JP3658337B2 - Spot welding method for shear reinforcement - Google Patents

Description

【００３７】
【発明の効果】
以上説明したように、本発明のせん断補強筋のスポット溶接方法においては、その焼き戻し溶接時における溶接電流あるいは溶接エネルギーを、本溶接時における溶接電流あるいは溶接エネルギーに対して約７０％としている。
【００３８】
本発明によれば、主筋に対するせん断補強筋の溶接強度を、せん断補強筋の規格降伏点強度以上にしながらも、主筋の伸びを溶接前の規格基準値以上の値に保持できる。また、主筋の引張強度も溶接前の規格基準値以上の値に保持できる。よって、本発明のスポット溶接方法を採用すれば、剛性および靭性のある溶接鉄筋枠ユニットを製造することができる。
【図面の簡単な説明】
【図１】本発明のスポット溶接方法を用いて製造された溶接鉄筋枠ユニットおよび継ぎ手枠ユニットから構成されるＩ型継ぎ手構造を示す説明図である。
【図２】本発明のスポット溶接方法の工程を示す説明図である。
【符号の説明】
１、２ 溶接鉄筋枠ユニット
１１、２１ 上側の梁主筋
１２、２２ 下側の梁主筋
１３、２３ あばら筋（せん断補強筋）
３ 継ぎ手筋ユニット
３１、３２ 継ぎ手筋
３３ あばら筋
４ 継ぎ手位置
Ａ 予熱工程
Ｂ 本溶接工程
Ｃ 冷却工程
Ｄ 焼き戻し溶接工程[0001]
BACKGROUND OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is suitable for use in welding a stirrup as a shear reinforcement bar to a beam main bar in a beam frame unit for single bar arrangement suitable for use as a reinforced concrete beam with a single bar in a residential building or the like. The present invention relates to a spot welding method for a shear reinforcing bar.
[0002]
[Prior art]
As a reinforced concrete beam, a foundation beam, and the like used for a residential building or the like, there is known a single reinforcing bar having a configuration in which a pair of upper and lower beam main bars are attached with a stiff bar at a constant pitch. Further, as such a beam reinforcing bar, a reinforcing bar frame unit having a configuration in which the upper and lower ends of the upper and lower beam main bars are spot-welded at the upper and lower ends of the reinforcing bar is known. Such a rebar frame unit is manufactured by factory production, and a rebar frame unit of a predetermined length is constructed by connecting the rebar frame units to each other at the construction site, and the rebar frame units are connected at right angles or in a cross shape. This makes it possible to arrange the corners of the fabric foundation.
[0003]
Such a reinforcing bar frame unit and a reinforcing bar structure using the same are disclosed in, for example, Japanese Utility Model Publication No. 7-48881 by one of the present applicants.
[0004]
Here, in a reinforcing bar, when hardening is carried out by welding, although the hardness will increase, toughness will fall, elongation rate will fall and it will become weak. In a reinforced concrete structure, a tensile force is borne by the reinforcing bar to prevent brittle fracture, so the reinforcing bar is required to have a sufficient elongation rate. From this point of view, the welding strength of the reinforcing bar is controlled to be about 1/3 to 2/3 of the standard yield strength of the reinforcing bar base material so as not to impair the toughness of the reinforcing bar.
[0005]
[Problems to be solved by the invention]
By the way, the basic idea of reinforcing bar arrangement design in conventional reinforced concrete is to increase the bond strength between the reinforcing bar and the concrete and to integrate the two, so that the compressive force generated by the applied load is applied to the concrete and the tensile force is applied to the reinforcing bar. It is to let you. Based on this idea, it is necessary to avoid using welding for beam reinforcement as much as possible because the toughness of the reinforcing bars will be reduced.
[0006]
However, there are still many unclear points regarding the behavior of reinforcing bars, especially the stress sharing state of the stirrups and the actual stress state at the joint of the beam. In view of this point, the present inventors have changed the coupling strength of beam bars and stirrups, etc., and devised a new bar arrangement design concept by conducting a load test of reinforced concrete beams, etc. In the specification of Japanese Patent Application No. 2001-50609, the beam arrangement unit for single reinforcement newly devised on the basis of the concept of the new reinforcement arrangement, and the joint portion of the beam arrangement unit for this new arrangement of single reinforcement. A joint structure is proposed in which a suitable joint frame unit and a joint portion of such a new single reinforcing bar frame unit are configured using the new joint frame unit.
[0007]
In other words, the beam frame unit for single reinforcement of a reinforced concrete beam proposed by the present inventors has upper and lower beam main bars extending in parallel at predetermined intervals, and rib bars welded to these at a predetermined pitch. And the welding strength between the beam main bar and the stirrup is not less than the standard yield point strength of the reinforcing steel base material.
[0008]
In the single reinforcing bar beam frame unit having this configuration, the in-plane rigidity of the unit assembled in a ladder shape is high, and this rigidity can withstand tensile force and compressive force acting on the beam. Since the welding strength of the beam reinforcement and the stirrup reinforcement is higher than the standard yield point strength of the base metal, the welded portion does not break or separate before the reinforcing bar is in the yield state. For this reason, even if the concrete reaches a compression fracture state, it is held by the unit, so that the toughness of the reinforced concrete beam as a whole can be increased and its brittle fracture can be prevented.
[0009]
In this way, not only the bond strength between concrete and reinforcing bars, but also the rigidity of the reinforcing bar frame unit consisting of beam bars and stirrups assembled in a ladder shape by welding, the reinforcement is arranged. Even if the fixing length is made shorter than before, a reinforced concrete beam having high strength and high safety as a whole can be realized.
[0010]
Further, the joint bar unit used for the joint portion of the upper and lower beam main bars of the reinforced concrete beam that has been proposed by the present inventors is composed of upper and lower joint bars extending in parallel at a predetermined interval, and these joint bars. A plurality of stirrups attached at a predetermined pitch to each other, and the upper and lower ends of each stirrup are welded to the upper and lower joints, respectively. Is characterized by being above the standard yield point strength of the reinforcing steel base material.
[0011]
In the joint bar unit of this configuration, instead of securing the strength of the joint part only by the fixing strength as in the conventional joint line, the joint of the beam bar is determined by the fixing strength and the rigidity of the strongly welded joint bar unit. The strength of the portion can be ensured. Therefore, the fixing length of the reinforcing bar can be shortened compared to the conventional case.
[0012]
Here, it is desirable that each rib is welded to the same side with respect to the upper and lower joint bars. Further, it is desirable that the distance between the upper and lower joint bars is set such that the upper and lower joint bars fit between the upper and lower beam main bars to be joined.
[0013]
In this way, the joint bars can be placed within the beam main bar's occupied width, so the rebar width required for the joint part is determined by the outer diameter of the beam main bars and the outer diameter of the stirrups located on both sides. It can be the sum of the dimensions. Therefore, the beam width made of reinforced concrete can be reduced.
[0014]
The problem of the present invention is that in such a single reinforcing bar frame unit or the like, the shear reinforcement can be welded to the beam reinforcement so that the welding strength is equal to or higher than the standard yield point strength of the shear reinforcement, and The purpose is to propose a spot welding method in which the tensile strength and elongation can be secured before welding.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention relates to a spot welding method for a shear reinforcing bar that is spot-welded to a beam main bar of a reinforced concrete beam for residential use at a predetermined pitch by energizing a predetermined welding current for a predetermined time. Welding, placing a predetermined tempering cooling time, conducting tempering by energizing a tempering current of about 70% of the welding current for a predetermined time, and welding strength of the shear reinforcement to the beam main bar, The value is equal to or greater than the standard yield point strength of the shear reinforcement.
[0016]
When tempering was performed in this manner, it was confirmed that the elongation of the main beam of the beam could be maintained at or above the standard reference value even after welding.
[0017]
In this case, it is desirable that the time for energizing the tempering current is the same as the time for energizing the welding current.
[0018]
Further, the present invention provides a method for spot welding of a shear reinforcement which is spot-welded to a beam main bar of a reinforced concrete beam for residential use at a predetermined pitch, performing a main welding by energizing a predetermined welding current for a predetermined time, A tempering current and its energization time are determined and tempered so that the welding energy is about 70% of the welding energy defined by the product of the welding current and the energization time in the main welding. The welding strength of the shear reinforcement with respect to the beam main reinforcement is a value equal to or higher than the standard yield point strength of the shear reinforcement.
[0020]
According to the present invention, it has been confirmed that the elongation of the main bars can be reliably maintained at or above the standard reference value even after welding.
[0021]
Moreover, it is desirable that the tempering cooling time is the same as the time for applying the welding current.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Below, with reference to drawings, the example of the spot welding method of the shear reinforcement which applied this invention is demonstrated.
[0023]
Fig.1 (a) is explanatory drawing which shows the I-type joint structure of the single reinforcement beam manufactured using the spot welding method of this invention.
[0024]
First, the structure of the welded reinforcing bar frame units 1 and 2 to be spliced will be described. These are basically the same structure, and a pair of upper and lower beam main bars 11, 12 and 21, 22 are fixed between them. The stirrups 13 and 23 are provided at a pitch, and the stirrups 13 and 23 are spot-welded at their upper and lower ends to the beam main bar. When the beam length is high, the abdominal muscles may be arranged in the middle position so as to be parallel to the beam main bars, and there may be a plurality of beam main bars arranged vertically. Such welded rebar frame units 1 and 2 are generally produced in a factory and carried into a construction site. What should be noted is that the welding strength of the stirrups 13 and 23 with respect to the beam main reinforcing bars 11 and 12 is set so as to be a value equal to or higher than the standard yield point strength of these reinforcing steel base materials.
[0025]
The joint bar unit 3 for connecting the welded bar frame units 1 and 2 includes a pair of upper and lower joint bars 31 and 32 and a plurality of ribs 33 spanned between them at a constant pitch. In the example shown in the figure, four streaks 33 are bridged. The upper and lower ends of each stirrup 33 are spot welded to the joints 31 and 32, respectively. The joint line unit 3 is also generally produced in a factory. Further, the welding strength between the stirrup and the joint is set to a value equal to or higher than the standard yield point strength of these reinforcing steel base materials. If it does in this way, the in-plane rigidity of joint frame unit 3 can be raised, and a part of force which acts on a joint part can be borne by the rigidity concerned.
[0026]
As can be seen from FIGS. 1 (b) and 1 (c), the stirrups 33 are welded to the same side with respect to the upper and lower joint bars 31 and 32. Further, the distance between the upper and lower joint bars 31 and 32 is determined so as to fit between the upper and lower beam main bars 11 and 12 and between the beam main bars 21 and 22. In the welded reinforcing bar frame units 1 and 2, the stirrups 13 and 23 are welded to the upper and lower beam main bars 11, 12, 21, and 22 on the same side.
[0027]
When the I-shaped joint portion is configured using the joint frame unit 3, the joint frame unit 3 is arranged such that the center in the length direction is positioned at the joint position 4 of the welded rebar frame units 1 and 2 arranged in a straight line. Is attached to the welded rebar frame units 1 and 2 from the side. That is, it is attached to the side opposite to the stirrup attachment side in the welded reinforcing bar frame units 1 and 2 so that the joint position 4 coincides with the center 3a of the joint reinforcement unit 3. Moreover, the side where the stirrup 33 of the joint reinforcing unit 3 is not attached is overlapped with the side where the stirrups 13 and 23 of the welded rebar frame units 1 and 2 are not attached.
[0028]
As a result, as shown in FIG. 1 (b), the upper and lower joint bars 31, 32 enter between the upper and lower beam main bars 11, 21, 12, 22, and each joint bar 31, 32 is a beam side stirrup 13. , 23. In this state, the joint bars 31 and 32 are bound to the upper and lower beam main bars 11, 12, 21, and 22 using binding lines (not shown), respectively. In this way, the I-type joint structure shown in FIG.
[0029]
In the I-type joint structure of this example, since the joint bar unit 3 having high in-plane rigidity is overlapped and bundled with the joint parts of the welded bar frame units 1 and 2, the rigidity of the joint part can be increased. As a result, the tensile force acting on the joint portion is shared by the adhesion force of the joint bars 31 and 32 to the concrete and the support pressure by the rib bars 33 welded to the joint bars 31 and 32.
[0030]
Therefore, compared to the conventional joint structure in which the tensile force acting on the reinforced concrete beam through the concrete adhesion force is borne by the joint muscle, the dependency on the adhesion force can be reduced, so the required length of the joint muscle is required. The length L1 can be shortened.
[0031]
In this example, as shown in FIG. 1 (b), the joint bars 31 and 32 are accommodated within the width of the upper and lower beam main bars 11, 21, 12, and 22. Therefore, the required beam width W at the joint part. May be a dimension obtained by adding the left and right concrete cover thicknesses to the total dimension of the diameter of the main beam bars and the diameters of the left and right stirrups. Therefore, an increase in beam width can be suppressed.
[0032]
(Spot spot welding method)
Next, the welded rebar frame units 1 and 2 and the joint frame unit 3 having the above-described structure are produced at the factory, and a method of spot welding the stirrups to the beam main bars in them will be described. FIG. 2 is an explanatory view showing one step of spot welding in this example. As shown in this figure, the spot welding process itself is the same as a general one, and includes a preheating process A, a main welding process B, a tempering cooling process C, and a tempering welding process D.
[0033]
In this example, the energization time s1 of the welding current in the main welding process B, the cooling time s2 of the cooling process C, and the energization time s3 of the tempering welding process D are the same time. Further, the welding current in the tempering welding process D is set to a value of about 70% of the welding current in the main welding process B. Accordingly, the welding energy defined by the product of the welding current value and the energization time is about 70% at the time of tempering welding, assuming that the main welding is 100%.
[0034]
When spot welding was performed under these welding conditions, it was confirmed that the welding strength could be made higher than the standard yield point strength of the stirrup, and the tensile strength and elongation of the main reinforcement could be kept above the standard reference value before welding.
[0035]
Here, suitable welding conditions for the combinations of the main reinforcing bar diameters and the shear reinforcing bar diameters are shown in the following table. The pressurizing force during the main welding was 550 kg or more, SD345 was used for D-19 and D-22 of the main bars, and SD295A was used for the other reinforcing bars. By performing spot welding according to the conditions in this table, it was confirmed that the welding strength could be higher than the standard yield point strength of the shear reinforcement, and the tensile strength and elongation of the main reinforcement could be maintained above the standard reference value.
[0036]
[Table 2]

[0037]
【The invention's effect】
As described above, in the spot welding method of the shear reinforcement according to the present invention, the welding current or welding energy at the tempering welding is set to about 70% with respect to the welding current or welding energy at the main welding.
[0038]
ADVANTAGE OF THE INVENTION According to this invention, the elongation of a main reinforcement can be hold | maintained to the value more than the standard reference value before welding, while making the welding strength of the shear reinforcement with respect to the main reinforcement more than the standard yield point strength of a shear reinforcement. Also, the tensile strength of the main bars can be maintained at a value equal to or higher than the standard reference value before welding. Therefore, if the spot welding method of the present invention is adopted, a welded reinforcing bar frame unit having rigidity and toughness can be manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an I-type joint structure including a welded bar frame unit and a joint frame unit manufactured by using the spot welding method of the present invention.
FIG. 2 is an explanatory view showing a process of the spot welding method of the present invention.
[Explanation of symbols]
1, 2 Welded bar frame units 11, 21 Upper beam main bars 12, 22 Lower beam main bars 13, 23 Stirrup (shear reinforcement)
3 Joint Bar Units 31 and 32 Joint Bar 33 Stirrup 4 Joint Position A Preheating Process B Main Welding Process C Cooling Process D Tempering Welding Process

Claims (5)

In the spot welding method of the shear reinforcement which is spot welded to the beam reinforcement of the reinforced concrete beam for residential use at a predetermined pitch,
Energize the specified welding current for a specified time to perform the main welding,
Set a predetermined tempering cooling time,
Conducting tempering welding by energizing a tempering current of about 70% of the welding current for a predetermined time;
A method of spot welding a shear reinforcing bar, wherein a welding strength of the shear reinforcing bar to the beam reinforcing bar is set to a value equal to or higher than a standard yield point strength of the shear reinforcing bar. In claim 1,
A method for spot welding a shear reinforcement , wherein the time for applying the tempering current is the same as the time for supplying the welding current . In the spot welding method of the shear reinforcement which is spot welded at a predetermined pitch to the beam main reinforcement of a reinforced concrete beam for residential use,
Energize a specified welding current for a specified time to perform the main welding,
Set a specific tempering cooling time,
The tempering current and the energizing time are determined so that the welding energy is about 70% of the welding energy defined by the product of the welding current and the energizing time in the main welding, and tempering welding is performed.
A method of spot welding a shear reinforcing bar, wherein a welding strength of the shear reinforcing bar to the beam reinforcing bar is set to a value equal to or higher than a standard yield point strength of the shear reinforcing bar. In claim 1 or 3,
The method of spot welding a shear reinforcing bar, wherein the tempering cooling time is the same as the time for applying the welding current. In claim 1 or 3,
The current value and energization time during the main welding, the tempering cooling time, the current value during the tempering and the energization time with respect to the combination of the beam main bar diameter and the shear reinforcement bar diameter are as shown in the following table. A spot welding method for a shear reinforcing bar characterized by the above.

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