attached to the tip of the bolt 9. The reinforcing bar 3 is gripped and fixed to the reinforcing bar 3 by bolting the reinforcing bar side holding metal 6A to the pulling metal 6B.

The jig 1 is thus attached to the reinforcing bar 3. Note that a high-rigidity steel material other than the grooved steel is also used as the main material of the jig 1, and the connection of various hardware may be replaced by another ordinary method.

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 2 is a front sectional view for explaining a construction procedure.

(1) The ends of the two reinforcing bars 3, 3 whose ends are restrained by concrete are trimmed, the gap between the ends is set to about several mm, and a ring-shaped backing metal 7 spans between the ends. Is fitted. (FIG. 2 (a)) (2) Reinforcement gripping portions 4, 4 at both ends of the jig 1 are attached close to the restrained ends (concrete) of the respective reinforcing bars 3, 3. (FIG. 2B) (3) A bolt hole 11 at an appropriate position is selected from a large number of bolt holes 11 drilled in the channel steel 2, and the reinforcing bar pushing means 5 and the reinforcing bar pulling pushing means 6 are attached. By rotating the bolts 9 of the respective means, the rebars 3, 3 are curved to the opposite side to widen the gap between the tips of the rebars 3, 3. (Figure 2
(C)) Rebar pushing means 5 and rebar pulling / pushing means 6 at this time
May be performed one first and the other later,
It is preferable to carry out the operation step by step in parallel with each other.

(4) The gap between the tips of the reinforcing bars 3 and 3 is welded with a weld metal, and after the weld is cooled, the jig 1 is removed from the reinforcing bars 3
Remove it from Step 3 to complete the work. (Fig. 2 (d))

[0015]

According to the present invention, since the unconstrained portions of the two rebars are curved to the opposite sides and the gap between the ends of the rebars is slightly widened, the butt welding is performed. No shrinkage strain remains in the rebar.

[Brief description of the drawings]

FIG. 1 shows a state in which a jig used in the present invention is attached to a reinforcing bar to be butt-welded, (a) is an elevation view, (b) is a longitudinal sectional view of a reinforcing bar gripping portion, and (c) is a reinforcing bar pushing means. Longitudinal sectional view of the
(D) is a longitudinal sectional view of the reinforcing bar pulling means.

FIG. 2 is a front sectional view showing a construction procedure of the present invention.

[Explanation of symbols]

1. Bending jig, 2. Steel, 3. Rebar, 4. Rebar gripping part, 4A Rebar gripping metal, 4B Steel gripping metal, 5 Rebar pushing means, 5A・ Reinforcement side gripping hardware, 5B ・ ・ Steel material side receiving hardware, 6 ・ ・ Reinforcing bar tension means, 6A ・ ・ Reinforcing bar side gripping hardware, 6B ・ ・ Tension hardware,
7. Ring backing metal, 8. Iron plate, 9. Bolt,
10. Nuts, 11 bolt holes

Claims (1)

(57) [Claims] In a butt welding of unconstrained ends of two rebars, one ends of which are constrained by concrete,
(A) a step of trimming the ends of the reinforcing bars to a predetermined length, and fitting a ring-shaped backing metal so as to straddle the ends of the two reinforcing bars, and (B) a straight line having reinforcing bars at both ends. The steel material is fixed to the restraining side of each rebar by the rebar gripping portion, and the rebars are bent to opposite sides by rebar pulling means and rebar pushing means provided respectively in the middle of the linear steel material. (C) removing the linear steel material from the rebar after the weld has cooled, and a butt-welding method for the rebar.