JP2720765B2 - 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 two rebars, and (B) one or both of tensioning jigs in which one rebar grip is welded to each end of a plurality of turnbuckles. And tightening the tensioning jig to shrink one or both reinforcements and widen the gap between the ends of the two reinforcements. (C) The welding jig is cooled after the weld is cooled. More removing process,
Butt welding method for reinforcing bars.

The most important point of the present invention is that a special tensioning jig is attached to one or both rebars, and the tensioning jig is tightened to shrink one or both rebars to widen the gap between the two rebar ends. Is the point of butt welding. The length reduced by the tension jig is a length corresponding to the length of the rebar contracted by welding. Therefore, when the weld is cooled after welding and the tension jig is removed from the reinforcing bar, the contraction of the reinforcing bar is absorbed by the unconstrained portion.

In the present invention, a special tensioning jig is used to shrink the unrestricted portion of the reinforcing bar. This jig is obtained by welding one rebar gripping portion to each of both ends of a plurality of turnbuckles. It is arranged so as to surround the unconstrained portion of the turnbuckle rebar. Usually, four or six turnbuckles are used, and each of these turnbuckles is arranged around the rebar in a well-balanced manner. The tensioning jig is preferably attached to both reinforcing bars to be butt-welded,
It may be attached to only one reinforcing bar having a long unconstrained portion.

[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 tension jig used in the present invention is attached to a reinforcing bar to be butt-welded, (a) is an elevation view, and (b) 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 part 4, respectively. The rebar gripping portion 4 includes two partially curved iron plates 6 and 6 and a packing 5.
And two bolts 7 for tightening the two iron plates 6. Insert this tension jig from the longitudinal direction of the reinforcing bar 1A,
After being separated into two parts, the reinforcing bar 1A is sandwiched from the lateral direction or attached to the reinforcing bar 1A, and the bolt 7 is tightened via the packing 5 to be fixed to the reinforcing bar 1A.

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 2 is a longitudinal sectional view of butt welding of unconstrained ends of two vertical reinforcing bars whose ends are constrained by concrete.

(1) The ends of the reinforcing bar 1A whose upper end is constrained by concrete and the reinforcing bar 1B whose lower end is constrained by concrete are trimmed, the gap between the front ends is set to about several mm, and the reinforcing bars are straddled between the front ends. A ring-shaped backing metal 8 is fitted.

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

(4) The gap between the tip of the reinforcing bar 1A and the reinforcing bar 1B is welded with a weld metal, and after the weld is cooled, the bolt 7 is loosened and the tension jig is removed from the reinforcing bar 1A or the reinforcing bar 1A and the reinforcing bar 1B. Is completed.

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

It is easier to operate when it is welded while being slightly curved.

FIGS. 1 and 2 show a reinforcing bar 1A and a reinforcing bar 1B.
Has been described in the vertical direction, but the present invention can be implemented in exactly the same manner when the reinforcing bars 1A and 1B are arranged in the horizontal direction.

[0018]

According to the present invention, the unconstrained portions of the two rebars are contracted in advance, and the butt welding is performed with the gap between the ends of the rebars slightly widened. Shrinkage strain does not remain in the rebar due to absorption.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of butt welding of unconstrained ends of two vertical reinforcing bars whose ends are constrained by concrete.

[Explanation of symbols]

1A ... upper welded reinforcing bar, 1B ... lower welded reinforcing bar, 2
A, 2B, 2C, 2D, turnbuckle, 3A, 3
B, 3C, 3D Screw screw, 4 Rebar gripping part, 5 Packing, 6 Rebar gripping iron plate, 7 Bolt, 8 Ring backing metal.

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 rebar to a predetermined length and fitting a ring-shaped backing metal over the ends of the two rebars; (B) one step at each end of a plurality of turnbuckles. A step of attaching a tension jig to which one of the rebar gripping portions is welded to one or both rebars, tightening the tension jig to shrink one or both rebars, and performing a butt welding in a state where a gap between two rebar ends is widened. (C) a step of removing the tension jig from the rebar after the weld is cooled;