JP2006037549A - Anchorage reinforcing bar and anchorage structure of hoop using its reinforcing bar - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the anchorage structure of a hoop having an excellent earthquake-resistant performance and having a superior workability. <P>SOLUTION: The superposing sections of the hoops 2 are engaged by an anchorage reinforcing bar 3 formed by bending one reinforcing bar at a center thereof at 90° and folding back the same at both ends at 180°, thus anchoring the hoops 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing reinforcing reinforcing bar used for a reinforcing bar of a column part in RC structure (reinforced concrete structure), and a fixing structure of a reinforcing band using the same.

  In the 1995 Great Hanshin-Awaji Earthquake, there were many reports of destruction of RC structures, but it was pointed out that the RC rods that had broken down were poorly anchored by the right angle hook method that had been widely used in the past. According to the Japan Society of Civil Engineers concrete standard specifications at the time, “When using deformed reinforcing bars for hoops and reinforcing bars, in principle, semicircular or acute hooks shall be provided”. The semi-circular hook is a 180 ° bent hook, and the acute angle hook is a 135 ° bent hook. The inner diameter of the end part of the reinforcing bar end is specified in the Architectural Institute of Japan Building Standard Specification 5 (JASS 5) Reinforced Concrete Work or Japanese Industrial Standard JIS G 3112, and the nominal diameter d of the reinforcing bar is 16 mm or less. In this case, it is set to 3d or more.

  An example of a semicircular hook is shown in FIG. 1 is an axial rebar, 2 is a band rebar, and 21a is a semicircular hook. In this way, if the bending angle is large, the rebar will not open even if it is no longer constrained by the cover concrete on the outside, so it is excellent in seismic performance. Reinforcing bars cannot be attached and they can only be dropped from the top. In recent years, however, deformed bars are also commonly used for the axial main bars, so it is difficult to drop the strip bars outside the axial bars with a semi-circular hook or an acute angle hook, and bending is not possible during assembly. It may be necessary.

  On the other hand, FIG. 8B shows an example of a right angle hook bent at 90 °, and 21b is a right angle hook. Since it can be opened and closed freely using the elasticity of the reinforcing bars, it is easy to construct, so it tends to be used anyway. However, when an alternating repeated load such as an earthquake is applied, the fixing function is lost if the outer cover concrete is peeled off. Therefore, in the concrete standard specification earthquake-resistant design edition established by the Japan Society of Civil Engineers in 1996 after the Great Hanshin-Awaji Earthquake, mechanical joints or flare welding were used when a right-angle hook was used in addition to the acute angle hook as a means for fixing the reinforcing bar. Added to use together. FIG. 9A shows an example of a mechanical joint, in which a metal pipe 22 is placed on the overlapping portion of the right angle hooks 21b and fixed by caulking from the outside. However, this requires not only a special machine for caulking work at the construction site, but also the joints tend to concentrate on a specific surface due to the ease of construction, and the concrete at the time of placing on this specific surface Anxiety arises in going around. FIG. 9B shows an example of flare welding, and reference numeral 23 denotes a flare weld. Welding has excellent strength when a highly skilled welder is honest, but it has the disadvantage that it cannot be determined by just looking at the appearance after construction. It cannot be a fixing structure that satisfies both workability.

On the other hand, Patent Document 1 describes a fixing method using a ring-shaped fixing tool. This will be briefly described with reference to FIG. This embodiment is an example of a fixing structure of an axial rebar such as a beam or a column, or an intermediate rebar connecting the band rebars. 1 is an axial rebar, 2 is a band rebar (in this case, the main bar of the beam), and 4 is a band. An intermediate band rebar connecting the reinforcing bars (main bars) 2, 41 is a right angle hook portion, and 5 is an ellipse-shaped fixing tool. As shown in FIG. 10A, the fixing tool 5 is inserted from the right angle hook portion 41 to the position beyond the band rebar 2 and is tilted in the direction indicated by the arrow so that the L-shaped portion of the intermediate band reinforcing bar 4 and the fixing tool 5 are inserted. The band rebar 2 is fixed between the two. In this method, since the tip of the fixing device 5 needs to pass through the tip of the right angle hook 41, there is a problem in construction such that attachment is not possible if the extra length of the right angle hook 41 is too long.
JP 2003-253814 A

  An object of the present invention is to solve the above-mentioned problems in the prior art and to realize a fixing structure that satisfies both seismic performance and workability.

  The fixing reinforcing reinforcing bar for fixing a reinforcing bar according to the present invention is formed by bending one reinforcing bar at 90 ° in the center and folding back both ends by 180 °, and preferably folding the 180 ° folding direction of the both-end folded portions at 90 °. The fixing reinforcing reinforcing bars for fixing the above-described band reinforcing bars, which are opposite to each other in the plane.

  Further, the fixing structure of the strip reinforcing bar of the present invention is a reinforced concrete column reinforcing rod structure in which a rectangular reinforcing bar is wound around a longitudinal axial reinforcing bar in the longitudinal direction, and both ends of the strip reinforcing bar are bent at a right angle. It is overlapped on both sides of the directional reinforcing bar, and the overlapping part of the band reinforcing bar is locked inside the folded portion of both ends of the fixing reinforcing bar.

  According to the present invention, since the rebar is a right-angle hook, the workability is very good, and the use of the fixing reinforcing rebar provides an excellent effect that the seismic performance equivalent to that of the semicircular hook can be realized.

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

  FIG. 1 is a perspective view showing an embodiment of a fixing reinforcing bar according to the present invention. Reference numeral 3 denotes a fixing reinforcing bar, and reference numerals 31a and 31b denote folded ends formed at both ends. That is, the fixing reinforcing reinforcing bar 3 for fixing the belt reinforcing bars is formed by bending one reinforcing bar at 90 ° in the center and folding back both ends by 180 °, and the folding-back direction of both-end folded portions 31a and 31b is 90 °. They are opposite to each other with respect to the folding surface. Since the rebar is processed by bending 90 ° or 180 °, it is easy and easy to manufacture.

  FIG. 2A is a perspective view showing a state where the fixing reinforcing bar 3 is about to be attached to the right-angle hook 21b portion of the band reinforcing bar 2. FIG. Since the folding directions at both ends are opposite, one is attached from above and the other is attached from below. A state where the attachment is completed is shown in FIG. That is, the fixing structure of the band reinforcing bar according to the present invention is a reinforced concrete column reinforcing bar structure in which a band reinforcing bar 2 is wound around a longitudinal axial reinforcing bar 1 in the longitudinal direction, and both ends of the band reinforcing bar 2 are perpendicular to each other. The bent right-angle hook 21b is overlapped with the band reinforcing bar 2 on both sides of the axial reinforcing bar 1, and the overlapping portions 2 and 21b of the band reinforcing bar 2 are engaged inside the folded ends 31a and 31b of the fixing reinforcing bar 3. It will stop.

  FIG. 3 is a horizontal sectional view of an RC column according to the fixing structure of the present invention. Each reference numeral is the same as described above, and C is concrete. The fixing reinforcing bar 3 is bent at 90 ° in the horizontal direction, so that the right-angle hook 21b is locked perpendicularly to the belt reinforcing bar 2 from the inside of the column, that is, from the direction in which the tensile force of the reinforcing bar is fully exerted. You can see that The length of the fixing reinforcing bar 3 is preferably within the limit of the overlapping portion of the band reinforcing bar 2 and the right angle hook 21b. However, the extra length of the end of the reinforcing bar when bent by 90 ° is described in JASS 5. According to this, since it is defined to be 8d or more with respect to the reinforcing bar nominal diameter d, the length of the fixing reinforcing reinforcing bar 3 naturally corresponds to this.

  Since the rebar 2 is constrained from the inner side of the column by the anchor reinforcement bar 3, the rebar 2 is fixed to the inner concrete even after the surrounding cover concrete is peeled off by alternating repeated loads such as earthquakes. It is possible to prevent the collapsed concrete from protruding after the yielding of the directional reinforcing bars.

  FIG. 4 shows a case where the folding directions of the folded portions 31a and 31b at both ends of the fixing reinforcing steel bar 3 are the same, unlike the conventional ones. Since the bending of the reinforcing bar is a cold bending at the processing site, there is some error even if it is 180 °, and there is also a gap between the two reinforcing bars on the inside. Therefore, when the folding is attached in the same direction, the fixing reinforcing reinforcing bar 3 tends to hang down as shown by an arrow due to its own weight as shown in this figure. This does not cause any problems as far as fixing is concerned, but it is more preferable to reverse the folding direction as shown in FIG.

  In order to confirm the fixing effect of the fixing reinforcing reinforcing bar of the present invention, a test body as shown in FIG. 5 was manufactured, a horizontal alternating load was applied to the position of the arrow, and the displacement was measured. P is a pillar and F is a footing. As for the column P, the width in the left and right direction in FIG. 5 is 400 mm, the width in the depth direction of the paper is 800 mm, the rise from the footing F is 1650 mm, the reinforcement is 50 mm in thickness of the surrounding concrete, and the longitudinal axial rebar is as shown in FIG. Eight pieces each were arranged on the left and right sides, and 300 × 700 mm band reinforcing bars were arranged in eight steps at a pitch of 200 mm so as to surround them. The axial rebar is a deformed steel bar called D19 with a nominal diameter of 19 mm, and the strip rebar is a deformed steel bar with a diameter of 9 mm.

  As for the fixing part of the band reinforcing bar, three types of the fixing reinforcing reinforcing bar of the present invention, the right angle hook shown in FIG. 8B as a conventional example, and the semicircular hook shown in FIG. 8A were manufactured. .

First, regarding toughness, the displacement when the reinforcing bar yields is δy, the displacement with respect to the load of 80% of the maximum proof stress is the ultimate displacement δu, and the toughness ratio μ is
μ = δu / δy
The measurement results are as shown in FIG. That is, in the right angle hook, the toughness ratio μ is about 6 times, but the fixing reinforcing bar of the present invention shows 7 times that of the semicircular hook.

  Next, the energy absorption capacity obtained by accumulating the absorbed energy for each cycle is 1746 kJ for the right angle hook as shown in FIG. 7, whereas it is 2334 kJ for the fixing reinforcing bar of the present invention, which is a semicircular hook. Almost equal to 2399kJ.

  Attachment of the reinforcing reinforcing bar of the present invention is very simple by simply hooking the folded portions at both ends to the band reinforcing bar. Its seismic performance is equivalent to the semicircular hook recommended by the Japan Society of Civil Engineers.

  Although the example of the column in the RC structure has been described above, the fixing reinforcing bar of the present invention can be applied to a column, a beam, a bridge pier, and the like in the RC rigid frame structure.

It is a perspective view which shows the Example of the fixation reinforcement bar of this invention. It is a fragmentary perspective view of the reinforcing bar structure which shows the situation where the fixation reinforcement bar of the present invention is attached. It is a horizontal sectional view of the RC column using the fixing reinforcement bar of the present invention. It is a fragmentary perspective view of the reinforcing bar structure which shows the other Example of the fixation reinforcement bar of this invention. It is a front view of the test body for confirming the effect of the fixation reinforcement bar of the present invention. It is a graph of the toughness rate which shows the effect of the fixation reinforcement bar of this invention. It is a graph of the absorbed energy which shows the effect of the fixation reinforcement bar of this invention. (A) which shows the fixing structure in a prior art is a horizontal sectional view of the reinforcing bar structure in the case of a semicircular hook, and (b) in the case of a right angle hook. (A) which shows the fixing structure in a prior art, (b) is a partial perspective view of the reinforcing bar structure in the case of flare welding. It is a perspective view which shows the fixing structure in another prior art.

Explanation of symbols

1 Axial rebar (main bar)
2 Reinforcing bars 3 Reinforcement reinforcing bars 4 Intermediate belt reinforcing bars 5 Fixing tools
21a Semi-circular hook
21b, 41 right angle hook
22 Pipe
23 Flare weld
31a, 31b Folded part on both ends C Concrete F Footing P Column

Claims (3)

  A fixing reinforcing bar for fixing a reinforcing bar, which is formed by bending a single reinforcing bar at 90 ° in the center and folding back both ends by 180 °.   2. The fixing reinforcing bar for fixing a reinforcing bar according to claim 1, wherein the 180 ° folding direction of the both-end folded portion (31) is opposite to the 90 ° folding surface.   In the reinforcing bar structure of a reinforced concrete column in which a longitudinal reinforcing bar (1) is wound around a longitudinal reinforcing bar (2), both ends of the reinforcing bar (2) are bent at a right angle to make an axial reinforcing bar. A band formed by overlapping on both sides of (1) and locking the overlapped portion of the band reinforcing bar (2) inside the both ends folded portion (31) of the fixing reinforcing bar (3) according to claim 1 or 2. Reinforcing bar anchoring structure.

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