JPH07102777A - Butt welding method of rebar - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a butt welding method for reinforcing bars that does not leave shrinkage distortion due to welding. [Constitution] One end is constrained by concrete 2
In butt welding of unconstrained ends of two reinforcing bars,
(A) A step of aligning the ends of the reinforcing bars to a predetermined length and fitting a ring-shaped backing metal 8 so as to straddle the ends of the two reinforcing bars, (B) a plurality of turnbuckles 2A, 2D A state in which a tension jig having one reinforcing bar gripping part 4 welded to each end is attached to one or both reinforcing bars, and the tension jig is tightened to shrink one or both reinforcing bars to widen the gap between the two reinforcing bar ends. Butt welding in step (C), and (C) the step of cooling the welded portion and then removing the tension jig from the reinforcing bar.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a butt welding method for joining unrestricted ends of two rebars having one end constrained by concrete.

[0002]

2. Description of the Related Art Joining by joints is insufficient in performance, and joining by butt welding has been widely adopted as a joining method for reinforcing bars in places where joining by pressure welding cannot be performed.

[0003]

Conventionally, in the case of butt welding, the influence of the contraction of the reinforcing bar due to welding has not been considered so much. However, if the reinforcing bar cannot be fully contracted after welding, the contraction strain naturally occurs in the reinforcing bar. It remains as an internal stress, which upsets the design assumption that there is no initial internal stress in the reinforcing bar. This contraction strain increases as the restraint at the end of the reinforcing bar increases, and increases as the reinforcing bar in the unconstrained portion decreases. Conventionally, the contraction strain is ignored as it is not so large, or the contraction strain is taken into consideration and the number of distribution muscles is increased to deal with the situation. However, when the reinforcing bar ends are completely constrained by the reverse striking method and the unconstrained part of the reinforcing bar is short, this contraction strain becomes a size that cannot be ignored.

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

[0005]

According to the present invention, in butt welding of two unconstrained ends of two rebars, one end of which is constrained by concrete, (A) the ends of the rebars are cut into a predetermined length, Step of fitting a ring-shaped backing metal so as to straddle the ends of two reinforcing bars, (B) One or both of tension jigs in which one reinforcing bar gripping part is welded to both ends of a plurality of turn buckles Butt welding with the tensioning jigs tightened by tightening one or both of the reinforcing bars by expanding the gap between the ends of the two reinforcing bars, (C) after the welded part has cooled, More removing process,
It is a butt welding method for reinforcing bars.

The most important point of the present invention is that a special tension jig is attached to one or both rebars, and the tension jig is tightened to shrink one or both rebars to expand the gap between the two rebar ends. It is the point of butt welding at. The length shortened by the tension jig corresponds to the length of the reinforcing bar contracted by welding. Therefore, when the welded part cools after welding and the tension jig is removed from the reinforcing bar, the contraction of the reinforcing bar is absorbed in the unconstrained part.

In the present invention, a special tensioning jig is used to shrink the unconstrained portion of the reinforcing bar. This jig is made by welding one reinforcing bar grip to both ends of a plurality of turn buckles, and the reinforcing bar grips at both ends fix the unrestricted part of the reinforcing bar with bolts through packings. The turnbuckle is arranged so as to surround the unrestricted part of the reinforcing bar. The turnbuckles used are usually four or six, and these turnbuckles are arranged around the reinforcing bar in a well-balanced manner. It is preferable to attach the tension jig to both reinforcing bars to be butt welded,
It may be attached only to one rebar having a long unconstrained portion.

[0008]

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

1A and 1B show a state in which a tensioning jig used in the present invention is attached to a reinforcing bar for butt welding. FIG. 1A is an elevation view and FIG. 1B is a plan view of a reinforcing bar gripping portion.

In this example, the tension jig is composed of four turnbuckles 2A, 2B, 2C and 2D. The upper and lower ends of the screw rods 3A, 3B, 3C, 3D of each turnbuckle are welded to the reinforcing bar gripping portion 4, respectively. The reinforcing bar gripping part 4 includes two partially curved iron plates 6 and 6 and a packing 5.
And the two iron plates 6 and the bolt 7 for fastening the steel plate 6. Insert this tension jig from the longitudinal direction of the reinforcing bar 1A,
The rebar 1A is separated into two parts and is attached to the rebar 1A from the lateral direction so that the rebar 1A is attached to the rebar 1A.

An embodiment of the present invention will be described with reference to FIG. FIG. 2 is a vertical cross-sectional view of butt welding between two unconstrained ends of two vertical reinforcing bars whose one end is constrained by concrete.

(1) The rebars 1A whose upper ends are constrained by concrete and the rebars 1B whose lower ends are constrained by concrete are trimmed so that the gap between the ends is about several mm and they straddle between the ends. Fit the ring-shaped backing plate 8.

(2) When the tension jigs can be attached to both the reinforcing bars 1A and 1B, the tension jigs are fixed to the reinforcing bars 1A and 1B by the reinforcing bar gripping portions 4. (Fig. 2
(A)) When the reinforcing bar 1B is extremely short and it is difficult to attach the tension jig, the reinforcing jig is fixed to the reinforcing bar 1A only by the reinforcing bar gripping portion 4. (Fig. 2 (b)) (3) Rotate the turnbuckles 2A, 2B, 2C, 2D to pull the screw rods 3A, 3B, 3C, 3D. In the case of Fig. 2 (a), rebar 1A and rebar 1B Shrink,
In the case of FIG. 2B, the reinforcing bar 1A is contracted.

(4) The gap between the tips of the reinforcing bars 1A and 1B is welded with a welding metal, and after the weld is cooled, the bolts 7 are loosened to remove the tension jig from the reinforcing bars 1A or the reinforcing bars 1A and 1B. Is complete.

In the case of FIG. 2 (a), the inside 2A, 2B of the turnbuckle attached to the rebar 1A is tightened to shrink the rebar 1A to a curved shape, and the inside 2C, 2D of the turnbuckle attached to the rebar 1B. Is tightened and the reinforcing bar 1B is contracted in a direction opposite to that of the reinforcing bar 1A so as to be curved and welded, and the contraction strain is completely absorbed by the bending portion and is linearly welded.

[0016] It is easier in operation to contract by bending and then weld.

In FIGS. 1 and 2, rebar 1A, rebar 1B.
Although the example in which the bars are arranged in the vertical direction has been described, the present invention is carried out in exactly the same manner when the reinforcing bars 1A and 1B are arranged in the horizontal direction.

[0018]

According to the present invention, since the unconstrained portions of the two reinforcing bars are contracted in advance and the butt welding is performed with the gap between the ends of the reinforcing bars slightly widened, the shrinkage due to welding is reduced in the unconstrained areas. It is absorbed and contraction strain does not remain on the reinforcing bar.

[Brief description of drawings]

FIG. 1 shows a state in which a tensioning jig used in the present invention is attached to a reinforcing bar for butt welding, (a) is an elevation view, and (b) is a plan view of a reinforcing bar gripping portion.

FIG. 2 is a vertical cross-sectional view of a butt weld between two unconstrained ends of two rebars in the vertical direction, one end of which is constrained by concrete.

[Explanation of symbols]

1A ... upper welded rebar 1B ... lower welded rebar 2
A, 2B, 2C, 2D ... Turnbuckle, 3A, 3
B, 3C, 3D ... Screw rod, 4 ... Reinforcing bar gripping part, 5 ... Packing, 6 ... Reinforcing bar gripping iron plate, 7 ... Bolt, 8 ... Ring-shaped backing plate.

Claims (1)

[Claims] 1. In butt welding of two unconstrained ends of two reinforcing bars, one end of which is constrained by concrete,
(A) A step of aligning 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, (B) 1 at each end of the plurality of turnbuckles Attaching the tension jigs welded to each rebar grip to one or both rebars, tightening the tension jigs and shrinking one or both rebars, and butt-welding with the gap between the two rebar ends widened , (C) a step of removing the tension jig from the reinforcing bar after the welded part has cooled, and a butt welding method of the reinforcing bar.